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General Electric Review
INDEX TO VOLUME XVIII
January, 1915 — December, 1915
TK
/
INDEX TO VOLUME XVIII
PAGJ
Absolute Zero, The, by Dr. Saul Dushman 93, 238
Acid-Dipping, Electroplating and Japanning Plant, A
Modern, by Horace Niles Trumbull 1121
Agriculture. Electricity in, by C. J. Rohrer 483
A.I.E.E , History of Schenectady Section of the, by S. M.
Crego 1006
A.I.E.E., Notes on the Activities of the. 71, 148, 222, 301, 405. 594
Air Cleaning Apparatus for the Ventilation of Generators
and Transformers, by Wm. Baum 801
Air Supply, Test for Dirt in an, by S. A. Moss 622
Altitude, Effect of, on the Spark-over Voltages of Bushings,
Leads and Insulators, by F. W. Peek, Jr 137
Aluminum Company of America, at Massena Springs,
N. Y., The 45,000-kw. Synchronous Converter
Substation of the, by J. L. Burnham and R. C. Muir 873
Apprentice System at the Lynn Works of the General
Electric Company, The, by Theodore Bodde 35
Automobile Industry, Electricity in the, by F. M. Kimball 550
Ball Bearings in Electric Motors, by F. H. Poor 631
Berkshire Street Railway, Semi-outdoor Portable Sub-
station for, by W. D. Bearce 44
Bethlehem- Chili Iron Mines Company, The 2400- volt
Railway of the, by E. E. Kimball 12
Burning Powdered Coal, Some Problems in, by Arthur S.
Mann 920, 959
Butte, Anaconda & Pacific Railway, Contact System of the,
by J B. Cox 842
Gars, Small, Economies in Operating, by J. F. Layng . . . 790
Car Operation and Power Consumption, Relation Between,
by J. F. Layng 973
Cathode Rays and Their Properties, by J. P. Minton . . . 118
Cathode Ray Tube and Its Application, The, by M. E.
Tressler 816
Cathode Ray Tubes, Some Characteristics of, by J. P.
Minton 636
Central Station, The Possibilities Open to the, in Solving
the Freight Terminal Problem, by Jas. A. Jackson 1142
Chicago, Milwaukee & St. Paul Railway Company, The
First 3000-volt Locomotive for the, by E. S. Johnson 1 1.34
Chicago, Milwaukee & St. Paul Locomotives, The, by
A. H. Armstrong 600
Chicago, Milwaukee & St. Paul Railway. The Electrifi-
cation of the Puget Sound Lines of the, by A. H.
Armstrong 5
Chicago, Milwaukee & St. Paul Railway, The 1500-volt
Electrification of the, by W. D. Bearce 644
Coal, Powdered, Some Problems in Burning, by Arthur S.
Mann 920, 959
Coatings, Protective, for Metals, by H. B. C. Allison 878
Coffee Plantation, Hydro-electric Installation on a, by
J. H. Torrens 219
Cohoes Company at Cohoes, N. Y., Hydro-electric
Development of the, by B. R. Connell 340
Columbia University, The New Advanced Course in
Electrical Engineering at, by W. I. Slichter 940
Compensators for Mazda C Lamps, by H. D. Brown 596
Consumer, The Small: A Problem, by A. D. Dudley .... 657
CONTROL. (See also Protection).
Sprague-General Electric PC Control, by C. J Axtell 985
Control and Protection of Electric Systems, by C. P.
Steinmetz 887
Coolidge Tube. Application of the. to Metallurgical
Research, by Dr. Wheeler P. Davey. 134
Cooling Power Transformers, Principal Factors Governing
the Choice of Method of, as Related to Their First
Cost and Operating Conditions, by W. S. Moody. . 839
Corona and Spark-overin Oil, The Law of, by F. W. Peek, Jr. 821
Current, Growth of, in Circuits of Negative Temperature
Coefficient of Resistance, by F. W. Lyle 1129
PAGE
Dark Room, X-Ray, A Model, by Wheeler P. Davey . .. 1107
Depreciation of Property, by W. B. Curtiss 1099
Developments in Electrical Apparatus During 1914, by
John Liston 80
Direct Current, High Potential Methods of Obtaining,
by Stuart Thomson 1084
Drill. Rock, The Fort Wayne Electric, by C. Jackson .... 273
Earth Connections, Proper Construction of, by G. H.
Rettew 904
Economies in Operating Small Cars, by J. F. Layng 790
Electric Power Industry, The, by D. B. Rushmore 427
Electrical Development, The Trend of, by Paul M. Lincoln 784
Electrical Engineering at Columbia University, The New
Advanced Course in, by W. I. Slichter 940
Electricity in the Automobile Industry, by Fred M.
Kimball 550
Electricity in the Construction and Operation of the
Panama Canal (Supplement to July issue), by
Edward Schildhauer 679
Electriquette. The Osborne, by O. E. Thomas 299
Electricity in Agriculture, by C. J. Rohrer 483
Electro-culture: A Resumed of the Literature, by Helen R.
Hosmer 14
Electron Discharge, The Pure, and Its Applications in
Radio Telegraphy and Telephony, by Irving
Langmuir 327
Electroplating, Acid-Dipping and Japanning Plant, A
Modern, by Horace Niles Trumbull 1121
ELECTROPHYSICS
Application of the Electron Theory to Various
Phenomena, by J. P. Minton 287
Electromagnetic Radiation from the Viewpoint of the
Electron Theory, by J. P. Minton 387
Cathode Rays and Their Properties, by J. P. Minton 118
Electron Theory of Electric Conduction in Metals, by
J. P. Minton 204
Some Characteristics of Cathode Ray Tubes, by J. P.
Minton 636
Emergency Transformer Connections, by George P. Roux 832
Enameling Ovens, Electrically Heated, by C. W. Bartlett L130
Engines, Internal Combustion, Parallel Operation of
Alternating Current Generators Driven by, by
R. E. Doherty and H. C. Lehn 167
Engineer, The Status of the, by Dr. E. W. Rice, Jr 234
Engineering in the Navy, by W. L. R. Emmet 1097
Eye and Illumination, The, by H. E. Mahan 268
Factory Lighting, by G. H. Stickney 67
Factories, Isolated Power-house for, by W. E. Francis. . . 1057
Fire Departments, Portable Searchlights for, by L. C.
Porter and P. S. Bailey 1144
Freight Terminal Problem. The Possibilities Open to
Central Stations in Solving the. by Jas. A. Jackson 1142
Frequency Changers, Parallel Operation of, by G. H. Rettew 836
Gases, The Kinetic Theory of, by Dr. Saul Dushman . . .
952, 1042, 1159
Gases, Noble, Notes on the, by W. S. Andrews 226, 40S
Gears and Pinions, Railway Motor, Operating Conditions
of, by A. A. Ross 249
Genemotor, The, by M. J. Fitch 384
General Electric Company's Exhibits at the Panama-
Pacific International Exposition, by G. W. Hall. . . 561
GENERATORS
Air Cleaning Apparatus for the Ventilation of Gener-
ators and Transformers, by Wm. Baum 801
Parallel Operation of Alternating Current Generators
Driven by Internal Combustion Engines, by R. E.
Doherty and H. C. Lehn 167
Grounding, General Notes on, by H. M. Wolf 991
PAGE
Heating and Heating Appliances, Electric, by C. P.
Randolph s23
High Frequency, by F. W. Peek, Jr 934
High Potential Direct Current. Methods of Obtaining, by
Stuart Thomson 1084
High Voltage Direct-current Substation Machinery, by
E. S. Johnson 641
High Voltage Arrester for Telephone Lines, by E. P. Peck 189
Hoists, Large Steam. Tests of, by H. E. Spring 179
"Home Electrical" at the Panama-Pacific International
E xposition. The. by Don Cameron Shaffer 572
HYDRO-ELECTRIC DEVELOPMENTS
Hydro-electric Development of the Cohoes Company.
at Cohoes. N. Y„ by B. R. Connell 340
Water Powers of New England, by H. I. Harriman . . 358
Hydro-electric Installation on a Coffee Plantation, by
J. H. Torrens 219
Impregnating Cods, The Process of, and a Large Impreg-
nating Plant, by Robert Reid 48
Industrial Applications of Electricity, Some, by A. R.
Bush 46D
Industrial Research, by L. A. Hawkins 416
Industry, The Electric Power, by D. B. Rushmore .... 4L'7
Industry. The Individual and Corporate Development of.
by C. P. Steinmetz 813
Insulating Materials, The Volume Resistivity and Surface
Resistivity of, by Harvey L. Curtis 996
Insulations, Solid. Electrical Characteristics of, by F. W.
Peek, Jr 1050
Insulation Testing, by G. B. Shanklin 1008
Iron-cobalt Alloy. FeaCo, and Its Magnetic Properties, The.
by Trygve D. Yensen 881
Japanning. Acid-Dipping and Electroplating Plant, A
Modern, by Horace Niles Trumbull 1121
Jitney Problem, The, by J. C. Thirlwall 604
Kenotron. The. A New Device for Rectifying Alternating
Currents, by Dr. Saul Dushman 156
Kinetic Theory of Gases, The, by Dr. Saul Dushman
952, 1042, 1159
I. A MPS
Compensators for Mazda C Lamps, by H. D. Brown 596
Electric Lamp Industry, by G. F. Morrison 497
High Candle-power Mazda Lamps for Steel Mill
Lighting, by G. H. Stickney 377
Incandescent Lamps for Projectors, by L. C. Porter. . 371
Modern Street Lighting with Mazda Lamps, by H. A.
Tinson 659
LIGHTING
Brief Review of the Electric Lighting Industry, by
C. W. Stone 439
Eye and Illumination. The, H. E. Mahan 268
Factory Lighting, by G. H. Stickney 67
High Candle-power Mazda Lamps for Steel Mill
Lighting, by G. H. Stickney 377
Illumination of the Panama-Pacific International
Exposition, by W. D'A. Ryan
Lighting of Ships. The, by L. C. Porter 143
rn Street Lighting with Mazda Lamps, by H. A.
Tinson 659
Sign and Building Exterior Illumination by Projection,
by K. W. Mackall and L. C. Porter 2S2
Lock Entrance Caisson for the Panama Canal, by L. A.
Mason 210
LOCOMOTIVES
Chicago, Milwaukee & St. Paul Locomotives, The,
by A. H. Armstrong 600
Firs' 300(1- volt Locomotive for the Chicago, Milwaukee
& St. Paul Railway Company. The. by E. S. Johnson 1154
Operation and Rating of the Electric Locomotive. The.
by A. H. Armstrong 828
Towing Locomotives for the Panama Canal. The.
by C. \V. Larson iQl
page
Lubrication. The Theory of, by L. Ubbelohde. Translated
by Helen R. Hosmer 966. 1074. 111S
Magnetic Properties of Steel, The Effect of Chemical
Composition Upon the, by W. E. Ruder 19?
Magnetization Curves, Some Notes on, by John D. Ball 31
Marine Work. Electricity in, by Maxwell W. Day 504
Metal, Protective Coatings for, by H. B. C. Allison 878
Metals, Radiography of, by Wheeler P. Davey 795
Meter Design, Induction, Some Notes on, by W. H. Pratt 277
Mica, Built Up, X-Ray Examination of, by C. N. Moore 195
Mine Haulage Motor, The Modern, by C. W. Larson. . . . 264
Mining Work. The Use of Electricity in, by D. B. Rushmore 527
Motion Picture Machines, Current Supply for. by H. R.
Johnson 895
MOTORS
Electric Motor in the Printing Industry. The, by
W. C. Yates 1136
Ball Bearings in Electric Motors, by Frederick H. Poor 631
Methods of Removing the Armature from Box Frame
Railway Motors, by J. L. Booth 908
Modern Mine Haulage Motor, The, by C. W. Larson 264
Power Consumption of Railway Motors, by H. L.
Andrews and J. C. Thirlwall 944
Railway Motor Characteristic Curves, by E. E.
Kimball 296
Short Method for Calculating the Starting Resistance
for Shunt, Induction and Series Motors, A. by
B. W. Jones 131
Subdivision of Power as Solved by the Small Motor,
The, by R. E. Barker and H R. Johnson 555
MOTOR DRIVE
Electrical Equipment of the Vermont Marble Com-
pany, by John Liston 1015
Electricity in Agriculture, by C. J. Rohrer 483
Electricity in Marine Work, by Maxwell W. Day .... 504
Electric Power in the Textile Industry, by C. A. Chase 540
Industrial Applications of Electricity, Some, by A. R.
Bush 460
Supplying of Power to the Quaker Oats Company, by
J. M. Drabelle 42
Use of Electricity in Mining Work. The. by D. B.
Rushmore 527
Multi-recorder, A Cursory Account of the First Lightning
Storm of the Season as Given by the Records of the,
by E. E. F. Creighton 860
Navy, Engineering in the, by W. L. R. Emmet 1097
Negative Temperature Coefficient of Resistance. Growth
of Current in Circuits of, by F. W. Lyle 1129
N.E.L.A. Lamp Committee Report, A Review of the, by
G. F. Morrison 925
New England, Water Powers of, by H. I. Harriman 358
Noble Gases, Notes on the, by W. S. Andrews 226, 408
Obituary
In Memoriam: Douglas S. Martin 76
In Memoriam: John P. Judge 672
In Memoriam: Dr. and Mrs. F. S. Pearson 930
In Memoriam: George Crellin Cartwright 1169
Oil, The Law of Corona and Spark-over in. by F. W. Peek, Jr. 821
Ontario Municipal Railway, The 1500-volt Direct-current
Electrification of the, by G. H. Hill 10
Oscillations, Damped, the Production of, by Leslie O.
Heath 1110
Ovens, Enameling. Electrically Heated, by C. W. Bartlett 1130
Panama Canal. Electricity in the Construction and Opera-
tion of the. by Edward Schildhauer 679
Ancon Quarry 688
Balboa Sand Dock 688
Control of the Lock Machinery 748
Distribution at Locks ■ 716
Gatun Hydro-electric Station 688
Gatun Locks and Dam 679
Interlocking (Panama Canal Lock) 754
PAGE
Panama Canal, Locomotive Design, Details of 732
Machinery for the Operation of the Locks and Spillways 722
Pacific Locks and Dam 687
Reserve Station 70S
Towing Locomotives 729
Transmission System 709
Panama Canal, Lock Entrance Caisson for the, by L. A.
Mason 210
Panama Canal, The Towing Locomotives for the, by C. W.
Larson 101
Panama-Pacific International Exposition, The Illumination
of the, by W. D'A. Ryan 579
Panama-Pacific International Exposition, The General
Electric Company's Exhibits at the, by G. W. Hall 561
Panama- Pacific International Exposition, The "Home
Electrical " at the, by Don Cameron Shafer 572
Parallel Operation of Alternating-current Generators
Driven by Internal Combustion Engines, by R. E.
Doherty and H. C. Lehn ' 167
Parallel Operation of Frequency Changers, by G. H. Rettew 836
Paths of Progress. The, (Editorial)
3, 79, 155, 231, 314, 415, 599. 783. 867, 939, 1011, 1091
Periodic Law, The, by Dr. Saul Dushman 614
Pinions (See also Gears)
Power, Subdivision of, as Solved by the Small Motor, by
R. E. Barker and H. R. Johnson 555
Power Consumption of Railway Motors, by H. L. Andrews
and J. C. Thirlwall 944
Power House, Isolated, for Factories, by W. E. Francis. . 1057
Practical Experience in the Operation of Electrical
Machinery, by E. C. Parham
Alternator Speed Low 58
Armature Threw Solder 1082
Belts, Loose 58
Brush-holders Shifted 59
Burn-out due to Core Loss 57
Brake Adjustments, Electric 217
Capacity Current 40 1
Clutches. Adjusting Single-phase Motor 929
Commutators, Loose 56
Commutator Winding, Improvised 403
Connection, Loose 5G
Contact-shoe Pressure, Excessive 217
Crane Troubles. . 1003
Core, Loose 5S
Deflections, Misleading . 402
Devices, Misapplication of 401
Elevator Trouble 1 155
Elevator Speed, Erratic 59
Equalizer on the Wrong Side 305
Field Connection Error 928
Generators Motoring at No-Load . . 305
Hot Box Indications 57
Instrument Connections Wrong 404
Load was Unbalanced. 1082
Motor Acceleration, Jerky 218
Motor Heating, Repulsion 667
Motor Mounting, Changing 306
Motors, Repulsion Induction, Heating and Sparking of, 147
Motor Reversed 115o
Motor Stopped and Reversed 1004
Motor Throwing Oil 307
Motor on an Inertia L^ad, Variable-Speed 667
Motor Would Not Start 928
Power-Factor, Low 56
Pump Output, Excessive 147
Reactor Starting-Box Trouble 403
Repulsion-induction Motors, HeatMig and Sparking of 147
Resistance Wire Crossed 1154
Rotor Rubbed Stator 218
Shunt Ratio, The Wrong 666
Slip-ring Contacts. Imperfect - . .. 304
Stations in Series 861
Stator Coil Connections 1083
Transformer Connections SOU
PAGE
Practical Experience, etc., by E. C. Parham -Cont'd
Transformer Failures j^g
Transformers, Parallel ggj
Voltage, Service, Too Low ggx
Voltage, Unstable | q, , -,
Printing Industry, The Electric Motor in the, by W. C.
Yates 1136
Projectors, Incandescent Lamps for, by L. C. Porter 371
Protection and Control of Industrial Electric Power, by
C. P. Steinmetz gyg
Protection of Railway Signal Circuits against Lightning
Disturbances, by E. K. Shelton 1127
Quaker Oats Company, The Supplying of Power to the,
by J. M. Drabelle 42
Radiography of Metals, by Dr. Wheeler P. Davey 795
Radio-telephony, by W. C. White 33
Radio Telegraphy and Telephony, The Pure Electron
Discharge and Its Application In, by Irving
Langmuir 327
Railways, Electric, A Review of, by W. B. Potter and
G. H. Hill 444
RAILWAY EQUIPMENT
Automatic Railway Substations, by Cassius M. Davis 976
Contact System of the Butte, Anaconda & Pacific
Railway, by J. B. Cox 842
Operating Conditions of Railway^Motor Gears and
Pinions, by A. A. Ross 249
Selection of Railway Equipment, The, by J. F. Layng 126
Railway Motor Characteristic Curves, by E. E.
Kimball 296
Sprague-General Electric PC Control, by C. J. Axtell 985
Rectifying High Tension Alternating Currents, A New
Device for, by Dr. Saul Dushman 156
Refrigeration Field as It Exists Today, A Survey of the, by
H. I. Hollman 65
Refrigeration, A Standard in, by L. A. Simmons 1170
Research, by Dr. W. R. Whitney 1012
Research, The Relation of, to the Progress of Manu-
facturing Industries, by Dr. W. R. Whitney 868
Research, Industrial, by L. A. Hawkins 416
Resistance Standards, Precision. Ten-to-one Ratio for
Comparing, by C. A. Hoxie 915
Resistance, Starting, for Shunt, Induction, and Series
Motors, A Short Method for Calculating the, by
B. W. Jones 131
Resistivity, Volume, and Surface Resistivity of Insulating
Materials, The, by Harvey L. Curtis 996
Resolutions Presented to C. A. Coffin and E. W. Rice, Jr..
by Association of Edison Illuminating Companies,
Reproduction of the (Supplement to March issue).
Rheostats. Water, by X. L. Rca 1001
Rock Drill, The Fort Wayne Electric, by C. Jackson 273
Searchlights, Portable, for Fire Departments, by L. C.
Porter and P. S. Bailey 1 144
Ships, The Lighting of, by L. C. Porter 143
Short Circuits, Electrical, Mechanical Effects of, by S. H.
Weaver 1066
Sign and Building Exterior Illumination by Projection, by
K. W. Mackall and L. C. Porter 282
Signal Circuits, Railway, Protection of. Against Lightning
Disturbances, by E. K. Shelton 112/
Slot Insulation Design, Some Aspects of, by H. M. Hobart 360
Status of the Engineer, The, by E. W. Rice, Jr 234
Steel Castings, An X-Ray Inspection of, by Dr. Wheeler P.
Davey 25
Steel, Magnetic Properties of. The Effect of Chemical
Composition Upon the, by W. E. Ruder 197
Steel Mill Lighting, High Candle-power Mazda Lamps for,
by G. H. Stickney 377
Spark-over Voltages of Bushings, Leads and Insulators,
Effect of Altitude on the, by F. W. Peek, Jr 137
Sprague-General Electric PC Control, by C. J. Axtell. . . . 985
SUBSTATIONS
Automatic Railway Substations, by Cassius M. Davis 976
45.000-kw. Synchronous Converter Substation of the
:r.inum Company of America at Massena Springs.
N. V.. The. by J. L. Burnham and R. C. Muir. . . . S73
High Voltage Direct-current Substation Machinery,
by E. S. Johnson 641
Semi-outdoor Portable Substation for Berkshire Street
Railway, by W. D. Bearce «
"Supplies": Devices and Appliances for the Distribution.
Control and Utilization of Electricity, by S. H. Blake 553
Switchboard Apparatus. Some Recent Developments In.
by E. H Beckert 646
Telephone Lines. High Voltage Arrester for, by E. P. Peck 189
Temperature Coefficient Formula; for Copper, by John D.
Ball 669
- Dirt in an Air Supply, by S. A. Moss 622
The High Tension . by Wm. P. Woodward 39S
Tests. Electrical. Made in 1883 and Their Influence on
Modern Testing. A Series of. by A. L. Rohrer 22
Tests of Large Steam Hoists, by H. E. Spring 179
Textile Industry. Electric Power in the, by C. A. Chase . .540
Thury System of Direct-current Transmission. The, by
Wm. Baum 1026
TRACTION"
nomies in Operating Small Cars, by J F. Layng. 790
Electrification of the Puget Sound Lines of the
Chicago. Milwaukee & St. Paul Railway, The. by
A. H. Am-strong 5
Relation Between Car Operation and Power Con-
sumption, by J. F. Layng 973
Review of Electric Railways. A. by W. B. Potter and
G. H. Hill 444
Semi-outdoor Portable Substation for Berkshire Street
Railway, by W. D. Bearce 44
2400-volt Railway of the Bethlehem-Chili Iron Mines
Company. The. by E. E. Kimball 12
1 500-voIt Direct-current Electrification of the Ontario
Municipal Railway. The. by G. H. Hill 10
1500-volt Electrification of the Chicago. Milwaukee
& St. Paul Railway, by W. D. Bearce 644
PAGE
TRANSFORMERS
Air Cleaning Apparatus for the Ventilation of Gener-
ators and Transformers, by Wm. Baum 801
Emergency Transformer Connections, by George P.
Rous 832
High Potential Transformer Testing Equipment, by
Wm. P. Woodward 398
Mechanical Stresses in Shell Type Transformers, by
J. Murray Weed 60
- on the Operation of Transformer used with
2-ka-., 100.000-cycle Alternator, by S. P. Nixdorff 308
Open-delta or V Connection of Transformers, by
George P. Rous 52
Principal Factors Governing the Choice of Method of
Cooling Power Transformers as Related to Their
First Cost and Operating Conditions, by W. S.
Moody 839
Transients, The Infinite Duration of, by Charles L. Clarke 73
Transmission Line Calculator, A, by Robert W. Adams. . 28
TRANSMISSION'
Electric Transmission of Power, by R. E. Argersinger 454
Theory of Electric Waves in Transmission Lines, by
J. M. Weed 1148
Thury System of Direct Current Transmission, The.
by Wm. Baum. . , 1026
Wireless Transmission of Energy, by Elihu Thomson 316
Ventilation of Generators and Transformers, Air Cleaning
Apparatus for the, by Wm. Baum 801
Vermont Marble Company, Electrical Equipment of the,
by John Liston 1015
Waves. Electric. Theory of in Transmission Lints, by
J. M. Weed 1148
Welfare Work, by Jesse W. Lilienthal 1092
Wireless Transmission of Energy, by Elihu Thomson 316
X-rays, by Dr. Wheeler P. Davey 258, 353, 625
X-ray Dark Room, A Model, by Wheeler P. Davey .... 1107
X-ray Examination of Built-up Mica, by C. N. Moore. . . 195
X-ray Inspection of a Steel Casting, An, by Dr. Wheeler P.
Davey 25
X-rays. Some Notes on, by W. S. Andrews 152
Zero. The Absolute, by Dr. Saul Dushman 93. 238
QUESTION AND ANSWER INDEX
1913 — 1914 — 1915
ARRESTER. LIGHTNING Q- * A.
Charging. . No. 79
Charging resistance; Function of ... . No. 39
Desirability for steel mill circuits . . . Xo. S8
loisture in Xo. 44
BATTERY. STORAGE
Battery auxiliary vs. overload capac-
ity of d-c. generator Xo. 82
Peak load in a-c. installations; Suit-
ability to carry
BRACES, CROSS ARM
Position on side of pole; Choice of, . No. 115
BRUSHES
Location on d-c. dynamos Xo. 60
BUSBAR
Mounting, type depended
CABLE
and losses
various arrangem <.-:
ng capacity
■
YEAR PAGE
(1914) 159
466
(1914) 338
538
(1914) 159
160
(1914) 1002
755
(1913) 1001
116S
936
(1915) 410
CABLE— Cont'd
Pot heads; Necessity for
Size for a certain installation
Varnished cambric, advisability of
using this type in ducts
CANDLE-POWER
Concentrated beam of light; Suit-
ability to use as a measure of
CELL
Electrolytic
Current conduction when copper
plating
Primary
Polarization reduced by zinc amalgam
COILS
Choke
Iron vs. air core
Reactance formula for various shapes
Field
Polarity, testing while on machine. . .
Short circuits in field winding of
railway motor; Detection of
Q. &. A.
YEAR
PAGE
Xo. 156
(1915)
1169
Xo. 81
(1914)
159
Xo. 74
(1913)
1002
Xo. 36
(1913)
465
No. 14
Xo. 49
Xo. 84
No. 102
No. 42
Xo. 150
(1913) 275
(1913) 539
(1914) 160
(1914) 507
(1913) 537
(1915) 1086
COILS — Cont'd Q- & A. YEAR PAGE
Reactance
Current division between two parallel
circuits interconnected by coil;
Calculation of No. 58 (1913) 683
110.000-volt coil; Impracticability of
constructing a No. 154 (1915) 1168
Protection by a coil automatically
inserted in a line; Lack of No. 154(1915) 1168
Reactance resulting from varied com-
bination of coils; Method of cal-
culating No. 11 (1913) 274
(And relays). Troubles on lines;
Practicability of segregating No. 146 (1915) 935
COMMUTATOR
Grooving; Reasons for No: 2 (1913) 207
CONTACT
Area and pressure, relative electrical
importance of each No. 43(1913) 538
CONVERTER, SYNCHRONOUS
Brushes raised at starting a commu-
tating pole machine, reasons No. 77 (1914) 80
Connections and unbalanced three-
wire d-c. load No. 142 (1915) 670
Line drop; Limit and effect of No. 109 (1914) 772
Neutral for three-wire d-c. line de-
rived from machine's step-down
transformers No. 89(1914) 338
Polyphase machine operating single-
phase; Effect of No. 118 (1914) 1003
Shunt around commutating pole
winding should be inductive;
Reasons why No. 29 (1913) 463
CORONA
Insulation; Effect on No. 63 (1913) 999
CURRENT
Charged dust particles; Effect of
direct current on No. 103 (1914) 508
Earth; Possibility of obtaining from. No. 100 (1914) 506
CUT-OUT, FILM
Substitute for standard material ... . No. 25 (1913) 344
ENGINE
Hunting caused by relation of gover-
nor to automatic voltage regulator
on driven generator No. 55 (1913) 612
EXCITER
Control by automatic voltage regu-
lator No. 98 (1914) 606
Driving methods No. 16(1913) 276
FEEDER
Trolley circuit considerations No. 119 (1914) 1003
FIRE
Checking in electrical machines;
Methods of No. 38 (1913) 466
FREQUENCY-CHANGER
Advantages and disadvantages of
synchronous motor and induction
motor driven sets for tying-in two
systems No. 51(1913) 609
FURNACE, ELECTRIC
Construction, special design No. 71 (1913) 1002
Melting of non-ferrous metals; Ref-
erences on No. 66 (1913) 1000
GENERATOR
Forced-draft ventilation for low-speed
machines No. 157 (1915) 1 169
Alternating-Current
Armature reconnection for a different
voltage; Possibility of a certain. .. . No. 92 (1914) 428
Bearing current; Explanation of No. 26 (1913) 344
Bearing current; Detection and meas-
urement of No. 136 (1915) 311
GENERATOR — Cont'd Q- & A. year page
Alternating-Current
Control of two paralleled machines
individually by twe automatic volt- „T
age regulators jNo' 107 <1914> >71
iNo. 116 (1914) 1002
Coupling two machines mechanically
to run in parallel No. 91 (1914) .(40
Flux; Full-load value relative to no-
load value of No. 106 (1914) 771
Induction machines driven by low-
pressure steam turbines No. 96 (1914) 431
Overheated solid core when three-
phase machine runs single-phase. . . No. 132 (1915) 228
Power-factor on short circuit No. 54 (1913) 612
Power-factors 70 and 100 per cent,
difference in input No. 143 (1915) 671
Regulation; Question of improving. . No. 20 (1913) 343
Wave shape of inductor type machine No. 56 (1913) 683
Direct-Current
High-voltage machines existent and
design limitations No. 140 (1915) 410
Load divided disproportionately
between two paralleled machines. . No. 3 (1913) 207
Overload capacity vs. storage battery
auxiliary No. 82 (1914) 159
Shunt around commutating pole
winding should be inductive; Rea-
sons why No. 29 (1913) 163
Voltage of two machines in series,
difficulty in maintaining on increase
of load No. 47 (1913) 638
Voltage regulation of automobile
lighting generators by third-biush
method No. 114 (1914) 932
Turbine
End-thrust, possible effects when un-
balanced No. 105 (1914) 508
Integral vs. external fan ventilation . . No. 110 (1914) 772
GROUNDING
National Electrical Rules for neutral . No. 125 (1915) 74
Street lighting circuits, protection
against grounding by trees. ....... No. 33 (1913) 464
HARMONICS
Definition and testing for presence. . . No. 147 (1915) 936
HORN-GAP
Breakdown voltages compared with
those of needle-gap No. 52(1913) 611
INSULATION
Corona 's effect No. 63 (1913) 999
INSULATOR
Leakage current, its nature, and why
it takes place No. 59 (1913) 755
KW., APPARENT KV-A., WATTLESS KV-A., AND P-F.
Inter-relationship No. 151 (1915) 1086
LAMP
Efficiency of carbon and tungsten
incandescent types No. 83 (1914) 160
LIGHTING
Mines supplied from 230-v. taps of
4600/2300-v. transformer No. 27 (1913) 463
Voltage regulation of automobile gen-
erators by third-brush method .... No. 114 (1914) 932
LINE, TRANSMISSION
Current division between two parallel
circuits interconnected by react-
ance coil No. 58 (1913) 683
Multiple vs. single No. 65 (1913) 1000
Reactance of three wires in a plane. . No. 28 (1913) 463
Sag and size of conductor No. 139 (1915) 410
LOAD
Steel mill; Average running load for. . No. 80 (1914) 159
Three-wire circuit ;Calculation for a. . No. 69 (1913) 1001
MET£R Q. & A. YEAR PAGE
Hot-Wire
Construction and uses for which it is
especially suited No. 10 (1913) 274
Watt
Curve-drawing, connections No. 75 (1914) 80
Reversal of one on low power-factor
when two are measuring three-
phase power No. 4 (1913) 208
Power-factor of three-phase line ob-
tained from ratio of two readings. . No. 35 (1913) 465
Watthour
Frequency, effect of change on ac-
curacy No. 99 (1914) 506
Protection against lightning No. 73 (1913) 1002
METERING
Three-phase power; Explanation of
two-meter method of measuring. . . No. 48 (1913) 539
MILS
Square and circular mils; Difference
between and method of calculating No 7 (1913) 208
MOTOR
Explosion-proof types; Construction
of No. 21 (1913) 343
Open and enclosed types; Definition
of. (Later, See: Standardization
Rules of the A.I.E.E. edition of
Feb. 1. 1915, 5§ 160-172) No. 86 (1914) 338
Output of d-c. machine, proof that
maximum occurs when loaded to
half speed No. 34 (1913) 465
Induction
Brass rs. fiber slot wedges for holding
in coils No. 41 (1913) 537
Dynamic braking of squirrel-cage
type by application of direct cur-
rent to stator No. 68 (1913) 1001
Generator; Ability to act as a No. 104 (1914) 508
Half-voltage; Characteristics at No. 93 (1914) 428
Knocking sound No. 97 (1914) 431
Low-speed type; Characteristics of. . No. 108 (1914) 771
Low-voltage; Characteristics as af-
fected by No. 50 (1913) 539
Phase-wound rotor type; Relation of
heating to speed of No. 57 (1913) 683
Poles, change in number limited by
certain factors No. 145 (1915) 864
Quarter-phase to three-phase recon-
nection No. 153 (1915) 1168
Rotor-bar insulation charred, its
effect on machine's characteristics. No. 126 (1915) 74
Rotor-bar insulation charred, its re-
pair and effect on machine's char-
acteristics . No. 137 (1915) 409
Starting difficulty No. 72 (1913) 1002
Three-phase machine operating on
two-phase circuit No. 1 (1913) 207
Twenty-five cycle machine operating
on 60-cycle supply . No. 101 (1914) 506
Unbalanced phase voltages; Heating
of three-phase machine on No. 135 (1915) 311
Unbalanced phase voltages; Heating
of two-phase machine on No. 128 (1915) 75
Railway
Commutator bars burned as a result
of reversed armature coil No. 12 (1913) 275
Field coils; Detection of short cir-
cuits in . . . No. 150 (1915) 1086
Low voltage a cause of increased de-
terioration in mining locomotives. . No. 120 (1914) 1003
Synchronous
Power-factor; Calculation of improve-
ment produced in No. 37 (1913) 466
MOTOR— Cont'd Q- * A*
Synchronous
Power-factor ; Explanation of influ-
ence on No. 46
NEUTRAL
Delta connected transformers; Method
of bringing out from No. 149
National Electrical Rules on ground-
ing of No. 125
OZONE
Concentration, Degree of No. 62
Respiration; Effect on No. 6
PHASING-OUT
Combinations that are possible in
connecting two three-phase lines. . No. 78
Voltage measurements between two
lines, peculiar readings Xo. 121
PHASE-RELATION AND ROTATION
Definitions and determination No. 144
POLARIZATION
Reduction by zinc amalgam in pri-
mary cells No. 49
PORCELAIN, ELECTRICAL
Wet and dry process product; Char-
acteristics of No. 17
POWER-FACTOR
Combination of several ; Calculation ot No. 8
Improvement by synchronous motor;
Calculation of No. 37
Synchronous motor influence No. 46
Three-phase value obtained from
ratio of two wattmeter readings. . . No. 35
REGULATOR
Automatic Voltage
A-c. to d-c. operation; Change from. . No. 117
Control of two paralleled a-c. genera- „ _._,_
tors individually by two regulators \* ' t,_
LNo. lib
Exciter controlled by No. 98
Hunting caused by relation to gover-
nor on engine driving generator. . . No. 55
Induction
Three-phase unit operating single-
phase No. 87
RELAY
Rupturing capacity of oil switch; Ef-
fect of time limit on No. 30
RESISTANCE
Temperature coefficient of copper. . . No. 113
Transformer windings; Measurement
of No. 129
Charging
Function of as applied to lightning
arrester No. 39
Field Discharge
Action; Explanation of No. 23
ROD, LIGHTNING
Effectiveness of protection No. 90
SIGN, FLASHING
Control of electric lamps No. 13
SWITCH. OIL
Bafflers; Purpose of No. 95
Connections of circuit-opening equip-
ment No. 94
Direct current; Utilization on No. 32
Interrupting action; Explanation of. No. 9
Rupturing capacity and time-limit
relay No. 30
TEMPERATURE
Kelvin scale, basis and layout No. 141
YEAR PAGE
(1913
(1915)
1085
(1915)
74
(1913)
999
(1913)
208
(1914)
159
(1914)
1004
(1915)
863
(1913
(1913
(1913
(1913;
(1913
(1913;
(1914
(1914
(1914
(1914
(1913
(1914
538
539
276
274
466
538
465
1002
771
1002
506
612
338
(1913)
463
(1914)
932
(1915)
75
(1913)
466
(1913)
343
(1914)
340
(1913)
275
(1914)
431
(1914)
(1913)
(1913)
429
464
274
(19i3)
463
(1915)
670
TRANSFORMER
Boosting with an ordinary single-
phase unit No.
Breakdown due to high electrostatic
stress on a certain grounded neutral
circuit No.
Burnout; A peculiar No.
Division of load between two paral-
leled units No.
Exchange current between two paral-
leled units No.
Internal explosion, cause and preven-
tion No
Lighting of mine by 230-v. tap on
4600/2300-v. unit No.
Neutral brought out from delta con-
nected secondaries No.
Overheating of one delta leg No.
Overheating of one paralleled with
another No.
Parallel operation of two banks, con-
nections Y-delta, delta-delta No.
Phasing-out of small polyphase units. No.
Phasing-out of large three-phase units No.
Power-factor when short circuited . . . No.
Ratio change by bringing out a tap. . No.
Regulation; Method and example of ...
114." iN0"
calculating s ,T
I No.
A. YEAR
PAGE
155 (1915)
1169
40 (1913)
24 (1913)
537
344
22 (1913)
343
31 (1913)
464
122 (1914)
1230
27 (1913)
463
149 (1915)
131 (1915)
1085
228
45 (1913)
538
61 (1913)
112 (1914)
111 (1914)
76 (1914)
70 (1913)
999
932
931
80
1001
5 (1913)
53 (1913)
208
612
Q. & A. YEAR PAGE
TRANSFORMER— Cont'd
Resistance measurement of windings. No. 129 (1915) 75
Two-phase to three-phase transfor-
mation, per cent taps and vectors . . No. 130 (1915) 227
Two-phase to three-phase transfor-
mation with three units No. 133 (1915) 310
Twenty-five cycle unit operating on
60-cycle supply No. 64 (1913) 1000
Meter
Advantages to be gained from their
employment No. 18 (1913) 276
Leads (current and potential) in the
same conduit No. 127 (1915) 75
Protection against lightning .. No. 73 (1913) 1002
Series
Open circuited secondary, reason for
excessive voltage rise No 15 (1913) 276
TURBINE
Relief valve on low-pressure end .... No. 124 (1914) 1230
WELDING, ARC
Alternating current inapplicable No. 134 (1915) 310
WIRE
Enameled
Advantages and properties of this
type of insulation No. 19 (1913) 343
Trolley
Catenary suspension; Stress formulae
for No. 123 (1914) 1230
INDEX TO
PAGE
Adams, Robert W.
Transmission Line Calculator 28
Allison, H. B. C.
Protective Coatings for Metal 878
Andrews, W. S.
Notes on the Noble Gases 226, 408
Some Notes on X-rays 152
Andrews, H. L.
Power Consumption of Railway Motors 944
Argersinger, R. E.
Electric Transmission of Power 454
Armstrong, A. H.
Chicago, Milwaukee & St. Paul Locomotive, The. . . . 600
Electrification of the Puget Sound Lines of the Chicago,
Milwaukee & St. Paul Railway, The 5
Operation and Rating of the Electric Locomotive,
The 828
Axtell, C. J.
Sprague-General Electric PC Control 985
Bailey, P. S.
Portable Searchlights for Fire Departments 1144
Ball, John D.
Temperature Coefficient Formula? for Copper 669
Some Notes on Magnetization Curves 31
Baker. R. E.
Subdivision of Power as Solved by the Small Motor, The 555
Bartlett, C. W.
Electrically Heated Enameling Ovens 1130
Baum, Wm.
Air Cleaning Apparatus for the Ventilation of Gener-
ators and Transformers 801
Thury System of Direct-current Transmission, The. . 1026
Bearce, W. D.
Semi-outdoor Portable Substation for Berkshire Street
Railway 44
1500-volt Electrification of the Chicago, Milwaukee
& St. Paul Railway, The 644
Beckert, E. H.
Some Recent Developments in Switchboard Apparatus 646
AUTHORS
PAGE
Blake, S. H.
"Supplies:" Devices and Appliances for the Dis-
tribution, Control and Utilization of Electricity. . . 553
Bodde, Theodore
Apprentice System at the Lynn Works of the General
Electric Company, The 35
Booth, J. L.
Methods of Removing the Armature from Box Frame
Railway Motors 90S
Brown, H. D.
Compensators for Mazda C Lamps 596
Burnham, J. L.
45,000-Kw. Synchronous Converter Substation of the
Aluminum Company of America at Massena
Springs, The 873
Bush, A. R.
Some Industrial Applications of Electricity 460
Chase, C. A.
Electric Power in the Textile Industry 540
Clarke, Charles L.
Infinite Duration of Transients, The 73
Connell, B. R.
Hydro-electric Development of the Cohoes Company
at Cohoes, N. Y., The 340
Cox, J. B.
Contact System of the Butte, Anaconda & Pacific
Railway, The 842
Crego, S. M.
History of Schenectady Section of the A.I.E.E 1006
Creighton, E. E. F.
Cursory Account of the First Lightning Storm of the
Season as given by the Records of the Multi-recorder 860
Curtis, Harvey L.
Volume Resistivity and Surface Resistivity of In-
sulating Materials, The 996
Curtiss, W. B.
Depreciation of Property 1099
Davis, Cassius M.
Automatic Railway Substations 760
Davey. Wheeler. P., Dr.
Application of the Coolidge Tube to Metallurgical
Research 134
Model X-Ray Dark Rwm. A 1107
Radiography of Metals 7fl5
X.rays 258. 353, 625
X-ray Inspection of a Steel Casting. An . 25
Day. Maxwell W.
Electricity in Marine Work 504
Doherty. R. E.
Parallel Operation of Alternating Current Generators
Driven by Internal Combustion Engines 167
DrabeUe. J. M.
Supplying of Power to the Quaker Oats Company. The 42
Dushman, Saul, Dr.
Absolute Zero. Th( 93. 238
Kinetic Theory of Gases. The 952, 1042. 1159
New Device for Rectifying High Tension Alternating
Currents, A 156
Periodic Law. The. . . 614
Dudley. A. D.
Small Consumer, The: A Problem 657
Emmet. W. L. R.
Engineering in the Navy - . ■ 1097
Fitch. M. J.
Genemotor, The 384
Francis, W. E.
Isolated Power House for Factories 1057
Hall. G. W.
General Electric Company's Exhibits at the Panama-
Pacific International Exposition. The 561
Harriman, H. I.
Water Powers of Xew England 358
Hawkins. L. A.
Industrial Research 416
Heath. Leslie O.
Production of Damped Oscillations. The 1110
Hill, G. H.
1500-volt Direct-current Electrification of the Ontario
Municipal Railway. The 20
Review of Electric Railways. A. . . 444
Hobart. H. M.
Some Aspects of Slot Insulation Design 366
Hollman. H. I.
Survey of the Refrigeration Field as it Exists Today, A
Hosmer, Helen R.
Electro-culture. A Resume of the Literature
Translation: The Theory of Lubrication. L. Ubbe-
lohde 966. 1074.
Hoxie. C. A.
Ten-to-one Ratio for Comparing Precision Resistance
Standards. A 915
Jackson. C.
Fort Wayne Electric Rock Drill. The 273
on, Jas. A.
Possibilities Open to the Centra! Station in Solving
the Freight Terminal Problem, The . . 1142
Johnson. E. S.
for the Chicago. Mil-
waukee & St. Paul Railway Company. The 1154
High-voltage Direct-current Substation Machinery.. 641
Johnson. H. R.
Current Supply for Motion Picture Machines 895
Subdivision of Power as Solved by the Small Motor.
The. 555
B. W.
Short Method for Calculating the Starting Resistance
for Shunt. Induction and Series Motors. A 131
Kimball. Fred M.
Electricity in the Automobile Industry . 550
Kimball. E. E.
haracteristic Curves 296
of the Bethlehem-Chile Iron Mines
[2
65
14
1118
PAGE
Langrnuir. Irving
Pure Electron Discharge and its Application in
Radio-telegraphy and Telephony, The 327
Larson. C. W.
Modern Mine Haulage Motor. The 264
Towing Locomotives for the Panama Canal, The. . . . 101
Layng. J. F.
Economies in Operating Small Cars 790
Selection of Railway Equipment. The 126
Relation between Car Operation and Power Consump-
tion 973
Lehn, H. C.
Parallel Operation of Alternating Current Generators
Driven by Internal Combustion Engines 167
Lilienthal, Jesse W.
Welfare Work 1092
Lincoln, Paul M.
Trend of Electrical Development. The 784
Liston. John
Developments in Electrical Apparatus During 1914 . . 80
Electrical Equipment of the Vermont Marble Company 1015
Lyle. F. W.
Growth of Current in Circuits of Negative Tempera-
ture Coefficient of Resistance 1129
Mackall. K. W.
Sign and Building Exterior Illumination by Projection 282
Mahan. H. E.
Eye and Illumination, The 268
Mann. Arthur S.
Some Problems in Burning Powdered Coal 920. 959
Mason. L. A.
Lock Entrance Caissom for the Panama Canal 210
Minton. J. P.
Electrophysics: Cathode Rays and their Properties. . 118
Electrophysics: Electron Theory of Electric Conduc-
tion in Metals 204
Electrophysics: Application of the Electron Theory
to Various Phenomena 287
Electrophysics: Electromagnetic Radiation from the
Viewpoint of the Electron Theory 387
Electrophysics: Some Characteristics of Cathode Ray
Tubes 636
Moody, W. S.
Principal Factors Governing the Choice of Method of
Cooling Power Transformers as Related to their
First Cost and Operating Conditions 839
Moore, C.X.
X-ray Examination of Built-up Mica 195
Morrison, G. F.
Electric Lamp Industry. The 497
Review of the N.E.L.A. Lamp Committee Report... 925
Moss. Sanford A.
Test for Dirt in an Air Supply 622
Muir, R. C.
45.000-kw. Synchronous Converter Substation of the
Aluminum Company of America at Massena Springs.
N. Yi. The 873
Xixdorff. S. P.
Xotes on the Operation of Transformers used with 2
kw., 100.000 Cycle Alternator 308
Parham. E. C.
Practical Experience in the Operation of Electrical Ma-
chinery, 56, 146. 21 7, 304. 401 , 666. 861 . 928. 1003. 1082. 1 1 4H
Peck, E. P.
High Voltage Arrester for Telephone Lines 189
Peek, F. W„ Jr.,
Electrical Characteristics of Solid Insulations 1050
High Frequency 934
Law of Corona and Spark-over in Oil, The 821
Effect of Altitude on the Spark-over Voltages of Bush-
ings. Leads, ar.d Insulators ." 137
Porter. L. C.
Incandescent Lamps for Projectors 371
Lighting of Ships, The 143
PACE
Porter, L. C.
Portable Searchlights for Fire Departments 1144
Sign and Building Exterior Illumination by Projection 282
Poor. F. H.
Ball Bearings in Electric Motors 631
Potter, W. B.
Review of Electric Railways, A 444
Pratt, W. H.
Some Notes on Induction Meter Design 277
Randolph, C. P.
Electric Heating and Heating Appliances 523
Rea, N. L.
Water Rheostats 1001
Reid, Robert
Process of Impregnating Coils, and a Large Modern
Impregnating Plant, The 48
Rettew, G. H.
Parallel Operation of Frequency Changers 836
Proper Construction of Earth Connections 904
Rice. Jr. E. W.
Status of the Engineer, The 234
Rohrer, A. L.
Series of Electrical Tests made in 1883 and their
Influence on Modern Testing. A 22
Rohrer, C. J.
Electricity in Agriculture 483
Ross, A. A.
Operating Conditions of Railway Motor Gears and
Pinions 249
Roux, George P.
Emergency Transformer Connections 832
Open-Delta or V Connection of Transformers 52
Ruder, W. E.
Effect of Chemical Composition Upon the Magnetic
Properties of Steel, The 197
Rushmore, D. B.
Electric Power Industry. The 427
Use of Electricity in Mining Work, The 527
Ryan, W. D'A.
Illumination of the Panama-Pacific International
Exposition 579
Schildhauer, Edward
Electricity in the Construction and Operation of the
Panama Canal (Supplement to July Review) 679
Shafer, Don Cameron
"Home Electrical" at the Panama-Pacific Interna-
tional Exposition, The 572
Shanklin, G. B.
Insulation Testing 1008
Shelton, E. K.
Protection of Railway Signal Circuits Against
Lightning Disturbances 1127
Simmons, L. A.
Standard in Refrigeration. A 1171
Slichter, W. I.
New Advanced Course in Electrical Engineering at
Columbia University, The 940
PAGE
Steinmetz, C. P.
Control and Protection of Electric Systems 887
Individual and Corporate Development of Industry,
The 813
Protection and Control of Industrial Electric Power. . 979
Stickney, G. H.
Factory Lighting 67
High Candle-power Mazda Lamps for Steel Mill
Lighting 377
Stone, C. W.
Brief Review of the Electric Lighting Industry. A... 439
Spring, H. E.
Tests of Large Steam Hoists 179
Thirlwall. J. C.
Jitney Problem, The 604
Power Consumption of Railway Motors 944
Thomas. 0. E.
Osbcrne Electriquette. The 299
Thomson, Stuart
Methods of Obtaining High Potential Direct Current 1084
Thomson, Elihu
Wireless Transmission of Energy 316
Tinson, H. A.
Modern Street Lighting with Mazda Lamps 659
Torrens, J. H.
Hydro-electric Installation on a Coffee Plantation, A. 219
Tressler, M. E.
Cathode Ray Tube and Its Application, The 816
Trumbull, Horace Niles
Modern Acid-Dipping, Electroplating and Japanning
Plant, A 1121
Ubbelohde, L.
Theory of Lubrication, The 966. 1074. 1118
Weaver, S. H.
Mechanical Effects of Electrical Short Circuits 1066
Weed, J. Murray
Mechanical Stresses in Shell Type Transformers. ... 60
Theory of Electric Waves in Transmission Lines. . . . 1148
White, W. C.
Radiotelephony 38
Whitney, W. R., Dr.
Research 1012
Relation of Research to the Progress of Manu-
facturing Industries, The 868
Wolf. H. M.
General Notes on Groundin ; 991
Woodward, Wm. P.
High Potential Transformer Testing Equipment 398
Yates, W. C.
Electric Motor in the Printing Industry, The 1136
Yensen, Trygve D.
Iron-cobalt Alloy, FejCo, and its Magnetic Prop-
erties, The 881
General Electric Review
A MONTHLY MAGAZINE FOR ENGINEERS
,, „ t»t^t- T7J* taum r> Ti-cTtT-n'r*'!* Associate Editor, B. M. EOFF
Manager. M. P. RICE Ed.tor. JOHN R. HEWETT ^.^ ^.^ & & SANDERS
Subscription Rates: United States and Mexico, $2.00 per year; Canada, $2.25 per year; Foreign, $2.50 per year; payable in
advance. Remit by post-office or express money orders, bank checks or drafts, made payable to the General Electric Review,
Schenectady, N. Y.
Entered as second-class matter, March 26, 1912, at the post-office at Schenectady, N. Y., under the Act of March, 1879.
VOL. XVIII., NO. 1 hy Ge.^E&uiUany JANUARY, 1915
CONTENTS
Page
Frontispiece 2
Editorial : The Paths of Progress 3
The Electrification of the Puget Sound Lines of the Chicago, Milwaukee & St. Paul Railway 5
By A. H. Armstrong
The 1500- Volt Direct-Current Electrification of the Ontario Municipal Railway . 10
By G. H. Hill
The 2400- Volt Railway of the Bethlehem-Chile Iron Mines Company ... .12
By E. E. Kimball
Electro-Culture, a Resume of the Literature 14
By Helen R. Hosmer
A Series of Electrical Tests Made in 1883 and Their Influence on Modern Testing . . 22
By A. L. Rohrer
An X-Ray Inspection of a Steel Casting 25
By Dr. Wheeler P. Davey
A Transmission Line Calculator 28
By Robert W. Adams
Some Notes on Magnetization Curves .31
By John D. Ball
The Apprentice System at the Lynn Works of the General Electric Company ... 35
By Theodore Bodde
Radiotelephonv 38
By W. C. White
The Supplying of Power to the Quaker Oats Company 42
By J. M. Drabelle
Semi-Outdoor Portable Substation for Berkshire Street Railway 44
By W. D. Bearce
The Process of Impregnating Coils; and a Large, Modern Impregnating Plant ... 48
By Robert Reid
Open-Delta or V-Connection of Transformers 52
By George P. Roux
Practical Experience in the Operation of Electrical Machinery 56
Loose Commutator; Loose Connection; Low Power-Factor; Hot'Box Indications; Burn-
out Due to Core Loss; Alternator Speed Low; Loose Core; Loose/Belts; Erratic Elevator
Speed; Brush-holders Shifted.
By E. C. Parham
Mechanical Stresses in Shell-Type Transformers .... .... 60
By J. Murray Weed
A Survey of the Refrigeration Field as it Exists Today . .... 65
By H. I. Holleman
Factory Lighting .... 67
By G. H. Stickney
Notes on the Activities of the A- I- E. E. . 71
From the Consulting Engineering Department of the General Electric Company . . 73
Question and Answer Section .74
In Memoriam: Douglas S. Martin 76
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THE PATHS OF PROGRESS
It is particularly gratifying that we are
able to announce the closing of so large and
important a contract for steam road electri-
fication as that of the Chicago, Milwaukee
& St. Paul Railway in this the first issue of a
new year. We have included in this issue
also a brief description of the 1500-volt
direct-current electrification of the Ontario
Municipal Electric Railways, and the 2400-
volt railway of the Bethlehem-Chile Iron
Mines Company. We feel that the very fact
that such important work as the above under-
takings represent is being actively pushed at
the present time should be a distinct en-
couragement, as showing a marked improve-
ment in the industrial and financial conditions
and a faith in the immediate future of the
economic status of the country.
The electrification of the Puget Sound Lines
of the Chicago, Milwaukee & St. Paul Rail-
ways is the most important steam road elec-
trification ever undertaken or even seriously
contemplated; in fact the letting of this
particular contract would seem to mark a
new era in electric railway work. The initial
work includes the electrification of one com-
plete engine division 1 13 miles in length
and the total mileage, when yards, sidings,
etc., are considered, amounts to IBS miles.
This work is already under way and in the
early future, if the initial work proves success-
ful, three additional engine divisions will be
electrified, making approximately 440 miles
of main line track or a total of 650 miles, when
yards, sidings, etc., are included. It would
appear that all this work is well assured and
plans are even being made to extend the
electrified zones to the coast which would
mean S50 route miles of main line steam road
converted to electric operation.
One of the most interesting, and at the
same time most important features concern-
ing this large contract is that the change in
motive power is not being brought about by
any local conditions such as the necessity
of abating the smoke nuisance, but is being
made by the railway company on the straight
plea of the economies that are to be secured
by electric traction. The operating results
of the Butte, Anaconda & Pacific Railway,
which we published in the November issue
of the Review, would indicate that there is
every justification for anticipating economies
that will more than offset the added interest
charges on the capital to be expended in
effecting the change.
The whole engineering world that is in-
terested in railway work will undoubtedly
pay special attention to the fact that the
three contracts we have mentioned in this
editorial are all to be operated at higher
direct-current potentials. The Chicago, Mil-
waukee & St. Paul Railway will operate at
3000 volts, the Ontario Municipal Railways
at 1500 volts, and the Bethlehem-Chile Iron
Mines Railway at 2400 volts. It surely
must be considered a most significant fact
that, in such a very great percentage of the
large contracts that have been placed during
recent years in this country for heavy trac-
tion work, higher direct-current potentials
have been specified. The reason for this is
undoubtedly the success that has already
been achieved with direct-current apparatus
working at higher voltages. The very fact
that the Chicago, Milwaukee & St. Paul Rail-
way Company has adopted a trolley potential
of 3000 volts shows that the limit had not
previously been reached where economies
could be secured by increasing the trolley
potential without sacrificing any of the vital
attributes of traction work, such as safety,
reliability of operation and an all-round effi-
ciency.
Another point of great interest concerning
two of these electrifications, namely, the
Chicago, Milwaukee & St. Paul and the rail-
way of the Bethlehem-Chile Iron Mines
Company is that the locomotives are to be
provided with regenerative control. On an
electric railroad scheme of the magnitude
GENERAL ELECTRIC REVIEW
of the Chicago. Milwaukee & St. Paul Rail-
way distinct operating advantages should
result from the provision of electric braking
for the heavy trains on the steep down
grades, necessarily encountered in railroad
work in such mountainous regions. This is
distinctly in line with the "safety first"
policy of modern railroading, as electric
braking removes any danger of accident due
to overheated brakeshoes and wheels, and
furthermore results in powTer economy and a
lower cost of maintenance.
The direct-current railway motor has long
been recognized as the most reliable, efficient
and flexible means of delivering power to the
drivers of a locomotive and now that direct-
current regenerative braking has become an
accomplished fact it makes the high voltage
direct-current system most admirably fitted
to fulfill all the requirements of general steam
railroad electrification. We consider the
introduction of electric braking, while still
retaining the well tried and proved direct-
current apparatus, to be a distinct step in
the advance of the art.
Referring to the Chicago, Milwaukee & St.
Paul electrification, each locomotive, of 260
tons local weight, will have 200 tons on
drivers, an equipment of eight motors, having
a combined rating of 3440 horse power, and
a hauling capacity of 2500 tons trailing load
on a one per cent grade at a speed of approxi-
mately 16 miles per hour. This great hauling
capacity, combined with such a high speed on
ruling grades as 16 miles per hour, is of par-
ticular interest to the steam railway operator
who has been educated in the school of Mallet
operation, in which speeds as low as seven
miles per hour constitute frequent practice.
The introduction of such an advanced type
of motive power should result in somewhat
radical changes in the methods of operation
standardized with the use of the steam
engine.
The adoption of a trolley potential of 3000
volts enables an economic distribution of the
feeder copper with the spacing of substations
35 miles apart. The reduction of the neces-
sary substation apparatus that will be secured
in this manner, in spite of the fact that such
heavy trains are to be hauled up mountain
grades, brings the cost per mile of track
electrified down to a very reasonable figure,
and further, it emphasizes the sturdy capa-
bilities of the direct-current substation ap-
paratus.
Mr. A. H. Armstrong in his article shows
the ample provisions that have been made
for power supply, and that owing to favorable
local conditions the railway company has
been enabled to enter into a contract whereby
energy will be supplied at 0.536 cents per
kw-hr. based on a 60 per cent load factor.
Such figures for energy, even when taken in
bulk, are unusual and can only be obtained
in cases where the hydro-electric resources
have been so wisely conserved and so thor-
oughly developed as in the case of the
Montana Power Company. If such thorough
developments take place in other localities it
will play an important part in stimulating the
futher electrification of our steam railways.
As we said at the outset, we hope that work
of such a magnitude as that described in this
issue being undertaken at this time will
encourage others to look on the bright side
of present conditions. As this is the first
issue of a new year, it seems appropriate to
express the hope that 1915 may be full of
prosperity and that we may have the pleasure
of recording many notable steps of progress
in the engineering arts and industrial re-
search during the next twelve months in this
Review.
THE ELECTRIFICATION OF THE PUGET SOUND LINES OF THE
CHICAGO, MILWAUKEE 8b ST. PAUL RAILWAY
By A. H. Armstrong
Assistant Engineer, Railway and Traction Engineering Department,
General Electric Company
The author gives a brief account of the scope of the work to be undertaken on this the most important
of steam road electrifications. He gives a description of the power supply available, the cost of power to the
railway company, the type of substation and rolling stock equipment, and the overhead construction to be
adopted. It is of special interest to note that the trolley potential is to be 3000 volts, which is the highest
direct-current potential yet adopted in this country for railway work. — Editor.
Plans for the electrification of the first
engine division of the Chicago, Milwaukee &
St. Paul Railway have now been completed
and contracts have been let with the General
Electric Company for electric locomotives,
substation apparatus and line material, and
with the Montana Power Company for the
construction of transmission and trolley lines.
The initial electrification of 113 miles of
main line between Three Forks and Deer
Lodge is the first step toward the electrifi-
cation of four engine divisions extending
from Harlowton, Montana, to Avery, Idaho,
a total distance of approximately 440 miles
with approximately 650 miles of track,
including yards and sidings. While this
comprises the extent of track to be
equipped in the near future, it is understood
that plans are being made to extend the
electrification from Harlowton to the Coast,
a distance of 850 miles, should the operating-
results of the initial installation prove as
satisfactory as anticipated.
The plans of the Chicago, Milwaukee &
St. Paul Railway are of especial interest, as
this is the first attempt to install and operate
electric locomotives on tracks extending over
several engine divisions, under which condi-
tions it is claimed the full advantage of
electrification can be secured. The various
terminal and tunnel installations made in the
past have been more or less necessarv by
reason of local conditions, but the electrifi-
cation of the Chicago, Milwaukee & St. Paul
is undertaken purely on economic grounds
with the expectation that superior operating
results with electric locomotives will effect
a sufficient reduction in the present cost of
steam operation to return an attractive
percentage on the large investment required.
If the savings anticipated are realized in the
electric operation of the Chicago, Milwaukee
& St. Paul Railway, this initial installation
will constitute one of the most important
mile-stones in electric railway progress, and
it should foreshadow large future develop-
ments in heavy steam road electrification.
The success of electric operation on such a
large scale will at least settle the engineering
and economic questions involved in making
such an installation, and will limit the future
problems of electrification to the ways and
means of raising the required capital to effect
the change in motive power.
The first step taken towards electrification
by the Chicago, Milwaukee & St. Paul
Railway was to enter into a contract with
the Montana Power Company for an adequate
supply of power over the 440 miles of main
line considered for immediate electrification.
The precautions taken both by the Railway
Company and Power Company to safeguard
the continuity of power supply should guaran-
tee a reliable source of power, subject to few
interruptions of a momentary nature only.
The Montana Power Company covers a
great part of Montana and part of Idaho
with its network of transmission lines which
are fed from a number of sources of which
the principal are tabulated below:
Madison River 11,000 kw.
Canyon Ferry
7,500 kw.
. 14,000 kw.
Big Hole
Butte, steam turbine
Rainbow Falls
Small powers aggregat
ing
3,000 kw.
5,000 kw.
21,000 kw.
7,390 kw.
Total power developed 68,890 kw.
Further developments part of which are
under construction are as follows:
Great Falls 85,000 kw.
Holter 30,000 kw.
Thompson Falls 30,000 kw.
Snake River 20,000 kw.
Missoula River 10,000 kw.
Total power undeveloped 175,000 kw.
Total power capacitv developed and un-
developed, 244,000 kw."
GENERAL ELECTRIC REVIEW
The several power sites are interconnected
bv transmission lines; the earlier ones are
supported on wooden poles and operate at
50,000 volts and the later installations are
supported on steel towers and operate at
100,000 volts. Ample water storage capacity
(300,000 acre-feet), is provided in the Hebgen
Reservoir and this is supplemented by
auxiliary reservoir capacity at the several
power sites which brings the total up to
418,000 acre-feet. The Hebgen Reservoir is
so located at the head waters of the Madison
River that water drawn from it can supply
in turn the several installations on the
Madison and Missouri rivers, so that the
same storage water is used a number of
times, giving an available storage capacity
considerablv greater than is indicated bv the
which will permit feeding each substation
from two directions and from two or more
sources of power. This transmission line
will be constructed with wooden poles and
suspension tvpe insulators, and will operate
at 100,000 volts. It will follow in general
the right of way of the Railway Company,
except where advantage can be taken of a
shorter route over public domain to avoid
the necessarily circuitous line of the railwav
in the mountain districts.
The immediate electrification of 113 miles
will include four substations containing step-
down transformers and motor-generator sets
with the necessary controlling switchboard
apparatus to convert 100,000 volts, 60 cycles,
three-phase power to 3000 volts direct
current. This is the first direct-current
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Miles from St Paul
Profile of Section of the Chicago, Milwaukee 8b St. Paul undergoing Electrification
figures given. It would seem, therefore,
in changing from coal to electricity as a
source of motive power, that the railroad is
amply protected as regards reliability and
continuity of power supply.
Due to the great facilities available and the
low cost of construction under the favorable
conditions existing, the Railway Company
will purchase power at a contract rate of
0.536 cents per kilowatt-hour, based upon a
60 i ter cent load-factor. It is expected under
these conditions that the cost of power for
locomotives will be considerably less than
is now expended for coal. The contract
between the Railway and Power Companies
provides that the total electrification between
Harlowton and Avery, comprising four engine
will be in operation bv lanuarv 1
HUN.
In order to connect the substations with
the several feeding-in points of the Montana
ission lines, a tie-in transmission
line is being built by the Railwav Company
installation using such a high potential as
3000 volts, and this system was adopted
in preference to all others after a careful
investigation extending over two years. The
2400-volt direct-current installation of the
Butte. Anaconda & Pacific Railway in the
immediate territory of the proposed Chicago.
Milwaukee & St. Paul electrification has
furnished an excellent demonstration of
high-voltage direct-current-locomotive opera-
tion during the past year and a half, and
the selection of 3000 volts direct current for
the Chicago, Milwaukee & St. Paul Railway
was due in a large measure to the entirely
satisfactory performance of the Butte, Ana-
conda & Pacific installation.
The equipment for this road was also
furnished by the General Electric Company,
and a comparison based on six months steam
and electric operation shows a total net
saving of more than 20 per cent on the
investment or total cost of electrification.
These figures, of course do not take into
ELECTRIFICATION OF THE CHICAGO, MILWAUKEE & ST. PAUL RAILWAY 7
account the increased capacity of the lines,
improvement to the service, and the more
regular working hours for the crews. The
comparison also shows that the tonnage
per train has been increased by 35 per cent,
while the number of trains has been decreased
by 25 per cent, with a saving of 27 per cent
in the time required per trip.
Substations
The substation sites of the Chicago,
Milwaukee & St. Paul Railway electrified
zone provide for an average intervening
distance of approximately 35 miles, notwith-
standing that the first installation embraces
L500-volt direct-current generators connected
permanently in senes for 3000 volts. The
fields of both the synchronous motors and
direct-current generators will be separately
excited by small generators direct-connected
to each end of the motor-generator shaft.
The direct-current generators will be com-
pound wound and will maintain constant
potential up to 150 per cent load and will have
a capacity for momentary overloads up to
three times their normal rating. To insure
good commutation on these overloads the
generators are equipped with commutating
poles and compensating pole face windings.
The svnchronous motors will also be utilized
Map showing Section of the Chicago, Milwaukee & St. Paul to be Electrified
20.8 miles of two per cent grade westbound
and 10.4 miles of 1.66 per cent grade east-
bound over the main range of the Rocky
Mountains. With this extreme distance
between substations and considering the
heavy traffic and small amount of feeder
copper to be installed, it becomes apparent
that such a high potential as 3000 volts
direct current permits of a minimum invest-
ment in substation apparatus and consider-
able latitude as to location sites.
The substations will be of the indoor type,
the transformers being three-phase, oil-cooled,
with 100.000-volts primary and 2300 volts
secondary windings. The synchronous motors
will operate at the latter potential. The
transformers will be rated 1900 and 2500 kv-a.
and will be provided with four 2Y2 per cent
taps in the primary, and 50 per cent starting
taps in the secondary.
The motor-generator sets will comprise a
(iO-cycle synchronous motor driving two
as synchronous condensers and it is expected
that the transmission line voltage can be so
regulated thereby as to eliminate any effect
of the fluctuating railway load.
The location and equipment of the several
substations is as follows:
Morel, two 2000-kw. motor-generator sets;
Janey, three 1500-kw. motor-generator sets;
"Piedmont, three 1500-kw. motor-generator
sets; and Eustis. two 2000-kw. motor-gener-
ator sets.
Overhead Construction
Trolley construction will be of the catenary
type in which a 4/0 trolley wire is flexibly
suspended from a steel catenary supported
on wooden poles, the construction being
"bracket" wherever track alignment will
permit and "cross span" on the sharper
curves and in the yards. Steel supports
instead of wooden poles will be used in yards
where the number of tracks to be spanned
GENERAL ELECTRIC REVIEW
exceeds the possibilities of wooden pole
construction. Poles for the first installation
are already on the ground and 30 miles of
poles are set. Work in this direction will be
pushed with all speed and will be completed
ready for operation in the fall of 1915, on the
delivery of the first locomotives.
As the result of careful investigation and
experiments a novel construction of trolley
will be installed composed of the so-called
will weigh approximately 200 tons and will
have a continuous capacity greater than any
steam or electric locomotive yet constructed.
Perhaps the most interesting part of the
equipment is the control, which is arranged
to effect regenerative electric braking on
down grades. This feature as yet has never
been accomplished with direct-current motors
on so large a scale. The general characteristics
are tabulated below.
Outline of 260-Ton Electric Locomotive for the Chicago, Milwaukee & St. Paul Railway
twin-conductor trolley. This comprises two
4 0 wires suspended side by side from the
same catenary by independent hangers alter-
nately connected to each trolley wire. This
form of construction permits the collection
of very heavy currents by reason of the twin
contact of the pantograph with the two trolley
wires and also insures sparkless collection
under the extremes of either heavy current
at low speed or more moderate current at very
high speeds. It seems that the twin-conductor
type of construction is equally adapted to
the heavy grades, calling for the collection
of very heavy currents, and on the more level
portions of the profile where maximum
speeds of 60 m.p.h. will be reached with the
passenger trains having a total weight of
over 1000 tons. The advantage of this type
of construction is due partly to the greater
surface for the collection of current, and
partly to the very great flexibility of the
alternately suspended trolley wires, a form
of construction which eliminates any tendency
to flash at the hangers either at low or high
speed. Including sidings, passing and yard
tracks, the 113 miles of route-mileage is
increased to approximately 168 miles of
single track to be equipped between Deer
Lodge and Three Forks in the initial installa-
tion.
The locomotives to be manufactured bv
the General Electric Company are of special
interest for many reasons. They are the first
locomotives to be constructed for railroad
service with direct-current motors designed
for so high a potential as 3000 volts. They
Total weight
Weight on drivers
Weight on each guiding truck
Number of driving axles. .
Number of motors
Number of guiding trucks
Number of axles per guiding truck
Total length of locomotive
Rigid wheel-base
Voltage of locomotive. . . .
Voltage per motor
H.P. rating one hour — each motor
H.P. rating continuous — each motor. .
H.P. rating one hour — complete loco-
motive
H.P. rating continuous — complete loco-
motive
Trailing load capacity, two per cent. . .
Trailing load capacity, one per cent. . . .
Approximate speed at these loads, and
grades
260 tons
200 tons
30 tons
8
8
2
2
1 12 feet
10 feet
3000
1500
43(1
375
3440
3000
1250 tons
25110 tons
10 m.p.h.
The Chicago, Milwaukee & St. Paul Rail-
way, from Harlowton to the Coast crosses
four mountain ranges. The Belt Mountains
at an elevation of 576S feet, the Rocky
Mountains at an elevation of 6350 feet, the
Bitter Root Mountains at an elevation of
4200 feet and the Cascade Mountains at an
elevation of 3010 feet. The first electrification
between Three Forks and Deer Lodge calls
for locomotive operation over 20.8 miles of
two per cent grade between Piedmont and
Donald at the crest of the main Rocky
Mountain Divide, so that the locomotives
will be fully tested out as to their capacity
and general sen-ice performance in over-
coming the natural obstacles of the first
engine division. The initial contract calls
for nine freight and three passenger locomo-
ELECTRIFICATION OF THE CHICAGO, MILWAUKEE & ST. PAUL RAILWAY 9
tives having the above characteristics. The
freight and passenger locomotives are similar
in all respects except that the passenger
locomotives will be provided with a gear
ratio permitting the operation of 800 tons
trailing passenger trains at approximately
(50 m.p.h., and will furthermore be equipped
with an oil-fired steam-heating outfit for the
trailing cars. The interchangeability of all
electrical and mechanical parts of the freight
and passenger electric locomotives is con-
sidered to be of very great importance from
the standpoint of operation and main-
tenance.
The cab consists of two similar sections
extending practically the full length of the
locomotive. Each section is approximately
52 feet long and the cab roof is about 14 feet
above the rail exclusive of housings for the
ventilation. The trolley bases are about five
feet about the roof owing to the unusual height
of the trolley wire which will be located at a
maximum elevation of 25 feet above the
rail. The outer end of each cab will contain
a compartment for the engineer while the
remainder is occupied by the electric control
equipment, train heater, air-brake appa-
ratus, etc.
Motors
The eight motors for the complete locomo-
tive will be Type GE-253-A. This motor
has a normal one-hour rating of 430 h.p.
with a continuous rating of 375 h.p. The
eight motors will thus give the locomotive
a one-hour rating of 3440 h.p. and a con-
tinuous rating of 3000 h.p. which makes it
more powerful than any steam locomotive
ever built. The tractive effort available for
starting trains will approximate 120,000 lb.
at 30 per cent coefficient of adhesion.
Each motor will be twin-geared to its
driving axle in the same manner as on the
Butte, Anaconda & Pacific, the Detroit
River Tunnel and the Baltimore and Ohio
locomotives, a pinion being mounted on each
end of the armature shaft. The motor is of
the commutating-pole type and has openings
for forced ventilation from a motor-driven
blower located in the cab.
The freight locomotives are designed to
haul a 2500-ton trailing load on all gradients
up to one per cent at a speed of approximately
1G m.p.h., and this same train load, unbroken,
will be carried over the 1.66 and two per cent
ruling grades on the west and east slope of the
Rocky Mountain Divide with the help of a
second similar freight locomotive acting as
a pusher. Track provision is being made at
Donald, the summit of the grade, to enable
the pusher locomotive to run around the
train and be coupled to the head end to
permit electric braking on down grade. In
this case the entire train will be under
compression and held back by the two loco-
motives at this head end, the entire electric
braking of the two locomotives being under
the control of the motorman in the operating
cab of the leading locomotive. It is con-
sidered that electric braking will prove very
valuable in this mountain railroading, as in
addition to providing the greatest safety in
operation, it also returns a considerable
amount of energy to the substations and
transmission system which can be utilized
by other trains demanding power. In this
connection, the electric locomotives will have
electric braking capacity sufficient to hold
back the entire train on down grades, leaving
the air-brake equipment, with which they
are also equipped, to be used only in emer-
gency and when stopping the train. There is
therefore provided a duplicate braking system
on down grades which should result in safety
of operation, and should eliminate break-
downs, wheel and track wear and overheating,
as well as leading to a reduction in mainte-
nance and an improvement in track condi-
tions.
With the completion of the remaining
engine divisions it is proposed to take ad-
vantage of the possibilities afforded by the
introduction of the electric locomotive by
combining the present four steam-engine
divisions into two locomotive divisions of
approximately 220 miles length; changing
crews, however, at the present division points.
As the electric locomotive needs inspection
only after a run of approximately 2000 miles,
requires no stops for taking on coal or water,
or layover due to dumping ashes, cleaning
boilers or petty roundhouse repairs, it is
expected that the greater flexibility of the
locomotive so provided will result in con-
siderable change in the method of handling
trains now limited by the restrictions of the
steam engine.
The electrification of the Chicago, Mil-
waukee & St. Paul Railway is under the
direction of Mr C. A. Goodnow, Assistant
to the President in charge of construction,
and the field work is under the charge of
Mr. R. Beeuwkes, Electrical Engineer of the
railwav.
10
GENERAL ELECTRIC REVIEW
THE 1500-VOLT DIRECT-CURRENT ELECTRIFICATION OF THE
ONTARIO MUNICIPAL RAILWAY
By G. H. Hill
Assistant Engineer, Railway and Traction Engineering Department,
General Electric Company
The general faith in higher direct-current potentials for railway work is exemplified by the equipment
selected for the important work described by the author. The work now being done on the Ontario Municipal
Railway is only the nucleus of much more extensive undertakings by the same road in the future. The
scope of the present work is shown in the accompanying article. — Editor.
Various municipalities of the Province of
Ontario, Canada, have been considering for
some time an extensive system of inter-
connecting electric railways. The general
scheme provides for a network of interurban
roads supported, as it were, by a backbone of
main line electrification handling a relatively
heavy freight service. The links connecting
the cities and towns will be municipally
owned and operated, thus continuing the
already extensive municipal ownership fea-
ture existing in Canada.
The scheme, in brief, contemplates new
roads, or electrification of existing roads
through the central part of that portion of
the Province lying between Lake Erie and
the Georgian Bay from Sarnia on the west to
Toronto and Whitby on the east, passing
through London, St. Mary's and Guelph.
This route follows generally the transmission
system of the Hydro-Electric Power Com-
mission from Niagara Falls. Several branches
and connections are contemplated communi-
cating with all the larger cities in that portion
of the Province.
The proximity of the transmission system
affords excellent facilities for substation
locations and precludes the necessity of
building a distributing transmission line
along a large part of the right-of-way.
The Hydro-Electric Commission of Ontario,
Sir Adam Beck, Chairman, and Mr. F. A.
Gaby, Chief Engineer, will perform the
double function of consulting engineer and
contractor for the entire project, installing
all equipment ready for operation. The
individual sections of the system will then be
turned over to ihc municipalities to operate.
The city of London has taken the initial
step aid is now proceeding with the elect rifi-
cation of i hat portion of the main line between
Port Stanley on Lake Erie and London, about
2 1 miles north thereof.
This road has for several years been leased
by the city of London to the Pere Marquette
Railroad and forms an important connecting
link between the Lake Erie freight ferries
and distributing centers of the Province. The
chief commodity for transportation is coal
from Pennsylvania.
The single track line is approximately
23.5 miles long and passes through Whites,
St. Thomas, Glanworth and Westminster,
connecting with the main lines of the Grand
Trunk. Michigan Central and Canadian
Pacific Railroads. The profile includes a
maximum of 1.0 per cent grade north of
Port Stanley and contains other grades of
0.8 per cent and 0.5 per cent for short dis-
tances.
The scheduled service will comprise a
locomotive freight traffic and multiple-unit
passenger car trains between the two terminals.
Sixty-ton locomotives will take loaded freight
cars from the ferry boats at Port Stanley and
haul them in trains of approximately 800
tons to St. Thomas and London, returning
with trains of empty cars. In addition to the
above there will be local merchandise freight
between the stops along the line. The
passenger service will be performed by
limited and local trains consisting, a large
part of the time, of a motor car and one trail
car providing a half-hourly service in each
direction, the limited and local alter-
nating.
The Hydro-Electric Commission made a
careful investigation of operation when using
both high voltage direct current and single-
phase alternating current on the trolley, with
the final adoption of 1500 volts direct current.
The energy will be supplied from two
substations: One located at London in an
extension of the present Hydro-Electric
substation, and the other at a distance of
14.2 miles from London near St. Thomas.
The latter will be a new substation. Each
will be equipped with' synchronous converters
with their respective transformers and switch-
boards, converting from 110,000 volts, 25-
ELECTRIFICATION OF ONTARIO MUNICIPAL RAILWAY
11
cycle alternating current to 1500 volts direct
current.
The overhead structure will be of the
familiar single catenary type supported on
side brackets from lattice steel poles placed
approximately ISO ft. apart on the tangent.
The 0000 B.&S. copper trolley wire will be
supplemented by suitable copper feeders.
The rolling stock covered by the initial
order placed with the General Electric
Company includes three 1500-volt, 60-ton
locomotives, five 4-motor 1500-volt passenger
car equipments complete with multiple unit
control and air brakes, and four trail car
control and air brake equipments.
The locomotives are of Type 4-0-4 and
will be carried on two swivel trucks bringing
all the weight on the drivers, the equipment
being housed in a steel box type cab extending
over practically the entire length of the
locomotive. Each will be provided with four
GE-251, 750 /1500-volt motors designed for
750 volts across each armature and insulated
for 1500 volts. Two motors will be connected
permanently in series and the two-motor
groups thus formed will be capable of con-
nection in series or parallel for speed control.
The cab will be divided into three compart-
ments, one at each end for accommodating
the operator and the intervening compart-
ment where the control equipment and
accessories will be located. The operating
compartments will be provided with 1500-volt
electric heaters.
Each of the GE-251 motors will have an
hourly rating of 245 h.p. with 1500 volts on
the trolley. At this rating the locomotives
will exert a tractive effort of 21,500 pounds.
Control will be effected by a double end
Type M standard equipment, a master con-
troller at each operating position actuating
the main 1500-volt contactors by means of a
600-volt circuit supplied from a dynamotor.
Multiple-unit train operation is arranged
for so that the simultaneous control of three
locomotives coupled together can be accom-
plished from any master controller. The
equipment is also so designed that a locomo-
tive may haul a train of eight or ten passenger
trail cars and provide lighting energy for them.
The current collectors will consist of panto-
graph slide trolleys having two contact pans
pressing against the trolley conductor. Two
of these devices will be furnished on each
locomotive. They will be electro-pneumati-
cally controlled from any operating position
with one, two or three locomotives hauling
a train.
Each motor passenger car will be driven
by four GE-225-750/ 1500-volt fully venti-
lated commutating-pole motors connected
two groups of two in series. The one-hour
rating is 125 horse power with 1500 volts
on the trolley.
Each motor car has sufficient capacity to
haul one trail car and provision is made for
the motor and trail cars to be operated in
trains up to a total of three motor and
three trail cars. All trail cars will be equipped
with master controllers at each end so that
multiple-unit train operation is possible
from either end of any motor or trail
car.
Control energy for a motor and trailer
will be derived from a 1500 /600-volt dyna-
motor on each motor car. The dynamotor
will also supply energy for lighting one motor
and one trail car. Alain and auxiliary train
cables will run continuously throughout a
train, provision being made for the simul-
taneous raising and lowering of all panto-
graphs and also for simultaneous sanding
(by electro-pneumatic valves) of all cars
from any operating position. The panto-
graph trolleys will be identical with those
on the locomotives.
Each car will carry a combined straight
and automatic air-brake outfit of the variable
release type, with the air supply furnished
by 1500-volt compressors. The compressor
governors will all be equalized on a special
wire running throughout the trains in the
auxiliary train cable.
The cars which will be placed in service
on the London and Port Stanley Railway will
be built to the Commission's specification.
They will be all steel, 59 feet long and thor-
oughly modern in every respect. The motor
and trail coaches will be identical except
for motors. The former will weigh approxi-
mately 51 tons loaded and equipped, while
the latter will have an approximate loaded
weight of -')2 tons.
The growth of the Ontario Municipal
system will be watched with much interest
since it marks a rather novel departure on a
large scale from the usual American pro-
cedure.
12
GENERAL ELECTRIC REVIEW
THE 2400-VOLT RAILWAY OF THE BETHLEHEM-CHILE
IRON MINES COMPANY
By E. E. Kimball
Railway and Traction Engineering Department, General Electric Company
The work to be done in developing the rich iron mines at Tofo, Chile, includes the construction of a very
difficult line of railway which is to operate at 2400 volts direct-current, the building of a steam power station
and transmission line, "the installation of electric shovels and crushers, and the building of a settlement for
the officers and operators of the company. The author gives a short outline of the work contemplated and
cites some of the local conditions which make this undertaking one of particular difficulty. — Editor.
One often notices in technical papers and
popular magazines articles describing the
wonderful mineral resources of South America,
especially large deposits of iron and copper
ores, but few realize how rapidly and on
what a large scale these resources are being
developed and where the products find a
market. A remarkable deposit of iron ore is
found at Tofo, Chile, where the Bethlehem-
Chile Iron Mines Company is preparing to
mine this ore with the aid of electric power
and to ship it to the United States for use
in the blast furnaces at South Bethlehem, Pa.
These mines occupy the summit of two
hills, approximately 2000 ft. above sea level
and about four miles in an air line from the port
of Cruz Grande. The remarkable feature
of these mines is that there are great quanti-
ties of ore in sight and it is nearly pure iron
(67 per cent Fe.). With the opening of the
Panama Canal to commerce this ore can
be mined and shipped by that route from
Chile to Xew York and thence to South
Bethlehem, Pa.
An electric railway operating at 2400 volts
is now being built to develop these mines.
In addition to this electric railway the
development will include a steam-power
station and high tension transmission lines,
from the port of Cruz Grande to Tofo. and
the installation of electric shovels, crushers
and other machinery for mining operations
at Tofo. Ore pockets and vessel loading piers
will be constructed at Cruz Grande. It
requires also the building of residences for
officials and establishing ample water supply
and fire protection as well as the provision
of an electric lighting system for the villages,
piers, etc.
At present a certain tonnage of ore is mined
by steam drilling and transported to the coast
over a telpherage system which consists
of a string of ore buckets suspended from a
steel cable supported on steel towers and
operated by the weight of the loaded buckets
riding, which furnish power for taking
up the empties. This system is started by a
it when once started it requires
no external force to keep it running, in fact.
part of the energy is dissipated in operating
a large fan which is used for governing the
speed. Probably one of the chief reasons for
adopting this system was on account of the
small amount of power required to operate
it.
It was essential that means be provided for
saving water and fuel, in other words, power.
Obviously, the power taken by the empty
trains ascending the grades, if supplied by
loaded trains descending, would represent a
saving which could not be effected by minor
economies of fuel. This feature in the railway
electrification, therefore, received a great deal
of attention both from the standpoint of
saving power and on account of other practical
operating advantages.
The railroad from the mines to the piers
is approximately 15 miles long with an
average grade for nearly the entire distance
of three per cent. This is also the maximum
grade. Its alignment is far from straight,
as may be seen from the fact that in an air
line the mines are only four miles from the
coast, whereas the railroad reaches the same
height only after traversing 15 miles.
In the operation of heavy grade sections
of steam railroads great difficulty has been
found in getting rid of the heat from brake-
shoes and wheels, which is another argument
in favor of electric braking on the locomotives.
In the study of this problem it was shown that
regenerative braking could be accomplished
successfully on a high voltage direct-current
system, that is, the motors under the loco-
motive are made to act as generators and
return energy to the trolley to be used by
another locomotive ascending, or back to the
power house where it would help supply the
demands of the mines.
These locomotives will weigh 110 tons
on drivers and will be equipped with four
300-h.p., 1200 2400-volt motors operated two
connected permanently in series on 2400
volts. The initial installation will consist of
three of these locomotives, each having a
capacity to haul a 450-ton train up grade at
10H m.p.h. and exerting the same braking
effort when regenerating at 12 m.p.h.
BETHLEHEM-CHILE IRON MINES COMPANY
13
In case the locomotives are operating with
the maximum train weights down grade a
portion of the braking will be done with air
brakes, and when stopping air brakes will be
used alone.
The trolley will be of 4/0 grooved copper
wire, catenary suspended from a steel messen-
ger supported by a mixture of bracket and
cross span construction on wood poles. These
poles will be of cedar and will be shipped
from the United States, as Chile grows no
timber suitable for this purpose. A duplicate
22,000-volt high tension transmission line
will in general follow the trolley and will be
carried on the same poles when possible.
In places, however, it will leave the railroad
right of way for a more direct route to the
mines. These transmission lines will supply
power for the operation of crushers, electric
shovels, pneumatic tools and machine shops,
as well as for pumping water and other
sundry purposes.
The mining of this ore will be accomplished
by blasting the ore exactly as in modern
rock quarries, and then by means of elec-
tric shovels it will be loaded onto side-
dump cars, when it will be hauled a short
distance to the crusher plant and crushed
to a size suitable for use in blast furnaces.
The crushed ore will fall by gravity into bins
ready for loading into hopper cars ; it will then
be hauled to the vessel loading piers and
dumped into ore pockets. From here it is
loaded by gravity into 17,000-ton steel
vessels specially constructed for this purpose
and shipped to unloading piers in New Jersey,
and there loaded onto cars for South Bethle-
hem, Pa., where it is ready for the blast
furnaces. The transportation of the ore is,
therefore, a big item of its cost and every
facility has been provided to save the expense
of handling it.
In the power house oil-fired boilers are to
be used which will permit of an easy control
of the heat with every fluctuation of load,
and because of absence of dirt the usual
partition between the generator room and
the boiler room will be omitted so that the
operators will be able to anticipate changes
in load in time to make proper adjustments.
The oil is received in tank vessels and pumped
to an oil storage tank above the power
station. From the main reservoir it runs
by gravity to the auxiliary reservoir near the
station and is fed to the burners by means
of a small pump. The boilers will be set high
so that grates may be installed if there is any
advantage to be obtained from the use of coal.
One of the interesting features of this
installation is the ingenious method employed
for evaporating boiler "make-up" water
from sea water. This is done by an evaporat-
ing condenser through which is "by-passed"
a part of the exhaust steam from the turbines.
By adjusting the difference in the vacuum
between the main and the evaporating
condensers the amount of evaporation can
easily be governed without affecting the
economy of the steam turbines appreci-
ably.
The generating room contains two 3500-kw.
three-phase, 60-cycle, 2300-volt Curtis G-E
steam turbines with direct-connected exciters
for supplying power to the railroad and the
mines; two 300-kw. three-phase, 60-cycle,
(i()0-volt turbines for operating motor-driven
auxiliaries, fire pumps, etc., and at night,
lights for the piers, villages and mines when
the main turbines are shut down. To accom-
plish this result there is installed a small bank
of step-up transformers so that the high
tension lines may be energized at minimum
loss. This arrangement avoids considerable
complication in the switchboard wiring and
avoids providing steam-driven auxiliaries
with complicated steam and water piping.
Power for the operation of the mines and
crusher plant is stepped up by means of two
banks of transformers, each bank consisting of
three 667-kv-a., 60-cycle, 22, 000 /2300-volt
oil-cooled transformers. At the mines
the voltage is stepped down again to 2300
volts for local distribution. Power for the
operation of the railroad is taken through two
1000-kw., three-unit motor-generator sets,
each consisting of one 1400-kv-a., O.S-p-f.
three-phase, 60-cycle, 2300-volt synchronous
motor-generator set direct-connected to two
500-kw., 1200/2400-volt direct-current gener-
ators, designed to operate two in series on
2400 volts. These sets have direct-connected
exciters on each end for exciting the synchro-
nous motor and d-c. generators. Space has
been left in the design of the building for
future boilers, main turbines and motor-
generator sets when required.
The power station building will be located
on solid rock foundations and a type of
construction employed which is particularly
adapted to resist earthquake shocks, which
are frequent and sometimes violent and
followed by tidal waves. It will, therefore,
be located back from the water's edge, on
high land reasonably safe from these dis-
turbances. A pump house of very sturdy
construction will be erected at the water's
14
GENERAL ELECTRIC REVIEW
edge to supply circulating water to the
condensers and for fire protection for the
village and piers.
Nearly all the sources of fresh water supply
are located in the valley behind the mines and
it requires pumping to the mine level for use
at the mines. The excess is stored in reser-
voirs between the mines and Cruz Grande
for such purposes for which it is suitable and
also to relieve the pressure on the pipes at
Cruz Grande. At the present time a great
deal of this work has been completed and a
temporary pumping and lighting plant is
installed near one of these springs and
supplies water for the mines and lights for
the villages.
ELECTRO-CULTURE: A RESUME OF THE LITERATURE
By Helex R. Hosmer
Research Laboratory, General Electric Company
The literature published on electro-culture is extensive but scattered. The writer has made an excellent
review of this published matter, dividing the subject according to the different methods used to stimulate
plant life by electricity. The progress, or lack of progress, made by the application of each method, is dis-
cussed, and the conclusion is reached that these investigations, on the whole, have been too cursory. A valu-
able list of references is also given. — Editor.
The scientific literature of the last ten
vears has contained frequent references to
the art of increasing plant growth and yield
bv the application of electric stimuli of cer-
tain kinds, an art most commonly designated
as electro-culture. The material given, how-
ever, represents very little experimental
work in proportion to its volume, consisting
in the main of more or less complete his-
torical review? concluded by a few para-
graphs describing some recent investigation.
The effect upon a reader desiring to become
acquainted with the work done within a
reasonable length of time is irritating, to say
the least. In view of the growing interest
in intensive methods of agriculture, and also
in methods of filling in the valleys in the load
curves of central stations, there is reason to
expect a much more exhaustive investigation
of this subject in the not remote future. For
this reason it has seemed desirable to collect
the facts from the scattered sources, and
attempt to arrange them in a form more
convenient for use, that is, from the point
of view of the invader of the province rather
than the historian.
It has been found that the experiments of
the past fall naturally into five classes,
differing principally in the method of appli-
cation ( if elecl rical energy. These methods are :
Illumination by electric light.
action of atmospheric electricity
from an elevated collector to an
electrode in the soil, or to dis-
charge points above the plants.
Constituting the soil the electrolyte
of a voltaic cell by burying in it
two plates of dissimilar metal con-
nected bv a conductor.
IV.
II.
Ill
V.
Passing current from an external
source through the soil between
electrodes buried therein.
Production of a silent or glow dis-
charge through the air from over-
head antennae to the soil.
These methods will be taken up in the
order given, which is approximately that of
their importance.
METHOD I
Illumination by electric light.
There seems to have been relatively little
work done upon the effect of illuminating
plants by artificial or electric light. In 1861
"Herve" Mangon found that electric light
influences the formation of chlorophyl in a
way similar to that of sunlight. That the
absorption and assimilation of carbon dioxide
occurred as usual under the electric arc was
shown by Prellieux eight years later.1
In 1880 Wilhelm Siemens confirmed these
observations, but found that under certain
conditions injurious effects were obtained,
and hence he used an opalescent glass shade
over the light.
These facts were further confirmed by
Schraier in 1881, and by Bailey, Cornell
University, in 1891. Bonnier in 1S92, and
Couchet in 1901, studied the structure
alteration in plants and the leaf growth in
relation to the electric light.
Since 1891 this line of attack has been
neglected, probably because of the attention
attracted by the work of Lemstrom, and the
success of his method.
Dorsey, however, in 1914, mentions the
treatment of hothouse radishes and lettuce
for three hours each day beginning at sunset,
ELECTRO-CULTURE: A RESUME OF THE LITERATURE
15
with red light from a 100-watt lamp, and with
blue light from a Cooper-Hewitt lamp. The
lettuce was affected favorably, the radishes
unfavorably.2
METHOD II
Conduction of atmospheric electricity from
an elevated collector to an electrode in the soil,
or to discharge points above the plants.
Among the earliest attempts to apply
atmospheric electricity to plant culture ap-
pears to have been that of Abbe Bertholon, in
1783. He called his apparatus the electro-
vegetometer. It consisted of a number of
metal points similar to a lightning rod, sup-
ported at a considerable elevation, and con-
nected by a conductor to an iron bar furnished
with discharge points which hung down just
over the plants treated. The whole apparatus
was insulated by wooden supports. The
Abbe stated that the use of this arrangement
always produced an increase in the fertility,
vigor, and growth of the plants.3
Later, 1879, Grandeau and his pupil
LeClerc showed by careful comparative
measurements, analyses, etc., that protection
of plants from atmospheric electricity by
enclosure in wire cages often retards the
growth over 50 per cent. But Naudlin re-
peated his experiment a little later with
results diametrically opposite. The more
recent experience of Pinot de Moira agrees
with that of Grandeau.
A modification of Bertholon's method
called the geomagnetifere system has been
quite commonly used in France. This con-
sists of an elevated conductor connected to
wires running through the soil under the
plants to be influenced. A typical installa-
tion is that of Pinot de Moira at Clifton,
Eng., which was in operation for several
years to good advantage.
Berthelot carried on considerable work at
Meudon in France. He found that the
growth of plants on the top of a 28-meter
tower was greater than at the foot.
Lieutenant Basty experimented with metal
rods terminating in a ball of non-oxidizable
metal at the lower end which was buried in
the ground as deeply as the roots of the
plant were likely to penetrate and projected
from two and one-half feet to six and one-
half feet above the surface, depending upon
the plant treated. The first height was used
for strawberries. He claimed that beneficial
results were noted about each rod for a radius
equal to half the height.4
METHOD III
Constituting the soil the electrolyte of a
voltaic cell by burying in it two plates of dis-
similar metals connected by a conductor.
Speschenew in Russia obtained marked
results from plates of different metals buried
in the ground connected by wire.
More recently, 1906, Rawson and Le
Baron5 have used the same method in green-
houses. Plates of copper and zinc were sunk
at opposite ends of lettuce beds and gave a
potential difference of 0.5 volts and current
of from 0.4 to 15 milliamperes. The lettuce
thus treated was ready for market a week
sooner than that not treated.
Priestly3 tried the method of Speschnew,
using plates of copper and zinc between which
beans were planted. The plants treated
appeared two days earlier, developed more
rapidly, and the average size and weight of
the mature beans was about a third greater.
Some other qualitative experiments were
inconclusive. The current in very damp soil
was twelve milliamperes between plates of
200 sq. in., four feet apart.
Newman,6 however, states that the results
of a dozen experiments indicated no effect
whatever, and that the reports of others have
been in confirmation of this fact.
METHOD IV
Passing current from an external source
through the soil between electrodes buried
therein.
This method of plant stimulation has been
the source of numerous conflicting reports,
and its applicability seems still to be in doubt.
A number of investigators have found that
it increases the rate and proportion of
germination.
E. H. Cook7 states that this is the only
effect that he was certain was produced by
currents of 100 milliamperes at 20 volts.
Kinney8 in 1898 and Ahlfvengren in 1899,
confirmed his results. The former con-
sidered three volts the optimum, but the
latter believed this to vary for different
plants, and, under different conditions, for
the same plant. Lewenherz's conclusions
also agreed with the above, but he con-
sidered also that the direction in which the
current traversed the seed was of importance.
Kovessi,9 1912, on the other hand, as a
result of over 1100 pot tests, came to the
conclusion that direct currents through the
soil are without exception harmful both to
1(3
GENERAL ELECTRIC REVIEW
germination and later growth. Schnecken-
berg,10 commenting upon this paper, remarks
that he ought to have known this fact from
a knowledge of the simple laws of electro-
chemistry and endosmosis before performing
the 1100 experiments, but goes on to point
out that Kovessi's statement should read
"horizontal direct currents through the
soil ' ' and must not be extended to cover any
other type of electrical treatment. Kovessi
does not state what strength of current he
emploved.
Geriach and Erlwein,11 1910, describe
experiments with low potential direct cur-
rent, 6 volts, 0.2 to 0.4 amperes, at Bromberg,
upon an area of 914 sq. ft. planted to barley
and cabbages. Iron plates buried in the soil
were used for electrodes. The treatment was
continuous night and day until harvest.
No beneficial effect was obtained.
Peaslee,12 1910, using direct current in
greenhouse experiments on the germination
and rate of growth of seedlings, such as
cauliflower, cabbage, beets, etc., experienced
failure until he lowered his current density
and adopted carbon electrodes, which, unlike
some metals, do not react with the soil to
form deleterious salts. He obtained the most
favorable results at a power consumption of
between 0.5 and 0.(i watts per cu. ft. which
gave increased fertility of seed, more rapid
and vigorous development, and increased
size of plant, especially of the root. In the
case of a cauliflower, the advantage in respect
to growth was nearly 150 per cent. Radishes
carried through to a marketable size had a
root growth 403 per cent, and a top growth
1 1 7 per cent greater than the control* plants.
Similar tests with alternating current were
consistently negative again until the watts
per ru. ft. were reduced to 0.0114 (current =
0.000034 amp. per sq. in.) when an increased
fertility of 50 per cent and an increased
growth of 32 per cent was obtained.
Dorsey,2 1913, tried some greenhouse
experiments using direct current (1.5 volts
arid 0.0003 to 0.07 amp., and 3 to 8 volts and
ooiio, to 0.05 amp.) and also 60-cycle after-
current, 110 and 220 volts between
carbon electrodes. The results were bad in
The temperature of the treated
was a degree higher than the controls.
It is evident that the investigation of this
lectric treatment has been entirely
insufficient to lead to any trustworthy con-
* The expressions "control." "control plants." etc., are used
comparative experiments carried on
v- under the same conditions, but without elec-
trical stimulation.
elusions. The controlling factors have scarcely
been indicated as yet.
METHOD V
Production of a silent or glow discharge
through the air from overhead antennae to the
soil.
The stimulation of crops by a discharge
of electricity through the air to the soil seems
to be the method best founded upon theory
and most promising in practice.
Prof. Lemstrom13 of Helsingfors Univer-
sity, Finland, first remarked upon the fact
that the extraordinarily rapid and fruitful
growth of such vegetation as survives the
frosts in the Arctic and sub-Arctic regions
can not be accounted for, as has been sug-
gested by the long hours of daylight. He
showed that the total light and heat supplied
are actually less than at the latitude of
Petrograd or Christiana, on account of the
low elevation of the sun above the horizon.
It has been proved beyond doubt that there
exist in the atmosphere of these high lati-
tudes much stronger currents passing to the
earth than is the case further South. These
are evidenced by their luminescent effects,
such as the Aurora. A great proportion of
the vegetation, especially that peculiar to
northern regions, is equipped with pointed
leaves, etc., which are especially adapted
to electrical discharge. Moreover, in study-
ing sections of fir trees, Lemstrom found a
periodicity in the occurrence of especially
large growth which is the same as that of the
occurrence of sun spots and auroras, i.e.,
every 10 or 11 years. Lemstrom goes into
these indications and the further electrical
phenomena and facts from which he was led
to begin his investigations in considerable
detail in his book "Electricity in Agriculture."
He supected that the electrical influence
played a part hitherto overlooked in the
growth of vegetation in other parts of the
world. With this in view, he tried to redupli-
cate the conditions of the Arctic by producing
a similar electrical tension in the atmosphere.
He applied a positive potential from an in-
fluence machine of which the negative was
grounded to a wire network suspended above
the plants, producing a silent discharge to
the earth. He worked first with pots, and
then in the open field. His power consump-
tion was low, as indicated by the fact that a
0.1 horse power motor served to drive his
influence machine.
Lemstrom extended his researches to dif-
ferent farms in Finland and, in later years, to
ELECTRO-CULTURE: A RESUME OF THE LITERATURE
17
other countries. The procedure was tested
under his supervision at Durham College,
England; in Burgundy, near Breslau in Ger-
many, and at Atvadaberg. His book con-
tains full details as to the extent, circum-
stances, and results of all these experiments.
As a result of his experience he concludes
that the minimum increase in yield for all
crops under the proper conditions should be
about 45 per cent. For certain crops it may
rise as high as 100 per cent. Improvement
occurs whether the network be charged
positively or negatively to the soil, but
better results were obtained in the former
case. The effect is not apparent alone in the
quantity, but an improvement of quality,
and a shortening of the period of growth,
sometimes by 50 per cent, is general. An-
alyses are given to indicate that in the case
of grain there is an increase in the proteid
content. Frequent instances were encoun-
tered where the electric current was delete-
rious, but repetition of the work under im-
proved conditions eliminated the trouble.
Thus it was found that during drought or
in hot sunshine the plants suffer harm, and
certain species, among which may be men-
tioned peas, cabbages, and carrots, are par-
ticularly sensitive. Watering, and discon-
tinuing the treatment during the middle of
the day has produced equally good results
with these vegetables. Lemstrom points out
that lack of uniformity in cultivation, nature
of soil, and fertilization between the experi-
mental and control 'plots often leads to
erroneous conclusions. The better culti-
vated and fertilized a field is, the larger the
percentage increase in yield due to electro-
culture.
Lemstrom devotes a chapter to directions
for the choice and installation of apparatus,
with an estimate of costs.
Lemstrom 's procedure suffered from a
great disadvantage. His influence machine
was quite inadequate for the purpose, hence
his overhead wires could not be hung more
than 16 in. above the plants, which inter-
fered with economical cultivation of the soil.
At Gloucester,3 experiments with a some-
what more powerful machine, enabling the
elevation of the wires to five feet above the
ground gave results with various crops as
follows :
Beets, 33 per cent increase.
Carrots, 50 per cent increase.
Turnips, increase: not quantitatively meas-
ured.
The beets raised under electrification gave
on analysis about 14 per cent more sugar
than the control crop.
This increase in sugar content has been
confirmed by almost every investigator,
irrespective of whether his results were
favorable to the process in other ways.
In 1904, Newman3, 6 performed some sim-
ilar tests with a small Wimshurst machine
driven by an oil engine, operating upon
fifteen greenhouses, and upon an area in
the open amounting to about a thousand
square yards, including control plots. The
wires were strung about 16 in. above the plant
tops and were furnished with downward
directed points of fine wire for discharge
points. Ordinary telegraph insulators were
sufficient except in wet weather, when
almost all the energy was lost by leakage
down the supports.
The treatment was applied for a period of
108 days, 9.3 hours daily, the first half of the
time mainly by day, the last half by night.
The results from the electrified plants were
as follows:
Cucumbers, 17 per cent increase.
Strawberries, five-year plants, 36 per cent
increase.
Strawberries, one-year plants, 80 per cent
increase, and produced more runners.
Broad beans, 15 per cent decrease, ripened
five days sooner.
Cabbages, (spring) mature 10 days sooner.
Celery, two per cent increase.
Tomatoes, no effect.
The cucumbers were all affected by a
bacterial disease about the middle of their
growth, and this made much greater headway
on the non-electrified plants. Aside from
the troubles with the influence machine and
oil engine, which were rather inadequate, -the
installation required no attention except for
the clearing away of cobwebs and stray
shoots, etc., from the network.
This work was continued on a larger scale,
Newman3 working in conjunction with Sir
Oliver Lodge. The latter overcame several
of the inherent difficulties of the process by
the invention of a mercury arc rectifier
supplying a 100,000-volt direct current. The
new installation consisted of an oil engine
and dynamo producing three amperes, at
220 volts, which was transferred by an induc-
tion coil and then rectified.
This higher potential made it possible to
raise the conducting network to 16 ft. from
the ground, thus permitting of easy cultiva-
18
GENERAL ELECTRIC REVIEW
tion without lessening the beneficial effect of
the current.
Preliminary experiments upon wheat at
Gloucester having been very favorable. New-
man subjected 11 acres to treatment. The
overhead network consisted of stout tele-
graph wires mounted upon poles in rows 102
yards apart, the distance between successive
poles being 71 yards, and thin galvanized
wires stretched 12 yards apart crosswise to
act as discharge wires. A difference in the
rate of growth was noticeable vers- early,
and at harvesting the straw averaged from
four to eight inches taller, and the Canadian
wheat ripened three or four days sooner.
The yields were 39 per cent better for Cana-
dian wheat, and 29 per cent better for English.
Further, the electrified wheat sold for 7.5
per cent better price on account of its supe-
rior quality.
Breslauer.1 who has written a critical
review of the subject up to 1910, and kept in
close touch with the progress of the work in
Germany, tells (1909) of the results obtained
at Halle by Kuhn, and at Holstein, Neumark,
and Westpreussen.
At Halle experiments were made under
various conditions of fertilization and irri-
gation upon a total area of about 14 acres,
besides the control areas. This field installa-
tion was also raised to 16)4 ft. above the
ground. The good effect upon rye was
already noticeable in June. It was observed
here especially that when the wind blows the
effects of the treatment are felt from 10 to
lti ft. and sometimes 50 ft. beyond the limits
of the field experimented upon, and whenever
the control fields are adjacent, reduces by so
much the apparent improvement due to
electrification. This wind effect was also
noted in work at Holstein.
After the completion of these experiments,
a year later. 1910, Prof. Kuhn,14 the German
"Nestor of agriculture," under whose im-
mediate supervision they were conducted,
was not enthusiastic as to the results. He
stated that little was to be expected from the
English procedure, as the advantage apparent
during growth did not appear in the yield.
His control fields of grass and grain gave the
r results. Only fodder and sugar beets
bettered, the latter indeed having an
increased sugar content. Clover and cab-
bages gave uncertain results. He considered
that would demand at least a 15 per
cent increase in yield.
Breslauer1 concludes that the investiga-
tions already made show that the process and
apparatus is entirely practicable. He esti-
mates the cost of an equipment for 61.8
acres as follows:
Generating apparatus $595.00
Field equipment 595.00
Power consumption, 5kw-hrs. per day
(at 5c) = 25c, for season, 150 days = $ 37.50
Interest on $1190.00 at 5 per cent. . $ 59.50
Sinking fund at 7 per cent 83.30
Repairs at 2 per cent 23.80
Power 37.50
Labor (one man two hours a day). . . . 47.60
Total $251.70
Medium to poor yield from wheat: 2000
lb. per acre,
For 61.8 acres $23S0.00
30 per cent increase 714.00
Profit $714.05— $251. 70 = $462.30.
Ordinary profit from 61.8 acres = $71.40.
In a later contribution Breslauer15 describes
the measurement of current and power con-
sumption by typical installations at Hoppe-
garten.
A movable coil ammeter of great sensitive-
ness was inserted in the ground wire. The
order of magnitude of the voltage was deter-
mined by measuring the length of spark in
the air, it being known that between balls
of 25 mm. diameter it requires about 3000
volts per mm. to produce a spark.
In dry, and not extremely hot weather,
with an east wind, the voltage averaging
about 65,000 volts, he estimates that, allow-
ing for a certain inequality of distribution,
the current for every 10 sq. ft. is about 0.43
X 10~5 milliamperes.
Hence the energy consumption is about
0.26. 10"3 amp. X 65,000 volts =17 watts =
0.28 10"3 watts per 10 sq. ft.
This is from 1000 to 10,000 times the
transfer of electric energy occurring naturally
during a year, as estimated by Kahler.16
Gerlach and Erlwein11 give an account of
agricultural experiments upon the Kaiser
Wilhelm Institute of Agriculture Experi-
mental Grounds at Mocheln for which the
equipment was supplied by the firm of
Siemens & Halske.
The electrical treatments included high
tension static electricity, making the net
positive in some cases, and negative in others,
and high tension, single-phase alternating
current.
The network consisted of a heavy galva-
nized wire supported on well insulated poles
around the outside of the field, and suspended
ELECTRO-CULTURE: A RESUME OF THE LITERATURE
19
from this, across the field, thin galvanized
iron wires at a height of 20 ft.
The electrical equipment consisted of a
four-horse power alcohol motor belted to a
direct-current dynamo, and a transformer.
The two influence machines were run In-
direct-current motors.
The experimental plots comprised an area
of 800 sq. yds. besides control plots of one-half
this area located at a distance of 330 ft. The
plots were treated with various kinds of
fertilizer, some were irrigated and others
not. The crops included cabbages, barley
and oats.
The alternating-current antennae averaged
a voltage of about 20,000, the static antennae
30,000 volts. The power consumption for
the former was about 770 volt-amperes, for
the latter about 30 watts. The irradiation
was begun after planting, and continued 45
days continuously day and night. No
difference was apparent between the electri-
fied and untreated plants, though there was
a considerable difference between the watered
and unwatered, and between those differently
fertilized. Mention is made of the occurrence
of a drought. The harvest, occurring 120
days after sowing showed practically identical
yields for treated and untreated plants, with
slight evidence of injury by the alternating
current.
The account gives the most extreme detail
of electrical outfit and arrangement, but is
vague as to the weather conditions, etc.,
which other investigators have found so
important.
Hostermann,17 1910, used a network of
telephone wires from 63^2 to 8 ft. above the
ground and 13 ft. apart, and obtained his
current from the atmosphere by means of
a steel cable 820 ft. long, supported by a
balloon or by several kites. He estimated,
having an instrument reading to only five
volts, from other measurements, that he got
a potential of about 25,000 volts. This
method gave him the best results of any,
increasing the yield on various crops from 15
to 40 per cent. He found that the atmos-
pheric potential gradient varied with the
season, the time of day, the temperature,
and the weather, reaching maxima from
December to February, shortly after sunrise
and just before and during dusk, at low tem-
peratures, and during fog, snow, hail or rain
and especially during thunderstorms.
The conditions under which treatment is
applied are important, it being very essential
that there should be moisture in the air as
irradiation during dry and sunny weather
often results injuriously to the plants. The
most favorable times for treatment corre-
spond with those of maximum potential
gradient, i.e., very early morning and evening,
and especially during a fog. He points out
that the climate of England is especially
adapted, and should give good results, espe-
cially as the treatment seems to compensate
in part for lack of sunshine.
Exclusion of the influence of atmospheric
electricity reduced the yield nearly 15 per cent.
Hostermann, also using high potential
pulsating direct current from a dynamo
machine and transformer found that extended
treatment was of little, or injurious effect, but
more moderate application increased the yield
in some cases 25 per cent. The crops treated
included strawberries, spinach, lettuce, rad-
ishes, etc.
Stahl,18 1911, claims he was able, using
electrical stimulation, to bring a crop of
corn to maturity after the winter wheat was
reaped on July 25. He used a direct-current
potential of about 250,000 volts (600 cycles)
stepped up from a 60-cycle, 110-volt line
and rectified mechanically. The wires were
mounted eight feet from the ground, and
two to three feet apart. The treatment was
applied to one acre morning and evening,
and the electric bills averaged two to three
dollars per month. A variety of vegetables
were treated. All matured much more
quickly and resisted drought better. Only
qualitative results are given.
Gloede19 used the treatment in growing
flowers and found greatly increased vigor as
well as resistance to harmful fungi. In a
small outdoor plot 20 feet square he ripened
362 muskmelons from seed in less than nine
weeks, and the fruit was noticeably sweeter
than usual.
An installation near Prague,20 designed by
Breslauer, operated upon an area of 89 acres
by means of a network of iron supported
by porcelain insulators upon wooden poles at
intervals of 328 feet apart across which was
stretched a network of 0.008-in. wire at a
height of 13 feet above the ground. Direct
current at 120 volts, 2 amp., was supplied by
means of a mercury interrupter, a trans-
former, producing 100,000 volts, and a rectifier.
The network was always made positive, and
the treatment applied only a few hours each
day, being always discontinued in case of
rain, which caused leakage, and of great heat,
under which latter condition the current is
injurious. In spite of an unusually dry
20
GENERAL ELECTRIC REVIEW
season yields in some cases double that of the
control plots were claimed. Details as to
sort of crop and actual yields are not given.
Basty.4 experimenting on a regimental
garden, in France claimed good results.
Dorsey2 applied to small greenhouse beds
for an hour night and morning, daily, alter-
nating current of 200,000 cycles frequency,
at 1(1,000 volts from a Tesla machine and
transformer, consuming about 130 watts.
He used a network of 0.01-in. wire at a height
of 15 in. above the bed. He found by weigh-
ing representative plants a marked gain
amounting to 75 per cent for lettuce. This
method gave better results than illumination
or earth currents.
He next applied a silent discharge by
means of a network of O.OS-in. copper wire,
nine feet above the ground, 15 feet apart on
insulators designed for 60,000 volts, to over
an acre of garden using 10,000 to 20,000 volts
at 30,000 cycles for five hours daily for two
months and 50.000 volts for one month.
Interruption of service makes the results only
qualitative in value. Almost all of the
irradiated plants, including radishes, lettuce,
beets, cabbages, cucumbers, turnips, melons,
tomatoes, and parsnips, gave a better growth
than on the untreated acre. Beans and peas
were affected slightly, but all the other plants
matured at least two weeks earlier than the
control plants. Tobacco showed a 20 per
cent gain.
Peaslee,12 1913, applied 100,000 volts from
a Wimshurst machine on wires 10 in. from
the soil to seedlings, with results which he
describes as disastrous, at first. Later, by
applying the voltage only at night and on
cloudy days he increased the growth of straw-
berries 27 per cent, and beetroots 14 per cent,
tops 39 per cent. He could not establish
any optimum voltage. He found that the
size of the wires made no difference. Cli-
matic variations appeared to have consider-
able effect.
Preliminary tests with a Tesla coil gave
qualitatively similar results.
CONCLUSION
The impression gained from the literature
of electro-culture is that the last word is by
no means said. From the nature of the
publications it would appear that the indi-
vidual investigations have been too cursory.
There has been too little systematic varia-
tion of conditions, and especially of the elec-
trical conditions. It seems highly desirable
that a much more extensive investigation,
providing the possibility of trying different
intensities of electrification under various
conditions of cultivation, irrigation, etc., all
during the same season, should be carried out.
It is significant that the only investigator to
attempt an extended examination of the field
was able to locate and eliminate many faults
in his method, and thus obtain good results in
the end in almost every case, often reversing
his previous experience. If Lemstrbm, working
with his very imperfect equipment and limited
resources could attain so much success, greater
development still should be possible with the
more adaptable apparatus now available.
The theories as to the actual mechanism of
the action of the electric discharge upon
plants, involve questions of physiological and
botanical chemistry whose answers are still
too uncertain to make their consideration
here of profit. Lemstrom,13 Priestly,3 Es-
card,21 and Peaslee12 discuss the subject
briefly, and references to points more or less
related to it are given in the bibliography
appended to this article.
REFERENCES
<ii Breslauer, M. Elektrochem Z. 16, 1-5(1909)
35-9
72-5
L'L'I S
History. Experiments. (Method V)
at Halle and in Holstein. Estimate
of costs and profits of installation.
(?) Dorsey. H. G. Elec. (L) TS. 4+2-3 (1913)
Elektrotech Z. 35, 236-8 (1914)
(Methods I, IV and V.) Experi-
ments at Dayton. Ohio.
Method IV unfavorable. Others
good,
i i) Priestly. J. H. Proc. Bristol (Eng.) Naturalists Soc.
/. 190-203 (1907).
History and account of experiments.
(Method V) by Lodge and Newman
at Bitton. Gloucester and Eve-
sham. Theory and references.
hi Charriere. G. Abstract. Elektrochem Z. 10,15(1912).
(Methods II and V.) Note on ex-
periments of Davidoff on Long
Island and Bastv in France,
(s) Rawson and LeBaron Elec. World. 47. 1067 (1906).
Elec. (L) 57, 305-6 (19061.
(Method III.) Favorable.
Unconvincing reporters account.
(«) Newman. J. E. Elec. (L) 66. 915-6 (1911).
(Method V.) Experiments at Bitton.
Favorable. Very brief.
;> Cook, E. H. Elec. (L) 41. 787-8 (1898).
(Methods II and V.) Favorable
especially to germination.
-i Kinney. A. S. Bull. 43. Hatch Experimental Station
Mass.. Agricultural College.
"Electro-Germination."
Detailed Abstract. Electric Engi-
neer (N. Y.) A3. 289-92 (1897).
(Method IV.) Laboratory experi-
ments. Favorable. Minimum
optimum, and maximum voltage.
(») Kovessi La Houille Blanche ft. 223 (1912).
Compt. Rend. 154. 289-91 (1912).
Abstract. Elektrochem Z. 19. 224
(1912).
(Method IV.) 1100 experiments
Unfavorable.
Compt. Rend. loo. 63-6 (1912).
Electrochemical explanation of pre-
ceding.
ELECTRO-CULTURE: A RESUME OF THE LITERATURE
21
(10) Schneckenberg. E.
(n) Gerlach and Erlwein
(12) Peaslee, W. D.
(13) Lemstrom, S.
(M) Kuhn, J.
(15) Breslauer, M.
(ie> Kahler. K.
( 171 Hustermann
(13) Stahl. W.
Gloede, R.
(w) Cook, F. L.
Cm) Editorial
(21) Escard. J.
Heber. G.
Lodge, O.
Elektrochem Z. 19. 151-4 (1912).
Kovessi duplicated facts known which
apply only to Method IV.
ElektrochemZ. ./7.31-6, (66)-8 (1910).
(Method IV.) Experiments at Moc-
heln. Unfavorable. Engineering
details.
J. Elec. Power and Gas 88, 69-72 (1914).
< Methods I and V.) Favorable under
proper conditions.
Electricity in Agriculture, 72 pp. Van
Nostrand.
Detailed account of experiments
1886-1903. Favorable. Theory,
etc.
Elektrotech Z. 31, 380 (1910).
(Method V.) Experiments at Halle,
(see also 1). Injurious to some
crops, favorable to others. Brief.
Z. Elektrochem. 16, 557-9 (1910).
* Method V.) Energy and current
required.
Phys. Z. 9, 258-60 (1908).
Measurement of electrical precipita-
tion.
Abstract; Elektrotech Z. 31, 294-5
(1910).
(Method V.) Experiments at Dah-
lem. Favorable under proper con-
ditions.
Elec. World 58, 1549-50 (1911).
( Method V.) Experiments at Evans-
ton, 111. Favorable.
Elec. Review. West. Elect. 59, 975-6
(1911).
(Method V.) Brief account. Gloede's
experiments. Favorable..
Elektrotech Z. 33, 1108-9 (1912).
(also p. 1200).
(Method V.) Experimentsat Prague.
Brief. Favorable.
Rev. gen. des. Sciences pur. et app.
April 30. 1913.
History and summary. Fundamental
Electrical facts and theory.
West Elec, 30, 59 (1902).
( Method IV.) Small scale experi-
ments. Favorable.
Elec. Engr. (L) Zjg, 110-14 (1908)
History, brief. Experiments near
Gloucester. Favorable.
Breslauer, M. Elektrotech Z. 29. 915-6 (1908).
Brief review of data.
Clark, T. Elec. Rev. West. Elec. 69, 976 (.1911).
Improved static machine for electro-
culture.
Guarim. E. Elec. World. 41. 554-6 (1902).
Review of Lemstrom 's work.
L'Eclairage Elect rique 37, 101-8(1903).
Review of subject and theory.
Chouchak Compt. Rend. 158, 1907 fl914).
Effect of Method IV upon absorption
of ammonium phosphate from solu-
tion by live and dead seedlings.
Bose, J. C. " Plant Response as a Means of Physio-
logical Investigation" (Longmans
Green & Co., 1906).
Effect of various stimuli, including elec-
tricitv.
Berthelot Compt. Rend. 131. 772-8' (1900).
Chemical and electrical conditions
during silent discharge.
Lob.W. Abhand deut. Bunsen Ges. 1914.
Abstract; Elektrotech und Maschin-
enbau 32. 640-1 (1914).
Effect of silent and glow discharge
upon starch, peptone, etc., solu-
tions. Chemical reactions.
Elster. J. Ann. Phys. S, 425-46 (1900).
Geitel, H. Dissipation of electricity into the
atmosphere.
Schneckenberg. E. Elektrochem Z. 17, 333-7 (1911).
Elektrochem Z. IS, 5-7 (1911).
Motion of plants and animals in the
electric current. Review of litera-
ture.
Waller. A. D. Proc. Roy Soc. 67, 129-37 (1900).
Electrical effects of light upon green
leaves.
Green. R. Phil. Trans. Roy. Soc. 1SS, 188.
Action of light on diastase.
Pollacci. G. Atti. Inst. Bot. 2, (No. 11) 7-10 (1905).
Influence of electricity upon carbo-
hydrate formation.
Bach Compt. Rend. 26, 479.
Possible effect of electricity upon for-
mation of formaldehyde from car-
bon dioxide.
Euler Ber. deut. Chera. Ges. 37, 3415 (1904).
Finds Bach's supposition untrue in
experiment.
22 GENERAL ELECTRIC REVIEW
A SERIES OF ELECTRICAL TESTS MADE IN 1883 AND THEIR
INFLUENCE ON MODERN TESTING
By A. L. Rohrer
Electrical Superintendent, Schenectady Works, General Electric Company
Because of the phenomenally rapid advance that has been made in the development of electrical devices
and their applications, it is only natural that our interest is mainly focused on our present activities in the
industry and on the future possibilities in the science. Under these conditions it is refreshing to turn and
glance backward at the results of a series of tests made about thirty years ago to determine the relative
merits of the pioneer engineering work of that period. — Editor.
The celebration of the thirtieth anniversary
of the 1SS4 Electrical Exposition (held in
Philadelphia, last June, under the auspices
of the Franklin Institute), calls to mind some
important electrical tests made for the
Committee on Scientific and Educational
Appliances of the eleventh Cincinnati Indus-
trial Exposition, which was held in 1883.
This committee was headed by the very
active Chairman, Professor Wm. L. Dudley,
the other members being Messrs. W. A.
Collord, Alfred Springer, F. W. Clark, and
Joseph H. Feenster — all successful business
men. The Committee determined to under-
take a series of tests of the efficiency of
electric lighting systems and so advertised
the situation in its circulars, which were
widely distributed. Special premiums were
offered for (1) the best system of arc lighting,
(2) the best system of incandescent lighting,
(3) the best dynamo machine for arc lighting,
i 4 ) the best machine for incandescent lighting,
(5) the best arc lamp, and (6) the best
incandescent lamp.
Professor William L. Dudley selected the
jury, which consisted of Dr. T. C. Menden-
hall, of Ohio State University, Chairman;
Professors H. T. Eddy and Thomas French,
Jr., of the University of Cincinnati, and
Mr. Walter Laidlaw, Mechanical Engineer,
with Lane & Bodley Company, of Cincinnati.
This jury, in turn, selected as its assistant
Mr. A. L. Rohrer, who was then a student
in physics at the Ohio State University.
The jury was instructed to make such tests
and measurements as seemed desirable and
possible under the circumstances, and which
would aid in arriving at a verdict upon the
relative merits of the different exhibits.
In response to the proposal four systems
of electric lighting were entered for compe-
tition.
(1) The Thomson-Houston Electric
Company submitted a svstem of arc
lighting.
(2) The Edison Company for Isolated
Lighting submitted a system of incandes-
cent lighting.
(3) The United States Electric Lighting
Company offered a system of arc lighting.
(4) The United States Electric Lighting
Company also submitted a system of
incandescent lighting.
The exposition opened on September 5,
1883, closed on October 6, and the jury
was requested to make its report of the
awards one week before the closing date.
Several things conspired to make these tests
less complete in some respects than was
thought desirable by those interested. The
time at the disposal of the jury was short,
however, which, combined with the fact
that the members of the jury were all engaged
in professional work and were therefore
unable to devote their entire time to the
work, had much to do with governing the
completeness of the tests. The general plan
adopted was to have all the energy that was
consumed by the dynamo measured by means
of dynamometers, and all the electrical
energy in the circuit was to be determined
by well-known methods. The energy con-
sumed by the lamps was also to be measured,
as was the illuminating power. The measure-
ments were therefore of three kinds: —
Dynamometrie, electric, and photometric.
It is rather interesting to relate that the
dynamometrie measurements were deter-
mined by the use of the cradle dynamometer,
which at that time was a recent invention of
Professor C. F. Brackett, of Princeton
University, and that was the first time the
cradle had been built in practical form (a
small model having been built previously by
Professor Brackett). The form of this
dynamometer is now well known so that even
a general description of it is unnecessary.
It is also interesting to relate that the
measurements of electrical energy were made
by the use of a pair of Sir William Thomson's
A SERIES OF ELECTRICAL TESTS MADE IN 1883
23
graded instruments, the ammeter and the
voltmeter. This set of instruments had been
imported by the Electric Supply Company
of New York especially for the use of the
jury, and at that time were known as the only
reliable instruments of their kind.
During the tests of the arc-lighting ma-
chines, the whole current was taken through
the current galvanometer. With the incan-
descent system, the total current in the cir-
cuit sometimes was as much as 175 amperes,
so that the jury found it necessary to make
use of a shunt, probably the first time a
shunt had been used on such a large scale.
This shunt was of sufficient capacity and
resistance that about one-fifth of the current
was taken through the galvanometer.
The photometric measurements presented
the most difficult problems for the jury.
Even at that time the expression of illuminat-
ing power in candles was considered a matter
of uncertainty and, as the test was intended
to be purely a competitive one, the jury-
decided to ignore entirely the question of
candle-power and confine itself to a com-
parison of the lamps under consideration.
A 16 c-p. lamp was used as a standard and
all measurements were made in terms of
that.
It is not necessary in this article to go
into all of the interesting details with regard
to these tests. The jury was working in
practically a new field, and there arose many
problems which had to be solved. As a
result of these tests, a unanimous verdict
was agreed upon by the jury, which recom-
mended the following to the Committee on
Scientific and Educational Appliances:
(1) To the Edison Company for Iso-
lated Lighting, a silver medal for the
intrinsic merit and superior excellence and
efficiency of their dynamo-electric machine
for incandescent lighting.
(2) To the Thomson-Houston Electric
Company, premium of $500 for intrinsic
merit and superior excellence in the
following particulars, namely, highest total
efficiency, construction of lamp, and con-
trol of system.
(3) To the Edison Company for Iso-
lated Lighting, gold medal for trie intrinsic
merit and superior excellence and high
efficiency of their incandescent electric
lamp.
(4) To the Thomson-Houston Electric
Company a special premium of a gold medal
for the intrinsic merit and superior excel-
lence of their lamp for arc lighting in the
following particulars, namely, efficiency
and regularity of action.
(5) To the United States Electric
Lighting Company, silver medal for the
intrinsic merit and superior excellence
of their dynamo-electric machine for arc
lighting.
(6) To the United States Electric
Lighting Company of New York, a pre-
mium of $300 for the intrinsic merit and
superior excellence for the second best
system of incandescent electric lighting.
(7) To the United States Electric
Lighting Company, a premium of $300
for the intrinsic merit and superior excel-
lence of the second best system of arc
lighting.
During the progress of the tests the jury
listened to the briefs which were submitted
by the representatives of the various com-
panies which had entered their apparatus.
It might be interesting to give the names of
these gentlemen. The Edison Company for
Isolated Lighting was represented by Messrs.
John W. Howell and Luther B. Steringer.
The Thomson-Houston Electric Company
was represented by Professor Elihu Thomson,
Mr. vS. A. Barton, General Manager, and
Mr. E. F. Peck, who was in charge of the
exhibit. The United States Electric Lighting
Company was represented by Messrs. Curtis,
Hine, and one or two others whose names
have been forgotten.
A detailed description of the tests made
by this jury, and a summary of the results
obtained will be found in Science, Vol. Ill,
No. 54 (the issue of February 15, 1884).
It is very interesting because of the detailed
reference to the methods employed in making
the tests and because of the fact that, after
many years of experiments with various
apparatus and methods, it appears that the
methods which are now thought most suit-
able (at least for precision), are in most cases
those that were used in these 1883 tests.
For example, the efficiency was determined
by the input-output method using a direct
means of measuring the power supply. The
cradle dynamometer was employed which,
in modified form, is what is used today in the
standardizing laboratory and which gives
very satisfactory results as far as accuracy
goes.
During the 31 years which have passed
between the time when these tests were made
and today, we have passed through a long
series of methods, based on the separate deter-
mination of "stray power" or loss, in testing
24
GENERAL ELECTRIC REVIEW
efficiencies. A few years ago some awoke to
a realization that we were expending much
more time and effort to get at the result by
indirection than would be required to go
straight to the answer by direct measure-
ments. The fact was also quite strongly
brought out at the Convention of the Ameri-
can Institute of Electrical Engineers held in
February, 1913, that, even when the extreme
amount of detail which is demanded is
carefully observed, there are certain "un-
determined losses" which are appreciable
and which cannot be taken care of now.
In the various discussions covering this
point, some strongly contended that what
we want to know ultimately is the efficiency
and that it would be better to go after this
directlv as we did in some instances with
success. Eventually, this point of view will
no doubt prevail, although just now it is
considered to be not advisable to say much
about it on account of the impression that
prevails in some quarters that such processes
are necessarily much more expensive and
require more time than the methods that are
now used, namely, the separate determination
of the losses.
In other words, the tendency now is to go
back to the methods of this 1883 test.
With regard to the electrical measurements,
the situation is quite similar. The output was
measured in some cases by a shunted ammeter.
and the development of this idea has produced
the most perfect current measuring instru-
ments which have so far been known.
For a long time after these 1SS3 tests,
attempts were made to produce accurate
and convenient instruments for switchboard
use, as well as for precision testing, in which
the total current was passed through the
instrument. With the exception of the
Siemens dynamometer and the Kelvin
balance, they have all passed into history
and. although these instruments can still be
classed as the best which were ever produced,
they have not remained in use for direct-
current measurements on account of their
inconvenience.
In reference to the photometric measure-
ments, the incandescent lamp standard was
used. This is now almost exclusively em-
ployed as a standard. We have passed
through a long series of standards for photo-
metric work, most of which were unheard of
after a few years and all of which now have
practically been abandoned. One can recall
a few of these, such as Methvens standard,
the amyl-acetate standard, the pentane
standard, the Carcel standard, and others.
Outside of a few national physical labora-
tories and museums none of these will be
found at the present time.
With reference to the tests of the gal-
vanometers, standard cells were used. These,
of course, were not the perfect Weston cells
which wTe now have available, but were
Daniell cells. Working with standard cells
found little practical support for many years
but now we have completely returned to this
apparatus. Potentiometers and improved
standard cells are the recognized methods
found in the highest class of work. In fact, the
desirability is now being considered of making
terrestrial magnetic measurements with refer-
ence to the standard cells, instead of by the
inverse process which was formerly employed.
The permanence and sensitivity which can
be obtained with modern cells and gal-
vanometer is such that a magnetic needle
suspended in a coil of known constants
can- be used to determine the earth's mag-
netism by the deflection obtained with much
more accuracy than the electromotive force
of the cell can be determined from the coil
and independent measurements of the earth's
magnetic field.
Further comments would serve to bring out
the same main point, which is that we are
proceeding today along the same broad
lines that were laid down in these 1883 tests,
and that we have tried almost everything
else in the meantime but have returned to
these older methods. This is not due to
chance development, but can be explained
by the fact that those who had this matter in
hand at this early date had more than
ordinary appreciation of the proper way to
attack a problem, that is, directly from the
front, to which method we have been com-
pelled to return.
AN X-RAY INSPECTION OF A STEEL CASTING
By Dr. Wheeler P. Davey
Research Laboratory, General Electric Company
In the August, 1914, issue of the Review we published an article illustrated with "X-ray" photographs
which gave an idea of the extraordinary ability of the Coolidge X-ray tube to successfully penetrate both
thin and thick objects. In the following article is described one of the most recent commercial applications
of the tube, viz., that of detecting flaws in steel castings. The service that this tube may render in the art
of steel founding can easily be realized. — Editor.
It has always been true that as soon as a
new tool is perfected unsuspected applica-
tions of that tool rapidly develop. This has
been expecially true in the case of the Cool-
idge X-ray tube. It is planned to publish from
time to time results of such special applica-
tions as may come within our experience.
Possibly the question of observing the "pipe"
in a steel ingot by the use of the X-ray,
thereby being able to determine just where
the ingot should be "cropped" may seem
still somewhat removed, at least in so far as
commercial applications are concerned. There
is nc inherent impossibility in the process
however. The case now being described is a
long step in this direction. It is the object
of this article to describe in detail what has
already been done in the way of an X-ray
examination of a certain steel casting of
which suspicion had been aroused as to its
homogeneity when in the machine shop.
The original casting was two and one-
half inches thick and weighed about a ton.
When received at the Schenectady Works
of the General Electric Company it had
been machined down to approximately the
desired shape and thickness. The amount
still to be taken from the faces was not
more than one-eighth inch and in some
places was only one-sixteenth inch, but
when this was removed it was found that
some small imperfections had been cut into.
These extended over an area -^bout five
inches long and one and one-half inches
wide.
The mechanical department at once
chiseled away a part of the surface at this
point, and then sent the casting to the
Research Laboratory to determine if, by
means of an X-ray examination, it might
be possible to reveal still other hidden blow
holes or imperfections.
A Coolidge tube especially made for use on
high voltages was set up in front of that part
of the casting where the imperfections had
been found. An 8 by 10-inch Seed X-ray
plate was mounted immediately behind the
casting and the plate was backed by a large
sheet of lead. The distance from the source
of X-ray to the plate was 20 inches. The
tube was excited by an induction coil with a
mercury-turbine interrupter. The current
through the tube was 1.25 milli-amperes and
the potential across the terminals of the tube
corresponded to that sufficient to break down
a 15-inch spark gap between needle points.
The X-ray plate was exposed two minutes.
At the place where the radiograph was taken,
the finished casting was about nine-sixteenths
of an inch thick. The radiograph obtained
is shown in Fig. 2. The casting was then
moved eight inches and another radiograph
made. In this way a number of exploratory
fLEAD PLATE
/X-RAY PLATE
COOL/DGE TUBE
-STEEL CAST/A/G
Fig. 1.
Diagram of Set-up for Taking Pictures of Steel Casting.
Drawn to one-eighth scale
radiographs were taken through different
points of the casting.
All the radiographs thus taken showed
plainly the tool marks on the surface of the
casting. All but one showed peculiar markings
26
GENERAL ELECTRIC REVIEW
Fig. 2. Radiograph of Steel Casting. Some of the imperfections have been chiseled out of the steel.
The chisel marks and some remaining imperfections show plainly
Fig. 3. Radiograph of Steel Casting showing flaw in center of casting.
The circle shows where a piece was later punched from the casting
AN X-RAY INSPECTION OF A STEEL CASTING
27
which were of such shape as to strongly
suggest that they were indeed the pictures of
holes in the interior. In the words of the
surgeon it was decided "to confirm the
diagnosis by making an exploratory incision."
Fig. 4. Photograph of Top Surface of Casting at
place where piece was punched out. Note that
no imperfections are visible. The U is a
punch mark to identify top of
piece cut out
This has proved, then, that with the proper
X-ray exposure blow holes or cavities may be
disclosed in apparently solid metal of con-
siderable thickness. A careful comparison of
the X-ray photographs and the button photo-
Fig. 5. Photograph of Bottom Surface of Casting
at place where piece was cut out. Note that
no imperfections are visible at the surface
A circular piece, one inch in diameter, was
punched from the casting at a point where
one of the radiographs indicated that a blow
hole should be found. (Location of sample
Fig. 6. Photograph of one Edge of Button which
was cut from the Casting (see Fig. 3) showing
position of hole. Button was rs inch thick
shown by circle on Fig. 3.) Figs. 4 and 5
show that the surfaces of the casting were
entirely free from blow holes at the point
where the button was removed. Figs. 6 and
7 show the ends of the hole in the button.
graphs leads to the conclusion that very small
air inclusions are made visible; and the fact
that the tool marks are plainly visible on the
X-ray plate confirms this fact.
Fig. 7.
Photograph of Edge of Button opposite
to that shown in Fig. 6
Such studies point to the desirability of
great care in metal casting where imperfec-
tions, ordinarily invisible, are of great danger,
and where X-ray analysis or some other
method is not used to check them.
2s
GENERAL ELECTRIC REVIEW
A TRANSMISSION LINE CALCULATOR
By Robert W. Adams, E. E.
The transmission line calculator described in this article was developed to simplify the calculation of the
voltage drop and power loss in a-c. transmission lines. The author condenses the preliminary work neces-
sarv for a graphic solution of vector diagrams and then explains how, by means of the curve and charts
published herewith, the succeeding steps necessary to a complete solution are arrived at. — Editor.
Perhaps the most tedious problem which
confronts the average electrical engineer
is the accurate calculation of voltage drop
and power loss in alternating-current trans-
mission lines. This calculation is one that
frequently has to be repeated several times
before the most economical and efficient
design is secured, and on this account the
orthodox trigonometric method, while not
in itself unduly difficult, becomes very
laborious in its practical application.
Accordingly, there have been proposed a
number of "short-cut" methods, designed
to reduce the labor of computing voltage
drop in lines of moderate length in which
capacity can be neglected; and one of these,
the Mershon chart, has been very successful
in abbreviating a portion of the process
without departing from the strict mathe-
matical solution of the vector diagram. This
chart, however, in common with most of the
other graphic methods, cannot be applied
to a specific problem until a certain amount of
arithmetical calculation has been performed,
and it is this extra labor which is the most
fruitful source of error and delay.
With the idea of shortening this labor and
lessening the chance of error, the author has
Fig. 1. Diagram Representing the Magnitude and Phase
Relation of the Transmission Generated Voltage,
Receiver Voltage, and Line-
Drop Voltage
condensed into two steps the preliminary
work necessary to the graphic solution of the
or diagram.
(1) The first step is the determination
of a "Transmission Factor" from the
formula :
K=
kv-a. X distance in miles
10 X kilo volts2
This formula combines the load kilovolt-
amperes, the distance that the power is
transmitted in miles, and the pressure in
thousands of volts between the wires at the
receiver end of the line, in such a way that
both decimals and large numbers are
avoided and the fraction can frequently
be solved by mere inspection.
(2) The second step is the determination
of the percentage resistance and reactance
components of the line drop (represented
i
}/
7
JA
6
A
t$-
Kr
1
r
/
<0 A
J
%
i4
A*
^
/
V
<0
h
1
k
'O^
/•
L
/
1
0
0
fin
t
is
/Ffe
Z
S/i
stt
5
tnc
4
e
Fig. 2. Curve Sheet Showing the Relation between the
Resistance, Reactance, and Length for No. 0000
Wire, for 60 Cycles and 18-Inch Spacing
by the base OD and the altitude DB of the
line-drop triangle in Fig. 1 ) . This is accom-
plished by multiplying by K: (a) the
resistance in ohms per mile of a single wire
of the size selected, (b) the reactance in
A TRANSMISSION LINE CALCULATOR
29
ohms per mile of this wire at the given
frequency and spacing of conductors.
When the per cent resistance and
reactance drops have been determined in
this manner, they can be applied to the
Mershon chart or used in the trigonometric
. BY n w AOAMS POOVfftNCE i
Fig. 3.
A Chart from which the Transmission Factor K may
be obtained for Various Wires at 18-Inch
Spacing and 60 Cycles
solution of the line-drop diagram (it being
noted that they refer to three-phase work
and are to be multiplied by two if the
circuit is single-phase).
In order to express graphically the whole
simplified method just outlined, the author
has constructed a calculating device that
As the computing scale requires no special
explanation, we may proceed to describe the
evolution of the wire diagram.
Considering first a single No. 0000, B.&S.
copper wire at 60 cycles and 18-inch spacing,
we find that it has a definite resistance and
reactance for a given length in miles, as shown
in Fig. 2. For instance, a ten-mile length has a
resistance of 2.6 ohms and a reactance of
.5.6 ohms, as indicated by the heavy triangle.
This triangle corresponds in shape to the
line-drop triangle of the vector diagram, and
can be converted into such a triangle by
multiplying the three sides by a factor which
takes proper account of the nature of the
load.
The three sides then become :
Ohms resistance X
V3X three-phase current X 100
receiver voltage
= per cent resistance drop.
Ohms reactance X
V&X three-phase current X 100
receiver voltage
= per cent reactance drop.
Miles X
V 3 X three-phase current X 1 0( )
receiver voltage
= K.
Fig. 4. A Transparent Chart, which when Superimposed on
the Chart of Fig. 3 with due Respect to Power-Factor,
Indicates the Line-Drop in Per Cent
of Receiver Voltage
consists of a circular slide-rule scale for
computing the value of K, together with a
wire diagram for locating the apex of the
line-drop triangle, and a transparent chart to
indicate the actual drop in per cent of the
receiver voltage.
CO*> RiGHT 191* BV (1 W ADAMS. PROVIDENCE, R I
Fig. 5. An Illustration of a Setting of the Chart of Fig. 4
Superimposed on that of Fig. 3
It follows that for any given value of A"
(as previously determined for the given load
by means of the computing scale), there is a
corresponding point on the sloping line for
No. 0000 wire which locates the apex of the
per cent line-drop triangle representing the
30
GENERAL ELECTRIC REVIEW
effect of this load on a circuit of this wire.
Similar sloping lines can be drawn for the
other sizes of wire and the corresponding
points can be connected up to form curves,
Fig. 6. A Photograph of a Page of the Calculator showing
the Curves which were illustrated in part
in Figs. 3, 4 and 5
by means of which the apex of the line-drop
triangle can readily be determined for any
value of K.
The result is shown in Fig. 3, which is a
reduced view of one quadrant of the station-
ary diagram of the Transmission Line
Calculator. The resistance and reactance
scales are omitted from the final diagram,
as they are not essential to the practical
working of the device.
We can now, by means of K, locate on the
diagram the apex of any line-drop triangle,
and it remains to make use of this graphically
with due reference to the power-factor of the
load so as to indicate the true percentage
drop in the transmission line. In other words,
referring again to Fig. 1, we have the point B
and wish to know the distance OC, which is
determined in the figure by the arc BC.
drawn with its center at .4 and intersecting
AO prolonged.
In order to reproduce this arc graphically
we construct a transparent chart consisting
of a series of percentage arcs drawn from a
common center A, and pivot this chart at the
lower left-hand corner of the wire diagram.
This chart, a portion of which is shown
in Fig. 4, is furnished with a central reference
line which corresponds to OC and which can be
set at any angle to the base line of the diagram
by means of a suitable power-factor scale.
When the transparent chart has been set
in this manner to correspond with the load
power-factor, as shown in Fig. 5, and the
apex of the line-drop triangle has been
located for the given circuit conditions as
previously explained, we have only to find
the arc nearest this apex and follow this arc
to the graduated reference line of the chart.
There the true line drop, corresponding to
the distance OC, can be read directly in
per cent of the receiver (or load) voltage.
If, instead of following the arc as outlined
above, we follow the nearest vertical line of
the diagram to the reference line of the chart,
we can there read the power loss in the circuit,
expressed in per cent of the delivered power.
This appears in Fig. 1 as the distance OL,
which obviously bears the same ratio to the
line AO, representing 100 per cent, as the
resistance drop OD bears to the power com-
ponent AE of the load voltage.
We can, therefore, by means of this wire
diagram and transparent chart, determine the
line drop and power loss correctly for any
circuit of 18-inch spacing at 60 cycles; and,
by constructing similar diagrams for other
common spacings and frequencies, we can
expand the range of the device so as to include
the whole field of transmission and distribu-
tion at moderate voltages.
The result appears in Fig. 0, which shows
a complete page of the Transmission Line
Calculator as arranged for four standard
spacings at 60 cycles. It is equipped with a
transparent chart which is in the form of a
disk having at its edge a circular slide-rule
for computing the value of K for any given
load, voltage, and distance of transmission.
31
SOME NOTES ON MAGNETIZATION CURVES
By John D. Ball
Consulting Engineering Department, General Electric Company
The study of magnetics is one which in the past has received a large amount of attention. In recent
years, however, its necessity for successful electrical design has become more and more realized; and, as a
result, we are rapidly gaining additional information from day to day which is making itself apparent in the
manufacture and characteristics of the machines now placed on the market. The following group of three
short articles contains ideas that will similarly prove to lie a valuable addition to our knowledge of magnetiza-
tion curves. — Editor.
I. EXTRAPOLATION OF MAGNETIZATION
CURVES
For designing machines and for various
other purposes, it is often necessary to know
the values of magnetization for higher
induction than is usually given by test which,
with the ordinary apparatus employed for
testing magnetic material, is usually limited
to an upper range of values of magnetization
forces of from 200 to 400 gilberts. Obtaining
higher values therefore involves special testing
apparatus (attended with considerable cost
and care in making the determinations) or the
extrapolation of the curves obtained in the
ordinary way.
Because of the nature of the magnetization
curve, direct extrapolation is difficult and,
for a given induction, the value of the mag-
netization taken from such an
extrapolated curve is likely to
be in considerable error. A
rational extension to the curve
may be made, however, by means
of the equation that is found
by the use of the reluctivity
curve, which is the reciprocal of
the permeability plotted against
H. Such a curve approximates
a straight line over a wide
range of values as has been
described elsewhere. *
The reluctivity, p, has been
expressed by the equation
p — a+oH , wherein a is a
constant representing the dis-
tance from the A-axis to the
intercept of the p-H curve if Fig. i.
continued along the straight line
and a a constant representing
the slope of the line. Therefore, the
induction
This is approximately true within the range
of ordinary test when the total 0 of the mag-
netic material and of the air are taken to-
together and also when the metallic density
/3o which is equal to /3 — H is considered. The
true or metallic reluctivitv
Po= a0+a0H
(2)
wherein a0 and c0 are constants, calculated
on the basis of metallic density, and in
consequence differ slightly from a and a.
Fig. 1 gives magnetization, permeability,
and reluctivity curves for sheet steel plotted
from the data given in Table I.
It will be noted that /3 and 0O are practi-
cally identical up to H = 10 and differ but
slightly at H = 200. Taking values of H
and p from H = 50 to H = 200 as representing
0 =
H
or
H
a+a H
(1)
» Trans. A.I.E.E., Vol. VIII, p. 485 et. seq.
" Engineering Mathematics." Steinmetz. Ed. 1911, p. 294.
General Electric Review, Vol. XVI, 1913. p. 750.
Curves of Magnetization, Permeability, and Reluctivity for sheet steel
plotted from the data furnished in Table I
the straight line, we obtain by the 2 A
methodf the equations :
p = 0.00058+0.0000475 H
S= *
p 0.00058 + 0.0000475 H
+ "Engineering Mathematics," Steinmetz, Chapter VI.
32
GENERAL ELECTRIC REVIEW
p„ = 0.00062 +0.0000479 H
a= H
Po 0.00062+0.0000479 H
These equations show close agreement
between p and p0.
Theoretical considerations prove that the
use of po is much better, as the curve
representing po — H may persist as a straight
line; whereas the curve p — H must con-
tinually bend downwards and have the
curve p = 1 as its asymptote (otherwise it
would show the material to become diamag-
netic at very high inductions and eventually
possess infinite reluctance or zero permea-
bility, which cases could only be true if
metallic densities are considered).
When obtaining extrapolations of the fi — H
curve, by the means outlined above, (as
£ and not /30 is desired in the curves used for
design purposes), it might be a temptation
to use equation (1), but if such is done, we
would become involved in considerable incon-
sistencies. Therefore, when extensions of the
ji — H curve are desired, it is necessary to use
the equations of 0o and to add to the results
obtained the values of H, which gives the
equation :
<>-db+fl (3)
A study of the equations will readily show
the advisability of using the latter equation.
When high values are reached a or ao
becomes negligible and the equation becomes
0= —, which is to the effect that a final value
of saturation is reached which, in amount, is
the reciprocal of the slope of the p — H curve.
As a matter of fact /3 does not represent an
absolute saturation value as, after the
material is saturated, /3 continues to increase
by the same amount as the increase in H.
Fig. 2 gives curves showing the plotted
results of Table II. These data were calcu-
lated by equations (1) and (3).
TABLE I
H
(3
&>=P-H
H
H
-4
200
19,960
19,760
0.01002
0.01012
99.8
150
19,240
19,090
0.00780
0.00786
128.2
100
18,390
18,290
0.00544
0.00546
183.9
50
17,130
17,080
0.00292
0.00293
342.6
30
16,390
16,360
0.00183
0.00183
646.3
10
14,500
14,500
0.00069
0.00069
1,450.0
0
12,540
0.00040
2,508.0
3
10,620
0.00028
3,540.0
2
8,700
0.00023
4,350.0
1.5
6,900
0.000217
4,600.0
1.2.5
5,810
0.000215
4,645.0
1.0
4,260
0.000235
4,260.0
0.7.5
2,060
0.000364
2,750.0
0.5
590
0.00085
1,180.0
TABLE II
ft
Results for p
obtained by
equation (3)
0
Results for /3
obtained bv
equation (1)
Difference
Per Cent
Difference
500
20,400
20,900
20,500
400
1.9
1,000
20,650
21,650
20,800
850
3.9
1,500
20,700
22,200
20,900
1,300
• 5.9
2,000
20,800
22,800
20,900
1,900
8.3
3,000
20,800
23,800
20,950
2,850
11.9
5,000
20,820
25,820
21,000
4,820
18.6
10,000
20,820
30,820
21,000
9,820
31.8
SOME NOTES ON MAGNETIZATION CURVES
33
It will be noted that the per cent error in
0 at H= 10,000 is not large, but that if the
errors of H at a given value of /3 were con-
sidered, the errors become enormous.
Conclusion
In extrapolations of mag-
netization curves the equation
introduces large er-
enon, but is largely a function of the scale
selected to represent the magnetizing forces.
This fact may be illustrated by reference to
Fig. 3. The data from which these curves
necessary to use
-H or some other
^ a+aH
TOTS. It is
a0+<T0H
form that provides for the metallic
density to which the H values are
added.
II. SO CALLED "KNEES" OF THE
MAGNETIZATION CURVES
When discussing magnetization
curves we frequently hear state-
ments that machines are designed
at inductions which are defined
with reference to the "knee" of
the saturation or magnetization
curve. As example : In such and
such an apparatus the flux density should
be below the "knee," in a certain magnet the
design is to have the flux density well on or
above the "knee," or the "knee" of the curve
for a certain magnetic material occurs at a
certain densitv.
800 900
160 ISO
40 45
0
H
JV!
s-
s
7>nnn
s
*
s
u
/
uu
—
1
~r
u
10
:o
JO
30
OO
~0
00
V
OO
60
00
•o
»
m
V
90
V
Fig. 3. Successive Portions, plotted to differing scales, of a single Magneti-
zation Curve. Note the startling fact that the "knee" appears
to be located at different 0 and [I values
were plotted will be found in Tables I and II
of Section I of the present article. A glance
at Fig. 3 will readily show that the point of
maximum curvature (which is usually the
interpretation of the "knee"), occurs at
different densities on the different curves,
which are all plotted from the same
data, and differ only in that different
scales for H are employed.
The "knee," if derived from these
curves, would be in the vicinities of
the following values:
Curve No.
Flux Density at "Knee"
1
2
3
4
20,500
16,500
14,500
12,500
Fig. 2. Extrapolations of Magnetization Curve plotted from
the calculated results of Table II
This conception of matters has beyond a
doubt led into many errors and uneconomical
designs due to the fact that this so-called
"knee" is not entirely a magnetic phenom-
Fig. 4 shows the second curve of
Fig. 3 taken alone in which the
above induction values are empha-
sized by small circles. Fig. 4 shows
there are no evidences in this case of
bends which are shown by plotting to the
other three scales. Referring to Fig. 5 and
Fig. 6, wherein the data are plotted on
logarithmic and semi-logarithmic paper re-
34
GENERAL ELECTRIC REVIEW
spectively, we have curves in
which equal percentage of in-
crease of H gives equal abscissae.
Here we have no evidences of
"knees." at points in the above
tabulation, which further proves
the point. The top curve of
Fig. 3 is steeper at the high
inductions than the other three.
due to the fact that the iron is
saturated and the increase of /3
is mostly due to the air.
The above discussion applies
to related curves, as for example,
wherein line voltage of machines
is plotted against field current.
etc.
The conclusion is that the so-
called "knee" of the curve is a
mechanical bend, the position
of which is due largely to
the scale selected. This fact —P~
should be carefully consid-
ered when interpreting
curves of this nature.
p
1
■
22000
-
—
-4-
_ L
2OO00
•
j
— =
1
18000
asm
joOOC
)
12000
1
10000
8000
6000
I
■>nnn
i
ZOOO
0
|
no
JOS
500
-\,
H
BOO
TOO
too
900
Fig. 4. The Complete Magnetization Curve shown in parts in Fig. 3.
circles indicate the locations at which the "knee" occurs if curve
was drawn to each of the scales used in Fig. 3
The
III. MAGNETIZATION
CURVES PLOTTED ON
LOGARITHMIC PAPER
Owing to the shape of
the regular /3 — H curves
used for design purposes,
the curves are usually divi-
ded and plotted to several
scales to facilitate clear-
ness. If this is not done it
is difficult to determine 0
values at low values of H
up to the mechanical bend.
or so-called "knee," unless
results are calculated from
a permeability curve. It is
likewise difficult to deter-
mine values of H at high
values of /3. Several scales
are likely to lead to con-
fusion and the number of
changes of scale is thus
limited. If only one scale
be used, we have a typical
curve such as shown in
Fig. 4. This figure is drawn
from data in Tables I and
II in Section I of this
article.
It is desirable to select
a method of drawing mag-
netization curves which
|
—
.
— r-
7000
eooo
--
A
— -
— L
4—
-£_
!
"
1
1
.'000
1
30 40 50 60 70 SO 100
H
loo xo too eoo too
Fig. 5. A Magnetization Curve plotted on paper having logarithmic abscissa
and ordinate scales 'same values of tf and H used as in Fig. 4)
fi
— i — r— T
1 1
|
.
[
I
4
-4
?fXVX1
(AAXf
1 1
^L^— ■
-
i :
' 1
I — \—
+ ~
/eooo
!
—
r ~^r*
-r
' 1 1
-h
^ —
*" !
! |
T
1 I
1
i
i
!
ii--
i
lTI.
! ' T"
" T-
""LT "
xi
:
f i
-
u -r
i — f—
-_,._.
1
1
-4-
±±~
T"
i i
T
|
* S 6
78 tO
J
■>
i
40 X60
70$o no
a
10 A
V
■kV
600
300
Fig. 6. A Magnetization Curve plotted on paper having a logarithmic abscissa
scale and a uniform ordinate scale (same values of 0
and // used as in Figs. 4 and 5^
APPRENTICE SYSTEM AT THE LYNN WORKS OF THE G-E COMPANY 35
will give a wide scale for H at low values,
and which will cause the scale to be con-
tracted at high values. On general prin-
ciples, it is also desirable to obtain a curve
having a general slope of approximately
45 deg.
A method of obtaining such a curve as
above outlined would be to plot the data on
logarithmic paper. Such paper is on the
market and is easily obtained. On such paper
the vertical and horizontal scales are both
divided according to logarithmic progression.
Plotting the data of Fig. 4 on such paper gives
the curve shown in Fig. 5. This draws out
the H scale in an excellent manner but the
arrangement is poor considering the ordinates,
as at high values of /3 the scale is contracted
and at low values it is needlessly exaggerated.
A better scheme for plotting such a curve is
to use paper with a logarithmic scale for the
abscissae and a straight, or even-division
scale, for the ordinates. The data of Fig. 4
so plotted are shown in Fig. 6. This gives a
very desirable H scale and a very good scale
for 0. It also gives a good mechanical slope.
Paper of this ruling possesses a great advan-
tage in that any desirable scale may be used
for ordinates, whereas for a logarithmic
scale in both directions, the choice is much
restricted. Considering Fig. 5 we have a
single very readable curve. The knee of the
saturation curve is not so pronounced in this
case as when plotted on regular even-division
paper, but this constitutes a further change
in favor of the logarithmic paper because, as
has been shown in Section II of the present
article, the knee is not in reality a definite
point as its location depends upon the scale
employed when plotting the curve. Fig. (i
contains three blocks of abscissae. An addi-
tional block either way would give either a
very wide H scale at low values or a very-
contracted one at high values, which is in
accordance with what is desirable.
THE APPRENTICE SYSTEM AT THE LYNN WORKS OF THE
GENERAL ELECTRIC COMPANY
By Theodore Bodde
The advantage accruing from the employment of specially trained men is fully realized by most large
manufacturers, and the results in improved products and more efficient service from such employees have led
many concerns to introduce the so-called apprenticeship course, which is simply a school for the education
of the workmen in the fundamentals, theoretical and practical, on which a particular industry is built. The
essentials of such a course are outlined in this article. — Editor.
In a large factory building belonging to the
General Electric Company, at West Lynn,
Massachusetts, there exists a unique school of
practical electrical and general technical
knowledge; unique, because it combines and
mingles intimately the practical factory at-
mosphere with the theoretical ether of science.
This educational institution, commonly
called an apprentice system, gives practical
instruction through factory work and theo-
retical knowledge through class room lectures.
The class room work is so arranged as to
occupy slightly less time in years than the
practical work. If a student therefore fails to
pass in one of the classes and is obliged to
repeat it, he can still finish all classroom
work within the prescribed time limit of
apprenticeship.
The educational institution provides ac-
well for young men with no more than a
grammar school education as for high school
graduates. The grammar school graduates
are placed in the so-called apprentice school,
while the high school graduates enter the
engineering school. They are selected out of a
large number of applicants.
In the apprentice school, the young men are
developed into efficient skilled workmen,
assistant foremen and foremen, and tool
designers. In the engineering school they are
converted into efficient practical engineers.
The classroom work of the apprentice
school stretches out over a period of nine terms
of 14 weeks each. That of the engineering
school covers a period of seven terms of 14
weeks each. There are three terms in each
school year.
The teaching staff consists of six instructors
and one superintendent.
The above outlines in a general way the
system of this technical school. We will now
consider some of the different principles and
methods which are followed in the electrical
department, in order to give a general idea
of the system.
To the apprentices one term of electricity is
given, while to the students of the engineering
school five terms of electricity are allowed.
The first principle followed, for the purpose
of effectually impressing the mind of the
young man, is that of concrete representation
of the different truths which are taught him.
The reason for this lies in the fact that these
young men have generally left school at an
early age. Consequently, theory and its
demands on the imagination are almost
36
GENERAL ELECTRIC REVIEW
unknown to them and the imagination has
not been trained to its full strength. On the
other hand, having been in contact with
matter and material things during the greater
part of their lives, they can, with no difficulty
whatever, see through material things and
material representations, where they would
be powerless were those representations only
abstract ones. Therefore, it is through this
concrete method of representing things that
one must appeal to them.
Technical education consists in impressing
on the mind the relations between natural
phenomena; in other words, in leading the
pupil to discover the links connecting different
facts. In popular language this discovery is
expressed by the saying: "I see," which
means nothing else than "I see the link; I
understand;" for when we see a thing we
understand it. Now if this connecting link
can be made visible by means of really visible
things, instead of by things which are only
visible through an effort of the imagination,
we shall be able to make all things under-
standable to those whose imagination is not
strong enough for that effort, and technical
education for the masses will become possible.
It is true that education consists also in
training that very effort of the imagination
which is needed for the concentration of the
mind. It is this branch of education which
produces thinkers. It produces, however,
perfect fruit only when applied to the very
few who have a natural aptitude for thinking.
The large mass take up only facts and relations
and become effective tools, but very few
among them become thinkers and leaders.
In our present civilization it is well that this
should be so. At the same time we may long
for some future in the advancing ages when
this condition will no longer be necessarv,
and everybody will be trained for the beautv
and development of himself and of the race.
At present, the world needs many tools for
its material growth, and the General Electric
Company, which is itself a small world,
daily feels the need for efficient tools, and
all efforts are exerted in this direction. If,
now and then, thinkers are mixed among the
tools, they will be recognized sooner or later,
and will step out of the mass through their own
efforts. Hence, for the present, the methods
of education should not be molded for them
but for the large masses. Neither should the
methods of education be molded for the other
extreme, the dummy. In the General Electric
apprentice and engineering school, the dum-
are eliminated while passing from the
lower classes to the higher ones. This is
done by a simple weeding out process,
through keeping a close observation and a
just record of their doings and progress
throughout each term. An educational com-
mittee meets every week and carefully elimi-
nates the chaff from the wheat, the result being
that the higher classes are very nearly perfect.
The following are some examples of the con-
crete representation of things as applied in the
electrical engineering department of this
school :
Throughout the first term, the text book of
W. H. Timbie. "Essentials of Electricity," is
used. The beginners have special trouble in
grasping the idea of line drop in transmission
lines and other similar very real and impor-
tant phenomena in power transmission. The
reason is obvious. Transmission lines are so
large that they have never been grasped in
their entirety in the imagination of the
student ; they are too long to be contained
in the narrow space of his vision. In order to
overcome this difficulty, a miniature trans-
mission line was made, reproducing in every
way the phenomena of a large power trans-
mission. The lines are made of thin resistance
wire and are stretched across the whole length
of two blackboards which run along the wall of
the classroom. A set of incandescent lamps at
about the middle of the line produces one
load, and another set of lamps at the end of the
line produces another load there. The begin-
ning of the wires are switched to two binding
posts, between which are 275 volts d-c.
By varying the number of lamps, different
loads are put on the line at different points,
thus producing different currents and different
line drops in the sections of the line. These
values are measured in a direct way by the
students. This gives them practice in the
manipulation of d-c. voltmeters and amme-
ters. The readings are then written down in
chalk directly over the corresponding sections
on the blackboard. From these results,
calculations are made relating to power loss in
the different sections of the line, voltage on
the loads, power delivered to the loads, total
power transmitted, etc. All these calculations,
written dowTn again on the blackboard over
the corresponding part, are then finally
checked up by means of direct measurements.
The three-wire balanced and unbalanced
systems are also reproduced in miniature by
the same means, and the general run — first
measurements, then calculations, and at last
checking up by other measurements — is
essentiallv the same as before.
APPRENTICE SYSTEM AT THE LYNN WORKS OF THE G-E COMPANY 37
It is remarkable what good results this
method of teaching has produced.
In a latter part of the term the d-c. gen-
erator and motor phenomena are illustrated
by means of an old fashioned bipolar shunt
wound dynamo which has been fixed for the
purpose and provided with a flywheel. This
makes possible the illustration of the counter-
electromotive force which exists in a running
motor. Suppose the dynamo has been
connected up at the end of the above de-
scribed miniature transmission line, and runs
as a motor. A set of lamps on the same trans-
mission line shows its bright lights as a
result of the power which it takes from the
same source. If now the double-pole switch
between the binding post and the trans-
mission lines is suddenly opened, the motor,
because of the inertia of its flywheel, will
become a generator, and the lamps will
still show their bright lights, this time,
however, taking their power from the dynamo
side; for the current on that side is reversed,
as is clearly shown by means of an ammeter.
The voltage on the line can be measured at
the instant that the double-pole switch is
opened, which serves to illustrate in a clear
and real way the counter-electromotive force
which existed an instant before while the
dynamo was still running as a motor.
Thus the student becomes familiar with all
the secrets of the dynamo. Even this
counter-electromotive force, so often the
stumbling block to beginners, becomes visible,
almost palpable to them, and impresses
itself on their minds. The measurements of
voltage and currents, in relation to the speeds
through which the flywheel passes, are then
written down, calculations are made and
again experimentally verified, and it is thus
that the different phenomena enter into the
mind almost without effort; for the student is
interested in these different operations from
start to finish, and is not tired out by an
undue effort of the imagination. The chan-
nels between his senses and his mind are wide
open, and the knowledge enters without effort.
During the second term of electricity,
Swoope's textbook, "Lessons in Practical
Electricity," is used. This textbook is rich
in material, and in this lies its great merit,
for it offers many topics to be treated and
talked about in the classroom. It describes
many experiments, and to follow these de-
scriptions requires a certain amount of the
student's imagination. It is to be noticed
again that the student of the engineering
school is a high school graduate and has had
his imagination trained originally to a greater
extent than has the average apprentice. As
the time is limited, considering the large scope
of the book, this term is mainly devoted to
theory, though here and there concrete
illustrations are made if the described experi-
ments of the book do not convey the fact
clearly enough to the mind.
The third term of electricity is devoted
entirely to experiments and laboratory work.
Large d-c. and a-c. dynamos and the necessary
instruments are put into the student's hands,
and under the direction of their instructor
they make the usual practical tests relating to
voltage, speed, load, losses and efficiency. It
is surprising how quickly the students get
hold of this term's work and of the right way
of doing things. Their enthusiasm and
pleasure in the work is very visible in the
neatness with which they make up their
reports. Some of these are almost pieces of
art, so carefully are the sketches drawn and
the curves traced.
After this term of heavy practical work,
the student goes back again to pure theory.
Two terms of advanced electricity along the
lines of Franklin & Esty's textbook of
electrical engineering now follow. During
this time the student has ample occasion to
verify and think theoretically over the
different points and phenomena which have
come up during the former term, and thus the
last foundation stone of electrical knowledge
is deposited in his brain.
The classroom in which the student gets
these advanced courses of electrical engi-
neering is in the laboratory, so that the
whole atmosphere is impregnated with the
practical developments of the great industry.
Dynamos, rheostats, and all kinds of motors
look at him from all sides while he ponders
over some intricate problem, and like real
friends suggest ideas to him. The walls carry
charts illustrating such useful rules as the
famous Fleming's three-finger rules for motor
and generator directions, and the unconscious
daily look at these charts produces on the
student's mind a lasting impression, in the
same way as in daily life the advertising
poster impresses the public mind. If there
is any formula, any figure, difficult yet
useful to remember, there is no better and
easier way of mastering it in one's memory
than by posting it in some conspicuous
place to which the eye is turned every day.
These repeated impressions will leave their
mark without requiring any acrobatic effort
of the brain.
38
GENERAL ELECTRIC REVIEW
RADIOTELEPHONY
By W. C. White
Research Laboratory, General Electric Company
Radio communication, the term recently adopted by the profession in lieu of the popular but inappropriate
word "wireless" can be divided into two general classes — telegraphy and telephony. During the past ten years
or more many experiments in radiotelephony have been recorded, but communication by this means has never
enjoyed the practical or commercial applications that are common to radiotelegraphy. This article describes
the principles involved in radiotelephony, and the difficulties encountered which have so far kept it more or
less in the experimental stage. — Editor.
Introduction
Shortly after radiotelegraphy had become
an accomplished fact, radiotelephony was
proposed and experiments undertaken along
that line. The fact that apparatus was at
hand by which the voice could be made to
give a variable form of electric current and
apparatus by which this form of current could
be made to reproduce the original voice made
the problem seem simple in comparison with
the original development of the telephone.
In order to understand the problems of
radiotelephony and why it has made so
much slower progress than radiotelegraphy,
it is necessary to review some of the principles
involved in radiotransmission in general.
Fundamentally, what happens in radio-
transmission is that a certain amount of
energy is generated and liberated at the
transmitter, from which it radiates more or
less in every direction, and a very minute
portion of it is intercepted at the receiving
station where it energizes the receiving
apparatus. This is therefore a transfer of
energy and as such requires a medium.
It has been shown that light and radio-
waves are similar phenomena in this medium
which we call the ether. Now as to how these
radio or electromagnetic-waves are set up in
the ether, a rough analogy will help to make
the theory clear. Imagine a paddle dipped
vertically into a body of water; if this is
moved very slowly back and forth water will
merely flow from the volume in front of the
advancing paddle around the edges to the
space just vacated. Floating corks arranged
in a circle about the paddle and at a radius
of several feet away would not show any
movement, proving that all the energy used
in moving the paddle was expended as fric-
tion at its surface or in eddies or currents set
up in the immediate vicinity.
Now suppose the frequency of the back
and forth motion is increased. Common
experience tolls us that waves will be set up
which hi ppreciable after a certain
frequency of motion has been passed. Bodies
floating in the water at a distance will be
moved up and down (even against an applied
friction) as the waves pass them, showing
that in the case of the rapidly swinging
paddle its energy is used up in two ways;
in the first place, as friction, as already
mentioned and, in the second, by waves
which transfer the energy through the medium
away from the source until it sets some mass
swinging whose friction dissipates the energy
transmitted. Naturally, if one wishes to
make short length waves a small paddle would
be moved rapidly, and for long wave lengths
a large paddle moved slowly.
In order for a medium to transfer energy
away from a source by wave motion, it must
have inertia; and of the tangible mediums
with which we are familiar, the less their
density the higher the rate of vibration must
be before an appreciable portion of energy
leaves the source by means of wave-motion
radiation.
Returning now to electromagnetic-waves:
If a straight conductor in space is carrying
an alternating current at GO cycles frequency,
the only loss we could measure would be that
due to its resistance. It is trite, of course,
that if a conductor of a second closed circuit
were to parallel the first conductor, a current
would be induced in the former which would
consume energy. This is due to a magnetic
field about the first conductor which may be
said to grow from and collapse upon its
source twice each cycle, but never traveling
away from it continuously.
If a conductor carries a current at say
100,000 cycles, energy in the form of electro-
magnetic-waves will leave it and travel away
with the velocity of light, and, if these waves
intercept another circuit, a current of 100,000
cycles frequency will there be set up. The
amplitude of these waves- decreases as the
distance from the source increases; and ex-
perience shows that a certain loss of energy
occurs as the waves travel in space, due,
undoubtedly, to atmospheric conditions, which
loss is termed "absorption."
RADIOTELEPHONY
39
It is not to be inferred from these argu-
ments that there is any theoretical reason
why water waves or electromagnetic-waves
of very low frequency cannot be produced.
For instance, a huge barrier 1000 miles long
moved through an amplitude of, say 1000
miles, in the middle of the Pacific ocean with
a swing once a day, would set up waves of
enormous power, probably causing a tidal
flood on the shores of the ocean.
In a similar way, a huge electrical capacity
in the transmitting radiating circuit, charged
at an enormously high potential, would
radiate waves at a frequency of 60 cycles.
It is impractical, however, to construct an
aerial radiating system of sufficient capacity,
and corona losses prevent the utilization of a
high enough voltage.
The simplest and most commonly employed
method of obtaining high-frequency currents
is by spark excitation. A weight suspended
by a spring will have a natural period of
vibration, depending upon the stiffness of the
spring and the mass of the attached body.
It will take up this frequency of vibration
when struck an upward or downward blow
and continue its oscillations for some time.
In an analogous way an electrical circuit
having inductance and capacity will have a
high-frequency electric current set up in it
when its circuit is completed by a spark
which allows readjustment of the charge
stored in it.
As mentioned, a high-frequency current is
set up in the circuit of the distant receiver,
due to the aerial wires (these intercepting
the electromagnetic-waves from the trans-
mitter). As these currents are minute, the
most sensitive form of current indicator must
be employed.
In order to get an idea of the magnitude
of the currents and the amount of energy
involved, a few quantitative examples will
be given. The radiating circuit of a radio-
transmitter is said to have a certain number
of ohms resistance which may be defined as
that quantity which when multiplied by the
square of the current in amperes gives as a
product the number of watts dissipated. A
large station designed to transmit a distance
of 1000 miles or more may use 75 amperes
in a circuit of 8 ohms so-called antenna
resistance.
In a receiving station 2000 miles away,
having a resistance of 25 ohms in its receiving
circuit and apparatus, a current as high as
•50 microamperes may be set up, which means
about 6X10_S watts." When we consider the
distances, this current seems large; the
pointer of the usual type of sensitive, portable,
direct-current voltmeter will give about a
one millimeter movement with such a value
of direct current. It is to be remembered,
however, that in the receiver circuit the
capacity and inductance are adjusted for
resonance for the incoming frequency, so that
in order to realize this amount of current in
any indicating device, its resistance must be
very low.
Now for direct currents the d'Arsonval
galvanometer principle, such as employed in
most direct-current indicating instruments,
is the most practical form of sensitive current
indicator. For alternating currents of fre-
quencies of about 150 to 2000 cycles, the
Bell telephone receiver is most sensitive and
simple. A good telephone receiver is respon-
sive to one-tenth of one microampere alter-
nating current at a frequency of 500 cycles.
The currents induced in the receiving cir-
cuit, from a transmitter generating its oscilla-
tions by spark discharges as mentioned, con-
sist of groups of very high frequency current
coming at intervals determined by the rate
of spark discharge.
It is evident, then, that in the receiving
circuit some device must be utilized which
will respond to the minute high-frequency
currents set up, or they must be transformed
into a form of current to which a galva-
nometer or telephone is adapted.
This latter method is most commonly
employed, several rectifying devices being
available which change the high-frequency
groups more or less perfectly into a half -wave
alternating current having the same frequency
as the spark intervals at the transmitter.
Such a form of current will actuate a galva-
nometer or give response in a telephone, the
latter being ordinarily used because of greater
convenience and speed of operation. In
practice, the sparks at the transmitter are
made to occur at rapid and regular intervals,
so that a fairly pure musical note is heard in
the receiving telephone.
Differenl spark frequencies will produce
corresponding tones in the receiving 'tele-
phones. This really illustrates the funda-
al principle of a radiotelephone trans-
mitter, viz.. the radiating of high-frequency
electromagnetic-waves in groups correspond-
ing to the tone to be transmitted.
Modifications Necessary for Telephony
In order that the voice may be reproduced
in an ordinary Bell telephone receiver, a
10
GENERAL ELECTRIC REVIEW
current must be passed through its winding
which has an alternating-current component
corresponding in frequency and wave shape
to the fundamental and overtones in the
voice, and in amplitude to its loudness.
Thousandths ofa Second
Fig. 1. A Series of Direct-Current Waves which are made
up of a 1000-Cycle Alternating Current
and a Continuous Current
.37
40 SO
Mi/Z/oM/ts of a Second
Fig. 2. An illustration of a Rectified 50,000-Cycle Alternating
Current. The dotted line indicates the average
of the instantaneous peak values
Now, if in a receiving circuit as described
a continuous high-frequency current were
induced in the aerial circuit, instead of in
groups periodical^ by the spark trans-
mitter, a direct current would flow through
the telephone receiver pulsating at a fre-
quency far too high to hear, the effect being
identical to that of a continuous current.
The alternating-current component neces-
sary to reproduce speech may be obtained
by varying the amplitude of this continuous
current at the proper variable rate, which in
turn can be accomplished by varying the rate
of amplitude change in the high-frequency
waves, intercepting and setting up corres-
ponding currents in the receiving aerial.
These various forms of currents can best
be made clear by some simple diagrams
illustrating the principles involved.
Fig. 1 illustrates a direct current consisting
of an alternating current of 1000 cycles fre-
quency superimposed upon a continuous
current. Such a frequency passing through
a telephone receiver would produce a high
pitched musical tone.
Fig. 2 illustrates a rectified high-fre-
quency current of 50,000 cycles, the negative
half of the wave being suppressed by the
rectifying device. Such a form of current
passed through a telephone or direct-current
instrument will give a response or indication,
as if a continuous current were passing whose
value is equal to the average of the instan-
taneous values, or about 32 per cent of the
peak value of the rectified wave. This is
shown by dotted line.
Fig. 3 represents a high-frequency current
of 50,000 cycles, varying in amplitude so
as to reach a minimum every 0.0005 of a
second, or at a rate corresponding to 1000
cycles per second.
Such a current, passed through a rectifying
device, is shown in Fig. 4 and the dotted line
shows the equivalent average current which
is of 1000 cycles, and produces the effect of
such a current in a telephone receiver. A
direct current added would make it identical
to Fig. 1. A musical tone may thus be pro-
duced in the receiving circuit by a periodic
variation in the value of the current in the
transmitting circuit.
Under actual conditions the variations will
follow an irregular curve, due to the over-
tones and inflections of the voice, and the
rectified high-frequency wave form will be
complicated by the fact that the rectifying
devices used do not rectify perfectly, -and
because condensers are used to store the
energy of succeeding waves so that the high-
frequency current does not actually have to
pass through the telephone windings.
The usual form of radiotelegraphic receiv-
ing apparatus is therefore suitable for tele-
tiundred Thousandths
of "Second
Fig. 3. A Representation of a 50,000-Cycle Alternating
Current of Varying Amplitude
n n
MMA4^
IS 20
hundred Thousandths ofaSecand
Fig. 4. The formation which the wave shown in Fig. 3
assumes when rectified. The dotted line is of
an equivalent 1000-Cycle Current
phony, so that the modifications necessary are
in the transmitting equipment.
The first feature is that the transmitting
station must be capable of generating high-
frequency currents and radiating them so
RADIOTELEPHONY
41
that the currents induced in the receiving
apparatus when rectified will cause no dis-
turbing noise in the telephone receiver. This
may be done in two ways, either by a con-
tinuous high-frequency wave, or by one gen-
erated by the spark system described, the
sparks, however, occurring one after the
other so rapidly that their frequency is above
the audible range where the telephone and
ear are not sensitive and any resultant tone
would not interfere with the reception of
speech.
So far, the former method has proved the
more practical, and the continuous high-fre-
quency currents are generated either by an
alternator of special design, or by some form
of high-voltage direct-current arc shunted
by a capacity and inductance. The Poulsen
arc-generator is an apparatus of this type.
The second important feature in the trans-
mitter is some method by which the amplitude
of the high-frequency current may be con-
trolled and modulated by the voice so that
the amplitude of the radiated waves follows
closely every variation in the voice. Since
the voice in speech is a complex set of sound
waves varying continually in frequency and
amplitude, and containing overtones, it will
be realized that it is very difficult to modulate
a current of, say, even 10 to 20 amperes
through a wide variation and preserve at the
same time the correct relative intensity of
the different voice frequencies involved in
order that the articulations at the receiving
station is good.
This matter of sufficient energy control
is the one big problem in long-distance radio-
telephony, and is the factor which has made
it impossible so far to attain anything like
the distance range that is accomplished in
radiotelegraphy.
A great deal of work has been done by
different investigators on the improvement
of microphone transmitters which will handle
heavy currents and give good articulations.
The ordinary microphone transmitter, such
as is in use on all telephones, operates with
about a quarter of an ampere and about 10
volts across it. This means a control in energy
variation of but a few watts. Modifications
in such a type of microphone transmitter
may be made so that it will control several
amperes, and special microphones have been
built to handle considerably more current,
but so far none have been perfected to control
the large currents such as are used in high-
powered radio-stations.
There are two promising fields for radio -
telephony. The first is for long distance,
where wire telephony at present is impossible
over submarine cables, and expensive on land.
The other is for relatively short distance, for
use between ships and from shore to nearby
ships; the latter being used in connection
with the land lines, so that conversation may
be had with vessels not too far from land with
the same ease that we now talk from one city
to another.
For the realization of this latter application
several additional difficulties remain to be
overcome. The great difference between
transmitted energy and received energy pro-
hibits the simultaneous use of sending and
receiving apparatus, so that some form of
throw-over device has been found necessary
to change connections to either one or the
other. Although the high-frequency alter-
nator and the Poulsen arc give good results,
both require more or less' attention and are
not suitable for small ship installations.
For use in connection with existing land
lines, the problem of control is even more
difficult, as here we have only minute cur-
rents to effect the control of a large amount
of energy.
It is doubtful whether radiotelephony will
ever supersede our present wire system on
short distances over land, but it will un-
doubtedly be of immense value in fields where
the wire telephone is impracticable.
42 GENERAL ELECTRIC REVIEW
THE SUPPLYING OF POWER TO THE QUAKER OATS COMPANY
By J. M. Drabelle
The Iowa Railway & Light Company
These note< describe the method adopted for supplying power to the Quaker Oats Company's plant after
the growth in business had rendered the original plant too small for the present requirements. — Editor.
A rather unusual and interesting installa-
tion has been made by the Iowa Railway
& Light Company of Cedar Rapids. Iowa,
to supply electric power and high-pressure
steam to the plant of the Quaker Oats Com-
pany, which has at Cedar Rapids the largest
cereal mill in the world.
The Iowa Railway and Light Company
generates power at 2300 volts, two-phase,
(10 cycles; the Quaker Oats plant generated
its power at 240 volts, three-phase, 60 cycles.
The problem of arranging for the supply of
purchased power may be stated as follows: A
maximum of 3000 kw. at 85 per cent power-
The power plant of the Quaker Oats Com-
pany originally consisted of one 800-kv-a.
engine-type alternator and one 400-kv-a.
engine-type alternator. Two years ago,
owing to the increased requirements for
power, that company installed a 500-kw.
85 per cent power-factor steam turbine and
generator. The demand for power, however,
kept increasing, and since the entire mill
had been built around the engine room and
boiler room, no space was available for the in-
stallation of the needed additional machinery.
The milling company therefore contracted
with the local power and light company
Fig. 1.
The Method of Mounting the Potheads at the End
of the Lead-sheathed Cables
Fig. 2. Control Board, Showing Operating Lever of the
Oil Switch and the Curve-drawing Instruments
svo-phase, 2300 volts, was to be
transmitted in underground cables a distance
of 1S50 i< 'ansformer substation, that
was located in the mill and there by means of
the T conne< :ransformed to three-
phase power Its.
for electric power to be -used in driving the
machinery, and for steam to be used in the
cooking processes.
The underground cable installation consists
of three 750,000 cir. mil., two-conductor,
concentric cables. Two of these cables are
THE SUPPLYING OF POWER TO THE QUAKER OATS COMPANY 43
Fig. 3.
Photograph Showing the Switchboard, and the
Massive Busbars with their Supports
maintained in service, and the third is held
for a spare. One end of the cables, with their
potheads, are shown in Fig. 1. An insulation
of 5^-in. varnished cambric was used between
the inner conductor and the outer conductor;
a similar one being used between the outer
conductor and the lead sheath. The lead
sheath was }/% in. thick.
Three water-cooled, 1500-kv-a., 2300 volts
lu 1240 volts, two to three-phase transformers
were supplied. Two are used in the T-con-
nection and the third is held as a spare. The
transformers are provided with round-pattern
thermometers and with water bells.
The switchboard installation, which is
shown in Fig. 3, is particularly interesting
and is easily the most unusual feature of this
installation. The leads after leaving the pot-
head are brought to an oil switch that is con-
nected to the transformers. For protecting
the cable from static disturbances, graded-
shunt multigap arresters are provided. The
low-tension leads of the transformer are
brought through a single opening in the tank
to prevent eddy currents; from the ter-
minal board, 10-in. by 1^-in. copper bars run
to a disconnecting switchboard that consists
of six 6000-amp., single-pole lever switches.
From this disconnecting switchboard, the
Fig. 4. Photograph of the Indicating Recording
Integrating Flow Meter used in
this Installation
Fig 5. Diagram of the Switchboard Wiring, Back View
4-4
GENERAL ELECTRIC REVIEW
bus system is carried approximately 40 feet
to the distributing board of the Quaker Oats
Company. The busbars consist of six bars,
two sets in parallel per phase, and each
phase bar is made up of two 10-in. by 34 -in.
copper bars. The weight of copper used in
making these connections was 18,000 pounds.
The control panel has an oil switch mounted
on the back, and the following instruments
are mounted on the front : One 3-phase,
3-wire, 60-cycle, 240-volt, 10,000-amp. watt-
hour meter; one curve drawing voltmeter,
180-260 volts; and one curve drawing watt-
meter, 4000 kilowatt scale.
Calibrating links are provided for in order
that testing instruments may be readily
inserted in the circuits for checking. Two
10,000-amp., 2000 to 1 ratio, current trans-
formers operate the current coils of the
wattmeters.
Steam is supplied to the Quaker Oats
Company through an 8-in. extra heavy pipe
line. 1 150 feet long. All flanges, fittings, etc.,
are of cast steel. Expansion is allowed for
by long bends. The steam pressure is 190
pounds with 100 degrees superheat. The
steam is metered by an indicating, recording,
integrating steam flow meter, an illustration
of which is shown in Fig. 4.
This load of the Cereal company, which is
being carried by the Iowa Railway &
Light Company, is the largest power load in
the state carried by a public service cor-
poration.
SEMI-OUTDOOR PORTABLE SUBSTATION FOR
BERKSHIRE STREET RAILWAY
By W. D. Bearce
Railway and Traction Engineering Department, General Electric Company
The semi-outdoor portable substation, consisting of an open section for the transformer, oil switch and
other accessories, and two closed compartments for lightning arresters and the synchronous converter, is
especiallj- suited for service on roads with limited overhead clearance. A small reduction in weight and total
cost over the totally enclosed type is also possible, owing to the omission of a portion of the superstructure,
and a further advantage lies in the fact that all high tension apparatus is kept on the outside of the cab.
The following article describes in detail the equipment of a portable station of this type now being operated
by the Berkshire Street Railwav. — Editor.
In order to increase the flexibility of sub-
station equipment many electric railways
have adopted the expedient of equipping
a portable substation which can be put in
service at any point on the system on short
notice. Temporary power requirements may
occur at outlying amusement parks and fair
grounds, or on extensions where permanent
substations are under construction. An
equipment of this kind can also be used in
emergency as a reserve unit available at any
of the permanent substations.
During the past summer the Berkshire
Street Railway placed in service a number of
300-kw. commutating pole synchronous con-
verters, one of which was installed in a port-
able substation. The railway system on
which this equipment operates includes about
110 miles of interurban trackage in Western
These lines radiate from
Pittsfield. extending north to North Adams
and Bennington, Vt.
This portable substation is of the semi-
outdoor type, consisting of an open section
for the outdoor type transformer, oil switch,
current transformer, choke coils, discon-
necting switches, etc., and an enclosed sec-
tion divided into two compartments for the
lightning arrester and synchronous con-
verter with switchboard equipment. Owing
to the low clearances of several overhead
bridges the car height has been limited to
1 1 feet 6 inches above the rails.
The car body is an all-steel structure built
in accordance with Master Car Builders'
standards and fitted with steps, hand rails,
ladders etc., as required by the Interstate
Commerce Commission under the safety
appliance acts.
The under frame is made up of four 12-
inch steel channels extending the entire
length of the platform. The two center
channels are tied together by three-eighth-
inch top and bottom plates, forming a box
girder, thus securing the. necessary stiffness
without depending upon the car flooring.
All of the channels are securely fastened
together at the ends by steel members and
cross-braced by 12-inch steel channels. ■
There is also a cross bracing of six-inch steel
SEMI-OUTDOOR PORTABLE SUBSTATION
45
angles in the intervening central section of
the framing.
A suitable foundation for the converter
is provided by two pairs of six-inch steel
channels placed across the car and firmly
riveted to the underframing. The space
between each pair is filled with concrete.
Provision is also made for the usual levelling
plates and anchor bolts. Ventilating open-
ings in the floor of the car insure a supply of
cool air when the machine is in operation.
These openings are fitted with removable
sheet iron covers and permanent wire mesh
screens.
The car flooring consists of one-quarter-
inch sheet steel, which extends across the
formed by thin sheet steel framed with angle
iron. This shield protects the high tension
bushings of the transformer which are
brought out in a horizontal direction on
account of the very limited overhead clear-
ance. Some protection is also afforded tin-
oil switch units and the current transformer.
At the other end of the supporting frame, a
short cover extends over the incoming line
leads and those to the lightning arrester
compartment. The incoming insulators at
each side of the choke coils are suspended
from cross steel angles tied into the framing.
Doors are provided on each side of the
closed' compartment and there are two glass
windows located in each side of the operating
Fig. 1. Side View of the Semi-outdoor Portable Substation
plates on top of the center girder. The side
and roof framing of the closed section and
partitions of the car consist of steel channels
and angles suitably braced and riveted to-
gether. The sides and roof are enclosed with
sheet steel. A section of the roof over the
converter is fastened with bolts so that it
may be readily removed for installing or dis-
mantling the apparatus when a crane is
available. A galvanized sheet metal ceiling
is built on the interior, forming air pockets
which prevent any direct radiation of heat
when the car is standing in the sun and also
to drain any condensation to one side of the
car away from the apparatus.
At the open end of the car a framework
of channels is erected which forms a support
for the disconnecting switches and choke
coils. The framework, together with the
transformer, also supports a snow shield
compartment. The windows are pivoted at
the center to allow for suitable ventilation.
The trucks are of the diamond frame, arch
bar type equipped with 33-inch wheels
mounted on Master Car Builders' standard
steel axles and fitted with cast iron journal
boxes. They are designed to take a curve of
approximately 40 foot radius.
Standard automatic air brake equipment is
supplied with shoes acting on all wheels and
with hose connections, thus conforming to
the Master Car Builders' standards for steam
railroad lines. A handwheel and brake shaft
is also provided for operating the brakes at
one end of the car. Current is taken into the
car through three 33,000-volt disconnecting
switches designed for outdoor service. These
switches are so connected that they cut out
all of the apparatus in the station, including
the lightning arrester. An eight-foot switch
46
GENERAL ELECTRIC REVIEW
Fig. 2. The 300-kw., 600-volt. Commutating-pole
Synchronous Converter Installed in the
Portable Substation
hook is furnished for manual operation of the
switches. From these switches current passes
through three 200-ampere choke coils sup-
ported in a horizontal position and thence
to the 300-ampere. 45,000-volt, triple-pole oil
switch. This switch is enclosed in three
separate tanks, the mechanism being operated
from a single handle mounted on the control
panel. A separate current transformer is
provided for automatically tripping the oil
switch in case of overload and for operating
a bell alarm to notify the attendant when the
switch opens. The oil switch is instantaneous
in action, thus affording complete protection
to machines and feeders under short circuit
conditions.
The transformer is an oil insulated, self-
cooled, outdoor-type unit, rated 330-kv-a.,
three-phase, 25 cycle- Voltage taps are
arranged on the primarv side for operating
13,000 or 11,000 volts Y, by using
either series or multiple connection of the
primary coils. The substation can thus be
connected to any of the high tension lines on
the company's system. The secondary wind-
ing is designed for 385 volts and has 50 per
cent -aps. The secondary lea*1
enclosed in a sheet iron box from which con-
nections are made through a conduit to the
operating compartment.
The transformer is of the standard railway
type, designed with high inherent reactance
and giving a practically flat compounding
on the d-c. side of the converter. The con-
tinuous rating is in accordance with the
A.I.E.E. recommendations, the allowable
temperature rise after 24 hours' operation
at full load being 35 degrees C. The tem-
perature rise after two hours' operation at 150
per cent load will not exceed 55 degrees C.
The operating compartment of the car
contains a three-phase, 600-volt commutating
pole synchronous converter operating at
750 r.p.m. and a three-panel controlling
switchboard. The converter has a normal
rating of 300 kw. continuously, standard 50
per cent overload for two hours, and a
momentary capacity of three times normal,
or 900 kw. The machine is started from the
a-c. end from 50 per cent starting taps on the
transformer. There is also a series resistance
in circuit to cut down the initial rush of
current. The temperature guarantees and
insulation tests follow the recommendations
Fig. 3.
The Control. Feeder and Starting Panels left to right'
of the Portable Substation Switchboard
SEMI-OUTDOOR PORTABLE SUBSTATION
47
of the A.I.E.E. The compound field is de-
signed to give a practically flat compounding
at all loads without shunt field adjustment.
The machine is equipped with speed limiting
device, mechanical end play, field break-up
switch, equalizer switch, negative line switch
and shunt field rheostats. There is also the
usual brush raising device to be used with
a-c. starting. An opening is provided in the
floor for connecting the equalizer to the
stationary substation, if parallel operation is
desired.
The switchboard is of natural black slate
mounted on pipe framework and includes a
transformer panel, d-c. feeder panel, and an
a-c. starting panel. The transformer panel
is 4S inches by 20 inches and the feeder and
starting panel 48 inches by 16 inches. All
the panels have 20-inch sub-bases. The
transformer panel carries a 1500-ampere
ammeter with shunt, a 750-volt voltmeter,
a 300-0-300 scale wattless component indica-
tor, two two-point potential receptacles, and
the operating lever for the automatic high
tension oil switch.
The d-c. feeder panel is equipped with a
single-pole, 600-volt, 1000-ampere carbon
break circuit breaker which is hand-operated
and has a bell alarm switch; a back-of -board
mounted rheostat with handwheel for the
converter field; a single-pole, GOO-volt, 1000-
ampere line switch; and a 600-volt, 500-
ampere, two-wire recording watthour meter
mounted on the sub-base.
On the synchronous converter starting
panel there is a double-pole, double-throw,
SOO-ampere starting switch and two double-
pole, single-throw, 100-ampere switches with
enclosed fuses for lighting and heating circuits.
The d-c. lightning arrester for the 600-volt
feeder circuit is of the aluminum cell type and
is mounted in the rear of the switchboard
panel. The high-tension multigap lightning
arrester is contained in an enclosed central
room and consists of a series of spark gaps
shunted by graded resistances, but without
series resistance. It may be connected for
protection of either the 33,000-volt circuits
or the 13,000- and 11,000-volt high tension
lines.
The current for lighting and heating is
taken from the partial voltage taps on the
transformer secondaries. The heaters are
fastened to the partition and side of the car
. 4. The Outdoor Section of the Portable Substation
Showing Transformer. Oil Switch, Choke Coils
and Current Transformer
at one end of the switchboard. They con-
sist of three units normally rated at 900 watts
each. Separate switches are provided to
secure a gradation of heat.
The principal dimensions and data of this
substation are as follows:
Length overall 38 ft.
Width over sides of car S ft. 4 in.
Maximum width (over side channels! s ft. 6 in.
Heightoverall (includingrunningboard ll 1 ft. 6 in.
Height of floor above rails 3 ft. 8}^ in.
Total length of enclosed cab. 23 ft. Li in.
Length of converter or operating room . . 14 ft. 6 in.
Length of lightning arrester compart-
ment . 9 ft.
Length of outdoor section 14 ft. 6 in.
Truck base 25 ft.
Wheel base 5 ft. 2 in.
Wheels 33 in.
Track ■ i tandard 4 ft. 8% in.
Total : 80,0U0 lb.
48
GENERAL ELECTRIC REVIEW
THE PROCESS OF IMPREGNATING COILS; AND A LARGE,
MODERN IMPREGNATING PLANT
By Robert Reid
Mechanical Superintendent's Office, General Electric Company
The author of the article below first briefly reviews both the method of impregnating coils with an
insulating compound and the equipment necessary for the process. Following this is a description of the
design and the recent installation of a plant which is capable of impregnating nine-foot by twenty-foot
coils. — Editor.
The proper impregnation of the various
types of armature coils, field coils, relay coils
and coils used in industrial control work,
also the drying and filling of wood is a subject
which is of vital interest to all electrical
engineers. How best to secure the complete
penetration and filling of all the interstices
of the coils with an insulating compound
that will not be too brittle when cold, and
yet capable of withstanding a reasonably
high degree of temperature, is the problem.
While undoubtedly all engineers are more or
less familiar with the general process of
impregnation, the following facts in con-
nection with the apparatus may be of interest.
The installation consists principally of two
tanks; one is known as the mixing tank in
which the compound is
melted and thoroughly
mixed by being stirred with
paddles on a vertical shaft,
the other is known as the
treating tank in which the
articles to be impregnated
are placed. The two tanks
are connected at the bottom
by means of a pipe with a
shutoff valve. Suitable
When the proper period of time for complete
exhaustion has elapsed, the valve in the pipe
connecting the two tanks is opened thus
allowing the compound to flow into the
treating tank. The temperature of the
treating tank in the meantime has been
maintained at such a point as to insure the
thorough drying of the articles and also to
prevent any deterioration of the material.
In some cases, when sufficient impregnating
material has entered, the valve is closed and
air compressed to about 100 or 12.5 lb. per
sq. in. is admitted directly on top of the
compound. This pressure is maintained for
about one or one and one-half hours. This
method gives good results when the coils are
short and do not lie near the surface of the
vacuum pumps, air com-
pressors, condensers, and air
dryers are also essential
parts of the outfit.
A description of the oper-
ation of impregnating fol-
lows:
The treating tank having
been filled with the coils,
etc., the cover is placed and
securely fastened with
heavy swing bolts and nuts.
The vacuum pump is then
started and a vacuum as near as possi-
ble to 29 in. or 30 in. is maintained
for from one to one and one-half hours.
During this time all the air from the
interior parts of the coil and wrappings is
exhausted.
'rlS^
&re mm~2Z&P*<*
iq|fe
/
^i^S
|^7^^^^ ftttwe
uL
ftl*-fi3
1
^^i^C^-Ji^
wf Mj^i < !J5bE Bk"^
Fig. 1. Lower Forms for Impregnating Pit Walls set in place
compound, otherwise there might be great
danger of some portion being exposed.
The other method is to pass all of the
compound over from the mixing to the treat-
ing tank and then turn the air pressure into
the mixing tank. This method ensures the
THE PROCESS OF IMPREGNATING COILS
40
treating tank being always full during the
operation, and eliminates all danger of any
parts being exposed during the time that the
coils are under pressure (in this method also
the time is usually equal to about one or
one and one-half hours). The compound is
then returned by opening a valve in the
mixing tank to the atmosphere and introduc-
ing compressed air to the treating tank,
which forces the compound back.
The air dryer, as the name implies, is for
drying or removing as much moisture as
possible from the compressed air before
allowing it to enter the tanks, while the
condenser takes care of the air on the vacuum
side.
The impregnating tanks are usually made
double, that is, with an inner and outer wall.
Some of the smaller sizes are made of cast iron,
but all of the larger sizes are of steel plate
with riveted or welded joints as may be
preferred.
The chamber between the two shells is
for the heating element; steam at such pres-
sure as will yield the required temperature
being used direct. In some cases, in the
larger tanks, a steam coil submerged in oil
is located in this space. The body of hot oil
Fig. 2. Loads as placed on the Tank to Facilitate Sinking it into place
tends to maintain a more uniform temperature
in the tanks.
There are other designs consisting of only
a single tank with a steam coil inside it.
In such a tank the heating coil comes into
direct contact with the compound. All tanks
regardless of the type are covered with
asbestos or magnesia covering.
In one of the latest impregnating plant
installations, the tanks have a double shell
and the space between contains only hot oil
as the heating medium. This appears to have
many points of interest and advantage.
When steam-heating coils are used the pres-
sure must be maintained at all times because
if. for any reason, the pressure drops there is
a corresponding drop in the temperature
of the compound. In the case of direct
healing by oil, if the body of the oil is
sufficiently large, a more uniform condition
can be maintained. The temperature is
not easily affected ; it will decrease very slowly,
and yet is capable of being raised in a
very short space of time to the required tem-
perature.
The great length of armature coils for
horizontal turbine-generators was largely
responsible for the installation of this latest
and also one of the largest sets of its kind in
existence. The inner shell of each tank is
9 ft. inside diameter by 20 ft. deep in the
straight part while the outer shell is 10 ft.
in diameter, which gives about a 4 in. space
between the two shells. The lower heads are
of dished steel, rolled to
shape. The upper part of
the shells are securely riv-
eted to a heavy cast steel
flange that carries forty-
eight 2 in. eyebolts by
which the cover is fastened
down. The cover also is
made of a dished steel head
with a cast steel flange.
Both mixing and treating
tanks are similar in con-
struction except for a slight
difference in the covers. The
mixing tank is provided
with a stirring device and
its cover carries the neces-
sary gearing, bearings, mo-
tors, etc., for this operation.
Oil having been chosen
after careful consideration
as the heating medium, it
became necessary to con-
sider its heating and proper
circulation. Each tank has its own heater,
circulating pump, piping system, and tem-
perature recording gauges and thermometers,
so that it is possible to see at all times
just what temperatures have been obtained,
both in the oil and in the compound.
50
GENERAL ELECTRIC REVIEW
Fig. 3. View of the Tank in place within the Pit
horse power on the compressor to 5 horse
power on the oil pumps.
When it is considered that these tanks
must be of sufficient strength to withstand
both a collapsing and a bursting effect it can
readily be seen that the material and work-
manship must be of the best. Roughly, a
vacuum of 30 in. will give a collapsing
pressure of about one ton per sq. ft. of surface.
This means that the cover of the tank must
sustain approximately a total load of 65
tons while under vacuum.
It may be of interest to know that a total
of about 3600 gallons of heating oil are
required for both tanks, while 220 barrels
of compound are required to fill the mixing
tank. Both tanks, and all of the piping and
valves are very carefully covered with
magnesia covering so that the difference of
temperature of the heating oil entering and
leaving the heater is very small (about 5 deg.
variation).
The installation of this plant presented
many difficulties. Only about 4 ft. of the tanks
project above the floor level, the remainder
being below in a basement. This basement
(the outside measurements of which are
4(1 ft. by 26 ft. by 25 ft. deep), made of
Hot oil leaving the lower
part of the heater passes to
the bottom of the large
tanks, thence around the
bottom and up the sides
leaving at the top, going
thence through the circu-
lating pump to the top <,;'
the heater, etc.
While both tanks have
an independent circulating
or heating system, they are
both connected to a com-
mon expansion tank that
placed at the highest point
on the line. The top of
this tank is sealed to pre-
vent oxidation as far as pos-
sible, and has an overfly
connecting with the sewer
so that any unforeseen ex-
pansion of the heated oil
Vie taken care of.
All machinery (air com-
vacuum pump, stir-
ring pad r hoist for
ting tanks, and oil circulating pumps),
connected with the apparati motor
n, the m arving in size from :!.">
Fig. 4. General Interior View of the Impregnating Plant. The Tops of the Two
Nine-foot by Twenty-foot Tanks are shown in the center
concrete, is very strongly reinforced, and is
damp proof. Due to its nearness to a massive
building, and to the nature of the soil, it was
THE PROCESS OF IMPREGNATING COILS
51
decided to make only a partial excavation and
to construct this enormous concrete tank in
the excavation, and by removing the soil
underneath, allow it to
gradually settle to the re-
quired depth. It was first
attempted to remove the
soil by washing it out with
water under pressure but
the air-lock system was
finally adopted. Two air
locks were used and the
concrete tank was success-
fully lowered to place. (A
number of branches of trees
were encountered at a depth
of about 25 to 30 ft., the
wood resembling that of the
elm tree. It was very light
in color when broken but
rapidly turned dark when
exposed to sun-light).
Fig. 1 shows the setting up
of the forms for the concrete.
Fig. 2 shows how the tank
was loaded down to assist
in lowering it into place,
and Fig. 3 shows the tank
in place and the workmen
removing the air-locks pre-
paratory to closing the openings in the floor.
Figs. 4 and 5 show views of the completed
interior. Fig. li shows a smaller outfit of
which the impregnating tanks are 3 ft. in
diameter and 4 ft. deep. The heating element
Fig. 5.
The Air-Compressor. Vacuum Pump, and Condenser installed for use
in the Impregnating Plant
in these tanks is steam introduced directly into
the space between the inner and outer shells.
Fig. 6. A Three-foot by Four-foot Impregnating Set of Tanks at the Left and a Four-foot by
Eight-foot Synthetic Resin Vulcanizer at the Right
52 GENERAL ELECTRIC REVIEW
OPEN-DELTA OR V-CONNECTION OF TRANSFORMERS
By George P. Roux
Consulting Electrical Engineer, Philadelphia, Pa.
The merits of the scheme of employing the open-delta or V-connection of transformers in a case of
emergency or as a permanent condition has often been questioned. The proposition has both been opposed
and defended. The following article presents a clear analysis of the matter and after considering the scheme
from the standpoints of capacity, stresses, stability, etc., conclusions are drawn which are formulated at the
end of the article. — Editor.
A style of connection of single-phase
transformers for three-phase transformation of
voltage which is very often used, not only in
case of emergency but also in ordinary opera-
tion, is the open-delta or 1 '-connection.
For ordinary and permanent operation, the
use of two single-phase transformers V con-
T
IOOVolts\
/73Amperes
line B
lOOMts
WOVMs
L_
/73/ifnperes
Li'neC
/ZJAmperes
Fig. 1. Diagram of Three Single-Phase, 10 kv.a., Trans-
formers Connected in Closed Delta
nected to transform a three-phase current
to a lower voltage, appeals to many of us,
especially in cases where an increase in load
is expected in the future, when a third trans-
former can be added changing the connec-
tions from open to closed delta. The initial
investment in transformers is reduced one
third, while provision is made for the future
addition.
As an emergency connection of two trans-
formers in a bank of three, for example, in
case of an accident to the third one, this
style of connection is very often resorted to,
with acceptable results, while the disabled
transformer is being repaired.
In both cases, however, we are apt to lose
sight of the fact that the capacity of two trans-
formers connected in open delta is not equal
to the sum of the capacity of each one, and
furthermore, that a number of conditions are
changed which affect the operation of both
primary and secondary circuits, as well as the
operating characteristics of the transformers
themselves. These conditions we propose to
review and analyze in this article.
In order to have a clear view of the situa-
tion, let us take first the case of three single-
phase transformers connected in delta, each
transformer having a capacity of 10 kv-a.,
100 volts and 100 amperes, as shown in Fig. 1 ;
and deal in all the following cases with trans-
formers of the same ratio, same impedance,
and connected to a non-inductive load with
each phase balanced. We have then at full
load a voltage per line of 100, and a current
per line of 100X2 cos. 60 deg. = 100 X 1.73 =
173 amperes. Since the phase-angle relation
between the transformers is 120 deg., or twice
60 deg., the relation between the line current
and the phase current is therefore 30 deg. for
one branch, and 60 deg. between two
branches.
Adding vectorially the two currents with a
phase angle of 60 deg., as in Fig. 2, OA +OB =
OC, the line current. Also (CM +05) cos.
30 deg. =line current OC.
As each line is in parallel with each phase,
the phase voltage is equal to the line voltage
or 100 volts. Thus, the total power in the
bank of transformers as shown and con-
nected in Fig. 1 is 3X100X100=30 kv-a. or
V3 X 100 X 173 = 30 kv-a.
Assume, for some reason, that transformer
77/ must be removed from the delta-con-
nected bank, leaving only transformers / and
II in sendee, as for instance in case of a
breakdown in transformer 777.
Fig. 2.
Vector Addition of Two Currents 60 Electrical
Degrees Apart
We now have a bank of only two trans-
formers which are connected as in Fig. 3,
and each is of the same size and capacity
as those in Fig. 1.
It is obvious that in a three-phase system,
in order to supply 30 kv-a. from two trans-
formers instead of three, the line current and
OPEN-DELTA OR V-CONNECTION OF TRANSFORMERS
53
voltage must be the same in each case, that is,
100 volts and 173 amperes.
The capacity of each transformer in a bank
of three, as in Fig. 1 connected in closed
delta, was
V3X 100X173 ,_.
— = 10 kv-a.
o
The capacity of each transformer in a bank
of two, as in Fig. 3 connected open-delta
or V, would appear to be
V3 X 100X173 1E1
— - — = 15 kv-a.
We see at once that the two remaining
transformers, 7 and 77, in this new system of
connection will be loaded above their rated
capacity, which is 10 kv-a. only; and, although
it may seem that the increase of current in the
winding of each transformer is only 50 X 33^3
= 16% per cent, such is not the case.
Analyzing the conditions set forth in Fig. 3
as to phase relation of the current in each
transformer, we see conditions peculiar to
two transformers operating in series, viz.
across lines A and C.
First: The current in line A (173 amperes),
entering transformer 77 at a must neces-
sarily flow with all its intensity in the wind-
ing, and therefore the value of the current in
transformer II is 173 amperes, it being raised
from 100 amperes in the closed delta connec-
tion to this 173 in the open-delta connection.
This is due to the fact that since the total
power to be supplied is equal to EI \/^~t
where E is the line voltage and I the line cur-
rent, each transformer in the open-delta con-
EI VH
nection has to supply — - — : and each
winding will be subjected to a voltage E,
(line voltage), and in addition to a current
Line A
IMWts
l73Amperes
LineB
newts
lOOVolts
173Amperes
LineC
/73/lmperes
Fig. 3. Diagram of Two Single-phase, 10 kv-a.,
Transformers Connected in Open Delta or V
equal to 7, (line current). Such a condition
gives rise to a phase displacement, between
the line voltage E and the current in the
transformer winding, equal to:
V3
~ =0.866 = cosine 30 deg.
In the delta connection, we note that they
were connected with a phase relation of 120
deg., or 180 deg. — 120 deg. =60 deg. between
currents in the windings.
In the open delta this condition has been
changed and the difference in phase between
the current in each winding is 180 deg.-
Fig. 4. Vector Addition of Two Currents
120 Electrical Degrees Apart
(2X30 deg.) = 120 deg. The resultant of
two currents 120 deg. apart has the same
value as either of the components as shown
vectorially in Fig. 4, where OA plus OB = OC,
as also OA cos. 120 deg. = 0.4 because cosine
120 deg. =1.
Therefore the line current 7=173 amperes
has a value of 7 cos. 120 deg. = 173X1 = 173
amperes in the winding of transformer 77:
and, as transformer 7 operates under identical
conditions, the current flowing in it is of
equal value.
In Fig. 5 we have represented the three
transformers connected in delta. The imme-
diate effect resulting from the release of trans-
former 777 is similar to the case of a step
ladder in which the braces, which keep the
legs from spreading, have been severed owing
to the weight on the ladder and to other con-
current conditions; the legs have spread apart,
each one to an angle greater than the former
by 30 deg., therefore the stress in each leg
has increased to a value equal to
= 5.
cos. 30 deg.
Fig. 5. Diagram of a Closed-Delta Connection
Made up of Three Single-phase Transformers
We can realize that this new condition
is very unstable, as there is nothing to prevent
the legs from spreading further apart, on
account of the absence of the connecting
member 777, which, to a certain extent
54
GENERAL ELECTRIC REVIEW
and within a certain limit, kept the two legs
/ and II in a determined angular position.
We can then write again, but this time
correctly, that the output of the two trans-
formers left in open delta, from the previous
bank of three in closed delta, is
Fig. 6. A V-Connection Constructed from the Delta of
Fig. 5 by Disengaging Transformer III and Spreading
the Phase Angle Between I and II
El \ 3
iniiX173X1.732
34.04 kv-a.,
cos. 30 deg. 0.866
and each transformer must have a capacity i if
3464 I7Q01
— — — = 1 , ..il kv-a.
It follows that when two transformers are
left in open delta from a bank of three in closed
delta, to supply under the same conditions
the full load of the three delta-connected
transformers, they will each be subjected to
an overload of 73.2 per cent, or, vice versa,
the line can be loaded to only 57.7 per cent
of its rated supply capacity to operate the
transformers under normal rating conditions.
The voltage and current relation in the
two systems of connections is best shown in
Figs. 7 and 8, from which it can be seen that
while the three delta-connected transformers
operate with current and voltage in phase in
their winding, in the open delta they operate
a1 86.6 per cent power-factor, or specificallv.
with a current lagging behind the voltage
30 deg. in one transformer and leading by
30 deg. in the other.
Taking for instance the current in line C
of the delta-connected transformers in Fig. 7,
which is in phase with the imaginary Y cur-
rent of the transformers, we can see that upon
reaching the point of connection of transform-
ers II and III the line current splits itself
into two components each 30 deg. apart
from the line current or in proportion to the
impedance of the paths offered to its flow.
which in our case is the same, each component
being equal to '—- = 100 amperes. If
2 cos. -in deg
ance of each transformer is not the
-ante, as in the case of unbalanced load, then
urrent will divide in the inverse ratio to
dance. We note that each current
component is here in phase with the voltage.
Looking now at the open-delta connection
of transformers I and 77 in Fig. S, and taking
the line C again, the line current is, as in the
above case, in phase with the Y voltage of the
transformers; and when it reaches trans-
former II it finds only one path to follow,
instead of two as before, and strikes trans-
former II at an angle of 30 deg. behind the
voltage, thus lagging 30 deg. or 0.S66 per
cent.
In line B similar action takes place (except
that line current, B, leads voltage of trans-
former I) and the two currents emerging
from transformers / and II combine with a
phase angle of 120 deg. into a resultant equal
to each of its components, as explained
before and shown in Fig. 4, or 173 amperes
which flows back to the generator through
line .4.
This operation is repeated in each cycle
and in each phase, and needs no further
explanation.
There are other peculiarities inherent to
the open-delta connection which materially
affect the operation of three-phase trans-
formers or apparatus so connected.
Fig. 7. Diagram of the Phase Relations of the Voltages and
Currents in a Closed-Delta Transformer Connection
The line current entering a system of inter-
connected transformers divides itself in the
inverse ratio to the impedance of the paths
offered for its flow. Any difference in the
value of the respective internal impedances
is likely to cause an unbalance of the sec-
ondary voltage and primary current, which
OPEN-DELTA OR V-CONNECTION OF TRANSFORMERS
55
under certain operating conditions very often
met may reach dangerous proportions.
Likewise, the production of electrostatic
stresses has fatal consequences, due to the
fact that the mean potential of the primary
windings is not the neutral potential.
For these reasons, the use of the open-
delta connection with transformers of high
voltage is not recommended, as destructive
potentials may be caused by unbalanced
loads with electrostatic stresses, due to the
instability of the internal impedance of the
transformers under operating conditions which
in turn cause an unbalanced voltage in the
system.
For low primary voltages, 10,000 volts or
less, and relatively small installations, this
system can be used sometimes to decided
advantage.
At non-inductive load, it will be found that
the current is lagging in one transformer, and
leading in the other. When the load becomes
Fig. 8. Diagram of the Phase Relations of the Voltages and
Currents in an Open-Delta Transformer Connection
inductive, the relation of current to voltage
changes and the phase angle displacements
increase in one transformer and decrease in the
other, thus making very unstable conditions.
Therefore, if, when supplying a balanced
three-phase load it is found necessary to con-
nect a single-phase non-inductive circuit to
the open-delta connected transformers, it is
advisable to take this circuit off the leads a
and c of the bank (see Fig. 3) rather than off
one or the other transformer leads.
Concerning the reduction in the transformer
bank capacity, it is worth noting that in
three-phase to three-phase transformation the
three styles of connection commonly used also
give different ratings.
Taking single-phase transformers provided
with all necessary taps and connecting them
in different ways, their rating taken as a
bank compares as follows:
Three transformers in closed delta — Total
capacity 100.00 per cent.
Two transformers in open delta — Total
capacity 57.7 per cent.
Two transformers in T or Scott connection
■ — Total capacity 62.2 per cent.
In figuring the proper capacity of trans-
formers which are found advisable to operate
in open delta to supply a certain load, the
size of each transformer in kv-a. is found by
dividing the total load to be supplied by 2
and adding 15.466 per cent to the result, in
order to supply the kv-a. due to the lagging
current peculiar to this type of connection.
From the preceding discussion, which is
based on permissible heating, it appears
that the T, double- T, or Scott connection of
two transformers for three-phase operation
is more economical than the open-delta
connection, on account of the somewhat
greater available kv-a. capacity.
However, since the open-delta connection
uses no taps, it permits a greater simplic-
ity in the construction of a transformer
which naturally lowers the cost of the unit
and renders attainable a greater degree of
ruggedness for the same cost than can be
obtained in a transformer for T connection
which requires taps. Transformers without
taps are better balanced internally to with-
stand electromagnetic and electrostatic
stresses.
In conclusion, it may be said that there may
be cases, however, where transformers having
special taps for the T connection might well
be found useful in times of emergency or m
cases of temporary installation, because of
their greater kv-a. capacity as brought out in
this article.
56
GENERAL ELECTRIC REVIEW
PRACTICAL EXPERIENCE IN THE OPERATION OF
ELECTRICAL MACHINERY
Part IV (Xos. 19 to 2s inc.)
By E. C. Parha.m
Constriction Department, General Electric Company
(19) LOOSE COMMUTATOR
A common symptom of disorder in direct-
current generators and motors is the blacken-
ing of the commutator bars and the ultimate
eating out of the mica from between them, if
the cause of the symptom continues. The
simplest case to diagnose is where the black-
ening is local to two or more pairs of bars
that are so located at intervals around the
commutator that the locations seem to be
associated with the plan of winding and con-
necting the armature. A poor soldering job
throughout will cause so many poor con-
nections that the commutator will blacken
all over. An actual open circuit due to a
coil being mechanically injured, or to its
having burned in two, or to one of its leads
having burned free from the commutator,
will cause a traveling spark that will soon
bum the mica from between the affected bars
and characterize the trouble at once.
A certain motor had been driving shop
shafting for several years, during which time
the commutator held a high polish. The
motor was then transferred to duty in which
the armature was reversed frequently while
under load, under which conditions it soon
developed armature open-circuit symptoms.
Resoldering of the leads brought about
no permanent improvement. The brushes
sparked badly, but the machine was main-
tained in service until a new armature could
be obtained. The new armature performed
its functions perfectly.
It was decided then to rewind the old one
because its insulation had become too dry.
On stripping, several coil leads were found to
be actually broken and several more were
about to break. Further inspection dis-
closed the fact that the commutator was so
loose that it could be worked back and forth
one-quarter of an inch. (The armature had
not been designed for reversal operation and
consequently it could not withstand the
i at service.
20 LOOSE CONNECTION
Plau ill mptoms may sometimes prove
misleading. An operator was using a three-
phase induction motor to run a laundry
machine. The motor had worked satis-
factorily for two years and then began to give
starting trouble. Sometimes the closing of
the compensator would start the motor and
sometimes it would not. At such times as
the rotor failed to move it would hum; any-
one familiar with the symptom would have
immediately suspected single-phase operation,
hence a loose or open connection. In all the
preceding cases the last of several attempts
to start the motor had been successful.
One day the motor could not be started
at all ; the operator opened the compensator
and cleaned the contacts; the motor then
started promptly and ran without trouble all
the forenoon. The next afternoon the motor
again could not be started, and the cleaning
of the compensator contacts this time did
no good. While the operator was throwing
the compensator "on" and "off," trying to
humor the motor into a start as he had done
many times before, a workman threw a
rolled-up wet shirt at another workman.
The shirt hit the ceiling and then dropped
onto the stator wires just where they come
out of the motor. The motor started at
once and after throwing the compensator
over normal operation continued.
The operator was quick to connect the
throwing of the shirt and the starting of the
motor; and he had a mind to leave the shirt
where it was as a permanent institution but
more mature thought prevailed and he found
that the pushing in of the stator wires was as
effective as the shirt. The trouble was a
stator lead which was loose inside the sleeve
connector, the two being held together by
the tape that bound the joint. Sometimes
the two made contact and at other times they
did not, hence the erratic starting actions.
(21) LOW POWER FACTOR
When an alternating-eurrent generator
supplies under-loaded transformers and in-
duction motors, the current of the generator
lags behind its e.m.f. Under this condition
more exciting current must be furnished by
the exciter if the alternating voltage is to be
OPERATION OF ELECTRICAL .MACHINERY
57
maintained at normal. (The effect of lagging
armature current is to cause the magnetizing
action of a given armature coil to oppose the
magnetizing action of that field pole which
it is opposite. This decreases the resultant
field cut by the armature conductors so that
they do not generate as high an e.m.f. as they
do when the voltage and current are in phase
and the opposing armature reaction is at a
minimum. In other words, a lagging current
tends to demagnetize the field poles, and. if
normal voltage is to be maintained, the
field strength must be restored by increas-
ing the amount of current drawn from the
exciter.)
An operator complained that his exciter
commutated badly and that he was unable
to keep up the voltage on the alternator.
These two symptoms in themselves suggested
that an overload was the trouble and excessive
heating of the exciter confirmed this suspicion.
Since the exciter circuit included no ammeter
its output was not shown. An inspector cut
in an ammeter which indicated the exciter
to be continuously overloaded 40 per cent.
The operator then stated that the exciter was
guaranteed to maintain normal a-c. voltage at
0.8 power-factor and that his power-factor
was better than 0.8. Rough calculations
based on station wattmeter, ammeter, and
voltmeter readings showed that the power-
factor was between 0.55 and 0.60 at the time
of the readings. The operator was well
enough satisfied with these results to sub-
stitute a larger exciter for the work.
(22) HOT BOX INDICATIONS
If trouble of any kind occurs in lay-outs
that involve electrical apparatus it is usually
the case that some one of the electrical
devices is promptly blamed as being the cause.
Apparently it never occurs to many operators
that troubles may arise from abnormal con-
ditions in the connected load.
In a certain instance an operator com-
plained to the power company that the volt-
age supplied was varying widely and was
causing speed variations in an induction
motor that was driving a centrifugal pump
The power company failed to see how this
could be possible but, to satisfy the con-
sumer, applied a recording voltmeter, which
showed the voltage to be well maintained.
On looking further for the trouble, it was
found to be due to a hot box on the pump
shaft; the box would alternately bind and
release, thereby causing the motor speed to
vary according to this variable load which
was imposed upon its regular load. (The
operator should have observed that voltage
variations could not have been the cause of
trouble because other induction motors on the
same service were not affected.)
A short time afterward, the same pumping
unit, after working all day, refused to start
on closing the control switch the next morn-
ing. The panel starting-contactor closed
promptly but the operator reported the motor
was "dead." It took an inspector about five
minutes to find out that there was nothing
wrong with the motor. On turning the rotor
back to let out the back-lash due to the belt
coupling, and closing the control switch, the
rotor promptly took up the back-lash but
refused to rotate further. An investigation
showed the trouble to be in the same pump
bearing that had given trouble before; it was
now frozen tight. A new lining, plenty of
oil, and a smooth shaft remedied matters.
(23) BURN-OUT DUE TO CORE LOSS
A solid iron core would offer such a low
resistance to the eddy currents set up by the
core cutting the magnetic lines of the field that
these currents would be very large and cause
prohibitive heating. Laminations, when in-
sulated from each other, introduce resistance,
and thereby reduce the volume of current in
tlic core to a very small value.
A certain armature had been burned out
by the power current that followed a lightning
discharge to the core. The damaged coils
were removed, the core cleaned and scraped,
and new coils installed. The machine ran
without trouble for several months and then
burned out again in the same place. Attrib-
uting the second failure to poor repair work,
about twice as many coils were removed as
before and the machine again repaired.
Before it had a chance to fail again, the
operator had a whiff of burning insulation,
investigated and found excessive heating,
which was confined to the repaired area.
An "armature man" was called in. On
removing the repaired coils, inspection dis-
closed that the insulation armor of some of
them was being burned from the outside; the
cotton insulation on the wires was in good
condition, showing that the trouble did not
come from within. The armature was
stripped, the core disassembled to and in-
cluding the burned area, several inches of
new laminations installed, and the coils re-
placed. On drying out and again placing the
machine in service, no tendency to heat more
in one place than in another was exhibited.
58
GENERAL ELECTRIC REVIEW
The cause of the heating had been the
burning together of the laminations; the
effect was equivalent to having a part of the
core made of solid iron.
(24) ALTERNATOR SPEED LOW
Exciters for alternators may be steam-
driven, water-driven, or motor-driven; or
the exciter armature may be wound upon an
extension to the alternator shaft or may ln-
belted to that shaft. In either of the two
latter cases, an}- factor that affects the speed
of the alternator will directly affect that of
the connected exciter. With an independently
driven exciter, low alternator speed will not
affect the exciter speed, excepting insofar as
the increased exciter current required may
overload the exciter and reduce its speed for
that reason. In any event, low alternator
speed means more exciting current to main-
tain normal alternator voltage. With low
exciter speed, the exciter field current must
be increased to maintain the exciter voltage,
even if the alternator speed is normal. There-
fore, with direct-connected sets, low alter-
nator speed lowers the alternator e.m.f., not
only because the relative motion between
armature conductors and the magnetic lines
is slower, but because the lower exciter speed
produces lower exciter voltage, hence less
exciting current and a weaker alternator field
for the alternator armature conductors to cut.
An operator once complained that he could
not maintain his switchboard voltage, even
with the exciter and alternator rheostats all
cut out. What was really needed for the
fluctuations of his load was automatic voltage
regulation (which he afterward installed);
but, to meet the immediate requirements, an
inspector analysed the conditions and found
most of the trouble to be due to low speed
of the alternator and connected exciter.
Readjustment of the engine governor to give
normal speed at full alternator load and
more attention given to keeping up the steam
pressure during the load swings, which lasted
for an appreciable time, improved the
operation considerably.
(25 LOOSE CORE
In the older types of armature core con-
struction a single key, in conjunction with
the end-plates, was relied upon to hold the
core laminations securely. For the work to
which motors were then assigned and for
the comparatively moderate speeds that then
i iled, this method was satisfactory.
Today, however, speeds are high and motors
are applied to carry practically every type
of load; consequently, their mechanical fas-
tenings are designed accordingly. Occasion-
ally, one of the old types of motor (many of
which are still in use) is applied to work
which it cannot continue to perform because
it was not designed for that service; trouble
soon follows.
As an example of such a case an inspector
was called to determine the cause of sparking
and eating out of the commutator mica of a
large 500-volt bipolar direct-current motor
that recently had been applied to operate a
stone crusher. The crusher was equipped
with a very insignificant flywheel. As the
operator had just resoldered the armature
leads thereby eliminating possible poor con-
tacts, the inspector ripped off the armature
hood and examined the leads themselves.
Several of them were found to be broken but
their ends still made contact; several other
leads were about to break. After blocking
the armature shaft and the crusher so that
the shaft could not rotate, he applied a crow-
bar to the core and found the core to be loose
on the shaft. Of course, there was no alter-
native but to reassemble the core.
The sparking had been due to open cir-
cuits which had been caused by the relative
movement between the commutator and the
core breaking the armature leads. The
service was improved further by later increas-
ing the size of the flywheel and by providing
a special water-rheostat to start the outfit
without unduly overtaxing the motor.
(261 LOOSE BELTS
Belts, as well as motors, are liable to be
gradually overloaded without the fact Vicing
realized that abnormal service is being called
for.
A small alternator from which a number of
single-phase motors were to be supplied with
energy for operating printing presses, cutters,
etc., was recently installed. It was found
impracticable to run the printery with the
motors because they would not hold up their
speed under the conditions normally to be
expected. The operator and all concerned
of course blamed the generator and motors,
because they were the new part of the outfit.
An inspector was called in and he diagnosed
the trouble as a case of general belt slipping.
The prime-mover was a low-head waterwheel
of ample size, but the several pulleys used in
the transmission were small and their speeds
were low. One intermediate six-inch belt,
which was running at but 000 feet per minute,
OPERATION OF ELECTRICAL MACHINERY
59
was called upon to transmit 25 h.p. or more.
When an attempt was made to start the
largest motor while other loads were active,
the exciter field fell to almost zero on account
of reduced speed. The pressing of an iron
pipe against one belt as an idler increased
the alternator speed 400 r.p.m. : the same
application to another belt increased the
alternator speed another 100 r.p.m. By
systematically tightening the belts through-
out the line, the alternator and exciter speeds
were brought to normal value at moderate
loads, but still the speeds would not hold up
under the conditions imposed by taking a
heavy cut on the cutting machine. It was
necessary to substitute larger belts and
pulleys in two places.
Excessive belt tensions are of course to be
avoided; but, inasmuch as loss in production
is equally objectionable, the speed of the
prime mover and its dependent belted ma-
chines should be periodically checked and,
if the efficiency of transmission is shown there-
by to be immoderately low, measures should
be taken to eliminate the defect so far as is
possible. This axiom applies of course irre-
spectively of whether the machines concerned
are electrical or mechanical.
(27.) ERRATIC ELEVATOR SPEED
A conservative ' ' rule of thumb ' ' often used
for checking the safe carrying capacity of
leather belts is: One inch of single belt
traveling at the rate of 1000 feet per minute
will transmit one horse power. It is assumed
in this statement that the belt is tight
enough to prevent slipping. An operator
once complained that his elevator speed was
surging and that, under the heavier but
permissible loads, the speed dropped suffi-
ciently to interfere with his production. As
the armature of the driving motor had just
been repaired and as the elevator had given
no trouble up to the time of this repair, the
motor was blamed for the trouble.
An inspector could find nothing electrically
wrong with the motor, but he did determine
that the motor was 50 per cent overloaded
when the elevator was loaded to its rating.
This overload did not last long enough, how-
ever, to do any harm. Operating conditions
were favorable as the motor ran continuously
and the elevator was controlled by means . <\
tight and loose pulleys. At the time of
shifting to the tight pulley with a loaded
elevator, the motor drew 70 amperes at 115
volts, which corresponded to approximately
10 h.p. The five-inch motor pulley turned
at 1450 r.p.m. when under heavy load; this
meant a belt speed of 1900 feet "per minute.
From the rule given the single belt could
transmit 1.9 h.p. per inch of width at this
speed. The four-inch width, then, was good
for 4X1.9 = 7.0 h.p.
As a matter of fact the belt was earning
more than this amount. Tightening it
increased its capacity but, to make assurance
doubly sure, a two-ply belt was substituted
for the single one and all trouble ceased.
128) BRUSH-HOLDERS SHIFTED
Operators who are accustomed to running
reciprocating pumps may be surprised at
some of the characteristics of centrifugal out-
fits. One of the differing features is the rate
at which a centrifugal pump's output will
increase with the speed.
An operator purchased a motor-driven
centrifugal pump set and installed it.
Immediately after starting it up the motor
sparked badly and in a few minutes was so
hot that it smoked. (If the operator had
known as much about the output of a cen-
trifugal pump as he did about that of a recip-
rocating pump he would have suspected the
cause of the trouble at once.) As is usual in
such cases, the motor was blamed and an
inspector called in to locate the origin of the
trouble. An ammeter cut into the supply
wires showed that the motor was heavily
overloaded and a rough measurement of the
water delivered by the pump showed the
amount was far in excess of that which the
operator had specified.
In measuring the speed, however, to check
some readings, the speed was found to be
greater than that ordinarily corresponding to
about three-quarters load; this of course
could not be the case with a perfectly normal
accumulatively-connected compound-wound
motor, the speed of which drops rapidly on
increase of load. The field connections were
checked and found to be correct, but in check-
ing them the inspector noticed that one of the
brush-holder insulating washers was 'broken.
The operator explained that it had received
a blow at the time of installing the set. It
developed that at the same time, the whole
brush-holder construction had been forced
around against rotation, thereby enabling
the armature reaction to weaken the motor
field and thus increase the motor speed.
60 GENERAL ELECTRIC REVIEW
MECHANICAL STRESSES IN SHELL-TYPE TRANSFORMERS
By J. Murray Weed
Transformer Engineering Department, General Electric Company
A quantitative knowledge of the magnetic stresses in transformers is becoming more and more important
as the size of the apparatus and system increases. In this timely article the author discusses various factors
which have a bearing on the magnitude of the magnetic stresses at short circuit, and their bearing upon the
size and cost of transformers. He points out that the stresses in large transformers are much greater than in
small ones of a similar design, and therefore that an increase in the cost, for an equal degree of safety, must
necessarily result. Also, the greater the capacity and the lower the voltage of the transformer the greater
will be the extra cost for limiting the stress to a safe value. Therefore, in the latter case it is often more eco-
nomical to introduce external reactance than to have it self-contained in the transformer. He concludes by
checking his equations with equivalent ones derived by Dr. Steinmetz, and gives experimental verification of
the formula?. This article is a continuation of the matter given under the subject "Magnetic Leakage in
Transformers" in the December, 1912, and the January, 1913, issues of the Review. — Editor.
The following formula for the calculation
of mechanical stresses in a transformer was
derived in the former article and appeared
as equation 28.
S„„,
2.82X10-7«,
l-
lb. per sq. inch (1)
This formula gives the stress due to the
leakage field in any gap between coils (see
Fig. 1) in terms of the number of turns
effective at the particular gap, the length
of leakage path and the current flowing.
The term >;,. I equals ampere-turns effec-
tive between coils where the stress is calcu-
lated, the current being that for which it
is desired to calculate the stress, presumably
the short-circuit current. The length of
the leakage path, /, is taken empirically as
Vkh. (See Fig. 2.)
The preceding formula is very convenient
for calculating the stress when the limiting
value of current is known; but when the
current is limited by the reactance of the
transformer, with full voltage applied, the
following formula? are of convenience to
the designer in showing just how the design
may be altered to the best advantage for
reducing or limiting the stresses.
Confining ng in equation (1) to its maxi-
mum value, which occurs between the
primary and the secondary coils, we may sub-
stitute for I the value obtained by dividing
the voltage of the transformer by its reactance
(neglecting the resistance component of the
impedance) .
The approximate formula for reactance,
as obtained from equation (9) of the former
article (Dec. 1912 issue of the Review) is
■2fnHmlt)d^_ (2)
X-
ohms
10' I G
where / is the frequency, and n the total
number of turns in the transformer winding.
The term (mlt) stands for mean length of
turn (see Fig. 2) and is one dimension of the
leakage area and d the other.
is the distance between primary and second-
ary windings plus one-third of the distance
through the high-tension and the low-tension
coils (including ducts) of a single group of
coils (see Fig. 1). G is the number of such
groups of coils.
Equation (2), and those which follow in
this article, apply only when the number of
turns in all of the coil groups of the trans-
former are equal, so that the total number
of turns in a transformer is
n — nsG ( 4 )
Attention should be called with emphasis
to the fact that, since the maximum stress
in the transformer is that found in the gap
between high-voltage and low-voltage coils
where ng is maximum and is proportional to
(rig max.)2, no transformer is properly de-
signed from the standpoint of mechanical
stresses which does not have equal numbers
of turns in all high-voltage — low-voltage
groups. Unequal grouping will increase the
reactance somewhat for a given number of
groups, thus reducing the factor / in equation
(1), but n£ max. will be increased much more
than / will be reduced. Unequal grouping
is also unfavorable from the standpoint of
eddy-current loss. Only designs of equal
grouping are considered in this article.
From equation (2), we now have
T-E - 10? l G E
X 2fn* (mlt) d {o)
whence, substituting this value of I in equa-
tion (1)
5„„„ = 7.05 X 106X^(^)2c/2 lb. per sq. in. (6)
MECHANICAL STRESSES IN SHELL-TYPE TRANSFORMERS
61
The only quantities appearing in equation
(6) that can be changed in the design are
n, (mlt) and d. These quantities appear
also in equation (2) for the reactance. A
study of these two equations will show how
the stress may be limited to a required
safe value with a minimum increase in the
reactance. Attention must also be given,
of course, to the effects which the changes
in the quantities n, (mlt) and d have upon
the other characteristics of the transformer,
such as cost and efficiency. The designer
will note, also, that these quantities are not
independent of each other, as an increase in
n for instance with constant magnetic density
in the core will result in a decrease in the
cross-section of the core and consequently in
Fig. 1. A Sectional View taken through the Conductors
of a small Shell-type Transformer
the dimension (mlt), though the decrease in
this dimension will not be in the same pro-
portion. It requires one who is familiar with
all of these relations to interpret the equa-
tions to the best advantage for any particular
case.
An increase in the number of turns, with a
corresponding reduction in (mlt) to maintain
constant density in the core, will increase
the reactance by a larger factor than that by
which the stress is reduced, since (mlt)
appears in the numerator of equation (2)
in the first power and in the denominator
in equation (6) in the second power. If the
size of the core is not changed, keeping (mlt)
constant and allowing the flux density to
decrease as the number of turns increases,
the factor of increase in the reactance is the
same as the factor of decrease in the stress,
since n appears in the second power both in
the numerator of equation (2) and in the
denominator of equation (6).
Having a constant flux density in the core,
allowing the dimension (mlt) to reduce as n
increases, the cost will increase or decrease
depending upon the number of turns as
compared with the cross-section of the core,
since there is a definite relation of these two
quantities which gives the minimum cost.
On the other hand, their relative values may
be varied through a considerable range on
either side of this most economical relation
with but a small increase in cost. But if
the design is varied too much, by increasing
the number of turns with a corresponding
reduction in the cross-section of the core,
the cost will begin to increase rapidly.
Where the cross-section of the core remains
constant, permitting the flux density to
decrease as the number of turns is in-
creased, the cost of the transformer will
always increase with increased number of
turns.
Turning our attention now to the factor
d, a decrease in the number of high-voltage —
low-voltage coil groups will increase the A'
and Y terms of this factor. Since these
terms are divided by 3, however, and since
no change is made in the Z term (distance
between primary and secondary) , the increase
in the value of d is much smaller than the
decrease in G. It is seen, therefore, that the
increase in reactance is much larger than the
decrease in stress since, while d appears in
the second power in the denominator of
equation (6) and only in the first power in
the numerator of equation (2), G is found in
the denominator of equation (2) and not at
all in equation (6). This change will always
result in a reduction of cost, however, since
the necessary length of the magnetic circuit
is reduced by the elimination of some of the
insulation spaces between the high-voltage
and the low-voltage groups.
62
GENERAL ELECTRIC REVIEW
On the other hand, if the value of J is
increased by increasing the distance between
the high-voltage and the low-voltage wind-
ings, without changing the number of groups
(increasing the Z term only), the decrease
in the mechanical stress at short circuit is
large as compared with the increase in
reactance. Moreover, since this term (Z)
enters into d at full value, this is an effective
manner of reducing the stress. It results in
an increase in cost, however, due to the
necessary increase in the length of the
magnetic circuit. This is often the only
method by which the stress may be limited
to the desired value without excessive re-
actance, and without excessive loss due to
eddy currents, which, as shown in the former
article (Jan., 1913, issue of the Review i is
proportional to the square of the maximum
density of the leakage flux, or to ;//. It is
always necessary to consider this loss in
high-reactance transformers and it must be
calculated as well as the mechanical stress
and the reactance.
Equation (6) may be somewhat simplified,
reducing the number of constants to a single
numerical value, by substituting the value
of E from the fundamental voltage equation
of the transformer, namelv
E =
whence
_ \ 2 ir fn 4>
10*
(7)
5,„a,= 1400,
<t>2
\mltyd2 (g)
where <p is the total flux of the transformer,
i.e., its maximum value.
Although not so convenient as equation
(6) for studying the relation of the mechanical
stress las affected by various factors of
design' to the reactance of the transformer,
equation (S) shows more clearly the direct
relation of some of these factors to the
mechanical stress.
This equation shows again that the stre-- i -
reduced by reduction in the flux, with (mlt)
constant, which means an increase in the
number of turns with constant cross-section
re. It shows also that the stress is
reduced by increase in (mlt), with constant
flux, which means a constant number of
turns and an increased cross-section of the
The flux density of the core is reduced
in either case, which shows very clearlv
that high flux densities in the core' result iii
increased mechanical sti With a given
he core, the - pro-
nan of the flux density.
This conclusion is based upon the assumption
that the change in the number of turns
accompanying the change in flux does not
affect (mlt) or d, which is not correct unless
it can be effected by the elimination of an
entire high-voltage — low-voltage group.
The effect of increased kv-a. capacity
upon the mechanical stresses may be seen
from equation (S). Thus, if we start from a
normal design for a 2.30 kv-a. transformer
and increase all dimensions alike, keeping
the same magnetic and current densities in
core and windings, and assume that the
space factor is not changed, a 4000 kv-a.
transformer will have all the dimensions
doubled, and the total flux <j> will be multi-
plied by four. The two factors in the denom-
inator, which are dimensions, are both
doubled, while the factor in the numerator
is multiplied by four. The stress is, therefore,
the same as before. This conclusion is based
upon the assumption that d was doubled,
which means not only that the space factors
within the high-tension and the low-tension
groups of coils have not been reduced by the
increased size of the transformer, but also
low Vo/tage
Co//-
Coi/-
X
z-\TW
Fig. 2.
\
= =
>
\\ (mlt.)
A Sectional View Parallel to the Conductors
of a small Shell-type Transformer
that the distance between the high-tension
and the low-tension has been doubled. Since
the space factors are actually reduced, the
distance between the high-tension and the
low-tension must be more than doubled to
give this result. Also, if in accordance with
common practice, the number of groups has
been increased in the larger transformer.
MECHANICAL STRESSES IN SHELL-TYPE TRANSFORMERS
63
which would reduce the value of d, the
distance between the high-tension and the
low-tension must have been still further
increased to give the same value of d as that
used before. the grouping was changed. Nor-
mally, from the standpoint of insulation, the
distance between the high-tension and the
low-tension would be the same for the large
transformer as for the small one. It is
thus seen that with otherwise normal design
the stresses will be much larger in the large
transformer than in the small one and that,
in order to limit them to the same value, the
cost of the transformer must be considerably
increased above that of the otherwise normal
design.
The greater the capacity, and the lower
the voltage, the greater will be the extra
cost for limiting the stresses. There is a
point where the cost will be less to supply
an external reactance in connection with
the transformer, for limiting the current and
thereby the stresses in the transformer, than
to adopt the abnormal and expensive design
that would otherwise be required for this
purpose.
It is interesting to note that if the value
of / in equation (4) be substituted for but
one of the factors in equation (1), the result
will be
EI
Fmax = 14 1— j-r. lb. per sq. inch. (9)
/aCr
This is the equation obtained by Dr. Stein-
metz in his paper on "Mechanical Forces in
Magnetic Fields."*
Dr. Steinmetz's derivation for this formula
is as follows:
Assume that the secondary group is moved
toward the primary group until the centers
of the groups coincide. The turns of the
primary coils cut the leakage flux producing
a voltage
at
The work done during this motion is
w '= j eldt = nl<t> X 10~8 joules
but
whence w = PL
The energy stored in the magnetic field,
which has been eliminated was
n
W\ =
PL
The mechanical work done is
u>2 = w-wi= —— =Fdg 10~7 joules
where d is a distance in centimeters corres-
ponding to the force F in grams which
existed in the initial position, and g the
acceleration due to gravity is 981. This
gives
J-T
F=itiQ7
2gd
grams.
Substituting the value of L from the equation
E = 2ir fLI
we obtain
-^-10'
47T fgd
F= - )' grams per sq. cm.
Reducing to practical units,
per sq. inch
EI
F = 0.705=5-lb.
fd
where d is in inches. This value of F corres-
ponds to the effective values of voltage and
current, and is the average force. The
maximum value will be proportional to the
product of the maximum values of current
and voltage, so that
EI
Fmax= 1 .41 — r lb. per sq. inch.
ja
This force corresponds to a single group of
coils, the voltage E being the proportional
part of the total voltage of the transformer
corresponding to this group. If E is the total
voltage of the transformer, and the groups
of coils all have equal numbers of turns, and
are equally spaced so that the total voltage
will be divided equally among them, the
force corresponding to each group, and there-
fore to the entire transformer, is
EI
/<"„,,„■ = 1.41-^= lb. per sq. inch.
This equation does not show the distribution
of the stresses within the .transformer, nor
the effects of the factors of design upon the
stres:
Tests have been made to confirm the
calculations made for the total force developed
in a transformer. The formula? for these
calculations, which have been given in the
former article, are
_7wg2J2MQ_
= 2.82X10"
I
pounds
10)
and
F,;,, = 1.41 = lir
*A.T.E.E. Proceedings, December, 1910.
. ng"P\ uilt)
I
pounds (11)
64
GENERAL ELECTRIC REVIEW
A description of the tests referred to will
now be given. Two sets of low-tension coils
from 25-cycle, self-cooled. 200 kv-a. trans-
formers of 33,000 /3300-volt rating were
assembled loosely on the same core, with
rinuni
Fig. 3. A Photograph Showing the Scheme Employed for
Experimentally Testing the Correctness of the
Mechanical Stress Calculations
pressboard collars between the coils. With
the core on its side and the coils in a hori-
zontal position, channel irons were placed
through the openings supporting a platform
upon which weights were placed. The eight
coils were connected, four as primaries and
four as short-circuited secondaries, and, with
different weights upon the platform, the
voltage and current were increased until
the weights were lifted (see Fig. 3). As the
current increased a point was reached where
vibration began. The vibration became more
and more violent until the weights were
actually lifted. The current which caused
vibration to begin was that giving a maximum
force equal to the weight lifted (equation 10).
while the current which lifted the weights
was that corresponding to an average force
equal to the weight (equation 11). Up to a
point where primary and secondary coils
began to separate, lifting the weights, the
current and applied voltage were directly
proportional to each other. If the voltage was
increased beyond this point, the distance
between the primary and the secondary coils
was increased, giving increasing reactance,
while the current increased very little. The
tit to which the weights were lifted
depended upon the separation between the
primarv and the secondary which was required
to give a reactance voltage corresponding to
the applied voltage. The data for the calcu-
lation of the forces by equation -(11) are. in
this case,
(mlt) =9.65X12 = 116 in.
Z=8M in-
«g = 41 Xnumber of coils effective.
The results obtained from these tests are
given in Tables I and II.
TABLE I
TESTS AT 24 CYCLES
Coil Arrange-
ment
Cur-
rent
325
Volt-
age
Per Cent
Full
Load
Lifted
Calcu-
lated
S-P-S-P-S-
218
535
* 400
340
P-S-P
505
365
834
*1000
S25
597
485
987
*1600
1155
732
650
1210
*2200
1730
764
675
1260
"3,400
1885
P-S-S-P-P-
370
450
610
1700
1 765
P-S-S
444
6 1 5
732
•2900
2540
582
800
960
*5300
4370
S-S-S-S-P-
125
300
206
700
805
P-P-P
168
607
277
1300
1450
203
712
335
1900
2120
230
848
380
2500
2730
276
908
455
3700
3920
314
113(1
518
•5500
5080
401
1365
661
7900
8290
TABLE II
TESTS AT 40 CYCLES
Coil Arrange-
ment
S-S-S-S-P-
P-P-P
Cur-
Volt-
rent
age
128
930
170
1030
21 12
i nil)
230
1350
261
1530
285
1725
336
1680
Per Cent
Full
Load
Lifted
Calcu-
lated
211
280
333
380
430
470
552
700
1300
1900
2500
3100
3700
5500
844
1490
2100
2720
3510
4200
5810
The tabulated weights in the "lifted"
column include the weights of the coils, the
channel irons, and the platform. The read-
ings were necessarily rough, since they had
to be taken hastily in order to prevent the
weights from being shaken off the platform
and the coils from getting too hot. The
weights indicated by the asterisks(*) were
not actually lifted, the tests having to be
stopped too soon for the reason stated.
65
A SURVEY OF THE REFRIGERATION FIELD AS IT EXISTS TODAY
By H. I. Holleman
Construction Engineering Department, General Electric Company
Refrigeration as applied to the preservation of perishable products has long been practiced, but the
attention which has been given the art as a means of increasing human efficiency and comfort has not been
commensurate with its possibilities. The following article briefly reviews past and present work, then pre-
dicts the future developments of refrigeration as applied to bettering living conditions, and finally describes
the benefits which will be derived therefrom by the electrical industry. — Editor.
The addition of heat to various substances
under various conditions for various purposes
that tend toward the comfort and general
advancement of the human race, is a practice
which dates from pre-historic times. On the
other hand, the extraction of heat, which,
taken in its broader sense is of but slightly
less importance, has been left to the present
generation to bring into its fullest development.
The addition of heat had an early origin
probably because of the fact that it was
practically necessary, that the process was
easy, and that the needed materials were
readily obtained; whereas, the delay in the use
of heat extracting mediums can be attributed
to the fact that practically the reverse con-
ditions existed. Today, however, the effi-
ciency of every individual and the preserva-
tion of the perishable products of his labors
are of such vast importance that heat extrac-
tion or refrigeration has become a necessity.
Its practicability has been secured through the
advancement of science, which has put
within our hands the necessary mediums
and machines for its successful accomplish-
ment.
The great drawback now is the cost. This,
however, is of small importance compared to
the benefit derived; and it merely remains to
give the public at large the correct viewpoint,
before refrigeration will become practically
as common as heating. The value of refrig-
eration to humanity is impossible of expres-
sion in terms of dollars and cents. For
instance, what is the value of a ticket for a
theater which is too warm for comfort as
compared to one for the same theater when
refrigerated to a comfortable temperature.'
Or what is the relative efficiency of men work-
ing in rooms at 70 deg. F. and 90 deg.
respectively? Or how much more fit for a
day's work is a man who has slept in a room
at 70 deg. F than a man who slept in a room at
90 deg? The value of refrigeration as a pre-
servative of food products is well recognized
and yet there is no way of estimating the vast
saving accomplished each year in this manner.
There are a great many ways of refrigerat-
ing; in fact, so many that this article could
not cover even a brief description of them.
However, we can classify refrigeration under
three general heads as follows :
1 . By natural ice.
2. By refrigerating mixtures.
3. By mechanical refrigeration.
Refrigeration by natural ice is of great
importance in the colder climates. The
unreliability of the supply and the high cost
of transporting the ice to the wanner climates
make this form of refrigeration of small
importance, however, when the subject is
considered as a world-wide proposition.
According to some of the most eminent
authorities, the application of this form of
refrigeration (even in the colder climates) is
rapidly on the decline and it is predicted that
the near future will see mechanical refrigera-
tion replace that by natural ice in the majority
of its uses.
The use of refrigerating mixtures is of still
less importance than the use of natural ice.
In fact, at its present development, it is of
practically no commercial value.
This then brings us to the last general class,
which is the one most widely used today and
the one upon which we must rely for future
development. Under this head, we have two
subheads which include all mechanical refrig-
erating systems that are of real commercial
importance, viz.:
1. The compression system.
2. The absorption system.
The compression system is the one in which
a gas is compressed and cooled under compres-
sion (usually to a liquid) and is then expanded;
and, in expanding, absorbs heat from the
material to be refrigerated either directly or
indirectly. The expanded gases are then
drawn into the compressor again and thus the
cycle is completed.
The absorption system is the one in which
the expanded gas is absorbed by a liquid whose
evaporating point is much higher than that of
00
GENERAL ELECTRIC REVIEW
the refrigerant. The mixture is then heated,
driving off the refrigerant as a gas at a high
pressure. This gas is then cooled under com-
pression (usually to a liquid) and expanded as
in the compression system, the expanded gas
being absorbed in the simpler systems by
another tank of absorbing fluid which in turn
is heated.
Each of these systems requires power in
some form in order to operate. The com-
pression system, which bids fair to become the
most popular, requires more; and herein lies
one of the greatest opportunities for the future
expansion of the electrical industry. The
uses of refrigeration are many, and the total
power load required when developed is
enormous. The applications of refrigeration
can be classified under two of the general
heads mentioned before, viz. :
1. Refrigeration for the preservation of
perishable products.
2. Refrigeration for the comfort and
increased efficiency of humanity.
There has been so much said and written
about the former, that the importance of the
latter has been neglected. It is, therefore, to
this latter class that it is wished to call
attention. The one great function in this
field is the cooling of workshops, offices,
sleeping rooms, public halls, etc. When we
consider that such a tremendous portion of
the habitable surface of the earth (the tropical
and semi-tropical countries) is more in need of
refrigeration than heat for buildings, we are
astounded to see what little progress has been
made in this direction. There is, of course, a
greater cost to refrigeration but it is not as
great as we would at first imagine.
If we compare heating with refrigerating
it will be seen at a glance that, in comparison
with direct heating from coal or wood, the
cost of refrigeration will be excessive, since
the B.t.u. in generated power is seldom
greater than 12 per cent of the B.t.u. in coal.
However, if we compare refrigeration on the
same basis as heating (that is, refrigerate and
heat with same form of power, say for instance
electricity) it will be found that much less
1 ii iwer is required to refrigerate under average
summer conditions than to heat under average
winter conditions.
Take for example the heating of a room in
winter as compared to the cooling of it to a
ifortable temperature in summer.
i room 12 ft. by 15 ft. l.\ 10 ft.,
with an a -adiation of 0.2 B.t.u. per
hour per degree difference per sq. ft. surface,
and with one change of air per hour at 1
B.t.u. per 50 cu. ft. of air degree rise in
temperature.
Radiating surface of the room = 450 sq. ft.
Cubical contents of the room= 1800 cu. ft.
Temperature at which the room is to be
kept = 70 deg. F.
Take the average temperature of atmos-
phere in the winter as 30 deg. F.
Taking the average temperature during the
summer months as 90 deg. F.
Assume the cost of electric current as 2
cents per kw-hr.
The heat units per hour necessary for
maintaining the room at 70 deg. F. during
the winter amount to
V''0-30)=:
°<«°+T>
On the other hand, the heat units per hour
necessary to be absorbed from the room in
order to maintain it at a temperature of 70
deg. F. during the summer amount to only
'+ 1--!!'-VcJ0-70) = 1S70 B.t.u.
0.2(450+^),
To reduce these figures to comparative
costs, we find that the 3744 B.t.u. per hour
for heating corresponds to 1.1 kw-hr., which
at 2 cents per kw-hr. equals 2.2 cents per hour
or 52.8 cents per day of 24 hours.
According to the best authorities, we find
that a small ice plant will produce a ton of ice
for $1.50 per ton (including all overhead
charges etc.), when buying power at 2 cents
per kw-hr. A ton of ice represents a cooling
effect of 364,000 B.t.u. From this we see
that one ton of ice will cool
304,000
1S70
1 51 1
= 141 such
rooms, or each room will cost :rjr = 1.06 cents
per hour or 15.45 cents per 24 hours for
refrigeration as contrasted against 52.8 cents
for heating electrically.
Applying the above to hotels, as being the
easiest way to estimate the value of refrigera-
tion, we feel safe in saying that that portion of
the traveling public which would refuse to pay
15 cents a day for a refrigerated room is quite
small. Also, when we take into consideration
the fact that the size of the plant necessary
for hotel refrigeration would be large and
would produce refrigeration more cheaply
than the plant under consideration, and that
the rooms under most conditions would only
need refrigeration for 10 hours per day, and
that hotels can be built with a much smaller
FACTORY LIGHTING
radiation factor than those of today, it is easy
to see that the actual cost per room for refrig-
erating a hotel will be very low in comparis m
to the comfort derived. The same is true-
when applied to theaters, churches, sleeping
rooms, workshops, office buildings, etc., but
each needs to be approached from a different
angle in order to properly realize the value
in each case.
It has been predicted, by those in best
position to know, that refrigeration will
some day be to the South what heating is now
to the North. The uses of refrigeration in
tropical countries are almost innumerable;
and even in the southern part of this country
we find that the physical and the mental
well-being of a large portion of the popula-
tion suffer from continued excessive heat.
In that section of this country, the refrig-
eration of sleeping rooms, hospitals, schools,
and public halls would be of incalculable
value.
It takes but a glance at the situation to
realize that the possibilities for such use of
electric power are vast; and it is to be hoped
that the large power companies will soon be
brought to realize' this condition and wage an
active campaign for the double purpose of
profit and education.
It is only within the last few years that the
central-station management has begun to
realize the possibilities of a marked increase
in their load factors resulting from the use of
electric power in ice plants.
Since that time, electrically-driven ice
plants have sprung up all over the country,
both as isolated plants purchasing power from
a central station and as those in connection
with and a part of a central station. When we
analyze a refrigeration load, such as one of
those previously enumerated, we find that it is
just as beneficial for the central station as for
the ice plant and is, moreover, much greater
in its possibilities. It is easier to show profit
in applying refrigeration to the preservation
of a product than in applying it for increasing
the efficiency of the producer; therefore, the
producer has suffered. However, judging
from the reports published in the engineering
magazines of the installation of refrigerating
plants in some of the new theaters, hotels,
offices, buildings, etc., we believe the time has
come when the producer's welfare will be
valued as highly as his product.
FACTORY LIGHTING
By G. H. Stickney
Edison Lamp Works, Harrison", N. J.
The lighting of factories and offices has received a great deal of attention during the past few year-;, and
we have published several articles in the Review on this subject. Xot so long ago the matter was given
little attention; but it did not require much time for the illuminating engineer to prove conclusively to the
manufacturer that it was poor economy to keep down the light bills at the expense of the workman's
efficiency and the quality of his product. The campaign inaugurated in the cause of safety has focused
further attention on the subject of correct lighting; and in this article, which was presented at the Safety and
Sanitation Conference held under the auspices of the American Museum of Safety, it is shown that it is not
sufficient to provide merely enough light, but that the position of the light sources and the proper diffusion
of the light are important factors in securing the best illumination, with the least fatigue to the work-
men's eyes. — Editor.
Believing as I do, that good lighting in
factories is one of the most effective agents
in promoting industrial safety, I especially
appreciate the privilege of being designated
by the Illuminating Engineering Societ y to
address you on the subject.
While a very conspicuous advance in light-
ing methods has been made by progressive-
manufacturers, notably in the iron and steel
industry, there are still a large number of
manufacturers who seem to regard the light-
ing as an expense to be reduced to the lowest
possible minimum.
The increased appreciation of daylighl is
indicated by the modern type of building
construction; in which the light-finished,
high studded workroom, with large window
areas, often equipped with diffusing glass,
and sometimes supplemented with saw-
tooth roofs, permits the fullest possible
utilization of natural light.
It is in the artificial lighting, however,
that the greatest progress has been made.
The wonderful developments in high .effi-
ciency units have greatly enlarged the
bilities of factory lighting during the
hours of diminishing daylight and darkness,
or in places where daylight can not penetrate;
so that now a proper lighting installation is
not only an important safeguard, but an
actual economy. Manufacturers who are
today securing poor illumination with older
form of illuminants, can by a revision of
their lighting equipment, procure a good
.is
GENERAL ELECTRIC REVIEW
illumination, not only without much addi-
tional cost, but in many cases with an actual
reduction in the operating cost.
The Association of Iron and Steel Elec-
trical Engineers, in 1910, turned their atten-
tion to good lighting as a means of accident
prevention. They found, as a result of
probably the most extensive investigation
of the subject that has as yet been made,
that a higher standard of illumination was
demanded for efficient manufacturing than
simply for accident prevention. Their report
of progress, presented at the convention in
September, 1913, showed from actual figures
that in the last two years the amount of
illumination furnished in iron and steel mills
has increased 35 per cent; and in this con-
nection, it is interesting to note that this 35
per cent increase was accompanied by a
reduction of five per cent in the power con-
sumption.
The economic value of good illumination,
aside from accident prevention, is evident
when we consider the greater facility with
which an employee can work under good
illumination, and the greater accuracy with
which gauges can be read and tools set.
One large manufacturer, on investigating
his lighting conditions, found certain depart-
ments in which, during the winter months,
the operatives were practically idle for about
an hour a day solely on account of darkness.
Good artificial illumination can be fur-
nished in such a factory for eight hours a
day at a cost equivalent to about five minutes
of the time of the workmen benefited. This
illustrates the extravagance of poor lighting.
If time permitted, one could readily demon-
strate that, for a great variety of conditions,
good illumination reduces the manufacturing
costs by increasing production, raising the
quality of workmanship and reducing the
number of defective parts and "seconds."
The question of safety as influenced by
illumination presents two phases: First,
the prevention of accidents; and second, the
preservation of eyesight. While these two
phases are often closely related, there are
many conditions in which they are entirely
independent of each other. The phase of
accident prevention is illustrated in the case
of the foundry or other shop where cranes
or other powerful machinery are in opera-
tion.
The liability of crane and elevator accidents
is very much reduced with proper lighting.
In the foundries and yards of a plant, it is
practically impossible, even with safety
committee inspection, to eliminate irregu-
larities under foot. If not illuminated these
may readily cause falls, with resulting
injuries; and in foundries where molten metal
is carried and hot metal abounds, they may
often cause serious burns.
Even though guarded to the fullest extent,
powerful machinery — in which materials are
machined and fashioned into articles of com-
merce, and in which the arms and limbs are
as readily crushed — presents a menace unless
the operatives are given an opportunity to
see and thus avoid the danger points.
Xow let us consider the preservation of
the eyesight. Although the blind are trained
to do remarkable work in certain lines, there
is practically no manufacturing operation in
which a blind person is not at a disadvantage,
while there are many which cannot be carried
on without accurate visual inspection. Some
of these operations produce considerable
strain even under good illumination, and to
require their performance under poor illumina-
tion is certain to result in more or less rapid
impairment of vision. While economy should
in all cases require the best lighting practice,
humanity demands it.
In view of the preceding discussion, one
might very properly ask : ' ' What is good
illumination?" Judging from some of the
attempts that have been made to solve light-
ing problems, the conclusion might be drawn
that simply a higher intensity of light is the
answer. Undoubtedly a higher intensity of
illumination is needed in most workrooms,
but there are other features of equal and
sometimes greater importance. The mini-
mum intensity acceptable generally depends
upon the reflecting power of the surfaces to be
seen, the fineness of the detail to be observed,
the time of observation and the closeness of
application. Unless glare be introduced, a
higher intensity of light is rarely objection-
able, except from the standpoint of cost.
Owing to the remarkable adaptability of
our eyes, we are able to get along satisfac-
torily with very much lower intensities of
artificial light than are usual with natural
light. The gain secured by the increase of
intensity is not proportional to the intensity,
and there is a point beyond which the gain
would not warrant the additional cost.
However, the standard 'of artificial lighting
intensities is being raised, on account of the
lessening cost of light, increasing cost of
labor and overhead charges, and especially
the increasing appreciation of the value of
light.
FACTORY LIGHTING
69
Perhaps the best way to consider the oth< r
feature of good illumination will be to point
out some of the most common shortcomings
found in factory lighting.
From my own observations, the most
common defect is excessive glare and absence
of diffusion. Glare is usually caused by
bright lights in the field of vision. This
may emanate directly from the light source
or may be reflected to the eye by a glossy
surface; it can also be caused wherever
excessive contrast of intensity appears in
adjacent fields of vision. The dazzling effect
is not only unpleasant, but interferes with
seeing. Under continued exposure, eye strain
and even permanent injury to the eye may
result.
I have seen lights intended to illuminate
stairways so arranged that, on descending,
one could hardly see where to step on account
of the glare. Such conditions are conducive
to bad falls, whereas if the eyes were properly
shielded from the glare, a lower intensity
would have been ample.
The unshielded light hung over a machine
is a common source of eye fatigue. The
glare may not be very evident at first glance,
but when the workman's eyes have been
subjected to such light for a long time, dis-
comfort and inability to see result.
The workman frequently complains of
insufficient light when in reality the intensity
may be higher than is required for the work.
In case an attempt is made to meet the com-
plaint by installing a larger light, the work-
man's eyes are subjected to a still more
severe strain. The proper correction should
be to shield the light by means of a proper
reflector, and as such a reflector would tend
to direct more of the light upon the work,
the working intensity would be increased;
so in many cases it is possible to reduce the
size of the lamp, or better yet, to relocate the
lamp so as to enlarge the area illuminated.
When a light can not be removed entirely
from the field of vision, its brilliancy should
be reduced by means of diffusing globe or
reflector, so as to increase the apparent size
of the light source and reduce the contrast
between it and the background. This has
the additional advantage of reducing the
sharpness of shadows in the illumination, a
result which is of considerable importance in
rendering the various parts of a machine or
other object readily discernible.
Glare received from specular reflection of
glazed paper, desk tops, polished metal, etc.,
often induces eye trouble, headache, and other
indispositions; though the sufferers may not
be aware of the cause. The remedy is to
change the relative positions, so that the
reflected light is kept out of the eyes as much
as possible, and to enlarge the dimensions of
the light source, as already mentioned.
Another defect commonly found in in-
dustrial lighting is improper distribution.
This may be due to too wide a spacing of
lighting units. Under this condition some
parts of the room are insufficiently lighted
while other parts may have more light than
is necessary.
Improper direction of light may illuminate
the wrong side of the machine, leaving the
important parts in shadow. If the bright
parts are near the shaded ones whatever
illumination may fall upon the shaded portion
is rendered less effective by contrast.
Unsteady or flickering illumination is
always objectionable; both on account of
discomfort and the inability to see. Such
variation should always be avoided, whether
caused by the units themselves or by the
light passing through moving wheels, etc.
Since the purpose of the lighting is to
enable the operative to see, good illumination
can not be prescribed until we have some
knowledge of the use to which it is to be put.
In order to plan the lighting of a factory
properly, one should be familiar with the
processes employed, the arrangement of the
machinery and the work tables, as well as the
quality of the product manufactured. Prac-
tice has established certain methods of light-
ing which, if properly applied, are satisfactory
for the different processes of manufacture.
Thus we know approximately how much
illumination is necessary for the ordinary
grade of work as performed on a lathe, as
well as the direction desirable. As far as
possible, therefore, the experience gained in
well-lighted factories should be utilized in
planning the lighting installation. The
pamphlet entitled "Light; Its Use and
Misuse" which has been issued by the
Illuminating Engineering Society, is full of
useful suggestions in connection with the
lighting problem, while the pamphlet,
"Modern Industrial Lighting" issued by the
Commercial Section of the National Elec-
tric Light Association, endeavors to make
some specific application of this information.
A similar booklet has been issued by the
National Commercial Gas Association. Books
and articles, manufacturers' publications,
etc., furnish much useful data on this sub-
ject.
ro
GENERAL ELECTRIC REVIEW
Where extensive lighting problems are to
be solved, it is advisable to retain a com-
petent engineer with illuminating engineering
experience. However, the following com-
ments on various methods of factory lighting
will give some idea of the general practice.
The practice in factory lighting has de-
veloped along a few fairly definite lines,
which may be designated as localized light-
ing, general lighting, combined general and
localized lighting and localized general or
group lighting.
Localized lighting originated with the low
power portable or semi-portable lighting
units. These were under the control of the
individual workman, to be placed or shifted
wherever he desired. Such lamps were com-
monly used without reflectors and produced
small patches of uneven illumination, as well
as more or less glare. In many cases lighting
with these lamps is now being supplanted by
other methods, on account of the following
disadvantages. Lamp breakage is likely to
be high, and the expense for installing,
energy supply and maintenance excessive,
depending upon the conditions and arrange-
ment of work. Moreover, the attention of
the workman is called to the lighting and
much time is often lost from his regular work
in adjusting the lamp. There are, however,
certain operations which require light inside
of a small cylinder or other enclosed space;
or where very high intensities are required
over small areas, and for these no other
method is as practicable as localized lighting.
For such conditions, the lamp should be
equipped with a reflector to shield the work-
man's eyes and reflect the light in useful
directions. Localized lighting should also
be used in connection with general lighting,
as referred to later.
"General lighting" came into common
practice with high power lamps. Since with
these units economy makes a wide spacing
necessary, the best method of applying them
is to equip them with diffusing globes and
reflectors, so arranged as to distribute the
illumination as evenly as possible. Lamps
are hung high, in proportion to their power
and the intensity required, and equally
spaced throughout the room. The ideal
sought is equal intensity over the entire area.
General lighting is provided in three principal
ways, which are known as direct, indirect and
semi-indirect lighting. With direct lighting,
the larger part of the light is distributed
directly from the lighting unit to the surfaces
to be lighted. With indirect lighting, the
light source is concealed and the light thrown
upon the ceiling or wall and thence redistrib-
uted for use. With the semi-indirect light-
ing, the light source is shaded by a trans-
lucent reflector and the larger part of the
light thrown upon the ceiling or walls for
redistribution. Direct lighting, depending
upon the equipment, may have excessive
brilliancy or any degree of diffusion. It is
used to a much larger extent in factory light-
ing because factory ceilings are seldom good
reflectors. Direct lighting units are less
affected by dust accumulations. The in-
direct and semi-indirect give excellent diffu-
sion, and are often applied with good effect
in offices and drafting rooms when light
ceilings are available.
"Combined general" and "localized light-
ing" is often desirable. With this, a low
general illumination is supplied by large
units and more intense localized illumination
at particular points by low power units. The
localized lighting may be supplied con-
tinuously or temporarily as needed. For
example, in lighting automatic machinery, a
moderate illumination may be sufficient at
all times except when a machine is being
inspected, set up or adjusted, when a localized
light may be needed for the particular
machine.
"Localized general" or "group lighting"
is a recent practice which has sprung up since
a range of intermediate sizes of lighting units
has become available. This practice differs
from general lighting in that, instead of
striving for even intensity throughout the
room, lamps are arranged to give higher
intensities and correct direction of light at
the machines or tables and a lower intensity
at intermediate points. It differs from
localized lighting in being planned so as to
give some illumination, sufficient for the
needs, in all parts of the room. It is, there-
fore, an intermediate practice between the
extremes of localized and general lighting.
Its application is extending very rapidly,
since it meets effectively and economically
factory requirements for a large portion of
the ordinary processes and buildings.
Each of these various methods of lighting
has some field in which it is to be preferred
to any of the others. The selection depends
upon the character and construction of the
building, the process of manufacture, the
source of energy available and various local
conditions.
That the progress in good factory lighting
will be even more rapid in the future seems
NOTES ON THE ACTIVITIES OF THE A.I.E.E.
71
unquestionable. The interest of the public
has been indicated by the recent labor
legislation passed in New York State;
and the broad basis on which this is
being undertaken is indicated by the
fact that the Museum of Safety and
the Illuminating Engineering Society were
consulted with regard to those portions
of the law which had to do with factory
lighting.
While good factory lighting is likely to be
made compulsory by law, it is hoped that the
manufacturers will be sufficiently . awake
to their own interest to take any necessary
steps of their own initiative rather than
through compulsion.
NOTES ON THE ACTIVITIES OF THE A.I.E.E.
Standardization Rules
A new edition of the A.I.E.E. Standardiza-
tion Rules bearing the date of Dec. 1, 1914,
is now in effect and supersedes the 1914
edition. Many radical changes have been
made. Copies may be obtained from the
office of the Secretary of the A.I.E.E., 33
West 39th St., New York City.
Institute Meeting in New York, Dec. 11, 1914
The 302d meeting of the American In-
stitute of Electrical Engineers was held at
the Engineering Societies Building, 33 West
39th St., New York, on Friday, December
11th. Two papers were presented at the
meeting as follows: Insulator Depreciation
and Effect on Operation, by Mr. A. 0. Austin
and Effect of Altitude on the Spark-Over Volt-
ages of Bushings, Leads and Insulators, by
Mr. F. W. Peek, Jr.
These two papers appear in the December
issue of the Proceedings of the Institute.
LYNN SECTION
On December 2d, Prof. Elihu Thomson
addressed a meeting of about 370 members
on Wireless Telegraphy.
The lecture was illustrated with numerous
lantern diagrams. Prof. Thomson first spoke
of very early experiments by himself and
Prof. Houston, which were conducted much
before those of Hertz, and which showed
definitely the propagation of ether disturb-
ances to distances very great in proportion
to the dimensions of the apparatus employed.
He then showed by means of a series of well
chosen diagrams the close relation of wireless
to metallically-directed transmission, and
pointed out the difference between the con-
ditions obtaining in a Hertzian oscillator and
a wireless transmission. It was shown how
one-half of the figure which represents the
ether disturbance, in the case of the Hertz
experiments, is absent in wireless trans-
mission, being suppressed by the conducting
surface of the earth. The importance of the
conducting surface, principally the salt water
surface of the earth, was carefully brought
out, and the effect of dry earth masses in
obstructing the waves was described. It was
also shown how interference waves may occur
when alternative paths of different lengths
are present.
The manner in which the wireless waves
follow the earth's surface was illustrated,
and Prof. Thomson explained his theory of
why this should be as it is. It is to the effect
that the surface electric currents which are
necessarily positioned in the water surface
of the earth, compel the electrostatic and
electromagnetic waves with which they are
untied to follow the earth's curvature. The
losses due to corona were mentioned and an
explanation of daylight wireless transmission
losses was proposed, which was to the effect
that the liberation and re-absorption of irons
produced by ultra-violet ionization caused a
frittering away of the energy of the waves.
On December 14th, Mr. Howard W.
DuBois, Consulting Mining Engineer, spoke
in Burdett Hall to a large audience. The
subject was Alaska, Our Land of Midnight
Sun. The speaker outlined some of the large
hvdro-electric projects in connection with
mining operations, spoke of the Govern-
ment's new railroad policy, and made ex-
tended reference to Alaska's agricultural
possibilities. The Alaskan coal deposits and
the large scale mining operations in con-
nection with low grade gold ores and the very
high grade of copper ore in the Copper River
district were described. The lecture 'was
illustrated by 100 very beautifully colored
lantern slides taken from photographs made
by the speaker when in Alaska.
On January 6, 1915, a paper entitled,
Modern Views of Electricity will be read by
Prof. D. F. Comstock of the Massachusetts
Institute of Technology.
On February 3. 1915, Major J. A. Shipton,
United States Army, addresses the Section on a
subject which will be announced in due course.
72
GENERAL ELECTRIC REVIEW
PITTSFIELD SECTION
At the November 19th meeting of the
Pittsfield Section of the A.I.E.E. Mr. W. L.
R. Emmet read a paper, illustrated by lan-
tern slides, on The Mercury Vapor Turbine.
The main outlines of the paper have been
covered by the author in the General
Electric Review of Januarv and Februarv,
1914.
Prof. W. S. Franklin, of Lehigh University,
will lecture to the Section on January 7th,
his subject being Electric Waves.
The Section each year conducts for its
members, classes in advanced theory, the
subjects this year being, Electro-chemistry
and Electric Waves.
SCHENECTADY SECTION
The Ninth Season of the Schenectady
Section of the A.I.E.E. was opened by an
introductory address by Mr. F. C. Pratt on
October 6, 1914. This was followed by an
illustrated lecture by Mr. J. B. Taylor,
entitled, The Color of Light.
On October 20th a lecture was given by
Dr. E. J. Berg, on Differential Equations used
in the Study of Transient Phenomena.
On November 17th a large audience was
addressed by Dr. E. K. Mees, Head of the
Research Laboratory of the Eastman Kodak
Company, on the subject of Methods of Photo-
graphic Investigation.
On December 1st and 2d, Mr. J. B. Taylor
addressed the Section on The Choralcelo and
Other Electrical Musical Instruments.
Applications of electricity to the musical
field were considered briefly under three
general heads.
The use of electric motors, more as forms
of mechanical energy, in which application
the "blowing" of pipe organs is the most
extensive. Automatic pianos or orchestrions
make use of electric motors. Large solenoids
have been used to strike the bells forming
chimes in church towers.
In the second group electricity is used for
control. Here again the pipe organ is the
typical example; contacts are made on
pressing the keys, or on actuating the other
devices which energize the magnets by electro-
pneumatic valves controlling the admission
of air to the pipes. This electric control,
as distinguished from simple mechanical
connections or tubular pneumatic action,
gives quicker response, greater freedom of
arrangement of the key-board and instrument
proper, and affords the player a variety of
effects and greater ease of handling.
In the third application, of which the
choralcelo is an example, the musical tones
themselves are produced more directly by
the electric currents. The telharmonium
was referred to and described briefly. In
this instrument a "musical central station,"
consisting of 150 or more alternating current
generators of different frequencies produce
music at points more or less remote from the
center of control through the medium of
telephone receivers and wound re-enforcing
horns.
In the choralcelo the musical tones are
produced on steel strings like those in a
piano. The strings are made to vibrate
continuously by an electromagnet placed a
few millimeters away and supplied with
a pulsating current of the same frequency as
the natural vibration period of the string.
Similarly flat bars of wood or metal, of
proper length and weight to correspond
to the musical scale, are vibrated contin-
uously by the application of electro-magnets.
The variety of tonal effects available by
various combinations of strings and bars as
well as further variety from applying har-
monic frequencies was demonstrated.
The December loth meeting was devoted to
the subject of Abnormal Luminous Manifesta-
tions. The speakers and their subjects were:
"Lightning," by Prof. E. E. F. Creighton.
and "Phosphorescence and Fluorescence,"
by Mr. W. S. Andrews. Each paper was
accompanied bv experimental demonstrations.
On January^, 1915, Mr. S. H. Blake will
read a paper on Electric Illumination. Mr.
Halvorson and others will collaborate and
there will be experimental demonstrations
of an especially interesting nature.
73
FROM THE CONSULTING ENGINEERING DEPARTMENT OF THE
GENERAL ELECTRIC COMPANY
THE INFINITE DURATION OF TRANSIENTS
Many mathematical formulas relating to various
operations of electricity pertaining to transients
indicate that the transient period never ends — as
oscillatory current never ceases to oscillate, the
current resulting from suddenly applying a con-
stant voltage to a circuit with self-induction never
stops increasing in strength, etc., at least not within
finite time. Such equations involve exponential
functions of e related to time, all of which lead to
infinite time as essential to a steady electrical state.
We are told in the textbook that after a certain
time the oscillatory current has "practically dis-
appeared," that in a fraction of a second, or within
a few seconds, the difference between the rising
current in the circuit with constant impressed volt-
age and its value at infinite time is "negligible,"
etc. But they never imply that the theory of
operations is defective in the slightest degree, or at
least not in respect to the infinity of the time-
element when the steady condition is attained.
The question once arose in the mind of the
writer: Do the formulas correctly express the facts
as to time, or do conditions exist that have not been
taken account of, which, if embodied in the formulas,
would show that a steady condition will be attained
in finite time?
The possible influence of the increase in resist-
ance due to the heating effect of the current, as an
agent for bringing about a steady current flow in a
finite time, was naturally thought of. Reasoning
directly applied to the simple case of constant volt-
age applied to a circuit having only resistance and
self-induction, and indirectly by analogy derived
from other domains of physics involving the effect
of heat, at first appeared to indicate a steady cur-
rent in finite time; and likewise in the still simpler
case of a circuit with only resistance, in which latter
case, however, although the current instantly
arrives at maximum value, and thus at zero time
instead of infinite time, it is obvious that the heat-
ing effect of the current will at once begin to in-
crease the resistance and decrease the current
strength. But a little further consideration of the
problem determined an opposite conclusion in both
the above cases. As a matter of reasoning, the
reader must be left to consider the subject, if he
so chooses, in his own way.
An effort was made analytically to test the ques-
tion from the heat standpoint for the simplest case,
that of current in a circuit of simple resistance and
constant voltage:
We then have
ir = E, (1)
and the well-known empirical formula r = r0 (1 +
ah-\-(ih2), expressing the relation between resistance
and temperature of a conductor. To condense, we
will omit the last term, and write
r = r„ (1 + ah). (2)
In fact, it would make no difference in the final
result, so far as determining whether the current
becomes constant in finite time, if we wrote r—$ h.
The rate of heat generation in the circuit is Ei;
if the temperature of the surrounding medium is
hi, which we assume constant with no detriment to
the accuracy of the particular problem in hand, the
rate of heat dissipation will be expressed, with no
inaccuracy for our purpose, by -q (h — hi); whence
the rate of heat accumulation will be S [Ei —
r)(h — hi)] and we have for the equation representing
rate of temperature rise:
~=\i[Ei-n {h-h)}.
From (1) and (2)
ir0 (1+ah) =E,
or
a r0i
Differentiating (4)
di + a h di + a i dh = 0,
and substituting from (5) in (6)
Edi
dh= --
aro i'
(3)
(4)
(5)
(6)
(7)
Substituting (5) and (7) in (3), and reducing, we
finally have
Edi
[X«ijE-XSij rQ (l + a hi) i- a\S r0 Eil\i
which is of the form
Edi
-dt, (8)
(a+bi + ci2) i
Therefore,
= dt.
p M = C'dt,
J p(a+bi + ci2) i J o
whence
_£ ; :
2a°ea+bi+ci
log
2ci+b-i/-(
2ci + b + \/
which q=iac
V -Eh( '■
i'\p 2a\V
/Ji> Jo
(9)
b2 is < 0, and p =
r„ (1 + a hi)
represents the current value at zero time, when the
conductor will be at the temperature hi of the sur-
rounding medium.
From the last equation, the value of the current i
will include an exponential function of the logarith-
mic base c in respect to time. Therefore the heating
effect of the current upon the resistance of the circuit
will not cause the diminishing current to arrive at a
steady value in finite time, and obviously the same
may be said in respect to a rising current when
self-induction is present.
The limiting or steady value of i in infinite
time is
_V-q+b
2c
(10)
which in the final numerical result will have a plus
value.
Chas. L. Clarke.
74
GENERAL ELECTRIC REVIEW
QUESTION AND ANSWER SECTION
The purpose of this department of the Review is two-fold.
First, it enables all subscribers to avail themselves of the consulting service of a highly specialized
corps of engineering experts, or of such other authority as the problem may require. This service provides
for answers by mail with as little delay as possible of such questions as come within the scope of the Review.
Second, it publishes for the benefit of all Review readers questions and answers of general interest
and of educational value. When the original question deals with only one phase of an interesting subject,
the editor may feel warranted in discussing allied questions so as to provide a more complete treatment
of the whole subject.
To avoid the possibility of an incorrect or incomplete answer, the querist should be particularly careful to
include sufficient data to permit of an intelligent understanding of the situation. Address letters of inquiry to
the Editor, Question and Answer Section, General Electric Review, Schenectady, N. Y.
GROUNDING NEUTRAL: N. E. CODE RULES
(125) Fig. 1 illustrates a single-phase three-wire
distribution system using two step-down trans-
formers. What are the requirements of the
National Electrical Code with regard to ground-
ing the neutrals b and e?
Assuming that lines a, b and c are of the primary
or high-potential side of the system, the grounding
of b as shown in Fig. 1 is not specified in the National
Electrical Code. The direct grounding of the
neutral of a high-potential system is left to the dis-
cretion of the company operating the system. The
protection of high-potential lines by lightning
arresters, however, is required by the Code.
a
6
I
-Ct
-e
-r
Fig. 1
Assuming that lines d, e and /, Fig. 1, are the
low-potential secondary of the system, the National
Electrical Code requires that e must be grounded
if the voltage between e-f or e-d is less than 150
, and may be grounded if the voltage exceeds
150 volts.
Private industrial lighting or power plants are
exempt from the above rules unless the voltage of
the primary exceeds 500.
While the National Electrical Code is non-com-
mittal in regard to grounding the neutral of a high-
potential system, it insists on the use of lightning
arresters and recommends several methods for
grounding them. The Electrical Committee of the
Fire Underwriters has regarded the grounding of
electric systems as a means of reducing the risk of
shock or injury to persons, but which at the same
time tends to increase rather than reduce the tire
hazard. In view of the fact that the standard
lighting voltage is now almost universally used
by all classes of consumers, the " fire hazard " yielded
"life hazard" only in that field of a-c. and d-c.
service covered by a voltage not exceeding 150, and
beyond that voltage the grounding is optional.
Some measure of this sort was considered necessary
because of our every-day personal contact with
lighting fixtures and their wires, which, as a result
of familiarity, naturally engenders carelessness.
Since the voltage of this type of circuit usually
ranges from 100 to 125, the arbitrary value of 150
volts was chosen as the high limit in order that the
entire field of ordinary lighting circuits would be
covered, and thus a greater assurance of personal
protection be obtained. F.A.B.
INDUCTION MOTOR: ROTOR BAR INSULATION
1 126,1 If the fiber insulation in the slots between
the bars and the rotor iron of a squirrel cage
induction motor becomes charred: {1 ) Will
the motor take more power? (2) Will the speed
be affected? The question has reference to rotor
slot insulation only, the stator windings being
assumed to be in perfect condition.
The electrical characteristics of such a motor,
so far as we have been able to determine, will be
the same whether bar insulation is used or not.
The present method of placing copper bars in
the rotor slots is to use no packing or insulation
whatever. The bars and the slots are made approxi-
mately the same size, which necessitates that the
bars be forced into the slots under pressure. Before
adopting this method, machines of this type were
carefully compared in test with others of the
insulated rotor bar type. The test results of the
two types were so nearly alike that the rotors could
not be identified by them.
The whole matter resolves itself into the question:
"What will be the mechanical stability of the bars
in case their insulation is burned out?" If an
insulating packing is used and later becomes burned,
the bars might become loose in the slots and tend to
rattle, which action may ultimately break the joint
between the bars and the end rings. There are,
nevertheless, a number of motors operating in this
manner and comparatively no difficulty has been
experienced with them. By using no insulation,
there is no packing that can be destroyed and conse-
quently the bars will always remain firm in the slots.
It is to be noted that practically all motors with
so-called "slot armor" are grounded in one or more
places due to the sharp edges of the iron laminations
against the copper bars, and also that the horn
fiber is used for mechanical packing, while its value
as an insulator is purely incidental.
A.E.A.
QUESTIONS AND ANSWERS
METER TRANSFORMERS: CURRENT AND
POTENTIAL LEADS
(127) Is there any trouble likely to result from
placing the leads of both the potential and current
transformers for a polyphase meter in the same
conduit?
Provided the insulation used on the leads is suffi-
cient to withstand the voltage strain, we see no
objection to this practice, for the effect of mutual
induction of the leads upon the registration of the
polyphase meter is too small to be considered.
F.P.C.
INDUCTION MOTOR: HEATING ON UNBALANCED
POLYPHASE SUPPLY
(128) What would be the effect on the character-
istics and the heating of a two-phase, squirrel-cage
rotor, induction motor to run it from a supply
consisting of T-connected, three-to-two-phase
transformers in which a teaser tap of 92.5 per
cent is used instead of one of the correct value,
86.7 per cent?
A three-to-two-phase T transformer connection,
even when employing correctly spaced taps,
will cause a small flow of wattless current in the
transformers. If the voltages are not correct in
ratio, as when the 92.5 per cent tap is used, the
amount of this wattless current will be considerably
increased.
The effect of such a supply on the operating
characteristics of a motor cannot be definitely
stated for it will depend entirely upon the motor's
design constants. The tendency of the unbalancing,
however, will be to cause the motor to act as a
phase converter, drawing power from the lightly
loaded line and distributing it to the heavily loaded
line.
This phase-converter action will cause additional
heating of course. Considering an average polyphase
motor, this 7 per cent unbalancing may cause an
increase of 30 to 40 per cent in the temperature
of its hottest part.
A.E.A.
TRANSFORMERS: RESISTANCE MEASUREMENT
(129) What is the best and quickest method to
employ in measuring both the hot and cold
resistances of a large number of transformers
when under test?
Specify the ranges of the instruments and the
standard resistances required.
The method which has afforded the most satis-
factory results under the conditions named is that
of direct-current potential drop. In the employ-
ment of this method a steady reliable source of
direct current and a rapid but accurate means of
measuring the current and its potential drop are
necessary.
As a source of supply a storage battery will main-
tain a steadier value of current than will the usual
generator and be more completely satisfactory as a
whole. If the measuring set is to be constantly in
use, it would be better to use two sets of storage
batteries so connected by switches that while one is
discharging the other is charging. By means of a
four-pole double-throw switch this operation can be
accomplished automatically.
For measuring the current, the most convenient
method is undoubtedly that of a milli-voltmeter
used in connection with the shunts calibrated
especially for it. The location of these are
indicated by S and MV in Fig. 1. By changing the
position of plug P, any shunt may be placed in the
circuit so that the milli-voltmeter will register the
drop across it. It has been found convenient, in
measuring the resistance of the usual run of trans-
formers, to have these shunts calibrated so that 0.15
amperes through the smallest shunt and 50 amperes
through the largest shunt will produce a full-scale
deflection.
For measuring the voltage drop across the trans-
former windings a second milli-voltmeter combined
with multipliers provides the most convenient method
of reading from 1 to 50 volts. The multipliers are
represented in Fig. 1 by M, the milli-voltmeter by
MV. The key, K, serves to complete the circuit
through the milli-voltmeter and also to prevent the
liability of burning out the instrument by allowing
instantaneous trial contacts to be made.
Fig. l
It may then be convenient to arrange two or
more voltmeter circuits, as shown by /, ,2 and 8 in
Fig. 1, so wired through a three-circuit switch,
TCS, that each in turn may be connected to the
voltmeter. The transformer windings 7\, Ti and T3
may then be connected in series and the resistance
of each be measured in such quick succession as to
be made almost simultaneously. This practice
will be found particularly effective in measuring
resistances at the completion of temperature tests.
Although a milli-voltmeter may be said to be
automatic, and consequently furnishes quick results
for that reason, for potential drops of one volt or
less it becomes rather unsatisfactory. Under such
conditions a potentiometer, though slower in making
the measurements, should be used. Its superiority
lies in the fact that a dry battery of standard voltage
is bucked against the drop across the windings and,
when a balance is obtained as shown by a galva-
nometer, there is no current flowing in the so-called
"drop lines" (which are the voltage measuring
lines that are tapped to the transformer windings).
The most suitable current to hold while measur-
ing resistance appears to be from 10 to 15 per cent
of the current capacity of the windings which are
being measured; this is usually great enough to
give a good reading on the instruments and is yet
so low that the temperature of the transformer
windings will not be materially affected.
H.C.C.
IN MEMORIAM
It is with the deepest sorrow that we record
the death of Douglas S. Martin, a former
editor of the Review, which occurred in a
military hospital at Boulogne, France, on
Sunday, November 22d.
Mr. Martin was wounded by shrapnel on
the battle field at Messines near Ypres, on
November 1st. He was carried to a field
ambulance by two men in his own squadron,
and his wounds were attended to at a field
hospital. He was then taken to the hospital
at Boulogne, where it was at first thought he
would recover; but after three weeks of suffer-
ing septic poisoning de-
veloped, and on Nov.
22d he joined the ranks
of those who had " served
to the uttermost."
Mr. Martin was a
student of the Central
Technical College of
London, and after his
graduation he entered
the employ of the Brit-
ish Thomson-Houston
Company at Rugby,
England. In 1911 he
came to the United
States to accept the posi-
tion of Assistant Editor
of the General Elec-
tric Review, and
succeeded to the editor-
ship in 1912. He was
an energetic and capa-
ble writer on technical
subjects, and as an editor
his initiative and person-
ality did much to increase
the usefulness and pres-
tige of the Review.
With the object of improving his knowledge
of practical field work, particularly in regard
to high tension transmission systems, he
resigned his position as editor in July, 1913,
and went to Vancouver, B.C., from which
point he traveled south along the Pacific
coast, working in various capacities on a
number of engineering projects. During this
period, he continued his literary contributions
to the technical press, and early in 1914 re-
turned East, becoming a member of the
editorial staff of the Electrical World. He
organized the more recent statistical work of
the paper, constituting practically a new
department, of which he remained in charge
until his departure for the front. Although
only 27 years old, Mr. Martin had already
attained a high standing in his profession.
DOUGLAS S. MARTIN
Upon the outbreak of the European con-
flict, Mr. Martin, who had had considerable
military training in the yeomanry of his
country, immediately volunteered for active
service, and as he was an accomplished
horseman, a good shot, and in excellent
physical condition owing to his activity in
outdoor sports, his services were accepted
promptly. He was assigned to the 16th Lan-
cers, which was part of the first British ex-
peditionary army, so that within a very short
period he had exchanged the quiet of the
editorial office for the gruelling turmoil of the
battlefields of Flanders.
This, in a letter written
at this time, he charac-
terized as the "greatest
of good luck."
Again, in a letter dated
Monday, August 31,
1914, he says: "I got
home here last Friday
afternoon. I signed up
for Kitchener's Army
on Saturday, and took
the shilling this morn-
ing. I expect to be de-
tailed to some regiment
tomorrow and, of
course, shall be with
them till the end of the
war." He wrote again
on September 20, 1914.
"I am working myself
awfully hard with sword,
lance and rifle, so that
I can get away with
one of the early drafts.
Tired but fit."
Although the bones
of the lower leg were
broken, the knee cap injured, and the muscles
and tendons of the leg torn, in writing from
his bed in the Boulogne hospital he made
light of his wounds, representing them as
being slight.
Douglas Martin was a young man of finest
qualities; his engaging personality, finished
and able conversation, and his accomplish-
ments in vocal and instrumental music won
for him many admiring and devoted friends.
Talented, lovable, and loyal to the core,
with the promise of a brilliant future, his
untimely death is a great and irrepar-
able loss to all who knew him well. The
sincere sympathies of his many friends in
America are extended to his mother and
the other members of his family in their
bereavement.
General Electric Review
.4 MONTHLY MAGAZINE FOR ENGINEERS
w w n r>r^c r,,^ InIIM t, „„„.„_„ Associate Editor, B. M. EOFF
Manager, M. P. RICE Editor. JOHN R. HEW ETT ..... ' „ .,„.„.-
Assistant Editor, E. C. SANDERS
Subscription Rates: United States and Mexico, $2.00 per year; Canada, $2.25 per year; Foreign, $2.50 per year; payable in
advance. Remit by post-office or express money orders, bank checks or drafts, made payable to the General Electric Review,
Schenectady, N. Y.
Entered as second-class matter, March 26, 1912, at the post-office at Schenectady, N. Y., under the Act of March, 1879.
VOL. XVIII- NO. 2 by r.eJir^E&iucLpany FEBRUARY, 1915
CONTENTS
Page
Frontispiece 78
Editorial : The Paths of Progress .... ... .79
Developments in Electrical Apparatus During 1914 ... 80
By John Liston
The Absolute Zero 93
By Dr. Saul Dushman
The Towing Locomotives for the Panama Canal 1(11
By C. W. Larson
Electrophysics: Cathode Rays and their Properties 118
By J. P. Minton
The Selection of Railway Equipment 126
By J. F. Layng
A Short Method for Calculating the Starting Resistance for Shunt, Induction and Series
Motors 131
By B. W. Jones
Application of the Coolidge Tube to Metallurgical Research 134
By Dr. Wheeler P. Davey
Effect of Altitude on the Spark-Over Voltages of Bushings, Leads and Insulators . . 137
By F. W. Peek, Jr.
The Lighting of Ships 143
By L. C. Porter
Practical Experience in the Operation of Electrical Machinery 146
Current Transformer Failures; Heating and Sparking of Repulsion-Induction Motors;
Excessive Pump Output.
By E. C. Parham
Notes on the Activities of the A. I. E. E 148
From the Consulting Engineering Department of the General Electric Company . .152
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ELEOfl
THE PATHS OF PROGRESS
In our February issue we usually try to
review the progress made during the year
just past, so in this number we publish an
article that outlines the progress made in the
development of electrical apparatus during
1914. Of necessity this review must be very
incomplete as many developments are not
learned till long after their inception and
usually a considerable time elapses between
the inception and application in actual
practice. It will be noted that the progress
cited is mostly in the nature of details of
design and an increased capacity of ap-
paratus.
It would be a great mistake to surmise
that this condition of affairs foretells any
slowing down of progress in the electrical
industry. Indeed, it rather lays emphasis
on how far and how fast the art has advanced .
We should note with interest and encourage-
ment the almost daily invasion of electrical
appliances to fields of work where formerly
methods less up-to-date and less efficient were
employed. The inherent characteristics of
electrical apparatus and appliances seem
bound to extend the use of electrical ma-
chinery far beyond even its present enormous
field, as we are verifying every day the fact
that electricity furnishes the most flexible,
reliable and efficient medium for trans-
mitting energy from its source of origin to
its many points of application.
As we become more and more dependent
on machinery for our economic progress,
in just such a measure are we increasing our
dependence for future developments on those
who are perpetually increasing the efficiency
of our electrical apparatus and rendering it
more effective in its everyday applications.
In reviewing progress we are apt to cite
brilliant examples of discoveries, and to
neglect giving due credit to those responsible
for improvements in detail. In reality we,
as a community, owe a tremendous debt to
the "detail man" — the silent but perpetual
worker, whose energy year in and year out is
devoted to making improvements in details.
These improvements in details constitute a
host of inventions, many of them so small in
themselves that they seldom merit the name,
nevertheless we are becoming more and more
dependent on them for our progress.
The growth of the electrical generating unit
to 35,000 kw. has only been made possible
by an incessant study of, and improvement in,
details; and the ever increasing potentials
at which we can transmit our energy are due
to the small rather than the large advances
made in the art of design and construction.
The advantage derived by the electrical
industry as a whole and especially by the
operating fraternity from this gradual advance,
in distinction from a spasmodic development,
have been great. To cite a specific example
direct-current railway apparatus has de-
veloped from the old standard of 600 volts
through successive stages — 1200 volts, 1500
volts, 2400 volts, up to the most recent
3000-volt apparatus to be employed by the
Chicago, Milwaukee & St. Paul Railway.
As each step in advance was made new fields
for electric traction were opened by the added
economies to be secured — and old installa-
tions in many cases adopted the higher
potential apparatus as a means of effecting
more economical operation on systems that
had already been running for years. In no
case was a wholesale discarding of electrical
machinery, that still was capable of many
years' good service, made necessary, which
would have been the case had radically new
development been substituted for a gradual
improvement in details.
So many of our modern developments are
dependent upon the discovery and applica-
tion of new materials, better suited to the
severe conditions imposed by the constant
demand for higher efficiency in weight, out-
put, etc., than the materials formerly in use,
that the research work done in this direction
is constantly tying the industrial research
laboratory closer and closer to the design
office and the workshop. This phase of our
industrial life has now reached a stage where
the research laboratory must be looked upon
as an indispensable factor in the modern
manufacturing plant, if we are to keep abreast
of the times and show a satisfactory rate of
progress as each year passes.
so
GENERAL ELECTRIC REVIEW
DEVELOPMENTS IN ELECTRICAL APPARATUS DURING 1914
By John Liston
Publication Bureau, General Electric Company
It is often difficult clearly to comprehend the scope of the numerous minor changes effected in electrical
manufacture during any given period, but a knowledge of the improvements thus made is essential in defining
the yearly progress of the industry. In this article the author presents in a logical manner the improvements
made in certain important classes of apparatus. — Editor.
While some unique developments have
characterized the progress made by the
electrical industry during 1914, the general
advance has consisted very largely of improve-
ments in apparatus which had already
attained relatively high efficiencies, both
electrically and mechanically.
Although man}' of the changes effected
apparently concern only minor details of
construction, their cumulative results show
marked progress for the past year for the
electrical art as a whole. Briefly stated, there
has been achieved, refinement in design
resulting in increased efficiencies for man)'
classes of apparatus, economical concentra-
tion of large energy values in single ma-
chines, and a broadening of the field of appli-
cation based on experiment and analysis of
exhaustive operating data.
In order adequately to represent the trend
of design and manufacture, this review will
refer briefly to certain specific cases which
will serve to indicate the character and extent
of recent improvements made in General
Electric products; the data for the various
sections being segregated under apparatus
headings.
Steam Turbo-Generators
Early in the year the first of the large
horizontal Curtis steam turbine generator
sets was placed in commercial service: It
consists of a 20,000 kw. unit installed for the
Commonwealth Edison Company of Chicago,
and has already been in successful operation
for almost a year.
A still larger unit having an output of
30,000 kw., 6600 volt, 25 cycles, at 1500
r.p.m., operating normally under 185-pound
steam pressure was placed in service by the
New York Edison Company in November,
1914, having been constructed and installed
in less than a year ; a remarkably short period
for a generating set of this capacity. The
effective concentration of energy value
achieved in the construction of this machine
Fig. 1. 30,000-Kw. Steair. Turbo-Generator, New York Edison Co.
DEVELOPMENTS IN ELECTRICAL APPARATUS DURING 1914
81
is clearly indicated by the relatively small
amount of space required for its installation;
the overall dimensions being: Length, 57
ft. 4 in.; width 19 ft. 8 in.; and height 14
ft. 3 in. We hope to publish a detailed de-
scriptive article covering this installation
in an early issue of the General Electric
Review.
A number of similar machines, ranging in
capacity from 20,000 kw. to 35,000 kw., are
on order, and several of these have been
shipped, or are nearing completion in the
Schenectady Works. It should be borne in
mind that all of these large machines consist
of a single generator direct connected to and
mounted on the same bedplate with the
turbine. They constitute the largest single
generating units so far designed or con-
structed by any manufacturer, and those
already placed in service have without ex-
ception established gratifying records in
regard to reliability, steam economy and
overall efficiency.
The inherent simplicity and relatively
compact arrangement of these large turbo-
generators have made it possible to effect
their installation in remarkably brief time
when their great output is considered. As
an example of this, a 12,500 kw. set was
completely installed for the Toledo Railway
Fig. 2. 100-Watt Steam Turbo-Generator for Steam
Locomotive Lighting
& Light Company, and placed in commercial
service within fourteen days of its arrival at
Toledo.
In striking contrast to the large machines
referred to above is the diminutive turbo-
generator developed during the year for sup-
plying current for incandescent headlights
and cab lights on steam locomotives. This
set has a normal rating of 100 watts, 6 volts,
at 3600 r.p.m., and a maximum continuous
capacity of 140 watts.
A steam pressure of about 90 pounds is
maintained constantly by means of an auto-
matic regulating inlet valve, and a safety
pop valve is also provided. The turbine is
a single-stage unit direct coupled to a direct-
current compound wound generator, and by
means of a differential brake magnet coil any
fluctuations in the load are automatically
compensated for so that constant voltage is
maintained from no load to full load.
This little self-regulating set has ample
mechanical strength and has to date success-
fully withstood severe practical service tests
of more than six months duration, and it will
undoubtedly have a wider field of application
than that for which it was originally designed.
Its overall dimensions are: Length, 23 J^ in.;
width 15 in.; height, 14% in.; and its weight,
130 pounds.
Waterwheel Type Generators
Conspicuous among the improvements for
this class of apparatus is the suspension thrust
bearing designed for vertical shaft type water-
wheel generator sets, the bracket of which is
rigidly supported by the generator stator,
with the bearing carrying the entire weight
imposed by rotor, waterwheel and water
thrust. Among the larger machines for which
these thrust bearings have been provided may
be mentioned two 11,170-kv-a., 6600-volt,
60-cycle sets, operating at 180 r.p.m.; three
9000-kv-a., 12,000-volt, 40-cycle sets, operat-
ing at 185 r.p.m.; four 10,000-kv-a. units,
6600-volt, 60-cycle sets, operating at 200
r.p.m. All of these generator sets are tested
to withstand double normal speed, and the
thrust bearings of the four groups referred to
sustain respectively aggregate weights per
unit of 75, 77, 100 and 175 tons.
An indication of a recent tendency in hydro-
electric development, brought about pri-
marily through improved efficiency in water-
wheels, is the use of generators of relatively
small capacity and low speed which have
rendered it possible effectively to utilise
numerous low head water powers which here-
tofore could not be economically developed.
Among the machines which have been con-
structed to meet these conditions during the
past year, with a rating lower than 1000
kv-a., are generators having rated capacities
of 600 kv-a., at 48.5 r.p.m., down to 150
kv-a. at 180 r.p.m. Slightly larger units
have been utilized at relatively low speeds
and these may be typified by reference to
82
GENERAL ELECTRIC REVIEW
six 2000-kv-a., 6600-volt, 25-cycle sets, which
are designed for operation at 68.5 r.p.m.
Among the larger sets mav be mentioned
the two 12,000-kv-a., 6600-volt, 60-cycle
Fig. 3. 12,000-Kv-a. Waterwheel-Driven Generators,
Light & Power Co.. Grace, Utah
Utah
vertical shaft waterwheel-driven generators
placed in operation by the Utah Power &
Light Company at its main generating station
at Grace, Utah. While these machines have
been exceeded in capacity by generators of a
similar type previously installed, they have
been designed and constructed for operation
at the highest speed at which sets of this
capacity have as yet been called on to operate ;
i.e., 514 r.p.m.
In order to obviate the destructive effects
frequently produced by corona in high
potential generators and synchronous motors,
there has been devised a corona shield which
has proven thoroughly practical in operation
and has been used to a constantly increasing
extent during the past year. It consists of a
layer of tinfoil placed over the ordinary
insulation and covers that part of the coil
which is enclosed by the slot, extending far
enough beyond the slot to give ample room
for protecting, with tape and varnished cam-
bric, the projecting ends of the tinfoil covering.
The corona shields are finally connected.
by thin copper strips, with the stator lamina-
tions, through which they are effectually
grounded.
A number of direct-current generators of
exceptional capacity, designed for water-
wheel drive, have also been constructed
during the year, and at present work is near-
ing completion on a lot of 1 1 horizontal shaft
direct-current machines of this type, each
having a rated output of 5200 kw., 520 volts,
at 170 r.p.m. These exceed in size any gen-
erators of their type previously built.
Gas-Engine Driven Generators
Due to improvements in design and regu-
lation, the past year has witnessed consider-
Fig. 4. 6250-Kv-a. Waterwheel-Driven Generator Showing Construction of
Suspension Thrust Bearing Bracket
DEVELOPMENTS IN ELECTRICAL APPARATUS DURING 1914
83
able advance in the use of
60-cycle gas-engine driven
generators, and at the pres-
ent time there are nearing
completion three units of
1390 kv-a. capacity, 2300
volts, 60 cycles, arranged
for operation at 116 r.p.m.
They will be utilized by
the Monongahela Traction
Company of Fairmont, West
Virginia, and are the largest
60-cycle generators designed
for gas-engine drive. Other
and larger units had, how-
ever, been constructed prior
to 1914 for 25-cycle opera-
tion; the rating for these
machines, which were built
for the Bethlehem Steel
Company, being 3125 kv-a.
An equitable basis of
guarantee for the parallel
operation of both gas-engine
and steam-engine driven
generators has been devel-
Fig. 6.
5. 5200-Kw., 250- Volt Direct Current Generator
for Waterwheel Drive
the General Electric Company
generally accepted, should prove
oped by
which, if c
of considerable value to the builders of engines
and generators, and to the operator.
2250-Kw. Synchronous Converter with Synchronous
Booster, Boston Edison Co.
This guarantee is based largely on the
determination of the natural period of the
generator in relation to the various character-
istics of the complete unit, including flywheel
and the operating features of engines and
governors, and presents in a logical manner
the data necessary for an accurate pre-
determination of results.
Synchronous Converters
The advance in this class of apparatus has
been marked chiefly by the increased unit
capacity of 60-cycle machines produced; a
representative installation consisting of two
2250-kw., 225/275-volt converters equipped
with synchronous boosters has been con-
structed for the Boston Edison Company.
These machines have approximately 50 per
cent greater capacity than any 60-cycle
machines of this type heretofore developed,
and their successful operation has resulted in
the adoption of still larger units.
As evidence of this a single order was
received for eighteen 500-volt, 60-cycle syn-
chronous converters with commutating poles,
having an output of 2500 kw. each ; an aggre-
gate rating of 45,000 kw. They are to date
the largest 60-cycle synchronous converters.
This record order has already been partially
filled, and the machines will be installed at
Messine, N. Y., for the Aluminum Company
of Americp..
84
GENERAL ELECTRIC REVIEW
The equipment of synchronous converters
with synchronous boosters which are integral
parts of the complete machine, together with
an arrangement for automatic control, con-
stitutes a most important improvement in
synchronous converter operation and insures
a positive and automatic adjustment of the
direct-current voltage. This is accomplished
through control of the field excitation of
synchronous converters provided with com-
mutating poles, and insures correct excitation
at all loads and voltages.
Synchronous Condensers
A horizontal shaft 6000-kv-a., 50-cycle,
500-r.p.m. synchronous condenser constructed
for the Southern California Edison Company
of Los Angeles is of unusual interest due to
the fact that it was designed for operation
on a 16,500-volt line; no machines of this
type having previously been built for poten-
tials exceeding 6600 volts.
In addition to the precautions necessary for
insulation against this unusual potential,
special efforts were made in designing the
machine to minimize the losses, and as a
result there was produced a synchronous
condenser of vers- high efficiency which is
utilized for power-factor correction. It is
self-starting by means of a compensator and
requires less than half its rated kilovolt-
amperes for starting.
Phase Advancers
While synchronous condensers are ordi-
narily applied for improving the power-factor
of a system, the phase advancer is designed
primarily for improving the power-factor of
individual induction motors, although in
special cases it is capable of wider application.
This machine, which has been made com-
mercially practicable within the past year,
is described in the June, 1914, General
Electric Review, but its characteristics
may be briefly outlined as follows:
The phase advancer stands in the same
relation to an induction motor as an exciter
does to a synchronous motor. However,
for the induction motor, continuous current
can not be used for the magnetizing current
in the secondary because the motor slips
under load. The magnetizing current must
be a polyphase current of low frequency
which corresponds in each instance to the
slip of the induction motor.
The phase advancer consists of a con-
tinuous-current drum armature with a com-
mutator having three brush studs per pair
of poles displaced relatively to one another
by 120 electrical degrees. The stator merely
consists of a frame with the laminations
assembled but having no slots or windings.
The phase advancer is direct connected to a
small squirrel cage constant speed induction
motor. The power necessary to drive the
phase advancer is only that required to supply
the friction windage and hysteresis losses and
is therefore comparatively small, i.e., about
one h.p. for a 600-h.p. 2200-volt induction
motor. The copper losses are provided by
the main induction motor rotor.
Frequency Changers
A notable frequency changer set was
recently installed to interconnect the Boston
Edison and Boston Elevated systems. This
is a horizontal shaft set, the 60-cycle unit
being rated at 9500 kv-a., 13,800 volts, and
the 25-cycle unit rated at 9000 kv-a., 13,200
volts; it operates at 300 r.p.m. and is rever-
sible. It is totally enclosed and provided
with inlet for external air supply which dis-
charges into the station. One frame is ad-
justable so that if the equipment is duplicated
Fig. 7. 7500-Kv-a., 12.000 24,000 Y, Three-Phase
Water-Cooled Core Type Transformer
both sets may be arranged equally to share
the load, and in order to facilitate inspection
or to make repairs each frame is arranged
to move on steel rollers parallel to the shaft.
This is the largest frequency changer set
DEVELOPMENTS IN ELECTRICAL APPARATUS DURING 1914
85
produced by the General Electric Company,
and is probably the largest machine of this
type in service today.
Transformers
Prior to 1914 the largest core type trans-
formers produced by the General Electric
Company did not exceed 2000 kv-a. in rated
capacity, but during the year the maximum
rating was carried up to 7500 kv-a.
The maximum rating of single-phase water-
cooled shell type transformers has also been
increased by the construction of four units of
8333-kv-a. capacity.
There has been a marked reduction in
interruption to service in transformers of
recent design as they are now capable of
withstanding momentary short circuits under
sustained primary voltage without injury to
the coils. This has been accomplished
largely through changes in the grouping of the
coils and working to higher inherent re-
actance.
A feature of unusual interest for the year
is the development of a combination trans-
of normal load without the circulation of
water and without exceeding its specified tem-
perature rise. On the other hand, this trans-
former may be designed for normal operation
as a self-cooled unit, and be provided with
Fig. 8. 8333-Kv-a. Single-Phase Water-Cooled Shell
Type Transformer
former which may be operated either self-
cooled or water-cooled. It may be designed
for normal operation with water circulated
through the cooling coils, in which case it
may also be safely operated at 50 per cent
Fig. 9. 1250-Kv-a. Combination Self-Cooled-Water-
Cooled Outdoor Transformer
the necessary cooling coils which, when
utilized, permit operation efficiently at 50
per cent above the normal capacity. The
economical advantages of such transformers
are obvious, expecially for localities where
the purchasing rate of water is high and the
transformer is fully loaded only part of the
time. This design also provides a factor of
safety in case of interruption in the water
supply, in which event the apparatus may
still be operated at partial load instead of
being shut down.
Feeder Regulators
Early in 1914 a single order for 100 feeder
regulators was received from the Common-
wealth Edison Company, Chicago, 111. These
regulators are rated at 36 kv-a., 60 cycle, 150
amp., and are of the automatically operated
induction type, designed for 2400-volt pri-
mary and 240-volt secondary. When placed
in service they are utilized for maintaining
constant voltage on alternating-current
feeders having an aggregate capacity of
36,000 kv-a. Prior to the placing of this,
the largest single order for this type of ap-
S6
GENERAL ELECTRIC REVIEW
paratus, the Commonwealth Edison Company
had already installed approximately 300
General Electric regulators for similar ser-
vice, making a notable aggregate equipment
of 400 units of this type.
Reactances
With the steady growth in the size of power
plants and distribution systems, there has
arisen among operators a fuller conception
of the practical value of providing ample
protective equipment, such as voltage reduc-
ing devices for cutting down the station volt-
age under short circuiting conditions, arcing
ground suppressors for short circuiting arcs
caused by grounded phases on delta connected
transmission systems, and the recently de-
veloped and improved current limiting react-
ances. A fuller appreciation of such devices
is amply attested by a continual increase in
the number of propositions for power station
equipment which include this class of ap-
paratus.
The reactance developed by the General
Electric Company has been improved to a
considerable extent during the past year and
the changes made have been based largely
on the experience gained in numerous applica-
tions of the earlier types utilized for the pro-
tection of feeder lines. In order to facilitate
calculations on the equipment necessary to
meet the requirements of power systems hav-
ing widely varying operating
conditions and capacities, these
reactances are now made in
three distinct forms.
Electric Railways
The decision of the Chicago,
.Milwaukee & St. Paul Rail-
way Company to electrify its
mountain grade divisions in
Montana marked one of the
most important steps ever
taken in steam road electri-
fication. The order for high-
voltage direct-current electrical
equipment placed with the General Electric
Company includes nine freight and three
passenger locomotives, weighing approxi-
mately 260 tons each, all equipped for regen-
erative braking; 10 three-unit synchronous
motor-generator sets with transformers; and
switching apparatus for the equipment of
four substations totaling 17,000 kw. in ca-
pacity. Overhead line material is also in-
cluded for the initial electrification of 113
miles, or 168 miles on a single track basis.
The railroad company has plans under way
for the electrical operation of the entire 440
miles of main line transcontinental road
between Avery, Idaho and Harlowton, Mon-
tana.*
In the selection of 3000 volts direct current
as the operating voltage, this road was
doubtless influenced to a large extent by the
attractive performance of the 2400-volt
direct-current equipment of the Butte, Ana-
conda & Pacific Railway, t
An interesting railway is being constructed
by the Bethlehem-Chile Mines Company in
Tofo, Chile. This road will be used for con-
veying iron ore from the mines about 2000
feet above the sea level, a distance of about,
15 miles to the Port of Cruz Grande on the
coast. The equipment of this road will
include three 110-ton, 2400-volt direct-cur-
rent electric locomotives which will be sup-
plied by two three-unit 1000-kw., 2400-volt
synchronous motor-generator sets. This sub-
station will be fed over a 22,000-volt trans-
mission line from a main power house which
will contain three 3500-kv-a. and one 300-
kv-a. Curtis steam turbines.
The average grade on this road is about
three per cent and the locomotives are to be
equipped for regenerative control feeding
power back into the system on the down
grades.
Work is proceeding rapidly on two other
Fig. 10. Motor-Generator Set for Canadian Northern Railway. 2100-H.P.,
11,000-Volt MotorlDriving Two 750-Kw., 1200-Volt DC. Gener-
ators Connectedlin Series~for~2400-Volt Railway Service
2400-volt railway electrifications, the Michi-
gan Railway Company and the Canadian
Northern Railway, which are expected to be
in commercial operation early in 1915.
Another important endorsement of the
high voltage direct-current system is the
decision of the Ontario Hydro-Electric Power
Company to employ 1500 volts direct current
for the electrification of the London & Port
* See General Electric Review. Nov.. 1914.
t See General Electric Review, Jan.. 1915.
DEVELOPMENTS IN ELECTRICAL APPARATUS DURING 1914
Stanley Railway.* Orders have been placed
for the initial rolling stock, including three
60-ton electric locomotives, five four-motor
multiple unit cars, and four trail cars. This
road is about 24 miles long and connects
Port Stanley on Lake Erie with London,
Ontario. The electrification of this
steam road division is the beginning
of an extensive system owned and
operated by the municipalities in
this section.
High-voltage, direct-current
equipment has also been ordered
during the year for a number of other
interurban railways, including the
following: Chicago, Milwaukee &
St. Paul, (Great Falls Electrifica-
tion), 1500 volts; Imperial Railways
of Japan, 1200 volts; Toronto Sub-
urban Railway, Canada, 1500 volts;
Willamette Vallev Southern Rail-
way, 1200 volts.
The Pacific Electric Railway has
ordered 96 ventilated motors for
new cars on the Los Angeles-San
Bernardino-Riverside division.
The principle of ventilation as employed
on all modern General Electric motors "has
been adopted by many railways in all parts
of the world. Motors of this type have been
selected by the New York Municipal Railway
Company for the operation of 200 new cars
in the new Brooklyn Subway, and 334 motors
of a similar type have also been ordered by the
Northwestern Elevated Railway of Chicago.
cars. Four-hundred of these motors are being
placed in service on the Pittsburgh Railways.
Mine Locomotives
All of the mine locomotives manufactured
by the General Electric Company in 1914 were
Fig. 11. GE-248-A Railway Motor Adopted for New
York Municipal Railways
The Chicago Surface lines are using 200
GE-242 ventilated motors which were ordered
during the year, and delivery is being made
on an additional order for 456 of these motors.
The GE-247 is a new ventilated type railway
motor designed for 24-inch wheel low floor city
* See General Electric Review Jan., 1915.
Fig. 12. 50-Ton 1200-Volt Locomotive for Willamette Valley Southern Railway
provided with commutating pole motors and
ball bearings as standard equipment, and
the operating records of those placed in service
during the year show that these improve-
ments have reduced the number of interrup-
tions to service and have resulted in de-
creased maintenance costs.
The increasing output of many mines has
rendered it necessary to equip them with
locomotives of relatively large capacity,
capable of handling heavy trips over steep
grades and for long hauls. For this class of
service there have been built a number of
three-motor, 15- and 20-ton locomotives.
The 20-ton unit combines some unusual
features in design and construction: The
body is made of rolled steel, each side frame
being cut from a solid rolled steel slab, while
steel slabs in conjunction with steel channels
are used for the end frames. The three
driving motors are each rated at 85 h.p. and
are of the split frame type. These particular
locomotives were built for 42-inch gauge, but
the same construction and capacity can be
utilized for a minimum of 36-inch gauge.
Up-to-date practice in haulage locomotives
may be represented by reference to the con-
structive features of a typical 16-ton single-
truck three-motor unit. In this, the latest
type of industrial locomotive, the truck frame
is built of steel throughout, both the sides and
ends being cut from single pieces of solid
slab. The platform is built of steel channels
88
GENERAL ELECTRIC REVIEW
and plates, and the cab of steel sheets. It is
a standard gauge machine and, in so far as
possible, all details have been developed
along the lines of standard railway practice,
the wheels, axles, journal boxes, brake beams,
brake shoes and couplings being all in accord-
Fig. 13. 20-Ton, Three-Motor Mine Locomotive, 42-In. Gauge
ance with MCB requirements. It is driven
by two 60-h.p., 500-volt motors and equipped
with straight air brakes.
An interesting type of locomotive has also
been constructed for service at the mines of
the Braden Copper Company in Chile, S. A.
It is a 25-ton double-truck machine for 30-
inch gauge, and has an overall height of only
seven and one-half feet. The four driving
motors are each rated at 45 h.p., 250 volts,
multiple unit control and automatic air
brakes being also included in the equipment.
It is probable that this locomotive is the
heaviest and narrowest gauge, and has the
lowest overall height of any machine of this
type ever built.
There has been a definite increased demand
for the storage battery type of locomotive
for gathering work, as it has been demon-
strated that in this service each locomotive
will effectively displace at least two or three
mules. Heavy units are not as a rule re-
quired and the locomotives of this class so
far provided have been rated at from three to
seven tons. Most of these are of the straight
storage battery type, but a limited number
have, in addition, been equipped so that they
can operate from a trolley wire when in the
main headings of a mine. The advantages
of this arrangement are obvious in that bv
means of a small self-contained motor-gen-
erator set, the battery may be automaticallv
charged while the locomotive is running on
the trolley. When the locomotive is working
in the rooms, gathering the cars, a varying
percentage of the battery charge will be con-
sumed, but as soon as the locomotive is again
operated on the trolley, these losses are auto-
matically compensated for and with this dual
system of operation the battery need never
be entirely discharged and if space limitations
are severe it permits the use of a smaller
battery than would otherwise be necessary.
A representative machine of this type has
been in operation in a West Virginia mine for
a period of about four months. It runs on a
42-inch gauge track and its overall height
does not exceed 30 inches.
Mine Hoists
The largest induction motor shaft hoist
equipment in America was placed in operation
in November, 1914, at Lansford, Pa., for the
Lehigh Coal & Navigation Company. The
driving motor is rated at 750 h.p., 300 r.p.m.,
three-phase, 25 cycle, and drives through a
single reduction gear.
Positive control of the hoisting speed is
secured by means of an improved type of
liquid rheostat and high tension air break
contactors; the motor circuit being 2300
volts. This hoist serves a 600-ft. vertical
shaft hoisting 11,500 pounds per trip at the
rate of 90 trips per hour, with a maximum
rope speed of approximately 1600 feet per
minute.
The liquid rheostat referred to above was
developed primarily for mine hoist service
and insures safe operation at quick reversal.
It employs two sets of fixed electrodes at
different elevations; one set being widely
spaced, while the other set has large electrode
areas and has small spacing in order to obtain
a very low final slip. The two sets of elec-
trodes are connected in parallel after the
electrolyte has reached a certain level corre-
sponding to a predetermined decrease in rotor
Fig. 14. Combination Storage Battery and Trolley Type Mine
Locomotive with Platform Removed to Show
Internal Arrangement
voltage. All parts of the rheostat itself are
stationary, thus insuring absolute reliability;
the electrolyte level being varied through the
operation of a movable weir and a small
motor-driven pump.
DEVELOPMENTS IN ELECTRICAL APPARATUS DURING 1914
89
Steel Mills
The tendency toward the exclusive use of
electricity for all power application in modern
rolling mills is indicated by the equipment
selected by the Bethlehem Steel Company for
its new plant at South Bethlehem. In equip-
ping the new buildings no steam drive or
steam auxiliaries have been provided. The
electrical energy is generated with gas engine
drive and for power application three-phase,
25-cycle, 6600-volt induction motors have
been used throughout. In this new plant
Electric Furnaces
The fact that the electric furnace offers a
compact, reliable and economical method of
manufacturing crucible quality steel has
now become more generally recognized among
iron and steel founders and, in consequence,
there has been an appreciable increase in the
number and size of the equipments recently
installed or in process of construction, and a
concomitant improvement in details tending
toward improved efficiency.
Perhaps the most striking advance has been
Fig. 15. 750-H.P. Induction Motor Driving Mine Hoist
there are General Electric motors ranging
from 350 h.p. to 3000 h.p. both of the single-
speed and two-speed pole changing type, the
aggregate rating being approximately 12,000
h.p.
In order to provide speed control for in-
duction motors which will meet the variable
load requirements of rolling mills a speed
regulating set applicable for this class of
work has been developed, and during the
year has been practically applied by the
American Iron & Steel Company, Penn-
sylvania Steel Company, Forged Steel Wheel
Company and Union Rolling Mills. These
speed regulating sets enable the induction
motor to carry varying loads at constant
speed, giving it for all practical purposes the
speed characteristics of the shunt wound
direct-current motor, while at the same time
retaining the simple and strong mechanical
features of the induction motor.
in the induction type of furnace as, prior to
1914, the largest unit of this type in the
United States had a capacity of only two
tons, whereas during the year this was carried
to 20 tons, two units having been completed.
This 20-ton furnace is of the two-ring type
and in operation utilizes single-phase current
of five-cycle frequency at 5000 volts, and it
has been necessary to supply a special motor-
generator set in connection with it, consisting
of a two-pole single-phase generator having
an output of 4000 kv-a. at 5000 volts, five
cycles, which is direct driven by a three-phase,
25-cycle, 2300-volt synchronous motor.
The exceptional size of the furnace, which
is the largest of any type in the United States,
used for refining steel, is best illustrated by
reference to the core and coils, which ele-
ments for each furnace have a weight of
approximately 60 tons. In operation the
furnace rings are charged with molten metal,
90
GENERAL ELECTRIC REVIEW
every part of which is thereby subjected to
intense, uniform and positively controlled
heat, and is then poured off after a treatment
lasting from 60 to 90 minutes.
For the arc type of electric furnace special
forms of transformers and auxiliary equip-
ment have been designed, together with a
reliable system of automatic control which is
particularly interesting to the practical oper-
ator, in that, except for a short period after
starting the furnace, a constant power input
is maintained at such a value as may be pre-
determined by the operator.
The resistance type of furnace, which
utilizes heat generated by passing the electric
current through a resistor composed of
Fig. 16.
Arrangement of Core and Coils for 20-Ton,
Two-Ring Induction Furnace
foundry coke, with auxiliary heating from a
carborundum arch which radiates heat down-
ward on the charge, has also been provided
with a simple current relay control which
insures the maintenance of a constant tem-
perature over a range of approximately 600
to 1300 deg. C.
Switching Apparatus
There are numerous localities remote from
low-voltage distribution, but accessible to
high-voltage transmission lines, where the
small rural substation can be economically
utilized for the distribution of electrical
energy in capacities as low as 3 kv-a. Under
proper conditions a market of this kind offers
the operating company a sound financial
basis for sendee, providing that the equip-
ment can be installed at a reasonable price,
and can be depended upon to operate with
low maintenance expense. The great extent
of the field for this class of electrical equip-
ment is indicated by numerous successful
substations in small towns, farms, mines and
quarries, pumping outfits, small isolated
manufacturing plants and various contracting
and construction jobs.
Experience has shown that to avoid inter-
ruptions to service the equipment supplied
to meet the operating conditions indicated
above must be proof against damage from the
weather and, in order to provide this protec-
tion, all operating parts of switching appara-
tus supplied by the General Electric Com-
pany, which are liable to rust, are given a
very effective protective treatment.
While considerable work has been ac-
complished in the effective equipment of
Fig. 17. Resistance Type Annealing Furnace with Control
Panel — Later Forms of this Furnace are Sheathed
with Cast Iron Plates
rural substations prior to 1914, the activities
of the past year have been along the line of
standardizing apparatus suitable for use in
connection with various transmission volt-
ages, and in improving or redesigning standard
apparatus previously utilized. The complete
standardized line now available has been
proven reliable in service and is designed to
minimize danger to the equipment in case of
disturbance on the main line, and while it
is proof against injury to itself or other
apparatus, it does not require skilled attend-
ance. Furthermore, it is very largely semi-
portable, so that it can be installed or re-
moved promptly and economically, and the
fact that the entire line .has been standard-
ized permits an accurate predetermination
of the cost of a rural substation when the
operating conditions and service required
are known. It also makes it possible to secure
for the small community many of the econo-
mies inherent in high tension transmission.
DEVELOPMENTS IN ELECTRICAL APPARATUS DURING 1914
91
Fig. 18.
2500-Volt, Three-Phase Switch House
for Outdoor Installation
A new type of solenoid-operated manhole
oil switch has been developed which is entirely
self-contained, and gives the advantage of
remote control in that the switch may be
operated from a distance with absolute
reliability, even if the switch compartment is
completely flooded. The compact arrange-
ment and water-tight construction of this
oil switch render it specially valuable for
manhole service, or for use in other locations
liable to flood.
A number of notably large circuit breakers
have recentlv been constructed, the maximum
Fig. 19. 2500-Volt, Three-Phase Switch House Showing
Inside View with Meter Panel Removed
capacity provided for being 20,000 amperes.
This type of breaker is operated by a single-
coil solenoid with the usual automatic over-
load trip, and has, in addition, a shunt trip
coil plunger which acts directly on the cir-
cuit breaker locking latch, instead of on a
trip on the solenoid.
A new and ingenious electrostatic syn-
chronism indicator has been developed. The
instrument case resembles an ordinary round
pattern switchboard instrument, and inside
of this are receptacles for holding three
special glowers which project through holes
in the case cover. All connections from the
line to the device are made through con-
densers which consist of suspension insulators
, ™_ ...
a
Fig. 20. Arrangement of Switching Apparatus and Three Single -
Phase Transformers for Supplying 150 kv-a. at 2300 Volts
from a Three-Phase 35,000- Volt Transmission Line
«!
Fig. 21. Electrostatic Synchronism Indicator
92
GENERAL ELECTRIC REVIEW
having an insulation equal to that used on the
line.
Normally, the glowers have the appearance
of ordinary spherical frosted incandescent
lamp bulbs, but when there is a proper
difference of potential across the terminals,
they glow with a reddish hue, due to the use
of a special gas.
crease in size and modifications in the shape
of the lamp which were found advisable due
to the concentration in a single incandescent
unit of the large candle-powers which the
high efficiency type of lamp permitted, but
largely because of the increased temperatures
experienced in their operation.
During the past year these lamps have been
successfully adopted for street lighting in a
number of cities, and for series operation
they have been provided with a new type of
compensator having efficiencies of from 93
to 95 per cent with power-factors of from 97
to 98 per cent.
There has also been developed by the
General Electric Company a prismatic re-
fractor which, in combination with suitable
Fig. 22. Compensator Type Incandescent Lighting Unit
Equipped with Concentric Reflector and
Prismatic Refractor
-—'
— s— ^_
m.
A\^>
>-£*"* Dlt ' TVk*^^\^\^^)(
>//%
v\ 7-i
"J^K
vX/
Fig. 23. Characteristic Distribution Curve of the Above
Unit with 600 c-p. Mazda Series Lamp
The instrument can be operated on a line
having a pressure as low as 13,200 volts, and
can be made suitable for practically any
voltage above this by simply cutting in the
proper number of insulators.
Lighting
The commercial application of the high
efficiency mazda lamp involved the design
of a complete new line of fixtures. These
were rendered necessary, partlv bv the in-
Fig. 24. Luminous Arc Lamp with Prismatic Refractor
reflectors, insures a more effective control of
the light distribution than any type of globe
yet developed.
For street car headlights a new line of con-
centrated filament incandescent lamp has
been provided, and a large percentage of
those now in service are equipped with a new
and highly efficient form of glass parabolic
reflector.
The improved efficiencies which have been
obtained during the year in luminous arc
lamps have been due very largely to the pro-
duction of an electrode which, for a given
current consumption, produces from 30 to
50 per cent more light than any electrode
previously utilized.
This has been accomplished through ex-
haustive research work resulting in new
electrode compositions, containing a larger
proportion of titanium than older electrodes.
The use of this element in suitable combina-
tion enables this type of arc lamp to give
THE ABSOLUTE ZERO
93
the highest illumination efficiencies yet ob-
tained by any commercial lamp. In addition
to this the arc lamp mechanism has been
simplified and the light distribution improved
by the adoption of a prismatic refractor
similar in principle to that designed for the
high efficiency mazda lamp, but differing
from it in form.
These cumulative improvements have re-
sulted in the production of a new line of 5-
ampere luminous arc lamps which give
practically the same illuminating values
formerly obtained with 6.6-ampere lamps. A
5-ampere series rectifier is also available for
operation in connection with the new lamps.
The vast number and varied character of
the developments in the modern electrical
industries renders it exceedingly difficult
to give in a necessarily limited article, a truly
comprehensive description of the progress
made in any year, but in the foregoing the
writer has endeavored to show the general
trend of the changes inaugurated in the manu-
facture of electrical apparatus, by reference
to a limited number of specific examples and,
in conclusion, it may be reiterated that most
of the equipments cited have already been
subjected to the stresses of commercial ser-
vice and have successfully withstood the
pragmatic test.
THE ABSOLUTE ZERO
Part I.
By Dr. Saul Dushman
Research Laboratory, General Electric Company
During the last three or four years a large number of important investigations have been carried out on the
properties of substances at extremely low temperatures. The results obtained have been intensely interesting,
both from a practical and theoretical point of view. In the first part of the paper the author discusses the
logical foundations of our present temperature scale and the various methods that have been used to attain
extremely low temperatures; while in the next issue he will deal with the behavior of different substances at
low temperatures and point out the important bearing of these investigations. The original conception of tem-
perature was simply that of denoting the state of heat or cold of a body. Subsequently, the necessity arose for
quantitatively comparing different states of heat or cold. — Editor.
Conception of Temperature
Early conceptions of temperature, heat,
cold, and quantity of heat were very confused.
There was a great deal of groping in the dark
before the idea of measuring heat quantita-
tively was arrived at and the difference between
quantity of heat and temperature was under-
stood. It was generally known that the
volume of a body altered with its state of
heat or cold and so there followed the idea
of using a volume of a mercury or a gas
column, placed in contact with the body, as
a mode of determining its temperature.
Having noticed that there is no change
in volume at the melting point of ice and
the boiling point of water (at constant
atmospheric pressure) it was also agreed to
use these two fixed points for the graduation
of thermometers.
There arose, however, the necessity of
indicating temperatures above and below
these two fixed points, and the question also
arose as to the manner in which the scale
between the two fixed points should be
divided.
On comparing the expansion of different
substances it was observed that the expansion
in most cases is approximately linear. Thus
when we use as thermometric substance a
mercury column and divide the volume
between the two fixed points into one hundred
equal divisions, we find that whether we take
air, alcohol, or glass, each of these substances
has an approximately constant coefficient
of expansion throughout the same range of
temperatures. It thus became possible to
extend the scale of temperatures below the
freezing point of water and above its boiling
point.
A further generalization was observed.
All gases expand about — — of their volume
at the melting point of ice when the tem-
perature is raised to that of boiling water.
Here then we have a property which is
independent of the nature of the substance
used. What could be more natural than the
decision to use a gas as standard thermo-
metric substance?
94
GENERAL ELECTRIC REVIEW
Gas Thermometry
It is necessary to distinguish in this con-
nection between the gas thermometer at
constant pressure and that at constant
volume. Denoting the temperature on the
Centigrade scale by t, and the corresponding
pressure and volume by Pt and V respec-
tively, the temperature is denned as follows:
t = 273
at constant volume
at constant pressure
where P0 and V'0 denote the pressure and
volume respectively at the freezing point of
water.
p
Now if we plot / as abscissa and ■=■ as
l o
ordinate, we find that at t = 273, PtjP0 be-
Vt
comes equal to zero; similarly j? becomes
equal to zero at t=273. In other words, on
the constant volume thermometer, the pres-
sure vanishes at a temperature of — 273 deg.
C, while on the constant pressure ther-
mometer, the volume vanishes at this tem-
perature. Here then we apparently reach a
non ultra plus in the region of low tem-
peratures. We might, therefore, be justified
in designating this lowest temperature as an
absolute zero.
At first glance, the conclusion based on
the above considerations that there must
exist a lower limit of temperatures might
seem rather arbitrary. Why choose -273
deg. C. any more than -5500 deg. C, which
corresponds to the temperature at which a
volume of mercury would vanish? (The
coefficient of expansion of mercury is --,.,.
per degree Centigrade.) When it is, however,
considered that all substances in the gaseous
state exhibit practically the same coefficient
of expansion, and furthermore that gases
probably represent the simplest state in
which matter can be obtained — when these
facts are duly considered, it is seen that the
choice of -273 deg. C. as the absolute zero
is not so arbitrary.
There is, however, a much more cogent
reason for concluding that an absolute zero
actually exists and that it coincides with the
absolute zero as defined on the ideal gas
thermometer.
Absolute Scale of Temperature
It was first pointed out by Lord Kelvin
that the scale of the ideal gas thermometer
coincides with another scale of temperatures
which can be based upon the second law of
thermodynamics and is therefore independent
of the properties of any particular substance.
In its most general form this law states
that for the conversion of energy in the form
of heat into mechanical energy there is
required a difference in temperature; and the
maximum fraction of the total heat energy
at any given temperature that is convertible
into work depends upon the available tem-
perature drop only and not upon the nature
of the engine used for the operation. It is
for this reason that we cannot withdraw heat
from the ocean and convert it into mechanical
work. The steam engine, as well known, is
a direct application of the above principle.
The greater the difference in temperatures of
boiler and condenser, the greater the effi-
ciency.
Let us denote by Q\ the amount of heat
absorbed at the higher temperature, Qu by
any sort of reversible engine that is capable
of converting heat into work. For our
present purpose we do not need to worry
about the exact thermometric scale which
we adopt to measure 0. Let 02 denote the
temperature of condenser and Q* the heat
given out by the engine at this temperature.
The difference 0\ — Qi corresponds to the
amount' of heat converted into work, and the
fraction (Qi — Qi)!Qi measures, therefore, the
efficiency of the process.
According to the second law of ther-
modynamics, this efficiency depends upon the
temperatures 0i and 02, that is, upon the tem-
peratures of the hot and cold reservoirs. We
can assign to B\ and 02 such values that they
represent the ratio of the quantities of heat
Q\ and Q2; that is, we write
Q* = 02
01 Ox
This manner of reckoning temperatures
immediately leads us to the notion of an
absolute zero of temperature, for the equation
can be written in the form
At 02 = 0, all the heat Qi taken in from the
hot reservoir will be converted into work,
and since we cannot imagine any better
efficiency than this, it- is impossible for 0?
to be negative. "Thus 02 = O is the lowest
temperature conceivable. The zero on this
scale is consequently an absolute zero of
temperature independent of the properties
of any particular substance, for when the
THE ABSOLUTE ZERO
95
efficiency of one reversible engine is unity,
the efficiency of every other reversible engine
working between the same source and con-
denser will also be unity, and hence if 0 is
zero for one substance, it will also be zero
for every other. This zero is therefore ab-
solute."
We are still at liberty to choose the size
of a degree on this scale. If we choose the
new scale so that there may be 100 degrees
between the freezing and boiling points of
water, we find that the absolute zero is 273
degrees below the freezing point of water.
Definition of Ideal Gas
The scale of an ideal gas thermometer is
therefore identical with the absolute scale
defined in the above manner. In this con-
nection we may define an ideal gas as "one
which follows Boyle's law and in which a
free expansion, with no external work, would
cause no change in temperature * * * * No
real gas satisfies these conditions exactly,
but all the common thermometric gases, as
they are used in gas thermometers, do satisfy
them approximately. Hence it is that the
ordinary gas scales and the thermodynamic
scale are all approximately the same, and the
problem of finding the mutual relations of the
various scales is reduced to the investigation
of the departures of the actual gases from the
ideal state and the computation of corrections
for-the departures."*
The kinetic theory of gases enables us
probably to obtain a clearer conception of
what is actually meant by an "ideal gas."
According to this theory trie pressure exerted
by any gas against the walls of the containing
vessel is due to bombardment by a large
number of infinitesimally small particles
(molecules) which are in rapid motion. The
pressure therefore increases with the number
of molecules per unit volume and their aver-
age velocity. The volume actually occupied
by the molecules themselves is assumed to be
infinitesimal as compared with the volume
in which they are present. The collisions
between the molecules must be perfectly
elastic, otherwise the energy of the gas would
tend to decrease indefinitely. Heat applied
to the gas is converted into kinetic energy
of the molecules; thus the average kinetic
energy forms a measure of the temperature
of the gas.
When the gas expands, heat is absorbed
because the molecules have to perform a
certain amount of work against the external
*E. Buckingham, Bull. Bur. Standards, 3, 237 (1907).
Reprint No. 57.
pressure acting on the walls. In a perfect
gas the amount of heat absorbed is exactly
equal to the amount of external work done.
If, however, additional energy is required
to overcome any attractive forces between
the molecules themselves, the amount of
external work will be less than the total
energy absorbed. Similarly, if the forces
between the molecules are repulsive, the dis-
crepancy between external work and heat
absorbed is in the opposite direction. We are
thus led to conceive of a perfect gas as one
in which the volumes of the molecules are
practically reduced to points, while the forces
acting between them are diminished to a
negligible factor.
From the kinetic point of view the absolute
zero is the temperature at which the molecules
of a gas lose all kinetic energy. That such a
state may be impossible to realize in practice,
only leads to the further belief that we can
never actually attain the absolute zero.
Gay-Lussac's Experiment
The notion of a perfect gas arose from
two facts: first, the validity of Boyle's law
over very large ranges of pressures and tem-
peratures for nearly all the ordinary gases,
and second, the demonstration by Gay-
Lussac that the temperature of a gas does not
change by any noteworthy amount when the
volume merely increases without doing ex-
ternal work.
The latter experiment has become a classic
in the history of science. Gay-Lussac con-
nected two receivers by means of a tube
furnished with a stop-cock, and immersed
them in a bath of water which served as a
calorimeter. One of the receivers was filled
with air under pressure, the other was ex-
hausted. On opening the stop cock between
the two vessels, the pressure naturally be-
came equalized. However, the temperature
of the surrounding water remained at the
same value as before the expansion. The
conclusion drawn was therefore that "no
change of temperature occurs when air is
allowed to expand in such a manner as not to
develop mechanical power, "f
Porous-Plug Experiment
The experiment was subsequently repeated
by Joule and Thomson under much more
accurate conditions and the conclusion of
Gay-Lussac shown to be not quite true for
ordinary gases. The latter investigation is
known as the "porous-plug" experiment
and for a detailed description of this the
t Preston, p. 286.
96
GENERAL ELECTRIC REVIEW
reader may refer to any text-book on heat.
In this experiment the gas is forced to flow
steadily through a porous plug, which is so
insulated that no heat can enter or leave it by
conduction. The pressure and temperature
are observed on both sides of the plug and
from these observations it is possible to
determine whether there is any change of tem-
perature when the gas expands without per-
forming mechanical work. It was found by
Joule and Lord Kelvin that hydrogen becomes
warmer, while all the other ordinary gases
become colder in passing through the capil-
laries of the plug.
With the data obtained from the porous-
plug experiment and the further observations
on the manner in which the different gases
deviate from Boyle's law at different pressures
and temperatures, it is therefore possible
to calibrate the indications of the ordinary
air or hydrogen gas thermometer (the usual
form is that at constant pressure) in terms of
absolute or thermodynamic scale.*
Radiation Scale of Temperature
It was shown experimentally by Stefan,
and deduced theoretically by Boltzmann that
the radiation within an enclosure whose walls
are maintained at a uniform temperature
is absolutely independent of the nature of the
enclosure, and varies with the fourth power
of the temperature. If E denotes the amount
of energy radiated per unit area of a black-
body radiator at temperature 0, we have the
relation
E = bd*
At the absolute zero, the energy radiated
is zero, and if we choose a suitable value of
the constant b, we. can make the radiation
scale of temperature agree with the absolute
scale at all temperatures. We are thus pro-
vided with another method of calibrating
thermometers and pyrometers in terms of the
thermodynamic scale.
Methods of Attaining Low Temperatures
The different methods which have been
used for attaining low temperatures may be
classified under the following heads:
(1) Methods involving the use of freezing
mixtures.
(2) Methods involving the liquefaction of
gases under pressure and the subsequent evap-
oration of these liquids.
(3) Cooling of gases owing to adiabatic
expansion.
(4) Cooling of gases owing to the Joule-
Thomson effect.
Freezing Mixtures
The addition of salt to water lowers its
freezing point by an amount which increases
with the concentration of the salt in solution.
On the other hand, the solubility of salt in
water decreases with the temperature. Con-
sequently, at a certain definite temperature
the solution freezes as a whole, the composi-
tion of the solution being the same as that of
the ice-salt mixture which separates out.
This temperature, which is the lowest at which
salt and ice can exist in equilibrium with a
solution of salt in water, is known as the
cryohydric temperature, and the mixture of
ice and salt which has this definite melting
point is known as a cryohydrate. From these
facts it is easy to give an explanation for the
cooling effect of such freezing mixture.
If we mix ice, salt and water at a tempera-
ture above the cryohydric point, the water will
tend to dissolve salt until it becomes saturated;
on the other hand, ice will melt and tend to
dilute the solution which will again dissolve
more salt, and this will result in the melting
of more ice. As the freezing mixture is
assumed to be well insulated thermally, the
temperature must decrease owing to the
latent heat abstracted for melting the ice,
until finally a temperature is attained at
which the solution has the same composition
as the ice and salt mixture which separates
out from it on freezing.
The temperatures obtainable by the use of
cryohydrates range as low as —55 deg. C.
The following table gives the compositions
of a few of these cryohydrates together with
the temperature of the cryohydric point.
CRYOHYDRATES
Cryohydric
Percentage of
Name of Salt
Point
(Degrees
Anhydrous Salt
in Freezing
Centigrade)
Mixture
Calcium chloride
-55
29.8
Sodium bromide
-24
41.33
Sodium chloride
-22
23.60
Sodium nitrate
-17.5
40.80
Ammonium chloride . .
-15
19.27
Magnesium sulphate.
-5
21.86
* E. Buckingham, Bull. 57, Bur. of Standards.
Liquefaction of Gases by Pressure
The freezing of water at ordinary tempera-
tures owing to very rapid evaporation is a
familiar phenomenon. The temperature of
any liquid tends to maintain itself at that
value which corresponds to the pressure of
the vapor above it. If now a vessel of water
is placed under the receiver of an air-pump
THE ABSOLUTE ZERO
97
and the water vapor pumped out very rapidly,
the temperature of the water is decreased,
owing to the heat absorbed in evaporation, to
a point at which the pressure of the water
vapor in the receiver is in equilibrium with
the water.
Similarly the temperature of any liquid can
be lowered very considerably if it be allowed
to evaporate very rapidly, and upon this
principle depends the use of liquefied gases
in producing low temperatures.
It is possible, by the use of very high pres-
sures, to liquefy a large number of gases at
Atm —-
Fig. 1. Decrease in.Temperature of Air Obtainable with Adiabatic
Expansion (full line curves) and Joule-Thomson
Expansion (dotted lines)
ordinary temperatures. Faraday was one of
the first experimenters to make extensive
use of this method for liquefying gases.
He used thick-walled glass U-tubes, generated
the gas in one limb and allowed it to condense
under its own pressure in the other limb,
which was cooled in an ice-salt mixture. The
following gases were condensed by him by
this method: S02, HL, CL2, NH3, C2N2,
H2S, HBr, PH3, HC1, N20, C02 and C2H4.
By evaporating liquid C02 at ordinary pres-
sure it was found possible to attain a temper-
ature of —78 deg. C. In present practice,
the liquid carbon dioxide contained in a steel
cylinder is allowed to evaporate at atmospheric
pressure; and owing to the rapid evaporation
some of the out -flowing liquid solidifies to a
snow-like mass. This is mixed with ether or
toluene and used for maintaining a constant
temperature of —78 deg. C.
In the case of liquefied ammonia and sul-
phur dioxide, the temperatures obtainable by
allowing these to evaporate at atmospheric
pressure are —31 deg. C. and —10 deg. C.
respectively. By allowing these liquids to
evaporate at 0.1 atmospheric pressure, the
temperature is lowered still more, and in the
case of C02, Faraday obtained a temperature
of —110 deg. C. by evaporating the liquid
under very low pressure.
Critical Temperature
There remained some gases, however, which
Faraday and subsequent experimenters were
unable to condense even with the highest
available pressures. These were therefore
designated as "permanent" gases, and
included CH4, NO, C02, 02, N2 and H2.
Subsequently there were added to this list
the so-called' "noble" or rare gases, krypton,
argon, neon and helium.
Andrews (1869) first pointed out that ex-
tremely great pressure alone is not sufficient
for the liquefaction of gases. It is also neces-
sary to cool the gas below its critical tempera-
ture. At this temperature the gas may be
condensed by a pressure which is known as
the critical pressure, while at higher tempera-
tures the gas remains incondensable no matter
how high the pressure is raised. The following
table gives the critical temperature and criti-
cal pressure of a number of gases.*
Gas
Helium
Hydrogen
Nitrogen
Carbon monoxide. . .
Argon
Oxygen
Nitric oxide
Methane
Carbon dioxide
Hydrogen chloride . .
Ammonia i NH
Sulphur dioxide SOj
Water I H»0
Mercury I Hg
He
H2
N2
CO
A
02
NO
CH,
CO*
HC1
Critical
Temp.
(Degrees
Centi-
grade)
-267.84
-241.1
-146
-139.5
-122.4
-118.8
- 92.9
- 81.8
31.1
51
131
157
374
1270
Critical
Pressure
(Atmos-
pheres)
2.26
11.
35
35.5
48
50.8
64.6
54.9
73
81.5
113
78.25
217.5
* K.'Jellinek. Lehrbuck der physikal. Chemie. I (1), p. 444.
98
GENERAL ELECTRIC REVIEW
It can be observed from this table that the
gases which had been condensed by Faraday
and others before the investigations of
Andrews have this feature in common, that
their critical temperatures lie above 0 deg. C.
As a result of Andrews' work, it became
evident that in order to liquefy the so-called
permanent gases it is necessary to cool them
to temperatures still lower than those hitherto
attained.
Cooling of Gases by Adiabatic Expansion
When a gas is allowed to expand reversibly,
that is, in such a manner that the pressure
of the gas is always just equal to the external
pressure, work is done against this external
pressure. If the gas is maintained at con-
stant temperature, the expansion is said to be
isothermal, and the energy required to over-
come the external pressure is absorbed from
the constant temperature reservoir. If,
however, the gas is insulated thermally, so
that heat can neither enter nor leave it, the
energy required for expansion is absorbed
from the kinetic energy of the gas molecules
themselves, so that the temperature of the
gas decreases. Such an expansion is said to
be adiabatic, and the relation between the
pressure and temperature in the case of an
ideal gas is given by the equation
^ . .. JC-l
Tl
T~
where A" is a constant for each gas. In the
case of air the value of this constant is 1.40.
The curves shown in Fig. 1 indicate the
cooling effect to be expected by expanding
air adiabatically at different initial tempera-
tures from higher pressures to 1 atmosphere.
Thus starting with air at 20 deg. C. and 50
atmospheres, the temperature can theoreti-
cally decrease to -177 deg. C. (96 deg. K.)*
If the compressed gas is initially cooled to
— 60 deg. C, the lower limit of temperature
becomes -204 deg. C. (69 deg. K.). It is
evident therefore that it is possible to obtain
considerable cooling bv adiabatic expansion
(A).
L. Cailletet condensed in this manner the
gases oxygen, nitrogen and carbon monoxide
in small amounts. More recently Claude has
applied the same principle to the construction
of an apparatus for the continuous production
of liquid air.
Cascade Method of Liquefying Gases
R. Pictet developed a very useful method
of liquefying gases which has since then been
* We will use the symbol "deg. K." to denote degrees abso-
lute (Kelvin scale).
applied to great advantage by Kammerlingh
Onnes in his cryogenic laboratory at Ley den.
The fundamental principle of this method
consists in cooling a gas (A) below its critical
temperature by the rapid evaporation of
another condensed gas, then using the lique-
fied gas A to cool a third gas B below its
critical temperature, and so on.
Kammerlingh Onnes attains a constant
temperature of —217 deg. C. (56 deg. K.)
as follows: Methyl chloride is condensed by
pressure at ordinary temperature and then
allowed to evaporate under reduced pressure.
This produces a temperature of —90 deg. C.
and is used to condense ethylene (critical
temperature, 10 deg. C). The latter, in turn,
when evaporated under reduced pressure
produces a temperature of —165 deg., which
is below the critical temperature of oxygen.
By liquefying the last gas at the temperature
of — 165 deg. and evaporating the condensed
product under reduced pressure it is possible
to obtain a temperature of —217 deg. and
maintain it for quite a long time.
Fig. 2 illustrates the method diagram-
maticallv. The methvl chloride is condensed
/ \
v_
/
D
Fig. 2. Cascade Method of Liquefaction
by the compressor B and drawn through d
into the outer tube of the condenser C. It
is there evaporated by the exhaust pump A
at a temperature of —90 deg. C. The
ethylene passes through a similar cycle by
means of the compressor F and exhaust pump
THE ABSOLUTE ZERO
99
E, producing a temperature of —165 deg.
in H. The oxygen is generated in L and con-
denses under its own pressure in the tube M.
A consideration of the vapor pressure
curves of different gases as drawn in Fig. 3*
shows that this method is not applicable to
the liquefaction of either hydrogen or helium,
since the critical temperatures of both these
gases are much below the lowest temperatures
obtainable by evaporating the gases of higher
boiling point.
Cooling of Gases Owing to Joule-Thomson Effect
If a gas is allowed to pass through a capil-
lary tube from a higher to lower pressure, it
ought, in the ideal case, to show no change
• Normal Boiling Point
o Critical Point.
-213 SO tO W 200 SO SO *0 20 -100 SO SO HI 20 0 20 40 SO SOfIOO
Deqrees -»
Fig. 3. Liquefaction Temperatures of Gases at
Different Pressures
in temperature, since no external work is
gained or lost. The porous plug experiment
which has already been mentioned, shows
however, that all ordinary gases, with the
exception of hydrogen and helium, experience
* K. Jellinek, loc. cit. p. 451.
a lowering of temperature when expanded
through a capillary. In the case of hydrogen
and helium, there is a heating effect; but this
gradually diminishes as the temperature at
which expansion occurs is lowered, and below
the so-called inversion temperature ( — 90
Fig. 4. Linde's Process for Liquefying Air
deg. C. for hydrogen) there is a cooling effect
as in the case of the other gases.
Linde's process for the liquefaction of air
depends upon this principle. It is illustrated
diagrammatically in Fig. 4. The air is com-
pressed to 20 atmospheres in the compressor
e and then passes into the smaller compressor
d where the pressure is increased to 200 atmos-
pheres. The gas then passes through the
pipe Pi and the water-separator / into the
cooling spiral g which is immersed in ice and
salt (-20 deg. C). The cooled gas then
passes through the series of pipes P2 and
expands in the nozzle o to 20 atmospheres.
The temperature falls during this operation
to —78 deg. C. By passing this cooled air
over other pipes carrying air at an initial
temperature of —20 deg. C, the latter is
cooled still further, so that when it expands
in the nozzle a, its temperature falls well
below —78 deg. By using three systems of
concentric pipes the air is finally cooled down
to a temperature at which it can be liquefied.
The expansion valve b is then opened, so that
a fraction of this cooled air expands from 20
atmospheres to 1 atmosphere and condenses.
The liquid air is collected in the Dewar
flaskf C.
t In order to prevent the rapid evaporation of liquid air and
similar products, Dewar suggested the use of double-walled
flasks in which the space between the walls has been well evacu-
ated. A vacuum is the best heat insulator known.
100
GENERAL ELECTRIC REVIEW
The cooling effect actually produced in a
Linde machine under operating conditions
is shown in Fig. 4 by the fine dashed lines.
Thus, air at — 20 deg. is cooled to — 36 deg. by
expanding from 50 atmospheres to 1 atmos-
phere. If this cooled air is compressed and
again expanded, the temperature drops to — 54
deg., and then to —101 deg., —136 deg. and
finally —190 deg. At this temperature liquid
air has a vapor pressure of 1 atmosphere,
so that the expanding air condenses.
In 189S Dewar succeeded in liquefying
hydrogen by the same method. As this gas
has an inversion temperature of —90 deg.
C, he cooled it in liquid air before subjecting
it to the Joule-Thomson process.
By evaporating liquid hydrogen at low-
pressure it becomes possible to obtain tem-
peratures ranging from —252 deg. C. (the
boiling point at atmospheric pressure) to
-259 deg. C, that is, from 21 deg. K. to
14 deg. K. This is still, however, above the
critical temperature of helium.
As the inversion temperature of this gas
occurs at 33 deg. K., its liquefaction presented
immense difficulties. In 190S, Kammerlingh
Onnes succeeded in liquefying helium by
cooling the gas first in liquid hydrogen and
then cooling it still further by the Joule-
Thomson process. The boiling point of
helium at atmospheric pressure is 4.29 deg.
K., and by evaporating the liquid under
reduced pressure, Onnes has been able to
obtain a temperature of 1.48 deg. K. ( — 271.6
deg. C). These temperatures were measured
by means of a low pressure helium ther-
mometer, on the assumption, of course, that
the gas laws are perfectly valid for helium
under these conditions. Whether this
assumption is justifiable cannot as yet be
definitely stated. This much, however, is
certain, that by evaporating liquid helium
under very low pressure we are able to obtain
a temperature which is within less than two
degrees of the absolute zero.
In the next issue we shall discuss the
behavior of different substances at these low
temperatures, and point out the theoretical
importance of the study of these low-tem-
perature phenomena.
101
THE TOWING LOCOMOTIVES FOR THE PANAMA CANAL
By C. W. Larson
Industrial Locomotive Designing Engineer, General Electric Company
The January, 1914, number of the General Electric Review contained eight articles describing the
electrical and mechanical controlling devices for the lock machinery of the Panama Canal; and the July, 1914,
number contained three articles describing the hydraulic turbines and equipment, the electric generators, and
the controlling switchboard equipment located in the power station at Gatun which furnishes energy for operat-
ing the canal. The following article describes the ship towing locomotives used at the locks. The first part of
the article is devoted to the presentation of the reasons why none of the hitherto existing systems of maneuver-
ing ships in close quarters could be satisfactorily applied to the locks of this canal. Following this is a descrip-
tion of the system developed to fulfill the conditions. Next is a minute description of the locomotives them-
selves. These, it is very satisfying to know, are fully in keeping with the other unique devices which have
been developed to make this wonderful canal possible. — Editor.
The President of the United States in June,
1905, appointed a Board of Consulting
Engineers, men of international reputation,
"for the purpose of considering the various
plans proposed to and by the Isthmian Canal
Commission for the construction of a canal
across the Isthmus of Panama."
The majority report of this Board of Con-
sulting Engineers contains the following:
"The three accidents at St. Mary's Falls
Canal occurred within a period of nine years,
where there is only one lockage of about 20
feet. If six locks should be adopted in a
plan for the Panama Canal, each having a
lift of 30 feet or more, as has been proposed
in several projects, it would not be unreason-
able, with an equal number of vessels, to look
for six times the number of accidents in the
same period of time, which would be at the
rate of two per year. If groups of locks
should be arranged in flights, as has also been
proposed in some projects, the imminence of
disastrous accidents would be greatly en-
hanced, as would be the amount of damage
to the structures and to the vessels involved.
Indeed, it is highly probable that the grave
disaster of a great ocean steamship breaking
through the gates of the upper lock and
plunging down through those below might be
realized."
It is true that the majority of the Board
favored the adoption of the sea-level canal,
but the foregoing quotation showed the
necessity, in their opinion, of safeguarding
the passage of vessels through the locks.
Investigations of collisions between ships
and lock gates invariably show that "there
was a misunderstanding in signals between
the captain and the engineer." Bearing in
mind that the engineer of the ship is so
situated that he does not know the exact
position of the ship, with respect to the lock,
he cannot check his actions by the probable
result.
A system, therefore, which permits the
checking of the movement of the ship with
the signal given by the pilot or captain of
the ship will eliminate improper manipula-
tions to a very great extent.
Various systems are in vogue at dry-docks
which are based on the principle that the
operator sees the result of his action. The
employment of winches or capstans has been
looked upon with a great deal of favor.
These are usually placed at intervals along
the dock walls, and the lines from the ship
are carried forward to the successive capstans
as the ship advances. Such a system in-
volves the risk of the ship not being properly
safeguarded when the lines are transferred
to the successive capstans. An improve-
ment has been made by the installation of a
capstan at the head of the dock, centrally
located, and used for imparting a straight
motion to the ship. Numerous lines from the
ship to the dock wall are carried by men, and
the capstans are employed to counteract
any wind pressure, currents, etc., and assist
generally in maneuvering the ship. While
an improvement over former methods, it
did not, however, possess the flexibility and
reliability required for the operation of the
locks of the Panama Canal, neither would
it have eliminated the breaking of the lines
at critical moments, which is regarded as one
of the essential requirements in successfully
handling ships in canal locks.
After a very thorough study of the entire
problem of maneuvering the ships through
the locks of the Panama Canal, it became
evident that the ships should not proceed
through the locks under their own power,
and that a substitute for the ship's power
should embrace the following requirements :
102
GENERAL ELECTRIC REVIEW
(a) The ability to place the ship in
proper relation to the lock.
(b) The capability of keeping the ship
in its course.
(c) The accelerating and retarding of
the ship without rupturing the
lines.
(d) The lines when once attached should
be used without change for lock-
age in flight.
(e) The services of a small number of
skilled operators rather than a
large number of unskilled men.
The towing system described in the fol-
lowing pages was designed and patented by
Mr Edward Schildhauer, Electrical and
Mechanical Engineer of the Isthmian Canal
Commission.
Towing System
In passing through the canal from the
Atlantic to the Pacific, a vessel will enter the
approach channel in Limon Bay, which ex-
tends to Gatun a distance of about seven
miles. At Gatun it will enter a series of three
locks in flight and be raised 85 feet to the
level of Gatun Lake. It may then steam at
full speed through the channel in this lake,
for a distance of 24 miles, to Bas Obispo,
w-here it will enter the Culebra Cut. It will
pass through this cut, which has a length of
nine miles, and reach Pedro Miguel, where
it will enter a lock and be lowered 30 feet.
Then it will pass through Miraflores Lake for
a distance of one and one-half miles until
it reaches Miraflores, where it will be lowered
55 feet through two locks, to the sea level,
after which it will pass into the Pacific
through an eight and one-half mile channel.
The main features of all the lock sites are
identical and the following brief description
of the Gatun Locks, with especial reference
to the arrangement of the towing tracks,
ship channels, inclines and approaches, is
given to present a clearer conception of the
towing scheme in general. A more detailed
description of the locomotive itself will then
follow.
The general layout of the Gatun Locks is
clearly shown in Fig. 1. It will be noted that
there are two ship channels, one for traffic
in each direction. The channels are separated
by a center wall, the total length of which is
6330 feet. There are two systems of tracks
for the locomotives, one which they use when
towing and the other when they are returning
idle. This, however, refers onlv to the outer
walls, since for the center wall there is only
one return track in common for both the
towing tracks. The towing tracks are
naturally placed next to the channel side,
and the system of towing normally utilizes
not less than four locomotives running
along the lock walls. Two of them are op-
posite each other in advance of the vessel,
and two run opposite each other following
the vessel, as seen in Fig. 2. The number
of locomotives is increased, however, when
demanded by the tonnage of the ship.
Cables extend from the forward locomo-
tives and connect respectively with the port
and starboard sides of the vessel near the
bow, and other cables connect the rear
locomotives with the port and starboard
quarters of the vessel. The lengths of the
various cables are adjusted by a special
winding drum on the locomotive so that the
vessel will be placed substantially in mid-
channel. When the leading locomotives are
started they will tow the vessel, while the
trailing locomotives will follow and keep all
the cables taut. By changing the lengths
of the rear cables the vessel can be guided,
and to stop it, all the locomotives are slowed
down and stopped, thus bringing the rear
locomotives into action to retard the ship.
Therefore, the vessel is always under com-
plete control thoroughly independent of its
own power, and the danger of injury to the
lock walls and gates is thereby greatly les-
sened.
The illustration in Fig. 12 shows how effec-
tively the four locomotives keep the vessel
under control and in the center of the channel,
while Figs. 8 to 13 give a general idea of the
method of handling vessels of various sizes.
They also show general views of the lock
walls, towing tracks, and inclines, the steep-
ness of the latter being especially noticeable.
Of particular interest is Fig. 11, which repre-
sents a trial tow approaching the second
level. The water in the middle lock or at
this second level is at sea-level, a condition
not obtained in regular operation; and this
trial was made to demonstrate that the tow-
lines would clear the lock walls.
The towing tracks have a specially de-
signed rack-rail extending the entire length
of the track and centrally located with
respect to the running rails. It is through
this rack-rail that the locomotive exerts
the traction necessary for propelling large
ships and for climbing the steep inclines.
Rack-rail is also provided on short portions
of the return track so as to lower the loco-
~'4
t
Fig. 1. A Drawing of the General Layout of the Gatun Locks. The heavy dot-dosh line indicates the portion of the towing locomotive track that is equipped with rack-rail
Pig. 2. Diagram Showing the Relative Location of the Locomotives, Cables and Ship During
the Operation of Towing
'm'MCiLlF
Fig. 3- A Section of the Fixed Rack-Rail at the Left to
which a Section of Movable Rack-Rail is Hinged at C.
One of these movable sections is located at each
end of the rack-rail
Fig. 4. A Section of the Conduit Showing the Current Collecting
Device for Two Phases and the Underground
Rails from which the Current is Taken
I
Fig 6 The Plan View of a Towing Locomotive with the Covers Removed from the left-hand End
Fig. 7. A Cross Sectional View. Near tbe Winding I
of a Towing Locomotive
THE TOWING LOCOMOTIVES FOR THE PANAMA CANAL
103
motives safely from one level to the next.
The steepest slope is 26 deg. or 44 per cent,
hence the need will be seen for rack-rail even
on the return track, it being
known that any traction loco- • —
motive with the usual wheel
drive, even with brakes set,
would begin to slide on a 10
per cent grade and could there-
fore not be controlled. With
a rack-rail, however, traction
is limited only by the capacity
of the driving motors and not by
the adhesion of the wheel treads
to the rails.
A small portion of rack-rail
is shown in Fig. 3, A being the
rack-rail proper and B the
approach to it. B is hinged at
C so that it can be depressed on
the approach of the rack-pinion
of the locomotive. The teeth
of the approach section are
under size and are shaped off at
the extreme end so that the
teeth of the pinion will mesh
properly and thus prevent ex-
cessive strain on the pinion and
the axle. The spring D restores
the approach to proper position after the
locomotive has passed over. The rack-rail is
of the shrouded type, and each tooth space
the walls. A further feature of the rack-rail
is the projecting edges which permit thrust-
wheels attached to the locomotive to run
Fig. 9. The "Ancon" Entering the Upper Gatun Lock from the Middle West
Chamber under the Tow of Electric Locomotives
has a drain-hole cast in the bottom to carry
off water and other accumulations to suitable
drain pipes or ducts set in the concrete of
Fig. 8. Electric Locomotives Locking 85-ft. Piles through the Pedro-Miguel Locks
along the under side and prevent the over-
turning of the locomotive, in case some un-
foreseen operating condition should produce
an excessive pull on the tow-
line. These thrust-wheels serve
to counteract the lateral com-
ponent of the tow-line pull
and the flanges act for emer-
gency only, as the weight of the
locomotive is sufficient to pre-
vent overturning with the nor-
mal pull of 25,000 pounds on the
tow-line. These thrust-wheels
are shown in Fig. 7.
Three-phase, 25-c)rcle, 220-
volt alternating current is used
for operating the locomotives,
and the current is supplied to
the locomotives through an
underground contact system .
The collecting device is illus-
trated in Fig. 4, while Fig. 7
shows its position with respect
to the track, it being adjacent
to the running rail on the side
remote from the lock. Two
T-rails (shown in black section) form two
legs of the three-phase circuit and the third
leg is formed by the main track rails. A
104
GENERAL ELECTRIC REVIEW
Fig. 10.
The First Trial Run of the Towing Locomotives at the Gatun Locks.
in making this test
A barge was used
specially designed contact plow slides between
the two T-conductors and transmits the
power from the rails to the locomotive.
This contact plow passes through the slot
opening in the conduit cover and is flexibly
connected to the locomotive in such a manner
as to follow all irregularities in the tracks and
crossovers, and therefore insures a continuous
supply of power.
Locomotive Design
The working parts of the locomotive are
supported by two longitudinal upright cast-
steel side frames, No. 1, Fig. 5, connected by
transverse beams, No. 2, Fig. 6. These
frames are, in effect, deep rigid trusses, hav-
ing upper and lower members connected by
posts, No. 5, and diagonal braces, No. 6,
Fig. 5. The middle portion of each frame
Fig. 11. The First Trail Tow with the Barge at the Second Level of the Gatun Locks, Rear Locomotives
Ascending the Incline. The water in this middle lock (second level) is shown at sea level,
a condition not obtained in regular operation. This trial was made to
demonstrate that the tow lines would clear the lock walls
THE TOWING LOCOMOTIVES FOR THE PANAMA CANAL
105
Fig. 12. Four Towing Locomotives Attached to the Submarine Tender "Severn" in a Gatun
Lock Ready for Lowering the Water-Level. A group of submarines may
be seen at the far end of the lock
has its upper and lower members parallel
and horizontal, but the end portions have
their lower members inclined upward toward
the ends of the frame. The pedestals, No.
7, for the wheel axles, No. 8, are located at
the junction of these end portions with the
middle portion, and are of the usual locomo-
tive type, having vertical parallel jaws
between which the journal, No. 9, slides.
Springs, No. 10, are interposed between the
tops of the journal boxes and the tops of the
pedestals, and the locomotive is thus mounted
upon four wheels, No. 11, carried on the two
axles, No. 8, the wheel-base being 12 feet and
the overall length of the locomotive over 32
feet.
Each axle is driven by its own motor, in-
dependent of the other, and as the construc-
tion is identical at both ends of the machine,
a description of one end will suffice for both.
Fig. 13. The "Severn" Leaving the Upper East Chamber in the Tow of Electric Locomotives
106
GENERAL ELECTRIC REVIEW
A cast-steel suspension bracket, No. 12, Fig.
14, is hinged at one end upon the axle. Its
bearings, No. 13, which fit the journals on
the axle are secured in place by caps, No. 14,
Fig. 14. A Side Elevation of the Traction Brackets
which are provided with oil cellars. No. 15.
The bracket is provided with bearings for a
transverse jackshaft, No. 16, parallel with
the axle, and it has pillow blocks. No. 17, for
a countershaft, No. 18, also parallel with the
axle. It has a substantial horizontal plat-
form, No. 19, to support the driving motor,
No. 20, and its outer end is supported at each
corner by two springs, No. 21, placed above
and below a stationary angle-iron, No. 22,
and connected to the bracket by a bolt. No.
23, so as to afford a yielding support in both
upward and downward movements of the
bracket.
3940 I Ui^>C — ~-&
Fig. 15. A Longitudinal Horizontal Section of
a Clutch Shaft
The motor, No. 20, is of the three-phase,
slip-ring type, enclosed, and identical to the
rugged steel-mill design, and it is geared
by pinion, No. 24, and spur gear, No. 25,
to the countershaft, No. 18, which carries
a pinion, No. 26, meshing with a spur gear,
No. 27, Fig. 15, keyed to the jackshaft, No.
16. On the outer side of the spur gear, No.
27. are formed clutch teeth which cooperate
with similar teeth, No. 28, on the adjacent
side of a gear, No. 29, which is sleeved upon
the jackshaft, and which can be slid length-
wise thereon to engage and disengage the
clutch teeth. The means for sliding this gear
consists of a disk, No. 30, secured to the gear
and having a central hub, No. 31, fitting over
the end of the jackshaft, Fig. 15. A rod, No.
32, Fig. 15, runs through a central hole in
the shaft and through the center of the hub.
No. 31, to which it is connected by nuts, No.
33, in such a manner as to permit the disk
to rotate with the wheel, and at the same time
to cause it to slide the wheel axially when the
rod is reciprocated. A pinion, No. 34, Fig.
17, is keyed to the axle, No. 8, and is wide
enough to always mesh with the gear, No.
29, so that when the clutch teeth, No. 28,
are engaged, the motor will propel the loco-
motive by the adhesion between the wheels.
No. 11, and the rails of the track, and this
only when running without load and between
inclines.
When the locomotive, however, reaches
one of the inclines between the locks, the
grade of which may be as much as 44 per cent,
or when it is towing a ship, the cog-rail
system is utilized to enable the locomotive
to climb the grade or to exert the traction
necessary for pulling large ships. The cog
or rack-rail is laid between the track rails,
and the locomotive is provided with a cog
wheel or rack pinion, No. 35, Fig. 17, secured
to or integral with a sleeve, No. 36, which
rotates freely on the axle. A gear wheel, No.
37, secured to or integral with this sleeve,
meshes with a gear, No. 38, Fig. 15, which
turns loosely on the jackshaft. Clutch teeth,
No. 39, on this gear can be engaged by teeth,
No. 40, on a clutch, No. 41, which is splined to
a jackshaft. A two-armed lever, No. 42,
fulcrumed on a bracket, No. 43, straddles
the shaft, No. 16, and is pivoted to a collar,
No. 44, riding in a groove in the clutch, No.
41. The lever is connected by a link, No. 45,
to one end of a lever, No. 46, Fig. 15, turning
loosely on a vertical rockshaft, No. 47. An
elastic arm is keyed to 'the shaft and engages
lugs on the lever, No. 46. The arm, No. 4S,
is composed of a laminated flat-steel soring,
Fig. 16, and a second arm, No. 49, is keyed
on the shaft and connected by a rod, No. 50,
to a handle in the cab of the locomotive. The
THE TOWING LOCOMOTIVES FOR THE PANAMA CANAL
107
handle can be locked by a suitable latch and
notched quadrant, and the other end of the
lever, No. 46, is pivoted to the rod, No. 32,
so as to throw out the clutch, No. 28, when the
clutch, No. 40, is thrown in, and vice versa.
The elastic arm, No. 48, serves to throw
the clutches automatically; it being under-
stood that the four-jaw clutches in most
cases do not mesh when thrown but that the
operating handle is thrown full stroke and
locked. This puts the springs under heavy
tension. The locomotive is then started
slowly and when the clutches are in align-
ment the springs throw them without any
attention by the operator.
The two rocker shafts at opposite ends of
the locomotive are connected by the rods,
No. 52, pivoted to rocking arms, No. 52a, on
the shafts and to an intermediate lever,
No. 52b, fulcrumed on the pedestal sup-
porting the winding drum. Figs. 16 and 19
will be of assistance in making clear the
foregoing description of clutches and gear.
Fig. 16. A Drawing of the Clutch Operating Mechanism
The two traction motors, No. 20, are con-
trolled by suitable controllers installed in the
cabs at the ends of the locomotives, and the
circuits are such that both motors can be
controlled from either cab, and can be
operated singly or in multiple as desired.
Current is taken from the supply conductors
by the special current-collecting device pre-
viously described and shown in Figs. 4 and
7.
It will be observed that each motor, with
all its gearing and clutches, is mounted in-
dependently of the frame of the locomotive,
to which it is connected only by the springs,
No. 21, which give an elastic support for the
outer end of the bracket, No. 12, Fig. 14, on
which the mechanism is carried.
In connection with each motor a powerful
brake is installed, and as during operation the
motors are at all times geared either to the
axles or to the cog wheels, the truck wheels,
No. 11, are not provided with any brake
rigging. The motor brake is shown in Figs.
5 and 6, but it is more clearly illustrated
in Figs. 18 and 20. On the motor shaft is
keyed a brake disk or drum, No. 53, Fig. 18,
and to opposite sides of it are applied the
brake shoes, No. 54, carried bv the brake
ijnrr
Fig. 17.
py
Oia
? c
1
D C
A Longitudinal Horizontal Section of
an Axle Shaft
levers, No. 55, which are pivoted at No. 56
upon a stationary bar, No. 57, projecting
from a frame, No. 58, which supports a
solenoid, No. 59. The movable core of this
solenoid is pivoted to the long arm of a lever,
No. 60, which is fulcrumed at No. 61 on one
of the brake levers. A rod, No. 62, connects
the angle of this lever with the other brake
lever, thus constituting a sort of toggle
between the two levers. When the core of
the solenoid drops, it actuates the lever and
the rod in such a manner as to draw the two
brake levers toward each other, thereby
applying the brake shoes to the drum. The
winding of the solenoid is in circuit with the
controller of the motors, so that when the
Fig. 18-5 A Side Elevation of the Combination Hand and
Solenoid Brake and Rigging
current is turned on to energize the motor
windings, the solenoid will lift its core and
thereby release the brakes. The first point
of the controller releases the brakes without
applying power to the motors, thereby pro-
108
GENERAL ELECTRIC REVIEW
viding a coasting point. But should the motor
current be shut off, either intentionally or
accidentally, the core will instantly drop by
gravity and its weight will exert a powerful
Fig. 19. A Front View of a Traction Motor Unit with
a Journal Box in Place
leverage upon the brake levers to stop the
motors and the locomotive. This action
occurs simultaneously on both motors, and
brake action is powerful enough to stop the
locomotive within two revolutions of the
wheels.
In addition to this automatic brake, means
are provided for applying the brakes manually
in order to supplement the action of the auto-
matic feature, 'if necessary, when descending
a grade or when approaching a rack-rail. An
upright shaft, No. 63. Fig. IS, provided with
a hand-wheel, No. 64, has attached to it one
end of a chain, No. 65, which runs under a
stationary pulley, No. 66, up over another
pulley. No. 67, on one end of an elbow-lever.
No. 6S, pivoted to one of the brake levers,
and thence under a stationary pulley, No. 69,
to the opposite end of the locomotive. The
elbow-lever, No. 6S, has its other arm con-
nected by a rod. No. 70, to the other brake
lever, the rod being adjustable in length as
shown. The lever. No. 6S, and rod, No. 70,
constitute a toggle connecting the brake
levers. A spring. No. 71. tends to lift the arm
carrying the pulley. No. 67, and thus hold off
the brake shoes. When the brake staff is
turned, it winds up the chain and draws down
the pulley, No. 67, thereby applying the
brake shoes to the drum. In this way, t he-
operator can add hand power to the effect of
the electric brake and thus produce a greater
braking action without interfering with the
automatic operation of the solenoid.
As appears from Fig. 6, the brake levers,
No. 55, are double, only the rear member of
each being shown in Fig. IS. This avoids
any bending strains on the pivots. The
levers, No. 60, and No. 68, and the rods,
No. 62 and No. 70, constituting the two
toggle systems, are located between the two
members of each lever, as are also the brake
shoes, No. 54. The chain, No. 65, extends
from the pulley, No. 69, to the similar point
in the brake rigging of the motor at the other
end of the locomotive, so that the operation of
either of the brake staffs will apply both
brakes simultaneously.
It will be noted that while the hand and
the solenoid brake mechanism operate entirely
independent of each other, both apply break-
ing power through the same levers and wheel.
Passing now to the features which render
the locomotive peculiarly adapted for towing
purposes, it is observed that the drum, No.
72, Fig. 22, on which the cable, No. 73, Fig.
5, is wound, is located midway between the
ends of the locomotive and above the upper
member, No. 3, Fig. 5, of the side frames,
so that the cable can be led off on either side
of the machine and through a wide range of
angles to the line of travel. The hub, No. 74,
Fig. 22, of the drum is pivoted to the hub, No.
75, of the spider, No. 76. which in turn rotates
upon the upper portion of a massive, tubular,
Fig. 20. Rear View of a Traction Motor Unit
vertical cylindrical column. No. 77, rising
from a pedestal, No. 78, Fig. 25, secured to
the base plate or floor, No. 79, Fig. 7, which
is supported upon the lower members, No. 4,
THE TOWING LOCOMOTIVES FOR THE PANAMA CANAL
109
of the side frames. The upper portion of
the pedestal is held in a brace, No. 80, Fig.
24, which is shown as a heavy X-shaped
casting, fastened to the upper members, No.
3, of the side frames and to two of the cross
beams, No. 2. This brace fits the pedestal
just below the shoulder, No. 81, Fig. 22, on
which the hub, No. 75, is stepped.
The spider; No. 76, Fig. 22, supports a
circular rim, No. 82, which has a horizontal
upper surface, No. 83, and a flange, No. 84.
On the surface, No. 83, is secured a flat
smooth bronze ring, No. 85, and a second
brass ring, No. 87, similar to the first, lies
on top of a steel ring and is secured to a
flanged follower, No. 88. Sixteen studs, No.
89, project up from the rim, No. 82, through
holes in a horizontal flange of the follower
and are encircled by strong springs, No. 90,
which abut between the flange and nuts, No.
91, on the studs and press all three rings
tightly together. The steel ring, No. 86, is
secured to lugs, No. 92, on a flange, No. 93,
projecting downward from the winding drum,
No. 72, so that the rings constitute a friction
clutch between the spider and the drum.
Inside the flange, No. 84, on the spider is
secured a large internal gear, No. 94, with
which mesh two driving pinions, Nos. 95
and 96, Fig. 7, secured respectively to two
upright shafts, Nos. 97 and 98. Step bear-
ings, Nos. 99 and 100, are provided for these
shafts in the base of the pedestal, No. 78,
Fig. 21. Plan View of the Cable Guiding Devices
Fig. 7, while arms, Nos. 101 and 102, Fig.
6, projecting from the upper portion of the
pedestal just below the brace, No. 80, Fig.
7, constitute guide bearings, Nos. 103 and
104, for the upper portions of the vertical
shafts. A worm gear, No. 105, Fig. 7, is
clutched to the shaft, No. 97, and is driven
by a worm, No. 106, on the shaft of an elec-
tric motor, No. 107, bolted to the base, No.
79, of the locomotive. This gearing is pro-
Fig. 22. Cross Sectional View of the Cable Guiding
Devices taken through Line x — x of Fig. 21
tected by a casing, No. 10S. A bevel gear, No.
109, is keyed to the upright shaft, No. 98,
and meshes with a bevel pinion, No. 110, on
the shaft of an electric motor, No. Ill,
fastened to the base.
The motor, No. Ill, with bevel-gear pinion
is used for driving the drum at a high speed
when coiling the cable that has been cast
off, and it remains permanently in gear. The
other motor, No. 107, with worm-gear drive
is used for taking in the cable when it is
under load, and the drum operates as a wind-
lass or capstan.
Due to the greater gear reduction, it
operates the drum at a much slower speed, and
consequently with motors of approximately
equal size, a greater force may be exerted on
the tow-line than would be possible with the
lower speed reduction which is used with the
high-speed coiling motor, No. 111. The
worm-gear drive is disconnected from the
drum when not in use. To accomplish this
a clutch is provided, having one member, No.
112, Fig. 7, splined to the shaft and the other
member, No. 113, attached to the hub, No.
114, of the worm gear, which is sleeved on the
shaft. A lever, No. 115, Fig. 26, fulcru'med
to a lug, No. 116, on the arm,- No. 101, is
pivoted to the hub of the clutch member, No.
112, and its other end is attached to the mov-
able core of a solenoid, No. 117, which is
connected in the controller circuit of motor,
No. Ill, so that whenever the circuit of the
latter is closed to coil up the cable rapidly,
the solenoid will lift its core and also lever,
No. 115, thus throwing out the clutch of the
winding motor. The first point of the con-
110
GENERAL ELECTRIC REVIEW
troller which operates motor, No. Ill,
raises the clutch and on the second point the
motor starts.
The guide which directs the cable, as it is
paid out or wound up, is mounted so as to
Fig. 23. Cross Sectional View of the Cable Guiding
Device taken through Line Y — Y in Fig. 21
revolve on the axis of the drum. It com-
prises two angularly adjustable portions,
Nos. 1 IS and 119, Figs. 21 and 22, the former
being a circular bell which serves as a cover
for the winding drum. The hub, No. 120,
Fig. 22, of the bell is journalled on the upper
end of the column, No. 77, being stepped on a
shoulder thereon. At one side the housing
is cut away to admit the cable to the drum,
and on each side of this opening is bolted one
end of a frame comprising box-like ends, No.
121, Fig. 23, connected by two parallel bars,
No. 122, Fig. 22, one above and the other
below the opening. Between the bars and on
either side of the opening are two upright
guide rolls, No. 123, Figs. 21 and 22, having
cylindrical faces, and rotating on journals
held by the bearings in the bars, No. 122. At
each end of this frame arms, No. 124, Figs.
7 and 23, extend downward and support two
rollers, No. 125, Fig. 7, mounted on hori-
zontal studs, No. 126, Fig. 23, secured in the
arms. These rollers are adapted to travel
between the upper and lower flanges of a
Fig. 24. Plan View
of the Pedestal
and Base
Fig. 25. Vertical Cross Section of
the Pedestal and Base taken
through Line z — 2 in
Fig. 24
circular channel-iron, No. 127. Fig. 23, which
ed on top of the side frames con-
centric with the column. No. 77, and forms a
track supporting the outer end of the frame,
Nos. 121 and 122, thus relieving the column,
No. 77, of the weight. Stops, No. 128, Fig.
5, are fastened to the top of the channel-
iron, No. 127, to limit the angular play of the
guide member, No. 118. They can readily
be taken off, and the housing can be turned
until the rollers, No. 123, are on the opposite
side of the locomotive, after which the stops
can be attached on that side to limit the
movement of the housing.
The other guide member, No. 119, is a
radial casting having one end turning freely
on the hub of member No. 118, Figs. 7 and
21. A cap, No. 129, Fig. 21, is provided at
the top of the column, No. 77, which protects
the joint and prevents the guide members from
accidentally coming off. The outer end of
member No. 119 is an upright rectangular
frame, No. 130, in whose top and bottom is
journalled on a vertical axis a swivel, No. 131,
carrying two grooved sheaves, No. 132, these
37-
115
c^qUo
—
16
112
J-
Fig. 26. Clutch Operating Mechanism for Slow-Speed Winding
also being led one above the other on hori-
zontal axes. The edges of these sheaves are
in close contact, so that their grooves form
an opening through which the cable, No. 73,
passes, approximately in line with the middle
of the guide rollers, No. 123. The frame, No.
130, is supported by rollers, No. 133, Fig.
7, running in track, No. 127, and the guide
member has an angular movement with ref-
erence to member No. 118, limited by the
frame No. 130 striking the ends of the frame
No. 121. When the cable is pulled either
forward or backward from the middle posi-
tion, which it occupies in Fig. 5, the swivel
permits the grooved rollers, No. 132, Fig. 22,
to move with it, and the guide member, No.
119, swings also, so that the rollers, No.
132, continue to support the rope in a line
with the middle of the rollers, No. 123, with-
out being themselves subjected to any side
strain. All lateral strains are sustained by
heavy guide rollers, No. 123, the cable moving
THE TOWING LOCOMOTIVES FOR THE PANAMA CANAL
111
up and down between them as it winds on the
drum. The latter is in the form of a deeply
grooved wheel, the groove, No. 134, being
U-shaped. Figs. 27, 28 and 29 clearly illus-
trate the construction of the equipment just
described.
Fig. 29 shows the cable guard. This is a
steel casting having a thickness of only three-
eighths of an inch. The diameter is four feet
six inches and the circular flange is 17 inches
deep. This casting was pronounced to be
beyond the possibilities of the ordinary
open-hearth furnace by a number of steel
foundries. They were eventually produced,
however, in the contractor's electric furnace,
where it was possible to intensify the heat,
thus making the metal flow more rapidly.
No failures occurred. With the exception
noted, all the other principal steel castings
for these locomotives were produced at the
plant of the Wheeling Mold & Foundry
Company, Wheeling, W. Va.
In order to resist the tendency of the loco-
motive to tip over when an excessive load
comes on the cable, a stout rack-rail, No.
135, Fig. 7, is, as previously mentioned, laid
between the traction rails of the track, and
two horizontal flanged wheels, No. 136, are
arranged between each pair of wheels, No. 1 1 ,
and engage the opposite sides of the rack.
These wheels are carried on heavy bars, No.
137, whose inner ends are pivoted at No. 138,
Fig. 5, to the base of the machine, so that
One of the most important parts of the
locomotive is the "slip-friction" device con-
sisting of two special alloy rings, mounted on
the spider, as has been previously explained.
Fig. 27. Complete Assembled Windlass and Base
Between these rings a steel disk is fastened
to the rope drum, and the amount of tension
on the tow-line is adjusted by the pressure
Fig. 28. Parts of the Windlass and Base and a Partial Assembly
Fig. 29. Guard for the Towing Cable
the bars can move horizontally. Their outer
ends are engaged by strong springs, No. 139,
which afford the necessary flexibility for
smooth operation.
between these three disks, and is obtained
by tightening the spiral springs on the clamp-
ing ring. In order, therefore, to make the
slipping tension of the tow-line proportional
112
GENERAL ELECTRIC REVIEW
to the pressure between the friction disks,
a rubbing surface having an absolutely con-
stant coefficient of friction is essential. In
order to find such a metal, certain tests were
made as indicated by the curves in Fig. 30,
which is self-explanatory. The low-friction
metal, having a friction coefficient of 0.1, is
practically constant under all pressures and
condition of the surfaces, and therefore was
selected for the work. This metal also showed
but very little difference in friction coeffi-
cient between starting and running. The
results of the special tests were furthermore
amply verified by the final test of the friction
disks of each machine under the full rated
tow-line pull of 25,000 pounds by means of
the dynamometer testing outfit shown in
Fig. 31. All 40 machines were given this slip
test 25 times from each cab and all passed
the government requirements not to exceed a
variation of five per cent above or below the
normal of 25,000 pounds.
In connection with the slip test, further
data on the slow-winding motor was ob-
45
o2
o
_
'
■TiOh T~r
ct
SM«a"-J^-
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w.
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1
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,,-vton t
Aetal^Kunniti^) Lubricated witnuil.
'M
\C "
30 40 50 60 70 80 90 100 110 1Z0 130 140 150
Lb. Pressure Per Sq Inert.
Fig. 30. Curves Showing the Results of Tests to Determine
the Proper Friction Metal
tained, as furnished in curves shown in Fig.
32. The winding motor is a 20-h.p. (one-
hour rating), three-phase, high- torque, squir-
rel-cage type, induction motor controlled
Fig. 31.
Dynamometer and Stand for Testing the Towing
Pull of the Locomotives
from a drum-type reversible controller in
either of the two cabs. From the curves it is
seen that the motor has ample power to take
care of any sudden pull on the tow-line up
to 40,000 pounds, which is well above the
normal requirement of 25,000 pounds. The
speed of winding is at the average rate of 12
feet per minute.
D 0
13
C. .1
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35,000
bi
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W u
30,000
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2^000 100 fc
£ 90 5
x -1
20,000 40 80 400
70
JO 60 300
50
?0 40 200
30
0 ZO 100
10
15000
IQ000
3000
s
s
y
fy
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y
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C 1
/
k
\\ 1 1 1
"l
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H P
0 0 0
50 60 70 80 90 100
Ampcras
Fig. 32. Characteristic Curves of the Windlass Motors
THE TOWING LOCOMOTIVES FOR THE PANAMA CANAL
113
The rapid-coiling motor is permanently
geared to the drum and is of the same type,
size, and capacity as the winding motor,
and is subjected to its maximum load when
accelerating the heavy drum to the high speed
required for coiling or paying out the rope,
this being 16 times the slow- winding speed at
full load, or about 200 feet per minute.
The slow-winding and the rapid-coiling
motors are operated by similar controllers
and the circuits electrically interlocked so as
to prohibit application of power to either
motor unless the controller of the other motor
is in the "off" position.
Each of the two main traction motors has
a rating of 75 h.p., and is of the slip-ring induc-
tion type, operated by a system of contactors
with a master controller in each cab. The
motors, by means of the change in gearing
from straight traction to rack-rail towing
previously described, drive the locomotive
at a speed of two miles per hour when towing
and five miles per hour when returning idle.
These motors act as induction generators
running above synchronous speed when the
locomotive is passing down the steep inclines
and thereby exert a retarding brake effect to
keep the speed uniform. Speed tractive effort
and efficiency tests were made with results
as plotted in the curves of Fig. 33.
The curves in Fig. 34 give some interesting
data on the time of acceleration of ships in
the lock chambers. These values have been
obtained from certain tests and theoretical
calculations based on data given by several
well-known authorities.
For determining the resistance of ships iff
deep open water, the following formula is
1.2
1.0
8
.6
-a
„
|Q
v^
L
>
** ° TJ
9
i
'■ ,
« N "*
4
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--
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Tr
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~~7
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.;
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V
£-
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Of
tr
-fk
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_J '"'n o
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w
til
fesv
'r
*>W"*
Av-
v"
u
..•'■
h
sv
'
0
200 400
Amperes
600
nput 2 Mo
800
.ors
1000
1200
■100
Fig. 33. Characteristic Curves of the Traction Motors
given by Captain Charles W. Dyson in his
work, "The Estimation of Power for Pro-
pulsion of Ships:"
1-85 5 jji y\
R=fSV + T
-L \ -I » '
i[iiniini/|i i in ii in ii inn/if
-- — _: XU
: 7^
it
± -+- 4
tZ
</ T
ti^r *i/ ' rj
~T~-$
n\>y ± _ _,dLiSi ?
$>* _ WyE- si
"^ 'i'r~ j
& _t &
y*ir ?fl
S'V -l ti>Y-
. . -j,e3S - - -i-5E
\' TT^r
TTjS^L^ - "S
<t% -t- " ' " :<X
(^1-1 ?-°
.'. >>'
Wr* T T^ P
•/ ~SZt
■+&&', ^ ■>£
$ 3&
+ Ao5g2''T x - S
' ■»/ . Syr
jOC^ + 8s
-' '<
m. ' ' J!*
--ai
& ~3&r ^ i
i- - -a?
/ '
■?
pi
t ' "X-
E
j 5
-4- — -H- S>«
t"""i"t ~ 8
Kg
1 f- i — ' *
J! . I j JT "T a
-E.-C - -H -»?+- -1- - o
* iS & ^
.1 -U - - - 4i 1 '
t ' J3~ S -3
-F -3- T_3I S
r I Tt s— ----*>
"=f • i T ., I
Thousand Tons Dispto
cement
Fig. 34. Curves Showing the Time Required for the Acceleration of Ships
114
GENERAL ELECTRIC REVIEW
Where
R = Resistance in pounds.
/= Surface friction coeffi-
cient, varying from
0.008 to 0.009.
5 = Wetted surface in square
feet.
1 ' = Speed in knots per hour.
b = Form-factor, varying
from 0.35 for fine
long ships to 0.50 for
freighters.
D = Displacement of ship in
tons.
L = Length of ship in feet on
load water line.
This formula gives, as stat-
ed, the resistance in deep open
water, and it is well known
that this is greatly increased
when the ship is passing
through narrow channels, due
to the reaction of the water
on the side walls and bottom.
This additional resistance
may be found by the follow-
ing formula, given in a report
by the State Engineer of New
York on the proposed Barge
Canal (see Engineering
Record, June 29, 1901) :
Where
r = ratio -.
r-1.3
canal section
<]N3 HldON
midship boat section
In order to obtain the total
ship resistance the value of R
previously obtained should be
multiplied by the value ob-
tained for R\.
Space does not permit of a
detailed description of the
locomotive control apparatus,
but a fairly good idea will be
had by reference to the dia-
gram of connections shown
in Fig. 35.
Figs. 36 to 43 are of interest
in showing the progress of the
work during the construction
period.
The contract for the loco-
motives was awarded to the
General Electric Company at
Schenectadv. N. Y., U. S. A.,
May 24, 1913. Shipment was
THE TOWING LOCOMOTIVES FOR THE PANAMA CANAL
115
made of the first machine January
12, 1914, and the total shipment of
the forty locomotives was com-
pleted November 6, or at the very
high average rate of one locomotive
per week. The maximum rate
of production was, however, even
higher, twelve locomotives being
completed in nine weeks' time.
The interest and untiring energy
of the factory employees engaged
in this work demand particular
notice. The men individually
made it their task to accomplish
a maximum each day to meet the
urgent needs of the Panama Canal
and evinced a striking spirit of
patriotism and pride in the carry-
ing out of their share of the big
undertaking.
The locomotives have a net
weight of 86,000 lb. and a gross
shipping weight of 92,500 lb. They were
mounted on specially designed skids and
shipped by rail to New York, where they were
loaded on board ship, as deck cargo, by means
of aMerritt-Chapman 125-ton floating derrick.
Fig. 40 shows the loading on the S.S. "Ancon,"
which in this case carried six locomotives to
the Isthmus.
Summary
The towing locomotives as described and
illustrated possess the following operating
characteristics:
(1) When towing, the speed can be accel-
erated from zero to two miles per hour.
(2) When running idle, the speed can be
accelerated from zero to five miles per hour,
permitting return trips at increased speed.
(3) The windlass will pay out or wind in
cable at the low rope speed and at the full
tow-line pull of 25,000 lb. either with the
locomotive running or at rest.
Fig. 36. A Portion of the Assembly Floor of the Contractor's
Showing a Locomotive Truck Partially Assembled and
Additional Finished Material
Factory
Fig. 37.
Front View of a Traction Motor Unit with !
Journal Box Disassembled
Fig. 38. A View of the Locomotive Shown in Fig. 38, but Taken from the Opposite
Side, with Covers and One Cab Removed Showing the Controllers
and Front of One Control Panel
116
GENERAL ELECTRIC REVIEW
v
THE TOWING LOCOMOTIVES FOR THE PANAMA CANAL
117
(4) The windlass will pay out or coil
in cable at the high rope speed with tow-line
taut either when the locomotive is running or
at rest.
(5) The windlass is equipped with a
safety friction device which is adjustable to
any predetermined value of tow-line pull.
Conclusion
The first impression may be gathered that
these machines are somewhat complicated,
but considering their many functions and
great flexibility to perform them, it must be
agreed that the design is peculiarly simple.
The locomotives have fully demonstrated
in actual operation that the requirements
contemplated by the Engineers of the Isth-
mian Canal Commission under Circular 650
have been successfully met.
During the first three months of com-
mercial operation of the Canal, from August
15 to November 15, 1914, the cargo trans-
ported through the Canal and towed through
the locks by the locomotives amounted to
1,079,521 tons.
During the fiscal year ending June 30, 1914,
Fig. 42. A View of a Locomotive Crated and Mounted on a
Flat-Car Ready for Shipment to the Steamship that
was to Carry it to Canal Zone
the Panama Railroad carried 643,178 tons
of through freight between the two seaboards,
and in the preceding fiscal year 594,040 tons.
From this it is seen that between six and seven
times as much cargo is passing over the
Isthmus now as passed over this route when
goods were transhipped by rail.
Fig. 43. A Towing Locomotive on the Test Track in the Contractor's Yard
US
GENERAL ELECTRIC REVIEW
ELECTROPHYSICS
Part I.
By j. P. Minton
Research Laboratory, Pittsfield Works, General Electric Company
This is the first of a series of articles dealing with "electrophysics" that we propose to publish during
the year. These articles will not all be written by the same author. The present contribution on the cathode
rays and their properties forms an interesting introduction to the subject, and will be followed next month by
an article on the "electron theory." It is hoped that these contributions will give a useful outline, in simple
language, of a subject which we feel is of great interest and importance to the engineering fraternity. These
articles originated in a series of papers presented before the Electrophysics class of the Pittsfield Section
of the A.I.E.E. They are being revised and amplified by the authors for our columns. — Editor.
CATHODE RAYS AND THEIR PROPERTIES
Introduction
The purpose of this article is threefold;
first, to demonstrate experimentally that
there are small negatively electrified particles
of "something" which are called electrons
or corpuscles; second, to show that the
properties of these particles are entirely
independent of the substances from which
they come, and, therefore, lead us to the
fundamental conception of matter; and third.
to give us a working knowledge of the elec-
trons in order that we may pursue our future
study on the electron theory and its applica-
tions. In the succeeding articles, we shall
develop the electron theory of electric con-
duction through solids and gases, and apply
it to a number of different phenomena.
We shall consider in the present article :
1. Historical review (1859 to 1S92).
2. Experiments on cathode rays, and the
conclusions derived therefrom which lead us
to the fact that there are small negatively
electrified particles called electrons. (a)
Chemical; (b) Heating, (c) Mechanical; (d)
Electrical; (e) Magnetic; (/) Experimental
conclusions.
3. Experimental determination of the
charge (e), the mass (m), and the velocity
(v), of electrons.
4. The constancv of the ratio — , and its
m
significance on the fundamental conception
of matter.
">. The origin of the mass of the electron,
and the variation of this mass with the
velocity of the electron.
6. Distinction and relation between
mechanical and electromagnetic mass.
7. Summary and conclusions.
I. HISTORICAL REVIEW
In the preparation of this historical review
Prof. J. J. Thomson's book on "The Con-
duction of Electricity Through Gases" has
been freely made use of.
Cathode rays were discovered by Pluecker1
in 1859; he observed on the glass of a highly
exhausted tube in the neighborhood of the
cathode a bright phosphorescence of greenish-
yellow color. He found that these patches of
phosphorescence changed their position when
a magnet was brought near them, but that
their deflection was not of the same nature
as that of the rest of the discharge. He
ascribed the phosphorescence to currents of
electricity which went from the cathode to
the walls of the tube and then retraced their
path for some unknown reason.
The subject was next taken up by Pluecker's
pupil, Hittorf,2 to whom we owe the dis-
covery that a solid body placed between a
pointed cathode and the walls of the tube
easts a well-defined shadow, whose shape
depends only upon that of the body, and not
upon whether the latter be opaque or trans-
parent, an insulator or a conductor.
This observation was confirmed and ex-
tended by Goldstein,3 who found that a well
marked, though not a very sharply defined
shadow was cast by a small body near the
cathode, whose area was much greater than
that of the body. This was a very important
observation, for it showed that the rays pro-
ducing the phosphorescence came in a definite
direction from the cathode. If the cathode
were replaced by a luminous disk of the same
size no shadow would be cast by a small
REFERENCES
'Pluecker. Pogg. arm., 107. p. 77. 1859; 116. p. 45, 1862.
-Hittorf, Pogg. ann., 136. p. 8. 1869.
'Goldstein Berl. Monat., p. 284. 1876.
"Varlev. Proc. Row Soc. xix, p. 236. 1871.
sCrookes, Phil. Trans. Pt. 1. 1879. p. 135. Pt. 2. p. 641, 1879.
'Hertz Weid., ann.. xlv. p. 2S. 1892.
TBancroft. Jour. Franklin Inst.. Feb.. 1913.
'Millikan. Phys. Review, Vol. 32, p. 349-397, 1911; Aug., 1913.
pp. 109-143.
J. J. Thomson. (1) Corpuscular Theory of Matter. (2) Con-
duction of Electricity through Gases. These two books will be
found helpful.
ELECTROPHYSICS
119
object placed near it, for though the object
might intercept the rays which came nor-
mally from the disk, yet enough light would
be given out sideways by other parts of the
disk to prevent the shadow being well marked.
Goldstein, himself, introduced the term
" Kathodenstrahlen " (cathode rays) for these
rays, and he regarded them as waves in the
ether, a view which received much support in
Germany.
A very different opinion as to the origin
of these rays was expressed by Varley,4 and
later by Crookes,5 who advanced many
weighty arguments in support of the view
that the cathode rays were electrified particles
shot out from the cathode at right angles to
its surface and with great velocity, causing
phosphorescence and heat by their impact
with the walls of the tube, and suffering a
deflection when exposed to the magnetic
field by virtue of the charge they carried.
The particles in this theory were supposed
all are familiar. A diagram of the tube
is given in Fig. 1, an explanation of which
follows: Suppose the vacuum in this tube
has been reduced to 0.006 m.m. of mercury,
or six microns, and that a static potential
of, say 15 kv. is applied between the cathode
(c) and the grounded anode (a) ; the negative
terminal being connected to (c). A discharge
will pass through the tube due to the applied
potential.
(a) Now let us see what happens from a
chemical point of view. First, we shall
notice a great number of phosphorescent
patches or spots of light on the glass wall
over the distance (c) (d), Fig. 1. The color
of these patches depends on the nature of the
glass ; thus with soda glass the light is yellow-
ish-green, with lead glass it is blue. These
spots can be made to move over the surface
of the glass by means of an electric or mag-
netic field without affecting the nature of the
discharge. This will be made clearer later
Fig. 1. Cathode Ray Tube
to be of the dimensions of the ordinary mole-
cules. The discovery made by Hertz6 that
the cathode rays could penetrate thin gold
leaf or aluminum was difficult to reconcile
with this view of the rays, although it was
possible that the metal when exposed to a
torrent of negatively charged particles, itself
acted like a cathode and produced phosphor-
escence on the glass behind. This view,
however, is not startling since radio-activity
has been developed, for here we have particles
going through metals much thicker than gold
leaf.
During the past 20 years the workers in
the field have increased wonderfully, and
include such men as Weidemann, Schmidt,
Van't Hoff, Drude, Lorentz, Aberham, Ein-
stein, J. J. Thomson, 0. W. Richardson,
Kaufmann, Comstock, Millikan, and many
other men. No attempt will be made to
follow their work, but, in a general way the
results of their experiments which lead us to
the conception of an electron will be given.
II. EXPERIMENTS ON CATHODE RAYS
For these experiments let us consider the
discharge in a cathode ray tube with which
in this article. The phosphorescence noted
is evidently due to something striking the
glass at these particular places, rather than
to any wave motion of light, for this could
not be made to move over the surface in the
manner described below.
We also note that there is a violet-reddish
colored stream of "something" which ap-
pears to come from the center of the cathode
(c), and extends over a distance of perhaps
three inches toward (d), depending on the
conditions of the experiment. This stream
is perhaps from one-sixty-fourth inch to
one-eighth inch in diameter; the larger
streams being observed the greater the
pressure in the tube, up to perhaps 12 or 15
microns. If we put in the tube a diaphragm,
(d) Fig. 1, of some material, say brass, with
a hole through it about one-sixty-fourth
inch in diameter, part of this stream will be
intercepted while the rest of it will continue
until it strikes the screen (5) at the point (p).
This is shown by the fact that, if the screen
is made of potassium bromide, there will be
a round bluish-yellow colored spot about one-
thirty-second inch in diameter on the surface
of this salt. It appears, therefore, that this
120
Salt on the
Screen (s)
NaCl
NoBr
Xal
K CI
K Br
K I
GENERAL ELECTRIC REVIEW
COLOR OF LUMINESCENCE
Cathode Rays
Bluish-white
Bluish-white
Greenish-white
Bluish-white
Blue
Green
Chemical
Reaction
Blue
Blue-white
White— (greenish?)
Blue
Blue
Greenish-white
Precipitation
Bluish-white
Bluish-white
Greenish-white
Bluish-white
Blue
Green
stream of "something" starts from the
cathode (c) and moves to the other end of the
tube very rapidly, for we can detect no
difference with the eye in the time of ap-
pearance of the stream at (c) and at (p).
The name " Kathodenstrahlen " (cathode
rays) was given to this stream of "something "
by Goldstein in 1876. The phosphorescence
produced by these rays is a chemical phenom-
enon as is shown by the above table taken
from the works of W. D. Bancroft.7
The following is another table taken from
the same reference.
Light Color
Pb 504-f-cathode ravs - Blue
Pb + 0 = PbO None
PbO + S03=Pb SO,..- White
Pb + (XH,)« S2Os=Pb SO, + (\H,), 504Blue
Zn SOi-f-eathode rays Bluish-white
Zn+O =ZnO Green
Zn 0 + S03 = Zn SO, Green
Zn + (XH,)2 S?Os=Zn SO, + (.NH,h 504Bluish- white
Cd 504 + cathode rays Yellow
Cd + 0 = Cd O Yellow
Cd 0 + S03 = Cd SO, Yellow
Cd + {NH,h 5208 = Cd S0, + (NH,) SO, White
Considering the first table, suppose that
solid ATaCl is precipitated out of a solution
of XaCl. This action consists in Na and CI
ions uniting to form XaCl which is precipi-
tated when the solution becomes over satu-
rated. If this formation of XaCl from its
ions is observed in a dark room, a bluish-white
phosphorescence will be observed. Now, this
is the color caused by the action of cathode
rays on XaCl. So we conclude that the
cathode rays cause NaCl to split up into its
ions, and the immediate combination of these
ions give off the bluish-white light that we
observe. Similar remarks apply to the other
salts listed in the table. With reference to
the second table, we see that cathode rays
cause lead and zinc sulphates to break up
into zinc, lead, and sulphate ions, and the
reverse action emits the light of the color
stated. Particles of zinc and lead have been
found where the rays fell on the sulphates
of these metals. Sometimes the reverse
action is very slow as in the case of KBr
which requires several hours to reach the
initial conditions again. In the case of other
salts, like calcium tungstate, the reverse
action is practically instantaneous. The
former is called phosphorescence and the
latter is called fluorescence.
If the screen (s) is an oxidized copper
plate, the cathode rays soon cause a bright
copper colored spot to appear: that is, these
rays exert a reduced action. The rays also
affect photographic plates as was shown in a
recent article (Comptes Rendus, 158, pp.
1339-1341, May 11, 1914) by A. Dufour on
"The Cathode Ray Oscillograph." He ob-
tained photographs corresponding to a deflec-
tion of the ray stream of 1 mm. in 3 X 10~6 sec.
It was necessary to use very strong rays to
obtain such results.
(b) Having considered some of the chem-
ical effects produced by these rays, let us
next take up their thermal effects. These
have been investigated by J. J. Thomson,
E. Weidemann, Ebert, Ewers, and others,
all of whom have found that these cathode
rays heat bodies on which they fall. If the
rays are concentrated by using a spherical
shell cathode, platinum may be raised to
incandescence, thin pieces of glass fused,
and the surface of diamond charred. A
simple example will give some idea of the
amount of energy carried by these rays.
It must be stated first, however, that these
rays are composed of negatively charged
electrons as will be shown later. So let n
be the number of electrons striking the sur-
face in unit time, m the mass of the electron,
and v its velocity, the energy E given up to
the body in unit time by the electrons is
E=-r n m v- where this is the total kinetic
energy transformed into heat energy on
striking the surface. If e is the electronic
charge, then the current carried by these
ravs is I = ne, or n =
I
Hence E-
1 , m
:277*
:
ELECTROPHYSICS
121
Now 10~5 amperes is a fair value for I, and if
d = 5X109 cm. per sec., — = 6X10_S, then
e
£ = yX10-5X6Xl(T8X25X1018 = 7.5X107
ergs. Since one calorie equals 4.2 X107 ergs,
E equals approximately 1.7 calories. All of
this energy does not produce heat, but some
is used in producing Rontgen rays, second-
ary cathode rays, and some electrons are
reflected.
(c) Mechanical effects of cathode rays
are also important. A typical example of
this was carried out by Crookes in 1879.
He placed the axle of a very light mill with a
series of vanes on glass rails in a vacuum tube.
When the discharge passed through the tube
the cathode rays struck against the upper
vanes and the mill rotated, traveling toward
the positive end of the tube. If the potential
was reversed, the direction of rotation also
reversed, showing that the cathode rays were
now moving in the opposite direction. Since
the upper limit of the momentum given to
the vanes by the rays is of the order of magni-
tude of 10~2 dynes, this alone cannot account
for the rotation of the vanes. It was shown
later to be largely due to the heating effect
produced by the cathode rays on the side on
which they impinged.
Another exceedingly important mechanical
effect is that these rays pass through a thin
gold leaf, and where the velocity is quite
high they have passed through 1 mm. of
aluminium. This is equivalent to passing
through 250 miles of molecules if they were
two inches in diameter. This had an impor-
tant bearing on the final acceptance of the
view that cathode rays consisted of very small
particles and were not a wave motion of any
kind.
It may be mentioned here, as stated under
/, that the fact that the cathode rays came
from the negative terminal in a definite
direction was a further proof that these
rays consisted of particles of "something."
The name electrons was given to these par-
ticles in 1890. It was also shown that these
electrons came directly from the cathode,
otherwise they would not have been inter-
cepted by an object placed in their path.
(d) The electrical effects produced by
these rays- show conclusively that they are
particles of matter. First of all, if a beam of
light passes through the air and falls on the
wall, the spot of light will not be affected
by presence of a magnetic or an electric field
near this wall. Furthermore light does not
possess an electric charge, for electricity
always associates itself with matter.
It has been shown that cathode rays move
from the negative to the positive terminal,
and must, therefore, possess a negative
charge. This is further affirmed by the fact
that, if a direct current potential is applied
to the set of quadrants QQ, Fig. 1, the phos-
phorescent spot on the screen (s) will move
in such a direction as demanded of a negative
charge by the fundamental laws of electricity.
Bodies upon which the rays strike acquire
a negative charge. Those experimental facts
will suffice to show that the cathode rays
possess a negative charge, and must be
associated with small particles of matter.
The charge on these particles is a certain
definite quantity (as will be shown later),
and one never finds an electric charge which
is not a multiple of this fundamental and
elementary unit of electricity. This, then,
indicates that the cathode rays are atomic in
structure and the electricity resides on these
small particles.
(e) Cathode rays are deflected by a mag-
net when the field is not parallel to the direc-
tion of motion of the electrons. This also
indicates that we are dealing with concrete
particles which carry a negative charge as
shown by the direction of the deflection. .
(/) To summarize: It has been shown
that there are such things as cathode rays as
revealed by the effects they produce, viz.,
chemical, thermal, mechanical, electrical, and
magnetic. Furthermore it has been shown
that they are atomic in structure, being com-
posed of small negatively electrified par-
ticles. These are the accepted conclusions
of the scientific world.
III. DETERMINATION OF (e), (m), and (v)
Let us, now, investigate the properties of
these electrons somewhat in detail. We shall
first determine experimentally their charge
0), their mass im), and their velocity (v).
Referring to Fig. 1, suppose that we have a
stream of electrons passing through the tube
and that they produce a phosphorescent spot
at (p). Now suppose to the quadrants QQ
is applied a steady known potential which
causes the spot to move to a new position
(p1) . Let (h) be so large that h = hl for our
purpose.
In moving over the length h, the electrons
fall through a distance D due to the electric
field applied to QQ. As in the case of falling
122
GENERAL ELECTRIC REVIEW
bodies, we have: D = -at2, where a is the
acceleration of the electrons due to the
electric force E applied to the quadrants, and
t is the time required to move over the path
h
h Now t = — , and the force on an electron
v
Ee
equal Ee = Ma or a = — . If we substitute
these values for t and a in the equation for
, . „ 1 Eeh2 e 2 D v2
D, we obtain D = - „ , or — =
2 mv2
m
EW
In this equation you will find the three
fundamental quantities of an electron, viz.,
e, m, and v. If we know v, we can, therefore,
obtain — which is called the specific charge.
m
To do this a magnetic field is superimposed
upon the electric field at the quadrants QQ
in such a way as to balance the effect pro-
duced by the latter field. Now Rowland
showed experimentally that the force on an
electron due to the magnetic field is H e v sin 8,
where 6 is the angle between the electric and
magnetic fields and H is the strength of the
latter. Making 0 = 90 deg. (or sin 0=li we
E
have, therefore. H c v = Ee or b=tj. Both E
and H can be easily measured, so that » is
known. This velocity never exceeds 3X1010
cm. per sec. the velocity of light: 109 is a fair
velocity for the electrons. In radio-activity v
is perhaps 2.5 X 1010 cm. per sec. and in the
cathode ray tubes it is about 5X108 cm. per
sec. Putting this value of v in the equation
for — , we obtain — = 1S00 X 104. Now — for
m m m
the hydrogen ion is 104, so that the specific
charge of an electron is about 1S00 times as
large as that of the hydrogen ion, the smallest
particle of matter yet known. To settle
this point we need only to measure the charge
(c) of the electron. At least eight different
methods have been used for this purpose.
These methods are two radio-active, one
Brownian movement, one radiation, two
"cloud formation," one Zemarm effect, and
the famous oil-drop method of R. A. Milli-
kan7 of the University of Chicago. It is
well to note that the values given by these
methods agree within three per cent of that
given by Millikan, who is absolutely certain
of his value to 0.1 per cent. The other in-
vestigators do not claim any such accuracy
for their results. His method of determining
e is briefly as follows :
He immersed a brass vessel in an oil bath
to maintain a constant temperature. Within
this vessel were two parallel metallic plates
1.6 cm. apart. The air pressure in the brass
chamber could be varied at will by means of
pumps. X-rays could be passed through a
glass window so as to ionize the air between
the plates, thus causing free electrons to
exist in this space. Now, by means of an
atomizer extremely small (0.0005 cm.) drops
of oil could be sprayed between the plates,
and when either an ion or an electron stuck
to the drop it would acquire a corresponding
charge. He applied a potential to the plates
and so could move the oil drop up and down
at will. He could also detect, by a change in
the velocity of the drop, when a new charge
attached itself to the drop ; which was viewed
by means of an optical system. He used the
following formula to calculate the charge on
the drop due to (n) elementary charges:
47T (9rf\ 1 ( 1 V/fa+tfrA
1 3\,2/ \&Qr-P))\ F )
Vl
where (77) is the coefficient of viscosity of
air, (a) the density of the oil, (p) the
air density, (vi) the speed of descent of the
drop under gravity, and (i'2) its speed of
ascent under the influence of an electric field
of strength F. All of these quantities were
known to 0.1 per cent. The equation was
based on three assumptions, viz., the drag
which the medium exerts upon a given drop
is unaffected by its charge ; neither distortion
due to the electric field nor internal con-
vection within the drop modified appreciably
the law of motion of the drop; the density of
the oil drops is independent of their radii
down to 0.0005 cm. Millikan not only
showed that these assumptions were justi-
fiable, but their effects were not present
at all.
By means of the above equation he ob-
tained a series of values for (e„), and taking
the lowest one he found all the others to be
exact multiples of it. This value we naturally
accept as the elementary charge. He has
carried out a great number of tests under
various conditions as regards size, tempera-
ture, pressure, and gives e = 4.774 ± 0.009 X
10~10 electrostatic units.
Now, this value is the same as that carried
by a hydrogen ion, which must, therefore,
carry one of these elementary charges. We
are led then to the experimental conclusion
ELECTROPHYSICS
123
that the mass of the electron is
1
1S00
of that
of the hydrogen atom, which until now was
the smallest particle of matter we had known.
We are forced, therefore, to the fact that
matter is still further divisible than we were
led to believe by the atomic hypothesis.
The mass of the electron is, therefore, m =
4.8X10-l0X3X10-10 . .
1SX107 ' whlch glves '" = 8><
10-27 grams. This is true for velocities which
are not very close to 3X1010
will be shown shortly.
cm. per sec. as
IV. CONSTANCY OF
The ratio
i0 (A
\mj
(e), and (w), have been
measured for many different kinds of gases,
solids, and elements under various conditions.
In every case all of these quantities were
constant (except for velocities near that of
light) and entirely independent of the sub-
stance from which they were obtained.
Consequently, the electron is a fundamental
unit of electricity and matter, and all matter
must have it as one of its constituents. The
other constituent or constituents, as the case
may be, must be matter which acquires a
positive charge by losing electrons and gain
a negative charge by addition of electrons.
If there are positive electrons, however, this
conclusion need not be true; but the scientific
world has tried in vain to discover them for
the past 15 years. Until they are discovered,
we must content ourselves to build up a
theory of matter with the electrons as a
basis. This is the so-called electron theory
of matter, and, since they always possess a
negative charge, they form the basis of the
electron theory of electricity. Both of these
theories, which will be developed in the next
article, are "subject to change without
Fig. 2
notice." As to the nature of positive elec-
tricity we know nothing except it must exist.
V. ORIGIN OF THE MASS OF THE
ELECTRON
It is a"well-known fact that when a current
of electricity flows through a wire a magnetic
field is set up in the space around it. Simi-
larly, a charged body moving through space
sets up a magnetic field in the surrounding
space. Hence, if we have a charged body, it
will require more energy to set it in motion
with a velocity (i>), than would be required
*; — x
Fig. 3
to set it in motion with the same velocity
if it were not charged. In the first case the
energy required is - M v* plus the magnetic
energy, and in the second case it is - M v2.
Since the velocities are equal, it follows that
the charged body apparently has a greater
mass than the uncharged one. This fictitious
mass due to a magnetic field surrounding a
moving, charged body is called the electro-
magnetic mass of the body.
Now let us determine the electromagnetic
mass of a charged sphere of radius a, moving
through space with a velocity (v), where (n)
is not too nearly equal to the velocity of
light (c). Let 0) be the charge on the sphere.
Rowland has proved experimentally that the
magnetic force at a point p. Fig. 2, due to the
charge (e) moving along OX is:
tt _e v sin d
H~ ~1*~~- (1)
The energv density at (p) due to the mag-
H2
netic field alone is Dm = ;
or, by equation (1) :
8 (pi = ir)
c- v- sin 20
8T(pi=w) rk
(2)
124
GENERAL ELECTRIC REVIEW
Changing Fig. 2 to Fig. 3, the volume
(it)
abcdefgh = -~ r sin 6 r d r d 6.
Multiplying this equation by 4, we have
4 a b c d e j g h = 2 (w) r2 sin 6 d d dr (3)
This equation gives the volume of an element
of an imaginary sphere in the space surround-
ing the charged sphere. The magnetic
energy in this volume is, therefore, by equa-
tions"^) and (3).
(A) EH= ^ffx20r)r'sin 6 dd dr
or
(A) EH =
8(x)r<
e2v"sm36 dd dr
4r2
Hence, the total energy due to the magnetic
field in the space surrounding the sphere is
EH
Eh
'±aJo
[
c-v-si>!36
4r
1 <iird
dd dr
>■-
dd dr
Eh=V-
) sin36 dd
e-v-
ia
1 3 cosO (sin2 6 + 2)
Eh=1/3
e' i-
(4)
The total energy, Et. therefore, possessed
by the moving charged sphere is
. e2 ;•'-'
ET=1 2 .1/ v2+l 3
or
ET=l/2
[(M+Hl
where M is the mechanical and
(5)
the
2 e-
3a
electromagnetic mass. If we assume an
electron to be spherical and that it acts as
though the charge were located at the center,
equation (5) applies to it just as it does to
the sphere.
In 1901 Kaufmann determined experi-
mentally the value of the quantity in brack-
ets in equation (5) for different velocities
of the electrons. The results he obtained are
illustrated in Fig. 4, where (c) is the velocity
of light. From this curve we see that the
apparent mass of an electron becomes infinite
when v = c, and that it changes very little up
to 2X1010 cm, sec. If the curve were con-
tinued to v = o, it would cut the ordinate
v = o at M, which is the mechanical mass of
an electron. Since this latter mass does
not change with v, it follows that the electro-
magnetic mass must increase very rapidly
when v=c (means v approaches c as a limit).
This is also the conclusion at which one
arrives from a purely mathematical con-
sideration. The deduction is quite compli-
cated and I shall not frighten you by giving
it in this article. The equations show, how-
ever, that when vi=c there is a weakening in
both the electric and magnetic fields in the
regions of a o b and cod, and an increase in
the regions a o d and b o c, see Fig. 5. When
v = c, the fields are zero except in the plane
g o h, where they are infinite. Hence when
v = c, the electromagnetic mass of an electron
becomes infinite. Since by far the greater
part of the mass of an electron is electro-
magnetic, it must necessarily possess very
little inertia, even up to velocities comparable
with those of light.
( ,_^
i j _n j m
& j 1 — X-ttt-tif 11
£ 4==: _ix_iii_i± xxtrxLT
iniiiiiiii" t ii in id
I I Li)! It J Lilt
IIIIIII IJJT j i_ ! Tj~i~
— r-H — i — i — H — ^K
— i — i — I — , — i — i — i — ! — i — i — -\ —
— ----- -j — h±--—3B:
iiiflill
SiZO*
1,/D"> Z*/0'°
Velocity.
Fig. 4
3*/0"
C
Equation (5) must be modified to cor-
respond with this change in mass according
to the following equation
EB=\ -lUl+j (v) 2
3 a
(6)
ELECTROPHYSICS
125
where / {v) = l when v = o, and / (v)= in-
finity when v = c. In this connection the
following table, which was taken from J. J.
Thomson's Corpuscular Theory of Matter,
p. 33, will be interesting.
From equations (5) :
^L
9
^a
^T^e
(N.
■^c
i
^\«?
Fig. 5
Velocity of
Electron
Ratio of
Total Mass
to that of
a Slow
Electron
/(»)
2.36 X1010 cm /sec.
2.48 X1010 cm /sec.
2.59 X1010 cm /sec.
2.72 X1010 cm /sec.
2.85 X1010 cm/sec.
1.65
1.83
2.04
2.43
3.09
1.50
1.66
2.00
2.42
3^10
A consideration of these values obtained
by Kaufmann will show that the mass of an
electron is almost wholly due to the magnetic
energy in the space surrounding it. Thomson
concludes that the mass of an electron is
entirely electromagnetic in origin. This
conclusion is not justifiable for velocities
below 2.59X1010 cm/sec. as is seen from the
table above so that the electron must possess
some mechanical mass even though it may
be an extremely small per cent of the
total.
Assuming the mass (m) of an electron to be
wholly electromagnetic, we can calculate its
radius (a) as follows:
2
eP-
n,
—
or
3
a
0
e?-
a
:= —
■
3
m
(7)
We have seen that — =1.SX107, and that
m
e=10~20 electromagnetic units. Substituting
these values in (7), we obtain a = lCT13cm.
approximately; the radius of an atom or
molecule is about 10~8 cm.
The relation and distinction between me-
chanical and electromagnetic mass in the
above discussion have been pointed out. In
addition, it has been shown that:
(1) Electromagnetic mass must have weight ;
or
(2) Electromagnetic mass = constant X me-
chanical mass. Some theoretical physicists
even go so far as to assume all mass is electro-
magnetic. On account of insufficient time,
however, the line of argument leading up to
these conclusions is not given.
VI. SUMMARY AND CONCLUSIONS
From the information here given we must
conclude that there are small negatively
electrified particles called electrons, the prop-
erties of which are entirely independent of
their source. We have seen that these elec-
trons exist in matter as well as separated
from it like cathode rays, Beta particles from
radioactive substances, in gases where a
discharge of electricity is passing, etc.
In concluding this article the author
wishes to say that he has endeavored to
briefly present the experiments upon which
the electron theory is based, and has not
developed it at all, simply suggesting it.
He has also endeavored to familiarize you
with the electronic conception sufficiently to
develop the theory and apply it to various
phenomena in the succeeding articles.
126 GENERAL ELECTRIC REVIEW
THE SELECTION OF RAILWAY EQUIPMENT
By J. F. Layng
Railway and Traction Engineering Department, General Electric Company
The author deals with some of the important considerations governing the selection of car equipments
for city and suburban service. By making an analysis of the pressures of wheel treads, he determines the
method of mounting the motors that will give the maximum adhesion available for traction. It is then
possible to determine the equipment that will be most suitable to operate on severe grade conditions, and
also to obtain the best schedule speed on all rail conditions. — Editor.
The purpose of this article is to designate,
in a general way, the facts concerned in the
selection of car equipments to meet the
varied conditions which confront railway-
engineers when purchases are to be made.
The situation can best be covered by an
analysis.
In general, there are at least six different
classes of service for equipment at the present
time, viz.. city, interurban, elevated, subway,
steam railway terminal electrification and
main line railway electrification. Insofar as
the present discussion is concerned, only
city and interurban service will be considered.
The electrical equipment of city car service
may be divided into two classes, viz., two and
four-motor equipments; of trucks, in general,
there are three types, viz., single trucks,
maximum-traction trucks, and double trucks.
The number of combinations that can be
made when applying power to the car with
these elements is surprising. The proportion
of the total car weight on the driving wheels
largely determines the schedule possibilities
and the grade-climbing capacity of a car.
With the single-truck, two-motor equipment,
all the weight is on the driving wheels so
that this combination would be ideal were it
not for the fact that the demands of seating
capacity and riding quality put limitations
on the single-truck car that usually make it
necessary to have double-truck equipments.
With the double-truck car there are many
complications which arise when selecting a
distribution of power for the driving axles.
A selection which will give uniform weights
on the wheel treads will, of course, give the
ideal car, for it will reduce wheel slippage
to a minimum under all conditions. Dur-
ing the period of acceleration there is a
shifting of the car-body weight so that
there is a lesser weight on the front center-
plate than on the rear center-plate. The car-
body weight assumed for all the double-
truck cars considered in this discussion is
20,000 pounds or 10 tons, and this mass is
assumed to be accelerated at the rate of 1^2
miles per hour per second. There is-a retard-
ing pressure of 137 pounds per ton, or a total
of 1370 pounds, due to acceleration. It is
assumed that the center of this mass is 24
inches above the center-plate, and that the
king-pins are 20 feet between' centers. When
the car is accelerating there is a shifting of car
body weight around the center of the mass,
which, with the car body as described when
accelerating at IJ2 miles per hour per second,
gives 9S63 pounds weight on the front
center-plate and 10,137 pounds on the rear
center-plate. The same shifting of weights,
but in different proportions, takes place on
the trucks. This action is independent of
the position of the motors on the trucks.
Later on it will be shown that with a four-
motor equipment and motors "inside hung"
it is possible to secure the nearest approach
to equalization of the weights on the wheel
treads.
h / »l
Fig. 1
L = Distance between truck centers.
H = Distance of center of gravity of car body above center
plate.
W —Weight of car body in pounds.
T = Retarding pressure of car body during acceleration.
P = Pounds pressure transferred from front truck to back
truck at king-pin.
Id —Weight on front center-plate.
Wi = Weight on rear center- plate.
pi = Pounds pressure transferred from front to rear axle
(center-plate load).
pi = Pressure transferred from front to rear axle (truck load).
P = pi+pi-
W = Weight on front axle exclusive of truck weights.
W = Weight on rear axle exclusive of truck weights.
b = Weight of truck.
/ = Retarding pressure of truck during acceleration.
The question is frequently asked — "What
equipment shall we buy, two-motor or four-
motor?" To this question a direct answer
cannot be given; it is a question of judgment.
The answer is determined by the amount of
wheel slippage that is allowable On this
THE SELECTION OF RAILWAY EQUIPMENT
127
account, generally speaking, double-truck
two-motor equipments are not satisfactory
where the grades exceed five per cent, or
on a bad rail such as is produced by snow,
sleet, mud, or leaves on the track. Wheel
slippage is the factor which usually decides
whether or not four-motor equipments are
chosen.
The combinations of weight distribution
and the weight on the individual wheel treads
during the period of acceleration present a
very interesting problem. The maximum
schedule will of course be maintained by the
equipment which has the most nearly equal
weight distribution on the wheel treads.
In addition to the many combinations of
motor mounting for a single car, we have trailer
operation to consider and also the effect of
these trailers on wheel slippage, both on level
track and also on grades. An analysis of the
weight distribution on single-motor cars in-
dicates clearly the reason for usually selecting
four-motor equipments when trailer opera-
tion is to be considered. This analysis of
weight distribution shows why, when the
grades to be negotiated are more than five
per cent it is the general practice to use four-
motor equipments for double-truck cars.
There are at least twelve to fifteen dif-
ferent combinations of mounting motors on
the different types of trucks in general use.
For 'the present purpose, twelve combina-
tions will be considered. With each of these
there is a different weight on wheel treads
during the acceleration period. In arriving
at the values given in Fig. 2, it is assumed:
1st. The car is accelerating at one and
one-half miles per hour per second on tangent
level track.
2nd. The single-truck car weighs complete
10 tons, has a ten-foot wheel base, and the
center of gravity of the car is 24 inches above
the center-line of the axles.
3rd. All double-truck car bodies complete
with car-body equipment weigh 20,000 pounds
each with no live load.
4th. Double-truck cars have trucks weigh-
ing 6000 pounds each. Those having inside-
hung motors have 72-in. wheel-base and those
having outside-hung motors have 54-in.
wheel-base. The distance from the surface
of the center bearing-plate to the center-line
of the axle is 12 inches, the wheels are of 33-
in. diameter, the center of gravity of the truck
with motors is 16^ in- above rail for motors
shown in Fig. 2, and the distance between the
truck centers is 20 feet. The weights and
lengths of each end of the car are equal.
5th. There is a slight downward tilting
of the car body and trucks during the accel-
eration which will make a slight variation
in the figures as given, but as these variations
are inappreciable and would complicate the
explanation, no allowance has been made for
this variation. The rotative effects of dead
Direct /on of cor motion —
Tot ol cor body weight ZOOOOIb
]^000-l37.3863lb.as3gn,A I
S069/b
t36?
S436
SOOO
/04-36
S069/b.
-367
4702
SOOO
S702
-zsa
49381b.
+356
S283 4S76
SOOO SOOO
49321b
-3S6
'0288
+ 228
/os/e/c
9S76
93481b.
/O 66 4 lb. 94741b
Weights os given are for iveightson wheels of each axle.
Fig. A. Specific example of how to determine the distribution
of car weights when the center of gravity of the trucks
and motors is taken as 18 in. above head of rail
Distribution of Car Weights on Wheel Treads
During Period of Acceleration (Four
Motors Outside Hung)
Car body weight. 20.000 lb.
Truck weight, 6000 lb. +two motors, each 2000 lb. =
10.000 lb. total.
Wheels 33 in. diameter.
Wheel-base 54 in.
Truck centers 20 ft. or 240 in.
Center-plate 12 in. above center-line of axle and 28 } ■• in.
above wheel tread.
Center of gravity of car 24 in. above center-plate.
Center of gravity of trucks with motors IS in. above
wheel tread.
Car acceleration 1 K miles per hour per second.
Ninety-one lb. required to accelerate one ton one mile per
hour per second XI H =137 lb.
Car body weight transferred from front to rear center-
137X20,000 lb. X24in. ,_, ,, ...
P'ate=^000 1b.X240 1b. =137 lb' Wh'Ch B'VeS
9S63 lb. weight on front center-plate and 10.137 lb. on
rear center-plate.
The 9S63 lb. on front truck has transferred weight from
137X9863X28!-^
front to rear axle as follows:
2000 X 54
'=356 lb.
transferred weight.
The 10.137 lb. on rear truck has transferred weight from
front to rear axle as follows:
137X10.137X28H
2000 X 54
3671b.
transferred weight.
Within the truck and motors there is also weight trans-
37X10.000X18
f erred from front to rear axle as follows:
2000 X54
= 22Slb.
axles have not been considered, as the varia-
tion would be slight.
Based on these facts, the outlines in Fig.
2 have been made.
The formulas from which the weight pres-
sures were calculated are derived in the fol-
lowing, in which the diagram in Fig. 1 and
its key are used as a base.
12S
GENERAL ELECTRIC REVIEW
be
The retarding pressure of the car body will
T =
137 IT
2000
<ap- W U&o oW
1 392 3 SSOB €s&2 tg 77'
&@y t®«
t®©
6 30O Z2&29
1377/ SOS2 '3 929 S2eB '377/ Sa32
'2339 6739 ';;« 6602 >0&03 92SS 69tX »»J"B
10
(§P®
90+3 --eoss I07++ 3"&
m®
&2ST *07+6 O'-a
II
-1 t=3Tsa
1 fe-B — a L
■0SO4 9360 1049? 964/
'03 GO 9S04-
0if?eCT/O* Of fit- L CA/?3 *-
r/ft/#£-S G'V£# fif£ V*£lGH7SOff WHEEL Ttf£ffPS WHEN
accELEtRT/NG /^ M F? H P£F S£C0MI>
Fig. 2. Twelve Methods of Mounting Motors on Trucks,
Showing Relative Weight Distribution
During Acceleration
The transfer of weight from the front
center-plate to the rear center-plate is found
by taking moments^ about a point X as
follows.
137JI7/ L
2000 2
137 WH
2000 L
The transfer of car-body weight from the
front axle to the rear axle is determined, as
follows :
T
-^K=pih+pik=pi(.k+h)=:pil.
TK
The transfer of truck weight from the front
to the rear axle is determined thus :
, 137 b 137 b h
t = ~^X7^ —^T^TT = Pit
2000
137 bh
>000
yi 2000 I
ti * TK , 137 bh
Then^=2T+2000l"
And the distribution of wheel pressure will
be as follows:
Front truck
W=W1lj+p
Rear truck
W' = W^-p
W=Wslf+p
Considering the weights on the individual
wheel treads, it will be seen that with the
single-truck car, shown in Fig. 2, there is a
noticeable shifting of the weight from the
front axle to the rear axle during acceleration.
The wheel-tread weights for the maximum-
traction trucks are also somewhat different
from those we would naturally expect from
the static weights (in all the assumptions
made for maximum-traction truck calcula-
tions, it has been assumed that the static
weights on the driving wheels are 70 per cent
of the total). It is a natural conclusion that
with four-motor equipments the nearest to
equal distribution of weight on wheel-treads
under all conditions would be procured.
However, by comparing diagrams 1 1 and 12,
Fig. 2, it will be noted that the inside-hung
motor arrangement shows a considerable
improvement over four-motor equipments
with outside-hung motors. All of the weights
as given in the different diagrams are for cars
accelerating at 1 J/£ miles per hour per second
on straight level track. When accelerating
on grades the values will be somewhat dif-
ferent, but not as much as one would naturally
be led to expect.
Another feature of these calculations which
should be considered in connection with the
weights is that cars which have long plat-
forms on one end only have not been con-
sidered. There are so many variations in
this respect in cars operated in regular service
that it would be impossible to make general
statements covering this condition. Dimen-
sions and weights on both ends of the cars
have therefore been assumed to be equal.
After the question of deciding how many
motors are to be used on a car, the next
factors to consider are how to get the greatest
THE SELECTION OF RAILWAY EQUIPMENT
129
amount of work out of the motors per pound
of weight, how to secure the motor that will
use the least power, and at the same time
to obtain an equipment at a price that will
be justified by the results of these savings.
It is a universally accepted fact that a
ventilated motor will have a greater work
capacity per pound of weight than a non-
ventilated motor. The past few years' ex-
perience has led all of the truly progressive
engineers to specify that the motors which
they are about to purchase must be ventilated.
It is also a generally recognized fact that by
using field control the work capacity of a
motor, that is properly designed, is increased.
When considering the use of field control, the
service should be carefully reviewed to see if
the increased cost and the complications of
the field control are warranted by the savings
in power and weight of the extra control
apparatus required. The cost of a motor
designed for field control is but slightly
greater than that of one for full-field running
only, but there is also an increased cost in the
control and car wiring for the former type of
motor. There are practically twice as many
field connections as are found in the ordinary
full-field equipments. These extra con-
nections make the locating of trouble more
difficult. All of these factors must be taken
into consideration. Practically all the sav-
ings secured by field control are made during
the period of acceleration, and, since this is
the case, rapid acceleration decreases the
power saving. Another way of partially
expressing this idea is that where steps are
infrequent the saving is proportionately small.
On account of the complications in wiring and
control but comparatively few field-control
four-motor equipments have been installed.
However, for two-motor equipments many
purchases of field-control equipments for
frequent stop city service have been made.
During the past three years there has been
an increased amount of interest exhibited
regarding 24-inch wheel equipments for city
service. Motors that are particularly effi-
cient and well constructed have been designed
for use with these equipments. Due to the
decreased weight of the wheels and trucks
as well as to the reduction in the weight of
the motors, this subject has engaged active
study. In addition to the weight savings there
has also been an innovation in control which
consists of a change in the standard motor
circuit connections so that three running
speeds are obtained. With this combination
of control there is a considerable saving in
power consumption. In some cases a saving
of seven or eight per cent may be expected.
It is necessary, however, in connection with
this control to carefully analyze the service,
for experience has shown that the heating
is not equally divided among the four motors
of the equipment. Referring again to the
reduction in the weight of trucks for these
equipments, it can be stated that for the
standard 33-inch wheel equipment (which
it was formerly the practice to use) these
trucks would weigh approximately 12,000
pounds per pair, and that it is now possible
to purchase trucks with 24-inch wheels which
will weigh but 8000 pounds per pair. The
weight of an individual motor which was
formerly designed to operate with the 33-inch
wheels would be approximately 2000 pounds
while the 24-inch wheel motor complete
weighs but 1750 pounds. It can therefore
be seen that a saving of 4000 pounds can be
made in the trucks alone and in the motors
1000 pounds additional, making a total re-
duction in car weight of 5000 pounds. This
weight saving is something that cannot be
ignored. There have been a number of 24-
inch wheel equipments purchased during the
past year and the results of their performance
will be followed very carefully. In all proba-
bility, within the next year or two, some very
pertinent facts will be available.
In the selection of interurban equipments
the same considerations in regard to motor
distribution apply as have been mentioned
for city cars. Practically all equipments in
this class of service employ four motors, and
it is the usual practice for the motors to be
inside-hung. There has not been a general
adoption of field control for interurban work
due to the fact that as a rule the stops, as
compared with city service, are relatively
infrequent and therefore the savings which
can be made with city equipments is not so
apparent in the interurban equipments.
When purchasing any large number of new
equipments the savings which may be pro-
cured with higher voltages than 600, which
has been the standard in past years, are very
attractive due to the savings which would
seem to be possible. However, an analysis
of many of the existing interurban road con-
ditions develops the fact that these interurban
roads also supply city service to a large
number of small towns through which they
pass, and that on these city equipments very
extensive changes would have to be made.
That is, the electrical equipment would all
practically have to be renewed on these cars.
130
GENERAL ELECTRIC REVIEW
Provided this change is not made the line
must be so sectionalized that the town sec-
tions would still operate on 600 volts, and
after all of the savings and the additional
costs have been taken into consideration, it
has been found that in a great many cases
the change was not warranted. Of course,
if these properties were entirely new the prop-
osicion would be a much different one, and in
all probability the installation of the higher
voltages would be more than warranted.
A large number of interurban roads have
practically reached the limit of their earning
power as they are securing all of the busi-
ness which there is at the present time,
and the only additional business which can
come to them is through the natural increase
of business due to the growth of the com-
munity. This has lead the management of
these properties to carefully consider and to
estimate the cost of entering into the business
of hauling car-load freight. As a result it
would not be surprising if a large number of
roads purchase locomotives in the near
future in order to increase their earnings per
mile of track. To select the motors for this
service, it has usually been the practice to
start with locomotives weighing approxi-
mately 40 tons. Sometimes
these units are of the regular
locomotive type and some-
times of the baggage-car type.
These units as a rule are
equipped with four 125-h.p.
motors. On some properties 3
this business has grown to g'^7^'"
such an extent that it is
necessary to use 60-ton loco-
motives which are usually
equipped with four 225-h.p.
motors.
In the selection of an equip-
ment for either city or inter-
urban work, it is necessary to
have a very definite picture
of the work to be done. Very
careful consideration of the
actual work that is desired to
be accomplished should be
given by the management of
the railway company; and
when working up data for
a proposition, it is very dangerous for the
railway company to put leeway in the figures
which they give to the manufacturing com-
pany. When certain equipment is recom-
mended by a manufacturer the railway com-
pany can always place dependence upon it,
zoo 27
180 18
160 16
140 ^u
JZO^lZ
80<r>8
60% 6
40 4
zo z
for in the recommendation the manufacturer
has of necessity already embodied a certain
margin of safety.
If there has been an allowance made
earlier by the railway company as to schedule
speeds, stops per mile, duration of stops,
etc., and then the manufacturing company,
ignorant of the previous allowances, also
makes additional ones in each of these factors ;
the equipment will be larger than is actually
required to perform the work, and this would
be caused simply by doubling the allowances.
The number of stops and the duration of
stops which are made per mile by any equip-
ment are very deceptive. The only way in
which this info-T>-+:~n can be obtained is by
actual observation and careful records. The
problem is not a difficult one, but is just
an actual statement of the facts. If
these few statements were given careful
consideration frequently, considerable of the
extra figuring and time of all parties con-
cerned would be saved. The securing of
accurate service data insures the purchase
of the proper size equipment. This means
an equipment which will give satisfac-
tion and also will be secured at a reason-
able cost.
^""" ~"~~-^ J
: v *>'" " *S
X^ VU-
Y xV
-Zk ^S
7 V Sv
- v S * ±
-■ -7 ^ its
= ■ 7 *-, S\ I
7 "I t\ i
/ S '
/ \ ^ i
.' ~~ ">>P P
(-— i_ v^
6 8 10 12 IA 16 18 20 22 24 26 23 30 32 34 36 38 40
Tin-i& - Seconds
Fig. 3. Speed-time and Energy Curves for 20-ton Cars
Showing
Comparison of energy consumption for
slightly different schedules.
Service assumptions:
Two-motor equipment — 50-h.p. motors.
20 tons total car weight.
o50 volts average
7-75 stops per mile.
1H m.p.h.r.s. accelerating and braking
rate.
20 lb. per ton friction.
Dotted line curves indicate:
Maximum schedule 9.6 m.p.h. No
coasting.
Energy consumption 145 watthour per
ton-mile.
Full line curves indicate slightly de-
creased schedule, 9.45 m.p.h., coasting
about 30 per cent distance. Energy con-
sumption 122 watthour per ton-mile.
Showing a saving of 19 per cent in energy.
In a general way, it can be said that at-
tempting to run a faster schedule than normal
is very expensive. An illustration of what
happens to power consumption under this
condition with 20-ton cars is shown by the
speed-time and energy curve shown in Fig.
A SHORT METHOD FOR CALCULATING STARTING RESISTANCE 131
3. This is based on 7.75 stops per mile.
With 9.6 miles per hour schedule speed,
145 watthours per ton mile will be used. Bv
slowing this schedule to 9.45 miles per hour,
122 watthours per ton mile are required; a
saving of 19 per cent. It would seem that
in the selecting of the equipment and in the
laying out of schedules a considerable power
saving could be made by being a little more
reasonable in the running time. Of course
there is a natural tendency to run the highest
possible schedule speeds at the present time,
which has been brought about by the recent
increase in "platform" wages.
A SHORT METHOD FOR CALCULATING THE STARTING RESISTANCE
FOR SHUNT, INDUCTION, AND SERIES MOTORS
By B. W. Jones
Industrial Control Department, General Electric Company
Since at the present time p.c^Mcally all motors are shipped from the factory complete with the proper
starting rheostat, the information given in this article will be of use mainly to the factory designing engineer;
yet at the same time formula; of the kind will be of great assistance in some cases of temporary motor instal-
lations where it is necessary to regulate the starting characteristics of the motor. The author deduces simple
formula; for the resistance steps for maximum and minimum given values of accelerating current with given
number of rheostat divisions and value of internal motor resistance, for shunt, series and induction motors
singly, and for two and four series motors in series-parallel. The theory on which the method is based is then
given, and a concrete example for each of the cases assumed is worked out. — Editor.
In commercial practice it is necessary to
calculate a large number of starting rheostats
for the shunt, induction, and series types of
motors, and therefore it is essential that a
short method be used. Of the methods
available, the one described in the present
article has been found in practice to give
remarkable satisfaction.
First, either the maximum or the minimum
accelerating current peak is assumed, together
with the number of rheostat divisions and the
internal motor resistance. If it is a series-
motor resistance, then the speed character-
istic curve of the motor is necessary. During
acceleration the successive divisions of re-
sistance are short-circuited as fast as the
current decreases to a fixed assumed value,
and all the current peaks are of equal value.
It should be noted that if all values are in
percentages it will cause less confusion.
Therefore, all of the series-motor formuke
will be expressed on that assumption.
Let
Ri = Total
R
current =
resistance to give minimum
V
I{
Total resistance to give maximum
V
It
= Internal resistance of motor.
; r*; r-i\ ?C etc., = Resistance of the
successive divisions of the rheostat.
= Number of rheostat divisions.
maximum acceleration current
current :
X = Ratio
Y
Ai =
Z :
minimum
~n
■■(Si-S,)*
100 V-hr
Sili
100 V
acceleration current
hr
S, I,
~A*
V =Line volts.
1"
i i = Minimum acceleration current = -=-.
rii
Si = (For series motors) speed correspond-
ing to II.
V
Is = Maximum acceleration current =
For Shunt or Induction Motors
I. Assume that the minimum accelerating
current, the number of rheostat divisions, and
the internal resistance of the motor are known.
Log X
1
log
Ri
Rt
5j = ( For series motors) speed corre-
sponding to h.
5.3 = Speed corresponding to 1.5 h*
M+l
n=(X-l)r.
rt = Xri.
r3 = Xr2.
r„ = Xr n-\.
*See footnote, page 132.
132
GENERAL ELECTRIC REVIEW
II. Assume that the maximum accelerating
current, the number of rheostat divisions, and
the internal resistance of the motor are known.
Log A =- logy.
n = (A-l)r.
n=Xn.
r3 = Xr1.
r„ = Xr „-i.
It is apparent that if any three values are
known, the fourth can be found.
For Series Motors
III. Assume that the minimum accelerating
current, the number of rheostat divisions, and
the internal resistance of the motor are known.
The following is an empirical formula:
1 . /?!
'n + 1
n+2
Then, from the article "Determination of
Resistance Steps for the Acceleration of
Series Motors" by E. R. Carichoff and H.
Pender in the General Electric Review.
July, 1910, we take
n = Ax (Si- S2).
r2 = Zrx.
r3 = Zr2.
rn = Zr „_i.
IV. Assume the same conditions as in III.
but that there are two motors to start in series-
parallel.
For the series position:
1 . R
n+1
Log
n -f
!"L
1.5
(:-£)
Y
Log X
log
r2 = Zn.
r3=Zr2.
Yn =Zrn—i.
For the multiple position
Log A = - — log
-Ri
n+ 1
ri=iii(S!-
r2 = Zrx.
r3 = Zr2.
r„ = Zr„-i.
■St).
* Note that the denominator, 1.51
(5i - 5» \
J.-/,/
(Si) '—(Si)
It is sometimes convenient and slightly more accurate to make
/a as near equal to li as can be approximated instead of h =
l.o/i.
V. Assume the same conditions as in III, but
that there are four motors to start in series-
parallel. Four motors are to be in series at
starting and two are to be in series for permanent
running.
With this condition if r = internal resist-
ance of two motors then the formulas in
V are to be applied.
THEORY
I. From geometrical progressions:
Sum = r+rX1+rX2+rX3+. . .rX" + r+X"+'-
(Where n equals two less than the number
of terms which correspond to the number
of rheostat divisions.)
Therefore the last term, R\, which is the
sum of all the previous terms is:
R^rX'+K
X"+1 =
Ri.
LogA =
1
loi
Ry
n+1
II. If n represents three less than the
number of terms, then the next to the last
term is
R, = rX",
r
t v l i R*
Log A =- log-.
III. For series motors a modification of
the above is necessary. Since there are
already too many variables to solve the
equation, it is necessary to resort to an
empirical formula which is accurate enough
for all practical purposes.
The motor field flux varies as a function
of the current, and the current fluctuation is
a function of the motor's internal resistance
and the number of rheostat divisions. There-
fore in place of
r there is placed 1.
in + 2)
Y
LogA =
1
n+1
log-
Ri
'■•<:->■
IV. The only difference between starting
one motor from rest to full speed or two
motors in series from rest to one-half speed is
that an extra resistance, (r), is inserted in the
circuit. Since the two motors in series
attain only one-half speed, the sum of the
two counter e.m.f. increments are the same
as those of one motor running full speed when
A SHORT METHOD FOR CALCULATING STARTING RESISTANCE
133
the current peaks in each case are the same.
Therefore, the formula becomes
Log X =
1
n+l
log-
Ri
r+1.5
Sn±l\
\n + 2)
Y
When the two motors are changed to the
parallel connection and are accelerated from
one-half to full speed, then the extra resist-
ance (r), that was in the series connection, is
eliminated and the average counter e.m.f.
increment corresponding to each current peak
is doubled. Therefore, the formula becomes
Log X =
1
n + l
log
Ri
\n+2j
Y
V. For the series-parallel operation of four
motors, the motors are assumed to be con-
nected as follows: During series operation
all the motors are in series, and during parallel
operation two sets each consisting of two
motors connected in series are across the line.
Then, if the internal resistance of two motors
is considered as r, the same formula? as given
in V hold true.
EXAMPLE I
Assume: A 25 h.p., 230-volt shunt motor.
Minimum accelerating current =100 amp.
Internal resistance of motor = 0.2 ohms.
Number of rheostat divisions = 4.
Formula
Log X =
1
1
n+l
2.3
lo£
El
r
1
= Tlog0.2 5
= 0.212
Therefore A'= 1.63.
Then n=(X-l)r
to = Xr i
n = Xr»
Ti = A>3
log 11.5 =
\- (1.061).
5 v
= 0.126 ohms
= 0.205 ohms
= 0.334 ohms
= 0.544 ohms
Total external resistance 1.209 ohms
Internal motor resistance 0.200 ohms
Total resistance
Therefore as a check
1.409 ohms
230 volts
1.409 ohms
163 amp.
EXAMPLE II
Assume : Same conditions as in Example I,
except that the maximum current is known
(163 amps.) and the minimum current is to
be found.
Formula
Log X
1
1 , i?2
=— log —
n r
ilogw=Tlog7-05=r(0-S49)
= 0.212.
T -3T
-t- i
Y^
4te
V+:
- i
\
§~
_?--'
~T - % x
&
s _
s:
V - - Z
X i ,<!+'-.
H \ =' J'
J ' 't-^c'f''^.. 1 ;<!■- X !
\ i "** t-jsp"'
\ ' 4-i^7 *■?
\ ! 4- tf£ ^'J-
i_L .tiz "~0&&.
•s ~-t— -S*" ^ V 1
/ ! sf ~~ 7 — ~~ * '° •**
? ■ £?• ^ — —
v7 Jti' ^
*^ ,E'
Z ' ^' •
. 1
a IS
■ SOO 120
//OO //a
/ooo ^too soo
900 %9(.
800 0. 30 400
0, 600 * 60 \ 300
300 \ JO
S '
OO 0 ^ 4C
i
300 Jj 30
200 $ 20
/OO /O
0 /CO 200 300 400 SOO COO 700 aOO 900 /OOO //OO /SOO '300 1400
TorqtJB- lb at /ft ra^'tjs
Fig. 1. Characteristic Curves of a 50-H.P., 230-Volt
Series Motor
Therefore X= 1.63 (same as in Example I).
The remaining is the same as in Example I.
EXAMPLE III
Assume: A 50-h.p., 230-volt series motor.
Minimum accelerating current = 185 amp.
Internal resistance of motor = 0.087 ohms.
Number of rheostat divisions = 4.
Referring to characteristic curves of this
motor, Fig. 1, all values should be reduced to
percentages. The speed and current for
minimum accelerating values, together with
line voltage, will always be considered 100
per cent.
Let
V =230 volts = 100 per cent volts.
I\ = 185 amp. = 100 per cent amp.
Si = 578 r.p.m. = 100 per cent speed cor-
responding to 100 per cent amp.
S3 = 487 r.p.m.=S3 per cent speed cor-
responding to 150 per cent current.
y = (S, -S3 = (100-83) = 17 per cent.
134
GENERAL ELECTRIC REVIEW
Formula
L°g* = ^lo=
Ri
1.5
» + l
W+2
= 1_ 100
~5 g 1.5X5/6X17
1/5X0.674.
= 0.135.
Therefore, A" =1.364.
. 100X100-100X6
A\ =
= 9- log 4.7 =
A2 =
100X100
100X100-136.4X6
87 X 136.4
0.94
'USD
" 11850
4^=2=1.21.
rx = .Ai(Si-S») =0.94(100-87= 12.20
per cent ohms.
H=Zr\= 14.80 per cent ohms.
r3 = Zr2= 17.95 per cent ohms.
r4 = Zr3 = 21.75 per cent ohms.
Total external resistance 66.70 per cent
ohms.
Internal motor resistance 6.00 per cent
ohms.
Total resistance in circuit 72.70 per cent
ohms.
V V 230 1 Ol V,
R=y-= r^ = 1-24 ohms.
1\ loo
Therefore, to reduce the percentages to
actual values
12.20 per cent of 1.24 = 0.151 ohms
14.S0 per cent of 1.24 = 0.184 ohms
17.95 per cent of 1.24 = 0.222 ohms
21.75 per cent of 1.24 = 0.270 ohms
0.827
The other variations for two or four motors,
if worked in per cent volts, current, speed,
and resistance, are so similar to those just
given that it is not considered necessary to
work out an example.
APPLICATION OF THE COOLIDGE TUBE TO METALLURGICAL
RESEARCH
By Dr. Wheeler P. Davey
Research Laboratory, General Electric Company
Two other articles describing the applications of the Coolidge X-Ray tube have appeared in the
Review, one "Some Interesting Applications of the Coolidge X-Ray Tube" in the August, 1914. number,
p. 792, the other "An X-Ray Inspection of a Steel Casting" in the January, 1915, number, p. 25. The
present article deals with the examination of the interior structure of copper castings and presents an inter-
esting stereoscopic radiograph of a block of porous copper from which, by the aid of a stereoscope, the pores
can be viewed in perspective. — Editor
Dr. Weintraub in the February, 1913,
number of the Journal of Industrial and
Engineering Chemistry describing boron and
its compounds says:
"Boron suboxide, a by-product obtained
in the manufacture of boron, can be used for
obtaining high conductivity cast copper.
Copper cast without additions is full of pores
and blowholes, and therefore mechanically
unfit and of very low electric conductivity;
the removal of the gases from copper by the
known deoxidizers is liable to give an allov
containing a small amount of deoxidizer, an
amount sufficient, however, to lower the con-
ductivity of the copper very considerably.
Boron suboxide, however, has the property
of deoxidizing copper without combining
with it, as boron suboxide has no affinity for
copper. Tons of copper are cast now by this
process, improving the quality of the product
and at the same time cheapening it."
In the refining of copper for electrical
purposes, the electrically deposited metal is
melted in a reverberatory furnace. A world
of delicate chemical control is connected with
this furnace refining. When ready to pour,
the metal is cast into open iron moulds
which give a copper pig or bar of about 75
lb. in weight.
If the metal were merely melted and then
poured the casting would be full of blow-
holes and would be of low electrical conduc-
tivity. The molten copper is allowed to
oxidize in the furnace and the oxidation is
augmented by air blown into the metal.
When the melt contains five or six per cent
of oxide, the major part of the other impuri-
ties have been burned away and the work of
APPLICATION OF THE COOLIDGE TUBE TO METALLURGICAL RESEARCH 135
Fig. 1. Radiograph of a Block of " Unboronized " (Pure) Copper side by side with a Block of " Boronized "
(Pure) Copper. Note difference of internal structure
reduction is started. As ordinarily done, this
consists in the so-called "poling." Green
sticks are submerged in the molten copper
and the gases and carbon reduce the oxide,
and such harmful products as sulphur
dioxide are driven out of the metal. The
proper time for pouring is not that represent-
ing complete reduction of all oxide, as
it has been determined by experience that
over-poling also gives a porous inferior
ingot.
It was once believed that the copper
absorbed carbon which in over-poled copper
caused the rising in the mold and the porous
condition when cast. Hampe corrected this
idea and attributed the porous state of over-
poled copper to the effect of absorbed hydro-
gen and carbon monoxide. In any case the
fact remains that if we merely melt copper
and cast it we get a porous casting, and if we
thoroughly remove dissolved oxygen by car-
bon or similar reducing agents, we also get a
porous casting.
The use of the boron flux of Weintraub has
done away entirely with the difficulty of
obtaining sound castings of high electrical
conductivity. It seemed interesting to illus-
trate the effect on the porosity by an investi-
[
i
HH
1 1
i
Fig. 2.
Ordinary Photograph of the Block of
" Unboronized " Copper
Fig. 3.
Ordinary Photograph of the Block of
" Boronized " Copper
136
GENERAL ELECTRIC REVIEW
gation using X-rays. For this purpose some
high grade copper was melted in the usual
way and poured into a sand mold to give
a block 10 by 10 by % inches. Another portion
was treated with one per cent of the boron
flux at the time of pouring and was cast in a
similar mold. These two castings were then
placed side by side on an S by 10-inch Seed
X-ray plate, 22 inches from the focal spot of a
Coolidge X-ray tube and exposed for two
minutes. The current through the tube was
2.8 milli-amperes and the potential difference
across the tube corresponded to a 10-inch
parallel spark gap between points. The
resulting radiograph is shown in Fig. 1. The
copper cast in the ordinary way is seen to be
full of pores. The cast with the boron flux
is so perfect that no holes are visible. The
two castings were then taken to the machine
shop and a portion of the surface of each was
machined as smooth as possible. Ordinary
photographs were then taken, see Figs. 2
and 3. As was to have been expected from
the radiograph, Fig. 1, the holes were clearly
visible in the common copper. In the "boron-
ized" copper the holes are either entirely
absent or are microscopic.
The advantage of the radiograph in experi-
mental work is obvious. Without the use of
X-rays it is necessary to machine off layer
after layer of the sample in order to expose
to view any hidden defects. Even when this
is done it remains for the experimenter to
build up a mental picture of the defects in his
casting on the basis of what he has seen on
each of the exposed layers. From the radio-
graph it is possible to see all of these defects
at once without destroying the casting. If
it seems desirable, it is easily possible to make
stereoscopic radiographs whereby the de-
fects may be seen in their entirety and their
depths easily estimated. Such a stereoscopic
radiograph of a portion of the pure copper
casting is shown in Fig. 4. This figure should
be viewed through an ordinary stereoscope.
In view of the results shown above, the
X-ray examination of metals as a means of
metallurgical research seems to have certain
attractive and desirable features not found in
other methods and to open a wide field for
further work.
Fig. 4. Stereoscopic Radiograph of a Portion of the Block of Unboronized Copper (Actual Size).
When viewed through a hand-stereoscope this shows the size and relative depths of the pores
137
EFFECT OF ALTITUDE ON THE SPARK-OVER VOLTAGES OF
BUSHINGS, LEADS AND INSULATORS
By F. W. Peek, Jr.
Consulting Engineering Department, General Electric Company
It has been a long-established fact that geographical altitude (or air pressure) and temperature has a
very material effect on the value of an insulator's spark-over voltage. Although these influences have been
recognized, we believe that the following article records the results of the first comprehensive tests to determine
their amounts. When given sufficient data regarding an insulator, the tabulations and charts in this article
enable the spark-over voltage to be determined at any temperature and atmospheric pressure. The article
was presented as a paper at a meeting of the A.I.E.E. in December, 1914. — Editor.
The following investigation was made to
determine the effect of air density, and there-
fore of altitude or barometric pressure, and
temperature, upon the spark-over voltages
of leads, insulators, etc.
The dielectric strength of air decreases
with decreasing pressure and increasing tem-
perature; that is, with the relative density
or with the average spacing of the molecules.
If the relative density is taken as unity at a
standard pressure of 76 cm. and a temperature
of 25 deg. C, the relative density at any other
pressure and temperature is
* 3.926
5 = 273 + * Where
b = barometric pressure in cm . , and
t = temperature in degrees C.
For the uniform field between parallel
planes the spark-over voltage decreases di-
rectly with 8. If e is the spark-over voltage
for a given spacing at 5 = 1, the spark-over
voltage ex at 5 = 0.5 is
^1 = 0.5 e.
The effect is the same for the same value of
5 whether 5 is changed by temperature or by
pressure. This has been shown elsewhere.*
For non-uniform fields, as those around wires,
spheres, insulators, etc., the spark-over volt-
age decreases at a lesser rate than the air
density. The theoretical reasons for this
have been given, as well as the laws for
regular symmetrical electrodes, for cylinders,
and spheres, f
It is, however, not possible to give an exact
law covering all types of leads, insulators,
etc., as every part of the surface has its effect.
* Law of Corona II. A.I.E.E. Trans.. 1912, p. 1051.
t Law of Corona II, A.I.E.E. Trans., 1912. p. 1051. and
Law of Corona III, A.I.E.E. Trans., 1913. p. 1767.
Fig. 1.
Cask for Study of Variation of Spark-Over and Corona Voltage with
Air Density or Altitude
13S
GENERAL ELECTRIC REVIEW
TABLE I
SUSPENSION INSULATOR
Bar.
Vac.
Pressure
Temp.
Kilovolcs
Cm.
Cm.
Cm.
Deg. C.
Arc-over
75.4
37.4
38.0
22
0.50
121.0
75.4
34.3
41.1
22
0.54
131.0
75.4
30.0
4.5.4
22
0.60
144.0
75.4
26.4
49.0
22
0.65
158.5
75.4
23.0
52.4
22
0.70
165.0
75.4
19.3
56.0
•79
0.74
177.5
75.4
17.5
57.9
22
0.77
183.2
75.4
15.0
60.4
22
0.80
195.0
TABLE II
LEADS See Fig. 17)
CORRECTION FACTOR FOR LEAD SHOWS IN
Fig. 2 Fig. 3 Fig. 4 Fig. 5
1.00
1.00
1.00
1.00
1.00
0.90
0.92
0.91
0.92
0.92
0.80
n sy
0.82
0.83
0.85
0.70
0.74
0.72
0.75
0.77
0.60
0.70
0.65
0.64
0.66
0.50
0.61
0.56
0.54
0.57
The following curves and tables give the
actual test results on leads, insulators, and
bushings of the standard types. The cor-
rection factor for any other lead or insulator
of the same type may be estimated with
sufficient accuracy. When there is doubt, b
may be taken as the maximum correction.
It will generally be advisable to take 5 because
the local corona point on leads and insulators
will vary directly with 5. This is so because
the corona must always start on an insulator
in a field which is locally more or less uniform.
The tests were made by placing the leads
or insulators in a large wooden cask 2.1
meters high by 1.8 meters inside diameter,
exhausting the air to approximately 5 = 0.5,
gradually admitting air and taking the
spark-over voltage at various densities as
the air pressure increased. The temperature
was always read, and varied between 16 and
25 deg. C. The cask is shown in Fig. 1.
At the start a number of tests were made
to see if a spark-over in the cask had any
effect upon the following spark-overs by
ionization or otherwise. It was found that
a number of spark-overs could be made in the
cask with no appreciable effect. During the
test, the air was always dried and the surfaces
of the insulators were kept clean.*
Table I is a typical data sheet. Tables II
and VI give even values of 5 and the corre-
sponding measured correction factors. If the
spark -over voltage is known at sea level or
5 = 1 (76 cm. bar., temperature 25 deg. C.)
the spark-over at any other value of 8 may
be found by multiplying by the corresponding
* In these tests, corrections have been made for wave shape,
etc., and the voltages checked by sphere gap. Voltages measured
by needle gap are incorrect and indicate higher voltages than
really exist.
1 £~4.:^--
™ffi3
Y
/
§
/
0.2
')*
0.8
RELATIVE DENSITY
Fig. 2. Arc-Over Voltages at
Various Densities
'
1'
1_
-A
T8cr
f
60
i
y
RELATIVE DENSITY
Fig. 3. Arc-Over Voltaees at
Various Air Densities
'
- . -
■ iV:
-
/
-1-
^
x\
(ft
f
O
Y
,
/
/
70
/
a
1
A,
7 8cr
\
.
^
i
i
100
Ht -~T ■£ DENSiT*
Fig. 4. Arc-Over Voltages at
Various Densities
RELATIVE DENSITY
Fig. 5. Arc-Over Voltages at
Various Densities
EFFECT OF ALTITUDE ON SPARK-OVER VOLTAGES
139
correction factor. It will be noted that in
most cases the correction factors are very
nearly equal to 5.
Fig. 15 is a curve giving different altitudes
and corresponding 5 at 25 deg. C. If the
spark-over voltage is known at sea level at
25 deg. C, the spark-over voltage at any other
altitude may be estimated by multiplying
by the corresponding <5, or more closely if
the design is the same as any in the tables,
by the correction factor corresponding to 8.
If the local corona starting point is known at
sea level, it may be found for any altitude by
multiplying by the corresponding d. The
barometric pressure corresponding to dif-
ferent altitudes is given in Fig. 16. Figs. 17
1
11
_r
J
r
Iro
bo*
-
fas
era
RELATIVE DEM
Fig. 6. Arc-Over Voltages at
Various Air Densities
3 5 cr
u
i
u*-1
16
cm
RELATIVE. DENSITt"
Fig. 7. Arc-Over Voltages at
Various Densities
r
-■36cm -
*
h
^1
tV24cm\-
|
VAV
RELATIVE OENSITV
Fig. 8. Arc-Over Voltages at
Various Densities
to 20 show the insulators used in these tests.
As an example of the methods of making
corrections: Assume a suspension insulator
string of four units with a spark-over voltage
TABLE III
POST AND PIN INSULATORS (See Fig. 20)
CORRECTION FACTOR FOR INSULATOR
SHOWN IN
b
Fig. 6 Fig. 7 Fig. 8
Post Pin
1.00
1.90
0.80
0.70
0.60
0.50
1.00 1.00
0.93 0.91
0.84 0.81
0.76 0.73
0.68 0.62
0.60 0.52
1.00
0.94
0.86
0.75
0.65
0.53
TABLE IV
SUSPENSION INSULATOR, FIG. 9 (See Figs. 18 and 19)
CORRECTION FACTOR FOR UNITS IN STRING AS
FOLLOWS
b
Number of Units
1
2 3
4
5-
1.00
0.90
0.80
0.70
0.60
0 50
1.00
0.96
0.91
0.86
0.80
0.72
1.00 1.00
0.93 ii 'in
0.84 0.80
0.76 0.70
0.66 0.60
0.55 0.50
RELATIVE DEMSIT
Fig. 9. Arc-Over Voltages at
Various Air Densities
140
GENERAL ELECTRIC REVIEW
of 205 kv. (at sea level, 25 deg. C. tempera-
ture). 5 = 1. What is the spark-over voltage
at 9000 ft. elevation and 25 deg. C?
From Fig. 15, the 5 corresponding to 9000
ft. is
5 = 0.71.
TABLE V
SUSPENSION INSULATOR, FIG. 10 (See Figs. 18 and 19)
CORRECTION FACTOR FOR UNITS IN STRINGS
\S FOLLOWS
Number of Units
1
2
3
4 '
5
1.00
1.00
1.00
1.00
1.00
1.00
0.90
0.95
0.91
0.90
0.90
0.91
0.S0
0.89
0.81
0.81
0.81
0.82
0.70
0.80
0.72
0.72
0.72
0.73
0.60
0.70
0.63
0.63
0.63
0.65
0.50
0.57
0.53
0.53
0.53
0.57
TABLE VI
SUSPENSION INSULATOR, FIG. 11 (See Figs. 18 and 19)
CORRECTION FACTOR FOR UNITS IN STRINGS
AS FOLLOWS
Number of Units
1.00
0.90
0.80
0.70
0.60
0.50
1.00
0.94
0.87
0.81
0.72
0.62
1.00
0.92
0.84
0.73
0.63
0.52
3
4
1.00
1.00
0.90
0.90
0.80
0.80
0.70
0.70
0.60
0.60
0.50
0.50
Then the approximate spark-over voltage at
9000 ft., 25 deg. C. is
ex = 0.71X205 = 145 kv.
If this happens to be the insulator of Fig.
10, the correction factor corresponding to
5 = 0.71 is found in Table V, by interpolation,
to be 0.73. The actual spark-over voltage
for this special case is
<?2 = 0.73 X 205 = 1 50 kv.
The first estimate is on the safe side and close
enough for all practical purposes. Thus, for
practical work the correction may generally
be made directly by use of Fig. 15.
The spark-over voltage of an insulator is
100 kv. at 70 cm. barometer and 20 deg. C.
What is the approximate spark-over voltage
at 50 cm. barometer and 10 deg. C?
3.92+70
5l-273X20-°-94
= 3.92X50
2 273 + 10 =
= 0.61
ei=100X^ = 65kv.
If the local corona starting point is known
at, say, sea level, it may be found very closely
for any other altitude by multiplying by the
correction 5.
The spark-over voltage of insulators will
vary somewhat from day to day, due to
humidity. There is also some variation for
different units. The humidity voltage varia-
tion on the insulator is possibly as high as 7
RLLATIVt DENSITY
Fig. 10. Arc-Over Voltages at
Various Air Densities
i
f
-i
•
i.~
4 units
h
/
inits
/ -
!
/
/
x^.
/
/
III
l '
I
nits"
T
—
(7 cm
---
V
,/
A
/
/ '
/
,
/ ,
/
]
0.2
04
.0.6
08
RELATIVE DENSlTr
Fig. 11. Arc-Over Voltages at
Various Air Densities
EFFECT OF ALTITUDE ON SPARK-OVER VOLTAGES
141
si |
10 !
5 i
.5 Q
■S 6
.S Q a
CO z£
142
GENERAL ELECTRIC REVIEW
TOG
J units .
/T
90
170
160
ISO
1 1
6 2*crn^
/
I
-ItsL-Jl j
1
/
2umis
u—
■ 26
i.
7^
/
130
120
h
I
/
100
iur
in
- 1 u
nil —
go
J
I
70
/
50
RELATIVE 3EHSITY
Fig. 12. Arc-Over Voltages at
Various Air Densities
per cent, from day to day. Comparative
tests of different types, when desired, should
be made at the same time. The humidity
correction, on the insulator itself, is too com-
plicated to make and of no practical value.
liOOO
\
\
12000
11000
-
s
id
o 7000
WOO
4000
3000
2000
1000
3 »
^J
L
>J
/f
\ 1
3?=
Si S" ■
i J>
HEUA-nvE DENSITY
Fig. 13. Arc-Over Voltages at
Various Air Densities
Horn gap spark-over. Gap spacing 14 cm.
Diameter of horns 1.27 cm.
G
"^ITrrr, -
^~
/
RELATIVE DEN5.T
Fig. 14. Arc-Over Voltages at
Various Air Densities
Care must be taken, however, to use a measur-
ing gap unaffected by humidity; that is, a
sphere gap.
iwoo
\
1
v
\
12000
\
9000
7000
WMO
WOO
4000
wrm
2000
■ 000
t RELATIVE AIR DENSITY
Fig. 15
CM OF MERCuH*-e»"OMETER
Fig. 16
143
THE LIGHTING OF SHIPS
By L. C. Porter
Edison Lamp Works, Harrison, N. J.
Much has been published regarding the superiority of the drawn-wire tungsten-filament lamp over the
old carbon-filament lamp in installations on land. This article analyses the conditions which determine
illumination on shipboard; and shows that the new lamp when installed there displays the same excellent
qualities that it does on land. — Editor.
Lighting practice ashore has advanced so
far and so rapidly during the past few years
that the public, now, not only appreciates
but demands good lighting everywhere. As
a result, ship owners have been made to feel
this influence; and, in consequence of this,
a large amount of attention and study has
been given to the lighting of passenger and
naval ships. The vast superiority of the
tungsten-filament lamp over the carbon-
filament lamp having become universally
recognized on land, it is only natural that the
newer lamp should also replace the older
when used on shipboard. As a matter of
fact, this is what is taking place.
The use of tungsten lamps aboard ships
offers several mechanical advantages in addi-
tion to those obtained by their use ashore.
Space and weight are of considerable moment
on board our modern high-speed passenger
boats. Reliability is also of great importance.
Repairs when necessary must frequently be
made at short notice and without most of the
and lighter generating apparatus, lighter wir-
ing throughout the ship, less coal storage space
necessary, etc.
It frequently happens, when changing over
the lighting equipment of a ship from carbon
Fig. 2.
Dining Room on the "Adirondack" of the
Hudson Navigation Company
Fig. 1. The Saloon on the Steamship "Priscilla"
of the Fall River Line
facilities obtainable ashore. The use of
tungsten-filament lamps, consuming approx-
imately 1.10 watts per c-p. as against 3.10 to
3.50 by carbon-filament lamps, means smaller
lamps to tungsten lamps, that one generator
may be shut down and held in reserve.
Smaller and lighter storage batteries for emer-
gency use are required for tungsten lamps
than for carbon lamps.
On certain steamers, people often ride
solely for pleasure or for pleasure and business
combined. To assist in drawing their patron-
age a lighting system must be devised which
is not only necessary but ornamental as well.
For this reason all-frosted lamps are almost
invariably found on passenger vessels. These
lamps frequently are made further decorative
by the use of round bulbs and occasionally by
placing them in elaborate chandeliers or
equipping them with fancy reflectors. The
general interior finish aboard ships is white.
The bright all-frosted tungsten-filament lamps
harmonize well with white wood work. Artis-
tic effects are given the most consideration on
ocean liners and the least on ferry boats. Be-
tween these two comes the great class of
coastwise, river, and lake steamers.
144
GENERAL ELECTRIC REVIEW
The lighting problems of passenger vessels
may be divided into five main parts: (1) social
halls, (2) dining rooms, (3) smoking rooms,
(4) staterooms, and (5) passageways. In
Fig. 3. Smoking Room on one of the Old Dominion
Line Steamers
addition to these there are certain parts of
the ship where a relatively small number of
lamps are used, such as engine rooms, bar
rooms, barber shops, boiler rooms, freight
holds, etc.
Investigation shows that there are two
general types of steamers in the coastwise,
river, and lake class, those making compara-
tively short runs and those making trips of
several days. On the former, the social halls
consist of a large well, or opening running up
one or two decks above the main deck. This
class of social hall is well illustrated by the
photograph taken on the Fall River Line
steamer "Priscilla," Fig. 1. On ships making
long trips, the social halls are smaller and
generally but one deck high. Also they are
usually not lighted quite as elaborately.
Ceiling lamps are found frequently supple-
mented by lamps in wall brackets.
Illumination measurements, taken on a
large number of ships lighted with carbon
lamps, showed an average foot-candle in-
tensity, on a plane three feet above the floor,
of 1.1 on long trip ships, and 1.5 for the short
run class.
An interesting demonstration of the great
improvement obtained by substituting tung-
sten-filament lamps for carbon lamps was
made in the social hall of a boat of the
short run type. Thirty-eight sixty-watt
all-frosted carbon lamps, giving an average
intensity of 1.4 foot-candles for an energy
consumption of 2.3 watts per square foot, were
replaced by thirty-eight twenty-five-watt
all-frosted tungsten lamps. These lamps gave
2.7 foot-candles illumination with an energy
expenditure of 1.0 watt per sq. ft.
Dining rooms are very similar on each class
of ship. Round-ball enclosing globes located
on the ceilings were considerably used. On
one ship the 16-c-p. clear carbon lamps in
enclosing globes were replaced lamp for lamp
by 25-watt clear tungsten lamps. The carbon
lamps gave 1.1 foot-candles for 1.5 watts per
sq. ft., while the tungsten lamps in the same
fixtures gave 1.4 foot-candles for 0.6 watts
per sq. ft. Fig. 2 shows a section of the dining
room of the Hudson River Line steamer
"Adirondack."
Smoking rooms have a fairly high ceiling
on the short run ships and a low one on the
long trip class. Fig. 3 shows the arrangement
employed in the smoking-room of a steam-
ship on the line of the Old Dominion S. S. Co.,
which illustrates the latter type of lighting.
All-frosted lamps located overhead are usually
used. The average illumination 3 feet above
the floor was found to be 1.25 foot-candles for
an energy consumption of 2.09 watts per
square foot.
In passageways a low illumination is all
that is needed. This is frequently obtained
by small lamps located on the ceiling spaced
about 10 feet apart. The average intensity is
about 0.S foot-candles.
Fig. 4.
Stateroom on the "City of Montgomery,"
Savannah Line
The staterooms are generally rather poorly
lighted, having but one lamp located in the
center of the ceiling. Great improvement is
obtained by locating this lamp over the center
and one foot out from the mirror, thus allow-
THE LIGHTING OF SHIPS
145
ing comfortable shaving, etc., and at the same
time giving good general illumination in the
room. A stateroom on the Savannah Line
steamer "City of Montgomery," having a
lamp for lamp by 40-watt medium efficiency
tungsten lamps. The former gave an average
of 1.13 foot-candles, on a plane 3 feet above
the floor, with an energy consumption of 1.96
60 Watt Carbon Lamps
40 Watt Mazda Lamps
Figs. 5 and 6. New York City Ferryboat "Richmond"
lamp at the center of the ceiling and a portable
lamp near the berths, is shown in Fig. 4.
The lighting of ferries was found to be very
uniform. In practically all cases the cabins
were lighted by carbon lamps, in one- or two-
light fixtures located on the walls over the
tk ** ""
- ,-:;
*-» -diH
t - -
' : «-> 1
gjggg^**^
l^JBJI
^'w^^y
jjflfrfrjl
H^Xil
Fig.
Palm Garden on the "Victoria Louise", of the
Hamburg-American Line
seats. In a few cases round-ball all-frosted
lamps were in use. On the N. Y. municipal
ferry boat "Richmond," one hundred 60-watt
high-efficiency carbon lamps were replaced
watts per sq. ft., while the latter gave 3.36
foot-candles for 1.50 watts per sq. ft.
Figs. 5 and 6 show this cabin before and
after the change.
Battleships present a different lighting
problem from any other class of vessels. A
warship's ability to fight, fight hard and
effectively, is its primary function. The
lighting must be so arranged as to enable the
men to use the apparatus to the best advan-
tage. A battleship is also the business office,
the factory, the recreation ground, and the
home of a thousand men. The happier and
more contented these men are, the more
efficient will they be. Realizing that plenty of
light correctly applied increases the efficiency
of the human machine, the U. S. Government
has taken up the lighting of its ships from a
scientific standpoint. Drawn-wire tungsten-
filament lamps have proved by actual test
that they will stand up under the severe
strains of battle practice, the tropics, the
extreme cold of a Maine winter, a storm, and
a full-power run; in short all the various con-
ditions encountered by our ships. These
lamps in connection with scientifically de-
signed reflectors are now being generally
adopted by the Navy for use aboard ship.
On ocean steamers, great attention is paid
to obtaining sesthetic effects, as illustrated by
146
GENERAL ELECTRIC REVIEW
the photograph of the palm garden of the
Hamburg- American Line steamer "Victoria
Louise," Fig. 7. Investigation shows that
round-bulb all-frosted tungsten-filament
lamps are most generally in use for this class
of ship lighting. Overhead lighting supple-
mented by table lamps and lamps in wall
brackets is found to be a most usual arrange-
ment. The illumination intensities vary
quite widely, averaging however about 2
foot-candles on a plane 3 feet above the floor.
The introduction of the rugged drawn-wire
tungsten-filament lamp has opened up a big
field for its application to practically all
classes of marine lighting.
As the result of many tests, several steam-
ship companies are arranging to equip their
boats with drawn- wire tungsten-filament
lamps in place of the carbon lamps previously
used.
In many instances it is impractical to
change the existing wiring of a ship and, for
this reason, the recommendations for a new
ship would vary considerably from those for
a ship at present in commission. When the
wiring is already installed, the expense in-
volved in changing the outlets may more
than offset the advantages to be secured bv
such a rearrangement of units as will provide
the most economical and effective operation.
On the ships which have been studied it was
usually apparent that a better economy, and
often a more effective illuminating effect
could be produced by the use of a smaller
number of tungsten-filament lamps of higher
c-p., but in every case it was considered
unwise to change the existing outlets. How-
ever, advantage has been taken of the higher
efficiency of the tungsten-filament lamp to
increase the intensity and, at the same time,
reduce the lighting cost by substituting, lamp
for lamp, 25- and 40-watt tungsten-filar"
lamps for the high wattage carbons. I
instances it was possible to also impro^
diffusion by substituting frosted bulbs
clear ones.
PRACTICAL EXPERIENCE IN THE OPERATION OF
ELECTRICAL MACHINERY
Part V. (Nos. 29 to 31 Inc.)
By E. C. Parhaai
Construction Department, General Electric Company
(29) CURRENT TRANSFORMER FAILURES
Neglecting the no-load or magnetizing
current of a constant-potential transformer,
the primary current is proportional to the
secondary current as is shown by the follow-
ing succession of actions. Increased second-
ary current increases the opposing secondary
flux which neutralizes more of the primary
flux and thus decreases the counter e.m.f. of
the primary coil, thereby permitting the
primary current to increase until the core
flux is restored to approximately its no-load
value. In other words, the core flux is main-
tained at a practically constant value because
the primary current automatically responds
to changes in the secondary current.
With current transformers the conditions
are different. The value of the primary
current depends upon an external load over
which the current transformer has no con-
trol. Assume that the current-transformer
primary current, which is the current out-
put of some generator, is kept constant at
full-load value. A suitably calibrated instru-
ment, placed in the secondary circuit, will
indicate the value of the primary current,
although the secondary current to which the
indication is due is but a small known part
of the primary current. Owing to there being
many more secondary than primary turns,
the ampere-turns of the two windings are
approximately equal and the opposing flux
caused by the secondary is able to neutralize
the flux of the primary to such an extent as to
keep the core flux density below the value
that would generate objectionable heating.
Next assume the secondary to be short-
circuited, another instrument placed in series
with the existing one, and the temporary
short-circuit (used to avoid opening the
secondary) removed. The secondary resist-
ance will now be greater than it was with but
one instrument in circuit and consequently
there will be a tendency for the secondary
current to decrease. Any decrease in the
secondary current, however, increases the
core flux because less of the primary flux will
be neutralized. The increased flux cutting
the secondary turns increases the secondary
e.m.f. and thereby restores the secondary
current almost to its former value. Up to
the instrument capacity of the transformer.
OPERATION OF ELECTRICAL MACHINERY
147
additional instruments further increase the
core flux and, hence, the secondary e.m.f.
The secondary current is thus maintained
so close to the correct value that the error
may be neglected except in precision work.
The greater the number of instruments
used in series, the greater will be this error,
the hotter the transformer will become on
account of the greater flux density at which
the iron is worked, and greater will be the
voltage to which the secondary insulation
is subjected.
If the secondary be opened, its flux-neu-
tralizing capacity ceases entirely and the
core flux density, due to the unopposed pri-
mary flux, becomes abnormal and the heat
resulting from rapidly reversing the flux at
this density soon raises the iron to a tem-
perature dangerous to the coil insulation.
Furthermore, this greatly increased flux
cutting the secondary turns induces therein
an e.m.f. far exceeding that which obtains
under normal conditions. These two effects
conspire to break down the secondary in-
sulation.
Therefore it is necessary to issue a warning
against operating a current transformer with
its secondary circuit open.
(30) HEATING AND SPARKING OF REPUL-
SION-INDUCTION MOTORS
Repulsion-induction motors operating
under normal conditions are characteris-
tically free from sparking. Even when ir-
regularities exist, the sparking may be so
slight as to mislead one who is accustomed
to operating only the other kinds of com-
mutator motors.
Once, an operator noticed that one of his
press motors was overheating and was spark-
ing; similar motors operating similar presses
were giving no trouble. In an effort to
determine the cause of the difficulty, the
operator interchanged two of the motors —
a good one and the one under consideration.
The trouble remained with the same motor.
This cleared the press and the starter from
suspicion and focused his attention upon the
motor. He then cut an ammeter successively
into the stator circuit of each of three dupli-
cate press motors, which had evidenced no
trouble, and thereby found that the current
required under regular working conditions
was 2J/2 amperes. The faulty motor was
operating under exactly the same conditions
of load as were the three good motors just
mentioned, but the ammeter when placed in
its circuit indicated 5 amperes. Since the
full-load current rating of the motors was
3.8 amperes the motor under examination
was carrying a current overload of nearly 30
per cent.
Reversing the compensating field con-
nections only made matters worse. By
shifting the brushes a little at a time, he found
a position where the current was of the same
value as for the good motors. He was now
reasonably sure that the motor would not
overheat, but as the sparking had not been
lessened he called in a repair man whose
examination disclosed an open-circuited arma-
ture lead. This condition was indicated by
the burning out of the mica between dia-
metrically opposite pairs of commutator bars.
The repair of this lead resulted in perfectly
normal operation.
(31) EXCESSIVE PUMP OUTPUT
The amount of water delivered by a cen-
trifugal pump depends, among other things,
upon the speed of the impeller. The delivery
and speed variations, however, are not
directly proportional to each other for, by
reason of the characteristics of this type of
pump, a certain per cent increase in speed
produces a greater per cent increase in the
amount of the water delivered. Therefore,
if on account of high or low line voltage, or on
account of design irregularities, the speed of
the motor of a motor-driven centrifugal
pump falls below or rises above the per-
missible five or six per cent speed variation,
the water delivery may be materially affected ;
and, in the case of increased speed, the motor
may be overloaded seriously. All conditions
will be covered in a specification stating the
speed at which the pump shall deliver water
at a certain rate without the motor tempera-
ture rise exceeding a certain number of
degrees after the motor has operated con-
tinuously for a stated length of time.
A certain operator once complained that
his pump motor was running "red hot" on
regular duty but was otherwise entirely
satisfactory. Ammeters connected into the
motor circuit showed the motor was heavily
overloaded. Measurement of the water
delivery rate showed it to be about twice
that which had been specified. The pump
maker was notified and his subsequent
investigation revealed the fact that the wrong
impeller had been supplied with the outfit.
The pump manufacturer got out of his diffi-
culty to advantage, however, because the
operator was so much pleased with the water
output that he had been obtaining that he
readily agreed to pay the difference in price
between the motor that had been furnished
and the one that was large enough for the
work.
1-iS
GENERAL ELECTRIC REVIEW
NOTES ON THE ACTIVITIES OF THE A.I.E.E.
Standardization Rules
The January issue of the Proceedings of
the A.I.E.E. contains an article by Dr. A. E.
Kennelly. Chairman of the Standards Com-
mittee, of which the following is an abstract:
The American Institute of Electrical Engineers
maintains, among its standing committees, a
"Standards Committee,'' which is charged with the
important duty of maintaining a series of Standard-
ization Rules for the benefit of the Institute and its
members. The fifth and most recent edition of the
Standardization Rules, which is dated December 1,
1914. was adopted by the Board in July, 1914. It
covers 96 pages.
Object of the Rules. The main purpose hitherto
aimed at by the Standards Committee in the rules
has been to draw up engineering definitions of terms,
phrases, and requirements, relating to electrical
machinery and apparatus, so that the meaning of
technical terms might be standardized among the
members of the Institute. Particular effort has been
directed towards defining, in engineering terms, the
rating of electrical machinery, and the requirements
connoted thereby. This work serves the entire
electrical industry, including manufacturers, pur-
chasers, technical advisers, operators, and con-
sumers. It is therefore desirable that the represen-
tation of electrical interests on the Standards Com-
mittee should be as wide as possible, in order that
the needs of all classes of electrical workers should
be adequately presented and mutually protected.
Relations of the Standards Committee to other
Engineering Bodies. The work of the Standards
Committee naturally brings the committee into
contact with bodies engaged upon standardization
in neighboring fields. Thus, it has for a number of
years co-operated with the Bureau of Standards at
Washington, D. C. The Bureau has not only been
continuously represented by one or more of its
i .fixers on the Committee, but it has also under-
taken important researches in electrical engineering
at the request of the Committee. Thus, in 1910,
the Bureau, at the request of committee, made an
extensive investigation into the conductivity of
commercial copper and has since published complete
copper wire tables* based on those researches, for
the benefit of the electrical industry.
The A.I.E.E. Standards Committee has also at
different times worked in co-operation with Stand-
ards Committees of the American Society of Me-
chanical Engineers, the Illuminating Engineering
Society, the Institute of Radio Engineers, the
American Society for Testing Materials, the National
Electric Light Association, the Association of Edison
Illuminating Companies, and other bodies, upon
questions of standardization involving work in their
ive fields. It is probable that a standards
committee representing the entire engineering force
of America may ultimately be secured for dealing
with general engineering questions.
International Standardization. The conditions
which affect the mutual relations of different engi-
neering societies in America regarding standardiza-
naturally extend themselves internationally
rresponding engineering societies in other
t. *_Cir<?Tlar -N'°- 31 of the Bureau of Standards, "Copper Wire
Tables.
countries. It becomes impossible to carry stand-
ardization beyond a very elementary stage in any
one country, without influencing the work and pro-
cedure along similar technical lines in other count :ies.
It therefore becomes desirable to enter into mutually
co-operative relations with electrical engineering
societies and their standardizing committees
abroad. Co-operative relations have been entered
into at different times between the A.I.E.E. Stand-
ards Committee and corresponding committees
in other countries, to considerable mutual advan-
tage; but especially through the influence of the
International Electrotechnical Commission, an
international body engaged in international electrical
engineering standardization. The American Stand-
ards Committee of the A.I.E.E. was the first
national committee to formulate and publish elec-
trical standardization rules, and similar com-
mittees have since come into existence in various
other countries. It is neither necessary nor desirable
that electrical apparatus built in one country should
conform in structural details to that built in other
countries; but it is surely desirable that the rating,
and rating terms, employed in specifying the be-
havior in different countries should correspond,
since no country can permanently profit by ambi-
guity, in the meaning of its technical phraseology,
as applied to the physical behavior of apparatus.
The Standards Committee of the A.I.E.E. has
no direct representation on the International Elec-
trotechnical Commission (I. E. C); but it has close
relations with the U. S. National Committee of the
I. E. C, and, through the intervention of the latter
committee, it has been able to present its needs and
recommendations to the I. E. C. Various rulings
of the I. E. C. at past international meetings are
now incorporated in the latest edition of the Rules.
The Relations of the Standards Committee to the
Institute Membership. The work of its Standards
Committee constitutes a distinct asset to the
Institute, and to the membership. The committee
meetings usually occur at monthly intervals in the
New York headquarters of the Institute. Notices
of these meetings are communicated in advance to
the Standards Committees of other engineering
societies, and are regularly announced at head-
quarters. Suggestions regularly reach either the
A.I.E.E. Secretary, or the Secretary of the Com-
mittee, and receive careful consideration by the
Committee. It is very desirable to secure frequent
and copious suggestions, from the Institute mem-
bership at large, as to how the Rules operate in
practice, and how they may be improved.
The Standards Committee is thus a body earnestly
devoting its time and service to the welfare of the
electrical engineering industry, in the belief that
precision in standardization means an advance in
the ethics, the science, the business and the welfare
of engineering.
The 303rd meeting of the American Insti-
tute of Electrical Engineers was held at the
Engineering Societies Building in New York,
on Friday, January S, at 8:15 p.m.
Mr. I. W. Gross presented a paper
entitled, Theoretical Investigation of Electric
Transmission Systems Under Short Circuit
Conditions. The leading features of the trans-
NOTES ON THE ACTIVITIES OF THE A.I.E.E.
149
mission system under short circuit conditions
were treated as follows :
First. Mechanical forces between the
phases of three-conductor, three-phase cables
when carrying short-circuit current. Under
this heading the forces between busbars were
also investigated.
Second. The heating of the conductors of
the cable from the instant of short circuit to
a time 0.8 second later was traced analyti-
cally, during the transient state of the current,
and typical computed heating curves were
presented.
Third. The effectiveness of the method of
placing reactors between generator terminals
and the bus from which power is taken, and
additional reactors between generators and an
auxiliary synchronizing bus were analyzed.
This latter scheme was compared with the
present well-recognized schemes of feeder and
busbar reactors.
It was shown that the average mechanical
forces existing between conductors of a three-
phase cable carrying short-circuit currents.
and between busbars, rise to relatively high
values at the instant of trouble. These forces
can be reduced in cables by either limiting
the current or increasing the distance between
conductors. The same applies to busbars,
and in addition, the position of the busbars
can be adjusted by placing them in the same
plane so that the mechanical forces may be
considerably reduced.
The heating of the cables may be the limiting
feature in controlling the short-circuit current,
since it is quite possible for the temperature
of the conductor to rise to such a point as to
endanger the insulation of the cable even in
the very short time that it takes an oil switch
to operate after the short circuit has occurred.
When the characteristics of the generators
under short-circuit conditions are known, it is
possible to compute the temperature rise,
even although the current is of transient
character.
In using reactors to limit the current flow
on a power system, the method of plain
feeder reactance is not fully effective, as
trouble on the main station bus is almost
certain to cause to drop out of step all syn-
chronous apparatus on the system. Further,
this method offers no protection to machines
against poor synchronizing.
Station busbar reactance is effective under
short-circuit conditions, but under normal
operation is objectionable on account of
the large voltage drop in transmitting power
from one end of the bus to the other.
The scheme of feeding from the machine
terminals, and paralleling generators on a
separate bus, as brought to light by Mr.
Stott, is extremely flexible and very effective
in furnishing protection. It can limit the
current to a safe value without an excessive
amount of reactance in the circuit; it can
protect the machines against mechanical
injury due to poor synchronizing; and can
transmit power from between different points
of the bus with far less voltage drop than with
the bus reactance scheme. It makes possible
the use of generators having a low inherent
reactance, provided, of course, the machine
is designed to withstand dead short circuit
at its terminals. Further, the lower the
reactance of the generator the less is the
probability that the synchronous apparatus
on the system will be out of step due to
reduced power house voltage. The possibili-
ties of this system are as yet probably not
fully realized.
The full text of the paper appears in the
January issue of the Proceedings of the
Institute.
LYNN SECTION
The regular meeting of the Lynn Section
of the A.I.E.E. was held on the evening of
January 6th and was attended by 250 mem-
bers. Prof. Comstock, of the Massachusetts
Institute of Technology, gave a most interest-
ing talk on the Modern Theory of Electricity
and Matter. The subject was introduced by
a review of the older theories of the molecular
constitution of matter and the kinetic theory
of gases, and it was pointed out how the recent
measurements of the Brownian movements
of particles confirmed the kinetic theory, and
how in the spinthrascope the effect of the
impact of single particles of atomic magnitude
is made evident. The general magnitude
of molecules and atoms was described.
Electrical discharges through gases were
discussed and it was pointed out that here we
have the simplest means of studying the
phenomena of electric currents. The vacuum
discharge consists in the actual transport of
particles of electricity, and the particles
involved are all of one size irrespective of the
material from which they are torn, and all
carry the same electric charge, which is the
smallest quantity of electricity known to
exist, and is called the "Electron." Further,
these particles have a mass of about 1/2000
part of that of the hydrogen atom. To
illustrate the intensity of the electrical forces,
it was stated that could two particles of the
150
GENERAL ELECTRIC REVIEW
size of pin-heads, located a mile "apart, carry
charges in proportion to that of the electron,
they would act upon each other with a force
of hundreds of tons.
The electric current in a wire was described
as a slow migration of electrons and the con-
trast of the speed of the electrons to the speed
of propagation of electric disturbances was
emphasized.
The talk was illustrated by a number of
lantern slides and by many apt analogies.
The statements relative to the numerical
magnitudes of the quantities discussed made
the talk most interesting and instructive.
On February 3rd, Major J. A. Shipton will
speak before the Lynn Section on a military
topic, and on February 17th, Mr. J. L. Wood-
bridge will speak on The Characteristics and
Uses of Storage Batteries.
PITTSFIELD SECTION
On the 7th of January Prof. W. S. Frank-
lin, of Lehigh University, read a paper to the
Section on the subject of Electric Waves. His
paper was illustrated with lantern slides and
dealt mainly with the derivation of the
fundamental equations of wave motion.
It is hoped that an abstract of this lecture
may be given in a later number of the
Review.
On Friday, January 29th, Dr. Irving
Langmuir of the Research Laboratory,
Schenectady, will lecture to the Section on
the subject of Modern Theories of Electricity.
SCHENECTADY SECTION
There was a meeting of the Schenectady
Section of the A.I.E.E. at Edison Club Hall,
on the 5th of January. The general subject
for the evening was Electric Illumination and
after a few introductory remarks by Mr.
S. H. Blake, the following papers were
presented :
The Arc as a Street Ilhtminant, by Mr.
(". A. B. Halvorson, Designing Engineer
of the Arc Lamp Department at the Lynn
Works.
nparison of the Operation of Low-Current
and High-Current Gas-Filled Lamps on Scries
Circuits, by H. D. Brown of the Consulting
Engineering Department.
I haracteristics of Gas-Filled Mazda Lamps,
by Mr. L. A. Hawkins. Research Laboratory.
The papers were illustrated by lantern
slides and by means of a large variety of
experimental apparatus in operation.
Mr. Halvorson first brought out the point
that to render an illuminant suitable for street
lighting sen-ice even a very simple lighting
unit like a high-current mazda lamp must be
provided with various attachments such as
a weather protective casing, a compensator
coil, socket, globe holder, refractor or outer
globe, etc.. which in the end makes the
complete outfit look very much like the
familiar street-lighting arc lamp.
He then showed a vertical distribution curve
of the light from a clear-glass lamp of the gas-
filled mazda type, without reflector, refractor
or diffusing globe. This curve indicated that
as much light is thrown above the horizontal
as below. For street illumination the most
useful light is that which is distributed on
an average of 10 degrees below the horizontal.
In order therefore to utilize as much of the
total light flux of the lamp as possible, it is
necessary to equip the lamp with a suitable
reflector and refractor which redirect the
light from the upper hemisphere and from
under the lamp. By this means the maximum
light is thrown in the desired direction. Similar
curves were then shown of the light distribu-
tion of the flame lamp, the titanium lamp, and
of the magnetite lamp with high-efficiency
electrodes, with and without redirecting
and diffusing devices. Samples of the various
lamps mentioned were shown in operation.
Mr. Halvorson then analyzed and de-
scribed the evolution of the refractor, the
recent introduction of which into practical
use in connection with large street lighting
units he regarded to be of great importance.
He showed that without the refractor a
single reflector of suitable shape 16 feet in
diameter would be necessary to redirect all
the upward light from an arc lamp. By the
use of biplane or triplane small-diameter
(about 20 inches) reflectors it is possible to
obtain the equivalent of the effect of this
very large reflector. However, the refractor
has the further advantage that it not only
redirects the upward light but also the
light from under the lamp. The construction
of the refractor was shown to consist of two
clear-glass cone-shaped globes ground so that
one fits perfectly inside of the other. On the
outside surface of the inner globe, horizontal
prisms arc moulded to give the light-re-
direction desired, while on the inside of the
outer globe are moulded vertical prisms
designed to diffuse the light. When the
globes are fitted together the combined unit
presents smooth surfaces inside and out, so
that it can readily be kept clean.
NOTES ON THE ACTIVITIES OF THE A.I.E.E.
151
Curves were shown of the very remarkable
improvements in light efficiency obtained
with magnetite lamps by the use of the new
"high-efficiency" electrodes. It was further
shown that by the use of flattened electrodes,
about one-quarter inch wide, in place of round
electrodes of the same cross-sectional area,
not only is better distribution obtained,
but higher efficiency, greater steadiness,
cleaner burning, and it is possible to run the
arc satisfactorily at lower current and arc volt-
age. This latter fact means that the lamps
can be put out in smaller units, a matter
of the greatest importance in arc lighting.
A large ornamental globe and fixture of
the type used for street illumination in
Washington, D. C, was shown, and in the
globe were mounted a magnetite arc lamp
and a high-current mazda lamp of equal
wattage. The lamps were switched on
separately so that the color and intensities
of the lights could be compared.
In closing, Mr. Halvorson commented
briefly on the subject of maintenance and
operating costs.
The paper indicated that arc lamp devel-
opments have been keeping step with the
remarkable advances that have been made in
the incandescent lamp field and show that
the arc lamp, for street lighting purposes at
least, is a very important factor.
In Mr. Brown's paper the author explained
that with the development of gas-filled lamps
there appeared two types, designated re-
spectively as "low-current" and "high-cur-
rent." He compared the use of these two
types on similar series circuits. The low-
current type may be operated directly on
existing series systems, while the high-current
type is adapted to standard circuits by
means of auto-transformers whose functions
are to transform the line current to the
proper value for the lamps, and also to
protect the lamps against abnormal condi-
tions. From calculations based on experi-
mental and design data, the following
conclusions were drawn:
(1) For abnormal conditions of primary
voltage fluctuation or accidental shorts on
the secondary, the compensator units are
better protected against extreme conditions;
and, even for moderate fluctuations, the result-
ing effect on the lamp is appreciably less and
therefore the use of compensators offers a
greater reliability.
(2) For normal operation it is shown that
the lowering of the primary power-factor,
due to the . introduction of compensators
in the secondary, is not a serious loss, since
the use of the more efficient high-current
lamps allows the operation of a few more
units for full load on the series transformers
and consequently more available light of a
better quality.
Mr. Hawkins in his paper very clearly
explained the principle of operation of gas-
filled incandescent lamps, the various stages
of their development, and the reason why
this construction which now seems so simple,
was not obvious before. He carried out two
striking experiments, one showing the very
remarkable improvement in candle-power
and efficiency effected simply by winding the
tungsten-wire filament of the gas-filled lamp
in the form of a tight spiral instead of looping
it on supports as with vacuum lamps, and
the other showing the marked advantage
to be obtained from the use of high-current (15
to 20 amp.) over low current (6 to 7)4 amp.) in
securing high-efficiency at equal wattage.
On the 19th of January, Dr. W. D. Coolidge,
Assistant Director of the Research Laboratory
of the General Electric Company, presented
a paper entitled Recent Developments with
X-Rays. This paper will be abstracted in
the March issue of the Review.
152
GENERAL ELECTRIC REVIEW
FROM THE CONSULTING ENGINEERING DEPARTMENT OF THE
GENERAL ELECTRIC COMPANY
SOME NOTES ON X-RAYS
In view of the remarkable improvements in X-ray
generators, recently achieved by Dr. W. D. Coolidge
and Dr. I. Langmuir in the General Electric Re-
search Laboratory, and in view also of the wonderful
use of these rays lately made by Dr. W. H. Bragg
and his son, W. Lawrence Bragg, in the determina-
tion of the atomic structure of crystals, etc., it may
be timely to present a brief retrospective sketch
pertaining to the general subject of X-rays.
From time almost immemorial three states of
matter have been recognized: The solid, the liquid,
and the gaseous; but in the year 1816, that pro-
found philosopher, Michael Faraday, conceived of
its existence in a fourth state, to which he gave the
peculiar and significant name of "Radiant Matter,"
and he considered this state of matter to be as
distinctly different from the gaseous state as the
gaseous is from the liquid, or the liquid from the
solid.*
In 1879, 63 years after the date of Faraday's
remarkable conception, Sir William Crookes delivered
his memorable lecture on "Radiant Matter" before
a meeting of the British Association at Sheffield,
England. In this lecture he exhibited and described
very highly exhausted tubes which were almost
identical in outside form and internal construction
with some of our present X-ray tubes, being fur-
nished with large concave cathodes, small anodes,
and intermediate pieces of iridio-platinum, the
latter corresponding to the targets of our X-ray
tubes.
Sir William Crookes unquestionably produced
X-rays when he made his classical experiments on
"Radiant Matter," but he did not chance to bring
any substance within range of their influence that
would have made them directly or indirectly ap-
parent, so their existence at that time remained un-
discovered.
In 1893, fourteen years after the delivery of this
lecture, we hear of Dr. Philip Lenard experimenting
with Crookes' tubes in Heidelberg, Germany. Len-
ard made a tube with a little aluminum window-
through which the cathode rays could shine out
into the open air, whereas they had previously
been confined to the inside of the tube by the glass '
wall which they could not penetrate. Lenard then
discovered that these rays, which have been called
"Lenard Rays," could be deflected by magnetism,
could produce photographic action and cause fluores-
cence in certain substances, barium-platino-cyanide
being affected in the highest degree.
Two years later we find Prof. Wilhelm Konrad
Rontgen also experimenting with Crookes' tubes in
the Institute of Physics in Wurzburg, Bavaria.
He covered one of these tubes with black paper, and
when it was excited by the current from an induction
coil, noticed that a piece of cardboard which had
been coated with barium-platino-cyanide, and was
lying on the table near by, glowed with a bright
green 0 , e, although the black paper com-
every ray of visible light that was
produced in side the tube bv the electrical discharge.
Rontgen's trained intell him at onci
arkable phenomenon with the exist-
o unknown radiation, to which
both the glass of the tube and its covering of black
*S« Dr. Dence Jones' "Life and Letters 0f Faraday," Vol. I.
paper were transparent, and which caused the
fluorescence of the barium-platino salt. Placing his
hand between the glowing screen and the darkened
tube he saw not only the dim shadow of his hand on
the shining surface, but also the darker outlines of
the bones within.
Thus were the X-rays at last brought to light:
foreshadowed in Faraday's conception of "Radiant
Matter" in 1816: actually produced, but unrecog-
nized, by Crookes in 1879; carried to the very verge
of revelation by Lenard in 1893; and discovered by
Rontgen on November 8, 1895.
The announcement of his discovery was made by
Dr. Rontgen in a paper read at the Institute of
Physics of the University of Wurzburg in Bavaria,
in December, 1895.
In this paper the method of generating X-rays
was explained, their fluorescent effect on a cardboard
screen coated with barium-platino-cyanide was
described, and their action on the photographic
plate recorded as a fact of special significance. The
relative transparency of various bodies to the newly
discovered rays was also noted, and some negative
results were mentioned regarding attempts to reflect
and refract them. He also stated in this paper
that the term "rays" was used for the sake of
brevity, the prefix "X" being given to distinguish
them from other rays, such as Lenard's for example.
On January 7, 1896, the news of Prof. Rontgen's
marvelous discovery was cabled to this country and
its extraordinary character and value were imme-
diately recognized, while its novel and almost magical
possibilities appealed so strongly to the public at
large that the announcement spread in an incredibly
short period.
Some time naturally elapsed after the discovery
of X-rays by Dr. Rontgen before their curative as
well as their destructive qualities were fully recog-
nized. During this period many ardent and enthu-
siastic experimenters received serious injuries as as
result of their inexperience, and in a few lamentable
cases X-ray burns produced even fatal results.
This stage of unfortunate ignorance, however,
soon passed, and improvements in X-ray apparatus
generally were rapidly developed, so that the rays
could be properly administered without danger to
either the patient or the operator, and at the present
time every well equipped hospital in the country
has an efficient X-ray generating apparatus. Thus
in the course of less than twenty years Dr. Rontgen's
great discovery has developed into one of the most
beneficent agents for the alleviation of many bodily
ailments, and by reason of the later improvements,
referred to in the beginning of this article, their
further scope, not only in medical treatment, but
also in many branches of scientific research, will
be greatly enlarged. W. S. Andrews.
ERRA TA: Attention is called to two corrections to
apply to the article "From the'Consulting Engineering
Department of the General Electric Company" in the
January number of the GEXERAL ELECTRIC
REVIEW.
Twenty-one lines from the bottom of the right-hand
column, p. 73, the equation as printed
,' Edi /* /•■ Edi /*•
I (a + bi + 'ciVi I dt should be \ 'a+bi +«•) i I dt
Eight lines from the bottom of the same column the
word "infinite" should be "infinite".
General Electric Review
A MONTHLY MAGAZINE FOR ENGINEERS
Manager. M. P. RICE Editor, JOHN R. HEWETT Associate Editor, B. M. EOFF
Assistant Editor, E. C. SANDERS
Subscription Rates: United States and Mexico, $2.00 per year; Canada, $2.25 per year; Foreign, $2.50 per year; payable in
advance. Remit by post-office or express money orders, bank checks or drafts, made payable to the General Electric Review
Schenectady, N. Y.
Entered as second-class matter, March 26, 1912, at the post-office at Schenectady, N. Y., under the Act of March, 1879.
VOL. XVIII., No. :i by c^T&WLtany March, 1915
CONTENTS Page
Supplement: Reproduction in Colors of Resolutions Presented to C. A. Coffin and
E. W. Rice, Jr., by the Association of Edison Illuminating Companies
Frontispiece . I."i4
Editorial: The Paths of Progress 155
A New Device for Rectifying High Tension Alternating Currents. . . 156
By Dr. Saul Dushman
Parallel Operation of Alternating Current Generators Driven by Internal Combustion
Engines 167
Part I : Factors Affecting Generator Design.
By R. E. Doherty
Part II: Factors Affecting Engine Design.
By H. C. Lehn
Tests of Large Steam Hoists . 179
By H. E. Spring
High Voltage Arrester for Telephone Lines .... . 1S9
By E. P. Peck
X-Ray Examination of Built-Up Mica . 195
By C. N. Moore
The Effect of Chemical Composition upon the Magnetic Properties of Steels . 197
By W. E. Ruder
Electrophysics: Electron Theory of Electric Conduction in Metals . . 204
By J. P. Minton
Lock Entrance Caisson for the Panama Canal . . .210
By L. A. Mason
Practical Experience in the Operation of Electrical Machinery, Part VI . 217
Excessive Contact-Shoe Pressure; Electric Brake Adjustments; Rotor Rubbed
Stator; Jerky Motor Acceleration.
By E. C. Parham
A Hydro-electric Installation on a Coffee Plantation . . 219
By J. H. Torrens
Notes on the Activities of the A. I. E. E. . • 222
From the Consulting Engineering Department of the General Electric Company . 226
Question and Answer Section . . • 2-7
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THE PATHS OF PROGRESS
With this issue we publish a unique
supplement. It gives us special pleasure to
meet the request to give greater publicity
to the resolutions which we reproduce, as
we feel that from the very nature of things
few are in a position to recognize the
great service done the electrical industry by
some of those who were so active in its
infancy.
Twenty-five years ago there were some
few active workers who by their energy,
faith and forethought were laying the founda-
tion stones on which the electrical industry
of today stands. The number of workers
soon greatly increased and some, that un-
doubtedly did much to further the great
enterprise, have been lost sight of, but it is
inevitable in all human affairs that many
workers never get their due reward.
The electrical industry of today when
viewed from its broadest aspect is the'
greatest of all industries and has, so far as
the human mind can judge, the greatest
future before it. No one factor with the
single exception of the invention of the
steam engine, with which it is so inseparably
connected, has done more to bring about
the changes in our economic and social mode
of living which we have witnessed during
the last quarter of a century. When we add
to the electrical industry proper the activities
it has stimulated in a host of others such as
the iron, copper, power, lighting and railway
industries, etc., we are forced to a recognition
of the growth of the electrical industry as
the most potent factor in modern industrial
life; and when we add to these the scientific
accomplishments which would have been
non-existent but for the advent of an electrical
age we have to acknowledge that the electrical
industry has been a most mighty factor in our
modern intensive scheme of civilization.
In some future issue we shall attempt to
review the electrical industries and show
their scope, but what we are particularly
interested in at this present writing is the
thought — whence all these wonderful develop-
ments have sprung.
A final analysis could only lead to the
conclusion that it is a tremendous triumph
of mind over matter — the useful forces of
nature converted to the service of man.
It is of special importance to note that these
great things have been accomplished by the
mind of man firstly, by the hand of man
secondly; the thought came before the work
and accomplishment, and that during the last
quarter of a century we have been witnessing
to a greater extent than ever before the de-
velopment of the experiments of yesterday,
which are the first fruits of productive
thought, into the industries of today.
The men to whom the electrical industry
owes most today are those who thought of
its possibilities and the part it could play
in our future development. Without their
activities and forethought, without their
resourcefulness and faith, the work of a great
industrial army would never have been
brought into being. The type of mind that
has the power to originate and the type of
mind that has the power to organize are the
greatest capital assets that the industrial
world possesses. These are the foundation
stones on which the whole fabric of our
modern structure rests. In spite of anarchy,
in spite of socialism, in spite of government
and mis-government, in spite of the ever
continuing war of the many against the few.
of those that have against those that have
not, the work of the brain must always take a
higher stand, whether the thinkers get their
reward or not, than the work of the hand.
Both types of the work are absolutely
essential to our modern scheme of life, but
it is inevitable that the creative genius must
always be greater than the hand which fash-
ions the material thing created by the mind.
The foundations of the great operating
companies were being laid at the same time as
those of the great manufacturing companies,
and so it gives us special pleasure to record a
tribute from the representatives of the great
Edison Illuminating Companies to two of those
who have not only been pioneers of the in-
dustry, but who have been active workers
from its inception up to the present time.
156
GENERAL ELECTRIC REVIEW
A NEW DEVICE FOR RECTIFYING HIGH TENSION
ALTERNATING CURRENTS
THE KENOTRON
By Dr. Saul Dushman
Research Laboratory, General Electric Company
In the following paper the writer discusses an interesting application of the theoretical investigations
on electron emission from incandescent metals. The construction of a high voltage rectifier illustrates the
old expression that the theory of the present may become engineering practice of the future. — Editor.
Introduction
The emission of negatively charged cor-
puscles or electrons from heated metals may
be illustrated by the following arrangement.
In an ordinary lamp bulb containing a
tungsten or carbon filament there is also
sealed in a metal plate. After the lamp is
well exhausted it is observed, on charging
the filament negatively (making it cathode)
with respect to the plate, that a current
passes across the vacuous space. If the
filament is charged positively this current
disappears. Furthermore, the magnitude of
this electron emission (thermionic current)
from the heated cathode increases with
increase in the temperature of the filament.
This effect had been observed by Edison
and was more fully investigated in the case
of carbon lamps by Fleming.* In view of the
unilateral conductivity possessed by such
an arrangement as that described above,
Fleming applied it as an "electric valve" to
rectify electric oscillations such as are ob-
tained from a "wireless" antenna, and
therefore render it possible for these oscil-
lations to affect a galvanometer or telephone. f
That the current from a hot cathode in an
exhausted bulb is due to a convection of
electrons, that is of negatively charged
corpuscles having a mass which is about
1 1 MMJth of that of a hydrogen atom, may be
shown by deflecting the current in magnetic
and electrostatic fields and determining the
ratio e/tn. Another method is that described
below and which depends upon the space
charge produced by the electrons under
certain conditions.
The relation between thermionic current
and temperature of cathode was further
investigated by Richardson and he found
that in all cases the relation could be accu-
•Proc. Roy. Soc.. Lond.. J,7, 122 (1890).
tProc. Roy. Soc.. Lond.. 74. 476 (1905). See also J. A.
tleming, Principles of Electric Wave Telegraphy and Telephony
pp. 477-482 (second edition). *
rately represented by an equation of the form,
T
i = ay/jt (i)
where a and b are constants for the particular
metal and i is the saturation thermionic
current per unit area at the absolute tem-
perature T.
Subsequent experiments, however, by other
investigators tended to throw much doubt
upon the actual existence of a pure electron
emission from a heated metal in a good
vacuum. It was found that different gases
affected the values of the constants a and b
to an immense extent, so that at the same
temperature the thermionic currents obtained
varied over a very wide range. Furthermore,
it seemed that the greater the precaution
taken to attain high vacuum, the smaller the
thermionic currents obtained, and the con-
clusion was drawn that in a "perfect"
vacuum the thermionic currents would dis-
appear altogether. In fact, the view generally
held until the past year by the German
physicists and by quite a few English phy-
sicists was that the thermionic currents were
due to chemical reactions in a gas layer at the
surface of the heated metal, and that there-
fore there was no justification for believing
in the existence of a pure electron emission
per ipse from a heated metal.
This subject was taken up in the Research
Laboratory of the General Electric Company,
by Dr. Irving Langmuir, and he found that
in the case of heated tungsten filaments the
electron emission at constant temperature
increased as the vacuum improved until a
constant value was attained which varied
with the temperature in accordance with
Richardson's equation. Dr. W. D. Coolidge
applied this fact to the construction of a hot
cathode Rontgen ray tubej in which elec-
trons are produced from a heated filament
in a highly exhausted bulb. A tungsten
}W. D. Coolidge. Phys. Rev.. Dec. 1913.
DEVICE FOR RECTIFYING HIGH TENSION ALTERNATING CURRENTS 157
target is used as anode and by applying very
high voltages (50,000 to 100,000) the electrons
are given velocities great enough to produce
very penetrating X-rays when they strike
the target.
During the last few years Dr. Langmuir
has carried out a detailed investigation of the
whole subject of electron emission from
heated metals and the results obtained have
led to a large number of interesting and
highly important applications.
While a complete summary of these appli-
cations will be presented by Dr. Langmuir
at a future meeting of the Institute of Radio
Engineers, it has been considered advisable
to publish a preliminary account of one
important application of hot cathode tubes
in the development of which the writer has
been interested. This concerns the appli-
cation to the rectification of high tension
alternating currents.
The Hot Cathode Rectifier
As mentioned above, the fact that an
exhausted tube, containing two electrodes,
one of which is heated by some external
source, acts as a rectifier, has been known for
a number of years. But difficulties were met
with in the way of applying this practically.
The magnitude of the current obtained was
apt to vary quite erratically, especially with
slight variations in degree of vacuum. Fur-
thermore, in the types of hot cathode rectifiers
exhausted by ordinary methods, the electron
emission is accompanied by a blue glow.
This glow becomes more and more pronounced
the higher the voltage at which the rectifier is
operated, and it is found that under these con-
ditions the cathode gradually disintegrates so
that the rectifier becomes inoperative.
An explanation of these phenomena grad-
ually developed as a result of the above
mentioned investigations on thermionic cur-
rents in high vacua. It was perceived that
the blue glow is due to the presence of pos-
itively charged gas molecules (ions), and that
the disintegration of the cathode is due to
bombardment by these positive ions moving
with high velocity. But when the vacuum is
made as perfect as possible, the conduction
occurs only by means of electrons emitted
from the hot cathode, and there is no evidence
whatever of any blue glow or other forms of
gaseous discharge. Thus, while it had
previously been considered that a certain
amount of gas is absolutely essential to
obtain conduction from a hot cathode, and
the presence of blue glow was taken to be a
necessary accompaniment of conduction in
such cases, it was found that by adopting
certain methods of treatment and the use of
high vacua, a hot cathode rectifier could be
constructed in which all of the difficulties
discussed above are avoided.
Special methods have been developed for
treating all metal parts and glass walls so
that they are made as free of gas as possible.
A Gaede molecular pump in series with two
other pumps is used to evacuate the tubes.
It has been shown by the writer* that by
using this arrangement together with a liquid
air trap inserted between rectifier and molecu-
lar pump, it is possible to attain a vacuum as
high as 5X10~7 mm. of mercury. At this
pressure the mean free path of an electron
is so great that the chance of its colliding with
any gas molecules and thus forming ions by
collision is reduced to a minimum.
In the Coolidge X-ray tube there is no
difficulty in obtaining such a good vacuum
that no gaseous discharge occurs even when
150,000 volts is applied across the electrodes.
There appears to be no limit to the voltage
for which the tube may be constructed
except that due to electrostatic strains. A
further discussion of this point is, however,
reserved for a subsequent section.
Electron Emission in High Vacuum
Regarding the difficulty of obtaining con-
stant values for the thermionic currents at
given temperatures, it has already been
mentioned that in a sufficiently good vacuum
the results obtained are perfectly definite and
reproducible. In the case of tungsten in a
"perfect" vacuum the value of the constants
a and b in the Richardson equation are 23.6 X
109 and 52500 respectively, where i is meas-
ured in milli-amperes per square centimeter-!
Using these constants, the values of i
calculated for different values of T are as
given in the following table:
TABLE I
T
t'/cm*
2000
4.2 milli-amps.
2100
15.1
2200
48.3
2300
137.7
2400
364.8
2500
891.0
2600
2044.0
*S. Dushman. Phys. Rev., April, 1914. The complete paper
will appear very shortly in the same journal.
fl. Langmuir, Physikal. Zeit., IS, 516 (1914).
158
GENERAL ELECTRIC REVIEW
In Fig. 1 these results have been plotted
on semi-logarithmic paper. Plotting directly
values of i against those of T one obtains a
curve of the form shown in Fig. 2.*
Space Charge Effect
It was observed by Langmuir that in addi-
tion to this temperature limitation the elec-
tron current may be also limited by space
charge. With a low potential difference
between the electrodes the phenomena ob-
served are as follows:
As the temperature of the cathode increases,
the electron emission increases at first in
accordance with the equation of Richardson.
However, above a certain temperature this
current becomes constant; further increase
in temperature does not cause any correspond-
ing increase in thermionic current. The
temperature at which this limitation occurs
.increases with increase in anode potential.
The curves shown in Fig. 2 illustrate this very
well. They represent the results observed
when the thermionic current was measured
from a 10-mil tungsten filament situated
along the axis of a cylindrical anode 7.62
cm. long and 1.27 cm. in radius. Thus,
with a potential difference of 55.5 volts, the
electron emission increased according to the
equation of Richardson until a temperature
of about 2300 deg. K was attained. With
further increase in temperature, the ther-
mionic current remained absolutely constant.
But when the voltage was increased to 87.5,
the thermionic current continued to increase
up to 2350 deg. K. With a voltage of 129,
the increase in thermionic current was
observed up to 2400 deg. K.
This effect (which is observed only in
extremely good vacua) is due to the existence
of a space charge produced by the emitted
electrons. In other words, the electrons
emitted from the hot cathode produce an
electrostatic field which tends to prevent the
motion of any more electrons toward the
anode. As the positive potential on the latter
increases, more and more electrons are
permitted to reach the anode.
From theoretical considerations it was
deduced by Langmuir that the thermionic
current ought to increase with the three-halves
power of the voltage (until the saturation
* S. Dushman. Phys. Rev.. 4. 121 (1914). The area of the
hot filament used was 0.61 cm3. The experiments from which
this curve was plotted were performed some time ago. Both
the degree of vacuum attained and the accuracy of temperature
determination were not as good as that obtained in measuring
the values of. a and 6 given above. When it is considered that
an error of 25 degrees in the determination of the temperature
at 2400 deg. K. is sufficient to account for the difference between
these values of the constants and those given in the curve, the
discrepancy does not appear so great.
current as defined by the Richardson equation
is attained), that is, for electrodes of any
shape, the space charge current
*, = *. V* (2)
where V denotes the potential difference and
k is a constant depending on the shape of the
electrodes, their area and the distance apart.
For the case of a heated filament in a
concentric cylindrical anode (infinite length)
V
in r
(3)
*' 9 \m
where i, is the thermionic current per unit
length and r is the radius of the anode.
Converting into ordinary units (milli-
amperes and volts) this equation becomes
14 fi
xi^xio-3
r
(4)
/ 1
600
/
/
400
o
3
/-
too
8*
fi
/
1
/
o
/
i
/ Electron, Emission from "Tungsten
1 1
Calculated from Equation
&XC
7
/
/
■
i
l
3
/
I
/
b
/
/ — j>
8
1
/
N
A
1
/
Oeg Kelvin.
EC
00
SB:
»
£»K
K>
Z©
oo
Fig. 1. Electron Emission from Tungsten
in a "Perfect" Vacuum
The data shown in Fig. 2, which were
obtained in the course of an investigation
carried out by the writer, are in full accord
with the results calculated from this equation.
Substituting for r the value 1.27 cm., and
noting that the actual length of cylinder
used was 7.62 cm., the values of the constant
factor as obtained from the observed space
DEVICE FOR RECTIFYING HIGH TENSION ALTERNATING CURRENTS 159
*>2.32X10-3xV
x
charge currents for different voltages do not
differ by more than 2 per cent from 14.6.*
In the case of a heated tungsten plate
parallel to another plate, the space charge
current per sq. cm.
V*
(5)
where x is the distance between the plates
in centimeters.
It ought to. be observed that up to a point
at which the diameter of the filament amounts
to about five per cent of the diameter of the
anode cylinder, or of the distance between
the plates, the space charge voltage is
independent of the actual diameter of the
filament.
The thermionic current from a hot cathode
may tlicrefore be limited either by tem-
W
/ao
/00
80
60
40
ZO
'
-I
7
■^oQ
k
•1
-\L
f
r
1
II
1.5
*
-
v-u
*'
>i
^
t
\
it
V=8?S
ft/
\
V=*Z5.£
. —
- i)
A,
V-675
V=S£.£
V=4-7
1 1
| |
V=35
Degrees /felvip
2/00
2200
2300
24-00
2500
Fig. 2. The Effect of Space Charge on the
Thermionic Currents
perature or by space charge. With a given
temperature of the cathode, the thermionic
current will increase at first as the positive
potential on the anode is increased, and
for each voltage V, there will be a Corre-
ct is evident that equation (3) may be used as a method for
the determination of elm. The results obtained therefore serve
to confirm once more the conclusion that the negative current
from the hot cathode is due to electrons
sponding value of is according to equation
(2). When is has attained the value i which
corresponds to saturation thermionic cur-
rent from the filament at the given tem-
perature, further increase in voltage has
no effect.
On the other hand, with a given voltage
drop, the current increases with the tempera-
ture until t is equal to is, and further increase
in temperature leads to no corresponding
increase in thermionic current. This is the
case illustrated in Fig. 2.
The existence of this space charge effect is
evidence of the absence of any positive
ionization, and serves, therefore, as additional
confirmation of the conclusion that the
currents obtained from a hot cathode in a
very high vacuum are due to a pure electron
emission, and are not dependent upon the
presence of any small amounts of gas.
In this respect the behavior of a hot
filament in a good vacuum differs radically
from that exhibited by a Wehnelt cathode.
In the case of the latter the currents obtained
are due largely to the presence of positive
ions, as is shown by the absence of space
charge effects. The result is that the cathode
disintegrates under the action of positive
ion bombardment, and a rectifier containing
such a cathode therefore cannot be used with
potentials higher than a few hundred volts
at most. On the other hand, in the case of a
rectifier containing a hot filament as cathode
and exhausted to as high a degree of vacuum
as possible, there is no conduction except by
electrons. In order to distinguish the latter
type of hot cathode rectifier from other forms
in which positive ions play an essential role,
the designation, kenotron, has been specially
coined. This word is derived from the Greek
adjective kenos, meaning "empty" and the
suffix tron signifying an instrument or appli-
ance. The applicability of the name is
self-evident.
Having indicated the possibility of the
construction of a high voltage hot cathode
rectifier, we shall now proceed to discuss the
principles underlying the designing of such
rectifiers.
Principles of Design of Kenotrons
The question as to the proper design of a
kenotron may be treated under three headings :
1. The amount of current to be rectified.
2. The maximum permissible voltage loss
in the rectifier.
3. The proper form of electrodes to prevent
electrostatic strains on the filament.
160
GENERAL ELECTRIC REVIEW
(1) Current Carrying Capacity of the Kenotron
The current carrying capacity of a kenotron
when given sufficiently high voltage between
the electrodes, is limited only by the area
of the surface emitting electrons (that is,
length and diameter of filament) and its
temperature. The data given in Table I
and the curve shown in Fig. 1 are therefore
of fundamental importance in this connection.
The next consideration is, of course, the
"life"* of the filament at any temperature,
and normally the maximum temperature
at which the filament is maintained should be
such that the "life" of the filament is over
1000 hours at least.
Thus, a 5-mil filament at 2400 deg. K.
(corresponding to 1 watt per candle) has a
life of about 4000 hours. The electron emis-
sion per 1 cm. length of 5-mil filament at this
temperature, as calculated from Table I is
15 milli-amperes. The energy required to
maintain the filament at this temperature is
about 4.5 watts per cm. length.
Where the kenotron is required for currents
of 100 milli-amperes or more, it is better to
use a 7 or 10-mil filament. This is of advan-
tage in two respects. Not only is there an
increase in area per unit length, but also the
life is much longer at the same temperature.
On the other hand, the temperature can be
increased and the life of the filament still be
maintained at over 1000 hours. Thus, in the
case of a 10-mil filament at 2500 deg. K., the
life is pretty nearly 3000 hours, while the
electron emission is 70 milli-amperes per
cm. length.
The data shown in Table II are of great
interest in this connection. As "safe"
temperature we consider that at which the
life of the filament is over 2000 hours. The
last column also gives the watts per cm.
length of filament, a figure which is of
importance in calculating the losses in the
rectifier itself. 1
TABLE II
Electron -ut~**-
Diam. of „..„
Filament in T,„!!i!t„„ Emission per f^atTsp",,t
Mils Temperature Cm ^^ Cm. Lengtht
3.1
4.6
7.2
11.3
•The "life" of a filament is usually taken in this laboratory
as the time required to evaporate 10 per cent of the diameter. For
data on the rate of evaporation of tungsten filaments the reader
is referred to the paper by Langmuir. Phys. Rev., g, 329 (1913).
IThese figures are based upon data published by Langmuir,
Phys. Rev.. Si. 401 (1913).
tThe current necessary to heat the filame-.t varies from 2
to 10 amperes, according to the diameter of the filament and the
temperature, and may be obtained either from a storage battery
or small transformer.
(2) Voltage Drop in Kenotron
Owing to the existence of the space charge
effect it is evident that for any given current
carrying capacity i of a kenotron there will
exist a voltage drop V in the rectifier itself
and the relation between these will be of the
form indicated in equation (2).
We can now consider the manner in which
the kenotron operates when placed in series
with a resistance across a source of high
voltage.
Let E denote the value of this voltage at
any instant, and is the current rectified.
If V denote the voltage drop through the
kenotron, and R, the resistance of the load,
it follows from equation (2) that
is=kvi=k (E-isR)i (2a)
With constant value of E, the current
rectified increases as R is decreased until
is has attained the value i corresponding to
saturation thermionic current at the temper-
ature at which the cathode is maintained.
If now R is decreased still further, i remains
constant, and consequently the voltage over
the kenotron increases beyond that given by
equation (2). That is, this equation gives the
minimum voltage drop through the kenotron
when rectifying a given current is; but when
operating in series with a resistance, the
voltage drop in the kenotron is that available
above the isR drop in load. In case of a short-
circuit on the latter, where R decreases
indefinitely, the total voltage of the source is
taken up by the kenotron, thus liberating
the whole of the energy, Ei, as heat at the
anode, and the latter may be raised to a tem-
perature at which it will melt or volatilize
and ruin the tube.
It is necessary to emphasize this character-
istic behavior of the kenotron, and in practice
care should be taken to provide against
short-circuiting of the load, or some form of
protective device should be used.
The watts lost in the kenotron owing to the
space charge effect is
II"
Yi = kY*
(6)
Because of the high degree of vacuum,
none of the electrons lose energy by collision
with gas molecules. The whole of their
kinetic energy is therefore liberated as heat
at the anode, just as the energy of rifle
bullets travelling through a comparatively
frictionless medium is converted into heat
at the target. Denoting the number of
electrons emitted per unit area and per
unit time by n, and their velocity by v. it
DEVICE FOR RECTIFYING HIGH TENSION ALTERNATING CURRENTS 161
follows that the energy converted into heat
at the anode is
n (J/£ m v2) =n e V =i V (6a)
If to this be added the watts wh used in
heating the filament, then the total loss in
energy becomes
wl = u>h+wr (7)
Of this energy loss, the whole of wr and a
large fraction of wh are used up in heating
the anode.
It is evident that if the anode becomes too
hot the rectification will tend to become
imperfect. The rectifier must, therefore, be
so designed that the space charge voltage
is not great enough to cause heating of the
anode when the requisite current is being
carried by the tube. The amount of energy
(in watts per square centimeter) required to
maintain tungsten at a temperature T is
given by the equation,*
^=i2-54(t4)47
(8)
Table III gives the values of Ws for
different temperatures. The last column
gives the corresponding values of the electron
emission per unit area in milli-amperes.
TABLE III
T
W 5
j
1000
0.96
1.2 X10"11
1500
6.9
6 X10-*
1800
16.4
0.3
2000
26.9
4.2
2500
77.5
890
From these data it may be concluded that
about 10 watts per sq. cm. of anode area is
quite permissible. This would correspond to a
temperature of about 1600 deg. K., that is
a very bright red heat. At this temperature
the electron emission is still less than 0.02
milli-ampere per sq. cm.
(3) Electrode Design
There remains only one other point to
consider in the design of kenotrons and
that is the prevention of electrostatic strains
on the filament. As is well known, the
electrostatic force between two charged
surfaces increases as the square of the
voltage difference. At voltages of 25,000 and
over, this force becomes quite appreciable and
unless special precautions are taken in the
design of electrodes, it is possible at such
*I. Langmuir. Phys. Rev.. Si, -101 (1912). The same equa-
tion is also approximately true for molybdenum.
voltages to actually pull the heated filament
over towards the anode. When the kenotron
is used in series with a load on a high tension
alternating current circuit, there is a very
low potential difference between the electrode
during the half cycle that rectification occurs,
while during the other half cycle the whole of
the voltage drop generated by the transformer
or other source of alternating current occurs
in the rectifier itself. It is therefore necessary
to design the kenotron so that the electrostatic
forces acting on the filament are reduced
to a minimum.
Various types of construction have been
adopted to take care of this difficulty. A
straight filament in the axis of a cylindrical
anode; a V- or W-shaped filament placed
symmetrically between two parallel plates; or
■ a headlight filament inside a molybdenum
cap, each of these types of construction has
been found practicable up to certain voltages.
Of course, electrostatic forces can be
overcome by placing the filament at quite
a distance from the anode and shielding the
former in the same manner as is done by
Coolidge in his Rontgen ray tube. But
under these conditions the "space charge"
voltage (which increases with the first or
second power of the distance, see equations
4 and 5) becomes excessively high and the
energy loss in such a rectifier would be alto-
gether too large.
Different Types of Kenotrons
The different types of kenotrons mentioned
in the previous section are illustrated in
Figs. 3, 4 and 5. In the following section it is
intended to discuss briefly the characteristics
of rectifiers that have been constructed along
these lines and to point out the relative
advantages and disadvantages of each type.
Fig. 3 shows a molybdenum cylinder A
with a coaxial filament F. For direct current
voltages up to 15,000 the diameter of the
cylinder need not exceed one-half inch
(1.27 cm.), while the length may be made
as much as four inches (10 cm.) A 10-mil
filament is used as cathode.
At a temperature of 2550 deg. K. (see
Table II) the maximum current obtainable
from such a kenotron is about 400 milli-
amperes, and the voltage drop necessary to
produce this current as calculated from
equation (4), and actually observed, is
(;
'400 1.27
' lT6X 2 X
ipY
10/
= 145.
162
GENERAL ELECTRIC REVIEW
The space charge equation for this kenotron
is
is = 230 X 10"3 X V* milli-amperes.
At 145 volts, \YR= 145X0.400 = 58 watts.
Also a/H=72 (Table II). The total energy
used up in the rectifier is therefore 130 watts.
energy lost in the kenotron is about 125 watts
which represents only 1.25 per cent of the
total energy which the tube is capable of
rectifying.
Fig 4. Kenotron Containing Cylindrical Anode
Fig. 3. Molybdenum Cap Type of Kenotron
As the radiating area of anode surface is
about SO sq. cm., this energy loss corresponds
to slightly over 1.5 watts per sq. cm., which
is just sufficient to maintain the anode at a
dull red heat (1100 deg. K.). Since the
kenotron is capable of rectifying0.400 X 15,000
= 6 kw., the energy loss in the tube corre-
sponds to about 2 per cent of the total amount
of energy rectified.
For direct current voltages up to 75,000
or 100,000, the diameter of the cylinder is
increased to about 5 cm. For mechanical
reasons it has been found necessary, in this
case, to attach the filament to a molybdenum
rod framework, which serves to increase the
space charge voltage above that calculated
from equation (4). In a tube intended to
rectify 10 kw. at 100,000 volts the current
carrying capacity required is 100 milli-
amperes. This electron emission is easily
obtained from about 4 cm. of 7-mil filament
at a temperature around 2400 deg. K.
The space charge data of Table IV were
obtained with one kenotron (Xo. 72) of this
type:
These observations are in accord with the
equation
*'s=6xio-3xn
energy loss in the tube owing to this
space charge voltage amounts to 65 watts for
100 milli-amperes. Adding to this about 50
watts consumed by the filament, the total
Fig. 5. Kenotron with Filament Between Two
Parallel Plates
A form of kenotron which is suitable for
voltages not over 10,000 and currents ranging
up to 100 milli-amperes is that shown in
DEVICE FOR RECTIFYING HIGH TENSION ALTERNATING CURRENTS 163
TABLE IV TABLE VI
v
is
310
260
130
33 milli-amperes
25
9
Fig. 4. It consists of a small filament such
as is used in automobile headlights inserted in
a molybdenum cap about 1.6 cm. (^ inch)
in diameter.
The following table gives the currents
actually obtained with different voltages in
the case of kenotrons containing a 7-mil head-
light filament (No. 50), and 5-mil headlight
respectively (No. 51).
TABLE
V
KENOTRON NO. 50
KENOTRON NO. 51
V
is
V
i.
20
2.7
100
19
40
7.6
150
36
80
25.0
200
55
120
46.0
160
70.0
200
96.0
240
115.0
In the case of No. 50, the observations are
very accurately represented by the equation
*'S = 34X10-3XF
While in that of No. 51, the corresponding
equation is
/s=i9.5xio-3xr*
In neither case is it necessary to heat the
filament to a temperature above 2400 deg.
K. The radiating surface of the anode is
about 4 sq. cm. and the total energy loss for
100 milli-amperes is about 50 watts.
The case of a V-shaped filament between
two tungsten plates is illustrated in Fig. 5.
In one case (kenotron No. 66) the plates
were about 2 cm. apart, while in another
kenotron No. 70) the plates were twice as
far apart. Table VI gives the characteristics
for each kenotron.
The filament in kenotron No. 70 was about
7, while that in No. 66 was about 6 cm.
long.* Each tungsten plate was about 2.5
KENOTRON NO. 66
KENOTRON NO.
7(1
Fil.
V
i
Fil.
Temp.
Temp.
2340
260
25
2320
340
28
2370
260
35
2370
340
50
24111
260
90
2400
340
54
2450
260
100
2500
340
60
2500
260
100
2500
260
42
2500 130
35
2500
130
14
is =24X10"3 XVI
is=9.9X10-3
KVi
♦Owing to lead losses only the central portion of the filament
was at the temperature indicated.
X5 cm.; so that the total radiating surface
was about 25 sq. cm. Kenotron No. 66 could
be used up to about 40,000 volts, while No.
70 showed no sparking or straining of filament
up to 60,000 volts.
By using a W-shaped 7-mil filament (total
length about 20 cm.) between two tungsten
plates 5 cm. square and situated 1.25 cm.
apart (kenotron No. 54), the space charge
voltage for given current carrying capacity
was considerably reduced. The space charge
equation for this kenotron was found to be
i5=103X10-3XV^.
Owing to the small distance between the
plates, the filament was not situated exactly
symmetrically with respect to them, and it
was therefore not thought advisable to use
the kenotron with direct current voltages
higher than 25,000.
Here again, the energy loss in the kenotron
for a 10-kw. unit (current carrying capacity
of 400 milli-amperes) is well below 2 per cent.
A comparison of the different types of
kenotrons illustrated above leads to the
following conclusions :
(1) For current carrying capacities up to
500 milli-amperes, either a cylindrical anode
with a filament down the axis, or a W-shaped
filament placed between two parallel plates
may be used. The first named type can
apparently be made much more efficient' as
regards losses due to space charge effect.
(2) Where currents of the order of 100
milli-amperes or less have to be rectified, and
the maximum direct current voltage is not
over 15,000, the molybdenum cap type is
one that is simpler mechanically and also
quite efficient.
(3) For voltages up to 100,000, the.
cylindrical anode type has proven itself to be
very practicable and efficient.
164
GENERAL ELECTRIC REVIEW
Oscillograms of Performance of Kenotrons with
Alternating Current Voltages
In order to illustrate the characteristics of
a kenotron when used with a-c. sources,
a number of oscillograms were taken. Film
maximum voltage ISO. The lower graph
shows that the rectification obtained was
absolutely perfect ; also the peaked nature
of the current wave shows that it was limited
by space charge throughout the whole cycle.
Fig. 6. Half-wave Rectification, Upper Curve Gives
Voltage Over Kenotron; Lower Curve Gives
Current Rectified. Note the Effect of
Voltage Limitation
Fig. 7. Same as Fig. 6. Note the Effect of
Temperature Limitation
Fig. 8. Full Rectification, Using Arrangement Shown
in Fig. 10. Upper Curve — Voltage Over Primary
of Transformer; Middle Curve — Voltage
Over Load; Lower Curve — Current
Rectified. The Latter was Limited
by Temperature of Cathode
in Each Case
Fig. 6 was obtained with kenotron No.
54 placed directly across the 60-cycle, 122-
volt terminals. The upper curve represents
the voltage of the generator, while the lower
curve gives the current through the kenotron.
The effective a-c. voltage was 122 and the
Fig. 9. Same as Fig. 8. The Current Rectified was
Limited on One Half Cycle by Temperature and
on the Other Half by Voltage
It will be remembered that for this kenotron
the space charge equation as obtained from
direct current measurements, was
is = 103X10~3XVK
It was therefore expected that this relation
ought to hold quantitatively for simultaneous
values of voltage and current as measured on
the oscillogram. The results obtained con-
firmed this expectation splendidly.
DEVICE FOR RECTIFYING HIGH TENSION ALTERNATING CURRENTS 165
The following table gives the values of is
as observed and calculated for values of V
corresponding to different intervals of a
second t after the beginning of the cycle :
TABLE VII
V
:',
>.
(upper curve)
(lower curve)
(calculated)
0.0015
64
55
53
0.0022
130
150
153
0.0031
165
207
212
0.0042
180
250
251
A direct current milli-ammeter in series
with the oscillograph read 68 m.a.
Film Fig. 7 was obtained with the same
arrangement of apparatus, but the filament
temperature was made so low that the maxi-
mum current obtainable was well below the
space charge current for 180 volts. The
current curve begins to flatten at a point for
which V — 90. The corresponding space charge
current as calculated from the above equa-
tion is 88 milli-amperes, while the oscillogram
indicates 74 milli-amperes. The direct current
milli-ammeter showed a current of 28 m.a.
The oscillograms shown in films Figs. 8
and 9 were obtained with an arrangement of
apparatus similar to that shown in Fig. 10.
The low tension side of a potential trans-
former TT, ratio of coils 20 to 1, was con-
nected to the 122-volt alternating current
generator, while the high tension coils were
connected to two kenotrons AF and A'F'
as shown in the diagram. (The condenser
C shown in the diagram was omitted.)
The direct current was taken from the middle
point of the transformer and the filaments.
A load of two 250-volt carbon lamps (60-watt
type) was connected in series with a milli-
ammeter and the current strip of the oscillo-
graph to the terminals BB'. The kenotrons
used were not of the same construction,
with the result that the space charge voltages
for the same current were quite different.
The upper curve in each film gives the
voltage over the primary of the transformer,
the middle curve gives the voltage over BB' ,
while the lower curve gives the current
through the load. In taking film Fig. 8, the
temperature of the filaments was maintained
very low, with the result that both current
and voltage waves were flattened consider-
ably. The slight irregularity in the ampli-
tudes of the two half cycles was due to the
fact that it was almost impossible to adjust
the temperatures of the two filaments so that
they would possess the same electron emission.
The direct current milli-ammeter read 100
milli-amperes.
Film Fig. 9 shows an interesting case in
which the thermionic current from one keno-
tron was limited by space charge, while that
from the other was limited by temperature.
The d-c. ammeter indicated 140 m.a. When
taking the oscillogram of the current through
the load, the voltmeter strip was opened,
and when photographing the wave of voltage
over load the current indicating strip of the
oscillograph was short-circuited.
T(TJTOoT|T
Fig. 10. Arrangement for Rectifying Both Half-waves,
Using Middle Point Connection on Transformer
Summary
Summarizing briefly what has been stated
regarding the hot cathode rectifier (kenotron)
it has been shown that :
(1) The current rectification is due to the
emission of electrons from a heated filament
in as good a vacuum as can be obtained. The
current carrying capacity of the kenotron
depends only upon the area and temperature
of the filament, and increases with the latter
according to an equation of the form :
-= T
i = aV Te
(1)
where i denotes the saturation thermionic
current.
(2) The voltage drop in the kenotron
depends upon the area, shape and distance
apart of the electrodes, and increases with
the current actually rectified according to
an equation of the form
is = k.\" (2)
where i, denotes the space charge current.
When * is measured in milli-amperes, the
magnitude of k varies in ordinary cases from
5X10-3, for very high voltage kenotrons, to
166
GENERAL ELECTRIC REVIEW
250 X10~3 for lower voltage kenotrons. In
other words, for a potential drop in the
kenotron of 100 volts, the rectified current
varies from 5 to 250 milli-amperes.
As has been mentioned on page 160.
equation (2) gives the minimum voltage drop
over the kenotron when it is operated in
series with a resistance under most efficient
conditions. Owing, however, to the fact that
the filament temperature limits the maximum
current which the kenotron can rectifv, it is
F
B -
Fig. 11. Arrangement of Four Kenotrons for Making
Use of Full Voltage of Transformer
possible for the voltage over the latter to
exceed the value given by equation (2) as the
rectifier takes the difference between the max-
imum voltage available and that consumed in
the load. Care should therefore be taken in
using the kenotron to avoid short circuits of
the load, or some form of protective device
should be used.
(3) The actual energy losses in the
kenotron may be reduced to less than two per
cent of the "total energy rectified when the
tube is operated to its full voltage limit.
(4) Up to the present, kenotrons have
been constructed for direct current voltages
as high as 100,000; but there is every expecta-
tion of being able to extend the field of
application to 150,000 and even 200,000 volts.
The maximum current rectified has been
as much as 1500 milli-amperes (1.5 amperes);
but it is much more convenient to construct
these rectifiers in the form of 10-kw. units
where the voltages required exceed 25,000.
For lower voltages, smaller units are ad-
visable.
(5) A great advantage possessed by the
kenotron is that two or more of them can be
operated in parallel. From the remarks made
above in connection with equation (2-a), it is
evident that when a number of kenotrons
connected in parallel are placed in series
with a resistance, the current through the
latter will control the voltage drop and cur-
rent through each kenotron so that in each
case an equation of the form (2-a) is satisfied.
The kenotron thus possesses at least two
advantages over the mercury arc rectifier;
firstly, because it may be operated at higher
voltages, and secondly in the fact that several
kenotrons can be operated in parallel.
Applications of the Kenotron
No doubt a number of applications of this
device will suggest themselves to electrical
engineers and physicists. A few words,
indicating the possible fields of application
that have already been suggested, will prob-
ably not be out of place.
In the physical laboratory where small
direct currents of a few milli-amperes at
very high voltages are required, as for spec-
troscopic work, operating small discharge
tubes, etc., the kenotron ought to prove
exceptionally useful. An arrangement similar
to that shown in Fig. 10, and consisting of two
kenotrons of the headlight filament type
with a 60:1 potential transformer will act as
a satisfactory source of direct current voltages
up to 4500 or 5000. By inserting a con-
denser C of sufficiently high capacity between
the terminals BB' the direct current obtained
may be made as free from pulsations as
desired. The kenotron could also be used
for testing the dielectric strength of insulation
with high voltage direct currents.
The writer has obtained as much as 400
milli-amperes direct current at 6000 to 7000
volts by using in the same manner a 500-cycle
generator and a 100 to 10, 000- volt trans-
former.* By inserting capacity between
the high tension direct current terminals,
it was found possible to reduce fluctuations
in the resulting direct current to less than
five per cent when 100 milli-amperes was
being used at 6000 volts.
Fig. 11 shows an arrangement of four
kenotrons in which the whole of the voltage
generated by the transformer is utilized.
BB' are the direct current leads.
* The kenotron operates just as satisfactorily on 100.000
cycles as on ordinary frequencies.
PARALLEL OPERATION OF ALTERNATING CURRENT GENERATORS 167
The combination of kenotrons and trans-
former could be used to replace the cumber-
some static machines and the still more
complicated mechanical rectifiers that are
at present used to produce high voltage
direct current for X-ray tubes and the precip-
itation of dust, smoke, etc.
Another field of application that appears
to be very much within the limits of possi-
bility is that of high voltage direct current
transmission. While this system has not
been used to any extent in this country, it is
a well known fact that the Thurv system has
met with great success in Europe*. To trans-
mit 1000 kw. by 100 kenotrons, working in
parallel at a voltage of 50,000 to 75,000 is
quite a feasible proposition.
In conclusion the writer wishes to express
his indebtedness to Dr. Langmuir and Mr.
W. C. White of the Research Laboratory for
valuable suggestions and kind co-operation
during the work on the development of the
above device.
*J. S. Highfield. Journ. Inst. Elec. Eng.. London, SS. 471;
49, 848; 51. 640. In these papers the advantages of high voltage
direct current transmission are discussed very fully.
PARALLEL OPERATION OF ALTERNATING CURRENT GENERATORS
DRIVEN BY INTERNAL COMBUSTION ENGINES
IN TWO PARTS
In preparing the component parts of this article, each author (one representing the generator designer
and the other the engine designer) has presented his subject with the express purpose of assisting the other
to a better understanding of the factors that affect parallel operation of a-c. generators driven by internal
combustion engines, as determined by his end of the set; for it is only through co-operation between the
builders that generator and engine can be constructed with the correct characteristics to insure satisfactory
operation when coupled together. Excessive variation in angular velocity, or hunting, is the chief trouble
to guard against, and the greater part of the article is devoted to a discussion of the natural period, or fre-
quency, of the units, with the object of avoiding a condition of resonance. — Editor.
PART I. FACTORS AFFECTING GENERATOR DESIGN
By R. E. Doherty
Alternating Current Engineering Department, General Electric Company
The rotor of an alternator which is operat-
ing in parallel with others will tend to swing
to and fro at a definite frequency through the
position of uniform rotation, if the equilibrium
of driving and resisting forces is disturbed,
just as a weight suspended by a spring will
oscillate if the equilibrium of the force of
gravity and the tension in the spring is
disturbed. This is an inherent character-
istic of synchronous machines. Hence, when
an alternator is driven by a reciprocating
engine which develops, inherently, a period-
ically varying turning effort, or driving force,
there exists as a natural result a possibility
of unstable operation of the alternator — a
possibility that the natural frequency at
which the rotor tends to oscillate may be
equal to or very near the periodic variations
of the driving force. This condition of
resonance, like that of the spring and weight
receiving impulses in synchronism with
natural oscillations, will cause swinging,
or "hunting" of the rotor. The amplitude
of such rotor oscillations, as measured by
the maximum displacement of the rotor
from its stable position (the position of
uniform rotation) is determined by two
factors; namely, the magnitude of the varia-
tion in angular velocity (itself the result of
periodically varying driving force working
against the practically constant resisting
force of load and friction), and the proximity
to a condition of resonance. A large ampli-
tude of swing might be produced by a small
periodic variation in angular velocity, if
the natural frequency of the alternator is
very near the frequency of the variation;
and it is also possible to have a large ampli-
tude, even if the two frequencies are different,
if the periodic variation in angular velocity is
large. Yet, since both of these factors may
be fixed at predetermined values by the use
of proper flywheel effect, it is not necessary
to have either at a dangerous value.
These facts have been matters of record
for a long time, having been established in
the early days of steam engine units. But
even today a case now and then appears
where these factors were not properly inves-
tigated in the design of the unit, especially
in internal combustion engine units, and
the usual result in such an instance is excessive
hunting. In the case of internal combustion
engines, the additional and more serious
variations in the turning effort as compared
with the steam engine unit, make it very
168
GENERAL ELECTRIC REVIEW
necessary to consider carefully in each
instance the natural frequency as well as the
periodic speed variation, when the flywheel
is being designed. But of course the engine
builder, who ordinarily designs and builds the
flywheels, can not settle with accuracy the
proper value of natural frequency, unless he
has at his disposal the generator constants
on which the natural frequency depends.
In reviewing the theoretical considerations
of the problem, and in calling attention to
some serious operating conditions which
were found on an investigation of several gas
engine stations, the object of this article is
to encourage a further study of the problem in
general, and bring about co-operation between
the engine and generator builders in design-
ing new units.
In order to develop the relation by which
the natural frequency may be predicted,
and to study the limitations of permissible
variation in angular velocity which are
required by the alternator, it is necessary
first to look into the electrical effect of the
oscillatory movements of the rotor. Suppose
a generating system is delivering load: an
alternator is brought up to speed and synchro-
nized in the ordinary way; and the governor
or throttle is set so that the wattmeter reads
zero, that is, the alternator is carrying no
load. Under this condition the voltage
generated by the alternator reaches maximum
and zero at precisely the instants the line
voltage reaches its maximum and zero values.
That is, the two voltages are in phase opposi-
tion at all instants; and if the field excitation
is adjusted for a value of generated voltage
equal to the line voltage, then the ammeter,
as well as the wattmeter, will read zero. If
the field excitation is adjusted for a higher
or lower value of voltage, that is, if the alter-
nator is over or under-excited, the ammeter
will indicate the resulting wattless current
required to consume the difference in voltage ;
but the wattmeter will still read zero. If,
however, the engine is adjusted so that it
tends to run at a higher speed, the rotor will
tend to advance from the position in rotation
it maintained before adjustment. This of
course means that the center line of field
flux has advanced, and that therefore the
voltage generated by this flux reaches a
maximum at a relatively earlier instant.
Hence there has been produced a correspond-
ing difference in the phase of the line and
alternator voltages — in the time at which they
reach their respective maximum values.
This difference in phase, produced by the
advance of the rotor, allows current to flow,
which, by its distorting effect on the magnetic
field, restrains the advance; and in proportion
as the displacement from the original position
increases, the phase difference, and therefore
the current, also increases, the latter produc-
ing proportionally increased restraining force
(the force which tends to restore the rotor to
the original position). This force, working
at the peripheral velocity of the machine,
measures the power input to the alternator;
and the current produced by the displacement
is the working current, or the energy current
of the alternator. Obviously if the displace-
ment were produced in the opposite direction
by exerting a drag on the shaft, the alternator
would be operating as a synchronous motor.
Hence, to sum up, energy current is produced
by displacement alone; and this current and
the force produced by it, tending to restore
the rotor to the zero position, are both
proportional to the displacement. Also, if
the alternator is working at a given load,
the stable position of the rotor is naturally
at a given displacement from the zero position ;
but any tendency to change the rotor from this
stable position will be resisted, as in the case
of no load, by a restoring force proportional
to the displacement from the stable position.
Fig. 1
These considerations afford a working
basis, showing that the motion executed
by the rotor during an oscillation is harmonic,
because the restoring force, that is, the
accelerating force, is proportional to displace-
ment ; that the natural forces of the alternator
which characterize it as a synchronous
machine are the very forces that make it
oscillate or "hunt" when subjected to per-
PARALLEL OPERATION OF ALTERNATING CURRENT GENERATORS 169
turbing influences; and that aside from the
natural oscillations, the periodic displacement
which the prime mover imposes upon the
rotor, purely by reason of uneven turning
effort with its resulting variation in angular
velocity, will produce proportional current
and power oscillations.
The relations between voltages and also
between displacement and restoring force
are shown diagrammatically in Figs. 1 and 2.
In Fig. 1, Ei represents line voltage; E„, the
counter-generated voltage of the alternator;
0, the displacement angle; ee, the resulting
cross voltage, which, acting on the impedance
of the alternator, produces the working
current ie, almost 90 deg. lagging behind ee,
and therefore almost in phase with £;. In
Fig. 2, 6 again represents the displacement
angle from the zero position 0; and the
ordinates, /<>, represent the restoring force
at the different displacements; Fr, the force
corresponding to one electrical radian dis-
placement, that is, to the displacement
which would make ee equal to the line voltage.
(This, for convenience in proportionality,
carries the assumption that the arc and
chord of a circle are equal, slightly past
accurate limits, but the assumption as applied
involves error only to the extent of the
difference between arc and chord at the
angle of hunting, not at one radian. And
that difference is very small.)
To relate the factors operating during
natural oscillations of the rotor, assume that
any angle 0i is the limit of swing; that is, 2di
\^m\Fr
Fig. 2
is the total amplitude. The restoring force
corresponding to a displacement 0i electrical
degrees is
(1)
where Fr is the restoring force in pounds
corresponding to one electrical radian dis-
placement.
The work, W, which will be done on the
rotor by /» in the movement of the rotor
during oscillation, through the angle 0,
is represented by the shaded area, Fig. 2, and
is equal to
/.
'01
— X displacement of B\ deg.
(2)
A displacement of 0i electrical degrees rep-
resents — — feet at a radius of 1 ft., where
90 q
q = number of poles.
Fig. 3
Substituting in (2), the work becomes
"-mfc* <3)
When the rotor swings through the zero
position, this work will have been trans-
formed into kinetic energy,
y2MV*- (4)
where M= mass of rotating element,
V = maximum velocity of swing in feet per
second of the center of gyration. Reducing to
one ft. radius for convenience, M becomes
]VR2
where WR- = weight of. rotating element
g
X (radius of gyration)2 in lb. ft.2, g= gravity,
and V becomes the maximum velocity of
swing in feet per second at one ft. radius.
Substituting in (4), the kinetic energy is
WR*XV*^ ,,_ (5)
2g
ft. lb.
But since the motion is harmonic, V may be
taken as the constant velocity of a point,
p, moving in a circle whose diameter is
■*-£?**
(6)
as shown in Fig. 3. The movement of the
rotor during oscillation of 20i deg., being
harmonic, is such that the center line of the
pole, indicated by the arrow, is at all instants
under the point p.
Let T equal time in seconds required by
the point p to traverse the circumference of
17(1
GENERAL ELECTRIC REVIEW
the reference circle. This of course is also
the time required by the rotor to make one
complete swing. Then
Vr=-=rft. per sec. (7)
T= 0.001705 5
117?'-
From (6) and (7)
V-
T
7T-0!
45 q T
ft. per sec.
(8)
Fig. 4
and the kinetic energy is, from (5) and (8)
^^^f,lb. (9)
40o0 g q- T2
Equating (3) and (9)
79 WR-
p=.
(10)
Frqg
Putting g= 32.16 ft. per sec. - and substituting
•-^
where /= generator frequency in cycles per
second and
S = R.P.M.
p = 0.0205 WR*S (12)
Now, since
Fr =
Frf
33000 Pa
(13)
0.746 X 2tt 5
where
Fo= Kw. corresponding to the value of ee
at one electrical radian displacement,
and the current produced thereby when
acting across the impedance of the
machine; that is, the kilowatts corre-
sponding to normal voltage and short
circuit current of the alternat' ■-.
11 'R- S2
T* = 0.291 X 10- * „ 7 . and
\ Pof
= seconds per oscil-
lation. Hence the natural frequency in oscil-
lations per minute is
F- ^ JM (14)
V 117?-
An example will illustrate the application of
equation (14).
Fig. 4 shows the saturation curve and short
circuit characteristic for a 500 kv-a. three-
phase, 60-cycle, 200-r.p.m. 2300-volt alter-
nator. At the field excitation, SO amperes,
which gives 2300 volts on open circuit, the
corresponding short circuit current is 250
amperes. These values correspond to
„ \ 3X2300X250
Fo= 1000 =100(Jk^
The combined ITT?'2 of the flywheel and
alternator is 2S5.000 lb. ft.-. Hence the
natural frequency is
„ 35200 /1000X60 , _ ....
F~20TV 285000 = 8°° osclllatlolls
per minute.
The accuracy of equation (14) applied as
above is probably within 4 or 5 per cent as
indicated by tests made by a majority of
investigators, the calculated result usually
being lower than the actual. The writer
has had the opportunity of observing accu-
rately the natural frequency in two instances.
In these cases the calculated value was 4
per cent low in one, a 75 kv-a., 60 cycle, 276
r.p.m. generator; and exactly right in the
other, a 300-h.p., 60 cycle. 720 r.p.m. synchro-
nous motor. Whatever error occurs is due
principally to the fundamental assumption
that the distortion of the magnetic field
under load is not affected by the increase in
reluctance which the distorted field encounters
in a salient pole alternator.*
It is of interest to note, in passing, that
the natural frequency of a given unit is
independent of speed, and depends only
upon the magnetic loading of the alternator.
Because, for a given value of field exciting
current (which corresponds to a definite mag-
netic loading when the machine is operating
on open circuit), the short circuit current is
practically the same for any speed, except
zero, of course; and the voltage Ea is pro-
portional to the speed S, as is also the fre-
quency /. That is, the product, P0X/, in
•For a further studv of natural frequency the reader is referred
to 'Notes on Flywheel." H. H. Barnes. Jr., A.I.E.E. vol. 23.
p. 353; "Operation of Alternators," A. E. Everest. J.I.E.E..
vol. 50. p. 520; "Parallel Running of Alternators," F. Punga.
Elek. Zeit. June 11. 1914; "Coupling Flywheel Alternators in
Parallel." Boucherot. Int. Elec. Congress. 1905. vol. I. p. 692.
PARALLEL OPERATION OF ALTERNATING CURRENT GENERATORS 171
/40 /60 /80 200 220
f?eYO/ut/ons per- m/nute.
280 300
Fig. 5
172
GENERAL ELECTRIC REVIEW
equation (14) is proportional to S2. Hence
F must be constant, if the magnetic loading
is constant, and if this loading is changed — if
the magnetism in the machine is changed — F
changes in proportion. For instance, if the
voltage of a system of alternators in parallel
is increased, say 10 per cent, by increasing the
field excitation, the natural frequency of all
the alternators will be increased by about 10
per cent.
Load and power-factor conditions some-
what modify the value of natural frequency
as given by equation (14), which, with the
factor Po as defined, applies to no-load con-
ditions. The synchronizing-force-per-degree-
displacement has a different value under no-
load conditions, as already pointed out. Under
load and low power- factor conditions this
force has a different and greater value, and
the difference is a measure of the change in
natural frequency. That is, if under load con-
ditions the synchronizing force is increased
by, say, 10 per cent, it is equivalent to
increasing the value of P0 by the same per-
centage ; and the natural frequency is changed
by the extent to which the increased P0 modi-
fies the value of equation (14), or about 5 per
cent. Ordinarily, the change in natural fre-
quency under load conditions is not serious if
the voltage is kept reasonably constant.
Roughly, one can estimate the change by the
increase in the internal voltage, that is, in the
magnetic loading.
Returning to the question of design of
new units, it is possible to determine P„
from the design of the alternator. This
makes it possible to design the flywheel by-
equation (14) to produce any desired value
of natural frequency, and therefore to avoid
values dangerously near frequencies of the
engine variations or impulses. Experience
has shown that if the natural frequency of
the unit is at least 20 per cent different from
the frequency of any of the periodic impulses
of any of the engines in parallel, there will
be no trouble from resonant hunting. The
critical frequencies to be avoided are:
For a four-cycle engine: particularly one-
half the revolution of the crank, but also the
revolutions of the crank.
For a two-cycle engine: particularly the
revolutions of the crank, but also twice the
revolutions of the crank.
It will be noted that the lowest critical
frequency in either case is the cam shaft
revolutions.
As an illustration, the danger zones of
natural frequency for a generator to be driven
by a twin-tandem, double acting, four-cvcle,
200-r.p.m. gas engine is 80 to 120, and" 160
to 240 periods per minute. For a two-cycle
engine running at the same speed, the danger
zones would be 160 to 240, and 320 to 480.
In Part II of this article the causes and
the relative magnitude of the several engine
impulse frequencies are discussed.
IDS-
IS
|»
\%-
\^ c
95-
j
j
1
0 25
SO
75
100
es
Percent offlormol Ltxzcf
Turning now to the permissible periodic
displacement of the rotor due to variations
in angular velocity, it has been shown that,
regardless of how a displacement is produced,
it will cause a proportional flow of energy
current. If a current I0, corresponding to
the power P0, flows at a displacement of
one electrical radian, then for one degree the
current will be
Io
57.3
Since the permissible value of such a
pulsating current is properly based on the
normal rated current of the alternator, the
permissible number of degrees displacement
is related to P0. For the older type of steam
engine driven units which were put in service
before the days of voltage regulators, and
which therefore had close voltage regulation
(large value of P0 as compared with the nor-
mal rating), the limit was set at ±2.5 electri-
cal degrees. But for modern units, designed
for use with regulators, and especially the single
(maximum) rated generators for use with in-
ternal combustion engines, P0 is much smaller
— of the order of 1.4 to 2.0 times the normal
rating. For these machines, the permissible
angle has been increased to ± 3 degrees, which
would give, in the case of P0=l-5 normal
rating, a pulsating current
3X.1753/"=0.079/„
where I„ = normal current. If the generator
was operating at a power-factor lower than
PARALLEL OPERATION OF ALTERNATING CURRENT GENERATORS 173
unity (and most generators are operated
under that condition) , the pulsations would be
somewhat reduced , because there would be very
little variation in the wattless component.
Hence the flywheel must fulfill two con-
ditions: It must limit the periodic variation
in angular velocity so that the resulting
displacement will not exceed ± 3 electrical
degrees, and at the same time must give
a natural frequency 20 per cent different
from the frequency of any of the engine
variations. That is, if it works out that the
flywheel effect which is required to limit the dis-
placement to ±3 degrees gives a dangerous
natural frequency, then the flywheel must be
increased to remove the natural frequency
from the danger zone.
The curves shown in Fig. 5 give the plotted
results of equation (14). Three values of
flywheel effect are given for each speed for
60-cycle alternators, driven by either two or
four-cycle engines: the upper and lower
curves give respectively the required value
of (total WR2 ■¥ P0) for a natural frequency
20 per cent below and 20 per cent above the
lowest engine impulse frequency, which is
the cam shaft revolutions. The middle
curve gives the critical value which will
make the natural frequency equal the cam
shaft revolutions.
Yet, the factor of flywheel effect, while
of primary importance, is not all that must
be considered if satisfactory parallel operation
is to be assured. It is a well-known fact
that if the governors of the several units
operating in parallel do not have similar
characteristics (in that the curve of per cent
speed against per cent load is the same for
all units), then parallel operation will be
unsatisfactory because the division of load
among the several units will not be in pro-
portion to their capacities. In Fig. 6, curves
a and b are the load characteristics of units
A and B respectively. The governor char-
acteristics determine these curves. For
this case there is only one point (98 per cent
speed) at which the units divide load in pro-
portion to their capacities. At 96.5 per cent
speed, for instance, A would carry 100 per
cent, B 125 per cent of rated load. If the
curves a and b are made to coincide by ad-
justing the governors, then, of course, a
proper division of load will occur at all loads
and speeds. But these points are sometimes
overlooked. Trouble from this source occurs
chiefly in stations where engines of different
manufacture are installed.
The governor is sometimes the cause of
trouble of a different sort. When a momen-
tary change in speed occurs, say at a change
of load, the governor, by reason of the prin-
ciple on which it operates, tends to over-
compensate for the speed change, with the
result that oscillations will be set up unless
there is sufficient friction in the governor
mechanism, or in a suitable dashpot, to
damp them out. This also is a fact, long
established, yet now and then overlooked
on gas engines.
Nor is this all. It is essential to good
parallel operation that the adjustments of
feeding and igniting mechanisms, when once
made properly, do not change. Poor opera-
tion would naturally be expected if the
adjustments were bad to the extent of giving
an enormous difference in work of the dif-
ferent cylinders. Experience has shown in
a number of instances that although the
parallel operation was satisfactory at the
time the engine was put in proper adjustment,
yet after a few weeks of work, large swinging
of meter needles occurred because the adjust-
ments had become defective. In many
instances the operator has no means of
indicating the engines, and is therefore
helpless to make accurate readjustments.
Hence the permanence of adjustments is
a seriously important point to be considered
in the design of the engine.
If all of the above points were considered
in the design of new units, the parallel opera-
tion would probably be quite satisfactory,
without having to take any additional
precaution in the design of the generator
over what is taken in the ordinary steam-
engine driven generator. But, in view of the
remaining possibilities of the unfavorable
conditions just described, it is advisable
for the present to equip the rotor of the
generators with a low resistance amortisseur
winding, which dampens any tendency to
oscillate by consuming as loss the energy
of the oscillation. However, it should be
remembered that to get good parallel opera-
tion by such means, i.e., by overcoming by
the use of a loss producer on the generator
the effect of certain features of the engine
which have not yet been perfected in all cases,
the object is being accomplished at a constant
running expense. And therefore in the interest
of progress and efficiency, as well as of quiet
meter needles, it seems that by working
along lines which have been suggested,
the engine designer could achieve a great
deal toward carrying further the remarkable
progress which has already been made in
perfecting the gas and oil engines for driving
alternators in parallel.
174
GENERAL ELECTRIC REVIEW
PART II. FACTORS AFFECTING ENGINE DESIGN
By H. C. Lehn
Snow Steam Pump Company
In the preceding pages, the electrical func-
tions involved in the solution of this problem
are investigated, and their prime importance
as factors thereof is shown. There is also
pointed out the desirability of co-operation
between the generator and engine builder
in the design of new units, since the generator
builder only is in possession of the required
electrical data. It is to be noted further
that as data of the mechanical factors
involved are in general available only to the
engine builder, co-operation is mutually desir-
able. Generally, the amount of data required to
be interchanged is small, and its comparison
will at once determine the most desirable
flvwheel effect. In some few cases, however,
the correct solution will not be so readily
apparent, and more accurate and complete
data will be desirable, assuming that a gener-
ating set of the highest possible efficiency
is to be produced.
Turning now to a consideration of the
engine factors of the problem, it has already
been shown that electrical considerations
make necessary the limitation of the
angular displacement by a certain amount.
The magnitude of the displacement is depend-
ent upon the variation in the turning effort.
In particular, its graph is the space curve
of which the plotted turning effort is the
corresponding acceleration curve. The latter
is the resultant of various forces acting in the
engine, and in its calculation there are met
a considerable number of factors which do not
lend themselves readily to the ordinary
mathematical operations. Hence, the usual
method of determining the displacement is
by two graphical integrations of a plotted
turning effort curve. This procedure requires
considerable time, and has the further dis-
advantage of not showing the relative value
of the various factors, a change in any one
of them necessitating a complete redrawing
of the curve. In the present article an analytic
method will be used, in which these dis-
advantages are not present, and by means of
which a comparison of various types of
engines with regard to displacement and
natural period will be possible.
The analytic solution may be arrived at
as follows: The varying turning effort acting
on the crank is a periodic function of the time
and hence, by the Fourier theorem, may be
expressed in a series of multiple sines and
cosines. If then there is obtained an equation
for the acceleration of the rotating parts due
to the varying turning effort, in a series of
sines and cosines, the second integral, which
will be the curve of displacement, can be
at once written.
The turning effort equation in this form
will then be:
t|^= S (Ai sin qt + A. sin 2qt +
at iVc
B\ cosqt-\-etc.)
from which
e , A»
5/= ., ( — A\ sin qt — — sin 2qt.—
wcq- 4
B cosqt — etc.) (1)
in which,
5/ = displacement in feet on the crank pin
circle.
wc = equivalent weight of the rotating parts
at the crank pin circle.
2ir
q= where T is the time in seconds of
the longest forced period (which in the
present case will be one revolution of
the engine), so that,
tN
: 30 '
where AT equals rev. per min. of
the engine.
g = gravity = 32.2.
t = time in seconds.
The variation in speed is very small and
may be considered constant; hence 0, the
crank angle, may be put for qt, and since
only the maximum displacement is required,
it will be convenient to write Z for the
maximum value of the series of sines and
cosines, with their coefficients.
(1) then becomes
if-
900 AZ
WC 7T2 g W
PARALLEL OPERATION OF ALTERNATING CURRENT GENERATORS 175
where .4= cylinder area in square inches, Z
being taken on the basis of one square inch.
Reducing to mechanical degrees :
, /360\/ 900 AZ\
where r = length of crank in feet, and finally
to electrical degrees for 60-cycle current, and
reducing
A7
5 = 6.03 X 10s T;.-^
H rN3
or in terms of WR-, the flywheel effect,
5 = 6.03 X 108 ,„L l,„ and
WR? N3'
WR* = 6.03 X 10s
ArZ
SN3
(2)
(3)
(2) and (3) are in terms of the engine
dimensions and speed except the factor Z,
which is determined by the values of the
coefficients of the terms. These values will be
initially dependent upon the height and slope
of the indicator card, and upon the inertia
force of the reciprocating parts, and will be
further modified to a considerable extent
by the number of cylinders and arrangement
of cranks. If then there is obtained a relation
between the contour of the indicator card
and the values of the coefficients, by properly
combining for each cylinder and for the inertia
the equation for any type of engine can be
written. The most convenient form in which
to establish this relation will be to express
the coefficients in terms of the indicated
mean pressures, since the latter is the
basis of the engine output. With a given
mean pressure, the slope of the expansion
line will vary with the clearance volume,
and with the time of ignition and regularity
of combustion. The slope of the compression
line will depend almost entirely upon the
clearance volume. The latter ranges from
about 22 per cent of the piston displacement
for natural gas to about 11 per cent for blast
furnace gas; and with fairly even combustion
the exponent of the curve may be taken as 1.3.
Where there is after-burning, the exponent
will be lower at the beginning of the stroke,
increasing more or less regularly with the
piston travel; and in such cases it will be
found that the expansion curve agrees closely
with a curve having a constant exponent of
1.3 but greater clearance volume, which in
only a very slow burning card will be greater
than 25 per cent. Natural gas cards with
large clearance volume seldom show after
burning to a great extent, so that a range of
clearance volume of from 10 to 25 per cent
should include all fairly normal cards from
any gas. Such minor irregularities as the
flattening of the card at the beginning of the
stroke and the drop of pressure near the end
do not affect the turning effort appreciably,
and need not be considered.
To include oil engines, it would be necessary
to extend the lower limit of the range for
clearance volume percentage to about 6.
Besides, the indicator cards are normally flat
to an appreciable extent at the beginning
of the stroke. For these reasons it is best
to deal with oil engines separately.
In order to facilitate the forming of the
equations for any combination of cylinders
and cranks, it is best to derive the values of
the coefficients separately for each event of
the engine cycle. In the derivation of the
formula, the fundamental period was taken
as one revolution of the crank and this
corresponds to the impulse period of a single
cylinder, single-acting, two-cycle engine, and
a twin-cylinder, single-acting, four-cycle
engine, which are the simplest types used
Clearance
Volume
EXPANSION
OVERSTROKE
Pa TIMES
EXPANSION
UNDERSTROKE
Po TIMES
Per Cent
25
10
25
10
Sin 8
Sin 2 8
Sin 3 8
Sin 4 8
Cos 8
Cos 2 8
Cos 3 8
Cos 4 8
-0.450
-0.086
-0.014
-0.004
-0.242
+0.023
+ 0.105
+ 0.006
-0.405
-0.080
-0.023
-0.008
-0.318
-0.018
+0.007
+0.008
+0.474
-0.048
+0.008
-0.002
+0.169
+ 0.037
-0.009
+ 0.005
+ 0.437
-0.074
+0.017
-0.003
+ 0.25S
+ 0.015
-0.009
+ 0.006
Pt = absolute mean pressure.
S = crank angle measured from inner dead center.
for parallel operation. In any single acting
engine only two events are possible; namely,
expansion on the overstroke and compression
on the understroke. In a double-acting engine
occur the additional events of expansion
understroke and compression overstroke. It
develops, however, that the values of the
coefficients for compression understroke are
the same as those for expansion overstroke,
but the cosine terms take the opposite sign,
and exactly the same relation holds between
compression overstroke and expansion under-
stroke. Thus the matter is simplified to
176
GENERAL ELECTRIC REVIEW
deriving the coefficients for two events only,
and for each event for the maximum and
minimum percentage of clearance volume.
The values of the coefficients to the first
four terms for the displacement curve are
given on the preceding page. It will be
observed that the relative value decreases
rapidly with the number of the term, and it
was found that terms beyond the fourth are
negligible.
While it is unnecessary to review in detail
the principles upon which the construction
of the turning effort diagram is based (which
may be found in any text book on mechanics) ,
it may be well to note, that instead of the
usual form of P for the resultant
cos <(>
turning effort of a force P at the wrist pin,
there has been used its equivalent (within
sin 2 6)
negligible error) of P (sin 6-\ ^-. — , where
the constant I, the connecting rod length
divided by the crank length, replaces the
variable <f>, the connecting rod angle. The
table above is for 1 = 5, the usual value and
the coefficients will change but slightly for
other values of /. It is also to be noted that
the table is based on the absolute mean
pressures, so that for single acting engines,
in which one end of the piston is subjected
to the atmospheric pressure of 14.7 lb. per
sq. in. (at sea level) there must be subtracted
from the equation 14.7 sin 0 + 1.47 sin 2 6.
The equation of the inertia turning effort
is easily formed. The expression for the
accelerating force at the wrist pin due to the
inertia of the reciprocating parts is given in
all text books, and is:
K0= -0.000341 GrW (cos 6 + c^sAel (4)
where
K0 = inertia force at the wrist pin per sq.
in. of piston area.
G = weight of the reciprocating parts per
sq. in. of piston area.
r = crank length in feet.
AT = r.p.m.
Multiplying (4) by sin 0+~-7~- gives the
inertia turning effort at the crank pin per
square inch of piston area. The resulting
expression easily reduces to
Kc = 0.000341 GrN2X
sin 6 sin 2 6 3 sin
1 2~
(+T
4/
4Z2
)
for which the corresponding displacement
equation is
A' = 0.000341 GrN2X
("
sind sin2 8 sin 3 6 sin 4 0
TT"1 8 +'l2l 64 I2
)
By forming from these values of the
coefficients the equation of the displacement
curve for the maximum and minimum condi-
tions, it is possible to determine the variatioh
of the displacement as the mean pressures
and contour of the indicator card change, and
the effect on it of a change in the inertia.
There can also be noted the effect of a differ-
ence in mean effective pressure in the separate
cylinders of a multi-cylinder engine — a condi-
tion which ordinarily exists, to a small extent
at least. In determining the maximum dis-
placement from the equations, the approxi-
mate crank angle at which it occurs will,
except in a few cases, be evident from the
predominating term, and it is then necessary
to plot a small portion of the curve only in
the locality of that angle.
Values of Z, the maximum ordinate of the
displacement curve for various types of
engines, are given in Table I. These values
include a fair, but not excessive, allowance
for slight differences in the mean pressures
of multi-cylinder engines, as well as for other
factors which do not appear in the indicator
diagram, such as scavenging pumps on
two-cycle engines, air compressors on oil
engines, and the varying friction of the
engine. For this reason the displacement
figured therefrom will be somewhat greater
than would be shown by a plotted curve
where these factors are not taken into
account. It is found that the difference in
displacement for the maximum and minimum
values of cylinder clearance volume is small;
and for the further reason that indicator
cards from an engine in operation will show
some variation in contour as well as mean
pressure, it has been considered unnecessary
to include a clearance volume factor in the
equations. Again, in all types of engines in
which the predominating torque has a
period of one revolution, the effect of the
inertia is very small, since the principal torque
of the latter has a period of one stroke. For
the same reason, in such combinations of
cylinders as result in a predominating torque
PARALLEL OPERATION OF ALTERNATING CURRENT GENERATORS 177
having a period of one stroke, the displace-
ment is determined largely by the inertia
forces, and in such cases it is necessary to
include an inertia factor in the equations.
The maximum initial displacement has
been fixed by electrical considerations at
three electrical degrees either side of mean.
Accordingly, this value has been substituted
for 5 in (3), and the resulting constant
combined with Z is given as C in the table.
Then WR2 for three electrical degrees
(4)
from which
6 =
N3
3 C Ar
(5)
WR2 N3
Both for 60-cycle current.
It will be of interest to establish a relation
between the formula for displacement given
above and that for natural frequency,
developed in the preceding article, and thus
correlate the two requirements. For this
purpose the equation for natural frequency
(14) in the preceding text will be put in the
following form:
273J000_ jE^Kl
N \ WR2
F='
in which kv-a. = rating of generator.
k = short circuit ratio,
and the constant is for 60-cycle current. This
formula may be put in terms of the rated
indicated mean effective pressure P and of
the engine dimensions as follows :
I.H.P. E £l
Kv-a. = — — —
1.34 p
where
I.H.P. = indicated rated horse power.
E = mechanical efficiency of engine.
El = generator efficiency.
p — power-factor,
and
2PAreN
33,000 '
where e is the number of impulses per revo-
lution.
Combining these two equations, substitut-
ing the value of kv-a. thus found, and also
substituting for WR2 equation (3) and
dividing by N gives :
Q = 0.075
P e EEl k
X~YT
where
Q =
natural frequency
engine rev. per min.
TABLE I
FORMULAE FOR DISPLACEMENT
No.
z
C
Type of Engine Betwe«
Deg.
Torque
Period
Gas Engines Oil Engines
Gas Engines Oil Engines
Single-cylinder ■ o«g
Two-cycle
e
P \.\P
2X108P 2.2X108P
C
Twin-cylinder ngQ
Four-cycle
e
1.1P 1.2P
2.2X108P 2.4X88P
<
0>
Three-cylinder 9.q
Four-cycle
1.59
0.7P O.SP
1.4X10»P 1.6X108P
M
c
CO
Four-cylinder ls(,
hour-cycle
29
0.5\K-0.23P |0.51A'-0.23P
1.02X108 1.02 X108
(A--0.45P) (K+0A5P)
Twin-cylinder lgQ
1 wo-cycle
2d
0.23A'-0.15P
(a) 0.24K -
0.27P
(b) 0.14P
4.6X10' 4-8(%Zl2P)
(K-0.65P) 2.8XWP
ible
ing
Single tandem jgg
Four-cycle
e
(c) 0.14A--
l.WP
2.8 X107
(K-10y/P)
3 X 10s \/P
o o
Twin tandem gQ
Four-cycle
0
0.056 K+0.09P
1. 12X10'
(A- + 1.6P)
p
K
(A)
(a)
(b)
= Rated indicated mean effective pressure. . ..™„v-nnnmii r r \'»
■ Centrifugal force of reciprocating weights per sq. in. of piston for one crank -0.000341 C r .V.
With equal pressures in all cylinders.
For AT. not less than 160 (<:) For K, not less than 1 <o.
For K. 160 or less (d) For K. 175 or less.
17s
GENERAL ELECTRIC REVIEW
Values of £, £' and p ordinarily met with in
practice which would make F a maximum are :
£ = 0.85; £'=0.92; p = 0.70 which for
5 = 3 electrical degrees gives
0 = 0.139
N
Pen
(6)
and likewise values for a minimum
■ ■
=£cs Engines
=^W Eng/nes
Sectioned 'areas /ncf/coCe
Danger Zor>es
s
^ ' '( i I J J l{ 1 y\
Lp !
i
1
!
\
i iy>
:--
; 1 j n r;: r
r" :' ' j
7
k
Y
! ( I
1
5 1 J
;
i ..:..
2*-
■
/
/
V
/
■«$
t
/
/
/
[
,'
/,
I '-
J
; | ;
i 1 I
v?
i
/
&
i
\ t $'
! I !
:
A
s
^
: t ;
■■; | r
i
1/
• \
--
I-
*■
i
;
*
;
!
•i
^
S
h
*
-*
^
>'
^
y
s
'
'. ,
^
S*
P*
^f
L.
r,
^
;-
^
i^r
-"-
^
/4 -J<?
f/t
J
/
3
•ao
-tC.TCis t RottO' *4£o3.0 for eacfi type
the natural frequency approaches and passes
the danger zones, necessitating the considera-
tion of both frequency and displacement,
and in the extreme cases, frequency only, in
calculating the flywheel weight.
In applying the formulas for displacement
due regard should be given to the increase
in the initial displacement as dependent upon
the ratio of the forced and natural fre-
quencies, which increase is equal approx-
imately to ,_^ ., damping neglected,
*bS -¥o3 X04- ' Yo6
Fig. 7
£ = 0.70; £' = 0.S8; p = 0.90. giving
(5)'
<2=o.io
75 y
Pe
(7)
From equations (6) and (7) it will be observed
that, for any given displacement, the ratios
of the frequencies are independent of the
engine dimensions and speed. Equations (6)
and (7) are plotted in Fig. 7 for the various
types of engines, and for maximum values of
P .
-= in equation (6) and minimum values in (7) ;
the figures referring to the corresponding
types in Table I. It will be noted that in
the simpler forms of engines the natural
frequency is far removed from the danger
zones, and that in such cases only the dis-
placement need be considered, while as the
number of impulses per revolution increases,
in which F is the natural and / the
forced frequency.
All of the foregoing indicates to
what extent the solution of the problem
is a matter of design, while the condi-
tions occurring in operation which affect
paralleling are described in the previous
article. The necessity of proper bal-
ancing of cylinders, and of designing
adjusting mechanism so that the adjust-
ments may be maintained, is referred
to; and in connection with this it is
interesting to note that in the case
of double-acting engines, it has been
possible in actual cases to reduce the
displacement by operating with a higher
mean effective pressure in the under-
stroke ends. The reason for this fact is
apparent when the signs of the overstroke,
understroke, and inertia torques of one rev-
olution period are compared.
Again, with regard to governors, it is almost
entirely a case of adjustment in the field.
Governor action is hardly susceptible to
calculation, but analysis seems to show
the presence of a natural period, which may
in some cases approach the forced period of
the engine and thus cause hunting, even when
the other characteristics of the governor are
correct. The actual governor period, however,
is altered by friction, so that accurate pre-
determination is impossible.
The general tendency, when not in conflict
with the other requirements, should of course
be toward a light flywheel ; for then not only are
the natural vibrations more quickly damped
out, but by reason of less bearing friction the
overall efficiency of the unit is improved.
179
TESTS OF LARGE STEAM HOISTS
By H. E. Spring
Power and Mining Engineering Department, General Electric Company
In order to present a convincing argument for the substitution of electric motors for existing steam
engine equipment on mine hoists it is necessary to be able to show the mine owner some figures on cost of
operation, as the question of economy is uppermost in any undertaking that is conducted for profit making.
Complete and accurate tests on motor operated hoists may be obtained with relatively little difficulty, but a
test of the average steam hoist, to be of value, involves a great amount of work and oftentimes proves to be
a serious problem. In this article the author recommends a procedure for conducting tests on steam operated
hoists that will give accurate figures on performance and cost of operation over any desired period of time.
— Editor.
There is unquestionably great need of a
series of carefully conducted tests on the
various types of large steam hoists operating
under the different conditions found in
practice. Conditions obtaining at mines
are usually unsatisfactory for the economical
generation and transmission of steam; the
boiler plants- are usually small and scat-
tered, and if centralized, steam lines of 1000
to 4000 feet in length are not uncommon.
Some properly conducted steam hoist tests
would most certainly furnish still further
convincing evidence of the economy and
other advantages of electrically operated
hoists.
A few tests, results of which have been
published and which really approach actual
operating conditions, are mostly of foreign
origin. Tests of too short duration and
occurring under as near ideal conditions as
possible are of little value except possibly
for attractive advertising. Tests true to
conditions are difficult to carry out in a re-
liable manner and require prolonged, patient,
and conscientious effort on the part of all
concerned. Besides the expense involved,
the special arrangement necessitated for ac-
curate results would in many cases hinder the
work at a busy mine, and this is no doubt
the reason for the lack of information on the
subject.
The service required of a steam hoist is
of a distinctive character, and includes among
other things, variation of speed and horse
power output from zero to a maximum and
back to zero again every time a hoist trip is
made, heavy starting requirements, , and no
defined length of cycle or interval between
cycles; these being factors that are not en-
countered in the tests of steam engines as
applied to ordinary industrial installations.
Installations rarely if ever occur where
only the hoist engine is fed from the boiler
plant and often the steam line is in common
with that of other apparatus. It is particu-
larly essential in testing that arrangements
be made to secure a self-contained unit
and at the same time to retain actual operat-
ing conditions as nearly as possible. The
conditions under which the rearrangement
and changes of apparatus around the plant
must be accomplished are usually not of the
best. Preparation is more or less handicapped
because the greater part of the work has to
be done at night or on Sunday ; and in addition
to this it is necessary in most cases to keep up
steam and have the hoist in readiness at all
times for miscellaneous hoisting or removal
of the men from the mine in an emergency.
If a separate man and supply hoist are utilized
in addition to the main hoist, the situation is
relieved somewhat and more freedom is
allowable for rearrangement; but in any case
due precaution must be exercised at all times
to avoid any possibility of a serious tie-up
in the operation of the mine, or the jeopardi-
zation of human life.
Because of the pulsating flow of the steam
taken by the hoist, the measurement of the
steam consumption by the use of a flow meter
gives unreliable results. » Even though a flow
meter were at all applicable it would only be
effective in measuring the steam for running
purposes, and would not be sufficiently
sensitive to include standby losses. On
account of the clearance space in the cylinders,
the varying conditions of load, and the vary-
ing quality of steam, the determination of
steam consumption from indicator cards is
only a makeshift method at best.
The extent to which a steam hoist test may
be carried is almost unlimited and is deter-
mined by the anticipated scope and useful-
ness of the results. The cost of operation is
usually the main information wanted and this
may be obtained by taking a short cut, there-
by sacrificing data which really are not
necessary in determining the total cost of
operation, but which would prove of value
and interest, and might point out possible
L80
GENERAL ELECTRIC REVIEW
means of improving the existing steam opera-
tion. Operating conditions at any one mine
are usually indicative of general practice
in that particular locality, and an insight into
methods employed may prove widely useful,
especially so if electrification is contemplated.
If it is the intention to determine, in addition
to the cost of operation, the fuel and steam
consumption during different periods of the
day (segregating the idle period as far as
practical from the active period), the power
delivered by the engine, the quality of the
steam, and various other results, very com-
plete tests and data are necessary.
No hard and fast rules can be made for
conducting steam hoist tests because of the
variance in mine plant practice, different
types of engines, different kinds of mines,
and the ultimate results desired. Each case
demands its own particular solution, and for
that reason any attempt to set down rules
covering all tests is impossible. The best
that can be done is to outline in a very general
way how the ordinary difficulties can be met
and the tests carried out. It is hoped that
the following suggestions, explanations, and
reasons why some things are done will prove
of benefit in conducting a steam hoist test
where complete information is the object,
and will serve as a guide for any steam hoist
test whatever the scope of the ultimate
results.
Preparation
Proper preparation and forethought will,
as in any tests, prevent a great deal of con-
fusion and misunderstanding during the
tests, and will insure complete data and
results. The time selected for the test and
the rearrangements of the plant should be
such as to permit a continuous .test of at
least a week's duration at a time when the
mine is operating under normal conditions.
The most important and usually the most
difficult procedure is that of cutting off the
necessary boiler capacity for operating the
hoist. The first problem is that of estimating
the boiler requirements of the hoist, either
by estimating for the hoist itself, or for the
other apparatus and leaving the remainder
for the hoist. Every effort to accurately
determine and isolate the necessary hoist
boiler capacity will be well repaid, as the
temporary changes effected must not ma-
terially change the ordinary everyday opera-
tion. In the majority of cases all the boilers
of the same boiler plant feed into the same
steam header, and it is possible to blank
flange sections of this header, thereby seg-
regating the boilers. The difficulties depend
on the manner in which the steam lines are
connected into the header.
A separate boiler feed pump is necessary
for the isolated boilers. Any auxiliary ap-
paratus, such as boiler feed pumps and
blowers which are necessary for the operation
of the boilers or hoist, should be fed, if
possible, from the same system, so that the
arrangement constitutes a complete self-
contained steam generating unit and hoist
equipment.
Exhaust steam for feed water heaters is
seldom if ever drawn from the hoist engine
itself. Other apparatus being the source
of exhaust steam for feed water heaters, the
true economy of the hoist engine will not be
obtained unless the heaters are eliminated
from the hoist system. Of course there may
be exceptions to this statement in case the
exhaust steam can not be utilized for any
other purpose, and it is a very important
factor in increasing the hoist engine economy.
Feed water drawn from the condenser hot
well of condensing hoist engines must ordi-
narily receive further heating from heaters,
and such feed water heaters should receive
the same consideration as with simple or
compound non-condensing engines.
The total steam consumed must neces-
sarily include all steam chargeable to the rear-
ranged hoist system, and the only reliable
way to get accurate results is by measure-
ment of the feed water. Water meters, as
a rule, cannot be relied upon for accurate
work and should only be used as a check on
other measurements. Means of weighing
the feed water can easily be provided for by
the use of two receptacles (tanks or barrels)
arranged one above the other, the water being
admitted to the upper receptacle, weighed, and
then allowed to flow into the lower receptacle,
to which the feed pump is connected.
Arrangements for weighing the coal for
hand firing are easily carried out. One
means of doing it is by the use of an ordinary
pair of scales and wheel-barrow. Where
mechanical stokers are employed, the boilers,
as a rule, can be hand fired if necessary, and
the same method pursued as outlined above;
but more nearty normal operating conditions
will be maintained if arrangements are made
to weigh the coal in such a manner that it
can be fed by the mechanical stokers. Pre-
caution must be taken in any case to prevent
use of coal which by accident or otherwise
has not been weighed.
TESTS OF LARGE STEAM HOISTS
lsi
The necessary arrangements at the hoist
engine proper ordinarily make up a small
part of the total difficulties of preparation.
The cylinders of practically all modern
engines have one-half-inch tapped holes for
making the indicator pipe connections. If
the holes are not bored, the cylinder heads
should be removed, if possible, so that the
exact position of the piston and the size of
ports and passages may be known; thus
insuring that the holes will be bored in the
correct place and facilitating the removal
of all chips and particles of grit. This
method involves a great deal of time and
labor, and probably for that reason would
not be permissible with a hoist engine. It
is possible to drill the holes without removing
the heads by admitting a little steam just be-
fore the drill penetrates the shell, thus blow-
ing the chips and grit outward. Care must
be taken, of course, to protect the workman
operating the drill. Indicator cards are im-
portant, but the physical impossibility of
obtaining them should not interfere with the
carrying out of the remaining tests. No
putty or red lead should be used in making
any of the pipe joints, as particles of these
materials are liable to cause trouble with the
indicators. Steam-tight joints can be made,
if a connection fits loosely, by winding a
little cotton waste into the threads. If an
indicator for each end of each cylinder is avail-
able the piping will need to contain a two-way
cock for each indicator. Where only one
indicator is obtainable for each cylinder, a
three-way cock for each indicator will pro-
vide the means of transferring from one end
of the cylinder to the other.
Up-to-date indicators have a self-contained
or a separate attachment for reducing the
motion of that part of the engine from which
the indicator is primarily driven. The cross-
head is usually chosen as the most reliable
and convenient part of the engine for this
connection. It is hardly worth while explain-
ing in detail the various accessory appliances
which have to be made up in the field for
taking indicator cards, as a little judgment
and ingenuity will easily . determine the best
methods for meeting the conditions at hand.
Single indicator cards are valueless as far
as the total power developed by the hoist
engine during a complete hoist trip is con-
cerned, and therefore continuous indicators
must be utilized. A detailed description of
the parts and the operation of continuous
indicators is unnecessary, as such information
is always accessible in engineering handbooks
or can be obtained by application to the
manufacturers.
The usefulness of continuous indicator
cards depends on the record of the engine
speed in r.p.m. kept at regular intervals
during the time the cards are taken. The
CONTINUOUS INDiCPTORS
^
HOIST
DRUM
CONTACT /"JflK£»<
1
1
_y .... STROKE COUNTER
Q^sCONTINUOUS INOICRTOnS
Tine CLOCK
M
pTT)
SPRING MQTQR
_L
Fig. 1. A Convenient Arrangement of Apparatus for Taking
Continuous Indicator Engine Diagrams
arrangement shown in Fig. 1 will prove
convenient and reliable for recording the
speed graphically. The spring motor feeds
the paper along at a uniform rate; A and B
are pens actuated by magnets; A is con-
trolled by the time clock and divisions repre-
senting time in seconds are recorded on the
paper; B is operated by the contact-maker
and every stroke of the engine is indicated
on the paper.
The contact maker is shown operated by
the tail rod of the engine, but it can be placed
at any other convenient place; the more
contacts made per revolution the better,
especially with a low speed engine. From
the complete record on the paper, speed-
time curves can be plotted. The signal bell
can be displaced by some other means
of signalling, if advisable, as the amount of
signalling will not be great. The stroke
counter is of use in recording the total number
of engine strokes and serves as a check on the
graphic instrument; it is also useful in estab-
lishing and checking the number of hoist
trips for various periods, particularly when
the hoisting is all done from one level.
Steam pressure records, temperature read-
ings, and determination of quality of steam in
the hoist house will require various tappings
182
GENERAL ELECTRIC REVIEW
into the steam line for gauge connections,
thermometer wells, etc.. and such apparatus
should be located as near as possible to
the hoist engine. The same general prepar-
ation applies for obtaining boiler plant
pressure and temperature readings of the
feed water and steam. Readings of tem-
peratures, pressures and quality of steam are
not of extreme importance as far as the hoist
test results are concerned, but will prove
interesting information and could possibly
be used in getting at approximate operating
characteristics of the boiler plant alone. A
little judgment of the conditions will decide
whether the information is worth the time
and labor required.
The application, limitations, and operation
of calorimeters for determining the quality
of steam are carefully explained in the various
engineering handbooks and in manufacturers'
catalogues or pamphlets, and therefore will
not be dealt with here. It is assumed that a
throttling calorimeter can be used; but if
the percentage of moisture is very irregular
and is in excess of three per cent, a separator
must be used in connection with the throttling
calorimeter, or else a separating calorimeter
substituted for the throttling calorimeter and
separator.
It is essential that the records be complete,
that the readings be consistent, and that
they bear definite relation to each other.
One great asset in promoting this is by prop-
erly prearranged log sheets. The required
number can easily be prepared before the
tests, by means of carbon copies or by
mimeograph. Plenty of blank space should
be left for possible changes, additional data
and remarks. A sufficient number should
be provided so that each day's tests can be
put together and kept separate from the
succeeding day's tests, as this will be advan-
tageous in working up the tests.
The following headings for log sheets will
serve as a guide, and can be modified to fit
the conditions encountered:
BOILER PLANT
Coal, Steam Pressure and Temperature
1. Time.
2. Coal consumed.
Number barrow loads.
(b) Weight in pounds.
a pressure.
4. Steam temperature.
Remarks.
Feed Water
1. Time.
umber receptacles measured.
3. Weight water in pounds.
4. Feed water temperature.
5. Remarks.
HOIST DUTY
1.
Time.
2.
Productive.
(a)
Number trips and origin.
(i)
Weights.
3.
Non-productive.
(a)
Men (No. trips, weights and origin).
Lowered.
Hoisted.
(b)
Material (No. trips, weights and
origin.)
Lowered.
Hoisted.
(c)
Waste (No. trips, weights and origin).
4.
Remarks.
HOIST ENGINE
1.
Time.
2.
Steam
(a)
Pressure.
(b)
Temperature.
3. Indicator cards.
(a) Number of card.
(6) Weight hoisted and classification.
(c) Stroke counter readings.
4. Remarks.
MISCELLANEOUS HOISTING
OBSERVATIONS
1.
Time.
(a) Beginning of trip.
(6) Time for acceleration.
(c) Time for retarding.
(d) End of trip.
(e) Rest period.
2.
Maximum engine r.p.m.
3.
Total revolutions of engine.
4.
Load and classification.
5.
Remarks.
♦QUALITY OF STEAM TESTS BY
THROTTLING CALORIMETER
1. Time.
2. Gauge pressure in steam line (p).
3. Gauge pressure in calorimeter (/>,)■
4. Atmospheric pressure (/>„).
5. Temperature in calorimeter (/,-).
6. Absolute pressure in steam line (P).
7. Absolute pressure in calorimeter (P.-).
S. Total heat corresponding to P, (X).
9. Heat of vaporization corresponding to P (r).
10. Heat of liquid corresponding to P (Xq).
11. Temperature of saturated steam correspond-
ing to P .
The above headings can be rearranged or
combined to give the most convenient ar-
rangement in taking the data.
* Priming = 1 —
•v--»s < -t„)-a
TESTS OF LARGE STEAM HOISTS
1S3
By productive hoisting is meant the hoist-
ing of coal, ore, or whatever material the
mine derives its revenue from. Non-pro-
ductive hoisting includes all remaining hoist-
ing, such as men, material, supplies and waste.
Origin refers to the point from which the
hoist load comes, and applies mainly to a
multi-level shaft or slope mine. If two
recording pressure gauges are available,
readings from indicating gauges can be
eliminated except for calorimeter tests.
Graphic records of pressure at the boilers
and hoist engine give a much better picture
of all-day operation.
Procedure
All testing apparatus, steam and water
lines, and other rearrangements should be
thoroughly inspected in order to make sure
that everything is in shape for accurate
results. Apparatus for weighing or measuring,
such as scales, tanks, gauges, etc., must have
their accuracy established before beginning
operations, as well as occasionally during
the tests.
Preliminary sample indicator cards should
be taken, as they will show the operating
characteristics of the engine and may be the
source of permanent improvement of the
engine economy through resetting the valves.
Such discrepancy in valve setting is rather
remote, but if it exists and it is deemed
advisable by the owner to remedy it, much
time and energy will be saved by its detection
before starting a series of tests.
The time of beginning the test is not very
important, since the total time should con-
sume at least a week, thereby taking account
of day-to-day conditions. In any case the
test should include Sunday, as a better con-
ception of standby losses is then obtained
than at any other time.
In order to associate one reading with
another, readings for the different sections
of the rearranged plant must all be taken at
the same time, and the simplest method is to
read on the hour and half-hour. Consistent
and associated readings provide means of
segregating the various periods from each
other, make ' the tests complete for this
period, and thus permit of definite results
being obtained for any particular period
desired.
The depth of the fire in the boilers can be
estimated at the beginning and the same
depth approximated as near as possible at
the end. An assistant will have to be in
constant attendance to oversee and register
the amount of coal consumed. If wheel-
barrows and a pair of scales are used, an
average wheelbarrow load can be weighed
and the scales locked at this weight; succeed-
ing loads are then added to or reduced to
meet this predetermined weight. Approxi-
mately the same amount of weighed coal
should be maintained before the boilers; the
quantity depends on conditions, but should
be definitely known at the beginning and end
of the test. In order to avoid error, every
time a load is weighed a notation should be
made; the total weight per half hour being
computed from these notations.
The height of the water in the boilers as
shown by gauge should also be noted and
this water level maintained throughout the
tests, so that the weights of feed water will
line up consistently with the other data for
any period.
The duties of weighing and recording the
amount of feed water require the attention
of two assistants, one for weighing the water,
and the other for feeding the water properly
to the boiler. The receptacle, whatever it
may be, to which the feed water pump is
connected should be kept filled to approxi-
mately the same level all the time. The
receptacle in which the feed water is weighed
must not be of too great a capacity com-
paratively, as the weights may appear in-
consistent when segregating a short period
of operation.
Continuous indicator cards represent the
total work done by the engine, and cards
should be taken for each distinctive condition
of load and speed under which the hoist
engine operates. Diagrams for special con-
ditions, such as for determining the frictional
losses of the hoist, head sheaves, and shaft
itself, will also prove instructive and valuable,
and opportunity for obtaining such cards
should not be neglected. It is necessary
that diagrams be taken on both ends of each
cylinder, as a satisfactory card from one end
does not prove in any way that like con-
ditions prevail at the other end. A contin-
uous indicator for each end of each cylinder,
when operated simultaneously, gives the
whole story.
Referring to Fig. 1, the method of taking
cards simultaneously is as follows: The
spring motor is started and the man in charge
signals his assistants to get ready for the
next hoist cycle; he then starts the time clock,
and also makes sure that the circuit for B
is all o.k. 'All indicators can be put into
working order with the exception of the con-
184
GENERAL ELECTRIC REVIEW
tinuous feed before the above signal is given.
At the signal which occurs before the hoist
starts, the continuous feeds are turned on.
Succeeding cycles may now be taken without
further adjustment, unless the time between
cycles makes it undesirable to let the clock
and spring motor run continuously. Record
the reading in log sheet of the stroke counter
at the beginning and end of each cycle, as
this serves as a check on the record made by
B. Also note time at which cards are taken,
the weight of productive, or non-productive
material hoisted or remarks concerning con-
ditions, and the number of each card. A
simple system of numbering on the time
records and indicator diagrams themselves
will establish their relation to each other.
Notation must also be made on the indicator
diagrams to show whether they were taken
on head end or crank end, and whether left
or right cylinder. One assistant can manip-
ulate both indicators on one cylinder, as the
difficulties of starting and stopping the
indicators simultaneously, such as experienced
with constant speed engines, are eliminated;
no record being made on the cards until the
engine starts, and the record ceasing when
the engine stops.
In case only one indicator per cylinder is
available, trial continuous cards must be
taken simultaneously on both ends of the
cylinder. From these cards a definite ratio
of power delivered by head and crank ends
of the same cylinder is established, and in
order to accomplish this result two indicators
will have to be temporarily attached to one
cylinder. This ratio can be determined
approximately also by taking a continuous
card on one end of the cylinder during one
cycle, and then with the same indicator
taking a continuous card on the other end of
the cylinder, during a cycle when the condi-
tions are practically the same as those at
the time the first continuous card was taken.
A sufficient number of cards should be
taken each day to be certain that day-to-day
conditions are covered, as well as to make
sure that the operating characteristics of the
engine are maintained constant.
Unless extremely difficult conditions pre-
vail, one assistant can take the readings
classified under "Hoist Duty." The magni-
tude of the daily record of output kept
at the mines by the mining companies varies
greatly. The quantity of data and the
difficulties of getting authentic data depends
entirely on whether the mine is opened by a
shaft or by a slope; whether hoisting is all
done from one level or from several levels;
and if a slope, whether a skip or several cars
are used for transporting the product. If a
shaft, the number of levels will not be great;
they will be definitely located, because of
their distance apart, and a complete record
will be comparatively easy to obtain. If a
slope, it will be exceptional if hoisting is all
done from one loading station; usually nu-
merous levels or headings situated at rather
irregular intervals branch off on either side
of the main slope, each in itself constituting
a loading station; consequently a full under-
standing of where each trip comes from
requires a rather elaborate record. The total
number of the productive trips per day, and
the total weights of product with its segrega-
tion into quantity per level, if more than one
level, will ordinarily be obtainable from the
tipple record. The total productive trips
for each period can also be taken from the
tipple record, if it is consulted every half hour,
and by a little pressure brought to bear on the
right place it may be possible to obtain the
origin of the product as well; otherwise the
origin must be obtained by observation, as will
also the information concerning non-produc-
tive hoisting. The non-productive weights will
have to be estimated. The total daily mine
record will serve as a check on the total daily
readings obtained by observation.
The taking of indicator cards, sampling
coal, and steam calorimeter tests can be filled
in between the regular half -hour readings,
thus making it possible to obtain some help
from the assistants taking the half-hour
readings. At night, or during any other
period outside of the regular hoisting period,
it will be possible to double up on the keep-
ing of records and arrangements made
whereby the force can be materially reduced,
probably only two men being required.
"Miscellaneous Hoisting Observations "
give a very good idea of how the hoist is
operated during light and heavy hoisting
periods, with regard to maximum rope speed,
total running period and rest period. These
observations may be dispensed with in case
the indicator cards and time records are
sufficiently complete to supply the informa-
tion.
Before recording any readings for deter-
mining the quality of steam, live steam should
be admitted to the calorimeter for at least
ten minutes, to insure the temperature of
the instrument coming to full heat. When
all is ready, take the following readings
simultaneously: p, tc, pc and pa\ P and Pc
TESTS OF LARGE STEAM HOISTS
185
come directly from readings taken; /„, A',
r, q and ta are taken from steam tables.
Sufficient sets of these readings should be
obtained at various times and under various
conditions to cover any contingency which
might arise.
Sampling coal for moisture and heating
value is a rather extensive process, and if
carried out, a handbook or some other source
of detailed information should be consulted.
Samples for moisture can be taken every day,
while two samples for heating value and
analysis, tested in two separate laboratories,
will suffice.
There is a certain amount of miscellaneous
information which is necessary in getting
at the total cost of operation (which is usually
the ultimate object in view) ; also for getting
at steam consumption per unit of useful
work and various other results. As regards
the boiler plant, this data should cover the
entire boiler plant from which the boilers
for operating the hoist were segregated. It
will usually be easier to obtain the data in
this way, and from this determine what
belongs to the hoist account. Practically
the only way of arriving at the boiler plant
operating costs chargeable to the hoist is by
applying the cost per ton of burning the coal
under regular conditions to the coal burned
during the test. It may not be possible to
obtain installation costs, labor costs, coal
burned, and maintenance, repairs and supplies
as outlined below, because of the various ways
of accounting, and in that case it is necessary
to make the best of what is available. Some
of the data may appear superfluous, but it is
better to have too much information than not
enough. The following notes, as well as any
useful pencil diagrams or layouts, should
therefore be taken at some time during the
tests:
Boiler Plant
Installation cost and present value.
Type and make of boilers.
Rating in horse power and dimensions.
Grate surface.
When installed and present condition.
Mechanical stokers used (if any).
Economizers or feed water heaters (if any).
Feed pumps (type and size).
Injectors.
Boiler house, cost, dimensions, etc.
Boilers blanked off
Accessories blanked off.
Diameter, length and condition of steam main
to hoist.
Kind and price (delivered) of coal burned.
Number of firemen and wage.
Number of ash handlers and wage.
Number repair men and wage.
Maintenance, repairs and supplies for past six
months or year.
Tons coal burned during past six months or year.
Engine and Hoist
Installation cost and present value.
When installed and present condition.
Type and make of engine.
Size of steam cylinders.
Diameter of piston rod.
Kind of valves.
First, second or third motion.
Type of drum (cylindrical or conical, etc.).
Single or double drum; clutched or fixed.
Drum dimensions.
Balanced or unbalanced hoisting.
Type of brakes and how operated.
Dimensions and value of building.
Number of hoist engineers and their wage.
Engine and hoist maintenance, repairs and
supplies for past six months or year.
Mine
Total length of haul.
Length of haul (ground level).
Inclination to horizontal.
Number of levels.
Location of levels (profile of slope or shaft).
Weight of cage.
Weight of car.
Weight of skip.
Number of cars per trip.
Size of rope.
Condition of shaft or slope.
Tons productive for past six months or year.
Tons non-productive for past six months or year
(estimated).
Calculations from Tests
It is first necessary to arrange and con-
dense the data into the most convenient form
for quickly arriving at the final results and
for making up the report. Time will be saved
by arranging the data so that the day and
night, or hoisting and idle periods, can be
totaled separately for each 24 hours. The
idle period referred to includes all time
besides what is considered the regular hoist-
ing period, or periods. Tables for each
24-hour results, with the following headings,
are suggested.
Boiler Plant and Steam Readings
1.
Time.
2.
Coal.
(a) Pounds consumed.
(b) Heating value.
(c) Moisture.
3.
Pounds feed water.
4.
Steam pressure.
(a) At boiler plant.
(b) At hoist engine.
5.
Steam temperature.
(a) At boiler plant.
(b) At hoist engine.
6.
Quality of steam.
7.
Remarks.
186
GENERAL ELECTRIC REVIEW
Hoist Di 1 v
1.
Time.
2.
Trips.
(a) Productive.
(ft) Non-productive.
Lowered.
Hoisted.
(c) Total.
3.
Weight in tons.
(a) Productive.
(ft) Non-productive.
Lowered.
Hoisted.
(c) Total.
4.
Average haul in feet.
(a) Productive.
(ft) Non-productive.
5.
Average vertical lift in feet.
(a) Productive.
(6) Non-productive.
6.
Horse power hours net work.
(a) Productive.
(ft) Non-productive.
(c) Total.
i .
Remarks.
Indicator Cards
l.
Time.
2.
Card number.
3!
Weight hoisted, or lowered, and classification
•4.
Length of haul in feet.
5.
M. E. P.
(a) H. E. each cylinder.
(ft) C. E. each cylinder.
ii.
Total revolutions of engine.
1 .
Average r.p.m.
8.
I. H. P. hours.
a 1 H. E. each cylinder.
(ft) C. E. each cylinder.
(c) Total for engine.
9.
Remarks.
Every item under "Boiler Plant and Steam
Readings" is available directly from the log
sheets, with the exception of heating value of
coal, moisture in coal, and priming of the
steam.
The results covered by "Hoist Duty" re-
quire rather extensive calculations, especially
if hoisting is not all done from one level.
The "Average Haul," when hoisting from
several levels, is determined for the period
by dividing the sum of the net weights hoisted
multiplied by the distance hauled, by the
total net weights hoisted for the period.
If a vertical shaft, the "Average Vertical
Lift" is the same as the "Average Haul."
Horse power hours net work =
Net weight in lb. hoisted X vertical lift
1,000X60
The continuous indicator diagrams should
first have lines drawn perpendicular to the
-pheric line through the points which
mark the ends of the strokes. If an ordinary
planimeter is used, the area of each individual
diagram must be taken separately and
then all added together, taking cognizance of
positive and negative areas; but, if an
integrator is put into service, the resultant
area of the continuous diagram can be
obtained direct from the planimeter. The
mean effective pressure in either case is
obtained by dividing the resultant area by
the product of the length of an individual
diagram (shown by the vertical lines) and
the total revolutions, and then multiplying
this average height by the scale of the
indicator spring. Now by multiplying
together the mean effective pressure, effec-
tive area of piston in square inches, length
of stroke in feet, and total number of revo-
lutions, the result will be foot-pounds of
work produced by one end of one cylinder
during a hoist cycle; and this result divided
by 60X33,000 gives indicated horse power
hours. The sum of the indicated horse
power hours of the different cylinders is
the total indicated horse power hours per
trip. The total number of revolutions per trip
is taken from the graphic speed record and
checked by the stroke counter. Providing
that a sufficient number of cards have been
taken, it will be possible to determine closely
the indicated horse power hours required for
each kind of trip made, and from this the
approximate total indicated horse power
hours per day, or for any period of the day.
The individual diagrams on the continuous
cards may show reverse power, and if so
indicate that the engine is being "plugged"
during retard for the purpose of bringing the
hoist to rest without applying the brakes.
So-called "plugging" is brought about by
reversing the engine and admitting steam.
The piston, however, is going in the reverse
direction to that of the steam, and the result
is that the steam and air confined in the
cylinder are finally forced back into the steam
line. Usually the overall economy is not
affected materially by this operation, be-
cause no steam is exhausted to the atmos-
phere, and the only detrimental effects accrue
from radiation and the admission of cold air
through the exhaust ports and thence into
the steam line. Another method of retarding,
which is sometimes used but which is not as
effective as "plugging," consists of throwing
the valve gear on the central position (point
of no valve movement) thereby closing all
the ports and causing the air and steam con-
fined to be compressed and expanded alter-
nately. The only retarding effect resulting
from such practice is that incident to the
difference of power required to compress the
TESTS OF LARGE STEAM HOISTS
1ST
Fig. 2. Continuous Indicator Diagram of Twin Simple Hoist Engine
air and the power obtained from it by ex-
pansion.
Fig. 2 shows a continuous indicator card
taken on a twin simple hoist engine.
Fig. 3 gives the curves that were made up
from the set of cards, including the one shown
in Fig. 2. Typical curve sheets such as these
should be made up in addition to the above
results.
The final test results can be expressed in
several different ways, depending on what
unit basis is used and on the detailed results
desired. Some of the following items sug-
gested for making up the table of final results
may not be desired, but nevertheless the list
will give the form of the various results ob-
tainable. The totals for the complete test
should be given at the bottom of this table.
1.
2.
4.
5.
6.
ie ib so sa e*
Time IN SECONDS
Fig. 3. Curves Plotted from Continuous Indicator Diagrams
Date.
Time in hours.
(a) Hoisting.
(6) Idle.
Tons hoisted.
(a) Productive.
(6) Non-productive.
(c) Total.
Pounds coal consumed.
(a) Hoisting time.
(6) Idle time.
(c) Total.
Pounds feed water.
(a) Hoisting time.
(b) Idle time.
(c) Total.
Indicated horse power hours.
(a) Productive.
(6) Non-productive.
(c) Total.
Horse power hours net work.
(a) Productive.
(b) Non-productive.
(c) Total.
The test records will also permit still
further segregation of the active hoisting
period or the idle period so that results con-
cerning some distinctive period of the day
can be obtained.
The Report
The value of a report does not depend on
its length, but on convenient arrangement, on
the brief, concise statement of facts and
results, and on the curves and diagrams in-
cluded. The very first part of the report,
after a general idea of the conditions has been
obtained, should be the summary of results,
the detailed information making up the latter
part of the report. The best arrangement is
subject to personal opinion, but the following
outline with accompanying explanation is a
very good arrangement:
General. — Brief introduction concerning
location of mine, product mined, and normal
method of operation.
Object of Tests. — A short, straight-to-the-
point statement of what ultimate result, or
results, the tests were made for.
Existing Conditions. — List of apparatus
with its condition and arrangement before
rearrangement for test was effected. The
188
GENERAL ELECTRIC REVIEW
data given under "Procedure" for "Mine"
should also be included here.
Rearrangement for Tests. — List of rear-
ranged apparatus, specifying its arrangement
in conjunction with the plant itself and with
the extra test apparatus.
Procedure. — A brief outline concerning the
method of running the test.
Summary and Conclusions. — The length and
scope of the summary depends on how much
detail is desired. The following list of results
for the complete test may be revised to suit
conditions and requirements.
Total hoisting time in hours.
Total idle time in hours.
Total length of test in hours.
Total number productive trips.
Total number non-productive trips.
Total number trips.
Total productive tons hoisted.
Total non-productive tons hoisted.
Total tons hoisted.
Total pounds coal consumed during hoisting time.
Total pounds coal consumed during idle time.
Total pounds coal consumed.
Total pounds feed water during hoisting time.
Total pounds feed water during idle time.
Total pounds feed water.
Total indicated horse power hours productive.
Total indicated horse power hours non-productive.
Total indicated horse power hours.
Total horse power hours net work productive.
Total horse power hours net work non-productive.
Total horse power hours net work.
Pounds coal per hour hoisting time.
Pounds coal per hour idle time.
Pounds coal per ton hoisted.
Pounds steam per ton hoisted.
Pounds steam per pound of coal consumed.
Pounds steam per indicated horse power hour.
Pounds steam per net horse power hour.
Heating value of coal.
Moisture in coal.
General quality of steam.
The conclusions drawn depend on con-
ditions met with, but are ordinarily con-
fined to ways and means of possible increase
in economy in operating the plant and to an
explanation of the test results, which are not
self-explanatory.
Detailed Report. — This part of the report
is simply for reference in getting details con-
cerning the results given in the summary.
All the tables made up in the form given under
the section "Calculations from Tests," should
be included here. Sample copies of log sheets
and indicator cards may also be included if
advisable. Tables of capitalization and
operating cost should not be incorporated
in the report unless the final results and
summary cover cost of operation.
Curves. — Almost innumerable curves can
be made up. The most instructive will
probably be a curve sheet for each day's
operation plotting pounds coal consumed,
pounds feed water used and horse power hours
52°PM 5X*tm?2!PM
Sun Mon *tan.
Fig. 4. Curves showing Engine Performance as Determined by One Week's Test
HIGH VOLTAGE ARRESTER FOR TELEPHONE LINES
189
net work, against time. A curve sheet such
as this can also be made up for the total test
using each day's results as a point. Fig. 4 is
illustrative of curves made covering a week's
test.
No doubt the lists of test data, etc., have
appeared to be of a more detailed nature than
necessary, and have included data which
have nothing to do with the hoist test itself.
Such data and information are mentioned,
however, because of their value and applica-
tion to the final test results. With this end in
view, the final results can now be used,
in conjunction with the data at hand, for
obtaining the total cost of operation per year
for this particular mine; and all the results
thus possible to obtain can in turn be applied
to other mines, providing proper cognizance
is taken of the idle time, tonnages, and the
various other vital points involved.
HIGH VOLTAGE ARRESTER FOR TELEPHONE LINES
By E. P. Peck
Asst. Electrical Engineer, Georgia Railway and Power Company
The ordinary telephone instrument, with its fine wire coils, contacts, etc., is a very delicate instrument
and when used on lines paralleling high tension transmission lines requires a protective device that will effec-
tively shield it from the abnormal stresses resulting from a cross between the telephone line and the trans-
mission line, a stroke of lightning, etc. This article describes a telephone lightning arrester, built in three
sizes, which will adequately protect the instrument on transmission systems operating at voltages up to
250,000, or higher.— Editor.
The protection of telephones and other
terminal apparatus connected to telephone
lines paralleling high voltage power lines
has been a very serious problem. The require-
ment is that the delicate telephone windings
of approximately 0.005 wire, hook switch
contacts, etc., with very close spacings,
must be so protected that they will remain
in good operating condition after an almost
unlimited voltage has been repeatedly applied
to the lines to which the telephone is con-
nected.
This extreme requirement has apparently
been fulfilled by an arrester that has been
designed and that has stood tests and operating
service which seem to prove that it will give
the telephone good protection when voltages
of any value or frequency are applied to the
telephone lines. So far we have found but
one exception: When the power impressed
on the telephone line is not sufficient to blow
a five-ampere fuse, but with voltage high
enough to keep the arrester continually
discharging, the telephone equipment will be
eventually damaged. An explanation of this
will be given later in the article.
The telephone high voltage arrester, which
is designed for voltages from 33,000 to 250,000
or higher, is satisfactory, as far as protection
is concerned, for use on any telephone, but
its size and cost prohibit its use on lower
voltage lines. For this reason a smaller
arrester is being designed for use on telephone
lines paralleling power lines of from 2600
to 35,000 volts, and another one has been
made for use on lines which are not subjected
to higher voltages than 2500. All of these
arresters apparently give thorough protection
from any instantaneous application of high
voltage, such as a stroke of lightning. The
high voltage arrester was mentioned by
Mr. C. E. Bennett, Electrical Engineer for
the Northern Contracting Company, in an
article in the December number of the
General Electric Review.
About three years ago it was necessary to
protect some telephone lines which were
subjected to crosses with a 22,000-volt
power line. An arrester, shown in Fig. 1,
was made up of an old marble slab, glass
tube expulsion fuses, and some other material
which was on hand. It was our intention to
190
GENERAL ELECTRIC REVIEW
try out the practicability of this arrester
with as small a cost as possible and later
build one with better mechanical arrange-
ment. In this arrester the line wires con-
nected at the top and the telephone wires
Fig. 1. First Experimental Arrester
and ground wires at the bottom. A spark
gap of 0.004 inch between knurled brass
cylinders was placed from line to line on
the telephone side of the fuses. This gap
was set very close for the reason that it was
desired to hold the voltage across the ter-
minals of the telephone to a very low value,
as it is voltage from line to line and not the
voltage from line to ground which bums up
the telephone coil. Just below this line-to-line
gap are gaps from line to ground.
An examination of a number of damaged
telephones showed that in very many cases
the end turns of the telephone bell coils were
the ones that were damaged. Therefore two
small choke coils were placed on the arrester,
although at that time the idea was not to
consider them as choke coils but simply as
very highly insulated end turns of the tele-
phone coils. Our tests have proved, however,
that these coils also act very definitely as
impedance coils when subjected to high
frequency impulsi .
This arrester has since been rearranged
mechanically and a vacuum gap, man-
ufactured by the General Electric Company,
has been added in parallel with the air gap
from line to line. The vacuum gaps that
were used break down at approximately
350 volts, thereby limiting the voltage
across the telephone terminals to this low
value. These vacuum gaps were first wired
to the existing arresters and it was found
that after they were added, practically com-
plete protection was furnished the telephone.
The arrester shown in Fig. 2 is one de-
signed for lines which are not subjected to
crosses with power lines of more than
Fife. 2. Low Voltage Telephone Arrester
2500 volts. In this arrester standard
fuses are used and vacuum gaps are used
entirely for relief gaps;, the two outside
vacuum chambers being connected from
each line to ground and the center -vacuum
chamber connected from line to line. This
arrester cannot be used where the operating
voltage of the telephone line from line to
ground is higher than about 50 volts. On
HIGH VOLTAGE ARRESTER FOR TELEPHONE LINES
191
ordinary telephone lines the voltage from
lines to ground is much lower than this.
Another arrester is being made for use
where the voltage, in case of a cross with a
power line, will be between 2.~i00 and 35,000
volts. This arrester will be similar to the
larger arrester in all electrical details but
will be much smaller.
The next arrester was made for use on
telephone lines which were strung on the
same towers and about ten and one-half
feet from 1 10,000-volt power lines. This
arrester is shown in front and side views in
Figs. 3 and 4. The telephone lines are
insulated for 22,000 volts and have a normal
operating voltage to ground of approximately
5.300 volts when drainage coils are discon-
nected. The voltage from line to line is
normally too low to be measured with com-
mercial instruments. Fig. 5 shows the
arrangement and connections of this arrester.
Fig. 3. High Voltage Telephone Arrester
Attention is called to the horn gaps shown
at the top of this figure, which should pref-
erably be mounted outside of the building,
but between the telephone instrument and
the first tower. This horn gap, which is set
at about three-eighths of an inch, is a very
essential part of the arrester, as it protects
the top of the arrester frame and the fuses.
and also the top insulator of the arrester.
This protection is necessary, as an application
of 50,000 volts or higher, continuously, on
Fig. 4. High Voltage Arrester — Side View
the top of the arrester will destroy this
portion of it, although the arrester itself will
afford the telephone instrument complete
protection. It would be possible, of course,
to build an arrester which would stand a
continuous application of 110,000 volts with-
out these auxiliary gaps, but the expense of
providing 20-foot fuses mounted independently
on 1 10,000-volt insulators is entirely out of
the question when the same results can be
achieved so simply.
The arrester proper consists of what we
call the gap unit, and expulsion fuses between
the gap unit and the telephone line. The
expulsion fuses are two feet long and are
mounted on a very substantial frame which
serves as a disconnecting switch. With the
switch pulled the main part of the arrester
is dead and fuses can be changed safely.
The mechanical arrangement is very similar
in principle to the 25,000-volt telephone
arrester made by the General Electric
Company.
The gap unit is mounted on a separate
insulator and is tied with a plate to the bottom
insulator of the fused switch. This stiffens
the switch base and the gap unit base, making
them both quite rigid. A number of materials
were tried for the gap unit base before one
192
GENERAL ELECTRIC REVIEW
was found which would stand the necessary
high voltage test and also be sufficiently
strong mechanically. Some samples of marble
were found which were satisfactory, but
more than half the bases made from selected
■W.
- — Norn gaps, $g settmy, from each line to ground.
Gaps mounted outside building.
- — Samp fzpu/s.on fuses, Zft Zona.
« — Cylinder gaps from each line to ground
for tine near Sett/ng
IIOOOO fotts Z Inches
BSOOO • 06 ■■
/IOOO - 04- -
Cylinder gap from tine to fine set . 0O4- inches.
Choke coils wound *it h SO turns Mo 20 dec wire and
cotton cord mound together cimitor to Parley coil, each
layer insulated win three touens af ram/shed cambric
1/acuum gap, from /me to tine, which breolfs down at
3S0 volts
Telephone transformer 25000 volt insulation
bet wee n primary and secondary
Telephone
Fig. 5. High Voltage Arrester. Connections and Data
marble had to be discarded because of par-
tially conducting veins in the marble. The
material finally used is a kind of Bakelite
fiber.
The gap unit consists of three brass cyl-
inders connected as shown in Fig. 5, the two
outside cylinders connecting to the telephone
lines and the center one to ground. The
spacing of these cylinders, which are adjust-
able, should be such that the gaps between
them will not arc over with the normal
voltage of the telephone line, but should
arc over at approximately 25 per cent higher
voltage than normal. These gaps to ground,
on account of their wide spacing (approx-
imately 0.2 inch) offer practically no protec-
tion to the telephone coils, but they do relieve
the strains from line to ground which are
impressed on the high voltage winding of the
telephone transformer, and also act as a pro-
tection against high voltage reaching the
operator. Just below the ground gaps are two
brass cylinders connected from line to line.
These gaps, also adjustable, are set at 0.004
inch and arc over at approximately 700 volts.
In parallel with this air gap is a vacuum gap
which breaks down at 350 volts.
Choke coils, with the individual turns
highly insulated, are mounted between the
relief gaps and the telephone transformer.
This telephone transformer, which has 25,000-
volt insulation between the primary and
secondary windings, is recommended in all
cases on account of the protection it furnishes
the operator.
With the arrester connected we have not
lost a single telephone transformer and only
one telephone coil after several months
service. Before the arresters were installed
telephone transformers and telephones were
burned out every few days during the light-
ning season.
Referring again to the expulsion fuses:
these are fused with five-ampere fuse wire.
This size was chosen because we did not
wash to get a fuse so low that it would blow
in case of a slight disturbance on the line;
but on the other hand we did not wish a
fuse so large that the gap units would be
damaged after the fuses were blown repeatedly
in sen-ice. Our operating results have shown
that this size fuse is very satisfactory.
Calibration curves were made of the arc-
ing voltage between the particular cylinder
gaps used on this arrester. It was found
that the arcing voltage varied greatly with
different kinds of knurling on the cylinders.
When taking voltage measurements on
the telephone line it was found that the
voltage readings taken with a dynamometer
voltmeter were very greatly in error. On
the telephone line in question, the wave
form of the voltage as shown by oscillograph
records is very irregular, having a high peak.
Therefore the voltage shown by the voltmeter
was much lower than the voltage shown by-
sphere gaps. As the spacing of the ground
gaps should be in proportion to the voltage
from the telephone line to ground, it is
important that this point be noted as it
caused us considerable trouble before we
found out the reason for .the cylinder gaps
discharging after they had been apparently
set above the arcing voltage.
High voltage may be applied to telephone
lines in several different ways, all of which
must be taken care of. The action of the
arrester under different conditions of voltage
HIGH VOLTAGE ARRESTER FOR TELEPHONE LINES
193
application will be explained. If one tele-
phone wire becomes crossed with one high
voltage line, the current will flow over this
wire and across the ground gap to ground
without flowing through the telephone, pro-
vided both ground gaps are set exactly the
same. If it happens that the ground gap on
the opposite side is set one or two thou-
sandths of an inch closer than the gap on the
wire carrying the high voltage, the current
will tend to flow through the telephone
instrument and discharge through the smaller
gap. In this case the vacuum gap will come
into action, shunting out the telephone and
preventing damage to it. In addition to
the current flowing to ground, another
current must pass through the telephone
or the arrester to charge the other line wire.
This also is taken care of by the vacuum gap.
If both telephone wires are crossed with
one high voltage wire, the action of the
arrester is practically the same, as the smallest
ground gap will arc over first and the vacuum
gap will discharge the other line without
damage to the telephone.
It is possible, although not probable, that
each of the telephone wires will become
crossed with separate power wires, thus
impressing full line voltage across the tele-
phone lines. In this case the vacuum gap
will take the full discharge.
The tremendous currents carried would
destroy any piece of apparatus of reasonable
size, if the cross continued for an appreciable
length of time; therefore the five-ampere
expulsion fuses are connected between the
relief gaps and the line. In any of the cases
above mentioned, or of a stroke of lightning
on the line, these fuses clear up promptly.
After the fuses have blown there is no further
strain on the telephone or the arrester, but
in case of a cross with the power line the
tops of the fuses are still subjected to extreme
voltage. The gaps outside the building will
then arc over, relieving the stress at the top
of the fuses until the telephone line burns
down. This of course would take place
anyway, because the insulators on the tele-
phone line would arc over. Therefore these
horn gaps will not cause any added trouble',
but simply ensure that the protective appa-
ratus is not damaged before the line does
burn down.
On tests made on the arrester it was
found that if the voltage were raised slightly
above the breakdown voltage of the vacuum
gap. the vacuum gap would be destroyed
after a time if the current were too low to
blow the fuses and were held on continuously.
It has been found that this condition is
unusual and that the expense of renewing
vacuum gaps has been negligible. After
the vacuum gap has been destroyed, the
cylinder gaps connected in parallel with it,
Fig. 6. Telephone Arrester Operating on 118,000
Volts from Power Line
which are set at 0.004 inch, will arc over,
thus preventing an extreme rise in voltage
on the telephone. This cylinder gap breaks
down at approximately 700 volts and will
not entirely protect the telephone if the
voltage is continued for a long time. None
of these occurrences are necessary, however,
if there is an operator in the station, as the
telephone bell will continue to ring as long
as voltage is applied. This should be a
signal to the operator to clear the arrester
by pulling out the fused switch. As the
telephone is inoperative on account of exces-
sive noise at this time, there is no objection
to clearing the arrester from the line.
Very extensive tests have been made on
this arrester for the purpose of finding out if
it would give complete protection to the
194
GENERAL ELECTRIC REVIEW
telephone in cases of crosses with extremely
high voltage lines. Tests were made in the
General Electric Company's research labo-
ratories with high voltage at 200,000 and
.500,000 cycles. Other tests were made with
power from high voltage 60-cvcle lines at
22.000, 50,000 and 110,000 volts.
Fig. 6 shows the arrester operating on
118,000 volts connected directly on the
that the cylinder gap which is in parallel
with the vacuum gap did not discharge,
but that the vacuum gap carried the full
current. The expulsion fuses blew and the
arc extinguished with a very sharp report,
and immediately after the expulsion fuses
cleared up the three-eighth-inch horn gap
arced over. Then the lines connecting the
horn gaps to the power line were fused.
Fig. 7. Bank of Four High Voltage and Four Low Voltage Arresters at
Boulevard Substation, Georgia Ry. & Pr. Co.
power system from line to line. A standard
General Electric telephone transformer and
a telephone bell were connected to the .lower
side of the arrester. When the test was
completed this telephone transformer and
bell were put back in service and are still
operating, as they were not damaged. It
will be noted that "three-eighth-inch horn gaps
are connected two in series from line to
line on the line side of the arrester, and that
gaps are wired directly to the 110,000-
volt power lines. Very close observation
of the arrester at the time of this test showed
This connection was made with 25-ampere
fuse wire, as we did not wish to subject the
110,000-volt power system to a continued
short circuit.
This test, as well as a number of others,
showed that the vacuum gap will apparently
take care of an enormous current without
damage to itself, provided the current is
interrupted promptly, as is done by these
expulsion fuses. Before this extreme test
was made, the breakdown voltage of the
vacuum gap was 350, after the test the
breakdown voltage was 390.
195
X-RAY EXAMINATION OF "BUILT-UP" MICA
By C. N. Moore
Research Laboratory, General Electric Company
Until very recently the thought of an X-ray tube immediately called to mind its application to medicine
and surgery. The Coolidge tube, however, has broadened the useful scope of the application of X-rays so
successfully that it is now employed widely for engineering purposes. In recent issues of the General
Electric Review we have described the method of examining steel castings and copper castings for internal
defects; and the present article treats of the X-ray inspection of built-up mica. — Editor.
The process of manufacturing "built-up"
mica for use as an insulating material in
electrical machinery consists essentially in
pasting together, at an elevated temperature
under pressure, thin flakes of mica with a
suitable binder, planing down the resulting
product to the required thickness, and
cutting it into sheets of the required size.
In this process, certain defects which would
affect the insulating qualities of the finished
product have to be guarded against. Among
these are the presence of foreign materials
of a metallic nature, and of areas not of the
required thickness. In practice, these defects
are detected by subjecting the material to
very careful visual inspection and
gauging with a micrometer. This,
however, entails considerable labor.
The successful application of X-rays
to the detecting of defects in such
materials as steel and copper cast-
ings, already described in earlier
issues of this publication, suggested
the possibility of utilizing X-rays as
a means of increasing the efficiency
of the regular inspection of mica.
With this end in view, Dr.
Davey and the writer obtained
micas (some known to be good
and others known to be defective)
for examination in the Research
Laboratory. These samples
were about 0.032 of an inch in
thickness and had been cut into
small sheets of the required size for
placing in the commutators. These
pieces were placed upon a fluores-
cent screen in a specially designed
viewing box (Fig. 1) at a distance
of 20 inches from a Coolidge X-ray
tube. When the tube was operating with a
current of about 6 milli-amperes and a parallel
spark gap of six inches, the structure of the
mica, as shown on the fluorescent screen, could
be viewed from the outside of the box by means
of a mirror set at an angle of 45 deg. to the
Some of the samples examined contained
small particles of iron oxide not visible to
the eye on the surface of the sheet of mica.
As iron oxide is much more opaque than
mica to X-rays, this material showed up as
black spots in the image of the mica on the
fluorescent screen. Other samples examined
contained small sections not as thick as the
main portion of the sheet. • These sections,
being more transparent to X-rays, showed up
as light spots in the image on the screen.
Samples of uniform thickness which con-
tained no foreign material gave images of
uniform density upon the screen. It was
found that the examination could be made
/v£D W& vV'/vc
Fi8
1 . Arrangement of Coolidge Tube and Viewing Box for
Inspection of Built-up Mica
very accurately and rapidly, one glance at
the" image on the screen being sufficient to
detect the presence of any defects.
The nature of the images on the fluorescent
screen is shown in the radiographs. These
were taken on Seed X-ray plates, with an
exposure of five minutes at a distance of
196
GENERAL ELECTRIC REVIEW
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THE EFFECT OF CHEMICAL COMPOSITION UPON STEELS
197
30 inches from a Coolidge tube. The tube
was operated from an induction coil on 10
milli-amperes with a parallel spark gap of
four inches. Fig. 2 shows the radiograph
of three sheets of fairly uniform thickness.
The various flakes of mica which go together
to make up the finished sheet are plainly
visible. As these flakes are in most cases only
a few thousandths of an inch in thickness,
this radiograph shows what small differences
of thickness may be detected by means of the
X-rays and the fluorescent screen. Fig. 3 illus-
trates this more clearly. In this case a sheet of
mica 0.050 of an inch thick was p'laned down so
that successive sections were 0.045, 0.035 and
0.020 inch thick. The radiograph of this sheet
shows that a difference in thickness of 0.005 of
an inch may readily be detected.
The ease with which foreign material
may be detected is shown by Fig. 4. The
particles of iron oxide present in this par-
ticular case were not visible on the sur-
face, but they are plainly visible as black
spots in the radiograph taken of the sheets
of mica.
Fig. 5 shows a radiograph of four sheets of
mica 0.032 of an inch thick with small areas
considerably thinner than the main portion
of the sheet. These thinner areas show up
as light spots in the radiograph.
The results obtained on an experimental
scale in the laboratory have demonstrated
the adaptability of the X-ray apparatus as
a factory tool for the inspection not only of
"built-up" mica but of any similar material
of not too great a thickness.
THE EFFECT OF CHEMICAL COMPOSITION UPON THE
MAGNETIC PROPERTIES OF STEELS
By W. E. Rvder
Research Laboratory, General Electric Company
A number of years ago it was universally believed that the purity of a piece of iron was a direct indication
of the serviceability of the magnetic properties of that sample. Later experiment has disproved this belief
and showed that the changes produced in the magnetic characteristics of iron by the addition of certain
foreign materials is, in reality, commercially beneficial. The following article discusses the effects upon tin-
magnetic properties of iron by the addition of silicon, aluminum, arsenic, tin, copper, cobalt, nickel, chro-
mium, tungsten, molybdenum, sulphur, phosphorus, and oxygen. It also discusses the non-ferrous alloys and
makes reference to several prominent theories purporting to explain the phenomenon of magnetism. — Editor.
There is a legend that 24 centuries B.C.
Hoang Ti, Imperial navigator for China,
piloted his fleet of junks to victory by means
of a floating piece of loadstone.
It was not until the time of Marco Polo,
however, that its use as a compass was known
in Europe. Frequent mention of its peculiar
properties were made before this by Lucretius,
Pliny and Plato, and it is said that the
Priests of Samothrace made a steady and
comfortable income from the sale of magnet-
ized iron rings which were supposed to cure
all manner of ills. Thus was born the idea
which we now have expressed in the modern
' ' electric belt, ' ' and magnetism has been a most
lucrative field for all kinds of medical quacks
down to the present day.
The two metals most used in the electrical
industry of today are copper and iron, and
any saving, even in the smallest amount, of
either, in electrical design, means an immense
saving in the total quantity used. In iron,
two diametrically opposite sets of properties
are desired depending upon the uses to which
it is to be put. For permanent magnets, it
is desirable to have a high coercive force and
a high remanence; while for magnetic cir-
cuits a high permeability combined with low
coercive force is most desirable. The latter
of these two uses is by far the most important
in that it involves considerably more material
and all kinds of electrical generating ap-
paratus.
Besides the desirability of having a high
permeability and a low watt loss, it is also
necessary to have permanency of magnetic
quality, i.e., the losses as calculated in the
design must not change under the conditions
in which the apparatus is operated. A high
electrical resistivity is also desirable so that
the Foucault currents may be limited.
For a long time pure iron was considered
the best possible material for magnetic cir-
cuits, and specifications always called for a
pure grade of Norway iron — then, the
purest commercial grade of iron. This
material satisfied the demands for a fairly
good permeability and low hysteresis loss,
but unfortunately after running for a short
time it was found that both the permeability
198
GENERAL ELECTRIC REVIEW
and hysteresis had deteriorated, often in the
case of the latter, as much as 100 per cent or
more. Several years ago some engineers
discovered that slight amounts of impurity,
such as silicon and manganese, did not injure
20
IS
0
b - Coercive - Porce
-*•
^
+
X
^*^
■
jr"*^
^
i
as y.o is
Percent C.
2.0
as
1.0 AS
Percent C
so
Fig. 1. Effect of Carbon Content upon Resistivity and Coercive
Force. ^Gumlich)
the magnetic properties and did prevent to a
large extent the deterioration of magnetic
quality with time. These impurities are of
the same kind, and are about the same in
amount, as exist in the best grade of basic
open hearth steel. This represented the first
great step forward, and in 1900, Barrett,
Brown and Hadfield published their results
obtained on alloys of iron with as high as
five per cent of silicon or aluminum which
showed the remarkable fact that additions
of non-metals or semi-metals, which had no
magnetic properties in themselves, would
still improve the magnetic quality of iron.
Since that time there have been several
improvements, but mostly in the mechanical
working of the sheets and in their annealing
and heat treatment. The useful magnetic
properties of iron and its alloys are effected
in three ways; first, by composition, second,
by mechanical treatment during the process
of manufacture, and third by the crystalline
structure.
This article will deal only with the effect
of chemical composition upon the magnetic
properties of steel.
Carbon, always present to a greater or less
extent in commercial steels, has a decided
influence upon their magnetic properties.
Gumlich, working at the Physikalisch-Tech-
nische Reichsanstalt, recently published some
interesting results upon the influence of this
element. These are given in part below.
The electrical resistance rises about 0.06
ohm per m. and sq. mm. for each per cent of
C. The curve, however, bends at about one
per cent C. and above that the increase is less
rapid. Practically the same result is obtained
when the coercive force is plotted against
per cent carbon.
We know that in all slowly cooled iron-
carbon alloys the carbon exists as pearlite
up to the eutectoid point, i.e., about 0.85
per cent C, above this percentage the carbon
exists as cementite (FeaC), the normal carbide
of iron, and the curve indicates that the
cementite carbon diminishes the conductivity
less than does the pearlite carbon. This is
explainable by the lamellary structure of the
pearlite which is made up of alternate layers
of FesC and pure iron each about 1/25000 of
an inch or less in thickness.
The effect upon the hysteresis loop is to
make it broader and lower because the per-
meability is decreased from about \i max =
5000 for 0.02 per cent C. to y. max. =450 for
1.8 per cent C.
220O0
81000
vj SOOOO
^ /SOOO
k /eooo
* /?000
/6000
0_
O OS 1.0 15 2.0 2S 30 SS 40
Percent C.
Fig. 2. Showing Decrease in Saturation Value for Increased
Carbon Content in Annealed and Hardened
Steels. (Gumlich)
The value of saturation, 4 it I, which is the
true index for magnetic quality, diminishes
about 1400 for each per cent of carbon present,
so that for pearlite (0.86 per cent C.) its value
is 20,200 and for cementite it can be calculated
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THE EFFECT OF CHEMICAL COMPOSITION UPON STEELS
199
to be about 12,500, considering pure iron to
have a value of 21,600 (see curve, Fig. 2).
For hardened steels it will be observed that
the decrease is more rapid owing to the per-
centage of C. held in solution. The break at
1.4 per cent is due to the fact that at the
quenching temperature, 850 deg. C, no more
carbon was dissolved so the curve becomes
parallel to that for the annealed samples which
have no dissolved C.
If, now, these alloys be subjected to harden-
ing at different temperatures, we find that
the coercive force and resistance rise directly
in proportion to the percentage of dissolved
carbon as is shown in the curve (Fig. 3).
Only the curve for specimens quenched
at 800 deg. C. are given and it will be observed
that there is again a sharp break at about
one per cent C. This is due to the fact that
only this percentage of carbon is soluble in
the iron at this temperature. At higher
temperatures the curve is smooth, though
it bends a little due, no doubt, to the forma-
tion of austenite at the higher quenching
temperatures.
Silicon and Aluminum
It has been mentioned before that silicon
has a decided effect upon the magnetic quality.
It is difficult to understand at first how so
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Fig. 3. Effect of Hardening upon the Electric Resistance of
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magnetically inert an element as silicon could
produce a better magnetic quality. The
term "better," however, is used in the sense
of{more useful, rather than in an "absolute"
sense, for the improvement obtained from
silicon is not a direct one; first, because the
magnetic quality does not improve in pro-
portion to the increasing silicon content, and
second, because the saturation value falls off
steadily with increased percentage of silicon
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Fig. 4 Showing Decrease in Saturation Value of_ Steels with
Increased Si Content. ^Gumlich)
from 21,600 to 16,500 for 8.5 per cent silicon,
as shown in the curve, Fig. 4.
This curve shows that the silicon acts
largely as a foreign substance, diminishing
the active cross-section of the iron and there-
fore the saturation value.
In brief, the real effect of the silicon upon
the steel is this:
(1 ) It prevents the formation of hardening
carbon, even with comparatively quick cool-
ing, and with the higher percentage (3-5)
even the formation of pearlite is prevented
and all the carbon exists in the harmless
graphitic state.
Charpy and Cornu (C.R., May 26, 1913),
show that at least 800 deg. must be attained
in annealing to change all of the pearlite to
graphite for steels having a silicon content
of 3.8 per cent, and in general the temperature
at which the separation begins is lower as the
silicon content is higher.
(2) It cleanses the metal of harmful oxides
and dissolved gases.
(3) It produces a larger grain structure in
the metal.
200
GENERAL ELECTRIC REVIEW
(4) It increases the resistivity of the
metal from 12 to about 60 or 75 microhms per
cm. cube, depending upon the contents.
(See curve, Fig. 5.)
O / 2 3 4~ &
Per cent Si
Fig. 5. Effect of Si upon Resistivity. (Burgess)
Paglianti (Metallurgist 9, pp. 217-230)
made up a series of Si alloys containing 0.2
to 5 per cent Si and drew the following con-
clusions: The specific gravity diminishes
regularly from 7.87 to 7.57 with increased Si
over the range studied. For high induction
the permeability falls off with increased Si,
but for B = 7000 there is a considerable en-
hancement of the quality with the addition of
Si. With annealed alloys the maximum
value of n was 1500 with 0.2 per cent Si,
3300 with 2 per cent Si, and 2800 with 5
per cent Si. For B = 13,000 the hysteresis
loss with 2 per cent to 5 per cent Si was
only half that with 0.2 per cent Si.
The results obtained by Burgess (Met.
Client. Eng. 8, 131) are shown in the curves,
Fig. 6.
The results which have been obtained in the
laboratory with ring samples of 0.015-inch
sheet differ somewhat from each of these and
are shown in Fig. 7.
Silicon has the effect, however, of making
the sheets more brittle. Brinell hardness
numbers increase fairly uniformly from 125
with 0.2 per cent Si to 290 with 5 per cent Si
(Paglianti). Its use is therefore limited to
stationary apparatus such as transformers,
although some alloys with 1 to 2J4 per
cent are used in induction motors. In general,
however, generators and motors operate at
such high flux density that the advantage of
low watt loss is offset by the decrease in per-
meability at these high densities, so it is still
the practice in this kind of apparatus to use
a pure grade of open hearth steel with only
about 0.02 to 0.1 per cent Si to limit the
aging.
In general, aluminum has the same effect
upon the magnetic properties as silicon. It is
not, however, in as general commercial use as
silicon.
Arsenic and Tin
Burgess and Aston have shown that these
elements, like silicon and aluminum, also have
the effect of raising the electrical resistance
of the steel and of inducing a large grain
structure which has a good effect upon mag-
netic hysteresis.
The effect of tin is to increase the permeabil-
ity of higher ranges and to decrease the hyster-
esis loss to a lower value even than silicon.
This loss decreases gradually with increasing
percentage content of tin.
Tin is, in this respect, better than arsenic
which also reduces the hysteresis loss more
than silicon when as much as 3.5 per cent is
added, but it has the disadvantage of being
verv brittle.
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Fig. 6. Magnetization Curves. Iron-Silicon Alloys. Annealed
675 Deg. (Burgess)
Both arsenic and tin have the advantage
over silicon of increasing the permeability
in the higher working ranges of density.
This increase is hard to explain in view of
the fact that, like silicon, they are both non-
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THE EFFECT OF CHEMICAL COMPOSITION UPON STEELS
201
magnetic elements, and more accurate work
on these alloys is necessary before we can
explain their results. The action is, no doubt,
in view of the more recent work on gases in
pure iron, one of a cleansing nature.
Copper
The addition of copper has been suggested
as a means of increasing the permeability of
iron. In fact, a patent has been taken out upon
such a process. The writer has been able to
find no case, however, in which the permea-
bility was increased or the coercive force de-
creased. In fact, the contrary was found
to be true, the magnetic quality deteriorating
almost in proportion to the percentage of
copper added. The one advantage to be
gained is that of increased tensile strength in
1 per cent to 2 per cent copper alloys
without a very great decrease in magnetic
quality. The electrical resistance also rises
to a maximum of 17 microhms for 1^ per
cent copper at which point it is about 1.40
times that of standard iron.
Cobalt and Nickel
The writer knows of no published results
on a systematic study of cobalt alloys with
iron, and such results would undoubtedly
be quite instructive in view of the interesting
results obtained from nickel. Weiss has
found, however, that the alloy Fe2Co has a
saturation value 10 per cent higher than pure
iron. This is the only alloy known having
such properties. The writer's own results
have checked this finding.
Nickel (Burgess & Aston, Met. Chem. Eng.
8, pp. 23-26), when added in quantities less
than 2 per cent, causes little change in
magnetic quality. With increasing nickel
content, the permeability rapidly falls off and
the alloys of 25-30 per cent of nickel are almost
completely non-magnetic.
A still further addition of nickel again
improves the quality up to 50 per cent, so
that for fields under 14,000 B the permea-
bility is higher than that of pure iron and its
hysteresis loss is only 50 per cent of that of
iron. The sudden drop in permeability above
14,000 B, however, together with its cost
prohibits its use as a transformer material.
Chromium, Tungsten, Molybdenum, etc.
Metals, such as chromium, tungsten, molyb-
denum and manganese, have the general
property of increasing magnetic hardness,
that is, they increase the remanence and more
particularly the coercive force. These are the
properties which are desirable for permanent
magnets. It has been found that they work
best in combination with carbon or some other
element, such as silicon or vanadium. Nickel,
though it sometimes aids, in general is found
to be injurious to permanent magnetic
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Fig. 7. Effect of Silicon upon the Permeability and Magnetiza-
tion Curves
quality. Moir (Phil. Mag., May, 1914), has
made a study of the magnetic properties of a
graded series of chromium alloys.
The curve (Fig. 8) shows the considerable
decrease in permeability caused by the addi-
tion of 25 per cent of chromium, both before
and after annealing.
Steels which are practically non-magnetic
can be made by the addition of 12 per cent
Mn with about 1 per cent C. which is known
as Hadfield's manganese steel. This material
has a practically constant permeability of
about 1.3. The manganese may be increased
to 18 per cent in some cases with the same
result. A slight change in heat treatment may
create or destroy the magnetic property in
such a steel, because Mn has the property of
lowering the change point so much that the
gamma iron remains unchanged with reason-
ably quick cooling and gamma iron is non-
magnetic.
Sulphur, Phosphorus and Oxygen
Of the elements, sulphur, phosphorus and
oxygen, it may be said in general that they
202
GENERAL ELECTRIC REVIEW
are all injurious. Even though they exist
in most cases in very small percentages, they
combine in such a manner with the iron to
form sulphides of iron and manganese,
phosphides and oxides, that they occupy
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0.2 per cent carbon. No. 1, Unannealed Rod; No. 2. Annealed
1000 Deg. C. in Vacuum, Burrows Method.
considerably more space than the analysis
indicates.
In any case their removal always results
in a considerable increase in magnetic quality.
This brings us to a consideration of some
of the more recent work on pure electrolytic
iron. As pure as commercial iron is, the
further purification by electrolysis has made
it possible to produce material having a very
high permeability and low hysteresis loss.
Dr. Breslauer in an article in the E.T.Z. has
calculated that a saving of from 15 to 50 per
cent in the weight of iron is possible.
The chief disadvantage of this material is
its low resistivity — 10 microhms per cm-3.
In generators, however, its high permea-
bility more than offsets its high eddy loss,
which is of less consequence in this form of
apparatus.
In spite of the high purity of this material,
a still greater improvement has been obtained
by heating the sheets of alloyed or pure iron
to a high temperature in vacuo, or by fusing
in vacuo. The effect of this treatment is evi-
dently to remove practically the last traces of
impurity, notably sulphur and oxygen.
The important point about this work on
extremely pure iron is that it shows that the
good results obtained by additions of other
elements are all secondary, i.e., their effect
is one of removing material that is more
injurious, magnetically, than the metal added.
The additional effects are those of increased
resistivity — always at the expense of magnetic
quality however — and an increase in the size
of the grain.
Non-Ferrous Alloys
About the non-ferrous
magnetic alloys much is
yet to be learned. These
alloys are named after
Dr. Heusler who first
called attention to them
in 1898. A clear under-
standing of the reason for
their magnetic properties
and the laws governing
them would add much to
our understanding of the
ultimate nature of magnet-
ism and a brief word here
as to their composition and
properties would not be
out of place. They consist
approximately of 62.5 per
cent Cu, 23.5 Mn and 14
Al, i.e., Mn and Al in the
proportion of their respec-
tive atomic weights. Their magnetic values
are very low compared with good iron; the
best value of permeability being about 90-100
at a density of 2200 B. A magnetizing force
of 70 which gives a flux of about 17,000 B
(lines per sq. cm.) in soft iron gives only 4000
B in the best of these alloys.
The likeness in structure between these
alloys and iron is striking, but no definite
structure or kind of cryst al has been attachable
to the strongly magnetic forms as differing
from the weak or non-magnetic modifications.
Prof. A. A. Knowlton describes three kinds
of crystals separated by their different be-
havior under the action of the etching re-
agent, and finds a definite relation between
one of these and the saturation value of I,
but subsequent workers have not been able
to find this relation or to isolate this particular
crystal structure. The following statement
is taken from a paper by Heusler and Take
(Trans. Faraday Society, October, 1912):
1. In order to account for the pronounced
ferro-magnetism of the Heusler alloys, aluminum
or tin-manganese bronzes, Guillaume assumes with
Faraday that pure manganese exists in a strongly
magnetic modification, which undergoes transforma-
tion at a very low temperature; this temperature
is said to be raised by the addition of Al or Sn, so
that the magnetism of these alloys becomes appar-
ent. This hypothesis is not based upon facts, and
the arguments are not sufficiently supported; it
would, moreover, not explain the strong ferro-
THE EFFECT OF CHEMICAL COMPOSITION UPON STEELS
203
magnetism of the Heusler manganese alloys with
As, Sb, Bi and B.
2. Heusler, on the other hand, has advanced a
hypothesis which explains all the phenomena; for
he has not only discovered the ferro-magnetie
alloys, but he also first proved, in 1903, that the
appearance of the strong ferromagnetism is due to
the formation of chemical compounds, and that
the ferromagnetism is thus a molecular phenomenon.
This article may appear more or less a
jumble of facts having, in many cases, no
continuity of reason. This is largely due to
the fact that no theory has yet been evolved
which fits in with all of the facts, and research
along magnetic lines is largely a matter of
cut and try, especially when dealing with
alloys of a possible commercial importance.
Several theories have been evolved and they
are all ingenious, but they have always
followed, rather than led, the experimental
work. The latest and most interesting theory
has been the adaptation, by Langevin of
Paris, of the electron theory to magnetism.
It does not attempt to predict, of course,
what element is to be added to iron to make it
more useful, or what element is the most
harmful, but these things must be left to be
decided by experiment.
As far as a practical use can be made of it,
Langevin's theory scarcely goes much further
than Ampere's resistanceless circuit theory or
the well known molecular theory of Ewing.
From a mathematical and theoretical point
of view it undoubtedly adds much toward
correlating our recent views of energy and
matter. (See Dushman, General Electric
Review, 1914, July, Sept., Oct. and Dec.)
The recent work of Bragg (Phil. Mag.,
Sept., 1914), who has succeeded in determin-
ing not only the crystalline structure but the
relative location of different atoms in a mole-
cule, has opened the way for an explanation
of the ultimate nature of magnetism which will
take into consideration the relation of the
position of the elements in the crystalline
space lattice to the resulting external effect
which we call magnetism. After a thorough
study of iron and its alloys by this method
we shall be able to completely correlate the
jumble of facts which now constitutes our
knowledge of the effect of added elements
upon the magnetic properties of iron. The
magnetic and non-magnetic phases of the
Heusler alloys, or Hadfield's manganese steels,
may then be explained by a deformation, or
permanent alteration of the atoms from their
original equilibrium in their crystalline space
lattice. Magnetic hardening which so often
accompanies real hardening may then be
explained on the same ground, viz., that of a
strain set up between the atoms in their space
relation in the crystal.
The chief difficulty encountered by the
experimenter has heretofore been that of
obtaining accurate magnetic tests. Most
workers along this line have used rods or
wires for convenience, and have obtained
results which, while they have a comparative
value, are quite inaccurate and misleading.
Burgess and Aston, who have covered more
ground than any one else in the investiga-
tion of alloys for magnetic quality, used
this form of test piece, recognizing its limita-
tions.
The ring method has long been the standard
of magnetic testing. C. W. Burrows (Bull.
Bur. Stds., 6) has developed an end compen-
sation method for straight bars which makes
it now possible to obtain permeability results
on bars which are as reliable as those obtained
from rings.
This article has only dealt with the effects
of composition upon magnetic quality. The
mechanical treatment and crystalline struc-
ture also have a very decided influence which
can, in extreme conditions, wipe out all the
beneficial results of a proper composition.
204 GENERAL ELECTRIC REVIEW
ELECTROPHYSICS
Part II
By J. P. Minton
Research Laboratory, Pittsfield Works, General Electric Company
In our previous article of this series the author dealt with the properties of cathode rays and electrons.
In the present installation the principles of the conservation of electricity and the nature of its flow are
considered first; followed by a discussion of the electron theory of matter and electricity and its application
to the electrical and thermal conductivity through metals, and also the relationship between these two phe-
nomena. A modified electron theory is also discussed, and the article concluded with a brief summary of the
subjects covered in this contribution. — Editor.
ELECTRON THEORY OF ELECTRIC CONDUCTION IN METALS
Introduction
In the first article, on the properties of
cathode rays and electrons, we considered the
experimental results upon which the elec-
tron theory is based. No conclusions were
drawn, whatsoever, except those which could
be drawn from the data at hand. In this
article, however, the electron theory of matter
and electricity will be briefly developed, and
applied to the conduction of electricity
through metals. Some contradictions will be
encountered, but this means that the nature
and the dynamical behavior of a complex
piece of matter is certainly not fully known.
and does not mean that we are on the wrong
path. On the contrary, it is believed that we
are, indeed, on the right path to the real
understanding of matter and electricity, even
though this understanding may be far dis-
tant.
The subjects to be considered in this article
are:
I. Preliminary statements on the Prin-
ciple of the Conservation of Elec-
tricity, and on the nature of Flow
of Electricity.
II. Electron Theory of Matter and
Electricity.
III. Application of this theory to:
(a) Electrical Conductivitv through
Metals.
(b) Thermal Conductivitv through
Metals.
IV Relation between Thermal and Elec-
trical Conductivities of Metals.
V. Number of Free Electrons in a
Cubic Centimeter of Metal.
VI. Modified Electron Theory, and its
Application to Electrical and Ther-
mal Conductivities of Metals.
VII Summary and Conclusions.
We shall now take up these various subjects
in the order riven.
I. CONSERVATION OF ELECTRICITY AND
THE NATURE OF ITS FLOW
Electricity, like matter and energy, is inde-
structible'and cannot be created. If a certain
amount of electricity disappears from one
place, it always appears in another. For
example, if a positively charged sphere is
connected to one which is not charged, there
is a flow of electricity from the former to the
latter. The quantity of electricity lost by
one is exactly equal to that gained by the
other. Furthermore, the apparent destruc-
tion of electricity is due to the neutralizing
effect of positive and negative charges on
each other.
Again, a positively charged body will in-
duce a negative charge on a body placed near
it. At first thought one might say that
electricity has been created in this case.
Such is not the case, however, for the posi-
tively charged body simply attracts the nega-
tive constituents and repels the positive ones
of the uncharged material. Hence, electricity
is separated, not created, and this separation
continues until equilibrium exists between the
forces thus set up. Hence, there is no such a
thing as a generator of electricity, but should
properly be called an electrical separator.
Consequently, any theory of electricity must
explain how this separation of the already
existing charges is brought about. We shall
see that the electron theory of electricity-
does this very nicely.
Since we are to consider metallic conduction
in this paper, it will be important to first
point out how electricity is carried from one
place to another. There are displacement
(Id), convection (Ic), and conduction (Ic)
currents, and the total current (I) passing
through any medium is, I = (Jd+Iv+Ic)-
In regard to displacement currents we can
imagine an air bubble within a piece of soft
rubber. Now. if the air bubble expands or
ELECTROPHVSICS
205
contracts, the rubber will be displaced
throughout its volume, and this corresponds
to displacement currents, as in a perfect
vacuum condenser where there are only dis-
placement currents. For an alternating
potential there is a corresponding displace-
ment current, but for a direct potential the
displacement current becomes zero when the
stress in the medium balances the force pro-
ducing the strain.
The flow of ions through electrolytes and
gases, of charged particles of mercury vapor
in mercury lamps and rectifiers, of electrons
in gases and solids, correspond to what are
called convection currents. The electron
theory deals entirely with these currents.
Now, as to the nature of conduction current
we know nothing, and do not even know that
there is such a thing. Indeed, in the light of
our present knowledge of the electron theory
of metallic conduction, it appears that there
is no such a thing as a conduction current in
metals, but that it is all convection current
due to the electrons. Let us, then, take up
the development of the electron theory and
its application to metallic conduction.
II. ELECTRON THEORY OF MATTER
AND ELECTRICITY
We have seen in the previous paper that
electrons come from metallic cathodes and
they must, therefore, exist in metals, being
torn out of them by the electrical forces
brought into action. We also saw that when
the cathode rays strike a fluorescent sub-
stance, say calcium tungstate, some of the elec-
trons remain in the substance. There are many
other illustrations which we could use to show
that electrons form an important part in the
formation of a piece of matter. It has been
shown, as in the case of cathode rays, that
electrons exist free from matter. Now, the
question is how do the}' combine with matter '
Since in gases there are neutral molecules and
atoms, it follows that electrons must exist
within these in order that the positive and
negative electricity may balance each other.
So when gases are solidified, electrons must
form an important part of the resulting solid
matter being bound within the molecules
and atoms. We have ample evidence to
prove the free electrons exist in gases, and
therefore solids if the gases are solidified.
Similar remarks apply to vapors, such as
mercury vapor for example. Electrons are
shot off from radio-active substances and
metals heated to a high temperature. In the
same way we can show the electrons exist in
all substances. Since, in many cases, they
can be liberated from these substances with-
out apparent disintegration of the material,
it follows that these electrons must exist in
the free as well as the combined states in all
substances. The free state refers to their
existence outside the atoms or molecules, and
the combined state means that they exist
within these.
Having shown that electrons exist in all
substances, let us see to what extent they are
in the free and combined states in these
substances. Now, all electronegative ele-
ments, like chlorine, sulphur, etc., take on a
negative charge, and hence most of the
electrons are in the combined state within
these. In the case of electropositive ele-
ments, like silver, copper, zinc, etc., we have
just the opposite state of affairs, and in these
there are a great many free electrons as com-
pared with those in the electronegative ele-
ments. This means that there is always
negative electricity in a piece of matter, and
there must, therefore, always be positive
electricity. Take the case of a salt, say silver
chloride, as an example. The silver is electro-
positive while the chlorine part of the molecule
is electronegative. An atom being electro-
positive means, from the theory we are
developing, that the atom has liberated some
of its electrons. Hence this leaves the silver
part of the molecule positive, and, therefore,
it is difficult for the silver atom to lose more
electrons because of the electrical forces
brought to bear as a result of the loss of
electrons. Since the chlorine part of the
molecule is electronegative (that is, it has a
capacity for taking on electrons to give it a
negative charge) it means that the electrons
liberated by the silver atom are taken up by
the chlorine radical. After this radical has
taken on some electrons, its negative charge
will tend to oppose the taking on of any more
of them. Both of the actions here described
continue until equilibrium is established, when
the exchange of electrons ceases. We natu-
rally expect, therefore, that most of the elec-
trons in a salt are in the bound or combined
state. However, it is quite likely that a small
percentage of all the electrons present are in
the free state. This same line of reasoning
applies to acids and bases. The conception
of free and bound electrons will be utilized
in applying the electron theory.
Our conclusions are based upon our ex-
periences, and our experiences indicate that a
piece of matter is built up of positive and
negative electricity, electrons, atoms, mole-
206
GENERAL ELECTRIC REVIEW
cules, bound and free energy, and things that
we do not yet know about. So, a piece of
matter is an extremely complicated thing.
Let us, now. take up the electron theory of
the conduction of electricity through metals.
III. a ELECTRON THEORY OF
METALLIC CONDUCTION
From the above discussion we see that there
are a great many free electrons in a piece of
metal as well as combined ones. Now, the
first theory we shall develop considers only
the free electrons and that these are in a
continual state of vibration between the
metallic molecules and atoms. This movement
is in all conceivable directions, so that there
is no resultant transfer of electrons along a
wire. In this case there is no current flowing.
Suppose, however, an electric force (2s) is
applied to the wire. Then, there will be a
resultant transfer of electrons along the wire
in the direction opposite to the electric force
on account of the electrons possessing a nega-
tive charge.
We see, therefore, that we are dealing with
two electronic velocities; the first (v) being
that due to the random vibration between the
collisions of the electrons with one another and
with the molecules and atoms, and the second
(U) being the resultant drift of the electrons
along a wire constituting the flow of current ;
(U) and (v) are average values, of course.
Xow, in this theory we apply Boltzman's
principle, namely, that in any gas the mean
kinetic energy of all molecules are equal. So,
we assume that the free electrons of a piece
of metal act like a gas, and hence, the kinetic
energy of the electron must be the same as
that of a hydrogen molecule at the same
temperature. Since the mass of the electron
is about — of that of the hydrogen molecule,
it follows that (tr) must be about 3500 times
the square of the velocity of the hydrogen
molecule. The mean velocity of the latter,
as shown by the kinetic theory of gases, at 0
deg. C. is about 1.7 X105 cm. sec. so that v2 =
<(1.7X105)2, or i' = 2X107 cm. sec.
approximately, which is the velocity (y) of
the electron. (U) is so much smaller than
this that it need not be considered in obtain-
ing the mean kinetic energy of the electron
within the wire under consideration. For,
suppose [7 = 1 cm. sec, then from equation
(1) below I = Xe. Now, we shall see later
in this article that .V= 1024 approximatelv, so
tbatr.'°"X4.8x1o-.-xl0orJ,10>amp
approximately, which is very large. Since
this current is excessive, it follows that (U)
must be small.
Let us, now, derive expressions for the mag-
nitudes of the current and the electric con-
ductance from this theory. We all know that
the current (I) flowing across an area of
one sq. cm. equals the charge per cu. cm.
multiplied by the velocity of drift (U). If
there are (Ar) free electrons per cu. cm. and
e is the charge on each electron, then Ne
equal the charge per cu. cm. So that.
I=NeU. (1)
We can get an expression for (U) in the
following manner. During the time an elec-
tron is moving along its mean free path it
traverses a distance due to (E) :
D = 1/2 at" (2)
where o, the acceleration due to the force Ee
acting on the electron between collisions is:
Ee
a = — (3)
w
Substituting equation (3) in (2) we obtain:
2 m
Since D= U t, we have from (4)
1 =Ym- (5)
now equation (5) applies to the electron dur-
ing its motion between collisions, so that (t)
is the average time between the impacts of
all the electrons. From the kinetic theory
of gases,
h
(6)
where (h) is the mean free path of the elec-
trons, and (v) their average velocity of vibra-
tion over this path. Eliminating it\ from
equations (5) and (6) we get:
TT E e h
2 m v
Hence, when we substitute this value of I IT)
in equation (1) we have: (See note at the
end of this article.)
I = N**k (8)
2 m v
which is an expression for the intensity of the
electronic current in any substance. If there
are only a few free electrons (N) in a sub-
stance, as in the case of glass, and other in-
sulating materials, salts, as well as in electro-
negative elements, there must, according to
this theorv, be a relatively small current
ELECTROPHYSICS
207
passing. On the other hand, if there are a
great many free electrons in a substance, as
in the case of the electropositive elements
(metals), then there will be a relatively large
current flowing. All this is in agreement with
experimental observations. In this theory
the atoms have played no part in the metallic
conduction which, of course, is also in agree-
ment with observation. If (E) is a com-
plicated function, as in the case of high fre-
quency phenomena, then equation (8) will
be modified accordingly. In fact, (E) can
represent a steady potential, a harmonic one,
or any sort of a potential. It would be
necessary, of course, to start with the fun-
damental differential equations of motion for
such an analysis of the problem.
Before passing on to the thermal con-
ductivity, it will be well to show that equation
(8) is in agreement with Ohm's law. Before
showing this, however, let us modify this
equation. The kinetic theory of gases tells
us that the average kinetic energy of a hydro-
gen molecule at an absolute temperature
(T) is a T= =- m v2, so that this is also,
according to our theory, the average kinetic
energy of the electron at an absolute tem-
perature (T). (a) is a constant and equals
1.5 XIO-16 approximately. Putting 2aT =
w v- in equation (8), we have:
NElhv
L~ 4:OCT
and since the conductance <x is the current
per unit electric force,
<r=4^ (10)
■i a 1
Now, Ohm's law states that the conductance
is independent of (£), which is in agreement
with equation (10). It may be further
stated that since resistance equal ( - ) equation
(10) shows that the resistance varies directly
as the absolute temperature. We may look
upon resistance as being due to the collisions
between the electrons and the atoms. One
would also expect frequency to have an
effect on the resistance because of the change
in the number of collisions per cycle with
increased frequencies. All these effects have
been noted.
III. (b) THERMAL CONDUCTIVITY
If one part of a piece of metal is at a higher
temperature than another, then the average
kinetic energy of the electrons in the hotter
regions will be greater than that of those in
the colder portions.
Considering that the electrons act like a
gas, then it is clear that across any section
separating the hot from the cold portions,
a transfer of electrons will take place. Due
to the greater kinetic energy of the electrons
on the hot side of the section, there is a
transfer of heat to the cold portion of the
metal as the electrons pass from the former
to the latter. If we assume that all the heat
is carried in this manner, then it has been
shown in works on the kinetic theory of gases
that k, the thermal conductivity, is given bv:
K=l/3 N v a h ' (11)
IV. RELATION BETWEEN THERMAL
AND ELECTRICAL CONDUCTIVITIES
Having obtained the expressions for the
thermal and electrical conductance, let us
see what relation exists between them. To
do this we simply divide equation (11) by
equation (10) thus,
k , /„ »t i /N e-h v
- = 1/3 Nv a h =r
<j 4 a T
k _ 4 a2 T
a~ 3e2
or at 7 = 300 deg. C, absolute.
K = 4X(1.5)2X(10-'6)-X3X102
a 3X(5X10-10)2
(12)
4X10"11
approx. in C.G.S. electrostatic units. Equa-
tion (12) shows us that the first theory of
electronic conduction in metals leads us to the
conclusion that the ratio of the thermal to the
electrical conductivity should be the same for
all metals, and should vary directly as the
absolute temperature, being entirely inde-
pendent of all metals. So that with good
electrical conductivity goes good thermal
conductivity. The following table shows how
nicely these theoretical conclusions are veri-
fied by actual experiments.
Metal
(at 18° C.
Temp. Coef. of — add
.4/
7.08X10""
0.043 X 10-"
Cu
7.4 X10-"
0.039 X 10""
Ag
7.6 XIO""
0.037 XIO""
Au
8.0 XIO"11
0.036 X 10""
Pb
7.9 X10""
0.040 X 10""
«
8.3 XIO""
0.046 X 10""
We shall have occasion to point out some
variations in this ratio in the next article.
208
GENERAL ELECTRIC REVIEW
Since (k) is very nearly constant over a certain
range of temperature, it follows from this
theory that (<r) must decrease with increasing
temperature; this agrees with experiment.
V.
NUMBER OF FREE ELECTRONS
IN METALS
It will be of interest to obtain an approxi-
mation to the number of free electrons there
must be in one cu. cm. of a metal according
to this first theory. In the case of silver for
example a =
1
KillO
at 0 deg. C. Now, we will
not be far wrong if we assume the mean free
path of the electron (h) to be about 10-7 cm.
Substituting the various values which have
been given for the quantities involved in
equation (10), we get N= 10;4 approximately,
which is equivalent perhaps to five or six
free electrons for each atom of silver.
Perhaps it will be well at this point to
refer to values obtained by other methods.
J. J. Thomson concludes from work on the
coefficient of absorption of radiation by a
metal that the number of free electrons in
silver appears to be not less than about 11
for every atom of silver. Earlier than this
Drude and Schuster in determining the ab-
sorption of light by metals concluded that
silver possessed about one, mercury about
three and one-half, and antimony about
seven and one-half, free electrons for each
atom of metal. Work with Dulong and
Petit's law, that the product of the atomic
weight and specific heat is nearly the same for
all metals and is constant, has led to the
conclusion that the maximum number of
free electrons is two per atom of metal.
This conclusion is based on the assumption
that all the heat energy be attributed to the
free electrons associated w-ith the atoms. In
the next article will be given another method
by which we can estimate the number of free
electrons in metals. Since the order of magni-
tude for the number of free electrons in metals
is the same when determined from such dif-
ferent methods as here indicated, it would
appear that there is some element of truth
in this theory of free electrons. It will be
well to note that equation (8) shows that
the electric conductivity does not depend
only on the number of free electrons in a
metal. The value of (A7) might be somewhat
greater for poorer conducting metals than
for good ones. The difference is accounted for
by (h) and (v) being different for different
metals.
It is very important to notice in connection
with equation (10) that if (<r) is constant (as
it is under given conditions), then (N h v)
must be constant. Now, if the mass of the
carrier of electricity was much greater than
the electron, then (h v) would be less, and
hence, (N) much larger than given by the
above values. So that the number of carriers
of electricity in this case would be much larger
than the number of atoms of silver. We are
forced to say, therefore, that these carriers
cannot have masses comparable with those of
the atoms, which likely take little part in the
phenomenon of electric conduction.
Perhaps it will be well to point out a very
noticeable contradiction in the theory as
developed here. The energy required to
raise the temperature of an electron 1 deg.
C. is a=1.5X10~16 ergs, about. So, if there
are 1024 free electrons in one cu. cm. of silver,
then to raise the temperature 1 deg. C. of
the electrons alone would require (1.5X
10-16X1024) = 1.5X108 ergs, or about 4 cal-
ories. But to raise the temperature 1 deg. C.
of one cu. cm. of silver requires only 0.6
calories. Hence, the electrons alone use more
energy, according to our theory, than do the
electrons plus the atoms by actual experiment.
(See note at the end of this article.) W.e
must therefore modify the theory, somewhat,
in order that it shall agree with the experi-
mental fact. This change is made as follows:
VI. MODIFIED ELECTRON THEORY
On account of this contradiction in the
case of specific heats, it is quite certain that
the electrons cannot be in thermal equilib-
rium with its surrounding metallic molecules.
In order to overcome this discrepancy J. J.
Thomson has modified the above theory, and
supposes that the electrons shoot from one
atom directly into another one, and thus
thermal equilibrium is not established between
the atoms and electrons. This motion is in
every possible direction, and hence, there is no
resultant flow of current. (The positive and
negative atoms form small electric doublets.)
If, however, a potential is applied to the wire,
then he considers the atomic doublets are
polarized, much the same as some people
consider the atoms of a permanent magnet
are polarized. The negative sides of the
doublets will be pointing in one direction,
and the positive sides in the other. The
result of this polarization is that more
electrons move in one direction under the
action of an electric force than in any other,
so that a passage of current occurs.
ELECTROPHYSICS
209
The final equations he obtained were:
_ 2 e2d p nb
a~ 9 (a) T
_ n b2 p a
K
a
3
3 b (a2) T
13
14
15
2 de2
Where (p) is the frequency with which a
doublet liberates electrons, (n) is the number
of polarized doublets per cu. cm., (b) is the
distance between the charges in the doublet,
and (d) is the distance between the centers of
the adjacent doublets. In a metal (b) is
nearly equal to (d) so that -j = 1 (approxi-
mately). Hence, in this case the ratio of the
conductivities on the new theory would be to
that on the old in the proportion of 9 to 8 as
given by equations (12) and (15). This
theory as well as the old is in agreement with
facts, but this theory tells us that this ratio
is not an absolute constant on account of the
factor ( -j J , which varies slightly for good con-
ductors and more for bad ones. This is in
agreement with fact.
VII. SUMMARY AND CONCLUSIONS
In this article have been mentioned the
principle of the conservation of electricity
and the three methods by which we con-
sider it to flow. It has been pointed out how
the electron theory applies to this important
principle in that it explains the separation of
the already existing charges. We have seen
that this theory deals with convection cur-
rents entirely, and that it explains fairly well
both qualitatively and quantitatively the
part now played by conduction currents,
about which we know nothing.
Although we have not developed an entirely
satisfactory electron theory, as has been
pointed out, yet, since we are learning more
about electrons and the laws which they obey
under all conditions, we are fairly certain that
we are advancing toward a more complete
understanding of the various pnenomena of
electric conduction.
Note : — A more rigorous treatment of
this problem along the same line for a steady
electric force (E) would lead to the result:
1 = 2,
N E e2h
\37T
(See G. H. Sirens, "Electron Theory of
Metallic Conduction," Phil. Mag. pp. 173-
183, Jan. 1915.) This is also the same result
that Lorentz obtained in his book on "The
Theory of Electrons." H. A. Wilson (Phil.
Mag. Nov. 1910) obtained still another
expression for (7) ; it differs, however, from
these only in the constant term. The above
equation is about twice as great as indicated
by equation (8). The above equation would
lead to a value for (Ar) about half as great
as does equation (8). Even this, however,
would not yield values for specific heats
that were in agreement with observations.
In connection with the question of specific
heats one may refer to Lindemann, "Theory
of Metallic State" Phil. Mag., p. 129, Jan.
1915. In this article the author states.
"The hypothesis put forward in this paper is,
that far from forming a sort of perfect gas the
electrons in a metal may be looked upon as a
perfect solid." Statements similar to this
indicate that our conception of the electron
itself has not changed so much as has our
conception of its intimate association with
matter.
210
GENERAL ELECTRIC REVIEW
LOCK ENTRANCE CAISSON FOR THE PANAMA CANAL
By Lewis A. Mason-
Assistant Designing Engineer in Office of the Engineer of Maintenance of the Panama Canal
Eight articles describing the devices controlling the lock machinery of the Panama Canal appeared in
the January, 1914, number of the General Electric Review; three articles describing the generation and
distribution of electric power for the Canal Zone were contained in the July, 1914, issue; and the towing system
and locomotives were described in an article in the February, 1915, issue. The following pages present an
interesting description of the mechanical, hydraulic, and electrical features of the lock entrance caisson which
is to be used at the locks to hold back the water and to pump out the chambers when repairs are to be made to
apparatus that is normally submerged. — Editor.
In connection with the various equipment
required for the maintenance of the Panama
Canal Locks, the Union Iron Works Company,
of San Francisco, has recently completed
a huge floating gate or caisson which will
be used for closing the entrance to any one of
the lock chambers of the Panama Canal
when it is desired to paint or make repairs
to any one of the mitering lock gates and for
similar use in the Balboa dry dock. It also
can be used for unwatering any one of the
lock chambers, for the purpose of making an
inspection of the culvert, rising stem gates,
or cylindrical valves.
The clear width of the lock chambers is
110 feet. Beyond the line of the emergency
dams, the approach is widened by an offset
of three feet on both sides. The shoulders
so formed, with the connecting horizontal
sill across the bottom of the chamber, afford
a frame or seat into which the caisson is
fitted to dam off the interior of the lock
chamber.
This is accomplished by floating the caisson
from its mooring position by means of a tug
boat, or other motive-power water craft, to
the particular lock chamber entrance which
is to be dammed. After being placed in its
recess across the lock entrance, water will
be let into the lower compartments, thereby
causing it to sink until properly seated.
When this is completed, an electric power
cable will be connected from the main power
cables, provided within the lock walls, to
a terminal box located on the top deck and
at the end of the caisson. This point is
electrically connected through the switch-
board within the caisson to the various
motors that operate the pumps. The pumps
will then un water the lock chamber, and the
water pressure on the outer side of the caisson
will force it securely against its seat in the
masonry.
When it is desired to remove the caisson,
the lock chamber will first be filled with
water by opening the culverts within the
lock walls. This will balance the water
pressure on both sides of the caisson, at
which time the water within it will be pumped
out, thereby causing it to float and allow
it to be towed awav.
Fig. 1.
An End View of the Caisson Taken but a Short
Time Before it was Launched
The caisson is designed for use at all of
the lock entrances, and has a light-draft of
32 feet to permit its being handled convcn-
LOCK ENTRANCE CAISSON FOR THE PANAMA CANAL
211
a
E
w
4
>.
a
[0
212
GENERAL ELECTRIC REVIEW
iently through the various locks. The top
of the sill at the Pacific end of the Mira-
flores locks is 50 feet below mean sea-level.
and with the tidal fluctuation which raises
the level of the water as high as 11 feet
above mean tide this requires that the caisson
be sunk to a draft of 61 feet when used at
high tide. Provision for a proper freeboard
requires an aggregate depth of the structure
of 66 feet. The achievement of statical
stability at the various depths of immersion
without undue bulkiness or excessive weight
in the different drafts makes the caisson of
especial interest.
In form, the bottom of the hull is convex,
the ends pointed, and the sides sloped inward
from the maximum width of 36 feet, at about
one-third the way up from the keel, to a
breadth one-half as great at the top deck.
framing built intercostally and extending
from the keel to the top deck transmits the
panel loading to the various horizontal
decks and breasthooks. The essential features
of the structure are the transverse and
longitudinal framing, with bulkheads; the
horizontal plate decks, girders and stringers;
the girders at the vertical ends and along
the keel; the end breasthooks; and the sheath-
ing plates to cover the skeleton for forming
the hull proper. These elements are made
from open-hearth structural steel.
The transverse framing system consists
of nine cross-frames, spaced 12 feet apart
from the middle of the caisson and extending
to its entire height, and the intermediate
frames, spaced two feet apart between the
main cross-frames. All are built intercostally
between the five horizontal decks.
HORIZONTAL W T PLATE DCCK
Fig. 6. Plan View of the 37 Ft. Deck Showing the Location of the Electrical Apparatus
A typical transverse cross-section of the
caisson resembles in outline the vertical
section through a pear-shaped, carbon-fil-
ament electric globe. The horizontal length-
wise sections vary with the inward slope of
the sides; in general, they resemble those of
the ordinary vessel of commerce, and may
be described as flattened ellipses, blunt at
the ends in order that they may connect to
the vertical end-girders, or stems. The
maximum length of the caisson from vertical
end to vertical end is 112 ft. 6 in. The
extreme length is 113 ft. 10 in. This includes
the timber cushions.
It is ^desired that the side walls of the
locks shall carry practically all the static
load from the caisson when it is supporting
the water pressure. Accordingly, there are
a number of horizontal decks and breasthooks,
or short decks, between the main decks at
'he ends which carry the hydrostatic load
to the vertical ends A system of vertical
The last cross-frame at each end is made
water-tight, by the same principle as is used
in merchant ships, in order to form peak
trimming tanks for maintaining a level
keel when placing the caisson in its recess
across any one of the lock chambers. The
seven other cross-frames serve as swash
bulkheads for controlling the water within it.
The five horizontal decks are located at
the respective following distances above the
centerline of the keel plate: 16 ft., 25 ft., 37 ft.,
49 ft., and 65 ft. The 16 ft. and 25 ft. decks
are entirely plated over with the exception
of openings left to allow for the removal of
pumps, valves, etc.
The 37 ft. deck is entirely plated over
and is made absolutely water-tight. It
has water-tight manholes for gaining access
to the various compartments below and
water-tight hatches for the removal of the
pumps or valves in case it is necessary to make
repairs, etc., to them. This deck is made of
LOCK ENTRANCE CAISSON FOR THE PANAMA CANAL
213
sufficient strength to withstand a hydrostatic
head of 25 ft. Upon it is placed the various
motors for operating the pumps, the switch-
board, the water gauges, the chain lockers,
etc. The horizontal deck 49 ft. above the
center line of the keel is of the open-truss
construction, and has diagonal bracing for
the central two-thirds of its length and
plating covering for the ends. The top deck,
65 ft. above the center line of the keel, is
plated over from end to end and has openings
for manholes, skylights, deck cranes, com-
panionways, ballast compartment vent pipes,
and scuppers.
The breasthooks, or short decks, of which
there are six in number, serve to transmit
part of the loading from the horizontal
decks to the vertical end-girders. In addition
to the decks and breasthooks, there are
located equidistant between the keel ■ and
the 16 ft. horizontal deck two lines of inter-
costals extending longitudinally and securely
riveted to the transverse frames and to the
sheathing.
For transmitting the end reactions from
the horizontal decks and breasthooks to the
vertical end-girders, or stems, steel castings
are provided and made to fit very closely
between the horizontal decks and breast-
hooks and the vertical ends, to which they
are securely riveted.
The skeleton or framing is entirely sheathed
over with steel plating worked in in-and-out
strakes, running longitudinally over the
transverse frames, making lap seams and
butt joints which have double splice plates.
Around all of the openings in the plate
decks, and in the sheathing, doubling or
reinforced plates are fitted. To protect the
sheathing when maneuvering the caisson
near the lock walls, fenders are provided
on the exterior of the sheathing along the
25 ft. and 49 ft. levels, and vertical fenders
are placed between the horizontal ones, at
seven of the amidship cross-frames. The
fenders are built of bent plates, securely
riveted and calked to the sheathing plates;
the space between is filled with "Petro-
lastic" cement — a by-product of crude oil.
Its specific gravity is 1.02; its expansion
at a temperature of 110 deg. is 0.0018, and its
melting point lies between 150 and 200 deg. F.
Because of the long towing distance from
the place where the caisson was built two
large towing rings are provided and are
securelv fastened to the sheathing and to
the 43" ft. breasthook at both ends and on
each side of the caisson. As a means for
towing the caisson from its mooring position
to any one of the lock sites, there are three
towing rings provided which are securely
riveted to the sheathing along the level of
the 37 ft. horizontal deck on both sides of
the caisson.
Along the exterior of the keel and the
vertical ends, steel castings (the cross-sections
of which are channel-shaped) are provided
and are securely riveted to the keel, vertical
ends, and sheathing. Into these there are
neatly fitted and bolted British Guiana
greenheart and Australian ironbark timber
cushions. There is also a cushion fitted
along the sides of the keel and along the sides
of the vertical ends, which are also made of
the timbers mentioned. These cushions
come into contact with the caisson's seat
provided in the lock chambers and form a
water-tight seal.
Miscellaneous Fittings
Through a water-tight companionway on
the top deck a stairway leads down to the
37 ft. operating deck. Ladders from this
deck are provided for gaining access to the
various lower compartments. Ladders are
provided in the end peak trimming tanks,
extending from manholes in the top deck
to the 16 ft. horizontal deck, or bottom of
the trimming tank. For getting aboard the
caisson a ladder is provided on each side
and is attached to the sheathing. It extends
from the level of the 32 ft. water-line to the
top deck.
There are three portable cranes located
on the top deck, one at each end of the
caisson and one in the center. The two end
cranes are similar in construction, and are
capable of raising or lowering a load of 3000
lb. at a radius of 14 feet by two man-power.
These cranes are used for lifting various
loads onto the caisson from the lock walls,
as well as for handling electric power cables.
The middle crane is heavier in construction
than the end cranes and is capable of raising
or lowering a load of 3000 lb. at a radius of
25 feet by two man-power. This crane will
handle the pontoon (stowed on the top deck )
when it is desired to make the pump suction
extension attachments, and is capable of
lifting the top sections of either one of the
two skylights. Hand-operated deck capstans
are provided and placed at each end of the
caisson on the top deck. The capstans are
installed for the purpose of warping the
caisson into its recess. Each is capable of
withstanding a pull of 10,000 pounds.
214
GENERAL ELECTRIC REVIEW
Two ventilators, each 16 inches in diameter,
with hoods and turning mechanism of the
standard navy type, are placed on the top
deck for ventilating the operating room.
Both of these ventilators extend from the
top deck to a short distance below the 49 ft.
horizontal deck. At the end of one is fitted
and connected an electric-driven multivane
exhauscer to supply a means for assisting
the air to escape from the various water-
ballast compartments when they are being
filled. There are eight 6-inch diameter air
vents, extending from the various ballast
compartments to the top deck, and one air
vent in each of the end peak trimming tanks
placed in the top deck. Two skylights 8 ft.
by 16 ft. in size are fitted in the top deck,
symmetrical about the axis of the caisson.
The tops are made in two parts, for easy
removal. In each top section there are
openings fitted with water-tight covers,
which can be opened or closed by means of
a raising apparatus located and secured
under the top deck and operated by means
of a handwheel from the operating deck.
To increase the draft of the caisson to a
depth sufficient to insure its stability at
light draft, without water in the ballast
compartments, approximately 800 tons of
permanent ballast, composed of iron punch-
ings, etc., and concrete, is placed in the
bottom.
An anchor chain, made of material 1^
inches in diameter, is provided at each end
for mooring the caisson to floating buoys
in the fresh water lakes when it is not in
service. The anchor chains are raised or
lowered by means of the hand-operated
winches, located at each end on the top deck.
Pumping System
The main pumping system consists of
four vertical-shaft, bottom-suction type cen-
trifugal pumps which, with their individual
driving motors, constitute four units. Each
unit is designed for an average capacity of
13,000 g.p.m. against a maximum head of
70 ft., this capacity being the average to
prevail between heads varying from zero
to the maximum (7(1 ft.). The suction
opening of each pump is 22 inches in diameter
and the discharge 20 inches.
From the illustration of the outline drawing
of the complete pumping unit, it will be seen
that the intermediate shaft connecting the
pump to the driving motor is supported by
an intermediate guide bearing. The drawing
at the thrust bearing, which
carries the load of the revolving element, is
located at the motor deck and is contained
in a base-plate which, in turn, acts as a support
for the motor itself. The thrust bearing is
of the ball-bearing type, and is made self-
oiling by means of an oil pump which takes
its supply from a revolving pin located
beneath the bearing and which returns the
oil to a reservoir that surrounds the ball
bearing. The intermediate guide bearing
and the pump bearing are water lubricated.
The pump casing, together with the impeller,
is made of cast-iron and' is bronze lined at the
points where the impeller comes in contact
with the casing, also where the shaft passes
through the bearing and the stuffing box.
The pumping plant is employed for a
double purpose: first, for emptying the
water ballast from the caisson when it is to be
removed from its position against the sill
and, second, for unwatering all lock chambers
except those which can be emptied by gravity.
(The only chambers in the Panama Canal
that can be emptied by gravity are the upper
lock chambers at Gatun; the elevation of
the floor there is 13% ft. above sea level.)
The capacity of the pumping system is
designed so that it will pump out, in not
more than 25 hours, all of the water in the
upper and lower chambers of one flight of the
Miraflores locks between mean sea-level
(elevation zero) and the top of the sill of
the lower chamber ( — .30 ft); the tidal level
to be at elevation zero when the pumping
is begun and the tide to be rising. The
total quantitv to be pumped is estimated
at 10,285,000" cubic feet. Of this quantity
5 IS, 000 cubic feet is allowed for leakage
through the various cylindrical and rising
stem gate valves in the lock culverts, as well
as allowances for leakage around the sills of
the mitering lock gates arid the caisson sill.
The pumps will pump out, when operating
at any stage of the tide, the water on the
floors of the lower lock, from the top of the
sill (-50 ft), to 2 ft. below it. To do this
22-inch suction pipes are attached to the
auxiliary suction inlets of the caisson, and
these extend to and into the nearest lateral
culvert in the lock chamber. When not in
service, the suction extension pipes, of which
there are four in number, are stowed in
cradles provided for the purpose on the 49 ft.
horizontal deck. They are handled by the
large deck crane located in the center line
of the top deck.
An electric-driven horizontal centrifugal
pump, with a 3V2 in. diameter suction and
LOCK ENTRANCE CAISSON FOR THE PANAMA CANAL
215
a 3 in. discharge, is located on the operating
deck. It has pipe connections leading from
the suction to a manifold and from the
discharge to another manifold. From these
manifolds piping is connected to the end
peak trimming tanks, to the deck scuppers,
to the sea, and to a mud-slushing device. The
mud-slushing device is intended to remove
mud from the caisson sill in an endeavor to
prevent it from adhering to its seat when in
the act of rising. The pumping equipment
was manufactured by Henry R. Worthington,
Harrison, N. J.
Electrical Equipment
The main pumps are driven by 200-h.p.
vertical induction motors, wound for 25
cycles, 2200 volts, three-phase, and which
have a speed of 750 r.p.m. The motors for
operating the ventilating fan and the 3-inch,
or auxiliary pump, are induction motors of
the horizontal type, and arc wound for 25
cycles, 220 volts, three-phase. For lighting
purposes, 110 volts are used. All of the elec-
tric motors (with the exception of the one for
driving the multivane exhauster, and their
controlling switchboard are located on the
operating deck, 37 ft. above the base line.
All of the valves in the pumping system are
operated from this same deck.
The switchboard consists of five panels,
and, from right to left, facing the front of
the board is arranged as follows: One,
three-phase, three-wire, incoming line panel;
two, three-phase, three-wire, double-circuit
motor panels; one, three-phase, three-wire,
motor feeder and lighting, transformer panel ;
and one, single-phase, two-wire, ten-circuit
lighting panel. Grille work having hinged
doors provided with locks enclose the ends of
the board and prevent access to its rear
except by those authorized persons who are
furnished with a key. From the top of the
panels, and extending upward for some
distance above the busbars, grille work is
also provided.
The arrangement of the switchboard ap-
paratus, including bus and connection bars,
is especially compact and is supported
in a most substantial manner. This can
easily be seen from the back view of the
installation. The bus and connection bars
are of three-quarter inch solid copper rod,
the connection bars being soldered into
terminals which are fastened to the busbars.
The busbars are supported to the pipe frame-
work by special bus supports designed for
use in connection with this and other Panama
Canal switchboard installations by the Gen-
eral Electric Company of Schenectady, N. Y.,
which also supplied the electrical equipment
for the caisson. The framework itself is of
standard type, but was specially galvanized
and painted to enable it to withstand the
^FLr^x
t
3Ft9'iln
Z4Ft 7,1/n
Fig. 7.
Elevation of the Pump Motor, its ]
Bearings and the Pump
Shafting,
particularly severe climatic conditions pre-
vailing on the Isthmus.
Another feature of interest is the method
employed for disconnecting the oil switches
from the circuit, when it is desired to remove
216
GENERAL ELECTRIC REVIEW
Fig. 8. Rear View of the Operating Switchboard
the oil cans or otherwise to do work about
the back of the board. By means of handles
located below the oil-switch operating handles,
a switch can be placed in or disconnected
from its circuit at will whenever the oil switch
contacts are open, but at no other time.
The pipe framework supports
vertical metal guides, which carry
the oil-switch operating mecha-
nism, and a slate base which
forms a portion of the switch-
board panel. By means of a lever
and toggle mechanism, the oil
switch, the slate base, and the
other parts carried on the guides
may be raised or lowered.
Above the oil switch and mounted
on the pipe framework is a station-
ary base which carries the discon-
necting studs of the oil switches.
The current leads are connected
to the tops of these studs; and at
the bottom of each stud is a flared
contact which engages with a wedge-
shaped contact on the upper end
of the oil switch stud, and thus
places the switch in circuit. Moulded
insulating shields surround (except
at the bottom) each disconnect-
ing contact and extend sufficiently
below the contact fingers to insu-
late the fingers and prevent acci-
dental contact, whether the oil
switch is or is not disconnected from
the circuit.
The oil switch can not be con-
nected to or disconnected from the
circuit except when it is in the
open position, which guards against
the circuit being closed or opened
by the disconnecting contacts. This
feature is made possible by an inter-
lock that prevents the oil-switch
lifting and lowering handle from
being operated unless the oil-switch
operating handle is in the open
position. This oil switch arrange-
ment is the development of a patent
by Mr. E. Schildhauer, Electrical and
Mechanical Engineer of the I.C.C.
The electric current is supplied
to the motors in the caisson from
the main power cables installed
within the lock walls. The motors,
therefore, cannot be operated until
the caisson is seated in one of the
recesses provided for it in the locks,
or when at its mooring position in Gatun
Lake or Miraflores Lake.
The purpose for having a power connection
at its mooring position is to permit the opera-
tion of any one of the pumps for examination
and inspection.
Fig. 9. Front View of the Operating Switchboard
217
PRACTICAL EXPERIENCE IN THE OPERATION OF
ELECTRICAL MACHINERY
Part VI (Nos. 32 to 35 inc.)
By E. C. Parham
Construction- Department, General Electric Company
(32) EXCESSIVE CONTACT-SHOE PRESSURE
Motor overloads are sometimes due to
rather unexpected causes. Electrical inspec-
tors are prone to exhaust the possibilities
of electrical diagnosis, in times of trouble,
before looking for mechanical irregularities
that would account for unusual actions in
electrical apparatus.
An inspector was called to find out why the
starting resistor of a certain three-phase
induction motor driving a monorail crane
would get white hot whenever an effort was
made to operate the crane.
The crane had just been installed and it
was, of course, to be expected that the start-
ing resistors would heat somewhat more than
normally, because the crane action is stiff
and the numerous bearings have not found a
seating. In this particular case, however,
the extent of the heating, considering the
promptness with which the crane would
start, suggested a condition more serious
than initial stiffness.
In order to make an electrical test of the
crane wiring, it was deemed advisable to
insulate the crane from its source of power by
inserting thin sheets of insulating fiber
between the three overhead contact rails and
the corresponding contact-shoes which are
pressed against the rails by means of springs.
To pry the shoes down from the rails required
two men with two four-foot jimmies. What
springiness there was to the contact-shoe
action was due to upward pressure springing
the 2 in. by ?g in. T-sections of which the
contact rails were made. When the shoes
happened to be directly under an insulator,
there was no spring action at all. This con-
dition of affairs was due either to the shoe-
stands being too high or to the contact
rails being too low; whatever was the
cause, the crane was being continuously
subjected to the retarding action of a strong
track brake.
Considering the fact that some high-speed,
third-rail, electric railway cars use shoe
pressures that do not exceed 30 pounds per
shoe, the load to which the two 3-h.p. crane
motors were being subjected may be appre-
ciated.
(33) ELECTRIC BRAKE ADJUSTMENTS
It would seem that the harder the service
and the more exacting the local conditions
to which electrical appliances are subjected,
the greater the equipment is neglected.
Where fastenings are most likely to be shaken
loose by unavoidable vibrations, inspections
for loose parts seem to be most lax. Really,
the opposite should be true. These impres-
sions are justified by the frequency with
which solenoid-braked foundry crane-hoist
motors giving slight troubles are permitted
to become serious troubles simply for want of
the prompt detection that would result from
regular inspection for loose parts.
An operator once complained that his
crane-hoist motor had "stuck with a pot of
metal in the air." Inspection showed that
if the motor had not stuck, it probably would
have been wrecked. The normal adjustment
of the air-gap of the solenoid brake was from
% in. to 1 in. The gap had been allowed to
become 3 in. As a result, the hammering at
the brake end of the motor, when the brake
operated, loosened every bolt on that end of
the motor. The end-shield bolts had worked
entirely out, notwithstanding the fact that
they had been secured by lockwashers, which
had let the rotor down onto the stator.
Fortunately the revolving magnetism did
not provide sufficient torque to turn the rotor
in this locked position; otherwise both rotor
and stator probably would have been ir-
reparably damaged.
The adjusting mechanism of a solenoid
brake is not complicated, and the attention
that it requires is not the attention of an
electrician but that of a crane-man. Nearly
every concern of sufficient size to use a power
crane has at least one mechanic qualified to
detect when a piece of apparatus is shaking
itself to pieces. Most operators, however,
seem to dissociate electrical apparatus from
218
GENERAL ELECTRIC REVIEW
every-day common sense relief measures
which are always worth at least a fair trial.
(34) ROTOR RUBBED STATOR
If the fuses used are not too large, the first
indication that an induction motor's rotor is
rubbing its stator, may be the melting of the
fuses because of the increased load incident
to the additional mechanical friction.
A certain 5-horse power, three-phase induc-
tion motor sometimes would start upon
applying the power and sometimes it would
not start; but the stator would give the
characteristic single-phase hum and the
rotor would oscillate through a very small
arc suggesting that it might start in either
direction. All of the windings and wiring
proved by test to be free from open-circuits,
grounds, and wrong connections, and the air
gap (which was normally 0.015 in.), freely
admitted a 0.01 in. "feeler" all around the
rotor and at both ends. These tests were
made with the motor disconnected by the
removal of its pinion. Upon reinstalling the
pinion and wedging the gear, so that it could
not move the load, and then applying the
power and observing the rotor closely, it
could be seen that upon each application of
the power the rotor would move upward in a
direction corresponding to the direction of
the force applied to the gear by the pinion.
On most trials, with the wedge withdrawn,
the movement was insufficient to cause the
rotor to touch the stator and on such occasions
the rotor would start, and after it was in
motion no irregularity could be observed.
Now and then, however, the rotor would rise
far enough to stick and it would start only
upon advancing the controller to farther
notches. The lifting of the rotor indicated
no bearing wear, but by removing the rotor
and linings a test of their fit showed a slight
wear just at the place that would account
for the symptoms noted. This slight wear,
probably in conjunction with a slight eccen-
tricity in the rotor core, accounted for the
fact that sometimes the motor would start
and sometimes it would not. The rotor sur-
face had so much oil on it that a slightly
rubbed place could not have shown very
plainly, but such a place undoubtedly existed,
and when this place was in line with the bear-
ing wear at the time of applying power the
rotor would stick.
The lesson to be drawn from this experience
is that the air gap of a motor at rest may be
thoroughly correct as far as a feeler will
indicate, but, if the bearing wear is in the
upper part of the linings and the direction of
rotation is such as to force the rotor upward
at starting, the rotor may strike the stator.
(35) JERKY MOTOR ACCELERATION
In some classes of foundry work that is
handled by electric cranes a smoothly grad-
uated motor acceleration is essential; espe-
cially is this the case during the period of
separating the cope from the flask, for then
an impulse may shake down sand and destroy
the mould. The binding between the cope
and the flask complicates matters, because it
introduces a condition where a comparatively
strong pull must be immediately followed by
an easing off, which is not always to be
obtained satisfactorily. Where a variety of
work is to handled smoothly, it is necessary
to use a controller that has many notches.
Where the weights to be handled are limited
to a few standards, the resistance graduations
can be refined to suit the weights involved.
In either case, wide fluctuations in the
supply voltage make it difficult to get equal
degrees of smoothness for all weights and
voltages.
An electric crane, the hoist control of which
had been entirely satisfactory for a long time
but which had been getting more and more
jerky during a period covering about two
years, finally became impracticable and an
inspector was called in. The crane evidenced
good care, as far as the crane man was con-
cerned, and the controller fingers and con-
tacts were in excellent condition. Being
convinced that neglect was not the cause of
the impulsive acceleration, the resistor was
next investigated. Tests with a voltmeter
showed widely varying voltage drops per
section of the resistor, and one of the sections
caused no drop at all. The resistor was
housed in a perforated box that served also
as a seat for the crane man. Upon removing
the box cover and sides to inspect for bad
connections and for broken and short-cir-
cuited grids, the causes of the^-impulses be-
came evident — they were two files, a screw-
driver without a handle, a cold chisel, an
oblong roll of copper wire, two carbon
brushes, and seven perfectly good cartridge
fuses. Without these the resistor was all
right, as was demonstrated by a trial. To
prevent a repetition of such a condition in
the future, a piece of one-quarter-inch mesh
wire netting was fastened to the under side
of the resistor cover before replacing it.
219
A HYDRO-ELECTRIC INSTALLATION ON A COFFEE PLANTATION
By J. H. Torrens
The author gives a brief account of the conditions existing in Guatemala where native labor still
performs many operations now done by machinery in more developed countries. He then proceeds to give
a description of the hydro-electric plant of the Finca Ona Plantation which is the largest in Guatemala. The
process of preparing coffee for the market and the different operations carried out by the aid of electric
motors are described. — Editor.
Guatemala is the largest, the most thickly
populated, and probably the furthest devel-
oped of any of the Central American Repub-
lics. Although more than the usual quota
of tropical products are raised there, the
industry of coffee growing is the one of
paramount importance.
Before entering into a description of
the hydro-electric installation that will be
considered, a few remarks concerning the
geography of Guatemala and the conditions
existing there will be of educational service
while they own as much as 85 per cent of the
coffee estates.
The primitiveness of the transportation
facilities will be easily comprehended when
it is considered that most of the freight
is carried on the backs of Indian porters.
These bearers will jog along easily at a five-
mile-an-hour pace with a pack of 150 lb.
and are ably capable of managing packs
weighing as much as 200 lb.
The work on the coffee plantations is
carried on by native Indians, and these
Fig. 1. View Showing the Old Rope Drive Transmission
, Fig. 2. Hydro-electric Power Plant at Finca Ona
in presenting a conception of the great and
practically unentered field of coffee plan-
tation electrification.
American capital is responsible for the
railways which connect Puerto Barrios of
the east with the capital, Guatemala City,
and witli San Jose and Ocas on the Pacific
coast. Except for the omission of a few-
miles of track between Coatepeque and
Pajapita (as a matter of fact this gap is now
nearly bridged) the Pan-American Railroad
makes it possible to travel from New York
City to the capital of Guatemala, which is
at an altitude of 5000 feet.
The commerce of the country is largely
under the control of European countries; and
it is said their investments in coffee plan-
tations alone amount to about $60,000,000,
receive about eleven cents a day for their
labor.
Located in the western part of the country,
among the foothills of the Sierra Madre
Range at altitudes of from 2000 to 4000 feet,
are some of the world's best coffee plan-
tations. The climate in that section is par-
ticularly suited to coffee growing. The Finca
Ona plantation, which is situated in that
vicinity, is one of the largest in Guatemala, its
annual production being about 1,000,000 lb.
The owners of this estate recently decided to
adopt electric drive for the various machines
used in preparing coffee for the market, and,
as the conditions on this plantation may be
considered to be typical of others throughout
the coffee growing districts a description of its
electrification should prove interesting to
220
GENERAL ELECTRIC REVIEW
Fig. 3. View of a Transmission Pole and a Group of
Coffee Trees
Fig. 5. Revolving Drum used for Drying the
Coffee Berries
■■K
Fig. 4. Electric Driven Retrilla or Coffee Huller
Fig. 6. Method Employed in Mounting the Motors
HYDRO-ELECTRIC INSTALLATION ON A COFFEE PLANTATION 221
the coffee planter, to the manufacturer of
coffee-milling apparatus, and to the electrical
engineer as well.
The original source of power for the planta-
tion was a Pelton waterwheel, for which it
was necessary to bring water a distance of
nine miles in a ditch. The difficulties which
arose in the wet season from this method of
water supply can be easily imagined.
The power generated by the waterwheel
was then transmitted 600 ft. by a rope drive.
Two steam engines, one of 25 h.p. and the
other 60 h.p., supplemented the waterwheel.
The extremely difficult conditions of trans-
portation from the railroad 30 miles away
rendered the cost of imported fuel almost
prohibitive, while the practice that had
cleared all timber from valuable coffee
lands made wood for fuel quite scarce.
Consequently, power generated by steam was
very expensive.
A site at a convenient water-fall, which
was about a mile from the factory, was
chosen for the location of the electric
generating station. From there the power
is transmitted to the various motors and
lights.
The hydraulic development was designed
for about 500 cu. ft. of water per minute at
an effective head of 270 ft., through 780 ft. of
18 in. pipe to two Pelton waterwheels mounted
on same shaft and rated at 230 h.p., 450 r.p.m.
A Pelton self-contained, oil-pressure governor
regulates the speed by the deflecting-hood
method.
The electrical apparatus in the power-
house consists primarily of one revolving-
field, 16-pole, 150-kv-a., 450-r.p.m., 2300-volt
alternator direct-coupled to the waterwheel.
The exciter is mounted on the same shaft.
Frequent earthquakes make it imperative to
mount the machines in a very substantial
manner on heavy stone and cement founda-
tions. All wiring is carried in conduit to a
blue Vermont marble switchboard mounted
on standard pipe framework. There are two
feeder panels, one supplying 120 kw. at 2300
volts to the main factor}* over a transmission
line about a mile long, the other supplying
a branch factory about one-half mile away
with 15 kw. at 2300 volts. Both lines are
thoroughly protected from lightning, first,
by a well-grounded barbed-wire running
from pole-top to pole-top throughout the
entire distance, and, second, at both ends
by the latest type of aluminum-cell elec-
trolytic lightning arresters. For transmis-
sion poles, 35-lb. iron rails 30 ft. long were
used. These were "footed" five feet in the
ground in concrete.
At the factories the power is transformed
to 220 volts for both motors and lights. All
motors are of the three-phase squirrel-cage
Fig.
Front View of the Distribution Switchboard
type, complete with starting compensators,
and designed for a no-load speed of 600 r.p.m.
To follow the coffee through the various
processes in its preparation may be interesting
as well as illustrative of the application of
the motor drive. A 20 h.p. induction motor
drives a battery of peeling machines to which
the red coffee berries are fed as they come
from the trees. These machines remove the
tough outside skin and separate the two
berries, or halves, which then go to the
fermentation tanks where they remain in
water for about 60 hours.
At the end of this time, the thin membrane-
like skin about the berries begins to loosen.
All the good berries (those which float are
not good) are taken out and placed in the
sun on the "patio" where they are dried (by
constant turning) to the extent that they
cease to adhere to each other. This process
requires several hours.
After the berries are superficially dried
in this manner they are placed in a large
sheet-iron cylinder called "the drier."
Those at Ona are about 6 ft. in diameter
and 12 ft. long and through them steam-
heated air at about 60 deg. C. is forced by
a blower. In this cylinder the coffee is
continuously revolved at 15 r.p.m. for 24
hours; this operation is a particular one and
222
GENERAL ELECTRIC REVIEW
requires close attention. It leaves these
drums perfectly dry. and is then raised to
the top of an ingenious machine which
removes and carries away the hulls, polishes,
and cleans the berries. From here the coffee
is carried to the classifying and separating
machines, the better grades being further
sorted by hand labor. Each drier, huller,
and separator has its own motor, the respec-
tive capacities being 10, 20, and 10 horse
power. All the starters are conveniently
grouped near the main switchboard, where
each motor has also an ammeter.
Among other useful motor applications on
the plantation might be mentioned a 1.5-h.p.
motor, direct-geared to a Goulds' triplex
pump which raises water 180 ft. for general
use. This motor is operated also from the
main switchboard. It is only necessary to
visit the machine from time to time to see
that the bearings are properly lubricated.
A 2 h.p. motor which drives an ice machine is
another valuable adjunct.
All the electrical apparatus is three-phase.
(iO-cycle, and was manufactured in America.
Because of the crude and primitive methods
by which the apparatus would have to be
transported, it was necessary that the design
employed be one that would permit of the
apparatus being conveniently dismantled
and, in addition, limit the maximum weight
of a single piece to 1500 lb. Transportation
part of the way was carried on by teams of
bulls hauling a crude cart which was arranged
so that when its two rear wheels were removed
the rear half rested on a pair of sled runners.
These latter were used to secure a braking
action on the steep down grades. In other
places the apparatus was carried on the backs
of Indians. Thirty men carried a 40-kw.
transformer weighing 1500 lb. in this
manner.
The best construction possible was used
throughout, and the work of installing all
the apparatus was carried to completion in
about three months.
The electrification holds a rather unique
position as it is one of the first installations
of American apparatus in that country
where European apparatus and interests
predominate. It is also the first electrifica-
tion of a coffee plantation of importance and
is consequently being closely watched.
Undoubtedly the continuance of the un-
usually successful operation already enjoyed
by this plantation, since its electrification, will
induce other coffee growers to duplicate the
change on their plantations.
NOTES ON THE ACTIVITIES
OF THE A. I. E. E.
Third Mid- Winter Convention
On Wednesday, Thursday and Fridav.
February 17th, ISth and 19th, the third
New York Mid-Winter Convention of the
American Institute of Electrical Engineers
was held at Institute headquarters, Engineer-
ing Societies Building, 29-33 West 39th
Street, New York.
A very attractive program was prepared,
including a number of pleasure events as
well as an interesting selection of papers.
The following papers were presented :
The Characteristics of Electric Motors In-
volved in their Operation, by D. B.
Rushmore.
Effect of Moisture in the Earth on Tempera-
ture of Underground Cables, by L. E.
Imlay.
Oil Circuit Breakers, by K. C. Randall.
Comparison of Calculated and Measured
Corona Loss Curves, by F. W. Peek, Jr.
A 100,000-Yolt Portable Substation, by
Charles I. Burkholder and Nicholas
Stahl.
Distortion of Alternating-current Wave Form
Caused by Cyclic Variation in Resistance,
by Frederick Bedell and E. C. Mayer.
Dimmers for Tungsten Lamps, bv Alfred E.
Waller.
Searchlights, by C. S. McDowell.
Electrical Precipitation — Theory of the Re-
moval of Suspended Matter from Fluids,
by W. W. Strong.
Theoretical and Experimental Considera-
tions of Electrical Precipitation, by A. F.
Xesbit.
Practical Applications of Electrical Precipi-
tation, by Linn Bradley.
Electrical Porcelain, by E. E. F. Creighton.
Institute Library
The American Institute of Electrical Engi-
neers, the American Society of Mechanical
Engineers, the American Institute of Mining
Engineers and the United Engineering Society
have a joint library consisting of their
individual collections. This library is located
on the two upper floors of the Engineering
Societies Building. The library is conducted
as a free public library of reference, and now
contains about 00,000 volumes, and over
000 sets of periodicals.
NOTES ON THE ACTIVITIES OF THE A. I. E. E.
223
One of the most important features of the
library is the research department, which
places the facilities of the library at the
disposal of out-of-town members. Upon
application to the library, bibliographies are
prepared on any desired engineering subject,
and abstracts, translations or photographs are
furnished. A small fee is charged for tnis
work.
LYNN SECTION
A Modern Army in the Field, by Major Shipton,
U. S. A.
The meeting of February 3rd was attended
by about 390 members and guests. The
speaker of the evening was Major J. A.
Shipton, U.S.A., Commandant at Ft. Terry,
New York. His subject was the Conduct of
a Modern Army in the Field.
The structure of an army division was
described, this being the smallest unit com-
plete in itself, containing elements of all
branches of the service; viz., infantry,
artillery, signal, engineering, aerial, hospital.
This unit contains 22,000 men, and 750
officers. Details were given in order to
bring out the definiteness of the structure
and purpose of the various elements. The
manner of maintaining communications with
the base by means of commercial railways,
military railways and wagon trains was
illustrated. The completeness and defi-
niteness of the organization were particularly
impressive, as illustrated by the specific
duties of the various officers and groups in
the general structure of the army.
Next methods of issuing orders were
described and here again the absolutely clear
cut manner of issuing commands by five
paragraph typewritten orders added further
to the impression of the absolutely methodical
manner of conducting military operations.
Finally the manner of conducting the army
at the time of an offensive engagement was
outlined.
The lecture maintained the interest of the
whole attendance and was very instructive.
Numerous lantern diagrams were used to
make the points under discussion clear.
Theories of Electricity and Matter, by Professor
Comstock
The lecture by Professor Comstock, of the
Massachusetts Institute of Technology, on
January 6th, so interested the membership
that in response to numerous requests a
special course was arranged for. On Tuesday,
February 9th, the first of the series of four or
five weekly lectures on Modern Theories of
Electricity and Matter was given by Prof.
Comstock.
Lectures for the Near Future
On February 17th, the Lynn Section
listened to a most interesting talk on the
Characteristics and Uses of Storage Batteries,
by Mr. J. Lester Woodbridge, Chief Engineer
of the Electric Storage Battery Company.
The talk was illustrated by apparatus
especially arranged for demonstration pur-
poses. A more detailed statement will
occur in the next issue.
On March 3rd, Mr. A. G. Davis, the head
of the Patent Department, General Electric
Company, will speak of the Relation of
Patents to Industrial Progress.
On March 17th, Dr. W. P. Davey, of the
Schenectady Research Laboratory, will speak
on Recent Development in X-Ray Work.
PITTSFIELD SECTION
Electric Waves, by Professor Franklin
Announcement was made in the February
Review of the Paper by Prof. W. S. Franklin,
of Lehigh University, on the subject of
Electric Waves, given January 7th.
The lecture covered the ground of Professor
Franklin's recent Institute paper on Line
Surges, but especial attention was given to
the underlying mathematics of that paper.
Indeed the primary object of the lecture was
to illustrate the use of differential equations
in physics by setting up the differential
equations of wave motion and integrating
and interpreting them in their application
to some of the simplest transmission line
phenomena.
The lecturer pointed out the two cases in
which the differential equations of wave
motion on a transmission line are integrable
in finite terms, namely: (a) the case in which
wire resistancejmd line leakage are zero; and
(b), the case in which voltage and current are
assumed to be everywhere harmonic and
synchronous. The latter case leads to the
ordinary problem of the alternating current
transmission line in its steady state, and
the former leads to an approximate solution
(approximate because of the neglect of wire
resistance and leakage) of the problem of
transient effects on a transmission line. The
lecture was devoted entirely to the latter
case.
Theories of Electricity, by Dr. Langmuir
Dr. Irving Langmuir, of the Research
Laboratory, Schenectady, read a paper on
224
GENERAL ELECTRIC REVIEW
Friday. January 29th, on Modem Theories of
Electricity.
Dr. Langmuir first sketched the historical
conceptions of electricity and matter, and
gradually led up to the atomic theory of
electricity and the electron theory of the
constitution of the atom, by means of which
theories he explained the modern ideas of the
conduction of electricity through gases and
metals. The operations of the Cathode Ray
Tube and the ordinary and Coolidge types of
X-ray tubes were explained.
Curves were shown of the radiation of
energy from black bodies, and an explanation
given of Planck's Law and the Quantum
Theory.
The various theories of the structure of the
atom were touched on, as well as the results
of the study of the spectra of the elements by
means of high frequency.
Finally, Dr. Langmuir showed how, by
means of the new theories, many phenomena
formerly obscure were now explained, how,the
periodic tables of the elements have been
supplemented and given increased importance;
also how the gaps have been filled so that a
continuous relation has been found between
waves of all frequencies, from the long 60-
cycle waves to the extremely short X-rays.
The lecture was illustrated by numerous
lantern slides and experiments.
SCHENECTADY SECTION
X-Rays, by Dr. Coolidge
Dr. W. D. Coolidge, Assistant Director of
the Research Laboratory of the General
Electric Company, addressed the meeting of
the A.I.E.E. January 19, 1915. in the audi-
torium of the Edison Club, Schenectady,
X. Y.. on the subject of Recent Developments
with X-rays. The following is an abstract
of his valuable address:
Prof. W. C. Rontgen of Wurzburg, Bavaria,
suspected that when a current of electricity passed
through a glass tube containing a gas at very low-
ire, invisible light waves were given off.' The
idea occurred to him that such rays might affect a
fluorescent screen in much the same manner as did
ultra-violet rays. In order to cut out the visible
light from his vacuum tube he wrapped it in heavy
black paper. Upon operating the tube to make
certain that the covering was completely light-
tight, he noticed to his surprise that the fluorescent
screen which he had left on the table three or four
■ - away glowed brightly.
r Rontgen investigated the properties of the
X-rays _with characteristic German thoroughness.
By 1897 he had amassed such a volume of infor-
mation about X-rays that nearly "every essential
piece of research on their properties up to 1908 can
be found in its more elementary form in his three
original memoirs.
Rontgen's original tube of 1895 was, judged by
modern standards, a pretty crude affair. The
cathode was flat and emitted a diffuse bundle of
cathode rays which, upon hitting the glass at the
far end of the tube, produced X-rays. In 1896
Campbell-Swinton added a platinum target upon
which the cathode stream hit. This increased the
penetrating ability of the rays obtained. In the
same year Jackson made the cathode concave so as
to focus the cathode stream upon a small area of the
target. By giving more nearly a point source of
X-rays this increased the clearness of radiographs
tor diagnostic purposes. The X-ray tube was soon
changed in form but not in principle. A device was
added by which the pressure inside the tube could
be increased at will, and various means were tried
for removing heat from the focal spot of the target.
Meanwhile in 1912, Dr. Coolidge discovered the
process of making ductile tungsten such as is used in
the filaments of mazda lamps. Shortly after this
discovery he became interested in perfecting a
wrought tungsten target for X-ray tubes. During
this work it became necessary to operate the tubes
up to the limit of their capacity in order to find out
how much abuse the tungsten targets would stand.
During the course of this work he found that the
ordinary aluminum cathode could be melted if
sufficiently high currents were sent through the
tube. He tried to remedy this by substituting a
cathode made of tungsten whose melting point is
very high. But such tubes were found to be very
unstable. When current was sent through such a
tube, the vacuum increased rapidly until finally no
current would pass through the tube until gas
had been liberated from the vacuum regulator.
From a practical standpoint such a tube was hope-
lessly unsatisfactory. Finally it was found that if
the process of operating the tube and immediately
reducing the vacuum were repeated rapidly enough,
the cathode became hot enough to glow, and that
after this the tube would operate for several minutes
at a time without it being necessary to let in fresh
gas from the regulator. This suggested the idea of
a cathode heated by some external means.
Richardson, and others in 1902, had shown that
electrons could be obtained by merely heating the
cathode, but had not been able to obtain constant
results. Dr. Langmuir, of the Research Laboratory
of the General Electric Co., had shown that the
rate of emission of electrons from a hot tungsten
cathode in a very high vacuum depended only
upon the temperature.
If we heat a tungsten filament, electrons are given
off and soon a condition of saturation occurs around
the filament. If the filament is made the cathode of
a low-potential circuit, a small current passes. If
the voltage is increased, a larger current passes.
Finally a voltage is reached which sweeps away
every electron as fast as it emerges from the hot
tungsten. For all voltages above this, the current
is constant, and is independent of the voltage.
Thus we have a resistance as far removed from the
ordinary Ohm's law resistance as possible. This
is not because the conduction is carried on in any
different way, but because the number of available
electrons is limited. (The reason that Ohm's law
holds in conduction through wires is that the supply
of available electrons in the wire is practically
unlimited.)
As a source of electrons in his tube, Dr. Coolidge
made use of a small spiral of tungsten wire heated
NOTES ON THE ACTIVITIES OF THE A. I. E. E. 22.3
white hot from a storage battery in exactly the effects of electrolytes and charged colloids
same way in which electric automobile lights are . „ • j •■;, ,, ., ? . , .
operated. This spiral is the cathode and a block of were reviewed, with the idea of pointing a
gas-free tungsten is the anode. The rate at which possible way for further study of the reactions
electrons are given off from the spiral depends of immunity which seem to occur usually,
upon its temperature, which is under the immediate if not always, in the blood between colloidal
control of the person operating the tube. The „ <.„ nc j.r.1 ~ 1 <-• <t> -j r
voltage across the tube is also controllable at will. PartS °f tte solution. To give some idea of
As the voltage employed in ordinary X-ray work tne. complexity of this field, the entire group
is much greater than is necessary to snatch all the of immunity reactions were reviewed. These
electrons across from cathode to anode as fast as included production of anti-toxins, precipitins,
they are evaporated irom the filament, even at the „„„i,.4.:„:„„ u i • i i_ 1 • j
highest currents now in use in X-ray work, the agglutinins bactenolysins, hemolysins, and
voltage and current passing through the Coolidge a review of phagocytosis. While the cases of
tube are totally independent. Both may be adjusted visibly complicated and augmented pha-
to any desired value with any degree of precision gocytosis are Certainly not yet explained by the
desired and at any such adjustment the X-ray simt)1e electrostatic "reactions nf nnrplv in
performance of the tube can be duplicated time slmPle electrostatic reactions ol purely ill-
after time. organic colloids, the assumption that the
specific nature and neutralizing process of
Lantern slides were shown illustrating the colloidally suspended toxins and anti-bodies
development of the X-ray tube, and the might be due to different magnitudes of
kind of work which it is possible to do with electric charges is worth considering. These
an X-ray tube. Many of these pictures are at present explained by the assumption
have already been published in the General of countless specific and different chemical
Electric Review, August, 1914, and January, compounds which are assumed to be normally
1915. present in all blood, to slight extent in all
cases of immune or anti-bodies, and to be only
Chemistry of the Blood, by Dr. Whitney. augmented by the process of immunization.
On the evening of February 2nd, at the
auditorium of the Edison Club, Dr. W. R. G- E' Mevine Pictures
Whitney, Director of the Research Laboratory, On February 16th, Mr. F. C. Bateholts
General Electric Company, delivered an delivered a lecture on the General Electric
interesting lecture on The Physical Chemistry Company's Moving Pictures for the Panama
of the Blood. The attendance was quite Exhibition. Mr. Bateholts displayed the
large, including a number of medical men educational-advertising motion pictures of the
who attended as guests. A lively discussion General Electric Company, and gave an
followed the lecture. Among those who interesting talk on the educational and
engaged in the discussion were W. L. R. advertising value of motion pictures. He also
Emmet, J. B. Taylor, Dr. W. L. Towne gave an interesting account of the General
and Dr. Krida. Electric Company's lecture bureau service.
Dr. Whitney's talk was a review of the Among the pictures shown were those of
properties of the blood, (with the intention of the Schenectady Works, Lynn Works and the
showing some possible advantages to be Harrison Works, and also some pictures of
gained by application of facts of physical the work on the Panama Canal,
and inorganic chemistry to such a complex
solution. It was pointed out that the blood Program for March
is all kinds of a solution : gaseous, electrolytic, During the month of March the following
simple osmotic, colloidal, and crass suspensoid. speakers will deliver papers in the auditorium
Through them all the electric effects of salt Df the Edison Club, viz:
ions and charged colloidal particles were March 2nd, W. L. R. Emmet, on Driving
called to mind by illustrations. The charac- Ships' Propellers.
teristic effects of the sodium and calcium March 16th, S. B. Paine, on a subject to
ions in true blood and in physiological be announced later.
salt solutions in case of excised hearts, and March 30th, C. D. Knight, on The Prin-
the activity of white corpuscles in pha- ciples and Systems of Control for Electric
gocytosis, were referred to. The mutual Motors.
226
GENERAL ELECTRIC REVIEW
FROM THE CONSULTING ENGINEERING DEPARTMENT OF THE
GENERAL ELECTRIC COMPANY
NOTES ON THE NOBLE GASES
The term "noble" has been conferred upon
certain rare gases of comparatively recent dis-
covery, for the same reason that this term was
long ago applied to certain metals such as gold
and platinum, indicative of their scarcity and
value, together with their general permanency
under ordinary conditions. The noble gases
now known are argon, helium, neon, krypton
and xenon, all of which appear to be absolutely
permanent, or chemically inert in respect to
one another and to every other element.
Argon
This is the most plentiful of all the noble
gases, being present by volume in atmos-
pheric air to the extent of about 0.9 per
cent. Nitrogen can be made to combine
with oxygen by the electric spark, but argon,
being without chemical affinity, cannot be
thus oxidized. Because of this peculiar lack
of affinity, argon was originally obtained by
Cavendish in 17S5 as a permanent gaseous
residue after the complete oxidation of atmos-
pheric nitrogen by the electric spark and the
absorptionincaustic potash of the products thus
formed. Cavendish, however, did not recognize
his residue as a new element and his interesting
experiment bore no fruitful results until it was
repeated in 1S94 by Rayleigh and Ramsay.
These distinguished scientists discovered its
elementary character by an examination of its
spectrum, and it was named "argon" from
two Greek words signifying "without work,"
i.e., without chemical affinity, for it has been
found impossible to produce a combination of
this gas with any other element.
Unlike the other noble gases, the lumines-
cence of argon under electrical excitation in a
vacuum tube is feeble. It is chiefly remark-
able for a change in color from red to blue
according to the density of the exciting cur-
rent; a weak current producing a red lumi-
nescence, which changes to a blue when the
current density is increased.
The spectrum of argon consists of many
lines extending throughout the visible range,
and the change in color of luminescence from
red to blue is chiefly caused by a strengthen-
ing or weakening of the red and blue lines
respectively, so that either one or the other is
presented to the unassisted eye as the pre-
dominating color of the light.
on is a monatomic gas, which signifies
that its atom and molecule are identical. It is
19.94 times heavier than hydrogen, its atomic
weight being 39. SS, considering oxvgen as 16.
Helium
A study of the spectrum of the sun's corona
by Lockyer in 1868 revealed a bright yellow
line which could not be found in the spectrum
of any other element known at that time. The
unknown clement which produces this line
was named "helium" (from the Greek work
for sun) and it remained a puzzle to scientists
until 1895, when Sir William Ramsay observed
the same bright yellow line in the spectrum
of a gaseous mixture extracted from the rare
mineral cleveite. He finally succeeded in
isolating an elemental gas from this mixture,
the spectrum of which showed many very
beautiful lines, prominent among which was
the brilliant yellow line that had been first
detected by Lockyer. This line is known in
spectrology as D3 and its wave length is
approximately 5S75.5 Angstrom units (1
A.U. = 10-scm.).
The complete spectrum of helium includes
seven principal lines, colored respectively
red, yellow, green, blue-green, blue, blue-
violet and red-violet, but the vivid brilliancy
of the yellow line D3 gives a strong pre-
dominating yellow tone to the luminescence
of this gas when it is confined in a capillary
tube and excited by electricity.
Helium is the second lightest of all the
gases, its specific gravity being 3.99 as com-
pared with oxygen at 16. It is particularly
remarkable in being a bi-product of the dis-
integration of radium, and therefore a strik-
ing example of the natural evolution of matter
from one apparently elementary state to
another, or, in other words, of the transmu-
tation of the elements. This gradual forma-
tion of helium from radium is, however, the
result of interatomic energy over which we
have at present no control, either to hasten
or retard its operation; so it cannot properly
be cited as a modern realization of the ideas
of the ancient alchemists who imagined the
possibility of transmuting one element into
another by a chemical process.
Helium is monatomic, and like its com-
panion noble gases, it shows no affinity for
any other element, no compounds of helium
having been discovered. It has been extracted
from other minerals besides cleveite and has
also been found in certain mineral waters,
notably in the hot water from the King's
Well in Bath, England, in which it is asso-
ciated with argon. It is also present in the
atmosphere in very minute quantity.
W. S. Andrews.
227
QUESTION AND ANSWER SECTION
The purpose of this department of the Review is two-fold.
First, it enables all subscribers to avail themselves of the consulting service of a highly specialized
corps of engineering experts, or of such other authority as the problem may require. This service provides
for answers by mail with as little delay as possible of such questions as come within the scope of the Review,
Second, it publishes for the benefit of all Review readers questions and answers of general interest
and of educational value. When the original question deals with only one phase of an interesting subject,
the editor may feel warranted in discussing allied questions so as to provide a more complete treatment
of the whole subject.
To avoid the possibility of an incorrect or incomplete answer, the querist should be particularly careful to
include sufficient data to permit of an intelligent understanding, of the situation. Address letters of inquiry to
the Editor, Question and Answer Section, General Electric Review, Schenectady, X. }'.
TRANSFORMERS: TWO-PHASE TO T'IREE-PHASE
TRANSFORMATION
(130) When two similar transformers are connected
for changing two-phase current to four-wire three-
phase, what are the percentages of the windings
included between the taps, and what are the
vector relations of the current and the voltage at
unity power-factor and at less than unity power-
factor?
Referring to Fig. 1, which shows the connections
for -transforming four-wire two-phase to four-wire
three-phase by two transformers, b is a 50 per cent
tap on the secondary winding of one transformer,
and c and / are 28.il and 86.7 per cent taps respec-
tively on the secondary of the other transformer.
Two -phase
\
vwwwwV'9 Cwwwww^
b e f
#/^A/wywv\/\c• ^A/wwvwwg
-£ H
? Neutral
Three-phase
Fig. 1
Fig. 2 represents the current and the voltage
vector relations in the primary windings, and Fig.
3 the same in the secondary windings. In the vector
diagrams, the voltage and current vectors at unity
power-factor are represented by the solid lines,
while the dotted lines indicate the position of the
current vectors when lagging at an angle of 6. The
direction of the vector is based upon the assumption
of the positive direction of the currents bem? as
shown by the arrows in the transformer windings
in Fig. 1 R-K.W.
D
A^r
\
I
6L
>V.
■>B
;i
^t!
Fig. 2
Two-phase vectors
AB=CD Voltages
I =11 Currents
Fig. 3
ah=bc=0.5E 1
Jf = 0.867E , Vnltaees
de=0.289E voltages
ac=cf = oj = E J
1 =2=3 Currents
22S
GENERAL ELECTRIC REVIEW
TRANSFORMERS: UNEQUAL CAPACITY
CONNECTED IN DELTA
(131) Please explain the reason for the following
phenomena.
A bank of three, 6600/220-110 volt, single-
phase transformers were connected with both
their primaries and their secondaries in delta.
One of these units was of 4 kv-a. and the other
two of 3 kv-a. Wishing to obtain single-phase
power to operate a contactor board, the discon-
necting switches 1 and 3 in the primary leads of
the transformers were closed (see Fig. 1). Not
having an a-c. voltmeter, a 250-volt lamp was
placed across the secondary of the 4-kv-a. trans-
former, but it did not burn at 220-volt brilliancy.
\
Open
Closed
3 A <* \\ 3 /OV. \ -4 KtV.
VvWvWW WWWV VVAW/WVW
AA/vWVW\ /vWvW, . A/vWvWWW
Trarts. |_l Trans. |_l Trans.
Primary
6600 fo/ts
Secondary
220 yolts
n
Load
Fig. 1
After about five minutes operation as just
described, the two 3-kv-a. transformers began to
smoke profusely and therefore all disconnecting
switches were opened. The two 3-kv-a. trans-
formers were then removed and the 4-kv-a.
unit was thrown across the line. The lamp
when placed across the secondary of this trans-
former burned brightly, and no further trouble
was experienced.
With such a connection as is shown, whatever
happened when the single-phase was connected
would also have happened if the three phases had
been connected. The action taking place, therefore,
indicates that there must have been some mistake
in the connections of the delta which produced a
circulating current of sufficient magnitude to heat
mail transformers far above their rated tem-
perature rise. It is possible that the polarities of all
three transformers were not the same, and that, in
connecting es in delta, a large unbalanced
voltage was obtained. With the connections as
given, the two 3 kv-a. transformers are in series
with each other, and both in multiple with the 4
kv-a. transformer. If the polarities of the 3 kv-a.
units are alike and the same as that of the 4
kv-a. nothing extraordinary could happen, but if
the polarity of the 4 kv-a. were opposite to that of
the two 3 kv-a. transformers the machines of the
whole bank would add their voltages in series and
the circulating current in the delta would be limited
only by the sum of their three impedances. A heavy
circulating current would also result if the two 3
kv-a. machines were unlike polarity, but con-
nected as though they were alike.
A possible difference in the ratios of the three
transformers would also give an unbalanced voltage
on the secondary side, which would cause circulating
current.
With connections as shown in Fig. 1, the trouble
was no doubt due either to a difference in polarities
or ratios. R.K.W.
ALTERNATOR: THREE-PHASE, RUNNING
SINGLE-PHASE
(132) Why does running single-phase produce such
disastrous results in a three-phase alternator?
Doubtless the effects referred to in the question
were noted in a solid steel rotor alternator and
were made known by the iron of the field becoming
seriously overheated.
The reason why such an action may take place in
a three-phase alternator under the conditions named
will be made obvious by a comparison of the behavior
of the flux in a polyphase alternator with that in a
single-phase alternator.
In a polyphase alternating-current generator the
armature reaction (or the magnetomotive force of
the current) is constant in intensity, and revolves
synchronously with regard to the armature, i.e.,
stationary in relation to the field.
In a single-phase alternator the armature reaction
is pulsating and ranges between zero and n I\/2
(«=the number of turns per pole and 7 = the cur-
rent per turn in effective amperes). The flux through
the field poles, which is the resultant of the constant
field excitation and the pulsating excitation of the
armature, is a pulsating flux of twice the frequency
of the machine. Consequently, in the field of a
single-phase machine there would be the heavy
hysteresis losses corresponding to double the fre-
quency of the machine, if some means of lessening
them was not employed. To accomplish this pur-
pose, a laminated construction is used in the field
of single-phase machines or heavy damping windings
are provided and arranged in such a manner as to
cut down the pulsating effect of the armature
current. In those single-phase machines where the
hysteresis losses would tend to be particularly
excessive, due to the flux pulsation, both of the
remedial measures named are embodied in the
design of the machine.
It will readily be seen from these descriptions
that the standard polyphase' alternator cannot be
expected to operate satisfactorily as a single-phase
machine except at a considerably reduced output.
T.S.E.
General Electric Review
A MONTHLY MAGAZINE FOR ENGINEERS
Manager, M. P. RICE Editor. JOHN R. HEWETT Associate Editor. B. M. EOPF
Assistant Editor. E. C. SANDERS
Subscription Rates: United States and Mexico, $2.00 per year: Canada, $2.25 per year; Foreign, $2. SO per year; payable in
advance. Remit by post-office or express money orders, bank checks or drafts, made payable to the General Electric Review,
Schenectady, N. Y.
Entered as 3econd-class matter, March 26, 1912, at the post-office at Schenectady, N. Y., under the Act of March. 1879.
VOL. XVIII., NO. 4 tyGeZT&UcLpany APRIL, 1915
CONTENTS
Page
Frontispiece .... . . 230
Editorial: The Paths of Progress . . 231
The Status of the Engineer . ... 234
By Dr. E. W. Rice, Jr.
The Absolute Zero, Part II ... 238
By Dr. Saul Dushman
Operating Conditions of Railway Motor Gears and Pinions . . ... 249
By A. A. Ross
X-Rays, Part I .... .258
By Dr. Wheeler P. Davey
The Modern Mine Haulage Motor ... 264
By C. W. Larson
The Eye and Illumination 268
By H. E. Mahan
The Fort Wayne Electric Rock Drill 273
By C. Jackson
Some Notes on Induction Meter Design . . . 277
By W. H. Pratt
Sign and Building Exterior Illumination by Projection . 282
By K. W. Mackall and L. C. Porter
Electrophysics: Application of the Electron Theory to Various Phenomena 287
By J. P. Minton
Railway Motor Characteristic Curves .... • 296
By E. E. Kimball
The Osborn Electriquette .299
By O. E. Thomas
Notes on the Activities of the A. I.E. E. . .301
Practical Experience in the Operation of Electrical Machinery, Part VII ... 304
Imperfect Slip-ring Contacts; Equalizer on the Wrong Side; Generators Motoring
at No-load; Changing Motor Mounting; Motor Throwing Oil
By E. C. Parham
From the Consulting Engineering Department of the General Electric Company . 308
310
Question and Answer Section . . • ■
The Coohdge X Ray Tube and Accessories. At the left is the tube inside a lead-glass" bowl, both
mounted on a stand so as to be easily adjusted to any convenient position and angle.
At the right on an insulating stand are the storage battery for heating
the cathode filament and the rheostat by which the
temperature of the filament is adjusted
THE PATHS OF PROGRESS
When the full text of the papers read on
"The Status of the Engineer" at the mid-year
convention of the A.I.E.E. in New York on
February 17th, is published in the Proceed-
ings of the Institute it will undoubtedly
attract wide attention and lead to consider-
able discussion, as the subject is one of
paramount interest to every unit of the
profession. We reproduce the very interest-
ing paper read by Dr. E. W. Rice, Jr..
President of the General Electric Company,
and feel sure that our readers will derive
considerable pleasure from the manner in
which he has handled the subject.
At present we do not propose to enter into
a discussion of the specific remarks in these
papers, but rather to make a brief analysis of
the general subject.
There has been, and we feel with perfect
justice, a very general feeling that the engineer
has not received due recognition or com-
pensation for the part he has played in
remodelling our state of civilization. We
also feel that every one who has anything
like an adequate conception of the changes
that have been made both directly and
indirectly by the activities of the engineer
will fully reciprocate in this feeling. If we
concede without argument that this is the
case, the interesting problem would seem to
be to ascertain the whys and wherefores of
this condition of affairs. We confess that
the problem is not particularly easy, but there
seem to be certain factors which upon analysis
are fairly evident. To make our point, a
brief mental picture of "what was" and
"what is "in one particular instance will help.
Let us consider the old warship of a hun-
dred years ago and compare it with
the latest modern superdreadnaught, and
we must remember these old men-of-war
aroused admiration and respect fully akin
to that accorded to the latest leviathans.
One hundred years ago the finest ship afloat
absolutely depended upon the wind for her
motive power and if becalmed was of little
more use than a log floating on the surface
of the waters. Her armament consisted
of cast iron muzzle loading guns which were
laboriously handled by manual labor and
there was nothing in her from stem to stern
that resembled a machine with the possible
exception of the pumps, composed of hollow
tree trunks, and the capstan that raised the
anchor in the good old fashioned way.
Such is the ship "that was" and what a
contrast to the ship "that is"! The modern
superdreadnaught with engines of 60,000
horse-power, and rumor has it that at a
pinch with forced draft 100,000 horse-power
is not impossible. A speed independent of
wind and weather of 25 knots and may be,
if necessary, this can be increased to nearer
30 knots per hour. Batteries of 15-inch guns
that could hurl projectiles weighing nearly
a ton for distances not far short of 20 miles.
Torpedo tubes capable of firing torpedoes
21 inches in diameter and every vital part
protected with solid steel 14 inches in thick-
ness. The modern battleship is indeed a
most highly developed organism with man-
made organs.
Now all these developments that have
changed the ship of yesterday into the ship
of today have been brought about by the
engineer, but it should be noted that in
talking of the engineer we use this term
throughout in the same broad sense as it is
used by Dr. Rice in his address. " * * * we
do not propose to limit our definition of
'engineer' to one educated in or following
the strictly technical professions of civil,
mechanical and electrical engineering, but
shall include in addition all educated men
laboring in the broad fields of chemistry,
physics, medicine and other organized sci-
entific activities."
With a picture of the ship of a hundred
years ago and of the ship of to-day in our
minds we are in a position to state certain
facts that are vital to our analysis :
There was no engineer on the old ship and
when the Admiral gave his word of command
232
GENERAL ELECTRIC REVIEW
he was telling others to perform operations
any one of which he would have been perfectly
capable of performing himself, and there
was not one technicality with which he was
not well versed. The ship was navigated,
fought and handled in every respect by
manual labor.
Today the Admiral can neither "go ahead"
nor "go astern," nor turn his ship, he cannot
bring his ammunition to his guns, he cannot
train or fire his modern monsters, he can-
not handle his torpedoes, he cannot even weigh
his anchor without his engineer. This is the
triumph of the engineer, but it must be noted
that the Admiral still gives the word of
command and it should also be noted that
it is only in comparatively recent years that
the engineer has been ranked as an officer.
This same general condition exists in all
of our industries, in railways, in lighting and
power stations, in mining, in our manufactur-
ing industries, in fact, in everything that is
modern and up-to-date. We owe the incep-
tion, development, and successful operation
to the engineer. The engineer is the one
indispensable factor, and without him and
his work progress would be at a standstill;
and yet he neither controls them nor dictates
the policies of the thing of his own creation,
and what is of more importance he apparently
is constantly seeing others reap the harvest
for which he has so diligently sown. Now
we believe that such is the case, but we know
that no effect is produced without a definite
cause, so the cause for this state of affairs is
the interesting thing:
Firstly, we believe that there is one fact
that is often lost sight of, namely, that when
the engineer is really successful, in the
material sense, besides doing what, for
want of a better term (and to avoid the
misnomer of pure engineering), we shall call
engineering work proper, he becomes active
in organizing the work of others, and
if successful in his broader activities his
work often leads him further and further
from engineering problems and more and
more to organizing and managing the work
of others until he is recognized as manager
or head in his particular sphere of work.
As he assumes wider responsibilities his
financial reward increases, but he is not then
the highly paid engineer, but the successful
manager or business man, as the case may be.
In these cases, and we believe they are many,
the engineer has reaped the harvest for which
he has sown, but not necessarily as an engineer.
So when the engineer gets to the stage of
giving the "word of command" he is often
lost sight of as the engineer and assumes
another title.
Again, there are many fields of engineering
activities where the engineer has done his
work so perfectly that the very work that
required engineering talent in the past has
been reduced to almost routine work and
can now be successfully performed by the
machines of his creation and a type of labor
partially or totally unskilled. In such cases,
and they are legion, the engineer has displaced
himself by the product of his own brains.
Indeed, in the field of operating engineers
this is particularly noticeable, where the
perfection of mechanical and electrical devices
has been brought to such a state that the
engineer holds much the same position as a
lifebelt — for the greater part of the time he
is not wanted, but when he is wanted his
services are imperative if a disaster is to be
avoided. This situation has reduced the
number of engineers employed in the operation
of large engineering undertakings, and we
often find only one or two engineers directing
the work of a host of less skilled attendants
from whom no great degree of technical
knowledge is required.
So it would seem that the engineer has in
a multitude of cases displaced other workers
by introducing new methods and again by
the perfection of his own devices in turn
displaced himself. This undoubtedly has led
to many men of good engineering training
having to perform work which those with a
less costly preparation could perform almost
as well, which naturally leads to dis-
satisfaction. This is most unfortunate for the
would-be engineer, but it seems inevitable
and apparently is the same in some other
professions.
So in the field of operation and construction
we shall still see the old rule of life prevail —
many will enter this field of activities but
comparatively few will become really suc-
cessful in the material sense — and we shall
still see many men discontented with their
lot not necessarily because their work is not
congenial, but rather because after an expen-
sive education and much self-sacrifice and
arduous labor in early life they are not able
to reap the harvest they feel that they have
sown for.
The real field for engineering is the same
today, and will be in the future, as it has
been in the past, namely, development work,
showing the world at large "how to do for
one dollar what a fool can't do for two,"
THE PATHS OF PROGRESS
233
and it is to this great field of development
work that we must call the most able young
men of this generation and of generations to
come ; our future absolutely depends upon the
engineer in just the same degree as our past
progress and prosperity has been due to
his work. Anything that discourages the
brains of future generations from wishing
to enter the engineering profession is a menace
to our future welfare, and it is for this reason
that we feel apprehensive of any movement
that would make the engineering field appear
less attractive.
If the feeling generally prevails that
engineering work is becoming so standardized
and so reduced to routine work that it is not
worth a young man's while to prepare himself
at the great cost involved for the profession,
or again if he should feel that , even if he were
fortunate enough to work himself up to a
position where he was really doing important
development work, that the reward would be
altogether inadequate for the effort he has
expended then we are not going to progress in
the future as in the past. The spreading of this
feeling must be avoided. We fully recognize
that our future economic stability demands
the organization of engineering work and that
it is essential after developments have been
made by the engineer that production and
operation must be standardized as far as
possible, and indeed, that this is one impor-
tant phase of the engineer's work; but we also
realize that if the idea prevails that this
organization is being pushed beyond its
limits to the extent that it is inimical to the
status of the engineer we shall have many
difficulties to face in the future. It seems
that we should certainly form our policies
in such a way that the engineering profession
shall never come to be regarded in the same
light as journalism, of which it has been so
often said that it is an excellent profession
to get into if you are quite sure you can
get out.
There is another side of the question; and
one of the speakers in New York thought
the engineer had nothing to complain of
and that all things being considered the
average engineer was as well rewarded for
his work as the average man in other pro-
fessions. This would be hard to prove or
disprove without a most exhaustive study,
and even if it were proved, the point would
still remain that the engineering profession
is giving more to the world than any other
profession, and it is essential that it should
be attractive to the voung man of the future.
Certainly there are many walks of life in
which the material rewards are all out of
proportion to the service rendered to the
state when compared with those in the
engineering profession. A young man in
choosing his profession naturally realizes
this, but in the recent past the engineering
professions have been talked of as those of
the greatest possibilities, so that if the feeling
becomes general that these possibilities are
not as good now as they were in the past we
shall fail to secure the most desirable young
men of today as our engineers of the future.
Up to this point we have only talked of
material rewards and now if we regard the
engineering profession in another light it
seems that the rewards are far above those
in most other professions. All those engaged
in the great modern science of development,
to which our engineering professions have
been so largely reduced, have the immeasur-
able joy of achievement or the possibility of
achievement, and it is the intense interest in
striving for accomplishment that makes the
engineering professions what they are, and
what has made the engineer the man of
courage and resourcefulness, of patience and
determination, of self-sacrifice and unending
work. The very intensity of work with
which the engineer devotes himself to his
daily task precludes the constant thought of
self-advancement and the desire to leave an
all absorbing field of activities for others
where the material reward would be greater,
but the interest and worth-whileness of life
would be less.
The engineer must often have the idea
that he is being exploited by others because
of this very loyal devotion to work rather
than to self-interest, and undoubtedly this
has been the case in many instances; but we
hope and trust that the very fact that the
engineer has changed the world to such an
extent that we are finding it every day more
necessary that our commercial men, finan-
ciers, etc., should know more of the engineer
and of his work to enable them to transact
business in a world whose modern foundations
rest on a structure of engineering accom-
plishments will lead to a more perfect under-
standing, and, may be, to a better material
reward for the engineer in the future. All
of these different units have a common
object; their work is the part of one great
plan, and any factor in our great scheme of
life that is so absolutely indispensable to our
future progress must surely hold an enviable
position in years to come.
234
GENERAL ELECTRIC REVIEW
THE STATUS OF THE ENGINEER
By Dr. E. W. Rice, Jr.
President, General Electric Company
The author, who has "lived with and worked alongside of engineers for more than thirty years," has written
this contribution from his rich experience. He relates some of the achievements of the engineer and calls
attention to the changes that this work has brought about in our state of living during the last four decades.
The personal characteristics of the engineer are referred to in an interesting manner, and stress is laid on the fact
that honest v is natural to the profession. Dr. Rice thinks that it is now incumbent on the engineer to take
a hand in the greatest work of all, the government of the country, by showing an active interest in the
framing of our laws and in guiding the work of the many commissions that form such a prominent part in our
modern government. This address was read before the A.I.E.E. on the evening of February 17, 1915. — Editor.
The status of the engineer is an important
subject, and should be of vital interest to
even- one of us.
It is well for us to pause a few moments
from our daily task and make a brief survey
of the engineer's work, to consider its impor-
tant influence upon the life of this busy
world, and especially to enquire what new
service awaits the engineer now and in the
immediate future.
During this discussion we do not propose
to limit our definition of "engineer" to one
educated in or following the strictly technical
professions of civil, mechanical and electrical
engineering, but shall include in addition all
educated men laboring in the broad fields of
chemistry, physics, medicine and other organ-
ized scientific activities.
I do not think that we can be accused of
serious exaggeration in saying that the world
is indebted to such men for the application
of steam to ships, cars and workshops ; for the
invention of the sewing machine, the type-
writer and the phonograph; for the intro-
duction of the bicycle, automobile and
aeroplane; they have brought the marvels
of photograph}' into existence, giving us the
moving picture, X-rays and colored photo-
graphs. High explosives have been created
to build and to destroy. We must thank such
men for the untold blessings of anesthetics;
for showing us how to successfully limit and
combat epidemics of dread diseases.
Coming to our own special field, the
members of our profession have given the
world the telegraph, the ocean cable, the
telephone and the wireless; created electric
lights for our homes, cities and workshops;
the electric motor to run our trolley cars,
railroads and factories; have designed' dyna-
mos and great transmission lines with which
to save and make useful the otherwise
wasted power of our waterfalls. These and
many other contributions equally wonderful
and equally useful — miracles at first but now
mere commonplaces and necessities — have
been evolved from the brains of our busy
scientific engineers largely during the past
40 years.
But I will not weary you with a further
recital of engineering achievements, as such
a recitation of even the shortest possible
catalogue would consume the entire evening.
My object in thus calling attention to the
relatively recent contributions of engineers
to the wealth and resources of the world is
not to tickle your pride in belonging to the
engineering profession, but rather to awaken
your sense of responsibility for the great
changes in our daily life, our methods and
opportunities of conducting business and
all other activities, which have been
brought about directly and indirectly by
such accomplishments, and to make some
suggestions for the meeting of this responsi-
bility.
Is it not a fact that civilization in its present
form would never have arisen and would
speedily come to an end if deprived of the
engineer and his services? Has not the
equilibrium of the world been upset by these
very gifts of the engineer?
Is it not evident that such tremendous
additions to our power, knowledge and wealth
must have a powerful influence upon every
phase of our existence? Have not our relations
with nature and with each other been pro-
foundly affected and as a result required
many new adjustments?
The discovery of new trade routes has,
as is well known, completely changed in
times past the history of nations and the
fate of their peoples. The discoveries of our
scientific engineers during the past 40 years
have been of greater importance than dis-
coveries in trade routes, and it is inevitable
that in adapting itself to the new conditions
society should be deeply affected. The
adaptation of man to his new environment
could not take place without strain and
friction. Are we not now in the midst of
such a process of adjustment?
Of course, we all appreciate that the labor
and thought of manv other men of vision
THE STATUS OF THE ENGINEER
235
and enthusiasm were needed; men experienced
in finance, commerce, trade and government,
to render the all essential aid required to
introduce and to adapt to our daily lives
these great contributions. But it would seem
to be self-evident that without the creative
work of the scientific and technical engineers
these things would not have seen the light
of day.
This remarkable development was fairly
started during the first half of the 19th
century under the guidance of the civil,
mechanical and chemical engineer, but was
tremendously accelerated by the advent of
the electrical engineer about 40 years ago.
His work during the past decades has reacted
upon that of the other engineering professions
and stimulated and made possible the almost
equally marvelous development in mechani-
cal, chemical and other lines of activity.
Therefore, I regard all those who have been
able to participate in the service of electrical
science as happy and fortunate individuals. It
is true that the financial reward has not always
been great; on the contrary, it has often been
extremely meager when compared with the
rewards which frequently come to the success-
ful lawyer, financier or merchant, but our
engineer has been rewarded by something
more valuable and precious than gold — the
thrilling joy of achievement. There can be
no greater satisfaction than that which
comes to a man who believes that he is the
first to discover some new force or to make
some new and useful invention.
I have lived with, and worked alongside of,
engineers more than 30 years. I think I
understand the engineer's aspirations and
character. I can say that it is a case where
familiarity has not bred contempt, but, on
the contrary, has inspired respect and
affection.
The engineer is popularly supposed to lack
certain qualities needed in a successful man
of business, or to make a good salesman,
or to handle important financial matters, or
to fill positions requiring general executive
ability. Is this popular idea justified? We
may admit that an engineer who has devoted
his entire time to his exacting work may be
lacking in the knowledge and experience of
other lines of activity, but it does not prevent
him from having certain natural qualities,
integrity, tact and aggressiveness combined
with general intelligence and common sense.
These qualities are personal and not pro-
fessional. No group of men has a monopoly
of such qualities and in none are they entirely
lacking. These qualities are to be found as
generally among engineers as among other
men.
It has been further charged that as an
engineer deals with nature and natural laws
his experience has been limited to impersonal
objects, and that he must fail to appreciate
or understand the complicated human ele-
ment which is the important factor in business
or in political life. This may be also partially
true, particularly in the case of some of those
whose work has been confined to that of pure
research or pure science, but is not a general
condition even among such men, and by no
means the condition among engineers who
of necessity are brought more or less in
contact with the human element.
I have noticed that an engineering educa-
tion and training have generally developed
a man's powers of observation and his desire
and ability to learn. He becomes skeptical
of mere theories, doubts tradition and spurns
superstition, but he constantly searches for
the truth and is not afraid of facts. He
habitually tries to see things as they are and
not as he thinks they should be. . He is never
satisfied that "whatever is, is right," but is
ever trying for something better. I do not
need to tell this audience that engineers
do not always agree as to the interpretation
of facts, but opinion is frankly based upon
facts and not upon preconceived notions.
One who refuses to face or acknowledge facts
loses his influence upon his fellows and his
standing among his brother engineers. The
engineer is always "from Missouri."
There is an old proverb which runs some-
what as follows: "One look is worth a
thousand words." I like that proverb, and
it is, I think, a fair description of an engineer's
point of view. How often you hear the
expression among engineers: "Well, let's go
and take alook at it." Is not this the spirit
which is needed in respect to other problems
in the social, industrial and political world?
Do they not need less talking about and more
intelligent looking at?
It is true that the engineer deals primarily
with nature, but nature does not lie. The
engineer, therefore, leams early in life the
utter uselessness and folly of deceit. He
knows that it would be silly to the point of
insanity to try to fool nature. He is constantly
on his guard not to fool himself and is there-
fore not likely to try to fool others. In fact,
he loses in time the desire to deceive, even
if he ever had it. Honesty becomes a habit,
not the honesty of the old line trader formu-
236
GENERAL ELECTRIC REVIEW
lated in the saying "Let the buyer beware,"
but the kind of honesty which scorns to take
advantage of the negligence or ignorance of
his customer, which involves honest thinking
as well as honest action. It is quite possible
that this habit may make him at first the
easy prey of dishonest men, but it is a quality
which commands respect and which wins in
the end. It is needed and appreciated in
business of all kinds and sizes, little and big.
It is helpful to little business. But big business
is doomed to big and disastrous failure unless
saturated with honesty.
The engineer's training also tends to
produce in him a fine blend of conservatism
and radicalism. He is not afraid of a thing
because it is new and he is not slavishly
bound to precedent; on the contrary, he is
frequently the creator of new things and a
breaker of precedent, but he also believes
in continuity and is not likely to let go of the
old until he has a good hold of the new.
He does not adopt an idea merely because of
its novelty, but demands before adoption the
acid test that it should be reallv better than
the old.
There is, therefore, a large field of service
open to the engineer in manufacturing,
commerce, farming and all other business
activities of our country for which his
education and training have made him
eminently fit. In fact, his work in science
and engineering, already briefly alluded to,
has succeeded in so increasing the magnitude,
variety and intricacy of manufacture and
trade that the special knowledge of the
trained engineer is already in demand in
almost all departments of our commercial
and business life. Even in the specialized
field of selling, the old type of salesman with
precious little technical knowledge has been
largely displaced by the engineer salesman.
There is, however, another opportunity for
service awaiting the engineer of a most
valuable and patriotic character. The biggest
business after all is that of running this great
country of ours. The United States not only
operates the largest businesses itself in its
various departmental activities, but through
its legislators and various commissions it has
taken a lively and paternal interest in private
business. It makes the rules for the conduct
of our business which fundamentally affect
our future for good or for evil. It seems to me
that the engineer ought to take an important
part not only in conducting this great
enterprise but in helping to make the rules
for our faith and conduct.
I recently heard a member of Congress
say that in looking at Congress one was merely
seeing as if reflected in a mirror the great
people who elected it, and that if we, the
people, did not like the looks of ourselves
we should not get angry and break the mirror '
but go and wash our faces. Now, while that
was a very humorous and witty simile it
seemed also to convey a homely truth and a
sensible suggestion. I began to wonder how
much there was in the suggestion, and thought
I would ascertain just how accurate a reflec-
tion of our people and its activities was to be
found in Congress and Legislature. I thought
it would be interesting to learn the profession
or avocation of those whom we have elected
to represent us in Congress. I have here a
list from which I will briefly abstract :
1914
SENATE OF U. S.
No.
Lawyers i 1
Farming 5
Banking 4
Publishing 4
Merchants, mfrs.,
railroads, real es-
tate 7
U. S. Navy 1
Medical profession 1
Not specified 3
Total . "96
HOUSE OF
REPRESENTATIVES
No.
Lawyers 275
Editors and pub-
lishers 23
Merchants and mfrs. 32
Other business 32
Farming 14
Banking 4
Educational profes-
sion 6
Medical profession 5
Architects 3
Engineers 1
Not specified 40
Total 435
It will be noted that 75 per cent of the
Senators are classified as lawyers, and 65
per cent in the House come under the same
classification. I may say, incidentally, that
I did not find a single one among the Senators
who professed to be an engineer, and only
one in the House of Representatives. An
examination of the roster of the State of
New York shows a similar condition, a large
majority of the membership of both the
Senate and Assembly being classified as
lawyers. Now, I do not know how these
facts impress you, but the witty simile of
which I spoke rather lost its point as a
conveyor of homely truth in the light of the
facts. A body whose composition is about
70 per cent lawyers cannot be considered as
a very accurate reflection of the people of this
countrv.
THE STATUS OF THE ENGINEER
237
Now, I have the utmost respect for mem-
bers of the legal profession. We are all
constantly trusting lawyers with our most
important business matters and intimate
private affairs. No profession has higher
ideals and no profession comes nearer to
realizing these ideals in practice. They
deserve our confidence. I also yield to no one
in my admiration of the ability, integrity
and patriotism of the great men whose
names have honored the legal profession and
shed luster upon our country; men who
frequently at great personal sacrifice have
given the best part of their lives to the
service of their country.
However, I think it is competent for us
to enquire as to whether there is not a dis-
proportionate number of members of the
legal profession in our law making bodies.
Is it for the best interests of this country
to have any one kind of talent and training
or point of view so overwhelmingly rep-
resented? There is a pretty general opinion
in this country that we are afflicted with
too large a number of laws, and it has been
suggested that there may be a connection
between the number of laws and the number
of lawyers in our legislative bodies. Is it not
also a strange anomaly that a country which
owes so much of its phenomenal prosperity
to the creative work of engineers should have
practically excluded such men from its
Congress and Legislatures? Would not our
general condition have been better if years
ago we could have injected into the composi-
tion of our law making bodies a number of
high class, sensible engineers?' It seems to me
that our engineers have a duty to perform,
that they owe it to themselves and to the
country not to be satisfied with being simply
hired to give their views and professional
opinion upon programs prepared by other
men, but should sit with our rulers and share
directly in the responsibilities of government.
It is reasonable to expect that men who
have been the greatest factor in the creation
and conservation of our material wealth
and resources should have sound and con-
structive ideas of practical value upon the
matters which our commissions are created
to control. Therefore, our great Commis-
sions which are charged with such tremen-
dous power and grave responsibilities
should have among their members com-
petent engineers of experience as well as
lawyers, practical business men and experts
in the special province over which the Com-
mission has jurisdiction.
One of the most hopeful signs of the times
is the great awakening of the business men
of this country to the imperative necessity
of taking an intelligent interest in our
Government, and it looks as if our business
men now propose to make a business of
seeing to it that they are properly represented
in the business of government. Engineers
should arouse themselves and participate
in this great movement.
While up to the present no better or more
practical means has been discovered than
our great political organizations for giving
effect to the wishes of our citizens, it is
becoming increasingly evident to thinking
men that no permanent advance can be made
by simply turning out one political party and
substituting representatives of another as
our rulers. An intelligent and continuous
effort should be made to improve the com-
position of our legislative bodies. We are
essentially a nation of manufacturers, traders
and farmers. We are all part of an organiza-
tion with a mechanism which is so delicate,
extensive and complicated that it must be
controlled and managed with the greatest
wisdom and intelligence if we wish to continue
to progress in prosperity and lead happy and
useful lives. It seems to me that in the
future it will be the duty as well as the
privilege of the engineer who so largely
contributed to the production of this compli-
cated mechanism to assist in its management
in order to assure its preservation.
238
GENERAL ELECTRIC REVIEW
THE ABSOLUTE ZERO
Part II
By Dr. Saul Dushman
Research Laboratory, General Electric Company
This article is a continuation of the contribution by Dr. Dushman that appeared in our February issue,
and contains a summary of the results that have been obtained during the last few years from investigations
on the properties of substances at extremely low temperatures. The discovery of a "superconducting" state
for pure metals at these temperatures is especially noteworthy. The general conclusion toward which these
investigations lead is that at very low temperatures the properties of all substances tend to obey very simple
laws and that all these properties are probably connected by functions which are of the same form for all
substances. — Editor.
INTRODUCTION
In a previous issue we reviewed very
briefly the logical foundations of our present
temperature scale and the various methods
that have been used to attain extremely
low temperatures. Before proceeding to
discuss the behavior of different substances
at these low temperatures, it may not be
out of place to digress briefly in order to
point out reasons which have impelled
physicists to undertake laborious and difficult
investigations in a field which at first sight
might appear so "impractical." For, after all,
we live in a pragmatic age and the layman
may be pardoned for asking the pertinent
question, "Of what use is it;"
We do not need to go further back than
25 years to realize that for a long time
scientific investigations were mostly con-
fined to a very narrow region of temperatures,
between approximately the minimum freezing
point of ice-salt mixture, — 22 deg. Cent., and
the boiling point of mercury, 360 deg. Cent.
Upon the results obtained in this manifestly
limited field were founded a number of
generalizations and theories for the interpre-
tation of the whole realm of natural phe-
nomena. The fundamental principles of
dynamics and statics, the laws of chemical
combination, the electromagnetic theory of
light, the classical system of thermodynamics,
and the kinetic theory of gases — this whole
structure was a magnificent attempt to
explain and correlate the results of observa-
tions in many different fields of investigation.
It is true that the structure was somewhat
contradictor)- in its style of architecture,
and rather unstable in a good many places;
but in spite of these deficiencies it appeared
fairly satisfactory, especially if one did not
it it as a whole, and merely considered
the separate portions.
But the past two or three decades have
seen a most amazing expansion in our
knowledge of the universe. The requirements
of the industrial arts on the one hand, and
the increased facilities and desire for purely
theoretical investigations on the other, have
both contributed to accumulate an immense
number of observations in diverse fields of
science.
It was in this manner that the development
of processes and operations involving the use
of very high temperatures led to a more
careful study of the properties of substances
at these temperatures. Furthermore, it was
necessary to devise methods of high tem-
perature thermometry. Hence arose a number
of investigations which finally led to a radical
revision of all our previous concepts of
energy. This story has been told in another
connection, and one can only refer here
briefly to the work of Lummer and Pringsheim
and others on the laws of radiation of a
black body which led Planck to formulate
an atomistic theory of energy. The Electro-
magnetic Theory, the Principle of Equi-
partition, the Law of Continuity of Dynamical
Effects — all of which are based upon the
same fundamental equation, nay, even these
equations, were called into question and the
necessity arose for re-stating them in new
language.
There was all the more incentive for doing
this, as discoveries in other realms of physics
seemed to demand equally radical changes
in our former views. The almost simultaneous
discovery of X-rays and radioactive phe-
nomena led to results that could not be
correlated with the classical views. The atom
could no longer be regarded as a metaphysical
entity; here were atoms actually disintegrat-
ing in front of our eyes ; we could count them
and trace the life historv of each one. But
THE ABSOLUTE ZERO
239
during the process of disintegration these
atoms emit sometimes positively charged
particles of atomic dimensions, and at other
times negatively charged corpuscles which
possess of the mass of a hydrogen atom.
1 sun
Therefore, the atom itself must be a very
complex structure.
The theory of discontinuous emission of
energy quanta propounded by Planck could
thus find a parallel in the theory of radioactive
transformations proposed by Rutherford and
Soddy. But Planck's theory war, found to be
capable of much further application than to
the explanation of the laws of radiation.
Almost immediately after Planck formulated
his theory, Einstein pointed out that on the
basis of the same theory it ought to be
possible to predict the specific heats of
bodies at different temperatures and that at
extremely low temperatures the specific heats
of all substances ought to decrease indefi-
nitely. This conclusion appeared all the
more interesting because it agreed with a
semi-empirical conclusion at which Nernst
had arrived from a consideration of the effect
of temperature on the equilibrium of chemical
and physical reactions. Since Einstein's
deductions appeared just as valid as Planck's
assumptions, it became of vital interest to
determine accurately specific heats at very
low temperatures.
But the determination of specific heats
has not been the only interesting problem
in the realm of low temperatures. The
electrical and thermal conductivity, and the
magnetic properties are equally important
subjects of investigations. We are still far
from being able to apply the electron theory
to calculate the conductivity of a metal at
any temperature. A knowledge of the laws
governing the variation in the electrical
resistance of pure metals near the absolute
zero would aid considerably in placing the
electron theory on a more definite basis.
The investigation of the properties of
substances at extremely low temperatures
thus appears of vital importance not only
in order to refute or confirm the atomistic
theorv of energy, but also in order to give
us more definite views of the actual mecha-
nism of electrical conduction in metals.
That the results of these investigations
are bound to profoundly affect our future
theories of the structure of matter is quite
evident. We have been accustomed to
considering the gas laws as typical of matter
in the simplest state. The kinetic theory of
gases attempts to explain these laws by
assuming that the molecules of the gas are
in constant motion with an average kinetic
energy that increases with the absolute tem-
perature. Similarly the heat energy of solids
is ascribed to oscillations of the atoms about
mean positions of equilibria. From this point
of view it would follow that near the absolute
zero all vibrations among the atoms ought to
decrease in amplitude considerably. Under
these conditions might we not expect some
general laws for solids corresponding to those
observed in the case of gases? Attempts
have been made in the past two or three
years to develop a theory of the solid state
along these lines, and while this work is as
yet far from complete, a few generalizations
have been deduced which are of extreme
interest.
In the following paper we shall discuss the
results of the investigations at low tem-
peratures under the following headings:
(1) Specific Heats.
(2) Electrical Properties.
(3) Magnetic Properties.
(1) SPECIFIC HEATS AT LOW
TEMPERATURES
The Quantum Theory
As the quantum theory has been discussed
very fully in another connection,* it will
be sufficient to state rather briefly the
fundamental assumptions of this theory and
the reader can refer to the previous articles
for more detailed discussion.
In electrical engineering, we are familiar
with the production of high frequency
alternating currents by the discharge of a
condenser through an inductance. We have
in this case, a continuous oscillation in the
electrical energy from a potential form (when
in the condenser) to a kinetic form in the
inductance, and the result is the emission of
electromagnetic waves whose frequency de-
pends upon the magnitudes of the inductance
and capacity. Since light and heat are similar
to those electromagnetic waves and differ
only in possessing much higher frequencies
we must conceive of their being likewise
produced by some form of oscillator. In the
case of visible light, the existence of the
Zeeman effect and analogous observations
lead to the belief that the radiation is pro-
duced by the oscillation of electrons around
positively charged centers.
Now "the fundamental assumption made
originally by Planck can be stated thus : In the
*S. Dushman, General Electric Review, Sept., 1914.
240
GENERAL ELECTRIC REVIEW
emission and absorption of electromagnetic
energy the interchange of energy between an
oscillator and the surrounding space can occur
only discontinnously, in multiples of a unit
quantum hv, where v denotes the frequency of
the radiation and h is a universal constant.
woo
y
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6
Fig. 1. Curves Illustrating Einstein's Formula for the Total
Energy (£) of Solids where E =3 RF
From this assumption Planck deduces the
conclusion that the average energy possessed
by anv oscillator is
u.-X-g^- (i)
(kT_l
for each degree of movability or freedom.
In the case of a linear oscillator possessing
two degrees of freedom the average energy
is double, and-so-forth.
Einstein's Formula for Atomic Heats at Low Tem-
peratures
As mentioned above, Einstein carried
this theory one step further by concluding
that in the case of heat emission and absorp-
tion there must exist similar discontinuities.
There are good reasons for believing that the
longer heat waves emitted by solids are due
to vibrations of the atoms themselves.
Moreover, consideration of the elastic proper-
ties of solids leads also to the conclusion
that the atoms in these cases are held together
by quasi-elastic forces so that they vibrate
about a mean position of equilibrium. Such
an atom possesses therefore both kinetic and
potential energy, is in fact an oscillator
similar to that used for producing electro-
magnetic waves. Einstein, therefore, felt
justified in applying the quantum theory
to this case and he deduced the interesting
result that while for ordinary temperatures
the atomic heat for most solids should be
about six (as demanded by the Dulong and
Petit law) this value must tend to diminish
with decreasing temperature until it becomes
equal to zero at the absolute zero.
Since a vibrating atom in a solid possesses
both kinetic and potential energy and the
average kinetic energy must be the same as
that of a monatomic molecule in the gaseous
state, it follows from equation (1) that the
average energy per atom of the solid ought
to be
r, = -|^ (2)
Denoting the total energy per gram atom
by W, and the number of atoms per gram
atom by N (6.06X1023), equation (2) becomes
H =-tt =3 Rir. —
e*r-l
(3)
R
where k = j-r denotes the atomic gas constant,
and /3 is written for h/'k.
It is evident that for small values of $v
or very large values of T, W becomes approxi-
mately equal to 3 RT, while in all other
cases it is less. Fig. 1 shows the form of the
function F=-
Pv
for different values of T
and for the values $v = 50, 200 and 400. As T
increases, the value of F approaches it more
and more until at T= » the two are equal :
but at any given temperature T, the value
of F differs from that of T more and more as
j3p is increased. According to the law of
Dulong and Petit the atomic heat of all
monatomic solids ought to be proportional to
the temperature. This would correspond to
the case where fiv is infinitesimal, and in Fig. 1
it is indicated by the straight line.
Debye's Formula for Atomic Heats
The actual observations of Nernst and
others on the specific heats of bodies at low
temperatures were found to be in fair agree-
ment with Einstein's equation at higher
temperatures, but discrepancies became more
and more noticeable as the temperature was
decreased. While there was a qualitative
agreement between the atomic heat-tem-
perature curves calculated according to this
THE ABSOLUTE ZERO
241
equation and those actually observed, the
formula was found to be completely inade-
quate as temperatures nearer the absolute
zero were approached.
Nernst and Lindemann were therefore led
to suggest a modification of Einstein's
equation which gave very good agreement
down to the very lowest temperatures. But
their formula had no theoretical basis, and
it was only very recently that Debye deduced
a formula which has proven to be valid over
the whole range of temperatures. According
to Debye, it is not right to assume that the
atoms of solids are capable of vibrating with
only one frequency: The propagation through
solids of vibrations of low frequency, such as
sound waves, shows that there must exist a
whole series of values of v. Only it is necessary
to assume that there is an upper limit to this
range of frequencies, and furthermore that
the total number of different frequencies
cannot exceed 3 Ar. Debye shows that the
maximum frequency (vm) and the distribution
of lines in this acoustical spectrum may be cal-
culated in the case of monatomic solids from
the elastic constants of the material, and deduces
the following formula for the atomic heat, Cv,
at constant volume.*
CV = ZR
[fJV^-^1 »
where x =
PVm= Q.
T T
In obtaining this formula Debye also
makes use of the quantum theory, but instead
of assuming like Einstein, that each oscillating
atom can absorb or emit different multiples
of the unit energy quantum hv, he assumes
that each individual frequency possesses the
average energy
hv
1
It is rather difficult to understand exactly
what this means physically, but we shall find
that Keesom and others have found it
necessary apparently to introduce somewhat
similar ideas in order to account for the
rate of change of the electrical conductivity
of metals at low temperatures.
The function 9 is designated by Debye as
the "characteristic" temperature of the
particular solid, and he shows that it can be
calculated from the density, compressibility,
* Ann. Physik. 39. 789 (1913).
Young's modulus of elasticity and the
modulus of torsion.
Equation (4) may be stated thus:
The atomic heat of monatomic solids is a
universal function of the ratio Q/T where 9 is
a characteristic temperature for each substance
depending upon its density and elastic constants.
C C
Fig. 2 gives the plot of the value zr-= = y^-
6 R C »
Fig. 2. Atomic Heat of Monatomic Solids According to
Debye's Formula
as calculated by Debye from equation (4).
At constant value of T/Q, the atomic heats
of all monatomic substances are the same.
Knowing therefore the value of 9 for any
substance it is possible from this graph to
determine the atomic heat at any temperature.
For very low .values of T/Q, that is large
values of x, equation (4) assumes the much
simpler form :
C„ = 3i?X77.94^3 (5)
That is, at sufficiently low temperatures
the atomic heat varies as the third power of
the absolute temperature, or the total energy
of monatomic solids at temperatures near
the absolute zero is proportional to the
fourth power of the absolute temperature.
This relation is therefore analogous to the
Stefan-Boltzmann law for the total energy
radiated by a black body.
At very high temperatures, that is ex-
tremely small values of x, the expression
inside the brackets in equation (2) reduces
to unity, so that,
C.-3.R,
which corresponds to the Dulong and Petit
law.
242
GENERAL ELECTRIC REVIEW
The actual observations at very low-
temperatures are in splendid agreement with
equation (5). In Fig. 3 are shown the curves
for the atomic heats of diamond, lead and
aluminum. The third-power law (equation 5)
is actually found to hold over quite a con-
siderable range of temperatures. Thus, in
the case of silver it holds up to 273 deg. K.,
(0 deg. C), and in the case of diamond up
to about 200 deg. K. Table I contains the
values of 9 for a number of different metals.
The data under 9i were calculated by Debye
from the elastic constants, while those under
02 were determined from the observations
on the specific heat.
TABLE I
Metal
fivtn =Ol
62
Al
399
396
Cu
329
309
Ag
212
215
Au
ltm
Xi
435
Fe
467
Cd
168
Sn
185
Pb
72
95
Bi
111
Pt
226
When it is considered that the elastic
constants were obtained at room temperature
and on different samples of metal from those
used in the determination of the specific
heats, the agreement must be considered
as very good.
It is interesting to note that while Debye
deduced his formula for monatomic solids
only, the third-power law was found by
Eucken and Schwers* to hold just as well for
the specific heats of the minerals fluorspar
(17.5 deg. to 86 deg. K.) and pvrite (21.7 deg.
(17.5 to 84 deg. K.).
More recently Nernst has attempted to
deduce a formula similar to Debye 's, making
use of the assumption that the distribution
of energy quanta takes place among groups
of atoms, rather than among different fre-
quencies, f But the experimental evidence is
hardly sufficient as yet to be able to decide
between these different theories.
Specific Heat of Gases
When a gas absorbs heat a part of this is
used up as increased energy of translation
of the gas molecules, while the other fraction
* Verh. d. Deut. phys. Ges. 16. 578 (1913).
t A. Eueken. Abh. d. D. Bunsen Ges.. 7. 390 (1914).
is used up in increasing the rotational energy.
According to the classical theory the specific
heat at constant volume per molecular weight
should be l/2 R=\ calorie for each degree of
freedom. Since a molecule consisting of two
atoms possesses three degrees of freedom
in virtue of its translational energy and
two in virtue of the rotational energy, the
specific heat per molecule should be — R = 5
calories.
Actual observation showed that at lower
temperatures the molecular heat of hydrogen
at constant volume tends to diminish to a
constant value 3,+ and Nernst suggested that
this must be due to the diminution in rota-
tional energy as the temperature is lowered,
just as the energy of vibration of atoms
decreases with decreasing temperature.
Applying equation (1) to the rotational
energy of a diatomic molecule (Er), we
obtain the relation
Er = -^~ (6)
AT .
1
where v is the frequency of rotation.
On the other hand, if I denote the moment
of inertia of the molecule rotating about its
center of gravity,
Er = \ {2-KVf
(7)
Eliminating v from these two equations
we should obtain an expression for the
variation with the temperature of Er. The
actual observations on the specific heat of
hydrogen between the temperatures 35 and
273 deg. K.§ were found to be quite different
from those expected on the basis of this
calculation.
Einstein and Stern** have therefore sug-
gested that instead of (6) we ought to write
the equation for Er thus:
hv
That
Er=-h
' kv
e»-l
thev
hv
(S)
assume the existence of an
hv
average latent energy — which is possessed
by the rotating molecule even at the absolute
zero. In this assumption they are in accord
t According to Keesom (see reference p. 243) the specific heat
of all gases at very low temperatures varies as the third power
of the absolute temperature, so that this value 3 for the specific
heat of hydrogen is only constant over a certain range of tem-
peratures.
§ A. Eucken. Berl. Akad. Ber. 1912. 141.
** Ann. d. Physik, 40. 551 (1913k
THE ABSOLUTE ZERO
24:;
with Planck's most recent modification of the
quantum theory. Furthermore, the photo-
electric effect and emission of electrons by
X-rays seemingly lead to the conclusion that
the electrons in a metal possess a similar
latent energy whose magnitude is — for each
4
degree of freedom.
The formula deduced for the specific heat
of gases on this assumption accords well with
the experimental data obtained by Eucken.
It is, however, only fair to state, that almost
as good an agreement has been obtained by
Ehrenfest* without introducing the idea
of a residual energy.
W. H. Keesom has also tried to apply the
quantum theory to the translational energy
of a gas.f He uses arguments analogous to
those of Debye, that is, from the elastic
properties of the gas (these can most readily
be calculated in this case from the velocity
of sound in the gas) he calculates a semi-
fictitious maximum frequency, vm, and then
derives a formula for the specific heat of gases
which is similar to that given above for solids.
From the observed measurements of the
pressure of helium at very low temperatures
he is also inclined to favor the assumption
that a zero point energy exists. In other
words, while the rate of increase of energy
per degree (the specific heat) tends to decrease
to zero as the temperature is lowered, it
absolute zero, a latent energy whose magni-
hv
tude is — for each degree of freedom. But
it must be stated that more facts will have to
be obtained before it will be possible to draw
any definite conclusions in this direction.
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Specific Resistance of Gold, Mercury and
Platinum at Low Temperatures
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Fig. 3. Atomic Heats of Diamond, Aluminum and Lead
does not necessarily follow that the total
energy itself becomes zero at the absolute
zero. There are a number of reasons for
believing rather that there exists, even at the
*Verh7d. D phys. Ges. 15. 451 (1913).
t Phvsik. Ztsch 14. 663 (1914).
{ Abh. d. D. Bunsen Ges. (1914), p. 246.
(2) ELECTRICAL PROPERTIES AT LOW
TEMPERATURES
Electrical Resistance
It has been known for a number of years
that the resistance of metals decreases with
the temperature. More recently a large
number of investigations have
been carried out in order to
obtain accurate data on the
variation of the electrical re-
sistance of pure metals at
extremely low temperatures,
and the results have led to
far-reaching speculations on
the mechanism of the con-
duction of heat and elec-
tricity in metals.
Fig. 4 gives the results
obtained by Clay and OnnesJ
on the resistance of mercury
(Hg), gold (Au) and platinum
(Pi) at temperatures ranging
from 100 deg. K. down to the
very lowest temperature at-
tainable. Fig. 5 shows the
same results plotted on a
much larger scale. The ordinate gives the
ratio between the specific resistance at T to
that of 0 deg. C. (273 deg. K.).
"Superconducting" State
The behavior of mercury is specially
noteworthy. At 4.3 deg. K., the resistance
244
GENERAL ELECTRIC REVIEW
is 0.0021 of its value at 273 deg. K.; but at
4.21 deg. the resistance decreases very
rapidly to a value which is less than one-
millionth of that at 0 deg. C. As Onnes
expresses it. the mercury becomes "super-
conducting." Very recently Onnes has
extended these results and finds that at
2.45 deg. K.. the resistance is less than
2X10"10 of that at 0 deg. C, the potential
difference at the extremities of the mercury
column (contained in a tube 0.004 mm2
cross-section) being only 0.56 microvolt
when the current density in the mercury was
1024 amperes per square millimeter .*
The same phenomenon has also been
observed by Onnes in the case of tin and lead.
The sudden disappearance of the resistance
in the case of tin takes place at 3.806
deg. K., the ratio of the resistance at 3.8
deg. K. to that at 273 deg. K being less
than 10"7.
Lead becomes "superconducting" when
immersed in liquid helium (4.3 deg. K.) ; the
change, however, from the ordinary to
the superconducting state occurs between
14 and 4.3 deg. K. All these metals show
the existence of threshold values for the
current density, that is, with current densities
above a certain definite value, the super-
conducting state does not occur. Using a lead
wire 0.025 mm.2 cross-section, the threshold
value at 4.25 deg. K. was observed to be
between 420 and 940 amperes per square
millimeter.t
Onnes applied this result to the production
of " resistanceless " coils having a great
number of windings in a very small space.
and therefore possessing high inductance.
It is well known that if a coil through which
a current is passing is suddenly short-
circuited, the rate at which the current in the
coil decreases to zero depends upon the
ratio of the resistance to inductance. Using
coils of lead wire immersed in liquid helium.
Onnes found that even after several hours,
the current through the short-circuited coils
had not diminished noticeably.
So far the existence of a superconducting
state has been noticed only in the case of the
three metals, mercury, tin, and lead. Each
of these metals could be obtained in an
exceptionally pure form. Onnes believes
that all the other metals will show similar
behavior at temperatures near the absolute
zero when they can be obtained in a suffi-
ciently pure state.
» Science Abstracts, A. p. 114 (1914).
t Science Abstracts, A. p. 385. (1914).
The behavior of the samples marked Pt-B,
Au (111) and Au (1") must be ascribed to the
predominant influence exerted by slight
traces of other metals at these very low
temperatures.
Failure of the Older Theory of Conduction
The curve for gold in Fig. 3 is typical
of the behavior of all the metals in tempera-
ture range 273 deg. K. to 20 deg. K. The
resistance tends to approach the value zero
asymptotically much in the same way as the
specific heat. This fact has led to attempts
to apply the quantum theory to explain
the variation in electrical resistance at low
temperatures.
According to the electron theory of con-
duction the specific conductance, ■=-, is given
by the relation}
' Rt
Rt
Ne*L
2 mu
(9)
where
N = number of free electrons per unit
volume
L = mean free path
e =unit electric charge
w=mass of electron
u = average velocity of the electrons.
The assumptions used in deriving this
equation are that electric conduction is due
to a convection of charged particles (elec-
trons) and that the collisions between atoms
and electrons are non-elastic. But by making
the further assumption that the free electrons
in a metal possess the same average kinetic
energy as the molecules in a gas at the same
temperature, that is, that
/2 mu^ = '-r feT§
(10)
it is possible to deduce a relation between the
thermal and electrical conductivities which
is known as the Wiedemann-Franz law. This
law states that the ratio of the electrical
to the thermal conductivity is a constant
for all metals at the same temperature and
varies directly as the absolute temperature. H
The agreement between the empirical law
obtained by Wiedemann and Franz and the
relation deduced by means of considerations
} E. P. Adams. Proc. Am. Inst. El. Eng., SS, 1159-1233 (1913).
N. Campbell, Modern Electrical Theory (1913), also
J. P. Minton, General Electric Review. March. 1915,
p. 204.
3
5 The constant — k is sometimes denoted by the symbol a.
t J. P. Minton, General Electric Review, March. 1915.
p. 207.
THE ABSOLUTE ZERO
245
based on the electron theory of conduction
was taken to be a signal confirmation of the
accuracy of these views. But it has been
shown by Lorentz and others that the assump-
tion that the average kinetic energy of the
electrons increases as the absolute tempera-
ture leads to conclusions which are at variance
with the known distribution formulas for the
energy radiated from a black body.*
Furthermore, on the basis of the ordinary
theory it is difficult to explain why the
kinetic energy of the electrons should not
exert an effect on the observed specific heats.
Thus, if the number of free electrons is
assumed to be the same as the number of
atoms, and each electron is assumed to
3
possess an average kinetic energy of — kT,
the observed specific heat per gram-atom
should be (6+tj) Nk = 7.5 calories, a con-
clusion which is not at all in agreement with
the observed values. (See section 2 above).
Wien's Modification of the Electron Theory of
Conduction
These difficulties have led physicists in the
past couple of years to discard the assumption
expressed by equation (10). This naturally
leads to the rejection of any theoretical basis
for the Wiedemann-Franz law. Since equation
(9) is merely an expression of Ohm's law in
terms of the electron theory, it is taken as the
starting point of the new theory which seeks
to explain the observed variations in the
specific resistance of metals as the temperature
is lowered.
While according to the older theory of
Drude and Riecke, the value of the ratio
N/u was assumed to vary with the tempera-
ture, Wien assumes that this ratio remains
independent of the temperature, while the
mean free path, L, is the only quantity that
does change. We know that in a metal the
atoms vibrate about equilibrium positions
which are arranged in regular lattice forms.
The electrons travel between the rows of
these atoms. The observed values of the
specific heats show us that at very low tem-
peratures the vibration of the atoms becomes
extremely small in amplitude, and the
number of vibrating atoms decreases rapidly.
Thus, an electron starting out under the
influence of even a small electric force, can
travel a big distance without suffering
collision with an atom; that is, the resistance
* S. Dushman. General Electric Review, Sept., 1914.
appears extremely small. At higher tem-
peratures the atoms begin to vibrate more
and more, so that the mean free path of the
electron between collisions decreases; the
kinetic energy of the electrons appears as
Joule's losses in the conductor.
As this theory requires that the kinetic
energy of the electrons should be independent
of the temperature, it is necessary to assume
the existence of this energy even at T = 0.
Here then we have again the conclusion which
has been mentioned above, that there exists
a zero point energy for the electrons in a
metal.
Assuming that the mean free path, L,
varies inversely as the square of the amplitude
of the vibrating atoms, Wien deduces a
relation of the form
Rt
7~2
-/(f)
(ID
where A is a constant, and / is a definite
function of the ratio between the quantity
Q = pvm and T. It will be remembered that
the quantity 0 has already been referred to
in section (2) as Debye's "Characteristic"
temperature.
At very low temperatures, the equation
reduces to
Rt = BT2 (12)
and at very high temperatures, it becomes
of the form
Rt = CT (13)
A, B, and C are constants which vary for
different metals.
Over an intermediate range of temperatures
the following relation holds fairly well:
Rt _T( 1 | e \ ,,9 , .
Rm ^273 "^ 298,000,/ /4 273 v ;
This is in agreement with the observation
that the specific resistance of most metals
varies linearly with the absolute temperature.
The values of the temperature coefficient
of the resistance calculated from this equation
are, however, found by Wien to be uniformly
higher than the observed values (which range
around 0.004 for most metals).
Corresponding States
The occurrence of the quantity Q = f$vm
in the expression for the electrical resistance
as a function of the temperature shows the
existence of an intimate relation between the
specific heat and electrical resistance. E.
Gruneisenf has drawn attention to this
t Verh. d. D. physik. Ges. 15, 186 (1913).
246
GENERAL ELECTRIC REVIEW
relation and has, in fact, deduced the empirical
relation
Rj=KCP (15)
where CP denotes the specific heat per gram-
atom at constant pressure, and K is a con-
stant.
0.010
*T
O.O/S
\ 0.0/0
O.ODS
0.000
w
4
II
/
I.
Vl/ III
.11 „
/
/
f;
1
$>'''
*
0°
s-
/0'
/£•
SO'
es-
■r
Fig. 5. Curves same as shown in Fig. 4, drawn on magnified
scale to illustrate the "superconducting"
state of mercury-
It has already been observed that the
function 9 has been designated by Debye
as the "characteristic" temperature. The
atomic heat of all monatomic substances is
a unique function of the ratio &/T. In a
similar manner we find that according to
Wien Rt T2 multiplied by a constant (which
varies with each metal) is a unique function
of 6,7'.
The ratio 8 T thus plays the same role
in connection with the properties of mon-
atomic solids at low temperatures, as the ratio
7 t T does in the consideration of the proper-
ties of gases and liquids, where Tc denotes
the critical temperature. There is no doubt
that in the near future it will be possi-
ble to develop an equation of state for
solids which will be quite as general as
the conclusions which Van der Walls has
developed for the transition from the gaseous
to liquid state, and just as the ratio Tc/T
is of importance in considering corresponding
states of gases and liquid, so the ratio 9 T
must be the standard of reference for con-
sidering the properties of solids at low
temperatures.
Fig. 6* is of interest in this connection as it
represents an attempt to correlate the
electrical resistance with the values of 9 = j3i^m
derived from specific heat determinations.
* H. Schimark. Ann. d. Physik, jfi, Tort I 1914).
There appears to be a general tendency for
the resistance to decrease with increasing
value of jivm.
Difficulties in Wien's Theory-
There are, however, some difficulties that
prevent us from completely accepting Wien's
theory as it stands. The Wiedemann-Franz
law remains completely unexplained, and it is
difficult to see how else it can be explained
except by assuming that at least a fraction
of the electrons possess an average kinetic
energy which is the same as that of the
molecules of a gas. Furthermore, as well
known, the electron emission from hot
metals increases exponentially with the tem-
perature as shown by Richardson. This points
to the conclusion that the kinetic energy
of the electrons must also increase with the
temperature — at least at the higher tem-
peratures.
On the other hand, Wien's theory does
accord quantitatively with the experimental
data at temperatures down to 20 deg. K.
(No theory seems to have been advanced
to account for the superconducting state.)
Keesom has therefore attempted to reconcile
the observations at low temperatures with
those at higher temperatures by applying
the conclusions which he has deduced regard-
ing the specific heat of monatomic gases.
He considers the electrons in the metal at
very low temperatures as similar in all
respects to a monatomic gas under the same
conditions, and applies the quantum theory to
calculate the variation in the concentration of
free electrons with the temperature. He finds
in this manner that at higher temperatures
the average kinetic energy of the electrons
is that demanded by the Law of Equi-
partition and the electron emission must
therefore vary according to a law which
is approximately the same as that deduced
by Richardson. With decreasing tempera-
ture, the number of free electrons decreases
and tends to a constant value at extremely
low temperatures. In this region the velocity
also tends to a constant value. The theory
advanced by Keesom thus leads to conclu-
sions which are in accord with Wien's theory
for low temperatures, and with the older
theory at higher temperatures.
Thermo-Electromotive Force. Peltier-Effect
The thermo-electromotive force is due to
the potential difference developed when
electrons are transferred from the hot junction
of two different metals to the cold junction.
THE ABSOLUTE ZERO
If Na and Nb denote the concentrations in
the two metals A and B, the difference of
potential at the surface of contact according
to the older theory is
T . 2 k „ , Na
Vab=-V T l0S'N-B (1,i)
Keesom shows that this formula holds only
at the higher temperatures. At low tem-
peratures the potential difference is
l'.4B = 2.52X10-22r3
\Nb2 Na2)
(17)
That is, the rate of change of thermo-
electromotive force with temperature tends
to vanish as the absolute temperature is
approached. The equation is in agreement
with the observations of Onnes and Hoist
at the temperatures of boiling helium.
The Peltier effect corresponds to the work
required to transfer unit electric charge
across the junction of two metals containing
different concentrations of electrons. Accord-
ing to Keesom the amount of heat developed
at very low temperatures owing to this
effect should vary as the fourth power of the
absolute temperature.
It is interesting to note that according to
the above conclusions, the electrical resistance,
the specific heat, the thermo-electromotive
force, the Peltier effect, and probably most
of the other properties obey such very simple
laws at temperatures near the absolute zero.
Not only do the actual values of each of these
tend to disappear at extremely low tem-
peratures,* but their differential coefficients
with respect to the temperature tend towards
the limit zero in the same manner. This is in
accord with the predictions made by Nernst
from a consideration of the rate of change with
the temperature of the total energy of mon-
atomic solids, and shows in another way
that there exists an intimate relation between
the specific heats and the other properties
of solids at very low temperatures.
(3) MAGNETIC PROPERTIES
Langevin's Theory of Paramagnetism
A large number of investigations have been
carried out during recent years in Onnes'
laboratorv, on the magnetic properties of
different " substances at low temperatures.
While a more complete discussion of our
present theories on the nature of magnetism
must be reserved for a future occasion, a few
remarks on Langevin's theory of paramag-
*This statement is not true of all the properties if it be
assumed (see pp. 242 and 2+8) that a zero-point energy exists.
netism is necessary in order to understand
why so much effort has been spent in investi-
gating the effect of temperature on the
magnetic susceptibility.
Langevin assumes that the magnetism
induced in paramagnetic substances is due
to an orientation of the elementary magnets
(which may consist of electronic orbits) under
| 1 1 | ! |
I
I 1 1 i
1 ]
1 ' 1
1 1
!
1 I
\
\
! /"
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/
7 |
0600
/
/
~?7
w
1
Rr
7
Metal i $v
4-
Rm
■
Cd
Au
Ag|
Ft}
Znl
Cu
Co
m
F» 1
136
180
215
325
401
406
413
'
-
{
/
/
■
[Z
'/
'/
/
/
]/
/
'"
'M
T<-
-
-■
.=■-.
\
110 160 ISO 200 220 2tO 260 273,1
Fig. 6. Specific Resistance of Various Metals from
273 deg. K. to 20 deg. K.
the influence of the magnetic field, which is
opposed by the ordinary vibration due to
heat energy. At any temperature there
results therefore a static equilibrium between
the force due to the outside magnetic field
and that due to thermal agitation. Langevin
was able to deduce from this the relation
which had been previously derived by Curie
from experimental data, and which states
that the paramagnetic susceptibility (X) is
inversely proportional to the absolute tem-
perature, that is,
x=w (18)
where C is a constant.
Deviations from Curie's Law at Low Temperature
Onnes and his collaborators have, however,
found that substances which follow this law
at higher temperatures may begin to deviate
from it at lower temperatures in such a
direction that the susceptibility is lower
than that deduced from the observations at
higher temperatures. In explanation of this
Oosterhuisj has suggested that most probably
t Phys. Zeitschrift, ; .(, 862 (1913).
248
GENERAL ELECTRIC REVIEW
it is no more justifiable to apply in this case
the laws of statistical mechanics than in
that of specific heats. According to the
quantum theory, the average energy of an
oscillator with two degrees of freedom is not
kT, as demanded by the principle of equi-
partition, but
hv . hv
U =
hv
tkT_X
(19
[Compare equation (8) above.]
Oosterhuis therefore writes equation (18)
in the form
A r
(20)
where U is determined from equation (19)
and v refers to the frequency of vibration
of the molecular magnet.
It is interesting to observe that according
to this equation the curves giving the relation
between the reciprocal of the magnetic sus-
ceptibility ( - ) and T are of the same form
(x)
as those indicated in Fig. 1 for the function F;
but the actual values of -^ are proportional
to the quantity I F +-~" )■ That is, the value
of = does not decrease indefinitely (as de-
manded by Curie's law) but tends to approach
a practically constant value which is equal to
~ 1 — 1, as the temperature approaches that
of absolute zero.
// v
The introduction of the term -=- is justified
on the following basis. If the thermal agita-
tion of the molecular magnets ceases at the
absolute zero, there is no force tending to
oppose that of the magnetic field, all the
elementary magnets must therefore orient
themselves under the action of this field,
that is, it must be possible to attain magnetic
saturation. The fact that such saturation
is not even approximately attained is taken
to indicate that the molecular magnets possess
a latent energv which is independent of the
hv
temperature and has the value — '■
Zero-Point Energy
As pointed out by Oosterhuis* and as
mentioned above, the existence of a zero-
* Science Abstracts. A, 1914. p. 59.
point energy is therefore made probable by
four different lines of investigations.
(1) The change in the specific heat of
hydrogen at low temperatures has been
explained by Einstein and Stern in a satis-
factory manner by this assumption.
(2) Keesom has shown that a similar
assumption seems to be required for the
translational energy of gas molecules in
order to explain the deviations from the
ordinary gas laws of a helium thermometer
at low temperatures.
(3) The assumption of a zero-point energy
has been shown by Keesom to be of great
importance in the theory of free electrons
in metals. Moreover by making this assump-
tion the views of Wien and the conclusions
of the older theory are reconciled.
(4) The deviations from Curie's law
observed at low temperatures may be corre-
lated and quantitatively explained by this
assumption.
While it may be possible to explain each
of these sets of observations without the
necessity of introducing a zero-point energy,
yet the cumulative effect of these four differ-
ent lines of investigations is strongly in favor
of the assumption that the molecules of a gas
and the free electrons in a metal possess a
latent energy which is independent of the
temperature and persists even at the absolute
zero.
CONCLUSION
The above are. briefly, some of the specu-
lations and conclusions which have been
suggested by the results of the investigations
at low temperatures. The absolute zero
appears to us from the point of view of the
present theories as a sort of unattainable
limit. As we approach this temperature
more and more closely, the practical diffi-
culties in the way "of obtaining still lower
temperatures become greater and greater
until finally they become insurmountable.
All the criteria by which we ordinarily
determine temperature gradually disappear
and the absolute zero itself becomes, as it
were, a will-o'-the-wisp which continually
draws us on and yet remains just as remote
from our reach.
However, the investigations at low tem-
peratures lead to this important conclusion :
that the properties of all substances tend to
obey very simple laws under these conditions,
and furthermore, that all these properties
are probably connected by functions which
are perfectly general and valid for all sub-
stances.
24VI
OPERATING CONDITIONS OF RAILWAY MOTOR
GEARS AND PINIONS
By A. A. Ross
Railway and Traction Engineering Department, General Electric Company
The following article contains information which should prove to be of much practical value to those
interested in the operation of railway motor gears and pinions. After locating and identifying those causes
which have produced unsatisfactory operation, the author discusses each one and formulates such recommenda-
tions as will lessen the premature breakage and excessive wear of bearings and teeth. The limitations of
motor design as influenced by the use of standard 14^2 deg. pressure angle and 20 deg. stub pressure angle
teeth are denned. The most beneficial relative hardness of gear to pinion is named, and a description of good
and bad methods of mounting and dismounting pinions is given. The article is concluded by a discussion
and statement of reasonable gear mounting pressures. — Editor.
The limitations imposed upon the space
available for gears and pinions in the design
of modern railway motors, and the severe
conditions under which railway motor gears
and pinions are operated, necessitate the
use of materials which will insure protection
against breakage and secure the maximum
resistance to abrasive wear. While the gear
and pinion manufacturers have been striving
to meet these conditions with various grades
of steel and special methods of treating the
steel, very few operators have taken steps
to improve operating conditions.
Apparently the average operator has never
given this side of the question serious con-
sideration, a pinion is a pinion and a gear is
a gear, and if they break or wear out rapidly
it is simply defective material and up to the
manufacturer to make good. If the manu-
facturer does not feel so inclined the operator
invariably changes to some other manu-
facturer's product, and in nine cases out of
ten the original trouble recurs. Had the
operating conditions been definitely known,
the trouble might have been overcome with
the original material and the operator, the
manufacturer and the trade benefited there-
by-
The mere replacement of a gear or pinion
covers a very small percentage of the actual
cost to the operator. The writer will endeavor
to briefly outline these conditions in the
following order:
Motor design limitations.
Variation in gear and pinion life.
Operators' responsibility for broken gears
and pinions.
Motor Design Limitations
The involute or single curve tooth is best
suited and most commonly used for railway
motor work, for two reasons; first, on account
of the greater thickness at the root of the
tooth, and second, because the distance
between the centers of the gear and pinion
can be slightly increased without seriously
affecting the mesh of the teeth.
In city service 3 diametral pitch teeth are
the most popular, with an occasional appli-
cation of 3 }/2 and 4 diametral pitch on small
motors for 24-inch wheel equipments. For
heavy high speed duty, such as interurban,
suburban and locomotive service, the size
of teeth is usually either 2}^, 2)4,, 2 or \%
diametral pitch. For the smoothest operation
the teeth should conform to the standard
14}/2-degree pressure angle, but on account
of high tooth loads the motor designer is
frequently forced to use the 20 degree pressure
angle stub tooth.
A comparison of the 2^ pitch standard and
20 degree angle stub teeth is shown in Figs.
1, 2 and 3. The contours of the teeth in the
layouts are theoretically correct and may
vary slightly from the actual teeth, but the
working contacts are sufficiently correct for
comparisons. They certainly will not improve
as the teeth become worn. It will be noted
that the diameter of the base circle from which
the involute or face radius of the tooth is
generated decreases as the pressure angle
increases. Consequently, the tooth with the
20 degree pressure angle is much thicker
at the base. The "Whole Depth" of a stub
tooth is usually made equal to the next half
size smaller standard tooth; that is, the
addendum or the distance from the pitch
diameter to the top, and root or the distance
from the pitch diameter to the base of 2}/%
pitch stub corresponds to the 3 pitch stand-
ard; the 2 pitch stub to the 2Yi pitch
standard, etc., but the pitch diameter, the
tooth thickness at pitch line, the face and
flank radii of the tooth are the same for both
standard and stub.
The stub tooth is from 40 to 50 per cent
stronger than the standard, but the mesh or
working contact of the teeth is not so desir-
able.
250
GENERAL ELECTRIC REVIEW
14 ANGLE STANDARD
20° ANGLE STUB
Fig. 1. Four Different Mesh Positions of a 2H Pitch, 18 Tooth Pinion, and 68 Tooth Gear
OPERATING CONDITIONS OF RAILWAY MOTOR GEARS AND PINIONS
251
Fig. 2. Angle of Action of the Teeth shown in Fig. I
PITCH DIAMETERS^
Fig. 3. Angle of Action of the Teeth shown in Fig. 1, but with Distance between Gear Centers Increased
252
GENERAL ELECTRIC REVIEW
Fig. 1 shows a 23-2 pitch, 18 tooth pinion
and a 6S tooth gear standard and stub in
mesh in four different positions.
Fig. 2 shows the angle of action of this
combination or the angle through which the
pinion passes while a tooth is in contact.
Teeth Nos. 1 and 1' are two successive teeth.
No. 1 is just coming in contact and 1 and 1'
travel to the 2 and 2' positions before 1' or 2'
as shown disengages. Therefore between
1 and 2 positions there are two teeth in
contact and between 2 and 1' positions only
one tooth is in contact. It is obvious at a
glance that the working contact of the
standard is much better than the stub and
that the contact of the stub tooth in thel'
position is at the extreme top or excessive
friction point before it is relieved by the
incoming No. 1 tooth.
In Fig. 3 the distance between the centers
of the gear and pinion have been increased
to represent the conditions when the armature
linings are worn yj in. and the axle lining
about yg in. No. 1' tooth is about to disengage
as No. 1 engages. While the working contact
is bad on the standard, it is considerably
worse on the stub.
Comparative tests which the writer has
followed, and reports from operators, would
indicate that 20 deg. stub tooth gearing is
more noisy than the standard. No doubt this
is due to the inferior mesh.
The increased angle of pressure will
increase the pressure on the bearing linings
but the increase is so slight that the effect
on the life of the linings is negligible.
The reader will, no doubt, ask the ques-
tions: Why adopt the 20 deg. angle stub
tooth since it does not give the best servicer
Why not gain the required strength by
choosing a larger standard tooth ? In this the
designer is usually limited to a ratio suitable
to meet service requirements. To maintain
this ratio and adopt a larger tooth is very
often impossible for the following reasons :
First. It would mean an increase in the
distance between the center of the gear and
pinion which adds to the weight and price
of the motor, both of which would be seri-
ously objectionable to the operator.
Second. The design of the trucks may not
permit an increase in the distance between
the center of the axle and suspension side
of the motor.
Third. The minimum number of teeth in the
pinion is limited to the diameter of the
shaft and thickness of the section of metal
between the base of the tooth and bottom
of the keyway. Consequently the larger
tooth invariably means a considerable in-
crease in the outside diameter of the gear.
Such an increase may not be possible on
account of the wheel diameter and track
clearance limits.
Regardless of the mesh there are large
quantities of stub tooth gearing being oper-
ated throughout the country, and with the
exception of the complaint on noise, they are
giving perfect satisfaction. Apparently, the
difference in total life has not been noticed.
However, the writer would recommend the
use of the standard tooth wherever it is
possible to apply it, for railway motor
gearing is bad enough at the best. If the use
of stub teeth is imperative, limit the practice
to teeth whose "whole depth" is not less
than the 3 pitch standard, for the average
operator will allow the same limits for lining
wear regardless of the length of the teeth
in his gearing. If the length of the teeth in
Fig. 3 were reduced the working contacts
would be still worse.
Variation in Gear and Pinion Life
From actual service observations it is
evident that in straight carbon steel or
non-alloy steel the harder the wearing
surface of the tooth, the greater the resistance
to abrasive wear. Case hardened material
now offered to the trade under various trade
''21
Fig. 4. Sand shown in Vial Represents One Per Cent of Sand
by Weight in 12 Lb. of "Gear Lubricant
names by practically all gear and pinion
manufacturers, affords about the hardest
possible tooth surface, but it does not afford
maximum protection against breakage. While
not wishing to offer excuses for manufacturing
OPERATING CONDITIONS OF RAILWAY MOTOR GEARS AND PINIONS 253
defects, the structure of this steel with its
glass hard brittle surface is very susceptible
to injury from shocks such as may be trans-
mitted to the teeth during motor flashovers
or when at high speed the wheels hit high
rail joints, frogs, etc. ; but the greatest source
of danger lies in the operator's methods of
mum protection against breakage and a
high uniform hardness which resists abrasive
wear almost to the same degree as case
hardened material, it devolves upon the
operator to determine by actual service
tests on his own equipment which is the most
profitable.
>
0
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,
' 4
. ■ <£' '.*
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Grease Containing 2 Per Cent of Sand by Weight
Grease Containing 5 Per Cent of Sand by Weight
V
fi-
4
Grease Containing 10 Per Cent of Sand by Weight
Fig. 5. Photo-micrographs (26 dia.) of a Popular
mounting and dismounting; this will be
referred to later. The material is also very
expensive to manufacture, but its total life
has been so much greater than the old
combination which consisted of oil treated
pinions and untreated cast steel gears that
its first cost and breakage has been overlooked
by the operator.
"With the advent of the less expensive
specially treated homogeneous steel having
physical characteristics which afford maxi-
Grease Containing 25 Per Cent of Sand by Weight
Motor Grease Containing Various Percentages of Sand
It is unsafe for one operator to use the life
values established on some other road for the
life is in a great measure affected by the
ratio. Still it is quite common to find a
radical variation in the life of the same
grades of gears and pinions on two roads
which have duplicate equipments. Such
variations can only be accounted for as
follows :
The first and greatest factor is the grit or
cutting substance which accumulates in the
254
GENERAL ELECTRIC REVIEW
■xy ajar
.^3>(^¥
T^JiJHM S3*A*s4*S SSNfKf?
3
•a
<
|M-L.-#-t 'S §
OPERATING CONDITION OF RAILWAY MOTOR GEARS AND PINIONS 255
gear pan and when mixed with the lubricant
acts as an abrasive lap on the gear, pinion
or both. Practically every Master Mechanic
will disclaim its presence, but it is there and
it has been found in quantities as high as
24 per cent.
It is doubtful if the reader appreciates what
even one per cent of sand really means.
The average amount of lubricant in gear pans
is about 12 pounds. The quantity of sand
in the vial, Fig. 4, represents 1 per cent of
sand in 12 lb. of lubricant. The vial is 1%
inches in diameter. Pause for an instant
and consider what 10 per cent or 10 times,
24 per cent or 24 times, this quantity means.
Fig. 5 shows photo-micrographs of a
popular motor grease containing various
percentages of sand magnified to 26 diam-
eters. The sand used in the mixture was first
screened through an SO-mesh screen.
The sand usually enters between the gear
hub and gear pan in the form of street dust,
brake shoe dust and wheel wash. Very often
the contour of the web and hub of the wheel
is such that the natural flow of the wheel
wash is against the opening in the gear pan
as shown in Fig. 7. It would be much better
if this were retarded by either making the
diameter of the wheel hub larger or smaller
than the gear hub. The clearance between
the gear hub and gear pan is sometimes
enclosed by a felt dust guard, but this is not
a permanent protection as the felt soon
fills up with sand, and breaks off. Careless-
ness when adding lubricant or when the
lower half of the pan is lying in the pit
during inspection is another source of dirt
getting into the grease. One of the largest
operators in the east traced the cause of rapid
wear to the presence of sand in the lubricant
which was carried into the pan by the wheel
wash during a period of heavy snow and slush.
The sand or stone dust seems to scour
the lubricant off the teeth.
Before shipment the finished surfaces of
gears and pinions are given a coating of
slushing compound to prevent rust. This
should be removed before the gears and
pinions are placed in service as it becomes
filled with lime and sand during shipment.
The second factor is excessive lining wear
which permits improper mesh as shown
in Fig. 3. The design of the motor and the
truck prevents the use of a bearing on each
side of the gear and pinion so that when
power is transmitted from the pinion to the
gear both the armature and axle shafts tend
to spring diagonally away from one another.
The armature shaft bearing adjacent to the
pinion becomes worn on the side which is
farthest from the axle, while the bearing
on the other end wears on the side near the
axle. The wear on both bearings is not
radial with the center of the axle but at t w. i
Fig. 7. Diagram showing the Natural Direction of Flow of
Wheel Wash Against the Gear Cover
points about 45 degrees above and below the
radial line, according to the direction of
rotation. This allows the pinion teeth to set
at an angle to the gear teeth, which means
that the ends of the teeth next the motor
receive the greatest percentage of shocks and
must perform the major portion of the work.
Such conditions account for the greater wear
on the motor ends of the teeth. Consequently,
very little would be gained by increasing the
present standard width of face. Furthermore,
the axle linings wear on the upper portion
of the bore away from the armature shaft
which tends to carry the pitch lines of the
gear and pinion still further apart and forces
the working contacts to take place on the
top or excessive friction points.
Some operators claim that it is impossible
to maintain J^j in. as the limit for axle lining
wear, as it forces too frequent renewals
and that the slight reduction in gearing
maintenance is offset by an increase in lining
maintenance. If gearing maintenance were
the only consideration there might be some
ground for the argument, but the improper
mesh also produces a noisy chattering, which
effects commutation and the nerves of the
population living along the route over which
the gearing is operated. If the operator doubts
the effect on the rest of the equipment -let
him get into the pit under a motor with the
axle linings worn say ^ in., start the car so
that the pinion climbs the gear and, as the
car gains momentum, note the blow on the
axle as the motor settles back into place.
This is especially severe on heavy equip-
ments.
The effect which axle lining wear has
on gears and pinions is shown in Fig. 6,
which is plotted from actual service tests.
The axle linings on No. 4 motor show the
256
GENERAL ELECTRIC REVIEW
least amount of wear; consequently, the
wear is less on No. 4 gear and pinion. A
handy gauge for checking lining wear is
shown in Fig. S.
Many of the latest types of motors are
provided with axle dust guards which com-
EACH GRADUATION 15 fe OF THE TOTAL l£N5TM
AND INCREASES THE DUMETefl .OIO
Fig. 8. Gauge for Measuring Lining Wear
pletely enclose the axle between the bearing
housings and prevent sand from getting
in the linings. This is a step in the right
direction, but there is a tendency on the part
of the operator to pay less attention to axle
lining wear limits owing to the trouble of
removing the guards for inspection. A very
fair idea of lining wear without removing the
guard can be obtained by jacking up the
bearing housing with a block and pinch bar.
The third cause is the consistency of the
lubricant. There are many good grades on
the market but, be the grade what it may,
the lubricant should be of such consistency
and used in such quantities that the gear
teeth will dip frequently. The writer has
absolutely no confidence in the virtue of a
lubricant so hard that the gear cuts a groove
through it and as soon as the grease in the
groove is deposited on the sides of the pan.
the teeth run dry. The lubricant should be
soft enough to level back and be again picked
up by the gear teeth. Also, if the lubricant
is soft the sand will more readily settle to
the bottom. The operator who uses a summer
grade during the winter months usually does
so at the expense of his gearing.
The number of stops in the schedule, the
coasting limits and the motormen's methods
of accelerating and braking may be considered
the fourth factor.
Operator's Responsibility for Broken Gears and
Pinions
By comparing the thickness at the base
of the gear and pinion teeth in Fig. 1, it will
be noted that the thickness is less on the
pinion. This is due to the under cut at the
root of the pinion tooth to give clearance
for the gear tooth. The pinion teeth being
the weaker of the two, it is obvious that the
greatest percentage of tooth failures will
occur on the pinion, and as previously
mentioned on the motor ends of the teeth.
The breaks usually begin in a V-shaped
fracture and progress irregularly to the top
of the tooth about one-third across the tooth
face. The usual question is: What causes
the failures, and why should one operator
have more than another? Invariably, the
operator will put the responsibility up to the
manufacturer, but there are many causes
for failures over which the manufacturer
has absolutely no control and for which the
operator is entirely responsible, especially the
methods employed when mounting and dis-
mounting the pinions. The most common
■ and injurious method for mounting is that
of driving a pinion home with a sledge.
Usually one man holds a babbitt metal ring
or cup-shaped protector over the end of the
pinion while another swings onto it with a
10 or 20-lb. sledge.
Now let us consider what happens to the
pinion. The shaft on which the pinion is to be
mounted has a tapered fit and every blow of
the sledge adds internal stresses to the body
of the pinion; the maximum stresses depend-
ing on the proficiency of the man who
swings the sledge and the number of blows
delivered. The section of metal between the
root of the tooth and the bore at the large
end or between the root of the tooth and the
bottom of the keyway on the popular pinions,
14 and 15 teeth, 3 pitch, 17 and 18 teeth.
2Jo pitch, is usually just about thick enough
to take care of the tooth load stresses, and if
excessive stresses are added when mounting,
the pinion after being placed in service
either splits through the keyway or a portion
of one or more teeth directly over the keyway
fails from fatigue at low mileage.
0 K*^6FAR COMER
Fig. 9. Diagram of Frame Head and Pinion showing
Clearance for Pinion Puller Ring
Some operators make it a practice to heat
the pinions in boiling water and then sledge
them on as just described. This method is
exceptionally severe for the metal is sub-
OPERATING CONDITIONS OF RAILWAY MOTOR GEARS AND PINIONS 257
jected to shrinkage strains plus the stresses
set up by sledging.
The following is the safest method and
is giving perfect satisfaction on several large
roads: The pinion is first slid onto the shaft
to make sure that it fits properly and
especially that it does not ride the key.
It is then placed in boiling water until it is
heated clear through; about 45 minutes.
(Flame or heating in an oven should never
be allowed as the temper of some grades
may be easily drawn and the virtue of the
treatment lost.) It is then seated quickly
on the shaft and rammed home with a
wooden block, three or four feet long, about
the diameter of the pinion and cupped at
the end to clear the shaft. The nut is immedi-
ately set up and the pinion rammed once
more and the nut again set up. If the pinion
is heated clear through and fits the shaft
properly it will not work loose.
The fit on the shaft is very important, if
the shaft is not perfectly round or if the metal
is swelled on each side of the key which can
easily be done by using force to seat a key
which is too wide for the key way, or if the
pinion rides the key there is a tendency for
the mounting stresses to localize at one of
the bearing points in the body of the pinion
which eventually results in a tooth failure
or a crack in the body directly over the point
of localization.
The method of dismounting is another
great source of pinion tooth failures. It is
still common practice to drive wedges between
the bearing housing and the end of the
pinion. The writer doubts if it is possible to
remove a pinion in this manner without
subjecting one or more teeth to injurious
shocks, especially so with case hardened
material which is easily damaged and which
is removed several times during its life.
A pinion puller which grips only two or
three teeth is equally bad. A puller which
grips all the teeth is the safest. There are
two or three on the market which can be
assembled on all types of split frame motors
providing the armature is removed from the
motor, but on some of the old types of box
frames it is impossible to assemble them
unless the outside diameter of the pinion
teeth is at least % in. greater than the
projection shown as C diameter in Fig. 9.
Space B will permit a puller jaw thick enough
to withstand the stresses. On the later types
of box frame motors the -frame heads are
chamfered as shown at D. Thus, plus the
space A, which is usually }'i in. will accommo-
date a puller jaw similar to E and permit
the use of satisfactory pullers. Rather than
use wedges it would be more economical for
the operator to chamfer his frame head in
the same manner.
On the other hand, all steel will reach its
life limit and break down from what is known
as "fatigue" if the load is repeatedly applied
even though the load is far less than it can
bear indefinitely. This accounts for a great
percentage of tooth failures on heavy equip-
ments where the tooth loads closely approach
the elastic limit of the material. The failures
may occur before the teeth have even ap-
proached the wear scrapping point. In such
cases the operator should establish a safe
mileage limit and scrap the pinions regardless
of the amount of wear.
There are so many different grades of
gears and pinions on the market that the
master mechanic is sometimes uncertain as
to which grade of pinion is the most eco-
nomical to operate with a certain grade of
gear.
In the first place it is unreasonable to
expect satisfactory results from a combination
in which the gear is harder than the pinion
for each pinion tooth makes from two to four
contacts to each contact of a gear tooth.
From actual service observations it is evident
that the best results will be obtained by
operating together a gear and pinion of the
same hardness. This means that the gear will
outwear two and sometimes three pinions,
and the second and third must mesh against
worn gear teeth which will produce noise
until the gear and pinion teeth have adjusted
themselves to the proper contour. While this
adjustment is taking place the wear seems
to have a greater effect on the new pinion.
The total life of the second and third pinion
will be less than the first or original pinion.
Some master mechanics ask: "Is it possible
for me to obtain a pinion which will give a
life equal to the gear?" With the grades of
gears and pinions on the market at present
the writer's answer — from an economical
standpoint — is "No." It can, however, be
accomplished by operating a hard pinion and
soft gear together, but I think the trade
learned from experience when the case
hardened pinions first came on the market
that such a combination resulted in a reduc-
tion in life of the gear, and the gear being the
more expensive member of the two it was
anything but a profitable combination.
The operator should, therefore, carefully
watch the performance of his gears for he
258
GENERAL ELECTRIC REVIEW
may be getting high pinion life at the expense
of his gears.
There seems to be an extreme and un-
reasonably wide range in the total tonnage
limits which various master mechanics have
adopted for mounting solid gears without
keys. The range varies from 20 to SO tons.
For city service 20 to 30 tons is sufficient and
is proving satisfactory on several roads.
For interurban service anything over 50 tons
seems unreasonable. For instance, take
40,000 lb. as equipment weight, 1.5,000 lb. for
passengers, 30 in. wheel and 5 in. axle and
the torque at the gear bore at the slipping
point of the wheels is as follows :
40,000 lb. weight of car equipment
15,000 lb. weight of passengers
55,000 lb. total
0.30 per cent coefficient of friction
16,500.00
16,500 =412.
4 (no. axles) '
lb. per axle to slip
0.30 per cent coeffi-
cient of friction.
30 X4125 = 24,750 1b.
= 123^2 tons torque at gear bore.
Considering the usual finish on the axle
and bore and the ironing effect between the
two surfaces when the gear is mounted, it will
take a much higher tortional pressure to twist
the gear on the axle than the pressure used
to mount it. It is common practice to use
the same limits for gears and wheels. The
high ranges may be necessary for the wheels
on account of the end thrusts, but as there is
no lateral pressure on the gear the tortional
pressure is only to be considered. Of course,
there are unknown torques to be considered
which may result from momentum when
motors are short circuited or suddenly
reversed. In the above case had the gear
been mounted at 20 tons there would have
been a sufficient factor of safety to take care
of the unknown torque. Therefore, why use
the high tonnage range which makes it
difficult to remove the gear and subjects the
gear to unknown internal stresses which
mav cause failures, when it can be avoided?
X-RAYS
Part I
By Dr. Wheeler P. Davey
Research Laboratory, General Electric Company
This is the first of a series of articles on the physics of X-rays. The present article deals with the theory
as to their nature. According to this theory these rays belong to that great family of electromagnetic
disturbances which includes the waves of the wireless telegraph, and those of infra-red, visible, and ultra-
violet light. Future articles will take up the properties of the rays and some of their uses. — Editor.
Of all the theories so far proposed as to the
nature of X-rays, the Electromagnetic Theory
seems to be the most useful.* This theory
seeks to account for X-rays in terms of the
properties of the electrostatic and magnetic
fields of electrically charged moving particles.
It is found that such a theory is capable of
giving a rational basis for correlating the
facts known at present about X-rays and is
also able to suggest fruitful topics for further
research.
It is well known that if a stationary body,
.4, is given an electric charge, the region
around .4 becomes altered in such a manner
that a force of repulsion is exerted upon any
other body similarly charged. For simplicity
*The word "useful" is used here purposely. No theory is
to be regarded as a statement of absolute fact. A theory may
be disproved, but it can never be completely proved. Of two or
more theories, all of which are equally consistent with the
known experimental data, the one to be preferred is that which
proves to be of the greatest use in producing results.
let .4 be spherical in shape and not situated
near any other charged body; then, the
electric force extends from it radially in all
directions. If the location of A or the amount
of charge upon it is changed, there is a
corresponding change in the electric force,
and this change in the electric force is propa-
gated from .4 with the velocity of light
(3X1010 cm. per sec).
Xow suppose that .4 is moving with uni-
form velocity and that this motion has
already been kept up for so long a time that
the whole electric field of force is in motion
with it. This condition of the electric field is
represented diagrammatically in Fig. 1. If
.4 is suddenly stopped, the condition of the
electric field is as represented in Fig. 2a.
The direction of" motion is represented by
XX'. If .4 had continued in uniform motion
for a time. /. it would have reached A', and
X-RAYS
259
would have had a field such as is shown bv
the lines A'DE, A'HI, A'X'. A' JK, etc. But,
since A has been stopped, it will finally have
a field such as is shown by the lines ABC,
AFG, AX', A LAI, etc. The intermediate
stage is shown bv the full lines ABDE,
AFHI, AX', ALJK, etc., where BD, FH, LJ,
etc. constitute the changing portion of the
electric field, which, as has been stated
before, moves out from A in all directions
with the velocity of light. BD has the same
relation to ABDE as the "crack of a whip"
has to the whip itself.
The movement of a line of electric force
calls into existence a magnetic field, and this
holds true independently of whether the
movement is caused as previously described
or is caused by electric charges passing
through a wire. Now, when a current passes
through a wire, the direction of the magnetic
field is mutually perpendicular to the direc-
tion of the electric field and to the direction
of the current. Since the electric field of each
elementary charge of electricity moves with
that charge, we may make this more general
statement — The direction of the magnetic
field due to a moving electric field is mutually
perpendicular to the direction of that electric
field and to the direction in which that field is
moving. We should therefore expect to find
that as BD, FH, LJ, etc., move outward from
According to the electromagnetic theory,
primary X-rays consist of such pulses as have
just been described. If negatively charged
particles of matter (variously called cor-
puscles, (3 particles, cathode rays, and
electrons) are shot out at high velocities
Fig. 2b
Fig. 1
A they would be accompanied by a magnetic
field perpendicular to the paper. The pulse
sent out by A upon stopping is therefore
partly electric and partly magnetic in its
nature and is called an "electromagnetic"
pulse.
toward the target of an X-ray tube, they will
experience a great decrease in velocity upon
entering the face of the target; and during
the time that this retardation occurs, X-rays
are produced. Their properties seem to
depend only upon the rate of retardation
which the cathode rays experience at the
target, and this in turn depends only upon
the voltage across the terminals of the X-ray
tube and upon the material used as a target.
If OH (see Fig. 2b) is drawn parallel to A" A'',
so as to represent the path taken by H, then
FO is called the "thickness" of the pulse FH.
We will call this thickness d. The electric
force along FH may be considered as being
the resultant of two forces, Pi along FO, and
P« along OH. Since the dielectric constant
of empty space is unity, we have at once
p^IAfy or £•
where e is the amount of the charge on A,
and
p-p QH-LyM
P'~Fl FO~r"-X d ■
260
GENERAL ELECTRIC REVIEW
Now let
w = the velocity of .4 just before being
suddenly stopped.
l" = the velocity of propagation of the pulse
FH (equal to the velocity of light).
T = the time A would have required to have
reached .4'.
Then
OH = AA' = uT
and since
r=VT
it follows that
OH--
V
and
r- d\
en
V7T
Since the pulse FH is moving in a direction
parallel to AF . we are only interested in that
component of P2 which is parallel to AF, viz.,
Pz , where
tube. If the charge on a cathode particle is
e then a voltage E will represent an energy
of Et. The mechanical energy of the electron
is 1 2 mu'2. By the law of conservation of
energy
Et = 3 2 mu2
or
E=h2~u2
For purposes of convenience this is often
written
u-
* /
] m
Now the value of *, „, is not a constant but
depends in a complicated way upon the value
of u. Table I has been calculated from data
given by Bucherer (1909), Steinmetz (1898),
and Algermissen (1906). Spark gap lengths
TABLE I
P,'.
rd\
-. sin d
Now the energy of the pulse is partly electro-
static, and partly magnetic. That portion
which is electrostatic is equal to - — times
8 w
the square of the electric force.
6- it2 sin2 6
EE =
Stt r2 d2 1 '-
The magnetic portion is
1
Stt Vi
times the
square of the magnetic intensity. But the
magnetic intensity is V times the electric
force which produces it.
j-. _\t- u- sin- 6
A/_8irr2d2F2
The total energy of the pulse FH is therefore
t2 u2 sin2 0
£?0 =
4 7T rn- d2 V2
The energy of the whole spherical pulse is
obviously obtained by integrating EFo, thus
giving
E = h
dV
where d depends for its value upon the values
of 0 and m and upon the atomic weight of the
material used as a target.
It will be useful to gain an idea of how u
depends upon the voltage across an X-rav
u in Miles
per Sec.
11,800
18,900
37,900
74,400
H in Cm
per Sec.
12.0
12.6
13.2
13.8
14.4
E in
Volts
1,000
2,330
10,300
16,200
56,800
9.00
9.60
63,000
10.2
10.8
11.4
44,000
49,100
54,300
59,900
66,100
130,200
21.0
172,900 .
21.6
188,100
22.2
205,300
22.8
224,000
23.4
245,200
142,600
24.0
268,900
24.6
296.000
25.2
327.700
E in Cm.
Spark Gap
Between
Needle
Points
(A-C.)
0.1
0.2
0.8
1.3
4.3
5.0
5.9
6.9
7.9
30.0
45.0
E in Cm.
Spark Gap
Between
Balls
5 Cm. in
Diameter
(D-C.)
0.2
0.4
23,770
2.0
0.7
27,200
2.3
0.8
30,900
2.7
0.9
34,800
3.1
1.0
39,300
3.6
1.2
1.4
1.6
1.8
2.1
2.4
93,000
15.0
72,800
9.3
2.7
15.6
79,700
10.6
3.1
16.2
87,200
12.0
3.6
16.8
95,400
13.6
4.2
17.4
104,200 1
[5.5
4.9
111,600
18.0
113,400
in li
5.6
18.6
123,500
20.0
6.8
19.2
134,100
8.1
19.8
146,100
10.1
20.4
158,900
13.0
16.2
19.5
X-RAYS
261
are to be considered only as approximate
measurements of voltage under ordinary
working conditions.
When the cathode rays strike the target
they are not stopped instantaneously at the
surface, but merely suffer retardation so that
they penetrate for some distance into the
body of the target.* After once entering the
target, the particles no longer all move in
the same general direction, but travel more
or less radially. If, for a given velocity of
cathode rays, we imagine the target to be
made thicker and thicker, a thickness will be
reached at last for which there are as many
particles emerging in one direction as in any
other. This thickness is called ' ' The depth
of complete scattering, "f
In aluminum it is 0.015 cm.; in copper,
0.001 cm.; in silver, 0.001 cm.; in gold,
0.00020 cm.; and in lead, 0.00025 cm. at
90,000 volts. It varies directly as the voltage
employed across the tube.
Those primary rays which are able to
overcome the absorbing effect of the target
reach the surface and emerge into the vacuum
space of the tube. Measurements have shownj
that if the voltage across the tube is made
very small, then the primary rays, at the
moment of generation, have their maximum
of intensity in a direction perpendicular
to the cathode stream, and a minimum of
intensity in a direction parallel to the cathode
stream. This effect is called "polarization."
As the voltage across the tube is increased,
the polarization is decreased, until finally il
becomes immeasurable. This is explained
by assuming that at the higher potentials
the rays formed by the initial retardation
of the cathode stream are negligible in their
effects, when compared with those rays which
come out in all directions from the depth of
complete scattering.
Secondary Rays
When X-rays are made to impinge upon
a substance, that substance itself becomes a
* W. R. Ham, Phys. Rev. xxx, Jan., 1910.
W. P. Davey, Jour. Franklin Inst.. Mar., 1911.
L. G. Davey, Phys. Rev., Sept.. 1914.
t J- A. Crowther. Roy. Soc. Proc, 80. A, pp. 186-206. Mar. 5.
1908.
W. R. Ham. Phvs. Rev. xxx, 1. pp. 119-121, Jan.. 1910.
{ R. Blondlot, Comptes Rendus. 136. pp. 284-286, Feb. 2,
1903. Nature, 69, p. 463. March 17, 1904.
C. G. Barkla. Rov. Soc. Phil. Trans., 204. pp. 467-479,
May 31. 1905. Roy. Soc. Proc. 74, pp. 474-475, March 16, 1905.
H. Haga, Konik, Akad. Wetensch. Amsterdam Versl.. 15.
pp. 64-68, July 20. 1906.
J. Herwig. Ann. d. Phys., 29, 2, pp. 398-400. May 21, 1909.
E. Basseler, Ann. d. Phys.. 28. 4, pp. 808-884, Mar. 16, 1909.
L. Vegard, Roy. Soc. Proc, Ser. A., S3, pp. 379-393, Mar.
22, 1910.
W. R. Ham, Phys. Rev., xxx. pp. 96-121, Jan.. 1910.
F. C. Miller. Franklin Inst. Jour.. 171. pp. 457-461. May.
1911.
source of X-rays, which are called " secondary
rays." Two distinct types of secondary rays
are recognized, viz., "scattered" and "charac-
teristic." When X-rays pass through a
substance, the emergent beam is found to act
in the same way that light acts on passing
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through a fog. The rays retain all the pecu-
liarities of the incident beam, but have
suffered a diffuse reflection or "scattering."
Scattered rays emerge from both the incidence
and the emergence faces, and the radiation
in the emergence direction is much greater
in intensity that that in the incidence direc-
tion^
Scattering increases with the thickness and
with the atomic weight of the scattering
substance, and, within the limits ordinarily
used, is greater the greater the penetrating
ability of the incident rays.
If X-rays of very low penetrating ability
are allowed to fall on a substance (called a
"radiator"), the emergent beam contains
only two components, (a) that portion of the
primary beam which has been unaltered and,
(b) the scattered rays. If, now, the penetrat-
ing ability of the incident beam is gradually
increased, a point is at last reached at which
a new type of radiation appears, which is
characteristic of the substance used as the
radiator.^
Barkla and Sadler] | have shown that if the
incident primary rays are less penetrating
than are the secondary rays which are
characteristic of the radiator used, then no
secondary rays are produced; but if the
incident primary rays are more penetrating
than the characteristic secondary radiation,
then "characteristic" rays are produced.
6 Barkla and Ayers. Phil. Mag., pp. 270-280. Feb., 1911.
Owen. Proc. Camb. Phil. Soc. vol. 16. p. 161, 1911.
Crowther, Proc Roy. Soc. pp. 478-494, Feb., 1912.
f C. J. Barkla and C. A. Sadler, Nature. 77, pp. 343-344.
Feb. 13. 1908, Nature, 80, p. 37. March 11. 1909.
|| Barkla and Sadler, Nature, 80, p. 37. March 11, 1909.
262
GENERAL ELECTRIC REVIEW
The production of characteristic X-rays
is very analogous to the production of
fluorescent light. In fact, the analogy is so
close that some writers are adopting the term
"Fluorescence Rontgen Radiation."
Chapman and Piper* tried to detect a
continuance of secondary radiation after
excitation from the primary rays had ceased.
but were unable to detect even 1/250 of
the original radiation 1 3000 of a second
after the exciting primary rays had been
removed.
Radiators may be classified into four groups
in the order of their atomic weights. The
radiations given out by the members of
each group are very much alike.
Group 1 (1-82). -H-S. When excited by
a beam from a "soft" tube the members
of this group give off little, if any, charac-
teristic radiation; almost the entire radia-
tion being of the scattered type and this is
polarized in a plane perpendicular to the
direction of the parent cathode stream.
If the tube is made moderately "hard"
(i.e., if it gives off rays of moderate pene-
trating power), a slight amount of charac-
teristic radiation will be displayed, and
if the tube is very "hard," a well-defined
characteristic beam is given off, having a
penetrating ability much different from
that of the exciting rays.
Group 2 (52-65). -Cr-Zn. This group
gives off a beam composed almost entirely
of a true characteristic radiation, even
when excited by rays from a "soft" tube,
but this radiation has little penetrating
ability. With a given excitation, the
ionization produced by it is almost 100
times that produced by an equal mass
belonging to Group 1.
Group 8 (107-125) .-Ag-I. If the exciting
beam is only of moderate penetrating
ability, this group gives off mostly a
scattered radiation, but, unlike that from
Group 1, it is unpolarized, and there is a
noticeable amount of characteristic radia-
tion present. The relative amounts of
< scattered and characteristic radiation vary
atly with small changes in the character
of the exciting ravs.
Group 4 (1 83-206). -\Y-Bi. These sub-
si ances resemble Group 2 in their action.
For all these elements the penetrating
ability of the characteristic rays is inde-
pendent of the intensity or of the pene-
trating ability of the exciting beam, but is
a periodic function of the atomic weights
of the radiating elements.**
If the radiator is a chemical compound,
the component atoms and radicals determine
the character of the secondary rays produced. f
The rays coming from salts are composed
of (1), a homogeneous radiation having the
same penetrating ability as that from the
metal itself, and, (2), a scattered primary
radiation considerably more penetrating than
that of (1) due to the acid radical. If a metal
occurs in the acid radical it has no individual
effect, but merely acts with the remainder
of the radical.!
There seems to be a real physical difference
between primary X-rays and characteristic
X-rays. From the electromagnetic theory,
primary rays seem to consist of an irregu-
lar succession of "splashes." Experimental
evidence (which will be taken up in a later
article) seems to show that characteristic
rays consist of trains of waves resembling
light waves, except for the fact that the wave
length is about 1/1000 that of ordinary light.
Each element is able to emit characteristic
rays whose wave lengths fall into certain
well defined groups. Two of these (called A"
and L respectively) are of great importance.
For any given radiator, rays of the A" group
are about 300 times as penetrating as those
of the L group. Table II shows the wave
lengths of the two most intense members
of each group for 39 elements. It will be
noticed that, to date, there are many gaps
still to be filled in the list. The values given
in the table were published by Mosely in the
Philosophical Magazine, April. 1914.
Chapman has shown§ that if the L radiation
of one element is of nearly the same wave-
length as the K radiation of another element,
then their atomic weights (Al and ^4*.-
respectively) are related by the formula
AK = V2(AL-i8).
Whiddington has shown*! that when any
given substance is used as the target of an
X-ray tube, it will give off characteristic K
rays if the speed in cm. per sec. of the cathode
rays is greater than 108 times the atomic
weight of that substance. From Chapman's
formula it follows that the characteristic L
rays would be obtained at a speed of %
(A — 48)X108 cm. per sec, where .4 is the
* Chapman and Piper, Phil. Mag.. 19. pp. 897-903. June. 1910.
** C. G. Barkla and C. A. Sadler, Phil. Mag.. 16, pp. 550-584,
Oct.. 1908.
t J. A. Crowther, Phil. Mag.. 14. pp. 653-675. Nov.. 1907.
t J. L. Glasson. Camb. Phil. Soc.. pp. 437-441. June 14. 1910.
§ Chapman. Proe. Rov. Soc. 1912.
1 Whiddington. Proc. Roy. Soc., 1911.
X-RAYS
263
TABLE II
WAVE-LENGTHS OF VARIOUS CHARACTERISTIC
X-RAYS
Note. — The most important line in each series is called ,
The next most'important is called 0.
TABLE III
MINIMUM SPEED OF CATHODE RAYS REQUIRED
TO EXCITE CHARACTERISTIC
RADIATIONS
K SERIES
L SERIES
Elements
a
a
a
0
XlO-s Cm.
XlO'Crn.
XlO-iCm.
-.1" 'Cm.
Al
8.364
7.912
Si
7.142
6.7211
Ci
4.750
K
3.759
3.463
Ca
3.368
3.094
Ti
2.758
2.524
V
2.519
2.297
Cr
2.301
2.093
Mn
2.111
1.818
Fe
! 114(1
1.765
Co
1.798
1.629
Ni
1.662
1.506
Cu
1.549
1.402
• Zn
1.445
1.306
Y
0.838
. ..
Zr
0.794
6.091
Nb
0.750
5.749
5.507
Mo
0.721
5.423
5.187
Ru
0.638
4.861
4.660
Rh
0.584
1.(122
Pd
1.385
4.1(18
Ag
0.560
4.170
Sn
3.619
Sb
3.458
3.245
La
2.676
2.471
Ce
2.567
2.300
Pr
2.471
2.265
Nd
2.382
2.175
Sa
2.208
2.008
Eu
2.130
2.057
1.925
Gd
1.853
Ho
1.914
1.711
Er
1.790
1.591
Ta
1.525
1.330
W
1.486
Os
1.397
1.201
Ir
1.354
1.155
Pt
1.316
1.121
Au
1.287
1 092
Radiator
Atomic
Weight
(0=16)
Critical
Velocity of
Cathode
Rays to
Excite K
Radiation
Voltage
Necessary
to Give
Critical
Velocity to
Cathode
Rays
Aluminum
Chromium
Iron
27.1
52.0
55.8
cm. /sec.
2.06 X109
5.09 X109
5.83 X109
volts
1200
7320
9600
Nickel
Copper
Zinc
Selenium
58.7
63.6
65.4
79.2
6.17 X109 ! 10750
6.26 X109 , 11080
6.32 X109 11280
7.38 X109 * 15400
atomic weight. Table III shows Whidding-
ton's experimental values.
The subject of electromagnetic disturbances
was discussed at the beginning of this article
from the standpoint of a single retardation
of the electron. It is evident that, if the
electron had been considered as having a
regular to-and-fro motion, the resulting
electromagnetic disturbance would have con-
sisted of a train of waves of a definite wave
length. It is therefore natural to assume that
characteristic X-rays are produced when
certain electrons in an atom are made to
vibrate at some natural frequency. Such
vibrations could be set up by giving the
electron a single impulse, provided that the
time consumed in communicating the impulse
is not more than half the time of one natural
vibration of the electron. We thus have a
theoretical basis for the experimental facts
that secondary rays may be produced both
by sufficiently "thin" primary rays, and also
by cathode rays of sufficiently high velocity.
It is plain why the wave-length of character-
istic rays remains the same when the breadth
of the primary rays is decreased or when
the speed of the cathode stream is increased
beyond the critical value, and why no charac-
teristic rays are produced until these critical
values are reached. In short, the electro-
magnetic theory gives us a rational basis
upon which we may correlate the facts known
at present about the nature of X-rays.
264 GENERAL ELECTRIC REVIEW
THE MODERN MINE HAULAGE MOTOR
By C. W. Larson
Engineer, Mine Locomotives and Motors
The author first gives a brief history of the step-by-step development that has culminated in the present
day high efficiency mine haulage motor, and then proceeds to discuss those features of its design that are
new and that have made it a success where the older types failed. Commutating poles, ball bearings, and a
proper consideration of the matter of accessibility are largely responsible for the satisfactory performance of
the latest type of mine haulage motor. — Editor.
The first motor used in mining service
was built by the Thomson-Houston Company
in 1889, and was of the bipolar open type,
much the same in design as the early Edison
generators. It was mounted on top of the
locomotive and geared down to the drivers by
double gear reduction. In 1891 another
type was brought out using the locomotive
frame for its field.
In 1S92 three other types were developed,
which were designed for mounting on the
axle, using single gear reduction in much the
same manner as is the standard practice todav.
In 1893 the LWP-5, LWP-20, NWP-12, and
the famous GE-800 were introduced to the
traction field. In 1896 the GE-1000 was
added, and in 1897 the GE-53.
In the next few years many new motors
were added to the list and most of the older
types dropped out, until in 1905 the following
motors by one manufacturer were available
for mine locomotives :
\WP2J4
CB 15,
CB
GE
14,
60
GE 800,
GE 52,
GE
GE
GE
GE
GE
GE
GE
GE
5h.p.
6 h.p.
15 h.p.
20 h.p.
25 h.p.
20 h.p.
20 h.p.
23 h.p.
27 h.p.
- h.p.
h.p.
h.p.
h.p.
79,
58,
59,
61
53,
97,
71,85 h.p.
,37
.42
,63
18-in
18-in.
24-in.
36-in.
42-in
48-in.
32-in,
24-in
39^-
3 5 -in
24-in
36-in
42-in
36-in
gauge, 20-in
gauge, 20-in
gauge, 20-in.
gauge, 28-in.
gauge, 28-in
gauge, 28-in
gauge, 28-in
gauge, 28-in
in. gauge, 28-
gauge, 28-in
gauge, 33-in
gauge, 30-in
gauge, 30-in
gauge, 33-in
wheels
wheels
wheels
wheels
wheels
wheels
wheels
wheels
in. wheels
. wheels
wheels
wheels
. wheels
. wheels
The GE types were primarily designed
for street car service, but were readily adapt-
able to mining locomotives.
The GE-53 was particularly well fitted
for mine sen-ice, and was considered to be
as powerful as would ever be needed for
locomotives of its gauge. It was known as
the best motor at that time on the market.
It was used on 10 to 13-ton locomotives,
and was thought to have ample capacity
to remain standard for many years to come.
But after the application of electric power
to mining requirements was better understood,
progress came fast, and in two or three years
it was found that even the large GE-53
was begging for more air. In other words,
the motor was too small for the service
required of the 12 and 13-ton locomotives.
As the demand for coal increased from
year to year, the hauls became longer and
the motors were soon too small for the
increased duty. Customers also demanded
that all motors be of the split-frame type,
while the best motors for this class of service
were of the box-frame type. It became
apparent that an entire new line of motors
was needed, and work was therefore begun
on them; and in 1909 eight sizes were put in
production, with the following ratings:
HM 701, 30 h.p.,
HM 702, 46 h.p.,
03, 26 h.p.,
HM
HM
HM
HM
HM
HM
705,
706,
707.
709,
712,
vy2h.p.
15 h.p.,
46 h.p.,
68 h.p.,
85 h.p.,
24-in. gauge,
24-in. gauge,
28-in. gauge,
, 18-in. gauge
24-in. gauge,
36-in. gauge,
36-in. gauge,
36-in. gauge,
28-in. wheels
33-in. wheels
24-in. wheels
, 20-in. wheels
22-in. wheels
28-in. wheels
30-in. wheels
33-in. wheels
These motors were designed for 250 and
500 volts.
Attention is called to the increase in horse-
power for the minimum gauge as compared
with the previous list of motors. These eight
sizes were then considered sufficient to take
care of all demands for some time to come;
but progress soon dictated that a mine locomo-
tive motor should be provided with com-
mutating poles, in order to give better com-
mutation and further increased continuous
capacity. Fortunately the 700 line was of
such design as to allow the addition of
commutating poles, and in order to identify
the commutating pole ' motors from the
non-commutating, they were classified in the
800 series. The armatures have also been
provided with ball bearings instead of oil
bearings. This constitutes the latest improve-
ment, and the complete line today consists
of nine sizes, as follows :
THE MODERN MINE HAULAGE MOTOR
265
HM 801,
HM 802,
HM 803,
HM 806,
HM 809,
HM 817,
HM 819,
HM 820,
HM 812,
HM 824,
30 h.p
46 h.p
26 h.p
15 h.p
68 h.p
12 h.p
38 h.p
85 h.p
100 h.p
125 h.p
24-in.
24-in.
28-in.
24-in.
36-in.
18-in.
30-in.
36-in.
36-in.
36-in.
gauge,
gauge,
gauge,
gauge,
gauge,
gauge,
gauge,
gauge,
gauge,
gauge,
28-in.
33-in.
24-in.
22-in.
28-in.
24-in.
28-in.
33-in.
33-in.
36-in.
wheels
wheels
wheels
wheels
wheels
wheels
wheels
wheels
wheels
wheels
We will now describe one of these motors
more in detail, and will select the HM-803,
in order to show the high efficiency and high
continuous capacity that is obtainable even
in the small sizes:
Figs. 1 to 3 show the form and general
appearance of the HM-S03 motor, which
are practically the same for all sizes. It
is of octagonal shape and the frame is split
nearly horizontally, with suspension lugs on
the bottom half. It will also be noted that
neither armature nor axle bearings project
outwards, this being due to the fact that
each size must be designed for maximum
power at a minimum gauge. This particular
motor will mount on 28 in. gauge, but is also
standard for all wider gauges. It should
therefore be appreciated that on account of
the narrow gauge conditions, every fraction
of an inch must be accounted for, and con-
sequently all dimensions must be reduced to
a minimum.
Fig. 4 shows the motor open, and that
it is necessary to remove only four bolts to
open it; also that the field leads are discon-
nected outside of the frame, while the brush-
holders and their leads remain intact. The
Armature
The armature laminations are built upon
a separate steel spider on which is also
mounted the commutator. The armature
shaft can thus be readily removed without
disturbing the commutator connections or
windings (see Fig. 6).
Type HM-803 Mining Locomotive Motor
Field Coils
The field coils are strap wound, asbestos
insulated, and impregnated with insulating
compound by the vacuum process, this
treatment resulting in a solid, moisture-
proof and heat-proof coil of practically
indestructible design.
Commutating Poles
There has been and is still today a great
deal of misunderstanding as to the correct
Figs. 2 and 3. HM-803 Mining Locomotive Motor Mounted on Axle
compactness and sturdy construction should
here be noted.
Fig. 5 shows the bottom half of frame,
with the armature and the ball bearings in
place, but with the clamping nut and cover
removed.
function of the application of commutating
poles. There are some who consider that the
improvement is necessary only for taking
care of high peak loads, and that for motors
not subjected to heavy overloads the commu-
tating poles are a luxury and therefore
266
GENERAL ELECTRIC REVIEW
unnecessary. Fortunately, however, the com-
mutating poles do improve the operating
conditions at all loads and speeds if properly
designed.
In a mine haulage motor, or any reversible
direct current motor, the brushes are per-
^*f a=43 ==0 IF*
Fig. 4. HM-803 Motor with Top Half of Field Removed
manently set on the mechanical neutral.
which coincides with the electrical neutral
at no load but which does not coincide with
the mechanical neutral on non-commutating
pole motors for loads other than stated above.
When a motor of the non-commutating
pole type with a fixed brush position is
put in actual operation, the field flux is
led into the leading end of the pole
face, against the direction of rotation of
the armature. This distortion or shifting
of the field flux is caused by the armature
current. The armature or load current
produces a magnetic field at right angles
to the magnetic field produced by the mam
field windings, and its effect is known as
anna Hire re-action. This armature re-action.
readily understood and as pointed out.
shifts the electrical neutral backwards and
that the brushes be moved
backwards to this new location if good
commutation is to be maintained.
From the above it will be seen that a
motor of the non-commutating pole type has
characteristics which are unfavorable to
commutation at all loads, and in addition is
liable to have more or less pitting and burning
of the commutator, thus causing excessive
heating and wear of the commutator and
the brushes. In order to overcome this
difficulty, the designer of a non-commutating
pole motor must increase the motor field
or magnetic density to a high point, so that
the effect of the armature re-action will
not greatly distort it. In this way he can
effect fairly good commutation and greatly
reduce the circulating currents and con-
sequently the heating of the short circuited
coils of the armature undergoing commu-
tation. But by doing this, he greatly increases
his core loss; for it will be remembered that
the core loss increases practically as the
square of the magnetic density, or with the
square of the strength of the field. It will
be seen, therefore, that the design of a non-
commutating pole motor of this type is more
or less a compromise.
For mine haulage this non-commutating'
pole type of motor is at a great disadvantage:
First, because the high magnetic density
at which the materials are worked will not
permit the motor to slow down in ascending
the grades, due to the fact that the high
saturation prevents an increase in the field
Fig. 5. End View cf HM-S03 Motor showing Ball Bearings
flux which is essential for reduction in speed.
Therefore the increased torque necessary
to haul the load over the grade must be
produced by an increase in current, whereas
if the motor could decrease in speed due to
an increase in flux, the increased torque
THE MODERN MINE HAULAGE MOTOR
267
necessary would be produced at a much
reduced current.
In the design of the commutating pole
motor the problem is different. It is no
longer necessary to rely on the high magnetic
densities. The auxiliary pole is magnetized
so that it directly opposes and
practically neutralizes the armature
re-action in the commutating zone,
producing a suitable flux for neutral-
izing the reactance voltage of the
short circuited coil. The motor is
therefore relieved of the injurious
effect of the armature re-action, and
because of this the motor is able to
run at lower densities in the magnetic
circuit, thus greatly reducing the core
loss and consequently the heating,
and at the same time enabling the
motor to decrease in speed as it
strikes the grade or when starting
heavy loads to exert a heavy torque
without drawing excessive current
from the line.
Commutating poles therefore remove the
effect of the distortion due to armature
re-action, fix the brush position for all loads
with either direction of rotation, prevent all
sparking and burning in the brushes, and
reduce the local current in the armature
curves of this type of motor is shown in
Fig. 8.
Ball Bearings
The advantages
brieflv as follows:
of ball bearings are
Fig. 6. Commutator and Armature (without winding I of HM-803 Motor
( 1 ) The armature is prevented from
sagging down on poles, thus saving burnouts.
(2) Inasmuch as no oil is used, the com-
mutator and windings are kept clean and the
occurrence of ' short circuits or grounds are
greatly reduced.
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16 1800
16 1600
14 1400
a 1200
10 1000
8 600
6 600
4 400
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Fig. 7. Current and Power Output Curves of HM-803 Motor
Fig. 8. Typical Characteristic Curves of Type HM Motors
windings to a minimum. This is clearly
illustrated by the curves in Fig. i , which
show that by the use of commutating poles
it is possible to construct a motor which will
have a continuous rating of over 50 per cent
of its one hour rating. A set of characteristic
' 3 I Increased efficiency, especially in com-
parison with plain bearings, not properly
lubricated.
Fig. 9 shows the ball bearing which has
been adopted as standard for HM motors.
These bearings are built on the radial prin-
26S
GENERAL ELECTRIC REVIEW
ciple with double rows of balls, and thus
carrv about three times the number of balls
divide the load. This bearing is also self-align-
ing, which is a most excellent feature, as there
Fig. 9. Ball Bearings used on all
Type HM Motors
as the single-row bearing. This means longer
life, as the pressure per ball becomes much less.
owing to the great number of balls which
is no binding to be encountered in mounting
or running. The mounting of the ball bearing
has proven very satisfactory in service.
THE EYE AND ILLUMINATION
By H. E. Mahan
Illuminating Laboratory, General Electric Company
This article first analyses the anatomy of the human eye, and then enters into an exposition as to the
manner in which the eye functions to distinguish different colors of light and to regulate the amount of light
which falls on the retina from sources of differing intensity. Having presented this information, the article
proceeds to show how illumination can best be arranged to permit of facile vision.- — Editor.
The eye passes final judgment on a lighting
system and. therefore, should receive con-
sideration from the illuminating engineer.
To do so, however, the engineer must leave
the domain of physics with its exact formulae
and enter the field of physiology. Here he
finds the available knowledge rather limited
and uncertain. He is not dealing with the
rational and coordinate laws of light, heat
and electricity, but with the delicate, human
organ of the sense of sight — the eye. True,
scientific investigators have provided us with
much information on the general action of
the eye and its relation to light, but there
still remains a great deal to be learned before
we can make exact allowances for its behavior
under artificial lighting systems.
The Anatomy of the Eye
The human eye is illustrated diagram-
matically in Fig. 1 and is shown to consist
of six essential parts, namely, the cornea,
the anterior chamber containing the aqueous
humor, the iris, the crystalline lens, the
cavity containing the vitreous humor and the
retina. From the following description and
the accompanying diagram, it will be ob-
served that the eye resembles very strongly
the modern photographic camera.
Let us follow a ray of light through the eye,
observe its path and the actions and pro-
cesses it sets up. The light is admitted
through the cornea, a transparent extension
of the eyeball shaped somewhat after the
fashion of a watch crystal. It passes through
the aqueous humor, a transparent jelly-like
substance, and reaches the iris. The iris
is the colored part of the eye and consists of
a circular curtain, a continuation of the middle
or choroid coat of the eye and is capable of
increasing or decreasing the diameter of
its opening — the pupil — allowing more or less
light to pass through as is required for correct
vision. The light next' strikes the crystal-
line lens, a transparent elastic body controlled
by a muscular ring — the ciliary muscles —
which enables it to change its curvature to
accommodate or focus the eye. Passing
through the vitreous humor, the light reaches
the retina, which is the delicate network of
THE EYE AND ILLUMINATION
269
nerve centers, possessing the property of
converting the radiant energy into the sensa-
tion of sight. The retina plays such an im-
portant part in the process of seeing that it
may interest the reader to know a little about
its essential structures.
Rod and Cone Vision
The retina is a very complex structure
which, while only about 0.01 inch thick, is
composed of ten separate layers, but for the
purpose of this article we will consider it as
consisting of tiny nerve centers called rods
and cones from their shape. The cones are
most numerous in the fovea, which is the
point of greatest sensitiveness, the ratio of
cones to rods decreasing toward the outer
regions of the retina. The rods are believed
to be active in the determination of form and
brightness and the cones in color perception.
Furthermore, in dim illumination the rods
only are effective, while for higher intensities
the cones become active and colors are sensed.
You have perhaps experienced at twilight the
ability to see objects, although unable to
distinguish their color. The cavities at the
ends of the rods contain a bluish watery-fluid
called visual-purple, which is continually
being decomposed by the action of light and
constantly replenished from the pigmentary
cells in the choroid coat of the eye. However,
when the eye is subject to too strong an in-
tensity of light this visual purple is bleached
out more rapidly than it can be secreted,
with the result that the vision is dimmed or
blurred. Darkness or dim illumination will
visually enable the eye to recover its normal
condition.
r*.ey fvocf-s-s*
•3-C-t-*-^
Fig. I. An Anatomical Diagram of the Human Eye
Color Vision (Young-Helmholtz' Theory)
The most reasonable theory of color sensa-
tion and the most generally accepted one is
the theory propounded by Dr. Thomas
Young in the early part of the nineteenth
century and more recently elaborated upon
by Helmholtz. This is known as the Young-
Helmholtz' theory and assumes the retina of
the eye to have three sets of cones, one sensi-
tive to red light, one to green light and one to
d
(s)
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(1) Red Vision.
(2) Green Vision.
(3) Blue Vision.
(4) Combination of above, showing over-lapping.
Fig. 2. Curves Illustrating the Young-Helmholtz* Theory
blue light. These colors — red, green and
blue — are known as the primary colors.
When all three sets of nerves are stimulated,
the sensation of white light is realized; when
excited separately the sensation correspond-
ing to the set of nerves responding is set up.
Intermediate colors are perceived by the
three different sets of cones in varying degrees
of excitation. The curves illustrating this
theory are shown in Fig. 2. The curve for
each color sensation is shown to extend be-
yond the point on the spectrum for which
that particular set of cones is particularly
sensitive, so that they overlap each other and
thus permit of intermediate color sensations.
The Eye as an Optical Instrument
In its path through the eye, the light en-
counters four refracting mediums, namely,
the cornea, aqueous humor, crystalline lens
and the vitreous humor, having indexes of
refraction of approximately 1.37, 1.34, 1.437
and 1.34, respectively. These refracting
surfaces are shown at 1, 2, 3 and 4 on dia-
gram. Fig. 1. It will also be noted that the
270
GENERAL ELECTRIC REVIEW
eye, unlike most optical instruments, does
not focus by changing the distance between
the lens and the retina, but by changing the
shape of the lens. This is shown by Fig. 1,
the position for nearby and distant focus
being indicated.
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Fig. 3. Curves showing Sensitiveness of the Eye for Different
Points of the Visible Spectrum
The eye is subject to the principal defects
of the ordinary optical instrument. These
are spherical aberration, which causes the
central part and the edges of the crystalline
lens to focus in different planes, and chromatic
aberration or the failure to focus all colors
in the same plane. These errors do not enter
to any serious degree and cause us no in-
convenience in the ordinary process of seeing.
On the other hand, the eye is capable of
functioning through a wider range of inten-
sities than would ordinarily be expected from
any scientific instrument. It serves us with
equal convenience for intensities correspond-
ing to faint moonlight or to the direct rays
of the noondav sun — a ratio of about 1 to
5,000,000.
The Eye, Light and Color
The eye responds to radiations having
wave lengths between approximately *0.76ju
and 0.39/i, or, in other words, the visible
spectrum extends through slightly less than
one octave. The long wave lengths give the
sensation of red and as they grow shorter
pass in succession through all the colors of
the spectrum: Red, orange, yellow, green,
blue, indigo, violet. Waves longer than the
visible red and shorter than the visible violet
* The Greek letter ti is the symbol for the micron which is
equal to 0.001 millimeter.
are termed, respectively, infra-red and ultra-
violet. These waves do not excite the retina,
but the former may be realized as heat and
the latter are characterized by their chemical
activity. These properties exist in the visible
spectrum to a certain extent, diminishing
from the two extremes mentioned to a min-
imum about at the yellow. Furthermore,
the eye does not respond with equal sen-
sitiveness at all points of the visible spectrum,
but follows the sensation curves shown in
Fig. 3. These curves indicate a zero response
at the extremes of the spectrum and a maxi-
mum response near the middle, shifting toward
the blue for faint illumination and toward the
red for strong illumination. In other words,
for an equal quantity of energy converted
into light, the maximum physiological effect
will be obtained from green-yellow light.
There also exists a quantitative relation
between the stimulus and the sensation, that
is, between the intensity of illumination and
the visional impression. This relation is
known as Fechner's Law and states that the
least perceptible increment is proportional
to the whole stimulus, that is, the same per-
centage change in intensity of illumination
calculated from the least amount perceptible
to the eye gives the same change in sensation.
This is graphically shown in Fig. 4 by the
logarithmic curve of intensities. The practical
application of this law in guiding the engineer
in reaching an economic compromise between
intensity of illumination and quantity of
power expended is self-evident.
Intrinsic Brilliancy and Glare
One of the fundamental laws to be observed
in placing light sources is to avoid locating
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Fig. 4. Carve Illustrating Fechner's Law
lights of high intrinsic brightness in the
field of vision. Intrinsic brightness is de-
fined as the candle-power emitted per unit
area of surface. For comfortable vision this
THE EYE AND ILLUMINATION
271
value should not exceed .5 to 10 candle-power
per square inch. When the eye is compelled
to view surfaces which exceed this value,
there is likelihood of eye strain, a decided
decrease in visual acuity and perhaps per-
manent injury. This condition may also be
brought about by specular reflection from a
glossy or polished surface, as is often ex-
perienced in reading a book having calendered
paper.
Glare, as a cause of industrial and traffic
accidents is receiving attention from "safety
first" advocates. We all have experienced
the difficulty of seeing behind the powerful
headlights of an automobile or of trying to
see with an unshaded incandescent lamp
shining in our eyes. These are everyday
examples of glare and might be multiplied
many times. A trip through almost any
industrial plant will furnish evidence of
lowered production, increase of spoilage and
general inefficiency of workmen, due to glare
in ■ some form or other from the artificial
lighting system.
You will recall previous mention of the iris,
i.e., the diaphragm controlling the pupillary
opening in the eye. The size of this opening
is regulated in accordance with the bright-
ness of the field of vision, being made large
to admit more light in the case of a dim field
and reducing the opening to exclude excess
light when exposed to a bright field. Further-
more, the pupil is regulated to conform to the
brightest area in view; therefore, when we
have a bright light in front of our eye the
pupil contracts to protect the eye from the
excess light and, hence, fails to admit suffi-
cient light from the less brightly illuminated
parts for vision. The sections of relatively
lower illumination, therefore, appear under-
lighted or dark.
There are two general ways of eliminating
glare from a lighting system; these are, first.
by removing the source from the line of vision
as in cove lighting, totally indirect lighting by
fixtures, or direct lighting with units placed
well above the line of vision; second, the
reduction of intrinsic brightness by enclosing
the source in diffusing glass or screening by a
correctly designed shade. All these methods
involve a sacrifice in efficiency as far as light
flux is concerned, but this is usually com-
pensated for by the increased facility for
vision as previously outlined.
Diffusion of Light
Daylight provides the most diffused illumi-
nation and absence of shadows. It is this
matter of diffusion of light and the presence
of shadows that is responsible for many
unsatisfactory systems of artificial lighting.
For example, under daylight conditions in a
factory the workman is surrounded by light of
approximately equal intensity. In this same
factory, under artificial lighting an operator
may have at his machine an intensity perhaps
greater than he received by daylight, but his
surroundings will be many times darker,
hence, when he looks away from his machine
to the darker zones he suffers momentary
blindness until the pupil is adjusted to the
new conditions. This man, therefore, is
disabled for a fractional part of his working
hours, is incapable of performing his duties
and, therefore, is an inefficient workman.
Furthermore, at these times when the eye
is incapable of functioning, the employee is
more susceptible to accident from revolving
machinery, etc. That this is actually the
ease is illustrated by the statistics on indus-
trial accidents, which show that the fatal
accidents occurring during the short- day
months of November, December and Jan-
uary are about 40 per cent greater than those
occurring during the long days of June. July,
August, etc. Strong contrast in illumination
intensity or the presence of dark shadows are,
therefore, inconsistent with good illumination
and should be avoided.
Another source of ocular discomfort is a
flickering light source, which causes the eye
to continually adjust itself for fields of vary-
ing intensity. This causes a strained con-
dition of the muscles of the eye and fatigue,
preventing the iris from properly protecting
the eye and leading in many cases to per-
manent injury.
Ultra-Violet Light
As previously stated, the eye does not
respond to waves shorter than about 0.39/*,
that is, to the ultra-violet light. This is
because they are almost totally absorbed by
the cornea and crystalline lens and because
the retina is not responsive to them. Evolu-
tion may enable future generations to see
these ultra-violet radiations and open up
wonderful sights at present closed to us.
Ultra-violet light undoubtedly has an
injurious effect upon the eye tissues when
present in appreciable quantities. Whether
it is the chemical effect of the ultra-violet or
the heat effect of the longer wave lengths
which has the greater injurious effect upon the
ej e is open to debate. The fact remains,
however, that there is less ultra-violet radia-
272
GENERAL ELECTRIC REVIEW
tion from artificial lighting sources than from
daylight, which fact should dispel fear of
ultra-violet light from commercial lighting
units. A further protection is guaranteed
the eye from the glassware used in connection
with most lighting units, ordinary glass being
opaque to the ultra-violet rays.
Conclusion
It is hoped that by this brief description
of the eye and light it has been shown that
there does exist a very important relation
between them, and that this relation is of
sufficient practical importance to demand
attention. Legislators are awakening to this
fact and are enacting laws that will protect
workers and the general public against
incorrect and inadequate lighting. Perhaps
a fifth of the states have laws defining in a
rather vague and indefinite way the lighting
requirements for factories, while a much
larger percentage have passed legislation
covering the lighting of mines and the use of
headlights. It is expected that these laws
will be amended in the near future to embody
the advances made in the science of illumina-
tion. Municipalities are turning their atten-
tion to this movement and exercising super-
vision over the illumination of streets, of
schools and other public buildings.
In the industrial field, lighting is one of
the first items to receive attention from the
scientific manager. He appreciates and can
actually prove that the quality and quantity
of production is enhanced by providing favor-
able working conditions for his employees,
that the liability of accident is minimized,
sanitation and health promoted and the good
will of the employee obtained thereby. These
conditions are all furthered by a properly
designed lighting system. All branches of
human activity are dependent to a greater
or less extent upon light, making it im-
portant and vital to the interests of mankind
and deserving of study and consideration.
REFERENCES
Artificial Illumination as a Factor in the Production of Ocular
Discomfort. Trans. I. E. S.. Vol. 6. 1911. Kelson Miles Black.
M.D.
Radiation, Light and Illumination. Steinmetz.
Lectures on Illuminating Engineering. Johns-Hopkins Uni-
versity.
Some Phenomena of Physiological Optics. Lighting Journal.
Vol. 1, 1913. F. K. Ricktmyer.
Outlines of Optics. P. G. Nutting.
The Essential Elements of Vision. Trans. I. E. S., Vol. 9.
1914. Hunter H. Turner. M.D.
Light, Photometry and Illumination. Burrows.
Color Matching on Textiles. Paterson.
Transactions British Illuminating Engineering Society.
Transactions American Illuminating Engineering Society.
273
THE FORT WAYNE ELECTRIC ROCK DRILL
By C. Jackson
Engineer, Rock Drill Department, Fort Wayne Electric Works of General Electric Company
The introductory portion of this article contains a brief but very interesting chronological review of the
development ot the mechanical percussive type of rock drill, an explanation of the physics of rock drilling
and a statement ot the mechanical principles which have been embodied in the design of the successful'
modern drill. The remainder of the article describes in full the construction, operation and merits of an
electric motor-driven rock drill which, because of its superior qualities, it is believed will in time supplant
those drills operated by compressed air. — Editor.
The development of electrical transmission
lines throughout the principal mining centers
of the world has led to the partial electrifica-
tion of large mining properties with excellent
economic results. There remain, however,
several very important mining appliances or
machines, with which wonderful economy
may be effected by the application of electric
drive. The most important piece of mining
apparatus that has baffled the efforts of
engineers in the past is the electrically-driven
rock drill.
It is the purpose of this article to briefly
review the development of the mechanical
percussive type of mining rock drill and to
describe in detail the construction and opera-
tion of the Fort Wayne Type "A" Electric
Rock Drill with notes regarding the drilling
and practical efficiency.
The idea of fastening a detachable tool or
chisel to a mechanically moved piston rod
dates from the invention of the steam ham-
mer, about 1842. In 1S44 Brunton in Eng-
land suggested the employment of compressed
air for a rock drill and invented a machine
called a "wind hammer." In 1S53 William
Pidding invented a hammer secured to a
frame and reciprocated by steam for rock
boring. In Germany at the same time
Schumann invented a machine for work in
the Freiberg mines which in many features
anticipated the present type of reciprocating
rock drill. In 1855 Bartlett patented a
machine which was tried in boring the
Mount Cenis tunnel. This drill was improved
by Sonneiller and used in boring the tunnel.
Two hundred machines had to be kept on
hand, however, to insure the constant opera-
tion of sixteen. The Sonneiller machine, a
true pneumatic percussive drill, was the
first to be actually used for tunnelling (1861)
and for mining in Belgium (1S63).
J. W. Fowle of Boston, in 1849, patented
a steam-driven reciprocating drill, the drill
bit forming an extension of the piston rod,
and arranged to feed toward the rock as the
bit advanced. The piston was rotated a
fraction of a revolution at each stroke.
This drill embodied the essential principles
of the modem reciprocating type air drill
and was covered by one of the first United
States patents issued on this class of ap-
paratus. The Fowle patent was followed by
the patents of Haupt, Taylor, Burleigh, Inger-
soll, Sergant, Wood and Leyner, the Burleigh
drill being used in driving the Hoosac tunnel
in Massachusetts in 1866.
The history of the rock drill might be called
the history of modern mining. Without the
rock drill, the matter of commercially pro-
ducing the world's supply of industrial and
precious metals would have proven a much
more serious problem.
Rock Drilling
Rock drilling is accomplished by over-
coming the cohesion of the rock particles by
the application of force. This is effected in
several ways: First, by abrasion alone, as
in the diamond drill. Second, by combined
abrasion and chipping. Third, by percussion,
i.e., chipping or crushing.
The modern mining drills are essentially
percussive drills and may be divided into two
distinct types; one of which is the piston or
reciprocating type in which the drill steel or
cutting bit is securely clamped to an extension
of the piston and contains a ratchet wheel,
pawl and rifle bar to rotate the piston and
boring tool. The cylinder is mounted in a
guide or cradle in such a manner that it may
be fed toward the rock, the cradle is attached
by its seat to a rigid support. In drills of
this type the mechanical efficiency is very
low, being estimated at from 5 to 10 per cent.
The mechanical construction of the piston
type drill is simple, being well adapted to
withstand the rough work and continued
strain to which it is subjected in service.
Although the earliest manual method of
drilling holes in hard rock was by hammering
and revolving a chisel we have no records of
274
GENERAL ELECTRIC REVIEW
any serious attempts by engineers to employ
this principle in the construction of a rock
drill actuated by power. It is obvious that
the efficiency of this hammer method of
drilling is higher than that of the "churn"
or reciprocating method. Recent notable
Fig. 1. Phantom View of Drill showing Working Parts
developments in the manufacture of mining
drills of this type are the Leyner, Jap, Sul-
livan and Fort Wayne. Although operating
on the hammer principle, the Fort Wayne
drill differs from those mentioned, since it is
motor-driven instead of being actuated by
compressed air.
The Fort Wayne Type "A" Drill
Since the force of the blow in all air drills
of the percussive type is obtained by a recipro-
cating piston within a suitable cylinder, a
description of the mechanism and construc-
tion of the Fort Wayne drill will be of interest
at this time.
As in the development of the air drill, the
pioneers in the electric drill field have traveled
a rocky road, meeting with almost unsur-
mountable obstacles and discouragement at
ever}' step. Looking backward over a period
of 20 years one is impressed with the fact
that in almost every attempt to construct
an electrically operated drill the designers
followed closely the principle employed in
the air drill of the reciprocating type wherein
the drill steel or cutting bit formed an ex-
tension of a piston or plunger.
Unless the drill were of the solenoid type,
which for obvious reasons is low in efficiency
and of a rather delicate construction, the
problem resolved itself into one of converting
the rotary motion of the motor armature into
a reciprocating motion designed to deliver
a blow or heavy impact at each stroke.
Efforts to construct a machine of this type
sufficiently light and compact to insure port-
ability and at a reasonable cost of upkeep
were abandoned after a most thorough ser-
vice test of many designs.
Before the Fort Wayne drill was designed
a thorough investigation of all previous
electric rock drills was undertaken, at the
conclusion of which an analysis of previous
attempts indicated:
First. That the drill should be motor-
driven by a substantial motor directly
mounted to the drill mechanism to insure
compactness and portability.
Second. That converting the rotary mo-
tion of the motor armature to a reciprocating
motion of either a piston or hammer for an
impact imparting device of this type had
been thoroughly tried and abandoned, and
obviously was not the proper solution of the
problem.
Third. There appeared to be no question
regarding higher efficiency of drills of the
hammer type, i.e., where the drill steel
remained stationary and was rapidly struck
by a hammer of suitable weight.
With these fundamental points in mind
the mechanism illustrated in Fig. 1 was
evolved.
The Type "A" drill is of the rotary ham-
mer design operated by an electric motor
attached to the frame of the drill proper by
means of two permanent studs and two
swinging bolts. When the swinging bolt
nuts are loosened and the bolts swung up, the
motor may be lifted from or replaced on the
drill body in one minute.
The mechanism of the drill consists of two
parts, a revolving element comprising the
Fig. 2. Left-hand Side of Drill showing Belt and Tightener
hammers and the chuck mechanism for
holding and rotating the steel. The revolving
helve or striking mechanism is flexibly con-
nected to the driving motor by means of a
special endless belt, see Fig. 2, which permits
a variation of speed to any degree desired.
THE FORT WAYNE ELECTRIC ROCK DRILL
275
Drill Casings
The drill mechanism is totally enclosed
within a heavy cast steel casing which pro-
tects the working parts from any foreign
substance, and is of sufficient strength to
withstand any strains incident to extremely
hard usage.
Striking Mechanism
Within the revolving element or flywheel
are two chambers, in each of which a hammer,
consisting of a solid block of special steel,
floats freely. As the helve revolves the ham-
mers are thrown outward by centrifugal
force and at each revolution strike a blow
upon the projecting head of the drill steel
cap which transmits the energy of the blow
to the drill steel. After delivering its blow
the hammer rebounds into the chamber
within the helve, where it is completely
cushioned upon air which it traps. During
the period of recoil (the helve continuing to
revolve) the hammer passes the projecting
drill steel cap. The hammer is again thrown
into the striking position by centrifugal
force, during the remaining portion of the
complete revolution of the helve. The
hammer helve revolves at a speed of 850
r.p.m., and at every revolution each hammer
delivers a blow to the drill steel cap. The
Fig. 3. A 60-Cycle Motor Drill Outfit Complete
energy of 1700 hammer blows per minute is
therefore transmitted to the drill steel.
Chuck
The chuck consists of two parts, the chuck
and the drill steel cap. The chuck is a steel
sleeve through which the "shank" of the
drill steel passes, and is designed to hold the
drill steel in position to receive the energy of
the hammer blow, as well as transmit a rotary
motion to it. The hammer blow is delivered
to the drill steel cap or tappet which in turn
transmits it to the drill steel.
Rotation
The rotation of the drill steel is effected by
means of a heavy worm gear reduction driven
from the helve shaft. A substantial slip
friction cone is mounted on the worm gear
shaft which serves to protect the gears and
motor from any undue strain in case the
rotation of the drill steel is suddenly checked.
Buffer Plates
The drill steel is held in the chuck by
several spring steel plates, one of which is a
split sliding plate fastened in the closed
position in front of the drill steel lug by means
of two heavy pins. When the drill steel is
not striking rock the energy of the hammer
blows is absorbed by these buffer plates
which also retain the drill steel in the chuck
when "backing out" of deep holes in broken
or uneven ground. The drill steel can be
changed without the use of wrenches or other
tools, the simple operation of pulling out two
heavy pins and sliding open the split inner
plate is all that is necessary.
Bearings
The rotating parts of the drill, and also the
belt tightening pulley, are provided with
heavy shock absorbing roller bearings, and
the motor with ball bearings of special design.
All the bearings are packed in grease to insure
satisfactory operation for thirty days without
the attention of the operator. All the bear-
ings used are designed for extra heavy duty,
and were adopted as standard only after
tests covering a period of over two years had
demonstrated their ability to withstand the
strains and absorb shocks due to the con-
tinuous operation of the drill under the most
severe conditions.
Motor
The motor is fully enclosed, splash-proof,
and capable of successful operation in wet
places. It is especially designed to meet the
requirements of rock drill service, and does
not require the usual starting rheostat or
speed controller which are a constant source
of trouble in the hands of unskilled labor.
The rock drill motor can be quickly connected
to the line by means of connector plugs of
such design that it is impossible for the most
276
GENERAL ELECTRIC REVIEW
inexperienced operator to make mistakes.
All motors are designed to stand a 50 per cent
Fig. 4. D.-ill Mounted on Gadder Post Operating in a
Marble Quarry
overload above their rated load capacity,
and provision has been made in the drill
Direct-current motors for 115, 230 and 550
volts and alternating-current motors of 25
or 60 cycle operating on one-, two-, or three-
phase circuits of 110 or 220 volts have
already been developed for these drills.
Drill Steel
It is necessary in all drills of the hammer
type to employ a simple and effective method
to remove the cuttings from the hole being
drilled. In order to avoid the use of hollow
steel, water under pressure or other methods
commonly used for sludging a hole, all of
which are inconvenient, and many times a
source of trouble and expense, a special steel
is used that automatically removes the cut-
tings from the hole while the drilling is in
progress. In this drill steel the well-known
principle of the spiral conveyor has been
used, and the veins or ribs on the steel proper
which give it an auger-like appearance have
nothing to do with the drilling, their sole
function being to remove the cuttings from
the hole.
Power Consumption
The Type "A" rock drill ' requires from
1J4 to 2Y2 h.p. as a maximum for its opera-
tion, including loss in transmission from the
generator to the drill, and is not affected by
change of altitude or by working in air locks
under air pressure. Tests have shown that
air drills of equal drilling capacity require
from 12 to IS h.p. not including the loss in
the air lines due to friction and leakage.
Economy
Records of the comparative cost of opera-
tion of these drills operating side by side with
Fig. 5. Drill as Employed in "Taking Down Roof" in a
Marble Quarry
Fig. 6. A Column Mounted and a Tripod Mounted Drill in a
Railroad Tunnel Heading
whereby a load in excess of this amount air drills of equal capacity have demonstrated
cannot be thrown on the motor. conclusively:
SOME NOTES ON INDUCTION METER DESIGN
■~>7
First. The cost of repairs and supplies
does not exceed that of air drills of equal
capacity.
Second. The cost of power shows a very
marked economy in favor of the electric drill,
averaging 85 per cent saving, which saving
alone is frequently sufficient to pay for the
drill within one year's time.
Third. The cost per ton of rock broken
is almost invariably decidedly in favor of the
electric drill, owing to the fact that it will
successfully drill any character of hole, in-
cluding fiat or horizontal holes.
The cost of installing and maintaining elec-
tric wires is much less than that of an air line.
The simplicity of design and small number of
working parts assure a low cost of drill main-
tenance.
SOME NOTES ON INDUCTION METER DESIGN
By W. H. Pratt
Meter and Instrument Department, Lynn Works, General Electric Company
In designing an instrument for measuring a-c. energy, there are a number of variable factors that must be
taken into account, among which are current, voltage, power-factor, frequency, wave form, and temperature.
A change in any one of the first three will directly alter the amount of energy flowing, and therefore the instru-
ment must be extremely sensitive to variations in these quantities. The other three factors may be considered
as of a disturbing nature, and provision made to guard against possible inaccuracies from any of these sources.
The effects of each of these factors on the performance of the instrument is reviewed, and the article concludes
with a short description of a modern type of induction watthour meter. — Editor.
The induction meter is a measuring device
capable of very considerable refinement, and
it will not be amiss to consider some of the
conditions under which it must operate, and
the manner in which these conditions reflect
in the design.
There are, in addition to time, six principal
variables of which account must be taken,
and no matter what their value (within
reasonable limits) the meter record must
closely correspond to the watthours con-
sumed. Here it may be remarked that, con-
sidering the range of conditions to be met
and the frequently adverse surroundings of
the meter installation, infrequent inspections,
etc., the performance of the modern meter
is truly remarkable.
The more ordinary form of electrical in-
dicating instruments are expected to be
correct, say within three-tenths of one per
cent of their full scale ratings, while the useful
scale range can hardly be taken as more than
from one-fifth scale to full scale (1:5). The
induction watthour meters are correct within
a few per cent at two per cent of their rated
capacity and become more and more accurate
as the load increases. Above full load, the
inaccuracies due to other causes begin to
increase, slowly at first, and not until two or
three times full load is reached are they
worthy of remark. Thus, while within its
useful range, the induction meter falls a little
behind the indicating instrument in actual
accuracy, yet in its particular field it leaves
little to be desired as far as accuracy goes,
and its useful working range, in contrast to
the 1:5 of the indicating instruments, is
1:100.
As already remarked, there are besides the
factor of time six other variables to be con-
sidered. These are, first, current value;
second, voltage; third, power-factor; fourth,
frequency; fifth, wave form; sixth, tempera-
' ture. The first three, together with time, are
direct factors of the quantity to be determined.
First. Taking these up in detail, the
effects of change of current are, first, a change
of torque directly proportional to the change
of field strength produced by the current.
This is the effect desired in a meter. The
departure from direct proportionality is
slight. Synchronous speed, if such a designa-
tion is permissible, would be about thirty
times full load speed, so that an approach to
synchronism cannot be suspected of appreci-
ably modifying the torque. The air gaps in
the laminated iron structure are so large that
the effects of the variable permeability of the
iron, working as it does down to a very low
density, are barely noticeable, so that the
field strength is almost exactly proportional
to the flow of current.
In addition to this primary effect, the field
from the current circuit of the meter acts as
a permanent magnet, producing a damping
in the disk which is proportional to the square
278
GENERAL ELECTRIC REVIEW
of the field strength, i.e., proportional to the
square of the current. This effect begins to
be noticeable after passing full load, and is
the cause of meters being slow at high over-
Fig. 1.
Exterior View of an Induction Watthour Meter,
5 Amp., HO Volts, and 60 Cycles
loads. In case of lack of electrical symmetry,
current in the series circuit may produce a
torque, acting forward or backward as the
case may be, which effect is also proportional
to the square of the current.
Second. Variations of the voltage im-
pressed upon the shunt circuit have much
the same effect as variations of current in the
series circuit, i.e., the desired effect of varia-
tions of torque occur which are closely pro-
portional to the variations in voltage. Damp-
ing from the field of the shunt coil is present
and, since the range of working voltage is
slight, this effect can be permitted to be more
prominent than can the corresponding effect
from the series coil. The symmetry of the
shunt field is deliberately disturbed by means
of the light load plate to furnish a slight
torque, just enough to balance the friction of
the meter.
Third. The third variable is power-
An induction meter without any
in its shunt circuit would behave much
as a watt-dynamometer without any indue-
in its shunt circuit, i.e., it would pro-
duce a torque proportional to the power in
the circuit to which it might be connected
it is not possible to have a circuit
ait losses, it is necessary to make the
lag of the current in the shunt circuit as large
as possible, and to correct the residual error
by some device.
The means actually employed for correc-
tion is a secondary circuit, the lag plate,
so arranged that the current induced in it
produces at the disk a m.m.f. approximately
at right angles, with respect to time, to the
m.m.f. produced by the shunt coil of the
meter, and of such magnitude as to give the
resulting m.m.f. the proper phase. This
phase correction cannot be made strictly
correct except for some particular frequency,
hence it is desirable to make it just as small
as possible.
Fourth. An increase of frequency causes
the disk eddy currents produced by the
series field to increase almost proportionately
to the increase in frequency, and causes a
corresponding decrease in the field from the
shunt coil with which they interact to pro-
duce torque. Conversely, the disk eddy
currents produced by the shunt field remain
practically unchanged, since the field strength
inducing them has diminished in proportion
as the frequency has increased, and interact-
Fig. 2. Interior View of Meter shown in Fig. 1
ing with the unchanged series field produces
almost unchanged torque. Thus the two
torque terms are, as a first approximation,
independent of frequency; in fact, a meter in
SOME NOTES ON INDUCTION METER DESIGN
279
which no attempt has been made to correct
for phase angle can be used over quite a
wide range of frequency without appreciable
errors. The disturbances introduced by the
devices used for phase angle cor-
rection are the principal causes of
the small errors which arise in the
meters, due to change of fre-
quency. Naturally these errors,
while small at high power-factors,
increase as the power-factor
diminishes.
Fifth. In many types of appa-
ratus, considerations of wave form
may be lightly passed over; not
so in meters. In fact, while the
user of modern meters needs
rarely to consider this point
except when deciding on a type,
it must be most carefully con-
sidered in the design. The two
principal factors in this connec-
tion are the phase angle of the
potential circuit and the phase
angle of the eddy currents in the disk.
Taking the second first, it is easily seen that
the disk eddy current circuit, surrounding,
say the shunt coil pole, may have an appreci-
able inductance if the gap in which the disk
is located is narrow enough.
The torque producing effect of the eddy
current is proportional to its magnitude, the
magnitude of the field upon which it reacts,
and the cosine of the angular difference in
phase of these two quantities. If we had
to consider only sine wave circuits, it might
be permissible to let the time constant of this
meter for phase angle without other devices,
bearing in mind that the eddies induced by
the series field must also be considered, and
in general, have a different angle of lag.
Pig
Fig. 3. Parts of the Meter shown in Fig. 1
eddy current circuit be such that there would
be a lag of, say ten degrees, in the current
behind the flux producing it. This lag might
even be chosen so as to nearly correct the
4. Elements of a Two-wire, 5 Amp., 110 Volt. 60 Cycle,
Induction Watthour Meter
However, while the cosine of 10 deg. is
not very far from unity, and the difference
could be allowed for, the corresponding de-
parture of a seventh harmonic would be
about 51 deg., of which the cosine is 0.63.
Also, the magnitude of current would be
diminished in proportion to the cosine of this
angle, so that the seventh harmonic would
be represented by a torque 0.63 times its
correct value, i.e., 0.4 only of the seventh
harmonic would be recorded. The cor-
responding meter error for a five per cent
seventh harmonic would thus be
about three per cent. For inductive
load conditions, the error would
in general be much greater. It may
be noted that the errors arising
from this source diminish much
more rapidly than the diminution
in time constant of the eddy cur-
rent circuit.
The other important source of
wave form error is the deficiency
below 90 deg. of the lag of current
in the shunt circuit. This is much
magnified by the action of the
phase adjusting devices. Consider
the phase adjustment to be so
made that the fundamental is
correctly measured. To achieve this, the
lag adjusting circuit will have been given an
appropriate impedance, which in general
will be totally wrong for any of the har-
■w^i
GENERAL ELECTRIC REVIEW
monies. The higher the harmonics, the less
important are the winding losses and the more
important the losses in secondary circuits.
Only by making the departure of the current
Fig. 5. Tag Plate for an Induction Watthour Meter
in the shunt circuit from 90 deg. slight can
the wave-form errors, even on non-inductive
load, be made unimportant. Here again the
betterment is much more rapid than the
diminution of phase angle deficiency.
Sixth. Variations in temperature produce
changes in the disk resistance which affect
both torque and drag nearly alike. They
also, by changing the resistance of the wind-
ings and adjusting circuits, modify slightly
the constants of the meter. There is also a
slight effect on the damping magnets.
In addition to the variables just enu-
merated, other conditions, such as vibration,
or the presence of stray field, may be of such
importance as to dictate features of the
design.
From the foregoing, many factors gov-
erning the design of an induction meter
may be drawn. Of course it is desirable to
have as high a torque as possible in order to
minimize the disturbances due to friction.
This requirement suggests strong series and
shunt fields, but here we begin to meet
limitations. It is desirable that the meter
shall be entirely free from the influence of
external fields. This is accomplished by
using two series poles and a single shunt
pole. The two series poles are naturally of
opposite polarity, and very close together,
and so no matter how small the current value,
their field at the disk is so increased on the
one hand and diminished on the other, that
the resulting effect is practically nothing with
highest stray fields that are ever met.
The field of the shunt coil is always close to
its full strength, so that in comparison to it.
stray field is of negligible value; indeed,
when the arrangement is reversed and one
series and two shunt poles are used, by at-
tending to certain points in the design, the
effect of external fields may be made very
small, although this latter arrangement can
never be as perfect as the former
for constant potential working.
To minimize the damping
effect of the series circuit field,
it is necessary to weaken this
field as far as possible, and
correspondingly strengthen the
shunt field, keeping their prod-
uct great enough to maintain
the requisite torque; and fur-
ther, to make the damping of
the permanent magnets very
high, since the overload drop
on the one hand and the errors
due to variation of voltage on
the other, are directly determined by the ratios
of series field to permanent magnet field, and
shunt 'field to permanent magnet field respec-
tively. To get the best performance, it is
of course necessary to so form the poles of
the motor structure that the}' shall produce
a maximum of torque with a minimum of
damping.
To secure good performance when working
under conditions of low power-factor, espe-
cially when variations in frequency or wave-
form may be expected, it is necessary to have
the lag angle of the current in the shunt cir-
cuit very high. This means either very small
losses or else a rather high exciting current.
The latter is undesirable and the former
requires the use of the best materials avail-
able, and compact, carefully made coils in
order to keep the structure within a small
compass. Small losses are in themselves a
great advantage, but the real point is that a
high lag angle with a proper attention to
other points makes superior performance
possible.
With a high lag angle, consequently with
small phase adjustment, errors due to change
of frequency and temperature are minimized,
and this in connection with the relation of
the disk to its surroundings practically deter-
mines the performance for change of wave-
form.
Economy, convenience, and esthetic con-
siderations (if this expression may be used in
this connection) dictate a small meter. This
naturally compels the use of small air gaps,
as otherwise too much space would be
occupied by the magnetizing coils and cores;
but narrow gaps increase the time constant
of the eddy current paths in the disk. To
SOME NOTES ON INDUCTION METER DESIGN
281
offset this, the disk may be made thin and
of high resistance, but this requires strong
magnetizing coils in order to obtain the
necessary torque, and this, in turn, demands
powerful permanent damping magnets. The
magnets are thus, to a large extent, the key-
note of the whole.
In the design of the 1-14 meter, there has
been one consideration placed in the fore-
front; that consideration has been definite-
ness. However carefulfy the electrical design
may have been made, the benefit would be
largely lost in the absence of good mechanical
structure. There is in this meter one central
casting, of unusual rigidity, to which are
directly attached all the elements of the
meter. Each element is securely fixed in its
proper relation to the frame, and thereby
to all other elements. The laminated iron
structure and coils are assembled as a unit;
the losses in the shunt circuit amount to only
one watt, thereby giving an extremely high
lag angle in the potential circuit, with the
accompanying benefits as pointed out in the
foregoing. The high lag angle has necessitated
a minimum of lag adjustment, thereby making
a very simple structure of the element
possible. The adjustment is, moreover, ob-
tained by the mechanical movement of the
lag plate whereby more or less flux of
the shunt coils is included within its circuit.
The lag plate is carried directly by the
light load adjusting plate, which together
constitute the means for light load adjust-
ing. The actual adjustment is accomplished
by turning a micrometer screw and then
clamping the plate.
The full load adjustment is accomplished
by a radial movement of the pair of damping
magnets controlled by an adjusting screw.
The magnets are clamped by two screws.
The damping magnets in this meter are made
with particular care, and by reason of their
arrangement make possible a high degree of
damping together with a considerable range
of adjustment. Very careful proportioning has
been necessary to secure these results, since
the disk of the meter is unusually small.
The moving element is worthy of par-
ticular remark. In order to secure great
freedom from wave-form disturbances the
disk has been made thin, and to avoid useless
weight, the shaft has been made of the light
alloy duralumin. Together these have re-
sulted in a very light moving system which
should render jewel wear, already a thing of
no importance, entirely negligible. Right
here let it be said, however, that jewels
should not be neglected as regards oiling.
The duralumin, of which the shaft is con-
structed, is a recently developed alloy of
aluminum and copper, the latter, however,
being present in a relatively small percentage.
Its hardness, which it acquires some hours
after appropriate heat and mechanical treat-
ment, is comparable to that of hard brass.
The alloy is peculiarly resistant to corrosion,
and in the manner in which it is used in this
meter, it will outwear brass.
The terminals of the meter are imbedded
in compound, in a compartment by them-
selves, adapted to separate sealing. Other
details and the general design can be seen
by reference to the cuts.
OfiO
GENERAL ELECTRIC REVIEW
SIGN AND BUILDING EXTERIOR ILLUMINATION BY PROJECTION
By K W. Mackall and L. C. Porter
General Electric Company. Schenectady, \. V.; Edison Lamp Works, Harrison. X. J.
Floodlighting, or sign lighting by projection from a distance, is an innovation which has resulted from
efforts to produce a method of efficiently illuminating advertising matter which, on account of its location,
cannot conveniently or economically be lighted by the older method of distributing low candle-power incan-
descent lamps on or in the neighborhood of the sign itself. This article defines the field to which floodlighting
can be successfully applied, describes the projecting apparatus and the method of installing it, and gives instruc-
tions as to how to make the adjustments. Curves and tables are included which, supplemented by descriptive
Text, furnish data from which to determine how many floodlighting projectors will be required for a particular
installation. — Editor.
Artificial light, as a medium for advertising
and attracting attention, is exceedingly val-
uable. This is a well-established fact and
is strongly emphasized by the appearance
of the business districts of our largest cities.
Light seems to produce a pleasing effect
on the human race, for we walk along the
best lighted streets, shop in the best lighted
stores, and amuse ourselves in the best
lighted resorts.
The matter of economically lighting a sign
on a water tank far above the ground, a bill-
board several hundred feet from power lines,
chimneys, walls, or the entire exterior of a
building has been a problem of no mean value.
In cases of this kind, power is not easily acces-
sible and structural conditions make lighting
by usual methods (employing
several lamps and reflectors
located on the signs them-
selves) too expensive to be
considered for an average com-
mercial installation. By pro-
jecting a beam of light from a
distance onto such signs, how-
ever, they can be made very
effective at night, in fact, more
conspicuous than during the day because of
their contrast against the surrounding dark-
ness. The field reached by this class of adver-
tising differs from and supplements that of the
regular electric sign on the business street
Floodlighting, the name given to this
illumination by projection, is very effective
when applied to the entire outer surface of
a building — particularly if the building is
light gray or white. Public buildings, statues,
and other beautiful pieces of architecture
can be made as attractive in appearance by
night as during the day by this method of
lighting. Such illumination is a dignified and
effective method of advertising for the
company whose building is so lighted.
The floodlighting projector, shown in Fig. 1,
has b ned to effectively and econom-
ically illuminate such advertising matter as
described, and thus enable it to continue its
value after dark.
This projector consists of a highly polished
aluminum parabolic reflector, one-sixteenth
Fig. 1. Sectional Drawing of Complete Floodlight Projector
of an inch thick and 16 inches in diameter,
mounted in an iron frame. The front of
the reflector is covered with a piece of rounded
SIGN AND BUILDING EXTERIOR ILLUMINATION BY PROJECTION 283
heat-resisting glass. This is clamped to the
reflector frame and packed in such a manner
that the whole is weatherproof and can, there-
fore, be operated out of doors in any kind of
weather. All parts exposed to the weather
are either made of non-corroding alloy or
protected by weatherproof coating. The pro-
jector is so ventilated that currents of cool,
fresh air enter near the base of the incan-
descent lamp, circulate around its stem and
bulb and then pass out at the front edge of
the top of the reflector, thus assuring proper
operation of the lamp. If the reflector of
this projector should become tarnished, it
can be brightened again by rubbing it radially
with a piece of soft cloth or chamois skin
(rubbing the reflector around its surface
tends to reduce its reflecting qualities).
The installation of the outfit is very simple.
The most convenient location within a
distance of from 25 to 500 feet from the
surface to be lighted is selected and the
projector bolted or screwed in place. It
may be located on the roof of a building, the
side of a wall, or mounted on brackets on
a telegraph pole. The base of the projector
has slotted bolt-holes, which permit of a
slight adjustment before the final location is
made. The best illuminating effect can
quickly be determined by test before per-
manently fastening the unit in place. Since
the power consumed by the lamp is only
500 watts at 110 volts, the projector may
be connected to an ordinary lamp circuit.
The entire outfit weighs about 30 pounds.
The lamp most commonly used is a 500-
watt focus-type mazda "C" lamp in a "G-40"
bulb with a medium screw skirted base.
The focus-type lamp has its filament con-
centrated into a very small space and, by
locating the filament at the focal point of
the reflector, a narrow beam of light may
be projected a great distance. If, however,
the surface to be lighted is close to the pro-
jector, the lamp filament should be located
behind the focal point of the reflector (drawn
further into the reflector) in order to spread
the beam sufficiently to cover the surface.
The very fact that the spread of the beam
and its effective distance can be easily and
accurately controlled by moving the lamp
in and out of focus makes this equipment
an ideal one for this type of lighting. The
beam may be concentrated to about 6 degrees
divergence with an apparent candle-power
in the center of slightly over 400,000, by
locating the filament exactly at the focus;
or, by drawing the filament behind the focus,
the beam may be spread to IS degrees, with
an apparent candle-power of approximately
150,000 in the center of the beam.
The locating of the filament at the focus
is accomplished by directing the beam on
any convenient surface 100 to 150 feet away
and moving the lamp backward or forward
Fig. 2. Focus Type, 500-watt Lamp Used in Projector
until the smallest spot of light is obtained
on the lighted surface. When this is deter-
mined the focusing device may be locked by
tightening a clamp provided for that purpose.
This keeps the lamp from moving after it has
been adjusted.
The point of cut-off or edge of the beam is
not sharply defined of course; and it is
assumed in this article that the point of
cut-off is located at that angle at which the
intensity falls to 10 per cent of its maximum
value. If the lamp filament is drawn too
far behind the focal point of the reflector,
a dark spot will appear in the center of the
beam. This should be avoided.
With the projector located 100 feet away
and the beam concentrated to six degrees,
the minimum spread of about 10 feet will be
obtained with an average intensity across its
diameter of 30 foot-candles. By spreading
the beam to 18 degrees, the maximum spread
will be about 30 feet, with an average intensity
of 10 foot-candles. If two projectors are
trained on the same area, the intensity will be
doubled; if trained side by side, thus keeping
2S4
GENERAL ELECTRIC REVIEW
TABLE I
Lengths and Widths of Area Lighted and Average Intensities with Beam Concentrated to 6 Degrees
Angle (a) of Axis
of Beam with Perpen-
dicular to Surface
Lighted
D
= 25 ft.
D
= 50 ft
D
= 75 ft.
£> = 100ft
D=150 ft.
I.
ir
/
L
II'
/
L
W
/
L
W !
/
L
W
/
0°
15°
30°
45°
60°
*5°
2.6
3.5
.5.2
10.5
39.0
42S.0
2.7 386.0
3.0 278.0
3.7 151.0
5.2 54.5
10.1 7.7
5.2
5.6
7.0
10.4
21.0
78.0
5.2
5.4
6.0
7.4
10.4
20.2
107.0
96.6
69.5
37.9
13.6
1.9
7.9
8.4
10.5
15.7
31.4
117.0
7.9
8.1
9.1
11.1
15.7
30.3
47.5
42.8
30.9
16.8
6.0
0.8
10.5
11.2
14.0
20.9
41.9
156.0
10.5 1
10.8
12.1
14.8
21.0
40.4
26.8
24.1
17.4
9.5
3.4
0.5
15.7
16.8
21.0
31.4
62.9
234.0
15.7
16.3
18.2
oi 2
31.4
60.6
11.9
10.7
7.8
4.2
1.5
0.2
Angle (a)
D
=200 Ft.
D
=300 Ft.
D
= 400 Ft.
D
= 500 Ft.
Beam with
Key to Symbols
Perpendicular
(Refer to Fig. 3)
to Surface
L
ir
/
L
ir
I
L
II"
/
L
ir
I
Lighted
0°
21.0
21.0
6.7
31.4
31.4
3.0
41.9
41.9
1.67
52.4
52.4
1.07
D = Perpendicular distance in
feet from projector to
surface lighted.
15°
22.4
21.7
6.1
33.6
32.5
2.7
44. S
43.3
1.51
56.0
54.2
0.97
L = Length in ft. of area lighted.
30°
27.9
24.2
4.3
41.9
36.3
1.9
55.9
48.4
1.08
70.0
61.0
0.70
II" = Width in ft. of area lighted.
45°
41.S
29.6
2.4
62.7
44.4
1.1
83.6
59.2
0.60
105.0
74.0
0.38
/ = Average intensity in foot-
candles on area lighted.
a = Angle which center line of
60°
83.8
41.9
0.9
126.0
63.0
0.4
16S.0
83.8
0.21
210.0
105.0
0.14
beam makes with surface.
75°
312.0
80.8
0.1
468.0
121.0
0.05
624.0
162.0
0.03
780.0
202.0
0.02
0= Spread of beam in degrees.
TABLE II
Lengths and Widths of Area Lighted and Average Intensities with Beam Spread to 18 Degrees
Angle (a) of Axis
of Beam with Perpen
£>=25 ft.
O=50 ft.
£>=75 ft.
D = 100ft.
D =150 ft.
dicular to Surface
Lighted
L
W
/
L
W
/
L
W
/
L
W
/
L
w
/
0°
15°
30°
45°
7.9
8.4
10.7
16.3
34.5
182.0
7.9
8.1
9.2
11.5
15.8
30.0
100.0
89.6
65.4
36.8
12.8
1.8
15.8
16.8
21.4
32.6
69.0
363.5
15.8
16.2
18.4
23.0
31.6
60.0
25.0
22.4
16.4
9.2
3.2
0.5
23.7
25.2
32.1
48.9
104.0
545.0
23.7
24.3
27.6
34.5
47.4
90.0
11.1
9.9
7.3
4.1
1.4
0.3
31.6
33.6
42.8
65.2
138.0
727.0
31.6
32.4
36.8
46.0
63.2
120.0
6.3
5.6
4.1
2.3
0.8
0.1
47.4
50.4
64.2
98.0
47.4
48.6
55.2
69.0
2.8
2.5
1.8
1.0
60°
75°
207.0
1090.0
94.S
181.0
ii ;ii
0.05
Angle (a)
D =200 Ft.
D
=300 Ft.
O=400 Ft.
D=500 Ft.
of Axis of
Beam with
Key to Symbols
Perpendicular
(Refer to Fig. 3)
to Surface
L W
/
L W I
L ir
;
L If
/
Lighted
0°
63.2 63.2
1.56
95.0
95.0 0.69
126.0 126.0
0.39
158.0 158.0
0.25
D = Perpendicular distance in
feet from projector to
surface lighted.
15°
67.2 64.8
1.40
101.0
97.0 0.62
134.0 130.0
0.35
168.0 162.0
0.22
/. = Length in ft. of area lighted.
30°
85.6 73.6 1.03
12S.0 110.0 0.46
171.0 147.0
0.26
214.0 184.0
0.16
W =Width in ft. of area lighted.
45°
130.4 92.0 0.57
196.0 138.0 0.25
261.0 184.0
0.14
326.0 230.0
0.09
/ = Average intensity in foot-
candles on area lighted.
a— Angle which center line of
60°
276.0 126.0 I 0.20
414.0 190.0 0.09
552.0 252.0
ii ii-
690.0 316.0
n.u;;
beam makes with surface.
1454.0 240.0
0.03
2180.0
361.0 0.014
2907.0 481.0
0.01
3635.0 600.0
0.005
0= Spread of beam in degTees.
SIGN AND BUILDING EXTERIOR ILLUMINATION BY PROJECTION 285
TABLE III
Beam Candle-power of Headlight Having
6 Degrees Spread
Center of beam
1 deg. either side of center
2 deg. either side of center
3 deg. either side of center
405,000
375,000
240,000
120,000
TABLE IV
Beam Candle-power of Headlight Having
18 Degrees Spread
149,000
148,000
1 deg. either side of
center
2 deg. either side of
center
105,000
3 deg. either side of
center
77,000
4 deg. either side of
center
61,000
5 deg. either side of
center
49,000
6 deg. either side of
center
37,000
7 deg. either side of
center -
23,000
8 deg. either side of
center
16,000
9 deg. either side of
center
11,500
the intensity constant, the area lighted will
be doubled.
The question of the intensity of light
required is one which depends largely on
Jocal conditions. If the lettering of the sign
is white on a dark background, a low inten-
sity is ample. If, on the other hand, the
sign is dark and surrounded by powerful
street lamps or viewed against other light
backgrounds, it may be necessary to use a
very high intensity to make the sign stand
out conspicuously. For average conditions
from 2 to 10 foot-candles produce very satis-
factory results.
For lighting long narrow surfaces, such as
a row of billboards, it is desirable wherever
possible to locate one projector at an angle at
each end. By locating the projectors at the
sides of the board, each one will cover a
greater area than if located in front and the
beam projected perpendicularly to the surface
lighted. For floodlighting the fronts of
buildings, it is desirable to locate the pro-
jectors at several different points, so as to
eliminate the sharp shadows which might
result if all the light came from one direction.
When the area of the surface to be lighted
and the probable location of the projectors
are known, it is a simple matter to calculate
the number of projectors required.
The beam of the projector is conical and,
if it is directed perpendicularly, it will light
up a circular area; but, if it strikes the surface
at some angle a, the area lighted will be
elliptical.
Table I gives the length and width of the
area lighted and the average foot-candle
intensity on this area, when the beam is
r
Fig. 3. Plan and Elevation of the Surface Lighted by a Projector when located at one side
286
GENERAL ELECTRIC REVIEW
concentrated to six degrees; and Table II
gives similar data for the beam spread to 18
degrees. These tables are calculated for
distances (D) from 2.3 to 500 feet and angles
(a) from 0 deg. to 75 deg. in 15-degree steps.
Only in extreme cases should it be necessary
Fig. 4. Billboard Lighted by a 500-watt Floodlighting Projector
to use figures below the heavy black lines in
Tables I and II.
These data should be sufficient for all
practical purposes, but if an elaboration is
desired it may be obtained from Tables III
and IV.
Tables III and IV give the candle-power
of the beam for each degree. By calculating
the length in feet of each one — degree ray and
dividing its square into the candle-power of
that particular ray, the normal foot-candle
intensity on surface dX will be found. This
normal foot-candle intensity on each area dN
should be multiplied by cos 0, the angle of
incidence to give the horizontal illumination
on surface dH. This should be done for each
degree along the length (L) of the beam and
Fig. 5. Water Tank Sign Lighted by a 500-watt
Floodlighting Projector
the results averaged. Similar averages taken
across the width (IT) will be found to be
almost identical with the average obtained
across the length.
Fig. 6. Public Library, Hartford. Conn., Lighted by 500-watt Floodlighting Projectors
ELECTROPHYSICS
287
It would seem at first glance that it was
unnecessary to calculate the average intensity
in this manner but when angle (a) and
distance (D) become large, there is a great
deal of difference in the length of the two
extreme rays (r) and (r'), the two outside
rays of the beam.
This floodlighting projector should find a
wide use for advertising purposes. Its first
cost and maintenance are low, the instal-
lation is easy, and it requires no attention
whatever, beyond an occasional rubbing up
of the reflector and replacing the incandes-
cent lamp at the end of its life.
ELECTROPHYSICS
Part III
By J. P. Minton
Research Laboratory, Pittsfield Works, General Electric Company
In this, the third contribution by Mr. Minton on Electrophysics, the author shows some further appli-
cation of the electron theory to some of the scientific phenomena with which we are most familar. Consider-
able attention is paid to the theory of magnetism. The Poltier, Thomson and Hall effects are discussed, and
thermo-electricity, the effects of currents passing through mixed metals, and the emission of electrons from
tungsten at high temperatures, are discussed in connection with the electron theory. — Editor.
APPLICATION OF THE ELECTRON THEORY TO VARIOUS PHENOMENA
Introduction
In the two articles of this series which
have already been published, the experi-
mental results which led to the electron
theory were discussed. The theory was then
briefly developed and applied to the metallic
conduction of electricity. Although the
results obtained were not as satisfactory as
one would wish, yet many theoretical con-
clusions were drawn which were verified by
experiments. There is hope, however, that
many difficulties now encountered will be
satisfactorily overcome before many years.
In the present article the theory will be
further applied to various phenomena. Since
the field of application is so large, it will be
impossible to cover it in a satisfactory man-
ner. More permanent good will be derived
if only those phenomena with which we
are more familiar are considered; most of
these will be discussed in a rather general way,
and a qualitative explanation given of the
observed facts rather than a quantitative
one. A bibliography will be found at the end
of the article, and those who wish to pursue
the work further will find in these references
ample material with which to occupy them-
selves.
With the above object in view, the following
subjects will be considered in the present
article:
I. Theory of Magnetism.
(a) The Molecular (old) Theory.
(b) The Electron Theory.
(1) Diamagnetic Substances.
(2) Paramagnetic Substances.
(3) Non-magnetic Substances.
(4) Permanent Magnetism.
II. Contact Difference of Potential or
Pokier-Effect.
III. Thermo-electricity.
IV. Effect of Current Passing Through
Mixed Metals.
V. Thomson- Effect.
VI. Emission of Electrons from Tungsten
at High Temperatures.
VII. " Hall-Effect "—Effect of Transverse
Magnetic Field on the Metallic
Resistance.
VIII. Summary and Conclusions.
These various subjects will now be taken
up in the order given.
I. Theory of Magnetism
(a) The Molecular Theory. This theory of
magnetism accounts for the various phenom-
2sS
GENERAL ELECTRIC REVIEW
ena by assuming that a magnetic substance
is made of small elementary magnets. In a
non-magnetic state these elementary magnets
are distributed with their axes pointing
equally in all directions. Under the influence
of an external magnetic field (//), each
Fig. 1
elementary magnetic is acted upon by a
turning force MH sin a, where (M) is the
moment of the elementary magnet and (a)
is the angle between (H) and the axis of this
magnet. The tendency of these couples is to
cause the magnets to turn with their axes
toward the direction of the existing field.
The magnitude of this rotation depends upon
the strength of the field and upon the tem-
perature of the substance. If there were no
thermal agitation of the molecules, all the
elementary magnets would revolve until
their axes coincided with the direction of the
existing field; this condition being obtained
at absolute zero.
In addition to the above effect there is
another one of importance. Each elementary
magnet has an effect upon the surrounding
ones, and thus there is a so-called molecular
magnetism, called (Hm). Ferro-magnetic
substances at high temperatures are but
slightly magnetic; as the temperature is
slowly decreased a- point is reached at which
the substances suddenly become very mag-
netic, a thing which indicates that a strong
molecular field has become active. The
resultant magnetic field (H), therefore, is
equal to the external field (He) plus the
molecular field (Hm) .
It is quite evident that the molecular
theory of magnetism throws absolutely no
light upon its real nature, and that it simply
considers a large magnet made of molecules
(or atoms, as the case may be) which acted
like elementary magnets. The question that
this theory evades is "Whv should molecules
act like magnets:-" This "is the real funda-
mental question, and the one that demands
an explanation in terms of more familiar
phenomena. This explanation is found by
the help of the electron theory of magnetism,
which will now be briefly developed and a few
familiar facts regarding magnetic substances
will be explained.
(b) The Electron Theory of Magnetism.
In the previous articles on the electron
theory it was pointed out that electrons
existed both within and without the molecules
and atoms. Let us first confine our attention
to the electrons within these in order to see
how the latter may act like elementary
magnets.
Fig. 1 represents a molecule, and (pi
represents an electron vibrating along the
path (ab) within it. Now, suppose there is
superimposed on the molecule a magnetic
field whose direction is down perpendicular
to the plane of the paper. There will be a
force acting on the electron (see first article
of this series) and if the electron is at (0)
when the field is put on, this force will cause
the electron to move along the path (0/1).
The direction of motion of the electron then
reverses at (A) which causes the force on the
electron to reverse also. Hence, the electron
moves along the path (AB). At (B) the
direction of motion and hence the direction
of the force are reversed again, and the
electron moves along the path (BC). These
reversals again take place at (C), (D), and
(E), so that the electron arrives at the place
of starting, where it again begins its journey
over the same path. The number of these
reversals depend on the frequency of vibration
of the electrons, which must be about 1014
in order to account for some of the observed
magnetic phenomena. The other electrons
within the molecule will be similarly acted
upon by the magnetic field. This change of
path of the electron to that of a closed curve
corresponds to a flow of current within the
molecule. The molecule must, therefore, be
a source of a magnetic field (provided the
effects produced by the various electrons
within the molecule are not neutralized) and
take the place of the elementary magnet
assumed in the molecular theory of mag-
netism. Let us now apply this theory to a
few more important observations.
(1) Diamagnetic Substances. Considering
again Fig. 1 and the above discussion, we see
that energy was required to set the electrons
moving along the closed paths as explained
above. This energy, of course, came from
the applied (external) field. Hence, the
internal (or magnetic field due to the elec-
ELECTROPHYSICS
289
trons within the molecules) field produced
must have been in such a direction as to
oppose the external field. Hence, the result-
ant magnetic field is weaker than the applied
field (H). Or if we consider a body instead
of the molecule, the same result must hold.
Such a substance is called a diamagnetic
body and is illustrated in Fig. 2. It is seen,
therefore, that diamagnetism is due to the
induced electronic currents within the mole-
cules or atoms by the application of an exter-
nal magnetic field. Ordinary bismuth is the
second strongest diamagnetic substance
known. Recently, Roberts has shown that
crystals of graphite are still stronger dia-
magnetic than bismuth.
(2) Paramagnetic Substances. We may
consider that if the electrons move of them-
selves in a closed path, they set up a magnetic
field which is opposite that set up by the
electrons moving in an orbit on account of
an external field. So that if such a body is
placed in a magnetic field, the two fields will
aid each other, and hence the lines of force
will be pulled in to the body as illustrated
in Fig. 3. Such a body is called para-
magnetic, and iron and steel are the best
examples of this. Ferro-magnetic bodies
are simply bodies which are strongly para-
magnetic.
(3) Non-magnetic Substances. If the
magnetic field set up by the electrons moving
of themselves within the molecules is exactly
balanced by the magnetic field set up by the
electrons which are set in motion along a
closed curve by an external magnetic field,
then the body will be non-magnetic. In this
case the para and diamagnetic effects neutral-
ize each other. If neither of the effects are
present, the body, of course, will be non-
magnetic. Copper is a good example of a
non-magnetic substance.
(4) Permanent Magnetism. Permanent
magnets are bodies which are paramagnetic
and which have more of the axes of their
molecular magnets pointing in one direction
than in any other. This is just the same as
they consider it in the molecular theory of
magnetism. The electron theory simply tells
us there are such things as molecular magnets
because of electronic currents within the
molecules.
Before passing on to the next subject it
might be well to remark that, due to the
random collisions (and thus no definite
direction of motion) of free electrons, these
(free) electrons do not enter into the electron
theory of magnetism.
II. Contact Difference of Potential
Peltier placed two metals Mi and M2 in
contact with each other and passed a current
of electricity across their junction. He noted
that a heating effect was produced at the
boundary when the current passed in one
Fig. 2
Fig. 3
direction and that the junction was cooled
when the current was reversed. In the first
case energy was consumed and in the second
case energy was liberated. We see, therefore,
that the junction of the two metals must be
the source of an e.m.f.
Let us see how this phenomena is accounted
for by the electron theory. Suppose that the
electronic pressure is greater in metal (Mi)
than in (M2) . Then more of the electrons will
diffuse into (M2) than into (Mi), so that the
former will acquire a negative potential and
the latter a positive potential due to their
diffusion. The positive potential thus set up
in (Mi) will attract the electrons and the
negative electricity in (M2) will repel them.
Hence, the flow of electrons will cease when
the attraction of the positive electricity in
(Mi) and the repulsion of negative in (M2)
just balance the effect of the difference in
electronic pressures.
This positive and negative electrification
at the surface of the two metals in contact
will set up a difference of potential. The value
of this difference of potential as given by
Drude is:
t- t- 4a t , -V'
1 , - 1 -i = ., - J loge
Ar2
(L)
Where T is the absolute temperature. The
other quantities have been defined in the
previous articles by the author.
290
GENERAL ELECTRIC REVIEW
From optical behavior of metals it is
inferred that log e jt=- is generally less than one,
that is, the ratio of Ni to Ni is never greater
than 2.179 = e. So that the maximum value
of this potential at T = 291 is
4 X3 X 10"10 X 1.5 X lO"16 X29 1
V
r= =
3 4.8X10"
t n-~v
= 3.6 X106
Ti-ar
y2
Fig. 4
electromagnetic units. Since one volt equal
108 electromagnetic units, the upper limit
of l"i— I'.j is about 0.04 volt. Antimony and
bismuth have about the highest contact
potential which is about 0.033 volt at 18
deg. C. We sec that this agrees with theory.
We also see that all the metals must contain
the same order of magnitude of electrons
per cu. cm.
III. Thermo-Electricity
Referring to Fig. 4, suppose we have two
wires made of different metals joined at
(.Li and (B) as shown. As explained under
the Pokier effect there will be a potential
(Vi) at (.4 ) and (V2) at (B) in the directions
indicated by the arrows. If (A) and (B) are
at the same temperature, then 1',- 1-2 = 0.
But if the temperatures at (.4) and (B) are
respectively T and (T+0T), then by equation
i bove where Vi — V2 = dE
dE = 4^<T+JT)logf-±-^Tlog
or
dE
dE--
Aa Ni
■■ — dl /0?e r^r
3e A -
A'i
125 dT logt *^r microvolts.
A,
-V,
Nt
(2)
3
It is here assumed that ^r1 is not a function
of the temperature, which is probable. It is
now clear to us that thermo-electricity is
simply a case of contact potential where the
junctions of the metals are at different
temperatures.
IV. Effect of Current Passing Through Mixed
Metals
Let us now make use of the Peltier-Effect
to explain why the ratio of the thermal to the
electrical conductivities of alloys is about
20 per cent greater than that of pure metals
as pointed out in the second article of this
series. This explanation is that given by
Lord Rayleigh. He imagined the mixed
metals (two different ones) built up in layers
as shown in Fig. 5, and that a current is passed
through them at right angles to their faces.
Now, on account of the Peltier-Effect being
present one face of one layer will be heated
while the other face will be cooled. As a
result of this, there will be a thermo-electric
potential V = V\— Vi set up for the first two
junctions. There will be a potential \ '" =
Yy, — 1 \ set up for the next two faces, and
V"' = Vi—Vt for the next two, etc. The
resultant thermo-electric potential is, there-
fore, V'+V" + V'"+etc. Each of these
thermo-electric forces are additive and are
opposed to the applied potential. Since this
thermo-electric potential is directly propor-
tional to the current, it acts just the same
as an added resistance and cannot be detected
except as such. This effect is not present in
the case of pure metals, and for this reason
the ratio of the thermal to the electrical
conductivities of alloys is greater than for
pure metals.
V. Thomson -Effect
Lord Kelvin showed that in some metals
an electric current carries heat from the hot
to the cold parts of the metal, while in
Mj M^
M,Mg
Mj Mg
/2 ei i.e gi iz gi
v/ *2 Ks v* "s y6
Fig. 5
other metals the transference of heat is in
the opposite direction. Let us explain this
by means of the theory we are discussing.
Consider the current flowing in the metal
from a place of higher temperature to one
of lower temperature. Then, the electrons
in the metal move from the colder to the
ELECTROPHYSICS
291
warmer part. So that electrons which possess
less kinetic energy due to their lower tem-
perature move into a region whose electrons
have a greater kinetic energy. Due to this
cause alone, therefore, the warmer part of the
metal will be cooled while the colder will be
heated.
But the number of free electrons in the
metal increases with the temperature (approx-
imately as the square root of the absolute
temperature). This means that the warmer
part already possesses a negative charge with
respect to the colder, and will, therefore,
tend to prevent electrons from flowing into
it. This effect opposes the one mentioned
above and may even balance or overcome it.
According to this theory, then, the effect
noted by Lord Kelvin is to be expected.
VI. Emissions of Electrons from Tungsten at
High Temperatures
Suppose that a cylinder of metallic gauze
is placed on the inside of a tungsten lamp,
and that a wire is brought from this gauze
to one side of a galvanometer; the other side
of the latter being grounded. Now, when the
filament is raised to a high temperature, the
galvanometer will be deflected, thus showing
that a current is passing from the hot tungsten
filament to the gauze, and then through the
galvanometer to the ground. This deflection
is in the same direction as would be caused
by negative electricity. J. J- Thomson first
showed in 1899 that this current was due to
electrons being emitted from the hot tungsten.
They were shot off from the filament, struck
the metallic gauze, and then passed through
the galvanometer to the ground.
In this connection O. W. Richardson says,
"This conception has proved a very fruitful
one, and its consequences have been verified
in a number of ways. It has provided a
quantitative explanation of the variation,
with the temperature of the body, of the
number of electrons emitted. It led to the
prediction of a cooling effect when electrons
are emitted by a conductor, and a corre-
sponding heating effect when they are ab-
sorbed. Both these effects have since been
detected experimentally, and found to be of
the expected magnitude, within the limits of
experimental error. * * * Finally, the same
general train of ideas has led to useful
applications in the direction of the theory of
metallic conductors, contact potential, and
photo-electric action."
Prof. Richardson has recently shown that
this current cannot be due to, (1) the evolu-
tion of gas by, the filament, (2) chemical
action or some other cause depending on
impacts between the gas molecules and the
filament, (3) the loss of tungsten by evapora-
ation, and (4) any interaction between
unknown condensable vapors which do not
affect the McLeod gauge.
He shows experimentally that the weight
of electrons given off from the tungsten is
three times the weight of the tungsten lost
by the filament and equal to 4 per cent of the
total mass of the tungsten. It is, therefore,
experimentally proved that this electronic
emission from hot tungsten does not involve
material composition. In conclusion he
remarks, "The experiment also shows that
the electrons are not created either out of the
tungsten or out of the surrounding gas. It
follows that they flow into the tungsten from
outside points of the circuits. The experi-
ments, therefore, furnish a direct experi-
mental proof of the electron theory of
conduction of metals."
No further remarks need be made on this
important conclusion by such a distinguished
physicist as O. W. Richardson. We will now
take up the last point to be considered in
this article.
VII. Hall-Effect — Effect of Transverse Magnetic
Field on Metallic Resistance
Hall found that the lines of flow of an
electric current through a metallic conductor
were distorted when the latter was placed
in a magnetic field. Referring to Fig. 6,
(A BCD) is a flat metal strip, and a gal-
vanometer is connected at two opposite
points (Pi) and (P2). Hall placed the strip
(ABCD) so that the plane faces were perpen-
dicular to a magnetic field. Then, when he
passed a current lengthwise through the strip,
the galvanometer was deflected, thus showing
that an e.m.f. was acting between (Pi) and
(Pt). Bismuth and silver gave a defection
in the same direction, while others, such as
iron, cobalt and tellurium, gave deflections
in the opposite direction. In some alloys
this e.m.f. between (Pi) and (P2) is in one
direction for small values of \H) and in the
opposite direction for larger values. In many
cases it is not proportional to the magnetic
field, otherwise it would not reverse in this
manner. This phenomenon is known as the
••Hall-Effect." The explanation of this effect
from the free electron theory we have
developed is somewhat as follows: If the
electrons drift with an average velocity (V)
from left to right in the metal strip, (H) the
292
GENERAL ELECTRIC REVIEW
strength of the magnetic held, (e) the charge
on an electron, then a force Hell (see hrst
article on "Cathode Rays and their Prop-
erties" by the author) will act on each
electron vertically upwards in the plane of
the paper. This "force will produce the same
effects in the metal strip as would be produced
by an e.m.f. acting on the strip in the same
direction. This explanation requires that
the effect shall always be of the same sign,
a thing which is not true. Some physicists
account for the observed phenomena by
assuming the presence of positive electrons.
This assumption is not satisfactory for
positive electrons have not been discovered.
Another objection to this assumption is that
it would require the effect to be proportional
to (H) which is not true as pointed out above.
To account for the observed facts, we might
consider that each of the metallic atoms act
like small magnets which tend to align
themselves in the direction of the magnetic
held (H). In the small regions between the
poles of the atomic (or molecular) magnets
and the external held it is easy to see that the
lines of magnetic force are in the opposite
direction to those of (H). In these regions,
therefore, the forces acting on the electrons
are also opposite to those caused by (H).
If these atomic magnetic forces are greater
than those caused by (H), then the observed
effect is opposite to that caused by the
latter field. For strong magnetic fields (H)
the effect might be in one direction and for
weak fields it may be reversed. For certain
values of (H) these two tendencies may
neutralize each other. This explanation is a
satisfactory one from a qualitative viewpoint,
but it may not be quantitatively satisfactory.
However, the application of the electron
theory to such phenomena is striking.
It becomes of interest, therefore, to investi-
gate the effect of a magnetic field on the
' ances of metals. A purely mathematical
treatment of this effect will be given and then
we shall see if the theory is affirmed by
experiment.
Consider a current passing along the strip
of metal (ABCD), from one end to the other,
and that a magnetic field is placed down
perpendicular to the plane of the paper in the
region of the strip. Let us then get the
equations of motion of one electron between
impacts with the metallic atoms and with
other electrons. The fifth fundamental
equation of the Maxwell-Lorentz electro-
magnetic theory states that the total force
(F) acting on the electron between impacts is :
F = Ee+etH sin 6
(1)
where (E) is the electric force in dynes on a
unit positive charge, (H) the magnetic force
in dynes on a unit north magnetic pole,
(e) the charge on the electron, (v) the velocity
of the electron, and (0) the angle between
(v) and (H). Let us write this equation in
rectangular coordinates, thus:
F = e (Ex + Ey + £s) + e[ [vzHy - vyHi) + (vxHz - v-.Hx)
+ VyHx-VXHy)] (2)
Assuming the current flowing along the
X axis, and the magnetic field along the Z
axis, then Ey = Ez = o, Hx = Hy = o. Let
Equation (2) then
EX = E, and HZ = H
becomes :
F=Ee+e(vxH-vyH)
(3)
Now, from the first article of this series,
the force of evyH is along the X axis, and
evxH is along the Y axis; there is thus no
force along the Z axis under the assumed
conditions. The total force on the electron
along the X axis is therefore :
as at
and along the Y axis:
d-y dx
mdf-=Hedi
(4)
(5)
where m is the mass of the electron. Let us
integrate equations (4) and (5). Integrating
(5) we get:
m -f- = Hex + Ki
at
dy
(6)
But when x = o, -y- = 0, therefore K\ = 0. So
at
that equation (G) gives:
m -y- = Hex
at
(7)
We obtain the value of (A') in equation (7)
from (4) in the following manner. Since the
effect produced by the magnetic field is
ELECTROPHYSICS
293
known to be small, it will be permissible to
take for (A') the value it would have if no
magnetic field were applied. Hence from (4) :
dt-
= Ee
(8)
(9)
Equa-
Integrating:
m -j- = Eet-\-Ki
at
dx
Now -rr = 0, when / = O, hence K-> = 0.
at
tion (9) then becomes :
mdx = Eet dt
or
mx = Y2 Eef + K-i (10)
when t = 0, X = 0, so that K3 = 0. Whence.
mx = Y2Eet- (11)
Equation (11) gives the distance over which
the electron moves due to the electric force
(E). Due to the random motion of the
electron during this time (t) between impacts
the electron will have moved an additional
distance vt, where (v) is the vibratory velocity
mentioned in the second paper by the writer.
So that the total x is :
Erf
' 2n
+vt
(12)
Substituting this result in equation (7) we get :
dy_He /Eef
m y 2 m
dy
dt
Putting this value of
,//
in equation (4) we
obtain :
integrating,
dx _ Eet
- dt m
d?x = Ee_ H-e-/Eet* \
dt" m m" \ 2m J
(Eet3 vf\
6m 2)
(14)
iir
+ K\ (15)
dx
When t = 0, Ki = ^- = v. Hence, equation (15)
at
becomes:
dx
dt
Eet
m
H-e
(Eet* vf\
6 hi 2 )
+v (16)
dx
This ^f is the instantaneous velocitv of drift
dt
of electrons along the strip. The average
velocitv of drift (£/) bet ween collisions due
to (E) and (H)
of average value,
is, therefore, by definition
7 = _1_ ( d£
T dt
<J 0
dt
(17)
Where (T) is the time required to transverse
the mean free path. Therefore, by equations
(16) and (17)
[Eet HV/Ea*
tn- \ 6m
U
1 fTTEet HV/Ee,* , vt?\ , 1,
Tj0[-^- ^\-6m- + T ) +V\ d>
1 TEe T- IPe> I EeT'v r>\ . ^1
e*(EeT> , vT'\ , ._.
n^+^v+!' (1S)
EeT HV
2m
by equation (1) page 206, in the second article
of this series, we saw that I = NeU, the current
flowing across a surface 1 sq. cm. in area at
right angles to the electric force. Hence,
from equation (18) :
NEe"-T NHV/EeT
0
6w2 I im
+vT*
)
(19)
(20)
The last term of equation (18) drops out
because on the average there will be as many
electrons which possess a negative (v) as
there are that possess a positive (v). The
second term in the brackets of (19) is not
zero because (7") is different for those elec-
trons whose initial velocities are in opposite
directions. This is due to (E) retarding the
motion in one case and aiding it in the other.
If we assume this to be the case, then it will
EeT3
be shown shortly that »P= . Putting
this value for vT2 in equation (19) we obtain:
NEfT NEHVT*
2m 8w2
Comparing equation (20) with (1) and (5) in
the second article of this series by the author,
we see that the first term of equation (20)
is the expression for the current when no
magnetic field is present. The effect of the
magnetic field, as shown by the second term of
the above equation, is to always cause the
current to increase. This, however, is not
true, and equation (20) must not be accepted.
J. J. Thomson argued that the collisions
between the electrons and atoms are greatly
influenced by the electronic charges, so that
the difference between the periods of electrons
moving with and against (E) is quite small;
in fact so small that vT- in equation (19)
EeT3
can be neglected in comparison with — ; — .
294
GENERAL ELECTRIC REVIEW
This assumption leads to equation (21)
below :
NEttT NEHWP
2m 2-im3 y~ '
This equation indicates that (7) always
decreases when the conductor is placed in a
magnetic field; just the opposite from equa-
tion (20). Neither of these equations are
satisfactory for in some pure metals equation
(21) holds, while in ferro-magnetic metals
equation (20) is in agreement with the
observations. For some ferro-magnetic metals
equation (20) holds for weak values of (H),
and for very strong values of (H) the effect
is reversed so that equation (21) is satisfied.
It is obvious, therefore, that neither of the
two assumptions made above were justifiable.
Let us look into the matter more carefully.
From the discussion on the electron theory
of magnetism it is evident that the presence
of the magnetic field will alter the arrange-
ment of the atoms and molecules within the
metal. This will probably alter the mean
free path of the electron, and hence its
periodicity (7~). Let the new period be (7"i),
then T=Ti + ST. Calling (I) the current
if the magnetic field did not exist and (i"j)
the current after the magnetic field caused
a re-arrangement of the atoms and molecules,
then by equation (19),
h =
XEe-Ti .XHVSEeT,3
6m"
a?+-o
(22)
Subtracting equation (22) from the first
term of equation (19) we get:
r-^^I+^f/^^rA (23)
2m bm- \ 4m ) y '
Substituting Tx=T — hT in (23) and neglect-
ing all terms involving (57") or higher order
terms we obtain :
/-/■
.V£(!«r ,.VH¥/£iP ZEeT-hT
-~
6m'- V
4m
4m
+l T--2:TiT
)(24)
Now, if (ti) is the periodicity of the electron
in the direction of (£), and \h) that in the
opposite direction, then if (/;) is the mean free
path of the electron.
t-u- h h
I'+L V—U
Putting in the values of (U) which we have
already obtained in the author's second
article of this series we get:
■iFeT^ST
-2vTbT=-^-^- (25)
and
rP= -
EeV
in
(26)
Putting equations (25) and (26) in (24) and
reducing we get:
. . NEe'-ST ,VHV / -3EtP .5E<r'{r\ ,.-,_.
' 1m + 6m= ( 4m H 4m ) \-<)
Since ST is negligible compared with (T)
equation (27) reduces to:
l-I,-^f>T-^Tl (28)
-(--'£?)
This is the final form for the change in
current due to the molecular and atomic
re-arrangement on account of the magnetic
field. It is seen to consist of two terms, one
positive and the other negative. In magnetic
substances, like iron, we have to assume that
{ST) is large enough to overbalance the
second term for small values of (H). Then
I >Ii, and its resistance therefore increases.
When magnetic saturation is reached (ST)
ceases to change, and with increasing values
of (H) the second term overbalances the
first. The I >Ii, and hence, the resistance
decreases with increasing values of (H).
We see. therefore, that the theory calls for a
reversal of the effect, and this is actually
what is observed.
so that
Now I
I-h-
E A T E
t and equati
(H)-£0r-
From this result and equation (28) we get:
H-e-T3>[
(29)
)
But in the second article of this series we
obtained:
1 AY-T
K 2m
Hence, equation (29) can be written:
1_ 1_ 1 / H-e-r\
R R,~ TR\° " 4m- )
or
R-RtST HWT*
' Ry ~ T 4>«2
and since (Ri) nearly equals (R),
8R b~T HV-r-
R ~
ST
T
H-c-T
Now,
(30)
1 4)11-
is very small in comparison with
4)HJ
for iron for large values of (H), so that
SRHVT*
R ~ 4mr
(31 i
ELECTROPHYSICS-
295
Grunmack gives for iron:
~S-§= 10~3. H = 2X K)4, -= 1.8X 107
Putting these values in equation (31) :
10-
4X108x:!.2X10H7"2
or
P = 3X10"26 or T= 1.7X10-'3, which accord-
ing to their theory is the average period of the
electrons in iron.
F or iron ~ = K)-\ e= 1.6X 10"-°,
1 Xc-T , , . .
and since -= = — — \vc get, by substituting
K '2)ii
in these values of — T, e, and »i,
N= 10-'-' approximately,
which gives the number of electrons per
cu. cm. in iron. You will remember that
according to the free electron theory as given
in the second article of this series the number
in one cu. cm. of silver is 102"1. We feel, there-
fore, that the number of electrons in a cu. cm.
of metal is of the same magnitude as the
number of atoms, and that the number of
electrons per cu. cm. in various metals is of
the same order of magnitude.
It will be well to note that since vT = h,
(the mean free path), (h) is equal to
107X1.7X10-13 = 1.7X10-6 approximately.
By investigating the change in metallic
resistance under the influence of a transverse
magnetic field, we have been able to account
for the noticed change in resistance, to
calculate the periodicity ( 7") of the electron,
to calculate their mean free path, and to
determine the number of electrons per cu. cm.
of the metal under investigation. The field
of application for the electron theory is thus
seen to be quite extensive.
VIII. Summary and Conclusions
This concludes the first three articles on the
electron theory and its application. The
theory has now been developed and applied
to many different phenomena. We have tried
to show that it is extremely fundamental and
far reaching. It is, indeed, applicable to all
phenomena observed in connection with
gravitation, etc., etc. It is the most searching
of all theories known, and because of this
fact its application requires great ingenuity
on the part of the investigator. One will find
attached herewith a bibliography which will
be helpful if he desires to pursue this theory
further.
BIBLIOGRAPHY
Theory of Magnetism
Curie, Archives des Sciences, ser. 4, .'i!, p. 5-19,
1911.
Weiss, Journal de Physique, 36, p. 661-690, 1907.
Langevin, Annales de Chemie et de Physique,
ser. 5, 8, p. 70-127, 1905.
Kunz, Physical Review, 30, p. 359-370, 1910.
Williams, Univ. of Illinois, Bull. 10. No. 10,
pp. 3-64, Nov. 4, 1912. (A good summary of work
already done on the electron theory of magnetism.)
Schrodinger, "Kinetic Theory of Magnetism,"
Akad. Wiss. Wien, Ber. 121, 2a, pp. 1305-1328,
July, 1912.
Holm, "Magnetism and Molecular Structure,"
Ark. for Mat. Astron. Och Fwsik, Stockholm, 8, 16,
pp. 1-59, 1912.
Contact Potential
Drude, Ann. der Physik, 1, p. 590, 1900.
Drude, Ann. der Physik, 1, p. 593, 1900.
Drude, International Electric Congress, St. Louis,
Vol. 1904.
J. J. Thomson, "Corpuscular Theory of Matter."
0. W. Richardson, Phil. Mag. 24, pp. 737-744,
Nov., 1912.
"Electron Theory of Thermo electricity." and
Vol. 23, i)]). 594, 1912.
Lord Ravleigh, "Collected Works" Vol. IV, p.
232.
Lord Rayleigh, Nature, LIV, p. 154
Emission of Electrons from Hot Metals
J. T- Thomson, Phil. Mag. Vol. XLVIII, p. 547,
1899
( l. W. Richardson, Camb. Phil. Proc. Vol. XI.
p. 286, 1901; Phil. Trans. A Vol. CCI, p. 497, 1903;
Phil. Mag. Vol. 26, pp. 345-350, Aug. 1913.
Richardson and Cooke, Phil. Mag. Vol. XX, p.
173, 1910, Vol. XXI, p. 404, 1911. Phil. Mag. Vol.
XXV, p. 624, 1913.
Metallic Conduction
1. J. Thon "' Corpuscular Theory of Matter."
O. W. Richardson, Phil. Mag. Vol. 23, p. 594,
1912. Vol. 24, p. 737, 1912.
One will find Owen's, "Recent Physical Research,"
a very useful book.
The reader can find a great many more references
in Science Abstracts, Sec. A. Physics.
296
GENERAL ELECTRIC REVIEW
♦RAILWAY MOTOR CHARACTERISTIC CURVES
By E. E. Kimball
Railway and Traction Engineering Department, General Electric Company
This article, which is part of the discussion of Mr. E. C. Woodruff's paper on the Graphic Method for
Speed-Time and Distance-Time Curves, read before the A.I.E.E. on Nov. 13, 1914, shows how the slide rule,
with the addition of two special scales, may be used as a sufficiently accurate substitute for the characteristic
curves of a d-c. railway motor. Equations for the curves plotted from the slide rule readings are evolved, and
their application illustrated by the solution of a concrete example, in which the horse-power of the motors to
fulfill a given set of conditions is determined. Another example is worked out to show how the motor losses
may be segregated and the resistance of the motor determined. — Editor.
The object of this article is to show by
means of two typical characteristic curves
of railway motors, how valuable the slide
rule is as a handy substitute for the charac-
teristic curves of an actual railway motor.
The steps leading up to the selection of a
motor to do a given service without over-
heating usually require exactly similar calcu-
lations or follow the calculations of speed-time
and distance-time curves; but there are
some short cuts which will lead to a close
approximation of the size of motors required.
Furthermore, the ordinary characteristic
curves giving speed, tractive effort, and
efficiency of a railway motor do not contain
sufficient information regarding the resistance
and core loss of the motor for one to determine
the losses which have to be radiated in
service, or to correct a characteristic curve
for a change in voltage conditions. From an
analysis of these characteristic curves the
writer expects to point out a procedure which
he has found to be very useful in supplying
this information when required.
The so-called polyphase slide rule (Fig. 1)
is the same as the ordinary slide rule except
that it has two additional scales, one in red
between the "B" and "C" scales, which is
the "C" scale inverted (reversed), and the
other on the edge of the rule, which is the
scale of the cubes of numbers on the "D"
scale. If the ends of the scales are made to
coincide, as shown in Fig. 1, and the values read
from the "CI" and cube scales are plotted
against corresponding values from the "A"
scale as abscissa?, the curves which result
resemble the characteristic curves of a d-c.
railway motor, as shown by the dotted lines
of Fig. 2. That is, from the 'A" scale is read
per cent amperes, from the middle scale per
cent speed, and from the scale on the edge of
the rule per cent tractive effort. The setting
of the slider in Fig. 1 gives the readings of
speed and tractive effort corresponding to
160 per cent normal amperes; that is, 79
per cent speed and 203 per cent tractive
effort. In this figure are shown in solid
lines the characteristic curves of a composite
or typical railway motor in which the vaiues
are given in per cent of the one-hour rating
of the motor. If the dotted lines are accepted
as representing the relation between the
amperes, tractive effort, and speed for
rough calculations then it can be shown that
the efficiency must be constant throughout
the entire range. The equation of the dotted
speed and tractive effort curves are as
follows :
% speed
/ i v
\% amp.y
♦Part of discussion of E. C. Woodruff's paper before A.I.E.E.
November 13. 1914. on The Graphic Method Jor Speed-Time and
Distance-Time Curves.
and
Per cent T.E. = (per cent amp.)3-'2
The writer has made no attempt to derive
an equation which will represent the charac-
teristics of a railway motor closer than the
ones just given, for the reason that the
chief value of these equations lies in the fact
that it is easy to remember to read per cent
amperes on the "A" scale, per cent speed
on the middle scale, and per cent tractive
effort on the cube scale.
For speed-time and distance-time curves,
one is not so much interested in the relation
between speed and amperes or tractive
effort and amperes as he is in the relation
between speed and tractive effort.
From the above equations it follows that
% speed = lc~o T.E. )
or in other words: The speed of a d-c. railway
motor is approximately inversely proportional
to the cube root of the tractive effort.
The dotted speed curve in Fig. 3 is plotted
with tractive effort instead of amperes as the
variable; that is, the two tractive effort
curves of Fig. 2 have been made to coincide
and the speed curve modified so as to main-
tain the same relation between speed and
tractive effort as exists in Fig. 2. The closeness
with which the dotted and solid speed curves
RAILWAY MOTOR CHARACTERISTIC CURVES
297
^Normal Amperes
^% Normal Speed
/o Normal Tract. ive Effort
Fig. 1. "Polyphase" Slide Rule
of Fig. 3 agree shows that the relation between
speed and tractive effort for the typical
railway motor is closely represented by the
rule just stated. The value of this relation
in determining the capacity of railway
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Per cent Voted Amperes
Fig. 2
motors for a given service is best illustrated
by an example.
Assume a 50-ton car to be geared for a
maximum speed of 60 m.p.h., a train resist-
ance value of 25 lb. per ton at 60 m.p.h., and
a rate of acceleration of 0.8 m.p.h.p.s. De-
termine the horse power capacity of motors
required.
At 60 m.p.h. the tractive effort delivered
by the motors just balances the train resist-
ance, viz., 25 lb. per ton. The final speed
reached on the control during the period of
notching up (beginning of motor curve
acceleration) is unknown, but we know what
the tractive effort must be to give 0.8 m.p.h.-
p.s. acceleration during the control period.
It is 80+15 = 95 lb. per ton if we assume it
takes 100 lb. per ton to produce 1 m.p.h.p.s.,
and if the train resistance at this lower speed
is taken at 15 lb. per ton.
By the rule just stated
60 VoV
or
T = 60X
(!)'=
60 (0.263)'/' = 38.5 m.p.h.
Likewise for any other speed the tractive
effort can be obtained; that is, at 40 m.p.h.
L /eoY
25 \w)
or
r=25Xf ±
(§)'=
84 lb. per ton.
Thus, given one condition which must be
satisfied, other points follow directly. That
is, given the maximum speed and friction
corresponding, the speed and tractive effort
for any other point can be closely estimated.
The usual procedure is as just outlined in the
example above.
The equipment selected must be able to
accelerate the car at the rate of 0.8 m.p.h.p.s.
up to 38.5 m.p.h. without overheating in
service. A car geared for a maximum speed
of lid m.p.h. would not usually be used in a
frequent stop service, hence high and frequent
accelerations are not likely to occur, and it
may be assumed that if this rate of accelera-
tion does not exceed the one hour rating of the
298
GENERAL ELECTRIC REVIEW
motors the equipment will have capacity
to do the service; that is
horse power required =
50X95X38.5
375
= 488
or let us say four 125-h.p. motors.
One would look for characteristic curves
of 125-h.p. motors and select a gearing which
would give sufficient tractive effort at 60
m.p.h. to balance the friction.
For lighter and slower speed cars, which
are generally used in frequent stop service, a
rate of acceleration of 0.8 m.p.h.p.s. is not
sufficient either for performing the usual
schedules nor does it leave enough margin for
radiating the losses in service. It is usual to
select an equipment for these services which
will produce an acceleration of 1.00 to 1.50
m.p.h.p.s. at the one-hour rating of the
motors. This is on the basis of non-ventilated
motors.
Ventilated motors radiate losses much
faster than the non-ventilated type, hence
the horse power rating of motors, if ventilated
motors are proposed, will be less than found
by the above method. As a first approxima-
tion 80 per cent of the values found above
will lead to some definite design of motor for
which the radiating constants are known.
From these it can be determined what the
probable heating will be in service.
To segregate the losses of a railway motor
and thereby determine its resistance, the
writer has found that the core loss may be
represented by the equation CL = K1'\
where K is a constant and / represents
current.
The standardization rules of the A.I.E.E.
Appendix I of Rules) suggests that the gear
and friction losses be taken at five per cent
for all loads above % load for approximate
determinations when tests are not available.
Then from an efficiency curve plotted in this
fashion we may select two points above %
load and write the equation for the total
losses, eliminate the terms containing core
loss and solve for R.
Thus for 3/4 and 3/2 load, if
7 = amperes at 3/4 load,
2 I = amperes at 3 2 load,
L = Core loss at 3 4 load,
\ 2 L = Core loss at 3 2 load.
A i and K« = total losses in per cent at 3 1
and 3/2 load respectively.
= 100 — per cent efficiency at 3 4
and 3/2 load respectively.
E = rated voltage of motor or volt-
age marked on curves.
Then
and
(W«-*5L-i£j*(iO-5i££Q
at 3/2 load (2)
or eliminating L and substituting 1.26 for . ■>
2.74 PR - 3?fL = (2 K*~}M A"> )EL
R =
simplified
R
100
100
(2 K2-
1.26 K"i-3.7) E
2.74X100X7
(8 Ki
- 5 /\"i — 15) E
1 100 I
From the derivation of this formula it
follows that care must be taken to select
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Per cent ffoted Amperes
Fig. 3
two points both of which are above 3 4 load,
and the load must bear the relation 2 to 1 ;
i.e., if one point is taken at 7/8 load the
other must be taken at 7/4 load, etc. / is
the current corresponding to the lesser of the
two points chosen.
THE OSBORN ELECTRIQUETTE
299
Example: Find the per cent copper and
core loss represented by the typical charac-
teristics shown in Fig. 2 or 3.
These curves are shown over a sufficient
range to obtain three determinations of the
resistance. For check readings, we will take
the losses in pairs as follows:
Ago, A.ico; A so, Ais
A 80=100-S6.5 =
A 100,
13.5
K"ieo = 100 -82.0 = 18.0
A 90= 14
Aiso = 20.5
A'10o=14.5
A,„o = 22.0
K%
R--
(8X18-5X13.5 -15)£
1100X80
-d.ooiiT /•:
R = (8X 20.5 -5X14- 1 5 ) E
1100X90
= 0.0008 E
R (8X22^0-5X14.5- 15) E
R— ^100X100 =0-000805 E
Ave. A = 0.00077 A
Per cent PR (1 HR rating) = PR X *00
= 100 X 0.00077 X 100 = 7.7 per cent
Per cent CL (1 HR rating)
= 14.5- (5 + 7.7) = 1.8 per cent.
The accuracy of this determination of the
resistance of a motor depends upon how
accurately the efficiency can be read. A
single determination may be 25 per cent out
because of accumulated errors in reading the
efficiency, but usually the error is much less
than this.
THE OSBORN ELECTRIQUETTE
By O. E. Thomas
Los Angeles Office, General Electric Company
This article tells of an interesting development, and shows the adaptability of the electric drive to new
fields. The control features are of special interest, and it should be noted that every detail has been worked
out to a point where it is practically "fool-proof." — Editor.
One of the latest and most unique appli-
cations of electric motor drive is to be seen
in the diminutive electric vehicle recently
placed on the market. The rolling chair of
the seaside resorts is to lose its attendant
and is to be propelled by an automobile type
motor, deriving its power from a small storage
battery. The electrically propelled chair will
be known as the "Electriquette."
It is not the plan to furnish operators for
these vehicles, care having been taken to
make them so simple, safe and practical
that any one will be able to operate them
without previous experience. How well the
designers have succeeded in this regard is
evidenced by the photographs.
The chair consists of the chassis on which
are mounted the motor, batteries, gearing
and operating mechanism, and a body made
of heavy rattan. Comfortable cushions for
the seat and back are provided. A brief
description may be of interest.
The frame is constructed of angle iron
bolted and reinforced with cross members.
The wheel base is 45 inches and the tread is
33 inches ; the motor and gearing are mounted
at the rear and the battery at the front.
All the wheels are of cast iron and are
provided with flat solid rubber tires. The
front wheels are 10 inches in diameter and
are mounted in swivel socket bearings at-
tached to the frame, and are assembled with a
tie rod and lever for steering. The rear
wheels are 14 inches in diameter and are
supported independently in bearings which
are attached to the frame. One wheel car-
ries the driving sprocket, while the other is
fitted with a hub and contracting brake band.
The motor is of special automobile type
manufactured by the General Electric Com-
pany, rated as GE-1042, 12 volts, 14 amperes,
2000 r.p.m. It is of the enclosed type, and, is
equipped with ball-bearings and aluminum
bearing heads. The weight is approximately
25 lb.
The battery is of the Gould lead cell type,
rated at 12 volts and 130 ampere-hours; the
normal discharge is 14 amperes at the chair
speed of three miles per hour. The battery
capacity is sufficient for about eight hours'
operation, or approximately a full day's
run. Recharging is carried on at a station
at night time. Tests have been made, driving
the chair fully loaded up a 20 per cent grade.
300
GENERAL ELECTRIC REVIEW
Under these conditions a battery output of
approximately 65 amperes is required.
The motor mounting consists of a single
casting comprising the motor cradle, back-
Fig. 1. Electriquette with Split Rattan Body
gear bearing housings and supports, as well
as the back-gear case. The motor is held in
the cradle by two straps. The complete
mounting is bolted to the frame and cross
members. The left rear wheel carries the
sprocket which is chain-driven from a pinion
electric warning bell, is located within con-
venient grasp of the operator. A safety
feature is provided, consisting of a metal
board labelled "Emergency Stop." This
extends across the floor within the reach
of the feet of both passengers. When
this stop is pressed, a line switch is
ripened and the wheel brake is applied and
locked. Before the chair can be started
again it is necessary to bring the controller
to the "off" position, which operation
releases the brake and closes the line switch.
This feature is of considerable importance and
is entirely effective. The chair can be stopped
so quickly that it may be safely operated on
a crowded thoroughfare.
The bodies are constructed of heavy split
rait an, amply reinforced. They are bolted
directly to the frame and can be readily
removed. The front hood covers the battery
and is hinged for easy inspection and charg-
ing.
The complete chair weighs 450 lb. It
will comfortably seat two persons. In
actual operation three or more are often
accommodated. In this development the
electric motor still further extends its use-
fulness.
A number of these chairs are already in use
on the grounds of the Panama-California
Exposition now being held at San Diego,
ft
^£f --
i »i
1 Nl
.lJI
*^SS
L_r«r/
9H -jprT ^3|^B
■PP^^^
Figs. 2 and 3. Front and Back Views of Electriquette Chassis
on the back mar shaft, the total gear reduction
of the back gear anil chain being 28 1 .
The controller is of the single knife-blade-
contact type, giving two speeds forward and
one reverse point. The controller .handle,
carrying at its end a push-button for an
California, and are proving very popular.
About one hundred and twenty-five chairs will
ultimately be in service at this exposition,
and four hundred or more at the Panama-
Pacific-International Exposition opening at
San Francisco, February 20. 1915.
301
NOTES ON THE ACTIVITIES OF THE A. I. E. E.
NEW YORK CONVENTION
The mid-winter convention was held in the
Societies' Building in New York on February
1 7th, I Nth and 19th. A large number
attended this convention. The papers were
of a very interesting character and the con-
vention was conducted in an able manner by
the chairman, all the papers being delivered
according to schedule, with ample time for
discussion.
The Status of the Engineer
An event of more than passing interest was
an evening session devoted to addresses on
the status of the engineer. The opening
address was by Mr. Lewis B. Stillwcll, which
was followed by short addresses by Messrs.
E. W. Rice, Jr., E. M. Herr, Alexander C.
Humphries, John Hays Hammond, George
F, Swain, H. G. Stott and J.J. Carty. All
of these gentlemen, who have been eminently
successful in their various lines of activities,
gave their views on the subject of the status
of the engineer. Some of the things said
about the engineer were very complimentary ;
but some were not, for he was treated with
entire frankness. It was pointed out, for
example, that the engineer took too small a
part in the law-making bodies of the states
and nation; that, being absorbed in his
enthusiasm for his work, he frequently lost
sight of the dollar, allowing the less deserving
to get it; etc. On the other hand, in the
engineer's favor, it was said that his constant
association with facts, and exact analyses of
conditions, made him valuable for practically
any line of work, and that it particularly
fitted him for filling high positions of trust
and executive ability. It was aptly remarked
by the chairman in this connection that two
of the speakers themselves, Messrs. Herr
and Rice, who had spent most of their lives
as engineers, were now presidents of two cor-
porations, among the largest in the world.
Electrical Precipitation
Among the many papers presented, the
three on the subject of "Electrical Precipita-
tion" attracted perhaps the most interest;
that is, they drew the largest audience and
those who had the opportunity of hearing
them felt especially privileged.
The opening address was made by Dr. F. C
Cottrell, who gave a historical sketch of the
steps in the development of the art. The
papers and their authors were as follows:
Electrical Precipitation — Theory oj the Removal
of Suspended Matter from Fluids, l>y \V. W.
Strong; Theoretical and Experimental ( \>n-
siderations of Electrical Precipitation, by A. F.
Nesbit; and Practical Applications of Electrical
Precipitation, by Linn Bradley.
The authors treated the theoretical and
practical aspects of electrical precipitation of
fumes, smoke, dust, etc., in very great detail,
and by means of motion pictures, gave a very
convincing demonstration of some of the
things actually accomplished. Several varie-
ties of chimneys were shown, rigged up with
equipment for electrical precipitation. In
these pictures, first a dense volume of smoke
would be shown issuing from the chimnevs
and then, after seeing a person throw a switch,
the chimneys almost instantly appeared
smokeless. The switch in the pictures, of
course, controlled the circuit supplying the
electric power, by means of which the elec-
trical precipitation was accomplished. These
motion pictures were thoroughly convincing.
However, Mr. Bradley added further to the
positiveness of these demonstrations by means
of a working model. This model consisted
of a chimney, attached to which was a blower,
the top of the chimney being equipped with a
co-axial electrode. A 5-kv-a., 100,000-volt
transformer, and a mechanical commutator
driven by a synchronous motor, were used to
supply the co-axial electrode with the proper
character of electrical pressure. The blower
was used to supply carbon dust, in order to
reproduce the approximate conditions exist-
ing in a chimney emitting smoke. By Mr.
Bradley's demonstration it was shown that,
although a dense mixture of carbon was
emitted from the chimney, all of this could be
electrically precipitated by means of the
device in question. The success of the demon-
stration wiin tin- appreciative applause of the
audience.
LYNN SECTION
Lead Storage Batteries, by J. L. Woodbridge
A particularly interesting lecture on the
Lead Storage Battery was given by Mr. J. L.
Woodbridge, Chief Engineer of the Electric
Storage Battery Company, February 17,
1915. The following is an extract of Mr.
Woodbridge's lecture :
The chemical changes taking place upon
charging and discharging were well brought
302
GENERAL ELECTRIC REVIEW
out by the use of diagrams and slides. The
chemical methods of forming the plates were
treated from the historical side, the speaker
in this connection giving a very good resume
of the development of the plate, from the
original experiments by Plante and Faure to
the most modern methods of plate manu-
facture. Numerous types of grids for holding
the active material in position, representing
the best European as well as American prac-
tice, were illustrated by slides. Special
stress was laid on the ability of the best
lead cells to deliver their charge at many
limes normal rating in case of emergency
without suffering permanent damage. This
point was demonstrated by short circuiting
and "iron clad" cell, of 600 ampere-hours
rating, through a 3s im by % in. steel bar,
."> in. long. The current at the beginning of
the test was 201 in amperes, which as the bar
heated up dropped to 1500 amperes, where it
held constant for five minutes; the bar in the
meantime being heated to bright incandes-
cence. On a dead short circuit this battery
showed 4000 amperes just previous to the
test. The plates were in no wise injured by
this strenuous discharge, having passed
through the same performance some fifty
times before.
Mr. Woodbridge then showed character-
istic curves relating to specific gravity volt-
age and temperature as affecting charging
and discharging conditions. Emphasis was
laid on the fact that charging should be based
on specific gravity measurements rather than
voltage measurements, and that in charging a
battery, the ideal conditions were most
nearly approached when the charging load
was varied to keep a constant voltage drop
across the cell, and the hydrometer relied
upon to indicate when the charging should
be discontinued. No reliance whatever could
be placed upon voltage readings taken with
the cell open-circuited. In discharging, the
voltage of the battery under load should not
be allowed to fall below a certain minimum
value, which varied somewhat with the tem-
perature of the cells.
The latter part of the lecture was devoted
to slides illustrating large battery installations
.in many of the big central stations in this
country where the batteries are relied upon
to carry a portion of the peak or even all the
load in case of an interruption to the generator
equipment. Several kinds of "end-cell
switches" were also described in this connec-
tion. Station records showing graphically
the effect of "stand by" batteries in large
installations in cases of sudden big demands
were shown, which illustrated the need of
such arrangements where continuity of service
was of paramount importance.
Problems that Confront the Physicist, by Professor
Comstock
On March 9th, at the fifth of the special
series of lectures by Professor D. F. Comstock,
of the Massachusetts Institute of Technology,
the speaker discussed the Present Day Prob-
lems that Confront the Physicist. This series
of lectures has been most heartily enjoyed by
those attending the course.
Up-to-Date Telephone Problems, by J. G. Patterson
On March 10th, Mr. J. G. Patterson,
Engineer of the New England Telephone
Company, spoke on Up-to-Date Telephone
Problems. The talk was illustrated by
lantern slides. An extract of this paper will
appear in our next issue.
Recent Developments in X-ray Work, by Dr. Davey
On March 17th, Dr. W. P. Davey spoke on
Ret i lit Developments in X-ray Work.
PITTSFIELD SECTION
The Sixth Annual Dinner of the Section
was held on Wednesday, February 24th.
Over one hundred members were present.
The principal speaker was Dr. W. L.
Tracey, of Pittsfield, who gave an outline of
some very interesting experiences in Europe
at the opening of the present war. Dr.
Tracey, it seems, was traveling in Switzer-
land at the time when the war broke out. The
lecture was illustrated by a very complete
set of beautifully colored lantern slides.
Leakage Reactances and Short-Circuits, by Pro-
fessor Adams
On March 11th Professor C. A. Adams, of
Harvard University, lectured on The Leakage
Reactance of Synchronous Alternators and Its
Relation to Sudden Short-Circuits. An extract
of this paper will be given in the next issue.
Program for April
The following meetings are scheduled for
April:
April 1st, Dr. E. B. Rosa, Recent Work of
the Electrical Division of the Bureau of Stand-
ards.
April 22nd, Mr. C. F. Bateholts, Educa-
tional and Advertising 1 ~aluc of Motion Pictures.
April 29th, Dr.W.R. Whitney, The Physical
( 'hemistry of the Blood.
NOTES ON THE ACTIVITIES OF THE A.I.E.E.
303
SCHENECTADY SECTION
Control for Electric Motors, by C. D. Knight
On March 2nd, Mr. C. D. Knight, Manag-
ing Engineer, Industrial Control Department,
General Electric Company, gave an interest-
ing talk on the Principles and Systems of
Control for Electric Motors. An extract of
this paper is given below:
Mr. Knight gave an outline of a program to be
carried out by the Industrial Power Committee of
the A.I.E.E. for the season of 1914 and 1915, of
which Mr. D. B. Rushmore is chairman, and himself
a member, the idea being to arrange for a series of
papers which could be published at the end of the
year in the shape of an industrial power volume
covering the latest methods of adapting motors and
control to the various industries, such as steel mills,
machine tool, mines, rubber, paper, printing,
textile and many others. Mr. Rushmore had read
a paper outlining the motor situation two weeks
previous at the midwinter A.I.E.E. meeting in New
York, and Mr Knight, without dwelling on the
details of any one application, reviewed the control
situation, stating that these papers would be fol-
lowed by others which would specialize on each
important industry as a unit.
Mr. Knight then described the several up-to-date
types of resistances which form the basis of all
control apparatus, demonstrating that their chief
function is to control the amount of current which is
applied to the motor, and so dissipate the energy
absorbed by radiation and ventilation as to keep the
temperature of the resistance within safe working
conditions. He then showed that the property of
absorbing energy in the form of heat is known as
thermo capacity, and that of transferring heat from
tlic unit into the cooler air as radiation. As the
thermo capacity is the capacity to store energy in
the form of heat for each degree rise of temperature,
a unit of small cross section carrying low current
may have as large a thermo capacity relatively as a
unit of large cross section carrying high current.
This was shown by two heating and cooling curves
for cast iron grids of different capacities.
Mr. Knight then took up the question of tem-
perature co-efficient, showing that a resistance with
a zero temperature co-efficient covered the ideal
condition. Many forms of wire have this, and that
of cast iron is 0.0007, which from a practical point
of view is satisfactory. He went on to show that
with resistance material having an exceedingly
high temperature co-efficient, frequent starting of
the motor would increase the resistance to such a
degree as to involve the danger of not having the
motor start on the first point of the control.
Passing briefly over the well known methods of
hand control Mr. Knight went considerably into
the latest development of magnetic and automatic
control, showing the different methods in vogue for
controlling d-c. and a-c. motors. For direct-current
the three accepted methods of automatic accelera-
tion are counter e.m.f., current-limit, and time-
limit, the first being applicable to d-c. motors only,
and the two last to both a-c. and d-c. motors.
In describing the counter e.m.f. method of con-
trol, Mr. Knight presented diagrams showing a
number of contactors with their coils connected in
multiple across the armature, these contactors
being adjusted to provide different air gaps between
the core and the armature, in order that they may
go m al different values of counter e.m.f. of the
motor as t hi^ increases. It was demonstrated that
this form of control was more satisfactory for use
with shunts than with series motors, because the
counter e.m.f. of the latter depends upon the current
as well as the speed, and it might he possible, if
the motor were starting under heavy load, to obtain
sufficient counter e.m.f. to close all the contactors
before the motor had time to accelerate properly.
Mr. Knight described current limit acceleration
as a function of the current; one method of obtaining
this consisting of a number of shunt contactors
energized by series relays, each relay being held
up when the inrush of current for the motor is high
at starting and dropping as the current falls, due
to the acceleration of the motor. As each relay
drops, it energizes the next contactor, which cuts
out a step of resistance, finally bringing the motor
up to speed.
Another method of current limit acceleration was
shown by means of a series contactor, in which the
operating coil is in series with the load and operates
in such a way as to lock out on high current, and
close at some predetermined lower value.
In describing time limit control two methods were
shown; one being a solenoid operating an arm over
contacts, and being retarded by some form of
dashpot in order to get the number of seconds
required in accelerating the motor and "the other
type a motor or magnetic ratchet operated dial
in which the variation in time element is obtained
by increasing or decreasing the speed of the motor
or the strength of the magnets operating the ratchet.
Mr. Knight showed that one very important
feature peculiar to the direct current motor is the
possibility of operating the motor as a generator for
quick stopping, or for retarding the lowering speed
when overhauled by a suspended weight, as in crane
service. For this purpose a resistance is connected
in the armature circuit, which dissipates the stored
energy as heat. This method is called "dynamic
braking." For quickly stopping an alternating
current motor use is sometimes made of a low volt-
age direct current circuit, which is connected to two
of the primary phases, after the motor has been
disconnected from the line. Another method,
called "plugging" is to connect the motor and
apply power in the opposite direction, but tin
circuit must be opened as soon as the motor has
stopped or the motor will run in the reverse direc-
tion.
Mention was made of the latest form of liquid
rheostat which is used for starting and regulating
the speed of large induction motors for mine hoist
work. By taking advantage of the water level in
the electrode chamber, auxiliary magnet switches
can be energized, bringing into action additional
resistance plates, this method having increased the
resistance range about nine times the former value.
In concluding Mr. Knight referred to the great
advantages of automatic over hand control, from
both a safety and time saving standpoint, and
showed several slides to demonstrate this fact, one
of the most interesting being that of a large boring
mill in which the automatic panel was totally en-
closed and quite a distance from the machine. The
operation of the motor was controlled by push
buttons, one of which was in the form of a pendent
switch hanging inside of the large casting on the
mill. The operator could remain inside this casting
and control the speed of the machine without being
obliged to climb up and signal to his assistant to
Mill
GENERAL ELECTRIC REVIEW
perform this feature, which was naturally inherent
in the old hand control system;
Driving Ships' Propellers, by W. L. R. Emmet
On March 30th, Mr. W. L. R. Emmet,
Consulting Engineer, General Electric Com-
pany, will present a paper on Driving Ships'
Propellers. This paper will be presented
before a joint meeting of the Schenectady
Section of the A.I.E.E. and the Eastern New
York Section of the N.E.L.A. Mr. Emmet's
paper will be of considerable interest, in view
of the fact that the United States Government
has decided to build the California, a new
dreadnaught, arranged for electric drive.
Mr. Emmet is certainly well qualified to
discuss this topic, as he has evolved much of
what is known about the subject of electric
drive for ship propulsion. The success of
the electrically propelled Jupiter has without
doubt been the means of bringing about the
present decision of the navy department to
build the California with this method of
drive.
Lectures for the Near Future
Among the lecturers scheduled for the near
future are the following:
Mr. G. Faccioli, Assistant Engineer, Trans-
former Department, General Electric Corn-
pan v.
Mr. Philip Torchio, Chief Electrical
Engineer of the New York Edison Company.
Prof. Elihu Thompson, Consulting
Engineer, General Electric Company.
Mr. E. B. Raymond, formerly General
Superintendent of the General Electric Works,
and at present Vice-president of the Pitts-
burg Glass Company.
PRACTICAL EXPERIENCE IN THE OPERATION OF
ELECTRICAL MACHINERY
Part VII (Nos. 36 to 40 inc.)
By E. C. Parham
16 IMPERFECT SLIP-RING CONTACTS
It frequently has been observed that copper
brushes when sufficiently burned, due to
sparking, will become so much oxidized as
to impair the conductivity of their contact
surfaces, with the result that a generator on
which such brushes are used may be unable
to build up its field magnetism.
An effect similar to this was encountered
in connection with a slip-ring induction
motor used on a foundry crane. The motor
was erratic in that sometimes it would start
promptly and at other times it would not.
Of the three motors used on the crane, the
motor in question was the only one that gave
this trouble. It would seem that this state
of affairs might exist because the other mo1 1 irs
were somewhat protected while this one was
unprotected and was swung low where it was
exposed to the dust and fumes from the
moulding floor. As the irregular action per-
sisted even after the pinion had been drawn,
the cause could not be attributed to parts
other than those local to the motor itself,
establishing an independent stator
circuit to the line and an independent rotor
circuit through temporary resistances, it
I that the uncertain starting feature
still existed. It was while applying an
ammeter to test for balanced currents that
the nature of the trouble was suggest ci I.
The stator circuits proved to be balanced
under all conditions and the rotor circuits
took equal currents at those times when the
motor started promptly. At other times, one
rotor circuit or another would take no current
that was readable on the only ammeter that
was available. In course of further testing of
i he rotor circuits with a voltmeter, it was
found that, with the rotor blocked and the
line voltage applied to the stator (which are
the conditions under which the voltage
generated in the rotor is at its maximum
because the slip is 100 per cent) uniform
voltages could be read across the slip-rings
if Hie voltmeter test lines were applied to
the sides of the rings. When, however, the
test lines were applied to the bearing surfaces
or to the brush shunts, the' results obtained,
if readable, were very uncertain. On using a
magneto, it was equally uncertain as to
whether its bell would ring upon applying the
test i ic lints to an}- pair of slip-rings. The
rotor was removed and the rings turned down.
There was no evidence of burning on the'
rings, but in turning them down the machinist
OPERATION OF ELECTRICAL MACHINERY
305
found it necessary to take off a full thirty-
second of an inch, in order to get under a
skin that the lathe tool would not cut. This
operation restored the normal characteristics
of the motor.
The crane man stated that the motor pre-
viously had sparked viciously on account of
the rotor rubbing the stator, and that this
condition had been aggravated by a loose
brush-holder stud. It was after these faults
had been corrected that the balky action had
become most pronounced.
(37) EQUALIZER ON THE WRONG SIDE
A properly connected equalizer between
two compound-wound generators places their
series windings in parallel.
If one machine is already connected to the
load and the other machine is to be paralleled
with it, the voltage of the incoming machine
should be adjusted to no-load value after
which the equalizer and the main switches
should be closed in the order named, unless
a special three-pole switch is provided to
close them simultaneously. In any event,
the instant the equalizer switch is closed
a part of the current from the loaded machine
passes through the series field of the incoming
machine, which increases the voltage of the
latter by an amount that represents the
voltage active in making it take its share
of the total load. Furthermore, assuming
that the machines are properly connected,
the equalizer current insures that incoming
machine will be of the right polarity and
it also minimizes the chance of the machine
Fig. 1
being "motored" should its no-load voltage
have been adjusted to too low a value.
An operator once complained that he
could not parallel a new compound-wound
generator with an older one "because there
was something the matter with the new one."
He further stated that there were fireworks
each time that he had tried to throw the
machines together. An investigation dis-
closed that the operator, who had done his
own installing, had connected the equalizer
as indicated by the full line a-b in Fig. 1.
It should have been connected as indicated
by the location of the dotted line c-d. In
other words, the equalizer was connected
on the side of the armature opposite to the
series field, which resulted in simply increasing
the capacity of the busbar g-h. Naturally,
when the machines were paralleled there was
no equalizing action and whichever one
happened to have the lower voltage was run
as a motor by the one of higher voltage.
If a properly connected equalizer is of
sufficient cross-section to permit of its
resistance being neglected and if the resist-
ances of the series fields of the two machines
are equal, the current from either loaded
machine should divide equally between the
series fields of the two generators as soon as
the equalizer switches are closed.
(38) GENERATORS MOTORING AT NO-LOAD
Fig. 1 illustrates the connections for
operating two compound-wound generators
in parallel by means of an equalizer. In
connection with this diagram will be con-
sidered an operator's complaint that one
of the two machines would always "motor"
the other one when the external load became
zero, either as the result of there being cars
in service using no current or because of the
station circuit breaker opening.
Assuming that the correct no-load adjust-
ments have been made, the currents of the
two machines combine to flow through the
external circuit, represented by the broken
line, as long as this path remains intact.
The function of the equalizer connection,
which places the series field windings of the
machines in parallel, is to minimize the
motoring tendencies incident to the machines
having unequal voltages. It does this by
strengthening the field of the lower voltage
machine, thereby increasing its voltage and
causing it to take more load as a generator.
When the external circuit is open and the
equalizer open but the local circuit around
the two machines closed, any difference
between the voltage of the two machines
will result in the higher voltage machine
backing current through the lower voltage
machine. As this current must pass through
306
GENERAL ELECTRIC REVIEW
the series field of the lower voltage machine
in the reverse direction, it opposes the field
due to the shunt winding and further de-
creases the generated e.m.f., which at this
time is really the counter e.m.f". of a differen-
tially connected motor. The motoring current
therefore further increases and this increase
r
-4—
^-Ser/es F/e/c/s
£quo//zen
-/frmaiare
Shunt F/'e/a'
~t *~ Shunt F/e/d'
Fig. 2
weakens the field more, thereby still further
decreasing the counter e.m.f. The net result
of these interactions is that the lower volt-
age machine quickly assumes the character-
istics of a short-circuit across the higher
voltage one. Unless circuit-breakers relieve
the situation promptly, the motored machine
is likely to have its rotation reversed; this
will occur if the series winding is strong
enough to overcome the shunt field and thus
reverse the polarity of the resultant field,
because the machine will then operate as a
series motor (which turns in the opposite
direction from what a series generator would
for given connections).
With the external circuit open and the
equalizer circuit closed (the condition under
which the operator claimed one machine
would motor the other) the series fields of
both machines are out of action, the equalizer
short-circuiting them and at the same time
serving as a conductor for completing the
local circuit between the two armatures
running in the fields excited by their respec-
tive shunt windings. The two machines when
under this condition may be considered as
shunt generators connected together with
voltages opposed. So long as the opposing
voltages are equal, no current will flow
between the armatures; but if for any reason
one of the voltages becomes a little higher
than the other the lower voltage machine will
be motored, ahhough it will continue to run
in the same direction because shunt gener-
ators and shunt motors operate in the same
direction for given connections. The extent
to which one machine will motor the other
depends upon the amount of the difference
between their voltages. Slight differences
ma)- be due to speed variations, to unequal
heating of shunt fields, or to different arma-
ture reactions incident to unlike brush shifts.
To whatever cause the motoring may be due,
the motored machine is apt to spark because
its brushes are located for generation and
not for motor operation.
Assuming the generators to be practically
similar in all respects, but that their brush
shifts are unequal, the armature reaction
of one machine will affect the magnetism
of its pole-pieces more than will the armature
reaction of the other machine affect its
pole-pieces. Although each machine may
have first been carefully adjusted to give the
correct no-load voltage, the result after the
two have been loaded and the load removed
(either by the main circuit-breaker operating
or by the external load decreasing to zero)
may be that the no-load voltages of the two
machines will be found to be very different
in amount because the residual magnetism
of one generator may be much greater than
that of the other.
This was the trouble in the case under
consideration. The flashing and motoring
at no-load was eliminated by giving the
brushes of both machines the same number
of bars forward shift. It was then necessary
to readjust the compounding of one of the
machines by changing the length of its series
field shunt.
(39) CHANGING MOTOR MOUNTING
Some motors are constructed to permit
of floor, wall, or ceiling mounting. In the
absence of instructions to the contrary, it is
customary to ship the motors arranged for
floor mounting.
To adapt them for wall mounting the end
shields are rotated 90 degrees, and for ceiling
mounting ISO degrees, in order to bring the
oiling devices into their normal position.
As a rule, the shifting of the end shields
shifts the brush-holders to a position which,
according to the number of poles, might
reverse the direction of rotation or render
operation impracticable on account of spark-
ing. One method of checking brush position
is first to arbitrarily mark' alternate field coils
-V and 5, as shown in Figs. 3 and 4. If the
holders are located midway between coils,
Fig. 1. two holders that include a N coil,
for example, are marked. After shifting the
shield, the brush-voke is shifted until the two
OPERATION OF ELECTRICAL MACHINERY
307
marked holders again include a field coil
marked N if the direction of rotation is to
remain unchanged. Where each holder is
located opposite the center of a coil, Fig. 4,
a holder opposite a marked coil N, for
example, is marked and after shifting the
shield the marked holder should be placed
opposite a field coil marked N, if the same
direction of rotation is desired.
These instructions expressed in terms of
angles would read as follows: After laying
the motor upon the floor in the position in
which it is later to be mounted on the wall
or the ceiling, as the case may be, and
rotating the shields to correct the position
of the oilers, the rocker arm or yoke should
be turned backward through the same angle
that the shield has been turned forward.
The brushes will then be in the correct
position for sparkless operation and for the
original direction of rotation. Such a double
shift is equivalent to loosening the yoke and
holding it stationary while rotating the end
shield. As far as sparkless operation in the
original direction is concerned, it is immaterial
whether the marked brush-holder be moved
to its original position relative to the marked
field coil or whether it be moved to the same
position relative to another field coil of the
Fig. 3
Fig. 4
same mark; in the latter case, however, it
• may be necessary to lengthen some of the
loads.
Failure to observe the requirements of
relative brush-position has caused much
trouble and delay to operators who have had
occasion to shift a motor from one mount to
another or who have changed their minds
after specifying that a motor should be
shipped for a certain mount.
(40) MOTOR THROWING OIL
The tendency of motor bearings to throw
oil, that is eventually drawn into the motor to
saturate its windings, may be due to a hot
bearing, or to a defective bearing, or to ex-
cessive and careless application of oil, or to
the overflow pipe being stopped up, or to a
pumping action that may become effective
as the result of excessive lining wear. In
most cases, however, excessive and careless
oiling is responsible.
Except where information is furnished
as to the amount of oil required to refill a
bearing, or to renew normal loss, it is the
better plan to apply the oil through the over-
flow pipe. By carefully noting the level of
the oil in this pipe, while slowly pouring it in,
a reliable indication of the oil level in the
bearing becomes available. Most care takers
resort to the quicker method of applying the
oil through the top opening of the bearing.
The objections to this method are that, unless
the oiler is careful, he will spill oil outside or,
if he is careful but continues to pour oil in
until he sees a little run out of the overflow
pipe, the overflow will continue for some time
after the oiler leaves, since a certain amount
of time is required for the oil to work its way
down from above, and up through the over-
flow pipe.
An inspector was asked to prescribe for an
elevator motor that was "throwing oil."
The motor windings, brushes, brush rigging,
slip-rings, floor and elevator platform were
saturated and wherever oil could stand in
pools it did. If the motor had been engaged
in pumping oil, it could hardly have made a
better showing. The inspector cleaned every-
thing concerned with the motor, flushed out
the bearings with gasolene, refilled the bear-
ings through the overflow pipe until the oil
came up to within \i inch of the top of the
overflow, and then had a heart to heart talk
with the oiler — which produced satisfactory
results.
308
GENERAL ELECTRIC REVIEW
FROM THE CONSULTING ENGINEERING DEPARTMENT OF THE
GENERAL ELECTRIC COMPANY
NOTES ON THE OPERATION OF TRANS-
FORMER USED WITH 2 KW. 100,000
CYCLE ALTERNATOR
The purpose of these notes is to give an
outline and general description of how a
current having a frequency of 100,000 cycles
ma}- be taken from a 2 kw. generator and
transformed so that the maximum output
of the machine may be applied to a tuned
circuit. This circuit may be a wireless
antenna having a given value of resistance,
have an effective resistance of about 2.5
times the ohmic resistance. This increase in
resistance is due to the eddy current loss in
each conductor, and also to the mutual effect
of adjacent conductors when considering a
stranded cable of bare wires.
The primary winding is sandwiched in
between the secondary to give a fairly close-
coupled transformer. The winding ratio is
also changeable so that the generator and
transformer may be applied to quite a wide
inductance and capacity, or a circuit arranged
to measure the energy input to a certain
particular insulation under investigation.
The no-load losses of the transformer, since
it has an air core, consists of insulation loss
and effective resistance loss. The insulation
loss is due to dielectric hysteresis in the
insulation between conductors and also be-
tween coils. The most efficient insulation is
air, and the transformer coils are so made that
air is used for insulation between turns. There
are several braids of cotton wrapped around
the conductor, which acts only as a spacer
to provide the desired thickness of air
between turns. Sample coils using cambric
as insulation between layers were made,
and considerable heat was generated from
the energy loss in the cambric.
At a frequency of 100,000 cycles per
second, the eddy current loss in the con-
ductors becomes an important item. As an
example, the coils used in this transformer
range of resistance and still obtain maximum
output. A representative load will be de-
scribed somewhat in detail:
Consider an antenna having a resistance of
20 ohms and a capacity-reactance of 1400
ohms. In this case we will take the magnetiz-
ing current flowing in the secondary and
let part of the antenna capacity-reactance
neutralize this inductance. Thus our circuit
is from the generator terminals direct to the
primary of the transformer, one terminal of
the secondary being grounded, and the other
connected to a variable antenna inductance
and then to the antenna proper.
Assume the following constants:
Frequency = 100,000 cyeles per second
Generator open circuit volts = 120
Generator full load current = 30
Generator synchronous resistance = 0.8
ohms at 100,000 cycles
Generator synchronous reactance = 5.8
ohms at 100,000 cycles
CONSULTING ENGINEERING DEPARTMENT
309
The transformer ratio is determined as
follows :
120 volts open circuit generator
30X0.8 = 24 volts IR drop in generator
96 energy volts available
,rr- =3.2 ohms resistance load
.30 amp.
Since antenna resistance = 20 ohms
Effective ratio of transformer =
V:
g-VSB-u.
Since the effective ratio of transformation
is somewhat less than the ratio of secondary
to primary turns, we will assume a ratio of
turns of 4:1.
We have then
Transformer (secondary open circuit) resist-
ance =1.06 ohms at 100,000
Transformer (secondary open circuit) react-
ance =15 ohms at 100,000
Transformer (secondary short circuit) resist-
ance =0.05 ohms at 100,000
Transformer (secondary short circuit) react -
ance = 1.08 ohms at 100,000
Voltage at generator terminals =
V/(120-30X0.8)2+(30X5.8)2 = 200
Thus we see that the voltage across the
generator has been increased from 120 at
no load to 200 under load.
With 200 volts across transformer primary :
Primary magnetizing impedance = 15
Magnetizing current = -"- =13.3
15
The secondary current or antenna current
will then be the vector sum of the load
current plus the magnetizing current divided
bv ratio of turns
^5=10.4
4
Thus current ratio = TfT7 = 2.9
The voltage ratio will be about 3.2 (see
vector diagram) ; and
Volts secondary = 640
Fig. 1 shows the vector relations of this
type of transformer, using 1 :1 ratio.
e = generator open circuit voltage = 120
eg = generator impedance voltage = 175
Since we are considering a circuit in reson-
ance, the energy volts delivered by the
generator .will be in phase with 'the generator
current and not the voltage at generator
terminals.
Thus the transformer primary will have a
terminal voltage of:
Ei =200, and current Ii = 30, lagging by
the angle a
e\ = transformer primary impedance drop
= 16
Ei' = transformer primarv induced voltage
= 185
<t> =flux
E% = transformer secondary induced voltage
= 185
// =JX=30
Secondary current It = vector sum of I\ and
/m = 41.5
ei = impedance drop in secondary = 23
Ei = secondary terminal voltage = 160
co = angle lag of 72 behind terminal volts Ei
It is interesting to note that owing to the
very large generator impedance, the mag-
netizing current is nearly in phase with the
load current. By operating with magnetizing
current in the secondary, the alternator
winding is relieved of this extra current.
In tuning, all that it is necessary to do is
to adjust the number of turns in the variable
inductance until the current in the antenna
circuit reads maximum, the generator speed
being held constant by a speed regulator.
Then the antenna capacity does two things,
namely :
(1) Supplies the magnetizing current for
transformer.
(2) Supplies the series capacity reactance
necessary to obtain resonance.
Returning to the case of the 4:1 trans-
former, we have a secondary or antenna
current of 10.4 amps. The antenna has
20 ohms resistance and 1200 ohms capacity
reactance at 100,000 cycles.
Antenna kv-a. = 10.42 X 1400 = 152 kv-a.
Antenna voltage = 10.4 X 1400 = 14,600 volts
Antenna kw. = 10.42X20 = 2. 16 kw.
2.16
Antenna per cent power-factor = -'—^ = 1 .42
S. P. Nixdorff
31(1
GENERAL ELECTRIC REVIEW
QUESTION AND ANSWER SECTION
The purpose of this department of the Review is two-fold.
First, it enables all subscribers to avail themselves of the consulting service of a highly specialized
corps of engineering experts, or of such other authority as the problem may require. This service provides
for answers by mail with as little delay as possible of such questions as come within the scope of the Review.
Second, it publishes for the benefit of all Review readers questions and answers of general interest
and of educational value. When the original question deals with only one phase of an interesting subject,
the editor may feel warranted in discussing allied questions so as to provide a more complete treatment
of the whole subject.
To avoid the possibility of an incorrect or incomplete answer, the querist should be particularly careful to
include sufficient data to permit of an intelligent understanding of the situation. Address letters of inquiry to
the Editor, Question and Answer Section, General Electric Review, Schenectady, N. Y.
TRANSFORMERS: TWO-PHASE TO THREE-PHASE
CONNECTION
(133) What is the effect on the current, voltage
etc., when using two separate transformers in
place of the "main transformer" in a T two-phase
to three-phase transformer connection?
The conditions as described in the question are
illustrated diagrammatically in Fig. 1 wherein the
letters and the "primed" letters serve to distinguish
the primary and the secondary windings of the
separate transformers. This substitution of two
separate transformers [aa1 and bb') of the ordinary
type for the "main transformer" of a T-connection
can never be depended upon to give satisfactory
service, for it is necessary that the "two halves" of
the "main transformer" (which are replaced by the
two separate transformers in this case) be mag-
netically interlinked. Although of small commercial
consequence, attention might be called to the fact
that the proposed scheme would give the proper
voltages at zero load. For unbalanced loads the
phase relations would be distorted badly.
Fig. l
Fig. 2
The feature of magnetically interlinked trans-
formers, which cannot be obtained for the T-con-
nection with ordinary transformers, can be secured,
nevertheless, by the use of transformers that have
multiple windings similar to those designed for
three-wire distribution. If two such transformers
are employed the windings of the one can be inter-
connected with those of the other so that they will
be able to react magnetically on each other when the
bank is under load. The winding scheme which
should be followed when these three-wire trans-
formers are utilized is shown in Fig. 2.
Especial attention is called to the fact that the
windings on the two-phase side of the main
transformer (aa'-bb') in Fig. 2 are parallel con-
nected. The windings of the two-phase side of
the teaser transformer (cc1) are connected in parallel
also. The arrows indicate the direction of current
flow when a load is drawn from the teaser winding
only, which is the most severe requirement that the
bank will be called upon to fulfill. Under these
conditions a circulating current flows through the
windings a' and b' and prevents unbalancing of the
phase relations and the delivered voltage.
R.K.W. and L.F.B.
ARC WELDING: USE OF ALTERNATING CURRENT
(134) Attempts have been made by a steel foundry
to fill holes in steel castings by using alternating
current for arc-welding. The energy was supplied
directly from a 50-cycle, 440/60-volt, 25-kw.,
single-phase transformer; and the welding current
has ranged from 100 to 400 amperes. Up to the
present time the welds produced have been
unsatisfactory. Is this due to the fact that
alternating current was used instead of direct
current; if not, wherein is the installed apparatus
unsatisfactory?
We would attribute the lack of success to the use
of alternating current for arc-welding. (It is well
known that various methods of resistance welding,
however, have successfully employed alternating
current.) A number of attempts have been made
to utilize alternating current for arc welding but,
so far as we know, all of them were practically
failures.
It is a recognized fact that, if the filling of holes
in steel castings is to be accomplished satisfactorily
by the arc-welding process, the current which is
employed must be direct current .
Practically all commercial equipments for this pur-
pose have a welding potential rating of about 60
volts. The range in current named in the question,
viz., 100 to 400 amperes, is sufficient to cover the
requirements of the arc-welding work in a steel
foundry, with the exception of cutting of gates,
risers, etc. For this purpose 600 to 1000 amperes
enables the work to be completed in a much shorter
time.
The best equipment for an installation of this
type would be a flat-compound-wound, direct-cur-
rent generator driven by a constant-speed induction
motor, the motor to have an automatic control
device for regulating the amount of current drawn
from the line and for preventing an injury to the
generator when starting the arc.
J.A.S.
QUESTIONS AND ANSWERS
311
INDUCTION MOTOR: HEATING ON UNBALANCED
THREE-PHASE VOLTAGE
(135) What will be the probable increase in the
temperature of the "hottest part" of an average
three-phase induction motor when supplied with
energy from a three-phase line that is fed by two
identical transformers "T" connected? (The
voltage delivered by the teaser transformer will
be the same as that by the main transformer,
instead of the correct value 86.7 per cent of it.)
The three-phase voltage will of course be un-
balanced thereby but it is otherwise to be sub-
stantially the normal three-phase voltage value
for the motor, and the frequency is to be of the
correct value.
The effects on the operation of an induction
motor, which are caused by unusual conditions, are
so dependent upon the design characteristics of each
particular type of machine that it is impossible
to make a general statement that can be expected
to cover motors of different rating or manufacture.
It will be of interest, nevertheless, to note the
test results which were obtained in the following
particular instance. A normal type of motor, under
test conditions very similar to those named in the
question, displayed local heating of about 85 to 90
per cent higher than when the motor was run under
balanced voltage conditions. In this particular
test the voltages were unbalanced 15 per cent and,
as mentioned, the local heating was nearly double.
A.E.A.
ALTERNATOR: BEARING CURRENT
(136) How can the presence of a current flow
through the bearings of an alternator be detected,
and how can the amount of such a current be
measured?
Detection
Probably the most convenient way of ascertaining
the presence of a bearing current, if there is one, is
to use the following method.
Run the alternator at normal speed and excite it
to normal voltage. By means of low-resistance leads,
securely connect one terminal of an alternating-
current ammeter (which is of about 60 amperes
capacity) to a clamping-down bolt of a bearing
pedestal and the other terminal to the shaft
by a rubbing contact which should be located near
the bearing pedestal just named. A brush made
of copper gauze or ribbon can be arranged to make
a very good rubbing contact on the side of the
shaft or on its end. (A carbon brush must not be
used because it has a relatively high resistance when
compared to that of the remainder of the circuit.)
Under these conditions the ammeter may indicate
a current or it may not.
If a legible reading is given, there is a current
flow through the oil film of the bearing as well as
through the meter. (This indirect proof of the
presence of a bearing current will apply only when
the bearing pedestal is not insulated from the frame
of the machine, which is the condition assumed
in this explanation.)
If no deflection does take place it may be due
to one of two causes:
(a) The magnetic design of the machine is
completely symmetrical, thereby no e.m.f. is
generated in the shaft that would cause a bearing
current to flow.
(/>) The current through the ammeter is too
small in amount to give an indication on the size
of meter which is used.
To determine which of these conditions exist,
replace the ammeter with one of 10or5amp. capacity.
If a reading cannot be obtained in this manner,
the conditions are as described in (a), i.e., because
of a completely symmetrical magnetic balance
there is no difference of potential generated in the
shaft and consequently bearing current is absent.
This information would conclude the test. If a
definite indication of a current flow can be obtained
by the substitution of a smaller capacity ammeter,
however, this shows that the conditions named in (b)
prevailed when the higher reading ammeter was used.
The conclusion to be drawn from such a finding is
that a current does flow through the bearings.
Should it be found that a current is present, the
mere fact that there is one should not be viewed
with uneasiness. The harmful action that can be
caused by such a current is limited to the pitting
of the shaft and bearing journals or the carboniza-
tion of the lubricating oil. Other injurious causes,
such as the use of impure oil or insufficient lubrica-
tion, are frequently more accountable for an
imperfect condition of the shaft and bearings than
is a bearing current. Moreover, an advanced stage
of bearing surface abrasion due to faulty oil or
lubrication may sometimes be erroneously regarded
as a condition which was originated by a bearing
current pitting the shaft. Therefore, if an investi-
gation of the shaft and bearing surfaces shows that
remedial measures are necessary, but the condition
of the surfaces cannot be positively identified as
having originated in pitting, the quality of the oil
used and the effectiveness of its application should
be examined, remedied if faulty, and exonerated
by further trial before the bearing current is held
accountable for the damage done. Should it be
proved, by eliminating these more prevalent lubrica-
tion troubles, that the stray current is responsible
for the bearing injury in that particular machine,
the harmful effect can be removed by preventing
the flow of this current. This can be accomplished
by simply removing metal shims to the amount
of at least & in. in thickness from under one of
the bearing pedestals, inserting that number of fiber
shims which will make up the same thickness in
their place, insulating the bolts and dowel-pins
with fiber tubes and washers, and breaking in
an equally positive manner all other metallic
connections from that bearing to the frame.
(Hand-rails, etc., should not be overlooked.)
Measurement
Attempts have been made to determine what is
the actual amount of the bearing current flowing
by means of the connections and ammeter readings
described under the previous heading Detection.
Because it is not frequently appreciated that the
application of such a method is useful only insofar
as it determines the presence or the absence of a
bearing current, it would be well to point out why
such meter readings are absolutely valueless as
indications of the amount of bearing current flowing.
The bearing current circuit, when free from
additionally inserted resistance or reactance such
as fiber shims, meters, etc., is one of low resistance.
In examining only a part of this circuit, that
through one bearing, the resistance dealt with is
of course much lower, and unfortunately is far
from being of constant value due to the change-
ableness of the oil film.
312
GENERAL ELECTRIC REVIEW
The actual readings given on the ammeter are,
therefore, not to be relied upon to determine the
amount of bearing current for two reasons: (1)
The amount of current shunted around the bearing
by the ammeter and its leads depends upon the
size of meter which is used, since in such a circuit
the impedance of an ammeter is quite comparable
to the resistance of the bearing side of the divided
circuit; and, (2), the fluctuating value of the
resistance of the oil film causes a varying division
of current through the bearing and the ammeter.
Even if it were possible to surmount these
troublesome factors, it would be practically impos-
sible to obtain the value of the resistance of that
Vor/op/e /IC Source
for Colibrot/ng
OPr/mory Col/ prating
Coil /fmmeter
Fig. 1
portion of the bearing circuit which the ammeter
and its leads shunt while the alternator is running.
Nevertheless it would be necessary to know the value
of this resistance to establish the ratio of division of
the current between the bearing and the ammeter.
There is a method of determining the natural
amount of bearing current, however, which can be
used; and which, by its application, does not alter
in any way the customary path of flow of the
bearing current.
This method employs the same principle as the
ordinary current transformer, and has been proved
in practice to give accurate and reliable results. A
description of the necessary apparatus and manner
of making the test follows.
Construct a transformer core (a rectangular
shape is convenient) of laminated iron to encircle
the shaft between the revolving field and either
bearing. See Fig. 1. Around this core wind a number
of turns of moderately small insulated wire (No. 14
would answer well) ; these will comprise the secondary
of the transformer. The terminals of this winding
are then to be connected to an alternating-current
ammeter on which readings are to be taken to obtain
the shaft (or bearing) current. The primary of the
transformer will be the shaft of the alternator.
It now only remains to calibrate the transformer
and meter. This is easily accomplished bv winding
ler coil of a few turns (the number should be
on the transformer core and bv it and an
external source of e.m.f. (between which two an
ammeter is connected) excite the core. The fre-
quency of this external source of e.m.f. must be
the same as that of the alternator being tested.
Fig. 1 shows diagrammatically an alternator and
the connections of the bearing current measuring
devices as described. Impress various voltages
on the transformer calibrating primary and take
a few simultaneous readings on the primary and
secondary ammeters.
Multiply each primary ampere reading by the
number of turns in the primary calibrating coil,
thus giving the exciting ampere-turns. Plot a curve
between these ampere-turns and the corresponding
ampere readings which were simultaneously taken
on the secondary ammeter. Such a curve is shown
in Fig. 2. The function of the calibrating source,
ammeter, and exciting coil is now complete and
these can be removed.
f
I'
1
I
a
-*
/
\
1
tfrnperesfeecondoryCvrrentrfinmeter)
Fig. 2
The circuit composed of the shaft, bearings, and
base of the alternator is to be the real primary of
the transformer and passes through the transformer
core only once. Therefore the amperes in this
primary circuit and the ampere-turns excitation
which they impress on the transformer core are equal
in number. For this reason the "primary ampere-
turn" scale of the curve, Fig. 2, may be renamed
"primary amperes" (shaft or bearing amperes).
If the curve is found to be practically a straight
line from the origin, the relation expressed graphi-
cally by the curve sheet may be replaced by the
average multiplying factor which links the values
of the primary and secondary amperes for the
same excitation. This factor is determined from the
curve and will of course be the ratio of transforma-
tion of the transformer.
The device is now ready for actual bearing current
measurement. (The same ammeter and leads must be
used in measuring the transformer secondary current
as were present at the time of calibration). The true
value of the current is arrived at by running the
alternator at normal speed, exciting it to normal volt-
age, and then taking the reading on the secondary
ammeter which, by reference to the curve or by
multiplying it by the transformer ratio, will be trans-
lated into the actual value of the bearing current.
Ref. " Bearing Currents," by E. G. Merrick, General
Electric Review, Oct., 1914, p. 936.
E.G.M. and E.C.S.
Po
General Electric Review
A MONTHLY MAGAZINE FOR ENGINEERS
.. ., „ tj.^.^ «,-. TAUV r, irT?Ti-^T>T Associate Editor, B. M. EOFF
Manager. M. P. RICE Editor, JOHN R. HEVl ETT .-,.. „ „ c.MnPDC
Assistant Editor, E. C. SANDERS
Subscription Rates: United States and Mexico, $2.00 per year; Canada. $2.25 per year; Foreign, $2.50 per year; payable in
advance. Remit by post-office or express money orders, bank checks or drafts, made payable to the General Electric Review,
Schenectady, N. Y.
Entered as second-class matter, March 26, 1912, at the post-office at Schenectady, N Y.. under the Act of March, 1879.
VOL. XVIII., NO. 5 by gJTe^U Company MAY. 1915
CONTENTS
Page
Frontispiece . . .... 314
Editorial: The Paths of Progress . . . 315
Wireless Transmission of Energy . ... 316
By Elihu Thomson
The Pure Electron Discharge and Its Applications in Radio Telegraphy and Telephony . 327
By Dr. Irving Langmuir
The Hydro-Electric Development of the Cohoes Company at Cohoes, N. Y. . . . 340
By B. R. Connell
X-Rays, Part II . .... ... 353
By Dr. Wheeler P. Davey
Water Powers of New England 358
By Henry I. Harriman
Some Aspects of Slot Insulation Design . 366
By H. M. Hobart
Incandescent Lamps for Projectors • .371
By L. C. Porter
High Candle-Power Mazda Lamps for Steel Mill Lighting . . . 377
By G. H. Stickney
The Genemotor • • 3S4
By M. J. Fitch
Electrophysics : Electromagnetic Radiation from the Viewpoint of the Electron Theory . 387
By J. P. Minton
High Potential Transformer Testing Equipment at Pittsfield ■ 398
By Wm. P. Woodward
Practical Experience in the Operation of Electrical Machinery, Part VIII .... 401
Capacity Current; Misapplication of Devices; Misleading Deflections; Reactor
Starting-Box Trouble; Improvised Commutating Winding; Instrument Connec-
tions Wrong
By E. C. Parham
Notes on the Activities of the A.I.E.E. . • 405
From the Consulting Engineering Department of the General Electric Company . . 408
Question and Answer Section .... .... . . 409
r-H"
r-H
U
=1
— 1
— 1,
in r-^1
THE PATHS OF PROGRESS
In this issue we publish a very interesting
article by Henry I. Harriman in which he
shows the vital part played by water power
in the development of the industries of
New England. He shows that practically
every large town and city in New England
can trace its origin to the presence of water
power in its immediate vicinity. It is
interesting to note in this connection that
these same general conditions were, until
recent years, true throughout the whole
world, namely, that the location of an indus-
try was dictated by the presence of a source
of power whether it were coal or water power,
the transportation of stored energy such as
coal being too expensive to afford profitable
operation. In recent years, with our improved
transportation facilities, coal has been trans-
ported in enormous quantities for manufac-
turing purposes, but the expense has been
great. Our modern flexibility in the choice of
a locality for manufacturing centers owes its
origin to the introduction of the steam-
electric and the hydro-electric power stations
and the modern high tension transmission
line.
This increased flexibility in our choice of
locality for manufacturing centers has greatly
stimulated industrial growth of almost every
character and is one of the many blessings
that has been given us by modern engineering
developments. All industry depends primarily
upon three factors: energy, material and
labor. Formerly we had to bring our material
and labor to our source of energy, now we can
bring our energy to our source of material
or to where our labor markets are satis-
factory. In fact, all three of our prime factors
arc now transportable, giving us a choice
which permits the selection of a manufactur-
ing site where operations can be carried out
at a maximum efficiency.
It is interesting to note that the same old
sources of power can be used with our modern
developments, only they are used more
efficiently.
Mr. Harriman gives some very impressive
figures regarding the available water power
in New England and the "theoretically
possible" saving in coal to be secured by its
development. These figures are as satis-
factory as they are large, as the national
wealth of a manufacturing country is so
inseparably tied up with its source of power
that future prosperity will depend in a very
great measure upon whether we use good
common sense in developing so important
a natural resource.
In the future we shall depend less and less
upon our coal supply and our rivers and
waterways will become of increasing impor-
tance. The network of high tension trans-
mission lines that is gradually covering certain
sections of the country will spread till it
becomes recognized as one of the greatest
and most important factors in our industrial
life. Our supply of electric energy in any
particular area, because of its inherent
characteristics that permit it to be generated,
converted and transmitted more economically
than any other form of energy, will govern
whether any particular area is to be indus-
trially prosperous or not. As time ' goes
on we shall devise means and ways of using
more energy and less labor in our manu-
facturing processes, as electric energy is
practically the only commodity that has
been steadily getting cheaper, while labor
has been gradually but insistently getting
dearer. This means that energy will play
an even more important part in our future
industrial progress than it has in the past.
316 GENERAL ELECTRIC REVIEW
WIRELESS TRANSMISSION OF ENERGY*
By Elihu Thomson
General Electric Company, Lynn
Professor Thomson shows in a most interesting way why it is that the wireless waves follow the curvature
of the earth. This whole article is so full of scientific interest that no resume: could attempt to indicate its
contents. His conception of the transformer as an iron atmosphere to accomplish the transfer of energy from
one electric circuit to another is of special interest; he points out that the corona loss governs the limits of the
Thomson potential that can be used on the sending antennae of a wireless system in exactly the same way that
it governs the limits of potential on our commercial high tension lines. — Editor.
It will be my purpose in the present dis-
course to outline the general nature of
wireless transmission and to indicate its
relationship to transmission by wire. It will
also be my object to show why the wireless
energy sent out follows the curvature of the
Fig. 1
earth and to explain other features which
to many have been more or less puzzling.
In short, I desire to present in simple terms
a view of the nature of such wireless work,
so that anyone reasonably informed about
electrical actions can obtain, as it were, a
mental picture of the process. I may here
state the fact that perhaps one of the earliest
experiments bearing on wireless transmission
was made in company with Prof. E. J.
Houston, while we were both teachers in
the Central High School in Philadelphia.
This old experiment to which I refer was made
about the latter part of 1S75, and briefly
described in the Franklin Institute Journal
early in lsTii. It consisted in using an induc-
tion coil which would give a spark length
of several inches, then known as a Ruhmkorff
coil, the coil resting on the lecture table, one
terminal of the fine wire or secondary of
which was connected to a water-pipe ground,
while the other was connected by a wire
four or five feet long to a large tin vessel
♦Lecture by Professor Thomson, reprinted bv the courtesy of
the National Electric Light Association, New York.
supported on a tall glass jar, insulating the
tin vessel from the lecture table. The coil
had an automatic interrupter for the primary
circuit, and when in operation the terminals
of the secondary were approached so that
a torrent of white sparks bridged the interval
between them, the gap being about two
inches or so in length. Fig. 1 shows this
arrangement. When the coil was worked in
this way, it was found that a finely sharpened
lead pencil approached to incipient contact
with any metallic object — such as door knobs
within the room and outside thereof — would
cause a tiny spark to appear at the incipient
contact between the pencil point and the
metal. This, of course, was not a very delicate
detector, but was improved, as in Fig. 2, by
putting two sharpened points in a dark box,
a device due to Edison. One or both points
were adjusted so as to make incipient contact,
and the tiny spark observed between the
points was an indication of a shock, com-
motion or wave, electrical in its character,
in the ether surrounding the tin vessel
mounted on the glass jar. The tests for
detecting the impulses were carried on not
only in rooms on the same floor, but on the
floor above and on the floor above that, and
finally at the top of the building, some
90 feet away, in the astronomical observatory.
Metallic pieces, even unconnected to the
ground, would yield tiny sparks, not only
in the basement of the building, but in the
Fig. 2
highest part, with several floors and walls
intervening. I mention this old experiment
particularly because it has in it the elements.
of course in a very crude form, of wireless
transmission, the wire and tin vessel attached
to one terminal of the coil being a crude
WIRELESS TRANSMISSION OF ENERGY
317
antenna with its spark-gap connection to
ground, as afterwards used in wireless work
by Marconi, and it also shows a rudimentary
receiver or detector, a metallic body arranged
in connection with a tiny spark gap, so that
electrical oscillations in such body would
declare themselves by a faint spark at the
gap. It was understood by us at the time
that after each discharge of the coil there
was, as it were, a shock, or wave in the ether
consisting of a quick reversed electrical
condition, and it was even imagined that
there might be in this process the germ of a
system of signaling through space. This
old work was almost forgotten when it was
recalled by the later work of Hertz, about
1887, who demonstrated by suitable electrical
apparatus that waves of the general nature of
light or heat could be generated, which waves
are transmitted with the velocity of light,
186,000 miles per second, and that by suitable
resonators or detectors these waves could be
made to declare themselves by tiny sparks.
The Hertzian oscillator was, as it were, an
electrical tuning fork, having an actual rate
of vibration peculiar to itself and dependent
on its form and dimensions. It was fed with
energy from an induction coil and across its
spark gap an oscillating discharge took place,
which, at each impulse, died out like the
discharge of a condenser, but during this
discharge it electrically stressed the ether in
one and the other sense, so that an electrical
wave was radiated in certain directions from
the oscillator. It was found that these waves
could be refracted, reflected and polarized,
and, in general, dealt with as extremely
coarse light or heat waves. We shall refer
to these, however, farther on. The general
result, however, of the Hertzian experiments
was to connect electrical waves in the ether
surrounding the apparatus with the light
and heat waves and prove the identity of
the two kinds of radiation, the differences
being only those of wave length or pitch.
Since the Hertzian waves were sent out
from the Hertzian oscillator in substantially
straight lines, and since in the early days of
wireless telegraphy it was common to regard
wireless waves as of the same nature or as
almost identical with Hertzian waves, the
fact that the wireless waves were found to
follow the curvature of the earth became a
difficulty to be explained. Speaking for
myself, I have never found the difficulty to
exist. There is really no reason why the
waves should not follow the curvature of the
earth, as it will be one of my purposes to show.
We will, however, approach the conditions
of wireless somewhat gradually.
We will first consider an ordinary wire
transmission of the simplest type. Let us
assume a line of wire, as in Fig. 3, insulated
and connected to one terminal of the battery
± \ I I l I I I I I I I i i i I i i l n \\\\\ \\
t 'i i i ' i i ' ! i i i // / i !
/ ! I I I'M1' I ' l ' I
Fig. 3
Fig. 4
T 'I i HK ■
' I i.i
LUlll
-^y^rM^r^-N^^^--
fl
Fig. 5
Fig. 6
while the other terminal is earthed or
grounded. A simple telegraph system on open
circuit would represent this arrangement.
The only effect is that the battery supplies
a small charge to the_ line producing a
potential difference between the insulated
line and the earth, assuming, of course, that
there is no leakage of any kind to disturb
the conditions. As soon as the charge is
established in the line at the full potential
of the battery, which, in ordinary cases, would
take place within a very small fraction of a
second, a steady or static condition is reached,
which might be indicated by electrostatic
stress lines drawn from the wire to the
ground, as illustrated in Fig. 3 by the fine
dotted lines connecting the horizontal line
to the ground surface below. If the wire be
viewed on end (Fig. 4), we must represent
these stress lines as extending out radially
from the wire and bending over to meet a
considerable portion of the ground surface
below. As this arrangement is constituted,
there is no energy transfer and the condition
is static only. If now the far end of the line
is earthed, as through an instrument or
device which uses energy, as in Fig. 5, at the
moment of such connection there would be a
lowering of the intensity of the stress toward
the receiving instrument and the line would
be discharged were it not for the maintaining
action of the battery, which still keeps up the
difference of potential between line and
ground. If the line is without resistance, this
318
GENERAL ELECTRIC REVIEW
potential will have the same value all along
the line, especially if the line is of uniform
section and of uniform distance from the
ground. The moment, however, the instru-
ment at I takes energy from the line a current
is found in the wire and a return in earth, and
Fig. 7
there is, so to speak, a flow of energy in the
space between the wire and earth and in the
ether surrounding the wire, in the direction
of the arrow — that is, from the generating
end to the receiving end. Surrounding the
wire at this time there will be a magnetic
field, which may be represented by whorls
or lines of magnetism, so called, wrapped
around the wire like so many hoops of all
sizes (Fig. 0), expanding in size away from
the wire in all directions; and a similar
magnetic effect, of course, is also produced
by the return current in the earth. But on
account of the conditions of conduction in
earth being very devious and irregular, it
would be difficult to map the magnetism
generated. The system of magnetic whorls
so developed on the flow of the current in
the system reaches, for any definite current,
a definite density after a short interval. In
other words, the density of the magnetic field
between the wire and the earth increases only
up to a certain point. If the current, however,
be doubled in any way, that field is doubled
in density or there are twice as many lines
packed in the space around the wire. If now
we look instead of an earth-connected circuit
one in which there are two wires extending
from the generating battery or generator, the
conditions will be the same except that the
stress lines will now radiate from each wire
and connect the wires by lines directly
between them and by other curved lines
outside. Such lines, or otherwise conceived
"tubes of force," represent the'static fie'd or
the density and directions of electrostatic-
stresses in the electrostatic field where one
wire will be positive while the other is
negative. If, as before, the ends of the wire
are free or open-circuited, no energy is
transmitted, and the mere static stress exists.
If, however, the wires are connected through
an instrument receiving energy or utilizing
the energy, then the magnetic system is
developed, surrounding each wire and passing
between the wires, and on the establishment
of any given current these lines accumulate
at a rapid rate until, in a small fraction of a
second usually, a limit is reached. The
magnetic field may then be said to be fully
developed. Outside of the pair of wires the
magnetic disturbance extends to very great
distances, but is necessarily weak far away.
The magnetic whorls in this case do not
center themselves in circular paths around
the wires and at equal distances therefrom,
but between the wires they are more con-
densed or pushed toward the wires themselves
— crowded, so to speak — while outside of the
wires they expand (Figs. 8 and 9). It must be
remembered that these lines of force are
merely symbols for what may be likened to a
magnetic atmosphere. They indicate the
density and direction of certain actions in the
ether, called magnetic. It will be important
to note, both in wire and wireless transmission,
that the energy is transferred in the surround-
ing medium. The wire in ordinary wire
transmission is, in fact, a sort of guiding
center or core around which this ether
disturbance carrying the energy exists. The
wire may be bent or coiled, expanded or
contracted without altering the essential
Fig. 8
F.g. 9
nature of the process. So far, then, ordinary
wire transmission it really a case of wireless
transmission, with the wire for a guiding
core for the energy (Fig. 10).
It would take us too far to attempt to
explain or theorize on the modern view of the
WIRELESS TRANSMISSION OF ENERGY
319
passage of electrons in the wire forming the
current, and the field they carry with and
about them in giving rise to the stresses
in the ether surrounding them. Suffice it to
say that a moving electron must not onlv be
accompanied or surrounded by the static
stress field which it produces in the ether but
also by a magnetic effect representing the
energy of motion possessed by it. When a
current which has been started in a circuit
reaches a definite value it may be said to have
reached a steady state. It would then be a
continuous current of constant value. Energy
can be steadily extracted from such a system
only by introducing some apparatus connected
with the wire which is the guiding core for
this energy.
Let us now consider the case of current
of a different character, a fluctuating — or
better, an alternating current. Let us sub-
stitute for the battery an alternating current
generator, and assume a single wire with an
earth or wire return, as in Figs. 3 and 5
Here the wire merely becomes positive and
negative alternately, for the circuit is incom-
plete or unconnected as a circuit, and the
stress lines from wire to earth or to other
Fig. 10
wires reverse periodically their direction
plus to minus and minus to plus. This is true,
of course, whether the earth be replaced by a
second wire or whether three or more wires
be involved, as in a three-phase alternating
current circuit. By connecting any two of the
wins through an energy-receiving apparatus
R (Fig. 11), the same action that takes place;
with the continuous current may be repro-
duced except that the energy now comes in
waves and is not a continuous flow. In
ordinary cases there are 60 complete waves or
Z3*
Fig. 11
complete changes from plus to minus and 1 »ack
to plus in each second, and the system is then
called one of 60-cycle frequency. A further
important difference is to be noted between
the alternating-current condition and the
continuous. The action in the ether around
and between the wires is now in the form of
waves, both magnetic and electrostatic.
Between wires there is an increase of electro-
static stress to a maximum, a diminution to
zero, a reversal, etc. The magnetic field also
rises, falls, reverses, and so on synchronously.
The condition is no longer static, the medium
around the wires is in a dynamic state and
it is now possible to abstract energy steadily
from it without actually diverting current
from the line. We can, in fact, by such a
system produce in neighboring conductors
similar disturbances or currents, and along
with these disturbances we may deliver
energy.
The alternating-current transformer is then
merely a device for bringing two or more
circuits together as near as possible and
enhancing the magnetic values which would
normally exist around such circuits by the
addition of an iron atmosphere, the iron core,
so that the greatest possible transfer of energy
from one (the primary circuit) to the other
(the secondary circuit) may be accomplished.
But in the wire itself, which leads from an
alternating-current source, since there is an
action called a current which changes, pul-
sates, or alternates, we have also around the
wire core waves in the ether which, in fact,
spread to very great distances; some small
portion of the energy of each impulse not
returning to the system, but passing outward
into space as radiated energy.
This radiation may be a very small amount
per cycle, especially where the outgoing and
return wires are near together and parallel.
320
GENERAL ELECTRIC REVIEW
and with low frequencies, such as GO cycles,
on account of the low number of waves per
second and the low speed or rate of change in
the fields surrounding the wire, the amount of
energy- carried off by free radiation into space
is indeed negligible. But if we raise the
^
r
T T T
-
"
-
-
Fig. 12
frequency we raise the amount of energy
which can be radiated proportionately to the
number of waves per second, and we also
make the rate of change higher and the wave
slopes steeper, so that as the frequency rises
the radiation factor becomes more and more
important in dissipating the energy of the
system. It will be noticed, however, that such
energy is not directed energy. It is diffused
through space around the electric system
at work and passes off to illimitable distances.
Since these impulses in the wire, the electrical
waves sent along the wire (with the wire as
a guiding core), can at the maximum move
with the speed of light — 186,000 miles per
second — it follows that if the line is sufficiently
long or the transmission sufficiently extended
or the path of radiation sufficiently distant
the wave stresses or fields or currents can
exist at different parts of the system in phases
either much displaced or entirely opposite.
This may be rendered clear by stating that
while one portion of a very long line might be
positive to earth another portion half a wave
length distant from the first along the same
line would be negative to earth (Fig. 12).
In other words, there may exist upon the
system at the same instant a succession of
waves in opposite phase. Just as in vibrating
strings in musical instruments or vibrating
columns of air in organ pipes there are station-
ary waves, nodes, and internodes, so in
electrical systems in vibration there can be
nodes and internodes if the conditions are
selected for obtaining that effect. Here the
dotted vertical line indicates the nodes of the
waves. We may thus have so-called station-
ary7 electric waves (Fig. 12).
We find that on raising the frequency of an
alternating-current system from, say, 60
cycles, the ordinary frequency, to 600 cycles,
an effect which at first was hardly detachable
now becomes important. It is the so-called
"skin effect" whereby the current in a wire
circuit tends to concentrate itself on the outer
skin of the conducting wire, neglecting the
inner copper, so that the inner core of the wire
might be left out. Consider the frequency
still further raised, say, to 6000 cycles, this
"skin effect" of the conductor still further
increases until the copper in the interior of a
circular wire of a considerable size is now
quite useless, and to get the advantage of such
copper we must, as it were, take it out or
spread it in a number of parallel wires spaced
apart, or make the metal of the conductor
in the form of a long sheet or in the shape of a
thin tube or a cage of wires (Fig. 13). This,
in electrical terms, improves the conductivity
and reduces the opposition due to self-
induction; the inductance counter e.m.f. Let
now the frequency be still further increased
to tens of thousands or hundreds of thou-
sands of cycles per second ; then our conductor
must necessarily become a still thinner or a
still more extended sheet.
At the same time, if there are considerable
differences of potential between the con-
ductors thus arranged, the radiation factor
may at last become very important, so that
if the parts of the circuit are far apart, free
radiation into space may dispose of a large
fraction of the energy sent out. In the
Hertzian oscillator, deducting that lost in the
spark gap, practically the whole of the
remaining energy supplied is radiated into
space. The wave frequency may be very
many millions per second, and the waves
produced are in the nature of coarse light and
heat waves. Fig. 14 exemplifies diagram-
matically the fact that with very high fre-
quency waves a conductor carrying such
waves will have surrounding it, if the space is
unrestricted, magnetic svstems of lines
Fig. 13
reversed in direction with nodes between,
the distance apart of these waves or nodes
being determined by the frequency in relation
to the velocity of light, each complete wave
outside the wire occupying a length equal to
the velocity of light. 186,000 miles per
WIRELESS TRANSMISSION OF ENERGY
321
second, divided by the wave length or
frequency.
Figs. 15 and 16 represent forms of Hertzian
oscillator, consisting of plates or spheres
a b of metal, separated by a small spark gap
and charged in any suitable way, plus and
minus with respect to each other, and
allowed to discharge across the gap. The
charges are then interchanged between a
and b at a very high rate, though the waves
decay rapidly, and the system vibrates only
for a short time or until the energy of the
charge is dissipated in ether waves of exceed-
ing high pitch into the surrounding medium.
Were there no energy lost in the gap itself for
forming the spark, and if the metal were a
perfect conductor, the full amount of energy
represented by any initial charge would be
dissipated in the ether in these ether waves.
Marconi, however, in his development of
wireless telegraphy did not use the complete
Hertzian oscillator. In setting up his trans-
mitting antenna he took substantially half
an oscillator, the other half being, so to speak,
a phantom — the reflected image of the first
half, as it were, in the surface of the earth,
generally the sea surface. It would be
represented by taking an extended copper
sheet or surface coated with a fairly good
conductor to represent the earth's surface
and mounting above it, but insulated from
it, a metal body, such as a vertical rod, which
could be charged and which could discharge
to the sheet through a small air gap. In this
arrangement not only would waves be sent
out into the surrounding ether space, but
there would be current traversing the sheet
as waves of current around the spot where
the discharge of the insulated body took place.
In fact, I think it would be possible to
represent experimentally a modern wireless
system with a diminutive antenna to repre-
sent the transmitting station, and extended
copper sheet to represent the earth's surface,
and with investigating or receiving antennas
o ) j ) | I ! 1 1 i 1 1 1
Fig. 14
set up here and there or moved from point
to point on the extended surface.
Here, although the disturbance and the
energy conveyance is in the ether around the
antenna (or the part representing the half of
the Hertzian oscillator), the energy is guided
in its direction by the current in the sheet
representing the surface of the sea, just as
in the wire transmission the energy is guided
by the wire as a core. On account of the
enormous extent of the earth's sea surface,
there is no need of a return circuit. The
Fig. 15
Fig. 16
energy sent out moves in all directions,
guided by the conducting water surface or
land surface, as the case may be. There will
necessarily be a rapid attenuation of the
energy as it leaves the sending or transmitting
antenna and spreads out to fill a wider and
wider space around it. The higher the sending
antenna the greater the distance which can be
reached before the attenuation is too great
for imparting signals.
Let us consider for a moment by the aid
of a figure the actions which must occur in
wireless transmission on the sending out of
energy from the transmitting antenna. Refer-
ring to Fig. 17, we will represent by e — e the
surface of the earth as if it were flat, and for
moderate distances this will be substantially
the case. We will erect on that surface a
tall mast A of conducting wire or wires
which, at the top, shall have an extension
to increase its capacity. This might be a
large ball of sheet metal. Usually, for con-
struction to be practicable, it is a set of
wires — a sort of cage or a skeleton body.
Now, by any system, inductively, con-
ductively, or otherwise, or by what is known
as close or loose inductive coupling or what
not (Figs. IS, 19 and 20) we cause electric
disturbances, such that at one instant the
top of the antenna becomes positive and at
the next instant negative, many thousands —
even hundreds of thousands — of times per
second. In other words, we impress a high-
frequency wave upon this vertical mast.
We will try to present an instantaneous
picture or form an instantaneous image of
what the condition is at the beginning of the
process.
Let us suppose that the charge is positive
at the top, and necessarily the surface below
322
OEXERAL ELECTRIC REVIEW
and surrounding the mast will be negative.
Electrostatic lines will extend from the mast,
and particularly from the expansion at the
top down to the earth's surface in all directions
around the antenna, as in the figure. The
medium around the antenna will be stressed
/_
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^Cx\
' ' 1 A
Ml
\\\\\V
Fig. 17
electrostatically. This would be all, provided
the charges were stationary, but the system
we are considering is dynamic. The plus
charge is replaced by a minus charge at the
top, and a current of a high frequency runs
up and down the antenna, but so also does
this current extend into the sea radially
from the foot of the antenna, replacing the
negatively charged area by a positively
charged zone, as it were, while the top of the
antenna is now negative where it was formerly
positive. (Fig. 21 A, one side only shown,
and Fig. 2 IB. in plan.)
As this action goes on, however, the zone
of charged surface widens, and ether waves
are, so to speak, detached from the antenna,
and electrostatic lines join now through the
air or ether above the successive zones which
surround the antenna as great circles or
flat rings of the sea surface. A plus area is
followed by a minus, a minus by a plus. etc..
and to indicate the effect in the space above.
we draw lines which follow these areas.
extending up into the ether above the surface,
but moving away from the antenna with the
velocity of light. The moving charges in
the sea surface represent radial currents
which are in opposite phase at different
portions of the sea surface, and spreading at
186,000 miles per second, and these currents
necessarily generate magnetism or lines of
magnetic force in the medium directly above
them. These lines extend around in zones
with diminishing intensity upward from the
sea surface as the distance from the surface
increases. Even within the water itself a
similar action, but more restricted, takes
place. The charges in the water are connected
by electrostatic stress lines, and the com-
pensating magnetic field follows the current.
but this "under water" effect does not con-
cern us, as what we work with is the energy
conveyed in the space above the sea, the other
not being so easily recoverable.
The system as thus far constituted is merely
an arrangement for delivering energy in
high-frequency waves to the widespread
medium around the antenna. There is no
selective action whereby it is focused any-
where— it is as a "voice crying in the wil-
derness." It can be picked up or recognized
in any direction by anyone who is within
range. If, now, we are to receive signals such
as are made by interrupting or disturbing at
intervals this system of radiation of energy,
as in ordinary telegraphy, we must set up
somewhere a receiving apparatus which will
enable us to pick up whatever small fraction
of the energy reaches it and, if possible, a
sufficient fraction of such energy for the
recognition of the signals. If the signal can
be recognized — no matter how small the
fraction of the energy sent out is which we
collect at the receiving station — the system
succeeds. There is no question of efficient
transmission, as there is in the ordinary
power-transmission systems. The latter are
for the transmission of energy with as little
loss as possible, the former for the trans-
mission of signals only.
In the antenna transmission just considered
it is assumed that the surface of the earth is.
generally speaking, a good electric conductor.
The surface of the sea is sufficiently good.
Dry land surface, however, is not a good
conducting sheet, and even though moist it
is generally so irregularly conducting that
Fig. 18
Fig 19
Fig. 20
obliteration of the waves and loss or absorp-
tion of the energy must necessarily occur.
Obstacles, such as dry rock ranges, may
absolutely prevent the waves from passing
over them. It must be borne in mind that
these waves have no inertia, as such, and
WIRELESS TRANSMISSION OF ENERGY
323
that the energy must be guided to its desti-
nation by a conducting sheet. This calls to
mind the efforts that were made to connect
Lynn and Schenectady by a wireless system,
but without success. Occasionally signals
were received, but in general they were too
indistinct to be recognized. It is more than
probable that the dry rock ranges of the
Berkshires in western Massachusetts were
sufficient of an obstacle to prevent the energy
of the waves getting across them.
It is also to be questioned whether there
may not be another action which interferes
with and disturbs the integrity of the waves.
It is conceivable that waves may follow a
water surface, even around a cape, and that
a portion of the energy may take a short cut
across the land of the cape. If this be so, the
longer course would be around the cape, the
shorter course across the land. The wave
lengths would remain the same, and an
out-of-phase relation or interference phenom-
enon would take place to a greater or less
extent. It is manifestly necessary that the
energy, by whatever course it follows, shall
reach the receiving apparatus in phase.
Let us now consider for a moment the
conditions at great distances over the earth's
surface. At moderate distances from the
transmitting antenna the surface may be
considered as flat. The conducting sheet
guiding the energy is flat or plane, but at
great distances the curvature of the earth's
surface becomes an important factor. For
a time there was a great deal of discussion as
to the reason why the energy in the wireless
transmission seemed actually to follow the
curvature of the earth, instead of going
straight away, as in the case of Hertzian or
heat and light waves. If the waves had
been generated by a large Hertzian oscillator,
it would not be possible for them to so follow
/^^>.
mMjmtm
Mmf-mm
jAlnii
Willi.
ill'lll
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Fig. 21 -A
the earth's curvature, but inasmuch as they
are in wireless work produced and, as it were,
positioned upon a conducting sheet (the sea
surface) , then it follows that the energy must
be guided by that conducting sheet or surface,
regardless of its extent or its curvature. I
have never been able to understand why so
much discussion has been needed to clear up
this point. Wireless waves have no inertia —
they follow the course of the charges which
produce the stress and of the magnetic field,
due to these charges in motion. These
Fig. 2 IB
charges in motion are the currents in the
conducting sheet, which may or may not
be curved. In the curved surface of the
ocean the zones of charge continually expand-
ing, plus and minus, respectively, are still
connected by the electrostatic lines above
them, and the moving charges still generate
the same magnetic field as they traverse
radially or outwardly in the curved instead of
the plane sheet (Fig. 22), and this curved
conductor still guides the energy, just as the
wire does in ordinary transmission. It
would seem, if this is the correct view, that
at a distance comparable with that of a
quadrant of the earth's circumference the
form of the wave would be such as to cause
the stress lines to lean backward with respect
to the surface, tending to keep their original
relation to the transmitting antenna as they
were detached therefrom (Fig. 22, at L).
This assumes that the velocity of transmission
is the same as that of the speed of light,
both for the currents in the sea and for the
stress above it.
Marconi's success as a wireless pioneer
depended largely upon the choice of a suf-
ficiently sensitive receiver. Two elements
are necessary in the receiver. First, a con-
ducting structure which gathers up the
energy from the medium, the ether, above the
earth's surface. The other element is a
sufficiently delicate means for detecting the
slightest changes of electrical condition, not
324
GENERAL ELECTRIC REVIEW
only actuated by what little energy is received,
but so modifying it that it can operate a
signal which can be seen or heard. Usually
the receiving antenna is a vertical conducting
mast or cage, like the sending antenna. In
fact, the functions of sending and receiving
^jf%lMe?%
ffr^li
Fig. 22
are interchangeably used on the same struc-
ture; the same antenna may be at one time
used for transmitting and at another time
for receiving.
The receiving antenna (Fig. 22) serves to
relieve the electrostatic stress in its vicinity,
much as a lightning rod may act to relieve
cloud to earth stresses. If its direction could
be made to follow or be parallel to the actual
course of the transmitted lines in the space
near it, it would be most effective, and if,
further, it could extend sidewise over a
considerable extent of the wave front, it
would gather up more energy. These con-
ditions, however, can at best be only ap-
proximately met. If the receiving antenna
were of such a character as to have no oscil-
lation rate of its own (a damped circuit) it
would receive energy in a small amount from
the transmitting antenna independent of the
frequency, but as this would in most cases be
far from sufficient, it is desirable to accumu-
late energy in the receiver from a train of
waves at a definite rate. To do this the
principle of syntony or tuning is brought in.
Everyone is familiar with the two tuning
forks, where one is sounded and the other is
placed at a distance away. If the two forks
are not in harmony, no effect of the one fork
on the other follows, but if they are accurately
tuned in unison, the sound of one fork at a
considerable distance from the other starts
the second in vibration and produces an
audible sound from it. The second fork is,
in fact, a structure particularly well adapted
to gather up the energy of the sound waves
which reach it. receiving from each wave a
small portion of energy and accumulating
such energy until the fork itself is brought into
palpable vibration. By applying this prin-
ciple in wireless telegraphy — that is, by
causing the rate of vibration or frequency of
the electrical waves to be the same in the
transmission and in the receiving antennas
systems, constructing both to possess a
normal rate as if they were to be electrical
tuning forks of the same pitch — the am-
plitude of the received impulses is so greatly
increased that signal strength is reached
where otherwise failure would have resulted.
The one thing which has characterized the
more recent advances in wireless telegraphy
has been the accuracy of tuning and the
removal of disturbing influences which would
interfere with the tuning.
Formerly the transmitting circuit was
excited by means which tended to disturb
the actual normal rate. If excited induc-
tively, the inducing or primary circuit had
a rate of its own, which was apt to interfere
with that of the vibrating antenna system.
However, what is known as loose coupling
(Fig. 20), instead of close coupling (Fig. 19),
to the primary or exciting circuit causes such
confusion of rates to be nearly negligible if,
particularly in the exciting circuit, the cur-
rent is well damped, as it is termed, or
confined to a single brief impulse as far as
possible. In such case the antenna circuit,
in transmitting, acts as if it were a bell
struck with a sudden quick blow, and it
vibrates at its own rate without disturbance
or interference. At the receiving end (and
there may be, of course, many receivers in
the space around the transmitting antenna),
the "listening-in" process consists in adjusting
the rate of vibration of the receiving circuit
by variable condensers or inductances, so
that the maximum loudness of the received
signals is attained. The two systems, trans-
mitting and receiving, are then in tune.
Accuracy of tuning is evidently very
important if stations are to be simultaneously
transmitting when near together, as only in
that way can one station send out energy
without interfering with the other; the
particular receiver for which the signals are
intended being tuned for the particular
antenna sending these' signals. In spite
of the accuracy of tuning, however, high-
power stations may, in fact, cause high
frequency waves of high potential in all
surrounding wire or metal structures if near
enough. Burn outs, or even fires, may occur
from this cause. Hence it is desirable that
high-power sending stations should be well
WIRELESS TRANSMISSION OF ENERGY
325
removed from centers of population where
there are electric circuits and electrical appa-
ratus likely to be interfered with or injured.
It may be here pointed out that the limit
of potential which is available in wireless
transmission is the same as that of long
distance transmission by wire and for the
same cause. Naturally, if the potential on
the sending antenna can be raised, the amount
of energy which can be put into the wave
impulses will be increased, but there comes a
time when an increase of potential on the
wires of the antenna gives rise to a corona
loss — much as the increase of potential in
wire transmission produces a corona loss.
The conductors of the system, in such a
case, are surrounded by a blue discharge
which is even visible at night and which
frequently can be heard. When this con-
dition is reached every further increase of
potential simply increases the corona loss
without adding correspondingly to the energy
transmission. Just as in wire transmission
it can be avoided by increasing the diameter
of the conductors, so in wireless work it
could be avoided by constructing the antenna
system of hollow tubes with smooth exteriors,
and the imagination may be permitted to
depict a sending tower of polished metal
surmounted by a sphere of similar material
and worked at millions of volts. No limit
can be set to the amount of energy which
might thus be radiated, and no limit as yet
can be set to the distance around the earth
to which signals might be sent by such means.
One curious fact which has been developed
in the work of wireless signaling is that
daylight, especially sunlight, is very detri-
mental to transmission as compared with the
night. That is to say, if the wireless waves
are to traverse the sea surface in sunshine,
the chance of receiving them in sufficient
force to produce signals at great distances
is far less than when they are sent at night.
It is probable that this difference is not due to
any single cause — it may be the effect of a
combination of causes. It is a notable fact,
too, that this difference between the effective-
ness of daylight transmission and night trans-
mission is accentuated at the higher fre-
quencies.
Though the cause is still somewhat obscure,
we may venture a suggestion or hypothesis
which may have a bearing on the case.
Referring to Fig. 23, we have tried to show the
condition. The electrostatic field at the
water surface at the same instant is as in
Fig. 21 produced in zones around the antenna
A, spreading with approximately the speed
of light. It is well known that under the
action of the violet and ultra-violet rays of
light any surface having a negative charge
will leak its charge and ionize the air near it.
This may occur in sunlight over such areas as
K — - \
Ll
AS1"',
M
«%
Fig. 23
are marked minus in the figures, and the
several minus signs would mark or indicate
air ionized and negatively electrified over
the negatively charged zones. No action
would be expected over the positive areas or
zones. But the zones are not stationary;
they are widening very rapidly, so that a
postive zone or zones takes the place of
negative so far as any location is concerned.
This may be expressed by saying that the
water surface which at one instant was
negative and gave out negative ions under the
influence of light would, in an exceedingly
small fraction of a second and before those
ions could get away from electric contact
with such surface, become positive and the
free ions would now return and neutralize a
portion of the positive charge. Thus the
negative zones or wave elements would lose
part of their charge to ionize air, and the
positive waves would be weakened by such
negative leak neutralizing them in part.
This action, however feeble at each wave,
would be continuous over hundreds if not
thousands of miles, and continuously damp
out the widening system of waves. The
effect would be less marked with low
frequency waves, as there would be a pro-
portionately less number of opportunities
for this neutralization per second. Besides,
with the lower frequency there is more
time for the separation of the negative
ions to such distance from the water surface
that they do not combine with the positive
charges; being, as it were, better insulated
from them or diffused in the air stratum.
In Fig. 24 an attempt is made to picture
this action of attenuation in the presence of
light. The negative charges in the air layer,
as in Fig. 23, have no positive charges under
them, the encircling lines about the + and —
signs indicating combination and neutraliza-
tion.
326
GENERAL ELECTRIC REVIEW
When the wireless waves reach the receiv-
ing antenna, owing to attenuation from
spreading or loss as above, they are very
feeble. The daylight effect, as pointed out
bv Fessenden. is much less with the lower
frequencies, such as 100,000 per second as
mu-
4?*„
. . .
Fig. 24
compared with 600,000 or 800,000 wave-
Consequently there is not the same great
difference in strength of signals between
night and day work with such lower fre-
quencies. Moreover, frequencies of 100,000
or even 200,000 are capable of being generated
directly by high-speed high-frequency dy-
namos with the added advantage that the
waves sent out are maintained at their full
amplitude and are not, as with waves pro-
duced by spark discharges, subject to damp-
ing or decay from maximum to zero after a
few oscillations.
Whatever the nature of the waves sent
out, there is in all cases the need of an exceed-
ingly sensitive apparatus for converting the
slight electric effects upon the receiving
antenna into signals. The original apparatus
of Marconi included the Branly coherer, used
by Lodge in Hertzian wave transmission as a
detector. It is indicated in Fig. 26 at K, with
its battery and sounder magnet M. The
receiving antenna discharge in passing to
earth broke down the insulation of the
filings of the coherer, so that the local battery
current could pass in the circuit, including
a magnet M and so record the signal. T^e
liquid barretter of Fessenden, the various
forms of rectifying crystal detectors and
magnetic detectors, have been extensively
used. Our time does not permit a detailed
description. Fig. 25 indicates at C a crystal
detector rectifying the impulses from antenna
A so as to work a high-resistance telephone
receiver T. to which the operator listens. Fig.
27 shows the same apparatus, but connected
inductively to the antenna circuit by a
transformer.
Fessenden found that if the succession of
decaying wave trains reaching the telephone
7 was such as to produce a low note, the
signals were easily drowned by extraneous
or induced effects. He found that
the human ear reached a maximum of sen-
sitiveness at about 900 waves of sound per
second, so that the signals were heard dis-
tinctly when otherwise they would have been
missed. This is the meaning of the sub-
stitution of dynamos of about 500 cycles for
exciting the wireless antenna in place of the
ordinary machines of lower frequency.
The problem of wireless telephony has
attracted attention for a number of years past.
I well remember witnessing some of the
earlier work of Fessenden in this fascinating
field, in which he was pioneer. The wireless
telephone speech was free from all disturbing
noises and interferences so common on
ordinary telephone lines. Briefly, such tele-
phony depends on the ability to control the
voice transmitting antenna and to do this
with a fairly large output of energy.
By employing a method I described about
1892, it is possible to generate a continuous
wave train by shunting a direct current arc
with a capacity (condenser) in series with an
inductance, the frequency rate depending
on the electrical constants of these parts of
the apparatus. This system, which was the
subject of the LTnited States patent taken
out by me in the early nineties, has been
variously called the Duddell singing arc, or
later the Poulsen arc. Poulsen employed it
with modifications in his system of wireless
telephony. Long before this work of Poulsen,
Fessenden had used a high-frequency dynamo
for securing the continuous train needed.
A suitable microphone transmitter was made
to so alter the relations of the waves in
transmitting and receiving antenna, that
Fig. 25
Fig. 26
Fig. 27
voice waves could be received in an ordinary
telephone connected with the receiving an-
tenna system.
Much progress has been made in this
department of wireless work, and such
telephony between Europe and America may
yet become practicable. Methods are being
worked out whereby it may be possible to
PURE ELECTRON DISCHARGE IN RADIO COMMUNICATION
327
mold outputs of many kilowatts of energy s< i
as to have them vary with the voice waves,
and when this is done many problems, the
solution of which now seems remote, may
become solved and the results prove of great
practical value. It was not, however, ray
intention to devote time to these later
researches, but to endeavor to present to the
mind's eye a view of the nature of wireless
transmission which should show the similar-
ities to ordinary transmission by wire and
also the difference. Furthermore, I hope I
have shown it to be evident that future
transmission of energy at high efficiencies
will still demand the wire core for guiding
that energv to its destination.
y
THE PURE ELECTRON DISCHARGE AND ITS APPLICATIONS
IN RADIO TELEGRAPHY AND TELEPHONY*
By Dr. Irving Langmuir
Research Laboratory, General Electric Company
The electron emission from heated metals at very low pressures is a subject which has been investigated
by scientists for many years, and the observations have been generally explained to be the result of chemical
reactions with slight traces of gas. The first half of the following article, which is arranged in the form of a
historical review, relates the experiments leading to the conclusion of the existence of pure electron emission
in even the highest attainable vacua. After outlining the fundamental principles which govern this phenom-
enon the author shows how, through the medium of the kenotron (a hot-filament vacuum rectifier described
in the General Electric Review, March 1915, p. 156) and the pliotron (a new type of amplifier) both of
which employ the pure electron emission from heated metals in extremely high vacua, a very simple and success-
ful equipment has been produced to send and receive radio-telegraphic and radio-telephonic messages. — Editor.
Historical
It has been known for nearly two hundred
years that air in the neighborhood of incan-
descent metals is a conductor of electricity.
Elstcr and Geitel studied this phenomenon in
great detail and published the results of their
investigations in a series of papers in Wieder-
mann's Annalen during the year 1882-1889.
In most of their experiments they placed a
metal plate close to a metallic filament within
a glass bulb, and studied the charge acquired
by the plate under various conditions of
filament temperature and gas pressure. They
found in most gases that the filament tended
to give off positive electricity when it was at
a red heat, but at very high temperatures it
gave off negative electricity more easily
than positive. When the vessel was exhausted
as completely as was possible in those days,
the tendency to give off positive electricity^
was much decreased and did nfft persist,
whereas the tendency to emit rr%ative
electricity was apparently stronger than ever.
A similar discharge of negative electricity
from the carbon filament of an incandescent
lamp to an auxiliary electrode placed within
the bulb was observed and studied by Edison
and has since been known as the Edison
effect. Fleming, in 1896 [Proc. Rov. Soc. 4-7.
US, (1890) and Phil. Mag. 1&, 52 (1896)]
investigated and described this effect in detail.
J. J. Thomson [Phil. Mag. 48, 547 (1899)]
showed that in the case of a carbon filament
in hydrogen at very low pressures, the
♦ReacTbefore the American Institute ..f Radio-Engineers, at
New York. April 7. I9T5. Published with their permission.
Copyrighted, 1915. by Institute Radio-Engineers.
negative electricity is given off by the
filament in the form of free electrons having
a mass about 1 / 1 800 of the mass of a hydrogen
atom, and constituting in realitv atoms of
electricity. Owen [Phil. Mag. 8, 230 (1904))
showed that a heated Nernst filament also
gives off electrons and Wehnelt [Ann. Phys.
/ (. 42.") ( 1904)] proved that the electric current
from a lime covered platinum cathode
(Wehnelt cathode) is carried in the same
manner.
Richardson [Phil. Trans. Wl, 516 (1903)]
applied the electron theory of metallic con-
duction to the electron emission from heated
metals, and was thus able to develop a theory
of this effect. In order to account for the
conduction of heat and electricity by metals,
Riecke and Drude had assumed that metals
contain electrons which are free to move
under the influence of an electric force and
which are in constant vibratory motion
similar to that of the molecules of a gas.
Richardson assumed that these free electrons
are ordinarily held within the metal by an
electric force at the surface, just as 'the
molecules of a liquid are prevented from
escaping by a surface force related to the
surface tension. If the velocity of an electron
is sufficiently high, it may be able to overcome
the surface force and escape. Since the
average velocity of the vibratory motion
increases with the temperature, the number of
electrons which reach the necessary critical
velocity to escape, will increase very rapidly
with the temperature. These considerations
are strictly analogous to those of the evapora-
32S
GENERAL ELECTRIC REVIEW
tion of a liquid, so that the number of electrons
escaping should increase with the temperature
according to the same laws as those governing
the increase of the vapor pressure of a liquid
as the temperature is raised.
It had already been shown that the vapor
pressure (p) of a substance varies with the
temperature (T) according to a relation of
the form
\
, — 2 T
p = AVTe
where .4 is a constant, X is the latent heat of
evaporation of the liquid (or solid), and e
is the base of the natural system of log-
arithms. Richardson was thus led to conclude
that the current from an incandescent metal
should increase according to an equation of a
similar form, namely
— T
i =a\ Te
Here i is the current per square centimeter at
the temperature T, and b is a constant which
should be half the latent heat of evaporation
of the electrons.
Richardson suggested that the currents
obtained by the emission of electrons or ions
from incandescent bodies should be called
thermionic currents, a term which has since
come into very general use. According to
Richardson's theory, an incandescent metal
at a given temperature emits electrons at
a definite rate which is independent of
the electric field around the heated body.
If a positively charged body is placed near
the heated filament, the electrons will all be
drawn away from the filament and will
strike and be absorbed by the positively
charged body. The motion of these electrons
constitutes an electric current, the hot
filament being the cathode and the positively
charged body the anode of the. discharge.
If, however, there is no electric field around
the heated filament, or if a negatively charged
body be placed near it, the electrons which are
emitted from the filament return to it again
and are reabsorbed and therefore no current
flows between the two electrodes.
According to this viewpoint the electron
emission is the same whether a thermionic
current flows or not. As the potential of the
cold electrode or anode is increased, a larger
and larger proportion of the electrons emitted
are drawn to the anode, so that the thermionic
current increases. As the potential is further
raised, a point is finally reached at which all
the electrons emitted pass to the anode, so that
a further increase in voltage causes no increase
in current. The current is then said to be
"saturated."
Richardson, in 1902. determined the rela-
tion between the saturation current from a
heated platinum wire and a cylinder around
it, and found that i varied with the tem-
perature in accordance with the equation
given above. For other substances also he
found the relation to hold.
Since 1903, Richardson's theory of ther-
mionic currents has been the subject of much
investigation and discussion. H. A. Wilson
[Phil. Trans. 202, 243 (1903)] found that the
electron emission from platinum at high
temperature was decreased to 1/250,000 of its
former value by a preliminary heating of the
platinum in oxygen or by boiling in nitric
acid. The admission of a little hydrogen
brought the current back to its former value.
Wehnelt [Ann. Phvs. 14, 425 (1904) and
Phil. Mag. 10, 80 (1905)] discovered that
platinum cathodes covered with lime emit
vastly more electrons than platinum alone.
He proposed using tubes containing such
cathodes as rectifiers for alternating current
of 100 or 200 volts, and described a Braun
tube in which very soft cathode rays (100 to
1000 volts) could be produced. Wehnelt
worked usually with gas pressures ranging
from 0.01 to 0.1 mm. of mercury, the lowest
pressure recorded being 0.005 mm. Under
these conditions the paths of the cathode
rays were visible, showing that there was
strong ionization of the gas.
Soddy [Phys. Zeit. 9, S (190S)] found that
the large currents obtainable from a Wehnelt
cathode stopped suddenly if the residual
gases in the vacuum tube were absorbed by
vaporizing some metallic calcium. This
work of Soddy attracted considerable atten-
tion and made many investigators feel that
thermionic currents in general were dependent
on the presence of gas.
Lilienfeld, however, considered that Soddy 's
experiments did not show that the electron
emission from the Wehnelt cathode had
decreased, but suggested that the decrease in
current might be caused by the building up of
a negative charge in the vacuum because of
the large number of electrons needed to carry
the current.
Fredenhagen [Verh. deut. phvs. Ges. 14,
384 (1912)] in 1912 studied the electron
emission from sodium and potassium, two
metals that Richardson had found par-
ticularly good sources of electrons, and
concluded that the electrons are onlv emitted
PURE ELECTRON DISCHARGE IN RADIO COMMUNICATION
329
as a result of the presence of gas. He sug-
gested that if a perfectly clean metallic
surface could be obtained in a perfect vacuum
the electron emission would cease entirely.
Pring and Parker [Phil. Mag. 23, 192,
(1912)] in the same year measured the currents
from incandescent carbon rods in a vacuum.
They found that with progressive purification
of the carbon and improvement in the
vacuum, the currents decreased to extremely
small values. They concluded that "the
large currents hitherto obtained with heated
carbon cannot be ascribed to the emission
of electrons from carbon itself, but that they
are probably due to some reaction at high
temperatures between the carbon, or con-
tained impurities, and the surrounding gases,
which involves the emission of electrons."
More recently Pring [Proc. Roy. Soc. A 89,
344 (1913)] repeated these experiments under
still better vacuum conditions and finds the
former results confirmed. He concludes that
"the thermal ionization ordinarily observed
with carbon is to be attributed to chemical
reaction between the carbon and the sur-
rounding gas." "The small residual currents
which are observed in high vacua after
prolonged heating are not greater than would
be anticipated when taking into account
the great difficulty of removing the last
traces of gas."
A similar feeling gradually arose in regard
to the photoelectric effect, a phenomenon
resembling the electron emission from incan-
descent metals, except that the electrons are
emitted by the action of light — usually
ultra-violet light, instead of heat.
Pohl and Pringsheim [Phys. Zeit. 14, 1112
(1913)] find that the photoelectric effect is
very much decreased by improving the
vacuum, and suggest that perhaps the whole
effect is due to interaction between the gas
and the metal. Wiedmann and Hallwachs
(the latter the discoverer of the photoelectric
effect) [Ber. d. Deut. Phys. Ges. 16, 107
(1914)] go further and state emphatically as
a conclusion from experiments with potassium
that "The presence of gas is a necessary
condition for appreciable photoelectric elec-
tron emission."
Fredenhagen and Kuster [Phys. Zeit. 15,
65 and 68 (1914)] conclude that the same is
true for the photoelectric effect from zinc,
and in a still later publication Fredenhagen
[Verh. d. Deut. Phys. Ges. 16, 201 U914)]
finds that both the photoelectric and ther-
mionic electron emission from potassium are
entirely dependent on the presence of gas.
We see, then, that there were the best of
reasons for believing that it would be impos-
sible to get any electric discharge through a
perfect vacuum, because one could not
expect to get any electrons from the electrodes.
In the operation of ordinary X-ray tubes it
was well known that a certain amount of gas
was necessary. Porter [Ann. Phys. Jfl, 561
(1913)] studied the dynamic characteristics
of the Wehnelt rectifier and found that with
pressures as low as 0.001 mm. there was a
tendency for the current to become unstable,
fluctuating periodically between zero and a
higher value. With higher pressures, this
difficulty was avoided, but the characteris-
tics clearly showed a sort of hysteresis
loop, the current with ascending voltage
being different from that obtained with
descending voltage.
My active interest in thermionic currents
began in connection with some experiments
on electrical discharges occurring within
tungsten lamps. According to Richardson's
data on the electron emission from such
metals as platinum and osmium, the currents
that might exist across the evacuated space
in a tungsten lamp would be very large; in
fact, the current density, at temperatures
close to the melting-point of tungsten,
might be expected to be several hundred
amperes per square centimeter. Of course it
is evident at the outset that the current
flowing from one part of a filament to the
other through the vacuum must actually be
very small in any ordinary lamp. It was
known that the vacuum in a tungsten lamp
is extremely high and measurements indicated
that in well exhausted lamps after 100 hours'
life the pressure was probably less than one
millionth of a mm. of mercury. Taking
these two facts into account, the very existence
of a tungsten lamp seems strong evidence
that thermionic currents in high vacuum
must be very small, if not entirely absent.
When this effect was studied in more
detail, it was found that the smallness of
the currents in a lamp was not due to any
failure of the filament to emit electrons, but
was due entirely to an inability of the space
around the filaments to carry the currents
with the potential available in the lamp.
In one case, two single loop tungsten
filaments were mounted side by side in a
bulb. After the bulb was exhausted in the
best possible way and the filaments were
thoroughly aged and freed from gas, one of
the filaments was heated while a positive
potential was applied to the other through a
330
GENERAL ELECTRIC REVIEW
galvanometer. The hot filament thus served
as cathode in the discharge occurring in the
lamp. As the current through the cathode
was increased, the thermionic current as
measured by the galvanometer increased at
first, according to Richardson's equation as
shown in Fig. 1; but beyond a certain point,
the further increase in the temperature of the
cathode produced no further increase in
thermionic current .
a
5L
if
/
F
/
o
~r
?
<-y
/Electron Emission from Tungsten
Calculated from Equation
g
i
900
8
i
Dea Xe/nh.
do
oo
set
»
SK
X3
as
50
Fig. 1. Electron Emission from Tungsten in a
"Perfect" Vacuum
The curve representing thermionic current
as a function of temperature therefore con-
sists essentially of two parts: first, a part in
which Richardson's equation applies; second,
a part in which the current is independent of
the temperature. In the first part of the
curve it is found that the current is inde-
pendent of the voltage, or shape and size of
the anode, but in the second part of the curve
the current is affected by both of these
factors and ma}- also be either increased or
decreased by placing the lamp in a magnetic
field. It is thus evident that the only reason
that the current does not continue to increase.
according to Richardson's equation, is that
between the electrodes is ohlv
capable of carrying a certain current with a
given potential difierence.
The explanation of this phenomena was
found to be that the electrons carrying t re-
current between the two electrodes con-
stituted an electric charge in the space which
repelled electrons escaping from the filament
and caused some of them to return to the
filament.
A further theoretical investigation on the
effect of this space charge led to the following
formulas by which the maximum current
that can be carried through a space (of
certain symmetrical geometrical shapes) may
be calculated.
In the case of parallel plates of large size,
separated by the distance v, the maximum
current per square centimeter, i, is
(1)
\ 2
= 1^;
V
Here, e is the charge on an electron, m the
mass of an electron, and V the potential
difference between the plates. If we sub-
stitute the numerical value of — and express
in
i in amperes per square centimeter and V
in volts, then this equation becomes
I '3 -
(2) t = 2.33X10-6 ,
.V
In the case of a wire in the axis of a cylinder,
the maximum current per centimeter of length
from the wire is given by the equation
C!)
. 2V 2 e
\
I '••' -
9 > in r
If we substitute numerical values as before,
we find
J/3/2
(4)
1 = 14.65X10-'
where i is the current in amperes per centi-
meter of length, and r is the radius of the
cylinder in centimeters.
These equations have been found to agree
accurately with experiments when the vacuum
is so high that there is no appreciable positive
ionization.
Extremely minute traces of gas, however,
may lead to the formation of a sufficient
number of positive ions to neutralize to a
large extent, the space .charge of electrons
and thus very greatly increase the current
carrying capacity of the space. For example,
a pressure of mercury vapor of about 1 100,000
mm. has. under certain conditions, been found
to completely eliminate the effect of space
PURE ELECTRON DISCHARGE IN RADIO COMMUNICATION
331
charge, so that a current of 0.1 ampere was
obtained with only 2.3" volts on the anode,
whereas, without this mercury vapor, over
200 volts were necessary to draw this current
through the space.
Besides this enormous effect on the current
carrying capacity of the space, many gases
have a great influence on the electron emission
from the cathode. But in every case where
the cathode is of pure tungsten, the effect of
gas is to decrease, rather than increase, the
electron emission. For example, it is found
that a millionth of a millimeter of oxygen, or
gas containing oxygen, such as water vapor,
will cut the electron emission down to a
small fraction of that in high vacuum.
As a result of this work, we became firmly
convinced that the electron emission from
heated metals was a true property of the
metals themselves and was not, as has so
often been thought, a secondary effect, due
to the presence of gas.
• Further investigation showed that with the
elimination of the gas effects, all of the
irregularities which had previously been
thought inherent in vacuum discharges from
hot cathodes were found to disappear. In
order to reach this condition, however, it
was not sufficient to evacuate the vessel
containing the electrodes to a high degree,
but it was essential to free the electrodes so
thoroughly from gas that gas was not liberated
from them during the operation of the device.
It was also necessary to free the glass surfaces
very much more thoroughly from gas than
had been thought necessary previously. The
difficulty thus consists not in the production
of the high vacuum, but in the maintenance of
this vacuum during the use of the apparatus.
As the voltage applied to the terminals was
increased and as the current density in the
discharge increased, the tendency for the
gas residue to become^ ionized became very
much more marked and the difficulties in
maintaining a sufficiently high vacuum
increased still further. However, by special
methods of exhaust and by special methods
of treating the electrodes, these difficulties
have been overcome and it has thus been
possible to construct apparatus in which a
large current density can be obtained and
potential differences of much more than
100,000 volts may be applied without obtain-
ing effects attributable to positive ionization.
In previous devices which employed dis-
charges through vacuum, either with or
without a hot cathode, there was always
evidence of positive ionization if the current
density was increased above an extremely
low value, or if potentials over 50 or 100 volts
were applied while a current of as much as a
few milliamperes was flowing. The effects of
this positive ionization manifested them-
selves in many ways. If the ionization was
sufficiently intense, a glow throughout the
tube was visible. For example, in the Braun
tube, with a lime covered cathode, Wehnelt
states that a vacuum as high as possible should
be obtained, but he speaks of being able to
see the path of the cathode rays. It has
apparently always been assumed that cathode
rays of sufficiently high intensity can always
be seen, but of course such luminosity is
direct evidence of ionization of the gas. One
of the most sensitive indications of the
presence of positive ionization is the failure of
the current to increase with the voltage in a
regular manner, as shown in equations (2)
and (4). If much gas is present, and by this
I mean a pressure in the order of 1/ 10,000th
mm., the current-voltage curve often shows
decided kinks when the voltage is raised
above 50 or 100 volts. In many cases the
discharge is unstable and fluctuates peri-
odically between two values. All these
effects tend to be extremely erratic, since
they vary with the composition and the
pressure of the residual gases, and these, in
turn, are altered by the discharge taking
place through them. For example, in the
ordinary X-ray tube, the vacuum con-
tinually improves, and it is necessary, from
time to time, to admit fresh portions of gas.
With the higher voltages, perhaps the most
troublesome features of positive ionization
is its tendency to disintegrate the cathode.
The positive ions, moving under the influence
of the electric field, acquire high velocity,
and when they strike the cathode cause
rapid disintegration and ultimate destruction
of the electrode. With a pure electron
discharge, however, there is no disintegration
of the electrode caused by the discharge
and the filament lasts the same length of
time as if no current passed through the
vacuum.
Another effect, produced by positive ioniza-
tion, is the emission of electrons from the
cathode under the influence of the positive
ion bombardment. These electrons, which
constitute the so-called delta rays, escape
from the cathode with considerable initial
velocity, and are therefore capable of charg-
ing up a third electrode in this space to a
potential of 10 or 15 volts negative with
respect to the cathode.
332
GENERAL ELECTRIC REVIEW
With the pure electron discharge, none of
these effects are present. The cathode rays
are entirely invisible, the current voltage
curve is a smooth curve, follows the 3,2
power law, in case the filament temperature is
sufficiently high and the shape of the elec-
trodes is such that the small initial velocities
of the electrons from the cathode do not play
too large a role. It is possible to obtain a very
high current in this type of discharge, but in
order to overcome the space charge effects, it
is then necessary to use a very strong electric
field close to the cathode.
Devices Employing a Pure Electron Discharge)
Dr. W.D. Coolidge [Phys. Rev. 2, 409 (1913)]
has used the pure electron discharge in the
construction of a new type of X-ray tube. In
this tube the cathode consists of a small,
flat spiral of tungsten wire, surrounded by a
small molybdenum cylinder which serves as
a focusing device, while the anode, or target,
consists of a massive piece of tungsten, placed
near the center of the tube. With this tube
it has been possible to use voltages as high
as 200.000 volts in the production of X-rays.
The current through the tube is absolutely
determined by the electron emission from the
filament, which, in turn, depends upon the
temperature, in accordance with Richardson's
equation.
The advantages of this tube over the
ordinary X-ray tubes previously used are
many. Perhaps the most important feature
is that the current and voltage are under
complete control at all times, the current
being fixed by the temperature of the cathode
while the voltage is simply that furnished by
the transformer or induction coil used. The
tube seems to have an almost unlimited life,
the temperature of the filament being so low
that no appreciable evaporation occurs and
the absence of gas eliminating the cathodic
disintegration usually characteristic of high
voltage discharge in vacuum. The tube is
entirely constant in its action and the erratic
effects usually observed in X-ray tubes are
eliminated.
Several other types of apparatus have been
developed making use of this pure electron
discharge, and these devices possess the same
advantages over apparatus formerly used as
the Coolidge X-ray tube possesses over the
ordinary X-ray tube.
In order to distinguish these devices from
those containing gas and in most cases depend-
ing upon gas for their operation, the name
"Kenotron" has been adopted. This word
is derived from the Greek kenos, signifying
empty space (vacuum), and the ending,
iron, used by the Greeks to denote an ' ' instru-
ment."
Kenotron Rectifier
The Coolidge X-ray tube is, of course, a
rectifier for high voltage alternating current,
but it is not suitably designed for this purpose.
In an X-ray tube, the voltage applied must
be consumed in the tube itself, whereas in the
rectifier the voltage in one direction should be
consumed in the load in series with the
rectifier, although the voltage in the opposite
direction should be taken wholly by the
rectifier. In the X-ray tube, because of the
great distance between the anode and cathode
and the presence of a focusing device around
the cathode, the space charge effects are very
much exaggerated, so that it is necessary
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The Effect of Space Charge on the
Thermionic Currents
to apply several thousand volts, in order to
get even 10 milliamperes of current. This
voltage necessary to overcome the space
charge is completely lost when the tube
is used as a rectifier.
To overcome this loss of voltage as far as
possible, the anode and cathode in the
PURE ELECTRON DISCHARGE IN RADIO COMMUNICATION
333
kenotron are placed close together and every-
thing is avoided which might tend to screen
the cathode from the field naturally produced
by the anode. In this way it has been possible
to build kenotrons which have supplied pure
electron currents of over an ampere, with a
voltage drop of about 200 volts. This current,
however, requires large anodes and cathodes,
so that it is usually more convenient to
build kenotrons with a current capacity of not
over 250 milliamperes, and if it is desired to
rectify larger currents than this, to place
several kenotrons in parallel.
There seems to be no upper limit to the
voltage at which a kenotron can operate.
A kenotron has been built capable of rectify-
ing 250 milliamperes at 180,000 volts, and
there seems to be every reason to think that
kenotrons could be used at very much higher
potentials if desired.
The design and the characteristics of
kenotrons has recently been described in a
paper bv Dr. S.Dushman [General Electric
Review, vol. 10, p. 156, 1915] and I will
therefore only briefly describe these devices.
Fig. 2 gives the characteristics of a typical
kenotron designed for rather large currents.
The curves show the current carried by the
kenotron for different filament temperatures
at given voltages between the electrodes.
Fig. 3. Molybdenum Cap Type of Kenotron
For example, if the temperature of the
filament is 2400 deg. the maximum current
that can be obtained with any voltage is
about 112 milliamperes. If, however, the
resistance of the load is able to hold the
current down to a value of say 54 milli-
amperes, then we see from the curves that the
voltage drop in the kenotron would be 75.5
volts, the remaining voltage, which may be
many thousands of volts, being consumed
in the load in series with the kenotron.
Figs. 3 and 4 illustrate two forms of
kenotrons, one for voltages up to about
10,000, and the other one suitable for use up
to 50,000 volts. With voltages higher than
about 12,000 to 15,000 volts, the kenotron
of the type shown in Fig. 3 is apt to fail,
because the electrostatic attraction of the
Fig. 4. Kenotron with Filament Between
Two Parallel Plates
anode pulls out the helically wound filament
and short circuits the device. At the higher
voltages, therefore, it is necessary to support
the filament and to balance, as far as possible,
the electrostatic forces acting on it.
The characteristics of the kenotron are
such that the current flowing through it is
always perfectly stable, so that several
kenotrons can be run in parallel and each
one will take its proper share of the current.
This is in marked contrast with the behavior
of mercury arc rectifiers, which have negative
characteristics and therefore, if several are
placed in parallel, one of them takes the
whole of the current.
334
GENERAL ELECTRIC REVIEW
Owing to the absence of gas effects, the
kenotron is a perfect rectifier, in that no
measurable current flows in the reverse
direction, even when voltages of 100,000
volts or more are applied. For similar
reasons, it is capable of rectifying high
frequency currents, as well as low frequency,
there being not the slightest sign of any lag
effects.
Amplifying or Controlling Devices: Pliotrons
In a pure electron discharge, as the tem-
perature of the filament is raised, a point is
always reached where the current becomes
limited by the space charge between the
electrodes. L'nder these conditions, only a
small fraction of the electrons escaping from
the cathode reach the anode, whereas the
majority of them are repelled by the electrons
in the space and therefore return to and are
absorbed by the cathode. From this view-
point it is evident that if a negatively charged
body is brought into the space between the
anode and cathode, the number of electrons
which then return to the cathode will increase,
so that the current to the anode will decrease.
On the other hand, if a positively charged
body is brought near the cathode, it will
largely neutralize the negative charges on the
electrons in the space and will therefore
allow a larger current to flow from the cathode.
In this way it is possible to control the current
flowing between the anode and cathode by an
electrostatic potential on any body placed in
proximity to the two electrodes. This con-
trolling effect may be best attained by having
this controlling member in the form of a fine
wire mesh, or grid, placed between the
electrodes.
The term "Pliotron" has been adopted to
designate a kenotron in which a third elec-
trode has been added for the purpose of con-
trolling the current flowing between the
anode and cathode. This word is derived
from the Greek "pleion" signifying "more.'*
A Pliotron is thus an "instrument for giving
more" or an amplifier. A similar use of the
prefix "plio" occurs in the geological term
"Pliocene."
The three elements, hot filament cathode,
grid, and anode, are. of course, similar to the
elements of the De Forest audion. However,
the operation of the audion is in many ways
quite different from that of the pure electron
device operating in the way I have described
above.
In the audion, as well as in the Lieben-
Reisz relay, the amplifying action appears
to be largely dependent upon gas ionization,
even when the device operates well below
the point at which blue glow occurs. The
action is probably somewhat as follows: there
is normally present a small amount of gas
ionization, due to the passage of the electrons
between cathode and anode. The presence
of the positive ions partly neutralizes the
space charge which limits the current flowing
between the electrodes. If a small positive
potential is applied to the grid, the velocity
of the electrons passing by it is somewhat
increased and they therefore produce more
ions in the gas. Besides this, as the potential
on the grid is increased, the number of elec-
trons passing the grid is increased, and this
again tends to increase the amount of ioniza-
tion. A very slight increase in the amount of
ionization brought about in this way very
greatly reduces the space charge and there-
fore largely increases the current that
can flow between the electrodes. Thus.
with a given construction of grid, filament,
and plate, the relaying action may be very
greatly increased beyond that which would
occur if no gas were present. The amount
of gas ionization which is necessary, in
order to practically completely eliminate the
effects of space charge, is often much too
small to produce a visible glow in the gas.
If too much gas is present, or if the potential
on the plate or the current flowing to the
plate is too large, then the amount of positive
ionization may reach such values as to almost
entirely neutralize the space charge and thus
allow a large current to flow. Under these
conditions, the relaying action of the audion
is lost. This is the case, for example, when
the audion gives a blue glow. In the
border land between these two conditions,
there is a region of instability in which the
sensitiveness of the audion may be enormously
great, but it is usually not found very practi-
cable to operate the device in this region
because of the difficulties in maintaining
adjustment, for any lack of adjustment may
cause the audion to go over into a condition
of blue glow.
The audion is often used with a condenser
in series with the grid. Under these con-
ditions, the audion requires the presence of a
certain amount of gas ionization so that the
positive ions formed may prevent the accumu-
lation of too large a negative potential on the
grid. With the pliotron, owing to the absence
of positive ions, if it is desired to use a con-
denser in series with the grid, this condenser
must be shunted by a hi<:h resistance and
ELECTRON DISCHARGE IN RADIO COMMUNICATION
335
often a source of potential must be placed
in scries with the high resistance, in order to
supply positive electricity to the grid as
rapidly as this tends to be taken up from the
electrons given off by the filament.
Construction of Pliotron
In the construction of pliotrons, it has been
found desirable to make the wires con-
stituting the grid of as small cross-section as
Fig 5
possible. In this way, even when a positive
potential is applied to the grid, the current
that flows to the grid may be made extremely
small. The use of very fine wire is made pos-
Fig. 6
sible by using a frame of glass, metal or other
suitable material, to support the grid. Thus,
in Figs, 5 and 6, the filament is mounted in the
center of a frame made of glass rods, on which
the fine grid wire is wound by means of a
lathe. The grid may thus consist of tungsten
wires of a diameter as small as 0.01 mm. and
these may be spaced as close as 100 turns per
centimeter, or even more.
In Figs. 5 and (i are shown two types of
pliotron. Fig. 5 shows a pliotron such as used
for amplifying radio signals in a receiving
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may be used for controlling as much as 1 kw.
of energy for radio telephony.
The characteristics of the pliotron depend
upon the length of filament used, the distance
between filament and grid, the spacing between
the grid wires, the diameter of the grid wires.
the distance between grid and anode, and
the size and shape of the anode. The impor-
tant elements in the characteristics of a
pliotron are, first, the relation between the
current flowing between anpde and cathode as
a function of the potential on the anode and of
that on the grid; second, the current flowing
to the grid, as a function of the potential of
the grid and the potential of the anode..
Fig. 7 gives the characteristics of a small
pliotron such as that shown in Fig. 5. Curve
A gives the current flowing to the anode for
different grid potentials, while the potential
of the anode is maintained constant at 220
volts. Curve G gives the current flowing to
the grid under the same conditions. For
different anode potentials, these curves are
shifted vertically, by amounts proportional
to the change in anode potential. In fact, it
336
GENERAL ELECTRIC REVIEW
is found that these curves can be represented
with fair approximation by a function of the
form
where i is the current flowing to the anode,
Ya is the voltage on the anode, Vg the voltage
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Fig. 8.
on the'grid, and k the constant which depends
on the relative shapes and positions of the
electrodes.
Fig. S gives similar characteristics for a
large pliotron like that shown in Fig. 6. In
this case, the anode potential was 8500
volts.
By using a fine grid, the current to the
anode can be stopped entirely by even a
very slight negative potential on the grid.
On the other hand, a rather low positive
potential will then be sufficient to draw a
large current to the anode. The amount of
current taken by the grid would be only a
very small fraction of that flowing to the
anode, in case the diameter of the grid wires
is small compared to the distance between
them. On the other hand, with a coarse
grid, that is, a grid in which the spacing is
large, a rather large negative potential may
be necessary, in order to stop the current
flowing to the anode. Similar results to
those obtained by changing the spacing
of the anode may be obtained by chang-
ing the relative distances between the
electrodes. The effects produced in this
way may be expressed approximately by
means of the constant k in the above
equation, the effect of fine spacing thus
being to increase the value of k, while coarse
spacing decreases it.
By using a fairly coarse grid, consisting of
fine wire, it is possible to obtain a control
of the current to the anode, always using a
negative potential on the grid. Under these
conditions, since there are no positive ions
present, no current flows to the
grid, except that necessary to charge
it electrostatically to the required
potential. It thus becomes possi-
ble to control very large amounts
of energy in the anode circuit,
by means of extremely minute quan-
tities of energy in the grid circuit.
There does not seem to be any
upper limit to the voltages that
may be used in the pliotrons. With
voltages over 30,000 it is often
necessary to space the electrodes
further apart and to use heavier
wires for the grid, in order to reduce
the danger of breakage of the parts
by the large electrostatic forces
which then occur.
The current carrying capacity
of the pliotron is limited only
by the size of cathodes that it
is found convenient to use and
by the voltage available. Large currents
cannot be readily obtained with low volt-
ages because of the space charge effects
described previously. With voltages above
500 volts, however, it is found practicable
to use currents of 300 or 400 milliamperes
for a pliotron of the type shown in Fig. G.
With high potentials, there is no difficulty
in using currents as large as this, provided
the energy is consumed in some device
in series with the pliotron. On the other
hand, if the full voltage is applied to the
anode while the current is flowing to the
anode, the energy liberated in the form of
heat may be so great as to volatilize the anode
or cause it to radiate so much heat that the
glass parts of the apparatus are softened.
In a pliotron with a five-inch bulb the amount
of energy that may be so consumed within the
pliotron is about 1 kw. Still larger amounts
of power may be dissipated if the bulb is
immersed in oil and if the grid frame is
made of quartz, or other heat resisting
material.
It is evident from the characteristics of the
pliotron that any number of these devices
may be placed in parallel and that in this
way. very large amounts of power may be
controlled.
PURE ELECTRON DISCHARGE IN RADIO COMMUNICATION
33;
PLIOTRON IN A RECEIVING STATION
Pliotron as a Detector
If the antenna of a receiving set is coupled
directly to the grid of a pliotron and a tele-
phone receiver is placed in series with the
anode, signals may be readily detected, but
the results obtained in this way are usually
very poor. Under these conditions, the
sensitiveness of the arrangement is pro-
portional to the curvature of the curve A,
Fig. 7 (or, more accurately, proportional to
the second derivative of the anode current
with respect to the grid potential). This
curvature may be somewhat increased by
applying a negative potential to the grid,
but even under these conditions the sen-
sitiveness of the arrangement is usually not
very high.
If it is attempted to use a condenser in
series with the grid and thus use the pliotron
in the way that the audion is often used (as
described, for example, by Armstrong, Elec-
trical World, December 12, 1909, p. 1149), it
is found necessary to shunt the condenser
with the resistance and often place a battery
of a few volts in series with the resistance, in
order to prevent a large negative charge
from accumulating on the grid.
It has been found, however, by W.C.White,
that a very minute trace of certain gases may
very greatly increase the sensitiveness of this
device as a detector. For example, by placing
within the bulb a small quantity of an amalgam
of mercury and silver, the characteristics
of the tube show a kink, as indicated in Fig.
9. With a detector of this sort, if the grid
potential is adjusted so that its average value
is approximately that at which the kink
occurs, there is a very marked increase in
sensitiveness. This is due to the fact under
these conditions either an increase or a
decrease in the grid potential causes a decrease
in the anode current. The sensitiveness of
this detector is then very high. The quantities
of mercury vapor necessary to give this
effect are so low that anode voltages of 200
or more may be used without any indi-
cation of glow discharge.
Pliotron as Amplifier
The value of a pliotron as an amplifier is
dependent primarily upon the slope of the
curve between anode current and grid
potential; for example, curve A, Fig. 7. A
second factor of importance is the magnitude
of the current taken by the grid. In order
to get the greatest amplifying effect it is
desirable to have this current as low as
possible. In a pliotron of the type shown in
Fig. 5, the current to the anode increases at
the rate of about 1 milliampere per volt
change in the grid potential.
By using larger anode potentials, the slope
of the curve can be made very much greater,
since it becomes possible to use grids of finer
mesh. For example, in Fig. 8 it is seen that
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the slope of the curve corresponds to two
milliamperes increase in anode current per
volt change in grid potential.
It has been found that there is no slug-
gishness in the characteristics of the pliotron,
even at the highest frequencies.
By connecting the pliotron as amplifier,
as shown in Fig. 10, the high frequency
currents received from the grid may be
amplified from one hundred to six hundred-
fold. In this arrangement, it is the high
frequency or radio frequency that is amplified,
and not the audio frequency. This ampli-
fication of the radio frequency possesses the
marked advantage that the detector circuit
may be tuned to the same frequency as the
amplifier circuit, and in this way a very
marked increase in selectivity is obtained.
In fact, it has been shown by Mr. Alexander-
son that the resonance curve of an outfit
338
GENERAL ELECTRIC REVIEW
consisting of amplifier and detector, both
tuned to the radio frequency as shown in
Fig. 10, may be obtained from the resonance
curve for the detector alone, by squaring the
ordinates. For example, if with a single
detector, the signals from one station i .4
are received one hundred times as strong as
those from another station (B), then, with
the above arrangement with the amplifier.
Fig. 10
the signals from -4 will be received one
hundred times squared, or ten thousand
times as strong as those from station B. If
two amplifiers be used in this way. the signals
from station .4 could be obtained one million
(or 100s) times as strong as those from
station B.
In practice, this arrangement has been
found to give a wonderfully high degree of
selectivity.
Of course a pliotron may also be used for
amplifying the audio frequency, coupling
the circuits together by means of an iron core
transformer. A single pliotron, under these
conditions, gives an amplification of current
of several hundred-fold, when voltages of
from one to two hundred volts are used on the
anode
Pliotron as Oscillator
By placing inductance in capacity in the
grid and plate circuits and coupling these two
circuits together, it is possible to use the
pliotron as a source of continuous oscillations.
Small pliotrons of the type shown in Fig. 5
may produce oscillations up to a few watts,
and these may be used in a receiving station,
according to the Heterodyne principle, for
receiving continuous oscillations. One plio-
tron may be used for both amplifying or
detecting, and for producing oscillations.
With the larger pliotrons, using vol;
of a few thousand volts, up to a kilowatt of
high frequency oscillations may readilv be
produced by a single tube.
USE OF THE PLIOTRON IN RADIO
TELEPHONY
By means of a single large pliotron, it has
been found possible to control about two kw.
of energy in an antenna, by means of the
currents obtained from an ordinary telephone
transmitter. There are many arrangements
by which this may be accomplished. For
example, a two-kw. Alexanderson alternator
( lou, 000 cycles) may be loosely coupled to
the antenna and the anode of the pliotron
may be connected to a point on the antenna
where the potential is normally high. As
long as the potential on the grid of the
pliotron is strongly negative, no current
flows to the pliotron and therefore the full
energy is radiated by the antenna. If, how-
ever, the negative potential on the grid is
decreased, a sufficient current may be drawn
from the antenna to strongly damp the
oscillations and thus greatly decrease the
energy radiated. With sufficiently high
potential on the grid, practically the whole of
the energy may be diverted from the antenna.
It is thus possible to control the output
of the antenna by varying the negative
potential on the grid of the pliotron. Since
the grid is always negative, no current flows
between filament and grid and therefore
practically no energy is required to maintain
the charge on the grid. In this way, therefore,
by connecting the secondary of the trans-
former between the grid and filament, and
placing the primary of the transformer in
series with telephone transmitter, it is pos-
sible by means of the variations in the currents
from the telephone transmitter to obtain
potentials on the grid of several hundred
volts and thus to control the output of the
antenna.
Instead of using an arc or alternator as a
source of high frequency current, the pliotron
may also be used as generator of the oscilla-
tions. One pliotron may be used both for pro-
ducing the oscillations and for controlling the
amplitude of the oscillations, in accordance
with the sound waves acting on the telephone
transmitter. It is usually preferable, how-
ever, to use a large pliotron for producing the
oscillations and connecting a small pliotron
in the grid circuit of the large pliotron for
controlling the output of the latter.
With the above arrangement an extremely
simple and efficient radio telephone outfit
can be made. Since the pliotron for produc-
ing oscillations requires comparatively high
direct current voltages, it has been found
convenient to combine the pliotron oscillator
PURE ELECTRON DISCHARGE IN RADIO COMMUNICATION
339
with a kenotron rectifier. Two types of
apparatus of this type have been in use a
considerable time, and it will be of interest
to describe these in some detail.
In the first outfit, which is a small outfit
having a capacity of about 20 watts in the
antenna, the source of power is the local
city supply, which is 118 volts, (i()-cycle
alternating current. This is connected with
the primary of a small transformer, having
two secondary windings. One of the second-
aries is designed to give about 5 volts and
furnishes the current used for heating the
filaments of the kenotrons and pliotrons.
The other secondary of the transformer is
wound to furnish a potential of about 800
volts. This is rectified by means of a kenotron
and serves to charge a condenser of about
six microfarads. In this way a source of
high voltage, direct current is obtained in a
very simple manner. The plate of the pliotron
oscillator is then connected to one of the
terminals of the condenser, while the filament
is connected to the other. The plate of the
second pliotron is connected to the grid of the
first, while the grid of the second is coupled
by means of a second small transformer to
the microphone circuit. With this outfit,
both pliotrons may be relatively small, and
in order to obtain an energy of about
20 watts in the antenna, it is found that
the current drawn from the condenser is so
small that the potential supplied by it does
not vary sufficiently to be audible in the
signals sent out. The different parts of this
apparatus may be made very compact and
no adjustments are found necessary in operat-
ing the system unless it is desired to change
the wave length. In this case, it is only
necessary to change the inductance or
capacity.
In the second outfit, which is suitable for
use up to 500 watts or more, the high voltage
direct current is obtained from a small 2000-
cycle generator. The current from this is
transformed up to about 5000 volts, rectified
by kenotrons, and smoothed out by means
of condensers. By the use of 2000-cycle
alternating current instead of (iO-cycle, it is
possible to store up large quantities of energy
and thus obtain as much as a kilowatt or
more of power in the form of direct current
with condensers of moderate size. This
high voltage direct current is then used, as
before, to operate a pliotron oscillator, the
output of which is controlled by means of a
small pliotron connected to the telephone
transmitter.
By means of this system of control the
amount of energy in the telephone trans-
mitter circuit need be no larger than those
commonly used in standard telephone circuits.
It has thus been found possible to connect
up this radio telephone outfit with the regular
telephone lines so that conversation may be
carried out between two people, both of
whom are connected with the radio stations
by means of the regular land lines. It has
also been found possible to communicate
both wavs over these lines.
340
GENERAL ELECTRIC REVIEW
THE HYDRO-ELECTRIC DEVELOPMENT OF THE COHOES
COMPANY AT COHOES, N. Y.
By B. R. Connell
Power and Mixing Engineering Department, General Electric Company
The development described in this article is one more instance of the profitableness of substituting
efficiency for inefficiency, of gathering in the pennies that have heretofore slipped through the cracks. The
plant, which will be rea'dv for operation by the time this issue is distributed, replaces with one station making
use of modern high efficiency apparatus and the most economical head, a number of scattered installations
employing waterwheels of more or less obsolete types, working under smaller heads than the maximum. The
fact that the expenditure required for a development of this kind was considered justified, forms a basis on
which to judge of the increased output that may be expected from the new plant.
General
The Cohoes Falls, on the Mohawk River
near its entrance into the Hudson, have long
been a point of interest locally and have been
utilized to furnish power to nearby manu-
factories since about 1830. The Cohoes
Company was organized a few years before
that date and secured control of the entire
water power rights at this point, except for
the water reserved for canal purposes by the
These early power developments, while
noted at the time of their construction, and
still of some historic interest, were far from
an economical development of the available
power, owing to the number of small instal-
lations and low heads used, as well as to the
fact that a number of the waterwheels are
now of an obsolete type. The Cohoes Com-
pany therefore decided to develop the power
privilege by one large modern hydro-electric
Fig. 1. Map of Mohawk River, Canal and Power Station of the New Development
State. This company built a dam a short
ways above the Falls, which has since been
replaced several times, the present structure
having been built in 1865. A power canal
was also constructed in the early develop-
ment, and was later enlarged and lengthened
several times until the present extensive
canal system resulted. This canal now fur-
nishes hydraulic power to a large number of
manufactories in the city of Cohoes. X. Y.
plant — the most economical manner — and
furnish electric power to each of the various
industries that had previously maintained its
separate power plant.
This new development is now practically
completed, and it is expected will be put into
commercial operation during the latter part
of April. The ultimate installation will have
a capacity of 50.000 h.p., 30,000 h.p. of which
is installed at the present time. The plant
HYDRO-ELECTRIC DEVELOPMENT OF THE COHOES COMPANY
341
when- completed will be one of the largest
and most up-to-date hydro-electric installa-
tions in this section utilizing the latest
developments in electrical and hydraulic
apparatus.
Watershed, Rainfall, Etc.
Practically the entire run-off
of the Mohawk Valley, except
the water reserved for canal
purposes, will be available at
this new plant for power pur-
poses, under a normal head
of 96 feet. The Mohawk is
the largest tributary of the
Hudson River and rises in
the western part of New York
State, flowing eastward for
the greater part of its length
of 145 miles, until it enters
the Hudson at Cohoes. From
the data of the latest U. S.
geological survey it has a total
drainage area, measured at
the Cohoes dam, of approxi-
mately 3472 square miles.
The yearly rainfall in the
Mohawk water-shed ranges
from 36 to 55 inches, and the
average run-off is approxi-
mately 24 inches. The geo-
logical survey readings taken
at Dunsback Ferry, which is
a few miles above the Cohoes
Falls, show a stream flow
exceeding 2400 second feet
for nine months of the year,
minimum for the year 1906,
taken as a good average year
Canal, Gate House, Etc.
In the new development the Cohoes Com-
pany will utilize their present dam across the
Mohawk. This is a masonry structure 1443
feet long, located about a mile above the
Fig. 2. Plan of Forebay, Gate-house and Power House
with 750 as a
which may be
The period of
low water usually occurs during the months of
August, September and October.
The Mohawk watershed has a rapid run-
off, as there are few large natural reservoirs,
and a large section of the country through
which it runs is cultivated land rather than
forest. The stream flow therefore is not uni-
form throughout the year, although the per-
centage run-off is relatively large, being
approximately 60 per cent as an average.
This condition will be improved considerably
by the completion of the New York State
barge canal system, which traverses the bed
of the river for over 100 miles, as numerous
dams are being erected to improve navigation
and furnish storage for canal feeders. This
will, of course, improve the power conditions
and make the stream flow more uniform
throughout the whole year.
power house. From this dam a canal leads
to a forebay and station gate house, and at
the entrance to the canal head gates are
provided, and just below these a spillway to
control and regulate the canal level. The old
canal, which has heretofore supplied the
various mills, has been enlarged for the new
development to about double its former capac-
ity, and when completed will terminate in a
small forebay directly above the power house,
the forebay being formed by concrete walls
built between the canal bank and the ends of
the gate house. Three small gateways are
provided at one end of the gate house for
cleaning ice and other material from the
forebay. After the completion of the new
plant the canal will be closed below the fore-
bay, as soon as the necessary arrangements
can be made by the city of Cohoes to take
care of the sewerage which is now emptied
into the canal in the upper section of the
city.
342
GENERAL ELECTRIC REVIEW
The station gate house is a brick and
concrete structure approximately 150 feet
long by 28 feet wide, and 31 feet high. Pro-
vision has been made in this for five gates and
penstocks, three of the penstocks being
installed at present. The gates are 20 feet
wide bv 22 feet high, made of heavy steel
framework with a steel plate in front, and
arranged to raise and lower on rollers. They
are each operated by a 22-h.p. motor through
a cable drum on each end, and can be con-
trolled by push buttons either from the gate
house or power house. A travelling hoist is
provided for handling the racks and stop logs
when necessarv.
The building is a brick and steel frame
structure set on a heavy concrete substruc-
ture, the outside being of red brick finished
with concrete copings which give it a very
neat and substantial appearance. The entire
power house occupies a ground space about
170 feet long by 6G feet wide. The generator
room faces the river and is approximately
40 feet wide, with an average height of 45
feet. Running the entire length of the gen-
erator room is the transformer and switching
section of the station, which is a two-story
structure with a basement. The headroom
on each floor of the section is about 15 feet,
and the width 24 feet.
Fig. 3. View of Power House and Cohoes Falls
From the gate house the penstocks drop
directly to the wheels, a vertical distance of
about 100 feet. These penstocks are
11 feet in diameter and approximately L90
feet long, and are made up of steel plates
ranging in thickness from % in. to Yi in.
They are anchored firmly in concrete piers,
which extend over practically the whole face
of the bank, and are also supported by the
heavy substructure of the gate house and
1 lower house
Power House
The power house is located at the foot of a
Steep cliff on the edge of the river, and a
concrete retaining wall extending into the
river has been built just above to prevent
any interference with the tail race water by
the river flow, specially al high water periods.
In the generator room there is a 50-ton
motor-operated crane, which is capable of
lifting the complete rotating element, con-
sisting of the generator rotor, waterwheel
runner, and shaft, this being the heaviest
single piece to be handled. The generators
are spaced on 33-foot centers, thus giving
ample room for working around the machines.
The station is constructed for the ultimate
installation, consisting of five units.
The basement under the switching station
is divided into ten bays by the supporting
columns, and, beginning with the first one
down stream, each alternate bay is occupied
by a penstock. Two are to be used for stor-
age, and in the other three are located the oil
tanks, filters for lubricating oil, transformer
reactances, and generator rheostats. A sep-
arate room, laid out with special arrange-
HYDRO-ELECTRIC DEVELOPMENT OF THE COHOES COMPANY
343
merits for ventilation, is provided for these
rheostats. Cool air from basement is taken
in through openings in the floor and after
passing through the rheostat grids is dis-
charged into an air duct located in the center
of the winding stairway in the tower. Arrange-
ments are also made so that this discharge
can be closed and the warm air passed into
the station when necessary.
On the main floor level of the gallery section
are located the locker room, storage battery
The bus work is made up of copper bars and
tubing mounted on open insulators, no
enclosed bus structure being installed.
On the second floor the benchboard is
located in the center of the building, with an
overhanging gallery directly in front, from
which an unobstructed view of the entire
generator room is obtained. To the left of
the benchboard is the vertical control board,
and beyond this are the arc panels and the
2300-volt bus, switching equipment and cor-
Fig. 4. Exterior View of Power House and Gate-house
room, governor pumps, exciter sets and com-
bination auxiliary and battery switchboard,
these occupying the downstream half of this
section. In the other half are located the two
SOO-kv-a. transformer banks and the 12,000-
volt solenoid-operated oil switches and busses.
The generator and line switches are installed
in two parallel rows, with the bus section
switches at right angles to them. These oil
switches are made up of three single-pole
units, each in a separate tank, and the com-
plete switch is set on a concrete base two feet
above the floor. The switch tanks are each
pi] ied to the main oil tanks so that the oil
can be convenientlv filtered when necessarv.
responding feeders. The bus structure here
is also of the open type.
On the other side of the benchboard is a
partition wall, and beyond this the 12,000-
volt lightning arrester room. Here are also
installed the reactances for each outgoing
12,000-volt line, these lines leaving the
building vertically through roof-entrance
bushings.
Directly back of the bench and vertical
control boards is a large office, the front wall
of which is formed by the rear panels of the
boards serving as a partition. A doorway
between the boards leads to the office from the
front of the gallery. Back of the office is a tower
344
GENERAL ELECTRIC REVIEW
which leads from the basement to a height of
55 feet above the roof, and in which are a
passenger .elevator and a winding stairway
with landings at each floor. From the top of
this tower a bridge leads to the gate house,
and affords passage to and from the power
house.
The power house is well lighted in the day
time by a number of windows. This is
specially true of the generator room, where
large corrugated glass windows are installed
on all three sides. These are arranged for
ventilation at both top and bottom, and have
metal framing throughout. In the switching
Fig. 5. Cross Section of Power House
HYDRO-ELECTRIC DEVELOPMENT OF THE COHOES COMPANY
345
sections all the apparatus, including the oil
switches and busses, is installed in the center
of the section, so that there are no obstruc-
tions in front of the window that will interfere
with the light. While nothing ornamental
is attempted for night illumination, good
lighting is furnished in the generator room by
400-watt gas-filled lamps supported in wall
brackets and fitted with reflectors. Nine
10,000 h.p. under an effective head of 96
feet and full gate opening. When operating
under an effective head of 90 feet and at full
gate opening, the rating is 8800 h.p. The
normal speed of the wheel is 185 r.p.m. and
the maximum runaway speed approximately
300 r.p.m.
The guaranteed efficiencies of the water-
wheel, under the normal head of 96 feet and
ZPh Power Circuits Auto ferdet Const Current Trans
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Fig. 6. Plan View of Generator Room and Gallery Sections
lamps are supplied for the generator room.
The various gallery sections are lighted from
ceiling fixtures containing 100-watt lamps.
The building is arranged for heating by
steam in winter when necessary, a small
boiler being provided for this purpose. Figs.
5 and 6 show the general plan and arrange-
ment of the power house and apparatus.
Waterwheel and Governing Equipment
The waterwheels are of the ve tical shaft
single-runner Francis type having a com-
bined radial and axial flow, and a single
downward discharge into concrete draft
tubes. The normal rating of the wheels is
at a constant speed of 185 r.p.m., are as
follows :
10,000 h.p 85 per cent
9,000 h.p 87 per cent
8,000 h.p 88 percent
7,(100 h.p 86.5 per cent
6,000 h.p 84 per cent
5,000 h.p 80 per cent
The speed regulation is based on a total
flywheel effect of 1,700,000 (WR2), a pipe
line diameter of 11 ft., and a pipe length of
190 ft., and is as follows for different load
changes :
Load change, 10% 25% 50%
Speed change. 0.9% 2.1% 3.5%
100<%
340
GENERAL ELECTRIC REVIEW
The governors will restore the speed of the
units to within 0.5 per cent of normal from
any change in load and will begin to act before
the speed has changed more than 0.5 per cent
from normal, thus giving a very close speed
regulation.
The runner is built of a special mixture of
cast iron in a one-piece casting, the cores
being specially treated in the foundry to give
a very smooth surface on the casting itself,
which was carefully machined on all exterior
surfaces and carefully balanced in the factory
The runner has a specific speed of approxi-
mately 60, and is 75 inches in diameter,
measured at mid-point between the hub and
pan of the runner.
The complete unit is steadied by two guide
bearings, one being furnished with the gen-
erator and one with the waterwheel. The
bearing on the waterwheel is lined with
lignum vitae and is lubricated by means of
properly filtered water.
The weight of each complete waterwheel
unit is approximately 135 tons; the weight
of each volute casing is approximately 60
tons, and of the runner approximately 712
tons.
The turbine gates, together with the stems,
are single-piece steel castings, and are ma-
chined to present the smoothest possible surface
to the water flow. The gates are supported in
proper position by hard bronze bushings in
the casing heads. Each gate stem is connected
to a main operating gate ring by a gate arm.
which is attached to the stem by a tapered
shank feather key, washer and nut. The
main operating gate ring is supported in
bronze bearings on the upper casing head and
is operated by means of two specially designed
servo motors, which rest upon the main cas-
ing itself. The governor actuators which
control the flow of oil to the servo motors are
located on the generator floor. The governor
pulleys are driven by means of geared and
belted connections to the main waterwheel
shaft, and anti-racing mechanisms are pro-
vided between the governor actuators and
the piston rods of the servo motors. Each
governor is provided with an electric syn-
chronizing motor and mechanism for operat-
ing the governor from the main benchboard,
and also additional means for efficient hand
control.
The governor oil system is of the so-called
open type. A central pumping station is
provided with two pumps of the triplex type,
and space for one more in the future installa-
tion. Each pump is large enough to supply
the demands of three units, thus allowing
one pump to be held as a spare in case of
emergency in either the present or ultimate
installation. The pump takes its oil from a
specially designed sump tank located beneath
the generator floor and delivers this oil to the
servo motors through an S-in. pipe line at a
maximum pressure of 200 lb. per square inch.
After being used by the servo motors the oil
is returned to the sump tank through a 12-in.
low pressure line, thus it passes through the
necessary filters and screens into the original
sump.
A specially designed band brake, capable
of stopping the entire rotating element in five
minutes, is provided on the main shaft
between the waterwheel runner and the gen-
erator rotor. This brake consists of a flanged
pulley rotating in a steel brake band into
which are bolted blocks of maple, the band
being tightened around the pulley by a worm
gear operated by a hand wheel on the main
generator floor. The complete brake mech-
anism is supported by a steel framework
resting on cast iron sole plates in the con-
crete foundations.
The complete w-aterwheel equipment, servo
motors, and governor oil pumping and piping
systems were furnished by the Piatt Iron
Works Company. The governor actuators
were furnished by the Lombard Governor
Company.
Generators
The present installation consists of three
generators of the vertical revolving field type.
They are three-phase, 40-cycle machines, and
are rated, on a maximum continuous basis,
0000 kv-a. (7200 kw., 0.8 power-factor), at
12,000 volts, 185 r.p.m. When operating
under normal load at 0.8 power-factor, the
temperature rise will not exceed 50 deg. C.
on any part of the machine. The machines
are designed with an internal reactance to
limit the current of each generator under short
circuit conditions to approximately eight
times the normal full load value.
The guaranteed efficiencies are:
Full
Load
»4
Load
1 ,
Load
9000 kw.
1.0 power-
96.9
96 ('
96.3
95.3
94.8
7200 kw.
factor
0.8 power-
93.5
HYDRO-ELECTRIC DEVELOPMENT OF THE COHOES COMPANY 347
The regulation at U.S power-factor is
guaranteed to be 14 per cent, and the maxi-
mum excitation required 55 kw. at 250 volts.
The armature winding consists of form
wound coils of the barrel type, all coils being
interchangeable. The windings are Y-con-
nected, but the neutral connection is not
brought out to the terminal board at present.
Temperature coils are installed in the arma-
ture winding in accordance with the latest
practice.
The entire weight of the revolving element,
including the generator rotor, turbine runner
and shafts, is carried by a standard Kings-
bury bearing. One guide bearing is also
supplied with the generator, and is located
directly below the thrust block.
Fig. 7 shows the general mechanical
arrangement of the generators, and the heavy
bracket arm construction on which is supported
the Kingsbury bearing. A gallery is provided
on the top of the machine to facilitate inspec-
Fig. 7. View of Generator Room showing the 9000-kv-a. Generators
The rotor spider is made up of one solid
steel casting, with the pole pieces dovetailed
to the main spider, and the whole rotor
designed to withstand 80 per cent over speed
with an ample factor of safetv. The flvwhecl
effect (WR2) of the rotor is 1,700,000 pound-
feet.
The collector rings are brought out below
the rotor, eliminating the necessity of carry-
ing the field connections to the top of the
machine, either outside the stator frame or
through a hollow shaft. Any inspection that
may be necessary can be made from the pit
below the machine.
tion of the bearing, etc., and from this a
bridge leads to the river side of the generator
room, where a long narrow gallery is provided
which connects with each generator and is
reached from the floor level by a stairway at
either end.
Particular attention has been given to the
ventilation of the generators in the design
of the station. The oversight of this im-
portant feature in stations otherwise well
designed has often led to considerable trouble
from overheating of the generators; for if
no provision is made for admitting fresh air,
the air in the machine pit is used over and
34S
GENERAL ELECTRIC REVIEW
Fig. 8. Motor-driven Exciter Sets
over. Fresh cool air is taken from the outside
to the generator pit through air passages
specially designed for this purpose, and from
this pit the air is drawn up through the
machine by the fanning action of the rotor,
and discharged through ducts in the stator
into the room.
The generator field rheostats are motor-
operated and controlled from the bench-
board, the motor panels being located back
of the auxiliary switchboard on the
first floor and the rheostats placed
beneath in the rheostat room
already described.
A very complete oiling system is
installed for the generators, each
generator oil line being equipped
with sight flow indicators, oil
meters, recording and indicating
thermometers. Two storage tanks
are located in the roof trusses and
a filtering equipment in the base-
ment.
The outside diameter of the
generator is 16 ft. 4 in. and that of
the rotor 12 ft. 5^ in.; the weight
of the stator being 57,000 pounds
and that of the rotor 64,400
pounds.
Exciters
Excitation is furnished by two
horizontal motor-driven exciter
sets, each exciter being rated ]i>5
kw., 250 volts, 800 r.p.m. The
driving motor is a two-phase, 40-
cycle 2300-volt, form "K" induc-
tion motor rated 250 h.p. The ex-
citers are compound wound, with
interpoles, and each of sufficient
capacity to provide excitation for
three generators at full load. In
the ultimate installation one addi-
tional set of a similar type will be
installed as a spare unit.
A TA voltage regulator is pro-
vided on the switchboard for use
with the exciters, and under normal
conditions each exciter will feed
into a common exciter bus, from
which the generators will receive
their excitation. As will be seen
from reference to Fig. 7, a double-
throw switch is also provided so
that either exciter can be thrown
on to the direct current power
bus, from which the crane is
operated.
The induction motors are started from
a starting bus taking power from 50 per
cent taps on the 2300-volt transformers, so
that no starting compensators are required.
Fig. 8 shows a view of the exciter sets.
Transformers
There is at present no high tension trans-
mission system, the bulk of the power being
delivered at the generator voltage of 12,000
Fig. 9. 400-kv-a. Transformers and Controlling Oil Switches
HYDRO-ELECTRIC DEVELOPMENT OF THE COHOES COMPANY
349
volts, and therefore step-up transformers are
not required-
Four single-phase transformers in two banks
are provided to furnish power to the 2300-vdlt
feeders, the street lighting circuits, and the
induction motors of the exciter sets. They arc
oil-insulated, oil-cooled units, each rated
400 kv-a., with 25 per cent overload for two
hours. They transform from 12,000 volts,
three-phase to 2300 volts, two-phase, and are
T-connected on the primary side and four-wire
on the secondary side. They have four 2^2
per cent secondary taps, and also 50 per cent
starting taps for the induction motors. The
guaranteed efficiencies at full load is 98.1.
Reactances are placed in each outgoing
12, 000- volt feeder and on the primary side
of each transformer circuit.
Switchboard and System of Connections
The switchboard equipment consists of
three separate boards, viz.. the main bench-
board, a vertical control board, and one
combination exciter and station service board.
There are also four independent constant
current street lighting panels. All the boards
are made of natural black slate, with the
exception of the four constant current panels
which are blue Vermont marble.
The benchboard controlling the 12,000-volt
section of the station, including the gen-
erators, exciters, 12,000-volt feeders and bus,
consists of seven panels, each with a vertical
panel back of it, the whole being enclosed by
grille work. There is one combination exciter
and transformer panel, two combination
generator bus sections and outgoing feeder
panels, one combination generator and out-
going feeder panel, two future generator and
outgoing feeders (one of which has one bus
section equipment installed at present), and
one station panel.
The bench section has a mimic bus, showing
in detail a complete one-line diagram of the
main station equipment. This also contains
the control switches for the remote controlled
oil switches and the synchronizing receptacles.
The vertical section above the bench contains
the indicating meters, each generator circuit
being provided with an ammeter in each
phase, a voltmeter and indicating wattmeter,
a power-factor indicator, a speed indicator,
and a field ammeter. Each exciter has an
ammeter, and one common voltmeter is
provided, which can be connected to any
exciter. The vertical section below the bench
contains the control switches for the remote
controlled rheostats and governors, the exciter
and equalizer rheostat handwheels, and the
station bell alarm relay.
The vertical section in the rear of the bench
panels, which as mentioned above is inside the
office, contains the recording and curve-
Fig. 10. View of Benchboard
drawing meters, relays and testing terminals
for this equipment. A rather novel and useful
arrangement is a flat slate bench or table
below the testing terminals, extending the
full length of the board and about 20 in. wide,
which is provided for convenience in meter
testing. A curve-drawing wattmeter is pro-
vided for the totalizing panel, and a recording
wattmeter for each of the outgoing ]2,iiun-
volt feeder circuits.
The double vertical board controls the
2300-vol1 section of the station, and the
general arrangement of this is similar to 'the
benchboard, except that there is no bench
section. This consists of seven panels wit It
corresponding rear panels. On the central
part of the panels is another mimic bus
showing a one-line diagram of the 2300-volt
equipment, with the indicating meters above.
A TA250, K22 voltage regulator is mounted at
one end of the board for maintaining the cor-
rect field voltage under all conditions of load.
The back section is similar to that of the
main benchboard and mounts recording watt-
350
GENERAL ELECTRIC REVIEW
Fig. 11. 2300-volt Control Switchboard
hour meters, relays and testing terminals.
It also has a testing meter bench similar to
that of the benchboard.
The solenoid-operated remote-controlled
generator field switches, the exciter line
switches, low-voltage station lighting and
power feeder switches, and storage battery
control are mounted on a vertical board
consisting of six panels.
This board is located on
the first floor near the
exciters, all other switch-
boards being on the first
gallery.
The general system of
connections of the whole
station is shown in Fig. 13.
From this it will be noted
that the control of the
station is really divided into
two sections, one the 12,000-
volt, three-phase section,
including the main genera-
tors, ring bus, and 12,000-
volt outgoing feeders; the
other the 2300-volt, two-
phase section, including the
induction motors, 2300-volt
outgoing feeders, constant
current feeders, and the
station service equipment
through the step-down trans-
formers.
The generator, bus sec-
tion, and outgoing 12,000-
volt feeders are all equipped
with K21, solenoid-operated
oil switches. The generator
switches are of 500 amperes
capacity, non-automatic.
The bus section switches are
800 amperes and also non-
automatic, but the two end
switches are arranged so
that they can be made auto-
matic by throwing in current
transformers and inverse
time limit relays through a
small knife switch on the
benchboard. The outgoing
line and transformer
switches are of 300 amperes
capacity, automatic type,
and are also fitted with
inverse time limit relays.
Provision is made for a
fourth oil switch in the main
generator circuit in case it is
later decided to bring out and ground the
neutral. On the 2300-volt equipment, Ko oil
switches are used throughout, and are solenoid-
operated except on the street lighting feeders,
which are hand-operated. They are auto-
matic and also equipped with inverse time
limit relays, with the exception of the
switches between the transformers and
Fig. 12. Exciter and Auxiliary Switchboard and Battery Charging Set
HYDRO-ELECTRIC DEVELOPMENT OF THE COHOES COMPANY 351
induction motor busses which are non-
automatic.
A 125-volt, 60-cell storage battery fur-
nished by the Electric Storage Battery Com-
pany is installed for supplying the control
circuit and emergency lighting. This has a
200-ampere maximum instantaneous dis-
charge rate and a 10-ampere, S hour rate.
For charging the battery a 3^-kw. battery
charging set is supplied and is operated
continuously with the battery floating. The
generator is driven by a 220-volt, two-phase
motor, the set being located on the first floor
near the auxiliary switchboard.
Lightning Arresters
The 12,000-volt feeders are each supplied
with triple-pole aluminum cell lightning
arresters arranged for an ungrounded system.
On the 2300-volt feeders double-pole multi-
gap graded shunt arresters are used and for
the constant current arc circuits, double-pole
horn gap arresters are supplied.
Distribution System, Etc.
There are at present six outgoing 5000-kw.,
12,000-volt, three-phase feeders, with pro-
vision for a future installation of four more;
two 2300-volt, two-phase, four-wire power
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Fig. 13. One line Diagram of Station Connections
Station Auxiliary Equipment
Energy tor the station lighting and small
motor service is supplied from the 2300-volt,
two-phase bus through two 50-kv-a., single-
phase transformers, giving 220/110 volts
on the secondary side, the motors all being
arranged for 220-volt, two-phase service.
One spare transformer unit is furnished.
Single-phase, induction type automatic
feeder regulators are installed in each of the
2300-volt local feeders and are supplied
complete with limit switches, contact-making
voltmeters, line drop compensators, etc.
They are designed to give five per cent buck
or boost. The constant current transformers
are rated 75 light. 2300 volts, 6.6 amperes.
A motor-driven air compressor with auto-
matic governor and supply tanks is installed
for general station work.
and tie feeders, four 2300-volt, single-phase
local feeders, and four arc lighting circuits.
The 12,000-volt lines leave the station
through roof entrance bushings in the roof of
the gallery section, and the 2300-volt lines
through wall entrance bushing. All lines
run to steel towers set on extensions of the
concrete foundation of the gate house, the
12,000-volt lines being placed at the top and
the 2300-volt lines below. From these towers
the Troy and Albany lines will go over the
roof of the gate house and across the canal,
then directly to these two cities; the Cohoes
lines running in a general downstream direc-
tion, the 12,000-volt lines going to the various
mills and the 2300-volt tying into the existing
distribution system.
The street lighting feeders will supply a
series incandescent system for the city of
352
GENERAL ELECTRIC REVIEW
Fig. 14. 12,000-volt Oil Switch and Bus Arrangement
Cohoes and the single-phase feeders will
furnish power for commercial lighting, etc.
The two-phase feeders will tie in for emer-
gency power with a small
water power station of the
Cohoes Company located
about three-quarters of a
mile- below, and known as
the Champlain Dam station,
and also with the steam
station of the Harmony
Mills. This steam station has
a capacit y of 251 )l I k w. , power
being generated at GOO volts,
40 cycles, three-phase, and
stepped up for the tie line to
2300 volts, two-phase by two
50-kw. T-conneeted trans-
it .micrs. This steam station
will be retained by the Har-
mony Mills, as steam is
required in some of their
manufacturing processes as
well as for heating, and it
can also be utilized for emer-
gencv service.
Of the 12,000-volt lines, two are to run to
Troy and two to Albany, the transmission
lines for which will be erected later, and the
other two will feed the numerous mills and
factories in Cohoes. This mill load will be
one of the principal divisions of the load on
the new station, as there are at present some
3G mills that it is expected will be connected
to the system, taking a total load of over 6000
kw. Of this amount over one-half will be
delivered to the Harmony Mills. At this
mill and some of the other larger ones,
outdoor transformer substations will be
installed to step down to GOO volts for the
mill service.
Organization, Etc.
The entire engineering work of the installa-
tion, including the hydraulic and electrical
work, has been done by Sanderson & Porter,
of Xew York City, with Mr. Thomas E.
Murray as Consulting Engineer. The con-
struction work has been carried on under
their supervision and directly by the Cohoes
Company, of which Mr. L. Semple is
President, Mr. W. P. Parsons, General
Manager, and Mr. A. C. Polk, Construction
Superintendent.
The electrical equipment of the power
station, with some minor exceptions, was
supplied by the General Electric Company.
Fig. 15. View of 2300-volt Oil Switch and Bus Arrangement; also Series Lighting Panels
353
X-RAYS
Part II
By Dr. Wheeler P. Davey
Research Laboratory, General Electric Company
This installment of the series of articles on X-rays treats of the general properties that are possessed by all
rays of this name. The introductory paragraph lists the properties, and these are described in detail under
their respective headings in the article. — Editor.
There are
are common
(1) The
(2) The
(3) The
(4) The
(5) The
(6) The
(7) The
(8) The
(9) The
certain general properties which
to all X-rays. Among these are
fluorescent effect
photographic effect
ionizing effect
chemical effect
dehydrating effect
photo-electric effect
action on a selenium cell
penetrating effect
physiological effect
(1) The Fluorescent Effect
Certain uranium compounds and certain
salts of the alkali and alkali-earth metals
have the property of fluorescing, i.e., of giving
off visible light when exposed to the action
of X-rays. Many of these compounds
phosphoresce, i.e., continue to give off light.
for a short time after the X-rays have been cut
off. In order to be of great use in X-ray
work, a fluorescent screen should possess the
following characteristics: (a) the color of the
light should be such as to give good visual
acuity; {b) the intensity of light per unit
intensity of X-rays should be as great as
possible, and should not decrease with con-
tinuous operation of the screen; (c) there
should be as little phosphorescence as possible,
and (d) the crystals of the fluorescent salt
must be so small that the "grain" of the
screen is not visible when the screen is in use.
The selection of a material possessing these
qualifications is a long tedious task, for the
fluorescent properties of a given salt are
greatly changed by the addition of minute-
amounts of impurities. A salt showing almost
no fluorescence when pure may fluoresce
brightly when mixed with but a fraction of one
I ler cent of some other salt. In spite of the fact
that each formula for fluorescent material is
entirely empirical, there are three or four vari-
eties of screens on the market which meet the
requirements given in the preceding paragraph.
All of these give off light whose intensity is
determined by the current through the X-ray
tube, the voltage across the tube, and by the
distance from the target of the tube. If the
intensity of the fluorescent light is plotted
against either the current or the voltage,
the resulting curve is a straight line or a
succession of straight lines.* As would be
expected, the intensity varies inversely as the
square of the distance between the fluorescent
screen and the target of the tube.
I 2 ) The Photographic Effect
X-rays have much the same effect on a
photographic plate as ordinary light. Just
as photographic plates are more sensitive to
certain wave lengths of light than to others,
in the same way they are found to be more
sensitive to certain wave lengths of X-rays
than to others. This is usually explained .
by assuming that the plate is most sensitive
when exposed to X-rays of such wave length
as will excite characteristic secondary rays
from one or more of the elements in the
emulsion. Since all manufacturers do not
necessarily use the same chemicals in making
their X-ray plates, it follows that (a) all
brands of plates do not have the same speed
when excited by X-rays of the same wave
length, (b) a plate which is exceptionally
"slow" when excited by rays of long wave
length (i.e., little penetrating ability) may
be quite "fast" when used with rays of short
wave length (i.e., great penetrating ability).
It is impossible to focus X-rays as one
would focus visible light in ordinary photog-
raphy. Radiographs arc merely shadow
pictures. If all parts of the object to be
radiographed were of the same transpafency
to the rays.f all that one could possibly
obtain would be a uniform blackening of the
photographic plate. But, if one part of the
object is more opaque to X-rays than some
other part, then the radiograph will show a
corresponding change in density-. Thus we
are able to obtain radiographs of the human
body because of the different opacities of
* J. S. Shearer, Amer. Jour. Roent.. November. 1914.
t Transparency to X-rays has no relation to transparency
to ordinary light. An object may be quite opaque to ordinary
light and yet be very transparent to X-rays, and vice versa.
354
GENERAL ELECTRIC REVIEW
various tissues, and it is possible to show-
holes in metal eastings because of the dif-
ferences caused in the thickness of the metal.
In ordinary photography the chief variables
to be considered are exposure and development.
In radiography there is an additional variable,
fTo Electrometer
To Earth
-5»XRo.J>6
ToEaj-lh
Fig. 1. An Ionizing Chamber
namely, penetration. In choosing the proper
penetration, the radiographer must con-
stantly bear in mind that as the penetrating
ability of the X-rays is increased there is an
increased tendency to blur the picture,
because of scattered rays. It is also necessary
to remember that a radiograph taken with
very penetrating rays is less "contrasty" than
one taken with rays of moderate penetration.
For any given amount of exposure, the
optimum penetration is, therefore, that
penetration at which the most opaque part of
the object permits only a very slight darken-
ing of the photographic plate.
Radiographs are always examined as neg-
atives. A radiograph is therefore of proper
density when it can be easily viewed against
a clear north sky. This is, as a rule, much
denser than is advisable for making the best
positive prints.
(3) The Ionizing Effect
If a charged body is exposed to X-rays, it
will be found to lose its charge. This is
explained by assuming that the air in the
path of the X-rays becomes broken up into
ions, or electrically charged atoms. The air
thus becomes a conductor of electricity and
causes the charge to leak away. While the
quantity of charge carried by different ions
is not always the same, still it is always some
exact whole number times 4.9016 X10-10
electrostatic units of charge.*
Fig. 1 shows an ordinary form of ionization
chamber. Two thin sheets of aluminum foil
form the ends of a metal cylinder. Midway
between them and insulated from them is
another thin piece of aluminum foil. This
middle sheet is connected to a quadrant
electrometer, or to an electroscope. In some
cases it is possible to obtain a current large
enough to measure with a galvanometer
connected between the inner and outer plates.
This type of ionization chamber has many
advantages. (Some of its objectionable fea-
tures will be taken up later.)
Suppose such an ionization chamber to be
exposed to the action of X-rays of constant
intensity and wave length. If the difference
of potential between the inner and outer
sheets is small, the ionization current will be
small. As this difference in potential is
increased, the ionization current increases,
but at last a condition of "saturation" is
reached in which the current is independent
of the voltage. At very high potential dif-
ferences the current once more increases and
sparking soon occurs. Fig. 2 shows the form of
the voltage-current curve of an ionizing
chamber.
Sa.rur^
Sparking / /
1 /
ion Current^/ —
* R. A. MUlikan, Science. 23. pp. 436-448. Sept. 30. 1910.
This is the strongest evidence we have that electricity has an
atomic structure. The charge on an electron is 4.9016 X10-"1
e.s. units.
C
L.
3
Applied Porenn&l
Fig. 2. Voltage-Current Curve of an Ionization Chamber
In scientific work quantity of X-rays is
measured in terms of the amount of electricity
which the rays are able to cause to flow from
one terminal of the ionizing chamber to the
other. In such measurements it is absolutely
necessary to have a saturation current
X-RAYS
355
through the ionizing chamber, otherwise
the amount of electricity carried across will
depend largely upon the potential difference
between the plates of the chamber. It is
also necessary to make sure that the chamber
is of proper design and of suitable material.
Owen,* and Barkla and Philpott have
shown that, except when characteristic rays
of the gas were strongly excited, ionization
in that gas was practically independent of the
wave-length of the X-rays employed. Their
results are collected in Table I. Methyl
Iodide appears to be an exception to this rule.
In a previous article it was stated that
when X-rays of sufficient penetrating ability
fell upon a body that body became a source
of characteristic X-rays. Under such con-
ditions the body also gives off a large number
of electrons (secondary corpuscular radiation) .
These electrons have the ability to ionize
any gas in which they find themselves. It
is at once evident that there are serious
limitations imposed upon an ionizing chamber.
Before the amount of electricity transferred
from one terminal to the other may be taken
as a measure of the quantity of X-rays, it is
necessary to make sure that the material
used in its construction is not giving off
secondary corpuscular radiation. It is equally
necessary to make sure that the gas used in
the chamber is not itself giving off secondary
corpuscular radiation. An ideally designed
chamber is so constructed that it is impos-
sible for the direct X-ray beam, or the second-
ary X-rays scattered by the gas, or the
secondary rays characteristic of the gas to
strike its walls. It is almost impossible to
design a chamber such that all these con-
ditions will be fully met under all circum-
stances. Usually the design is made such as
to be quite satisfactory for use with the wave-
length of rays that are to be measured.
In many cases it is necessary to measure
the total amount of energy in the X-ray
beam. This may be done by using an ioniza-
tion chamber long enough to completely
absorb all the rays.
C. T. R. Wilson has shownj that it is
possible to condense water-vapor upon ions,
thus making the path of the ions visible.
Fig. 3 shows the arrangement of his apparatus.
A steel ball was fastened to a very heavy
ball by a thread. The heavy ball was hung
by a stout cord. When the cord was suddenly
loosened the ball dropped a short distance,
opening a valve. This caused the bottom of
the expansion chamber to be quickly lowered
and produced a condition of supersaturation
of the moisture in the expansion chamber.
The stopping of the large ball broke the
thread, thus allowing the smaller steel ball to
fall freely. In its descent it closed a spark-gap,
allowing a condenser discharge to pass
through the X-ray tube. After a predeter-
mined interval it closed a second spark-gap
which allowed another condenser discharge
to pass through a mercury vapor lamp. This
illuminated the cloud in the expansion
chamber, and enabled the paths of the ions
to be photographed. A characteristic photo-
graph is shown in Fig. 4. As a result of his
work Wilson could find no direct action of the
* E. A. Owen, Proc. Roy. Soc. A, 86, pp. 426-439, 1912.
t Barkla and Philpot. Phil. Mag. xxv, pp. 832-856. 1913-
t Proc. Roy. Soc. A 85, p. 285, 1911.
Proc. Roy. Soc. A 87. pp. 277-292, 1912.
TABLE I
RELATIVE IONIZATION PRODUCED IN VARIOUS GASES BY HOMOGENEOUS X-RAYS
IONIZATION RELATIVE TO AIR =1
Emitting
Hi
0»
COl
SOi
CiHsBr
CH,I
K Radiation
(Beattyl
(B.&P.)
(Owen
(Owen)
(B.&P.)
(B.&P.)
Fe
0.00571
1.37
1.58
11.3
41.2
Ni
1.35
1.55
11.6
162
Cu
0.00573
1.38
1.55
11.8
42
152
Zn
0.00570
1.42
1.54
11.5
41.6
As
0.00573
1.27
1.51
11.7
42.2
158
Se
1.31
1.53
11.8
41.7
Sr
1.28
1.53
11.8
153
Mo
1.28
1.54
11.5
213
188
Ag
Sn
1.32
272
198
0.04
1.29
335
205
Sb
1.28
I
211
Ba
251
356
GENERAL ELECTRIC REVIEW
X-ray upon the gas. The only role of the
X-rays seemed to be that of causing the gas
to give off electrons (i.e., ionize the gas).
These electrons, by impact upon the mole-
cules of the gas, cause further ionization.
At-ing Sp^rk
^THrea.d
X Ro.y Spo,rk Go.p
H
h\H
I Mumino.rin6 Spa.rk Ofcp
Fig. 3. Diagram of Wilson's Apparatus for Photographing
the Paths of Ions
(4) The Chemical Effect
Except for the action of X-rays upon the
materials in the film of a photographic plate,
the only chemical actions so far noticed seem
to be a precipitating effect, and a hydrolytic
effect. Iodine is precipitated from its solution
in chloroform by exposure to the rays.*
Schwartz has found an ammonium oxalate-
mercury bichloride mixture which precipitates
calomel under the action of X-rays. f
When starch is exposed to the rays, it is
changed into soluble starch and then into
dextrin. |
(5) The Dehydrating Effect
Ammonium, potassium. barium, and
magnesium platinocyanides change color
when exposed to X-rays, due to dehydra-
tion^
* H. Bordier and J. Galimard. Arch. d'Elect. Med. 14.
Aug. 10. Sept. 10. 1906.
t G. Schwartz. Wein Med. Presse, xlvii, 2092. 1906.
t Colwell and Russ. Arch. Middlesex Hosp. xxvii, p. 63.
§ Bordier and Galimard, Arch d'Elect Medical. Mav 10.
1905.
G. Holzknecht. Arch. d'Elect. Med.. Oct. 10, 1910.
n-au, Comtes Rendus 129, pp. 956-957. Dec. 4. 1S99.
Athanasiadis. Annd. Phys..27.4. pp.890-S96, Nov. 26. 190S.
(6) The Photo-Electric Effect
As was stated in the discussion of ioniza-
tion, when a body gives off characteristic
X-rays it also gives off electrons. These
electrons leave the body with the same
velocity that a cathode stream would need to
in order to produce the X-rays characteristic
of that body, this is true no matter what the
intensity or wave-length of the exciting
X-rays may be. This effect corresponds in
every way to the well known photo-electric
effect in which a clean metal surface gives off
electrons when illuminated by ordinary light.
(7) The Action on a Selenium Cell
X-rays affect the electric resistance of a
selenium cell in the same manner as light, ^f
(8) The Penetrating Effect
All substances exert more or less of an
absorbing effect on X-rays. In general, the
absorbing effect of any given substance for a
given bundle of rays depends upon the
material used as a target in the tube, the
nature and thickness of the absorbing sub-
stance, the history of the radiation after
leaving the target, and the potential drop
across the tube at the instant the given
bundle of rays is given off.. Ordinarily, if the
target in the tube is "a substance of high
atomic weight, then rays from that tube will
be less readily absorbed than if the target
had been of low atomic weight.
Fig. 4. Photograph of Paths of Ions taken by C. T. R. Wilson
When rays from an ordinary X-ray tube
pass through a substance some of the radia-
tion is absorbed, so that the emergent beam
acts more feebly on a fluorescent screen,
photographic plate, selenium cell, or ionizing
chamber. If rays from a platinum-target
X-RAYS
357
tube, operating under ordinary working con-
ditions, are made to pass through silver,
the intensity of the emergent beam may be
calculated from the formula,
I = !„«->*
in which
I0 = intensity of the incident beam.
J = intensity of the emergent beam.
* = base of natural logarithms = 2.7182.
X = thickness of the absorber.
X = coefficient of absorption of the sub-
stance used as absorber.
X is very approximately independent of the
thickness of the silver.*
All substances for which the above law
holds true' are said to be "aradiochroic." If,
however, the rays are made to pass through
sheets of aluminum, tin, etc., the above law
does not hold. The value of X as calculated
by the formula is different for different
thicknesses of the absorbing sheet; but, as
the thickness is increased, X approaches
more and more nearly to a constant value,
and the law holds approximately if the sheet
is thick enough. The formula may also be
made to apply approximately if the difference
in thickness between two absorbing sheets is
so small that the value of X has not changed
appreciably, due to the change in thickness.
Absorbers which act in this way are said to be
"radiochroic," and are often called "filters."
These facts may be explained by assuming
that an X-ray tube sends out a complex
radiation ("heterogeneous beam") composed
of primary rays and secondary rays character-
istic of the target. In aradiochroic substances
the coefficients of absorption for the com-
ponent beams are approximately the same.
In radiochroic substances the beams arc
unequally absorbed. If the filter is thick
enough to completely absorb all but one of the
components, the emergent beam is said to be
"homogeneous," and the absorption law will
hold accurately for any absorber through
which the beam may subsequently pass,
provided no secondary rays characteristic of
the absorber are produced. It is to be noticed
that no substance is absolutely aradiochroic.
Silver is probably the most nearly aradiochroic
metal for the rays given off by a tube with a
platinum target; but it is quite radiochroic for
the rays given off by a lead target, f because
of being more opaque to the "secondary"
component than to the "primary" com-
ponent of the beam. If the absorber is of the
same material as the target, it is more opaque
to the "primary" component than to the
"secondary" component; but the two
absorption coefficients may be so nearly
equal as to cause the absorber to appear under
some conditions to be almost completely
aradiochroic. +
If the absorber is of the same material as
the target, then X decreases as the potential
difference across the tube is increased, and
the decrease of X with the increase of the
potential difference is much more marked the
higher the potential difference employed. §
If the absorber is a chemical compound,
the total absorption under any specified con-
ditions is the sum of the various absorptions
caused under those conditions by the various
atoms and radicals of which the absorber is
composed.^
As a rough-and-ready means of determining
the penetrating ability of X-rays, physicians
use what they call "penetrometers." Of
these the Benoist and the Whenelt are the
most accurate. In both of these instruments
the opacity of a standard sheet of silver is
matched against the opacity of aluminum of
various thicknesses. In the case of the
Whenelt penetrometer, a standard piece of
silver is fastened to a fluorescent screen. A
specially shaped wedge is slid past the screen
until a thickness is at last reached such that
the illumination of the screen under the
aluminum is the same as that under the
silver. The penetrating ability or "hardness"
of the rays is read on an arbitrary scale.
The Benoist penetrometer consists of a
disk of silver 0.11 mm. thick. Around this
disk, arranged like a circular staircase, are
steps of aluminum, each step being one
millimeter higher than the one preceding.
A radiograph of the penetrometer is taken
and the " hardness ' ' is defined as the number of
millimeters of aluminum which are as opaque
as the disk of silver. Care must be taken not
to over-expose the radiograph, otherwise
the whole negative will be blurred and a
correct reading will be found impossible.
(9) The Physiological Effect
When X-rays are directed toward a given
layer of flesh, in general, some of them pass
through while others are absorbed and give
up their energy to the flesh. If sufficient
* L. Benoist, Journal de Physique, 1901.
J. Beloit. Arch d'Eleet. Med., Aug. 10. 1910.
t W. R. Ham, Phys. Rev. sis, 1. Jan. 1910. pp. 104-105. 118-
120.
tG. W. C. Kaye, Camb. Phil. Soc. Proc. 14, pp. 236-24.5,
Oct. 15, 1907.
Rov. Soc. Phil. Trans. A. 209. pp. 123-151. Nov. 19, 1908.
5 W. R. Ham. Phys. Rev. x\x, 1, pp. 108, 111-113. Jan.. 1910.
11 W Seitz, Phys. Zeitschr. 13, pp. 476-480, June 1. 1912.
Blennard and Labesse. Comtes Rendus. 1S96, exxii. pp. 723-
725.
358
GENERAL ELECTRIC REVIEW
energy is thus delivered to the flesh, serious
pathological changes result which are of
great importance from the viewpoint of the
physician, but which do not concern the
physical investigator, aside from the question
of his own self -protection. A person in good
health may have several radiographs taken
(sufficient for ordinary diagnostic work) by
a well-informed operator, without any danger
of an X-ray burn; but the operator, or
* Archives of the Rontgen Ray, July, 1913.
research-physicist, must, because of the pos-
sibility of long-continued exposure or more
often because of frequent repetition of short
exposures, protect himself most carefully.
The German Rontgen Society recommends
that for work such as is ordinarily done by
physicians the protection should consist of
at least two millimeters of sheet lead, eight
millimeters of X-ray proof rubber impreg-
nated with lead, or lead glass from ten to
twenty millimeters thick.*
WATER POWERS OF NEW ENGLAND
By Henry I. Harriman
President of Connecticut Rives Power Company
Mr. Harriman shows how the industrial centers of New England owe their origin to the presence of water
power in their immediate neighborhood. He cites some of the early conditions governing the use of water power
and refers to the available supply and the economies to be secured by their development. — Editor.
Conservation and efficiency are the pass-
words of the Twentieth Century. Con-
servation deals with the creation of effort;
efficiency with its application, and together
they symbolize the fundamental philosophy
of our time, namely, that all energy and
effort should be created in the most eco-
nomical way, and applied in the most useful
manner. Efficiency and conservation deal
with all classes and kinds of human and
mechanical effort, but they are particularly
associated with the generation and appli-
cation of power, and in this special field
the use of electricity has become almost
synonymous with efficiency, and its generation
by water has, at least in the popular mind,
become associated with conservation. It is
therefore particularly fitting to briefly con-
sider the utility and value of New England's
very great water power resources.
The use of water power in New England
dates back to its very earliest history. John
Alden owned and operated a water mill near
Plymouth, and near Little Compton, Rhode
Island, can still be seen the old Peregrine
White mill, owned by and named after the
first white child born in New England.
Our forefathers in coming to this country
were dependent upon their own efforts to
raise their own food and build their own
shelter, and among the first necessities of life
that confronted them was the abilitv to
grind their corn and wheat into flour, and
to saw the timber from which to make their
homes. They were familiar with the grist
mills and the saw mills of England, and well
understood the construction and operation
of primitive dams and waterwheels, and the
use of the energy of falling water. It was
therefore natural that our streams should
have been put to useful labor in the very
earliest Colonial days.
So vitally necessary to the life of the
community did these water mills become that
within seventy-five years after the landing
of the Pilgrims at Plymouth, two of the
colonies had evolved the principle of the
Mill Act — a principle entirely unknown to
the common law of England — which gave to
the owner of a dam-site the right to flow
out the land of his neighbor in order that
water power might be created.
With this limited right of eminent domain
thus early created, there also went a limited
duty of public service, and in early Colonial
times definite rates were sometimes estab-
lished by law for the grinding of grain and
the sawing of logs. The establishment by
law of definite rates was, however, unusual,
and more frequently the water mill was
co-operatively owned and operated by the
largest timber owners of the district. The
opportunities for the development of power
were, however, so many, and co-operatively
WATER POWERS OF NEW ENGLAND
359
owned mills so numerous, that all vestige of
public regulation ceased long before the
outbreak of the American Revolution.
The doctrine of the English common law,
that the riparian owner on a non-navigable
stream owned the bed of the river to the
center of the stream, has always been accep-
ted in our New England states, as has also
been the right of the owner to construct
a dam upon his land, this right being sub-
ordinate, however, to the right of all owners
along a water course to have the water flow
by in a reasonably uninterrupted manner,
and to the rights of the public to float logs
and to exercise certain other public privileges.
The invention of the cotton gin, the loom
and the spinning-jenny ushered in a new era
in manufacturing, and greatly increased the
demand for mechanical energy, and whereas,
up to the beginning of the Nineteenth Century
the use of water power has been very largely
limited to the making of flour and lumber,
with the advent of the new century there
was witnessed a very great increase in the
development of our streams for the opera-
tion of cotton and woolen mills, and asso-
ciated industries. The process of manufac-
turing paper from ground wood was also
developed, and a large amount of power
so utilized. It is true that the steam engine
had been invented, coincidentally with the
other great inventions that signalized the
close of the Eighteenth Century, but it was
still a new and crude mechanism, and its
use very limited. In fact it is fair to say that
up to 1850, 90 per cent of the power required
by our industries was derived from the energy
of falling water.
New England has always been preeminent
as a center for all kinds of manufacturing.
Her rugged coasts and barren hills, and her
relatively poor soil, did not lead to such an
extensive development of agriculture as took
place in our Middle and Southern states; and
her trend was naturally toward the manipu-
lation rather than the growing of raw
products which could better be raised else-
where. Hence there sprang up, around her
more important and accessible water falls,
great manufacturing centers, such as Lowell,
Lawrence, Lewiston, Manchester, Holyoke,
and many other towns.
It was not then possible to carry power
any material distance from the site of the fall.
The industry must go to the water power and
not the water power to the industry. In fact,
there is hardly a single manufacturing city of
any size in New England whose origin cannot
be traced back to the development of some
water fall within its limits.
Manufacturing started in New England
long before coal was used, before the locomo-
tive was thought of, and almost before
the steam engine had been invented, and
the use of water power was almost universal
as a source of energy until the close of the
first half of the Nineteenth Century. Then,
as manufacturing facilities increased and as
the more desirable water powers were com-
pletely utilized, and as the efficiency and
reliability of the steam engine increased,
manufacturers turned from water power to
steam power, preferring to locate their mills
and factories on the sea-board, or in large
centers of population where labor conditions
were best, rather than to follow the courses of
the streams back into the high hills. Thus for
nearly forty years water power development
in New England was neglected. But with
the development of the art of electric genera-
tion and transmission it became possible to
bring the power to the manufacturer, and
to have the double advantage of locating
in the large cities, and of utilizing cheap
power generated by water.
The beginning of this century was marked
by a great development of the more remote
water powers of the country, and the trans-
mission of electricity therefrom to the large
centers of population. In the New England
states, however, the largest and most con-
spicuous powers had been developed and
utilized long before the advent of electric
transmission, and therefore the first great
distribution systems of the country were
built in the Western and Southern states.
The Pacific Coast was a pioneer in this class
of work, largely because of the scarcity and
high price of coal, and the first transmission
line to exceed 50 miles in length was built by
the predecessor of the Pacific Gas & Electric
Company, extending from the foot hills of
the Sierras into San Francisco. Another step
in electric transmission was marked by the
building of a line 150 miles long from the
Kern River to Los Angeles while the recent
construction of a line from Big Creek to that
same city spanning 250 miles marks the maxi-
mum transmission distance thus far attained.
Extensive electric transmission systems have
also been constructed in the Southern states,
the Southern Power Company having a
network of between 400 and 500 miles of
line which link together nearly all of the
larger manufacturing centers of North and
South Carolina.
360
GENERAL ELECTRIC REVIEW
While it is true that many of the large
water powers near the chief cities of the New
England states had been developed long before
the advent of electricity, it is still true that few
sections of the country offer greater opportuni-
ties for hydro-electric development and trans-
mission than our own New England states.
An interesting computation has been made
as to the theoretical amount of energy which
might tinder ideal conditions be generated
by water in our six states. On the assump-
tion that the average run-off in New Eng-
land is in excess of 18 in.; that its area
is approximately 60,000 square miles, and
that its average elevation above sea level
is 900 ft., it is computed that it would
be theorcticallv possible to develop, for
3000 hours of 'each year. 15,500,000 horse
power, this being equivalent to the use of
52,000,000 tons of coal annually. Of course
such a computation is nothing but an interest-
ing mathematical calculation. It is, however,
entirely possible that 10 per cent of this
theoretical power may at some time be devel-
oped from its streams, and that New England
may annually produce energy equivalent to
that which could be produced from the use of
5,000,000 tons of coal.
In the New England States there are
eight large rivers with very great fall, namely:
TOTAL FALL
IN FEET
Penobscot 1500
Kennebec 1 ill ill
Androscoggin 2200
St. Croix' 400
Saco 1900
Mcrrimac 269
Connecticut 2000
Hoosatonic 900
These rivers drain 35,000 out of the 60,000
square miles of New England, and because
of their great water shed and large drop, are
its greatest sources of present and future
power. Along these rivers are found its
greatest water power developments and its
largest manufacturing centers.
An estimate has also been made by the
Bureau of Corporations showing that in the
six New England states there is now developed
and in use over 600,000 horse power of water
energy, but that these same water powers if
properly reconstructed along modern scien-
tific lines could generate an add tional 200,000
horse power. The same report shows that
there is possible of creation in the New
England states water power developments
aggregating 1,000,000 horse power which
by storage and by the utilization of some of
the less desirable falls, can be ultimately
increased to 2.000,000 horse power. The
State of Maine leads, both in developed and
undeveloped water power, having a maximum
possible development of nearly 1,000,000
horse power; the power of New Hampshire,
Vermont and Massachusetts is reckoned
between 2(11), 000 and 300,000 horse power
each; Connecticut has Kill, ODD horse power,
and Rhode Island ends the list with a possible
16,000.
There is little doubt that New England
can absorb all of the power which can
be developed within its limits, for it is
one of the greatest and certainly the most
diversified center of manufacturing in our
country. The Census Department gives the
total value of all the manufactured products
of the United States at 820,000,000,000 per
year, and the six states east of the Hudson,
with approximately 2 per cent of the area
of the country and about 4 per cent of its
population, produce over 10 per cent of this
great total. The boots and shoes manu-
factured in New England are valued at
approximately $300,000,000; its cotton mill
products are worth an equal amount; its
woolen mills produce goods valued at
$200,000,000 and its paper mills add to this
an additional $100,000,000 of product. It is
also interesting to note that in no other
section are there so many small manufacturing
concerns. Massachusetts alone has over Mil in
separate manufacturing companies, the total
in the New England states being in excess
of 12,(100, and while centralization in the
ownership and control of industry has been
most marked in the Middle and Western
states, in New England there has been an
actual increase in the number of productive
concerns and a decrease in their average size.
The mechanical and engineering problems
connected with the development of water
power and with the transmission of electricity
therefrom, to any distance up to 200 or even
250 miles, may be considered solved, and the
question to be settled is now one of com-
mercial feasibility. The generation of elec-
tricity may properly be considered a form of
manufacturing, water being the raw product,
and electricity the resultant, but it differs
from ordinary manufacturing in two impor-
tant essentials. First, electricity cannot, to
any material degree, be stored or kept for
future use. It must be used when and as it is
manufactured. Second, it can onlv be trans-
WATER POWERS OF NEW ENGLAND
361
ported over wires reserved for its particular
service, and its market is therefore limited
to industries which are located within rea-'
sonable transmission distance. Conceive, if
you can, the difficulties which would face
the manufacturer of woolen cloth who must
manufacture his goods and deliver them on
the same day, who must use his own trucks
for the delivery of his own cloth, being denied
the use of railroads and other means of
transportation, and whose only market lay
within a radius of 200 miles of his plant;
and yet such is the problem that faces the
manufacturer of electricity.
But while great difficulties confront the
manufacturer and seller of electricity gener-
ated from either water or coal, yet few lines of
many cities carting and teaming can be
more cheaply done by the electric truck than
by the horse drawn vehicle, and it is estimated
that if the horse drawn teaming of New York
City was to be done by electric trucks,
the amount of electricity required would
exceed twice the present output of the New
York Edison Company.
Electricity as applied to railway trans-
portation is just beginning to prove its
reliability and its feasibility. Already 75 miles
of the New Haven Railroad passing through
one of the most densely settled sections of
the country is operated by electric locomo-
tives and the St. Paul Railroad is electrify-
ing over 400 miles of its lines west of Butte,
Montana. Wherever railroads have been
Fig. 1. An Exterior View of the Connecticut River Power Company's Hydro -Electric Station and Dam
industry offer greater opportunities if wisely
and conservatively managed. Of all the
forms of power, electricity is the most
transportable, and within reasonable limits,
can be cheaply carried from the place of
generation to the place of use. Again,
electricity is the most transmutable of all
known forms of energy. It can be easily
transmuted to the form of light; it can be
changed into the form of the most intense
heat for use in the electric furnace; it can be
applied to the locomotive to give tractive
power; it can be changed into mechanical
energy for the turning of the wheels of
industry. In fact, no other form of energy
can be so easily transmitted from place to
place, or so easily applied to useful work.
Despite the wonderful growth in the
generation and use of electricity within the
last decade, it is still fair to say that the
electrical industry is in its infancy. For
instance, it has been demonstrated that in
electrified much benefit has resulted, both
to the corporation and to the public. It has
been possible to give a more frequent train
service without added cost; there has been
great saving in coal, and even a greater
saving in maintenance and upkeep; the strain
upon the road-bed has been less serious; the
smoke nuisance is eliminated, and loss from
fires set by locomotive sparks has entirely
ceased. These advantages are so important
there is little doubt that a very great amount
of railroad electrification will take place as
soon as financial conditions warrant.
The great extent to which electricity is
being used for electro-chemical purposes is
hardly appreciated, yet two-thirds of the
energy generated by all of the companies
at Niagara Falls is now so utilized. In fact,
the number of kilowatt-hours consumed in
the electric furnace today exceeds the number
of kilowatt-hours generated for light and
power in the four largest cities of the country,
362
GENERAL ELECTRIC REVIEW
and yet the possibilities of this industry are
but faintly appreciated, and we smile at the
prophecy of the scientists that the fertility
of the earth will be maintained by the nitrogen
abstracted from the air by means of the
electric arc.
Fig. 2. View of a Bank of Transformers and Lightning
Arresters in the Outdoor Substation of the Connecticut
River Transmission Company at MiUbury
The manufacturer of electricity can also
to a very great degree claim exemption
from the serious labor problems which face
many other forms of industry. A modern
hydro-electric plant with its distribution
system does not spend more than 10 per cent
of its gross income in the employment of
labor, whereas the railroad and the trolley
must so expend about 50 per cent of its gross
receipts, and many manufacturing indus-
tries must pay out 75 per cent of their gross
income for human effort.
In a comparison of the operating costs
of a steam and a hydro-electric plant the
ultimate effect of the sinking fund upon the
cost of power is not fully appreciated. No
one would question the great advantage of
the hydro-electric plant over the steam plant
if the former could be had without cost, that is,
without capital outlay ; if its cost was $50 per
kilowatt its advantage would still be unques-
tioned; at $150 its value might be debatable,
and at $1000 every one would condemn it. In
fact, the relation between the water power and
the steam plant is very largely dependent upon
the capital cost of the former.
If it is assumed that each kilowatt of
machinery in a hydro-electric plant (costing
approximately $150) produces 4000 kilowatt-
hours per year, and if it is further assumed
that one mill per kilowatt-hour is put into a
sinking fund and re-invested in the 6 per cent
securities of the company, the fund thus
created will have reduced the cost of the plant
from $150 to $100 per kilowatt at the end
of the tenth year; at the end of the sixteenth
year its cost will have been lowered to $50,
and by the end of the twentieth year the
plant will have been entirely paid for, and
the company owning it will be in the very
desirable position of owning a hydro-electric
plant without capital charge, and with very
slight running expenses.
The economy of generating and distributing
electricity in great quantities is now so appar-
ent that no time need be given to its demon-
stration, and while it is true there are certain
industries which require* such large amounts
of steam for industrial purposes that the
central station can never hope to serve them,
they are in the great minority, and of the
1,500,000 horse power now used in New
England for manufacturing purposes, at least
1,000,000 horse power may and probably
will at some time be secured by the electric
company. No manufacturer who can buy
electricity at a rate equal to or less than its
cost if made in his own plant will desire to
make expenditures for boilers and engines
when that same investment in productive
machinery will bring in much greater returns.
The big central station is here, and it is here
to stay; it will grow larger and larger; it will
be located at the best place, and from it will
radiate lines which will carry energy for
lighting, for trolleys and railroads and for
every form of industry.
Assuming then that the great generating
plant with its network of transmission lines
will supply the energy of the future, the
question is often asked as to the relative value
of and the relation between the central
stations which produce their energy by water
and those that generate power by steam, and
this involves a consideration of the relative
costs of water powers and steam stations,
the ability of each kind of station to carry
peaks and loads of high load factor, the
requirements of the water power for auxiliary
electricity during seasons of low river flow,
and the ability of the steam station to supply
this need of the water power without added
capital expense.
A modern and efficient steam plant of large
capacity can today be constructed at a cost
of from $75 to $100 per kilowatt of installed
capacity, while a hydro-electric plant will prob-
ably cost from $100 to $150. Also, the hydro-
electric plant must, in many cases, be located
much further from its market than the
corresponding steam plant, thus adding to its
relative cost. It is therefore fair to assume
WATER POWERS OF NEW ENGLAND
363
that the first cost of the water plant will be
at least double that of the steam station.
But while the cost and consequently the
interest on the investment is double, the
depreciation and maintenance charges (ex-
pressed in percentages) are much less, as
there is practically no depreciation or upkeep
for water rights, dam or power house, and
waterwheels and slow speed generators depre-
ciate less rapidly than boilers, stokers and
high speed turbines. It is probably fair to
assume that while the fixed charges, which
will include interest, maintenance and depre-
ciation on a steam plant will be 15 per cent,
the corresponding expenses in connection with
from twelve to twenty-four hours. It is also
customary for such plants to have a very much
larger capacity of machinery than is required
for their average output, as additional
machinery can usually be added with a
proportionately small increase in outlay;
and this combination of the ability to hold
the daily flow of the stream and utilize it
during the exact hours of the day when most
required, and to have large capacity at low
cost, makes it possible for the water power
plant when run in conjunction with the steam
plant to take the winter peaks and the daily
swings in load most cheaply and economically,
it being far easier to throw on an additional
Fig. 3. A Near View of the Hydro-Electric Station of the Connecticut River Power Company,
taken from the Forebay
a hydro-electric plant will not exceed 1 1
per cent. Thus, the fixed charges on a steam
plant costing say $90 per kilowatt will be
$13.50 per year, whereas the corresponding
charges on a hydro-electric plant costing $150
will be approximately $16.50, the balance
being $3 per kilowatt per annum in favor of
the steam plant. The operating expenses of
the hydro-electric plant are of course very
much less than the corresponding costs for
the steam plant. One half-mill per kilowatt-
hour is a liberal allowance for a water power
plant of large size, whereas the corresponding
operating charges of the large steam plant
will run from four to ten mills per kilowatt-
hour, the variation in steam cost resulting
from difference in the size of the plant, its
load factor, and its efficiency.
Most successful hydro-electric plants are
so designed that their forebays or ponds
will hold the average flow of the stream for
waterwheel than to start up extra boilers
and steam turbines. Again, the steam plant
is of necessity relatively inefficient during
parts of the night and on Sundays, when the
load is light, but when steam and water
plants are run in combination the load can
be so divided between them that each plant
will carrv the load during the times of the
day when it can be most efficiently operated.
Finally, the water plant during the seasons
of the year when the stream flow is large, has
the ability to carry an output of high load
factor at very low cost, there being no added
cost for fuel because of the increase in load
factor.
Most of our large New England streams vary
greatly in their maximum and minimum flow.
For instance, at the Brattleboro plant of the
Connecticut River Power Company the flow
varies from a minimum of 1500 cu. ft. per
second to a maximum of 150,000 cu. ft., the
364
GENERAL ELECTRIC REVIEW
maximum flow being LOO times the minimum.
It would not be profitable to make such a
development on the basis of the minimum
run-off of the river, and in the plant in
instance its primary output requires a flow
of about 3300 cu. ft. The extreme low flow of
course occurs on only a relatively few days in
each year, and in an average year the plant
will have sufficient water to carry its full load
for nine months, the actual number of kilo-
watt-hours required from steam being about
3,000,000 out of a total annual output of
50,000,000 kilowatt-hours.
Among the large hydro-electric develop-
ments in New England is the plant of the
Rumford Falls Power Company on the
Androscoggin River at Rumford, Maine, the
plant of the Androscoggin Power Company
on the same river, near Lewiston, the plants
of the Cumberland County Power & Light
Company on the Saco River near Portland,
the plants of the Bangor Railway & Electric
Company near Oldtown and Ellsworth, the
plants of the Central Maine Power Company
near Waterville, the plant of the Turners
Falls Company on the Connecticut River at
Fig. 4. A General View of the Hydro-Electric Plant and Dam of the Central Maine Power Company
It is stated on reliable authority that
one-half of the capacity of our central stations
is idle 95 per cent of the time, but whether
this exact percentage is correct or not it is
certainly true that every such station must
have a very great spare capacity during
much of the year, and fortunately for both
the steam and hydro-electric plants, the
periods of low water occur during the summer
and early fall, when the central station load
is at its minimum. Thus the central station
can supply the deficiencies of the hydro-
electric plant without any increase in installed
capacity or fixed charges, and in so doing it
will increase its load factor and decrease its
unit operating cost.
All of these tacts lead to the conclusion
thai the large steam plant and the large
i-electric station can develop side by
-i'K'. each caring for the service to which it is
suited, and each giving to the other
; which neither could have alone.
Turners Falls, Massachusetts, the plant of
the Connecticut River Power Company on
the Connecticut River near Brattleboro,
and the plants of the New England Power
Company on the Deerfield River. These
various plants have an aggregate capacity
of about 25(1,0(10 horse power. Nearly all
of them have been constructed within the
last five years, thus indicating the rapidity
with which our streams are being utilized
and their energy transmitted to distant
cities and towns.
Very considerable progress has also been
made in the development of storage and the
consequent conserving of the flood waters
of the spring months. A dam at the outlet
to Moosehead Lake impounds a total in
excess of 20 billion cu. ft. and is capable
of more than doubling the minimum flow
of the Kennebec River at Augusta. Stor-
age reservoirs on the Rangelcy Lakes and
in the upper waters of the Androscoggin
WATER POWERS OF NEW ENGLAND
365
have assured a minimum flow of 2000
second feet at Rumford Falls and Lewis-
ton, and a reservoir created in Somerset,
Vermont, is now storing enough water to
produce in existing plants approximately
25,000,000 kilowatt-hours, which would other-
wise have been wasted.
We have thus far considered hydro-electric
developments in their relation to immediate
and present industrial conditions, but their
development should also be considered from
the broader standpoint of the conservation
and to the production of wealth in other
forms. Less than this number of men dug
the Panama Canal in nine years, or, in the
same period, could have built a double track
railroad from New York to San Francisco.
Therefore, there can be no doubt that the
utilization of our water resources stands on a
par with the great inventions and discoveries
of the age. Eli Whitney invented the cotton
gin, and made it possible for one man to do
50 men's work. Hargreaves, Arkwright and
others invented and perfected our cotton and
Fig. 5. Hydro-Electric Plant of the Rumford Falls Power Company
of human energy and the liberation of human
effort. The water powers of New England arc
today producing more than two billion
kilowatt-hours of energy, which is utilized
for the operation of manufacturing plants,
for the production of light, for the motive
power of trolleys and railroads, and for other
purposes. If this energy was produced by
coal it would mean the annual consumption
of three million tons, worth about 14 million
dollars, and to produce, handle and transport
this coal would require the continuous labor
of 30,000 men working 3000 hours a year.
Thus the development of our own home water
powers makes it possible for 30,000 men to
turn their efforts to other channels of industry
woolen machinery and gave power to one
weaver to produce more cotton and woolen
cloth than could 100 weavers, 100 years ago,
and likewise the great inventions in .the elec-
tric industry have made it possible for one
man at the switchboard of a hydro-electric
plant to draw more energy from Nature's store-
house than could 1000 men a century ago.
And while we may discuss the relative
merits of this development or that, or the
advantages of the steam engine, Diesel
engine or waterwheels, in the long run we
may feel sure that the energy of falling water
will be utilized to the fullest extent and that
the powers of our streams will be made to do
useful work for the benefit of mankind.
366
GENERAL ELECTRIC REVIEW
SOME ASPECTS OF SLOT INSULATION DESIGN
By H. M. Hobart
Consulting Engineer, General Electric Company
The phases of slot insulation design which are treated in this article are the voltage gradient through the
insulation from an alternator armature conductor to the sides of the slot, the necessity for using an insulation
capable of withstanding a high temperature, and the importance of obtaining complete information on the
useful life of insulation. The major share of the article is devoted to a comparison between the unit dielectric
stresses in the slot insulation of a low-voltage alternator and those in a high-voltage machine. A specific
example is assumed; and an analysis, which is made of several variations in the slot insulation design,
instructively demonstrates the magnitude of the influence which insulation thickness and specific inductive
capacity have on the design of slot insulation. — Editor.
The thickness of the insulation employed
in the slots of low-pressure armatures is
usually determined largely from considera-
tions of mechanical strength. Were it
practicable to ensure continuity and unim-
paired mechanical strength at all parts,
thinner insulations than those customarily
employed would usually afford ample factors
of safety so far as regards immunity from
disruption by the electrical pressure.
But for armatures wound for high pres-
sures, say, for example, 12,000 volts, the
insulation thickness is proportioned chiefly
with reference to the strength which the
material possesses for withstanding electrical
pressures. This ma}- be termed the disruptive
strength of the material. Quantitative in-
vestigations of the properties of insulating
materials are still disappointingly meager.
It may, however, be stated that the disruptive
strength of insulating materials of the sorts
employed for slot insulations does not
increase in proportion to the thickness
employed. As a rough guide for practical
purposes, we may take it that the disruptive
strength increases as the two-thirds power
of the thickness. If for a certain insulating
material,- furnished in the form of sheets, the
disruptive strength for a thickness of 1 mm.
is stated to be 30,000 volts when tested for
60 seconds, we are to understand that a
thickness of 1 mm. will, on the average,
withstand a crest pressure of 30,000 volts
for 60 seconds without puncturing. Applying
the rough "two-thirds power" rule, a 0.5 mm.
thick sample of the same material will have
a disruptive strength of 0.50" X 30,000 =
0.63X30,000=18,900 crest volts, while a
2 mm. thick sample will have a disrup-
tive strength of 2jX30.000= 1.59X30.000 =
47,500 crest volts.
The three results are brought together
in the following table.
It is desirable to again emphasize that
different materials exhibit different rates of
variation with the thickness as does also a
given material under varied conditions. It is
rare, howTever, that it is practicable to obtain
materials or conditions ensuring a disruptive
strength directly proportional to the thick-
Thickness
of Sample
" Disruptive
Strength"
in (Crest)
Volts
" Disruptive
Strength"
per Millimeter
in (Crest)
Volts
0.50 mm.
1.00 mm.
2.00 mm.
18,900
30,000
47,500
37,800
30,000
23,800
ness, and for the purposes of this article the
"two-thirds power" rule is assumed as being
convenient and also sufficiently represen-
tative.
In actual practice, slot insulations for
1200-volt armatures are generally about
2 mm. thick, while for 12,000-volt armatures
a thickness of about 5 mm. is usually em-
ployed. Such insulations have in practice
been shown to be adequate to withstand, not
only the conditions of usual service but also,
when new, the test required by paragraph
254 of the A.I.E.E. rules. This paragraph
reads as follows:
254. The Standard Test for all Classes of Appa-
ratus, except as otherwise specified, shall be twice
the normal voltage of the circuit to which the
apparatus is connected, plus 1000 volts.
The essential conditions of the test are
prescribed in paragraphs 248 to 252 inclusive,
which read as follows :
248. Condition of Machinery to be Tested.
Commercial tests shall, in general, be made with
the completely assembled machinery and not
with individual parts. The machinery shall be
in good condition, and high-voltage tests, unless
otherwise specified, shall be applied before the
machine is put into commercial service and shall
not be applied when the insulation resistance is
low owing to dirt or moisture. High-voltage tests
shall be made at the temperature assumed under
normal operation. High-voltage tests to deter-
mine whether specifications are fulfilled are
SOME ASPECTS OF SLOT INSULATION DESIGN
367
admissible on new machines only. Unless other-
wise agreed upon, high-voltage tests of a machine
shall be understood as being made at the factory.
249. Points of Application of Voltage. The test
voltage shall be successively applied between
each electric circuit and all other electric circuits
and metal parts grounded.
250. Interconnected Polyphase Windings are con-
sidered as one circuit. All windings of a machine
except that under test shall be connected to
ground.
251. Frequency, Wave Form and Test Voltage.
The frequency of the testing circuit shall not be
less than the rated frequency of the apparatus
tested. A sine wave form is recommended. The
test shall be made with alternating voltage
having a crest value equal to v'2 times the
specified test voltage. In direct current machines,
and in the general commercial application of
alternating current machines, the testing fre-
quency of 60 cycles per second is recommended.
252. Duration of Application of Test Voltage.
The testing voltage for all classes of apparatus
shall be applied continuously for a period of
60 seconds.
A 1200-volt armature will, in accordance
with the quoted rule, be tested with (2 X 1200)
+ 1000 = 3400 virtual volts (corresponding to
4800 crest volts). A 12,000-volt armature will
be tested with (2 X 12,000) + 1000= 25,000
virtual volts (corresponding to 35,400 crest
volts). Since the thicknesses in these two
cases are 2 mm. and 5 mm. respectively, the
"disruptive strengths" per mm. of thickness
must be at least:
= 2. OS times the working pressure than when
3400
we test a 1200-volt armature with
4 SI 10
and
2400 crest volts
= 7100 crest volts.
The materials must in the two cases be
such as shall, under the test conditions,
correspond to the following values for samples
of 1 mm. thickness:
Working
Pressure
of
Armature
Thickness
of
Insulation
in mm.
Disruptive Strength
of a Sample of
1 mm. Thickness
1200
12000
2
v 5
4|52= 3000 volts
35'4,00 = 12,000 volts
51
Evidently we are imposing a much more
severe stress on the insulation when we test
25 000
a 12,000-volt armature with only "^ '
1200
= 2.84 times the working pressure.
But even the higher value, namely, 12,000
crest volts for a 1 mm. sample, appears at
first sight to be exceedingly low when we
mention that a 1 mm. thickness of natural
mica, if free from impurities, has a disruptive
strength of from 80,000 to 90,000 crest volts,
while 1 mm. thick samples of many varieties
of impregnated fabrics and papers and
reconstructed micas test above 20,000 crest
volts.
But 1 mm. thickness of natural mica can
only be obtained in flat plates, and such plates
are rarely free from foreign substances. The
purity corresponding to the above-quoted
values of the disruptive strength is only
obtainable in selected and relatively small
pieces. When mica is split up and recon-
structed into a sufficiently flexible and
reliable form, the product is by no means
exclusively pure mica, but has quite a con-
siderable percentage of binding material
usually consisting of thin paper and cementing
varnish. Such a product when in the form
of a flat sample, or circular tube, of 1 mm.
thickness should still have a disruptive
strength of nearly 30,000 crest volts. But
when applied in ribbons or sheets so wrapped
on as to form a continuous and uniform
insulating covering around the slot portion
of the coil, a 1 mm. thickness would hardly
have a disruptive strength much in excess of
15,000 crest volts. A 5 mm. thickness would
not have five times as great a disruptive
strength but would only withstand some
5' = 2.9 times as great a pressure as that
withstood by a 1 mm. thick sample, or
(2.9 X 15,000) =43,000 crest volts,
, 43,000
corresponding to a pressure of — -j=-
= 30,000 rms volts. This leaves us a margin
of only 5000 rms volts above the 25,000-
rms-volt test required by the A.I.E.E. rules
for a 12,000-volt armature.
It must be remembered that the manu-
facturer requires his own factor of safety
above the A.I.E.E. test, since he cannot
afford to build machines which will be on the
ragged edge of breaking down when sub-
jected to the specified tests. It is now clear
that the margin, instead of being generous,
is, in the case of 12,000-volt armatures, so
moderate as to require great skill and care
in design and construction.
36S
GENERAL ELECTRIC REVIEW
The limits of this article will not permit
of allusion to, or much iess a comprehen-
sive discussion of, the many points requir-
ing attention in the design of the slot insu-
lation of high-pressure armatures. It has
been considered desirable to draw attention
to the order of magnitude of the quantities
involved. Let us, however, give further
consideration to the influence of the specific
inductive capacity of the materials entering
into the composition of the slot insulation.
Fig. 1 is a diagrammatic representation of
a 5 mm. thick homogeneous insulation
stressed by 12,000 rms volts. Each mm. of
c 12,000
thickness experiences a stress oi — z — =
2400 rms volts. In Fig. 2, the 5 mm. thick-
4000
= 1600 rms volts per millimeter, the
right-hand layer is stressed to the extent of
— - =.'3200 rms volts per mm. Both of
these values are quite moderate. But let us
now consider the conditions represented
diagrammatically in Fig. 3. The two layers
each have the same specific inductive capac-
ities as in Fig. 2, but while the thickness of
the left-hand layer has been increased from
2.5 mm. to 4 mm., that of the right-hand
layer has been decreased from 2.5 mm. to
1 mm. We now have
4 1
X : 12,000- A =
3
5
$ 4
£ 10000
X 8000
\ 6000,
£ AOOO
^ 2000
\
I
I 2 3 4
mm Thickness
Fig. 1. Homogeneous Insulation Stressed with 12,000 Volts
^/2000^
^/oooot
I 8000^
I 6000?
& 4000\
to 2000
b O'A
?
m
-Z.5mm-
Sp. Ind. Cap.6 Sp. Ind. Cap.=3
-2.5 mm-
-M.
0 12 3 4 5
mm Thickness
Fig. 2. Insulation of Two Layers of Equal Thickness and
Different Specific Inductive Capacity
ness of homogeneous insulation has been
replaced with two 2.5 mm. layers, the left-
hand layer being of a material with a specific
inductive capacity of (i and the right-hand
layer of a material with a specific inductive-
capacity of 3. The total stress of 12,000 rms
volts will be shared between the two layers
in direct proportion to their thicknesses and
in inverse proportion to their specific induc-
tive capacities. Letting X represent the
pressure across the left-hand layer and
12.00(1 — .V that across the right-hand layer,
we have
X : 1 2,000- A' = ^ :^zf
6 -i
Therefore
A = 4.000 and 12,000 -X = 8,000.
Consequently, as shown in Fig. 2. while the
left-hand layer is subjected to a stress of only
A = 8000. 1 2.000 - A = 4000.
The left-hand layer is now subjected to
= 2000 rms volts per mm. and the
right-hand laver to
4000
1
= 4000 rms volts
per mm. While these values are still moder-
ate, that across the right-hand layer is
12,000
considerablv above the
= 2400 rms
volts per mm., which is the average for the
total thickness.
In Fig. 4 the thickness of the right-hand
layer is still further reduced and is now only
0.1 mm., the specific inductive capacities
being, as before, 0 for the left-hand and 3
for the right-hand layer. We now have
SOME ASPECTS OF SLOT INSULATION DESIGN
369
X : 12,000- A" =
4.0
X= 11,500 rms volts.
12,000-A' = 500 rms volts.
For the left-hand layer
1 1 ,500
01
3
the stress
4.9
= 2350 rms volts per mm. and for
the right-hand layer it is
500
0.1
5(100 rms
volts per mm.
Now retaining the two thicknesses of 4.9
for the left-hand and 0.1 for the right-hand
layer, and the specific inductive capacity of
6 for the left-hand layer, let us consider the
case where the specific inductive capacity
§
S
\/ZOOO^
£ fOOOQ
% 8000,.
"I 6000'/,
to 2000'/,
\
I 2 3 4
mm Thickness
Fig. 3. Insulation of Two Layers of Different Thickness
and Different Specific Inductive Capacity
of the 0.1 mm. thick right-hand layer is
reduced from the value of three corre-
sponding to Fig. 4 to the value of only 1.
corresponding to air. Indeed, we may con-
sider that the right-hand layer is made up
of a film of air adjacent to the laminated
side of the slot of an armature. We now have
A' : 12,000- A:
<L9
G
0.1
A= 10,700 rms volts, and
12,000- A = 1300 rms volts.
The air film is stressed to the extern of
- '-— = 13,000 rms volts per mm.
It will be noted that in this last case we
have a stress of 1300 rms volts exerted on a
layer of air of only 0.1 mm. thickness. The
disruptive strength of 0.1 mm. of air is only
some 700 rms volts. While the precise value
depends upon several factors, we are evi-
dently in the neighborhood of values which
may occasion discharges across the film of air
between the side of the slot and the outer
side of the insulation. This will take place
more readily at corners, such as at the edges
of ventilating ducts.
Instead of employing for the left-hand
layer a material with a specific inductive
capacity of 6, let us, in the last case, substitute
a material with a specific inductive capacitv
of 2. This gives us
A' : 12,000- A = ^
X= 11,500 rms volts, and
1 2, 000- A = 500 rms volts.
or
l
O / 2 5 4 5
mm Th/cfrness
Fig. 4. Insulation of Two Layers of Greatly Different Thick-
ness, the Specific Inductive Capacity of the
Thick Layer being Six and that of
the Thin Layer being Three
This value of only 500 rms volts (less than
half of that obtained in the preceding case)
will not suffice to break down a layer of air
of 0.1 mm. thickness. Consequently, from
the standpoint of minimizing the slow eating
out of the insulation by static corrosion, the
material employed for slot insulation should
have a very low specific inductive capacity.
But the ideal way of eliminating the
difficulty is to fill up all spaces solidly, utterly
displacing the slightest traces of air. Since
this is exceedingly difficult of complete
achievement, it is well worth while providing
the further safeguard of also employing for
the slot insulation (so far as is consistent
with obtaining the other essential qualities)
material of very low specific inductive capac-
ity. Unobservablc discharges across the
thin air films between the insulation and the
370
GENERAL ELECTRIC REVIEW
sides of the slot may, under certain condi-
tions, produce ozone and nitric acid and thus
still further impair the insulation by setting
up corrosive chemical reactions.
HEAT-RESISTING QUALITIES
It is, however, not possible to select
whatever material best suits us in the matter
of disruptive strength and specific inductive
capacity. On the contrary, we must consider
several other features, notable among which
is the capacity for withstanding high tem-
peratures. Nowadays the leading manu-
facturers are entirely willing to be conserva-
tive in the matter of temperatures for those
classes of machinery which can be designed
for low-temperature operation. But machines
of certain types and ratings can only be so
constructed that their operation will be
attended by very high temperatures in
certain parts. There is no known way which
would at present meet with approval in
avoiding these high temperatures, in extra
high-speed turbine generators of very large
capacity, or in totally-enclosed motors. It
has become a matter of great importance to
develop insulating materials which, while
satisfactory in all other respects, will also
withstand temperatures of the order of 125
deg. C.
Although ordinarily the room temperature
is some 25 deg. C, there are summer days
when it will rise (in an engine room) to 40
deg. C. A thermometer rise of 50 deg. C.
brings us to an ultimate temperature of
90 deg. C, as observed by thermometers at
points on the surface. The nature of the
construction, which must for mechanical
reasons be employed in such machines, renders
it inevitable in high-voltage alternators that
there will often be local internal temperatures
some 30 to 40 deg. C. greater than the
maximum surface readings. This leads to a
temperature of 40+50 + 35 = 125 deg. C.
Usually the hot spots will be at the inside
surface of the slot insulation where it lies
against the copper coil. If the copper is, as is
usually the case, the hottest part, then the
temperature difference between the outside
surface of the insulation and its inside surface
will be greater the thicker the insulation and
the less perfectly air has been eliminated
from all parts of the insulation.
Consequently if only we can make a good
insulation from the standpoint of withstand-
ing the electrical stresses, an insulation which
is relatively thin and dense, we not only have
the great advantages of the saving in valuable
space in the slot, which can be devoted to
copper, but we also will have provided a much
better path for conducting away the heat,
than we should have with a thick insulation,
especially if it be not dense but more or less
permeated with air layers and particles.
Suppose, for instance, that by means of
immense pressure we could compress the
usual 5 mm. insulation so as to reduce its
thickness to 2.5 mm. We should thereby
expel all air particles. We should have
doubled the heat conductivity by virtue of
halving the thickness, and also we probably
should have again doubled it owing to the
elimination of all air layers. The resistance
to the escape of heat would, in this hypothet-
ical case, have been reduced in the ratio of
4 to 1; and, for the same temperature rise
of the copper, we could (assuming negligible
heating of the copper by losses in the sur-
rounding iron) allow the winding to absorb
an internal PR loss four times as great. Thus
we see that the same consideration, namely,
the obtaining of complete impregnation,
which eliminates gradual deterioration of the
insulation by static corrosion, also leads to
the best results from the standpoint of the
transfer of heat.
IOOOO ZOOOO
LIFE IN HOURS
30OQ0
Fig. 5. A Typical Life-Temperature Curve for a
Particular Insulation
LIFE OF INSULATION
There is still a serious insufficiency of
reliable data as regards the life of various
sorts of insulations. When slot insulations
have become exceedingly dried and brittle
as the result of long use, then, for instance
in the case of railway motors, mechanical
vibration plays a part in the further deteriora-
tion of the insulation. This is also the case,
to a certain extent, in stationarv motors and
INCANDESCENT LAMPS FOR PROJECTORS
371
in generators. It is here desired to draw
attention particularly to the case of such
materials as are required for the slot insula-
tion of large extra-high-speed steam turbine-
driven generators.
It would appear to be in the interests
of economy that such machines should be
worked hard during a short life than to spare
them and drag out their life over a long term
of years. By adopting the policy of getting
all we can out of them in a short space qf
time, we decrease the total interest and
insurance charges on the investment and
also the wages per unit of output. Ten years
would appear to be an appropriate life to
assign to such machines. By the end of ten
years the progress of the art is such that we
are certain to be able to procure a more
economical machine than was available at the
beginning of that term of years. In the
average lighting and power plant the load
factor on the station is of such a value that,
taking spare sets into account, we cannot
economically keep any one machine in service
for more than, say, one-third of the time.
Consequently, instead of being in service for
87,500 hours in the course of the ten years,
such a generator will only be in service for
some 87,500/3 = 29,200 hours or, say, 30,000
hours.
As good an indication as possible should
be available of the temperature at which an
insulation can be used, in order that it should
remain thoroughly sound and reliable for at
least 30,000 hours. It would be, of course,
impracticable to await the completion of
30,000 hour tests, but it should be practicable
to make some "equivalent" test consisting
of a higher temperature applied for a shorter
time. Knowing, for instance, from an actual
test, that a certain insulation remains thor-
oughly sound at the end of a run of 1000
hours at, say, 160 deg., there should be a
means, by use of the laws disclosed in such
investigations, of deducing data which would
enable us to know the life of this same
insulation when run at 150 deg., and again
at 125 deg. Curves of the type shown in
Fig. 5 should be obtained for many insula-
tions under all sorts of conditions.
INCANDESCENT LAMPS FOR PROJECTORS
By L. C. Porter
Edison Lamp Works, General Electric Company, Harrison, N. J.
The author first outlines the condensing lens and the parabolic reflector method of producing parallel, or
nearly parallel, rays of light when using a point source. Then he describes the high filament concentration
which can be employed in the new gas-filled incandescent lamp and shows by figures and curves how such
lamps admirably fulfil the requirements for projecting a high-power beam of light from a headlight, stereop-
ticon lantern, or flood-lighting projector. — Editor
The introduction of the focus type gas-
filled lamp has opened wonderful possibilities
in searchlight work. The color, steadiness
and reliability of the beam from this lamp,
together with the simplicity of its control,
make it an almost ideal light source for
certain classes of searchlight work, notably,
for headlights for street cars and railroad
locomotives, for small searchlights for boats,
for flood-lighting of signs and building fronts
and for stereopticon work, etc.
In order to understand why these applica-
tions have become practical for the incan-
descent lamp, let us review briefly some of
the principles involved in the production of
a beam of light. There are two general
methods of concentrating light into a beam:
One by the use of a parabolic reflector,* and
* See article "Notes on the Use of Tungsten Filament Lamps
with Parabolic Reflectors," by G. H. Stickney, General Elec-
tric Review, December, 1912, p. 800.
the other by the use of a condensing lens.
Either system requires a light concentrated
as closely as possible at the focal point of the
lens or reflector.
Theoretically, if the light were an actual
point located at the focus of a perfect par-
abolic reflector, or the proper lens system,
the light rays from it would be all turned
in a parallel direction and a beam of light
would be obtained which — neglecting atmos-
pheric absorption — would reach to infinity.
In practice, however, it is not possible to
produce an actual point source. The beam
of light has therefore spread, its maximum
divergence being equal to the angle at the
center of the lens or reflector formed by the
two extreme tangent rays to the light source
(A and B in Fig. 1). From the figure it is
evident that the larger the light source the
greater will be the spread of the beam; and
372
GENERAL ELECTRIC REVIEW
this is accompanied by a corresponding
decrease in the beam candle-power. Beyond
such a distance that the diameter of the
lens or reflector is negligible in comparison
to this distance (i.e., where a point in the
beam of light would receive light from every
turn, was placed in the same parabolic
reflector which was 11 inches in diameter
and of o-inch focal length, and the maximum
beam candle-power was measured. The
results were as follows:
Lamp
Maximum
Beam C-P.
32
c-p.
240 v.
carbon,
regular
268
32
c-p.
240 v.
carbon,
stereopticon
5.55
32
c-p.
120 v.
carbon,
stereopticon
1400
32
c-p.
40 v.
mazda,
stereopticon
3335
32
c-p.
6 v.
mazda,
headlight lamp
3600
Fig. 1. The Condensing Lens and Parabolic Reflector
Methods of Concentrating Light into a Beam
point on the reflecting surface of the parabolic
reflector) the intensity varies inversely as
the square of the distance from the light
source. We see, therefore, that the ordinary
type of incandescent lamp, having its fila-
ment in the form of a wire looped up and
down, is so large that practically no beam at
all can be obtained from it.
However, by winding this filament into
a closely coiled spiral and bunching this
spiral as much as possible, a
very much more highly concen-
trated light source may be
obtained. To illustrate: A cylinder
70 millimeters long by 30 millime-
ters in diameter would be required
to contain the filament of the
regular 100-watt 110-volt mazda
lamp, while that of the 100-watt
110-volt focus type mazda lamp
may be contained in a cylinder
12 millimeters by 12 millimeters.
The filament of the low voltage-
lamp can be concentrated into
even a smaller volume, because it
is not necessary to use so long
a wire for low voltage. The light
source of the (i-volt IDS- watt mazda
headlight lamp may be contained in
a cylinder 2!o millimeters in diame-
ter by 5 millimeters long, see Fig. 2.
To demonstrate the marked effect of the
concentration of the light source upon the
resultant beam candle-power, the writer
had five special lamps made up, each of 32
candle-power but of varying filament con-
ations, as shown in Fig. 3. Each, in
Xot only can the filament of the lamp be
wound into very small volumes, but it can
also be made in very high candle-powers.
The combination of a high candle-power
light source of small volume is the secret of
producing a powerful beam of light. Assum-
ing the concentration to remain constant,
the beam candle-power will vary directly
with the candle-power of the light source.
Thus, it can be seen that a much higher
wattage lamp will be required at 110 volts
than at 0 volts to obtain the same beam
candle-power. Tests have shown that a
( i-volt 108-watt lamp giving 150 candle-
power will produce in a 19^ inch parabolic
reflector of 2% inch focus (G-E Headlight
J-8) a beam of 960,000 beam candle-power
Fig. 2.
Relative Size of Filaments of the Regular lOOWatt 110-Volt Lamp,
the 100-Watt 110-Volt Focus-type Lamp, and the 108-Watt
6-Volt Headlight Lamp
( these tests refer to a specific type of head-
light), while a 500-watt 110-volt lamp of 714
candle-power in the same reflector gives
only 710.000 — each of these lamps being
at present of the highest practical filament
concentration. The ratio between the candle-
INCANDESCENT LAMPS FOR PROJECTORS
373
power of the light source itself and the
resultant beam is called the multiplying
factor of the equipment. For the two lamps
in question the multiplying factors are as
follows :
Lamp
Multiplying Factor
6 v. 150 c-p.
110 v. 714 c-p.
6400
994
Another element having considerable in-
fluence on the resultant intensity of the
beam is the focal length of the lens or reflector.
The focus type incandescent lamps have an
approximately even distribution of light
over the entire sphere; hence, the shorter
the focal length of the lens or reflector, the
greater will be the percentage of the total
light flux utilized. In Fig. 4 the shaded
portion represents the plane angle of light
utilized by reflectors of equal diameter but
of long and short focus. The surface of the
reflector also has a great deal to do with the
beam. The reflection coefficient of polished
nickel is approximately 54 per cent, of
polished aluminum (il per cent, and of pol-
ished silver 86 per cent. Mirrors made of
glass are generally used where the most
powerful beams are desired. They can be
ground very much more accurately than the
metal mirrors can be made and they also pro-
tect the silver backing from rapid tarnishing.
The most powerful beams at present are
obtained from arc lamps. The candle-power
of sufficient power for many classes of service
— such as street car and locomotive head-
lights, small searchlights, flood and spot-
lights, signal work, stereopticon lanterns,
etc., etc. — can be obtained. It frequently
happens that the simplicity of control and
safetv obtained by the use of an incandescent
Fig. 4. Diagram of the Amount of Light Utilized
by Two Reflectors of Equal Diameter but of
Different Focal Length
lamp, for such classes of service, more than
offset the somewhat higher intensity obtain-
able with an arc. The color of the light
from an incandescent lamp is also nearer the
red end of the spectrum, to which the eye
is most sensitive, under common working
intensities.* Tests have shown that this,
together with the steadiness of the beam from
an incandescent headlight, makes it possible
to discern objects at a considerably greater
distance than is possible with the same
beam candle-power from an arc headlight.
The question of color of the beam of a
headlight is being given more prominence.
Fig. 3. Five Special 32 c-p. Lamps with Various Size Filaments
per square millimeter of the crater of a
carbon arc is about 130, while the maximum
obtainable from the same surface of a tungsten
filament, at its melting point, is about 70;
therefore, it is physically impossible with
the present tungsten lamp to produce so
powerful a beam as with the arc. Yet, beams
probably partially for commercial reasons,
by the introduction of glass mirrors and
front plates which give an amber hue to the
beam. It is claimed that in this manner the
"pick-up" distance of headlights in fog is
♦Transactions of the Illuminating Engineering Society, 1914,
vol. IX, pp. 909-936.
374
GENERAL ELECTRIC REVIEW
increased, due to the reduction of back glare
from the fog itself; also, that when looking
directly toward the headlight, the glare is
largely reduced. It is. however, doubtful
if the reduction of glare — due to light re-
flected back into an observer's eves from the
Fig. 5.
The Standard Type of Locomotive Headlight for
the 6-volt, 108-watt. Focus-type Lamp
fog — will offset the decrease in intensity of
the beam, caused by the use of amber glass,
except in the case of very large headlights
having exceedingly high beam candle-powers.
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- — I —
&.
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Distance fn /eet from center of beam
0 I £ 3 d- £ 6 7 S 9 10 II /£ 13 /4- /5
Fig- 6. Distribution Curve of Light from Headlight
shown in Fig. 5
The three large classes of sen-ice to which
the focus type mazda lamp has been applied
with marked success are: (1) Headlights for
autos, trolleys, locomotives and ships; (2)
Stereopticon work for various types of pro-
jectors, lanterns and small moving picture
machines; (3) Flood-lighting of painted adver-
tising matter, building fronts, etc.
For the first class of service the 6-volt
lamps for auto headlights are well known.
Recently 6-volt lamps having highly con-
centrated filaments of 36, 72 and 108 watts
capacity have been standardized for locomo-
tive service. The lamps are operated from
storage batteries. There is also under
construction a 6-volt turbo-generator outfit
of sufficient capacity to take care of the 108-
watt headlight, the cab lights and classi-
fication signals; this makes the lighting of
the locomotive entirely independent of the
Fig. 7. Adjustable Socket for Converting an
Oil Headlight into an Electric one
remainder of the train.* The Southern Pacific
Railroad, after exhaustive tests of various
types of headlights, has adopted the 6-volt
108-watt Edison mazda headlight lamp as
standard, and is using several thousands of
them. Headlights especially designed for this
lamp are now manufactured, see Fig. 5. The
distribution curve of this combination is
shown in Fig. 6.
In many instances it is desirable to convert
an oil headlight already in use into an electric
headlight. This may be readily accomplished
by replacing the oil burner with an adjustable
lamp socket, which will allow of focusing the
headlight. A simple device, designed for this
purpose, is shown in Fig. 7.
There are at present in service a consider-
able number of 30-volt turbo-generator sets.
♦Journal of Electricity,
pp. 121-125.
Power, and Gas, Feb.
1914.
INCANDESCENT LAMPS FOR PROJECTORS
375
For use with these, 30-volt lamps of 100,
150 and 250-watt capacity have been designed.
While these are good substantial lamps,
they are not so rugged as the 6-volt type and,
on account of the longer filament, the con-
centration is not so good; consequently, the
power of the beam is considerably less for
equal wattages. These lamps, as well as the
6-volt lamps, are also used for searchlights
on boats equipped with 30-volt lighting
systems or 6-volt ignition systems.
For street car service, special focus type
lamps are available, of 23, 36, 56, 72 and
94-watt capacities, designed to burn in
series with four regular street railway lamps
of the same capacity on one of the car lighting
circuits. In some cases cars are wired so that
two circuits pass in multiple through the
headlight, which must then be of double
the capacity of the lamps in the car. Lamps
of 46 and 72 watts are available for use with
23 and 36-watt lamps, respectively, in the car.
There is also available an 80-volt 4-ampere
focus type mazda lamp for interurban
car service. This lamp can be used with
the same resistances previously installed for
4-ampere arc headlights, see Fig. 8. The
equipment shown in Fig. 8 will throw a
beam 'of about 75,000 candle-power.
Formula?, giving the distances at which a
man dressed in light, medium or dark
colored clothes can be "picked up" by
incandescent headlights of various beam
candle-powers, have been worked out by Mr.
J. L. Minick, of the Pennsylvania Railroad.
They are given in a paper by him, "The
Fig. 8. Incandescent Headlight Designed for
Use on Interurban Cars
Locomotive Headlight," in Vol. IX, No. 9,
Transactions of the Illuminating Engineering
Society for 1914, page 918. Fig. 9 gives
curves plotted from these formulas.
In the second field of application men-
tioned, i.e., stereopticon work, the chief
advantages of the incandescent lamp are
safety, simplicity and convenience. A stere-
opticon lantern so equipped is practically
free from fire risk. Once the switch is closed,
no further attention to the light source is
necessary. It is steady and free from the
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1
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eo
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O Z 4- 6 3 10 l£ 10- /6 /B 20 Z2 24 S6 26 30
^eet (Hundreds)
Fig. 9. Curves of "Pick-up" Distance of Incandescent
Headlights of Different Beam Candle-power
humming prevalent with many types of
lanterns. Focus type lamps, for use on the
ordinary lighting circuits, of 100, 250, and
500-watt capacity are available for this class
of service. A special 1000-watt lamp may
also be obtained * These lamps should
be used with a spherical mirror back of
them. The function of the spherical mirror
is to increase the flux of light through the
condensing lenses by about 30 per cent and
also to produce a more uniform field. ' It is
generally necessary to move the lamp slightly
out of focus to eliminate filament images on
the screen. There are already on the market
several well-known makes of stereopticon
lanterns using these lamps. Incandescent
lamps, sufficiently powerful for the large
commercial moving picture machines, are
not yet available, though progress is being
made toward this end. For the small
*A separate circuit should be installed where this lamp is
used.
376
GENERAL ELECTRIC REVIEW
moving picture machine, used in the home,
the 500 and 1000-watt mazda lamps have
proved very satisfactory.
The third class of service — flood-lighting —
is a new field, which has recently been opened
and bids fair to be large. A general de-
scription of flood-lighting will be found in the
April issue of the Review, page 282.
The accompanying table gives data on
the focus type mazda lamps now available.
tDATA ON FOCUS TYPE MAZDA LAMPS, JANUARY, 1915
AUTOMOBILE FOCUS TYPE LAMPS
Amperes
W.P.C.
Approx.
C-P.
Bulb
Dia. of
Bulb in
Inches
Light Center
Max. Over- (Cap of Base
all Length to Center of
Filament)
6 and 7
2 and 2 > .
12 and 15
0.95
12 and 15
G-12
1>2
Bav.
Cand.
2>2
6 and 7
2
12
0.95
12
G-16'-,
2ft
Bav
Cand.
3%
6 and 7
2 i ., and 3
15 and 18
0.95
15 and 18
G-16',
2ft
Bay
Cand.
3H
24-90
0.33-0.08
S
1 .25
6
G-10
IH
Bay
Cand.
2>4
24-90
0.62-0.18
15
1.2 5
12
G-12
l'j
Bay
Cand.
2'.
24-90
1.0 0.26
25
1.25
20
G-16'2
2ft
Bav
Cand.
3«
6 and 7
1
1.0
6
G-10
1>4
Bay
Cand.
2H
6 and 7
1
1.0
6
S-8
1
Bay
Cand.
2H
6 and 7
1'..
1.0
9
G-12
1>2
Bay
Cand.
2 '2
6 and 7
3 ,' 2 and 4
0.95
21 and 24
G-16 H
2ft
Bay
Cand.
3%
14
1 and 1 '4
0.95
15 and 18
G-16'2
2ft
Bay
Cand.
3Y»
18
H and 1
0.95
15 and 18
G-16'..
2ft
Bay
Cand.
3%
21
34 and 1
0.95
15 and 21
G-16H
2ft
Bay.
Cand.
3H
STEREOPTICON FOCUS TYPE LAMPS
105 -125 0.95-0.8 100
105 2.4-2 250
105-125 4.7-4 500
•105-1 25 I 9.5-8 1000
105-125 1 4.7-4 500
* Special lamp, t Subject to change.
1.23
SB
0.8
312
0 7
715
0.6
1670
G-30
G-30
G-40
G-48
3'4 Med.Scr.Skt.
3»4 Med.Scr.Skt.
5 Med.Scr.Skt.
6 Mogul Scr.
5 '2
8
13
FLOOD LIGHTING LAMPS
666 G-40
Med.Scr.Skt
lft
\%
l'A
lft
lft
1'2
IK
l\
lft
1 >2
1M
1>2
1H
i>>
4»4
Unit or
Standard
Package
Quantity
5
10
5
5
10
10
LOCOMOTIVE FOCUS TYPE
LAMPS
5 '2 and 6
6
36
0.70
51
G-l.xi ,
2ft
Med. Scr.
334
2H
100
5 ' 2 and 6
12
72
0.68
106
G-25
:;>.
Med. Scr.
Wt
2Vi
50
5 ! . and 6
18
108
0.65
166
G-30
3»4
Mogul Scr.
.V,
■■■> '2
24
30-34
3.3-2.9
100
0.80
125
G-25
3's
Med. Scr.
4"4
2%
50
30-34
5 4.4
150
0.75
200
G-25
3H
Med. Scr.
4%
2?4
50
30-34
8.3-7.3
250
0.70
357
G-30
334
Med. Scr.
5 > •
3H
24
STREET CAR FOCUS TYPE LAMPS
•105-115 1
no 120
0.21
23
1.55
15
G-18!-;
2ft
Med. Scr.
::;4
2ft
100
125-130
•105-115 1
110 120
125-130
0.33
36
1.55
23
G-1S':
2ft
Med. Scr.
3*4
2ft
100
•105-115 1
110-120
0.42
46
1.55
30
G-25
3's
Med. Scr.
4'4
2%
50
123-130
•105-115
110-120
0.51
56
1.38
40
G-25
3\i
434
"'4
50
125-130 J
•105-115
110-120
0.65
72
1 .38
52
G-25
3\4
4'14
234
50
1"5 L30
•105-115 1
110-120 :■
125 130
0.85
94
1.3S
68
G-25
3's
Med. Scr.
4'<4
z%
50
*80
4.0
320
0.75
426
G-40
5
Med.Ser.Skt.
4;,
4»4
12
24
24
12
12
377
HIGH CANDLE-POWER MAZDA LAMPS FOR STEEL MILL LIGHTING
By G. H. Stickney
Edison Lamp Works, Harrison, N. J.
This article deals chiefly with the characteristics of the gas-filled mazda lamps — how the lamps are con-
structed, their peculiarities, and what can be expected from them as illuminants. As is now generally
known, this lamp gives the best results with large diameter filaments, and hence are most efficient in large
sizes. For this reason it is not suitable for all installations, and below certain sizes the vacuum lamps are
preferable. The selection of a lamp for a given installation can best be made by consulting the data book
of the lamp manufacturers. Some remarks on reflectors for these lamps, with cuts and distribution curves,
are included. The paper was read before the Association of Iron and Steel Electrical Engineers. — Editor.
At the 1913 convention of the Association
of Iron and Steel Electrical Engineers, men-
tion was made of a remarkable increase in the
efficiency of the higher power mazda lamps,
through improvements involving the intro-
duction of an inert atmosphere within the
bulb.1 It was at that time possible to fur-
nish only meager information. Since then
these lamps have gone into standard produc-
tion, many thousands being now in commer-
cial use. And this type of lamp promises to
be by far the most important illuminant for
steel mills.
When we consider the recent origin of the
incandescent lamp, its present wide-spread
application is remarkable. Less than 35
years ago Thomas A. Edison made his first
practical incandescent lamp, and yet last
n
iao
Curve S/>owr><? ^Jate or"
J70
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7SOI
/eo
-
i.
1 1 1
400 *vT
Z50W—
-/SOW—
^ //o
(
,s
--
—
—
X
-40W.
^ *.
-
—
fxsiv
40
--"
J-
70
\
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-
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r-
<?<
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/9
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/<?
'O
/«
ft
/«
V
9s
r
*
<?/
•j
year /n Quarterns, <Jhr?.t SJpr:, <Jty/t/j Oct.
Fig. 1. Curve showing Date of Introduction and Increase in Efficiency in
Candle-power per Watt for each size Mazda Lamp
year about 120,00(1,(10(1 incandescent lamps
were made and sold in this country.2 Much
of this increase was made in competition
with more efficient illuminants and with higher
costs for electric current than is common at
the present time. This seems to indicate
that the great advantages of the incandescent
lamp are its simplicity, adaptability and
reliability.
Now that current cost forms a relatively
small part of the operating cost, it would
appear that the incandescent lamp will have
even greater advantages over competing
illuminants, no matter how efficient.
That the incandescent lamp has enjoyed
a remarkable rate of increase in efficiency
is evidenced by Fig. 1, in which the candle-
power per watt for mazda lamps, since 1907,
is given. These increases are spectacular when
compared with those of other machinery, either
for generating or utilizing electric current.
While the gain in lamp efficiency, due to the
adoption of the tungsten filament, was so
remarkable as to revolutionize the
lighting practice of the country, it
is interesting to note that the aggre-
gate gain since that time, due to
improvements in the tungsten fila-
ment lamp, is approximately as
great. Nor have the developments
been merely in the direction of
increased efficiency. Fragility, as
it existed in the early tungsten
filament kimps, has been elimi-
nated ; the blackening of the lamps
has been greatly reduced by the
elimination of water vapor and
other impurities effected by the
introduction of chemicals within
the bulb; and withal the cost of
lamps has been decreased.
The mazda lamp was so tho-
roughly perfected that the volatiliz-
ing point of the filament material
became a limiting factor, and it
appeared to most lamp users that the ultimate
possibilities of the tungsten filament had been
approximated.
1 Harrison and Magdsick. A Progress Report on Illumination,
Trans. A. I. and S. E. E.
- John W. Howell. General Electric Review, March, 1914.
378
GENERAL ELECTRIC REVIEW
Then came the news that half-watt tung-
sten filament lamps were under development.
It is not surprising that this news was re-
ceived with some incredulity. It is interesting
to note that this, like most of the recent
improvements in incandescent lamps, was
not a matter of accident or chance, but the
result of rational scientific research, such as
produced the ductile tungsten filament, and
was the product of the same laboratory.
These investigations are continually being
carried on in the research laboratories of the
General Electric Company. This particular
discover}' was the result of an ingenious
method of research to determine the effect
of various conditions of manufacture on the
tion involved an attempt to produce a high
vacuum.
Then followed the long and persistent re-
search along the new line of introducing an
inert atmosphere within the bulb, which
finally resulted in the brilliant discovery that
the tungsten filaments of large diameter in
such an atmosphere could be operated at
high enough temperatures so that increased
radiating efficiency much more than counter-
balanced the convection losses.3
Such lamps consumed too high a current
to meet the commercial requirements for
110-volt circuits. The advantage of the large
diameter filaments was their lower relative
convection loss, and it was found possible.
S-40 s-*o
600 c-p. 20 Amp. 1000 c-p. 20 Amp.
For Series Circuits
S-46 S-52
750 Watts 105-125 Volts 1000 Watts 105-125 Volts
For 110-volt (nominal) Multiple Circuits
Fig. 2. High Power Mazda Lamps
quality of incandescent lamps, especially
with regard to the vacuum. The vacuum was
so perfect that it was not possible to measure
the amount of gas or vapor within the bulb.
Lamps were therefore made as perfect as
possible, various gases introduced in definite
amounts, and the results studied.
One of the first results was a confirmation
of the recognized necessity of eliminating
water vapor, which has a particularly dele-
terious effect. In his early experiments,
Edison is said to have attempted to operate
carbon filaments in an atmosphere of nitrogen,
without success. The convection loss, due to
heat carried away from the filament by the
surrounding gas, exceeded the gain in radiat-
ing efficiency. And thereafter, for nearly
30 years, lamp improvements in this connec-
a Langmuir and Orange paper. Transactions A.I.E.E. Octo-
ber. 1913.
after further research, to secure approxi-
mately the same result from smaller fila-
ments by coiling them into helices of cor-
responding diameter.
There is still a relation between the fila-
ment diameter and the convection loss, since
there is a limit to the diameter of the helix
for a particular diameter of wire. The larger
the diameter of the wire, the larger the helix
can be made. With too large a helix the
filament is liable to sag, so that some turns
will close up and overheat or short circuit,
while others will open up and operate at a
lower temperature and efficiency.
This explains why high current mazda
lamps are more efficient than low current; or
at a constant voltage (for example 110) high
wattage lamps are more efficient than low
wattage. In fact, for low current lamps the
vacuum lamps are the more efficient, so that
HIGH CANDLE-POWER MAZDA LAMPS FOR STEEL MILL LIGHTING 379
for the present such lamps will continue to be
made.
The manufacturers can be relied upon to
use and standardize the construction which
yields the best quality of lamps. It is, there-
fore, important to avoid specifying whether
vacuum or gas-filled mazda lamps be furnished,
otherwise the specification may prevent the
user from securing the best possible lamps;
and although nitrogen has been largely
employed as the inert atmosphere, other
gases may be substituted when experience
has proved them advantageous. Therefore
the specification "nitrogen-filled" should be
avoided. The user's best interest will be
served by ordering mazda lamps, as described
in the latest data issued by the lamp manu-
facturers.
In the vacuum lamps, when tungsten is
evaporated from the filament, it travels
directly away from the filament and forms
a coating on that part of the bulb through
which the most light passes. In the non-
vacuum mazda lamps, any material evapo-
rated from the filament is carried upward by
the convection current, so as to form a coating
at a point directly above the filament. When
the lamp is burned pendant, this occurs near
DATA ON NEW MAZDA LAMPS FOR 110-VOLT (NOMINAL) CIRCUITS
(Lamps Provided with Mogul Screw Bases)
Rated Life of Lamp, 1000 Hours
Watts
Watt
per
C-P.*
C-P.*
per
Watt
C-P.*
Spherical
Reduction
Factor
Mean
Spherical
C-P. per
Watt
Total
Lumens
Style
Bulb
Maximum
Diameter
Bulb
(Inches)
Length
Overall
(Inches)
1000
0.55
1.82
1820
0.83
1.51
19000
S-52
6H
13^
750
0.60
1.67
1250
0.83
1.38
13000
S-46
Wa.
13
500
0.70
1.43
715
0.83
1.19
7440
S-40
5
10
400
0.75
1.33
530
0.83
1.11
5560
S-40
5
10
t 300
0.78
1.28
385
0.83
1.06
4000
S-35
Wt,
W
t 200
0.80
1.25
250
0.83
1.04
2600
S-30
3K
7%
* Mean horizontal candle-power.
t Medium screw base.
f DATA ON MAZDA SERIES LAMPS FOR 6.6 AMPERES
(Lamps Provided with Unskirted Mogul Screw Bases)
Rated Life of Lamp, 1350 Hours
Mean
Horizontal
C-P.
Average
Volts
Watts C-P.* Spherical
per per Watts Reduction
C-P.* Watt Factor
Mean
Spherical
C-P. per
Watt
Total
Lumens
Style
Bulb
Maximum
Diameter
Bulb
(Inches)
Length
Overall
(Inches)
600
400
250
100
80
60
55.5
37
23.9
9.8
8.0
6.1
0.61
0.61
0.63
0.65
0.66
0.67
1.64
1.64
1.59
1.54
1.51
1.49
366 0.80
244 0.80
157 0.80
65 0.76
53 0.76
40 0.76
1.31
1.31
1.27
1.17
1.15
1.13
7060
4020
2520
955
763
574
S-40
S-40
S-35
S-24J/2
S-24J-2
S-24Ji
5
5
W%
3iV
3re
3iV
10
10
9%
7%
7H
7M
* Mean horizontal candle-power.
t Lamps are also made for 7.5, 5.5 and 4 ampere. This table does not cover the full line of series lamps.
DATA ON SERIES LAMPS FOR USE WITH COMPENSATORS ON A-C. SERIES CIRCUITS
(Lamps Provided with Skirted Mogul Screw Bases)
Rated Life oi Lamps, 1300 Hours
Mean
Horizontal
C-P.
Average
Volts
Watts
per
C-P.*
C-P.*
per
Watt
Watts
Spherical
Reduction
Factor
Mean
Spherical
C-P. per
Watt
Total
Lumens
Style
Bulb
Maximum
Diameter
Bulb
(Inches)
Length
Overall
(Inches)
1000
600
400
25.0
15.0
14.4
0.5
0.5
0.54
2.00
2.00
1.85
500
300
216
0.78
0.78
0.78
1.56
1.56
1.44
9800
6800
3920
S-40
S-40
S-40
5
5
5
12 ^
V2V2
12V2
* Mean horizontal candle-power.
Current at lamp for 1000 and 600 candle-power, 20 amperes; 400 candle-power, 15 amperes.
Compensators are wound for 6.6- and 7-5-ampere circuits.
380
GENERAL ELECTRIC REVIEW
the end of the neck of the bulb, in a place-
where the least light is lost by absorption.
Except in a few special cases any darkening
of the bulb which may appear within the rated
life of a mazda lamp, is not likely to reduce
the effective illumination to any extent.
As will be appreciated, even after the dis-
covery of the principle there have been many
problems to solve, materials to select, and
dimensions and shapes to determine, in order
to produce lamps for commercial service. It
has been important to select such constants
as will allow best for future improvements.
Based on these selections, reflector and
equipment manufacturers have designed a
large number of accessories, of which many
are now installed in service, so that today
it is important to avoid changes which would
affect these designs, both because of the
expense to the equipment manufacturers
in changing their moulds and dies, and the
importance of securing interchangeability
for equipments already manufactured and
installed. These conditions had to be antici-
pated as far as possible.
The preceding tables give data applying to
some of the principal lamps standardized for
multiple and series circuits, while the gencr. 1
appearance of the lamps is shown in Fig. 2.
While the multiple lamp will undoubtedly
find greater use in steel plants than the
series, there is likely to be an economy in
using series lamps for outlying points, to
which the following advantages may apply:
1. Low cost of copper for line and small
line losses.
2. Convenience of station control.
•'!. Higher efficiency of smaller sizes of
lamps.
Scnes lamps are made in two styles, straight
series and compensator types. The straight
series type is intended for use directly on the
ordinary small alternating constant current
circuits, for example, (i.6 and 7.5 am;
The compensator types are also supplied
from such series circuits, but are for operatii in
in fixtures provided with compensators
for stepping the lamp current up to 2(1
amperes (400 c-p., 1.5 amp.), so as to take
advantage of the higher efficiency of the high
current lamp. The compensator may also
serve to protect the lamps from excessive
surges on the line. The multiple lamps can
be interchangeably operated on direct and
alternating current circuits and any com-
mercial frequency.
' Paper •Characteristics of Gas-filled Lamps. G. M. J.
Mackay. 1914 Convention. Illuminating Engineering Society.
None of these lamps, either multiple or
series, show perceptible flicker on 25-cycle
circuits. While most of the styles and sizes
as now made can be operated with the tip
up, it is desirable, when lamps are intended
for operation in this position, to specify
"for tip-up burning," as it has been found
desirable in some cases to slightly modify
the construction for this condition.
The light distribution differs a little from
that obtained with the ordinary vacuum
mazda. This is due to the coiled arrange-
ment of the filament, the effect of which is to
give a higher mean spherical reduction factor,
i.e., the ratio of mean spherical candle-power
divided by the mean horizontal candle-power.
This means that for a given mean horizontal
candle-power, the total flux of light from the
lamp is higher.
The variation of candle-power with voltage
is the same as for the older types of mazdas.
A number of engineers have inquired with
regard to the coiled arrangement of the
filament, whether considerable light were not
lost within the helix, and also as to the
temperature of the inner and outer surfaces
of the helix. With regard to the first inquiry,
it will be evident that no energy could be
lost within the helix, as any loss of light
occasioned by rays falling on the filament
would go toward raising the temperature,
and hence increase the efficiency of radiation.
However, in accordance with Provost's Phy-
sical Law. with reference to the "Theory of
Exchanges," parts of the filament cannot
lose energy by radiation to other parts which
are at the same temperature.
Then, as regards the second question, if
there is a tendency to produce a higher tem-
perature on one side of the filament, the heat
conduction of the material will tend to
equalize it. and the diameter of the filament
is not enough to allow any considerable
difference of temperature to be established.
Heat resistance calculations at the research
laboratory show that the actual difference
in temperature between the inner and outer
surfaces is about one degree C, which, of
course, is negligible.4
Again, a question has been raised as to the
allowable variation of voltage due to the
fact that the filaments are worked nearer
the melting point than in the vacuum lamps.
It is true that the new lamps will not with-
stand as high a momentary voltage as the
vacuum mazda lamp. They will, however,
stand considerable variation in this direction,
at least as much as the carbon filament lamps.
HIGH CANDLE-POWER MAZDA LAMPS FOR STEEL MILL LIGHTING 381
The higher heat capacity of the filaments is
instrumental in increasing the allowable
maximum voltage. Experience and investi-
gations lead the manufacturers to anticipate
no trouble from this cause in commercial
service.
Both the thickness of the filament and the
coiled arrangement make for ruggedness, so
that the lamps will stand fully as much vibra-
tion as any other type of lamp. The lamps
are designed to have pressure of the gas within
Angle (Asymmetrical )
Dome
Bowl
Fig. 3. Enamel Steel Reflectors for 750-
and 1000 watt Mazda Lamps
the bulb just below the atmospheric pressure
when the lamp is hot and somewhat lower
when cold.
Equipments
All forms of incandescent lamps are most
effective when provided with reflectors that
distribute the light in directions where the
illumination is desired, and reduce the light
in other directions where the intrinsic bril-
liancy may be objectionable. Such a reflector
also introduces diffusion, thereby softening
the shadows and reducing the glare. Since
these non-vacuum lamps operate with the
filament at a higher temperature, the bril-
liancy is a little higher than in the older types,
Angle (Asymmetrical)
Dome
Fig. 4.
Photometric Curves of Enamel Steel
Reflectors shown in Fig. 4
and the reduction of brilliancy more impor-
tant.
Reflectors for vacuum type mazda lamps
are suitable for corresponding new lamps.
The recent addition of the higher power
lamps required the development of new
382
GENERAL ELECTRIC REVIEW
equipments. It is even more important that
these lamps should have proper reflector
equipment than with the smaller sizes. In
the first place the lamps are likely to be
fl
Socket and Holder
Enamel or Galvanized
Steel Weatherproof
Cover
Fig. 5. Holder and Weatherproof Cover for
Use with Reflectors shown in Fig. 4
Fig. 6.
Outdoor Fixtures with Opal Globes, for High
Power Multiple Mazda Lamps
Fig. 7. Outdoor Fixture for High
Power Mazda Lamps (Fixtures for
series and multiple lamps are
similar in appearance1
Fig. 8.
Semi-indirect
Mazd;
spaced on wide centers so that good distri-
bution of light is necessary to insure good
illumination at intermediate points. The
concentrated arrangement of the filament
permits more accurate control of the light
distribution by means of reflectors, and con-
versely makes the use of the proper reflector
more necessary.
The higher wattage lamps have more heat
to dissipate from a small piece of apparatus;
furthermore, gas-filled lamps differ from the
vacuum lamps in that the internal convec-
tion currents carry heat upward, so that the
lamp base runs at fully as high a temperature
despite the fact that the heat loss per watt is
slightly less. On account of these considera-
tions special attention was required to insure
that proper ventilation was provided for in
the reflector designs. The experience in the
design of arc lamps was useful in this con-
nection.
The lamp manufacturers have endeavored
to cooperate closely with those responsible
for the design of reflectors and fixtures to
make sure that their product complied with
these requirements. As a result there are
now on the market a wide range of reflector
equipments for adapting these lamps to almost
any character of service. Practically all
of these which have been advertised take care
of the ventilation and provide distribution
of light for the purposes intended.
For interior lighting in a steel mill, the
porcelain enamel steel reflectors are likely to
be most extensively used. These are made in
three principal types; viz.,
extensive bowl, distributing
dome, and asymmetrical
angle. Fig. 3 shows these
reflectors as made by one of
the leading reflector manufac-
turers and gives correspond-
ing photometric curves. It
will be noted that the same
size reflector is used for both
the 750- and 1000-watt lamps.
Fig. 5 shows a holder and
some weatherproof housings
designed for use interchange-
ably with these reflectors.
The bowl and dome type
reflectors are well known,
while the angle type is being
more and more used where
the crane arrangement makes
it desirable to locate the light
sources along a wall, or edge
of a bay. These reflectors,
while more often used indoors, are sometimes
employed for exterior lighting.
For cases where the use of a diffusing globe
is desired, fixtures shown in Fig. S are avail-
Fixture for High Power
i Lamps
HIGH CANDLE-POWER MAZDA LAMPS FOR STEEL MILL LIGHTING 383
able. These are less efficient than those
shown in Fig. 3, and do not permit of as
effective control of light distribution, yet,
nevertheless, are preferred in many cases.
Fig. 7 shows another type of fixture for
use with series or multiple lamps for outdoor
service. These fixtures are arranged so that
different globe and refractor equipments may
be used interchangeably. These units have
been especially designed for street lighting
and will meet corresponding requirements in
large plants. For lower power series lamps,
both radial wave and refractor equipments
are available and advantageous.
Fig. 9 shows one of the several types of
refractor equipments. The radial wave
reflector is more efficient both in total and
in downward light, and gives a reasonably
wide spread. The refractor unit diffuses
the light, so that its entire surface appears
luminous, and also gives a remarkably wide
spread of illumination. The maximum candle-
power with the refractor is at 10 degrees below
the horizontal, and is approximately double
the rated candle-power of the lamp.
For the lighting of large general offices
and drafting rooms, having white or light
colored ceilings, it is often advantageous to
use semi-indirect or indirect lighting. Such
lighting provides excellent diffusion, which
facilitates the close and careful vision so gen-
erally required for bookkeeping, drafting, etc.
These methods of lighting are at their best
with the new high power lamp since it is
possible to produce even illumination with
wide spacing of units, while the high effi-
ciency of the lamps keeps the operating cost
relatively low. Fig. 8 shows one of the many
styles of semi-indirect fixtures.
The high efficiency lamps also offer new
possibilities in the way of advertising light-
ing, especially for plants located near rail-
ways and thoroughfares. Signs or building
fronts may be lighted effectively, at a rela-
tively low construction and operating cost, by
projected light.* When surrounded by a dark
background, an illuminated sign becomes more
conspicuous at night than in the daytime.
Conclusion
In this paper an attempt has been made
merely to collect and present briefly data
regarding these high power mazda lamps and
typical reflector equipments. No attempt
has been made to describe particular installa-
tions. Extensive installations have not been
in use long enough to contribute information
of great value; on the other hand, the Tran-
sactions of this Association contain reliable
Fig. 9. Refractor Equipment for Low Power Series Mazda
Lamp. (This particular unit is provided with a center
span suspension. Both bracket and eye suspen-
sions are also made.)
data on the lighting requirements of steel
mills,6 which, taken with the equipment data
here presented, will be sufficient to enable a
steel mill engineer to plan effective installa-
tions. It is believed that these units will
give an added impetus to mill lighting.
A few suggestions have been made for the
extension of artificial lighting. By selecting
units of most effective capacity, a higher
standard of illumination can be provided
in some of the important departments, with-
out increased cost, while it seems practicable
to extend artificial lighting to some sections
of plants where previously the cost has
seemed to exceed the advantage gained.
Safety has always been the watchword of this
Association; and good lighting is unquestion-
ably one of the most effective means toward
that end.
5 For example, paper on Iron and Steel Works Illumination,
C. J. Mundo, presented to the A. I. and S. E. E.. September.
1911.
* This subject is dealt with at length in an article in our
April issue, beginning on page 282: Sign and Building Exterior
Illumination bw Projection, by K. W. Mackall and L. C. Porter.
— Editor.
384 GENERAL ELECTRIC REVIEW
THE GENEMOTOR
(A Single Unit Starting and Lighting System for Moderate-Priced Automobiles)
By M. J. Fitch
West Lynn Works, General Electric Company
The author of the following article first names the reasons for developing the Genemotor, then describes
the functions, construction, and operation of the device, and concludes with a brief explanation of its com-
mercial distribution. — Editor.
Today, an automobile is hardly regarded as
being completely equipped unless it is fur-
nished with an electric starting and lighting
device. This regard is one of those examples
of our natural trend to welcome any thor-
oughly practical labor-saving device in our
daily activities. The manufacturers of high
and medium-priced cars were naturally the
first to embody such an equipment in the auto-
mobile. As a result of public demand, many
of the makers of low-priced cars have adopted
an electric lighting equipment as their
standard or are prepared to furnish a complete
electric starting and lighting equipment at a
small additional cost.
A good example of the type of low-priced
car. which as marketed by the manufacturer
does not include a starting equipment, is
the Ford. For cars of about this caliber, and
for this make in particular, the General
Electric Company has devised a starting and
lighting set to which the name Genemotor has
been given. This set combines the functions
of a generator and a motor in a single unit.
The machine possesses both main and com-
mutating poles and windings of a novel type,
and operates on 12 volts.
In starting the automobile engine, the
characteristics of the Genemotor are those of
a compound-wound motor having a heavy
series field. Later, when driven at a certain
predetermined speed by the engine, the unit
automatically assumes practically the same
functions as a shunt-wound generator, under
which condition it charges the storage bat-
tery connected to it.
The combination of windings that is used
secures an output of practically constant
current and voltage over a wide range of
speed; and, through the medium of this
inherent regulation, the use of vibrators,
voltage regulators, and other similar auto-
matic devices is eliminated.
The frame of the Genemotor is of mild sheet-
steel bent into cylindrical form with its
edges welded together. To the pinion end
of the cylinder is spot welded a die-drawn,
sheet-metal end head. The commutator end
head is of cast-iron which with the drawn
frame comprises a simple two-piece construc-
tion. The commutator and brush rigging
are protected by a punched metal insulated
cover. The shape of the frame, and to a
certain extent its construction, is shown in
Figs. 1, 2 and 3.
Mounted on the Genemotor is a small case
containing the starting switch and reverse-
current cutout as a single unit. The moving
member of the starting switch is composed of
Fig. 1. The Genemotor
a number of phosphor bronze leaves clamped
together; and the fixed member is a solid
copper contact which is an integral part of one
of the starting battery leads. The switch is
closed by a push-rod extending through the
dash, and is automatically opened when the
THE GENEMOTOR
385
386
GENERAL ELECTRIC REVIEW
rod is released. The reverse-current relay
connects the Gencmotor to the battery when
sufficient voltage is generated to charge the
battery, and breaks the circuit when the
Genemotor voltage falls below that of the
battery. This prevents the battery dis-
charging when the Genemotor is at rest.
This cutout, or its equivalent, is necessary
in all similar systems but is the only auto-
matic device necessary or employed with the
Genemotor.
Fig. 3. Genemotor Mounted on Ford Engine
The bracket by which the Genemotor is
fastened to the engine is a reinforced, strong
but light, sheet-steel punching. Three points
of attachment are used, these being both of
the water connections and the engine base
Incorporated in this bracket arc the
necessary screws, with lock-nuts for adjusting
the chain, and the steel strap to hold the
Genemotor in position.
Power is transmitted to the starting and
lighting unit by a single silent-chain of
special design and of approximately 2:1
gear ratio. The large sprocket replaces the
fan pulley on the engine shaft. All moving
parts are enclosed in a suitable dust guard
provided with suitable means for lubricat-
ing the chain when necessary. A split pulley
clamped to the regular fan pulley permits of
a continuance in the use of the fan
and belt tightening devices.
By means of a suitable connection,
furnished with the equipment, the
butterfly air intake valve of the car-
bureter can be closed when starting,
thus insuring the delivery of a rich
mixture to the cylinder which is very
essential in cold weather.
The lighting switch is of the three-
way reversible two-wire type which
permits the use of all the usual
lighting combinations. The necessary
lighting wire of correct length with
terminals properly tagged is furnished
together with starting cable of large
cross-section that insures but small
drop in the battery voltage.
The battery is of special design
and consists of six cells, each cell
containing seven 3^-inch plates. It
has a capacity of 42 ampere-hours at
the 5-ampere discharge rate and.
after being fully charged, can be
discharged at the rate of 250 amperes
with a voltage of not less than 1(1
at the beginning of the discharge.
The battery together with its sub-
stantial pressed steel container weighs
approximately 60 lb., and the com-
plete system including these batteries
totals about 140 lb.
The installation of the system can
be accomplished easily, especially so
by any of those mechanics who
specialize in such work. No changes
in the car are necessary and but
little fitting, if any, is required.
To start the engine, it is only neces-
sary to close the main switch and,
if necessary in extremely cold weather, the
butterfly valve. The Genemotor (as a motor)
will then produce approximately 100 lb. torque
at one foot radius on the engine shaft and will
ordinarily spin the engine at about 150 revo-
lutions per minute. When the car is driven at
a speed of from 10 to 12 miles per hour, the
ELECTROPHYSICS
387
cutout operates and automatically the Gene-
motor (now acting as a generator) will begin
to charge the battery. The maximum charg-
ing rate of 10 amperes is obtained at a
car speed of from 20 to 30 miles per hour ; and
at no speed will the ampere input to the
batteries exceed the safe normal charging
rate, even when the batteries are fully
charged.
The Genemotoris being distributed through-
out the country by Messrs. A. J. Picard & Co.,
1720-1722 Broadway, New York City, which
concern places the device in the hands of
local dealers of automobile supplies in the
principal cities. This arrangement greatly
facilitates the securing and installing of this
starting and lighting equipment for out-
standing Ford cars.
ELECTROPHYSICS
Part IV
By J. P. Minton
Research Laboratory, Pittseield Works, General Electric Company
In this installment the author deals entirely with free electromagnetic waves, and by assuming the
existence of electric lines of force shows how these waves are produced. A number of different kinds of
electromagnetic waves are discussed, and it is shown that we are justified in considering light waves, infra red
rays, gamma rays, Rontgen rays, etc., as of electromagnetic origin. A short discussion is given on the
effects of frequency on electrical measurements, with special reference to Maxwell's law. — Editor.
ELECTROMAGNETIC RADIATION FROM THE VIEWPOINT OF THE
ELECTRON THEORY
Introduction
In the three articles which the author has
already written on the electron theory for
this series on Electrophysics, the electron
conception of matter and electricity was
developed. It was shown how this con-
ception of matter and electricity greatly
simplified our previous ideas. Things which
appeared so divergent and unintelligible
become comparatively simple and easy to
explain with the idea of the electron. If
this does not appear to be evident from
previous considerations, let me call attention
to radioactivity. The chemists take matter
to be fundamental, but in doing so they
find it necessary to assume some eighty or
ninety different kinds of matter — these are
called the elements. No one will admit such a
conception as this to be simple by any means.
The physicists, on the other hand, do not
find it necessary to assume so many dif-
ferent forms of matter. Radioactivity shows
how one element breaks down into another
one of lower atomic weight, and when we
observe such a phenomenon as this, we are
justified in assuming only one form of matter
to exist. We might call this the parent form
and the other apparently different forms, the
deeendants. Both the parent and the decend-
ants are to be looked upon as made up
of exactly the same fundamental "things"
(whatever these may be), but each possesses
these fundamental "things" in different
combination so as to give different properties.
These "things" and their relation to one
another is what the theoretical physicist is
trying to fathom today. They consist of
electrons, electricity, energy and no doubt
other "things" about which we know little.
Certainly a view like this is more simple
to conceive and more far-reaching than the
old ideas of matter formerly held by the
scientific world.
What I wish to do in this article is to
harmonize so many apparently different
forms of radiation by snowing that they
may all be considered of an electromagnetic
nature, and hence, fundamentally all are
of the same kind. If this can be done, then
the engineer, who is so familiar with wireless
waves and waves along wires, will not be
struck with the power of mystery when
reference is made to gamma rays, Rontgen
rays, infra red rays, etc. The engineer will
also have a better understanding of the
connection between the electrons and the
electric and magnetic fields than he previously
had. Usually, he has no difficulty in thinking
about these fields, but he does have difficulty
in connecting up these fields with the electrons.
In order to eliminate this difficulty, if possible,
I shall endeavor to show the connection
388
GENERAL ELECTRIC REVIEW
that is assumed to exist between these fields
and the electrons. When the ideas here
set forth are fully developed and understood,
one ought to have a much simplified view of
the whole subject of radiation, just as the
scientist has a simplified view of matter as
outlined above.
In order to develop these ideas the follow-
ing subjects will be discussed:
I. Bound and Free Electromagnetic Waves.
II. Lines of Electric Force.
III. Production of Electromagnetic Waves.
IV. Kinds of Electromagnetic Waves.
(a) Ordinary Electromagnetic Waves.
(b) Infra Red Rays.
(c) Light Waves.
(d) Ultra-violet, Rontgen, and Gamma
Rays.
V. Energy Considerations for Electro-
magnetic Waves.
VI. Effect of Frequency on Electrical
Measurements.
VII. Summary and Conclusions.
With the object in view as outlined above,
we shall now take up these various subjects
in the order given.
I. BOUND AND FREE ELECTROMAGNETIC
WAVES
In discussing the subject of Electromagnetic
Radiation, we are concerned with what may
be called free electromagnetic waves. There
are also bound waves of this nature. We
must differentiate between these two kinds in
order to understand clearly with which kind
we are to deal. Many people have most
likely listened to the sound of an approaching
train by placing their ears against one of the
rails of the track. The transmission of these
sound waves along the rails may be called
transmitted bound waves. The free sound
waves would be those which pass through
the surrounding space so that a person
perhaps a mile from the track could hear
the approaching train. We may confine
light waves within tubes, or we may allow
them to pass in all directions through space.
The first are bound waves within the tube,
and the second are free waves. Similarly, all
are aware of the existence along wires of
electromagnetic waves, which are called
bound waves. Everyone is also familiar
with the existence of electromagnetic waves
met with in wireless telegraphy; these are
called free electromagnetic waves, and they
travel through space without the assistance
v guiding wires. These free electro-
magnetic waves, which travel through space
in this manner and which are produced in a
variety of ways, are the ones which will be
considered in this article.
II. LINES OF ELECTRIC FORCE
If there are two particles of electricity
(considering electricity fundamental instead
of matter) in space, they repel or attract
each other, depending on their signs, with a
force inversely proportional to the square of
the distance between them. But to say that
a force exists between these particles does not
satisfy us, because our minds are so con-
stituted that we must form a picture of how
this force is transmitted. Now, one way to
form this picture is to imagine a material
medium which will transmit the force; for
this purpose the idea of the ether prevading
all space was developed. But it is hard to
conceive of an ether, especially when it must
be thought of as a material medium. So, we
shall form another mental picture of the
peculiar way that the action between electric
charges may be considered to take place.
For this purpose we shall assume that each
particle of electricity carries with it lines of
force, which have been called Faraday tubes.
This was the assumption made by Faraday.
This is purely an assumption, and what these
lines of force are we cannot say any more
than we can say what electricity is or what
an ordinary piece of matter is. The idea is
far more simple than that of matter. There
is only one kind of line of force according to
this assumption, whereas there are many
different kinds of matter according to the
old ideas. This conception of a line of force
is just as fundamental and simple as that of
electricity; so, in this electromagnetic theory
we are going to develop, the line of electric
force is as much a part of electricity as the
electric charges themselves. Maxwell proved
that the forces between charged bodies could
be considered as resulting entirely from
tension along the lines of force and a repulsion
perpendicular to them1. So, the second
assumption we shall make is that these lines
of force, which are carried by every particle
of electricity, have the characteristic of
being in a state of tension, (similar to stretched
elastic strings) and of repelling one another
sideways. We may consider the force of
attraction resulting from stretched strings,
and repulsion due to compressed strings.
These lines of electric force may be con-
sidered as physical realities, because when a
disturbance of an electric charge occurs, this
ELECTROPHYSICS
389
disturbance is not detected instantly at a
distant point but at a certain definite time
later. We imagine the "news" (so to speak)
of the disturbance to be communicated to
a distant point by means of the electric lines
of force. If time is required for these lines of
force to carry the "news" to a distant point,
then it is absolutely necessary to think of
these lines of force as possessing inertia. They
are to be considered as concrete realities and
not merely as curved and straight directions
in space like boundary lines between states.
The idea of looking for the "electric" line
would not be as foolish as looking for the
state "boundary" line or a change of color
as illustrated on maps. In a number of
articles2 the idea of a line of electric force
being considered a reality has been developed.
We are now in a position to take up the
production of electromagnetic waves.
III. PRODUCTION OF ELECTROMAGNETIC
WAVES
The most simple way to conceive of the
production of electromagnetic waves is not
to consider a capacity and inductance in
series, but instead, to consider the electron
with its lines of electric force extending in all
directions into the surrounding space. Sup-
pose, then, we give our attention to an elec-
tron in free space and one of its lines of force.
If the electron has a sudden motion given to
it in a direction at right angles to the line,
then the end of the line at the electron will
be displaced in the direction of motion.
But since the line possesses inertia, it will
not be displaced over its whole length at the
same time. The parts nearer the electron
will be displaced sooner than those farther
away. Those parts of the line which are at
infinite distances from the electron will not
receive any displacement until infinite time
has elapsed after the displacement of the
electron. The result of the motion of the
electron is the production of a kink in the
line of force which travels outwardly in much
the same way a kink travels along a rope
when one end of it is suddenly jerked at
right angles to its length. The direction of
the electric force is, of course, along the line
at all its parts.
These ideas will be made clearer if we
consider a number of examples. Let us
consider two lines of force which leave the
electron. Imagine an electron to move
rather suddenly from .4 to B, Fig. 1. After
a short interval of time the state of affairs is
as represented in this figure. The two kinks
shown travel outwardly from the electron as
shown by the arrows, with a certain definite
velocity. Before each kink the line of force
is still in a position corresponding to A, and
behind each kink the lines are in the new
position, corresponding to B. The dotted
lines show the old positions of the lines of
electric force.
V
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o/Afot/on
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Qtrect/on
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Fig. 2
£/ec£*~on s/orr/y
snores fro/ri /fiofl
Fig. 3
If the electron moves from .4 to B in
zero time, after a short interval of time, the
condition of affairs is as represented in Fig. 2.
When the electron slowly moves from A to B,
the lines of force, after a short interval of
time, are as shown in Fig. 3.
When the electron moves parallel with the
lines of force, no kinks are produced and the
state of affairs is just the same as before the
movement took place. Then, let us consider
all the lines of force which are attached to an
electron. When the electron moves from A
to B, Fig. 4, all of the lines of force with the
exception of the two parallel to the direction
of motion have kinks produced in them.
Maximum kinks exist in those lines at right
angles to the direction of motion, and min-
imum kinks are found in those lines parallel
with the direction of motion. The arrows in
Fig. 4 indicate the direction of motion of
these kinks. The unsymmetry noticed in the
figure disappears farther away from the
electron.
The cases illustrated by Figs. 1, 2, 3 and 4
are the most simple. Let us now give our
attention to some examples which are more
interesting from an engineering point of view.
In this part of the discussion, the magnetic
field will be introduced. Oliver Heaviside
390
GENERAL ELECTRIC REVIEW
has shown3 that a portion of a line of electric
force, along which the force is E, moves with
a velocity V at right angles to itself (as
illustrated in Fig. 2), a magnetic field is
produced along this portion equal to H=EV.
If the portion of the line is not moving at
Arrows //?d/eoie
tf/rect/on of mot/on
E/ectron instantly
moves from rttoB
Fig. 4
right angles to itself (as illustrated in Fig. 1)
then H = EY sin 6, where 6 is the angle
between the direction of V and that of the
line of force. This magnetic force is at right
angles to both E and V. Consequently, the
magnetic field (or lines of magnetic force)
is produced by the motion of the electric
lines of force which themselves are caused to
move due to the motion of the electrons.
The electric lines of force are always present
whether the electrons move or not, but the
magnetic lines of force are present only when
the former lines are in motion. Therefore, it
is natural to consider the latter arising as a
result of the movement of the former.
In Figs. 1, 2, 3 and 4 we have shown no
magnetic lines of force; nevertheless these
are present in the kinks. If they were placed
in the diagrams, they would be represented
by dots in the kinks, showing that they were
at right angles to the electric lines of force
and to the direction of propagation of the
kinks. Since we have represented the electric
lines of force as being stationary, except in
the kinks, then it is clear that no magnetic
field exists along these stationary parts.
Let us plot, therefore, the magnetic and
electric fields surrounding a very long wire
in which electric oscillations arc taking place.
Xow. according to this theory, we are going
t<i think of the electrons in the wire as oscil-
lating, and the lines of electric force, which
can be represented as perpendicular to the
wire in all directions, having their ends
jerked backward and forward in unison with
the electrons. The result is the propagation
outward, along these lines of electric force,
kinks as represented in Fig. 5. The dots
represent the end-on view of the magnetic
lines of force; the circles show the magnetic
lines of force in the reversed direction. The
arrows indicate the direction of propagation
as before. These lines of magnetic force are
distributed in circles around the wire with
the centers on its axis, because the electric-
field extends radially (except in the kinks
where it tends to be parallel with the wire I
around the wire. These circles of magnetic
force are thought of as expanding outwardly,
as the kinks move away from the wire, in
much the same way that ripples on water
expand when a stone is thrown into it. As
the oscillations continue, there is a procession
of kinks or waves in the electric lines of forte.
These are first in one direction, and then in
the other, and move outward radially to the
wire. Mingled with these, and at right angles
to them, are the circular lines of magnetic
force, also alternately reversed. At any point
in space, not too near the wire, there is an
alternating electric force which is parallel
to the wire and an alternating magnetic
force which is at right angles to it and to the
direction of propagation. These two forces
are periodic and pulsate together, coming to
their maximum values at the same instant
at places not too near the wire. The result is
the propagation of what is called an electro-
magnetic wave outward with a certain definite
S/ect/~or?s
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c//rect/on ofmot'on
velocity depending only on themediumthn lugh
which it passes. If thie medium is free space,
then this electromagnetic disturbance is trans-
mitted without the assistance of ponderable
matter, and the process of this propagation has
been defined as electromagnetic radiation.
ELECTROPHYSICS
391
Next, suppose that electric oscillations are
produced in a wire of finite length rather
than of infinite length. These oscillations are
produced as a result of the to and fro move-
ment of electrons in the wire, just as stated
above, and the lines of force are jerked
backward and forward as previously de-
scribed. What happens in this ease is illus-
trated in Fig. 6. In this figure it will be seen
that the oppositely directed kinks of the waves
are joined together by closed loops of, what
may be called, electric forces. The diagram,
of course, shows only a plane section of the
space surrounding the wire. However, if
the whole space around the wire is considered,
then two symmetrical loops of electric force
may be thought of as expanding into a
closed shell of electric force. These shells
are thrown off, so to speak, from the wire
and travel out through space with a certain
definite velocity. The magnetic circles of
force also form closed shells of magnetic
force, and the direction of the magnetic
force in these is at right angles to both the
electric force and the direction of propagation
of the electromagnetic effect. These shells of
magnetic force are not shown in Fig. 6.
gap is inserted in the wire near the earth
(see Fig. 7). Imagine the portion of the
wire above the gap charged to a high poten-
tial. .Since the earth is a good conductor, we
may think of the earth and the vertical
wire as forming two plates of a condenser.
Fig. 7
Then, the lines of electric force will extend
symmetrically around the wire, starting,
say, from the wire and terminating on the
earth in all directions.
Now, suppose, a discharge occurs across the
gap. This causes the electrons in the antenna
to oscillate and the ends of the lines of force
are jerked back and forth as previously
described. After a short interval of time,
the kinks in all the lines have travelled out
equal distances from the antenna. In Fig. 8
is shown the condition of affairs for two
complete cycles. A vertical section only to
the right of the antenna is shown. In the
figure, the oppositely directed portions of the
lines of force are joined together in loops
of electric force. The dots represent the
circles of magnetic force, which may be
considered in clockwise direction around the
Arrows Jncf/cate d/rection of motion
£/ectrons osci/fating/ha short wire.
Fig. 6
' E/ectromagnet/c. ffodiation froma Marconi. Antenna.
Fig. 8
As a final example of the production of
electromagnetic waves, we shall discuss the
case of a simple Marconi antenna. It con-
sists of a wire, perhaps 100 feet long, placed
vertically with respect to the earth; a spark
antenna and the small circles are to represent
the circles of magnetic force which encircle
the antenna in anti-clockwise direction.
These electromagnetic effects are propagated
through space in the same manner as pre-
392
GENERAL ELECTRIC REVIEW
viously described and constitute what we
may call electromagnetic radiation. The
shape of the electric waves for the upper
portion of Fig. 8 is represented by the lower
part of the figure. Now, the shape of these
electromagnetic waves, as obtained by this
T/ieComp/ete Spectrum
H
0 *
1,8
toera /tea 'fieg/on
E/ectr/c
Wares
To/nfiiitty
0 iQ^mm to 4110 8*0 'O
Wa ve -Lengths -mm.
Fig. 9
theory, is exactly that as represented by
Fleming 4 and Franklin 5, who made use of
Hertz's 6 solution of the general equations of
the electromagnetic field in the neighborhood
of a small oscillator.
What we mean by electromagnetic radia-
tion, and how we imagine it to be produced,
is probably now fairly well understood.
It is important, now, to take up the dis-
cussion of the various kinds of electromag-
netic radiation, of which one frequently
hears.
IV. KINDS OF ELECTROMAGNETIC
RADIATION
(a) Ordinary Electromagnetic Waves.
The ordinary electromagnetic waves, met
with in wireless telegraphy, are those dis-
cussed above with the help of Figs. 5, 6, 7 and
8. Thus far, these have only been produced
by exciting oscillations in an electric circuit
which possess capacity and inductance. By
varying the capacity and inductance, it is
possible to obtain elective waves whose
wave-lengths extend from about 2 mm.
to infinity. These may be represented in the
spectrum, as shown by Fig. 9. Measurements
made with these short elective waves have
furnished an admirable proof of Maxwell's
electromagnetic theory. This will be pointed
out in the section on the effects of frequency
on electrical measurements. Our knowledge
of the very short electric waves is due to the
work of Lodge, Righi. Lebedew, Lampa,
Bose, v.Baeyer, and especially Prof. Rubens
of Berlin.
(b). Infra Red Rays.
The wave-lengths of the infra red rays
extend from about 0.0008 mm. to about
0.3 mm. These infra red rays can be detected
by the great heating power or by their action
on phosphorescent substances. They cor-
respond to the heat rays that come to the
earth from the sun. The portion of the
spectrum occupied by these waves is shown
in Fig. 9. It will be seen that an unknown
region exists between the shortest electric
waves yet produced and these infra red rays.
If the capacity and inductance of an electric
circuit could be made sufficiently small, then
it would be possible to produce electric waves
whose wave-lengths correspond to those of the
infra red region and to the unknown region.
So, we are inclined to believe that these
infra red rays are of an electromagnetic-
nature. This belief is further strengthened
by the pretty well established conclusion
that light waves are electromagnetic ones.
So, on both sides of these heat rays are found
electric waves as represented in Fig. 9. It
seems, therefore, that we are justified in
assuming that infra red waves are of an
electromagnetic nature. If this be so, then
we may consider them, according to this
theory, as due to the movements of electrons
within the substances emitting these infra
red rays. The movements of the electrons
would be oscillatory in nature and of a
frequency sufficiently high to produce the
waves of the magnitude shown in Fig. 9.
(c) Light Waves.
For a long time it was thought that electro-
magnetic waves were propagated through
space at infinite velocity, as appears to be
the case with gravity. Hertz, however,
proved experimentally that these waves were
transmitted through space at a velocity of
3X 1010 cm. per sec. which is also the velocity
of light through space. We see, therefore,
that a very close relationship exists between
the propagation of light and of these electro-
magnetic waves. Maxwell thought for a
long time before this that light waves were
electromagnetic in character, and he proved
theoretically that the velocity of these waves,
according to the electromagnetic theory
should be . — in transparent media, where
K is the dielectric constant and fi the mag-
netic permeability of any particular substance.
This law has received ample verification, as
will be pointed out later- in this article. For
these and other reasons, we feel fully justified
in saying that the propagation of light is an
electromagnetic disturbance of the nature
described above. If this be true, then we
must look for its explanation in the move-
ments of electrons and their lines of electric
force.
ELECTROPHYSICS
393
Let us assume this to be true, and the
frequency of oscillation of the electrons
about the positive atoms of various sub-
stances emitting light to be approximately
1015 per sec. (This corresponds to a wave-
length of 0.0003 mm. since wave-length
times frequency equal 3X1010 cm. per sec,
the velocity of light.) The phenomena of
light then receive a simple explanation.
Because, every electron describing a straight
or elliptical path sends out waves of both
electric and magnetic force, and every electron
revolving in a circle gives rise to a steady
magnetic field and a revolving electric field.
This revolving electric field sent out into
space is a twist something like that produced
by laying a rather stiff string on a table and
quickly twisting one end of it. If this electro-
magnetic wave is of proper frequency, it is
described as "circularly polarized" light in a
direction depending upon the direction of
rotation of the electron. When the electron
revolves in an elliptical path, it sends out
what is called "elliptically polarized" light,
and when the electron oscillates to and fro in
a straight line, it sends out "plane polarized"
light. The periodicity, of course, must be of
the proper magnitude to be visible as light.
We may think of ordinary light as being
produced by the random oscillations of the
proper frequency of the electrons within the
atoms of substances emitting light.
In order for the brain to receive the sen-
sation of light, we might regard the atoms of
the eyes as possessing electrons, which are
affected by the electromagnetic waves of
light. If, then, light waves of a frequency,
say, corresponding to yellow light enter the
eyes, the electrons within the eyes whose
frequency corresponds to that of yellow
light take up most of the energy due to the
phenomenon of resonance. The additional
energy possessed by these electrons is then
communicated to the brain. This can be
considered only a suggestion.
The portion of the spectrum occupied by
these light waves is indicated in Fig. 9, the
wave-lengths extend from 0.0004 to 0.0008
mm. If the capacity and inductance of an
oscillatory circuit could be made sufficiently
small, it would be possible, according to this
theory, to produce light directly by exciting
oscillations in such a circuit. On account of
the experimental difficulties encountered,
this has not been attempted.
(d) Ultra-violet, Rontgen, and Gamma Rays.
In the region extending from 0 wave-
length to that of the lowest visible light rays
are found waves which have been called
ultra-violet, Rontgen, and gamma rays.
The gamma rays are those produced by
Beta particles (electrons) when they suddenly
shoot off from radioactive substances. These
waves, therefore, are electromagnetic pulses
which move out through space, due to the
sudden movement given to the Beta par-
ticles as they are liberated from the sub-
stances. Since Beta particles move with the
highest known velocities, it is likely that
these rays possess the shortest wave-lengths.
For the slower moving gamma rays Ruther-
ford and Andrade 7 obtained wave-lengths
from 0.793 X10"7 to 1.365X10-' mm. Their
position on the spectrum scale is indicated in
Fig. 9.
A number of articles have recently appeared
in this magazine in connection with Rontgen
rays. We need say very little about these,
therefore, in this article. It will be well
to state, however, that since these rays are
produced by the sudden stoppage of electrons
within the X-ray tubes, it is safe to assume-
that these rays are also of an electromagnetic
nature and possess wave-lengths somewhat
greater than those of the gamma rays. Their
position on the spectrum scale is illustrated
in Fig. 9. The work of Laue, Friederick,
Knipping, W. H. Bragg, W. L. Bragg,
C. G. Barkla and others in connection with
reflection of Rontgen rays by crystals point
to the existence of homogeneous radiations
whose wave-lengths correspond to the order
of 10~7 or 10_s mm. which is about one ten-
thousandth that of ordinary light.
Ultra-violet rays are those whose wave-
lengths come immediately below those of the
visible spectrum. These waves are produced
by means of an electric spark between zinc,
cadmium, aluminum, and probably other
metallic electrodes. The ultra-violet light
from electric sparks between the first two
metals is strong, while that between the
third one is weak, and is easily absorbed
in a few centimeters of air. No doubt other
metals produce these rays, but they are so
feeble that one finds difficulty in detecting
them. Ultra-violet rays are also produced by
burning magnesium, and in the elective arc
strong ultra-violet rays are found. These
rays, coming from the sun, are nearly all
absorbed by the earth's atmosphere before
they reach the earth. Since these rays are so
easily absorbed by various substances, it is
difficult to learn much about them. The
shorter waves are more easily absorbed than
the longer ones, so that the minimum wave-
394
GENERAL ELECTRIC REVIEW
length yet measured is in the neighborhood
of 0.00010 mm. Quartz becomes opaque to
these ultra-violet waves at about 0.00015
mm., fluorite allows one to reach 0.00012
mm., air is opaque at about 0.0002 mm. and
with a concave reflecting grating, Lyman
l/mform/y Moving £/ectron Suctden/y Stopped at O.
Fig. 10
succeeded in reaching 0.000103 mm. As to
what will be done with the reflection of
Rontgen rays by crystals, we are not able to
state.
Many of the effects produced by the ultra-
violet rays are also produced by Rontgen
rays and gamma rays, both of which we
have seen to be of an electromagnetic nature.
All three of these kinds of waves are photo-
graphically active and cause fluorescence.
Light waves appear to be of an electro-
magnetic origin. The ultra-violet rays are
observed in electric discharges, so that it is
not at all unlikely that these rays are also of
an electromagnetic character. The position
of these rays in the spectrum is indicated in
Fig. 9. We may consider them resulting
from the movements of electrons whose
lines of force produce the effects observed in
connection with these rays. We shall now
take up that part of the article dealing with
the energy involved in these electromagnetic-
waves.
V. ENERGY CONSIDERATIONS
Thus far we have said nothing whatsoever
about the energy in these electromagnetic
waves. I should like, therefore, to devote a
short time to an elementary consideration of
this important phase of electromagnetic
radiation. In the first place, if oscillations
are set up in one system, these oscillations,
under the proper conditions, set up secondary
oscillations in another system some distance
away. That is, the energy in the first system
manifests itself in the second one, and there-
fore, energy disappears in the first and reap-
pears in the second. Consequently (since
energy is conservative), this energy must be
transmitted through that intervening space
in some manner. Since we know that there
are electromagnetic waves in the surrounding
space, it is quite evident that these waves are
waves of electromagnetic energy, or radiant
energy as it is more frequently called.
In order to understand more fully the
energy conditions which exist in these
electromagnetic waves, we may consider it in
the following manner: Imagine an electron
moving through space with a velocity (v)
small compared with the velocity of light
so that the electric field around it is uniform
for all practical purposes. Suppose the
electron is suddenly stopped in a time (7").
Considering just one line of force OM (Fig.
10), we can see that after a time (t) has
elapsed after stoppage, it is only the parts
of the lines of force which are inside a sphere
whose radius in ct (c being the velocity of
light) which have been stopped. The lines
of force outside this sphere will be in the
same position as if the electron had not
stopped; i.e., — they would be in the position
corresponding to the position (0') occupied
by the electron after the time (t) after stop-
page. Inside the sphere of radius c (t—T)
the lines of force are at rest; outside the
sphere of radius ct, the lines of force are
moving forward with a velocity (v). Since
the lines of force must remain continuous,
there is within these two spheres a tangential
electric and magnetic force moving outwards
with the velocity of light. The state of
affairs is as represented in Fig. 10.
Now let us calculate the values of the
electric and magnetic forces at a point (P)
within the spherical shell. Let (d) equal the
thickness of the shell and (r) equal the
distance 0P = ci (for our purpose), and 6
the angle POX. It is clear that the tangential
electric force in the shell is zero in the direc-
tion of motion and maximum in the direction
perpendicular to the motion. It is also clear
that we are concerned only with the tangential
component of the electric force in the shell
for this only is effective in the radiation. Let
then (Et) and (Er) equal the tangential
and radial electric forces respectively. From
the geometrv of the figure we have:
Et
Er '
QR _ vt sin e
d d
ELECTROPHYSICS
395
or
now
Er = Er-
vt sin d
(1)
op-
so that
but OP = ct
Hence
Et= =
evt sin 6
Er =
Op* d
ev sin d
cd OP
Dividing equation (2) by (1), we have
Tangential electric force after stoppage _ OP v sin 0
Electric force before stoppage cd
(2)
(3)
As (d) is very small compared with (OP),
this ratio is very large. Thus the stoppage
of the electron causes a thin shell of intense
electric force to travel outward with the
velocity of light. But we have seen 8 that
H=VE and since V = c, the velocity of
light, we have from equation (2):
„ ev sin 6
ti ===== — -j —
OP d
(4)
Since H before stoppage was 9
We have
Tangential magnetic force after stoppage
Magnetic force before stoppage
ev sin 6
OP*
ev sin 'i
or d
op-
Tangential magnetic force after stoppage _ OP
Magnetic force before stoppage d
(5)
which shows that there is accompanying the
pulse of intense electric force one of intense
magnetic force, both being propagated
through space at the velocity of light. The
equations (3) and (5) show that the electric
and magnetic forces outside the shell and
the electric force within the inside of the
inner shell are extremely small compared
with these values within the shell. These
same equations hold for any other pulse
which follows or precedes the one which we
have considered, as would be the case in an
electric oscillating system of any kind.
It is interesting to determine the total
electromagnetic energy in one of these pulses
and to see how much of the kinetic energy of
the electron is radiated away by its sudden
stoppage. In this determination we are con-
cerned only with (Et) and (H) after stoppage
as given by equations (2) and (4) respectively.
The total electromagnetic energy (6) in one
of the pulses which surround the electron is
given by the integral
=Mff^+H2)
dv
(6)
This integral was derived by Maxwell in his
electromagnetic theory, and has already
been made use of by the author 10 in this
series on Electrophysics. The integration of
this equation is to extend over the volume
occupied by one pulse. If (a) is the distance
out to the pulse and (d) the thickness of the
pulse, then the integration extends from (a)
to (a-\-d). Proceeding in the same manner
as illustrated on pp. 123-124 of the author's
first article in the Feb., 1915, issue of the
Review, we obtain for the total electric
energy (ce) and the total magnetic energy
(tM) in the pulse.
it (a +d)
""""'-XhfiMhUM* (7)
(a+d)
■"-■} f
and
*s o *s a
ns (7) i
■id d'- 1 I
c>d*>
- X2ir r- sin 6 da dr
(8)
Equations (7) and (S) reduce respectively to
r (a + d)
sin' 9 dS dr (9)
and
Jo *' <1
(a+d)
sin' e di) dr
(10)
Integrating equations (9) and (10) we obtain
e*v2
IE-
and
3c2 d
'3d
(11)
(12)
Equation (11) is in C.G.S. electrostatic
units, while (12) is in C.G.S. electromagnetic
units. Eliminating c2 in the former equation,
we have («e) in C.G.S. electromagnetic
units. It is then seen that the total electric
and magnetic energies in one pulse are equal
to each other, a thing that should be true
now.
e=tE + t.u (13)
or
e- v , e~ v
t = ~3d+lld
3d
(14)
(15)
Equation (15) shows us that the electro-
magnetic energy radiated away is greatest
396
GENERAL ELECTRIC REVIEW
when the thickness (d) of the shell is least.
4.e~
If (d) equals - — (which we have seen11 to
be equal to the diameter of the electron by
assuming its mass to be wholly electromag-
netic), then equation (15) becomes:
2e2v2
4e2
3xf^
3m
or
1 ,
e =— mi-
(16)
which is the whole of the kinetic energy
possessed by the electron before stoppage.
Hence, if the electron can be stopped quickly
enough to make the thickness of the shell
equal its diameter, then all the energy is
radiated away. If the electron is simply
accelerated, positively or negatively, electro-
magnetic energy is radiated away. When
oscillations are set up in a charged wire,
like an antenna, then energy will be radiated
away in accordance with this principle. For
anv given frequency of these oscillations,
the more abrupt the reversals of current, the
greater will be the radiated energy. Since
it is impossible to obtain an antenna of a
100 per cent radiative efficiency, it is clear
that the thinness of the shell of electromag-
netic energy never attains a value as low as
indicated above.
VI. EFFECT OF FREQUENCY ON
ELECTRICAL MEASUREMENTS
We have seen that the wave-lengths of
what we have called electromagnetic waves
extend from almost zero to infinity. This
corresponds to frequencies ranging from
very large values (perhaps 1020) to zero.
Can we imagine what the electrical properties
of various dielectrics would be when they
were tested over such a wide range of fre-
quencies? The discussion of this question
is entirely out of the scope of this article,
yet I should like to call attention to a few
facts relating to this important subject.
The first point is that pertaining to the
measurements of dielectric constants. In
section IV— C we stated that Maxwell proved
that the velocity of electromagnetic waves
through transparent media was equal to
—p==; K and yu being the dielectric constant
V/iK
and the magnetic permeability respectively
of any particular medium. Since we arbi-
trarily take n = K = 1 for free space, then
the ratio of the velocity of these waves in
free space to that in any transparent medium
is:
n = V~jiK (17)
Now, for all transparent media yu is practically
unity. Hence,
n = VK (18)
Now, (w) is called the refractive index of
a medium, and it is seen to be equal to the
square root of the dielectric constant of that
medium. If this relation were exactly true,
it would afford a means of obtaining the
dielectric constant of many materials for
electromagnetic waves of exceedingly high
frequency. At the present time the dielectric
constants of materials are measured for
steady or relatively low frequency electro-
motive forces. It becomes of interest to
investigate the dielectric constants for very
high frequencies, corresponding to that of
very short electric waves or ordinary light
and infra red rays. The refractive indices
for many substances measured at frequencies
corresponding to light (about 1015) give
values for (n2) which are very nearly equal
to (K) as measured by electromotive forces
of ordinary frequencies l;. In these cases we
are to conclude that the dielectric constants
do not change appreciably with frequency.
This furnishes an admirable proof of Max-
well's Electromagnetic Theory. This law is
found not to hold for many other substances.
For example, the dielectric constants of
water and alcohol are about 80 and 25 respec-
tively for the low frequencies, but the refrac-
tive indices for these substances vary consider-
ably with frequency as indicated by the fol-
lowing table13 of (n2).
water: K = 80
Wave-length
0.00059 mm.
0.082 mm.
5.0 cm.
60.0 cm.
600.0 cm.
1.78
1.98
78.0
75.6
79.2
Authority
Rubens
Cole
Drude
Cole
alcohol: K =25
Wave-length
«"
Authority
0.00059
mm.
1.88
0.108
mm.
1.96
Rubens
4.0
mm.
5.02
Lampa
5.0
cm.
10.24
Cole
60.0
cm.
22.5
Drude
259.0
cm.
27.4
Cole
ELECTROPHYSICS
397
This table shows us that n2 does not equal
K for water and alcohol over the whole range
of frequency recorded. For wave-lengths
above 5 cm. it will be seen that Maxwell's
law holds very nicely for water, but for the
shorter wave-lengths the discrepancy is
quite large provided we assume AT = SO to
hold for very short waves. We have no right
to assume that K = S0 for short waves for if
we could measure it, we would in all prob-
ability find it equal to (n2). The sudden
change in the value of the dielectric constant
for water is found in the unknown region to
the right in Fig. 9. The values of (w2) for
alcohol show a consistent decrease with
increasing frequency. This same change is to
be looked for in the values for (AT) for alcohol
— the value AT = 25 being one that corresponds
to some particular frequency. We are
inclined to believe, therefore, that the
variations from Maxwell's law simply mean
that the values for the dielectric constants
have not been investigated over a sufficient
range of conditions (including frequency) to
know much about them.
Generally speaking then, we may say
that the dielectric constants are independent
of or decrease with increasing frequency.
This means that the capacities of various
substances remain constant or decrease as
the frequency increases, other things being
the same. The above table giving values of
(n2) for water and alcohol would lead us to
believe that the dielectric strength of a
dielectric consisting of water and air would
experience an abrupt increase in the region
of wave-lengths corresponding to the sudden
change in (n2); in the case of alcohol and air
we should expect a gradual increase in the
dielectric strength rather than an abrupt one.
Of course, other peculiarities enter and tend
to nullify these effects. A further discussion
of this subject would lead us into a consider-
ation of these other effects, a thing we wish
to avoid in this article.
VII. SUMMARY AND CONCLUSIONS
In the present article we have dealt entirely
with the free electromagnetic waves, and
have shown how these waves are produced
by assuming the existence of electric lines
of force. These lines of force can be treated
as physical realities and are as much a part
of electricity as the electric charges them-
selves. A number of examples were discussed
showing the connection between the move-
ments of electrons and the production of
these electromagnetic waves. Various kinds
of electromagnetic waves were discussed, and
the positions of the spectrum occupied by
them were illustrated by means of Fig. 9.
It has been shown that we are justified in
considering light waves, infra red rays,
gamma rays, ultra-violet rays, and Rontgen
rays of an electromagnetic origin arising
from the movements of electrons and their
lines of electric force. The electromagnetic
waves were shown to carry a considerable
amount of radiant energy in the pulses, and
intense electric and magnetic fields existed
within these. Mathematical expressions were
obtained for the values of the electric and
magnetic energy in each pulse sent out into
space by an oscillating electron. A short
discussion was given on the effects of fre-
quency on electrical measurements with
special reference to Maxwell's law.
REFERENCES
(') Soc article by the Author on "Effect of Dielectric
Spark Lag on Spark Gaps," General Elec-
tric Review, July, 1913, pp. 514-518.
(2) (a) Faraday's "Experimental Researches on
Electricity" vol. 3, ser. 29, articles 3273, 3297
and 3299.
Faraday's Physical Lines of Magnetic Force"
and "Thoughts on Ray Vibration." Phil.
.Mag., ser 3, vol. 28, 1846.
(b) J. J. Thomson, "Electricity and Matter."
p. 63.
(c) J. J. Thomson, " Material Nature of Lines of
Force," Phil. Mag., ser. 6, vol. 19, p. 301,
Feb., 1910.
(d) J. A. Fleming, Phil. Mag., ser. 6, vol. 19,
p. 301, 1910.
(3) Oliver Heaviside's "Electromagnetic Theory"
vol. 1, p. 56.
(4) J. A. Fleming, "Principles of Electric Wave
Telegraphy" p. 408.
(6) W. S. Franklin, "Electric Waves" p. 210.
(6) Hertz, "Electric Waves" (Jones' Translation)
pp. 137-150.
(7) Rutherford and Andrade, "Wave-length of Soft
Gamma Rays from Radium," Phil. Mag., vol.
27, pp. 854-868, 1914.
(8) Oliver Heaviside, Loc. Cit. (3).
(') J. P. Minton "Cathode Rays and their Proper-
ties." General Electric Review, Feb., 1915,
eauation (1), p. 12.3.
('») J. P. Minton, Loc. Cit. (9), equations (1) and (2)
p. 123; also Loc. Cit. (1), pp. 517-518.
(») J. P. Minton, Loc. Cit. (9), equation (7) p. 125.
(") J. A. Fleming, Loc. Cit. (4), see tables p. 355.
(") David Owen, "Recent Physical Research,"
Table III, p. 128.
398
GENERAL ELECTRIC REVIEW
THE HIGH-TENSION TEST
PITTSFIELD WORKS, GENERAL ELECTRIC COMPANY)
By Wm. P. Woodward
Transformer Department, General Electric Company
The following article describes what is probably the most complete high-tension testing installation in
the world. Some of the features of the installation that are treated in the article are the building in which it
is housed, the source of the power supply, the equipment of transformers and controlling and measuring
devices. The conclusion points out the need for such a completely equipped test and names some of the
benefits that are derived from one. — Editor.
Power systems are growing in size, in
complexity, and in voltage. Their growth is
made possible by the transformer. The
design of transformers involves constant
research and their manufacture requires
special and elaborate testing arrange-
ments.
An establishment which has been devoted
to this work since the time when the trans-
former first became a factor in electric
systems, and whose growth has been
commensurate with the importance of its
work, has recently been newly housed and
equipped and is unique in its size and com-
pleteness.
In a building devoted exclusively to the
purpose there are three complete high-tension
testing sets, any one of which would, in itself,
be a notable feature of any electrical lab-
oratory.
The building is a modern structure of steel
with a brick facing and a concrete floor, and
is absolutely fireproof. Inside it measures
. 82 ft. wide, 121 ft. long, and 57 ft. high, with
a clear height of 47 ft. and a crane clearance
above the floor of 40 ft. There are no columns
and the space is absolutely clear. A capacious
pit 9 ft. deep gives a total crane clearance of
49 ft. Ready entrance is had through two
large doors, and two spurs of the factory
railroad enter the building. The doors do
not open directly into the outside air but
open into another building which houses the
Commercial Transformer Testing Depart-
ment. Thus the entrance of a car with
machinery does not introduce a blast of out-
side air and does not affect the temperature
of the room.
Abundant daylight is supplied by windows
which occupy practically all of the north and
east walls of the building; and at night the
building is brilliantly illuminated by mazda
lamps, hung near the ceiling above the crane
runway.
When a test involving the observation of
corona or other optical effects is in progress,
the building can be made absolutely dark at
any time of day by closing over the windows
a series of steel shutters which can be easily
and quickly manipulated.
Each of the three testing sets consists
essentially of a high-tension transformer,
Fig. 1. Five Minute Negative Exposure of Two Oil-Filled
Porcelain Leads in Multiple at 175,000 Volts. The
Resistance in Series with Lead on Left, 260,000 Ohms
in Series with_Lead on Right
with regulating outfit and the necessary
spark-gaps, condensers, resistances, and
reactances. In the 750,000-volt outfit the
principal unit is a 500-kv-a., 750,000-volt,
60-cycle transformer of the oil-insulated,
self -cooled, core type with a low-voltage
THE HIGH-TENSION TEST
399
winding arranged for a series-multiple con-
nection. Cylindrical low-voltage coils and
disc high-voltage coils are used. The high-
voltage bushings are oil filled. The trans-
former may be operated grounded or un-
grounded, as may be found necessary for the
various tests.
The control apparatus is mounted on an
elevated platform 20 ft. above the floor,
which location enables a commanding view
to be had over all the testing room. This
due to the reactance of the generator and the
slow building up of its field, the voltage
increases in a smooth curve. This avoids the
disturbances that would occur if the voltage
should be increased by cutting in turns of a
regulating transformer (directly attached to
the testing set) whose steps, however small,
would be abrupt.
Both needle-point and spherical-spark gaps
are available, but the burden of the testing
work at present is being carried on by sphere-
Fig. 2.
Four Minute Exposure of a High-Tension Lead
at 350.000 Volts
apparatus is composed of the necessary field
rheostats and measuring instruments and is
so arranged that the operator can observe
everything which occurs while a test is in
progress. Control is obtained by means of
rheostats in both the motor and the gen-
erator fields, so that the frequency as well as
the voltage is completely under the control
of the operator. There is sufficient resistance
in the generator field circuit to permit start-
ing a test at about 25 per cent of its final
value. The voltage is then increased by cut-
ting out field resistance in small steps so that,
Fig. 3. An Instantaneous Photograph of a 353,000-Volt Arc
Produced from a 300,000-Volt Testing Transformer by
Conversion Between Terminals 43 Inches Apart. Total
Length of Arc about 20 Feet
gaps of various sizes. Both classes of gaps
have a rigid base and a micrometer adjust-
ment from zero to the full capacity of the
transformer. The needle-point gap is of the
conventional type and needs no special
description. Its base and parts are of gen-
erous size, and give excellent rigidity for
accurate centering and setting. The sphere-
gap consists of two spheres heavily and
rigidly mounted, with micrometer adjust-
ments. The spheres of the largest gap are
75 cm. in diameter (29 H inches).
There is a large bank of condensers, and a
400
GENERAL ELECTRIC REVIEW
variable inductance having a range from
0.005 henrys to 0.750 henrys.
Conveniently near the transformer is an
oil tank built of concrete. It is arranged
Fig. 4.
Photograph of a High Tension Lead Flash Over
at 400,000 Voltt
largely below the floor level, and extends
above the floor only a sufficient distance to
afford facility in work. Such tests as require
immersion in oil are carried out in this tank
which has a capacity of 36,000 gal. An oil
dryer and filter is permanently installed at
the tank; and there are facilities for com-
pletely emptying when necessary for cleaning
or other purposes. To maintain a uniform
temperature of the oil, or to change the
temperature to any desired degree, a heater
is provided.
The entire testing set is enclosed by a high
steel netting barricade, the entrances of
which are closed by safety doors electrically
connected to the controlling apparatus so
that when the door is opened the primarv
circuit is broken, thus "deadening" the
entire test which makes it impossible for any
one to enter the enclosure while voltage is on.
Similar to the 750,000-volt testing set is a
300-kv-a., 300,000-volt set, which is provided
with the same facilities and is surrounded by
the same precautions.
The high-frequency, high-voltage testing
set gives 250,000 volts at 250,000 cycles.
This frequency is obtained by means of a
combination of gap, condenser, and trans-
former with adjusted time constant. A sine
wave, 60-cycle current is used as the funda-
mental.
In addition to these high-voltage sets,
there are several testing sets of lower voltage
but of equal completeness and usefulness.
One of these is for 30,000 volts and another is
for 10,000 volts, each with complete control
arrangements and with excellent facilities
for such research and investigation as can be
made within its range.
The generators are specially designed for
high-voltage testing service and are so
arranged as to give practically a true sine
wave at any load, frequency, and power-
factor. The armatures are stationary and
are so wound that they may be used at full
kv-a. capacity at one-quarter, one-half or
full voltage, and at three-quarters kv-a.
capacity at three-quarters voltage. The
alternators are driven by variable-speed,
separately-excited, direct-currentmotors which
can be supplied with. line voltages varying
from 110 volts to 550 volts so that a complete
range of frequency may be obtained. Two
of these generators are of 500 kv-a. each and
smaller units are arranged for use with the
smaller sets, each being of sufficient size to
prevent a change of wave form at the low
power-factor loads of this kind of service.
OPERATION OF ELECTRICAL MACHINERY
401
By means of the exceptional testing
facilities afforded by the elaborate and com-
plete equipment of this research and com-
mercial laboratory, each advance step in
transformer design and construction has been
made the subject of exhaustive and practiced
investigation. The results have produced a
symmetry of insulation design that no other
means can obtain. Every part of the trans-
former is continually and systematically
investigated with a view to added excellence
and strength; and new and improved methods
and materials are continually being evolved.
Tests are made on full-size working models,
on sections of transformers, and on complete
transformers, in accordance with the demand
of the subject under consideration. In this
way the turn insulation, the insulation
between coils, and that to ground have been
so developed that each is proportional
directly to the demand made upon it.
Varnishes, and other plastics, and the
textiles are here commercially tested in
advance of their application to machinery,
thus insuring uniform quality and strength.
They are also experimentally tested here
with a view to improving their inherent
qualities. This line of investigation has
resulted in the production of a very strong
and uniform line of varnishes, compounds,
and fabrics which by means of the High
Tension Testing Department is constantly
kept under the eye of experts.
All the insulation which is used, even that
for the lowest voltage commercial apparatus,
is subjected to a careful high-voltage test
before it is assembled in the machine and
again after the machine is complete when it is
tested as a whole. This obviates the possi-
bility of a defective piece of material, which
may be found in a lot otherwise excellent,
ever reaching a place in a machine.
It is true, some sort of a transformer can
be made by the time-honored method of
"hit or miss" but the efficient, sturdy
machine that carries the burden of big plants
and that saves the pennies which add into
dollars for the small user can only be the
result of evolution. This truly scientific
tool combines the ideas evolved from the
experience of the manufacturer and the ideas
evolved from the experience of the user,
after they have been tried out in such a fully
equipped laboratory as the one described.
In this way there has been developed a line
of transformers that is uniformly and admit-
tedly superior to any that are not the result
of such development.
PRACTICAL EXPERIENCE IN
THE OPERATION OF ELEC-
TRICAL MACHINERY
Part VIII (Nos. 41 to 46 Inc.)
By E. C. Parham
Construction Department, General Electric
Company
(41) CAPACITY CURRENT
Capacity current here refers to the current
that flows when an e.m.f. is applied to a
circuit that is open in the ordinary under-
standing of the word open as applied to a
circuit. A capacity current is due to the con-
denser effect incident to the fact that, in
any system of insulated conductors, the air
may serve as the dielectric of an actual
condenser in which certain conductors
serve as the positive plates and other
conductors (or the earth) serve as the negative
plates.
In the case of applying a continuous e.m.f.,
the capacity current or charging current takes
the form of a single impulse in one direction,
for as soon as the conductors become charged
all current flow ceases.
When an alternating e.m.f. is applied,
however, the capacity current must reverse
as often as does the e.m.f.; therefore, it takes
the form of an alternating current. Its value
may rise very considerably under certain
line conditions. If the line constants are
favorable, the "banking up" effect of the
surging current may very much increase the
measurable e.m.f.; just as water-hammer in
pipes may increase the water pressure
therein.
In a particular installation the capacity
of a high-tension transmission system was
such that when closing the station switches
upon the open external line (before the field
of the alternator exciter could be brought
up) both the station current and voltage were
observed to be so large that it was necessary
to open the oil switches. Owing to the
capacity current and its undesirable effects,
it was thoroughly unsatisfactory to close the
station switches until several transformers
had been connected across the transmission
line at the distant end, thereby introducing
an inductance to overcome the effect of the
capacity.
(42) MISAPPLICATION OF DEVICES
Misapplication of electrical devices may be
traced to either of two sources: They may
402
GENERAL ELECTRIC REVIEW
have been wrongly selected in the first place,
or they may have been thoughtlessly shifted
from one duty to another by the operator.
In either case the result is the same — unsatis-
factory operation. While the following may
sound like hypothetically stated generalities
intended to cover possibilities, too often they
exist as trouble brewing actualities that are
not covered at all.
(1) Direct-current, shunt-wound motors
should not be applied to duties that require
abnormal starting torque. (They are designed
to develop torque only after the connected
load is up to speed.) An efficient shunt-wound
motor is characteristically a constant-speed
motor, because its field current is independent
of the armature current excepting insofar as
abnormal armature current may pull down the
applied voltage, by producing an excessive
line drop. Furthermore, this feature of inde-
pendence precludes the field from exerting
on the armature current any limiting influence
proportional to it. Therefore, the current
required to start heavy loads is abnormal.
(2) Direct-current, compound-wound mo-
tors should not be applied where the
duties call for constant speed and moderate
starting torque. A differential connection
of the shunt and series windings, in order to
get automatic speed regulation, is likely
to produce an unstable condition, unless the
machine was designed with that automatic
feature in view. With the fields cumulatively
connected, as they generally are, the speed
variation per ampere increase in load is
greater than with the corresponding shunt-
wound motor, because the latter has no
series turns to strengthen the field when the
load increases. If only a compound-wound
motor is available and constant speed is
desired, the compound winding may be cut
out and the motor operated as a shunt motor.
If both abnormal starting torque and constant
speed are essential, a compound- wound motor
may be so arranged as to start with its series
field cumulatively connected, and, after the
motor is up to speed, the series field may be
cut out and the motor operated as a shunt
motor.
(3) Series motors are characteristically
variable-speed motors, because load changes
affect their field strength directly. On con-
stant potential circuits, their speed cannot
be held constant unless the connected load
is constant, and on light load racing results.
(4) Squirrel-cage induction motors should
not be applied to duties in which range and
flexibility in speed control are essential. The
speed control is generally limited to that
which can be obtainable by varying a resist-
ance that is connected into the supply mains.
Since the torque varies as the square of the
applied voltage and since the variations in the
voltage applied to the motor itself are much
greater than the external variations in the
supply voltage, this method of speed control
produces instability. For a strong starting
torque per ampere and good speed control,
the slip-ring motor with external resistor is
better.
(5) Induction motors of the internal
resistor type should not be applied to loads
of great inertia. Since the space available for
an internal resistor is limited and its heat
storage capacity is comparatively small, the
resistor is very liable to be damaged if the
motor is applied to heavy starting duty.
The field for the resistor type of motor is
similar to that of the squirrel-cage motor,
which it can replace to advantage where lights
are operated on the same circuit, and where it
is desirable to minimize the voltage fluctua-
tions incident to starting a motor.
(43) MISLEADING DEFLECTIONS
The indications of some of the forms of
ground detector used on alternating current
circuits depend upon the fact that current
will flow through a condenser which is con-
nected to a source of alternating e.m.f.
although the condenser does not metallically
close the circuit of which it is a part. This
fact explains why alternating current and
alternating-current instruments may give
very misleading results when used for measur-
ing insulation resistance between conductors
that include appreciable capacity. (A ca-
pacity current through the instrument will,
produce a deflection that may indicate low
insulation resistance when, as a matter of
fact, the insulation resistance may be very
high.)
An operator who installed a two-phase,
240-volt generator became alarmed because
with the machine at normal voltage he was
able to get a 40-volt deflection by applying
the voltmeter terminals to legs that belonged
to different phases. The deflection was due
to the fact that the conductors of the two-
phase windings, in conjunction with the
intervening insulation, acted as a condenser
that charged and discharged through the
voltmeter. A test made with a direct-current
voltmeter and voltage from the 140 volt
exciter indicated the insulation to be perfect
insofar as an e.m.f. of 140 volts could indicate.
OPERATION OF ELECTRICAL MACHINERY
4 IK',
A later application of a "megger" showed
the insulation between phases to exceed
20 megohms.
It is easy to imagine how a repairman,
unfamiliar with this characteristic of alter-
nating current, might become alarmed at
getting a large deflection between the phases
of a machine that he had just repaired.
Wherever there is an alternator, the direct-
current exciter should be used to furnish the
voltage for carrying out the insulation tests.
(44) REACTOR STARTING-BOX
TROUBLE
The reactor starting boxes that are used on
very small alternating-current motors are so
connected, in conjunction with a three-phase
winding on the stator, that a part of the
reactance is used to produce a current phase
displacement, hence a rotation of the mag-
netism, and a part is used as a choke coil by
means of which the motor speed is regulated.
Where motors are so controlled, the greatest
torque and highest speed are obtainable on
the first notch. This arrangement is used to
insure that the motor, when under variable
voltage conditions, will always have sufficient
torque to start and to make certain that the
controller will not be left on a notch on which
the motor might fail to start should the volt-
age be low. Under such a condition, the
current flowing might be insufficient to melt
a fuse but sufficient to injure the motor or
the reactance. When this connection is
employed, a lower speed can be secured after
the motor has been started by advancing the
controller to a notch on which some of the
reactance is cut into the circuit.
One of these outfits had been applied to the
exhausting of smoke from a restaurant the
proprietor of which complained that the
motor sometimes would start and sometimes
it would not and that occasionally the reactor
starting box would get very hot. Inspection
and tests indicated that the motor and the
controller were in good condition in all
respects, and the motor started promptly
each of several times that the inspector tried
it. The voltage was above normal and the
inspector was assured that the lights always
burned as brightly as they were burning then.
It began to look as if the inspector would
have to leave things exactly as he had found
them, when the operator made the remark,
in substance, that sometimes when he would
go to start the motor he would find it already
running backward and he wished to inquire
if it was safe to try to start it under this
condition. This information was the clue to
the trouble. The motor was installed in a
window the location of which was such that
at times the outside wind blew against the
fan with sufficient force to retard its motion
and overload the motor, or to prevent the
motor from being started from rest. The
installing of a wind shield to prevent the wind
from blowing directly against the fan per-
manently relieved the situation for nothing
more was ever heard of the matter.
Had the hotel proprietor not indirectly
suggested the trouble, the unit would have
probably been rejected as unsatisfactory,
unless the inspector had happened to visit
the plant when the wind was blowing against
the fan.
(45) IMPROVISED COMMUTATING
WINDING
A correctly proportioned commutating-
pole winding neutralizes the distorting effect
of armature reaction and thereby produces
commutation of a high quality that could
not be obtained otherwise except at a much
greater first cost. If the commutating poles
are either too weak or too strong, the commu-
tation will not be satisfactory. Should there
be reason to suspect that the commutating
winding is of improper strength, the suspicion
can be affirmed or can be disproved experi-
mentally. To test for excessive commutating-
pole strength, it is customary to shunt the
comnrutating-pole windings with a resistance
and to vary the amount of current passing
through the windings by varying this shunt
resistance. If there can be found any shunt-
ing value that gives satisfactory commutation,
the commutating coils as wound are too
strong; and, in order to get sparkless opera-
tion, the commutating winding must be per-
manently shunted to the extent indicated by
the experimental shunt.
In a certain instance, the experimental
shunting of the commutating winding made
the sparking much worse, thereby indicating
that the commutating field was too weak.
The electrician in charge then wound one turn
around the outside of each commutating coil,
taking care that alternate turns were wound
reversely, and connected them in series with
each other and with the existing commutating
winding. Upon putting on a load the brushes
sparked even worse than they did before the
extra turns were installed, because these
extra turns as a whole had been so connected
as to oppose the regular commutating wind-
ing. After reversing the experimental wind-
404
GENERAL ELECTRIC REVIEW
ing as a whole, commutation became about
perfect. Success on the first trial was a case
of exceedingly good luck, for in many cases
the addition of one turn per pole would have
made the commutating field too strong,
consequently it would have been necessary
to experimentally determine the value of a
shunt to be used with the improvised part of
the commutating winding.
On standard lines of motors and genera-
tors, if the facton- regulations in regard to the
brush setting are observed, commutating-
field shunts will seldom be required except
on large units.
(46J INSTRUMENT CONNECTIONS
WRONG
The primary and the secondary currents
of a transformer are in phase opposition.
The magnetic lines of force due to the sec-
ondary current thread through the core in
the direction opposite to that of the magnetic
lines due to the primary current. A tendency
to reduce the core flux is thereby exerted.
This tendency to lessen the core flux of a
constant-potential transformer results in
decreasing the primary counter e.m.f. and
in increasing the primary current, the in-
creased current restoring the flux practically
to its original value. With current trans-
formers, however, the weakening of the core
flux by the secondary current cannot mate-
rially affect the value of the primary current,
because that value is determined by the
external load of the unit, i.e., the current
which the current transformer is being used
to measure. This condition is the ideal one,
for no measuring device should appreciably
affect the value of the quantity that is being
measured.
If the secondary terminals of a constant-
potential transformer are short-circuited, the
heavy secondary current will, by neutralizing
the primary flux, cause a flow of primary
current so great that the primary fuses or
breakers will open. When the terminals of a
current transformer are short-circuited, the
resultant weakening of the flux cannot affect
the primary current. It does, however,
decrease the number of moving lines upon
which depends the value of the secondary
e.m.f. In well-designed current transformers
this automatic regulation of the secondary
e.m.f. is such as to maintain a practically
constant secondary current (for a given value
of primary current) between the limits of
short-circuited secondary and the secondary
resistance corresponding to the maximum
instrument capacity of the transformer. Of
course if the primary current changes, the
secondary current changes accordingly, other-
wise the connected instruments would not
follow the changing conditions. The primary
flux of necessity always exceeds the secondary
flux which is due to it; therefore v-ariations
in the primary' current, due to changes in the
load that is being measured, simply alters
the extent to which the primary flux prevails.
The volume of the moving flux is thereby
changed and with it the secondary e.m.f. and
the secondary current.
The preceding explanation was suggested
by the conditions disclosed upon investigating
an operator's complaint that although his
alternator was only partly loaded its exciter
was giving commutation trouble and diffi-
culty was experienced in maintaining the
engine speed.
As a matter of fact, the alternator was
carrying a heavy overload. The ammeter
was indicating only about one-half the actual
current flow, because in connecting the
ammeter and a wattmeter to the same current
transformer the current coils of the two
instruments had been connected in parallel
with each other, instead of in series with each
other. As the transformer secondary current
was of practically the same value that it
would have been had the instrument coils been
connected in series, each instrument coil was
getting approximately only one-half of the
current that it should have received. There-
fore, when the ammeter indicated that the
alternator was carrying three-quarters load, it
was really carrying 50 per cent overload.
After connecting the instrument coils in
series, the meter indications became correct,
and they disclosed the true state of affairs.
Incidentally, the exciter was carrying much
more load than its guarantee specified.
405
NOTES ON THE ACTIVITIES OF THE A. I. E. E.
Annual Convention
The 32nd Annual Convention of the
American Institute of Electrical Engineers
will be held at Deer Park, Maryland, June
29, 30, July 1, 2, 1915. The Convention
Headquarters will be at the Deer Park
Hotel.
The following papers will be presented:
The Electric Strength of Air-Vl, by J. B.
Whitehead.
The Reluctance of Some Irregular Mag-
netic Fields, by John F. H. Douglas.
The Measurements of Dielectric Losses
with the Cathode Ray Tube, by John P.
Minton.
Irregular Wave Forms; the Significance of
Form Factor, Distortion Factor and
Other Factors, by Frederick Bedell.
Classification of Alternating Current
Motors, by Val A. Fynn.
Alternating Current Commutator Motor
Classification and Nomenclature, by
Frederick Creedy.
Short Circuits on Alternators, by Comfort
A. Adams.
Electricity in Grain Elevators, by H. E.
Stafford.
Fields of Motor Application (Topical
Discussion), by D. B. Rushmore.
The Effective Illumination of Streets, by
Preston S. Millar.
Systems of Street Illumination, by Chas. P.
Steinmetz.
Construction and Maintenance Costs of
Overhead Contact Systems, by E. J.
Amberg and Ferdinand Zogbaum.
The Contact System of the Butte, Ana-
conda and Pacific Railway, by J. B. Cox.
Third Rail and Trolley System of the West
Jersey and Seashore Railroad, by J. V. B.
Duer.
Top Contact Unprotected Contact Rail for
600- Volt Traction System, by Chas. H.
Jones.
Under-running Third Rail Conductors, by
Edwin B. Katte.
Phase Angle of Current Transformers, by
Chester L. Dawes.
Instrument Transformers, by Chas. L.
Fortescuc.
The Induction Watthour Meter, by V. L.
Hollister.
Economic Operation of Electric Ovens, by
Percy W. Gumaer.
Class Rates for Electric Light and Power
Svstems, by Frank G. Baum.
LYNN SECTION
Telephone Problems, by J. G. Patterson
On Wednesday, March 17th, Mr. J. G.
Patterson of the Engineering Staff of the
New England Telephone Company talked on
Telephone Problems. Mr. Patterson presented
many details to illustrate the immensity of
the telephone plant in the country. The
entire Bell system represents an investment
of between $800,000,000 and $900,000,000.
There is a total of 16,000,000 miles of line.
The New England division owns about
500,000 instruments out of a total of 8,000,-
000.
Since the first commercial service of 40
years ago there have been in use 53 types of
receivers and 73 types of transmitters. Line
materials and equipment present some of the
largest problems. The demands of under-
ground service have recently resulted in the
development of cables only 2% in. diameter
containing 900 circuits, 1800 wires, and some
spares whose capacity can be further increased
by phantoming.
The high price of tin in recent years led to
the substitution of antimony for tin in the
lead alloy for cable sheaths, which resulted
in a very great saving. Details of cord and
jack construction have received the minutest
study. All these items must be brought up to
standard throughout the entire system in
order to make possible unrestricted communi-
cation over the long toll lines.
Mr. Patterson discussed the subject of
"phantoming" and loading telephone lines.
Numerous lantern slides were used to illus-
trate the lecture, of which those relating to
the Boston-Washington underground circuit
and the New York-San Francisco line were
of particular interest. The latter line consists
throughout of at least four wires, making
three talking circuits including the phantom.
Present Developments in X-ray Work, by Dr.
W. P. Davey
On March 17th, Dr. W. P. Davey of the
Schenectady Research Laboratory gave a
most interesting talk on X-rays, abundantly
illustrated by lantern slides.
The speaker defined and outlined the re-
lations of electrons, alpha particles, cathode
streams, alpha rays, beta rays, gamma rays,
etc., and gave figures to illustrate the numeri-
cal magnitude of the quantities involved.
The general phenomena of radiation were
discussed.
400
GENERAL ELECTRIC REVIEW
The sudden stopping of the electrons of the
cathode stream when they strike the target
rise To primary X-rays. The vibration of the
electrons belonging to the atoms of which
the target is composed produce characteristic-
X-rays. These characteristic X-rays are only
excited if the velocity of the cathode stream
is sufficiently high. It takes 1200 volts to
induce the characteristic radiation in the
aluminum. 11.000 volts for copper, and
about 95,000 volts for tungsten. The pene-
trating power of the rays increases with the
voltage necessary to produce them.
With a series of slides the history of the
development of the X-ray tube, which
culminated in the production of the Coolidge
tube, was shown.
In the Coolidge tube the performance is
entirely under control — in marked contrast
with the older forms of tube. The temperature
of the filament cathode determines the
volume of the radiation, while the potential
between cathode and anode determines the
penetrating power of the rays.
After this a series of slides was shown
illustrating the application of X-rays to
medical, botanical, industrial, and purely
scientific problems. Some of this work has
already been described in articles in the
Review. During the talk a Coolidge tube
was passed around the audience for examina-
tion.
PITTSFIELD SECTION
Leakage Reactance and Short Circuits, by
Professor C. A. Adams
Professor C. A. Adams, of Harvard Uni-
versity, gave a talk to the Section on March
11th. on The Leakage Reactance of Syn-
chronous Alternators and Its Relation to
Sudden Short-Circuits.
Prof. Adams developed a very interesting
theory of the distribution of the reactance in
alternators and its effect on the voltage and
current at short-circuit. The theory was
substantiated by a number of oscillograms
showing single-phase and three-phase short-
circuits. A method of decreasing by resistance
the time during which the excess current
persists was outlined. The subject will be
presented in greater detail in a paper by
Professor Adams to be given at the Annual
Convention of the A.I.E.E. in June.
Bureau of Statistics, by Dr. P. G. Agnew
On April 1st. Dr. P. G. Agnew. Assistant
Physicist of the Bureau of Standards, gave
an illustrated lecture on the recent work of
the Electrical Division of the Bureau. He
described in general terms the' precision
instruments in use; the care of the standard
weights and measures; the routine tests
carried on by the Bureau for the Govern-
ment, and for private individuals and firms,
etc. An outline was given of the recent work
of the Bureau in establishing standards of
e.m.f.. resistance, and illumination; of the
work done on the effect of barometric pres-
sure on heating, etc.
The Bureau has recently co-operated with
the navy in establishing methods of range-
finding, and is working on a standard safety
code in co-operation with the Electrical
Manufacturers, Public Service Commissions
and Electrical Societies. Altogether the
great and increasing value of the Bureau in
the economic life of the country was empha-
sized.
April 22nd, The Educational and Advertising
Value of Motion Pictures, by Mr. C. F.
Bateholts.
April 29th, The Physical Chemistry of the
Blood, by Dr. W. R. Whitney.
These papers were outlined in a previous
issue of the Review.
SCHENECTADY SECTION
Problems in Transformer Design, by Mr. G.
Faccioli
On April 6th. Mr. G. Faccioli, Assistant
Engineer of the Transformer Department,
General Electric Company, delivered a very
interesting talk in the auditorium of the
Edison Club on Problems in Transformer
Design.
Mr. Faccioli stated that engineers as a rule
believe that the transformer is an easy piece
of apparatus to design, thinking this to be
the case because there are no moving parts.
In improperly designed transformers, tons
of stress might exist, due to the attraction
and repulsion between the coils, but with
properly designed transformers, these stresses
can be reduced considerably and thoroughly
taken care of by means of the mechanical
strength of the parts involved. Substantially
all the important conditions involved can be
worked out mathematically and this in a
very simple way. The mechanical stresses
can be calculated very accurately and the
results checked by experiment.
Among the operating conditions about
which the designing engineer must concern
NOTES ON THE ACTIVITIES OF THE A.I.E.E.
407
himself, Mr. Faccioli mentioned high voltage,
high current and high frequency. He dis-
cussed the question of switching high voltage
lines on the high potential side and a number
of interesting points were brought out in
connection with high frequency transients
on the transmission line. He described the
effect of such transients very clearly and
simply, and presented the matter of magnetic
forces and transients in such a way that the
audience could easily follow him. Mr.
Faccioli's paper was discussed bv Messrs.
F. W. Peek and D. B. Rushmore.
Driving a Ship's Propellers, by W. L. R. Emmet
On March 30th, Mr. W. L. R. Emmet,
Consulting Engineer of the General Electric
Company, gave a talk on Driving a Ship's
Propellers before the joint meeting of the
Schenectady Section of the A.I.E.E. and the
Eastern New York Section of the N.E.L.A.
The meeting had the largest attendance of the
season and brought out a great deal of dis-
cussion from members of both sections. An
outline of the address follows:
It was shown that the turbine type of engine is
best suited to high speed and large powers. As an
illustration, a standard 25,000 kw. unit is run at
1S00 r.p.m. and gives efficiencies around 75 per cent
(Rankine cycle), while the turbines on the Lusi-
tania, of about the same horse power, run at only
180 r.p.m. and give an efficiency of 53 per cent, an
increase in steam consumption of over 15 per cent.
The propeller on the other hand has practically
opposite characteristics and gives its best efficiency
at very slow speed; for instance, the propeller
on the Lusitania showed an efficiency of only 55
per cent at 180 r.p.m., whereas the efficiency could
have been raised to 65 per cent had the propeller
speed been considerably lower. Some sort of speed
reduction must therefore be introduced between
the turbine and the propeller.
The U. S. Collier Jupiter, which is the first large
vessel to be equipped with electric drive, is a govern-
ment collier of 20,000 tons displacement, 542 ft. long
and 65 ft. beam, having a rated speed of 14 knots,
at which speed the propellers operate at 110 r.p.m.
The generating unit used is a standard Curtis tur-
bine driving a two-pole, 5450 kv-a., 1990 r.p.m. 2300
volt alternator. This generator supplies current to
two Form M 2750 horse power, 110 r.p.m. 2300 volt
induction motors.
The combined weight of all the electric driving
machinery in this boat is 156 tons, which is only
55 per cent of the weight of the reciprocating engine
equipment used in her sister ship, the Cyclops.
On her trials the Jupiter made 15 knots, at which
speed she consumed 7200 h.p. with a water rate
of 11.1 lb. per brake h.p. delivered to the propeller
shaft, the exact value as estimated by Mr. Emmet
before the machinery was built.
The collier has now been in operation for about
two years and gone through all kinds of weather.
She has been a perfect success from the start, and
her coal records show a saving of about 25 per cent
over any other boat of her size in the navy.
The Jupiter is not the type of vessel which will
show the greatest improvement with electric drive,
but the method is best suited to large war vessels
where economy at lower cruising speeds is of greater
importance than at maximum speed, and it also
lends itself very advantageously to driving large
ocean liners. The Jupiter was simply taken as a
practical demonstration of the suitability of electric
drive, all in view of obtaining its use for the pro-
pulsion of a large warship, and so satisfied were the
officers of the Navy department after the Jupiter's
two years of operation that it has been decided that
electric propulsion shall be used on the new battle-
ship California, now being built at the New York
Navy Yard.
By the use of one or both generators, with the
combination of either the slow or high speed con-
nections of the motors, the economy will only
vary one pound between the speeds of 12 knots
and maximum speed. In case one engine room
should be disabled, the ship could still maintain
about 85 per cent of full speed. When the bids from
the New York navy yard for the complete ship were
compared, the electric propelling equipment as
offered by the General Electric Company showed a
saving to the Government of $160,000 over direct
turbine drive as proposed by the regular specifica-
tions.
In turbine installations on ocean liners the small
space required in the engine room as compared with
methods now in use, the w-eight of the electric pro-
pelling machinery, which would be less than half
that of reciprocating engines now used, and the
saving in fuel, which would alone pay for the equip-
ment inside of two years are important factors.
The talk was concluded by a description
of the method of gearing used by Sir Charles
Parsons in England, and the methods pro-
posed by the Westinghouse Company. Mr.
Emmet also described the type of gearing which
the General Electric Company is now experi-
menting with, and gave some very interesting
figures as to its possibilities and limitations,
and compared figures as to economy.
The paper was discussed by Messrs. D. B.
Rushmore, Wm. Baum, C. L. Perry. J. R.
Werth, Eskil Berg and others.
Lectures for the Near Future
The program for the Section includes the
following lectures to be delivered in the
auditorium of the Edison Club:
April 20th, Philip Torchio, General' Elec-
trical Engineer of the New York Edison
Company, will talk on electric supply
in large cities.
May 18th, E. B. Raymond, formerly
General Superintendent of the Schenec-
tady Works, General Electric Company,
now Vice President of the Pittsburg
Glass Co., on plate glass.
June 1st, Professor Elihu Thompson. The
subject of this paper will be announced
later.
408
GENERAL ELECTRIC REVIEW
FROM THE CONSULTING ENGINEERING DEPARTMENT OF THE
GENERAL ELECTRIC COMPANY
NOTES ON THE NOBLE GASES (.Continued,
Necn
After Raleigh and Ramsay had succeeded
in extracting argon from atmospheric air in
1894, as previously described, they discovered
that their product contained minute traces
of yet other unknown gases. Owing to the
fact that all gases have different boiling
points when they are condensed into the
liquid state by intense cold and high pressure,
Ramsay was eventually able to isolate the
various elemental components, which existed
in minute quantity in the crude argon, by
refined methods of fractional distillation.
One of the new elemental gases thus obtained
was Neon, so named from the Greek word
"neos" meaning "new." Its atomic (and
molecular) weight is 20.2, ((02 = 32) for like
all of the other noble gases, it is believed
to be monatomic and also without chemical
affinity, as it forms no compounds with other
elements.
Neon can be ionized and thus made a
conductor of electricity more readily than
any other elemental gas. It is, therefore,
extremely sensitive to the influence of high
frequency electric oscillations, and vacuum
tubes containing neon can also be operated
at a lower potential than is required for
tubes that are charged with other gases.
When excited by electricity it glows with a
bright orange-red color, which becomes very
brilliant under conditions of high current
density.
Neon vacuum tubes have been developed
and used to a considerable extent in Europe,
and especially in France, where this gas has
been obtainable in larger quantities than
elsewhere during the process of liquifying
air for the production of liquid oxygen. The
eminent French scientist, George Claude,
has made these vacuum tubes in a great
variety of sizes and shapes, some being
adapted purely for illuminating purposes,
while others are manufactured in the form
of attractive advertising signs, etc. Owing
to the readiness with which neon can be
made to conduct electricity and the extreme
brilliancy of its luminescence (as before
stated) , the lighting efficiency of these vacuum
tubes is said to compare favorably with many
modern illuminants. La Revue Elec. (Nov. 24,
1912) states that under good working condi-
tions, "the specific consumption is about 0.7
watt per candle-power, including transformer
losses."
The spectrum of neon lies entirely within
the limits of red, orange and yellow, showing
no green, blue or violet lines, so that its
combined rays produce a beautiful orange
colored light, which — when compared directly
with ordinary artificial illumination — appears
inclined to red, but when seen by itself,
presents a pleasing golden orange hue.
The extremely small amount of neon which
exists in the atmosphere, viz., about 15
volumes in each 1,000,000 volumes of air,
and the difficulties attending its extraction
in purity therefrom has hitherto been a
serious bar to its more general use for com-
mercial purposes, and it is only where liquid
air is made in large quantities that neon
can be produced at anything approaching a
moderate cost.
The many interesting and valuable features
which this gas possesses warrants the hope,
however, that it may eventually become
more easily obtainable.
Krypton and Xenon
The two remaining members of this
interesting group of noble gases exist in the
atmosphere in such almost infinitesimal
quantities that they have only hitherto been
available for refined academic examination.
Krypton takes its name from the Greek word
"Kryptos," signifying "hidden." and it is
stated that 1,000,000 volumes of air contain
only 0.5 volume of Krypton, while Xenon,
named from the Greek "Xenos," meaning
"stranger," is yet more rare, only about
0.006 volume of this gas being found in every
1,000,000 volumes of air. Both of the above
gases show characteristic spectra, by which
their presence in exceedingly minute amounts
can be made visible. The atomic (and
molecular) weight of Krypton is 82.92, and
that of Xenon 130.22, based on 02 = 32.
W. S. Andrews
409
QUESTION AND ANSWER SECTION
The purpose of this department of the Review is two-fold.
First, it enables all subscribers to avail themselves of the consulting service of a highly specialized
corps of engineering experts, or of such other authority as the problem may require. This service provides
for answers by mail with as little delay as possible of such questions as come within the scope of the Review.
Second, it publishes for the benefit of all Review readers questions and answers of general interest
and of educational value. When the original question deals with only one phase of an interesting subject,
the editor may feel warranted in discussing allied questions so as to provide a more complete treatment
of the whole subject.
To avoid the possibility of an incorrect or incomplete answer, the querist should be particularly careful to
include sufficient data to permit of an intelligent understanding of the situation. Address letters of inquiry to
the Editor, Question and Answer Section, General Electric Review, Schenectady, N. Y.
INDUCTION MOTOR: ROTOR-BAR
INSULATION REPAIR
(137) An examination of a 40 h.p., squirrel-cage,
bolted end-ring induction motor, which had been
in service for some time, was made because it
ran at only 80 per cent of its normal speed. The
investigation revealed the fact that the rotor-bar
insulation was charred and the winding grounded
to the core. The stator was uninjured and the
motor, with the exception of the rotor-bar
insulation, appeared to be in good condition.
Since the frequency and voltage of the supply
were both normal and the motor was not over-
loaded at the time it was assumed that the
decrease in speed was accountable to this damaged
insulation and consequently the bars were with-
drawn, reinsulated, and replaced. After this
repair had been effected the motor resumed
running at normal speed.
The answer to question No. 126 of the Ques-
tion and Answer Section of the Review states
definitely that a squirrel-cage induction motor's
characteristics are the same whether rotor-bar
insulation is present or absent.
This case of unequal motor speeds before and
after reinsulating the rotor bars would seem to
contradict Answer No. 126; or else some other
influence was responsible for the action. Kindly
give an explanation.
The particular instance, described in the question,
is only one of a number in which the renewing of
charred rotor-bar insulation in a "slow-running"
squirrel-cage induction motor has been given credit,
by the operator, for bringing the motor's speed back
to normal. On first consideration, it might be natural
to assume that the increase in speed was the result
of repairing the defective insulation. As stated,
however, in Answer No. 126, the electrical properties
of a squirrel-cage motor are, for practical considera-
tions, independent of the rotor-bar insulation, i.e.,
they will be the same regardless of whether insulation
is used or not used around the rotor bars. The
truth of this fact has been proved conclusively by
comparative tests.
The action bringing about the restoration of
normal speed must have been a lowering of the
rotor resistance, which took place at the time the
reinsulating was done. (The speed of a standard
induction motor running at normal frequency and
voltage, and constant load, will be altered only by
a change in the rotor resistance.)
A permanent increase in the rotor resistance of a
bolted end-ring motor is likely to be brought about
if the motor is loaded to the point where the rotor
is heated excessively. The increase of resistance
takes place at the surface contacts between the
bars and the end-rings.
The fact that the rotor-bar insulation of the motor
under consideration was found to be charred shows
that the bars and end rings themselves must have
been very hot at some time. As the spring washers,
that are under the screws which hold the bars and
end-rings in contact, will lose their springiness at a
temperature which is considerably below the
charring point of the bar insulation, the decrease
in the motor's speed was undoubtedly due to the
fact that the joints between the bars and rings lost
their integrity at the time the spring washers
lost their temper.
When the motor was reassembled, after placing
new insulation around the bars, the contact joints
were undoubtedly cleaned and new spring washers
used. This decreased the rotor resistance to normal
and was the cause of the motor's resuming normal
running speed. If the defective spring washers had
been replaced in repairing this motor instead of
substituting new ones, as should have been done,
the speed would undoubtedly have increased to
normal, because the surface joints would have been
brought into tight contact when reassembling.
The use of defective spring washers is to be con-
demned, however, because the expansion and
contraction of the copper on heating and cooling
will soon loosen the joints, at which time the
decrease in motor speed will recur.
In case, therefore, that a bolted end ring (or even
a soldered end-ring) squirrel-cage motor is found
to be running at far below full-load speed under
normal load, frequency and voltage, the condition
of the bar and end-ring joints will altogether likely
be found to be defective and these poor contacts
must be repaired. If investigation at the same time
reveals the fact that the rotor-bar insulation is
charred, but still offers a secure mechanical support
for the bars, the damaged insulation need' not be
renewed. The insulation was placed there in the
first place for the purpose of mechanical packing,
not for electrical insulation.
In the most up-to-date squirrel-cage motors
this packing, misnamed "insulation," has been
dispensed with because of the adoption of welded
end-rings. Machines of this type are immune
from poor contact troubles in the rotor, because
the welded joints assure a perfect contact at all
temperatures. Also, since no packing is used,
there is none to char and burn out thereby possibly
allowing the bars to become loose.
A.E.A.
410
GENERAL ELECTRIC REVIEW
1. 138) The following are the data of an under-
ground transmission line:
Ducts: 3 ] 2 in. Orangeburg fiber laid in concrete
on 6-in. centers, two ducts wide, seven high.
The outside dimensions of the concrete (cross-
section through the ducts i are 17 in. wide
and 44 in. deep; these do not include the sub-
stantial concrete footing at the bottom. The
surrounding ground is on non-conducting
blast-furnace slag. Large manholes occur
at every 200 ft.
Cables: Three-conductor, 5000-volt, cambric-
insulated, lead-covered, carrying three-phase
current at 25 cycles and 2300 volts.
250,000 cir. mil 600 ft. long
250,000 cir. mil 800 ft. long
300,000 cir. mil 800 ft. long
300,000 cir. mil 1600 ft. long
1/0 1200 ft. long
4/0 1200 ft. long
No. 4 1200 ft. long
(a) What is the maximum current that can be
carried in the cables without overheating them?
i.b i What would be the proper amount of watts
loss to allow in these cables if the cost of gener-
taing is 0.9 cents per kw-hr?
(a) The maximum currents recommended for
the cables are as follows:
250,000 cir. mil 2.50 amp. per conductor
300,000 cir. mil 285 amp. per conductor
1 0 140 amp. per conductor
4 0 220 amp. per conductor
Xo. 4 74 amp. per conductor
It would not be possible, however, to run all of
these cables at full load at the same time in a duct
structure of the sort described.
The above current ratings arc based on a soil
temperature of 20 deg. C. With a lower earth
temperature the currents could be increased, but
with a higher one they must be decreased.
(b) It may be stated that, in general, it is question-
able whether in ordinary conditions in summer the
total watts lost per foot of duct structure should
exceed 40, if the cables are to be kept at a reasonable
temperature. (See paper by L. E. Imlav in A.I.E.E.
Proceedings, Feb., 1915, p". 263.)
It will be impossible to state what should be the
allowable watt loss in the cable installation described
unless the number of hours per day that the cables
operate is known, i.e., without having the load curve
of the cable.
For instance, the watts lost per duct-foot in the
250,000 cir. mil cable at 250 amp. are approximately
nine. If this load continues 24 hours per day,
365 days per year, the cost of energy wasted would
be $0.63 per foot of cable. On a basis of 10 hours
per day it would be $0.22, and for a duration of
five hours per day, $0.11. If the first were the
operating condition, cables as large as three-con-
ductor 500,000 cir. mil would be justified, whereas,
if the load were carried for an average of only five-
hours per day a three-conductor 300,000 cir. mil
cable would be approximately the- most economical,
figures were arrived at by adding together the
cost of cable and conduit, and allowing 10 per cent
of this valuation for interest and depreciation, and
then balancing this result against the cost of the
energy losses.
W.S.C.
TRANSMISSION LINE: SAG AND SIZE OF
CONDUCTOR
1,139,1 Please furnish formulae, or references to
them, which can be applied to the computing of:
(1) The sag in transmission conductors.
(2) The size of conductor for three-phase lines.
(1) In the A.I.E.E. Proceedings for 1911 there
are three articles which give formulae and tables
for computing sag in transmission lines. These
papers are:
"Solution to Problems in Sags and Spans," June,
p. 1111, W. L. Robertson.
"Sag Calculations for Suspended Wires," June,
p. 1131, P. H. Thomas.
"Mechanical and Electrical Characteristics of
Transmission Lines," July, p. 1379, H. Pender and
H. F. Thomson."
Any of the methods recommended therein will be
found" to be reliable, and they are described in far
more detail than could be attempted in the limited
space of these columns.
(2) In the General Electric Review, June,
1913, there appeared an article, on page 430,
"Practical Calculations of Long Distance Trans-
mission Line Characteristics," by F. W. Peek, Jr.,
which clearly describes the manner of calculating
the size of conductors for three-phast transmission.
F.W.P.
DIRECT -CURRENT GENERATORS: HIGH VOLTAGE
(1401 (a) What is the highest voltage for which
commercial direct-current generators are de-
signed and used today?
lb i What is the principal limitation that
would be encountered in designing a generator
of still higher voltage?
(a) So far as we know, 1500 volts is the highest
direct-current voltage that is derived from a single
commutator and regularly supplied for commercial
service in America (Brush arc-lighting circuits
excepted).
Voltages of this magnitude are restricted to use
in railway circuits.
There are today commercially successful railway
systems operating on 1200 volts derived from units
of one 1200-volt generator (for example: Southern
Traction Co., Dallas, Texas); 1500 volts derived
from units of one 1500-volt generator (for example:
Portland, Eugene & Eastern Railway, Portland,
Oregon); and 2400 volts derived from units of
two 1200-volt generators in series (for example:
The Butte, Anaconda & Pacific Ry. I
In a short time the Chicago, Milwaukee & St.
Paul R. R. electrification will be in operation at
3000 volts derived from units of two 1500-volt
generators in series.
(b) The greatest difficulty in developing the design
for a high-voltage direct-current generator is the
overcoming of the tendency to flash at the com-
mutator. To secure the usual factor of safety against
flashing, it is necessary to design a high-voltage
machine to run at a lower speed than a moderate-
voltage machine for a given number of poles; also,
it is necessary to use as high a surface speed as
permissible.
J.L.B.
0/(
GENERAL ELECTRIC
REVIEW
JUNE, 1915
A Special Number
on
The Electrical Industries
General Electric Review
A MONTHLY MAGAZINE FOR ENGINEERS
Editor, JOHN R. HEWETT £££ «£ * £2"^,
Subscription Rates: United States and Mexico, $2.00 per year; Canada, $2.25 per year; Foreign, $2.50 per year; payable in
advance. Remit by post-office or express money orders, bank checks or drafts, made payable to the General Electric Review,
Schenectady, N. Y.
Entered as second-class matter, March 26, 1912, at the post-office at Schenectady, N. Y., under the Act of March, 1879.
VOL. XVIII., No. 6 bycJ$y&kclri'c9SLpa«y June, 1915
CONTENTS
Page
Frontispiece 414
Editorial: The Paths of Progress .... 415
Industrial Research 416
By L. A. Hawkins
The Electric Power Industry . . 427
By David B Rushmore
A Brief Review of the Electric Lighting Industry 439
By C. W. Stone
A Review of Electric Railways . ... . .... 444
By W. B. Potter and G. H. Hill
Electric Transmission of Power 454
By R. E. Argersinger
Some Industrial Applications of Electricity 460
By A. R. Bush
Electricity in Agriculture 483
By C. J. Rohrer
The Electric Lamp Industry 497
By G. F. Morrison
HO
CONTENTS— Continued
Page
Electricity in Marine Work . . . . 504
By Maxwell W. Day
Electric Heating and Heating Appliances .... 523
By C. P. Randolph
The Use of Electricity in Mining Work . . . . ... 527
By David B. Rushmore
Electric Power in the Textile Industry 540
By C. A. Chase
Electricity in the Automobile Industry 550
By Fred M. Kimball
"Supplies": Devices and Appliances for the Distribution, Control and Utilization of
Electricity 553
By S. H. Blake
The Subdivision of Power as Solved by the Small Motor 555
By R. E. Barker and H. R. Johnson
The General Electric Company's Exhibits at the Panama-Pacific International
Exposition 561
By G. W. Hall
The " Home Electrical " at the Panama-Pacific International Exposition .... 572
By Don. Cameron Shafer
Illumination of the Panama-Pacific International Exposition . ... 579
By W. D'A. Ryan
Notes on the Activities of the A.I.E.E ... 594
From the Consulting Engineering Department of the General Electric Company . . 596
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u,i'
THE PATHS OF PROGRESS
The electrical industries have grown to such
huge proportions since their comparatively
recent conception that a complete review of
them would be quite impossible. But in this
special issue we attempt a review of some of
the most notable electrical industries in such
space as is available in a single issue of a
magazine.
We have now got to a stage in our develop-
ment that any further progress beyond a
mere multiplication of apparatus and devices
and a logical increase in the capacity of
individual units must depend more and more
upon industrial research. That the impor-
tance of this phase of our work is recognized is
evidenced by the activities of many of our
greatest industrial concerns. Scientific pro-
gress depends upon research work and the
industries, and very specially the electrical
industries, must depend in an ever increasing
degree on science. It is, therefore, a matter
of great satisfaction to note that research
work on an extended scale is carried out by
organizations that are primarily devoting
their energies to manufacture. A most
notable example of this is to be found in the
first article of this issue.
The generation, transmission, distribution
and application of electric power have, during
the last quarter of a century, made wonderful
changes in our mode of conducting commercial
activities and our future progress seems
largely to depend upon developing our natural
power resources and upon their economical
use. It is due to the fact that electrical energy
can be generated, transmitted, distributed
and applied more efficiently, and therefore
more economically, than any other form of
energy that electricity holds its present
enviable position, and further it is because
electricity can be so conveniently converted
to heat, light and mechanical power and can
be held tinder such perfect control that it
seems destined to supplant all other modes of
operation.
Older methods have given way to electrical
methods, in the vast majority of cases, on
purely economic grounds and it is of special
interest to note that many modern industries
have been made economic possibilities only
by the adoption of electricity in one way or
another to meet their particular require-
ments. It is to a broad extension of such
applications that we look to much progress
in the future, and it would seem that the
electro-chemical industries are likely to prove
a most active field for such developments.
What other new fields are open to develop-
ment by the application of electrical methods
must of necessity be a matter of speculation,
but we believe that such fields are enormous.
The consistent and persistent growth of the
electrical industries that are already well
established is one of the wonders of the age.
Some of the curves that we publish in this
review show a progress, and a continuation
of a rate of progress, that is truly astonishing
and brings one very forcibly to realize that
the facilities for generating and distributing
electrical energy show no signs of over-
reaching the demands. For some years past
we have recognized that the increase in
facilities for rapid transit in our large cities
cannot keep pace with the demands. Greater
and ever greater facilities are imperative,
and it seems that the same lesson is to be
learned about the other industrial applica-
tions of electricity.
We should naturally wish to make editorial
comment on some of the more comprehensive
articles that appear in this issue, but neither
time nor space will permit. The one essen-
tial feature that is of vital importance is to
be found recorded in the review of each in-
dustry, namely, that the progress which has
been enormous, is being maintained and that
the future possibilities seem limitless.
416 GENERAL ELECTRIC REVIEW
INDUSTRIAL RESEARCH
By L. A. Hawkins
Engineer, Research Laboratory, General Electric Company
The author shows that science and industry have dropped the old prejudices that have existed between
them, have joined hands and are working mutually for our progress. He touches on the influence of science
on industrial progress abroad, especially in Germany, and cites some notable research developments in this
countrv. A considerable part of the article is devotedto a description of the splendid new research laboratory
of the "General Electric Company and to the work that has been accomplished there. — Editor.
Industrial research is a relatively new thing.
It means the co-operation of business and
science for their mutual advantage. Not so
very many years ago such co-operation would
have been unthinkable. To the average
business man, the scientist seemed a rather
futile fellow whose putterings with test tubes
had little more practical value than the
researches of a classical scholar in the Greek
Dative, while the man of science, like his
classical brother, looked with some contempt
on the sordidness of trade, talked of "pure"
science, as something nobler than "applied"
science, and felt that he was losing caste if
he permitted his work to suffer contact with
' ' commercialism . ' '
Happily for both business and science,
those ideas are now dead — as dead as witch-
craft, or the divine right of kings. Repeated
object lessons have taught the business man
that nearly ever}' marked advance in science
has resulted, sooner or later, directly or
indirectly, in important effects on industry,
while the increasing dependence of modern
life on its complex industrial organization has
forced the scientist to realize that in benefit-
ing industry he is contributing efficiently to
the welfare of mankind, which is, and always
must be, the chief aim of all work that is worth
while.
The result of this awakening was that
business resolved to domesticate science, and
that science graciously accepted the home,
with all modern improvements, which was
offered her. Thus arose the research labora-
tory of the large industrial corporation.
Though such laboratories have been in
existence relatively few years, they have
already proved their value. They have been
a potent factor in Germany's wonderful
commercial development.
The extent to which research has permeated,
and made itself an essential part of, German
industry is clearly revealed in the address
delivered by Dr. Carl Duisberg before the
Eighth International Congress of Applied
Chemistry, entitled, "The Latest Achieve-
ments and Problems of the Chemical Indus-
try." The scope of the paper is almost
co-extensive with industry itself. Produc-
tion of power, refrigeration, the manufacture
of quartz, steel, special alloys of most diverse
properties, acids and other reagents, tin,
rare metals, and coal tar products including
explosives, dyestuffs, and medicinal drugs,
chemotherapy, or the treatment of infectious
diseases by chemical means, the production of
synthetic perfumes, artificial silk, cinemato-
graph films, non-inflammable celluloid and
its applications, including patent leather,
artificial leather, insulation, enamels, etc.,
and synthetic rubber, — each of these is cited
to illustrate notable recent achievements of
chemical research.
The coal tar dye industry is built entirely
on chemical research. Dr. B. C. Hesse, in the
Journal of Industrial Chemistry, Dec, 1914,
estimates the annual production of dyes in
Germany at $6S, 222,846, more than eleven
times the production in Great Britain and
about eighteen times the production in the
United States. In explanation of this fact
he quotes a prominent German chemist as
saying, in part, "In no country on earth are
those branches of the chemical industry
which demand versatility of thought, and
particularly a large body of scientifically
trained employees, so well developed as with
us."
Germany was the first country to perceive
the enormous monetary value of organized
industrial research, and great have been the
rewards of her foresight.
We, in this country, have been late in
starting, but progress has been rapid and the
results important. An article by Mr. A. D.
Little in the Journal of Industrial and
Engineering Chemistry, Oct., 1913, entitled
"Industrial Research in America," is an
impressive exposition of the extent to which
organized science has already become a
business asset in the United States. For
INDUSTRIAL RESEARCH
417
instances, he cites the DuPont Powder Co.,
employing 250 trained chemists, with a
laboratory comprising 76 buildings spread
over 60 acres, which estimates that its
laboratory yields an annual profit of $1,000,-
000, the world famous Edison laboratories
with their multifarious important products;
the automobile industry, in which one tire
manufacturer spends $100,000 a year on his
laboratory; the Bausch & Lomb Optical Co.;
the Eastman Kodak Co.; the electro-chemical
industries at Niagara Falls; the metallurgical
laboratory with a capable staff is an expen-
sive matter, and the financial returns are
seldom immediate. Years of costly failure
must often precede success, and not even
then is success always possible. But in
the end, industrial research, if wisely organ-
ized and efficiently conducted, does pay,
and both the corporation and the public
benefit.
The extent and quality of the equipment
required by an industrial laboratory, and the
character of the work that may profitably be
Fig. 1. Research Laboratory Building
industries, etc., all investing largely in
organized research and all reaping profits
from their investments.
In all this work, the public benefits, whether
by new devices capable of new results, by
more efficient apparatus, by better materials,
by cheaper goods, or by increase of scientific
knowledge. Indeed one of the important
advantages the public derives from the
existence of the big industrial corporation
is the result of industrial research, made
possible only by large aggregations of capital,
controlled by far-sighted, broad-minded,
men; for the maintenance of a well equipped
undertaken, of course vary considerably in
different branches of manufacture, but, in a
general way, the part that such a laboratory
may play in a modern manufacturing plant
may be illustrated by a description of one
such institution.
The research laboratory of the General
Electric Company, started on a small scale
14 years ago, has grown to be one of the
largest of its kind, and its work has given it a
wide reputation.
Its present staff of 150 employees is now
located in the modern seven-story building,
shown in Fig. 1, and occupies the greater
418
GENERAL ELECTRIC REVIEW
Figs. 2 and 3. Furnace Room
INDUSTRIAL RESEARCH
419
Fig. 4. Library
Fig. 5. Machine Shop
420
GENERAL ELECTRIC REVIEW
part of four floors and the basement, a floor
space of 66,500 sq ft.
In the basement are the laboratory power
plant and chemical storeroom. Power is
supplied from outside at 250 volts, d.c, three-
wire system, and at 40 cycles, three-phase,
120 volts. In the laboratory power plant arc
16 machines which deliver power at different
voltages, and at frequencies ranging from 25
up to 2000 cycles. Through transformers, cur-
rents as high as 12,000 amperes, and voltages
up to 200,000 ma}' be obtained. A switch-
board comprising 28 transfer sections makes
it possible to connect any machine to any
one of the 118 delivery panels distributed
through the laboratory. In the power plant
there are also a liquid air machine, an air
compressor, and two vacuum pumps, one
two-cylinder, 12 in. by 12 in. and the other
three-cylinder, 8 in. by 10 in.
All wiring and piping are carried in hori-
zontal ducts 8 ft. by 5 ft. running above the
corridors through the laboratory. There are
35 miles of wire, ranging in size from No. 6
up to 2000 cm. The building is piped
throughout with city water, river water,
illuminating gas, compressed air, vacuum,
high pressure hydrogen, low pressure hydro-
gen, oxygen, high pressure steam, and for
vacuum cleaning, Distilled water may be
delivered by gravity to any room, and 250
motors, 80 transformers, and 60 vacuum
pumps are distributed through the building.
In a one-story addition, shown in Figs.
2 and 3, are located a number of furnaces,
including a porcelain kiln, a frit furnace,
two pot furnaces, three calorizing furnaces,
two brush firing furnaces, all gas heated, and
two large vacuum furnaces, electrically heated,
There is also a furnace for argon purification.
Disk grinders, crushers, a pulverizer, two
large sets of rolls, 5 in. by 8 in., and four
smaller sets, eight swaging machines, ten
punches, and a 60-ton hydraulic press are
installed. The larger electric furnaces of the
laboratory, including a two-ton arc furnace,
are in a separate building.
The calorizing furnaces, just mentioned,
are used for giving to metal parts the heat-
proofing treatment, the results of which were
described in the General Electric Review.
October, 1914. The argon furnace purifies
argon gas for use in experimental incandescent
lamps.
On the first floor of the laboratory are
offices, the library of 1400 volumes, shown in
Fig. 4, three experimental rooms used for
X-ray investigations, and the machine shop,
part of which is shown in Fig. 5. The equip-
ment of this shop includes a milling machine,
a lathe, 20 in. by 16 in., two smaller engine
lathes, four bench lathes, a shaper, a radial
drill, two drill presses, a sensitive drill, a
forge, a band saw and sharpener, and 100
linear ft. of bench space.
The second floor is occupied by research
work on insulation, by production work on the
Coolidge X-ray tube, and by the carpenter
shop. The equipment for the insulation
work includes a paint grinder, barrel mixers,
compound mixers, electric drying ovens, a
vacuum impregnating machine, a hydraulic
press with steam attachment, a 60,000-volt
set for testing dielectric strength, and appa-
ratus for measuring insulation resistance hot
and cold.
Mews of two of the rooms devoted to
insulation work are shown in Figs. 6 and 7.
Because of the importance of insulation in
electrical apparatus, the laboratory con-
tinuously devotes much time to it. Many new
molded compounds have been produced,
improving and reducing the cost of countless
devices. Improvements have been made in
varnished cloth, enamels, and other standard
insulations, and new types of insulation have
been developed, such as the mineral insulation
used in the sheath wire now in production for
heating devices.
So much has been published lately on the
Coolidge X-ray tube that it needs no de-
scription here. It is manufactured entirely
in the laboratory. The equipment for pro-
duction and experimental work comprises
a Waite and Bartlett machine, a Snook-
Rontgen machine, a Scheidel-Western ma-
chine, a large static machine, a Waite and
Bartlett table for fluoroscopic work, a stereo-
scopic display frame, a Scheidel X-ray coil,
a Kelley-Koett tube stand, two Kny-Scheerer
interrupters, six exhaust ovens, three of which
are shown in Fig. 8, equipped with Gaede
molecular pumps, two Arsem vacuum fur-
naces, and a tungsten tube furnace.
In addition to the Coolidge tubes, the
laboratory manufactures targets for the
standard type of tube, comprising a tungsten
disk embedded in a copper block.
The analytical laboratory shown in Fig. 9
is on the third floor. The work tables are
covered with glazed roofing tile. There are
two double hoods, a work table equipped for
electrolytic work, and a draft-proof balance
room, shown at the right of the figure.
On this same floor is the work on trans-
former steel and other alloys, with an equip-
INDUSTRIAL RESEARCH
421
I
■
Figs. 6 and 7. Two of the Rooms for Insulation Work
422
GENERAL ELECTRIC REVIEW
Fig. 8- Exhaust Ovens for Coolidge X-Ray Tubes
ment comprising a set of small electric
furnaces for making alloys, eight small electric
annealing furnaces, two vacuum furnaces,
three melting furnaces, a set of rolls, a
potentiometer and Wheatstone bridge, a
Burrows permeability apparatus, storage bat-
teries, a photomicrography outfit, and
chemical balances. Even a slight decrease in
transformer core loss is of great importance
because of the enormous aggregate of trans-
formers in use, most of which have their
supply voltage on them twenty-four hours a
day, so that their core loss is a continuous
waste. For this reason continuous research
on transformer steel seems justified, even
though the results seem small. As for the
other work on alloys, there are always
demands for new characteristics, mechanical,
electrical, or chemical, so that hundreds of
special alloys have been made and tested in
the laboratory. Also composite metals have
been developed, such as "Binel metal," that
is, steel coated with a thin layer of Monel,
the natural copper-nickel alloy which stands
high temperatures with very little oxidation,
and composite wire for special purposes, such
as gold-coated tungsten and molybdenum
as a substitute for platinum in dental
work.
Fig. 9. Analytical Laboratory
INDUSTRIAL RESEARCH
423
Fig. 10. One of the Rooms for Lamp Experiments
Fig. 11. Tungsten Reduction Furnaces
424
GENERAL ELECTRIC REVIEW
On the same floor are diamond drilling and
jewel polishing machines, and apparatus for
testing motor and generator brushes. The
quality of the brush has so great an effect on
the operation of direct current motors and
generators that the laboratory has given
much time to developing new grades of
brushes better suited to the various machines
than any grade formerly on the market. In
this way they have made it possible to clean
up a number of complaints on motor opera-
tion, and in other cases to improve the opera-
tion or to lower maintenance costs.
The lamp work is located on the fourth
floor. From its beginning, the laboratory has
devoted a large part of its efforts to the
improvement of incandescent lamps, and has
originated the metallized carbon filament
lamp, the drawn wire tungsten lamp, and the
gas-filled lamp, thereby gradually sextupling
incandescent lamp efficiency. If one stops to
compare the status of incandescent lighting
fifteen years ago with what it is today, and
considers how much of the phenomenal
advance has been due to those three develop-
ments, he will need no argument to convince
hin that the research laboratory in the
electrical industry has justified its existence.
The laboratory equipment for lamp work
comprises a small but complete factory for
lamp manufacture with a maximum capacity
of about 100 lamps per day. There are four
large and four smaller exhaust ovens of
standard type, three special ovens for special
exhaust, a Thomson welding machine, three
sets of apparatus for making arced joints, one
for pinched joints, two filament winding
machines, two different types of apparatus
for making pure nitrogen, from air and
hydrogen, and from tank nitrogen and
ammonium carbonate, respectively, apparatus
for purifying argon, and a gas density balance.
For testing lamps there are three Lummer-
Brodhun prism photometers, two portable
photometers, one flicker photometer, one
Lummcr-Brodhun precision photometer, and
an optical pyrometer for filament tem-
peratures calibrated up to the melting point
of tungsten, 3450 deg. K. A storage battery,
30 amperes, 170 volts, is used for the photo-
metric work. The life test has a capacity of
60 kw. and facilities are provided for obtain-
ing voltages from 0 to 250 in one-quarter-volt
steps. A Tirrell regulator maintains constant
voltage on the busbars. Additional circuits
are provided for "shop tests" of 120 volts
a. a, and 125 and 250 volts d.c, and also an
outdoor series circuit of 6.6 amperes equipped
with compensators for the high current
series lamps.
A color booth for studying color values of
glasses, apparatus for studying residual gases
in vacuum lamps, and apparatus for photo-
graphing filaments while burning, are included
in the equipment.
One of the experimental rooms for lamp
work is shown in Fig. 10.
There is a photographic dark room on this
floor.
Part of this floor is devoted to production
work, including a room for chemical purifica-
tion of tungsten oxide, a battery of electrically
heated hydrogen furnaces, shown in Fig. 11,
for oxide reduction, with a capacity of 50 lb.
of metal a day, and a room for the assembly
and grinding of tungsten contacts for use in
spark coils, magnetos, relays, etc. One large
room, of which two views are shown in Figs
12 and 13, is devoted to the study of phe-
nomena in very high vacuum. This work has
thrown much light on the characteristics of
the electron emission from hot filaments under
various conditions, and the results have been
published in recent papers by Dr. Langmuir.*
The phenomena of pure electron emission,
resulting from operating a hot tungsten
filament in a vacuum so high that there is not
sufficient residual gas to produce ionization,
have been utilized in the Coolidge X-ray tube
and in the high voltage rectifier known as the
Kenotron, described by Dr. Dushman in the
General Electric Review, March, 1915,
A number of improvements in wireless trans-
mission also have been made possible by this
investigation. For this wireless work a
smaller room has been fitted up as a sending
and receiving station, and an antenna, over
800 ft. long, composed of two wires spaced
16 ft. apart, has been strung between steel
towers on the roofs of the laboratory and
another building. Before this large antenna
had been erected, wireless telephonic com-
munication between the Schenectady and
Pittsfield plants had been successfully ob-
tained, and wireless messages received from
Berlin, San Francisco, and Honolulu.
The laboratory is continually conducting
researches of a purely scientific nature and
publishing the results, in an endeavor to
contribute its share to the progress of scientific
thought, which is rapidly enlarging, modify-
ing, and clarifying our conceptions of the
fundamental things underlying all physical
sciences. These investigations may be in-
itiated because of their scientific interest,
•See General Electric Review, May. 1915.
INDUSTRIAL RESEARCH
425
Figs. 12 and 13. Room for Vacuum Tube Experiments
426
GENERAL ELECTRIC REVIEW
without any definite practical object in view,
but it has been already said that every marked
advance in science has resulted sooner or
later, directly or indirectly, in important
effects on industry, and these laboratory
investigations have certainly nearly always
had these practical results. The study of
electron emission, and the various practical
utilizations of the principles discovered, is
a case in point. The gas-filled lamp, now
known as the Mazda C, had its origin in the
results of an academic study of the laws
governing the loss of heat in small wires,
coupled with the results of an investigation of
the evaporation of tungsten. The metallized
filament lamp resulted from experiments with
a high-temperature vacuum furnace. In
none of these cases was the practical result
foreseen when the research that made them
possible was started.
It should not be supposed, however, that
all the important achievements of the labora-
tory have been thus brought about. Many of
them, of which drawn tungsten wire is a
notable example, were the result of persistent
and resourceful effort directed from the
beginning toward a perfectly definite goal.
Other examples are the sheath wire, with
mineral insulation, now in production for
heating devices, the magnetite electrode for
luminous arcs, and the commercial develop-
ment of the mercury arc rectifier.
Of course, even in those cases where unfore-
seen practical results are made possible by the
new insight into fundamentals, gained from
purely scientific research, they seldom first
appear in fully developed form, like Athena
sprung from the brain of Zeus, but much
work, inventive and experimental, specifically
directed to the end in view, is usually neces-
sary before that end is reached.
A third kind of work which constantly
requires the attention of the laboratory and
occasionally demands the full application of
its resources, is that which arises from the
specific problems of factory production, such
as the improvement of processes, the location
of hidden troubles, and the development of
new or better materials. Much of the work
on insulations and alloys falls within this
class, together with countless special investiga-
tions, each of which may be the work of a
few hours or ma}' extend over months or
even years.
The General Electric Company maintains
other laboratories than the one described.
There are laboratories at the Lynn and
Pittsfield plants, which specialize on the
production problems of those works. There
are lamp development laboratories at Harrison
and Cleveland which develop and standardize
new processes, materials, and lamp designs,
for the lamp factories. There is the physical
laboratory at Cleveland, which conducts
researches of a highly scientific order in the
physical and physiological aspects of light
and illumination. There is the Illuminating
Laboratory at Schenectady, devoted to illumi-
nating engineering, the selection of the best
lighting unit and the best method of utilizing
it for a given lighting system. There is the
Consulting Engineering Department Labora-
tory devoted to general and special engineer-
ing problems and particularly to the investiga-
tion of high tension phenomena. There is the
Testing Laboratory, investigating and testing
the physical and chemical properties of
materials. There is the Standardizing Labo-
ratory, in charge of the standardization of all
instruments, developing new instruments,
like the oscillograph, and investigating
and developing test methods. In addition
to the activities of all these laboratories, the
various engineering departments conduct
many special tests which they are specially
equipped for handling and investigations
which sometimes amount to research work
of a higher order. Research in general, how-
ever is delegated to the Research Laboratory,
which was organized and equipped for that
purpose.
By this description of the equipment and
work of a single laboratory, we have tried to
indicate the nature and function of industrial
research, to show how science and industry
may mutually profit by close co-operation.
We believe the subject is timely. The great
war is forcing us in this country to analyze, as
never before, our industrial position in the
world, to consider how far our industries are,
or may be made, independent of foreign
supplies, and to what extent we are prepared
to take advantage of the new markets, cut
off from their past source of supply and
turning naturally to us to fill their wants.
Our introspection shows us lacking in two
essentials, financial and technical. The
financial difficulties, our lack of the necessary
banking facilities and system of commercial
credits in foreign lands, will surely not be
beyond the ability of our banking houses and
business men to handle, now that they have
been brought face to face with the necessity
for action, for neither in wealth nor in business
ability need we feel incompetent to accom-
plish what other nations have done.
THE ELECTRIC POWER INDUSTRY
427
On the technical side, we find our lack is
not so much of raw materials, but of the
organized science on which so many of
Germany's industries and so much of her
product is based. It is not that our business
men are deficient in power to organize — all
the world knows the contrary — nor are we
lacking in men of great technical ability.
The means are all at hand. There has simply
been a tardiness in the recognition of the need
for just this kind of organization, the need of
extensive industrial research, adequately
equipped and financed, not only in our exist-
ing industries but in the new ones which
should and will spring from our present
necessities. With our unequaled wealth of
raw materials, we need only a more
thorough organized co-operation of the
American business man and the American
scientist to insure the technical independ-
ence and commercial supremacy of this
country.
THE ELECTRIC POWER INDUSTRY
By David B. Rushmore
Chief Engineer, Power and Mining Department, General Electric Company
The author gives a great deal of information in the form of vital statistics on this all-important subject.
He shows how modern tendencies in the operation of public utilities are leading to the economical generation
and distribution of energy by the centralization of the generating apparatus in large power houses. Statistics
showing the use of energy in the mining, railway and manufacturing industries are given. "Water-power,"
generating equipment, and transmission are also considered in detail. — Editor.
The development of our industrial life is A great many inferences, deductions and
necessarily dependent upon the manufacture conclusions may be based on these figures, and
of power and our ability to utilize it in such ought to serve a great variety of useful pur-
forms that it can be substituted for the poses. The fact that already animal power
physical work of man. forms only one-sixth of our national motive
Electricity is the most convenient form in power is a rather startling fact, but in view of
which energy can be transmitted and dis- its average inefficiency there is nothing
tributed. It is not in itself a source of energy, alarming about it. The horse will long be
but is obtained, either directly or indirectly, by with us, but the question is obviously how
transformation from energy in either a chem- much more we can do without it. If the 25
ical or mechanical form, and in all practical or possibly 30 million horses and mules now
cases is again transformed before being utilized. used in farm work were displaced by mechan-
Primary Power ica^ power 100 million acres of cultivated
Statistics have never been compiled giving land would be released for human require-
accurately the total mechanical horse power m^nts' a?d rt 1S safe to attribute the high cost
used in the United States. The following oHivmg to a yery great extent to the very low
estimate may, however, be considered to be £ffi£lency °f farm.lab°i; as compared to the
fairly close to the actual conditions, and it is hlSh? efficiency m other industries whose
safe 'to place the present value at approxi- raPld growth will continue to make even
mately 150 million horse power, or 1.5 horse gr,eater demands upon the farm productivity.
J ., c ,, *V- i .■ _ The use of electricity on our farms is therefore
power per capita for the entire population. , ,, .J , , ,, , ....
r r r it- sure £Q j-,e greatiy increased, and that this is
M table i h.p . becoming generally recognized by our central
Cen'tral'stations "Yooo'ooo station interests is clearly demonstrated by
Isolated plants. ..... ... ".'. 4[25o|ooo the extensive network of transmission and
Street and electric railways 4,000,000 distributing circuits which are being built
Steam railroads 50,000,000 an(j extended to cover the vast rural districts
Steam and naval vessels 5,000,000 „ , rnnntrv
Mines and quarries 6,000,000 a11 over tne country.
Flour, grist and saw mills 1,250,000 TT .,. .
Irrigation 500,000 Publlc Utilities
Automobiles 25,000,000 The importance of these utilities as an
Horses and mules 25,000,000 economic factor and as daily necessities is
Total 154,000,000 indicated by the volume of their business.
428
GENERAL ELECTRIC REVIEW
THE ELECTRIC POWER INDUSTRY
429
This has been estimated by a competent
authority for the year 1913, as follows:
TABLE II
Electrical manufacturing 8375,000,000
Electric railways 650,000,000
Central stations 450,000,000
Gas 200,000,000
Telephone service 350,000,000
Telegraph service 85,000,000
Isolated plants 125,000,000
Miscellaneous 125,000,000
Total $2,360,000,000
As the art of production, distribution and
application has progressed, these utilities
have become primary necessities of modern
civilization.
Central Stations
Public utilities are necessarily always under-
going very great changes. There is now a
strong tendency toward consolidation with a
view of concentrating the power supply for all
uses in a large territory from one system.
So, for example, a supply company in a large-
city expands so as to embrace the whole
district around it, and the service given
originally within a small area is unified over
hundreds of square miles. In other cases the
properties in a given territory are merged and
brought under one management. This is
strikingly illustrated by one large public
service company in the middle west where
nearly 100 communities were originally sup-
plied by about 50 separate generating stations.
These have now been shut down and four
modern stations will ultimately furnish all the
power needed for this service.
The inter-connection of hydro-electric
transmission systems is also a step in the
right direction, as demonstrated in our
southern states where half a dozen large
systems are tied together, furnishing power
to each other on an "inter-change" contract
basis. The advantages of this are obvious.
The peak loads of the different systems may
not coincide, the minimum stream flow may
occur at different times on the different water-
sheds, common steam reserve stations may
be used, and in general the operation may be
so improved that a most efficient and reliable
service can be rendered to the customers of all
the systems so tied together.
In some cases groups of established systems
although located in vastly different localities
may be brought together under one holding
company, and to the creation of such com-
panies may in many instances be attributed
the high-class service and financial success of
our small and medium-size light and power
systems. The economies due to a central
management, the benefits of the best technical
and expert advice applied even to the smallest
central station, the cumulative effect of
active up-to-date new-business campaigns at
every point, all have contributed to an
improved and cheaper service to the con-
sumer, and without the facilities of such a
control they could exist only in the larger
communities. Another very important advan-
tage is the great problem of financing all
these undertakings and providing funds for
extensions to meet the ever-growing demand
of the public for electric service. It is possibly
in providing ready financial facilities for these
purposes that the holding company performs
its most important function.
In order to give the people the best service
and the lowest rates all public utilities must
of necessity be natural monopolies, and the
public service regulation is a recognition by
the state of the essentially monopolistic
character of these enterprises. The favorable
showing of virtual monopolies in reducing
the cost of electric power is due mainly
to a reduction in the capital expenses, lower
operating costs and in no less degree to the
reduced risk to the investor. By effective
safeguards and a well-considered policy of
public control the electric securities have
become one of the most desirable investments,
and there is every indication that efficient
public service regulation will make possible
even further reductions in the cost of electric
power production of public service utilities.
The rapid growth in central electric light
and power stations, as taken from the latest
census report, is shown in Table III.
Aside from the growth in the number of
stations the striking features of this table are
the relatively larger increase in the kilowatt
capacity per station, while the cost of con-
struction and equipment remains practical ly
the same. That this cost has not been
materially reduced is no doubt due to the
increased cost of the distributing and trans-
mission lines, which form an important part
of the total cost of the system.
It is also of interest to note that the per-
centage increase in the use of water power for
the period of 1902 to 1912 was 463 per cent,
as compared to 254 per cent for steam power.
On the other hand, gas power increased 811
per cent, but this is not of any great impor-
tance as the horse power capacity of the gas
engines installed at the beginning of the above
period was very small.
430
GENERAL ELECTRIC REVIEW
Outputs of Large Generating Systems
The Electrical World in its issue for March
27th contained the accompanying very inter-
esting Table IV, giving statistics for 1914 on
the outputs, peak load and load factor of the
largest generating systems of the country.
Three of the companies in the list are in
Canada, although a large part of the output
is exported across the border into the United
States. The combined output of the 36 com-
panies listed is approximately 12,000,000,000
kw-hr. Of these, approximately two-thirds
was generated from water power. In the
census report for 1912. Table III, the total
output of the 5221 central stations of the
country was 11.502,963,006 kw-hr.; the total
horse power of steam engines and steam
turbines 4,946,532, and the total horse power
of waterwheels 2,471,081. It would appear,
therefore, that over half the electrical energy
generated by the central stations of the
country is obtained from waterwheel-driven
units.
Street and Electric Railways
In no other field has the application of
electric power been more startling than for
our street railway systems. Table V gives
a comparative summary of the street and
electric railways in this country for the period
of 1890-1912, and it is seen how completely
the electric drive has superseded the older
methods.
TABLE III
CENTRAL ELECTRIC LIGHT AND POWER STATIONS
Number of stations*
Commercial
Municipal
Total income
Light, heat, and power, in-
cluding free service
All other sources
Total expenses, including salaries
and wages
Total number of persons empl
Total horse power
Steam engines and steam tur-
bines:
Number
Horse power .
Waterwheels
Number. ...
Horse power
Gas and oil engines:
Number
Horse power
Kilowatt capacity of dynamos
Kilowatt capacity per station.. . .
Cost of construction and equip-
ment
Cost per kilowatt capacity
Output of stations, kilowatt-hour?
Estimated number of lamps wired
for sen-ice:
Arc
Incandescent and other va-
rieties
Stationary motors served:
Number
Horse power capacity .
1912
1907
1902
Per cent of
increase:
1902-1912
5,221
3,659
1,562
$302,115,599
4,714
3,462
1,252
$175,642,338
3,620
2,805
815
$85,700,605
44.2
30.4
91.7
252.5
$286,980,858
$15,134,741
$169,614,691
$6,027,647
$84,186,605
$1,514,000
240.9
899.7
$234,419,478
79,335
7,52S,648
$134,196,911
47,632
4,098,188
$68,081,375
30,326
1,845,048
244.3
161.6
308.0
7,844
4,946,532
8,054
2,693,273
6,295
1,394,395
24.6
254.6
2,933
2,471,081
2.4S1
1,349,087
1,390
438,472
111.0
463.6
1,116
111,035
5,134,689
983
463
55,828
2,709,225
574
165
12,181
1,212,235
334
576.4
811.5
323.6
194.3
$2,175,678,266
$425
11,502,963,006
$1,096,913,622
S404
5,862,276,737
$504,740,352
$416
2,507,051,115
331.4
358.8
505,395
562, 795
385,698
31.0
76,507,142
41,S76,332
18,194,044
320.5
435,473
4,130,619
167,184
1,649,026
101,064
438,005
330.9
843.1
♦The term "station" as here used may represent a single electric station or a number of stations operated under the same
ownership.
THE ELECTRIC POWER INDUSTRY
431
The plant equipment and output of the
power stations for street and electric railways
are given in Table VI. It shows the number of
companies having power plants, the number
and capacity of the primary power units, the
electric generators and dynamos, and the
subsidiary apparatus by kind, and the quan-
tity of current generated and purchased.
In 1912, 50.8 per cent of the street and
electric railways had their own power plant
equipments as compared with 61 per cent in
1907 and 70.6 per cent in 1902. In other
words, the number of operating companies
without power plant equipments, purchasing
their power, has increased from 240, or 29.4
per cent of the total number in 1902, to 480,
or 49.2 per cent of the total number in 1912.
Mining Industry
The advantages of using electric power for
mining operations are now fully recognized
and almost all new mines are being equipped
for electric drive, and a very large number of
old ones are changing over to this system.
TABLE IV
DATA ON LARGE GENERATING SYSTEMS
System
Commonwealth Edison Company
Niagara Falls Power Company
Ontario Power Company
New York Edison and United Companies.
Hydraulic Power Company
Pacific Gas & Electric Company
Public Service Electric Company
Shawinigan Water & Power Company.
Montana Power Company
Mississippi River Power Company.. ..
Duquesne Light Company
Great Western Power Company
Detroit Edison Company
Puget Sound Traction, Light & Power Company.
Pacific Light & Power Corporation
Southern California Edison Company. . .
Utah Power & Light Company
Pennsylvania Water & Power Company.
Philadelphia Electric Company
Toronto Power Company
Tennessee Power Company
Electric Company of Missouri
Boston Edison Company
Union Electric Light & Power Company
Portland (Ore.) Railway, Light & Power Company.
Washington Water Power Company
Wisconsin Edison Company
Brooklyn Edison Company
Georgia Railway & Power Company. . . .
Sierra & San Francisco Power Company.
Great Northern Power Company
Rochester Railway & Light Company. . .
New England Power Company
Minneapolis General Electric Company .
fAlabama Power Company
*Southern Power Comapny .
Peak
Load
in Kw.
306,200
131,520
130,500
229,787
87,457
124,000
123,539
85,000
61,000
73,700
72,000
56,300
83,300
67,200
70,565
53,835
47,048
74,000
77,728
72,000
47,600
52,528
65,342
51,072
44,315
29,641
44,124
49,300
44,320
40,080
30,400
28,500
35,000
27,955
23,500
Date of
Peak
Load
Dec. 15
Jan. 5
Sept. 23
Dec. 23
Mar. 27
Oct. 29
Dec. 23
July 7
July 21
Nov. 16
Dec. 21
Dec. 9
Dec. 15
Dec. 17
Sept. 17
Dec. 24
July 9
Dec. 17
Dec. 1
Dec. 4
Dec. 11
Nov. 18
Dec. 21
Dec. 7
Jan. 2
Dec. 29
Dec. 22
Dec. 9
Oct. 28
Jan. 6
Nov. 13
Dec. 16
Dec. 15
Dec. 7
Dec. 22
Yearly
Output in
Kw-hr.
[,114,130,000
906,513,620
781,664,400
719,193,535
703,105,872
658,298,000
430,818,532
430,000,000
402,663,369
356,578,000
315,210,796
315,000,000
313,718,600
299,622,508
292,545,094
288,549,552
287,792,765
277,200,000
250,697,952
236,328,680
228,504,650
228,209,988
194,137,400
189,677,593
184,766,149
169,691,800
159,665,804
153,946,900
145,684,800
179,444,960
136,733,810
123,850,785
120,000,000
110,346,460
55,837,740
Yearly
Load-
Factor,
per cent
43.6
78.7
68.4
35.7
91.7
60.6
39.8
58.0
75.0
55.6
50.0
64.0
43.0
50.9
47.37
61.1
70.0
42.5
36.8
37.5
54. S
49.78
34.0
42.4
47.7
65.4
36.2
35.6
37.5
51.2
52.0
49.6
39.0
45.06
27.1
t Main Station began operations April 14.
* No data received, estimated.
432
GENERAL ELECTRIC REVIEW
TABLE V
STREET AND ELECTRIC RAILWAYS IN UNITED STATES
1912 1907
1902
1890
Miles of track
Operated by
Electricitv
Cable...!...
Animal power . ....
Steam ....
Gasolene motor
41.064.S2 34,381,51
4O.S0S.39 34,037.64
56.41 61.71
57.42 136.11
76.34 105.06
66.16 40.99
22.576.99
21,901.53
240.69
259.10
169.61
8,123.02
1,261.97
488.31
5,661.44
711.30
TABLE VI
PLANT EQUIPMENT AND OUTPUT OF STREET AND ELECTRIC RAILWAY
POWER STATIONS: 1912, 1907, AND 1902
1912
Number of operating companies
Number of companies with power-plant equipments . .
Primary power:
Number of units
Horse power, rated capacity
Steam power —
Number of units
Horse power
Engines —
Number
Horse power
Turbines —
Number
Horse power.
Gas and oil engines —
Number
Horse power
Waterwheels and turbines —
Numl er
Horse power
Dynamos —
Number.
Kilowatt capacity . . .........
Direct current —
Number
Kilowatt capacity
: mating and polyphase current —
Number
Kilowatt capacity. ...
Subsidiary equipment :
Rotary converters and motor-generator sets —
Number -
Kilowatt capacity
Boosters —
Number
Kilowatt capacity
:.ge batteries, number of cells
Transformers —
Number
Kilowatt capacity .
Auxiliary generator
Number
Kilowatt capacity
Output of stations and current purchased, kilowatt-hours
for year:
Generated
Purchased
495
2,695
3,665,051
2,264
3,169,554
1,802
1.706,754
462
1,462,800
48
24,190
3S3
471,307
2,797
2,508,066
1,642
769,875
1,155
1,738,191
2.S40
1,637,260
183
24,807
31,059
8,436
2,357,397
144
12,227
1907
945
3,637
2,519,823
3,368
2,411,527
3,116
1,876,123
252
535.404
41
16,335
228
3,124
1,723,416
2,192
941,502
932
781,914
1,862
942,232
134
17,046
5,274
1,133,161
311
19,152
1902
817
577
2,811
1,359,285
2,637
1,308,207
15
1,925
159
49,153
3,302
898,362
2,861
725,346
441
173,016
441
160,053
104
13,666
40,477
1,657
212,569
71
3,763
6,052,699,008
2,967,31S,7S1
4,759.130,100 2,261,484,397
THE ELECTRIC POWER INDUSTRY
433
Not only does this reduce the cost of working,
but it also offers a much safer and more reliable
operation. The use of electricity eliminates
the necessity for long lines of steam and air
piping, which are expensive to install and
maintain and with which the danger of
breakdown and the difficulty of obtaining the
necessary working pressures increase with
every extension of the service. For these
conditions electricity substitutes a simple and
thoroughly flexible system of transmitting
power by means of conductors which can be
easily run and rapidly extended to meet the
frequent changes which are involved in the
progress of the development. The flexibility
of motor drive renders possible the use of
While the primary power increased about 85
per cent, the application of electric motors for
manufacturing industries alone increased close
to 900 per cent.
Figures are not available giving the present
amount of power used in the manufacturing
industry, but a conservative estimate would
probably place the total primary power at
25,000,000 horse power and the electric motors
at over 10,000,000 horse power.
Water power was used more extensively
than steam in the manufacturing industry
prior to 1870. Since that time, however, it
declined steadily, while the use of steam
power increased, reaching a maximum of
about 87 per cent in 1900. There has since
TABLE VII
POWER USED IN MANUFACTURING INDUSTRIES
1S70
Primary power, total 2,346,142
Owned, total
Steam.. 1,215,711
Gas
Water 1,130,431
Other
Rented, total
Electric
Other
Electric motors, total
Run by own power
Run by rented power
1880
3,410,837
2,185,458
1,225,379
1890
1899
5,939,086
5,850,515
4,581,595
8,930
1,255,206
4,784
88,571
88,571
15,569
10,097,893
9,778,418
8,139,579
134,742
1,454,112
49,985
319,475
182,562
136,913
492,936
310,374
182,562
1904
1909
13,487,707
12,854,805
10,825,348
289,423
1,647,880
92,154
632,902
441,589
191,313
1,592,475
1,150,886
441,589
18,680,776
16,808,106
14,202,137
754,083
1,822,593
29,293
1,872,670
1,749,031
123,639
4,817,140
3,068,109
1,749,031
portable machinery, and additions to, or
changes in the location of existing machines
can easily be arranged for without interfering
in any way with the operation of the remainder
of the equipment.
Statistical figures relating to the power used
in this important industry are given in the
article on "The Use of Electricity in Mining
Work" on page 527 of this issue of the Review.
Manufacturing Industries
Table VII shows for all industries combined
the horse power of engines and motors
employed by manufacturing concerns for the
period from 1870 to 1909. The figures for the
total primary power exclude duplication and
represent the primary power of engines,
waterwheels, etc., owned by the manufactur-
ing establishments themselves plus the electric
and other power purchased from outside
concerns.
Especially striking is the increased use of
electric motor applications during this period.
been a marked falling off in the percentage
of directly applied steam power and this has
been due to the rapid introduction of electric
power. The increased use of the electric
motor for driving industrial machinery has
been phenomenal and this is again best
illustrated by a reference to the census report.
The curves in Fig. 1 show the approximate
percentage relation that steam, water and gas
power bear to the total in the three principal
industry — central stations, electric railways
and manufacturing.
Water Powers
The total developed water power in the
United States does not exceed six million
horse power, while many times this amount
are at present available for an economical
development. The surveys and examinations
necessary to a thorough and accurate report of
the water power resources of the United
States have never been completed. While in
certain parts of the country they are fairly
434
GENERAL ELECTRIC REVIEW
well known, in other parts the information
is very incomplete.
An endeavor has been made to determine
the maximum power that might be produced
if all the practical storage facilities on the
drainage areas were utilized. Surveys on
many of the basins make possible a fairly
and on the assumption that the water power
per square mile is approximately 14 horse
power. This value has been found to be the
average of a number of investigations in
European countries. For Australia, however,
this value is entirely too high, and three
horse power per square mile has been assumed.
90
s
as
l^_
bH
t>~
09
70
60
i
f
40
30
Watt
r&o**
to
HT3 -',-■■■'• ~
TABLE VI»I
WATER POWERS OF THE WORLD
'900 190/ 1902 /903 /904 I90S 1906 /907 1908 !909 1910 /9// /9/2
rear
Fig. 2. Curves showing Steam, Water, and Gas Power,
in percentage of total for years 1900
to 1912 inclusive
close estimate, but inasmuch as fully three-
fourths of the country has not been surveyed
in a manner suitable for this purpose, only
rough estimates can be given for the entire
area. It may, however, be assumed with
confidence, with all practicable storage sites
utilized and the water properly applied, there
might be established eventually in the country
a total water power installation of at least
100 million horse power and possibly 150
million. It should, however, not be assumed
that all this power is economically available
today. Much of it, indeed, would be too
costly in development to render it of com-
mercial importance under the present con-
dition of the market and the price of fuel
power. It represents, on the other hand, the
maximum possibilities in the day when our
fuel shall have become so exhausted that the
price thereof for production of power is pro-
hibitive, and the people of the country shall
be driven to the use of all the water power
that can reasonably be produced by the
streams.
An endeavor has also been made to estimate
the total water powers of the world, the results
being given in Table VIII. The values are
based on the area of the different continents
Continent
Area in
Square Miles
Horse Power
Africa
America, North .
America, South .
Asia
Australia
Europe
11,513,579
8,037,714
6,851,306
17,057,666
3,456,290
3,754,282
161,190,116
112,527,996
95,918,284
238,807,324
10,368,870
52,559,948
671,372,538
isaooo is.000
IZO.000 IZOOO
//oooo uooo
/00.OOO to.ooo
% \
§ 70000 ^ 7/700
54000 5,000
40000 4000
zaooo ZJW7
/QOOQ 4000
O o
IS94 /OSS /893 /900 '902 /904 /906 /903 /90 19/Z
rear
Fig. 3. Curves showing Transformer Development
It is thus seen that the total water powers
of the world represent nearly 700 million
horse power. This vast amount can, however,
not be economically developed at the present
time, but the tabulation merely shows the
possibilities that may in the future be derived
from this natural source.
THE ELECTRIC POWER INDUSTRY
435
Electric Power Service
The quantity and quality are the principal
elements which determine the value of an
electric power service, and while the quantity
can readily be measured, there is no standard
of quality. It is generally a very difficult
matter to determine what under given con-
ditions is good service and whether the quality
of the service that has been specified is actually
rendered. An absolutely reliable service can
of course be obtained but at a very high cost
which is justified in only very rare cases. In
general, the more reliable the service is the
more it must cost, due to the superior con-
struction required and to the increased invest-
ment for emergency apparatus, etc. The
question therefore always arises: What
degree of reliability is justified under certain
conditions and what is the real value of such
service? It is evident that it varies very
widely for different industries.
Generating Equipments
For the generation of electric power the
steam turbine and the waterwheel stand
foremost, and it is an astonishing rate at which
the size as well as the efficiency of these
generating units have increased of late. A
35,000-kw. steam turbine unit is now nearing
completion and is the largest single turbine
built up to the present, although there is every
indication that the 50,000-kw. mark will be
reached before very long. Hydro-electric
turbine units are now also built for capacities
up to 17,500 kw. and a large number of notable
water power installations have been recently
completed or are under construction. Among
these may be mentioned the 200,000-h.p.
development of the Mississippi River Power
Company at Keokuk, Iowa; the Big Creek
Developments of the Pacific Light & Power
Company, California, and many others.
The type now generally adopted for the
Curtis turbine consists of one double wheel
followed by a number of wheels having single
rows; the number of these depending upon
speed, size and efficiency required. In units
above 20,000 kw., the turbine is divided into
two parts: one high pressure and one low
pressure. The low pressure is made double-
flow in order that the highest efficiency may
be obtained with vacuum as high as 29 in.
The high-pressure and the low-pressure parts
are both connected to the same shaft and one
generator is used, there being no advantage
whatsoever in splitting the units up into two
parts running at two different speeds. The
single row construction, now generally
adopted, requires a higher bucket speed than
on the older construction, having two rows of
buckets throughout the machine, but at the
same time it gives considerably higher effi-
ciencies and in addition permits utilizing
efficiently the best vacuum obtainable, which
is of the greatest importance, particularly at
such installations where the natural condi-
tions permit a good vacuum. As the vacuum
is of the greatest importance in turbine
installations, the benefit of same should be
given careful consideration, and, in judging
two different types of turbines, the one that is
able to efficiently utilize the best vacuum is
far superior to another one that is unable to
do so. A turbine designed for 29-in. vacuum
is very much larger and more expensive to
build than one designed for 28 in., or, putting
it another way, the turbine designed for 29
in. is capable of rating up at least 25 per cent
at a vacuum of 28 in.
Large Curtis turbines of recent design show
not only a performance representing the
maximum turbine efficiency so far obtained,
but also that the highest value is closely
sustained over the greater part of the load
range of the machine. The advantage of this
where machines are frequently required to
operate over considerable variations in load,
is apparent. In fact, the useful capacity of a
turbine is determined by the shape of its
load-water rate curve rather than by an
arbitrary rating assigned to it by the manu-
facturer. In general, any turbine can be made
to carry a load considerably in excess of the
most economical load, either by permitting
congestion of steam in the low-pressure end,
or by by-passing live steam to buckets operat-
ing at intermediate pressure. This practice
is only justified to a limited extent. That is,
an increase of a few per cent in steam con-
sumption at the maximum load, over that
of the most economical point, is permissible,
in order to insure good light load economy.
But where a small machine is given a very
large arbitrary rating, and the maximum load
secured at the sacrifice of economy at high
loads, the actual useful capacity is not the
maximum rating assigned to the machine,
but some lower value, determined by the
economical range beyond the best point. The
best practice is therefore to so rate turbines
that the steam consumption of the machine
at its maximum continuous rated load will
not differ greatly from that at the point of
highest economy.
Hydraulic turbine design has also passed
through a stage of wonderful development
436
GENERAL ELECTRIC REVIEW
during the past few years and remarkable
progress has been made toward bringing the
turbine to a high state of perfection. Ten
years ago it was considered a notable achieve-
ment to obtain a turbine with an efficiency
as high as 82 per cent, while today a maximum
value of 93.7 per cent has been secured.
This remarkable increase in efficiency is by
no means entirely due to superior runner
design. As a matter of fact, the improve-
ments in the design of wheel-casings, wicket
gates, draft chests and draft tubes have
increased the efficiency of the turbine as much
as the more efficient runners.
One of the most notable deviations from
the old practice of the multi-runner turbines
has been the general adoption of the single-
runner, vertical-shaft turbine for low and
and requirements of the prime movers them-
selves.
Probably the most obvious change in the
design of waterwheel-driven generators of
recent years, and the most important from a
commercial standpoint, is the large increase
in kv-a. output now obtained from a given
size of frame. In 1909 and earlier, it was
common practice of purchasers to require a
regulation of from 5 to 8 per cent at unity
power-factor. At the present time common
requirements for regulation are about double
these figures.
This change has resulted mainly from two
causes, viz.:
First: The doing away with hand control
and the more general use of automatic voltage
regulators.
Fig. 4. Cedars Rapids Manufacturing 8t Power Company on the St. Lawrence River at Cedars Rapids, Canada.
Exterior View of Power House with Transformer and Switch House on the Left
medium heads. This change in the type of
unit has been made possible by recent progress
in the design and development of high-
capacity runners. Thus, for a given head and
speed it is now possible to secure from a
runner a greater output than was possible a
few years ago, or, conversely, for a given head
and capacity it is possible to operate the more
recently designed runners at a much higher
rotational speed than was the case with
runners designed a few years ago. This
increase in the capacity of runners has been
secured without sacrifice of maximum effi-
ciency and with only a small sacrifice in the
efficiency at fractional loads.
The development of generators driven by
different types of prime movers must neces-
sarily also keep step with the development
Second: The necessity of a higher value
of inherent reactance as generators were
built in increasing capacities, due to the
destructive effects of short circuits with the
low values of reactance formerly used.
This sacrifice of inherent regulation and the
desirability of high inherent reactance enables
the designer to obtain from a definite frame a
very greatly increased kv-a. output, this
amounting to as much as from 15 to 30 per
cent over the old rating.
J2ven with the high values of the present
dfy alternating-current generators, it is often
insufficient where a large number of machines
of great kv-a. output are connected to a
common bus, in which case it frequently
becomes necessary to resort to external
reactances connected either in the generator
THE ELECTRIC POWER INDUSTRY
437
leads or the bus in order to limit the rush of
current resulting from a short circuit.
Considerable improvements have been
made in insulating materials and in the
development of suitable insulation for with-
standing higher temperatures than were per-
missible in the past. Similarly, the life of
high potential coils has been greatly lengthened
by providing protection against the destruc-
tive effects of corona. The use of so-called
"temperature coils" has also become very
general, these being small suitably shaped
coils of insulated wire imbedded in the arma-
ture windings of the machine for determining
the temperature rise by the increase of
resistance of the coils.
Considerable attention has of late been
given to the ventilation of generators and the
cleaning of the air. With the advent of very
slow speed machines with low peripheral
velocities, where fans attached to the rotor
cannot be effectively used, it has become
necessary to resort in certain cases to special
passages of the generators. The use of either
method of circulation depends largely upon
the generators and the power house design,
and the best arrangement must be worked
out for each individual case.
Fig. 5. Interior of Cedars Rapids Power House. Present
equipment, nine 10,000 kv-a., 136-pole, 55.6 r.p.m.,
three-phase, 6600-volt generators. Ultimate
equipment, eighteen similar units
ventilating arrangements in order to carry
away the heat generated. This may take
the form of large ducts leading air in from trie
outside of the building to the generator pit,
depending on the fan effect of the generator
rotor for circulation, or motor-driven blowers
may be used for forcing the air through the
Fig. 6. Massena Substation of the Aluminum Company of
America, containing eighteen 2500-kw. 360/500-volt
Synchronous Converters. Power supplied from Cedars
Rapids Manufacturing & Power Company
Transmission
The high-voltage transmission system has
undergone an evolution from the single
transmission line with a power station at one
end and with a receiving circuit at the other,
until it is more nearly a high-voltage dis-
tributing system into which network are fed
a number of steam and hydro-electric power
stations, and from which at various points are
tapped off distributing systems of lower volt-
age which feed local communities, many of
which secondary systems extend over a very
considerable area.
For the transmission and distribution of
electric energy the voltage continues to rise
as the distance and the amount of power to be
transmitted increases, and this in turn pre-
sents new problems of design and construction.
This involves mainly the transformers, the
line structure and the switching equipment.
As long as the transmission voltage and the
capacity of the generating stations were
moderate, no serious operating difficulties
were experienced. With the introduction of
transmission pressures of 100,000 volts and
above, and with the concentration of enormous
amounts of power in our modern power
stations, problems arose which were solved
only after very painstaking investigations and
great expense. So, for example, have the
transformer interruptions been reduced to a
43S
GENERAL ELECTRIC REVIEW
minimum by embodying designs which will
make them safely withstand the excessive
voltages which may be set up in the system
under transient conditions, while on the other
hand they are now capable of withstanding
the severe mechanical stresses imposed on the
windings under short-circuit conditions.
Fig. 7. A Substation and Outside Equipment of the
Utah Power and Light Co.
Fig. 8. Another view of the Outside Equipment
of the Substation shown in Fig. 7
The curves in Fig. 2 illustrate the astonish-
ing increase in the development of trans-
formers, both as regards capacity and voltage.
So, for example, are core type transformers
now built in sizes up to 7500 kv-a., while
single-phase, shell-type transformers have
been built in sizes of S333 kv-a.
Another notable feature in the transformer
development is the combination self-cooled,
water-cooled type, consisting of an ordinary
water-cooled transformer placed in a cor-
rugated or pipe radiating tank. It may thus
be designed for normal operation with water
circulated through the cooling coils, while
it may also be safely operated at 50 per cent
of normal load without the circulation of
water and without exceeding its specified
temperature rise. On the other hand, this
transformer may be designed for normal
operation as a solf-cooled unit, and be pro-
vided with the necessary cooling coils which,
when utilized, permit operation efficiently at
50 per cent above the normal capacity.
On account of its exposed position the
transmission line continues to be the weakest
link in a high-tension transmission system and
even the failure of a single insulator may cause
a complete shut-down of the entire system.
• While very great and encouraging improve-
ments have of late been made in the design
of insulators and in the methods of testing for
weeding out the defective units, it can, how-
ever, not as yet be said that the insulator
problem is solved.
The question of regulation of large high-
voltage systems involves a number of dif-
ficulties not encountered in low-voltage work.
In the latter case the energy loss is generally
the limiting factor and the regulation can
often be improved by installing larger con-
ductors, which at the same time will reduce the
line loss. With high-voltage systems the
gain of doing so is very slight and other means
must be resorted to for keeping the regulation
within commercial limits. The effect of the
inductance and capacity of the line causes
the voltage to vary within very wide limits
from full to no load. At no load the large
capacity current causes a rise of voltage from
the generating station to the receiving end,
while at full load the lagging inductive cur-
rent taken by the load, in general, more than
offsets the effect of the capacity current and
causes a drop of voltage from the generating
station to the receiving end. It is evident
then that by installing a synchronous con-
denser at the receiving end, and taking
advantage of the characteristics of this
machine, the receiving voltage can be kept
constant at a determined value by adjusting
the synchronous condenser field, causing the
condenser to draw a lagging current from the
line at no load and a leading current at full
load.
The engineering problems in connection
with the operation of these high-voltage
systems are very largely those which have
to do with preventing interruptions to service,
and which isolate and localize the electrical
disturbances before they can become of a
general nature. This involves itself not only
into the general design of the apparatus and
transmission lines but also to a careful study
of the best system of connections and switch-
ing equipment. Reliability and continuity of
service are the main considerations, but besides
this the protection of apparatus from injury
should be very carefullv considered.
A BRIEF REVIEW OF THE ELECTRIC LIGHTING INDUSTRY
i:;n
One of the greatest difficulties involved in
this work has been the problem of determin-
ing the exact nature of the disturbances, both
in kind and magnitude, to which the line and
apparatus is subjected, and while the many
interesting and valuable investigations which
have been made have brought forth much
light, more still remains to be accomplished.
On some systems where a careful and
detailed study has been made of the problem
of properly relaying the transmission lines,
very great improvement has been made. It
seems, however, almost impossible to so
arrange a system as to prevent a vicious
lightning stroke from doing any damage, but
experience has proven that it is possible to so
relay the system that such an interruption
becomes merely local in character and that
the supply of power is not in any way dis-
turbed.
A BRIEF REVIEW OF THE ELECTRIC LIGHTING INDUSTRY
By C. W. Stone
Manager, Lighting Department, General Electric Company
The author makes a rapid review of the early stages of the lighting industry noting many historical facts
and then recites some of our modern developments. He shows our rate of progress up to the present and
tells of the many different directions in which we may expect future developments leading to higher efficiencies
in the generation and distribution of electrical energy. — Editor.
The electric lighting industry, so-called, has
grown so rapidly and has expanded in so
many directions that it will be possible to
point out only a few of the factors which
have contributed to its growth.
The industry, considered as such, may well
be called one of our infant industries from
the point of years since its inception, but
from the point of view of its magnitude it is
probable that no single industry is of such
vast importance to modern civilization. It is
no longer a scientific toy or luxury, but is a
vital necessity to our present progress and
will become more so as we advance.
The Gramme dynamo completed in 1S71 is
usually referred to as being the first type of
machine to be used commercially for arc
lighting, but other work had been done with
other forms of machines which were fully as
successful. Progress in Europe was rapid
in the earlier days, but the greatest progress
later was on our own continent. Probably
the first commercial arc system installed
in this country was in Cleveland in 1879.
Immediately after this other systems were
installed both in this country and in European
countries.
In the earlier days the problems of success-
ful lighting were many. It was not only a
problem of building machines for the pro-
duction of the electricity, but instruments,
switch, etc., had to be developed, no con-
tinuous lengths of copper wire were available,
and in fact the engineer was confronted
with the most difficult problem possible.
Everything had to be invented, but the
interest was so great that many inventors
were attracted and the financiers were liberal
in their support, which resulted naturally
in very rapid advance.
Most of the early work was on the develop-
ment of arc machines and arc lamps, and it
was about 1883 that companies were formed
to take contracts for lighting city streets,
the price being about $1.00 per lamp per
night. Many difficulties arose, such as
poor and crooked carbons, poor and thick
globes, unskilled labor for the construction
of both lamps and machines and their opera-
tion.
It was soon recognized that the arc system
was the best suited for special lighting and
particularly for out-of-door work. Mr.
Edison then experimented with the develop-
ment of the incandescent lamp and after
many experiments success was reached.
The history of this type of lamp has been
described so many times that it is unnecessary
to describe it here except to point out the
date of the starting of the first commercial
station for this type of lighting at Appleton,
Wis., in August, 1882, the total capacity
of the station being for two hundred and
fifty 10-c-p. lamps.
At this time the systems for arc and
incandescent lighting were wide apart. Arc
lighting, due to its fundamental character-
istics, was suitable for outdoor service
440
GENERAL ELECTRIC REVIEW
lighting, especially in stores and manufactur-
ing plants, while the incandescent system
with its low-voltage circuits and small lamps
was naturally limited to small areas and
indoor sen-ice. These two systems of lighting,
each with its own admirers, naturally led to
rivalry and competition. At the same time,
new schemes and contrivances were developed
that would bridge the gap existing between
the series and multiple system in service;
while some of these were quite ingenious,
they only proved temporary and gradually
paved the way for the introduction of our
modern alternating-current system, which
perhaps more than any other factor has helped
to develop a uniform electric illumination
and power transmission. The alternating-
current system began to receive prominent
attention about 1883 and in the fall of 1885
the first regular alternating-current system
was installed at Buffalo, N. Y., when current
was generated at 500 volts and stepped up
to 3000 volts for transmission, after which
it was stepped down to 100 volts for service.
Even this installation was crude in a good
many respects.
The development of the polyphase gener-
ator, which was the next step, permitted the
development of the polyphase induction
motor with its high starting torque and
rugged simple construction.
From this time the growth of the central
station was rapid. The value of a day load
was soon apparent, campaigns were immedi-
ately inaugurated to develop power appli-
cations. This resulted in the rapid increase
in the size of the central station and created
a demand for larger generating units. This
demand later brought about the rapid
development of the steam turbine. The first
large units, 5000 kw., were built in 1900,
and the capacities have steadily increased
until todav turbines are in operation of
30,000 kw". capacity, and 50,000-kw. ma-
chines wih probably be built within a short
time.
It is not in steam turbines alone that this
increase has appeared. There are in operation
today waterwheel-driven generators of over
17,500 kw. continuous capacity. With the
increasing demand for electric service and
the development of larger waterwheel-driven
alternators the water power companies have
gone farther back into the mountains for
their water power sites until we now find
such stations 250 miles or more from their
distributing centers and operating trans-
mission lines at 150.000 volts.
In the control apparatus the development
of the oil switch has kept pace with the
increase in capacity and voltage until today
the oil switch not only breaks a potential of
150,000, but will withstand line disturbances
of three times this value.
Before the introduction of electricity,
manual labor was almost supreme because
the mechanical devices in service were
usually so crude that they required almost
constant attention for successful operation.
During this period many wonderful inventions
were nevertheless perfected, but their require-
ments were for very special conditions of
necessity to meet a particular requirement
without having direct bearing on the welfare
of the entire community.
The introduction of the central station for
the general distribution of electricity on the
other hand marked a decided step in the
advancement of civilization, because through
this medium it has been possible to generate
power at a cost so low and in such convenient
form that it is rapidly displacing all other
forms of power.
During the early stages of progress central
stations were developed mainly for lighting
purposes and, like all new business enter-
prises, the greatest activity was developed
in communities of sufficient size to plainly
warrant the expense. The outcome of all
these years of development has finally
resulted in the successful installation of about
8000 electric lighting plants in continental
United States.
The tendency in the past has been the
building of a central station for each locality,
but this idea is being gradually replaced by
the more economical system of distribution,
namely, the generation of large quantities
of energy at some central point or the con-
solidation of several central stations and
distributing the energy at high potentials to
other communities where it is again dis-
tributed at safe voltages for various purposes ;
for instance a large city plant expands so as
to include all the district around it and
service originally limited to a small area is
unified over a considerable territory. In
other cases the individual properties in a
territory are merged and brought under one
management, while other instances occur
where unrelated public service companies
widely dissociated in various states are placed
under one control and management. This
system of development has now progressed
until the electric properties have merged
their interests in other utility properties, such
A BRIEF REVIEW OF THE ELECTRIC LIGHTING INDUSTRY
441
as the gas and street railway systems. The
relative economic advantage of this method
of operating must receive universal approval
because it is of direct interest to each indi-
vidual and has a direct bearing on the low-
price of electric energy.
One of the most important advantages of
this method of operating is the utilization
of the diversity factor which is one of the
primary elements in determining a low price
for electric service. The station must be
designed to carry the maximum demand, but
the cost of the power will depend upon its
average 24 hours' demand.
The utilization of electrical energy in a
modern city home has reached such a stage
that it is now used not only for lighting, but
for heating, cooking, cleaning, refrigerating,
operating mechanical drive such as fans, wash-
ing machines, etc., and almost every other
conceivable purpose. In a similar manner
everything in which man is interested has
been benefited and the rapid development of
electricity along diversified lines has added
immeasurably to the progress of civilization.
In medicine and surgery it has proved of
inestimable value. Today we have the
Rontgen ray which is of great assistance to
surgeons in locating various troubles in the
organs of the body, thus simplifying the
necessary operation and greatly reducing
the time required, and in some cases making
it possible to avoid operating.
The X-ray is now being successfully used
in metallurgical research, as by its use
faults in metal substances can be shown.
Electricity is also used for cauterizing wounds
in the purification of air and water by the
ultra violet ray. The moving picture was
made possible by the development of the
high powered arc lamp.
These benefits are by no means confined
to the city because the central station with
its great network of distribution is in a
position to furnish electric energy to the
farmer, who, if progressive, is today able to
enjoy the same pleasures as his city neighbor,
and in addition can accomplish a greater
amount of work than heretofore in less time
and at a smaller cost. Another important
direct benefit is that it does away with
practically all the old drudgeries usually
found about the farm.
The technical growth of this industry has
brought out many interesting problems tend-
ing to reduce to a minimum the overhead
operating and distribution charges, so that
electrical energy may be produced and
delivered at the lowest possible cost. The
details involved are numerous and compli-
cated even from the proper handling of the
coal for the boilers to the delivery of energy
to the lamp filaments in the home.
In attempting to prophesy the future of an
industry one naturally looks to the past, for
guidance, although in this age of scientific
investigation and discoveries there are possi-
bilities of such radical changes as may
upset all prophecies based on past conditions.
It is interesting to note, however, that in
the last 20 years the increase in magnitude
of the central station industry has been at
the rate of about 15 per cent per year or
doubling itself every five years. If lighting
alone is considered, although the point of
saturation is far from being reached, we
should not anticipate a continuation of
increase at this rate. The central stations
are, however, making every effort to increase
their output and diversify their load by use
of current for every conceivable purpose
and a reasonable rate of increase in load
will be continued and possibly be increased.
Hand to hand with the growth of the
industry has gone a reduction of the cost of
lighting and of power, both of these move-
ments being related to each other reciprocally
as cause and effect.
It is to be expected that the reduction in
cost of electricity will be continued as new
discoveries and improved methods of genera-
tion, distribution and conversion are adopted,
although as the theoretical limits are
approached, the decrease in cost will not be
so rapid as it has been in the past.
Generation
With the improvement in load factors and
the increase in size of generating units and
generating plants and systems, it is to be
expected that improvements and refinements
in the various generating station operations
will be made. Some of these possibilities are
as follows: The utilization of a greater
temperature range in the thermal cycle, as
by higher degrees of super-heat, the increased
use of economizers, etc. One very important
improvement already in sight is the mercury
boiler and mercury turbine worked out by
Emmet. In this development coal is used in
a special boiler evaporating mercury. The
mercury vapor is expanded to a high vacuum
in passing through a turbine producing
power, the condenser for the mercury serving
also as a steam producer whence steam is
carried to steam turbines, thus the mercurv
442
GENERAL ELECTRIC REVIEW
is worked through the thermal cycle from
about 700 deg. F. to 400 deg. F., the steam
working through a cycle from 400 deg. F.
down to 70 deg. or SO deg. F. The addition
of the mercury cycle to the steam cycle
enables us to produce from 35 to 50 per cent
more power from a pound of coal than is
at present produced by the most efficient
steam generating stations.
For small and moderate sized plants the
high efficiencies shown by internal combustion
engines, particularly of the Diesel type, will
probably produce an extension of the use of
such machines as soon as improvements of
design and standardization of manufacture
sufficiently reduce the initial and main-
tenance cost.
The design of internal combustion turbines
is a field having large possibilities but sur-
rounded by apparently insuperable diffi-
culties, to which a solution may possibly be
found in the future.
Engineers are turning their attention to
methods of utilizing all of the1 heat generated
by fuel, and along this line efforts have been
made to utilize the heat of exhaust from the
heat of internal combustion engines. A
notable example of this is to be seen in the
Ford f acton,'.
Distribution
There is a considerable field for improve-
ment in methods of distribution. Develop-
ments of the past few years show an increased
tendency to connect together a number of
generating stations into a network and these
stations may be steam stations or hydraulic,
or more frequently both. The extension of
this network supplied from numbers of
central stations will undoubtedly increase.
We already have transmission and distribu-
tion networks covering several states and
the future will probably see the whole country
covered by distribution networks connected
together by transmission lines, just as the
steam railroads have been interconnected.
Improved methods of protecting these net-
works from lightning, high frequency, short
circuits, etc., will be developed.
Our knowledge of properties of insulating
materials is as yet imperfect. Investigation
and discoveries will probably produce con-
siderable improvement in the insulation of
conductors and thus allow the use of higher
temperatures and higher voltages tending
towards reduced losses and economy of
investment in the distribution svstem.
Substations
There has been a steady reduction in the
weight, size and cost of electrical apparatus
for substation use, enabling the central
stations to make considerable increases in
the kilowatts per square foot or floor space.
These changes have been brought about by
improvements in design, economizing in
material and the use of increased speeds.
It seems likely that some progress will still
be made along these lines but there is not
very much room for improvement unless
new types of apparatus are developed. Such
new types as various kinds of rectifiers are
being studied and may prove useful in the
future.
The automatic operation or the remote
control of substations has proved successful
in initial installations, both in lighting and
railway work. The constant demand for
economy in operation is likely to extend
to the use of this class of substation.
Lighting
Vast improvements have been made in the
past few years in incandescent and arc lamps.
The former are now approaching limits
fixed by the temperature of melting point of
tungsten and other of the most refractory
metals. There is no limit, however, to the
temperature of incandescent gases, hence
the arc lamp offers a field for improvement
limited only by the present methods.
A still greater field for improvement is a
possibility of the production of light without
heat. At present in all of our lighting most
of the energy applied to the lamp goes into
heat, only a small amount is turned into
light. For instance, in the half-watt gas
filled Mazda lamp, which works at about
0.02 watts per spherical candle-power, the
luminous efficiency is about 3.3 per cent,
that is to say, only 3.3 per cent of the energy
applied to the lamp is put into the production
of light, the remaining 96.7 per cent being
dissipated as heat. The most efficient arc
lamp has about 5 per cent luminous efficiency.
Thus we see that in spite of the great progress
that has been made, there is still a vast
field for improvement in the transformation
of electricity into light, and so offering a field
for improvement greater than any of the
other steps in the generation and distribution
of electricity and its conversion into light. _
In conclusion, I quote an interesting article
that appeared in the Brush Electric Light
Paper of March. 1882, which not only
A BRIEF REVIEW OF THE ELECTRIC LIGHTING INDUSTRY
443
represents the spirit of the times then but
now with regard to the possibilities of electric
service.
"The progress of electric illumination seems to be
on the advance all over the world. In London
two miles of streets are now lighted by the Brush
and Siemens systems. In New York the Brush
Electric Illuminating Company has just received
the contract to light Union and Madison squares,
Broadway and Fifth avenue, from Fourteenth to
Thirty-Fourth streets and Fourteenth and Thirty-
fourth streets, between Broadway and Fifth avenue.
A new style of street lamps will be used, more like
the common street gas lamp. It will be larger and
covered with ground glass setting fifteen feet above
the ground, instead of twenty-five feet, as now. But
the most important change will be the manner of
lighting Madison and Union squares. This will be
done on the same plan as is now in successful
operation at Akron, Ohio. Columns will be erected
in the center of the squares; on the top of each of
these columns will be suspended six electric lights
of 6000 candle-power each, or 36,000 candle-power
in all, eighteen times more powerful than the regular
Brush light, such as is now being used in Scollay
Square. This experiment will be watched with great
interest here in Boston, for few cities have so fine
large parks situated in the heart of a city as the
Common and Public Garden, and it is only a
question of time when these places will be lighted
by electricity.
"The opposition to electric lighting is very
strong, and some parties even object to have the
wires carried over their roofs, fearing they will be
set on fire or exploded. The Brush Electric Lighting
Company of Boston, to be on the safe side, use
nothing but insulated wires, so that if they touch
any other wire no trouble will come from it. The
contract for the New York street lighting was as
low as gas; and this fact has astonished the gas
companies very much, as they have always claimed
it cost double; and several of the companies, as well
as the newspapers, claim that it cannot be done at a
profit, and the low price was given as an advertise-
ment. This would be foolish, when the New York
Brush Company have all they can do to supply
the demand for lights. They have six stations now
fitted up and will add more as soon as they can
get machines from Cleveland. They have had a
good chance to thoroughly test what it costs to
generate the power which runs the electric machines;
and in one point in particular the Brush Company
have shown more judgment than some of the other
electric companies. They use the cheaper grades
of fuel, and have adopted the most approved
methods of burning it; so that from a ton of coal
screenings they get as much power as others get
from a ton of the highest cost fuel. This gives from
25 to 50 cent economy. In this country, the principal
companies before the public are the Brush, Edison
and Maxim. The Brush is on the voltaic arc system,
and the other two on the incandescent. The latter
will be used for indoor lighting. They claim to
furnish lights as cheap as gas; but this is a subject
that will be required to be proved, as they also
admit that they furnish seven lights to a horse
power; or, allowing that each incandescent light
is the same as gas, 16 candles, this will furnish
112 candle lights to each horse power. It costs less
than a horse power to furnish a single Brush light
of 2000 candle-power, and a dynamo machine of
40 lights takes only 33 horse power to run it. On this
basis neither the Brush Company nor the gas
companies have anything to fear from Edison or
Maxim."
444
GENERAL ELECTRIC REVIEW
A REVIEW OF ELECTRIC RAILWAYS
By TV B. Potter and G. H. Hill
Chief Engineer and Assistant Engineer, Railway and Traction Department,
General Electric Company
The authors in making a rapid review of electric railways show the growth of the industry by a series of
curves which are self-explanatory and which show a rate of progress and a continuation of progress that is
quite astonishing. They tell many interesting and instructive facts from their own experience and give some
valuable information on the early development of electric railway apparatus. — Editor.
It has become axiomatic that improved
means of transportation creates traffic possi-
bilities which may have been wholly unfelt
and unappreciated. From the very beginning
of rail transportation, this feature has been
much in evidence and the possibilities for the
creation of traffic have continuously exceeded
the most optimistic predictions.
Following the initial success of the steam
locomotive, the establishment and extension
of railroad facilities throughout the country
seem to have become the chief interest in
the national industrial life. Although we
After the extensive exploitation of steam
railroads there was plenty of enthusiasm as
to the possibilities of electric propulsion for
city cars, but the possibilities of electric
motor cars were not appreciated and even
the most optimistic failed to realize how
rapid would be the growth of electric railways
or how soon they would rank with the steam
railroad as a necessity to the traveling public.
In 1S90 there was scarcely more than 1000
miles of electric railways in the United
States. From this time up to the present
Fig. 1. Type F-30 Railway Motor Built in 1889
Fig. 2. GE-248 Railway Motor Built for New York Municipal
Railway Corporation — 1914. Hourly rating 160 h.p.
Provided with multiple fan ventilation
may not today appreciate the inconvenience
and tediousness of travel by stage and horses,
there is little to wonder at the popular in-
terest in this railroad development and the
extent to which the resources of individuals,
municipalities and even the Federal Govern-
ment were all devoted to the subject of
railroad extension.
The inception of electric railway trans-
portation had for its object a more economical
and practical means of street railway trans-
portation in large cities, where horse cars
had become insufficient and cable railways
and steam elevated trains were unable to
successfully meet the requirements.
the mileage of electric railways has steadily
increased at the rate of about 2000 miles
per year.
The mileage of steam railroads has increased
at the rate of about 6000 miles each year
for a number of years past, and during this
period there have been many consolidations
of the original smaller companies into large
trunk line svstems which may range from
5000 to 12,000 miles of track. A similar
consolidation of what were originally inde-
pendent railways has taken place among
many of the electric railway lines, some of
these consolidations now having a mileage
of over 1000 miles of track.
A REVIEW OF ELECTRIC RAILWAYS
445
During the first few years of electric
railway development the progress was slow
but convincing, despite the novelty of the
equipment and some skepticism as to the
reliability of electrical apparatus as then
constructed. It was obvious from the first
that the electric motor car fulfilled the
requirements of short haul traffic better than
any existing method. Increase in the mileage
equipped and improvements in the apparatus
both contributed to inspire confidence, and
commencing with the Sprague Road at
Richmond in 18S8, the real development
began in 1S89 with the general adoption of
electric service by the West End Railway,
Z. i
American enterprise. Certain factors in the
then existing lines of transportation, particu-
larly the headway between trains in steam
service, was not favorable to the development
of interurban travel such as has resulted
from the more easily accessible and more
frequent headway provided by the interurban
motor car.
Fig. 3. Original Type of Scries Parallel Controller, Form J,
built in 1892 for installation beneath the car platform
Fig. 4. Type E, Original Series Parallel Platform
Controller — 1892
Fig. 5. Type 51 Rheostat for Resistance
Control — 1888
Fig. 6. Type RG Cast Grid Rheostat — 1913
Boston. The interurban lines followed as a
natural course, earlier instances being merely
the joining of outlying extensions from the
more populous centers. The real interurban
development began in the early '90's and
was particularly, for a number of years, an
The first application of electric power to
heavy service and the first successful substi-
tution of the electric locomotive for the steam
locomotive was in the Baltimore and Ohio
tunnel, Baltimore, 1895. Some doubt was
expressed at that time, by those more familiar
446
GENERAL ELECTRIC REVIEW
Fig. 7. Early Type of Motor-driven
Air Compressor — 1893
Fig. 8. Latest Type of Motor-driven Air
Compressor — 1913
with the steam locomotive, as to the ability
of an electric locomotive to start a heavy
train. Such evidence as slipping the drivers
even with sufficient weight on driving wheels
as would ensure handling the train with a
steam locomotive was not regarded as
conclusive. This point, so far as the Baltimore
and Ohio was concerned, was settled to the
satisfaction of their engineers in the earlv
period of operation. One of their officials
who was doubtful of this point desired a
demonstration, and during acceleration of a
heavy train he mistook careful handling on
the part of the engineer as being necessary
to the protection of the locomotive. He
instructed the engineer to "open up," which
the engineer did after brief remonstrance,
knowing what was likely to happen, and so
effectually as to pull the end out of a box car
loaded with oats in bulk. Needless to say,
there was no further question as to whether
the locomotive could pull. In this connection,
Fig. 9.
Cylinder Type Controller built for early
B. & O. locomotives — 1896
Fig. 10. Master Controller for Butte, Anaconda 8t
Pacific Locomotive — 1913
A REVIEW OF ELECTRIC RAILWAYS
447
Fig. 11. 40-Ton Electric Locomotive Built in 1894 for
Cayadutta Electric Railroad, now a part of the
Fonda, Johnstown & Gloversville R.R.
a well known American artist, who had
looked over one of the New York Central
locomotives, remarked that it was all very
impressive, but that he would like to be
shown where the electric power was hitched
to the driving wheels. Being shown the
air gap between the armature and the motor
field and told that the hitch was across that
12. Latest Type N.Y.C. Passenger Locomotive — 1914
Total weight 133 tons — eight bipolar gearless
motors with a total of 2640 h.p.
space and as invisible as the air, he pondered
a few moments, and then expressed the
opinion that it was "hypnotism."
While not at first appreciated it was early
realized that the electric car required more
than the nominal two horse power of the
ordinary horse car. More rapid acceleration,
faster schedules and heavier cars soon
demonstrated that nothing less than two
10-h.p. motors would answer, and for the
earlier successful railways two 15-h.p. motors
came to be the accepted standard. Increase
in the requirements led to the use, in about
1S95, of two 25-h.p. motors. This was
Fig. 13. Chicago. Milwaukee & St. Paul Electric Locomotive, 21 of which are now under construction.
Locomotive is equipped with eight motors, totaling 3440 h.p.
Total weight 260 tons
448
GENERAL ELECTRIC REVIEW
Fig. 14. Early Panel
Switchboard — 1892
Fig. 15. Butte. Anaconda & Pacific Switchboard — 1913
followed by four motor equipments of the
same h.p., while today four 40-h.p. motor
equipments are in very general use.
After a brief and somewhat trying period,
during which motors were placed in every
conceivable position, and with belt, rope,
chain and bevel gear drive tried and dis-
carded, the mounting of motors directly on
the axle with spur gear drive soon became
the established arrangement. Of all electrical
apparatus more is required of a railway
motor under severe limitations than in any
other service. For railway work the motor is
limited in width by the gauge, in height by
the clearances below and above, and in
length by the wheel base.
The first railway motor to be widely used
was the Thomson-Houston F-30 rated at
Fig. 16. No. 25 Railway Generator afterward designated
D-62, Rating 62 kw— 1888
Fig. 17. 4000-kw. Synchronous Converters installed for the
Chicago Surface Lines — 1914. Campbell Ave.
and Homer Street substation
A REVIEW OF ELECTRIC RAILWAYS
449
15 h.p. The control consisted of a single
reversing switch for both motors, a rheostatic
control, the resistance being semi-circular in
form with an arm driven by a wire cable
from a handle on the platform, moving over
contacts interspersed between the resistance
plates. One of the earlier improvements was
to substitute a double reversing switch to
better equalize the work between the motors.
The double reversing switch introduced the
new feature that if thrown to reverse when
the car was moving, one of the motors
reacting on the other as a series generator
would stop the car without current from the
difficulty experienced in effecting the motor
combinations the rheostatic control was
continued until 1892. In the meantime there
were many unsuccessful attempts to build
a series parallel controller. Success finally
followed the realization that a series motor
would demagnetize its own field when short
circuited on itself. The "J" controller was
the first in which this electrical connection
was used and was the first series parallel
controller to be used in regular service. This
particular controller was designed for instal-
lation beneath the car body and was driven
from a handle on the platform by means of
Fig. 18. 30,000-kw. Turbogenerator, New York Edison Company — 1915
trolley. This led one superintendent to
protest against the use of the double switch,
for as he reasoned, if in the reverse position
it would stop the car without current from
the trolley, if thrown to the forward direction,
it must certainly drive the car, and he
considered it unsafe to operate an equipment
that, despite the brakes, would run by itself
with no connection to the power house. Upon
investigation the cause of his apprehension
in this particular case proved to be the
existence of an air gap between the wheels
and brake shoes due to defective brake
mechanism.
The advantages of series parallel control
of the motors, as saving 20 to 30 per cent in
energy and permitting efficient running at
half speed were realized, but because of the
shafting, bevel gears and gimble joints.
This method of drive was a study in "lost
motion" as those who had experience with
it will remember.
It was soon obvious that the operating
handle should be directly attached to the
controller shaft and preferable that the
controller should be on the platform as had
been the practice with a number of rheostatic
controllers.
Following the "J" controllers were first
the "E" and then the "K" controllers. The
latter, designed in 1S93, has with little change
since that date been the almost universal
series parallel controller as used on the
platform.
There is probably no feature of an electric
railway equipment on which so many
450
GENERAL ELECTRIC REVIEW
improvements have been suggested as the
device for collecting current, nor any feature
on which so many of the suggestions have
proven unsuccessful. The simple trolley pole
and wheel, both because of its simplicity
and its capacity for collecting current far
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Years
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Fig. 19. Growth of Steam Railroads in United States.
Total operated mileage single-track basis —
1870 to 1912
seem today an absurd device. Such a collector
was not without its unexpected danger, as an
instance of which, at the top of a long grade,
one of these collectors breaking away from
the car ran to the foot of the hill on the wires,
and jumping off at a curve, landed on a
passing team. On this same railway these
collectors were afterwards replaced with
trolley poles of oak, 4 in. by 4 in. at the butt.
Needless to add, these trolley poles stayed
with the car and incidentally collected at
times a considerable proportion of the
overhead construction.
1890
IB94
1698 002
yeans
1906
1914
Fig. 20. Growth of Electric Railways in United States.
Total single-track mileage and total motor
cars— 1890 to 1912
beyond what was originally anticipated, bids
fair to remain the standard device.
Collecting current by means of a 50-lb.
four-wheel carriage running on top of a
double trolley wire and towed by the car
through a flexible conducting cable, would
For collecting current exceeding the
capacity of the trolley wheel the third rail
was a natural recourse, although in the
Baltimore and Ohio tunnel installation the
original conductor was a catenary construc-
tion carrying two "Z" bars, within which
A REVIEW OF ELECTRIC RAILWAYS
451
the collecting shoe slid, being driven by a
tongue projecting through a slot between
the bars. It was a sort of suspended third
rail, but in service, owing to the drip in the
tunnel the inner contact surface became
covered with a semi-insulating deposit. The
result was an arcing at the contact surface
which proved extraordinarily destructive to
the collecting shoe. During early trials of the
locomotives, before means were provided
for keeping the surface reasonably clean, it
was not unusual for 10 to 15 pounds of metal
to be melted off the shoe during a single trip
through the tunnel.
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with overhead construction rather than third
rail.
One of the early railway generators, which
was very generally used, was known as the
D-62, the frame resembling the letter D in
outline, 62 being the kw. rating. Until within
recent years a large number of these machines
have remained in regular service in an annex
to what was the Central Power Station,
West End Railwav, Boston.
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Fig. 21. Growth of Steam Railroad Electrification. Total
route miles and total electrified mileage single-
track basis— 1900 to 1915
Yeor-
Fig. 22. Growth of High-voltage Direct-current and
Single-phase Railways. Total mileage single-
track basis — 1906 to 1915
Within possible requirements there is
practically no limit to the current that can
be collected from a third rail, 5000 to 6000
amperes not being unusual in service like the
New York Central. With higher d-c. voltages
requiring less current there is less necessity
for use of a third rail, as with a pantograph
collector from 2000 to 3000 amperes can be
collected without difficulty from an overhead
catenary, and it seems probable that much
of the heavy railway development will be
A very different machine, though honors
are even, is the modern rotary converter of
4000 kw. which is typical of the substation
apparatus through which so many of the
present railways obtain their power.
The earlier generators were belt-driven
and at the time of proposing generators direct
connected to the engine, which was about
1892, there was considerable discussion as to
whether this combination would prove reliable
under short circuits and the varying require-
452
GENERAL ELECTRIC REVIEW
ments of railway service. In view of the earlier
experience of flying belts and the later
experience with direct connection, it seems
strange there should ever have been any
question. The modern steam turbine of many
thousand kilowatts is an advance hardly
dreamed of in the earlier days of small
reciprocating engines, small turbines and
abortive attempts to build rotary engines.
1895
1993 1900 OZ 04 06 08 10
Years
12 14
Fig. 23. Growth of G-E Railway Motor Sales. Total
orders averaged for five-year periods. Total motors,
total horse power and average horse power —
1893 to 1915
In some of the early work on switchboards,
for what were then large power stations, plans
were made to use compressed air to extinguish
the arc in the automatic circuit breaker, as
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Fig. 24.
Growth of G-E Electric Locomotive Sales.
tons on driving axles and total h.p. hourly
rating — 1900 to 1915
Total
The earlier station switchboards were built
up on a wooden framework, not unlike a high
board fence, to which the instruments were
fastened, the main circuit connections being
usually a No. 0 bare copper wire.
Panel switchboards of slate or marble were
first used in 1892 and resulted in established
standards which have changed but little
except in the instrument and detail of
connections.
there was some doubt whether the magnetic
blowout would prove effective in handling
several thousand kilowatts. A few tests soon
demonstrated that the magnetic blowout
was all sufficient.
The steam locomotives as a motive power
for railway purposes consist essentially of a
boiler and engine; and, while this combination
permits many variations in arrangement, a
general design was early established from
A REVIEW OF ELECTRIC RAILWAYS
453
which there has been little departure in the
essential features of the mechanical design.
The general arrangement of the motor car
equipment naturally served as a model for
the earlier electric locomotives, and with
some modifications in design of the cab, the
mounting of the motor directly on the driving
axle and the use of swivel trucks, bids fair
to continue as the preferred design of electric
locomotives where conditions are favorable.
Many methods of drive with side rods and
combinations of gearing and side rods have
been tried, and while some of them have the
merit of allowing greater latitude in design of
the electrical equipment, it seems probable
that but few of these methods will survive.
For very high speed service in which the
armature speed would be same as the driving
wheel, the gearless motor is well adapted,
and as arranged on the New York Central
locomotives offers the further advantage of
a very simple mechanical design. Multiple
unit operation, of which the Interboro in
New York is the most prominent example,
has extended the use of motor cars into a
field that could otherwise be handled only
by very large electric locomotives.
Whatever the earlier development of elec-
tric railways may have lacked in magnitude
they more than made up for in the experience
gained.
It is impossible to cover a review of electric
railways in so short a space as is available,
so the writers have touched on some few of
the interesting features as met with in their
own experience, and for much of our modern
development work would refer the reader
to the November, 1913, and November 1914,
issues of the Review.
A very considerable part of the real
development of electric railways is told in
the curves which accompany this article.
The growth of both steam and electric rail-
ways will astonish many as it is hard to
believe that such a constant progress is
possible in so vast an industry. That these
curves should resolve themselves into straight
lines is no less gratifying than it is surprising.
The growth of steam railroad electrification
is no less satisfactory and emphasizes the
fact that this most important part of the
industry is showing more vitality than is
generally supposed. The curves depicting
the relative growth of high tension direct
current and single-phase railways speak a
whole chapter of the history of electric
railroad development more eloquently than
could be done in many pages of text.
454
GENERAL ELECTRIC REVIEW
ELECTRIC TRANSMISSION OF POWER
By R. E. Argersinger
Power and Mixing Engineering Department, General Electric Company
The author traces the early history of the electric transmission of power by citing some of the most notable
early installations and mentioning their most interesting features. Many of the early troubles that had to be
overcome are recorded; and the reader will be able to trace the development of much of our modern apparatus
and appliances to the work done in overcoming these difficulties and in meeting the constantly increasing
voltage of transmission. — Editor.
The development of electric power trans-
mission, as distinguished from power distri-
bution, has occurred chiefly within the last
25 years. There were, previous to 1890, a
number of direct-current systems, used largely
for railway or lighting service within the
limits of the municipalities which they served
and in many cases these systems carried power
for some considerable distance. Direct cur-
rent, however, has only been considered seri-
ously as a means of power transmission in con-
nection with the so-called "Thury" or series
system, which has reached its highest develop-
ment in Europe, and which was used for the
oldest commercial electric transmission scheme .
The first installation of this character was that
at Genoa, installed in 1889, transmitting
approximately 1300 h.p. for a total distance
of about 75 miles at 14,000 volts. This type
of system has never been used in this country,
and even in Europe has not attained very
great popularity as something less than 20
installations have been put in since the
original one in 1889, although it has been
considered many times in competition with
alternating-current systems. This is due
principally to the complications introduced
by the necessity of running a number of
direct-current machines in series to obtain
the required line voltage and the difficulty
and expense of designing high-voltage direct-
current apparatus. Further, the system does
not afford a convenient means for tapping off
small amounts of power at different points.
The highest voltage so far used with the
Thury system is 57,600, with a total trans-
mission distance of 224 miles. It has been
given considerable stud}- from time to time
by American engineers, since the absence of
inductive effects in the line proper, when using
direct current, make it peculiarly attractive
for high-voltage, long-distance work. Com-
parisons, however, have usually failed to
show sufficient advantage to warrant the com-
plications in station apparatus necessary for
its use.
The real development, therefore, of electric
power transmission has been made with the
alternating-current system. It is interesting
to note that the first dynamo machine built
was an a-c. machine, but due to the diffi-
culties experienced with regulation of the
lamps using a-c. solenoids, direct-current
apparatus was more generally used, and it
was not until the late eighties that single-
phase alternating-current machines began to
be produced for commercial service. The
advantages of this type of apparatus were
quickly realized, especially the ease with
which high voltages could be obtained for
transmission purposes, thus making possible
the development of water powers remote
from markets for driving alternating-current
generators.
In 1S90 the Willamette Falls Electric Com-
pany installed two 300-h.p. Victor wheels
belted to 4000-volt, single-phase generators,
and transmitted power 13 miles to Portland,
Oregon, for lighting purposes. This was the
first real power transmission in this country,
and so far as the writer knows, the first
alternating-current transmission in the world.
Its successful completion and operation was
followed quickly by the installation of a
second system by the Telluride Power Com-
pany in 1S91, transmitting at 3000 volts
about three miles and operating a 100-h.p.
synchronous motor. The importance of this
new instrument for economic progress was
called to the attention of the engineering
world by the famous transmission installed
in connection with the Frankfort Exhibition
in 1891, when power was carried a distance of
approximately 100 miles at 30,000 volts.
This was the first three-phase transmission
and its advantages were quickly realized.
In 1892, however, another single-phase trans-
mission plant was installed in California and
delivered power to Pomona, approximately
13 miles distant and about 29 miles to San
Bernardino. The voltage at the beginning of
operation was 5000, which was higher than
ELECTRIC TRANSMISSION OF POWER
4:>:)
any previously used commercially, but on
February 16, 1893, this was raised to 10,000
volts, and on May 2, 1893, by connecting
their transmission lines all in series, 120 kilo-
watts was carried 42 miles with a trans-
mission efficiency of 60 per cent, at that time
a great achievement and an indication of
the possibilities of electric transmission of
power.
These early single-phase plants had con-
siderable difficulty in starting the synchronous
motors which were used at the receiving end.
This was done in some cases by using four
transmission wires, over two of which direct
current would be passed from the exciter in
the generating station to the exciter in the
receiving station, bringing the latter up to
speed as a motor and consequently speeding
up the main synchronous motor to which it
was belted. When the latter was up to speed
it would be thrown on the main a-c. lines, its
exciter cut off from the other two lines and
connected to the synchronous motor field
while the two sets of transmission wires were
then put in parallel, carrying the alternating-
current supply.
The Willamette installation was the first
a-c. transmission supplying power for light-
ing— that at Telluride was the first supplying
the high operation costs incident to the gen-
eration of power from high priced coal.
Transformer design was still in its infancy
as shown by the fact that the Willamette
Fig. 1. Power Station at Redlands, California, put in Operation
in 1893. This was the initial three-phase transmission
system in this country
industrial power. It is worthy of note that
the Telluride installation made possible the
profitable operation of mines which otherwise
must have been shut down, as they were at
that time on the verge of bankruptcy due to
Fig. 2. Switchboard in the Redlands, California, Power Station
Company used 10 transformers in series to
step down from 4000 to 1100 volts and the
Pomona transmission at 10,000 volts was made
possible by connecting 20 units in series.
The advantages of polyphase transmission
were so apparent that a three-phase plant
was put into operation in 1S93 at Redlands,
California, carrying 250 kw. 1]4. miles at
2500 volts, and this was quickly followed by
three other plants, one at Taftsville, Conn.,
one at Hartford, Conn, and one at Concord,
N. H., built for three-phase operation, and an
additional plant at Pittsfield, Mass., designed
for two-phase operation. All five of these
polyphase plants were in operation in Jan-
uary, 1894. The Taftsville plant, although
used partially for industrial power, also
delivered power to a street railway system
from an a-c. transmission, for the first
time.
Even at the low voltages used with these
transmissions, much trouble was experienced
in connection with the insulation of the line,
due to the fact that insulator design had been
given no study and sufficient experience had
not been accumulated to show the character-
istics of a suitable insulator for transmission
purposes. An occurrence on the transmission
line from the Taftsville plant illustrates some
of the operating difficulties at that time.
Due to a combination of circumstances,
trouble occurred at one particular point in
456
GENERAL ELECTRIC REVIEW
the line where ares continually broke over the
supporting insulators. This line supplied
power to the street railway and to a cotton
mill containing 1700 looms. As the service
was very important a man was stationed on a
pile of earth close to the arcing insulators and
by throwing lumps of dirt at the insulator
when it flashed over and thus destroying the
arc, the service was maintained on the line
for an entire afternoon. This might be cited
as the first use of an arc extinguisher.
Troubles due to weather conditions, light-
ning discharges, etc., made it evident that
some protective features were desirable in
however, considerable discussion in regard
to the relative advantages of synchronous
and induction motors, but the latter finally
established its position. In this connection
it is interesting to note that Dr. Duncan in
1896 pointed out the great advantage of the
synchronous motor in correcting power-
factor, and also called attention to the
possibilities of its use purely as a synchro-
nous condenser — a feature which has since
made possible the voltage regulation of long
lines.
The rapid growth of transmission systems
after 1894 showed the need of an experimental
Fig. 3. 9000 Kv-a. Generators, Mississippi River Power Company, Keokuk, Iowa
connection with the transmission lines, and
in 1893 Air. A. J. Wurts introduced the non-
arcing metal gap arrester. Mr. Wurts also
showed by previous experiments in 1892 the
protective value of the ground wire paralleling
the transmission line.
The difficulties with single-phase motors
concentrated the attention of investigators
on the development of a three-phase machine
and resulted, about this time, in the intro-
duction of the well known induction motor.
Its wide range of application, its ability to
stand hard service and its ease of handling,
were so quickly recognized that a tremendous
impetus was given to the development of
power for industrial purposes. There was,
determination of many questions of insula-
tion and operation, and in 1895-6 the Tellu-
ride Power Company conducted a long series
of investigations, using transmission voltages
up to 50,000, which resulted in a considerable
addition to the accumulated data regarding
alternating-current transmission. It is inter-
esting to note that in the comparative tests
made at that time with glass and porcelain
insulators, the results showed glass to be
preferable, although slightly more expensive.
In commercial use, however, the glass
insulators of that period gave a great deal of
trouble owing to unequal expansion when
exposed to the sun's rays. It is possible that
these difficulties mav have been due to
ELECTRIC TRANSMISSION OF POWER
457
improper annealing, or to improper com-
position in material used.
Since the first three-phase transmission
in 1893, it has been recognized that this
system is most suitable for the purpose and
the development since that time has been
along the line of constantly increasing volt-
age. The table given herewith shows from
the best data in the writer's possession the
steps of the increase of transmission voltages
as they have occurred. As far as the writer
has been able to find, no previous attempt has
been made to tabulate these voltages in this
form and criticism of any possible inaccuracies
would be gladly welcomed.
The rise in voltage was rapid and the
increased spacing necessary to obtain suffi-
cient clearances made the construction of
wooden pole lines more and more difficult.
The Guanajuato Power Company in 1903
put into service the first transmission line
carried on steel towers and their success in
using such supporting structures led other
companies to quickly follow their example.
Incidentally, it might be noted that this
Guanajuato line was at first built without a
ground wire, but after carefully observing
the results of operation under this condition
a ground wire was added and it was found
that the number of disturbances was very
materially decreased. The protective value
of a ground wire has always been the subject
of discussion. Opinion today seems to favor
the use of at least one such wire and some
companies use two or even three grounded
wires strung at the top of the towers and
grounded to each. In some cases inter-
ruptions have been caused by mechanical
interference between ground and power wires
owing to improper spacing or relative sags,
but careful line construction should, in gen-
eral, prevent such difficulties.
As transmission voltages became greater
the difficulties with protective equipment
also became more and more complicated.
The multigap arresters, in common use, gave
a great deal of trouble and although expensive
were easily destroyed. This condition caused
the development of the aluminum cell
arrester, which was brought out in 1906 and
has since practically superseded for general
purposes all other types. Some criticism of
this arrester was made to the effect that
dangerous surges were caused by the charg-
ing arcs. The introduction of charging resist-
ances and short circuiting strips for horn gaps
has eliminated any such dangers as may have
been incident to its use. Practically no
multigap arresters have been used above
60,000 volts, and in fact, 60,000 volts has
come to be recognized as a sort of turning
point in line construction. This line voltage
represents about the limit of use of pin
insulators and a study of the possibilities
brought out the suspension insulator in
1906-7. The use of an insulator of this type
removed many of the mechanical limitations
of construction of transmission lines and its
influence was quickly seen in the upward
swing of transmission voltage. In 190S the
AuSable Electric Company operated one of
their transmission lines at 110,000 volts and
In Oper-
No.
Line
Line
Length
Company
ation
Phases
Voltage
Miles
13
1890
1
4,000
Willamette Falls Elec. Co., Portland, Ore.
1891
1
3,000
3
Telluride Pwr. Co., Ames, Colo.
1891
3
30,000
100
Lauffen to Frankfort, Germany (Experimental)
1892
1
5,000
28
San Antonio Lt. & Pwr. Co., Pomona, Cal.
1893
1
10,000
28
San Antonio Lt. & Pwr. Co., Pomona, Cal.
1893
3
2,500
-!Vi
Redlands Elec. Lt. & Pwr. Co., Redlands, Cal.
1894
3
11,500
22
Sacramento Elec., Gas & Rwy. Co., Sacramento,
Cal.
1895
3
19,000
35
San Joaquin Elec. Lt. & Pwr. Co., Cal.
1896
3
25,000
40
Pioneer Elec. Pwr. Co., Utah
1897
3
40,000
55
Telluride Pwr. Co., Provo, Utah
1901
3
57,000
65
Missouri River Pwr. Co., Butte, Mont.
1903
3
60,000
104
Guanajuato Pwr. & Elec. Co., Mexico
1906
3
72,000
66
AuSable Elec. Co., Grand Rapids, Mich.
1907
3
75,000
117
So. Calif. Edison Co., Los Angeles, Cal.
* 1908
3
110,000
35
AuSable Elec. Co., Grand Rapids, Mich.
1909
3
100,000
152
Colorado Pwr. Co., Denver, Colo.
1910
3
110,000
135
Hydro-Elec. Pwr. Commission of Ontario
* 1912
3
140,000
240
AuSable Elec. Co., Cooke, Mich.
1913
3
150,000
240
Pacific Lt. & Pwr. Co., Los Angeles, Cal.
* Voltage after some time reduced.
45S
GENERAL ELECTRIC REVIEW
in 1909-10 a number of systems were put into
operation at voltages from 100,000 to 110,000.
The difficulties in mechanical construction
of lines with the flexible support given by the
suspension insulator resulted in a great deal
Fig. 4. Control Board and Switchboards of the Keokuk Hydro-Electric Power Station
of line trouble from the crossing of wires, and
made necessary7 increased spacings with a
considerable increase in the size of supporting
structures. This increase in line troubles
was reflected in a great increase in troubles
with transformers to which the lines were
connected. It called attention to the in-
fluence of the inductance and capacity of
long lines in setting up dangerous surges in
the system, and resulted in a thorough study
of the effect of high frequency and transient
phenomena on apparatus design and con-
struction. The result of all of this experience
has been felt in the greatly improved trans-
formers which are now available, designed
with a thorough appreciation of the tremen-
dous stress from both high voltage and high
current to which they may be subjected in
long distance transmission work. It is quite
probable also that some of the recent failures
of line insulators have been due to this in-
crease of - insulation strength of apparatus
connected to the circuits. The surges
appearing on transmission systems must be
dissipated or discharged in some way. In the
early days the weak point was the line and the
insulator breakdowns acted as relief valves,
but with the improvement of line insulation
the station apparatus became relatively
weaker as shown by the increase in reported
failures. As apparatus has improved the trouble
has been thrown back on the
line with a consequent in-
crease in insulator damage
so that the study of the in-
sulation problem has been
transferred to the line insu-
lator and investigators are
now considering the vari-
ous factors of operation and
manufacture which affect
its characteristics. There
seems to be a growing feel-
ing that the line insulation
must be increased and that
it must be designed with
reference to the over-volt-
ages to which it may be
subjected. If such a pro-
gram were carried out it
would necessitate insula-
tion with respect to local
conditions of altitude, cli-
mate, frequency of light-
ning and sleet storms,
length of line, etc., and of
course to some extent the
character of, and methods
of operating the apparatus connected to the
circuits rather than with respect to normal line
voltage. It would mean also an increase in
strength of apparatus insulation to prevent its
acting as a relatively weak discharge path.
Such insulation would mean a material increase
in development costs and undoubtedly would
prevent the construction of many trans-
mission enterprises, particularly those of
comparatively small size and low voltage.
It is necessary, however, to improve such
details of insulator design and manufacture
as experience has shown to be faulty, and
assuming that this will be accomplished,
another increase in apparatus troubles must
be prevented by the further development of
protective devices. The aluminum cell arres-
ter, while it marked a great step in advance,
will not protect against high frequency
low-voltage disturbances and the develop-
ment of apparatus to supplement the action
of the aluminum cell presents probably the
most important problem connected with
electrical transmission today. It is known
that certain combinations of resistance,
reactance and capacity will absorb high-
ELECTRIC TRANSMISSION OF POWER
459
voltage and high-frequency surges, but a
successful combination of these elements
has not as yet been practically worked out.
One of the spectacular developments in
connection with high-voltage work was
brought out in 1909 in the introduction of the
outdoor substation. The use of high-voltage
equipment in buildings with the difficulties of
insulation encountered in carrying high-
voltage conductors through walls and in
obtaining the necessary space for their
installation emphasized the advantage of
placing such equipment out-of-doors where
space is not restricted and where walls need
not be pierced. The operation of high-voltage
equipment exposed to the weather is being
watched with great interest, and apparently
offers no insurmountable difficulties.
The improvement in the art of transformer
manufacture has so much increased the feel-
ing of security in connection with their opera-
tion that the operator now sees nothing alarm-
ing in units of much greater size than would
have been considered good practice some
years ago. This together with the high cost
of high-voltage switching equipment and its
installation, has led to a marked change in
the arrangement of stations. Where it was
formerly widely the practice to install trans-
formers as part of the generator circuit,
paralleling all circuits in a high-tension bus,
it now seems preferable to arrange trans-
former banks as part of the transmission line,
thus cutting down the number of high-tension
circuits and, consequently, the number of
high-tension switches and insulators, decreas-
ing the cost of transformers per kilowatt and
decreasing considerably the amount of auto-
matic high-tension switching that is neces-
sary. Investigations on many lines have
shown the dangerous rises in voltage set up
by the operation of automatic high-tension
switches and their elimination is very desir-
able. Further, the reduction in high-voltage
apparatus reduces the amount of exposed
material in case it is desirable to put the high-
voltage apparatus out-of-doors.
In general, high-voltage transmission has
been used in connection with water power
developments, and consequently the develop-
ment of the art of waterwheel construction
has had a very marked influence on the
development of electric transmission of power.
Many of the early transmissions were installed
at water power sites where high heads were
available and the impulse type of wheel was
used. The tendency has been to develop the
highest heads first, assuming, of course, that
they were equally near suitable power mar-
kets. The marked improvement in water-
wheel design in the last few years has been
reflected in the development of some of our
largest hydro-electric plants, such as those
at Keokuk and Cedars Rapids. Without the
introduction of the single runner turbine unit
of high specific speed, such developments
would have had prohibitive cost due to the
great number of units required to develop the
equivalent amount of power. The difference
in construction can be readily seen by com-
paring some of the older plants using two
or even three runners on the same water-
wheel shaft, as opposed to the single-runner
wheels in the Keokuk and in the Cedars
Rapids installations.
The standards of service required from
transmission systems are constantly becom-
ing higher and the voltage regulation is a
problem of continually increasing importance.
In the system having long lines at high volt-
age, apparently the only solution is the use
of synchronous condensers for regulation at
the substation in the manner which has been
so carefully worked by the Pacific Light &
Power Company in Los Angeles, and the
Utah Power and Light Company in Salt Lake
City. It appears at first thought a very ex-
pensive proposition to install machines of
7500 or 10,000 kv-a. to run without actual
energy output, but the influence of machines
of this character in reducing troubles on the
system from sudden rises in voltage, is
undoubtedly sufficient to more than pay for
their cost, to say nothing of the very greatly
improved service which can be given by sys-
tems so regulated.
The tendency in operating modern systems
is to interconnect various water power sta-
tions, thereby increasing reliability and per-
mitting more economical use of water. In
the South, for instance, the lines of the
Southern Power Co., Yadkin River Power
Co., Carolina Power & Light Co., Georgia
Power Co., Columbus Power Co., Central
Georgia Power Co., Tennessee Power Co., and
Chattanooga and Tennessee Power Co. are
all connected and tie together some 34 gen-
erating stations aggregating approximately
450,000 horse power and this has been done
about 20 years after the Redlands TJ^-mile.
250-kw. plant was, after careful consideration,
attempted.
460
GENERAL ELECTRIC REVIEW
SOME INDUSTRIAL APPLICATIONS OF ELECTRICITY
By A. R. Bush
Manager, Power and Mining Department, General Electric Company
It would be impossible to write a complete article on this inexhaustible subject, but the author shows in
a most interesting manner the application of electricity to some two dozen industries, pointing out the
particular conditions in each which make the electric motor an economic factor. A large part of the story is
told in pictures, and our limits as to their number have been governed only by the space available. — Editor.
The three principal creative divisions of
industrial enterprise have been given as
"industries producing from the earth,"
"manufacturing," and "public service." The
first two divisions are the ones which we
wish to discuss briefly as being greatly influ-
enced by the use of the electric motor. The
production from the earth — which includes
agriculture and mining as being the most
important — is becoming year by year more
dependent upon the application of electricity.
Arid lands of the west have been made
productive, as now the electric motor con-
trols the flow of water over vast territories
and proper irrigation has made possible larger
crops and reduced failures. In mining,
whether metal, or coal, one big problem is the
safe and rapid handling of materials. The
electric locomotive, the electric hoist, the
motor-driven pump and fan are essential for
the safety of mine operators, and for keeping
down the cost of production.
Manufacturing is the barometer which
indicates the improvement or decline in the
condition of commercial aflairs. The ease
with which a manufacturing concern can
adjust itself to varying conditionsof production
may be the one factor which brings about
success.
The operation of a machine, whether it is
a drill in a machine shop, a turret lathe in an
automobile factory, a loom in a textile mill
or a beater in a pulp mill, costs money. This
cost of operation depends on the first cost of
the machine or interest on the investment, the
cost of power to run it, the cost of repairs, the
value of the floor space which it occupies —
which may be considered as rent. AH of
these factors may be summed up in a word,
and expressed as wages paid a machine.
This wage is entirely independent of the
wage paid the operator and in many cases may
exceed many times that of the workman.
This is mentioned to emphasize the fact that
the question of choosing a proper machine
and arranging to supply it economically with
power is often of more importance than the
selection of its operator.
It can be safely stated that not an industry
exists in the country which has not been
influenced by the introduction of the electric
motor.
The number of employees of the electric
central station companies which are classified
among public utilities, show an increase of
about 165 per cent for the 10 years previous to
1912 while the average output per employee
in kilowatt-hours increased about 50 per cent.
This means an increase in the size of the
stations and in the efficiency of operation.
Automobile Factories
The phenomenal growth of the automobile
industry has been dependent to a large degree
on the use and dependability of the electric
motor. Manufacturing plants were built with
a certain capacity but in many cases the
demand for the machines has gone far beyond
the expectation of the promoters. This
demand made additional factories and equip-
ment necessary. In some cases assembling
plants were required which were entirely
separate from the main factory. These
changes and additions without the electric
motor would have been very expensive if not
prohibitive, but with it they were not only
possible but the silent workman came to the
rescue and helped put into place the brick,
steel and concrete necessary for the building
itself. A separate article is published in this
issue dealing with electricity in the automobile
industry.
Bakeries
Present day conditions make it necessary
for every baker to maintain a high standard
of cleanliness. It is difficult to obtain this
condition where overhead belting and shafting
are depended upon to transmit energy. The
amount of power required in many instances
is not sufficient to allow an economical power
plant so here again the electric motor has
come to the rescue.
Human hands need not touch the products
necessary to make a loaf of bread. The
flour is sifted, blended and measured auto-
SOME INDUSTRIAL APPLICATIONS OF ELECTRICITY
401
1
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Fig. 1. Block Test, Dynamometer Room. Automobile Factory
Fig. 2. Chassis Test Room. Automobile Factory
matically and dropped into motor-driven
dough mixers from which the dough may be
dumped into rising troughs. Then the dough
divider cuts it into loaves and a motor-driven
belt conveyor takes it to the loaf rounder.
After a short stay in the proving box it goes
through the motor-driven molding machine
and after the time required to "rise" in the
pan the bread is ready for baking.
The electric motor has done the work, and
a better and more uniform product is the
result.
Breweries
In a brewery you have a condition where
many widely scattered small motors are
necessary. For mechanical transmission long
lines of shafting, innumerable belts of all
sizes and other mechanical appliances are used,
and the application of power may be required
in a building adjoining the power house
making a long steam pipe necessary, all of
these are sources of constant loss.
By using an electric motor the proper
power may be applied at the bucket conveyor
Fig. 3. Motor-driven Bakery
Fig. 4. 5-h.p., 60-cycle, 220-volt, Three
phase, 1200-r.p.m. Motor Driving
Flour Sifter
462
GENERAL ELECTRIC REVIEW
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SOME INDUSTRIAL APPLICATIONS OF ELECTRICITY
463
for handling the malt and at the worm con-
veyor for taking the malt to the brew house or
mill. The mash tub, which is often located on
the second or third story of the building, is
brought under perfect control and it is here
that the quality of beer may be greatly
varied.
The pumps for wort and water can be
started at the moment of demand. All of
these applications have a profitable influence
with the brewer. Comparatively large motors
are necessary for operating the ammonia
the heavy motor-driven rolls of the dry-pans,
mixed at the pug mill, cut into proper shapes,
and then conveyed by belt to the represser
where the green bricks are subjected to heavy
pressure, and prepared for drying.
On account of the nature of the material
and the machinery necessary it is usually
desirable to have all these operations per-
formed on the ground floor, therefore con-
siderable space is required. The eliminating
of long heavy shafting, bearings, and belts,
usually unprotected from the flying dirt, and
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Fig. 9. Dried Beef Slicing Machine Driven by
Induction Motor in a Cannery
compressor for refrigeration, and even here
the demand for power varies with the season,
making the motor-driven compressor a desir-
able feature of a modern brewery.
Brick and Clay
The manufacture of brick and tile is prob-
ably the oldest of all industries. Many plants
have been in successful operation long before
the possibilities of the electric motor were
known.
The territory served by the central power
stations has, however, increased to such an
extent that the clay worker has found at his
door a source of power which cheapens the
manufacture of his product.
The up-to-date brick plant finds use for
a variety of motor applications. The clay and
shale is excavated by an electrically operated
shovel, hauled to the stock piles by an indus-
trial type of electric locomotive, crushed by
Fig. 10. Peanut Butter Machines Driven by Induction Motors
in a Cannery
the use of a motor close to its work can only
result in a greater production and a more
uniform product.
Canneries
The secret of preserving food in its natural
state was discovered, rather than invented,
about 120 years ago, and now we have reached
the point where the world could not dispense
with canned food.
The industry has developed to such an
extent that over $200,000,000 is represented
in its annual output, and the past ten years
has shown an increase of approximately 60
per cent. The number of canneries necessary
to take care of the various food products at
the proper time has made the element of
time of great importance. The electric motor
is now recognized as a time saver. Many
classes of machines are used for handling
different products and a change of use depend-
464
GENERAL ELECTRIC REVIEW
ent upon the season, becomes an easy matter
with the motor-operated machines.
Sanitation is the most important factor
and the elimination of shafting, belts or any
moving element which can catch and dis-
tribute dust is of great importance to the
canner of high class goods.
In the early history of the industry the
public was carefully excluded from the plant
for fear that trade secrets would be obtained.
The public sentiment of today has changed all
this so that the canner now realizes the
advertising value of a clean, airy, well lighted
motor-operated plant and invites the con-
sumer of his wares to inspect the place where
the food products are preserved and made
readv for distribution.
where trouble might develop, and take all the
necessary precautions to avoid delays is of
the utmost importance. All of this can be
accomplished with the electric motor.
Cotton Gins and Cotton Seed Oil
The value of the cotton seed products
is now second in importance in the cotton
growing states, being exceeded only by the
cotton mill itself. For every pound of cotton
produced there is an average of two pounds of
seed. Not many years ago the seed was con-
sidered worthless and burned. It is physically
composed of lint, hull, oil and meal, all of
which products find a ready market.
The average sized gin is one having six
70-saw gins, and with the baling press and the
Fig. 11.
50-h.p., 500-r.p.m., Form K, 25-cycle. 550-volt
Motor Driving Ball Mills in Plant
Fig. 12. 75-h.p., 500-r.p.m., Form K, 25-cycle, 550-volt Induc-
tion Motor Belted to Fuller Mills in Crusher
House for Cement
Cement Plants
It is interesting to note that the rapid
development of the cement industry from less
than a million barrels to over 90,000,000
barrels annually began with the development
of the electric motor. The advantages of
electric drive were so apparent that soon the
building of a mechanically operated mill was
not seriously considered, but on the contrary
the old plants were changed over and during
the past two years no less than five mechan-
ically driven mills have changed to electric
drive, and an equal number of new plants
which have been established have all adopted
electric drive. The price of Portland cement,
notwithstanding its enormous use, has made
economics in production necessary.
To keep the machinery operating at a
predetermined and economical speed is a
great factor. Then again to be able to
definitely locate the point of maximum load
necessary suction apparatus requires about
SO horse power and will bale 60 to 70 bales
of 500 pounds each per day. In the oil mill
steam is required for cooking, but since the
hulls can be sold for feed and central station
power is available for operating the motors, it
is found economical to use coal as fuel for
cooking. The operations, as in the gins, are
conducted in unison, no storage facilities
being provided between the various stages
makes reliable power essential. The elimina-
tion of shafting, belts, etc., avoid interrup-
tions in service.
Another advantage of motor drive which is
of great importance is the reduction of fire
risk.
The presence of excessive amounts of
inflammable lint and dust connected with the
various linting and cleaning operations makes
the use of the induction motor one of the
best forms of insurance.
SOME INDUSTRIAL APPLICATIONS OF ELECTRICITY
465
The power requirements for the oil mill
can be taken for various sized mills as about
2J^ h.p. per ton of seed per 24 hours.
Farming
To the ordinary farmer the use of elec-
tricity is gradually working from what he
considered an expensive luxury to a necessity.
The telephone was probably the entering
wedge and its use has emphasized to him
more than any other electrical device the
value of time. The desire for better light was
the next step and it is no uncommon sight to
find the small fanner of New England, as well
as the ranch owner of the West, reading his
newspaper with the aid of the electric light.
life which grows in the soil, the three principal
elements in commercial fertilizers being
nitrogen, phosphoric acid and potash. These
elements are best handled by being combined
with other elements known as "fillers" such
as water, fat, lime, soda, magnesium, sand.
etc.
To combine these elements the problems
of mining, conveying, grinding, mixing, bag-
ging, weighing, etc., are involved, all of which
require power. The fertilizer manufacturers
realize that it is to their advantage to put
their products into the hands of the farmer
at as reasonable a price as possible, so that the
latter may show a good margin of profit
between his increased crop and the amount of
Fig. 13. 100- h.p., 720-r.p.m., 2200-volt Motor Driving
Linters, Rolls and Presses in Cotton Seed Oil Mills
(Note Motor has replaced Steam Engine)
Then came the power problems such as
operating the cream separator, sawing the
winter's supply of wood, grinding feed for the
stock, cutting corn for the silo, and threshing
the grain, and to the housewife the turning
of the washing machines and wringer. The
development of water power and the extension
of lines from the central station has brought
the power to the farm so that with the aid
of the electric motor, sometimes called the
"electric hired man," work which at one
time was considered drudgery can now be
performed efficiently and quickly.
Fertilizer Factory and Phosphate Mine
The function of the fertilizer factory is to
furnish food for the soil or rather for the plant
Fig. 14.
35-h.p., 1800-r.p.m. Motor Driving Cake Mills in
Cotton Seed Oil Plant
his fertilizer bill. The greater this difference,
the more fertilizer will be bought. One
important economical factor in fertilizer
manufacturing is the electric motor.
In the mining of phosphate rock, the mineral
source for phosphoric acid, which is so exten-
sively carried on in Florida, large motor-
driven hydraulic pumps are used- for washing
out the pebbles. Electric locomotives and
motor-driven conveyors are employed for
handling the material to the drying bins.
The phosphate rock must be distributed to
the various fertilizer plants, the same as coal
from the mines must be distributed to the
central station, and here again the electric-
driven hoisting and conveying machinery
plays its part.
466
GENERAL ELECTRIC REVIEW
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SOME INDUSTRIAL APPLICATIONS OF ELECTRICITY
467
The grinding mills are similar to those used
in the cement industry where the induction
motor has shown its worth. So on through
the mixing and bagging operations where tons
of materials are handled daily by the ever
willing and untiring electric motor.
The best testimony as to the influence of
electricity in this industry is given by the
city of Baltimore, where without exception
all new fertilizer factories erected within the
last five years have chosen electric drive and
central-station service. The horse power in
question of fire hazard must be considered.
The accumulation of fine dust which is easily
ignited cannot be obviated. The mill which
requires shafting with long belts extending
from floor to floor affords many means for the
ignition of this dust either by hot bearings or
the friction of the belts due to the lapping
at the sides of the openings through the floor.
Instances may be cited where steam mills in
our large cities have been burned, to be
rebuilt and equipped entirely with electric
motors. The squirrel cage induction motor
Fig. 19. 200-h.p., Three-phase, 60-cycle, 440-volt, 360-r.p.m.,
Form P, Three-bearing Motor Driving Bolters and
Purifiers in Flour Mill
Fig. 20. Two 20-h.p . 1800-r.p.m.. 440-volt, Form K Motors
Driving 24-in. Double End Attrition Mill
motors has increased here during this period
over 450 per cent.
Flour and Feed Mills and Grain Elevators
The first flour mill built in New England
was naturally waterwheel-driven. For a
long time this form of power dominated,
then came the steam-driven mill or possibly
the combined water and steam plant, the
latter form of power being used in the summer
during low-water period. Now we find the
electrically operated grain elevator and flour
mill, a simple, natural evolution in power
application. The strictly water operated mills
at the present time probably do not exceed
25 per cent of the total in number, while the
percentage in total flour and feed output is far
below this rate. The handling of grain at the
elevator is naturally intermittent but the
power must be available at any time and must
be reliable. The electric motor meets the
requirements especially where central station
power is available, and statistics show that
electrically operated elevators are rapidly
increasing. In the flour or feed mill the
cannot spark and the controlling devices are
installed in enclosed cases with all wiring in
conduits, this obviating the chances of fire
and greatly reducing the fire hazard.
Garment Manufacturers
Clothing manufacturers are beginning to
appreciate that every dollar spent for electric
current is the best investment for power.
Clean aisles in the garment factories in New
York are required by law; this means the
elimination of all floor belt boxes. More
machines can be operated with the same
expense for power by using motors,' thus
reducing the cost of production. This item
is specially important where high rents must
be paid.
The motor may be installed underneath
the table or at one end where the work table
is extended and thus save 12 to 16 square feet
of floor space for every motor used. Each
machine may be driven at its best productive
speed and this speed kept constant. Wast-
age is reduced on account of steadier operating
conditions and freedom from oil drips. The
468
GENERAL ELECTRIC REVIEW
reduction of fire risk is also an important
consideration as well as improved ventilation
and better distribution of light. The demand
for output has high peaks due to rush orders
and the electric motor is best suited to meet
this demand.
Two and one-half horse power is required
to operate from 30 to 36 sewing machines.
Sponging and refinishing of the cloth is done
with motor-driven machines, and electric-
driven cloth cutters are extensively used.
Ice and Refrigeration
Although electric motors have been used
quite extensively in handling natural ice
by operating conveyors and in some instances
five times the January load. The motor-
operated ice plant can be located near the
center of distribution, thus reducing trans-
portation expense and wastage; but the most
important point from the consumer's stand-
point is the removal of the possibility of
contamination due to oil from the steam-
operated plant and obnoxious foreign matter
often found in natural ice.
Irrigation
Irrigation may be considered crop insur-
ance. The average rainfall in a certain dis-
trict ma)' be sufficient to take care of the crop,
but it is not always safe to be guided by this
figure.
Fig. 21.
3-h.p., 220-volt, 60-cycle, Three-phase Motor Driving
Sewing Machine Table
cutters, the large field is in the manufacture of
artificial ice. To within about four years the
steam-operated ice plant held a monopoly of
the field. This was due to the fact that
distilled water was used and the greater part of
this distillate was obtained from the exhaust
from the engines. With the recent use of
multiple-effect evaporators in connection with
the distilled water plants; and the introduc-
tion of the raw water system of ice making,
electricity has entered the field and become
an important factor in ice making. The
fact that this industry is virtually a summer
load, and comes at a time when the lighting
load is low, made the business attractive to
the central station manager. Instances are
known where the July load is approximately
Fig. 22. 3-h.p., 1500-r.p.m., Motors Driving
20 Heavy Woolen Garment Sewing Machines
The rain may not be properly distributed,
and may come at the time when the crop
least needs it. The problem then is to be able
to put water on your fields in exactly the
right quantity and at the right times during
the growing season. Ditch irrigation is
limited by the contour of the land, and good
land may lie idle because it cannot be reached
by ditch water. The use of electrically
operated centrifugal pumps and the extension
of electric power lines throughout the country
has enabled the farmer and ranchman to buy
this crop insurance at a very reasonable rate,
and, unlike the ordinary forms of insurance,
actual annual profits may be shown. The
little attention required, and the dependable
operation of the electric-driven pump coupled
SOME INDUSTRIAL APPLICATIONS OF ELECTRICITY
469
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with the comparatively small cost of operation
has made the working of even small tracts of
land profitable.
Here as in many otherindustrial applications
of electricity, the assured increased produc-
tion has brought about success. Poor crops
usually mean general depression in a country,
while good crops foretell prosperity.
Iron and Steel Mills
The application of electricity to the iron
and steel industry has undoubtedly been the
subject of more discussion than any other
industrial line in the country. This is not to
be wondered at when you consider that the
economical production of iron and steel, either
in the shape of ingots or manufactured prod-
ucts is a matter of national importance.
In the majority of applications the question
was readily solved on the basis of cheaper
power, but for many years the electric motor
was kept away from the main roll drive for
fear that it was not capable of doing the work.
The motor has now demonstrated its ability
to handle the main rolls so now in all power
applications of the mill it has to compete with
other forms of power primarily on the basis
of economy. On account of the large power
units required with the overloads which
must be taken care of, the question of handling
sufficient steam at anything like an economical
basis is a very serious problem. While it is
probably true that a great many improve-
ments are yet to be made in the application
of motors and control in the industry, it is
equally true that no new mill can be built
today and operated on a competitive basis
without the use of electricity.
Lumber and Wood Working
The most modern and largest lumber mills
in the country have adopted electric drive;
this fact is significant. The mills handling
cedar, hemlock and fir of the Northwest as
well as the yellow pine mills of the South have
demonstrated the value of the electric motor
as a money-saving factor in the industry.
One large steam-operated saw mill was
destroyed about four years ago by fire which
originated from a hot bearing. On the site
of the old mill has been built a complete
electrically operated mill and every modern
device has been installed with a view of
increasing the production and reducing the
fire hazard. Some of these mills require as
many as 300 alternating-current motors,
which gives some idea as to the extent and
completeness of the electrical equipment.
The high speed machinery in a planing
mill, such as profilers, surfacers, matchers,
moulders, rip saws, cut-off saws and band
re-saws, are well adapted for individual
motor drive, The output of these machines
is dependent to a large extent on the speed,
therefore the maintenance of the proper speed
is of importance. In practice it is found
that shaft-driven machines vary in speed
from 10 to 20 per cent from no load to full
load. This has a marked effect upon the
output, especially for power fed machines.
By the use of the individual induction motor
slippage is eliminated and production main-
tained. An official of a large lumber and
shingle mill was recently asked why he
installed electric motors; his answer is typical
and well worth considering: "First, a large
saving in the mill frame as we reduced it to
one story in height and used much lighter
construction. Second, the power plant
detached from the saw mill allowing lath
mill, picking table and hog house to be
separated from the saw mill, reducing the
fire hazard very materially. Third, a large
reduction in noise and in expense in annual
overhauling. Fourth, more continuous opera-
tion, as each individual drive has a limit of
concentrated power, which in a shaft-driven
mill is sufficient to either break up machines
or burn the belt when any machine becomes
blocked. Fifth, a very large reduction in
power required, not over one-third of what
the shaft-and-belt-driven mill would take.
This last claim may seem too large, but when
a large saw mill is all belted up there is a
multiplication of transmissions which waste
an enormous amount of power. In fact, it
is well known among millmen that very
large shaft-and-belt-driven mills are extremely
difficult to keep in running order even with a
small army of experienced millwrights, and are
subject to long shut-downs on serious breaks."
Mining
The problem to improve the conditions
under which men must labor is being studied
by every large corporation through the United
States. The man who works underground
has a hard lot, but electric lights now show
him the way without consuming his very
breath, and with the use of the electric-
driven coal cutter, locomotive, pump, fan
and hoist, the miner's work is more easily
performed with less risk to life and limb.
The ever increasing demand for electrical
equipment for mines, whether in the coal
fields or the metal mining districts, is suf-
472
GENERAL ELECTRIC REVIEW
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ficient evidence of its great influence in the
industry. To remove economically 10 tons
of water from a coal mine for every ton of
coal produced is one of the tasks set for the
motor-driven pump, and the work is being
performed on a paying basis. The emergency
demands on the operator are reduced by
electric automatic devices in the form of
signals, cutouts, etc., and in the case of hoist-
ing equipment entirely automatic operation is
made possible. The kw-hr. required per ton
of coal mined of course varies widely due
to the length of haulage, the grade, and the
amount of air necessary for the fans to deliver
to the mine, the amount of pumping neces-
sary, etc. Tests have been made in the
Pocahontas coal fields where the electric
as cheap as it could possibly be obtained, no
transportation charges being added. The
field may be considered limited as compared
with other industrial activities but a few
reasons showing the success of the motor may
not be out of place. The motor does not
necessarily work faster than the steam engine
but it eliminates delays, and in that way
increases production. Operating expenses are
decreased as no boiler feed water is required,
and the cost of oil and attendance is less.
Power bills stop when the work stops. Greater
safety of operation is obtained as the motor
cannot run away if a hoist line breaks. Fire
risks are reduced and operating conditions
can be measured by the current consumption.
It was only after exhaustive tests in the
Fig. 39. Motor-operated Wells in Kern River Oil Fields.
Bakersfield, Cal.
power per ton of coal mined shows results
varying from 1.7 to 6 kw-hr.
It is safe to say, however, that the figures
from one mine cannot safely be used for
determining the requirements of another
mine even with the same tonnage output.
But it was not until the introduction of
electricity that actual cost of power require-
ments were determined. In the mining of
metals such as gold, silver, copper, lead, tin
and zinc, stories could be written for each.
Suffice it to say that the power problems
peculiar to each kind of mining have been
solved successfully with the result of larger
productions at a less cost. A separate article
is published in this issue dealing with elec-
tricity in mining.
Oil Well Drilling and Pumping
The use of the electric motor for drilling
and pumping oil wells is of more than ordinary
interest. The steam engine was well estab-
lished in the work; the fuel was right at hand,
Fig. 40. Portable Hoist Driven by 20-h.p., 1200-r.p.m., Form
M, 440-volt Motor, Kern River Oil Fields of California,
Bakersfield, Cal.
California oil fields and after actual economies
were shown that the electric motor was
standardized for this work.
Pulp and Paper Mills
The centralization of the power generating
apparatus and the proper distribution of the
necessary power has made the adoption of
electricity desirable in pulp and paper mills.
As a matter of fact, paper mill engineers were
among the first to adopt electric drive on a
large scale and at the present time over
200,000 horse power in motors are in ser-
vice.
The motor-driven Jordan is not new but the
question of the longitudinal adjustment has
prevented some of the older installations from
being changed over. The recent introduction
of a telescoping coupling has, however, helped
to solve the problem, so that now the mechan-
ically-driven Jordan is being equipped with a
motor at a nominal cost and without sacrific-
ing the old machine.
SOME INDUSTRIAL APPLICATIONS OF ELECTRICITY
475
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Fig. 45. 30-h.p., 900-r.p.m., Form K, 60-cycle, 220-volt
Induction Motor Driving Battery of Sausage
Chopping Machines
Fig. 46. 20-h.p., 1200-r.p.m., 220-volt. Form K Motor, Direct
Connected to Meat Cutter with 40-in. Bowl,
200 Pounds Capacity
While the question of power distribution
was perhaps the main reason for the use of
the electric motor, the economical application
of the motor to the driven machine is probably
of no less importance.
The motor-driven pulp grinder is allowing
the pulp manufacturer to purchase his power,
or as in some cases utilize a water power
development which is situated some distance
from the paper mill, without making a sepa-
rate pulp mill necessary. The advantages of
individual drive are again shown in the beater
room where the beaters are driven in pairs.
The elimination of shafting and belts in the
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Fig. 47. 25-h.p., 1000-r.p.m. and 10-h.p., 750-r.p.m., 220-volt
Motors Driving Vacuum Pump, Meat Chopper,
Hash-r and Corn Beef Fillsr
Fig. 48.
Induction Motor Driving Meat Hashers
in Packing Plant
SOME INDUSTRIAL APPLICATIONS OF ELECTRICITY
477
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beater room basement is of some importance,
and economies are secured by being able to
repair one set without in any way affecting
production of the other sets.
The fact that electric motors are not
universally used on paper machines does not
mean that the mechanical speed changing
devices and variable speed engine are entirely
satisfactory.
The steam demand for paper mills varies
greatly, depending on the class of product
turned out and the method employed. But
the demand is present for motor-driven paper
machines and a large number of successful
installations are in operation.
Artificial refrigeration has been one of the
most important factors in building up the year
round packing business as it is now conducted,
and the motor-driven refrigerating equipment
is now firmly established in the industry.
Railroad Shops
The influence of electricity on the trans-
portation problems of the country is well
known. On one side of the innumerable trolley
and steam roads we find the manufacturing
plants, on the other side the repair shops.
It is the latter which comes under the direct
control and deeply concerns the operating
department of a railroad system.
Fig. 53.
40-h.p., 400,800-r.p.m., 220-volt Direct-current Motor
Driving a 22- by 60-in. Rubber Calender
Packing Plants
The preparation and packing of meats is
done on a large scale by a comparatively few
companies. Great quantities of steam and
hot water are required, but nevertheless the
electric motor is found in every department of
the packing plant. In hog killing it is not
uncommon to find the hog lifted from the pen
by a motor-driven wheel, which starts him
on his trolley journey, ending eompletelv
dressed ready for the refrigerator. Meat
packing is a line of work where the essential
requirement is to keep things moving. The
processes involved are comparatively few as
regards power applications, but the depend-
ability of the electric motor has made its use
indispensable.
The competition is so keen that nothing is
allowed to waste. The hair cleaning depart-
ment requires motors, and the dust removed
from the hair is worth over $40 per ton. The
operation of the fertilizer mill, where many
by-products are turned into money, depends
upon the electric motor.
Fig. 54. 40-h.p.. 720-r.p.m., Form M, 440-volt Alternating-
current Motor Driving a 10- by 36-in. Rubber Refiner
Car wheels must be made true, boiler flues
must be kept tight and a thousand and one
repairs must be taken care of efficiently and
without delay.
Various classes of metal and woodworking
machinery are necessary such as shears,
punch presses, lathes, boring mills, planers,
cold metal saws, milling machines, arc welding
apparatus, etc. The growing tendency on the
part of steam railroads is to purchase elec-
trical energy for the operation of the repair
shops, and of course this means the application
of the electric motor.
Better light and the "safety first" ideas in
a railroad shop are just as essential as in the
ordinary machine shop, shoe factory or
textile mill.
Rubber Mills
The transformation of crude rubber to
sheets, tubes, rods and molded sections for
commercial use requires comparatively heavy
machinery and considerable power. The pro-
cesses of washing, masticating, mixing, refin-
SOME INDUSTRIAL APPLICATIONS OF ELECTRICITY
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GENERAL ELECTRIC REVIEW
ing, wanning and calendering require mills
consisting of two, three or more rolls depend-
ing on the operation. The load is variable, as
in the case of a three-roll washer 30 h.p. may
be the average, with a peak load of 100 h.p.
The mixing mill may have an average load
of 55 h.p. with a maximum of 120 h.p. The
advantages in the use of electric motors are
due to the fact that the various machines,
each requiring considerable power, can be
operated independently.
Heavy overloads must be taken care of and
at the same time protective devices must be
furnished to avoid the breakage of the rolls
due to clogging. The question of individual
or group drive is dependent upon factory
conditions.
The polyphase squirrel cage motor is
especially suited to carry the high peak loads
and is most commonly used, except for the
calenders where a four-to-one speed range is
sometimes required, in which case an adjust-
able speed direct current motor is used.
Shoe Factories and Tanneries
The material decrease in the unit cost
of production is one of the principal advan-
tages attending the use of electricity in shoe
factories. The actual reduction of operating
cost is not, however, as important as the
increased production possible with the same
labor and equipment. As a fair example, the
cost of power for making a pair of shoes may
be taken as one cent. The entire elimination
of the power item is not as important as an
increased production of 10 per cent in the
number of shoes turned out. Shoe factories
are generally spread over large areas and a
long shaft driven by a reciprocating engine
often shows a 10 per cent speed variation at
the end farthest from the prime mover.
The slipping of belts between engine and
driven machines frequently results in 10 to
20 per cent loss of speed in the latter. The
steadiness of electric drive with a constant
angular velocity not only increases production,
but increases the useful life of the driven
machinery and greatly reduces wastage.
Where electric drive is used the routing of
material and good lighting conditions can be
the determining factors for location of
machinery. Corners which could not be used
with mechanical drive become productive.
Weak points in the long chain of production
may be readily strengthened without disturb-
ing other parts of the factory.
The tanning industry is usually closely
associated with the manufacture of shoes
although it is a separate industry and furnishes
material to a great variety of manufacturing
concerns. The tanner, however, has recognized
the advantage of the electric drive as some
concerns are using motors by the hundreds,
and others who originally use steam engines
have re-equipped throughout with modern
electrically-driven machinery.
Sugar
In all probability Cuba holds the dis-
tinction of being the pioneer in applying
alternating current on a large scale to sugar
mills, but now we find successful electrically
operated plants in other cane growing coun-
tries.
The conditions in this industry are interest-
ing from the fact that steam is necessary for
cooking, evaporation, etc., while on the other
hand conveyors, pumps, etc., are more
economically operated electrically than by
small steam engines. The crushing rolls for
breaking up the cane have in the past been
operated by large steam engines but now we
have one or two instances where motors are
doing this work successfully.
The steam turbine will undoubtedly help
solve the problem of furnishing the power
sufficient for crushing and operating auxiliary
apparatus and at the same time make avail-
able sufficient steam for cooking and evaporat-
ing. The annual overhauling expense of an
ordinary sugar mill is greatly reduced where
electric drive is used and the depreciation
item is not as big a factor.
In the beet sugar industry the electric
motor plays an important part. The success
of the beet crop is often dependent upon rain
at the proper time. If a dry season is experi-
enced irrigation is necessary and made pos-
sible by the motor-driven pump.
The season is comparatively short, rarely
over three and one-half months, but when the
"campaign" in on, continuous operation of
the factory 24 hours per day is necessary;
the shutdown of but a few hours means
serious loss.
The use of motors for the conveyors,
washers, slicers, mixers, granulators, crystal-
lizers and centrifugals has been found to
increase production and reduce to a minimum
the possibility of delays and shutdowns.
The "centrifugal" is considered one of the
most important machines in sugar making,
and the operating conditions the most severe,
due to the inertia of the load and the cycle of
operation. For individual motor drive the
peak load is approximately eight times the
SOME INDUSTRIAL APPLICATIONS OF ELECTRICITY
481
Fig. 59. 40-in. Weston Centrifugal Direct Connected to 20-h.p.,
850/1000-r.p.m., 230-volt Direct-current Motor
in a Sugar Refinery
Fig. 60. 30-h.p. Induction Motor Driving Cane Hoist
in Sugar Mill
Fig. 61. Motor-driven Portable Machine for Nailing Hoops
on Barrels in Cooper Shop
Fig. 62. 50-h.p., 900-r.p.m., Form K, 440-volt Induction
Motor Driving Crusher
482
GENERAL ELECTRIC REVIEW
Fig. 63. 200-h.p., 1200-r.p.m., Form K, 2200-volt Induction
Motor Driving a Seven-saw 12- by 72-in. Edger
in Lumber Mill
Fig. 64. Ten Upright Shingle Machines Each Driven by One
20-h.p., 1800-r.p.m. and One 3-h.p., 1800-r.p.m., Three-
phase, 60-cycle, 440-voIt Induction Motor
normal running load and the cycle approxi-
mately three minutes depending upon the
grade of sugar. But even here the electric
motor is doing the work.
When you come to the refinery, the advan-
tages of electric drive are so well established
that a general discussion is unnecessary.
Conclusion
The discussion of the industrial application
of electricity might be extended to the
chemical works, paint factories, gas works, ore
treating plants, publishing houses, textile
mills, tobacco factories, iron and brass foun-
dries, machine shops, quarries, watch making,
problems of freight handling and so on until
the complete list of industrial activity is
exhausted. In each the electric motor is found
lightening the burden^ of mankind and
performing its duty in the most careful and
economical manner.
No mention has been made of the various
types of electric motors or the complete
systems of control available for industrial
use, and it is thoroughly understood that no
one type is suitable for all requirements.
The few applications briefly discussed have
been made only after a careful engineering
study of the character of work to be performed,
the conditions under which the motor must
work, the cycle of operation, etc. It is
thoroughly understood that a motor with its
control devices to operate a reversing planer
equipment in a machine shop must be designed
with entirely different characteristics from
the motor best suited for operating a tipple
in a coal mine. Each individual application
must be studied. The direct-current motor
will probably always have a demand in the
industrial field, but in the large majority of
cases the alternating-current motor has taken
the lead.
483
ELECTRICITY IN AGRICULTURE
By Carl J. Rohrer
Agricultural Specialist, Lighting Department, General Electric Company
The application of electricity to agriculture is bound to be greatly extended in the next few decades and
therefore a review of what has been accomplished is of value. The author goes quite fully into some of the
most important phases of this work; the problem of getting the electric energy to the farmers is among the
many important things dealt with. — Editor.
Fifteen years ago an electric installation on
a farm was a rarity, ten years ago it was still
thought to be a great novelty and not until
about five years later did the farmer begin to
seriously consider the many advantages of
electricity. Since that time, however, the
fanner's change in attitude has been rapid
and today he is an enthusiastic advocate of
electric light and power. Almost every
expect them to lead in this particular line.
Austria-Hungary has a population of 196
per square mile, France 191, Germany 312
and Italy 313. All of these countries have
from six to ten times our population per unit
area and agriculture is practised in its most
intensive state. There, very exhaustive studies
have been made as to the possibility of agricul-
tural electrical development. Numerous
Fig. 1. German Exhibit showing Motor-driven Ensilage Cutter
Fig. 2. Dairy Section of a Foreign Exhibit
farmer who is not using electricity at the
present time is laying plans to do so as soon
as his financial condition permits. This is
conclusively proven by the fact that our
various agricultural colleges are being flooded
with inquiries on this subject. So heavy has
the pressure become that classes are being
organized and bulletins prepared.
This rapid change is really to be considered
remarkable when one stops to reflect that our
present population is only about 31 persons
per square mile and that only about 50 per
cent of these live in the rural districts.
In Europe, especially in Germany, the
electrification of the farm has reached a
very pronounced stage of development. How-
ever, Europe's population is so much greater
per square mile that one would naturally
exhibits have been held to educate the rural
population and every government has estab-
lished experiment stations where new farm
apparatus of all kinds has been tested and
tried out under the supervision of competent
government officials. If found wanting the
facts are so given and the machine is not
recommended, with the consequent result that
only suitable apparatus is purchased by the
farmer.
A large number of small central stations
have been established in the rural districts of
Germany supplying light and power to a few
small towns and the rural population of the
vicinity. Many of the German farmers carry
on other industries in connection with their
farm work because it enables them to keep
their help busy when work is slack or the
484
GENERAL ELECTRIC REVIEW
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ELECTRICITY IN AGRICULTURE
485
weather unfavorable for labor in the field.
This is a type of intensive agriculture which is
rarely practised in this country.
In Europe many of the farm machines are
supplied by their manufacturers equipped
with suitable electric motors. Feed grinders
and ensilage cutters with direct connected
motors are just as common in Germany as
motor-driven lathes and planers in the United
States.
Perhaps the most advanced step made by
Europe has been in the way of electric plowing.
France, Germany and Italy all have made
a very large number of experiments to
determine the adaptability of electricity for
plowing and such outfits have been put in
actual production by European manufacturers.
Germany has a considerable number of such
plowing equipments in actual operation.
Two systems of electric plowing are in
common use. In both systems the general
appearance of the plow is the same, it being
constructed in such a way as to enable it
to operate while traveling in either direction.
In one the current is supplied to the plow
by means of a two-conductor trolley. A
heavy chain is stretched across the field and
securely anchored at each end. This chain
passes around a drum mounted on the plow,
the drum in turn being driven by the electric
motor. The anchor wagons to which the
chain is attached at each end of the field
automatically move forward as the plow
travels back and forth across the field.
Fig. 7. Motor-driven Grain Cleaners and Graders,
European Exhibit
The other system requires two large trucks,
one at each end of the field, upon each of which
are mounted an electric motor and cable
drum. The plow is drawn back and forth
by means of a cable attached to each end of
the plow and to the drums. This equipment,
however, is more expensive to operate as it
requires at least three men and a duplicate
system of motors and winding drums.
A complete plowing equipment of the truck
and cable type capable of drawing five or six
14-in. plows across a field 1300 ft. wide will
cost in the neighborhood of $15,000. This
outfit is complete in every detail and includes
Fig. 8. Electric Plow of the Chain and Trolley Type
two 75-h.p. motors, transformers, switches,
plows, cables and trucks. A complete equip-
ment of the above capacity using a chain and
trolley and one 75-h.p. motor will cost approxi-
mately $10,500.
Little or no experimentation has been made
in this country to develop a suitable electrical
plowing equipment, primarily because elec-
trical transmission systems are not available
and also because of the low cost of coal and
fuel oils. A fortune awaits the man who will
develop and put into practical operation an
electrical plowing outfit which will be reason-
able in first cost and economical in operation.
In 1905 the government of the Province of
Ontario, Canada, created what is known as
"The Hydro-Electric Commission." This
Commission was primarily appointed to
develop, control and operate the water powers
belonging to the Province. In 1911 the
Provincial Legislature passed a law, the
object of which was to enable the Commission
to distribute electrical energy to the residents
of the rural districts. An extensive campaign
of education was conducted consisting of
meetings and exhibits throughout the Prov-
ince.
In addition, a number of demonstration
farms have been completely equipped. The
result has been that a large number of farmers
have signed power and lighting contracts;
however, no definite figures' are available as
486
GENERAL ELECTRIC REVIEW
to the actual number of farmers signing such
agreements.
In the United States the application of
electricity to the farm is advancing, as is
shown by the enormous increase in the number
of isolated plant manufacturers, there being
about 200 of such concerns at the present
Fig. 9. Portable Motor and Six-Inch Centrifugal Pump
for Irrigating Forty Acres of Alfalfa
in California
time. This coupled with the fact that central
stations are supplying at present between
50,000 and 75,000 strictly rural customers
gives some idea of the possibilities of rural
development.
Electricity at the present time can be
advantageously applied to over 125 various
uses on the farm. Electric applications even
in their simplest form bring great advantages
to the farmer not only in economy but because
they eliminate to a very large extent the
drudgery of farm life.
The hard work and the long hours of work
have made the farm labor problem a serious
one. It is so serious in fact that many farmers
instead of trying to get efficient labor have
turned their farms over to tenants or else
seeded their land to grass and pastured their
stock. Electricity perhaps as much as stay
other one factor will tend to alleviate or
minimize these conditions and make it easier
to secure farm labor by checking the migration
of our young men to the city. It will also make
possible the more economical performance of
farm operations by shortening the time
required and lessening the cost which will
in turn enable the farmer to pay higher wages
for shorter hours of work.
Perhaps the greatest progress in the rural
field has been in the application of electric
motors for irrigation and for the reclamation
of land. In our western sections, irrigation
is absolutely necessary in order to produce
crops of any appreciable size and in many
localities it is impossible for vegetation to
exist without the artificial application of
water.
The gravity system is perhaps the one most
extensively used in the west; however, it has
two serious disadvantages — namely, the in-
ability of the farmer to get his quota of water
any time he desires and also the impossibility
of irrigating any land situated at a level
higher than the canal itself. To overcome
these difficulties suitable pumping equipments
have been installed, the water being secured
from underground supplies or from rivers,
lakes and canals.
Steam, gasolene and distillate engines, as
well as electric motors, have been installed by
the thousand in this territory. The area
under irrigation by pumping in 1909 amounted
to 500,000 acres, the horse power required
being 243,500 h.p. Conservative estimates
show that these figures have been at least
doubled since the taking of the 1910 census.
The United States government and the
various state agricultural experiment stations
have spent thousands of dollars in experi-
mental work to determine the proper amounts
of water necessary for crops in the various
sections of the country. The government has
also assisted in financing the great irrigation
projects.
As in the case of all other farm operations,
labor is scarce and any mechanical device
which will eliminate the necessity of such
labor, unless such device is very expensive,
will be welcome with open arms by the fanner.
While steam, gasolene and distillate engines as
prime movers cut the labor cost to a consider-
able extent, they are in no way comparable
to the saving brought about by the use of
electric motors. In the arid regions, where a
large amount of water is required it is often
necessary to operate pumping plants 24 hours
a day for a month at a time and in many
cases six months. The engine-driven plants
require an operator to be in practically con-
stant attendance, while in the case of the
motor-driven plant a casual inspection every
two or three days will suffice. This difference
in the amount of attendance required means a
considerable monetary saving in the course of
a year.
The extended use of electrically driven
irrigation plants is a comparatively new
proposition, most of them having been
ELECTRICITY IN AGRICULTURE
4S7
installed in the last seven or eight years.
Perhaps the greatest development has been
made in California, where one company
alone has approximately 9000 farms using
electric power.
This power company derives a gross income
of approximately $500,000 per year from
motor-driven irrigation plants. Several other
companies in California have from 2000 to
7000 farmers on their lines. The amount
of irrigation load has been such that even in
the case of the very large companies, the
peak load has been shifted from the evening
hours of the winter months where it ordinarily
comes to the daylight hours of the summer
months.
The rural load of many of the smaller
power companies consists of as much as 60
per cent of the total. One company especially
has an ideal combination in the way of load,
as it consists of railway, lighting and irrigation
pumping with a yearly load factor of approxi-
mately 60 per cent. During the height of the
irrigation season, the peak load comes on at
about nine o'clock in the morning with another
peak almost as high as four o'clock in the
afternoon. The minimum load is at four a.m.
being approximately one-third of the morning
peak. This company's load factor during the
summer months is approximately 70 per cent.
Another California central station has a
rural load amounting to 33 per cent of the
total, another 50 per cent, while in the case
of a third it amounts to 67 per cent. The
rural connected load in motors in California
is at least 130,000 h.p., most of this being
for irrigation.
While California ?s the leading state as far
as irrigation is concerned, Washington,
Oregon, Colorado, New Mexico, Utah and
Arizona all have large numbers of farmers
using electric motors. The states of Wash-
ington and Oregon alone have at least
5000 h.p. in electric pumping motors.
This is in reality only a very small percent-
age of the prospective business, when one
stops to realize that California has 88,000
farms, Arizona 9000, New Mexico 35,000,
Oregon 45,000, Utah 21,000, Colorado 46,000
and Washington 56,000 farms. Probably 50
to 75 per cent of these farms can use irriga-
tion to advantage.
From these figures it can be readily seen
that the field for irrigation is by no means
exhausted and that the possibilities for
irrigation load are still very great.
It is perhaps the common impression that
irrigation is not usually practised except in
our far western states; however, this is not
the case. There are to be found a considerable
number of reclamation projects in the south
and in the Mississippi valley, where motor-
driven pumps are used, the apparatus being
so arranged that water can be pumped in
Fig. 10. 35-h.p. G-E Induction Motor Operating
1600-gaIlon Pump
either direction. During the flood periods the
water is pumped into the river or lake, while
during the dry season the water is pumped
from the river or lake back upon the land.
Rice irrigation is also of considerable
importance as the 1909 census shows that
there were about 1900 pumping plants in use
in Arkansas, Louisiana and Texas aggregating
1 18,000h.p.and capable of delivering 9,500,000
gallons of water per minute. If these pumps
operated 24 hours a day for one week, they
would cover 270 sq. miles of land two in. deep.
There is also another field in the humid
sections of the United States for the applica-
tion of water by artificial methods — namely,
the truck and market garden. In some sec-
tions of the east, this has reached a very
considerable stage of development.
It is a peculiar, but well established fact,
that when irrigation is inaugurated in a
truck or market garden region, the prices
4ss
GENERAL ELECTRIC REVIEW
obtained by the farmers using such irrigation
are so much greater that the other truck and
market gardeners in that vicinity have been
compelled to install irrigation or else accept
lower prices for their produce. This is due to
the greater quantity and better quality of the
products obtained under irrigation, coupled
Fig. 11. 35-h.p. G-E Induction Motor Driving a Pump
Delivering 2000 Gallons per Minute,
Irrigating 160 Acres of Alfalfa
with the irrigation farmer's ability to market
his crops earlier, thus getting the cream of the
market.
The United States Weather Bureau reports
show that almost every summer there are
considerable periods of time when a condition
of drought exists — namely, less than one inch
of rainfall in any 15-day period. These
droughts sometimes last for a month or six
weeks, completely exhausting the supply of
moisture in the soil and causing a decided
shrinkage in the quantity, and producing a
very inferior quality of product, which must
be sold at low prices.
The system of irrigation mainly used for
supplying water in the humid sections is
almost exclusively of the overhead type, or
what is commonly known as the sprinkler
system. By this method water is applied
under considerable pressure in order to deliver
it to the plants in the form of a fine spray.
The pressure ordinarily used is from 40 to 50
lb. per sq. in. at the nozzles; this means that
a large amount of energy will be required
to drive the pump as it must work against a
head of from 90 to 115 ft. plus the vertical
elevation of the pipes above the water in the
well together with the friction loss in the
pipes themselves.
Motors for this kind of irrigation are not
usually run continuously, ordinarily they are
installed in such capacities that they will
operate from three to eight hours per day
depending on the amount of rainfall. One to
one and one-half inches of water per week is
ordinarily considered sufficient to grow good
crops; if the rainfall drops below this the
additional water is supplied by irrigation.
Unless the s.eason is very wet, the plants are
usually sprinkled for a short period once a
day — either in the early morning or late in the
evening — as this has been found to materially
aid their growth.
The use of this type of irrigation equipment
requires a considerable outlay of money, the
piping, pumping equipment, etc., making the
installation cost from .1100 to $150 per acre.
The results obtained, however, have been
very satisfactory, and the increase in the
quantity and quality of product has made it
a paying proposition even when the addi-
tional cost of such systems has been con-
sidered.
There is a large amount of land in the
vicinity of all our large cities devoted to the
raising of such crops, and in view of the
severe competition in this particular phase of
agriculture it will be absolutely necessary in
the future for this class of farmers to install
pumping equipments in order to successfully
compete with those using irrigation. Already
many of the more progressive market gar-
deners have taken advantage of the additional
benefits derived and are using motors of
from 5 to 25 h.p. to operate pumping
equipments.
The load is ideal from a central station
standpoint, in that it is exclusively a summer
load and rarely if ever interferes with the
lighting peak. Those companies who have
such customers on their lines have found that
this is very good business providing only
short line extensions are required. If neces-
sary to run long lines the business is not
desirable unless the farmer consents to pay-
part of the first cost.
In the mind of the farmer lighting is
naturally the first consideration and, there-
fore, the conveniences derived from electric
lights are of almost inestimable value from
his standpoint. Ordinarily the farmer con-
siders that the lighting of the house and the
proper illumination of the barns is the first
and of primary importance; however, after
these lights have been installed and their
value fully realized, the next step is usually
the installation of a number of lamps around
the farm lots, situated at such points as to
give most satisfactory results.
ELECTRICITY IN AGRICULTURE
4S9
Of principal importance, however, is the
very material reduction of fire risk, great
losses each year being caused by lamps and
lanterns together with the habit of using
matches as a source of momentary light.
The amount of work required of the farmer's
wife is usually large to say the least and,
therefore, any conveniences or labor saving
devices are of great assistance in performing
the household duties. A good system of
domestic water supply, saving hundreds of
steps during the course of a day, is an example,
for such a system with an electric motor
drive and equipped with an automatic starting
and stopping device requires practically no
attention and pays for itself many times in the
saving of actual labor.
It is really remarkable what can be accom-
plished in the average farm home with the
aid of a small motor of ]4r or 34-h-p- capacity.
In a large number of instances a motor has
been installed at some convenient point in the
kitchen or pantry and belted to a line shaft
having a number of pulleys of various diam-
and grinder. Furthermore the motor was
mounted in such a manner that it could be
easily removed and used to operate the wash-
ing machine, chum and sewing machine.
For instance, the washing machine was
located in the basement, the churning was
done on the back porch in summer and in the
-
1
i-uuiif1
Ill t
Hi rfi&tLoi
Hu •••••
J ,w»«
' -..fff 1
umrJ *
iln=r-^
>..it9^!»\'i
,^^^
U-fc* :
Fig. 13. Electric Kitchen Installed at Headquarters Ranch,
California
Fig. 12. Motor-Driven Washing Machine and
Cream Separator
eters. On a suitable base has been mounted
a number of clamps convenient for holding
the different machines used in the kitchen.
In one particular instance, this outfit con-
sisted of a coffee grinder, flour sifter, meat
grinder, bread mixer, egg beater and buffer
kitchen in the winter, while the sewing
machine was equipped with clamps for hold-
ing the motor. In the case of the washing
machine, the wringer was also arranged to
enable it to be operated by power.
All the necessary equipment for trans-
mitting the power was designed and installed
by the farmer himself. The whole outfit
took very little room and represented a
comparatively small initial investment. This
particular instance is not an isolated case, as
investigation will show that there are hundreds
of such installations, perhaps not quite s*o
complete as to details, but still serving the
needs of a definite case.
Electric vacuum cleaners which can be
operated from the lighting circuit are also in
considerable demand, as they are great
labor savers and easily transportable from one
room to the other.
An electric fan in the kitchen on a hot sum-
mer's day is a piece of electrical equipment
which is very much appreciated by the house-
wife.
Of the heating devices, the electric iron is
almost in universal use wherever electricity
is available, especially during the summer
months, as it enables the housewife to do her
ironing in the coolest and most convenient
place. The various other heating devices are
not so popular, although there are a con-
siderable number of heating pads, hot water
490
GENERAL ELECTRIC REVIEW
heaters, toasters, hot plates and coffee per-
colators in use.
Perhaps the most important of the applica-
tions of electric drive is that of pumping
water for both domestic and general farm
purposes. An electrically driven pumping
equipment makes an ideal water system.
Fig. 14. Cream Separator Driven by J^-h.p. Motor
In many instances it is necessary that the
pump be situated a considerable distance from
the buildings. In such cases the starting
equipment can be installed at this central
point and the motor even though a half mile
away may be started and stopped at will, or
it can be made to operate automatically.
A motor-driven water system is not expensive
to operate and the first cost is no greater
than a similar installation using some other
source of power.
With the ever increasing population in our
country, the land has become well occupied
and it is becoming almost a necessity that a
system of water supply be secured which is
independent of the running streams, due to
the fact that the water of such streams may
easily carry a contagious disease to the farm
animals causing a very serious property loss.
Hog cholera and foot and mouth disease are
two of the most serious diseases at the present
time which can be easily transmitted in this
manner. Much of the loss from infectious
diseases among farm animals has been directly
traced to the running stream and the farmer
may easily pay the cost of an installation of an
adequate water system from the loss which
he would occasion by the spread of disease
among his herds. This danger has resulted
in a very material increase in the number of
such plants installed.
The cream separator at the present time
has come into almost universal use, and when
power-driven the saving in labor is quite
appreciable. For instance, it has been found
that an electrically driven separator of 500 lb.
capacity per hour, even if only 200 lb. of milk
is separated each day will show a saving of
$10 per year after all expenses are considered.
In addition there will be an actual saving in
labor of at least 24 minutes per day or over
two weeks' time during the year. This 24
minutes per day can be used to advantage in
doing other chores such as washing the milk
pails, etc., thus lessening the chore period by
that amount. A farmer separating 500 lb.
of milk per day would save in actual cash
$35 a year, this amount being left as profit
after depreciation, interest, labor and power
are charged against the operation. There
will also be available for other work during
each day a period of one hour or 36 working
days of 10 hours each which is a very con-
siderable item to the average farmer.
One of the principal advantages tending to
promote the use of the electric motor is its
simplicity. No other source of power can
compare with it in this respect. The horse
must be fed and cared for, the gas engine
must be adjusted, the steam engine requires
a licensed engineer, but the motor needs only
an occasional oiling.
Portability is another feature of the motor,
it weighing only two-sevenths as much as a
gas engine of the same capacity. A 5-h.p.
motor will weigh 340 lb. and can be easily
transported from one building to another.
This is of sufficient size to operate small feed
grinders, corn shellers, fanning mills, grain
elevators, concrete mixers, alfalfa mills,
grain graders, hay cutters, etc.
When the central stations first tried the
installation of portable equipments, it was
difficult if not impossible for the farmer to
change the motor from one point of use to
another. This meant that a representative
of the central station must make a trip to
disconnect and reconnect the motor to the
lines. However, a few simple instructions
have been found sufficient to eliminate this
inconvenience and ordinarilv motors are now
ELECTRICITY IN AGRICULTURE
491
changed from one place to another without
difficulty. Several hundred feet of armored
cable are usually kept ready, this being used
in case it is necessary to install the motor
some distance from the nearest outlet box.
It is really remarkable the number of things
which can be accomplished with one or two
motors about the average farm. On rainy
days they are used to grind feed clean and
grade grain, shell corn, etc., and at other times
to operate concrete mixers, grain elevators,
wood saws, etc.
Actual experience has demonstrated that a
farm of average size requires about four
motors as follows — a J^- or J^-h.p. for the
house, a 1-h.p. motor for the small farm
machines, a 5-h.p. for machines of inter-
mediate size and a 15- or 20-h.p. motor for
the heavier farm machinery.
In the past the tendency has been to have
the threshing, corn shelling, baling and ensilage
cutting done by a custom machine, i.e., a
machine owned and operated by a crew of
men separate and distinct from the farmer's
own organization. Indications point to the
fact that this system is rapidly going out of
use, the general tendency at the present time
being for the farmer to buy a small equipment
and operate it with his own help. For instance,
in the past a threshing equipment consisted
of a grain separator with a 32- or 36-in.
cylinder, necessitating a large traction engine
and a very considerable force of men to keep
the outfit in constant operation.
The president of one of the large threshing
machine manufacturing companies made a
statement not long ago to the effect that the
demand is rapidly shifting towards the smaller
machines. The reason for this is attributed
to the fact that the farmer can do his own
threshing with the assistance of but two or
three neighbors, whereas with the old system
it required the combination of from 10 to
20 farmers and from 25 to 35 men to keep the
machine in motion. The result was that one
or two weeks' time was required to complete
the threshing. If any breakage occurred, it
meant the loss of at least a half day for the
whole force. Another disadvantage, especially
during a rainy summer was that someone
had to have his threshing done last and would
in all probability suffer a considerable loss due
to damage from the weather.
With the new arrangement, the work can
go on without the loss occasioned by the old
system and in addition any postponement of
the work does not necessitate the replanning
of work of the whole neighborhood. The
points mentioned also hold true for ensilage
cutters, hay balers and clover hullers; how-
ever, the force of men required in this case
is not so large as in the previous illustration.
This change also means a larger market for
small sizedequipments of all kinds and further-
more it means that one or two farmers will
Fig. 15. Threshing by Electric Power
now combine and purchase a portable motor
and transformer of sufficient capacity to
operate these machines. This was impossible
before, because the large equipments required
from 75 to 100 h.p. to operate them, now
35 h.p. is usually the maximum needed.
A 15- or 20- or even a 35-h.p. motor can
be easily transported together with a suitable
transformer from one farm to another.
Formerly it was necessary for a representative
of the central station to disconnect and recon-
nect the transformer whenever such a change
was made; at present, however, an armored
cable is used having at one end suitable leads
equipped with hooks. These hooks can be
hung over the transmission wires or removed
with perfect safety by the farmer.
In some cases a fiat charge of from $5 to
$10 a day is made for the electricity, but
usually a meter is installed on the secondary
side of the transformer, the current used
being paid for at the regular rates. Such an
outfit is very flexible as it eliminates the core
loss of the transformer when not in use and
in addition gives the central station a very
good summer day load.
Instead of using horses to draw the hay into
the mow the farmer now uses a power hay
hoist. This is readily adaptable to electric
drive, the motor being belted to the hoist.
With these hoists all operations are controlled
from the load and of course this can be readily
accomplished in the case of motor drive.
492
GENERAL ELECTRIC REVIEW
In the potato-growing regions of the United
States motor-driven potato sorters have
come into considerable use. Motors are also
of value in the apple industry for driving belt
conveyors and apple wipers.
The newspapers and magazines have per-
haps published more articles describing the
Fig. 16. 250-Egg Electric Incubator
remarkable results obtained by stimulating
plants electrically than any other one farm
subject. However, the facts of the case are that
the whole matter is still in the experimental
stage and while results have been obtained
they have not been conclusive and further-
more their value from a practical standpoint
is still very much in doubt. The United
States government has been investigating this
subject and finds that, while the plants show
beneficial effects, these are not sufficient to
warrant the use of this application on a
commercial scale.
This lack of results may be due to the fact
that the action of the electric current on the
metabolism of the plant is not fully understood
and it may be that further investigation will
bring out important discoveries which will
make such applications practicable; however,
at the present time nothing of commercial
value has been developed.
Another innovation in the way of electric
drive has been its application to compressed
air spraying equipments for the protection
of orchards and truck gardens from the
injurious ravages of insects and beetles. The
outfit consists of a motor-driven air compressor
which supplies air at a pressure of some 200
or 300 lb. per sq. in. All equipments including
the mixing tanks are located at a central
point. The spraying carts are equipped with
two tanks, one for the spray liquid and the
other for the compressed air.
The two tanks are interconnected at the
bottom through a pipe containing a reducing
valve, thus giving a constant pressure in the
liquid tank of 100 lb. per sq. in., which is the
best pressure to use for spraying purposes.
The compressed air entering at the bottom of
the liquid tank also serves to keep the spraying
liquid agitated and prevents the solid con-
stituents from settling to the bottom.
This equipment, while costing a little more,
weighs less and requires practically no
mechanical skill. The man at the mixing
station can mix the liquids, the motor operat-
ing automatically when air is needed.
The farm shop is not complete without
electrical equipment, a small motor being
very convenient to drive small saws, grind
stones, emery wheels and forge blowers. An
electric portable drill is quite popular, as it
enables repairs to be made on machinery in
other buildings without tearing the machine
down and taking the part to the repair shop.
The electric soldering iron is another handy
device, as its convenience in attaching to any
lamp socket makes it available for use wher-
ever there is electric current.
Electric hot water heaters find many
applications, about the farm, especially in
cases of sickness among the farm animals, as
they make a supply of hot water available in
all the farm buildings. In several instances
they have been used as paint buckets to keep
paint warm while painting buildings.
These, however, are not the only applica-
tions of electricity for the electric vehicle
must be considered. At the present time
there is a great deal of agitation tending
towards the installation of hard roads through-
out the various states. In the east remarkable
progress has already been made in this direc-
tion. With the advent of these hard roads,
the use of the electric vehicle will be appreci-
ably increased. A number are already being
used in the East for the marketing of farm
products. Due to its simplicity and reliability
it is safe and unexcelled as a convenient
method of transportation for the farmer's
wife for it enables her to do the family market-
ing and attend to her social duties in a manner
never before possible. For this reason it will
ultimately be the principal means of trans-
portation for the feminine members of the
farmer's household.
A review of the applications of electricity
to agriculture would not be complete without
a few words concerning a gasolene-electric
harvester manufactured and used in Cali-
fornia.
ELECTRICITY IN AGRICULTURE
493
This machine cuts, threshes and recleans the
grain in the field all in one operation. The
outfit consists of an 80-h.p. six-cylinder gas-
olene tractor and a combined harvester cut-
ting a swath 35 ft. wide and having a capacity
of 2200 bushels of grain per day. Upon the
tractor is mounted a 20-kw. generator driven
by the tractor engine. A 25-h.p. motor
operates the moving parts of the harvester
such as the cylinder, sickle, conveyors,
recleaners, etc.
The principal advantage of this equipment
lies in its efficiency over the old method of
driving by power derived through traction.
1% per cent have milking machines.
12 per cent are now prospective custom-
ers for such machines.
60 per cent have fanning mills.
20 per cent have silos.
3.3 per cent have ensilage cutters.
9.5 per cent have threshing machines.
45 per cent have gas engines.
10 per cent have steam tractors.
20 per cent have feed grinders.
5 per cent have hay balers.
The above figures are from investigations
made in 1913 and there is every reason to
believe that all percentages have been
Fig. 17. Gasolene Electric Harvester
Other advantages are flexibility, light weight
and lower operating cost. The cost per acre
with this machine averages 80 cents against
$2.50 for a horse-drawn harvester and $3
per acre where a stationary thresher is used.
Some idea of the possibilities of rural
development may be gained from data
obtained by a number of farm papers by
means of circular letters addressed to their
subscribers, who total some 400,000. The
following figures give the approximate percent-
age of subscribers using the various types of
machines to which electric motors can be
applied :
64 per cent have washing machines.
15 per cent of these machines are power-
driven.
96 per cent have sewing machines.
65 per cent have cream separators.
80 per cent have pitmps.
6.2 per cent have water systems with
power pumps.
33 per cent have incubators.
increased by purchases during the last year
and a half.
For instance, these investigations show that
over 50 per cent of the farmers were planning
to buy and install water systems requiring
a power pump. As the number of farmers hav-
ing power-driven machinery increases, the
field for electric motors and for electric
power will also increase in proportion.
Many of the central station companies
throughout the United States have taken
considerable interest in the farmer as a pros-
pective customer and a large amount of
experimentation is now under way in order
to determine what revenue may be expected
from such installations and the most sat-
isfactory method of financing them.
This is not a surprising fact when one stops
to reflect that only a comparatively few years
ago considerable doubt existed in the minds
of electrical engineers and central station
managers as to whether or not the residential
lighting customer was a profitable proposition.
494
GENERAL ELECTRIC REVIEW
The same thing was true of the various
applications of power. However, most of the
difficulties of city distribution have reached
a satisfactory solution and today it is generally
agreed that city lighting and power is very
desirable business. The same difficulties are
now being considered in the distribution of
electric current to the farms and rural com-
munities.
It should be also remembered that the
problem of rural sendee requires special
treatment and should, therefore, be considered
as a separate and distinct branch of the central
station industry'.
Progress, however, will not be extremely
rapid due to the large number of questions
are some ten other small villages scattered
throughout the county, the largest of which
has a population of 1900 with eight or nine
others having a population of approximately
500 to 700. As the revenue from such small
towns is comparatively small, the principal
returns will have to ultimately be derived
from the rural inhabitants.
The president of this company is also a
contractor of very considerable importance
in his own state and he feels convinced that
his company can gradually make the necessary
extensions and that they will pay a reasonable
profit on the investment.
The prominence of this man in the business
world is such that the result of his endeavors
Fig. 18. Demonstration Car of the Pacific Gas & Electric Co.
which yet remain to be settled by experimen-
tation.
As an isolated illustration, a central station
company in the middle west proposes to cover
the county in which it is situated with a net-
work of transmission lines. The county has
an area of about 400 square miles and a
population of 27,000 or 67 persons per square
mile, the largest town having 5000 inhabitants.
This county has a rural population of 13,500,
this figure excluding all towns of over 100
inhabitants. This means a rural population
of 33.5 persons per square mile. At the
present time only a small area of this county
is being supplied with electric current; how-
ever, extensions are rapidly being made and
the ultimate plan is to completely cover the
whole territory with transmission lines. There
in this fine will have considerable weight
with a number of other central stations, who
are awaiting results before venturing into the
business on such an extended scale.
From the preceding figures, coupled with
the fact that the United States has only
about one-sixth of the population per square
mile that is found in Europe (or rather was
found in Europe), it can easily be seen that
the rural electrification in this country is
really in its infancy.
A number of companies, however, have
already conducted extensive educational cam-
paigns, the most prominent of these being the
Pacific Gas & Electric Company, the Edison
Electric Illuminating Company of Boston
and the Pacific Power & Light Company.
All have made exhibits showing the various
ELECTRICITY IN AGRICULTURE
495
applications of electric light and power to the
farm. While the immediate results obtained
have not been especially encouraging, the
officers of these companies are convinced
that this educational work will ultimately
result in a large amount of new business.
Ordinarily, from a central station stand-
point, farm lighting alone is not profitable, as
power applications are the deciding factor
which swings the balance from loss to profit.
The average city customer installs the neces-
sary number of lights, buys a flatiron and a
few other devices and the limit in revenue
from this source has been reached. The
farmer on the other hand keeps finding new
Other companies make the farmers build all
the supply lines, furnishing power and light
at a nominal rate, the lines remaining in the
customer's possession. Others follow the
same principle, but refund a certain percentage
each year in electric current. Then if the
line is a paying proposition this refund con-
tinues until the title of the lines ultimately
comes into the possession of the central
station.
Still other companies require at least four
customers per mile with a guarantee of a
certain monthly minimum. In addition a
connection charge is made which covers the
cost of the poles and their erection and some-
Fig. 19. Exhibit Farm of Edison Light & Power Company
Fig. 20. Exhibit Farm of Edison Light & Power Company
things to do with electricity, and the farm
load even though the number of customers
remains constant increases each year through
the addition of motors and various other
devices.
The power situation is one which the
isolated plant cannot economically meet
except where water is available, or under such
special conditions as the presence of cheap
natural gas. Until such time as central
station power can be made available, the gas
engine must be the farmer's only alternative.
The principal problems for the central
station are those of rates and first cost.
Various systems are now being tried out
throughout the country with varying degrees
of success. Some companies build their own
lines and consequently must charge a high
rate which will be unsatisfactory from the
farmer's point of view as it practically limits
him to the use of electricity for lighting and
absolutely discourages the use of power.
times even the transformer is added to the
charge where lines are especially costly.
A variation of this consists of a connection
charge with an alternative clause allowing the
farmers to haul and erect the poles under the
supervision of a competent foreman. This
latter method has been found to be very
satisfactory, as the farmer counts his time
as a very small item and, in the majority of
cases, he is more than willing to do this work
because it enables him to get electric service
without a large outlay of actual cash. ,
Sometimes the customer gets a refund in
current running over a series of years or else
all current consumed over a certain amount
goes to apply on the refund. A service
charge as a rule has been found to be unsatis-
factory and should be avoided whenever
possible.
By far the larger percentage of central
stations who have been assisted by the
farmers in erecting their lines are more than
496
GENERAL ELECTRIC REVIEW
pleased with their farm business and this
method is becoming more and more the
accepted practice among central stations.
For it very materially reduces the first cost
of such extensions and in addition gives
both the farmer and the central station time
to develop the consumption of electric cur-
rent to such an extent that, by the time the
complete cost of the line has been refunded,
the farmer is using enough electricity to pay
interest and depreciation on the investment
and still leave a fair margin of profit.
No central station company need expect the
farm business to pay from the very first, for
the farmer must be educated to the many and
varied uses of electric current before he really
becomes a paying customer and the only way
in which he can be educated successfully is
through actual experience.
The character of the farm load makes it
desirable business from the central station
standpoint, in that it is "off-peak." The
lighting peak very rarely corresponds with
those of the city customers and the power load
comes on almost exclusively during the day-
light hours, being heaviest during the summer
months.
Very little can be expected from this type
of business, unless an aggressive educational
campaign is carried on. Progress will not be
rapid until the pioneer central stations in this
branch of the industry have given this new
field a thorough test and proven conclusively
that it can be made a financial success.
The waiter's observation has been that those
central stations who have had farmers on
their lines for a considerable period are as a
rule quite enthusiastic concerning the pos-
sibilities of this business. However, there is
a great deal yet to be accomplished and this
can only be done by the active co-operation of
both the manufacturer and the central station.
Fig. 21. Exhibit Farm of Edison Light 8» Power Company
497
THE ELECTRIC LAMP INDUSTRY
By G. F. Morrison
Manager of Works, Edison Lamp Works, General Electric Company
As the author points out, electric lighting was the motive causing a demand for electric generating and
distributing apparatus, and while current is not generated for this sole purpose today the field of the electric
lamp is responsible for an enormous consumption of electricity. The following article is therefore of great
interest as it is essentially a review of the development, manufacture, efficiency, and cost of the various types
of electric lamp from the time of the first successful production by Mr. Edison up to the present day. — Editor.
The lamp occupies a place by itself in the
electric industry; no other electric appliance
or piece of apparatus affords a parallel to it.
All original generating and distributing equip-
ments were developed in order to supply
current for the operation of electric lamps,
either arc or incandescent. The Brush
Electric Company, the Edison Company,
and the Thomson-Houston Company were
all organized exclusively for the exploitation
of systems of lighting. Similarly, all the
early central station electric companies were
founded solely to supply lighting service, and
this purpose is still implied in their names.
The different systems of distribution were
evolved and the voltages adopted with the
lamp requirements as the determining factor.
Later came the electric railway, hundreds
of electric motor applications, electric heating,
and many other minor uses of electricity; so
that despite the remarkable growth of the
electric lamp industry, the lamp does not
today occupy so commanding a position as a
current consumer as formerly. Notwith-
standing this fact, the public still comes into
more intimate touch with the lamp than with
any other electric device, and gives more
thought to its adaptation. In no other
manner in which it serves our needs is electric
service so rigorously judged or so highly
regarded by the people.
The arc and incandescent lamps were
contemporaneously developed as practical
lighting equipments, the arc being slightly in
advance. The arc lamp was a high power,
efficient illuminant, suitable for the lighting
of city streets, and the incandescent lamp,
though less efficient, was available as a small
unit, such as was required for interior lighting
— it was safe, convenient and adaptable.
One of the early problems of designing
engineers, which even yet has to be solved, is
the "divisibility of the arc," or the attempt
to produce efficient arcs as small units. Both
illuminants have progressed side by side, an
improvement in one being nearly always
quickly followed by some corresponding
improvement in the other. Other illuminants
have come and gone, but these two still
divide the field much as formerly, except
that in recent years the incandescent lamp
has begun to be an important factor in street
lighting. It is interesting to note that,
despite the wonderful improvements as the
result of persistent research and engineering
development, the lamps of today, the mag-
netite arc and the Mazda incandescent lamp,
are fundamentally very similar to their original
prototypes. One point in illustration is
that the screw base which Mr. Edison devised
in connection with the early incandescent
lamps is now used as the standard throughout
the greater part of the world, having pre-
dominated over all other types. No essential
improvements have been made in this base,
and it is practically certain that no other
design would have met all requirements so
well.
A review of some of the important develop-
ments that have marked the progress of the
incandescent lamp may be of interest.
Quantity
In 1881, 35,000 incandescent lamps, mostly
of 16 candle-power, were manufactured in
this country. In 1914 the number per year
had increased to over 110,000,000, the average
candle-power of which was somewhat higher.
The world's production during 1914 was
about 250,000,000 lamps. The growth .since
the start has been a steady one, remarkably
free from abnormal years. The lamp is a
necessity and its market is so little affected by
hard times or business depression that it has
often been called the "bread and butter" of
the electrical business. This remarkable
growth has required a continual enlargement
of manufacturing facilities, beginning with
the small shop where Mr. Edison made his
first successful incandescent lamp (Fig. 1)
498
GENERAL ELECTRIC REVIEW
and extending to the large groups of factories
now located all over the country.
The magnitude of the industry is indicated
by the fact that the different divisions of the
General Electric Company manufacturing
Fig. 1.
Shop in which Edison Developed His First
Incandescent Lamp
incandescent lamps are located in 12 cities,
and employ 65 acres of floor space.
Development of Types
In 1881 the 16-c-p., 110-watt carbon
filament lamp was practically the only size
and type made. A few 55-volt, 8-c-p. lamps
were made, but these were comparatively
unimportant and soon passed away. Later,
10-, 20- and 32-c-p., and then 100-c-p. lamps
were made in small quantities. About the
year 1886 a three-ampere series street lamp
for operation on 1000-volt direct-current
circuits was developed, and shortly afterward
a few styles for alternating-current series
circuits up to 10 amperes were introduced;
but the series carbon lamp was never impor-
tant in street lighting.
Miniature lamps for decorative effects
appeared about 1886, the first lamps of this
kind being made for operation from low-
voltage batteries. Later, 110-volt lamps of
many shapes and sizes, including round bulb
and imitation candle lamps, were produced in
increasing numbers. Among these may be
noted the Christmas tree lamps, which were
modeled to represent colored fruits, flowers,
animals, etc. The number of types of minia-
ture lamps was greatly augmented when the
tungsten filament made them practicable for
automobile lighting and flashlight use; so
that in the year 1914 about 12,000,000 minia-
ture lamps were sold. While today much of
the sign lighting employs standard or large
focus-type lamps, small long-burning sign
lamps are extensively employed for outlining
the letters and designs of signs, building fronts,
etc. Since the perfection of processes for
drawing tungsten wire of very small diameter,
the low-voltage sign lamps are giving way to
110-volt lamps. About 3,000,000 Mazda sign
lamps were sold in 1914.
The tungsten filament, introduced com-
mercially in 1907 and followed in 1911 by the
drawn tungsten wire filament, not only
effected remarkable increases in efficiency, but
very greatly extended the range of sizes and
types. Carbon lamps larger than 32-c-p.
were never very successful, while the small
sizes were very inefficient. With the tungsten
filament both larger and smaller lamps than
those practicable with carbon are successful.
The tiny "grain of wheat" surgical lamp, of
almost immeasurably low candle-power, which
is used to illuminate the stomach in critical
Percent i/ar/ous Classes
Incandescent Lamps
Sold from /905-/9/4-
Total Number lamps forr~eor./oo%
/90S /90G /907 /9oe /909 /9/0 /9ft '9'^ '9/3 /9/-*
HU -Carbon
E3 -Gem
■ - Tan tat ' um
S - Mazda
Fig. 2. Per Cent Various Classes Incandescent Lamps
Sold from 1905 to 1914. Total Number of
Lamps for Year 100 Per Cent
operations, now marks the lower limit. A
considerable number of lamps of 1000 c-p.
and larger are now sold, and special lamps
giving 5000 c-p. have been made. The
indications are that the high power limit will
THE ELECTRIC LAMP INDUSTRY
499
be determined by the commercial demand
and not by limitations in design. The number
of lamps of the different types sold per year
from 1905 to 1914 inclusive, expressed in
percentages, are shown in Fig. 2. In the first
year for which figures are given practically
all the incandescent lamps were of the carbon
type, while in 1914, 70 per cent of all incan-
descent lamps sold in this country were
Mazda.
One of the outcomes of the use of ductile
tungsten wire filaments is the focus type
lamp. The effectiveness of a parabolic
searchlight or of a projecting lens system
depends upon the so-called "point source"
of light, in which all the light emanates from
the nearest practicable approximation of a
dimensionless point. It is possible to wind
a ductile filament into a very small space,
and therefore the usefulness and possibilities
of incandescent searchlights, headlights, stere-
opticon lamps, etc., have been very greatly
increased.
During 1914 a radically new type of lamp
was put in production. These lamps employ
an inert gas instead of a vacuum within the
bulb. They are made in both the series and
multiple types, and in the high power sizes
have efficiencies which not long ago were
almost inconceivable. They are known as
Mazda C lamps.
Therefore this new principle has made it
possible to extend the range of sizes to include
the highest power lamps for which there is
any commercial demand, and today standard
multiple Mazda C lamps cover a range from
100 to 1000 watts. Practically all of the series
incandescent lamps up to and including the
1000-c-p. units are made in this type, and
much higher power lamps, both multiple
and series, have been produced successfully.
Series lamps up to and including 600-c-p.
are made for direct operation on the 6.6 and
7.5-amp. circuits, fed from constant current
transformers. The 400, 600 and 1000-c-p.
units are made for operation on the same
circuits, with a compensator or transformer
at each lamp to step up the current through
the lamp to 20 amp. (in the 400-c-p. the
current is stepped up to 15 amp.). Thus it is
practicable to effectively operate all sizes on
the same circuit.
The great variety of lamp fixtures, housings,
reflectors, globes, etc., that have been pro-
duced to give various distribution of light
with the Mazda lamp, has given us a greater
flexibility of lighting systems than were ever
before attainable.
Efficiency
Mr. Edison's first commercial lamps oper-
ated at eight to the horse power and, while
not so rated, actually consumed 5.8 watts
per candle-power. Subsequent developments
/s — £rr/c/£ncr of Trf/cAL.
/. 7 —
Ca //&££ powe/? pet? Watt |_
/£_ /SS/-/S/S.
S7SO WATT
IMAZOA C
/s -
I , -
$ s -
S" 8 -
$ -
s -
■c —
.3 —
.2 -
./ —
i.oo
(£0 WATT
\AJAZDA
[25 WATT
KMAZOA
[So reow
t Gf"
$ 3> <*1 ^ 0> »j °> °) ^
Fig. 3. Efficiency of Typical Incandescent Lamps.
Candle-power per Watt, 1881-1915
lowered the consumption to 3.1 watts per
candle-power. The many years of extensive
investigation has not shown the possibilities
of improving the efficiency of the carbon
lamp any further.
The metallized carbon filament or Gem
lamp, which appeared in 1905, operated at
2.5 watts per candle-power. In the light of
later developments these lamps seem relatively
inefficient, but at the time this gain in effi-
ciency over the carbon lamp was considered
large, and, in fact, was great in comparison
with corresponding improvements in other
types of electrical apparatus.
The tantalum lamp, which appeared in
1906, was made in a few sizes between 20 and
60 watts, and operated at two watts per
candle-power. It represented a considerable
advance in efficiency, but was followed so
500
GENERAL ELECTRIC REVIEW
closely by the tungsten filament lamp that it
did not have an opportunity of taking an
important place in the industry. The tan-
talum lamp is now obsolete. Its greatest
influence was in connection with lampdevelop-
Thcandescent Camps
Average Cand/e Power, IVatts
and IVatts per Candie Power
/907-/9/4-.
(Weighted Mean)
I
60
in
V)
"
\
Average/
Watts
If
Ave.
Can
die/-
''ok/ei
1
5
Art
• Wa
its p
trCj
/907 /308 /9d9 /9W /9// '9'Z /9/S /9/4
Fig. 4. Incandescent Lamps. Average Candle-power, Watts
and Watts per Candle-power, 1907-1914. (Weighted Mean)
ment. It undoubtedly advanced lamp manu-
facture in bringing out the importance of the
metal filament.
In 1907 the tungsten filament came on the
market, with an immediate jump to 1.25
watts per candle, since which time efficiencies
have increased steadily, reaching the highest
point in the non- vacuum lamps.
At present, vacuum Mazda lamps range in
efficiency around one watt per candle-power,
those of 100 watts or above having a slightly
better efficiency; while with the non-vacuum,
or Mazda C lamps, the low consumption of one-
half watt per candle is commercially realized in
certain sizes and types, with double the
useful burning life that is obtained with the
3.1-watt carbon filament lamp. The efficiency
of the Mazda C lamp, which is largely a
function of the current, varies throughout
the line, the higher current lamps being the
more efficient. The 100-watt multiple Mazda
C lamp is slightly more efficient than the
coresponding vacuum lamp. Smaller sizes
are not made, since under present conditions
they would have no advantage over the
vacuum type. The advance in efficiency as
indicated in candle-power per watt for a few
typical lamps is shown graphically in Fig. 3.
Fig. 4 shows the average candle-power,
watts and watts per candle of all lamps for
the different years since 1907. A slight
falling off in the average wattage will be
noted, due to the rapidly increasing efficiency. .
The increase in wattage for 1914 is due to the
high power Mazda C lamps. Perhaps the
most interesting features brought out by
these curves are the rapid increases in candle-
power and efficiency, which very nearly
correspond.
Another illustration of the remarkable
advance in lamps and other electric apparatus
is shown in Fig. 5. In the early days of the
electric art, lighting generators were rated in
the number of 16-c-p. lamps which they
could supply. Such a rating today would, of
eo
1 I
i :
OAS£ G£-rV£/?*TOIV
/
/
/7
1
/
/s
/
/
\'[
/
1
N
r
,
/
/
/
V.
J
/
/
/
/
/
I
1
\/
/SS4 /dSS /#?£ /S96 '900 /SO* /SOJ 'S'2 '9'6
Fig. 5. Maximum Number of Lamps Giving 16 Candle-power
Supplied from one Generator. Multiple Incandescent
Lamps, 1881-1915. Shows Gain Due to
Increased Capacity of Generators
and Efficiency of Lamps
course, be impracticable, but the curve shows
how remarkably the capacity has increased,
owing to the increased efficiency of lamps and
the increased size of generators. Had the
chart taken into account the efficiency now
THE ELECTRIC LAMP INDUSTRY
501
obtainable with the 1000-watt Mazda lamps,
the equivalent multiple of 16 c-p. obtainable
with a single generator during 1914 would
have been over twice as great.
/L/sr s^ff/c^s
TrP/c<tt- Mazoa t-A/*t*s.
/SO 7- /9/S.
7-
6—
Z—
\ r/aooWArr
\#r*zoA c
rk:
Fig. 6. List Prices Typical Mazda Lamps, 1907-1915
Manufacture
In the early years of the industry it was
necessary to employ much skilled labor. All
the glass work was done by experienced glass
blowers, who received high wages. Through
constant study and experimenting, processes
have been developed and special machines
designed and built, so that better and more
uniform work is performed by the unskilled
operator than was formerly possible by the
best skilled labor. Furthermore, in spite of
the large number of types, the number of
lamps made per operator is now several times
what it was 25 years ago. Practically all the
lamp making machinery used in the world
has been developed in the American lamp
factories and the laboratories of the General
Electric Company.
The carbon filament incandescent lamp was
developed by Thomas Alva Edison. The
production of a practical commercial lamp
involved a world-wide search for materials,
and comprehensive experimental investiga-
tions which would have discouraged any but
the most persistent. The improvement of the
incandescent lamp has been the object of
more extensive exhaustive study than almost
any other article of commerce. In the year
1914 about 60,000 incandescent lamps were
destroyed in the life tests of the General
Electric Company's engineering organizations,
to determine the value of proposed variations
of construction. And when we consider that a
lamp throughout its life consumes in electric
current several times its cost, we obtain some
idea of the cost of this one element of invisible
service by which the lamp has been brought to
its present state of perfection.
Of recent years the scientific development
of the lamp has been carried on in the research
laboratory at Schenectady, where an organized
force of specialists, both chemists and phy-
sicists, are engaged in research and develop-
ers^ of E/ectr/c Current
onof
/.amp f?er)ot^o/s
for
/00,000 Cond/e Potver - Hours
/set - /9/5~.
i Cost of f.0m/> frenei~0/s ot
•Staio'aro' Poc/roge fr'ees.
Cost of £~/ectr/c Current.
Fig. 7. Cost of Electric Current and Lamp Renewals for
100,000 Candle-power Hours, 1881-1915
ment. The drawn tungsten filament and the
gas-filled principle are among the notable
inventions made in this laboratory. Such
inventions are applied to the practical con-
ditions of lamp manufacture for various
502
GENERAL ELECTRIC REVIEW
I
75-
70-
%65-
^ 60-
%
%55~
\50-
%
\45~
%40-
|*.
^5"
•s-
0-
5-
\
'■1
ll
/88d 1890 1902 /90£ /906 1907 /90d 19/0 19/3 /9/5
'389 /90/ I90A /909 /9/2 /9/4-
Fig. 8. Decrease in the Cost of Electric Light in New York City,
Resulting from Improvements in the Efficiency of
Incandescent Lamps and from Reductions in
the Rates Charged for Electrical Energy
20-
19-
/S
a-
7
Cost of Current J- /Pe-rtct-iStt/s
for /0O,OOO Car>c/{& >°<ji^tf>r-- /-/ours
v*it*t Ifar/ous J~r>CQr?di?scen£ Lamps
/Qpnf J9J5~.
Current G>&tp£>r /ft^Ar
Lamps at Standard f^acrfa^e f*r/ces
WLCoSt of Lamp ffenewals
o „ » 9) * i")
!i ■* -8 -8 $ o
5 S g « o -8
jiUll
* ** s ^ £ ^
u
-
Fig. 10. Cost of Current and Renewals for 100,000 Candle-
Power Hours with Various Incandescent Lamps, April, 1915.
Current at 8 Cents per Kw-hr. Lamps at Standard
Package Prices
types and sizes of lamps by the lamp engineer-
ing departments, which, with their develop-
mental laboratories, stand between the
research laboratory and the lamp factories.
In this highly organized industry manu-
factories are required, each of which makes
only a few types of lamps. Each factory
receives full detailed instructions from the
engineering department.
Cost
The increasing number of lamps, together
with the many improvements in manufactur-
ing methods, has resulted in steadily decreas-
ing costs, which in turn have resulted in
remarkable reductions in lamp prices. In
addition, the increased efficiency of lamps and
gradual reduction in the cost of electric
current have combined to very materially
lessen the cost of electric light. These tend-
encies are shown in Figs. 6 to 8.
400—
350-
3.00-
2. so -
0
/.amp /fenewai Cost for
\ /00,a<2a Candce/^otver- Hours
/SO/-/9/S.
60 h/att Mazda * Car 6 on
/,amps.J3ased on Standard
rr,ac/ra<fe> r^rtces.
eoo-
/.50-
/.OO-
.SO
S
S3
53
5
^
"5 s*-
S I $
K & °i
S> 5 ^
^ ^ Oj
Fig. 9. Lamp Renewal Cost for 100,000 Candle-Power Hours
1907-1915. 60-Watt Mazda and Carbon Lamps.
Based on Standard Package Prices
THE ELECTRIC LAMP INDUSTRY
503
Fig. 6 shows the reduction in price since
their standardization of a few typical Mazda
lamps.
In Fig. 7 are shown costs from 1881 to
date, of current and lamp renewals for pro-
ducing 100,000 candle-power-hours with the
most economical form of incandescent lamp
available, as indicated.
While the summation of these values does
not necessarily give the total cost of produc-
ing light, it makes a very interesting •com-
parison and fairly well indicates the rate of
decrease in lighting costs as the result of the
increased efficiency of lamps, increased life
of lamps, reduction in cost of lamps per
candle-power, and lastly the reduced cost of
electric current.
How much of this is due to lamp economies
is apparent when we note that, with the
assumed price of current in 1914 as 40 per
cent of that for 1881, the cost of current and
renewals is only 5 per cent of the original cost.
As a practical illustration of this point,
Fig. 8 showing the cost of 100 candle-power-
hours in New York Citv at the maximum rate
charged, is presented through the courtesy
of the New York Edison Company.
The first tungsten filament lamps were used
because of their current economy, and in
spite of the higher renewal cost. Now, even
with the moderate size lamps, the lamp
renewal cost alone usually figures less per
candle-power-hour than the carbon lamp.
This fact was brought out by a comparison of
the renewal cost of 60- watt Mazda and carbon
lamps, as shown in Fig. 9.
Fig. 10 shows the variation of lighting costs
between the different types of multiple lamps
available at the present time. In this chart
the cost of lamp renewals is indicated by the
ruled sections, the cost of current by the
clear sections, and the consumption is shown
by the total height of the ordinates.
It is not safe to make definite predictions
for the future, but the tendencies indicated
by the various curves are significant, especially
as the increasing appreciation of electric
light is furnishing incentive to the manu-
facturers to extend their efforts in producing
the most perfect lamps possible.
504 GENERAL ELECTRIC REVIEW
ELECTRICITY IN MARINE WORK
By Maxwell W. Day
Engineer Marine Department, General Electric Company
The applications of electricity on land have increased so rapidly in scope and in number that they are now
solidly established and are regarded as being thoroughly indispensable. On shipboard the applications are not
as numerous or various as on land, because maritime conditions have not demanded them. Nevertheless,
most readers of this comprehensive article will doubtlessly be surprised to learn through it of the already
extensive use to which electricity is put in marine work. — Editor.
The use of electric generators on shipboard
was at first limited to supplying lights and
searchlights and required comparatively small
installations, but the advantage of electric
operation of mechanical auxiliaries was soon
recognized and with the Kearsage and
Kentucky battleships, which were launched in
1898, the extended use of electrically driven
auxiliaries began. Previous to this,
electric motors had been used in small
numbers for ammunition hoists and
for turning two of the turrets of the
cruiser Brooklyn, which was launched
in 1895. Equipments for similar pur-
poses had been installed in Europe at
about the same time, but the Kearsage
and Kentucky were the first in which
the advantages of electrical operation
were more fully considered. Besides
the large number of electrical auxili-
aries on the Kearsage and Kentucky
several others have been added on the
later vessels until now the electrical
plant of a modern battleship is large
and complicated, including the light-
ing, many kinds of signaling devices
and a large variety of motor-driven
auxiliaries. For commercial work
electricity is used to a much smaller
extent, but on the transatlantic liners
large electric plants are used, which
include a large number of motor-
driven machines.
Because of moisture, special con-
struction is used; both on account of
securing water-tightness and resist-
ance to corrosion and due to the roll-
ing of the ship, the bearings are
specially designed to prevent the oil
from being spilt out or -'ater being
taken in.
Generating Plant
The generating plant varies in size from
about 2 kw. on very small vessels to 800 kw.
on large passenger steamers, and 1500 kw.
on some of the largest battleships.
For the small generating sets reciprocating
steam engines direct connected to the gener-
ators are generally used; for the intermediate
sizes either reciprocating engines or steam tur-
bines, and for the large sizes steam turbines.
The reciprocating sets are required to be
as compact and light as is consistent with
good design and enclosed engines with
Fig. 1. Generating Set with 9-In. by 7-In.
Forced Lubrication Engine
forced lubricationTare recommended. Abso-
lute reliability, durability of wearing parts,
ready accessibility, and freedom from vibra-
tion are important requirements.
Fig. 1 illustrates a reciprocating generating
set with 9-in. by 7-in. engine using forced
ELECTRICITY IN MARINE WORK
505
lubrication, its rating is 25 kw. 400 r.p.m.
110 volts to 125 volts. The internal con-
struction is shown in Fig. 2. This set has a
single cylinder with a piston valve; the
governor enclosed in crank case, and an oil
pump, driven by an eccentric, distributing
oil to the various bearings. For navy use
these sets are required to run without lubri-
cation in the steam spaces in order to avoid
oil in the boilers and special provision is
made to prevent the oil being carried by the
piston rod into the cylinder. These sets
Fig. 2.
Sectional View of Steam Engine showing
Lubricating Mechanism
may be operated either condensing or non-
condensing. The governor is of the Rites
inertia type designed for close regulation.
The single cylinder sets are built in various
sizes up to 50 or 60 kw.
In order to obtain a better steam economy,
tandem or cross-compound sets are sometimes
used, especially in the larger sizes. While
reciprocating sets are largely employed on
commercial vessels, most naval vessels are
Fig. 3. 300-Kw. Turbo-Generator
equipped with turbo-generating sets on
account of compactness, weight, and better
steam economy in the larger sizes. The
turbine sets are built in sizes from 5 to 375
kw.
Fig. 3 shows a 300-kw. set as frequently
used on naval vessels, operating at 125 volts,
1500 r.p.m. and at 200 lb. steam pressure,
condensing. On account of the large amount
of current these generators are provided with
two commutators, but for 250 volts only one
commutator is used as in the case of the
375-kw. generating set for the Argentine
dreadnoughts.
The turbines for the sets shown are of the
Curtis type and are provided with a sensitive
governor designed for close regulation. The
generators are compound wound adjusted
for flat compounding and are provided with
commutating poles. The saving in weight
by the use of turbines is shown by a com-
parison of the 25-kw. navy set the permissible
weight of which is 4300 lb. in the case of the
turbo set, and 7300 lb. for a reciprocating,
25-kw. set running at 400 r.p.m.
The governing is accomplished by different
methods in the various types and sizes. In
the smaller sizes a centrifugal governor of the
throttling type controls the supply of steam
but in the larger sizes groups of nozzles are
provided with individual valves and the
governor is so arranged, either by mechanical
or hydraulic means, that the proper number
of valves are opened to give the required
supply of steam as this gives a better steam
economy than to admit throttled steam to all
of the nozzles. In the case of the hydraulic
506
GENERAL ELECTRIC REVIEW
governor a small pilot valve is operated by a
centrifugal governor which controls the supply
of oil under pressure to a cylinder, the piston
of which operates a cam shaft, each cam
controlling one of the valves. On light loads
■ffmirt
r rTT-ttTi
w*m%
Fig. 4. Generator and Distribution Switchboard
most of the valves are closed, one valve may
be wide open and the next valve partly open.
As the load increases the cam shaft is rotated
by means of the hydraulic device and more
valves are opened.
With the mechanical type of governor
the valves are either entirely open or entirely
closed. On light loads most of the valves
are closed, one may be entirely opened and
the next one intermittently opened and
closed. Thus, if the load requires but slightly
more steam than that furnished by one
valve, the next valve may be open a short
portion of the time and closed a greater
portion of the time, but if the load requires
nearly as much steam as two valves supply,
the second will be open a large portion of the
time and closed a short portion of the time.
The oil is fed to the bearings under pressure
from a pump which also supplies the oil for
operating the governor when hydraulic gover-
nor is used. The bearings are cooled either
by a pipe carrying water in the bearings
themselves, or by carrying the oil through
a cooler.
The large sets are usually operated con-
densing but provision is usually made for
non-condensing operation. On some small
naval vessels using small turbines the sets
are frequently furnished for non-condensing
operation and the steam is discharged into
the feed water heater at considerable pressure
above atmosphere, and if required an auxiliary
hand valve is used to give the increased flow
of steam.
It is the practice in large war vessels to
provide four generators, two in each of two
separate dynamo rooms. This is considered
desirable for military reasons, as the disable-
ment of one dynamo room will not put the
entire electric plant out of commission.
Switchboards
In some plants the generator and feeder
panels are combined into one switchboard,
but in the largest vessels the generator
switchboards are sometimes separate from
the distribution feeder switchboard.
Fig. 4 shows the front view and Fig. 5
shows the back view of a distribution switch-
board installed on a modern battleship. The
center panel is the generator panel and
receives the current from two generators
and contains the instruments, circuit breakers,
and switches for connecting either or both
generators to the busbars of the switchboard.
The feeder circuits of large capacity are led
out through circuit breakers, while the
smaller circuits are provided with double-pole
fused switches.
According to American practice the switch-
board panels are of slate mounted on rigid
angle iron supports and sometimes cushioned
with rubber to prevent breakage. In Europe
many of the switchboards are made of steel
with the switches and instruments insulated
from it. In this country the generators are
generally run in parallel while in foreign
countries the practice differs, some boards
being arranged on a selective system, so that
certain circuits can be put on one of the
generators but no two generators are operated
in parallel.
In addition to the main switchboards as
shown, smaller boards are frequently used
in various parts of the ship for distributing
the current to motors and other auxiliaries
in the vicinity, and cabinets are frequently
provided with several small switches for
controlling the various lighting circuits.
Cables
On account of moisture the cables and the
fittings to which they are connected are
designed with special reference to moisture
resisting qualities. The cables are insulated
with a high grade of rubber protected by-
suitable braid, and in some cases by lead
and steel armor also. It was formerly the
practice in war vessels to install cables very
extensively in metal conduits but in recent
years the use of leaded cables protected with
steel braided armor has been adopted and
is now being quite extensively used. This
latter type of cable is convenient for instal-
ELECTRICITY IN MARINE WORK
507
lation and is fairly flexible, so that it can be
readily made to conform to the places in
which it is to be installed. Where cables are
carried through watertight bulkheads, water-
tight stuffing tubes are used. These cables
are usually attached to the bulkhead or
decks by means of metal cleats or bands,
and where it is necessary to cross beams, they
are carried through holes drilled near the
neutral axis.
For commercial work unarmored cable is
frequently carried through wooden moldings,
especially in places where a neat appearance
is desired, but in foreign countries the leaded
and armored cable is extensively used for
merchant work, as well as for the navy.
It is American practice to make all the
circuits double-pole, but in Europe a large
number of merchant vessels are equipped
with the single-wire system, in which the
ship itself is used as a common return for all
circuits. This method very much simplifies
the switchboard, as there is only one switch
to each feeder and reduces the amount of
cable to about one-half.
Wiring Fittings
Various junction boxes and switches are
required, which are of watertight construction
and consist of boxes made of composition
material supplied with stuffing tubes or in
the case of conduit with tapped holes for the
reception of the conduit, and the cover is
made watertight by a rubber gasket. The
covers in some cases are fastened with screws
and in some cases are threaded so as to be
screwed into place. In Germany boxes with
a hinged cover closed by a lever and cams are
frequently used and this quick closing device
has recently been used to some extent on ves-
sels built in the United States. Some of these
boxes are provided with a lock so that they
cannot be opened by unauthorized persons.
Lighting Fixtures
The various fixtures for the lamps are of
special design on account of the water-
tightness required, the vibration of the ship
and for protection from external injuries.
Lamps in exposed places are covered by
glass globes made watertight in the fixture
and the globes are protected by a guard.
Lamps in magazines require extra careful
protection and special enclosing cases for the
lamps are provided for this purpose. A large
number of portable lamps are used as well as
cargo lamps provided with reflectors and
specially protected lamps are used for divers.
On warships a special battle circuit is
provided independent from the general illumi-
nation and in some foreign ships blue lamps
are used for this purpose. Incandescent lamps
are employed for nearly all of this work,
Fig. 5. Generator and Distribution Switchboard, Back View
but in a few open spaces, such as the engine
rooms, use has been made of enclosed arc
lamps.
Signaling and Interior Communication Devices
The various signal lamps required by ships
at anchor or under way are electrically lighted
and the circuits for these are carried through
a special telltale board which will give an
indication if any of these lamps are out. For
signaling from ship to ship a night signal set
is provided on warships, consisting of four
double lanterns, one-half red and one-half
white, hung on a wire cable from the mast
and a specially designed keyboard is provided
with different push buttons corresponding to
different letters of the alphabet or other
desired signals. By pressing one of these
push buttons a combination of lights is
shown, consisting of a certain number of
white, a certain number of red, or a combina-
50S
GENERAL ELECTRIC REVIEW
tion of white and red which can be seen
from other vessels.
A single white light at the top of the mast
is also used for this purpose and the light
can be worked by a telegraph key, thus
making the dots and dashes of the Morse,
or other similar code.
For communication inside of the ship
various systems are in use. The communica-
tion from the bridge to the engine room,
steering flat, and for other similar purposes,
is very largely carried on by means of mechan-
ically operated telegraphs or by speaking
tubes, or by electric telephones, but the
electric signal method is coming into use more
and more and is at present quite extensively
used on foreign vessels. For the operation
of these systems various synchronous devices
are used so that by turning a lever or indi-
cating arm in the pilot house or central
station a similar signal is shown in the engine
room or in the steering flat, and when this is
answered from those stations an indicator
at the sending station shows that the signal
has been received. A revolution indicator
is often attached to each propeller shaft.
In many cases this consists of a small gener-
ator driven by the shaft, which operates a
voltmeter or frequency indicator in the pilot
house, so that the speed of each screw can be
readily noted. The engine room telegraph
indicates at what speed the ship should be
run in either direction.
In some cases fire room timing devices are
used to indicate the time and order of firing
the different boilers. This apparatus is
operated by a clock or similar device which
can be set at a predetermined rate of firing.
This insures regular and careful firing of the
entire steam plant.
The rudder telegraph is used in case there
is any disarrangement of the regular steering
apparatus when it becomes necessary to
transmit the orders for the movement of the
rudder to the steering flat itself. Also rudder
indicators are used which show in the pilot
house the position of the rudder in degrees
cither side of the midline.
Where power-operated, watertight bulk-
head doors are used, an indicator is provided
to show at the pilot house or other convenient
location whether the different doors are closed
or open. The use of all of these various devices
operated by electricity is not by any means
universal, but the largest and best passenger
ships are very largely equipped with this
apparatus. On warships the transmission of
orders for the ordnance is of very great
importance and electrical arrangements are
made for transmitting the range and deflection
of the various guns, so that they can be
pointed properly and orders given when the
gun should be fired. Lights are provided for
illuminating the sights of the guns and the
firing of the fuses is done electrically by
current from storage batteries, or static
transformers supplied by special alternating
current generators or rotary converters.
The turrets are also provided with danger
zone indicators to give warning when the
turret is turned so far that it might interfere
with another turret or with some other part
of the ship's structure.
Another important class of apparatus of
this character consists of the telephone, call-
bell, and fire alarm systems which differ from
land installations in being made thoroughly
watertight and in many cases a specially
designed loud speaking telephone is used.
On some vessels an alarm system is pro-
vided by which an alarm bell will be sounded
by closing a switch on the bridge when a
man falls overboard, so that life buoys can
be immediately thrown out and in some
cases the electric circuit is arranged to
automatically release the life buoy and drop
it into the water.
One of the most important systems of
signaling used on shipboard is the radio
telegraph, and this has become so important
that it has been the subject of International
Conferences and National Regulations.
This apparatus usually consists of one or
more motor-generator sets, even as large as
10 kw. in some of the largest vessels, giving a
range of transmission of many hundred miles.
With the motor-generator is supplied a
suitable switchboard for starting the motor-
generator set, and for making necessary
connections to the other parts of the appa-
ratus.
One of the most recent applications of
electricity for marine purposes is its use for
submarine signaling. The early history of
submarine signaling includes the develop-
ment of submarine bells for sending out the
signals from a buoy or light-ship, and the
development of electrical apparatus for receiv-
ing these signals on board ships. The more
recent development has been that in which
the apparatus for sending out the signals
electrically has been perfected by Prof. R. A.
Fessenden.
This device, manufactured by the Subma-
rine Signal Company of Boston is essentially
a large telephone diaphragm submerged either
ELECTRICITY IN MARINE WORK
509
by hanging it over the side of the ship
or by actually including it in the ship's
skin. This large telephone transmitter,
called the "oscillator," delivers powerful
impulses to the surrounding water, and in
order to make these impulses, when received,
readily audible, a frequency of approxi-
mately 500 cycles per second is used.
The diaphragm of the oscillator is set in
motion by the interaction of currents induced
in a copper tube, with a constant magnetic
flux passing through this tube. The tube is
mechanically fastened to the diaphragm itself.
The 500-cycle alternating current is passed
through windings around a stationary core
inside the tube, while the electromagnet
producing the constant magnetic flux is
concentric with, and outside of, the tube.
The signal is sent out by making and
breaking the alternating current passing
around the core, and of course in any one
signal there are many impulses of a frequency
of 500 in each direction per second imparted
to the water. On reaching a distant receiver,
which may be an exact duplicate of the
oscillator, or a much smaller diaphragm, these
impulses are used to effect changes of current
in an ordinary telephone receiver and hence
made audible at the receiving end.
By using an arrangement of two or more of
these oscillators, as one on either side of the
ship, means are provided for giving the exact
location of a ship, inasmuch as a receiving
vessel can change its course until the strength
of signals received are equal in both receivers,
when it will be known that the sending vessel
or station is dead ahead.
The apparatus for supplying the 500-cycle
current may be a motor-generator set of the
ordinary type. However, a dynamotor has
been developed which fulfills the require-
ments while weighing less than a motor-
generator set and having considerably smaller
dimensions. This dynamotor consists of a
d-c. armature of the ordinary type, revolving
in a d-c. field. In slots in the pole faces of the
d-c. field the alternating winding is placed
and by means of the variation in magnetic
flux caused by the teeth of the d-c. armature
the 500-cycle current is generated in this
winding. This type of construction allows the
use of the ordinary motor frames and most
of the other standard parts of motors.
The inherent feature of the dynamotor,
that the voltage and frequency can not be
varied independently, is not objectionable
for its use with the oscillator described above ;
as this oscillator has a power-factor of
practically unity, the voltage regulation of
the dynamotor is very good.
Up to the present time the navy depart-
ment has been the most active in applying
the oscillator to its ships, but it seems that
Fig. 6. 36-Inch Electrically Controlled Searchlight
the time is not far distant when merchant
vessels, as well as naval vessels, will be
equipped with this apparatus.
The general design of the apparatus
supplied, such as the dynamotor and control
equipment, must, of course, conform to the
usual requirements of apparatus used on
board ship.
Searchlights
Practically all war vessels, and many
commercial vessels are equipped with search-
lights. The number of these lights on some
large war vessels has been as high as 16, but
in many only four are used. For the large
vessels these usually have mirrors of 36-in.
in diameter. The mirror is made of glass
carefully ground to a parabolic shape and
silvered on the back surface. This mirror is
enclosed in a large barrel which also contains
the lamp. Fig. 6 shows a view of a 36-in.
electrically controlled searchlight. The barrel
is mounted on trunnions carried on two side
arms which are supported from a revolving
turn-table, this turn-table being supported
on a fixed base. Small searchlights are con-
trolled by hand and large searchlights either
by hand or electrically. In the electrically
510
GENERAL ELECTRIC REVIEW
controlled searchlight a controller is located
in a suitable place and connected, by a cable
containing several wires, to the controller
cable plug in the base of the searchlight. The
controller may be made portable and can be
carried around to any convenient location
which can be reached by the flexible cable
connecting it to the searchlight.
In some forms of controller two small
handwheels are provided and the searchlight
will turn around the tum-table in a horizontal
direction as long as the horizontal handwheel
of the controller is turned, and a certain
number of revolutions of the controller
handwheel corresponds to a definite number
of degrees of movement of the searchlight.
In a similar way the rotation of the vertical
handwheel of the controller will cause the
searchlight to move up or down a definite
number of degrees corresponding to the
amount of rotation of the controller hand-
wheel. These movements are accomplished
by small motors located in the turn-table
and controlled by a synchronous controller
operated electrically from the main con-
troller. By turning the handwheel of the
controller a small amount, electric connection
is made to the small motor in the searchlight
and after it has turned the searchlight to an
amount corresponding to the movement of
the controller handwheel, the current is auto-
matically cut off and the searchlight stops.
By continuing the motion of the handwheel
the searchlight will continue to move.
Disengaging clutches are provided by
which the electric control can be disconnected
and then the searchlight can be moved by
handwheels located on the side arms, as
shown in the illustration.
The front of the barrel is provided with a
glass cover consisting of vertical strips. These
narrow strips are less subject to breaking on
account of the heat of the lamp and to the
mechanical vibration of the ship than would
be the case with a solid disk of glass.
In many cases these lights are provided
with a shutter usually of the iris type, some-
what similar to those used in cameras, so
that when it is desired to shut off the light
for military reasons without disconnecting the
current supply, the shutter can be readily
closed.
Searchlights can be readily used for signal-
ing at sea by throwing the beam at a high
elevation and then interrupting it and
breaking it up in dots and dashes by a quick
closing shutter, usually of the Venetian blind
type.
The lamp consists of two carbons located
horizontally with the negative carbon toward
the mirror. This allows the light from the
positive crater to be thrown against the
mirror from which it is reflected forward in a
nearly parallel beam. The negative carbon
and its support should be made as small as
practicable in order to prevent, as far as
possible, obstruction of the light from the
positive carbon.
If the light were to issue from a point the
beam would be cylindrical, but inasmuch as
the crater of the positive carbon has an
appreciable diameter the beam is thrown out
in a diverging cone, the angle of which is
quite small and depends upon the relation
of the diameter of the crater to the focal
length of the mirror.
The lamp mechanism is located at the
bottom of the barrel and contains two
upright supports to carry the carbons. These
supports are moved toward each other as the
carbons burn away, either by means of a
small motor or by a magnet operating
through a ratchet on a screw. The operation
of the motor or of the magnet depends
principally upon the voltage of the arc which
increases as the carbons burn away.
An electric device is also provided for
striking the two carbons together and immedi-
ately pulling them a short distance apart to
start the arc when the current is turned on
the searchlight. The voltage of the arc
varies from 45 to 65 in various sizes
but the lamps will burn very unsteadily if
supplied with a constant potential of this
amount, and it is therefore necessary to
operate the searchlights at a higher volt-
age— not less than 80 — using a steadying
rheostat in the circuit. It is customary to
operate the searchlights at 110 to 125 volts,
corresponding to the voltage of the lighting
system of the vessel, and of course, a consider-
able amount of energy is dissipated in heat
from this rheostat. Arrangements are pro-
vided to disconnect the electric control of the
arc and use hand adjustment if desired.
For the purpose of properly observing the
condition of the arc a small side sight is
provided, consisting of a hole in the side of
the barrel covered by a colored glass which
allows the operator to look directly at the arc.
In order to avoid the loss of energy in the
rheostat, especially on vessels of 220 volts,
motor-generators or compensators have been
built which furnish current to the searchlight
with a drooping characteristic of voltage
instead of a constant potential. With this
ELECTRICITY IN MARINE WORK
511
design of generator the voltage will drop very
considerably in case of an abnormal increase
of current and will rise considerably in case
of a reduction of current. In this way the
current can be turned on the searchlight
with the carbons in contact without obtaining
a dangerous rush of current and this current
will immediately pull the carbons into the
proper condition for operating; but few of
these have been installed in the United States.
A compensator using one armature has been
used to some extent in England and motor-
generators either of this type without a
rheostat or of a constant potential type with
a rheostat, have been used considerably in
Germany.
Many of the German type are constructed
so that the shaft is vertical and can be readily
supported from the deck above, and in this
way take up but little valuable space.
In some vessels using a 250-volt generating
plant, a balancer set has been used, consisting
of two 125-volt dynamos direct connected.
These are connected in series across the
250-volt lights and a neutral is taken out
between them giving 125 volts on each side.
In this arrangement some of the searchlights
are connected on one side of the circuit and
the rest of them are connected on the other.
This method was used on the Argentine
dreadnoughts built in this country. These
ships were each provided with 12 searchlights
43.3-in. diameter and one of 13.8-in. diameter
for signaling, all made by the Siemens-
Schuckert Works.
A special type of searchlight has been built
for vessels making use of the Suez Canal.
These lights have special diverging glass
strips which deflect the light to each side and
leave a dark space ahead. This is done in
order to light both banks of the canal without
blinding the pilots of approaching vessels.
Cooking and Heating
The very convenient control of electric
heaters has led to their use for heating
staterooms, and several vessels have been
equipped with a large number of electric
ovens and ranges. These cooking devices
have the advantages of cleanliness, safety
and convenience of operation, besides obtain-
ing a uniform and very satisfactory product.
Power Equipment
By far the greatest amount of electric
energy is used for the operation of the various
auxiliary machines. The advantage of electric
operation of auxiliaries is due largely to the
simplicity of control, the small amount of
attention required, and the avoidance of
heavy steam pipes with consequent condensa-
tion of steam and the heating of living spaces.
The electric apparatus is also ready to operate
as soon as the switches are closed and it is not
necessary to warm up the apparatus and
get rid of the water of condensation.
The use of electric auxiliary machinery is
very much more extensive on war vessels
than on commercial vessels, as on these ships
convenience and reliability of operation are
considered of greater importance than the
first cost.
Steering Gear
The largest electric equipment on a large
ship is the steering gear, although very few
ships make use of electricity for operating
this gear. This apparatus has received at-
tention from electrical engineers for many
years, and various systems have been designed
both in Europe and the United States. In
some of these in the smaller sizes, magnetic
clutches have been proposed which connect
the motor to the rudder mechanism for either
direction of motion as desired. On others,
motors have been operated by rheostats in
the circuit or by controlling the field of a
special generator supplying current to the
steering motor. Several of the latter type
operating on the Pfatischer system have been
used on Russian war vessels and on several
American commercial vessels. This system
is controlled on the Wheatstone bridge
principle. A suitable rheostat connected to
the two mains is operated by the steering
wheel and another similar rheostat is operated
by the rudder mechanism. The line con-
necting the two switch arms is taken to the
field of a small exciter and the armature cur-
rent from the exciter is taken to the field of a
generator which may be driven either by a
steam engine or an electric motor. The
armature current of this generator is taken
to the armature of the steering motor. When
the steering wheel and the rudder are both
in the midship position the switch arms
connect the middle points of the two rheostats,
in which case the Wheatstone bridge is
balanced and no current passes through the
field of the exciter.
When the steering wheel is moved to one
side the switch arm is moved from the rheostat
contacts toward one main line and current
now passes through the field of the exciter.
This produces a current in the steering motor
which moves the rudder. This movemen
512
GENERAL ELECTRIC REVIEW
of the rudder actuates the switch arm of its
rheostat toward the same line toward which
the steering wheel has moved the other switch
arm, and when the rudder has moved to a
position corresponding to the position of the
steering wheel, the Wheat stone bridge is
again balanced, no current passes through the
exciter field, and the steering motor is brought
to rest.
This method provides a follow-up device
and the method of steering is the same as
used with the steam gear in which a definite
movement of the steering wheel results in a
corresponding movement of the rudder.
When it is desired to move the rudder in the
other direction, the steering wheel switch
arm is moved toward the other main line and
current now passes through the exciter field
opposite to the previous direction, and the
polarity of the generator and consequently
the direction of rotation of the motor is
reversed.
The steering gear motor is shunt wound
and excited by the same circuit that supplies
current to the rudder rheostat.
Some of the United States cruisers have
been provided with a rheostatic system in
which the steering motor is fed directly from
the ship's mains without the use of a separate
generator and the motor is reversed, started,
and controlled in speed by means of a con-
tactor control panel, the secondary circuits
of which are controlled by the steering con-
troller or switch.
One of these equipments was provided with
a follow-up device so that a definite movement
of the steering wheel would result in a
definite movement of the rudder, but it has
been found more satisfactory to dispense
with the follow-up device and operate the
contactor control panel by means of two-
speed master switches in the pilot house and
other steering stations. In this system a
movement of the switch lever to the first
point in either direction will cause the motor
to turn the rudder in that direction as long
as the switch lever is held in that position
unless the lever is kept in this position until
the rudder reaches the limit of its motion,
when an automatic limit switch cuts off the
current and stops the motor.
In this position of the switch lever, the
motor operates at a comparatively low speed
but if the switch lever be turned to the second
position the motor will operate at full speed.
Some large vessels have been equipped
with this system each making use of a 150-h.p.
motor, designed to move the rudder from
hardover to hardover, — an angle of 70 deg.
in about 40 sec, where the steam steering
gear is required to make this movement in
20 sec. Two of these equipments were
provided with non-follow-up control as men-
tioned above, and two others were provided
with a follow-up control. This controller con-
tained a cylinder driven by planetary gearing,
one set of gears being connected to the rudder
mechanism and the other set being operated
by the hydraulic telemotor or a Hanscom
drum used with the steam steering gear. By
this arrangement a certain movement of the
steering wheel moves the controller cylinder
in the desired direction, and as the rudder
itself is moved by the motor, the controller
is turned off and the motor stopped, so that
the total movement of the rudder corresponds
to the total movement of the steering wheel.
On a later vessel, where the electric gear is
required to make this movement in 20 sec,
two 150-h.p. motors are used, so arranged
that they may be connected either in series
or parallel.
Another arrangement making use of a
separate motor-generator working on the
Ward Leonard principle has been adopted
for several of the latest vessels. This system
avoids the use of a large number of contactors
for controlling, and makes the requirements
on the power station less severe as the load is
applied more gradually.
The equipment for moving and controlling
the rudder under the Ward Leonard non-
follow-up system consists of a steering gear
motor connected to the rudder by means of
the mechanical arrangements generally used
with steam engine, a motor-generator set,
controlling panel, steering stands, selective
switch and limit switch. The speed of the
steering gear motor is controlled by varying
the field strength of the generator, as is usual
with the Ward Leonard system.
In these equipments, this motor was rated
350 h. p., with 700 h.p. for short intervals, at a
speed of 250 r.p.m. at 250 volts. In order to
decrease the power required at extreme loads,
this motor is provided with a series field in
series with the armature of the driving motor
on the motor-generator set. In this way the
torque per ampere of the steering gear motor
is increased with the load. As the voltage
on the armature of the motor is reversed to
reverse the direction of rotation, it is not
possible to put this series field in series with
the armature in the usual manner. To
accentuate the same increase of torque per
ampere, on very extreme overloads the shunt
ELECTRICITY IN MARINE WORK
513
field of this motor is increased by means of a
relay.
The motor-generator set used with the
above motor has a generator rated at 290 kw.
at a speed of 1000 r.p.m., when it delivers
250 volts to the steering gear motor. The
driving motor takes its power from the ship's
mains at 120 or 230 volts. The generator is
provided with a differential compound wound
winding, so that at extreme overloads the
voltage on the generator will be reduced in
order to reduce the power demanded of the
ship's generating equipment. Also, the driv-
ing motor is arranged with a drooping speed
characteristic in order that the kinetic energy
stored in its armature may be utilized
under the heavy load conditions.
The controlling panel contains the neces-
sary contactors for starting the motor-
generator set as well as an ammeter to show
the input into the driving motor. It also
contains the necessary switches, the relay for
strengthening the steering gear motor shunt
field and an overload relay for limiting
such overloads as would otherwise injure
the apparatus.
In order to notify the attendant in case
the set should be shut down, due to failure of
voltage, a circuit is arranged to ring a bell
on such failure of voltage. The motor-
generator set is also protected from excessive
speed by means of a speed limiting device
on its shaft.
The selective switch is simply a device for
connecting the various controlling circuits
to the particular steering stand which it is
desired to use at any time. In the equipment
described there are four of these steering:
Fig. 7. Steering Gear Motor-Generator Set
stands; one on the bridge, the conning
tower, the central station and in the steer-
ing gear room.
The steering stands are of watertight
construction, made of non-magnetic materials
in order not to influence the magnetic com-
passes and they provide three speed positions
in each direction; in the first the field of the
generator is excited to give a low voltage for
slow speed of the steering gear motor, the
Fig. 8. Steering Gear Motor
next step strengthens the field and the last
fully excites it.
The excitation for the generator is carried
through the limit switch, which is operated
by the steering gear in case of over-travel
in order to cut off the power under such
conditions. This is accomplished without
interfering with the return motion after the
voltage is reversed at the steering stand.
This system is primarily designed to meet
the same quick movement of rudder as is
accomplished by the steam engine and yet
to hold the demand on the power plant of the
ship down to a reasonable value by means
of using high speeds at light loads and storing
energy in the rotating element of the motor-
generator set to be removed at heavy loads.
Figs. 7, 8 and 9 show the motor-generator
set, steering gear motor, and control panel
of one of these equipments.
The use of internal combustion engines for
propelling vessels is leading to a more exten-
sive use of electric auxiliaries and several
of these vessels have been equipped with an
English system of steering gear, in which an
oil pump is operated continuously by means
of an electric motor. The displacement of
the pump and the volume and direction of oil
514
GENERAL ELECTRIC REVIEW
delivered can be changed by suitable con-
nections from the pilot house. The oil is
delivered into two cylinders operating plun-
gers or pistons which move the rudder. This
apparatus is said to give very satisfactory
Fig. 9. Steering Gear Panel
results and inasmuch as the apparatus can
be arranged to deliver large volumes of oil
when the rudder moves easily and small
volumes of oil when the rudder requires a
large amount of torque, a motor of moderate
horse power is sufficient.
Anchor Windlass
It is only quite recently that electricity
has been applied to the equipment used for
raising anchors, and naval vessels have been
foremost in its use.
The requirements of an anchor windlass
are rather peculiar for an electrical equipment
to meet, inasmuch as provision must be
made for such conditions as arise when the
anchor becomes fouled or stuck in the mud.
In this case it is not sufficient to provide the
usual overload device, which would disconnect
the electrical equipment from the source of
power, but the current must be limited to a
safe value and the motor or motors allowed
to stall under these conditions in order that
the tension may be maintained in the anchor
chain and the equipment be left so that it
will immediately start on the removal of the
overload as is the case with a steam windlass.
In the case of the Argentine battleships
the anchor windlass equipment acts only as
an auxiliary to the steam windlass and is
designed to function at one-third the normal
speed of the latter.
The outfit consists of a 100-h.p. 475-r.p.m.
compound wound, commutating field motor
of the semi-enclosed type equipped with
a disk brake; two watertight, drum type,
reversing master controllers, one mounted
in the windlass room and one mounted on the
weather deck; a contactor panel, containing
the accelerating contactors, step-back relay,
overload relay, double-pole single-throw dis-
connecting switch, a single-throw testing
switch and a low voltage relay, and the
starting resistance. The control is semi-
automatic; i.e., the first three speeds are
controlled by the master controller but
beyond that the current limit relays on the
contactors will prevent them from closing
until the current in each preceding one has
been reduced to a predetermined amount,
regardless of the position of the controller
cylinder. The step-back relay will open the
contactors in case the load should be increased
beyond that for which the step-back relay
has been set and will introduce all of the
starting resistance, except one section, thereby
reducing the current to a safe overload
on the motor. When the overload is re-
moved, the step-back relay automatically
closes, the contactors close and in this way
produce the effect mentioned above. The
overload relay is intended to operate only
in cases of extreme overload, such as produced
by abnormal conditions, and completely
disconnects the armature from the power
supply.
The above equipment is, of course, designed
to operate on a constant potential system
and hence requires a great amount of rheostat
occupying considerable space.
For five of the recent American battleships
quite a different system has been designed.
Two of these equipments have already been
completed, although no ship tests have been
made up to date. The requirements to be met
are that two anchors, weighing about 20,000
lb. each and 60 fathoms of chain on each
shall be raised and lowered simultaneously
at a rate of six fathoms per minute. This
chain weighs approximately 600 lb. per
fathom.
Two electric motors of 175-h.p. rating for
one hour and an overload capacity of 350
h.p. for 10 minutes each, running at a full load
speed of 230 r.p.m., 230 volts, are coupled on
either end of a worm shaft in such a manner
that either one or both motors may be
operated. These motors are compound
ELECTRICITY IN MARINE WORK
515
wound and supplied with commutating fields
and a disk brake. Each worm meshes with a
worm wheel connected to a vertical shaft,
which is carried through various decks from
the windlass room to the upper deck, where
it is connected to the wildcat engaging with
the anchor chain.
The Ward Leonard system of control is
used, whereby the voltage on one of the two
generators connected to the turbines in the
forward dynamo room is varied by means
of its field excitation, the generator armature
being directly connected to either one or
both of the two motors, as occasion requires.
Referring to Fig. 10, showing the front
view of the control panel, it will be noted
that there are three sections, the one on
The large contactors are used for the lower-
ing connections and the relays are provided
in order to slow down the motors and limit
the current in case of severe overload and are
so arranged that the normal connections are
restored and the motors brought up to the
speed for which the controller is set after the
overload is removed.
The motor is similar to the steering gear
motor shown in Fig. S.
Boat Cranes
The method of boat handling varies in
different classes of vessels and in different
countries. On commercial vessels boats are
usually lowered by means of davits, but on
Fig. 10. Anchor Windlass Panel — Ward Leonard Control
the left and the center being in duplicate.
These contain a double-pole single-throw line
switch for connecting a motor to the gener-
ator; an ammeter; field rheostat; two relays;
a small and a large contactor. The right-hand
section contains a double-pole single-throw
fused control switch; two triple-pole single-
throw field switches and a multi-pole double-
throw control switch. The double-pole
single-throw control switch supplies all the
control circuits, while each triple-pole switch
supplies the field and brake circuits of one
motor, so that when only one is used, it is not
necessary to have the field and brake of the
other connected. The multiple double-throw
switch is used to connect the control circuits
to either one of the controllers. One of these
controllers is placed in the windlass room
and the other on the weather deck.
warships some form of boat crane or boat
boom is generally used.
The first electric boat cranes in this country
were installed on the Kearsage and Kentucky,
each ship having two cranes operated by
50-h.p. motors and two cranes operated by
20-h.p. motors. These motors were shunt
wound in order to provide a convenient means
for electrical control in lowering. As the
boats will drive the crane in lowering, the
ordinary system of rheostatic control is not
sufficient.
The conditions for hoisting are simple and
an ordinary rheostatic drum controller was
provided but, in lowering, the rheostat was
connected directly across the line, which
allowed sufficient power being delivered to
the cranes to lower the empty hook or to
start the boat downward but the rheostat
510
GENERAL ELECTRIC REVIEW
being connected in parallel with the armature
prevented the motor from acquiring an
excessive speed.
The shunt motor, however, runs at practi-
cally constant speed irrespective of the load,
Fig. 11. Boat Crane Motor
and therefore the empty hook could be
moved but little faster than the heaviest
boat. This led to waste of time and it is also
desirable for picking up the boat in a seaway
that the empty hook should be moved
quickly. On the next vessels equipped with
electric boat cranes, series motors were used,
and an automatic mechanical lowering brake
was provided similar to those used on land
cranes, so arranged that the brake would be
inoperative in raising the boat but would
not allow the boat to run away in lowering.
This always requires a moderate amount of
power to be delivered to the crane in order
to lower the boat, but on account of the
complication and heating of this automatic
brake, electric lowering systems have been
developed in which the principle of dynamic
braking is used, in lowering in a method
somewhat similar to that originally used on
the Kearsage and Kentucky, but the motors
are series or compound wound.
The system used on most of the recent
vessels is a German invention and makes
use of compound motors with the connections
so arranged that in raising the boat plain
rheostatic control is used, but in lowering,
except at the highest speed, the entire rheostat
and the series field are connected in series
with each other between the two main lines
and the armature is connected in parallel with
the series field and a portion of the regulating
rheostat.
When the controller is turned to lower a
boat, the shunt winding is energized from the
main line, and the current received from the
main line through the regulating rheostat
passes partly through the armature and
partly through the series field. As soon as the
motor begins to lower and drive the motor
as a generator, the current delivered by the
motor armature passes through a portion of
the rheostat and through the series field.
The hoisting motors, see Fig. 11, are usually
of 50-h.p. capacity and are required to lift a
load of 40,000 lb. at 20 ft. per minute, and to
lift the empty hook at over 60 ft. per minute.
This higher speed is obtained by cutting out
the series field on the high speed position only
when raising light loads, and the motor then
operates as a plain shunt motor. The appa-
ratus is so designed that in lowering a heavy
boat, it is impossible to lose control by
opening of the circuit breaker.
The cranes are also rotated so as to place
the boat in the proper place on deck. The
motors for this purpose are frequently of
50 h.p. and both shunt and compound wound
motors have been used. These require a
special rheostat connection, somewhat similar
to that used in lowering, so that the crane will
be under control when the ship is heeled over
and it must permit of ready starting and
stopping without causing the boat to swing.
Many of these cranes have been built to
revolve with the complete mechanism, in
which case flexible connections are required
to bring the current to the crane, but in later
types the boom is rotated about a fixed pillar
and the hoisting cable is carried down from
the center of the pillar to the hoist mechanism
located on the lower deck, in which case the
motors do not revolve with the cranes but
the hoisting cable twists in the pillar as the
boom is rotated.
On many foreign ships a swinging boom is
used, supported from a stationary pillar,
although the construction is considerably
different from that used in the United States.
The controllers for both hoisting and rotating
motors are usually combined in one frame.
For the early cranes these were of the regular
rheostatic type in which the full current
passed through the fingers of the controller,
but later types make use of small master
controllers at the crane which control con-
tactors on a switchboard panel generally
located below the deck. The hoisting motors
are provided with electric brakes of sufficient
strength to hold the load when the current is
turned off. Circuit breakers or overload
relays are provided to open the circuit in
case of an excessive load, in which case the
mechanical brake is set and the load preven-
ted from dropping. A rheostatic controller is
shown in Fig. 12.
ELECTRICITY IN MARINE WORK
517
Winches
Most of the winches for handling cargo
on commercial ships are steam operated, but
those on warships are generally operated by
electricity. These are used for taking coal
and cargo aboard and vary in number from
three to seven on various large vessels. Some
of the earlier ones were provided with drums
and winch heads but the later ones are
provided with winch heads only and a portion
of them have compound gearing so that by
changing a clutch they may be able to lift a
moderate load at high speed or a heavy load
at low speed. Winches now generally supplied
have a capacity of 5000 lb. at 200 ft. per
minute with the simple gearing and 20,000 lb.
at 50 ft. per minute with compound gearing.
Formerly these winches were provided with
a rheostatic cylinder controller and an
enclosed rheostat mounted on the bedplate
of the winch itself, but in later practice a
small master controller is mounted on the
winch and the contactor panel and rheostats
are located below the deck. The motor itself
•is located above deck and is therefore of
watertight construction, the same as the boat
crane motor shown in Fig. 11.
Fig. 13 shows a deck winch controller of
the rheostatic cylinder type. Fig. 14 shows
a complete deck winch.
Coaling winches are also provided on many
vessels but have been frequently operated
by steam. A few vessels have been equipped
Fig. 12. Rheostatic Controller for Boat Crane
with 150-h.p. motors driving a line shaft
connected by bevel gearing to vertical winch
heads above the deck. A 150-h.p. motor for
this purpose is shown in Fig. 15. This motor
being located below decks is semi-enclosed,
and is of particularly rugged construction on
account of the excessive loads that may occur
at times.
On some foreign vessels, small individual
electrically operated winches are provided
Fig. 13. Deckwinch Controller
having a winch head on each side and located
at convenient places on the deck. These are
also readily separated into different parts
so that they may be stowed below when the
ship is cleared for action.
Coaling at sea apparatus has been operated
electrically on several vessels, especially in
the Russian navy. For this purpose a special
design of electric hoist is installed either on
the battleship or on the collier. The collier is
towed at some distance behind the battleship
and a conveyor line is carried from mast to
mast on which bags of coal are carried from
the collier to the battleship. Special arrange-
ments are provided for keeping this line
tight as the distance between the two vessels
varies slightly in a rough seaway. The bags
of coal are raised by a hoist to the mast head
of the collier and then fastened quickly to the
conveyor rope which is kept in motion by a
special coaling-at-sea hoist, and a slipping
clutch or other suitable arrangement is
provided which will take up the slack in this
conveyor cable or pay out more cable as
circumstances may require.
518
GENERAL ELECTRIC REVIEW
Ventilation
On account of the large number of people
living in a small space where natural venti-
lation cannot be used, artificial ventilation of
vessels is very important. This was formerly
Fig. 14. Deckwinch
accomplished by steam-driven fans but elec-
tric fans have shown a great superiority
and the equipment of the modern battleship
may contain more than 60 electrically
operated fans delivering a combined volume
of more than 400,000 cu. ft. per minute.
These fans are used either for furnishing
fresh air to the various compartments, taking
it from a ventilator above the deck or for
exhausting impure air from the compart-
ments and discharging it through ventilators.
The fan wheels are usually carried on the
end of the armature shaft and the fans
usually receive air from one side only, being
connected to the inlet pipe and discharging
it through sheet metal ducts in the various
compartments, where the air is required for
the supply system, and for the exhaust
system these ducts lead from the various
compartments combining into a large duct
which leads to the inlet of the fan.
These fans are not only used for ventilation
but for heating and cooling air and in these
cases thermo-tanks or similar heating and
cooling coils are used. For heating, the pipes
are steam-heated, dampers being provided to
by-pass a portion or all of the air around the
heaters when the heat is not required. By
the use of water these thermo-tanks become
coolers and humidifiers, and the temperature
can be made comfortable in hot climates.
Frequently the casing of the fan is bolted
directly to the sub-base of the motor but for
navy work convertible sets of special design
are generally used and the fan casing can be
bolted to the motor supports at various
angles, so that any desired direction of
discharge can be used without building the
fan specially for that direction. Motors are
usually of the open construction, but where
located in exposed places, enclosed water-
tight motors are frequently employed, as
shown in Fig. 16.
For state-rooms desk and bracket fans
play an important part and some of the
larger battleships are furnished with as many
as 135 of these.
For temporary ventilation of compartments
where men may be working, portable venti-
lation sets, delivering about 400 cu. ft. of
air per minute and furnished with flexible
hose, are used; 18 being supplied on recent
battleships.
Electric operation has also been applied
to fans for supplying the forced draft for the
boilers both on commercial and naval vessels,
see Fig. 17. These vary from 20 to 40 h.p.
and from 15,000 to 28,000 cu. ft. per minute.
These motors are usually of the enclosed type
and are located near the tops of the boilers,
sometimes in passage ways near the uptakes
and sometimes in special compartments
located just above the fire room. These fans
take air from both sides and deliver it below
into the enclosed fire room, producing a
pressure of about 2 in. water gauge. The
earlier ones were furnished with hand-
operated dial controllers but later types have
been furnished with contactor controlling
panels, the master controllers for which are
Fig. 15. Coaling Winch Motor
located in the fire rooms. Several of the most
recent battleships are provided with fans
driven by steam turbines which permit a
greater range of control than the electric
sets and are somewhat lighter. This particu-
ELECTRICITY IN MARINE WORK
519
larly applies to oil burning vessels, where the
air pressure, and consequently the speed of
the fans is higher than in the case of coal
burning vessels. On torpedo boat destroyers
these turbine-driven forced draft fans are
usually of vertical construction. Fig. 18
shows the forced draft motor with special
provision for cooling.
Power Doors
On a large number of vessels many of the
watertight doors are operated by electric
motors. These equipments are provided with
local control at the door by which the door
can be readily opened or closed, and an
emergency station on the bridge is connected
to all doors so that in case of danger all of the
doors can be closed within a few seconds by
operating the emergency controller. These
motors vary in size from % to 1.2 h.p. They
are arranged with automatic devices so that
if a bunker door should be clogged with coal,
when the emergency controller is operated,
the door will close as far as the coal will
allow it and after the coal has been removed
or washed out by the water, the door will
automatically complete the closing operation.
Pumps
The Russian battleship Retvizan and cruiser
Yariag built for the Russian Government at
the Cramp shipyard at Philadelphia contained
several electrical devices not in common use
in the United States at that time, some of
Fig. 16. Watertight Motor
which have been incorporated in United
States practice since. These include electri-
cally driven pumps. The Russian battleship
had four 54-kw. vertical motors driving cen-
trifugal pumps for drainage purposes and two
similar equipments of 18-kw. capacity. The
cruiser was provided with three of the large
and two of the small pumps. Several years
later similar pumps were introduced in United
States vessels. These vary somewhat in
Fig. 17. MP-6-30-h.p., 620/775-r.p.m., 120-volt Motor
Direct Connected to Sirocco Fan
capacity, speed and power in the different
vessels, but the following applies to some of
the most recent vessels :
Six main drainage pumps of 3000 gallons
per minute against 35-ft. head.
One secondary drainage pump, 750 gallons
per minute against 35-lb. head.
Two flushing pumps, 500 gallons per minute
against 50-ft. head.
Two fresh water pumps, 200 gallons per
minute against 35-lb. pressure.
All of these pumps are of the centrifugal
type. The main drainage pumps are vertical
and are installed in the fire rooms, the motor
being supported several decks above and
connected by a shaft about 25 ft. long. On
account of the possible deflection of bulk-
heads, due to the pressure of water when the
compartments are flooded, special provision
is made for supporting the bearings of this
intermediate shaft. The motors are of the
semi-enclosed type. The motors for the other
pumps are watertight, enclosed and of
horizontal construction and in some cases
provided with ball bearings. The frames are
split for convenience in disassembling on
shipboard.
The control equipments consist of a
contactor panel controlled by a master switch,
which in some cases is located at the pump.
On some vessels drum type controllers have
been installed, providing also field control
of the speed of the motor, although usually
520
GENERAL ELECTRIC REVIEW
compound wound motors without speed
control are used.
The horse power of the recent equipments
varies from 50 h.p. main drainage pump to
14 h.p. for the flushing and fresh water pumps.
Fig. 18. Type MP-6-32 H.P., 725 930 R.P.M., 120-Volt
Totally Enclosed Forced Draft Motors, U.S.S. "Nevada"
Fig. 19 shows a 70-h.p. main drainage
pump motor for the Argentine dreadnoughts.
Fig. 20 the rheostatic drum controller with
field control and Fig. 21 the secondary
drainage pump motor for the same vessels.
This motor, which differs from the usual
construction, is enclosed but provided with
a fan on the armature shaft and has an air
inlet at the commutator end and a discharge
at the other end.
Ammunition Equipments
The handling of ammunition, the serving
and pointing of guns, is accomplished electri-
cally. For the broadside secondary battery
the ammunition is carried by endless con-
veyors driven by electric motors and then
is carried up to the guns themselves by
means of endless chain conveyors. Both of
these systems are operated by motors running
continuously and the supply of ammunition
delivered to the guns is controlled by the
quantity delivered to the conveyors or chain
hoists.
For the turret guns the ammunition is
usually hoisted by means of a car or hook
attached to a wire rope and after each shell
is hoisted to the gun the motor is reversed and
the hook or car returned for another load.
Electric motors operating by various methods
have been used for turning the turrets and
elevating and depressing the guns.
As these classes of apparatus, as well as
the various signaling devices for transmitting
orders for operating the guns, are purely
of a military character and do not in any way
represent commercial practice, no further
details will be given.
Gyroscopic Compass
An interesting development of recent years
is the gyroscopic compass. One form which
has been used considerably has been devel-
oped in Germany and another in the United
States. These compasses are entirely inde-
pendent of the earth's magnetism and arc
not affected in any way by the steel structure
of the ship. The directive effort depends
upon the reaction of the earth's rotation upon
a small flywheel revolving at high speed.
The wheel is driven by an induction motor
the current for which is furnished by a
motor-generator set having a generator of
comparatively high frequency.
Fig. 19. Main Drainage Pump Motors
The master compass is located in the
lower part of the ship, where it is well pro-
tected, and connecting wires are taken to
several secondary compasses in convenient
locations, which show the readings of the
master compass.
ELECTRICITY IN MARINE WORK
.321
Sounding Machines
Good results have been obtained from
sounding machines operated by electric
motors. This apparatus consists of a small
electric hoist containing a drum upon which
is wound the line which carries the sounding
lead. In lowering the lead the drum is
uncoupled from the motor and is controlled
by hand by means of a brake. An indicator
connected with the drum shows the length
of the line that has been let out. When it is
desired to raise the lead, the drum is clutched
to the motor, which winds up the line.
Ship Propulsion
The electric propulsion of vessels has
interested engineers for several years. At
the Columbian Exposition in Chicago a
large number of launches were propelled
electrically. Aside from these the first boats
of importance in the United States to be
equipped were two fire boats for the City of
Chicago. These boats had two 600-h.p.
turbines direct connected to 200-kw. gener-
ators and centrifugal pumps. When the
boats were being propelled the pumps ran
house and the engine room. The control of
these boats is very satisfactory and it is
possible to maneuver them without using
the rudder.
Fig. 20 Controller for Main Pump Motor
idle and the two generators furnished power
to two 250-h.p. 200-r.p.m. motors driving
twin screws. These equipments operate with
direct current on the Ward Leonard system,
controllers being located both in the pilot
Fig. 21. Secondary Drainage Pump Motor
A few boats have been equipped, in Europe,
with internal combustion engines driving
generators which furnish current for motors
which drive the propellers and in addition
magnetic clutches are provided by which the
propeller shafts can be coupled directly to the
engines. In this system the electrical opera-
tion is used for maneuvering the boat, going
ahead slowly and backing, but for full speed
ahead, the clutch is used and the electrical
connections are opened.
Considerable attention has been given to
electric propulsion in England, making use of
alternating current, and the Tynemount
equipped with this system is operating on the
Great Lakes.
The first large propelling equipment was
installed on the U. S. collier Jupiter. In this
vessel one steam turbo-generator furnishes
current for two induction motors driving twin
screws. The speed is controlled by adjusting
the governor of the turbine and reversal is
accomplished by reversing the electrical
connections.
The battleship California is to be provided
with electric propelling apparatus, consisting
of two turbo-generators supplying power for
four 7500-h.p. induction motors. These
motors are provided with a two-speed wind-
ing, the slow speed winding being used at
ship speeds less than 15 knots, and the high
speed winding at higher speeds. Between
these points the speed of the motors is
controlled by the speed of the turbines. For
full power, each turbine supplies two motors
522
GENERAL ELECTRIC REVIEW
and for moderate speeds one turbine supplies
power for all four motors.
Various articles concerning electric pro-
pulsion have been published in the technical
press and therefore no complete details are
riven here.
Fig. 2 2. Propeller Motors
Miscellaneous
In addition to the various equipments
which have been described somewhat in
detail, there are a large number of other
auxiliary apparatus operated electrically.
These consist of the laundry machinery, galley
appliances, and machine tools, of which a
considerable number are used especially on
large warships or on special repair ships.
Electric refrigerating apparatus has been
adopted in many cases where electric motors
are used to drive the compressors instead of
steam.
Elevators are used for the fire rooms in
warships, and for the general use of passengers
on passenger ships.
Submarines
At the present time submarine design is
undergoing a radical change, but of those built
in recent years many are from 150 to 200
ft. long and have a surface displacement
of from 400 to 650 tons. These boats have a
surface speed of approximately 14 sea miles
per hour and a submerged speed of approxi-
mately 10 sea miles per hour. The surface
cruising radius varies from 2500 to 4500 miles.
The submerged radius is about 150 miles.
The electrical equipment comprises pro-
peller motors operated from 220-volt storage
batteries and several small motors for the
auxiliaries.
When operating the boat on the surface, a
Diesel type of heavy oil engine is direct
connected to the propeller through friction
clutches and through the propeller-motor
armature shaft, which forms an integral part
of the propeller shaft.
The Diesel engine is used for surface pro-
pulsion only, on account of the difficulty of
supplying air for combustion purposes when
submerged. When operating submerged, the
propeller motors are connected across the
battery and the clutch between the engine
and motor is disengaged.
The motors are of the shunt wound type
and with fields separately excited from a
110-volt source; i.e., across half of the storage
battery. These motors are of the open type
and, as the inside diameter of the boat is
approximately 10 ft., these motors are
designed for the smallest diameter possible,
and where the output and speed necessitates
the furnishing of a machine having a diameter
beyond the allowable limits it is customary
to supply two machines having armatures
mounted upon a common shaft, as shown in
the accompanying illustration, Fig. 22, which
shows two motors, each rated 150 h.p., having
a full field speed of 125 r.p.m. and a weak field
speed of 250 r.p.m., the speed control being
accomplished by means of field rheostats.
Another scheme sometimes used, which will
permit of furnishing machines having the
smallest possible diameter, is to have the
motors connected as shown in the above
illustration but totally enclosing same and
mounting between the two machines a
ventilating fan, the intake of this fan being
through the openings in the lower half of the
commutator end shields.
The storage batteries have a range of from
246 volts to 200 volts over the discharging
period. These batteries are charged by throw-
ing out the clutch between the propeller
motors and the propeller proper and
driving the motors as generators by means
of the Diesel oil engines.
All submarines have two propeller shafts
and the equipment above described is always
furnished in duplicate.
The control of the motors consists of con-
tactor panels enclosed in a watertight case,
the operation of which is controlled by two
drum type master controllers mounted side
by side and so arranged that they can be
operated together by one handle through
gearing, or this gearing can be thrown out
of mesh and the two controllers operated
independently. The field rheostat for speed
control is mounted on a small panel immedi-
ately above the drum controllers and is
hand-operated.
527
THE USE OF ELECTRICITY IN MINING WORK
By David B. Rushmore
Chief Engineer, Power and Mining Department, General Electric Company
The author shows the broad scope of work included in the term "mining" and gives statistics to indicate
the magnitude of the industry. The importance of the application of electricity to mining work as set forth
by the author should be of special interest to those connected with the industry. — Editor.
are to furnish food,
incidentals to the
Economic activities are divisible into the
following general classification:
1. Hunting and fishing.
2. Lumbering and forestry.
3. Mining.
4. Agriculture.
5. Manufacturing.
6. Transportation.
7. Merchandizing.
8. Distribution.
9. Miscellaneous.
The objects of these
shelter, clothing and
ultimate consumer.
The mining industry draws upon natural
resources and deposits in order to furnish
fuel, building and structural material, precious
stones and metals, and the raw materials
for man)- manufacturing processes. The
principal products of the mining industry
are as follows:
Fuels: Anthracite and bituminous coal,
petroleum, natural gas and peat.
Metals: Iron, copper, precious metals,
lead, zinc, quick-silver, manganese and tung-
sten.
Structural Materials: Limestone, granite,
sandstone, marble, slate, traprock and blue-
stone.
Miscellaneous: Asbestos,
bituminous rock, barytes,
stones and millstones, clay,
emery, feldspar, fluorspar,
garnet, graphite, grindstones, gypsum, infu-
sorial earth and tripoli, magnesite, marl, mica,
mineral pigments, monazite and zircon, oil-
stones, scythestones and whetstones, phos-
phate rock, precious stones, pumice, pyrite,
quartz, sulphur, talc and soapstone.
The mining industry is world-wide and as
old as civilization. The man-power of early
mining operations had distinct limitations
with regard to possible depth, cost and output,
and while modern machinery and appliances
have made it possible to operate formerly
asphaltum and
bauxite, buhr-
corundum and
Fuller's earth,
unprofitable mines, new discoveries and
improvements in mining methods are to be
continually expected.
The number of men employed in the mining
industry in the United States and the division
of occupation are approximately as follows:
EXTRACTION OF MINERALS. . . .
Foremen, overseers, and inspectors ....
Foremen and overseers
Inspectors
Operators, officials, and managers
Managers
Officials
Operators
Coal mine operatives
Copper mine operatives
Gold and silver mine operatives
Iron mine operatives
Operatives in other and not specified
mines
Lead and zinc mine operatives ....
All other mine operatives
Quarry operatives
Oil, gas, and salt well operatives
Oil and gas well operatives
Salt well and works operatives ....
964,824
2 ,338
22,142
1,196
25,234
9,798
1,149
14,287
613,924
39,270
55,436
49,603
47,252
19,486
27,766
80,840
29,927
25,562
4,365
The table on page 538 also gives some im-
portant figures regarding the mining industry
in the United States and the power utilized.
Mineral, coal, oil and other natural deposits
occur over considerable areas much larger
than individual mines, which results in the
condition known as mining camps such as are
found at Butte, Cobalt, Bingham Canyon,
the Coeur dAlenes, the various anthracite
developments, the Messabe Range, and in the
various oil fields of Pennsylvania, California
and Texas.
Due to the fact that a large number of
mines in one locality have use for power and
that in each mine the machinery is separated
by considerable distances, the use of elec-
tricity as a means of transmission and applica-
tion of power has very decided advantages.
In fact, the age is passed when advocacy of
528
GENERAL ELECTRIC REVIEW
electrification of mines has to be put forward
as regards new developments. The replace-
ment of antiquated machinery in mines which
have been worked well on toward exhaustion
2.
3.
4.
5.
6.
Fig. 1. Power Station of Lehigh Navigation Electric Co., at Hauto, Pa
is, however, an economic problem which does
not always admit of the introduction of
electrical apparatus at such a late period.
The principal reasons for the use of elec-
tricityr in mines are:
1. The possibility of saving in capital
and in organization activities by the
purchase of power.
Efficiency and economy.
Convenience.
Flexibility.
Ease of extensions.
Safety.
7. Saving in space.
It also very frequently happens that mining
camps are possessed of poor conditions for
supplying condensing water, and such water
as exists is frequently of an acid nature,
which adds to the desirability of supplying
power from a central station which can be
located under the best of conditions.
The question as to whether mines should
generate or purchase their power is one which
arises where the camps are small and where
mines may be somewhat isolated. Profits in
power companies are usually small compared
with what they should be in mining operations
and therefore the capital should be much
better utilized in the mining work than when
invested in a separate power plant which
must be written off during the life of the
mine. Thus we find in such places as South
Africa, Cobalt, Butte, etc., that the power for
the whole mining district is
supplied from one or more
central source. In the case
of hydro-electric power, or
transmission over some dis-
tance from steam plants,
precautions against service
interruptions must be given
careful attention, but the
present state of the art
regarding power transmis-
sion work is such as to
remove any question of great
hazard.
The best system, fre-
quencyT, phase and voltage
for mining work is usually
dependent largely upon the
particular power systems
which are available for use
in these districts. The life
of most mines is now
sufficiently great to warrant
the development and exten-
sion of hydro-electric or
steam power systems to these territories, and
there is almost invariably a supply of three-
phase electrical energy at 25, 60 or some
intermediate frequency.
An interesting similarity exists between
the transmission of electric energy and the
transportation of commodities. Energy may
be transmitted electrically or transported
mechanically as is done with coal and oil.
Every industry has its waste products and
economy is best obtained where these are
utilized. In the preparation of commercial
sizes of coal there is obtained from the breakers
and crushers a refuse known as culm which is
unmarketable and which at present has no
commercial value except as it may be made
into briquettes.
In connection with the use of electricity in
coal mines it is therefore interesting to con-
sider the economical use of this by-product
or waste coal in commercial form. The best
and largest development of the kind in this
country is that of the Lehigh Navigation
Electric Company at Hauto, Pa. The refuse
from preparing the marketable coal of the
Lehigh Coal & Navigation Company is
sufficient, it is estimated, to supply con-
tinuously a power house of 100,000 kw. rated
capacity, 30,000 of which have been installed
THE USE OF ELECTRICITY IN MINING WORK
529
in the initial development. This power is
used for its own mining operations and also
sold to neighboring industries as well as to
the public utilities which are accessible.
Other developments, both in this country
and Europe, have been and are being made
to sell not only the refuse coal but also the
output of the mine as a whole in this way.
Especially noteworthy are the many studies
which have thus been made with regard to
the possibility of utilizing the culm piles of
Pennsylvania in this manner, but the burning
of the finest coal dust alone has not yet met
with complete success. In certain coal fields
in Virginia reached by the Appalachian
Power Company, the method of handling
coal, on the other hand, is such that a high
priced market exists for it all, and therefore
makes desirable the purchase of hydro-
electric power for coal mining work apparently
something of an anomaly.
The principal operations in mining have to
do with the handling of material in bulk,
while other factors are incidental, such as
arrangement for handling men, pumping
water, supplying power, illumination and
ventilation, as well as considerations of
safety.
Mining conditions are highly special and
reliable information on the details of mining
costs and power consumption are not to be
had. Methods of accounting in mining
The kind of mining operations varies
greatly even in one field, such as gold mining
for example, where we have the panning and
hydraulic mining of California, the dredging
work are yet to be standardized, and until
they are available figures can be used for
comparison only when the specific factors
are known which are necessary for their
interpretation.
Fig. 3. Crowding Motor and Controller on a 65-Ton Electric
Shovel Equipped with Four 550-Volt Series
Direct-current Motors
of Alaskan rivers, and the working at extreme
depths of the mines on the Rand in South
Africa, all to obtain the same metal.
The general power applications in mining
work to which electricity is applicable are in
connection with the following machines and
work :
Strippers, shovels and various forms of
excavating machinery.
Dredges and monitors.
Drills, coal cutters, etc..
Mining locomotives.
Hoists.
Pumps.
Air compressors.
Mine fans.
Coal crushers and washeries, etc.
Magnetic ore separators.
Signal and telephone systems.
Lighting and illumination.
The various power applications in mining
work and in the auxiliary work of reduction
often carried on in the vicinity of mines can
be accomplished by a number of different
types of motors, although generally some
specific form is most suited to each particular
case.
Shovels
On account of its simplicity, reliability and
economy the electric shovel is being used more
530
GENERAL ELECTRIC REVIEW
and more in places where current is available.
In mining work it may be used for stripping
over-burden or for excavating the ore itself
and loading it on the railroad cars. These
shovels must be exceedingly powerful and
carefully designed to successfully withstand
the severe shocks and strains incident to the
strenuous conditions under which they must
operate. Due to the absence of the steam
boiler equipment less attendance is required,
while the inefficiency of small engine and
boiler equipments is fully appreciated. The
electric control is very simple and, with
motor drive, power is consumed only while
operating, resulting in a high efficiency.
The duty cycle of a shovel is very short,
varying from about 20 to 30 seconds, while
the cycles of the individual motors are even
shorter. This necessitates rapid acceleration
and frequent reversals of the motors, which
for that reason must be of a very rugged
design. Their inertia should, of course, also
be as low as possible, and it is therefore
common practice to equip at least the hoist
with two motors, each of one-half the total
required power capacity. In this manner
the power consumption during acceleration is
considerably reduced.
Electric shovels are, as a rule, equipped with
three or four motors; one or two for the
hoist, one for the swing and one for the boom.
The two hoisting motors are located at the
back of the main machinery, and longi-
tudinally in relation to the car frame, one on
each side, and transmit their power to an
intermediate hoisting shaft through bevel
gears. This intermediate shaft gears direct
into the hoisting drum shaft which carries the
drum on which the hoisting chain is wound,
this drum being provided with friction and
check bands for controlling the hoisting and
lowering of the dipper. The friction band is
operated by means of an air set ram, while the
check band is operated by foot.
The swinging motor is geared to the swing-
ing drum through a system of spur gearing,
this drum carrying two cables, one on either
end, which lead forward and pass around the
swinging circle connecting directly to the
boom. This motor is provided with a brake
which, however, is used only in case of an
emergency.
The boom or crowding motor for controlling
the dipper handle, is located on the boom and
geared to the shipper shaft which carries two
pinions which engage with the racking of the
handle. The control for all of these motors is
placed at the rear of the machine, and the
arrangement of machinery is practically the
same as on the steam units.
The motors are provided with automatic
control, which is particularly adapted to this
class of work, as the acceleration is auto-
matically taken care of by the contactors,
and the master controller, being light, provides
free and easy operation. In addition to the
series contactors for the hoisting and crowding
control, jamming relays are used, which
limit the current flowing to the motors to a
safe amount, but do not cut the motors out
of circuit in case they are stalled or over-
loaded. No jamming relay is provided with
the swinging motor, as it is protected by the
circuit breaker.
The reversing master controllers for the
hoisting and swinging motors are placed at the
forward end of the cab, while the controller
for the crowding motor is placed on the boom.
The motors may be either of the alternat-
ing-current slip-ring or the direct-current
series-wound type. It is, however, generally
conceded that the direct-current series motor
is superior to the alternating-current motor
for shovel work. The characteristics of the
series motor closely resemble the steam
engine, which is giving very satisfactory
service as far as the actual working condition
is concerned. The power supply is, however,
generally alternating current, and the direct-
current equipment must therefore include a
motor-generator set, but nevertheless it has
proven cheaper than the alternating current.
H. W. Rogers in the Transactions of the
A.I.M.E. gives the power consumption for a
120-ton electric shovel as:
0.241 kw-hrs. per cubic yard for direct
current
0.273 kw-hrs. per cubic yard for alternat-
ing current.
His paper also includes the following table
giving comparative costs between steam and
electric shovels of the same capacity:
Steam
Electric
Direct
Current
Equivalent
Alternat-
ing Cur-
rent
Interest at 6 per cent.
Depreciation at i%
per cent.
Repairs at 15 per cent.
Repairs at 9 per cent.
Labor (3 shifts)
$5.20
4.03
13.00
90.75
$7.75
6.00
11.63
63.75
$10.85
8.43
16.28
63.75
Total Cost (3 shifts)
$112.98
$89.13
$99.31
THE USE OF ELECTRICITY IN MINING WORK
531
The foregoing table gives the costs for three
eight-hour shifts, during each of which it is
estimated that 2970 cubic yards of material
are excavated. It is assumed, however,
that owing to weather conditions, delays, etc.,
the shovel-working year consists of 150 days.
Dredges
A considerable part of the gold mined in the
United States is now recovered by motor-
driven dredges. Steam power is, of course,
still used to the greatest extent, but with the
rapid extension of the Western hydro-electric
transmission systems cheap power can now
be obtained in many mining districts. It
is, however, not only the cheaper power
which has made the electrically-operated
dredge superior to the steam-operated dredge.
Experience has proven that they are more
reliable and operations are thus less inter-
rupted, while the larger sizes which have
recently been built would have hardly been
possible if a steam equipment had been used.
The following table gives the production of
gold bv dredges in California for the years
1898-1910:
1898
$18,847
1905
$3,276,141
1899
133,812
1906
5,098,354
1900
200,369
1907
5,065,437
1901
471,934
1908
6,536,089
1902
801,295
1909
7,382,950
1903
1,488,566
1910
7,550,254
1904
2,187,038
The number of electrically-driven dredges
in operation in the United States at the
beginning of the year 1913 is given in the
following table :
Feather River
34
Yuba River
14
Folsom River
15
Bear River
1
Toulume
1
Clear Creek
1
Clamath
1
Jenny Lind
2
Montana
5
Scott Valley
1
Colorado
3
Mew Mexico
1
Idaho
3
Oregon
1
Dawson
10
Forty Mile Creek
4
Stewart River
1
Nome
2
Frazer River
4
Total
104
It is safe to say that since the above tabula-
tion was made at least a dozen more dredges
have been put into operation.
There are three kinds of dredges in use,
viz: dipper, suction and bucket dredges, of
which the latter type is most commonly used.
It is usually of the continuous chain, close
Fig. 4. Electrically-operated Gold Dredge
connected bucket type, varying in capacity
from 3 to 16 cubic feet per bucket and with
a bucket speed of from 50 to 75 feet per
minute. The machinery of a gold dredge
consists of the digger or bucket line, revolving
screens, sluice tables and boxes, stacker for
carrying the tailings, high and low pressure
pumps.
Dredge motors are mostly of the alternat-
ing-current class, the variable speed type
being required for the operation of the bucket
line as well as for the winch by which the
dredge is kept in place or moved about. All
the other motors are of the constant speed
type, with the screen and stacker motors
usually phase-wound. When a dredging
operation is commenced in a new locality the
load is usually light at first and the buckets
may be operated at maximum speed. As the
depth increases and the soil becomes harder
the load increases and the buckets do not fill
so easily, so that a reduced speed is required.
Bucket line motors vary in size from 75 to
400 horse power, winch and stacker motors
from 15 to 50 horse power, and screen and
pump motors from 25 to 150 horse power.
The power is transmitted to the dredges
by means of armored cable, carried on floats,
and if the transmission can be economically
carried out at 2300 volts, the motors are
usually wound for this voltage. For higher
transmission pressures step-down transformers
are, however, provided on the dredge and the
pressure reduced to a motor voltage of 440.
The cost of operation varies from approxi-
mately 2.3 cents per cubic yard for a 13 cu. ft.
dredge to 7.5 cents for a 3 cu. ft. dredge,
532
GENERAL ELECTRIC REVIEW
the power cost being
respectively.
0.5 and 1.5 cents
Coal Cutters
The production of bituminous coal by coal-
cutting machines in the United States dates
Fig. 5. Sullivan "'Ironclad" Electric-driven Continuous Cutting Coal Mining Machine in
Position to Cut Across the Coal Face under its Own Power. Object at
right is cable reel; equipped with 30 h.p General Electric
motor, direct -current
commercially from 1891, when a little over
500 of such machines were in use cutting
somewhat over six million tons of coal, or
6.7 per cent of the entire output. In 1912
over two hundred million tons, or 47 per cent
of the total production, were mined by coal
cutters, of which over 15,000 were then in use.
The actual mining operation consists in
undercutting the coal seam and blasting
down the mass by a small charge of powder
so as not to break up the coal in too small
pieces. The undercutting was formerly, and
is still to a great extent, done by compressed
air punchers. These are, however, being
rapidly superseded by electrically-driven
chain cutters. The first of these was the
breast type in which the cutter bar is fed into
the coal seam to its full length, after which it
has to be withdrawn and moved sideways and
again anchored before a new cut can be made.
This type is now becoming more and more
obsolete and is giving place to the continuous
cutting machine, which may be either of the
long- or short-wall type depending how the
cutting is to be done. This machine has many
advantages over the breast type. The
machine is entirely self-propelling and after
the bar has been fed under the coal at one end
of the wall it cuts its way across the face to the
other side continuously, and the economy in
time is obvious. Besides this, it requires
much less space, which is of importance as it
permits the props to be set up very close to the
working face, thus greatly increasing the
safety.
Modern coal cutters are now being equipped
with either direct or alternating-current
motors, which are designed to meet the various
mining laws of the country. The motors may
be changed readily from the open to the
enclosed type, or to the flame-proof pattern,
by alterations which may
readily be made in the field.
This is of great value in
many mines, where to
begin with there may be no
indication of gas. Later
on as the development
advances, gas is encoun-
tered, necessitating a gas-
proof machine.
The motors are rated
about 30 horse power for
one hour, totally enclosed,
or for three hours con-
tinuously at the same load
with open construction.
The average load when
cutting coal with continuous-cutting machines
is from 12 to 20 horse power for an average
period of 30 minutes, depending on the
hardness of the coal and the feed of the
machine.
The direct-current motor is of the multi-
polar, compound wound type, the voltage
being 250 or 500, and the alternating-current
motor is of the squirrel-cage type, wound for
220, 440 or 550 volts, and 25 or 60 cycles, as
desired.
Fig. 6. Electric Rock Drill in Operation in Coal Mine
Locomotives
The mine-haulage problem is one of the
most important features of the mining indus-
try. This is of course obvious, when it is
THE USE OF ELECTRICITY IN MINING WORK
533
realized that the aggregate amount of ore,
coal and waste rock handled in the mines of
this country during a single year is in excess
of one billion tons.
It is now a fully established fact that
animal haulage is not economical for mine
service, and while in most mines the mechan-
ical drive has long ago superseded the same as
far as the main haulage system is concerned,
it is now also being rapidly superseded for the
gathering service.
Mining locomotives may be of the com-
pressed air, the gasolene or the electric type.
Of these, the latter has so many advantages
that in the majority of installations it is the
only one being considered, and is now accepted
as the standard type for mining service.
Although alternating current locomotives
are used occasionally, most mining locomo-
tives are of the direct current two-motor
trolley type, with series and parallel control.
In this manner it is possible to obtain a very
efficient speed regulation, the motors being
connected in series for low speeds. Thus
for a given load with the motors in series,
the current consumption is only half of what
would be required by a single-motor locomo-
tive. The motors are of the series-wound
commutating pole type, equipped with ball
bearings.
The load which a locomotive is capable
of hauling depends on the weight of the
locomotive, the adhesion between the driving
wheels and the track, the frictional resistance
of the trailing load and the curvature and
gradients of the track.
Mining locomotives are rated according to
their weight in tons, the drawbar pull on
level track being approximately 20 per cent
of the weight. Experience has shown that
Fig. 7. Fifteen-Ton Mine Locomotive
for cast iron wheels this coefficient of adhe-
sion may be safely assumed for clean dry-
rails. The maximum drawbar pull is gener-
ally 25 per cent greater.
Two-motor locomotives are built in sizes
from 4 to 20 tons. For larger sizes six-wheel
three-motor locomotives may be used where
the curves are not too sharp, and where these
would not be objectionable. This type of
locomotive has the advantage of better
distributing the weight, so that lighter rails
may be used than for a two-motor locomotive
of the same weight. To obtain greater
capacity it is also possible to connect two
two-motor locomotives in tandem in such
a manner that all the four motors may be
controlled from one controller. Such locomo-
tives may also be operated singly as inde-
pendent units.
Locomotives used for gathering are gen-
erally of a smaller capacity than those used
for the main haulage. In order to obviate the
use of trolley wires in the entries, these loco-
motives are often equipped with cable reels,
containing several hundred feet of cable the
outer end of which can be connected to the
trolley wire in the main entries, and through
which power may be fed to the locomotive
when it enters the working rooms. The
cable reel is motor operated and automatically
controlled in such a manner as to keep the
cable taut and rewind the same when the
locomotive returns.
Some gathering locomotives are also in
addition provided with hoist drums to be used
for steep grades. When so equipped, the
locomotive can be blocked on the track
in the entries, and by means of the hoist cable
the cars can be hauled up or lowered on the
steep grades to and from the working face of
the rooms. When so equipped, there is
hardly any haulage problem that the loco-
motive can not take care of.
There has also been a steady increased
demand for the storage-battery type of
locomotive for gathering work, these being
built in sizes from 3 to 7 tons. Most of these
are of the straight storage battery type, but
a limited number have, in addition, been
equipped so that they can be operated from
a trolley wire when in the main headings.
By means of a small self-contained motor-
generator set the battery may then also be
automatically charged, while the locomotive
is running on the trolley.
Hoists
Electric mine hoists were first developed in
Europe and their use there had become
universal before the mining interests in this
country were ready to adopt them. After a
campaign of education lasting over several
vears their adoption in this country came
with unusual rapidity, and now it is only
534
GENERAL ELECTRIC REVIEW
under exceptional circumstances that any
other kind of hoist would be considered. In
the meantime, however, the large electrifica-
tion of hoists in South Africa was carried on,
in part by one American electrical company,
and the largest hoists in the world installed
there were designed by American engineers.
Due to the natural conditions of mining
the work of hoisting is not evenly divided
over the twenty-four hours, but is usually
concentrated during two or more periods of
the day when the ore is brought to the surface
with the greatest rapidity. At certain hours
adapted for hoist work. The current is
obtained from a shunt-wound direct-current
generator driven by a direct-coupled induction
motor, where the source of supply is alternat-
ing, as is almost invariably the case. Both
the hoist motor as well as the direct-current
generator are separately excited, the exciting
current being obtained from an exciter
direct connected to the motor-generator set.
The control of the hoist motor is then effected
by regulating and reversing the exciting
current of the generator, thus varying the
voltage impressed upon the motor terminals.
Fig. 8. Mine Hoist Driven by a 700-h.p., 300-r.p.m., 3300-volt Induction Motor
of the day. also, men are lowered or raised
from the mine shaft, and at still other hours
the work of repairing and lowering timber.
etc., into the mine is carried on. The load
on the hoist over a complete cycle is naturally
of a very fluctuating character and possesses
a sharp peak over a few seconds of time.
Where the hoisting of a group of mines is
done simultaneously a peak of considerable
magnitude, lasting over several hours, can
be expected. The latter can be taken care
of to some considerable extent where the
mines come under the same management or
where an understanding is reached to prevent
too great overlapping.
Mine hoists may be driven either by direct
or alternating-current motors. The charac-
teristics of slow-speed shunt-wound direct-
current motors make this type admirably
Induction motors for driving hoists are
usually of the phase-wound type, the speed
control being accomplished by inserting or
cutting out resistance in the secondary cir-
cuit, liquid rheostats being used for larger
equipments.
Where the terms of the power contract are
such as to penalize peaks in the demand, a
smoothing out of the energy demand on the
main system is important and it can be accom-
plished in a variety of ways. A large number
of such systems have been proposed with
many ingenious arrangements of storage
batteries, flywheel equalizing sets, etc., but
as usual where simplicity is greatly to be
desired a few of these have been found to
possess the most desirable characteristics.
With direct-current equipments as above
described, the simplest and. when properly
THE USE OF ELECTRICITY IN MINING WORK
535
applied, the most satisfactory method is by
adding a flywheel to the motor-generator set.
The use of flywheels is, of course, limited to
an acceleration of comparatively short dura-
tion, and to permit the wheel to take care of
the peaks the speed of the set must be varied
according to the load fluctuations, i.e., when
the peak comes on the set must be slowed
down, and vice versa. This is done by
inserting resistance in the secondary circuit
of the phase-wound induction motor driving
the set and this is automatically accomplished
by what is known as a slip-regulator.
With the induction motor-driven hoists the
peaks may be equalized by means of flywheel
There are two classes of mine pumps in
general use, the plunger and the centrifugal.
The former is essentially a slow speed ma-
chine and is less affected by gritty water. It is
extensively used for portable pumps, which
collect the water in a centrally located sump
from which it may be pumped by large centrif-
ugal pumps during periods when the other
mine load is light. The centrifugal pump is a
high speed machine, being operated at speeds
as high as 3500 revolutions per minute.
Consequently the motor drive is very efficient.
Plunger pumps may be driven by shunt or
compound-wound direct-current motors or
by squirrel cage and phase-wound induction
Fig. 9. Ten Thousand Pound Single-driven Electric Hoist with Handwheel Operated Clutch and Two
Handwheel Operated Handbrakes for Incline Hoisting, Equipped with a General Electric
160-h.p., 450-r.p.m., three-phase, 60-cycle, 440-volt Induction Motor and
Built for the Panther Coal Company, Castle Gate, by the
Denver Engineering Works Company
motor balancers. These consist of a direct-
current motor driving a flywheel, the motor
being separately excited by a direct-connected
exciter. The set is then connected to the
supply mains through a rotary converter or
motor-generator set. The speed of the
balancer set is then varied by regulating the
motor field, which is automatically done by a
regulator actuated by the line current.
The development of hoists which will
automatically load, dump and operate is a
new feature, and the recent installation of the
Inspiration Copper Company is novel in this
respect.
Pumps
Pumping is an essential part in the operatic in
of almost every mine, and this problem has
been greatly simplified with the introduction
of the electric drive.
motors, the latter being used when it is
essential to reduce the starting current to a
minimum. Synchronous motors are also well
adapted for driving reciprocating pumps, but
due consideration must be given to the
starting torque required.
Centrifugal pumps may be driven by
shunt-wound, squirrel cage or phase-wound
motors, while synchronous motors are not
as well adapted for this class of pumps on
account of their high speed.
A notable example of a large and very
satisfactory centrifugal mine pump installa-
tion is that installed for the Calumet & Hecla
Mining Company in Michigan. It consists of
five eight-inch, six-stage horizontal pumps
built by the I. P. Morris Company. Each
pump, which is driven by a 300 horse power
General Electric Company direct-connected
induction motor, is designed to deliver water
536
GENERAL ELECTRIC REVIEW
at the rate of 1,440,000 gallons per 24 hours,
against a head of 755 feet at a speed of 1460
r.p.m. The water is collected in a sump
mainly is used for draining flooded mines.
As these pumps are apt to be entirely sub-
merged, the motors must be specially built
Fig. 10. Portable Mine Pump. Manufactured by
Goulds' Manufacturing Co.
holding over 1,000,000 gallons, and this
sump is located over 3000 feet below the
surface of the ground, and the water is relayed
to the surface by means of four pumps.
Each of the four pump rooms contains a
wooden tank, which receives the discharge
water of the pump below it, and furnishes
the supply for the unit on its level.
Among other pumps used for mining work
may be mentioned the sinking pump, which
Fig. 11.
Mine Sinking Pump, Manufacturedby
Goulds' Manufacturing Co.
to withstand such severe service, while in
their selection consideration must be given
Fig.
12. Air Compressors Each Direct-driven by 450-kv-a.f 6000-volt, 125-r.p.m. Synchronous Motor.
Buffalo, Rochester and Pittsburg Coal and Iron Company, Punxsutawney, Pa.
THE USE OF ELECTRICITY IN MINING WORK
537
r^JBBBP
Fig. 13. One 1000-Gallon-per-minute Plunger Pump Driven by a 350-h.p. Induction Motor and One 1000-Gallon
Centrifugal Pump Driven by a 400-h.p. Induction Motor. Lift 1000 ft. Pumpj Installed at the
Gwinn Mine of the Cleveland Cliffs Iron Co. The centrifugal pump is used as spare
to the variation in the head against which the
pump has to operate.
Fans
In most deep mines it is just as important
to provide a fresh air supply as it is to keep it
Fig. 14. Magnetic Separator, Manufactured by Dings Electro-
Magnetic Separator Company, Milwaukee, Wis.
free from water, as upon a good ventilation
depends to the greatest extent the efficiency
of the working force. Coal mining takes
place under conditions pretty well covered by
State laws and adequate ventilation is com-
pulsory. In this country five hundred and
ten million tons of coal were mined last year,
Fig. 15. Electric Lamp Equipment
and under average conditions the amount of
air supplied to a mine per 24 hours weighs
from two to three times as much as the coal
538
GENERAL ELECTRIC REVIEW
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THE USE OF ELECTRICITY IN MINING WORK
539
taken out in the same time, and this will give
an idea of the tremendous field of this applica-
tion.
Most mine fans are of the centrifugal type
and the electric drive is about the only
economical and satisfactory method of opera-
tion, and as an uninterrupted service is of
utmost importance, the motors should pref-
erably be direct-connected to the fan.
Some mine managers consider it good
practice to provide less ventilation at nights
and during holidays on account of the proper
saving which this method renders possible.
For this reason it is often advantageous to
vary the speed of mine fans. With direct
current this is readily taken care of by shunt
motors with field or armature control or a
combination of the two.
For alternating current the speed regulation
can be obtained by means of phase-wound
slip-ring motors with rheostat control, but
this method is of course not very efficient.
For this reason a-c. speed control by means
of multi-speed windings, dynamic regulation
and brush shifting is now being used more
and more, and is giving very satisfactory
service, under the particular conditions for
which thev are intended.
Fig. 16. Air Compressor Driven by a 375-h.p., 3500-r.p.m., 6600 volt Induction Motor
540 GENERAL ELECTRIC REVIEW
ELECTRIC POWER IN THE TEXTILE INDUSTRY
By C. A. Chase
Mill Power Department, General Electric Company, Boston
Electric drive when applied to textile machinery has resulted in the same high degree of success that has
been attained by its application in other industries. The. early history of the introduction of electric drive in
textile mills is interestingly narrated in the first part of the following article. The body of the article is devoted
to an exposition of the general merits of individual "motor drive," an explanation of why this type of drive is
preferable to "group drive," and a conservative but attractive series of statements about the highly creditable
past performances of "motor drive" and the excellent prospects for growth in future application. — Editor.
General
The advent of the electric motor may be
said to have marked the beginning of a new
epoch in the development of the textile
industry of this country. The importance of
the part played by electric power in this
development is evidenced by the fact that,
although the electric motor, in any form, has
been available for industrial use for less than
thirty years, and the induction motor for only
twenty-three years, the textile mills of this
country are using them today to the extent
to either locate elsewhere or supplement the
water power with one or several steam engine
installations. Steam engine driven mills were
constantly confronted with the necessity of
either increasing the capacity of existing
installations and struggling with the problem
of mechanical power transmission or adding
isolated engines at great expense in first
cost, decreasing the economy of their plant
with its increased operating and maintenance
charges. The timely arrival of the electric
motor is well shown by a few typical examples
Fig. 1. First Induction Motor Used in Textile Mill. Picker
Room, Columbia Mills Company, Columbia, S. C.
Fig. 2. First Direct Connected Spinning Frame Motors in
Textile Mill. Anderson Cotton Mills, Anderson, S. C.
of about 750,000 h.p., or about one-third of
all the power required in the textile industry.
Before the electric motor afforded a solu-
tion of the power transmission problem, most
textile mills, like other industries requiring a
large amount of power, grew up around the
various water power sites of the East and
South. Some, not so fortunate in location,
were driven by steam engines which mul-
tiplied in number with the growth of each
such mill. In many cases the growth of the
mills soon outstripped the existing or possible
water power development, making it necessary
of electric power installations in mills located
on the Merrimack River.
Lawrence, Mass., with approximately
60,000 h.p. of motors in its textile mills, leads
all other cities in the world in the utilization
of electric power in this industry ; The textile
mills of Lowell, Mass., use about 38,000 h.p.
of motors; and Manchester, N. H., has
approximately 31,000 h.p.' of motors in its
textile mills.
The phenomenal growth of the textile
industry in North Carolina, South Carolina
and Georgia has been in a large measure due
ELECTRIC POWER IN THE TEXTILE INDUSTRY
541
Fig. 3. First Engine-driven, Three-phase Generator in
Textile Mill. Lancaster Mills, Clinton, Mass.
to the introduction of electric power, by means
of which mills, located with reference to other
Fig. 5. Individual Motors Driving Finisher Pickers.
Erlanger Cotton Mills, Lexington, N. C.
advantages, such as labor, material, shipping
facilities, etc., have been able to utilize the
energy of the large and numerous water
powers of those states.
Historical
It is always interesting and instructive to
review the beginning of any new industrial
development and in the introduction of
electric power to the textile mills of this
country there are found a number of note-
worthy and significant incidents. The first
textile mill in the world to adopt the electric
drive throughout was the Columbia Mills
Company, Columbia, S. C.
At that time no textile
mill in this country or
abroad had attempted to
drive its machinery by
motors and such a radical
departure from contempo-
rary practice shows the
remarkable courage and
foresight on the part of
the Columbia Mills Com-
pany, its engineers and
the manufacturer of the
electrical equipment. It is
also of interest to note that,
of the three electrical manu-
facturers which tendered
propositions, two recom-
mended the continuous
current system with a large
Fig. 4. Typical Group Drive in Picker Room
motor for driving each
•542
GENERAL ELECTRIC REVIEW
floor of the mill. One manufacturer recom-
mended the polyphase induction motor, then
but a few months on the market, and their
recommendations as to the power system as
well as to subdivision of motor units, were
finally accepted. It is scarcely surprising
that one prominent manufacturer termed this
installation "A most hazardous and dangerous
experiment."
The motor installation consisted of seven-
teen 65 h.p. motors inverted and suspended
from the ceiling, in most cases the shaft was
extended and provided with two pulleys at
each end of the motor, and in some cases the
motor shaft was directly coupled to a line of
shafting. It should be noted that the type
of motor selected and all the various details
of installation have ever since been followed
by practically all textile mills using what
became to be known as the "group system"
in applying electric power. Fig. 1 shows the
first induction motor used in a textile mill.
This motor, and sixteen similar units, were
put into service early in 1894, and are still in
constant use.
The advantages obtained by the sub-
division of power units were soon apparent,
and in 1897 the first direct connected spin-
ning motors were installed in the Anderson
Cotton Mills, Anderson, S. C, the original
installation consisting of forty-two induction
motors, each mounted between two spinning
frames and connected to the cylinder shafts
by friction clutches. These motors are shown
in Fig. 3, and, while this form of drive is no
longer used, they are interesting as the
"progenitors" of the modern individual
spinning frame motor.
Previous to 1898 generators for supplying
current to motors in textile mills had been
driven either by waterwheels or by steam
engines by means of belts or ropes, and little
consideration had been given to the pos-
sibilities of direct connecting large polyphase
generators to reciprocating steam engines.
The first installation of this character was
made at the Lancaster Mills, Clinton, Mass.,
in 1898. In 1899 another unit of larger
capacity was installed in the same power
house, as shown in Fig. 2. In this mill, as
well as in the case of all previous electric
power installations, motors had been used to
replace the existing mechanical svstem. In
1899, however, The Olympia Mills,' Columbia,
S. C built the first new mill using electric
power throughout with steam engines as
prime movers. Direct connected engine-
generator units have, however, been rapidly
Fig. 6. Finisher Picker Driven by Direct Connected Motor.
Edwards Manufacturing Company, Augusta, Maine
Typical Group Drive in Card Room
Fig. 8.
Individual Motors Driving Cards.
Company, Bondsville, Mass.
Boston Duck
ELECTRIC POWER IN THE TEXTILE INDUSTRY
543
superseded or supplemented by steam turbo-
generators of which approximately 275,000
h.p. are today in operation in the textile mills
of this country.
Past and Present Practice in Application of Motors
Electric drive was first used in textile mills
as a convenient method of solving trans-
mission problems which, due to local con-
ditions, were either very difficult or imprac-
tical of solution by means of the mechanical
drive. Also, since the electric drive was at
first used for the most part for replacing or
supplementing the mechanical drive in old
mills, it is only logical that the "group drive"
motor, permitting the utilization of the
countershafting already installed, should have
been used. Furthermore, the most important
advantages obtainable from the electric drive
were little understood, even by its strongest
advocates, and the high cost and relatively
low efficiency of the small motors available at
that period naturally tended to perpetuate
the "group drive" for more than a decade.
Even during the past five years, one large
mill using about 7500 h.p. in "group drive"
motors chose this system for an additional
new mill requiring 3000 h.p. The "group
drive" still has a few strong adherents, but
Fig. 9. Two Frame Drive. Intermediate Roving Frames.
Nyanza Mills, Woonsocket, R. I.
the most progressive textile manufacturers
and textile mill engineers are coming to
understand, for reasons given in paragraphs
to follow, that they cannot afford to use any
system other than that which employs a
suitable individual motor for nearly every
textile machine in their mills.
The "group drive" is, therefore, now being
rapidly superseded by the "motor drive,"
a term which it is desired to strongly empha-
Fig. 10. Four-frame Drive, Speeders. Sterling Cotton
Mills, Franklinton. N. C.
Fig. 11. Typical Group Drive in Ring Spinning Room
size in the scope of this brief article. In this
connection it is of interest to note. that ten
years ago the average size of motors installed
in the textile mills of this country was about
75 h.p., wh;le today it is less than 16 h.p.
In two new prominent southern mills, using
respectively 2200 h.p. and 1900 h.p. in motors,
the average s'ze of motor is in one case 1.49
h.p. and in the other 1.40 h.p.
The most notable progress in the application
of electric power has been made by mills
devoted to the manufacture of cotton goods.
This may perhaps be attributed to the fact
that the first installations were made in
cotton mills, and that those most interested in
this new development were more closely
544
GENERAL ELECTRIC REVIEW
identified with that branch of the industry.
The silk, worsted and woolen industries,
however, have not been far behind in the use
of motors, and have led the way in the applica-
tion of individual loom motors. A silk mill
Fig. 12.
Four-frame Drive, Spinning Frames.
Mills, Clinton, Mass.
Lancaster
in New England was the first to use individual
loom motors, importing them from England in
1901. The illustrations of motor installations
in this article represent some typical "group
drives" and a few examples of the modern
tendency toward the "motor drive."
Reasons for "Motor Drive"
"Motor drive" of textile machinery is of
great direct value; 1st, to the mill operative;
2nd, to the mill product and, 3rd, to the mill
stockholder. Anything that is of benefit to
the operative or the product is, of course,
indirectly of benefit to the mill stockholder
also, but the subdivision given necessitates
a broader consideration more in accord with
the merits of the subject.
The operative is benefited by the better
conditions of light and ventilation always
secured by "motor drive." Shafting and
belting not only cut off a large amount of
daylight illumination but also seriously inter-
fere with the proper distribution of either the
natural or artificial lighting of textile machin-
ery. Furthermore, dust and lint, always
present to a greater or less extent, is kept in
constant circulation by belts and pulleys and
the problem of supplying pure air for the
operators is much more difficult than when
"motor drive" is used and shafting and
belting eliminated. No one familiar with
textile mill conditions will fail to agree with
these statements and a glance at Figs. 19 and
20 will make it still more apparent.
The operative is further benefited by the
better conditions of safety secured by "motor
drive." The "Safety first" movement has
justly received a great amount of attention
during the past few years and in the future
it is certain to be an important consideration
of the textile industry. Fig. 31 shows what
has happened to a section of countershafting
in a textile mill. The insurance companies
are prompt in recognizing the proper relation
between "motor drive" and the "Safetv
Fig. 13. Motors Direct Connected to Spinning Frames.
Erlanger Cotton Mills, Lexington, N. C.
Fig. 14. Chain Drive with Motor Installed Under Spinning
Frame. Arlington Mills, Lawrence, Mass.
ELECTRIC POWER IN THE TEXTILE INDUSTRY
545
first" movement. A recent issue of The
Travelers Standard contained an article
entitled "Accident Prevention in Weave
Rooms," from which the following quotation
operated by "motor drive." This point will
be brought out more clearly in the discussion
of benefits to the products of the mill and to
the mill stockholders.
Fig. 15. Individual Motors Geared to Spinning Frames.
Riverside and Dan River Cotton Mills, Danville, Va.
is taken: "From the safety standpoint there
are a number of admirable features connected
with the use of individual electric motors.
Belting dangers are avoided and long lines
of shafting are eliminated." As an example of
Fig. 1 16.
Individual Motors Geared to Twisters.
Dunean Mills, Greenville, S. C.
!;■!•■
llliliilltMi
Fig. 17. First Special Individual Mule Motors in Textile Mills.
Saxony Worsted Mills, Newton, Mass.
Fig. 18.^. Special Individual Mule Motor.
Ware, Mass.
Otis Company,
loom motor installation the above mentioned
article contains a cut which is reproduced in
Fig. 32.
Finally the operator is benefited by the
increased earning capacity of the machinery
The mill product is directly benefited by the
better general conditions of cleanliness always
secured by "motor drive." While this
benefit applies to every branch of the textile
industry, it is of special importance in the
54 1 1
GENERAL ELECTRIC REVIEW
case of costly fabrics, such as are produced in
the silk industry. The dripping of oil from
overhead shafting, even where neither care
nor expense has been spared to prevent it,
is a constant menace to textile mill product.
Fig. 19. Weave Room Operated by Mechanical Drive
Fig.
20. Appearance of Weave Room Shown in Fig. 19
After Installation of Individual Loom Motors
A more serious matter, however, is the con-
stant circulation of dust, fly, and other foreign
matter, caused by the pulleys, belts and
overhead shafting. In the cotton industry
the importance of keeping the roving and the
yarn free from such material is well known
and in the silk industry, involving delicate
and costly fabrics and where much of the
silk is dyed in the skein, the item of strictest
cleanliness in all the processes and the preven-
tion of damage to product from foreign matter
of any sort is regarded as of the highest
importance. The efficiency or earning capac-
ity of nearly all the preparatory machinery
of a textile mill can be widely varied by giving
it more or less care in the way of keeping it
clean. It is logical, then, that the "motor
drive," by eliminating shafting, belting and
pulleys and giving better conditions of clean-
liness, must be of much benefit to the mill
product. Furthermore, there have been many
cases where manufacturers have acknowledged
securing a much better quality of product due
to the easily controlled and steady speed
afforded by the "motor drive."
"Motor drive" is of benefit to the mill
stockholder, indirectly because of all the
before mentioned benefits and. directly
because it secures for him a maximum return
from a given amount of money invested.
" Motor drive" of textile machinery increases
its earning capacity and gives the stockholder
a two-fold profit, that is, a profit due to
decreased cost of production and an added
profit on the increased output. A few of the
more conservative of the textile machine
builders and textile manufacturers are still
Fig. 21. Loom Motors. Dunean Mills, Greenville, S.C.
apparently doubtful about the increased
production claimed for the "motor drive."
It is a well established fact, however, and
there is nothing at all mysterious about it.
Almost all textile machinery has a maximum
productive speed at which it should be
operated under certain conditions in order to
ELECTRIC POWER IN THE TEXTILE INDUSTRY
547
secure the best results in both quantity and
quality of product. If operated below the
proper speed there is a loss in production. If
operated above the proper speed there will
be a loss in production due to poor quality,
breakages, etc. In the case of power trans-
mission by shafting and belting entirely, or
only in part, as in the case of "group drive"
with motors, it is absolutely impossible to
maintain a definite speed on any large group
of machinery. Some belts will slip more than
others, all will slip more or less under changes
of load and changes in atmospheric conditions,
with the result that in a large spinning room
or weave room a variation of 10 per cent in
the speed of machines supposed to operate at
the same speed is not uncommon. It is also
well known that in practically every mill
driven by shafting and belting, due to the
trouble and expense of changing pulleys, much
of the machinery is constantly operated at
speeds which will not permit the best results
in production. When such machinery is
driven by suitable individual motors each
is found that the individual motor not only
makes a "sweeter" drive and cuts down the
expense of machine upkeep but also maintains
a higher average speed and consequently
gives an increase in production. In long lines
Fig. 22. Loom Motors. Erlanger Cotton Mills,
Lexington, N. C.
Fig. 24. Individual Drive of Silk Looms.
Silk Company, Easton, Pa.
Stewart
machine may be constantly operated at its
maximum productive speed and maximum
earning capacity.
In the case of textile machinery which has
heavy reciprocating parts or a very irregular
duty cycle, such as the mule and the loom, it
Fig. 23. Motor Driving Ribbon Loom. Macungie Silk Co.,
Macungie, Pa.
of shafting there is also often present torsional
disturbances, due to slippage of belts, changes
in load, etc. Such disturbances are often
very apparent and serious in the case of belt
driven looms and especially so if the looms are
weaving wide delicate fabrics. A typical
example of such trouble occurred recently in
the mill of a well known silk manufacturer.
A group of belt driven 92-inch looms weaving
crepe-de-chine had been producing a very
.-,. s
GENERAL ELECTRIC REVIEW
unsatisfactory quality of goods. Individual
loom motors were installed and the effect of
the steady rotative speed was immediately
apparent. The manufacturer soon discovered
that he could raise the speed of these looms
Fig. 25. Motor-driven Embroidery Machine. E.^Neufer
Embroidery Factory. Jersey City, N. J.
and is now securing from them a perfect
product with an increase of 18 per cent in the
loom output. Narrower looms in the same
mill when changed over to individual drive
also showed a remarkable increase in pro-
duction and the manufacturer confidently
expects still better results after he has had
more experience with "motor drive." It
is a significant fact that this manufacturer
has changed over his entire plant from belt
drive to "motor drive" and estimates that
the overall production which has a yearly
value of $2,000,000 has been increased 15
per cent thereby.
It is the universal experience of manu-
facturers who have used loom motors that the
steady rotative speed, together with the
inherent flexibility of such motors, permits the
operating and maintaining of much higher
loom speeds than any other form of loom
drive. Many worsted and woolen manu-
facturers admit 10 per cent more production
from their motor-driven looms. For a number
of years after the loom motor had proved its
value in the silk, woolen and worsted indus-
tries it was not considered a commercial
proposition for cotton looms, the product of
which is, relatively, of much less value per
yard. It is of interest to note that today
several thousand loom motors are operating
cotton looms in various sections of the
country.
It should also be noted that, contrary to
the popular impression, the "motor drive"
with its many small units does not mean a
greater transmission loss than the "group
drive" with its few large motors. The small
motors especially designed for textile mill
Fig. 26. Induction Motor Driving Eight Full Automatic
Sweater Machines. F. A. Patrick Knitting
Factory, Duluth, Minn.
Fig. 27.
Enclosed Induction Motor Geared to Napping Machine.
Tremont & Suffolk Mills, Lowell, Mass.
ELECTRIC POWER IN THE TEXTILE INDUSTRY
549
Fig. 28. Two 2500-kw. Turbo-Generators. Ayer Mill,
American Woolen Co., Lawrence, Mass.
Fig. 29. 1250-kw„ 3600-r.p.m., 600-volt, Mixed Pressure
Turbine, Riverside Division, Riverside 8c Dan
River Cotton Mills
service are of high efficiency and, in prac-
tically any given case, it can be shown that
their efficiency is much greater than the
overall efficiency of the large group motors
plus the necessary countershafting and belts.
Ijgj
*\¥^M
■HEHE :^^V^^** mP * ^^B
1 i
■
Fig. 30. Enclosed Continuous Running Loom Motors,
Geared to Automatic Broad Sheeting Loom.
Naumkeag Steam Cotton Co.,
Salem, Mass.
Fig. 31. What Has Happened to Countershafting in a
Cotton Mill. The Safety First Movement
is Always Advanced by "Motor Drive"
In a cotton mill the spinning process con-
sumes a much larger amount of power than
any other department, in some cases being
from 50 per cent to 60 per cent of the total
power required by the mill. In this process
the value of "motor drive" has been strongly
demonstrated. The increase in production
which may be obtained by changing over a
spinning room from mechanical drive or
"group drive" to "motor drive" depends, of
course, to a large extent upon the layout and
condition of the mechanical transmission.
In one typical case of two mills, only a few
miles apart, operated under the same manage-
ment and spinning the same yarns, the spin-
ning frames in one mill being driven by the
"group drive" and in the other by individual
motors, a comparative test was made and the
results showed that the "motor drive" frames
were producing over 12 per cent more yarn
per spindle. Under the usual mill conditions,
using as a basis of comparison the production
of spinning frames operated by "group drive "
from large motors, it is safe to assume an
increase of production of 5 per cent with the
550
GENERAL ELECTRIC REVIEW
four-frame drive and 10 per cent with indi-
vidual motors. A still further increase in
production may be obtained with varying
speed spinning motors, used for some years
abroad and now available of domestic manu-
facture.
Thus far in this discussion the constant
speed motor has, for the most part, been
considered. Many kinds of textile machinery
in the bleaching, dyeing, finishing and print-
ing processes require variable speeds, which,
to a large extent in the past has been secured
by the use of small non-condensing individual
steam engines or various sorts of more or less
uneconomical speed changing transmission
devices. Individual variable speed motors
for such machinery always greatly improve
the economy of drive, while the flexibility
in speed and the facility of its control give a
large increase of product. One printworks
which changed its machinery from steam
engine to "motor drive" acknowledged an
increase in production of 33 per cent. Other
machinery, such as slubbers and roving frames,
the speeds of which are sometimes regulated
by changing pulleys, can be operated at greatly
increased economical output by the applica-
tion of suitable individual variable speed
motors available for that purpose.
In the light of results which are today
being secured from "motor drive." it is
confidently predicted that, before the next
five years have passed, no new mill of con-
siderable size, regardless of the primary
source of its power, will utilize any other
form of drive other than a suitable individual
motor for practically each and every textile
machine.
ELECTRICITY IN THE AUTOMOBILE INDUSTRY
By Fred M. Kimball
Manager, Small Motor Department, General Electric Company
The present article deals with the use of electricity in the automobile industry — in the manufacture and
testing of automobiles, and in the numerous electrical accessories which have added so much to the comfort
of the automobilist, as well as its application to the electric vehicle itself. — Editor.
That the use of electricity and electrical
accessories has come to play an exceedingly
important part in the automobile industry
is emphatically manifest to those who have
had the opportunity of visiting our larger
automobile factories, as well as to those who
are at all familiar with the construction and
equipment of the modern automobile.
Not only has electricity been very largely
employed to facilitate improvements in
numberless manufacturing operations em-
ployed in the construction and assembly of
motor vehicles, but through the use of recently
perfected electrical appliances, the final test-
ing of the complete automobile, whether
gas or electric, has been very much expedited
and simplified, as well as rendered far more
accurate and reliable than could be attained
by the use of the strictly mechanical methods
upon which manufacturers were formerly
obliged to depend.
Furthermore, electricity has made possible
the adoption and use of almost numberless
accessories in the equipment of the auto-
mobile, which contribute enormously to the
comfort and pleasure of those who employ
this form of vehicle either for business or for
recreation.
In considering the various uses of electricity
in the automobile industry, we naturally turn
at first to its employment in manufacturing
operations. Here we find the power required
by the great factories occupying acres of
floor area supplied either by a central,
privately owned generating station, or as is
not infrequently the case, by special circuits
from the city plant. The enormous areas
covered by these establishments make the
distribution of power throughout the plant
most unsatisfactory from nearly every view-
point when shafting and belts are largely
employed.
Furthermore, the efficiency of transmission
when long lines of heavy shafting and many
belts are employed is comparatively low, and
the average annual productive capacity of the
machinery at the ends of these transmission
lines is materially below normal. Hence,
when such plants are electrified, the machines
and machine tools are usually disposed of in
ELECTRICITY IN THE AUTOMOBILE INDUSTRY
551
small compact groups, or driven by individual
motors, thus largely improving efficiency of
power transmission and assuring highest
and most constant productive speeds of the
machinery employed.
It has been truly said that as a result of the
intensive developmental work carried on by
electrical designers and engineers during the
past decade, there is now available an electric
motor for every service, a controller for every
motor, and an engineer who is an expert in
the selection and application of the motor
drive for every variety of manufacturing
requirement. In the equipment of a plant
like those herein referred to, the motors are
usually selected with the utmost care to meet
the particular requirements of machines or
tools which they are to drive. Hence, motors
varying widely in size and characteristics and
method of control will nearly always be found
in the equipment of the most modern plants.
The elimination of such transmitting
devices as heavy shafting, hangers, pulleys
and belts, which interfere with adequate
lighting and proper ventilation and produce
and distribute dust and dirt and constitute
a latent source of danger to employees, and
the substitution of the unobtrusive, clean,
safe, and easily installed electric conductors
and motors contribute in no small degree to
the maintenance of hygienic conditions and
consequently to the efficiency of the workman.
As all millwrights know, it is difficult to
maintain the alignment of long lengths of
shafting, and equally difficult to maintain
suitable tension on the belts of a mechanical
transmission drive under the varying con-
ditions of heat, cold, moisture and dryness.
Hence, it results that extensive systems of
transmission employing shafting and belting
are always relatively uneconomical in opera-
tion and maintenance, and irrespective of how
carefully the adjustment of such systems is
effected periodically, or at what expenditure
of time and labor, their condition begins to
deteriorate the moment after adjustment is
completed.
The loss of power in such transmission
systems may be so great — especially if the
tools are widely scattered, the supports for
the shafting not rigid, or the condition of the
belt and pulleys neglected — that only a com-
paratively small portion, sometimes as little
as 25 or 30 per cent, of the total power gener-
ated is finally utilized in useful productive
work.
When the electric motor is employed, even
in group drive, the distributing shafts are
comparatively short and of small diameter.
Speeds are fairly high and belts moderately
small and light; hence, highest-efficiency in
power supply. Inasmuch as the motor will
maintain its speed under all reasonable con-
ditions of load in virtual synchronism with the
speed of the supplying generators, which are
usually driven by the most perfect engines or
turbines and constantly attended by capable
men, the speed variations are small and the
maximum productive capacity of the machines
driven by them maintained at all times.
Furthermore, the power losses in the
electrical conductors and the motors them-
selves are comparatively negligible, and of
course no shafting or mechanical transmission
supplying any machines need be operated
when the machine itself is not doing useful
work. The electric motor lends itself par-
ticularly to use in body shops where many
woodworking machines are employed, the
cutters of which must be run at high periph-
eral speeds to produce satisfactory work, and
as the ideal conditions for motor drive con-
template the use of fairly high speeds, the
electric motor, either direct connected or
supplying its power to the machine spindles
through one short belt, finds in this applica-
tion its ideal employment.
Suitably designed motors are also largely
employed for direct connection to lathes,
milling machines, shapers, boring mills and
similar machinery, while small separate groups
of drills, screw machines, grinders and tools
of kindred type can each be operated by
single motors to great advantage.
A large number of interesting special
electrical applications are also to be found in
these factories which do not require the use of
motors. Such are electric welding, brazing,
electroplating, the tempering of tools and
dies, and in some of the most modern shops,
the melting of small quantities of high grade
steel in electric furnaces.
"Running in" the engine and transmission
drive of the gas car is effected speedily and
very effectively by driving the mechanism
for a suitable length of time by an electric
motor, this being a great improvement over
the former method and expense of this opera-
tion under the engine's own power.
Almost from the first, electricity has been
employed for ignition purposes in gas cars,
and although in the earlier cars the current
was produced from primary batteries, in
modern cars it is almost universally obtained
from magnetos or the storage batteries which
form part of the central station plant of the
552
GENERAL ELECTRIC REVIEW
best types of automobiles. The advantages
of the electric light for automobiles were
early recognized, and secondary batteries
charged from external sources were to some
extent used for this purpose. It soon became
apparent, however, that the service given by
the secondary battery alone was not adequate
nor sufficiently reliable, and the attention of
inventors was focused on the production of a
central station plant which would be light
enough in weight, compact enough in bulk,
large enough in capacity, and cheap enough in
cost, to permit its installation on an auto-
mobile chassis, and efficient enough in opera-
tion to permit its being driven from the main
engine without unduly detracting from the
motive power. Extraordinary progress has
been made within five years in the design
of such plants, and as perfection has been
approached, more and more uses have been
found for the current thus made available.
Not only are cars provided with electric
side, head and tail lights, but they are started
by the electric motor, and in the more luxu-
rious cars, heating units are provided in
limousine bodies for tempering the air; dome
and side lights for interior illumination; and
provision made for semi-portable trouble
lamps, projectors or search lights, the beam
from which can be thrown in any direction
by a simple turn of the chauffeur's hand.
In addition, heating units may be employed
for preparing lunches or similar purposes,
and in a few cases, the gear shifting is accom-
plished electrically, as is to some extent
electric braking and steering.
In case of the electric vehicle, the driving
power is entirely supplied by an electric
motor, taking its current from a storage
battery mounted under the body of the car.
In the design and construction of these motors,
the batteries which supply them with current,
and the mechanisms by which they are con-
trolled, extraordinary ingenuity and resource-
fulness has been shown in so utilizing material
that the maximum of motive power and
dependability with highest efficiency may be
secured with minimum weight and bulk.
The use of the electric motor for vehicular
purposes seems to be expanding more rapidly
in the field served by commercial vehicles
than in the field served by pleasure vehicles
at the moment, for wagons ranging in load
capacity from 750 lb. to 10 tons are becoming
common, especially in our principal cities.
Many of these large trucks are equipped with
electrically operated winches and hoists,
these latter being most convenient in the
service of those who handle and transport
heavy machinery, building material, coal,
safes, and similar loads. The pleasure vehicle
occupies a field particularly its own, and is
admirable for use by ladies in shopping,
calling, for the theater, opera, and pleasure
riding in our parks, and along our magnificent
boulevards. Doubtless with further stand-
ardization and lower cost, which will follow
increased production, its use will be still
further enlarged, for it has the undeniable
advantages of simplicity in construction, low
cost of maintenance and ease of operation in
the service to which it is best adapted.
In the garage we find electrically operated
air pumps, portable polishing and buffing
wheels for cleaning the bright work of auto-
mobiles, as well as electrically operated
lathes and other machine tools, forges and
pumps necessitated in the conduct of a
modern repair shop.
The mercury arc rectifier and motor driven
generator are indispensable adjuncts in charg-
ing, maintaining and conditioning the storage
batteries used for starting and lighting gas
cars, and for lighting and propulsion on elec-
tric cars. Although the electric vulcanizer for
repairing rubber tires seems to be the handiest
and safest device which has been brought out
for the use of small garages or individual car
owners, it has not thus far secured the market
that its value should command.
Among other ingenious and valuable elec-
trical applications are the electrically operated
speedometers, horns and other warning
signals, as well as the ingenious rear-end
signals which enable the chauffeur to indicate
on an illuminated panel at the back of his
vehicle, his intention of turning to the right,
to the left, proceeding straight ahead, or
stopping.
Altogether, electricity and its applications
are now indispensable adjuncts to the auto-
mobile industry and its product, and their
contribution to safety, comfort and the
enjoyment of motoring constitute a factor of
the very first importance in the estimation of
owners and operators alike.
553
"SUPPLIES"
DEVICES AND APPLIANCES FOR THE DISTRIBUTION, CONTROL AND
UTILIZATION OF ELECTRICITY
By S. H. Blake
Chief Engineer, Supply Department, General Electric Company
The term "supplies" as used in the electrical industry today is a very much misunderstood word, and
therefore the present article is welcome as explaining its modern significance. The magnitude of the supply
business will astonish many of our readers. The author deals with many aspects of this varied business and
shows the important position it holds in the electrical industry. — Editor.
The term "supplies" is commonly accepted
as the name for that class of material that is
necessarily carried in the storeroom for cur-
rent and emergency needs. Thus in every
line of activity — at home, in the office, hotel,
store, or warehouse, on shipboard, in all
industiial plants, railroad shops, garages,
banks, hospitals, schools, colleges, public
buildings, etc., — certain quantities of ma-
terials, tools, utensils, repair parts and what
not of the kind that are constantly consumed,
or that fail from time to time due to wear and
tear, are held in reserve for use as occasion
requires. Such "supplies" are generally
thought of as being relatively small in size
and of infinite variety.
In the electrical industry the term "sup-
plies" has come to have a very important and
far reaching significance as it embraces
various complete lines of appliances and many
kinds and types of electrical devices. Elec-
trical apparatus is grouped by its application
into such classifications as lighting, power
and railway. None of this apparatus becomes
of service, however, except through the
medium of intermediary and auxiliary means.
Thus certain appliances such as wires and
cable, switches, instruments, meters, cutouts
and kindred devices for the distribution and
control of electricity are necessary to gain
any benefit from the operation of a generator
by transmitting its energy to where it can be
used. The electric motor is equally dependent
on such agencies to receive current, as like-
wise is the railway for its particular require-
ments. Those accessories, therefore, which
find application in common in all the so-
called departments of the electrical industry
and those other devices that aid in the
utilization of electric energy for useful pur-
poses, but that do not fall into any particular
class division, all group themselves under the
category of "electrical supplies" and con-
stitute a very large separate class division
or department that is handled commercially,
at least, as a single line of goods. These vary
in size, for example, from a 150,000-volt
lightning arrester to a fuse plug, and from a
200-kw. transformer to a three-watt AU-
Nite-Lite outfit, but the same description
holds ' good with respect to their infinite
variety. Furthermore, articles classed as
supplies ' ' are ever increasing in number and
diversity as from day to day and year to year
electricity finds novel and more extended
applications.
There is, however, no hard and fast rule
as to what supplies comprise. Commercial
expediency and the natural growth of the
electrical business have been potent factors
in determining such classification for each
manufacturing company and what has grown
to be considered "supply" material with one
concern is sometimes associated in another
company with a completely different division
of apparatus.
In the earliest days of electric lighting a
"system " consisted of an arc-lighting dynamo
and from one to four arc lamps. No ammeters
or voltmeters were available and wiring
methods and materials, judged from present
day standards, were of the crudest sort. It
is not unlikely, however, that there was a
tendency even at that time for the business
to divide itself into departments, namely
"apparatus" consisting of primary articles
initially sold, and "supplies" comprising
wire, line material, repair parts, etc. As time
went on the number of arc lamps that could
be operated from one machine was gradually
increased and additional auxiliary supply
devices such as instruments, lightning arres-
ters, insulators, weatherproof wire, switches,
etc., were added to the necessary equipment
for a lighting plant. Then came constant
potential d-c. generators and incandescent
lamps with new classes of supplies in the way
of lamp sockets, interior wiring devices,
ammeters and low-voltage voltmeters, while
incandescent lamps involved such radically
different manufacturing and selling problems
as to require segregation as a separate division
of the industry. The introduction of the d-c.
motor for railway and power work quite
554
GENERAL ELECTRIC REVIEW
naturally was the beginning of another specific
department, and brought rheostats, circuit
breakers, railway line material, rail bonds,
etc., into the "supply" line.
The successful commercial development of
alternating-current apparatus brought trans-
formers first for lighting circuits and later for
power purposes into the field of "supplies"
and also a-c. instruments of all kinds, current
and potential transformers and oil switches.
The change from the "flat rate" method of
charging customers for electric service to the
use of meters for actually measuring the cur-
rent consumed added watthour, maximum
demand and such metering devices for both
a-c. and d-c. The enclosed arc lamp first
proved popular for a-c. and d-c. constant
potential connection either for interior use
or for out of doors, and later was used very
extensively for series alternating street light-
ing in connection with constant current
transformers. Considerable numbers of series
enclosed d-c. lamps were also installed for
operation from 6.6-ampere arc machines.
This complete line of appliances comprising
lamps, transformers, panel boards, special
switches, hanger cutouts, mast arms, sus-
pension hangers, etc., are naturally con-
sidered as supply material. Since then, by
the introduction of the magnetite system
there have also been added to the above line
series rectifiers, magnetite and copper elec-
trodes, ornamental pole lamps and all the
various auxiliary devices necessary for its
successful operation. Series incandescent
street lights operated by means of constant
current transformers or reactance regulators
have become an important branch of supplies
and involve the use of special sockets, fix-
tures, individual compensators and trans-
formers, group transformers, film cutouts,
brackets, etc.
The wonderful growth of the use of electric
motors for power applications in the industries
has required the development of a very com-
prehensive line of motor control devices.
Other additions to supplies were generator,
voltage and feeder regulators, designed respec-
tively to maintain constant voltage at the
station and at the center of distribution on
long feeders, which became necessary as
refinements in service were required and the
territories served grew more extensive. The
requirements of modern lighting, railway and
hydro-electric transmission systems involve
the use of a great variety of lightning arresters
and protective devices covering the whole
ranges of a-c. and d-c. operating voltages and
conditions.
From year to year the demands for wire
and cable, wiring devices, meters, instru-
ments, transformers, switches, line material,
etc., have steadily increased until the pro-
duction requirements for these staple articles
have reached enormous amounts and must
continue to expand in unison with the growth
of the electrical industry as a whole, which of
late years has been at the rate of about 20 per
cent per year except in times of depression.
Besides the many and varied appliances
above mentioned there are certain others sold
as supplies that to the layman represent
electricity materialized into utility form.
Such articles are fan motors, heating devices,
X-ray tubes, multiple rectifiers, transformer
specialties, electric furnaces, mine lamps,
ozonators, mercury lamps, headlights, sign
flood lamps, etc.
It is a simple statement of fact to say that
no electrical installation, whatever its pur-
pose, can be made without using supply
materials. Instruments, rheostats and
switches and sometimes regulators and trans-
formers must be used in the generating
stations; switches, lightning arresters, pro-
tective devices and sometimes transformers
and feeder regulators on the transmission
lines ; and all the different kinds of appliances
enumerated and more too for providing,
installing, metering, operating and controlling
the connected load. The multitude of elec-
trical utility appliances that are among the
many devices of the supply line are, like
incandescent lamps and motors, the means
by which comforts, conveniences and safe-
guards are introduced into our lives, at home
and abroad, and efficiency and economy into
our industrial undertakings. The arc lamp
helps to make our streets as safe at night as by
day. Industrially it is used for the lighting
of yards, docks and large interiors in many
plants, and is also used for blue printing,
silver printing, photo-engraving and enlarg-
ing. High-candle-power carbon arcs and
sometimes mercury arcs are utilized in large
numbers for furnishing the very brilliant
illumination necessary for the taking of
moving picture films. Heating devices in
great variety are very convenient and useful
for cooking, heating and ironing in the hotel
and home and find many industrial applica-
tions such as drying various materials,
baking paint and enamel, -aiding chemical
processes, vulcanizing rubber, etc. The
multiple rectifier serves to charge the pleasure
vehicle at home and the motor truck at the
industrial plant. The transformer is equally
useful in house or factory furnishing the
THE SUBDIVISION OF POWER AS SOLVED BY
555
proper voltage for light and power. Trans-
former specialties of the bell-ringing and
All-Nite-Lite types also have wide useful
applications in both fields. Electrical ozo-
ators are used to aid ventilation, and indus-
trially for destroying disagreeable odors,
while greatly concentrated ozone is useful
as a strong oxidizing agent in chemical pro-
cesses and for the sterilization of water.
Electric resistance furnaces are of great
service industrially for securing the proper
temperature for melting metals, reducing
ores, etc., Thus we could elaborate to almost
anj' extent, for electricity has come to con-
tribute so much to our present day life that
it is difficult to realize, and impossible in a
few lines to describe, its many benefits. It
is no wonder that the aggregate sales of
electrical supply material of the nature out-
lined in this article, has grown in thirty years
to be over $100,000,000 a year, in this
country alone, and in the large electrical man-
ufacturing concerns such material comprises
about a third of the total amount of goods
produced.
No reference has been made in this paper
to telephone, telegraph, fire alarm, electric
elevator, and signal accessories, and such
novelties as flash lamps, annunciators, elec-
tric bells, buzzers and gongs, toys, burglar
alarms, automobile attachments of electrical
nature and a thousand and one other con-
trivances, the total yearly sales of which will
run into many millions of dollars.
THE SUBDIVISION OF POWER AS SOLVED BY THE SMALL MOTOR
By R. E. Barker and H. R. Johnson
Small Motor Department, General Electric Company
Only in very few instances is the total outgoing power of a power plant consumed intact. Efficiency in
power supply demands large generating units and "low friction" transmission; value in utility requires that
the total power generated be subdivided in order that portions can be used simultaneously at different machines.
This subdivision of mechanical power by purely mechanical means — gearing, shafting, belting, etc., — has
always been clumsy and inefficient. The substance of the following article comprises a general description
of the admirable manner in which mechanical power can be subdivided through the medium of the electric
generator and electric motor. — Editor.
From the beginning of time man has seen
the manifestations of power about him in
countless forms, and practically all develop-
ment in the material world has come from his
ever increasing efforts to obtain and control
power for supplementing and aiding the work
of human hands. Following the invention of
the steam engine the use of power increased
at an astonishing rate and, as larger and larger
units were built, so more and more study was
given to methods and means of subdividing
the power thereby rendered available. Re-
search along mechanical lines has produced
many ingenious solutions of the problem;
some of which were generally satisfactory and
have survived, while many others, not proving
practicable, have been relegated to oblivion.
Meantime the progressive demands for more
efficient and convenient methods of subdivid-
ing power have become more and more in-
sistent and the Twentieth Century brought
with it the electric motor, which at once
took pre-eminently first place as a means of
economical and adaptable power distribution.
When Michael Faraday made the discovery
of the principles of electro-magnetic induc-
tion, a new field was opened for investigation
and many were the experiments made as a
result thereof. Invention followed invention,
until, after a time, the electric dvnamo was
announced and its reversible action dis-
covered. This action whereby a dynamo
electric machine may transform electrical
into mechanical energy or vice versa is of the
greatest importance as upon it is based the
efficient conversion of power which every
electric motor illustrates. With'n about a
century after Watt's invention of the steam
engine, the direct current dynamo and motor
were in commercial use and the principle
of the polyphase induction motor demon-
strated.
To interest the users of power in any system
of subdivision employing electric motors was
at first not an easy task, but by diligent effort
backed by strong belief in the correctness of
the basic principles involved the pioneers in
the field of electric motor manufacture and
application developed a business which has
become of the first importance.
Although the rapid progress of the electric
drive as applied to the most diverse require-
ments is generally appreciated, it may be of
interest to fix numerically, by reference to
published statistics, the position held by the
electric motor. Census figures available up
to 1909 show that, out of a total of 18,680,000
horse power employed in the factory class of
manufacturing establishments in the United
States, 4,817,000 horse power or 25.8 per cent
556
GENERAL ELECTRIC REVIEW
was applied through the intermediary of the
electric motor. If it may be permitted to
introduce a present day estimate based on the
records of previous years, the total horse
power now used is probably about 25,650,000,
of which 11,000,000 or 42.9 per cent utilize
electric motors. When we consider, first,
that the figures quoted above do not include
certain industries using motors in large
numbers — for example, mining, transporta-
tion, etc. — second, that the electric motor
is a power transforming device and not a
primary source of energy, and finally, that
the commercial, as distinguished from the
experimental stage of the motor business
dates back not more than a score of years, the
position now held by electric power is of
striking significance.
This eager application of small motors by
nearly every class of trade and manufacturing
industry must be accepted as irrefutable proof
that in point of reliability, simplicity, useful-
ness and adaptability, the electric motor
possesses attributes solely its own.
Regarding the quality of the present day
electric motor, one cannot presume to say
that the future discoveries or evolutionary
progress may not cause it to appear in com-
parison crude, unwieldy and inefficient.
Nevertheless the improvements which have
been made thus far in its brief history are to be
regarded with justifiable pride. Compared
with the early bipolar designs with horseshoe
magnet frames, pedestal bearings, sight feed
oil cups, unprotected vital parts, etc., direct
current motors of today are incomparably
superior in compactness, symmetry, unified
construction, mechanical protection to the
windings or other current carrying parts, and
in the countless detail refinements which go
to make the near approach to mechanical and
electrical perfection.
Simplicity has always been a marked
feature of the electric motor as contrasted
with other power producers. It is unnecessary
to detail the marked reduction in the number
of working parts of an electric motor when
compared with the steam or internal com-
bustion engine. The elements of compact-,
ness, ruggedness and simplicity combine
inherently and to their greatest extent in the
modern electric motor.
The claim of the electric motor to a place
in the front rank of useful apparatus rests
upon its economy and reliability in both
small and great sizes, more effective appli-
cation of power, insuring increased produc-
tion and improved operating conditions.
The call for "intensified production" has
rapidly increased the use of power-driven
machinery in every line of manufacture, and
the average decrease in size of motor used
plainly indicates that larger quantities of
motors in smaller sizes are being employed.
Individual efficiency has been greatly
enhanced through the universal use of the
electric motor, while a large share of the
drudgery heretofore connected with many
occupations has met with permanent banish-
ment. For the work of the baker, blacksmith,
butcher, cobbler, grocer, job printer, etc., as
well as for the home, farm, laboratory or
private shop, the electric motor and central
station service readily and completely solve
the power supply problem, giving high grade
service with small initial investment com-
bined with an operating cost usually much
lower than could be obtained from an indi-
vidual generating plant of equivalent capacity.
This result is very largely due to the ease and
economy with which electric power can be
subdivided to suit widely differing demands.
While the cost of installation and main-
tenance as well as the loss of power in friction
strictly limit the distance that can be served
by mechanical transmission from a single
source, the introduction of electricity as a
power transmitting medium coupled with its
easy subdivision, has multiplied many times
the radius which can be served economically
by a single generating station.
The result in all thriving communities has
been the establishment of highly organized,
efficiently operated central stations capable
of successfully competing with the best prac-
tice in large isolated power plants. Generally
speaking, we find that, not far beyond the
economical limit at which the consumer can
afford to take his power from the central
station, comes the factory plant whose
machinery is so distributed that electric
transmission is again seriously to be con-
sidered. In fact, in a community adequately
served by the central station, there will be
found few plants, and those only under
exceptional conditions, that should not ulti-
mately adopt electric drive using purchased
power.
Of the many strong claims already estab-
lished for the electric motor as an indispen-
sible factor in modern industry, one of the
best arguments in a large number of cases is
not only the greater economy of generation
made possible by larger centralized units,
nor yet the salvage of power formerly lost
in friction of mechanical transmission, but
THE SUBDIVISION OF POWER AS SOLVED BY THE SMALL MOTOR 557
the highly developed and superior operating
characteristics of the electric motor itself,
which directly or indirectly contributes to
increased production with the same machinery
and personnel.
Increased production with motor drive may
be due to one or more of the following causes :
elimination of slipping belts and slowing down
of engines under heavy loads, thus making
possible the maintenance of maximum pro-
ductive speeds, and fewer interruptions to
service due to broken or thrown belts, broken
shafting, overheated bearings, repairs to
boilers, etc. With efficiently subdivided
motor drive the crippling of a single motor
will, at worst, put only one machine or
restricted group of machines out of business.
The electric motor is conceded to be the most
rugged and reliable driving unit in use at the
present time, and the service given by central
stations skillfully operated, with their reserve
equipment, makes failure of power during
working hours a remote possibility.
The increased sense of personal safety due
to the elimination of belts, shafting and
couplings, and the better lighting and ventila-
tion that result from electrification, is also
an important contribution to the working
efficiency of the working force.
Convenience in the sequence of operations
and general arrangement, absence of delays
in starting, stopping and regulating the speed
of machines through properly planned electric
drive and control, effect very marked increases
in production, particularly in the case of
certain machines, for example: lathes and
boring mills, due to the ease with which
maximum cutting speeds at different working
diameters may be regulated; printing presses,
due to absolute and centralized control;
electric reversing equipment of planers,
shapers and slotters, allowing uniform accel-
eration and retardation at the start and finish
of the stroke. There are also a large variety
of miscellaneous machines which xan be run
at the correct speed through the use of adjust-
able or multi-speed motors, thus avoiding
delays incident to the employment of cone
pulleys or change gears.
It is safe to say that in almost any factory,
where production is pushed energetically,
the output per employee attendant upon
machinery may be increased 5 to 15 per cent
by the introduction of approved arrangements
of electric drive. In the case of certain auto-
matic or semi-automatic machines and con-
trols, made possible only since motor drive
was adopted, production is often increased 50
per cent or more. In general, the cost of
power and fuel is only 2.5 to 5 per cent of the
value added or created by the manufacturing
process, while wages (exclusive of clerks and
salaried help) vary between 30 and 50 per
cent of the total manufacturing cost. These
figures show why a large majority of manu-
facturing industries profit very substantially
by the use of electric power, since a marked
increase in the cost for power is justified if
thereby the major item of wage expense be
reduced.
In addition to the foregoing there are
numerous attendant advantages to be gained
by the adoption of electric drive. By way of
illustration, a few of these advantages may be
briefly mentioned.
Small expense required to provide power
at out of the way places.
Electric transmission is practically un-
hampered by distances intervening between
buildings or the character of the existing
installation; e.g., presence of tanks, vats, etc.,
better light and circulation of air; less dust,
dirt and noise; reduction of accident risk;
less expensive building construction; free
overhead space for cranes; ideal freedom in
arrangement of machinery, due to flexible
nature of power conductors; accurate means
of checking power requirements of individual
machines or departments.
The electric motor in some one of its many
well standardized types is capable of driving
either by belting, gear, chain or direct con-
nection, practically any and every type of
machine devised for power drive. A list of
such everyday uses of electric motors would
form a fairly complete catalogue of our diver-
sified present-day trades and manufacturing
industries, and of the labor saving machinery
used by them.
The only limit to the possible economical
uses of the electric motor is to be found in a
limited class of portable and semi-portable
machinery operating over unrestricted areas,
such as traction engines, automobiles, con-
tractors' machinery, etc. Even in a large
proportion of such cases the problem of power
supply may often be solved by storage bat-
teries, portable generating sets or by service
lines from the source of electric supply,
employing flexible cables or temporary over-
head construction to the point of application.
Perfection in the design and application
of standard and special types of electric
motors have made practicable the develop-
ment of many devices where the obstacle of
securing an effective driving element had
558
GENERAL ELECTRIC REVIEW
previously baffled inventive ingenuity.
Again, machines which were operated in a
crude and clumsy fashion by steam, com-
pressed air, or other inefficient means, have
been rendered practicable and efficient solely
through the use of the electric motor. The
compactness of the electric motor and the
flexibility of power supply and control have
led to the design of machine tools and other
machines so that the motive power becomes
an integral part of a comprehensive scheme
rather than a scantily considered auxiliary.
The natural adaptability of the electric motor
will perhaps be most forcibly illustrated by a
few examples of the kind of application just
referred to :
Power-driven portable vacuum cleaners
replacing the rotary brush carpet sweeper.
Domestic washers and sewing machines,
formerly operated by manual or foot power.
These devices are not only conveniently and
cheaply run by electric motor but have been
greatly improved under the stimulus of a
motive power at once light, compact, durable,
and free from complication and operative
difficulties.
Chipping and riveting hammers, drills for
wood, metal and rock, formerly depending
for power upon compressed air or steam
supplied through pipes or hose, may now
receive power by flexible electric cable with-
out losses by leakage, condensation, plugging
up or pipe "kinking."
Convenient desk, wall and ceiling fans have
come into common use only since the develop-
ment of suitable electric motors.
Numerous types of hoisting apparatus,
ranging from the portable engine-driven
hoist to the largest traveling crane, find the
perfect means of operation through electric
motors.
The use of portable slotters for heavy
machine work is rendered feasible by the
ease with which power can be brought by
flexible conductors from conveniently located
outlets.
Electric starting motors have practically
superseded compressed air or mechanical
devices as a means of starting vehicle, sta-
tionary and marine engines.
The electric motor with its highly developed
control accessories makes possible the inde-
pendent and automatic functioning of dif-
ferent parts of such machines as turret lathes,
boring mills and screw machines.
The inherently high rotative speed of elec-
tric motors has permitted the efficient
redesign of many types of machinery, and
has given great impetus to the development of
centrifugal fans and pumps, whose normally
efficient speeds are particularly suitable for
direct connection to electric motors.
Motors especially des gned with extra
heavy frames for steel mill service, having
practically fireproof insulation and complete
mechanical protection for interior parts, are
equally suitable for numerous other classes of
work where extremely rough usage or high
temperatures must be met. The application
of electric motors to the various special uses
required in mines affords a good example of
adapting the driven device, even in the
smaller sizes, to very special conditions of
installation and service.
Standard adjustable speed motors equipped
with control apparatus specially designed for
printing establishments not only permit
delicate and positive speed adjustment but,
by means of extremely low speeds, "jogging"
control and stop buttons, save a great deal
of time and reduce the personal risk in pre-
liminary or "make-ready" operations.
The incorporation of electric motors into
the mechanical structure of the driven
machine is also well exemplified by specially
designed back geared alternating current
motors for driving Linotype machines, and
by small head stock motors for woodworking
lathes in which a hollow motor shaft actually
serves to carry the lathe face plate.
Fairly complete lines of vertical motors
provide for quiet and positive drive of vertical
centrifugal pumps, and also simplify the
driving arrangements to vertical shafts and
spindles of numerous other machines, such as
surface grinders, centrifuges, etc.
In the foregoing, the history of the electric
motor and the subdivision of power as solved
by electric energy has been sketched but
briefly and without attempt to cover more
than the smallest fraction of the uses to which
the ubiquitous motor is and can be applied
with a success as pre-eminent as universal.
If it be considered that the present radius of
action and effectiveness of the submarine
has been made possible solely by the use of
electric energy, that the propulsion of the
largest ocean going ships by electric motors
bids fair to be the greatest marine engineering
development of the near future, that the
problem of trunk line transportation as well
as the "short haul" will ultimately be solved
electrically, we will still fall short of realizing
the far reaching effect which electric power
exerts over the industrial, social and economic
life of humanity.
•
THE
GENERAL ELECTRIC COMPANY
AT THE
PANAMA-PACIFIC
INTERNATIONAL EXPOSITION
'
h-2
£ b
S-S
S E
c
I*
Sh
561
THE GENERAL ELECTRIC COMPANY'S EXHIBITS AT THE PANAMA-
PACIFIC INTERNATIONAL EXPOSITION
By George Weed Hall
Advertising Department, General Electric Company
This article together with the one that follows tells of the General Electric Company's exhibits at the
Exposition. The illumination of the Exposition is dealt with in detail by Mr Ryan in a separate article. Those
parts of the present article dealing with the exhibits should form a useful record for those interested in this
subject. — Editor.
Beginning with the first active operations
toward creating that stupendous undertak-
ing, the Panama-Pacific International Exposi-
tion at San Francisco, which transcends in
many ways all previous world's fairs, the
General Electric Company has been prom-
inently identified with achieving the success
of many of its great features. That this
splendid exposition was practically ready on
time is due in large measure to the service
rendered by electricity. As the Exposition
stands today, it may be said from many
standpoints to be a tribute to the progress
and efficiency of the electrical industry.
The Exposition is in a broad sense an
exposition of the greatness of electricity!
And the glory of the Expo-
sition is the electric illumi-
nation at night. At the very
inception of the Exposition
idea, this was the initial
factor considered that should
contribute to proud achieve-
ment.
The General Electric Com-
pany was consulted, and
Mr. W. D'Arcy Ryan, the
Company's Illuminating En-
gineer was specially com-
missioned at the request of
the Exposition officials to
create a new form of expo-
sition lighting. A consider-
able appropriation was made
by the General Electric
Company to defray the cost
of the preliminary work, and
Mr. Ryan and his corps of
assistants were loaned to
San Francisco to devise new
and beautiful effects in
illumination.
Mr. Ryan was made Chief of Illumination,
being given carte blanche to create a new
night grandeur. Over two years ago he and
his staff began the great work of designing a
scheme of illumination that would comple-
ment the brilliant plans of the architects
and of Mr. Jules Guerin, Chief of Color.
The Exposition was to be a wealth of soft,
blending colors by day, transformed into
beautiful harmony at night by a magnificence
of glowing flood-lighting. These plans have
been most effectively realized by the co-
operation of Mr. G. L. Bayley, Chief of the
Mechanical and Electrical Department of the
Exposition. The designs for the lighting
effects were worked out in the Illuminating
Laboratories of the General Electric Company.
Here were conceived the famous Exposition
jewels, the glory of the Tower of Jewels;
the great batteries of searchlights that light
Fig. 1. Palace of Manufactures
this tower and all the grand exhibition pal-
aces; the magnificent heraldic banners that
diffuse the wealth of light from powerful arc
lamps along the main avenues of the Exposi-
tion; the mammoth "scintillator," whose rays
562
GENERAL ELECTRIC REVIEW
flood the sky; the ever- varied display of fire-
works that draws throngs to the Marina and
the yacht harbor several nights a week; the
smoke bombs in variegated colors and the
wonderful, soft flood-lighting of all the beauti-
Fig. 2. "Mazda Service" Research Laboratory Exhibit of the
General Electric Company, from the South,
Palace of Manufactures
Fig. 3. "Mazda Service" Research Laboratory Exhibit of the
General Electric Company, from the East,
Palace of Manufactures
ful architectural triumphs. At night the hills
of San Francisco are darkened with crowds
eager to view the marvelous burst of this
aurora of light from a proper perspective.
Tuesday, April 13th, a special day, was
celebrated in honor of Mr. Ryan, with
appropriate ceremonies, followed at night by
a brilliant illumination display. The program
was carried out in the evening in the Court of
Honor, and a tribute was paid to Mr. Ryan
for his contribution to the Exposition, and
to the General Electric Company for its co-
operation. At the conclusion of his remarks,
President Moore of the Exposition Company
presented Mr. Ryan with a handsome bronze
plaque as a material expression of his appre-
ciation.
It is generally acknowledged that the
illumination surpasses anything of the kind
hitherto undertaken. Viewing it for the first
time, the spectator finds an analysis of it as
difficult as an analysis of the emotions it
inspires. Opinion is spontaneously expressed
that one has not really seen the Exposition
until the night fairyland bursts into view.
The illumination is best described by its
originator and the reader is therefore referred
to the article by Mr. Ryan in this issue.
Visitors at the Exposition are also much
impressed with the "Home Electrical," one
of the exhibits of the General Electric Com-
pany in the Palace of Manufactures. Homes
equipped with electric appliances for domestic
uses are not entirely new. It is several
years since electrically-operated devices
were first introduced into the home. Other
model homes, electrically equipped, have
been exhibited at various times; but now
that many of these devices have become well
known through use, the "Home Electrical"
at the Exposition is not so much the object of
public curiosity as it is of genuine interest and
investigation to learn what are the newest
applications of electricity in the home.
Judging from the crowds that throng the
"Home Electrical," it is one of the most
popular exhibits. Situated in that portion
of the building immediately adjoining the
Court of Flowers and the Court of Abundance,
this full-sized home, thoroughly modern, and
of simple Spanish-California bungalow design
of moderate cost, is complete in every detail,
read\r for occupancy. Electricity heats,
lights and cools it, and performs the house-
hold duties from cooking to sweeping. Each
of these applications of electricity is now
part of the life of innumerable American
homes. The "Home Electrical" is fully
described in an article by Mr. Don Cameron
Shafer in this issue.
We who are so intimately associated with
the manifestations of electricity, the most
flexible and efficient form of energy, do not
marvel at its accomplishments. We some-
times fail to reflect on the scope of its activities
until they are measured by' some striking
contrast. The "Home Electrical" typifies
electricity in its relation to the finer things
of life. Yet as easily as it adds comfort to
the home, it will gouge out huge, yawning
GENERAL ELECTRIC COMPANY AT THE PANAMA EXPOSITION
563
excavations; lift and transport mighty timbers
and steel structural members, and pour
concrete for great architectural piles.
Electricity was chosen to do most of the rough
work during the construction period at the
Exposition. Time and economy were vital
factors in building the Jewel City, and it was
determined to have this great undertaking
finished in its entirety when the grounds
were formally opened. The temporary light-
ing during these early operations, including
that for plastering and carpenter work in the
buildings at night, was generally furnished
by various types of lamps of General Electric
Company manufacture. Electricity not only
lighted, but was largely instrumental in
building the Exposition.
Motors manufactured by the General Elec-
tric Company were used very extensively
for power application during these building
operations. They ranged in size all the
way from fractional horsepower machines to
those of 50 and 60 horsepower. The variety
of service for which they were used serves to
illustrate the almost unlimited flexibility of
electric power. Saw-tables, planers and
sanders, electrically driven, worked timbers
and lumber into shape; electrically-operated
concrete mixers and plaster mixers poured
tons of concrete and stucco, the latter being
applied with electric cement guns. The
pumps that furnished gallons of water for
mixing and other purposes were electric-
driven, as were air compressors for rivet-
ing; drills, milling machines and boring
mills cutting iron and steel members and
shapes; derricks, hoists and conveyors lifting
tons of material of all kinds, and trucks
transporting raw and finished products of
every description to the centers of activity on
the grounds where needed.
While the general work of building the
Exposition proper was going on, electricity
also assisted in various ways in placing and
constructing the exhibits of other manu-
facturers. After installation, the successful
display and operation of many of these
exhibits is now possible only through the
application of electricity as power, heat or
light. But before referring to this phase of the
subject, we wish to call attention to the very
interesting display of the General Electric
Company in the large courtyard of the
"Home Electrical." This forms a part of the
"Home Electrical" exhibit, although it is in
a certain sense apart from it. The two com-
bined exhibits cover a total of some 6100
sq. ft. of area.
The courtyard is enclosed with a low
concrete wall having a front entrance gate of
ornamental design leading into the roadway
between the Mazda research exhibit and the
garage, and one opening from the side into the
Fig. 4.
Commercial Lamp Exhibit, General Electric Company
in Pergola, Palace of Manufactures
Fig. 5. Section of Wall and Roof of House showing how Wiring
and Wiring Devices are Installed, Exhibit of General
Electric Company, Palace of Manufactures
spacious pergola at the rear of the garage.
The courtyard is decorated with growing
palm trees attractively arranged to group the
different classes of exhibits. Glistening
through the palm trees back in the distance
is a large display sign of the universally
recognized G-E monogram mounted high on
the wall. This is made up of the famous
jewels similar to those on the Tower of
Jewels, and is illuminated by projection from
searchlights mounted on the house roof, in
the same manner as the general scheme of
flood-lighting from concealed sources of
buildings and groups of statuary about the
grounds.
564
GENERAL ELECTRIC REVIEW
Entering the courtyard through the front
gate, the first exhibit at the right is the
"Mazda Sendee" research laboratory dis-
play. This exhibit emphasizes strongly the
famous "Mazda Service," which has come to
Fig. 6. Interior of one of the Substations for the General Lighting
System throughout the Exhibition Grounds, in the Exhibit
of the General Electric Company, Palace of Manufactures
signify the greatest factor in the progress
of the science of incandescent electric lighting.
Here for the first time the public has an
opportunity to observe the interesting phases
of the development of the Mazda lamp from
the early stages. Visitors may listen to in-
structive and entertaining talks by laboratory
experts, explaining the painstaking work and
methods that enter into the perfection of these
wonderful lamps.
Mounted on special display boards are
raw materials, parts in process of construc-
tion and finished parts; tungsten ore, ground
ore, oxide metal and wire; tungsten contacts;
tungsten block, rods and wire; molybdenum
sheet, rods and wire; various types of brushes
and contacts; copper coated iron wire, com-
pensator, aluminum coated copper wire,
alumina dies, calorized samples, moulded
compounds; tungsten tube, copper clamp for
tungsten tube, binel metal, sheath wire, iron
crystals, section of a sheath wire unit, therm-
enamel coated copper wire; Coolidge tube
anode and cathode, X-ray targets; tungsten
steel tool and a typical shaving turned off
with the tool; compensator lamp, carbon
lamp, gem lamp, Mazda tungsten lamp and
gas-filled compensator lamp, etc.
There is an apparatus to show the strength
of tungsten wire; another to show the mag-
nified image of a lamp filament; spark inter-
rupter, to show tungsten contacts in opera-
tion; Coolidge X-ray tube and battery, to
show the filament in the tube lighted; lamp
mounts, to show the flexibility of Mazda
lamp filaments; copper castings and X-ray
photographs, to show the value of the X-ray
tube for discovering imperfections in castings;
photometer, to show how the candle-power of
lamps may be determined; various insulation
materials ; apparatus to show the tone of iron
and tungsten wire; nitrogen apparatus, to
show a typical nitrogen purifying installation ;
argon apparatus in miniature, to show how
argon is manufactured ; samples of pure
metallic boron and a boron regulator, a lamp
outfit used particularly to regulate car light-
ing; large incandescent lamps, to show the
maximum amount of light in a minimum
sized bulb; "lightning bug" display, whose
efficiency in producing "cold light" scientists
are striving to approach and still maintain the
proper color for an illuminant.
The commercial incandescent lamp exhibit
of the General Electric Company is arranged
in an Italian pergola at the left of the research
exhibit. The pergola, of spacious design,
extends from the garage back to the hotel
kitchen, and has a wing running to the side
entrance gate. This display comprises all sizes
and types of Mazda lamps, from the "grain
of wheat" to the large 1000-watt gas-filled
lamps.
The lamps are grouped in specially con-
structed cabinets, the multiple lamps and
street series lamps being wired and lighted.
Flashlight, electric vehicle and automobile
lamps are simply displayed in an appropriate
case. A case in which are shown the different
steps in the production of drawn tungsten
wire and a model illustrating the manufacture
of the Mazda lamp are interesting. The
latter is a minature lamp factory, in which
each part of the lamp appears from the roof
in the order of its assembly, the machine
operation of putting the parts together being
indicated, until the series is complete and a
lamp is entirely assembled and lighted. There
are transparencies giving relative data on the
cost of living and the cost of electric lighting,
etc.
A motor-driven, lamp-testing machine
attracts attention, as does also a shadow-box
exhibiting a facsimile of the original Edison
lamp and the present Mazda lamp. There are
also some interesting object-lesson devices.
A lamp bumper about 6 ft. tall is arranged to
permit a Mazda lamp to fall between baffle
plates, striking from side to side until it
GENERAL ELECTRIC COMPANY AT THE PANAMA EXPOSITION 565
reaches the bottom, where it lights and is
automatically carried up again for another
trip. The toughness of drawn tungsten wire
is obvious. Another "toy" is a large grand-
father's clock. The pendulum compartment
is glass-enclosed. On one side one lone penny
falls down, striking baffles as it goes; while on
the other side, three pennies make a similar
trip. The three pennies illustrate the cost
of electric light from an old style -carbon
lamp and the "loner" represents the cost of
the same amount of light from the modern
Mazda lamp. These and other devices
demonstrate simply the advantages of using
Mazda lamps, which are the only incandescent
lamps used by the Exposition.
When the high-efficiency, high candle-power
Mazda lamps for series and multiple circuits
were introduced, the new conditions under
which they operate required the design of an
entirely new line of fixtures to screen the
intense brilliancy, to provide proper ventila-
tion for the high temperatures, to bring the
light center to the correct location and to
provide an individual compensator to increase
the current. In the pergola there is a com-
plete display of the new Novalux fixtures and
accessories that have been designed for this
purpose. This includes pendant units, street
system brackets, ornamental street units, etc.
There are also concentric reflectors with
prismatic refractor, concentric reflectors with
opal diffuser, ornamental lamp posts, etc.
In the corner of the courtyard adjoining the
pergola is a rather interesting exhibit of
miscellaneous products. Among these are a
great many electrically-operated devices for
the home, such as washing machines, vacuum
cleaners, heating devices, cooking utensils,
etc., the products of several different manu-
facturers and driven by G-E motors.
These appliances are demonstrated in the
"Home Electrical" on different days, and
Fig. 7. Exterior of Station "A" of the Pacific Gas & Electric
Co., San Francisco, showing New Switch House
employed in turn to do the work in
the house. Here are also many industrial
electric devices for heating, light and
power, including projectors similar to those
lighting the grounds, a lightning arrester
display, fabroil gears and pinions, oil
tempering bath, glue pots, soldering irons,
drills, chippers, riveters, toy transformers,
fractional horsepower and larger motors,
motor-generator set, crane motor, vibrating
rectifier, switchboard, controllers, rheostats,
circuit breakers, voltmeters and ammeters,
Fig. 8. Palace of Transportation on the Marina
566
GENERAL ELECTRIC REVIEW
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GENERAL ELECTRIC COMPANY AT THE PANAMA EXPOSITION
567
oil switches, a wire and cable panel,
wiring devices, etc.
Perhaps one of the most instructive exhibits
in this display is a room adjoining the hotel
kitchen, in which all types of interior wiring
and wiring devices for homes and public
buildings are shown installed. These are
mounted in unfinished sections of the wall
and roof to make plain how this work should
be done, and the display includes even a
doorbell, buzzer and telephone wiring. Plugs,
sockets, receptacles, switches — everything of
interest to the building trade — form part of
this display.
We reach the hotel kitchen next, just back
of the pergola. This is a complete model
kitchen for a medium sized hotel, and is
arranged in a building of the same attractive
style of architecture as the "Home Electrical."
The entire cooking equipment is electrical.
One side of the building is removed to allow
better observation, all the equipment being
installed and connected up for operation to
permit demonstrations. There is a hotel
range, broiler, bake oven, toaster, vegetable
paring machine, coffee urn, steam table with
electric circulation water heater, etc. An
electrically-driven fan, reversible for exhaust
or ventilating, maintains a wholesome atmos-
phere. The room is lighted by two 100-watt,
bowl frosted Mazda lamps with Holophane
prismatic reflectors. The kitchen has a
sanitary brick floor.
Worthy of particular attention in the court-
yard is the substation room, situated back of
the "Home Electrical," at the left of the per-
gola. This is in operation and is one of the
substations furnishing current for the general
lighting and ornamental illumination for the
Exposition grounds. It is operated by the
Exposition Company, but was left open to the
public at the request of the General Electric
Company, to form part of its exhibit. It is fitted
up as a model substation with tile flooring. One
side is enclosed by the "Home Electrical" wall
and the adjoining end by the transformer
room. The front side and end are enclosed by
brass railing and brass chain, and are outlined
with six ornamental luminous arc lamps, which
light the exhibit. A number of ornamental
luminous arc lamps are also employed for
lighting avenues on the Exposition grounds.
The remaining sections of the courtyard are
lighted by Mazda lamps. In fact, this
entire exhibit is one of the few at the
Exposition artificially illuminated in the
daytime. All exhibit palaces are closed at
night.
The equipment in this substation con-
sists of G-E apparatus and comprises
a 1000-kw. motor-generator set, 250-kw.
balancer set, transformers, switchboard and
the necessary feeder circuits. The motor-
generator set is composed of a 1000-kw.,
275-volt, shunt wound, d-c. generator, direct-
connected to a 1400-kv-a., three-phase, 60-
cycle synchronous motor. Excitation for the
motor is obtained from the busses supplied by
the generators of the balancer set. The set
is started from the d-c. end. The balancer
is a three-unit set, consisting of two 125-kw.,
125-volt, shunt wound, d-c. generators, direct
connected to a 375-h.p., 2400-volt, two-phase,
60-cycle, induction motor started through
self-contained compensators. There are two
125-kw., 125/2400-volt, three-phase two-
phase, step-down transformers, the induction
motor being connected directly to the second-
ary through the compensator. The apparatus
is controlled by a nine-panel switchboard.
Specially constructed racks and benches
are employed in connection with this exhibit,
on which are mounted 1-h.p., 2-h.p., 5-h.p.
and 10-h.p. motors for industrial purposes,
for both alternating current and direct cur-
rent. They are connected up with instruments,
arranged for operating under load similar to
actual service and serve to demonstrate the
different types of controlling devices. An
indicating recording-integrating flow meter,
installed in the boiler room of the Horticultural
Palace, is measuring the actual steam con-
sumption.
As we might naturally infer, electricity
runs the Exposition, and we should here call
attention to its source. Nearly all this elec-
tric energy is generated by apparatus manu-
factured by the General Electric Company.
This is supplied entirely by the Pacific Gas &
Electric Company, largely from the city
stations of the company in San Francisco.
The principal generating plant is "Station A,"
which has a total capacity of 53,500 kw. and
in which are installed three large Curtis
steam turbo-generator units, two of 15,000
kw. and one of 12,000 kw., in addition to five
smaller machines. Considerable quantities of
G-E apparatus, devices and accessories used
throughout the Exposition by contractors
and exhibitors were secured through the
Pacific Gas & Electric Company and the
Pacific States Electric Company, acting as
distributors.
We shall now proceed to the most extensive
exhibit of the General Electric Company,
the Transportation Exhibit, which is located
568
GENERAL ELECTRIC REVIEW
in the Palace of Transportation adjacent to
the Court of the Universe. This exhibit
covers a total of over 9000 sq. ft., of which
some 7735 sq. ft. are used for the apparatus
display and the remainder for trackage
Fig. 13.
Ghirardelli Chocolate Shop and Factory in the
Amusement Zone
extending along Avenue C from the main west
entrance. The entire exhibit is of the open
type, not fenced in or enclosed. The dis-
plays are grouped and arranged particularly
to permit free inspection, as they are largely
operative and are designed to be broadly
educational. The exhibit is brilliantly
illuminated by Mazda lamps in Kovalux
ornamental units mounted on statuary bronze
standards. At the entrance is an inviting
reception room of pergola design.
The exhibit comprises electric locomotives
for various classes of service from underground
mine haulage to heavy steam railroad elec-
trification; railway motors and all kinds of
apparatus for electric railways, representing
the latest developments in modern city and
interurban electric service; signal accessory
electric devices; electric apparatus and equip-
ment for railway shops; electric illumination
for cars, shops, etc. All essential parts of
electric traction are demonstrated in operation.
A most impressive exhibit is the electric
locomotives, of which five different types are
included. The Butte, Anaconda & Pacific
locomotive, occupying the central space of
the group, is one of four units that have
recently been built for this road and is a
duplicate of the original seventeen units put
into service in 1913. These are the first direct
current electric locomotives for operation at
2400 volts ever built. Each unit weighs 80
tons. Two are, however, coupled together
for freight service to form a locomotive weigh-
ing 160 tons. The combination freight
locomotives are hauling main line trains of
4600 tons at a speed of 16 miles per hour
against the ruling grade of 0.3 per cent, and
at 21 miles per hour on level tangent track.
The two passenger locomotives, operating as
single units on this system, are geared for a
maximum speed of 45 miles per hour on level
tangent track.
The freight traffic on this road consists
largely of the transportation of copper ore from
the mines at Butte to the smelters at Ana-
conda. The initial electrical equipment was
intended for handling annually about 5,000.-
000 tons of ore, besides a large amount of mine
supplies and an extensive freight and pas-
senger sen-ice consisting of eight trains per
day between the terminal cities. On account
of diverting about 3000 tons of ore per day
from the smelters at Great Falls to those at
Anaconda, an increase of approximately 25
per cent is anticipated in the tonnage to be
hauled during this year, necessitating the
four additional locomotives. Based on six
months of steam and electric operation, a
comparison shows a total net saving for the
latter of more than 20 per cent on the invest-
ment or total cost of the electrification, with
an increase in tonnage per train of 33 per cent.
a decrease in the number of trains of 25 per
cent, and a saving of 30 per cent in the time
required per trip. This electrification includes
about 26 miles of main line, or with yards and
sidings a total of approximately 90 miles on
a single track basis.
A 60-ton electric locomotive of the type
standard for interurban freight and passenger
service and heavy switching duty is also shown.
This machine is designed for operation at
both 600 and 1200 volts direct current. The
cab is of all-steel construction and is divided
into three sections, the central operating cab
containing the controller and other apparatus
that should be within immediate reach of the
engineer, and the two end steeple-back cabs
containing the auxiliary electrical apparatus.
The motor equipment consists of four GE-251
commutating pole motors, one mounted on
each axle. They are arranged for forced
ventilation from a blower in the cab. The
GENERAL ELECTRIC COMPANY AT THE PANAMA EXPOSITION
569
well-known type M multiple unit control
is used and combined straight and automatic
air brakes are provided. The trucks are of
the equalized type and conform to MCB
standards. There is also an industrial 16-ton,
all-steel, electric locomotive of similar design
with steeple-back end cabs for light freight
and yard switching service. It is equipped
with two 600-volt, commutating pole, ven-
tilated motors.
The electric mining locomotives consist of
a large 20-ton trolley type equipped with
three motors and a six-ton combination trol-
ley and storage battery locomotive equipped
with two motors, all of the commutating
pole type. The latter is so arranged that it
may be operated on the storage batteries for
gathering beyond the point where the trolley
wire extends, the batteries being recharged
from a small charging set mounted in the
locomotive and operating on the trolley volt-
age, thus obviating the necessity of laying up
the locomotive while charging or changing the
battery.
The General Electric Company has adopted
the commutating pole ventilated type of
motor as standard for practically all multiple
unit railway equipments. Motors of this
construction have a greatly increased service
capacity when compared with motors of the
closed type and same hourly rating, because
of the positive circulation of air that is main-
tained throughout the interior by the system
of self-ventilation. The motors displayed
embrace GE-200, 203, 201, 222 and 247, all
600-volt motors of 40, 50, 65, 140 and
35 h.p. respectively; types GE-233 and 240,
600/1200-volt motors of 75 and 85 h.p.
respectively; GE-239, 140-h.p., 2400-volt
motor; and a GE-246, 60-h.p., 600-volt motor
in section, with partially-wound armature
and partially-insulated field coils, to show
the manner of construction.
There is a storage battery truck crane for
loading, unloading and carrying articles
weighing up to one ton, for use in industrial
plants, warehouses, on docks, etc., as well
as for hauling loaded trailers, "spotting"
freight cars, etc. Another industrial truck, a
storage battery platform truck, designed to
run inside of freight cars, has come into
extensive use for freight and package handling,
express, warehouse and other service. A
portable air compressor set for use around
factories is shown, the compressor being
fitted with a glass cover and the interior
illuminated to show the operation. This same
type CP-27 air compressor is employed with
air brake systems, one of which is mounted
on a rack in the same manner as it is installed
on a car, with all the valves and accessories
for combined straight and automatic opera-
tion.
A most interesting feature of the traction
exhibit is the two single-end type MK
control equipments, each mounted on a
separate rack in the usual manner of in-
stalling for service. The exhibition racks,
which represent the complete underframing
and equipment for a two-car train, are placed
end to end with control jumpers and air
brake hose connections for train operation.
Each control equipment consists of a master
controller, contactor box, etc., completely
wired for the actual operation of two GE-247
motors, which are mounted on a truck beneath
the rack. These equipments also include
complete straight and automatic air brakes,
with CP-27 air compressor, governor, valves,
etc. The motor trucks are equipped with third
rail shoes. The entire arrangement permits
operation to be demonstrated either as a
single car or two-car train on multiple-unit
control. Illuminated diagrams connected
with the control system indicate by lighted
lines the connections of the motor circuit at
each step on the controller.
Another working exhibition rack contains
a complete type M multiple unit control
designed for three-speed operation in city
service. The motor circuit connections at
each step are also similarly shown. The
controller exhibit includes the standard K-35,
K-36, K-51 and K-201 types. The last
named controller is designed for three run-
ning positions and is suitable for frequent
stop city service. A complete assortment of
line material is grouped on a large frame,
many of the devices being arranged in the
same manner as when installed in actual
service.
A large number of separate valves, con-
tactors, governors, fuse boxes, rheostats,
switches, lightning arresters and other devices
entering into car equipment form part of the
exhibit. Forged steel treated gears, cast steel
split and solid gears, and pressed steel gear
cases for city, suburban and interurban
service are shown, as well as several grades of
forged steel treated pinions and pinion pullers.
A display of railway lamps demonstrates effec-
tively systems of car lighting with modern
Mazda lamps. Automobile lamps and acces-
sories are also included. Shadow boxes and
photometric curves demonstrate the relative
value of the illuminating units. There is
570
GENERAL ELECTRIC REVIEW
GENERAL ELECTRIC COMPANY AT THE PANAMA EXPOSITION
571
also a complete line of incandescent and
luminous arc headlamps with semaphore
lenses and parabolic reflectors, for city,
suburban and interurban service.
The line of signal accessories includes
transformers, vacuum and multigap lightning
arresters, switchboards, instruments, etc.
Other interesting apparatus are a 50-kw.
motor-generator, a mercury arc rectifier of the
standard type for battery charging, an elec-
tric arc welding outfit, a new high frequency
oscillator shown in operation testing insulators.
a full line of insulators, the ' ' Genemotor
the new self-starting and lighting system for
Ford cars, a new multi-recorder for switch-
boards for automatically keeping a record
of the time of manipulation of the various
switches, a complete line of circuit breakers,
etc. Meriting particular attention is the
model of the Panama electric towing loco-
motive, an entirely new design of machine, of
which the General Electric Company supplied
forty for towing vessels through the Panama
Canal locks. A model of one of these "elec-
tric mules," as they are popularly called, is
also included in the Government exhibit.
A most attractive and instructive feature
of the exhibit is the several hundred illustra-
tions which a stereomotorgraph projects
automatically on a large translucent screen.
These illustrations, of which there are
several hundred, cover the range of modern
traction developments. They are made from
actual photographs taken in various parts of
the country and show important applications
of recent railway equipment in city, interurban
and heavy electrification service, as well as
many typical installations of new apparatus
in large power plants and substations.
While the illumination of the Exposition
signalizes beyond all else to the average mind
the greatness of electrical achievements, and
while the exhibits of the General Electric
Company have attracted exceptional atten-
tion from the public, especially the "Home
Electrical, ' ' the representation of this Company
is by no means confined to its own displays.
Evidence of its activities and the almost
unlimited diversity of the application of its
products in industrial and social development
may be said to permeate the entire Exposi-
tion. Many of the machines and devices
displayed by a very large number of exhibitors
in various buildings are operated by its
motors and apparatus, loaned to exhibitors.
A large number of sales of apparatus were
also made, particularly in the Amusement
Zone, mention of which is made below.
The application of G-E motors by other
exhibitors at the Exposition includes the
operation of pumps, clutches, hoists,
derricks, machine tools, silk machinery,
glove machinery, refrigerating machinery,
elevators, cotton mill machinery, dairy
machinery, flour mill machinery, shoe machin-
ery, dredging machinery, optical equipment,
dentists' tools, electric trucks, lumbering
machinery, woodworking machinery, steel
and iron mill equipment, etc. In fact, so
extensive is the application of electric power in
evidence, we are impressed that electricity is
coming more and more to do the world's
work.
But before we leave the Exposition, we also
find electricity "at play." Every one that
visits the Exposition takes in the novelties of the
Amusement Zone, or simply "The Zone," as
it is popularly called. Here there is a very large
representation of General Electric Company
apparatus. Machines and devices driven by
this company's motors are installed in numer-
ous concessions, including the Ghirardelli
chocolate making plant, the miniature work-
ing representation of the Panama Canal,
Bowls of Joy, Marine Restaurant, Orange
Blossom candy factory, Creation, Frankfurter
Inn, Neptune's Daughters, Forty-nine Camp,
Zone Cafe, Yellowstone Park, Desmond
Supply Company, London to South Pole,
Jester Palace, joy Wheel, Alt Nurnburg,
Shooting Galleries, etc. The concessions on
"The Zone" are generally lighted on the
interior and outline lighted on the exterior
by Mazda lamps, as are also the streets and
avenues in this section.
The Exposition in its entirety is not only
a beautiful vision, but will leave a lasting
impression of its greatness and grandeur on
the many thousands of visitors. It is a fit-
ting and adequate expression of the opening
of the new gateway to the East and the West,
the Panama Canal. And the one impression
of newness in expositions, a prominent differ-
ence that charms and lingers long with the
visitor, is the combined decorative and light-
ing feature, a modern esthetic achievement,
which has been so well termed "a new
symphony in color."
GENERAL ELECTRIC REVIEW
THE HOME ELECTRICAL AT THE PANAMA-PACIFIC
INTERNATIONAL EXPOSITION
By Don. Cameron Shafer
General Electric Company
For the purpose of demonstrating that electricity can easily and inexpensively be applied to reduce the
drudgery of housework in a home and to secure those conveniences which would be appreciated by all its mem-
bers, the General Electric Company is maintaining a full-size, fully furnished model house in the Palace of
Manufactures at San Francisco. This article describes the arrangement of the exhibit, its furnishings, and the
electric lighting, heating and power appliances. — Editor.
If it be true that the attainment of popu-
larity is the final test of successful advertising
then the Home Electrical, which is but a part
of the General Electric Company's exhibit at
the Panama-Pacific International Exposition
at San Francisco, is one of the most effective
publicity ventures at the exhibition. It is
certain that this thoroughly modern home,
where electric energy is converted into light,
power and heat to perform many of the most
important household tasks, has proven far
fashion and with a long columned portico
along two sides. There is also a small enclosed
patio, or garden, in the rear. The interior
arrangement provides for a large and com-
fortable living room, an attractive dining
room with a breakfast alcove, a bedroom with
a nursery and a bathroom adjoining, a sewing
room, a kitchen with auxiliary refrigeration
room and laundry. In connection with the
house there are also an electric garage, a
workshop and a small creamery. Every
Fig. 1. The "Home Electrical" Exhibit of the General Electric Company in the Palace of Manufactures
more attractive to the visiting public than any
other exhibit in the great Manufacturer's
Building.
The construction of this complete house
within the Manufacturer's Palace is an
engineering novelty which has added materi-
ally to the attractiveness of this special
exhibit. The home is a California mission
bungalow in design, built of gray stucco,
roofed with red tile in the picturesque Spanish
room is completely furnished and attractively
decorated, all in excellent taste, and yet
entirely within the means of an average
family.
Here at the very beginning it should be
said that the Home Electrical is in no sense of
the word an exhibition "stunt" designed
merely to demonstrate the wonders which
electricity can be made to do in the modern
home. It is not the purpose of this house to
HOME ELECTRICAL AT PANAMA-PACIFIC INTERNATIONAL EXPOSITION 573
astonish the visitors, or to astound them with
numerous bewildering and amazing electrical
performances which savor of the magical.
It is in every way a modern house and every
application of electricity therein is aimed to
lessen the work of housekeeping and to remove
the drudgery of housework. Not a single
electrical convenience is shown but what
would be entirely suitable for the average
family and well within the means of anyone
in moderate circumstances. Visitors have
often remarked with surprise that the elec-
trical equipment is so simple that anyone can
operate it without any previous study or
knowledge of electrical matters.
Approaching the Home Electrical one is
agreeably surprised to find that the house
number is an electric transparency, and the
portico, or veranda, is lighted with Mazda
lamps in ornamental porch fixtures. The
lamps are enclosed in six-inch light opal
globes with close ceiling type fixtures. The
doors are equipped with electric bells which
announce your presence to the servants.
Entering the house one steps into a spacious
and appropriately furnished living room
approximately 13 by 19 feet. It is furnished
in mahogany and the color scheme is a mul-
berry tone, with draperies, wall paper, lighting
fixtures, rugs, etc., in perfect harmony. The
woodwork is finished in fumed oak. The
illumination of this room is of the very latest
and approved system of semi-direet lighting
from hanging Holophane "Calla" bowl fix-
tures, the 60-watt amber dipped Mazda lamps
being hidden from the eye while the light is
distributed by reflection from the walls and
tinted ceiling to all parts of the room. The
u«zz
^i-CO1? f=-i_AN--HOME ELECTRICAL
GENERAL ELECTRIC COWPMW/ S EXHIBIT
F¥M-ACC CT ^MANUFACTURES
&ANAN1A- F*AClPtC INTERNATIONAL EXPOSITION
SAN FRANCISCO 13/*5
Fig. 2. Floor Plan of the "Home Electrical" Exhibit
574
GENERAL ELECTRIC REVIEW
lamps are controlled from wall push switches
located at convenient points. Three-way
push switch controls are located at the porch
entrance and also between the living room
and the dining room. There is also a small
lamp for the desk and a handsome table
Fig. 3. Living Room in the "Home Electrical" Exhibit
lamp. A telephone on a suitable stand con-
nects with local and long distance lines and
with the inter-house phone to every room, an
electric convenience which saves many steps
in the course of a day. An electric fireplace
of the four-bulb luminous radiator type
furnishes both warmth and a
pleasing glow in addition to the
regular three -kilowatt electric
heater. One of the most novel
electrical devices in the house
is to be found in this room —
an electric piano player, which
appears to be more satisfactory
to the music lover than the
ordinary piano players.
Adjoining the living room, after
the bungalow fashion, is the
dining room, in soft blue tones
and black walnut furniture.
Draperies, curtains, rugs, wall
paper — all harmonize to the blue
tone. It is completely furnished
with a table of the pedestal type,
chairs, tea wagon, buffet, china
closet, and with the necessary
linen, silverware and china. This
room is also lighted by Mazda lamps in
ornamental fixtures which provide direct
illumination through tinted shades which
harmonize with the color scheme. It is
heated with an electric heater and the
air is kept constantly stirred and refreshed
by a small oscillating electric fan located
on the wall. It is in this room that the
visitor is first impressed with the ver-
satility of the electric energy drawn from
the house wiring, it is converted into light,
heat and power to operate the lamps, the
heating and cooking devices and the electric
fan. The dining room is equipped with
electric heating and cooking devices for the
preparation of lunches and light refreshments
such as are so acceptable late in the evening
after the theater or on Sunday evening.
Among the devices may be noted a domestic
toaster, an electric coffee pot, a tea samovar,
a disk stove for general cooking; a uni-set.
a uni-set chafing dish for preparing hot soups
or desserts and a radiant grill for broiling,
toasting, preparing eggs, etc. In fact, if
desired, a very substantial meal can be cooked
right on the dining room table. Another
electrical feature is the warming closet at the
entrance to the butler's pantry where the food
is kept hot between courses. To the right of
the dining room is the breakfast alcove, very
cosily arranged and also equipped for "table
cooking." This breakfast nook is finished
in a blue tone and looks out upon a vim-
covered patio, upon ferns and flowers and a
little green yard wherein sparkles an electric-
fountain. This early morning meal is cooked
before your very eyes, just as you want it.
Fig. 4. Breakfast Nook in the "Home Electrical" Exhibit
from coffee to toast and bacon and eggs, and
even more if you are hungry for sausages and
cakes.
Between the dining room and the kitchen
is the butler's pantry, approximately seven
by nine feet in size. Here are installed a
combination butler's sink and dish-washer for
cleaning the light and valuable wares. On
HOME ELECTRICAL AT PANAMA-PACIFIC INTERNATIONAL EXPOSITION 575
a shelf there is a disk stove for making dressing
and sauces, and a small electrically driven
buffer for polishing nickel and silver pieces.
On the wall is the annunciator of the door
bell system which signals information to the
maid or butler.
Interest naturally centers about the
kitchen of the home because this is the house-
wife's workshop, and the entire housework
revolves around this important room with its
three-meals-a-day and the necessary labor of
preparation and cleaning up afterwards.
And it is but natural that here electricity
should find its greatest field of usefulness.
The dirty, insufferably hot, heat-wasting
coal range; the stuffy, odorous and dangerous
gas stove, have been replaced with a modern,
sanitary domestic electric range of the latest
design. The type R-3 range is a substantial
affair capable of the largest family dinner.
Roth oven and boiler are placed high enough
so the contents may be watched without
stooping. This range uses ordinary cooking
utensils and embodies many features of the
so-called fireless cooker, such as insulated
steam compartments and specially heat-
insulated oven and hot plates. The broiler
is combined with the oven and broils by
radiant heat above the meat. The range is
At the snap of a switch the stove is ready to
cook, at any degree of heat required, and at
the pressure of a finger the heat is gone until
it is wanted again.
Suitable electric lamps are located to give
an even distribution of light about the kitchen,
Fig. 5. Kitchen in the "Home Electrical" Exhibit
equipped with five hot plates, or grids, with
three degrees of heat. The convenience of
such an electric range is easily appreciated by
the woman visitor. No fires have to be built
or tended, no coal to lift and carry, no soot,
no ashes, no dirty stove to clean. Practically
no heat is radiated out into the room to make
the kitchen a place of torment in hot weather.
Bed Room in the "Home Electrical" Exhibit
and especially over the stove, work table,
sink and other centers of activity. The
unpleasant odors of cooking are no longer
noticed as a household ozonator and exhaust
fan combine to quickly remove them and keep
the air in the kitchen pure and fresh. Should
the day be chilly, a portable air
heater can be put into service by
inserting a small wall plug. The
kitchen, all white enamel, is
furnished with a kitchen cabinet,
sink and drain, combination work
and power table, chairs and all the
necessary pots, pans and cooking
utensils otherwise than the elec-
trical devices. In addition to the
range there are also an electric
grill, a two-pint percolator coffee
pot, a toaster and a small water
heater.
The electric refrigerating system
is a constant source of interest.
While the visitors cannot all
understand how this little mechan-
ical device keeps the refrigerator
at any predetermined ' tem-
perature they do appreciate its
convenience and labor saving factors. The
refrigerator proper is located in the kitchen,
handy to the kitchen cabinet, but the
motor-driven ammonia compression tanks,
etc., are located in an adjoining refrigerating
room. The refrigerator is lighted by elec-
tricity, an improvement worthy of note, and
small cubes of ice may also be obtained from
576
GENERAL ELECTRIC REVIEW
this machine if desired. With this may be
mentioned the electrically driven ice cream
freezer for ices and creams. A connection
with the inter-house phone for saving steps
is the final kitchen convenience.
Fig. 7. Laundry in the "Home Electrical" Exhibit
The bedroom is finished in a pleasing grav
tone with old rose furnishings. The furniture
is Kaiser gray oak, including the two beds, the
dressing table, the dresser, the chiffonier, the
chairs, etc. The color scheme is carried out
by including rugs, curtains and
wall paper, of a deep red tone.
This room contains many elec-
trical conveniences and articles
for the toilet, including an electric
massage vibrator, electric curling
iron, hairdryer, and boudoir lamps
There is a physician's heating pad
to take the place of the old
fashioned hot water bag and a
small electric water heater in case
of sickness. The bedroom is
heated by electricity in chilly
weather and cooled with an electric
fan when the nights are too warm.
There is a connection for the
vacuum cleaner when electric
energy is required to do the
sweeping and dusting, to clean
the rugs, curtains and furniture.
The room is also provided with a
telephone connection to all parts
of the house to save unnecessary steps.
The burglar switch located in the bedroom
cannot fail to interest the nervous and timid.
In the middle of the night, at the warning of
any suspicious noise in the house, one has
but to reach out and turn this switch and
instantly every room in the house will blaze
with light. Once on the lamps cannot be
turned off except from the master switch.
It has been proven that a flood of light is the
best guardian of any home and a
sure method of frightening away
intruders.
Near the bedroom is the nurs-
ery with its electric toys and an
electrical device at the window to
keep the room supplied with fresh
air without dangerous drafts.
This room is finished in white
enamel and provided with two
systems of lighting, flashed on
alternately at intervals of half a
minute by means of a sign flasher,
to demonstrate both methods.
The first method consists of
indirect lighting units on the
ceiling with "eye comfort"
fixtures equipped with 60-watt
clear Mazda lamps. The second
method consists of bracket lights
provided with pull sockets, and
equipped with two All-Nite-Lite outfits. It
is furnished with a small white bed, a small
chair and rocker, toys, etc. The curtains and
rugs are blue. The nursery is heated by
electricitv with a twin-glower radiator and
Fig. 8. Shed for the Stationary Vacuum Cleaning Outfit and High Pressure
Pumping System in Connection with the "Home Electrical" Exhibit
there is an electric uni-set nursery outfit for
preparing medicine, food, etc. An electric
heating pad is also provided to warm up
cold hands and toes or for use in case of
sickness.
HOME ELECTRICAL AT PANAMA-PACIFIC INTERNATIONAL EXPOSITION 577
The bathroom, of white tile and spotless
porcelain, in addition to a complete set of
bathroom fittings is equipped with such
electrical conveniences as a hot water cup for
shaving purposes, and various other uses, an
electric radiator in case the room should be
chilly in the early morning, an electric vibrator
and a hair dryer. There is the usual bathroom
equipment including shower, tiled floor, white
chair and stool. Curtains and shades are
white and the window glass is frosted. An
overhead lighting unit with (iO-watt Mazda
lamps furnishes illumination. In addition the
mirror is lighted from either side by white
side wall brackets with pull sockets. An
exhaust fan serves as a ventilator and draws
the steam from the hot water out of the room.
The fan, with an ozonator, prevents impure or
vitiated air. The hot water for the bathroom is
drawn from the hot water tank in the kitchen
in the usual manner.
The sewing room is also a point of special
interest with its electrical appliances for
sewing, pressing and dressmaking. The
electrically driven sewing machine is controlled
by the foot treadle and is so nicely adjusted
that it can be stopped in the middle of a
threads and scraps of cloth. A connection
to the interhouse phone saves many steps in
tending to various household duties during
sewing hours. A small air heater and a fan
keep the room warm and comfortable at all
Fig. 9. Garage in the "Home Electrical" Exhibit
stitch. The motor will run the sewing machine
all day for a few cents' worth of electricity
and remove entirely the drudgery of sewing.
A three- and a six-pound electric iron are
located on a convenient board and a small
portable vacuum cleaner is used to pick up
Fig. 10. Creamery in the "Home Electrical" Exhibit
seasons. The furniture includes a sewing
table and cabinet, rugs, curtains, etc.
Anyone who has ever done a family wash-
ing, or ever turned a washing machine, can
appreciate the electric laundry where the
little motor does all the hard work. This little
device, no larger than an ordinary flower pot,
runs the washing machine, washes and rinses
the clothes, and turns the wringer, all without
the slightest effort. An electrically driven
mangle makes ironing easy as all the large
pieces and many of the smaller ones can be
ironed very quickly with this machine. The
laundry is 1.3 by 13 feet in size. It is lighted
from a ceiling fixture equipped with an
enameled steel reflector. The equipment
includes stationary tubs, drying cabinet,
chairs, etc. A double eight-inch hot plate is
used for boiling the clothes. Electric flat-
irons in four sizes, three, six, eight and twelve
pounds respectively, are used for smoothing,
pressing and ironing in accordance with the
demands of the work. A collapsible ironing
board folds into a shallow closet and the
flatiron switches are equipped with pilot
lights to indicate whether or not the current
has been turned off when the work is done.
If wash day be hot and sultry an exhaust fan
removes all steam and heated air and main-
tains a comfortable working temperature.
An air heater is ready to be "plugged in"
when the day is cold.
Inasmuch as many homes are not located
where they can enjoy a civic water system
provision has been made in the shed for a
578
GENERAL ELECTRIC REVIEW
constant water pressure all over the house,
where a well is the source of supply. This
is an automatic air pressure system connected
to the water supply which keeps the pressure
constant at any desired point. Both the air
and water pumps are driven by a tiny electric
motor, controlled by a pressure switch.
When enough water has been used to lower
the tank pressure to a certain predetermined
point the switch starts up the motor. When
enough pressure has been secured the little
switch shuts off the current and stops the
motor. In this way a constant supply of
water is secured automatically, day or night
from any well or spring.
Men and boys handy with all kinds of tools
can appreciate the electric workshop which is
equipped for any ordinary repair or construc-
tion work, with a workbench, bench type
drill press, chipping hammer, electric riveter,
and grindstone. Then there is a buffing
outfit, saw table, bench type lathe, melting
pot, all electrically operated. Handy little
electric soldering irons and an electric glue-pot
aid in repairing of leaky utensils or broken
wood-work. An air heater of sturdy build
and generous capacity is ready at all times
to insure comfort in the shop.
In connection with the Home Electrical is
the modern electric garage where a light
electric coupe is kept automatically charged
and ready for service. The car batteries are
charged through the aid of a mercury arc
rectifier which changes the alternating current
of the lighting service into direct current for
battery charging. This charging is entirely
automatic and the batteries for car lighting
are charged by a small vibrator. A small
portable search lamp, which can be operated
on any electrically lighted car, is used for
examination of any part of the car, and a
portable electric tire pump complete the car
equipment. Connections are made to the inter-
house phone in both garage and work-shop.
An air heater is also installed in the garage.
Many visitors to the Home Electrical will
be from rural communities and they will wish
to see the electric dairy which is equipped
with an electrically driven cream separator,
bottle washer and churn to reduce manual
labor to an absolute minimum. In conjunc-
tion with these appliances is an automatic
refrigerator and milk cooler, operating to
keep the cooling chamber at the proper
temperature. Any time that the temperature
varies from the desired point the thermostat
control operates the motor switch and starts
the flow of cooling solution through the pipes.
When the temperature has dropped to the
proper point, the thermostat control again
operates to stop the motor.
The second floor of the Home Electrical is
finished off into a suitable office for the
transaction of such business as may be
necessary in connection with such a large
exhibit.
The success of the Home Electrical is due
to the impression it leaves with the casual
visitor that the electric light wires are a source
of energy not restricted to illumination but
which can also be used as heat and power to
banish drudgery and hard work from the
home. The devices shown are for the most
part inexpensive to purchase and cost but a
few cents a day to operate.
In conclusion it should be stated that this
exhibit, which is conducted entirely by the
General Electric Company, is co-operative
to the extent that it comprises a very complete
display of household devices operated by
the Company's motors but manufactured by
other concerns, many of whom have no other
representation at the exposition. The purpose
of this exhibit is more educational than com-
mercial, inasmuch as it effectively demon-
strates to every visitor the value of electricity
in the home and proves that the electric
labor saving devices and conveniences shown
therein are inexpensive and within the reach
of all.
579
ILLUMINATION OF THE PANAMA-PACIFIC
INTERNATIONAL EXPOSITION
By W. D'A. Ryan
Chief of Illumination
The text of this article, together with the illustrations that accompany it, will give the reader an idea of
the wonderful illuminating effects that have been achieved at the Panama-Pacific International Exhibition.
Special interest is attached to this contribution, as its author was responsible for the work he describes.
— Editor.
The illumination of the Panama-Pacific
International Exposition is a development
in the art of illumination made possible by
the science of lighting which grew up under
the name of illuminating engineering and
had its inception at the Thomson-Houston
plant of the General Electric Company at
Lynn, Massachusetts, nearly twenty years
ago.
While in charge of the expert course, the
writer came closely in contact with the
development of the Thomson '93 arc lamps
which in various ornamental forms were
designed for alternating and direct current
series and multiple circuits. The enclosed
arcs soon made their appearance and these
lamps added to the existing lighting sources
suggested the necessity of a careful scientific
study in the selection, location, reflectoring
and globing of the various units to obtain
maximum results at minimum cost for
industrial use, store and street lighting, and
other purposes.
That illuminating engineering was to form
such an important specialized branch of elec-
trical engineering was not at first recognized,
but after considerable progress had been made
in this particular field the title of Illuminat-
ing Engineer became generally acknowledged.
From that time on the development has been
very rapid. New photometers, luximeters,
and luminometers were built for laboratory
and field work. Lumichromoscopes were
designed for studying effects of different lights
on various colored materials, diffusers made
their appearance, scientific glassware and
reflectors swept over the land, extensive labo-
ratory and field tests were made and the
development became general.
Many papers were read at conventions,
colleges and elsewhere to stimulate public
interest in the importance of the work.
Contemporaries entered the field, scientific
journals gave considerable space to the
subject and publications, such as the Illumi-
nating Engineer and Good Lighting, devoting
their entire space to illuminating engineering,
were published in this country and abroad.
An Illuminating Engineering Society was
formed in the United States and this action
was quickly followed in England. The
membership was made up of engineers,
lighting specialists, architects, decorators,
oculists, glass manufacturers, fixture design-
ers, psychologists and others. Valuable
contributions were received from many
sources and the general interest created
thereby.
Today the General Electric Company has
Illuminating Engineering Laboratories, com-
mercial, experimental or developmental at
Schenectady, Cleveland, Harrison and Lynn.
In New York, Boston, Chicago and many
other cities proficient illuminating engineers
are doing excellent work and practically every
large manufacturer of lighting units or
appurtenances has either an illuminating
engineering department or an associated
illuminating engineer.
In lighting propositions involving special
effects or treatment, it has become the prac-
tice to employ an illuminating engineer in
addition to the electrical engineer. It was
therefore natural that when the Panama-
Pacific International Exposition decided that
its illumination should possess features of
novelty to correspond with its general policy
it recognized the necessity of establishing a
department of illuminating engineering in
addition to the electrical and mechanical
department, which came under the direction
of Mr. G. L. Bayley, as Chief.
Mr. Bayley's application to the General
Electric Company resulted in the writer's
appearing before Mr. H. D. H. Connick,
director of works, and the architectural
commission in August, 1912, to consider the
preparation of lighting plans along original
lines. Three months later a scheme and scope
was presented to the architectural com-
mission and the writer was officially appointed
"Chief of Illumination" in charge of the
illuminating and spectacular effects, also the
design of lighting standards and fixtures and
580
GENERAL ELECTRIC REVIEW
the selection of the glass for the buildings
and various lighting units.
The General Electric Company as a further
contribution to the Exposition agreed to
maintain a branch of the illuminating engi-
neering laboratory at the Exposition for this
purpose and in addition to the writer the
organization consisted of Mr. A. F. Dickerson,
first assistant; Mr. J. W. Gosling, decorative
designer; Air. J. W. Shaffer, chief draftsman;
Mr. H. E. Mahan, illuminating engineer,
and Mr. E. J. Edwards, illuminating engineer
representing the laboratory of the National
Lamp Works at Cleveland.
Supplementing this organization we had
the assistance of the entire illuminating
engineering force at Schenectady under the
direction of Major R. H. Ryan, where tests
were run on luminous arcs, Mazda lamps,
gas arcs, searchlights, glassware and various
devices entering into the illuminating effects.
As a result, for the first time in history the
lighting of an International Exposition was
completely designed and charted before the
buildings were erected.
No fundamental changes were made except
in one instance where, due to a difference of
opinion existing between some of the archi-
tects and the writer, as to the relative height
and mass of the nine-light standards in the
daylight picture, the night effect was unfor-
tunately sacrificed.
The general results obtained are due in a
great measure to the support of Mr. H. D. H.
Connick, director of works, and Mr. G. L.
Bayley and his excellent electrical and
mechanical organization. We also enjoyed
the co-operation of and assistance from the
chiefs of all departments, architects, designers,
sculptors, modelers and others too numerous
to mention in this article.
A detailed description of the lighting in a
limited space is, of course, impossible, and
it is the purpose of this article to convey a
general idea of the effects rather than the
means employed to produce them.
The illumination of the Exposition marks
an epoch in the science of lighting and the
art of illumination. Like many other features
of the Exposition, the illumination is highly
educational in character and emphasizes
more than anything that has gone before
the result of concentrated study in the best
uses and application of artificial light.
Previous exposition buildings have, in the
main, been used as a background on which
to display lamps. The art of outlining,
notablv the effects obtained at the Pan-
American Exposition at Buffalo, could
probably not be surpassed. This method of
illumination has, however, been extended to
amusement parks throughout the world and
is now commonplace. Its particular dis-
advantage is that it suppresses the archi-
tecture which becomes secondary and it is
practically impossible to obtain a variety of
effects, so that the Exposition from every
point of view presents more or less similarity.
Furthermore, the glare from so many exposed
sources particularly when assembled on light
colored buildings causes eye strain. Prior to
the opening night of the Exposition, there
were many who maintained that the public
would not be attracted except by the glare
of exposed sources and great brilliancy, which
was analogous to saying that the masses
could be attracted only by one form of
lighting. The results obtained, however,
clearly disproved this theory.
The lighting effects are radical, daring and
in every sense new, the fundamental features
of which consist primarily of masked lighting
diffused upon softly illuminated facades
emphasized by strongly illuminated towers,
and minarets in beautiful color tones.
The direct source is completely screened
in the main vistas and the "behind the
scenes" effects are minimized to a few
locations and are nowhere offensive.
Furnishing wonderful contrast to the soft
illumination of the palaces, with their high
lights and shadows, we have the zone, or
amusement section with all the glare of the
bizarre, giving the visitor an opportunity
to contrast the light of the present with the
illumination of the future. As we pass from
the Zone with its blaze of lights, we enter
a pleasing field of enticement or carnival
spirit. We are first impressed with the
beautiful colors of the heraldic shields on
which is written the early history of the
Pacific Ocean and California. Behind these
banners are luminous arc lamps in clusters
of two, three, five, seven and nine, ranging
in height from 25 to 55 feet. We look from
the semi-shadow upon beautiful -vistas and the
Guerin colors which fascinate in the daytime
are even more entrancing by night. The lawns
and shrubbery surrounding the buildings and
the trees with their wonderful shadows appear
in magnificent relief against the soft back-
ground of the palaces and the "Tower of
Jewels" with its 102,000 "Nova-gems," or so-
called exposition jewels, standing mysteriously
against the starry blue-black canopy of the
night, surpassing the dreams of Aladdin.
ILLUMINATION OF THE PANAMA-PACIFIC EXPOSITION
581
As we enter the ' ' Court of Abundance ' '
from the east, with its masked shell standards
strongly illuminating the cornice lines and
gradually fading to twilight in the foreground,
we are impressed with the feeling of mystery
analogous to the prime conception of the
architect's wonderful creation. Soft radiant
energy is everywhere; lights and shadows
abound, fire spits from the mouths of serpents
into the flaming gas cauldrons and sends its
flickering rays over the composite Spanish-
Gothic-Oriental grandeur. Mysterious vapors
rise from steam-electric cauldrons and also
from the beautiful central fountain group
symbolizing the Earth in formation. The
cloister lanterns and the snow-crystal stand-
ards give a warm amber glow to the whole
court and the organ tower is carried in the
same tone by colored searchlight rays.
Passing through the "Venetian Court," we
enter the "Court of the Universe," where the
illumination reaches a climax in dignity,
thoroughly in keeping with the grandeur of
the court, where an area of nearly half a
million square feet is illuminated by two
fountains, rising 95 feet above the level of the
sunken gardens, one symbolizing the rising
sun and the other the setting sun.
The shaft and ball surmounting each
fountain is glazed in heavy opal glass which is
coated on the outside in imitation of traver-
tine stone so that by day they do not in any
sense suggest the idea of being light sources.
Mazda lamps installed in these two columns
give a combined initial mean spherical
candle-power of approximately 500,000 and
yet the intrinsic brilliancy is so low that the
fountains are free from disagreeable glare
and the great colonnades are bathed in a
soft radiance. For relief lighting three
Mazda lamps are placed in specially designed
cup reflectors located in the central flute to
the rear of each column. This brings out the
Pompeian red walls and the cerulean blue
ceilings with their golden stars and at the
same time the sources are so thoroughly
concealed that their location cannot be
detected from any point in the court.
The perimeter of the ' ' Sunken Garden ' ' is
marked by balustrade standards of unique
design consisting of Atlantes supporting urns
in which are placed Mazda lamps of relatively
low candle-power. The function of these
lights is purely decorative.
The great arches are carried by concealed
lamps, red on one side and pale yellow on the
other, thereby preserving the curvature and
the relief of the surface decorations. The
balustrade of this court, 70 feet above the
sunken garden, is surmounted by 90 seraphic
figures with jeweled heads. These are cross
lighted by ISO Mazda searchlights, the
demarcation of the beams being blended out
by the light from the fountains of the rising
and the setting sun.
Passing through the Venetian Court to the
west, we enter the ' ' Court of the Four
Seasons," classically grand. We are now in a
field of illumination in perfect harmony with
the surroundings, suggesting peace and quiet.
The high current luminous arcs mounted in
pairs on 25-ft. standards masked by Greek
banners are wonderfully pleasing in this
setting. The white light on the columns
causes them to stand out in semi-silhouette
against the warmly illuminated niches with
their cascades of falling water, and the placid
central pool reflects in marvelous beauty
scenes of enchantment.
Having reviewed in order illuminations
mysterious, grand and peaceful, we emerge
from the West Court upon lighting classical
and sublime, the magnificent Palace of Fine
Arts bathed in triple moonlight and casting
reflections in the lagoon impossible to de-
scribe. The effect is produced by searchlights
on the roofs of the Palaces of Food Products
and Education supplemented by concealed
lighting in the rear cornice soffits of the
colonnade.
You have only passed through the central,
east and west axis of the Exposition. There-
are many more marvels to be seen. If you
wish to study the art of illumination you
could visit the Exposition every evening
throughout the year and still find detail
studies of interest. For instance, did you ever
see artificial illumination in competition with
daylight? On certain occasions the projectors
flood-light the towers before the sun goes
down. If you are fortunate enough to be
present, take up a position in the northwest
section of the "Court of the Universe" and
watch the marvelous effect of the "Tower of
Jewels" as the daylight vanishes and the
artificial illumination rises above the deepen-
ing shadows of the night. The prismatic
colors of the jewels intensify and the tower
itself becomes a vision of beauty never to be
forgotten.
The South Garden may very properly be
called the fairy-land of the Exposition at
night. When the lights are first turned on,
the five great towers are bathed in ruby tones
and they appear with the iridescence of
red hot metal. This gradually fades to delicate
582
GENERAL ELECTRIC REVIEW
rose as the flood-light from the arc projectors
converts the exterior of the towers into soft
Italian marble. The combination of the
projected arc light (white) and the concealed
Mazda light (ruby) produces shadows of a
wonderful quality. Each flag along the para-
pet walls has its individual projector which
converts it into a veritable sheet of flame.
As a primary line of color the heraldic
shields and cartouche lamp standards produce
a wonderful effect against the travertine walls
bathed in soft radiance from the luminous
arcs which also bring out the color of the
flowers and lawns and create pleasing shadows
in the palms and other tropical foliage. This
is supported by a secondary effect in the
decorative Mazda standards along the
"Avenue of Palms" and throughout the
garden. A finishing touch is added by the
effect of life within created by the warm
orange light emanating from all the Exposition
windows supported by red light in the towers,
minarets and pylon lanterns.
To the west we have the enormous glass
dome of the Palace of Horticulture converted
into an astronomical sphere with its revolving
spots, rings and comets appearing and dis-
appearing above and below the horizon and
changing colors as they swing through their
orbits. The action is not mechanical, but
astronomical.
To the east, we have the "Festival Hall"
flood-lighted by luminous arcs and accentuated
by orange and rose lights from the corner
pavilions, windows, and lantern surmounting
the dome, all reflected in the adjacent lagoon
and possessing a distinctive charm which will
long remain in the memory.
Purely spectacular effects have been con-
fined to the scintillator at the entrance of the
yacht harbor. This consists of 48 36-in.
projectors having a combined projected
candle-power of over 2,000,000,000. This
battery is manned by a detachment of
United States Marines.
A modem express locomotive with 81 -in.
drivers is used to furnish steam for the
various fireless fireworks effects known as
"Fairy Feathers," "Sun-Burst," "Chromatic
Wheels," "Plumes of Paradise," "Devil's
Fan." etc. The locomotive is arranged so that
the wheels can be driven at a speed of 50 or
fid miles per hour under brake, thereby
producing great volumes of steam and smoke,
which, when illuminated with various colors,
produces a wonderful spectacle.
The aurora borealis created by the search-
lights reaches from the Golden Gate to
Sausalito and extends for miles in every
direction. The production of "Scotch
Plaids" in the sky and the "Birth of Color,"
the weird "Ghost Dance," "Fighting Ser-
pents," the "Spook's Parade" and many
other effects are fascinating.
Additional features consist of ground mines,
salvos of shells producing "Flags of All
Nations," grotesque figures and artificial
clouds for the purpose of creating midnight
sunsets.
Over 300 scintillator effects have been
worked out and this feature of the illumina-
tion is subject to wide variation. Atmospheric
conditions have a great influence upon the
general lighting effects; for instance, on still
nights the reflections in the lagoons reach a
climax, particularly the Palace of Fine Arts
as viewed from Administration Avenue; the
facades of the Education and Food Products
Palaces as seen in the waters through the
colonnade of the Palace of Fine Arts; the
Palaces of Horticulture and Festival Hall
from their respective lagoons in the South
Garden; the colonnades and the Nova-gems
on the heads of the seraphic figures, and the
"Tower of Jewels" as reflected in the water
mirror located in the North Ann of the
"Court of the Universe."
On windy nights the flags and jewels are
at their best. On foggy nights wonderful
beam effects are produced over the Exposition
impossible at other times. When the wind is
blowing over the land the scintillator display
is different from nights when the wind is
blowing across the Bay. A further variety is
introduced in the action of the smoke and
steam on calm nights.
On the evening of St. Patrick's Day all the
searchlights were screened with green; not
only the towers but every flag in the Ex-
position took on a new aspect.
Orange in various shades was the prevailing
color for the evening of Orange Day and on
the ninth anniversary of the burning of
San Francisco the Exposition was bathed
in red, with a strikingly realistic demonstra-
tion of the burning of the "Tower of Jewels."
High pressure gas lighting plays an
important part in street lighting in the
foreign and state sections; low pressure gas
for emergency purposes, and gas flambeaux
for special effects.
The accompanying illustrations suggest
some idea of the illumination, but the addition
of color is absolutely necessary to convey
anything approaching a correct impression of
the night pictures of the Exposition.
ILLUMINATION OF THE PANAMA-PACIFIC EXPOSITION :,s:;
Reflection of the Italian Towers of the Court of Flowers in the East Lagoon of the South Garden
584
GENERAL ELECTRIC REVIEW
Reflection of the Tower of Jewels in the West Lagoon of the South Garden
ILLUMINATION OF THE PANAMA-PACIFIC EXPOSITION
585
Palace of Horticulture as Reflected in the West Lagoon of the South Garden
586
GENERAL ELECTRIC REVIEW
i
m
ILLUMINATION OF THE PANAMA-PACIFIC EXPOSITION
587
:,ss
GENERAL ELECTRIC REVIEW
Jm "»
SBSffct
West Entrance to Food Products Palace showing 35 ft. 3-light Luminous Arc Cartouche Standards
ILLUMINATION OF THE PANAMA-PACIFIC EXPOSITION
589
Entrance to Varied Industries Building Lighted by 3-Iight Lum
inous Arc Cartouche Standards
-,-mi
GENERAL ELECTRIC REVIEW
Reflection of Festival Hall in the East Lagoon of the South Gardens
ILLUMINATION OF THE PANAMA-PACIFIC EXPOSITION
591
o §
O
w
6
592
GENERAL ELECTRIC REVIEW
Fountain of Energy and 2 1 -light Mazda Lamp Standard at the Entrance to the South Gardens
ILLUMINATION OF THE PANAMA-PACIFIC EXPOSITION
593
Decorative Mazda Standard and Lantern, Court of Flowers
594
GENERAL ELECTRIC REVIEW
* NOTES ON THE ACTIVITIES OF THE A.I.E.E.
Institute Meetings
The annual convention will be held at
Deer Park. Aid., from June 29th to July 2nd.
The Panama-Pacific convention will take
place in San Francisco on September 16th
and 17th. At the Directors' Meeting recently
in New York, upon the recommendation
of the Meetings and Papers Committee,
authority has been granted to hold an
Institute Meeting at Philadelphia on October
11th under the auspices of the Philadelphia
Section, and also a meeting at St. Louis
under the auspices of the St. Louis Section.
The exact date of the latter is to be announced
later.
Specifications for Testing Porcelain Insulators
For a long time there has been a great
demand for a set of specifications to cover the
inspection and testing of high tension line
insulators. Under the auspices of the Trans-
mission Committee, a great many very
interesting papers have been contributed in
the past year or so on the general subject.
The scope of these papers has included
practically all the information available
about the operation and manufacture of
insulators, and the transmission committee
have now added to this important work by
preparing a set of specifications which can
be used as a model or skeleton in the prepa-
ration of specifications covering the inspecting
and testing of high tension insulators.
SCHENECTADY SECTION
Electric Supply in Large Cities
On April 20th, Mr. Philip Torchio, Chief
Electrical Engineer of the New York Edison
Company, gave a very interesting talk on
the subject of Electric Supply in Large Cities.
A large number of carefully prepared lantern
slides were used to illustrate the various
points brought out.
Mr. Torchio pointed out that most large
cities depend for electrical power on steam
generation, and that modem practice is
illustrated by a study of installations here
and abroad. He then took up the question
of the coal pile, and proceeded from this
point to a complete analysis of the subject.
A number of slides were shown, illustrating
the various methods of coal storage, coal
conveying and ash handling. Mr. Torchio
stated that large coal storages ensured a
constant supply of coal, even when the regular
*The Lynn and Pittsfield Sections have closed for the season.
delivery from the mines is interrupted. He
pointed out that coal handling apparatus was
necessary to supply the boilers with fuel, and
showed a number of lantern slides illustrating
the various types of coal conveyors.
Several methods of ash handling were
discussed, and it was stated that the removal
of ashes by vacuum is accomplished success-
fully in England, and that the success of the
system requires crushing of the clinkers in
ashes entering the vacuum pupe. The Paris
stations utilize the ashes with the addition of
10 per cent hydraulic cement for making
bricks.
Some American and foreign practices were
discussed and illustrated with regard to
boilers, stokers, etc. Water tube boilers of
different designs are generally prevalent, and
stokers reduce the boiler room operating cost.
Superheaters are used up to 300 deg. F., and
economizers are generally used abroad and
will probably come more into use in this
country. Cinder catchers have been installed
in New York to overcome objectionable
conditions to neighbors.
The Evase stack system to create induced
draft is very efficient and extensively used in
German and French installations. The
economic operation of a boiler room requires
a carefully organized system of tests.
With regard to some of the accessories of
a boiler, it was stated that steel valves and
fittings for steam piping are considered
essential for superheated steam. The pipe
run should be as short as possible to reduce
cost and heat loss.
Electrically driven pumps for boiler feed
and condensers are generally used abroad
where economizers are used for the heating
of the boiler feed water. Exhausting the
steam of auxiliaries into the low pressure
element of the turbine has also given good
results. Surface condensers for turbines are
universally used.
The new • Paris station is equipped with
10,000- and 15,000-kw. turbo-generators, each
with a direct connected exciter, and a separate
generator is used to supply the electrically
driven auxiliaries. Air filters are used for
generators abroad, while air washers are
coming into use in this country. Acoustic
frames in the air ducts are used in New York
to eliminate noise from turbo-generators.
Exciters are steam-driven, water-driven and
turbine-driven, respectively, depending upon
local conditions, but exciter bus batteries
NOTES ON THE ACTIVITIES OF THE A.I.E.E.
595
are now generally considered essential for
very large plants.
In this country, parallel operation prevails
for the generators in a single station as well as
that between those in several stations,
Abroad, however, the tendency is to sectional-
ize. The two methods of operation call for
different arrangement of busses and switch-
board connections. Protective reactors are
generally adopted in this country and are
rapidly gaining favor abroad. A number of
lantern slides illustrating various station
arrangements, particularly those used by the
New York Edison system, were shown.
As regards underground distribution, it was
stated that lead covered cables cannot be
safely used for high tension wiring without
special precautions, and favored braided
cables on insulators as an ideal layout.
The grounding of the neutral should be
designed to confine the grounding current
to the minimum necessary to obtain pre-
vention of an arcing ground and prompt
disconnection of the feeder when a ground
develops. Transmission cables in ducts are
more adapted to American conditions than
armored cables in earth, and the operation of
feeders to a substation is either in multiple
or independent, the latter giving greater
protection.
Characteristic direct current distributing
systems include substations with rotary
converters, stand-by batteries giving full
substation output for about 10 minutes,
regulation of feeder pressure by different
sets of busses operated at different voltages,
and pressure wires for each feeder from the
junction box. Concentric cables are preferable
for feeders, and neutral feeders and mains
should be single conductor cables. A network
of mains should be connected solid with
provisions for sectionalizing. if ever necessary.
This gives maximum efficiency of regulation.
An interesting fact is that the old Edison
tubes installed many years ago are doing
today just as full duty as the more modern
cable layouts.
Alternating current distribution includes
substations with main transformers, and
distributing feeders with automatic regulators
on each feeder. The practice of alternating
current distribution abroad is the ring system ;
in America, the independent feeder circuit.
Progress has been made, however, in tying
together different feeders, either normally or
automatically, in cases of emergency. Dis-
tributing transformers are placed in manholes,
vaults or kiosk.
Character of service includes ordinary
commercial business service supplied from
low tension distributing and regulated
systems, and the bulk business service
supplied as untransformed current for the
construction of public works, railways or
railroads, pumping stations, etc. Some of the
larger contracts being fulfilled by his Com-
pany were mentioned by way of illustra-
tion. Such developments forecast the pass-
ing of the small station and portend the
day of the unified system of large central
stations supplying all the needs of the com-
munity.
Mr. Torchio's paper was discussed by
Messrs. W. L. R. Emmet, A. H. Kreusi,
H. R. Summerhayes and others. Mr. Emmet,
in particular, paid Mr. Torchio a high tribute,
pointing out that Mr. Torchio had gained
for himself a most creditable reputation.
He said that he himself had been in the
central station business from its beginning,
and was, therefore, in a position to appreciate
just how much Mr. Torchio had done, and
how very valuable this work had been to the
central station profession.
596
GENERAL ELECTRIC REVIEW
FROM THE CONSULTING ENGINEERING DEPARTMENT OF THE
GENERAL ELECTRIC COMPANY
COMPENSATORS FOR MAZDA C LAMPS
For constructive reasons and to obtain the
advantage of a higher efficiency, the 0.5 watt
per candle high current gas-filled lamp is
desirable for street lighting purposes. Since
the majority of the series systems are either
G.6 or 7.5 amperes, it has been necessary to
Fig. 1. Vector Relations showing Use of an
Independent Phase for Power-
Factor Determination
employ a compensator to transform the
current to 15 or 20 amperes as the case may
require. In addition to this, these compen-
sators are designed to perform two other
functions.
By selecting the proper flux density and
arranging the primary and secondary coils in
separate groups, the leakage flux increases
rapidly as the line current tends to rise above
normal: the result is that the power-factor
falls off. Thus, for current excesses caused
either by the short circuiting of a section of the
series loop or by primary voltage surges, the
compensator has the same effect as an added
series reactance. This in turn protects the
lamp against injurious excess currents, thus
increasing the reliability of the system as a
whole. For an increase of 50 per cent line
current the lamp current increases approxi-
mately 23 per cent, while the reactance
increases from 1.6S ohms normal to 3.97
ohms at 50 per cent line current.
The same compensator may be used for
constant potential series operation where the
proper number of lamps in series are con-
nected directly across a constant potential
supply. For this class of work the compen-
sators must not only transform current, but
must possess inherent regulating character-
istics by fulfilling the requirements of a
variable reactance voltage and consequently
maintaining practically constant impedance
of the circuit. This is accomplished by
designing the device for a definite open circuit
flux density, that is, as the lamps burn out
the open circuit voltage of the compensator
decreases as the current wave becomes more
and more distorted, due to the saturation
in the magnetic circuit. The present type C
compensators are designed to meet the
requirements of either constant current or
constant potential operation and will in either
case protect the lamp against excess currents.
Determination of Power-Factor
The loaded compensator taking only a few
hundred watts has a high power-factor, and
since the variation of the cosine with the
angle is not rapid when the power-factor is
near unit}7 an error of even two or three watts
in reading the meter will introduce an
appreciable error in the final result. For
example at 6.6 amperes 50 volts 320 watts
the calculated power-factor is 97 per cent,
while if 323 watts were read a value about
1 per cent higher would be indicated.
If, however, a voltage having a phase
relation of about 45 deg. to the current be
used, small errors will not be magnified as
in the above case, since here the cosine varies
rapidly with change of angle. This method
is simple and accurate, and has an additional
advantage in that the potential coil currents
are in an independent phase and can not
possibly enter as disturbing elements in cur-
rent reading.
Referring to Fig. 1 the method of applying
the above may be more clearly seen. The
lamp circuit is supplied with power from the
phase indicated by E, but in order to
determine a it is necessary to connect the
potential coil across E« while the current coil
is connected in series with that part of the
circuit through which the current / passes.
Measurements of E->, W«, and / are recorded.
]Y„ = E« I Cos a.
W2
E-2I
iS = 60 deg. since E« = E3 = E^
7 = /3-a.
7 = 60 — a.
Cos y = Power-factor of compensator.
H. D. Brown
Cos ot =
y?7
General Electric Review
Manager. M. P. RICE
A MONTHLY MAGAZINE FOR ENGINEERS
Editor. JOHN R. HEWETT
Associate Editor, B. M. EOFF
Assistant Editor. E. C. SANDERS
Subscription Rales: United States and Mexico. $2.00 per year; Canada, $2.25 per year; Foreign, $2.50 per year; payable in
advance. Remit by post-office or express [money orders, bank checks or drafts, made payable to the General Electric Review,
Schenectady, N. Y.
Entered as second-class matter, March 26, 1912, at the post-office at Schenectady, N. Y., under the Act of March, 1879.
VOL. XVIII., No. 7
Copyright, 1915
by General Electric Company
July, 1915
CONTENTS
Frontispiece
Editorial : The Paths of Progress
The Chicago, Milwaukee & St. Paul Locomotives
By A. H. Armstrong
By J. C. Thirlwall
By Dr. Saul Dushman
By Sanford A. Moss
By Dr. Wheeler P. Davey
The Jitney Problem .
The Periodic Law
Test for Dirt in an Air Supply
X-Rays, Part III
Ball Bearings in Electric Motors
By Frederick H. Poor
Electrophysics: Some Characteristics of Cathode Ray Tubes
By J. P. Minton
High- Voltage Direct-Current Substation Machinery .
By E. S. Johnson
The 1500-Volt Electrification of the Chicago, Milwaukee & St. Paul Railway
By W. D. Bearce
Some Recent Developments in Switchboard Apparatus
By E. H. Beckert
The Small Consumer — A Problem
By A. D. Dudley
Modern Street Lighting with Mazda Lamps
By H. A. Tinson
Practical Experience in the Operation of Electrical Machinery, Part IX
The Wrong Shunt Ratio; Repulsion Motor Heating; Variable-Speed Motor
Inertia Load; Service Voltage too Low
By E. C. Parham
From the Consulting Engineering Department of the General Electric Company
Question and Answer Section
In Memoriam — John P. Judge ... . . . .
Page
598
599
600
60-4
614
622
625
631
636
641
644
646
657
659
666
on an
669
670
672
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•yag \i i g?'
General Electric Review
THE PATHS OF PROGRESS
We publish in this issue an article on the
"Jitney Problem," and while this particular
problem is of great interest at the immediate
present, it is the general fundamental prin-
ciple underlying this discussion that is of
greatest importance.
The problem is being met in various ways
in different localities, but roughly speaking,
one of two ways is generally adopted. One
is by attempting to meet this form of com-
petition by competitive service; the other is
by legislation.
Prior to the time when the people under-
took the regulation and control of Public
Utilities by the creation of Public Service
Commissions under statute in the several
States, competition was generally looked
upon as being the only means of obtaining
better service and lower charges. The
unsoundness of this principle, however, as
applied to Public Service Corporations, which
are usually natural monopolies, led to the
creation of Public Service Commissions and
an attempt to secure the desired improve-
ment in service under government direction.
Generally speaking Public Service Com-
missions have recognized that Public Service
Corporations, like street railways, should have
protection from competition, and their
decisions in cases arising throughout the
United States show a consistent effort to
prevent the economic waste resulting from
sporadic competition. Public Service Cor-
porations today are operating under regula-
tions which no longer leave them free to meet
such competition as they could prior to the
creation of the Public Service Commissions
and they are operating under Government
regulation upon a basis which can only be
profitable if they are reasonably protected.
When a street railway can be compelled to
extend its lines into sparsely settled districts,
it obviously should be protected in its rev-
enues in more densely populated sections.
At the time Public Service Commissions
first came into existence in 1907 it was
contemplated that the only competition to be
avoided was that of other similarly operated
companies — the steam railroad should be
protected from a new parallel steam railroad
serving the same territory — a street railway
should be protected from another street
railway operating through the same streets
or in the same general territory. While the
legislatures have generally been inactive
concerning the jitney problem the general
trend is to extend the power of the Public
Service Commissions either to place such
competitors as the jitney buses under the
same regulations and restrictions as are now
imposed upon their competitors or to elim-
inate entirely such competition in accordance
with the more modern policy of the States.
If jitney buses are to enter the field of public
service they should be required to give the
same class of service as their competitors, and
to accept the same responsibility as regards
accidents, proper equipment, hours of service,
area of service, etc.
The theory upon which Public Service
Commission Laws are based is that a com-
mission of men familiar with Public Service
questions and with the conditions under which
Public Service Corporations operate is in the
best position to determine whether it is for
public welfare to have competition or a
regulated monopoly in each instance. With
this in view commissions are empowered to
subpoena witnesses, hold hearings, and to
determine upon all the available evidence
whether the public convenience and neces-
sity requires any change or extension in a
particular service, and if so, whether it can be
best obtained from the Public Service Com-
panies already in the field, or whether a new
interest should be admitted to serve the
public. Before a new corporation or indi-
vidual can come into the field and before
an existing one can materially extend its
activities, a favorable decision by the com-
mission is required with an order that it
is to the public convenience and necessity
to permit the new company to operate as it
desires. This would seem the logical solution
of the "Jitney Problem" from the standpoint
of legislation.
The popularity of the jitney buses in many
localities may be a passing craze or it may
indicate a desire on the part of the public
for a quicker service at short intervals. Some
railway companies may find it desirable to
meet this requirement by a lighter type of
equipment operated under shorter headways.
600 GENERAL ELECTRIC REVIEW
THE CHICAGO, MILWAUKEE & ST. PAUL LOCOMOTIVES
By A. H. Armstrong
Assistant Engineer, Railway and Traction Department, General Electric Company
The author gives a great deal of valuable data on these most interesting locomotives. Among the points
which will attract special attention are the regenerative control, the large continuous capacity of the motors,
and the novel form of current collectors. The comparison given between these locomotives and the Mallet
engine emphasizes the size and hauling capacity of the electric locomotives. This article appeared in the
Electric Railway Journal of June 5, 1915. — Editor.
The flexibility in design and operation of
the electric locomotive afforded by the use
of electric motors renders this type of motive
power especially well suited to the hauling of
trains, either high speed passenger or slow
speed freight. In fact the electric locomotive
possesses inherent qualifications for haulage
service that are becoming more fully appre-
ciated as constituting the fundamental reasons
for bringing about the change from steam to
electricity, and interest in any new projected
electrification therefore largely centers in the
characteristics of the locomotives proposed.
Work has progressed upon the Chicago,
Milwaukee & St. Paul locomotives at the
Schenectady and Erie Works of the General
Electric Company to such an extent as to
make available certain facts as to the con-
struction and capacity that are of especial
interest owing to the magnitude of the prob-
lems involved in this extensive electrification.
The general data applying to the St. Paul
freight locomotives are as follows:
Tvpe of locomotive ( ™00 7olts .
- r L direct current
Length over all 112 ft.
Total wheel base 103 ft.
Rigid wheel base 10 ft. 6 in.
Total weight 520,000 lb.
Weight on drivers 400,000 lb.
Weight on driving axle 50,000 lb.
Weight on guiding axle 30,000 lb.
Diameter of driving wheel 52 in.
Diameter of guiding wheel 36 in.
Number of driving motors 8
Total output (continuous rating) .... 3000 h.p.
Total output (1 hour rating) 3430 h.p.
Tractive effort (continuous rating).. .71,000 lb.
Per cent of weight on drivers 17.75
Speed at this tractive effort at 3000
volts 15.75 m.p.h.
Tractive effort (1 hour rating) 85,000 lb.
Per cent of weight upon drivers 21.2
Speed at this tractive effort at 3000
volts 15.25 m.p.h.
A very exhaustive series of tests have just
been completed upon the first sample motor
built at Schenectady which have demon-
strated that it has ample capacity to meet the
heavy demands that will be placed upon it
under service operating conditions. The
motors are wound for 1500 volts and con-
nected two in series for 3000 volts. The
power axles are driven by twin gears, in this
respect being similar to the drive on the
Great Northern, Detroit Tunnel, Baltimore
& Ohio and Butte, Anaconda & Pacific,
except that springs are used in the axle gears.
On account of the high voltage for which the
motors are wound, the commutator width
is small, thus allowing more space for arma-
ture iron and copper, with the result that the
motor has a continuous capacity of 375 h.p.
In fact special interest attaches to the large
continuous capacity of the St. Paul loco-
motive as this is the first instance where such
a liberal motor capacity has been required
and provided for, and it should be noted that
this large capacity is secured in an axle motor
without departing from well known and
thoroughly tried out forms of construction.
A study of the train dispatcher's sheet
covering performance on mountain grade
divisions of our steam railways discloses the
fact that it is general practice to assign such
a trailing tonnage to a locomotive on ruling
grade as to demand a tractive effort at the
driver rims equivalent to approximately IS
to 19 per cent of the weight upon the drivers.
In other words, steam practice calls for a
locomotive which can operate for long
periods at a coefficient of adhesion of 18 to
19 per cent, leaving the difference between
this value and the slipping point of the
drivers as a sufficient margin with which to
start on ruling gradients. Under like track
conditions, the uniform torque of the electric
motor should make available some 10 per
cent more tractive effort than is possible with
the reciprocating drive of the steam locomo-
tive having the same weight upon the drivers.
Until sufficient operating experience is avail-
able, however, to prove that an electric
locomotive can be rated at 20 per cent coeffi-
cient of adhesion, it seems reasonable to
THE CHICAGO, MILWAUKEE & ST. PAUL LOCOMOTIVES
601
\5EJ
15-Sg
h46^ 72'-4~ 8-E"-4- 7Z"J — 11-6a — L-8'-6"J— ip-0"— J— 10-6 -J^IO'-O"— 1-9-0" — l-6LTzH
WEIGHT-LOCOMOTIVE aTENDER. 555.7001b
WEIGHT ON DRIVERS 324.500 -
TRACTIVE EFFORT 76.200-
WEIGHT-TOTAI 520.000 b.
WEIGHT ON DRIVERS 400.000 -
TRACTIVE EFFORT. 85.000 ••
CHICAGO. MILWAUKEE & ST. PAUL RAILWAY.
COMPARISON MALLET AND ELECTRIC LOCOMOTIVES
Fig. 1. Diagram of the Mallet Locomotive which has been used on the C. M. fit St. P. Ry., and of the electric
locomotive which is replacing the Mallet type on that road
Fig. 2. C. M. & St. P. 3000-vott Direct -current Locomotive, total weight, 260 tons
eight motors, total capacity 3440 H.P.
602
GENERAL ELECTRIC REVIEW
adhere to the present steam practice of a
somewhat lower value. The St. Paul loco-
motive, therefore, with its continuous motor
capacity of 17.75 per cent and a one hour
rating of 21.2 per cent of weight on drivers
Fig. 3. One of the eight direct-current motors used
on a C. M. & St. P. locomotive
gives ample assurance of ability to handle its
assigned tonnage under all service condi-
tions.
The St. Paul freight locomotive is guar-
anteed to have a hauling capacity of 2500
tons trailing load on all gradients up to 1 per
cent, and its heaviest duty will be to haul this
load from Lombard to Summit over the Belt
Mountains, a distance of 49 miles with a
ruling grade of 1 per cent and an average
grade of 0.7 per cent over the entire distance.
Including the locomotive of 260 tons, the
gross train weight of 2760 tons will require a
tractive effort of approximately 72,000 lb.
on the 1 per cent ruling grade, based upon a
train resistance of 6 lb. per ton. This prac-
tically corresponds to the continuous rating
of the locomotive as tabulated herein and
brings out the interesting fact that these
locomotives are so proportioned as to motor
capacity that they cannot be abused under
normal service operation.
The necessity of rating main line electric
locomotives upon a practically continuous
basis is still further emphasized in the case
of the St. Paul locomotives by the intro-
duction of electric regenerative braking. The
heavy demands upon the motors when operat-
ing up grade may be nearly duplicated during
the following down grade running when
regenerating, thus giving small chance for
the time element of the motor heating to
enter as a factor in proportioning its capacity
for such exacting service. A 2 per cent grade
requires a motor output of 46 lb. per ton up
grade and gives 34 lb. per ton motor input
down grade. Making due allowance for
internal locomotive losses, it is evident that
the motor output when operating as a gen-
erator down grade will approximate 60 per
cent of its input when hauling the same train
up a 2 per cent gradient, hence, the need of
making provision for a practically continuous
motor capacity in the St. Paul locomotives
in order to meet the service requirements of
the broken profile over which they are
designed to operate.
It is interesting to compare the relative
capacity of the new electric locomotives and
the Mallet engines they will replace.
COMPARISON MALLET AND ELECTRIC
LOCOMOTIVES
Total weight
Weight on drivers
Rated tractive effort
Per cent of weight on
drivers
Rated tonnage 1 per cent
grade
Tractive effort for above
tonnage
Coefficient of adhesion. . .
Wheels per guiding truck .
Weight per driving axle . .
Total weight on one rigid
wheel base truck
Mallet
Electric
555,700 lb. 520,000 lb.
324,500 lb. 400,000 lb.
76,200 lb. 85,000 lb.
23.5% 21.2%
1,800 tens 2,500 tons
54,000 lb. 71,700 lb.
16.7% 17.7%
2 4
54,000 lb. 50,000 lb.
162,000 lb. 100,000 lb.
Under favorable conditions the Mallet
engine can haul 2000 tons on 1 per cent grade,
thus bringing its tractive effort up to 59,000
lb. and the coefficient of adhesion on its
drivers up to 18.3 per cent. The electric
locomotive weighs 94 per cent of the com-
bined weight of Mallet engine and tender
and has a tonnage rating 23 x/2 per cent
greater based upon using the same coeffi-
cient'of adhesion in each case, that is 17.9
per cent. This comparison indicates that the
electric locomotive has a hauling capacity
one-third greater than the steam engine and
tender of the same total weight, has less
weight per axle, is provided with four-wheel
guiding truck in place of two-wheel, requires
no turn table, as it operates equally well in
either direction, and finally, eliminates the
necessity for stopping to take on coal and
water.
THE CHICAGO, MILWAUKEE & ST. PAUL LOCOMOTIVES
603
The same type of locomotive is used for
both freight and passenger service, the only
difference between the two being the gear
ratio, which is 4.56 for freight and 2.45 for
passenger service. This interchangeability
of all parts of the freight and passenger loco-
motive and the adoption of one uniform type
for all classes of service should be reflected
later in the low cost of maintenance of the
locomotive as well as prove of great benefit in
the economical handling of the traffic. For
facility in shop repairs, the locomotive is
constructed in halves, and in fact each half
can be provided with draft gear in place of
the articulated joint and operated singly in
service up to its capacity. One passenger
locomotive will haul a trailing load of S00
tons over all gradients of the road without
assistance except upon the 2 per cent grade
section over the main divide of the Rocky
Mountains. Even on this grade a 600-ton
train can be hauled without assistance. This
illustrates the exacting nature of mountain
railroading which demands in this instance
that the passenger locomotives shall have the
necessary motor capacity and smooth running
qualities to successfully haul an 800-ton
train at 60 miles per hour on level track and
also operate over 20 miles of 2 per cent up
grade. Add to this the regenerative braking
feature and steam heaters for train heating.
and the broad nature of the problem of
designing an electric locomotive for main line
mountain service becomes very apparent.
The locomotive superstructure contains space
for two oil fired steam heaters together with
ample provision for storage of oil and water.
All passenger locomotives and a certain
number of freight locomotives intended as
reserve passenger units will be equipped with
heater boilers.
A departure from the roller current col-
lector of the Butte locomotive has been made
in the St. Paul locomotives as the result of
numerous experiments made upon the test
tracks at Schenectady and Erie. These tests
indicate that a double pan collector bearing
against twin conductor trolley wires is capable
of taking off a current of 2000 amperes at
speeds as high as 60 miles per hour. This
is several times the demand upon one col-
lector of the St. Paul locomotives and the
double pan was adopted in place of the
roller collector although the latter has been
giving excellent results, reaching a life of
nearly 30,000 miles in the passenger ser-
vice of the Butte, Anaconda & Pacific Rail-
wav.
Provision has been made in the control to
enable two locomotives to be run together in
multiple unit, but the enormous starting
effort of two such locomotives, 240,000 lb.
tractive effort at 30 per cent coefficient of
S & £
Lt> 7/-acttve Effort
^^r cent Ffftc/ericy
S § 8 8 §
X X X
§ v ^ i
s ^r .. . v ;s== x
\i s *'- x
& »•-
§ rp&r H
s i^h t - -
*§ - SL .x X!$l_ X
* S*-X -5
s - Vt j> X X
Hi h*x -$
*S IX X
a X t \ <L
(J»- '**-
$ S - i
§ JX I ± ^ ±
. <f s
§ t ^
§ t x i v±
IX^X XX ^
Fig. 4. Characteristic curves of a C. M. & St. P. freight
locomotive. Direct current. 3000 volts: Gear
ratio 4.56; Diameter drivers 52 inches
adhesion, makes such a combination of use
only when it acts as a pusher on the rear of a
train. The motors and starting resistances
are designed to permit of a starting effort of
120,000 lb. being maintained on one locomo-
tive for a period of five minutes without
destructive heating and in this connection
the thermal capacity of the heavy slow speed
motors will be of great assistance.
The first completed St. Paul locomotive
will probably be placed upon the test tracks
at Erie during September and shipment of
these locomotives commenced soon there-
after. The construction work upon trolley
and substations of the first engine division
between Three Forks and Deer Lodge has
been so far completed as to give promise of
being finished and ready for the trial runs of
the locomotives as soon as they are received
this fall. Ample provision has been made for
power and transmission line facilities by the
Montana Power Company, so that electrical
operation of the Chicago, Milwaukee & St.
Paul Railway should soon be an accomplished
fact.
604
GENERAL ELECTRIC REVIEW
THE JITNEY PROBLEM
By J. C. Thirlwall
Railway and Traction Engineering Department, General Electric Company
In the first part of this article the author analyzes the jitney problem insofar as it affects the street railway
companies, and considers ways and means of meeting this competition. The second portion is devoted to a
study of the economies that are made possible by the use of lighter cars. The results of a comprehensive inves-
tigation of these economies are given in four tables. — Editor.
PART I: THE STATUS OF THE JITNEY, APRIL, 1915
A trip was made by the writer during
March and April last, which included visits
to a large number of the leading cities and
electric railways in Texas, Louisiana, Alabama,
Tennessee, Arkansas, Kentucky and Ohio.
More than twenty roads were visited and the
question of jitney competition discussed with
the chief operating officials of each, and the
following paragraphs give a consensus of
their opinions on the main points of dis-
cussion.*
1st. The jitney car or bus is making
serious inroads into the revenues of the
railway companies operating in eight out of
the 19 cities visited. In two places, city
ordinances regulating all common carriers
had prevented their advent. In some other
cities, excessive grades and poor pavements
prevent any extensive use of automobiles,
and in others the local officials attributed
their freedom from competition to the fre-
quency of their schedules and the high
character of their service or to other purely
local causes.
2d. Various methods of meeting the jitney
competition have been adopted; operators
in general are endeavoring to secure proper
regulation either through the state legis-
latures or city councils; some had cut down
their schedules and expenses; others had
increased their service. The latter method
appeared to be most effective in meeting
jitney competition.
3d. Without regulation by state or city,
the number of jitneys in service in a city
appears to pass through a period of very
rapid growth, followed by a decrease. This
is due to several reasons. As a novelty, when
the first machines appear, the riding in them
is very heavy and they carry good loads all
day long. There is a good profit in the
business at this stage which attracts so many
♦This, of course, represents conditions existent early in the
spring of 1915, and many changes may have occurred before
this article is published.
drivers that their average daily receipts drop
very sharply, even though the total number of
people riding in them is large enough to
seriously curtail the railroad's revenues.
Moreover, as the novelty of the new form
of transportation wears off, as accidents
increase, and as people find that they are
being crowded as much or more in the jitneys
as in the street cars, many passengers return
to the railway. Further, the maintenance on
the average small automobile, within two or
three months of running 150 to 200 miles a day,
becomes excessive. All these reasons combine
to cause a large number of drivers to drop out.
and their number usually exceeds that of
fresh recruits.
But as the total number of machines
decreases, the average daily earnings of those
remaining tend to again increase until a point
is reached where the driver can ordinarily
make a profit over his costs for fuel and
repairs which is sufficient to support himself
and in some instances to cover the deprecia-
tion on his car.
4th. Without city or state regulation, the
number of machines tends to become nearly
stationary at this stage, or to decrease very
slowly.
oth. The total earnings of the jitneys are
considerably in excess of what the railways
lose to them. They carry in pleasant weather
many pleasure riders and, due to the fre-
quency of their service, many people who
would walk short distances rather than
wait for a street car. The number of such
riders is considerable. Moreover, they fre-
quently charge more than five cents, par-
ticularly when operating late at night, or
when asked to deliver passengers at some
point off their regular routes.
6th. The larger busses, seating from 1 0 to 30
people, have made little headway, as yet,
compared to the small five- or seven-passenger
car.
THE JITNEY PROBLEM
6115
7th. It appears certain that even with
strict regulation some autos will remain in the
business, but probably at a rate of fare
amounting to more than five cents, and prob-
ably only in the higher class residential
sections.
8th. If regulation, particularly as to furnish-
ing bonds to guarantee settlement of accident
claims, is enforced, all but a small proportion
of the jitneys will disappear.
9th. The difficulty of depending upon reg-
ulation to meet this competition lies in a
fairly general public sentiment against put-
ting the individual under the same restric-
tions as a corporation. In many places
where regulation has been proposed after
the advent of the jitney, a strong protest has
developed against it, on the part of mam-
newspapers and a considerable part of the
public, and in at least two cities an attempt
has been made to submit the matter to a
referendum vote. These factors have in
general prevented the adoption or enforce-
ment of any real regulatory measures.
10th. There are three other means of
meeting the situation, until regulation can
be obtained.
(a) To decrease service and cut down
operating costs. This, it is realized, will
simply give the jitneys a better chance, but
would be adopted to bring most forcibly to the
attention of the city authorities the need of
protecting the railway company's interest.
(b) To put on a larger number of jitney
cars or busses, to run in competition with the
privately owned jitneys, and to either force
the others out by giving lower fares, or, to
compel regulation by the character of the
competition. It is realized that this would be
simply an emergency measure, that the
operation of these cars would be at a loss, and
that their success in driving other jitneys from
business would terminate in a heavy loss on
the machines which would then become
useless to the operators.
(c) To increase the service on lines subject
to jitney competition, and to cut down head-
ways, with the idea of taking back sufficient
passengers from the jitneys so that the narrow
margin of profit to their drivers now existing
would be entirely wiped out, or where they
are operating at cost or less, that they would
the quicker realize the hopelessness of con-
tinuing in the business.
1 1th. There was a wide diversity of opinion
as to the merits of these schemes, but the
big majority of operators declare the first
scheme suicidal, in that it enables the jitneys
to make a very much greater revenue, and
increases still further the complaints of
dissatisfied patrons.
The second scheme was also generally
considered a dangerous experiment, and likely
to lead to trouble with the public besides being
extremely expensive and probably not very
effective.
The third scheme was almost unanimously
agreed to as being the logical move, but the
opinions were almost equally unanimous that
it would involve too great expense, both in the
purchase of new cars, and in the costs of
operation, especially platform wages. It was
further thought by most officials that, if
adopted as a means to eliminate competi-
tion, they would be compelled to maintain
such service after the competition passed, thus
permanently increasing expenses.
12th. It was, however, agreed that if such a
measure were to be adopted, a different type
of equipment from what has been purchased
by most roads during the past few years would
be a necessity, and that power and main-
tenance cost would have to be radically cut
if platform wages should be appreciably
increased.
13th. This led to the question of one-man
cars. Nearly every operator asserted that
there were certain lines in every city where
one man operation would be feasible, and that
on nearly all lines such operation would be
entirely practicable during many hours of the
day. On the other hand, nearly every road
is compelled, either by the terms of its charter
or by state or city laws, to have two men on
each car. However, the use of prepayment
cars and the education of the public in nearly
every city to this system has automatically
relieved the conductor of most of his duties,
and it is believed that very little delay would
result from the motorman collecting fares and
issuing transfers. In Lexington, Ky., the rear
doors have already been closed off, the
conductors are located at the front platform,
and no trouble has been occasioned thereby.
But nearly everyone believed that before
the change to one-man operation could be
made, a long period of discussion and of
agitation with city councils and state legis-
latures would be necessary.
14th. Almost every operator stated that if
two men per car are to be used, the cost of
operation will increase even with extremely
light weight cars, if headways are materially
shortened, and there is a very general feel-
ing that this increase would not be made up
bv increased receipts. A number of operators,
606
GENERAL ELECTRIC REVIEW
however, do not agree with this, saying that
headways of 10 to 15 minutes apart lose a
very large proportion of short riders.
15th. Assuming the use of smaller, light
weight cars, however, as a future standard,
nearly all were agreed on the following:
such cars would have to be of a comfortable
easy riding type, which means cross seats, and
prohibits the use of the short wheel base
rigid single truck. The latter point was also
emphasized by the general impression that
cars on such trucks could not be successfully
operated in trains.
The use of radial trucks with relatively long
wheel base was favored by a few ; most opera-
tors questioned their use on short radii curves.
Low wheels, preferably 24 in., were favored
by nearly all.
Center entrance cars were not thought
desirable by most operators.
The use of multiple unit control, if cars of
a seating capacity of about 30 were used, was
considered a necessity by nearly all operators,
in the larger cities, to care for rush hour
conditions, both as a measure of platform
economy and to relieve downtown congestion.
PART II: OPERATING ECONOMIES MADE POSSIBLE BY THE
USE OF LIGHT CARS
The invasion of the street railway field by
the jitney automobile busses, during the past
six months, brought to the attention of the
railway manager more urgently than ever
before the vital necessity for reducing his
operating expenses. In the case of many
roads, indeed, it has become a question of
one of three things; a radical decrease in
operating costs, an increase in fares, or a
receivership. To increase fares, except by
some such means as the Milwaukee zone
system, is an absolute impossibility for
the average city system, under the present
feeling of the public and legislatures. Indeed,
it is becoming more and more difficult to
prevent radical cuts in the rate of fare, either
through being compelled to sell tickets at
three or four cents, or by compulsory extension
of lines or of transfer privileges.
The foregoing analysis of the jitney situa-
tion indicates that the majority of operators
do not feel very confident that their interests
will be adequately protected by legislation
against unfair competition ; before tremendous
losses have been incurred. There is also a
fairly general agreement that what success has
attended the operation of jitneys is because
they are a novelty and because they meet a
popular demand for quicker and more fre-
quent service. Most operators will further
agree that the railways are not securing all of
the traffic possible, and that a considerable
increase in receipts could be secured by pro-
viding shorter headways and faster schedules,
but that they are forced to compromise
between the service which the public demands
(and which they cannot afford to supply under
existing conditions), and what they could
most economically furnish, but which the
public will not tolerate.
Under these conditions, it logically follows
that on most roads, if it were possible to
operate faster schedules and to greatly reduce
headways without a material increase in the
operating expenses, it would be hailed with
equal joy by the operators and the public.
It cannot be done by the automobile; there is
no question of doubt, in spite of the claims of
individuals, that with the typical small
machine the platform costs per passenger
handled and the costs of power are so
much higher than on railway cars that
they cannot compete on even terms. With
the larger busses there appears to be a greater
difference of opinion. But even with these,
all experience in this country has shown that
they cannot be made to pay against a properly
managed electric railway; and when brought
down to the simplest terms it is again the well
known story of the wastefulness of small
scattered power plants as compared with the
large central station. An individual may
operate his own automobile for short distances
on city streets and, by working from 12 to 15
hours per day and making his own repairs and
replacements, make a bare living from his
machine after paying for fuel, tires and
depreciation. A company attempting to
operate such machines, however, could not
secure his services for anywhere near the
amount he is content to work for while he is
operating independently. These facts are so
self-evident that with very few exceptions
operators have dismissed the idea of employ-
ing the gasolene car.
To put into service a greater number of
electric cars of the present standard type, as
a temporary measure, in order to meet jitney
competition by cutting down the average daily
receipts of each private car and thus hasten
THE JITNEY PROBLEM
607
the inevitable conclusion of its driver that he
cannot make a living in the service, would
probably be effective in ending competition.
But most operators fear that this would result
in ordinances compelling them to maintain
such service after the passing of the auto, and
that the increased cost of the additional
service would not be offset by correspondingly
increased revenues, since platform wages,
power, and maintenance charges would all
advance, and at the same time the first cost
of such cars would considerably increase the
capital account.
The question then arises; Can the car
building companies and the manufacturers
of electric car equipment design and furnish
cars of a type acceptable to the public, but
which will combine the qualities of light
weight and strength to such a degree that the
savings in power and in maintenance secured
by their operation would offset the additional
platform expense where more of these are
used? The advance in car body and truck
design, and the introduction during the past
year of the low-wheel motor makes it possible
to answer "yes" to this inquiry.
The Third Avenue Railway Company in
New York was one of the first companies, so
far as the writer recalls, to utilize this feature,
and in their cars the weight per seated pas-
senger was cut to approximately 650 lb. as
compared with weights of 800 to 900 lb. in
the typical double-truck cars purchased by
most urban systems during the past two or
three years. The seating capacity of their
cars is 42; for many medium sized cities, a
smaller number of seats would be ample
during all hours of the day, except for one or
two trips in the rush hours.
Approximately the same weight per pas-
senger was secured in the latest cars put into
service in New Orleans, which seat 52 and
weigh less than 35,000 lb. This latter car, if
mounted on 24-in . wheels, using smaller motors ,
and taking advantage of other improve-
ments which have lately been developed,
could be brought down to about 30,000 lb.
A still further advance has been suggested
by a well known car designer, who has laid
out a single-end, one-man trackless car,
which seating 29 would weigh but 9000 lb.
and a double-end car seating 32 and weighing
about 12,000 lb.
Four of the former cars would provide as
many seats as five of the usual city type, and
with a 30 per cent reduction in weight. Three
of the second type could replace two of the
standard size and weigh 50 per cent less.
Either one offers considerable economies,
both in first cost and in power and mainte-
nance. The reduction in power consumption,
especially in the peak load during rush hours,
would be a measure of immense economy.
The reduced wear and tear on tracks, roadbed,
and special work would be even more marked.
Reduced current means less wear on trolley
wires. Reduction in brakesboe and wheel
wear is of course obvious.
The importance of weight reduction is so
well known that a figure of five cents per lb.
per year is commonly accepted as the saving
which can be secured in city service by any
cutting of weights on the cars. If this is true,
the substitution of 12,000-lb. cars for cars
weighing 36,000 or 40,000 lb., even when
more of the smaller ones are operated during
rush hours, would save the operator from
$1100 to $1700 per car annually. On the
other side of the ledger is only the increased
expense of platform operation for four or five
hours daily, which would not amount to
more than $300 or $400 per car annually.
There are, of course, other objections; first,
many operators say that the public will not
stand for the return to single-track cars, with
their bumping and swaying. To this the car
designer replies that, by the use of a radial
track, wheel bases can be lengthened to a
point where the riding qualities of the single-
track approximate those of the double-truck.
He will also refer to the English coaches, with
the pedestals and journal boxes mounted
beneath long elliptic springs, giving a cushion
effect equal to that of the automobile. Cross
seats can of course be as easily provided as in
any larger car. With these improvements,
the objection of discomfort to passengers is
removed.
The objection is also made that additional
units on the street during the evening rash
hours mean excessive congestion, slow move-
ment and more accidents. In many cities
this would be a severe handicap. Where
rash hour headways are four, five or six
minutes, and only single cars used, it would
not be burdensome. Where they are less,
and particularly where two-car trains are
already required, it would involve the use of
multiple unit control, and the operation of
three- or four-car trains, to prevent an
excessive number of units upon the street.
In smaller cities, two-car trains, using plat-
form control and jumpers, would not involve
excessive complications, and might provide
an increased seating capacity without shorten-
ing of headways.
,;i,s
GENERAL ELECTRIC REVIEW
But where rush hour congestion is really
severe, and train operation not desired, a car
of large seating capacity is essential. The
52-passenger car mentioned previously, run
singly, will give a distinct saving during the
periods of maximum travel, both in power and
in platform wage, over ordinary equipments,
and a reduction in platform cost over the
small car which will offset its greater power
cost unless power rates are unusually high.
i.e. to determine which will leave the net
revenues in the best condition, based on all
costs of operation under typical conditions,
becomes in order.
In the tabulated data herewith appended
a comparison is made between the assumed
costs and revenues on two lines, one in
Texas, and one in Alabama. In both cities,
the performance of the standard type of
equipment is contrasted with that of the
TABLE I
LARGE RAILWAY, LIGHT & POWER COMPANY IN ALABAMA
Typical Line — Distance 8.78 miles round trip.
A — Present cars — 56,000 lb., seat 48; pull trailers 33,000 lb., seating 60.
B — Suggested cars — 30,000 lb., seat 52.
C — Suggested cars — 12,000 lb., seat 32.
Headway 14 hours
Headway 4 hours
Running time 14 hours. .
Running time 4 hours. . .
Cars required 14 hours. .
Cars required 4 hours. . .
Seats per hour 14 hours.
Seats per hour 4 hours. .
Car miles per day
6
54
60
10-
1
1
nuns.
mins.
mms.
mins.
6
-2-car
320
080
520
Operating Costs per Day
Platform wages
Maintenance and depreciation . . .
Power
Other transportation and general.
Transportation revenue. . . .
: cars
Annual saving
Increase would pay on this .
$72.00
53.00
33.75
74.50
9 mins.
6 mins.
54 mins.
60 mins.
6
10-2-car
347
1040
1520
$72.00
45.60
20.90
74.50
9 mins.
6 mins.
54 mins.
60 mins.
6
10-3-car
214
960
1870
$82.00
46.75
11.60
74.50
$233.55
350.00
116.45
$90,000.00
$213.00
350.00
137.00
$100,000.00
7. .".00.00
7.5 per cent
$214.85
350.00
135.15
$78,000.00
6,825.00
8.7 per cent
Above figures are based on present operating costs and revenues with power and maintenance reductions
as indicated in "Discussion of Data" sheet.
One-man car operation, also, would have
a much better chance of success in the smaller
towns and cities than in larger places, and the
smaller the car the easier it would be to use but
one man.
All these things mean that local causes
would govern the selection of the particular
size of car that would have to be purchased,
and that some operators would prefer the large
capacity car and others the small car, regard-
less of their theoretical efficiency or relative
cost of operation. A comparison, however,
made from a purely economical viewpoint.
suggested light weight cars. In the first, a
sxnall number of cars purchased in the past
three years are somewhat lighter in weight
than the ones used in the present calcula-
tions, but the latter represents the greater
part of the existing equipment. In both
places, the majority of all cars are of the size
and weight shown.
On the Texas road, power costs are fairly
normal and rush hour congestion is not so
excessive as to require the use of trains, nor of
trailers during rush hours. Medium sized cars
of fairlv light weight have handled traffic
THE JITNEY PROBLEM
609
satisfactorily. The greatest handicap here
has been a very high number of stops per
mile, combined with slippery rail conditions
during a great part of the year, which has
resulted in extremely slow schedules on many
lines. The frequency of stops in spite of slow
speed has meant unusually high power costs.
The other city has large factory crowds
to handle, and has extreme congestion of
traffic during the rush hours, necessitating
paring what these are now with the two other
types of cars, the assumption in each case
being that an equal number of cars are run
during the lighter hours of the day when the
average load is usually less than 30 in all
cities, and that the same number of seats will
be furnished during rush hours by each type.
Tables II and IVmake the same comparisons
on the basis of improved service, or shorter
headways. All data is based on two-men per
TABLE II
LARGE RAILWAY, LIGHT & POWER COMPANY IN ALABAMA
B
Operating Data on Basis of Improved Service
Headway 14 hours
Headway 4 hours
Running time 14 hours. .
Running time 4 hours. . .
Cars required 14 hours. .
Cars required 4 hours. . .
Seats per hour 14 hours.
Seats per hour 4 hours. .
Car miles per day
6 mins.
4 mins.
48 mins.
56 mins.
8
6-2-car 8-1 car
480
1155
2010
6 mins.
4 mins.
48 mins.
56 mins.
8
6-2-car 8-1-car
520
1115
2010
Daily Operating Costs
6 mins.
3.5 mins.
48 mins.
56 mins.
8
16-2-car
320
1100
2465
Platform wages
Maintenance and depreciation
Power
General
Assume 20 per cent increase in revenue
Net
Increase over present
Annual increase
Cost of new cars
Increase would pay on this.
$90.00
$90.00
$104.00
70.00
60.30
61.75
64.10
27.70
14.95
74.30
74.30
74.30 .
$280.90
$252.30
$255.00
420.00
420.00
420.00
$139.10
$167.70
$165.00
22.65
51.25
48.55
$8,250.00
$18,700.00
$17,700.00
*$120,000.00
$100,000.00
$83,000.00
7 per cent
18.7 per cent
21.2 per cent
* All motor cars of present type.
large capacity two-car trains at present.
The stops, however, are comparatively infre-
quent due to long city blocks, schedule
speeds are high, and power consumption
is relatively low. The cost of power is also
unusually low here. These causes combine
to make the platform wage item much larger
in proportion to the power cost than it is in
most cities.
In both cities, the railroads have been hard
hit by the jitney competition. In both, the
substitution of lighter cars and operation of
shorter headways would seem to offer a
solution of the difficulty.
Tables I and III represent existing service
schedules, headways, costs and receipts, corn-
car except one column in Table IV. This is
inserted merely as an indication of the further
economies made possible by one-man opera-
tion.
In the foregoing figures (Tables I and II),
platform wages are taken at 50 cents per hour
for single cars and at 75 cents per hour for
two-car trains.
Maintenance and depreciation of equipment
and way is taken at 3.5 cents per car mile
with heavy equipment, at 3 cents per mile
with the medium weight cars, and at 2.4 cents
per mile for the small cars.
Power costs are figured at 0.55 cents per
kw-hr., and on a basis of 4.5 kw-hr. per car
mile for the large cars and 3.5 kw-hr. per car
6
GENERAL ELECTRIC REVIEW
mile during trailer operation. The type B
cars are figured at 2.5 kw-hr. per car mile
and the small cars at 1.1 kw-hr. per car mile.
Variations from these figures, due to total
causes, such as low voltage, improper handling
of the equipment, etc., would not change the
relative values.
Miscellaneous traffic expenses and general
expenses are totalled at 4.9 cents per car mile
Platform wages are taken at 50 cents per
hour for single cars in first three columns, and
at 30 cents per hour for the one-man cars;
for the two-car trains, at 75 cents per hour.
Maintenance and depreciation of equip-
ment is figured at 4 cents per car mile at
present, and at 2.7 cents per car mile with the
light weight cars, and at 3.5 cents per car mile
with the class B cars.
TABLE III
ELECTRIC RAILWAY COMPANY IN TEXAS
South End Line —
A — Present cars seat 44, weigh 36,000 lb.
B — Proposed cars seat 52, weigh 30,000 lb.
C — Proposed cars seat 32, weigh 12,000 lb.
distance 5.06 miles round trip.
Schedule time 10 hours daily
Schedule time 4 hours daily .
Schedule time 4 hours daily .
Headway 10 hours daily ....
Headway 4 hours daily
Headway 4 hcurs daily
Cars required 10 hours daily
Cars required 4 hours daily
Cars required 4 hours daily .
Seats per hour 10 hours daily
Seats per hour 4 hours daily
Seats per hour 4 hours daily '
Daily mileage
Total platform wages, daily
Maintenance and depreciation equipment and way
Power
General
Total operating costs, daily ,
Transportation receipts
Net earnings daily
Annual increase in net
Approximate cost new cars
Increase would pay on this
* One-man operation.
on the present mileage. The actual costs of
these two latter items are assumed to be
unchanged by the change in car type or by
increased mileage.
Transportation revenues are estimated at
23 cents per car mile.
All figures except platform wages and
power consumption are based on the average
cost of operation for this property in 1914,
and the power rate is also taken from their
cost sheets. Both wages and power consump-
tion agree closely with the actual averages
for all their equipment.
The figures used in Tables III and IV are
based on the following assumptions :
A
B
C
C*
36 mins.
36 mins.
30 mins.
36 mins.
40 mins.
40 mins.
32 mins.
40 mins.
40 mins.
42 mins.
35 mins.
40 mins.
12 mins.
12 mins.
10 mins.
12 mins.
8 mins.
8 mins.
8 mins.
8 mins.
5 mins.
6 mins.
o irons.
o mins.
3
3
3
3
5
o
4
o
8
-
3-2-car
3-2-car
4-1-car
o-l-car
220
260
192
160
230
390
240
240
528
520
nS4
528
641
606
800
740
$41.00
$39.00
$40.00
$28.20
2J.64
21.20
21.60
19.95
19.23
15.20
8.80
8.25
30.50
30.50
30.50
30.50
$116.37
$105.90
$100.90
$86.90
154.00
154.00
154.00
154.00
37.63
48.10
53.10
67.10
$3,800.00
$5,700.00
$11,000.00
35,000.00
26,000.00
28,600.00
11 per cent
22 per cent
38 per cent
Power costs are figured at 1 cent per kw-hr.
and on a basis of 3 kw-hr. per car mile for the
type A cars, 2.5 kw-hr. for the type B cars,
and at 1.1 kw-hr. for the type C cars. Varia-
tions from these figures for local causes, such
as low voltage, improper handling of the
equipment, etc., would not change the relative
values.
Miscellaneous traffic expenses and general
expenses are taken together at 4.75 cents per
car mile on the basis of the present mileage,
and the actual costs of these two items are
assumed to be unchanged by the use of a
different car type, or by increases in mile-
age.
THE JITNEY PROBLEM
611
Transportation revenues are estimated at
24 cents per car mile on the present mileage.
All figures, except platform wages and
power costs, are based on the average operat-
ing statistics for Southern Railways contained
in the United States census report of 1912,
and both platform and power costs as figured
above agree closely with the averages of the
census report.
DISCUSSION OF DATA
In the preceding data, slight variations in
the actual hourly wage of motorman or
conductors would not change the relative
values of platform expenses, nor would the
result be changed if somewhat different
values are assumed for general expense and
miscellaneous traffic costs. The two latter
items are inherently stable; and would not be
increased in any way that is apparent to the
writer by a change in the type of equipment,
nor by a moderate increase in the number of
cars in service.
The two items which might reasonably be
questioned are the maintenance and power
' charges. Assuming that maintenance and
depreciation are now 4 cents per car mile
(which is the average for Southern roads),
we find from Mr. Doolittle's article in the
March issue of the Aera that the items which
go to make it up are as follows: an average
being taken of the East South Central and
West South Central data.
Cents
A — Way structures, superintendence . . . 0.095
B — Maintenance of way 1.315
C — Maintenance of way, electric lines. . 0.330
D — Buildings and structure 0.08
E — Depreciation of way and structures. ! 0.15
F — Other operations i 0.11
G — Equipment superintendence j 0.085
H — Maintenance of power equipment . . I 0.21
I — Maintenance of cars and locomotives 0.84
J — Maintenance of electrical equipment
of cars ' 0.42
K — Miscellaneous equipment expense .'. ! 0.115
L — Depreciation of equipment 0.19
M — Other operations 0.115
Total ' 4.055
Of the above, items A, D, F, G, K and M
would probably not be affected, insofar as
total expenditures are concerned, but if the
mileage made is increased, the cost per car
mile for these items would be proportionally
TABLE IV
ELECTRIC RAILWAY COMPANY IN TEXAS
Improved Service, Shorter Headways
Schedule time 10 hours daily 32 mins.
Schedule time 4 hours daily 35 mins.
Schedule time 4 hours daily 36 mins.
Headway 10 hours daily 8 mins.
Headway 4 hours daily 5 mins.
Headway 4 hours daily 4 mins.
Cars required 10 hours daily 4
Cars required 4 hours daily 7
Cars required 4 hours daily 9
Seats per hour 10 hours daily 330
Seats per hour 4 hours daily 528
Seats per hour 4 hours daily 660
Dailv mileage » 920
Platform wages $52.00
Maintenance and depreciation equipment and way. . 36.80
Power 27.60
General 30.50
Total operating cost daily $146.90
Assumed 20 per cent increase in revenues 184.80
Net $37.90
Increase over present .27
Annual increase 98. oil
Cost of new cars $4,500.00
Increase would pay on this 2 per cent
* One-man operation.
B
c
C*
32 mins.
30 mins.
32 mins.
35 mins.
35 mins.
35 mins.
40 mins.
35 mins.
40 mins.
8 mins.
7.5 mins.
8 mins.
5 mins.
5 mins.
o mins.
5 mins.
3.5 mins.
4 mins.
4
4
4
7
7
7
8
2-2-car
3-2-car
8-1-car
7-1-car
390
256
240
624
364
364
(124
656
624
860
1067
1020
$50.00
$56.00
$36.00
30.10
28.81
27.54
21.50
11.74
11.22
30.50
30.50
$127.05
30.50
$132.10
$105.26
184.80
184.80
184.80
$52.70
$57.75
$79.54
15.07
20.12
41.91
5,500.00
7,300.00
15,300.00
$40,000.00
$31,200.00
$33,800.00
14 per cent
23.4 per cent
46.6 per cent
612
GENERAL ELECTRIC REVIEW
decreased. The average weight on the road
with the small cars would be about one-third
of what it is at present, and the actual effect
on damage to special work, and to the sub-
structure and paving should be reduced
proportionally. * Rail wear too would be about
proportional to the weights; but on the other
hand wear and tear due to other traffic and to
the elements would not be changed. It seems
reasonable therefore to place the figure for
light cars at one-half of the present value, or
0.(56 cents.
The maintenance of electric lines would also
drop as a result of reduced currents at the
trolley wheel. This reduction is estimated at
20 per cent, giving a revised figure of 0.264
cents.
Depreciation of way and structures might
decrease one-third, and becomes 0.10 cents.
Maintenance of power equipment, due to
the greatly decreased load should decrease at
least one-third and becomes 0.14 cents.
Car maintenance, due to reduced brakeshoe
and wheel wear, and the more modern design
of the parts, should be at least 20 per cent less
per car mile, or 0.67 cents.
Electric equipment maintenance, due to the
more modern design of the equipment should
average not over 0.05 cents. This is based on
actual records, on many roads, of motors and
controllers put out during the past four or five
years.
Depreciation of equipment should be some-
what less, due to improved design and better
materials, say 0.15 cents.
In this connection, should the present cars
be replaced outright by new cars, depreciation
charges would of course increase, as the value
of the new equipment would have to be added
to that of the outstanding value of the old,
and a rate set which would wipe out both
values within a reasonable period. But if the
old cars were retained in service, and used as
spares and for rush hour and holiday traffic,
they would still be carried in the capital
account. This of course would be the logical
method, and under these circumstances the
greater earning capacity of the new cars in
proportion to the capital investment should
mean a lower proportion of the gross receipts
would have to be set aside for depreciation.
The new total, on these assumptions,
becomes 2.63 cents, 60 per cent of the present
cost. To be conservative, however, the figure
of 2.7 cents has been assumed, a decrease of
one-third.
For the type B cars, a figure of 3.5 cents was
arrived at by a similar method of estimating.
The biggest item of economy is, of course,
in power. Consumptions per car mile are
calculated values, and probably agree fairly
closely with what is actually taken at present,
and the decrease in total power consumption
would unquestionably be at the ratios shown.
But many operators will not agree that the
cost per kilowatt-hour should remain the
same under the reduced output as under the
heavy load. In the case of a company which
sells lighting and commercial power there
should be no question of this. The reduced
railway load simply releases so man}' kilowatts
which can be sold at a profit elsewhere.
In the case of the railway companies that
purchase their power, any reduction in their
peak load should mean a decrease in rate
as well as paying for less kilowatt-hours, and
the combined value of these economies should
offset the increased cost per kilowatt-hour
of their overhead charges for distribution.
It is the operator, however, who neither
bins nor sells power who, often, can see no
benefit to himself in power reduction, save in
a slightly reduced fuel bill. If the reduction
is only a very small percentage of the total
output, this is ostensibly correct, provided
neither his machines nor lines are overloaded.
There would be no immediate reduction in
either his overhead or labor costs, and the
reduction in fuel and maintenance costs might
be negligible. But where the reduction in
load amounts to as great a proportion of the
total cost as in this instance, or approximately
two-thirds, it should be possible to shut
down some units, reduce the number of
firemen, and make a general reduction in all
the costs of operation of the power plant.
There would be a distinct reduction in the
line losses, which in many instances would act
to postpone the installation of additional
copper in the distributing system. If these
indirect economies did not manifest them-
selves immediately, they could unquestion-
ably be secured in the long run, by enabling
additional service to be supplied without
• increase in station or line capacity.
The actual cost of power at the station is of
course an important factor in this analysis.
On the Alabama property it is unusually low.
In fact, only a few of the largest railway
systems in this country can purchase or
produce power for approximately one-half
cent per kilowatt-hour; and this of course does
not include interest on their plant or on their
distribution system. These are of course part
of the real cost, but are carried in the fixed
charges and not under the operation. The
THE JITNEY PROBLEM
613
effect of this low rate, however, combined
with schedules which require a comparatively
low consumption of power, makes the cost of
power a relatively small item on this system,
and the extreme rush hour conditions makes
the platform account a greater percentage of
the total expense than on most roads.
These two reasons, combined, make a car
of large seating capacity of more importance
to them than one of low power consumption,
and the medium-weight car (type B) is
unquestionably the most efficient.
On the other hand, under normal rates for
power, which have been assumed for Texas,
and with schedules which require an unusually
high consumption per ton-mile, power charges
assume a greater importance. Since there is
moreover, here, a more even distribution of
traffic throughout the day and less pronounced
rush hour peaks, platform wages, while still
the largest item, are not so great a part of the
total as in some other places. Under these cir-
cumstances, the small car, even with two-man
operation, appears the more efficient ; and with
one-man operation the saving would amount
to a large sum.
Of the economies of one-man car operation
there can be no question. Of the advisability
of attempting to operate cars in this manner in
any save the smaller cities, there are grave
differences of opinion. It seems logical that
their use under any heavy condition of traffic
would materially slow down schedules. The
use of one-man cars is prohibited by law in
many communities. If the education of the
public in the prepayment of fares and the
use of transfer and change making machines
obviates the need of a conductor, and the car
can be operated as satisfactorily without one,
it is obvious that laws will have to be changed
to permit of such operation. Such permission
would probably be far more easily obtained
than an increase in fares. Whether one or two
men per car be employed, however, is purely
an operating matter; the only way on which
it enters into the present paper is that the
smaller the car the less the difficulty of single-
end one-man operation.
Upon the assumption, though, that in the
majority of cities no immediate change in
this respect is possible, the other apparent
advantages of the smaller cars are so evident
that, whether as a means of meeting and
fighting other forms of transportation, or
simply as a method of securing greater
economy under normal operation, it seems
perfectly logical to assert that their use will
prove decidedly advantageous to the great
many urban railways, and that many others
could secure greater efficiency by the use of
lighter equipment than they are using.
Certain assumptions have been made as to
the effect on transportation revenues of
cutting down headways and providing faster
schedules. In the case of cities where maxi-
mum traction trucks are largely used, both
accelerating and braking rates on poor rails
are necessarily low as compared to single-
truck or to four-motor equipments, and this
usually results in slower average schedule
speeds than could otherwise be secured, since
the schedules have to be laid out with the
most adverse conditions in mind. This
probably accounts in part for the slow schedule
speeds in Table III. Bad rail conditions, due
to greasy or muddy tracks, are common here
during many months of the year, and rates
of acceleration and braking are slower than
is usual even with maximum traction equip-
ments. The advantage of the single-truck
car in respect to rail adhesion, together with
the fact that the use of more cars will decrease
the average load per car per trip, and there-
fore there will be fewer stops made per trip,
make it certain the running time at all hours
of the day could be materially shortened.
This in itself would prove popular, as
passengers object strongly to slow schedules,
and especially to the loafing which motormen
so often resort to on the lighter trips of the
day when with a good rail and few stops they
get ahead of schedule. But the most potent
factor in promoting the riding habit, and in
securing business which is otherwise lost, is
a short headway and the running of cars
absolutely on time. It is no exaggeration to
say that a man who lives not more than two
miles from his business will very frequently
walk sooner than wait ten minutes for a car,
and that the average person who has a mile to
go will walk sooner than wait above five
minutes. The greater number of riders per
capita in the largest cities as compared with
smaller communities is due in part to the
longer distances between the business and
residential sections, but is also very largely
brought about by the greater frequency of
service in the former places.
If headways of from 6 to 12 minutes were
cut one-third, and a faster schedule at the
same time offered, it appears reasonably
certain that the number of passengers would
increase at least 20 per cent. The increased
receipts shown in Tables II and IV are based
on this assumption. Intermediate cuts in head-
way should produce increases in receipts of
614
GENERAL ELECTRIC REVIEW
from 10 to 15 per cent. These figures are, of
course, mere guesses, but are the estimates of
a considerable number of men, and based
largely on their own experience; in other
words, is an estimate of the number of rides
they take weekly on street cars as compared
with the number of times they walk in pref-
erence to waiting. Jitneys, of course, catch
numbers of such passengers; so do private car
owners who see friends walking and pick
them up.
In short, to furnish improved service will
bring in an increased amount of business, and
will at the same time reduce public criticism
and hostility, which is the most serious
handicap with which most public service
corporations have to contend. If it can be
done without a prohibitive increase in the
costs of operation, it will prove a mutual
benefit to the public and operators, and
should be the means of placing the electric
railways on a firmer financial footing.
THE PERIODIC LAW
By Dr. Saul Dushman
Research Laboratory, General Electric Company
For a number of years chemists have been familiar with the Periodic Table of the Elements as arranged by
Mendelejeff. With the discovery of the numerous radioactive elements there arose the problem as to their place
in this Periodic Table — a problem which has been solved only quite recently. In the present paper the writer
discusses the revised arrangement of the elements which is based upon the results of the most recent investiga-
tions.— Editor.
Historical Introduction*
Ever since the establishment of the atomic
theory by Dalton and Berzelius it was felt
among chemists that there must be some
relation between the atomic weights of the
different elements and their properties. It
was recognized very early that there exist
groups of elements possessing related chemical
and physical properties, and one of the earliest
attempts to bring out this point is due to
Dobereiner. In 1S29 he tried to show that
"many elements may be arranged in groups
of three, in each of which the middle element
has an atomic weight equal, or approximately
equal to the mean of the atomic weights of
the two extremes." As illustrations of this
method of arrangement may be mentioned,
the following groups: Li. Xa, K; Ca, Sr,
Ba; and CI, Br, I.
Passing over briefly the memoirs of Cooke
and Beguyer de Chancourtois, we come to
the "law of octaves" enunciated by J. A. R.
Xewlands in 1864. He drew attention to the
fact that "the eighth element, starting from
a given one. is a kind of repetition of the first,
like the eighth note of an octave in music,"
and thus made the most distinct advance
towards a system of classification of the
elements that had yet been accomplished.
It is. however, to the Russian chemist,
Mendelejeff, that chemistry owes the system
* This section is to a large extent based on Chapter XIII
(The Periodic Law) in P. Muir's "History of Chemical Theories
and L;-
of classification of the elements which is
based on the recognition of this fundamental
fact: "that the properties of the elements and
the properties and compositions of compounds
vary periodically with the atomic weights, of the
elements."
This principle, known as the Periodic Law,
was enunciated by Mendelejeff in two me-
moirs published in 1869 and 1871 respectively,
and the arrangement of the elements, based
on this law, which was finally adopted by
him is illustrated in Fig. 1.
While a discussion of this law may be found
in almost any text-book on chemistry, a few
remarks of a general nature may not be out
of place in this connection. #
Mendelejeff arranges the elements into
series and groups. In each series the order
of the elements corresponds to increasing
atomic weights, and accompanying this
change in atomic weight there is evident a
gradual variation in all the properties of both
the elements and their compounds. On the
other hand, the arrangement in groups
exhibits the periodical recurrence of elements
possessing fairly analogous properties.
The change in valency, as exhibited by the
formulas of the oxides and hydrides is
probably one of the most striking facts
brought out by the periodic arrangement of
the elements.
From the univalent elements like H, Li,
Na, etc., the valency for oxygen increases
regularly until in compounds like OsOt, the
THE PERIODIC LAW
615
elements exert a valency of eight. The
maximum valency for hydrogen appears to
be four, and while the valency for oxygen
increases from Group I to Group VIII, that
for hydrogen decreases in the same manner
from Group IV to Group VIII.
The compounds exhibit a gradation in
properties quite similar to that exhibited by
the elements themselves. Thus Na*0 is
strongly basic, MgO less so, Ak03 combines
with acids to form salts and with alkali
hydrates to form aluminates, that is, it acts
as an anhydride of both acids and bases.
In SiOi we have a weak acid anhydride,
while the acids formed from F2O5, SO3 and
CI2O7 range in strength in the same order.
state that the atomic volume is a periodic
function of the atomic weight. The specific
heats of the elements when plotted as ordi-
nates against the atomic weights show a
similar periodicity of maxima and minima,
and the same can be stated for other
properties.
Application of Periodic Law to Determine Atomic
Weights
One of the most important applications of
the Periodic Law suggested by Mendelejeff
was the determination of atomic weights
from the properties of the elements. In
other words, he stated as a fundamental
axiom that the atomic weight of any element
Group I.
Group II.
Group III.
Group IV.
Group V.
Group VI.
Group VII.
Group VIII.
Semis.
nil
BH>
HII
BH
It o
BO
B'O3
RO'
B'O'
EO'
B'O7
BO'
1
H-l
2
Li - 7
Be -9 4
B - 11
C = 12
N = 14
O = 16
F = 19
3
Na - 23
Mg - 24
Al = 273
Si - 28
P - 31
S - 32
CI - 35 5
4
K = 39
Ca ~ 40
— = 44
Ti = 48
V = 51
Cr - 52
Mn - 55
Fe - 56 Co - 59 •
Ni - 59 Cu - 63.
u
(Cu - 63)
Zn - 65
— - 68
— - 72
As = 75
Se = 78
Br - 80
6
Rb - 85
Sr - 87
?Yt - 88
Zr = 90
Nb = 94
Mo - 96
100
Ru - 104 Rh - 104
Pd = 106 Ag - 108
7
(Ag - 108)
Cd - 112
In - 113
Sn - 118
Sb - 122
Te = 125?
I = 127
_____
■
Oa - 133
Ba - 137
?Di - 138
7Ce - 140
-
-
—
9
(-)
—
~-
—
—
—
—
10
—
—
?Er - 178
?L» - 180
Ta - 182
W - 184
-
Os - 195 Ir - 197
Pt - 198 Au = 199
11
(Au - 199)
Hg - 200
Tl - 204
Pb - 207
B: = 208
-
-
12
—
—
—
Th - 231
_
U= 240
—
— — — —
Fig. 1. Periodic Table as Arranged by Mendelejeff
Atomic Volume as a Periodic Function of Atomic
Weight
Probably the best illustration of the
significance of Mendelejeff's Periodic Law
can be conveyed by plotting some property
of the different elements against the atomic-
weight. In Fig. 2, which is taken from
Holleman's Inorganic Chemistry, the atomic
volume (specific gravity divided by atomic
weight) has been plotted as ordinate with the
atomic weights as abscissa?. It will be
observed that elements possessing similar
chemical and physical properties occupy
similar positions on the curve. In mathe-
matics a periodic function is one which returns
to the same value for definite increments of
the independent variable. From Fig. 2 it is
evident that we can in a similar manner
must determine its properties. He illustrated
this conclusion by prophesying in detail the
properties of three unknown elements which
he named eka-boron, eka-aluminum, and
eka-silicon, and to which he assigned the
approximate atomic weights 44, 68, and 72,
respectively. His predictions were subse-
quently completely verified by the discovery
of the elements scandium (eka-boron), gal-
lium (eka-aluminum) and germanium (eka-
silicon).
It must be observed that without the
assistance of the Periodic Law the exact
determination of the atomic weight of an
element, whose compounds are all non-
volatile, becomes a matter of extreme diffi-
culty. Thus a chemical analysis of the oxide
of indium shows that the element has the
616
GENERAL ELECTRIC REVIEW
equivalent weight 38, that is, 3S parts by
weight of indium are equivalent to 1 part by
weight of hydrogen. At the time when
Mendelejeff published his papers the atomic
weight of this element was taken to be 76 and
the formula of the oxide was assumed to be
InO. A study of the properties of this oxide
and of the metal itself, from the standpoint
of the Periodic Law, led Mendelejeff to assign
it to Group III, along with B and Al. Con-
sequently the oxide must have the formula
ln*03 and the atomic weight must be about
114.
Discrepancies in the Periodic Table
It was already observed by Mendelejeff
that a discrepancy exists in the case of
tellurium and iodine. According to order
of atomic weights iodine should come before
tellurium; but even the most superficial
investigation of the properties of these
elements and of their compounds shows that
iodine belongs to the chlorine family, while
tellurium closely resembles sulphur and
selenium. Mendelejeff therefore argued that
the atomic weight of tellurium ought to be
smaller; but in spite of the most careful and
most elaborate investigations undertaken in
this direction, the results have always led
to the same conclusion.
Similar discrepancies have been observed
in the case of cobalt and nickel, and argon and
potassium (see "Rare Earths", page 620). It
will be shown in a subsequent section that
these discrepancies disappear in the light of
the most recent speculations.
Rare Gases in Relation to the Periodic Table
When the existence of the rare gases* was
discovered an interesting question arose as to
their place in the Periodic Table. As is well
known, these gases were found to be abso-
lutely inert chemically, thus differing rad-
ically from every other element known up to
that time. Consequently they could not be
placed in any of the known groups. However,
by arranging them in a group to the left of
Group I (see Fig. 4 ) they are shown as a
natural transition from the elements of Group
VI II to those of Group I.
Rare Earth's in Relation to the Periodic Table
The group of elements known as the "rare
earths" has presented an exceedingly inter-
esting problem as regards their arrangement
in Mendelejeff's system of classification.
* Those who are unfamiliar with the unique properties of the
rare gases will find a note on the subject in the General Elec-
tric Review. March. 1915, p. 226. and May, 1915, p. 40S.
The elements of this group and their com-
pounds resemble each other very closely in
chemical properties; in fact, it is possible to
separate them only because of slight differ-
ences in physical properties, such as solubility,
melting point, or color; so that the process of
isolating a salt of any one of the members of
the group is a most laborious process, involv-
ing probably over several thousand recrystal-
lizations.
Up to the present the existence of the
following elements has been definitely deter-
mined :
ATOMIC
WEIGHT
Scandium Group
Scandium
44.1
Yttrium
88.7
Cerite Earths:
Lanthanum
139.0
Cerium
140.2.3
Praeseodymium
140.6
Neodymium
144.:;
Samarium
150.4
Europium
1.52.0
Ylterbium Earths:
Gadolinium
157.3
Terbium
159.2
Dysprosium
162.5
Erbium
167.4
Thulium
168.5
Ytterbium
172.0
Lutecium
174.0
With respect to the first four of the above
elements, there has been no doubt as to what
place they ought to occupy in the Periodic
Table. When scandium was first isolated in
1879 it was recognized immediately as the
element eka-boron whose properties had been
prophesied by Mendelejeff. The position of
yttrium and lanthanum in Group III as
analogous elements to aluminum and scan-
dium has also not been questioned. As cerium
forms an oxide CeOz similar to SnOz and its
salts resemble those of tin and germanium, it
seems equally well established that this
element belongs to Group IV.
But up to the present time it has remained
quite an open question as to the manner in
which the other twelve elements should be
arranged. Prof. Meyer has suggested that
they should be grouped together in Group
III between lanthanum and cerium, thus
emphasizing the resemblance in chemical
properties of the different elements con-
stituting this group. This would, however,
place lutetium. with an atomic weight of
174. before cerium whose atomic weight is
14(1.
In view of the more recent work of Moseley
on the high-frequency spectra of the elements,
of which furhter mention will be made, the
THE PERIODIC LAW
617
O
1
B
u
£
u
W
writer has tentatively arranged
the rare earths as indicated in
Fig. 4. They are thus made to
come in below lanthanum and
cerium and before tantalum.
Radioactive Elements
The discovery of the radio-
active elements has naturally
led to the question as to what
relationship they bear to the
other elements in the Periodic
Table. There could be no doubt
about the position of elements
like radium, thorium, and uran-
ium which could be obtained in
large enough quantities to deter-
mine their atomic weights and
chemical properties, but up to
the past year there was a great
deal of speculation about the
manner in which the other
radioactive elements should be
arranged, and it was only after
an immense amount of careful
investigation and ingenuous de-
duction on the part of brilliant
physical chemists like Soddy and
Fajans that the whole situation
was cleared up, and another
epoch-making chapter added to
the history of the Periodic Law.
It is largely with the conclusion
reached by these investigators
that the present paper is spe-
cially concerned.
As is well known, the radioac-
tive elements are characterized
by a greater or less instability.
After a certain average period of
existence, which may range from
over a thousand million years,
as in the case of uranium (Ui),
to a millionth of a second, as in
the case of RaCi, the atom
disintegrates spontaneously and
yields an atom which possesses
totally distinct properties. The
disintegration is detected by the
expulsion either of alpha* or of
betaf particles. Accompanying
the expulsion of beta particles
there is also observed in a
* The alpha ( a) particle has the same mass
as the atom of helium but differs from the
latter in possessing two unit positive charges
2 « =9.54X10-'" e.s.u.).
f The beta (&) particles correspond in
mass and electric charge to the electrons
(unit of negative electricity, i =4.77X10-10
e.s.u.).
618
GENERAL ELECTRIC REVIEW
number of cases, an emission of
gamma rays. These are electro-
magnetic pulses of extremely short
wave length (about 10-9 cm.) and are
probably due to the bombardment of
the atoms of the radioactive sub-
stance itself by the beta particles.
As a result of the large amount of
careful work which has been carried
out during the past few years in
investigating the relationship between
the different radioactive elements
and their transformation products it
has been concluded that there exist
three well defined disintegration series
whose starting points are uranium,
thorium, and actinium, respectively.
Fig. 3 illustrates diagrammatically
the manner in which the members of
these series appear to be related.
When mesothorium II disinte-
grates it yields radiothorium and as a
beta particle is expelled during the
transformation there is no change in
atomic weight. Radiothorium is
chemically allied to thorium and
non-separable from it. These facts
lead to the conclusion that radio-
thorium belongs to Group IV and
mesothorium II must therefore belong
to Group III.
Passing to thorium X, we here again
come to an element which is chemi-
cally similar to radium, thus placing
it in Group II. The atom of thorium
X expels an alpha particle and yields
thorium emanation, a gas which is
inert chemically, and condenses at low
pressures between — 120 deg. C.
and —150 deg. C. The emana-
tion resembles therefore the rare
gases of the argon group.
Thorium emanation is the first
member of the group of trans-
formation products that con-
stitute the thorium "active deposit."
They are indicated in Fig. 3 as
thorium .4, B, C\, C2 and D.
The diagrams illustrating the
actinium and uranium series are self-
explanatory. In a general way the
three series are quite similar. The
most noteworthy feature about these
radioactive elements is the fact that
individual members of each series
appear to be chemically indistinguish-
able from certain members of the
other series. Thus thorium B and
URANIUM SERIES
(238Z\ Uranium I
\ai)J (PI)
(?2A2\ Uranium X,
/f52\ Uranium Zz
/\^0j iv)
Uranium H
\JS2)J (PD
(250T\ Ionium
/\&o)J UP)
THORIUM SERIES
/?J22\ Thorium
a A& im
l
(?j/3
(22B2\ Mesothorium t
\tss)J (n)
fZ2tZ\ Radium
\m) (m
(222Z\ Radium Emanation
We)/ (O)
m8Z\ Radium A
V»)/ (71)
/fl42\ Radium B
\IBZ)J UP)
(2\A2\ Radium C
/WVl"!
10 Z\ Radium C2
iff/)) OH)
/£i4^\ Radium C,
(228.Z\ Mesothorium U
s\i&») (a)
' \
/22&Z\ ffodio -Thorium
m'\&o)J (IV)
■ Y
R2AZ\ Thorium Z
• Y
/Z20-Z\ Thorium Emanation
1 I
(Z\6c\ Thorium A
I
/EI2Z\ Thorium B
y\&r w
Thorium Ct
■ .(V)
"hcrium C2 (2IZZ\ (708 2\ Thorium D
(PI) X&lJ V*iA^ UEl
" \^^/ a
(2082) Lead [Th D2)
\XS2)) (TV)
ACTINIUM SERIES
fc27T\ Actt/niufn
\i69)J {m}
J
f22lT\ fibdto dcitniom
y\S90)J {/V)
I
/223x\ Acttmum X
y'V&aJ { U )
a* N — -^
I
/7I9 ?\ Actinium Emanation
yvee'J 10)
J2^Z2\ Tho,
'.') IT
/£ia2\ Radium D
I
(fiSc\ Radium E
/a0^\ Radium E
iT06Z\ Lead (Radium 6)
Kxei)) UV)
2152\ Actinium A
W)J (PI)
(Z\\i\ Actinium B
I
©Actinium C
(7)
I
m3Vi\ Actinium D
(fifth lead
Fig 3. Method of Disintegration of Radioactive Elements
iff*
MENDELEJEFF'S PERIODIC SYSTEM OF THE ELEMENTS
Containing Atomic Weights, Atomic Numbers and Isotopic Radioactive Elements
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THE PERIODIC LAW
619
radium B possess identical chemical prop-
erties. If it were not for the difference
in period of existence of both substances it
would be impossible to differentiate them.
Isotopes
Soddy first drew attention to this and
similar cases of radioactive elements that are
chemically identical and since they must
occupy the same place in the Periodic Table
he has designated them isotopes. Thus the
elements uranium X\, ionium, and radio-
actinium are isotopic. A similar example is
furnished by the three emanations, and by
radium and thorium A'. A remarkable
feature about these isotopes is that although
they are chemically the same, they differ in
atomic weights. In other words, we have
here cases of elements that are absolutely
inseparable by all chemical methods so far
devised, and yet differ in that respect which
has hitherto been taken to be the most
important characteristic of an element — its
atomic weight.
Soddy's Law of Sequence of Changes
A comprehensive survey of the chemical
properties of the different radioactive ele-
ments has led Soddy and Fajans independ-
ently to an interesting and extremely impor-
tant generalization which enables them to
assign these isotopes to their places in the
Periodic Table.
It will be remembered that an alpha
particle is a helium atom with two positive
charges. By its expulsion, therefore, the atom
must lose two positive charges, and the atomic
weight must decrease by four units. Simi-
larly, the expulsion of a beta particle means
the loss of a negative charge or, what is
equivalent, the gain of one positive charge;
and since the. mass of the beta particle is
extremely small compared with that of the
atom, there is practically no decrease in
atomic weight. Now in the Periodic Table
the valency for oxygen, an electro-negative
element, increases regularly as we pass from
Group 0 to Group VIII, while that for
hydrogen, an electro-positive element, de-
creases, i.e., the electro-positive characteristic
increases by one unit for each change in the
group number as we pass in any series from
left to right. Furthermore, in each group
the electro-positive character increases regu-
larly with increasing atomic weight.
These considerations led Soddy and Fajans
to this conclusion:
The expulsion of an alpha particle from
any radio-active element leads to an element
which is two places lower in the Periodic Table
(and has an atomic weight which is four
units less) while the emission of a beta particle
leads to an element which is one place higher up,
but has the same atomic weight.
It is possible, therefore, to have elements
of the same atomic weight but possessing
distinctly different chemical properties, and,
on the other hand, since the effect of the
emission of one alpha particle may be neutral-
ized by the subsequent emission of two beta
particles, it is possible to have two elements
which differ in atomic weight by four units
(or some multiple of four) and yet exhibit
chemically similar properties.
As an illustration, let us consider the
Uranium Series. Uranium I belongs to
Group VI. By the expulsion of an alpha
particle we obtain uranium Xi, an element
of Group IV. This atom in turn disintegrates
with the expulsion of a beta particle. Conse-
quently uranium A'2 must belong to Group V.
In this manner we can follow the individual
changes that lead to the different members
of the series, and by means of the generaliza-
tion of Soddy and Fajans we can not only
assign to each element its place in the Periodic
Table but also its atomic weight, as has been
done in Fig. 3.
This generalization has been of material
assistance in elucidating some of the difficult
problems in the study of the disintegration
series. More than this, it has led to the
intensely interesting conclusion that the end
product of each of the three radio-active
series in an isotope of lead. The results of the
most recent work on the atomic weight of
lead are in splendid accord with this deduc-
tion, as it has been found that lead, which
is of radio-active origin, has a slightly lower
atomic weight than ordinary lead.*
In a couple of cases the isotope has not
been definitely isolated, but there can hardly
be any doubt of its existence. Thus, the
disintegration product of radium Ci must be
an element of Group IV, but the evidence
for its existence is very meager.
Nuclear Theory of Structure of the Atom
All these conclusions are in accord with an
interesting theory of atomic structure that
was first put forward by Rutherford and
elaborated by Bohr, Moseley and Darwin.
As this theory has been discussed at great
Length in connection with another series of
* J. Am. Chem. Soc. 36. 1329. 19U.
620
GENERAL ELECTRIC REVIEW
articles* we shall limit ourselves here to a
few remarks on its essential points.
Stated briefly, this theory assumes the
atom to consist of a positively charged nucleus
surrounded by a system of electrons which
are kept together by attractive forces from
the nucleus. "This nucleus is assumed to be
the seat of the essential part of the mass of
the atom, and to have linear dimensions
exceedingly small compared with the linear
dimensions of the whole atom."
According to Bohr, the experimental evi-
dence supports the hypothesis that the
nuclear charge of any element corresponds to
the position of that element in the series of
increasing atomic weights. The chemical
properties of the atom depend upon the mag-
nitude of this nuclear charge; since, however,
any given number of electrons may assume
different configurations it is possible for two
or more elements to exist having the same
nuclear charge, but possessing different atomic
weights. In other words, the possible exist-
en.ee of isotopes is deduced from Rutherford
and Bohr's assumptions.
The atomic weight thus assumes the role
of a secondary characteristic; the important
property of any element is its nuclear charge,
so that by arranging the elements in order
of increasing nuclear charge we ought to
obtain a much better approximation to a
periodic arrangement of the elements. It so
happens that in most cases the order of
increasing atomic weight coincides with that
of increasing atomic number ( nuclear charge ) .
but this need not be so in all cases.
High Frequency Spectra of the Elements
Bohr showed that there must exist a
definite relation between the charge on the
nucleus and the frequency of the character-
istic X-rays emitted by the substance.
Moseley, therefore, has measured the wave-
lengths of the characteristic X-rays emitted
by the different elements when these were
made anti-cathodes in an X-ray tube and
has determined, in this manner, the atomic
numbers of all the elements from aluminum.
13, to gold, 79. There appear to be only three
elements in this range which have not been
discovered by the chemist.
Periodic Table in Present Form
The revised form of Mendelejeffs Periodic
Table which has been drawn up in Fig. 4
presents an attempt to embody the most
recent results of the different lines of investi-
* General Electric Review. December, 1914.
gation that have been discussed herein.
Under each element is given the atomic
weight and the atomic number (in brackets).
A few remarks about different elements in
this table are, however, essential in this
connection.
Neon and Meta-Neon. Nebulium
Evidence for the existence of two isotopes
of neon has recently been deduced by Prof.
J. J. Thomson and Aston. By careful
diffusion experiments the latter was able to
separate from neon another gas of atomic
weight 22, which has been named meta-neon.
The two gases differ only in their gravita-
tional properties, but are chemically and
spectroscopically identical.
During the past year spectroscopic evidence
has been adduced for the existence of a new
element nebulium, having an atomic weight
of about 3. This element occurs in the
spectrum of the nebula of Orion. It is.
however, probably too premature to try to
-speculate about its place in the Periodic
Table. There are a number of elements like
nebulium for the existence of which we have
only spectroscopic evidence and it may be, as
has been suggested recently, that these are
the proto-elements out of which our terres-
trial elements have been built up.
Rare Earths
The case of the rare earths has already been
discussed in a previous section. The arrange-
ment shown in Fig. 4 is in accordance with
the atomic numbers determined by Moseley
in the case of the following elements: Lan-
thanum, cerium, praseodymium, neodymium.
samarium, europium, gadolinium and hol-
mium. The order of atomic numbers in the
case of dysprosium and holmium is apparently
the reverse of that of the atomic weights.
But this case, as well as those of tellurium,
iodine; cobalt, nickel; and argon, potassium,
no longer appears anomalous when the
elements are arranged in order of increasing
atomic number rather than that of increasing
atomic weight. The atomic weight of
neoytterbium has been determined during
the past year; it is, however, impossible to
state at present what relation it bears to the
other elements of the rare earth group.
Radioactive Elements
The radioactive elements have been ar-
ranged in groups of isotopes and the atomic
numbers are based upon the order of the
different elements in the disintegration series
THE PERIODIC LAW
621
(see Fig. 3), assuming the atomic number of
lead to be N2.
The atomic weight of actinium and its
disintegration products have not been deter-
mined. We have therefore adopted the
value suggested by Fajans which is about
227. All we can say definitely is that the
atomic weight is greater than that of radium
and considerably less than that of thorium.
The atomic weights of uranium and radium
are based on the following considerations:
Firstly, as radium is derived from uranium
by the expulsion of three alpha particles,
the atomic weights must differ by 3X3.99
units. Secondly, according to the most
recent report of the International Committee
on Atomic Weights there seem to be valid
reasons for accepting a value which is very
close to 238. 2 for the atomic weight of
uranium. The value actually obtained bv
Hoenigschmid (Z. Elect. 20, 452, 1914) varied
from 238.09 to 238.18; but the Committee
consider the latter value as being t-he more
accurate. The determinations of the atomic
weight of radium have yielded results varying
from 225.9 to 226.4, and the latter is the value
given in the Table of Atomic Weights issued
by the International Committee for the
present year. However, in view of the above
considerations we have used the value 226.2.
The nomenclature of the radioactive ele-
ments is based on that of Soddy.* At the
time when they were isolated, there was of
course no definite knowledge as to their
relationships and the result has therefore
been rather confusing. Thus the name
polonium has been applied to RaF, while
l'.\« is also known as brevium. The designa-
tion "niton" for radium emanation has
* The Chemistry of the Radio-Elements.
become quite well known. It has, however,
been considered advisable to use those names
which best convey the relationships of the
different elements, and an attempt has been
made to carry out this plan in tabulating the
isotopes.
Conclusions
Considering the relationships exhibited by
the different radioactive elements, one realizes
that the dream of the alchemists may not
have been as fatuous as has appeared until
recently. The concept of an absolutely
stable atom must be discarded once for all,
and its place is taken by this miniature solar
system, as it were, consisting of a central
nucleus and one or more rings of electrons.
But the nucleus itself is apparently the seat
of immense forces, and in spite of its exceed-
ingly infinitesimal dimensions it contains
both alpha particles and electrons. Once in a
while the nucleus of one of the atoms will
spontaneously disintegrate and expel an alpha
or beta particle. A new element has been
born What causes these transformations?
Can they be controlled ? These are questions
which only the future can answer. But if we
had it in our power to remove two alpha
particles from the atom of bismuth or any of
its isotopes, not only would the dream of the
alchemists be realized, but man would be in
possession of such intensely powerful sources
of energy that all our coal mines, water-
powers, and explosives would become insig-
nificant by comparison.
REFERENCES
1. Pattison Muir — History of Chemical Theories and Laws.
2. F. Soddy. — The Chemistry of the Radio-Elements,
Parts I and II.
3. K. Fajans. — Naturwissenschaften. vol. II, 429. 462
(1914).
622 GENERAL ELECTRIC REVIEW
TEST FOR DIRT IN AN AIR SUPPLY
By Sanford A. Moss
Tirbine Department, Lynn, General Electric Company
The dirt carried in suspension in a current of seemingly clean air will amount to a startling quantity if it is
collected for a period of time. While many objects inadvertently act as "dust collectors," electrical engineers
are primarily interested in preventing electrical machines, cooled by forced draft, from functioning in
this manner. Very satisfactory air cleaners have been devised, hut the old elaborate methods of testing the
amount of dirt in the air supply are both expensive and liable to give inaccurate results. A new method of
test, which possesses merits superior to its predecessors, is the subject of description in this article. (In our
next issue we hope to publish an article dealing very completely with air cleaning apparatus.) — Editor.
Introduction
A simple and comparatively accurate
method for determining the amount of dirt
in an air stream employs a coarse wire screen
which supports a thin film of absorbent cotton.
Fig. 1. A Sample of an Unexposed Screen
Fig. 2. A Screen Exposed for One Week in the Air to a Turbine
Generator Without Air Washer
Fig. 3. A Screen Exposed in Winter for 23 M Hours in the Air
to an Air Washer
Fig. 4. A Screen Exposed for 131 ] 2 Hours in the Washed Air
from a Defective Washer
Fig. 5. A Screen Exposed in Summer for 48 Hours in Washed
Air
Fig. 6. A Screen Exposed in Summer for 48 Hours in the Air
to an Air Washer
This filter screen is located in the air stream.
The method has been used for determining
the amount of dirt that is removed by an air
washer through which the air passes to a
turbine-generator. Cotton screens were ex-
posed in the cleaned and uncleaned air for
such periods that each collected about the
same amount of dirt. The relative length of
the periods gave a good indication of the
cleaning power of the air washer.
Dirt in Air
The air supplied to a turbine-generator or
to a public room contains what is really an
enormous amount of dirt. The turbine-gen-
erator alluded to later in this article draws in
about 15,000 cu. ft. of air per minute. If
it is assumed, as seems reasonable, that this
air contains 0.004 grains of dirt per cu. ft.,
there will pass through the generator in
the course of a year one ton of dirt.
A test screen made as will be described
later and put in the air intake of any
ordinary turbine-generator will collect a
very large amount of dirt in a relatively
short time. Such an experiment will
probably convince the user of the tur-
bine-generator that he should adopt some
means for keeping his air supply clean.
Fig. 2 shows a test screen which was
placed in the intake of the turbine-
generator later described, before any
means were used for cleaning the air.
The appearance of this screen, compared
with the appearance of an unexposed
screen, Fig. 1, shows the uncleanly
nature of the air supply. This is
probably an extreme case, but neverthe-
less the experiment mentioned is well
worth trying in any usual case.
Old Method of Testing for Dirt
A certain system of testing for the
amount of dirt contained in the pro-
ducer gas that is supplied to engines
or for dirt in other similar cases has
been used for many years. This same
system is also used for the purposes dis-
cussed herewith. It, however, requires con-
siderable apparatus and careful manipula-
tion, and the accuracy of the final result is
somewhat questionable. In arrangement,
the system consists of a small exhauster
which sucks a sample of air from a point in
the main flow, through a dirt collecting tube,
and then through a small gas meter. A small
intake tube is provided, say about 34 inch in
diameter, which is inserted in the stream.
This tube is sometimes led to a chamber
wherein is placed some dehydrating agent,
such as calcium chloride. Then the sample
TEST FOR DIRT IN AN AIR SUPPLY
G23
is passed through another chamber fairly
well packed with absorbent cotton. This
latter chamber usually consists of glass and
is so arranged that it can be readily dis-
connected from the remainder of the appara-
tus. Then the sample is led through a gas
meter.
The tube containing absorbent cotton is
very carefully weighed in a chemical balance
before the experiment is begun. The tube is
then connected into the pipe line, and the
exhauster allowed to suck a sample through
the system for an hour or more. The total
quantity of gas or air that has passed is
read from the gas meter. The cotton-filled
collecting tube is then weighed a second time.
Sometimes the tube is dried by heating before
each weighing. The difference in weight gives
the amount of dirt that was collected from the
measured amount of gas. This system is
open to the following objections:
The apparatus required is expensive. Extra-
ordinary care is required to get accurate
results. It is stated that moisture is very
difficult to eliminate, and it is quite possible to
have moisture on the cotton either before or
after the dirt has been collected. This will
vitiate the weighing of the amount of dirt.
The amount of dirt collected is always very
small when compared to the weight of the
cotton and vessel so that there may be
present the usual errors that develop in
obtaining a small difference between two
large quantities.
The most serious objection is the question
as to whether a fair sample of air can be
collected by sucking it into a small tube. In
the first place, the end of the small tube
usually has a very small area compared with
that of the duct through which the main
flow is passing so that the sampling tube may
unwittingly be placed at a point where there
is flowing an amount of dirt above or below
the average. This error might be eliminated
by moving the tube over all parts of the
duct.
Next is the question as to whether dirt and
air flow into the end of the tube in the proper
ratio. The air flows into the sampling tube
in curved stream lines forming a sort of vor-
tex. Do the dirt particles follow these curved
stream lines properly, or is there a tendency
for a greater or a less than normal percentage
of dirt to flow into the vortex? An experi-
ment was made in which sunlight was shining
on the dusty air that was sucked into the end
of a tube. Many of the dust particles followed
curved stream lines to the end of the tube.
but whether the proper ratio of air to dirt was
maintained could not be determined from the
appearance.
A number of other similar methods, some
of them not applicable to the case under dis-
Fig. 7. Test Screen in Uncleaned Air.
A similar screen is placed in the
cleaned air beyond the washer
cussion, are described in the Lancet, Sep-
tember 20, 1913, page 886. The general
conclusion from this paper is that none of
the methods known are wholly satisfac-
tory.
Cotton Screen Dirt Test
After considerable investigation of the
various methods of testing for dirt, the
method herewith discussed was devised and
it has proved very satisfactory. Many test
screens have been made and have been in-
serted in air currents carrying various
amounts of dirt, in washed and in unwashed
air currents, and in washed air currents
passing through washers operating at various
degrees of efficiency. Satisfactory compari-
sons have been secured in all cases. No
attempt whatever has been made to weigh
the dirt collected, as this would probably
be quite difficult. The system gives qualita-
tive results with a single screen, or quantita-
024
GENERAL ELECTRIC REVIEW
tive results by comparison of two screens
inserted at different places.
Tests for Cleaning Efficiency of an Air Washer
Many types of air washers are in use for
cleaning the air supplied to generators or
public halls. These may be any one of four
general classes. The most common are the
spray washers in which a portion of the con-
duit is enlarged and subjected to water sprays
in various directions which wash the dirt
onto corrugated eliminator plates placed just
beyond. Abroad, cloth filters are used which
consist of large areas of finely woven cotton
cloth through which all the air must pass,
and the dirt is trapped by the cloth fibers.
The area must be very large in order to avoid
restriction of the flow. Rotating drums
producing a centrifugal effect are also used.
These are usually accompanied by some sort
of water spray. They are used extensively
for cleaning gas and have been applied to
cleaning air. Finally, the passage of a cur-
rent through charged plates, according to the
Cottrell system, has been used extensivelv
for purifying smelting fumes and smoke; and
this method could of course be applied to
cleaning air.
Tests reported herewith show that although
such systems remove large amounts of dirt
from the air the cleaned air from an air
washer is often still somewhat dirty. Similar
conclusions have also been reached by Pro-
fessor Whipple, Engineering News, Sept. 18,
1913.
The following is the plan that has been
finally adopted for making such tests. Screens
are simultaneously inserted in the air current,
one in the entrance to the air washer and one
in its discharge. The screen in the uncleaned
air is allowed to remain for such a length of
time that there is an appreciable amount of
dirt collected, the time is recorded, and the
screen is removed. A second screen is then
put in the same place and is left until it is
(to the eye) as dirty as the first screen. The
time is recorded and the screen replaced by a
third one, etc. From time to time the screen
in the cleaned air is examined. When it
seems (to the eye) as dirty as any one of
the set of screens taken from the un-
cleaned air, the time is recorded and the
test is completed. The ratio of the aver-
age time of exposure for the screens in
the uncleaned air to the time of exposure
for the screen in the cleaned air gives the
percentage of dirt remaining in the cleaned
air.
Tests with a 3500-Kw. Turbine-Generator
Many tests have been made in the case of
a 3500-kw. turbine-generator that is installed
in the Lynn shop plant of the General Elec-
tric Company. This machine has fans in-
stalled on the rotor which draw air from an
inlet through various passages in the machine
and finally discharge it into the atmosphere.
These fans pass about 15,000 cu. ft. of air
per minute. Near the power-house are coal
storage piles. In summer the power-house
windows are open which combined with the
wind results in a large amount of coal dust
being present in the air supplied to the tur-
bine-generator. In winter, the closing of
the windows eliminates most of this coal dust.
The air supply is drawn from the interior of
the power-house at its lower level. There are
also nearby a number of auxiliaries which are
lubricated with oil. These latter undoubtedly
result in a considerable amount of oil vapor
entering the turbine-generator. The genera-
tor has been examined a number of times and
a considerable incrustation of a greasy sub-
stance has been disclosed which undoubtedly
contains coal dust.
Before any method of cleaning the air was
used, a screen was exposed in the inlet con-
duit for about a week. The final result is
shown in Fig. 2. The cotton was wholly
covered with a dense black coating. It is
quite probable that a screen thus exposed in
the air supply to any electrical machine will
show a considerable collection of dirt in a
comparatively short time.
In order to avoid the risk of the generator
burning out due to the accumulation of dirt,
a spray system washer was installed. This
apparatus collected an enormous amount of
dirt. Shortly after the installation but before
it was realized how much dirt was being col-
lected, a screen in the water supply, which
was supposed to remove the dirt from the
water prior to using it again, completely
clogged and permitted no water to pass. The
screen thereupon broke, destroying of course
the value of the apparatus. An improved
system for removing the dirt was then in-
stalled and various other changes have been
made from time to time.
In the course of these experiments the
screens shown in Figs. 3, 4, 5 and 6 have been
obtained. Fig. 1 shows an unexposed screen
for comparison. At first these tests showed
that the air washer while removing a consid-
erable amount of dirt also allowed a consider-
able amount to pass. Successive decreases
have been made in the amount of dirt thus
X-RAYS
625
passing. When the amount of dirt became
comparatively small the color of the screen
exposed in the cleaned air became yellow,
while the screen in the uncleaned air was
always black or grayish. This has been
attributed to the fact that the air washer
permitted the passage of a considerable num-
ber of oil particles. Thus, when the screens
are of different colors it has been suggested
that comparison be made bv transmitted
light.
Preparation of Screens
The testing screens have for a base a
section of coarse wire screen of about
one-half inch mesh and are from 6 in. by
6 in. to IS in. by IS in. One surface of
the wires is coated lightly with shellac, and
absorbent cotton such as is used for surgical
dressings is pressed upon it. After the
shellac has dried, the surplus absorbent
cotton is peeled off so as to leave a thin
uniform film.
X-RAYS
Part III
By Dr. Wheeler P. Davey
Research Laboratory, General Electric Company
This article is the last of a series of three on the physics of X-rays. The first dealt with the nature of the
rays, and the second with their properties. This installment gives an elementary explanation of the experi-
mental work which has given support to the theories treated in the initial article, and indicates briefly how
these results have been applied in physics, chemistry and crystallography. — Editor.
In Part I * of this series it was shown that
the electromagnetic theory of X-rays con-
siders characteristic X-rays as being light of
very short wave length. It would be reason-
able to expect that, if this were so, char-
acteristic X-rays would obey the same laws
of diffraction as light waves. The experi-
mental verification of this expectation is one
of the most signal vindications of the elec-
tromagnetic theory.
Before considering the experiments them-
selves it will be well to consider the diffraction
of ordinary light. Let XX' (Figs. 1, 2, and 3)
be a surface opaque to ordinary light, and let
B and E be narrow slits. If the two rays of
light AB and DE come originally from the
same portion of the same source by paths of
equal length, then the light-wave at B will
be in phase with the light-wave at E. There-
fore, B and E will act as exactly similar
sources of light. A lens placed at CF will
cause the light to appear at the focus as a
luminous spot, for the two beams of light will
meet in the same phase having traveled equal
paths from B and E. If the lens is moved
slightly to one side the intensity of the light
will be much diminished, for the light from B
and E will travel over paths of different
lengths. If the lens is moved further to one
* General Electric Review. 191">, April, p. 25S.
side, no light will be seen at the focal spot.
But if the lens is moved to a position GH
(Fig. 1) such that the difference in path-
length is one wave-length, then the two beams
once more meet in phase and light is seen.
In the same way light may be observed at I J
and KV (Figs. 2 and 3) where the difference
in path-length is two and three wave-lengths
respectively. The light appearing at CF
is usually called an image of the "zero order,"
that at GH an image of the "first order,"
etc. The intensity of the light falls off
rapidly as the "order" of the image increases,
so that only the first few "orders" can be
made use of.
An inspection of Figs. 1, 2, and 3 will make
it at once evident that, if the angles separating
the various orders of images are to be large
enough to be measurable with accuracy,
the distance d must be comparable with the
wave-length of the light used. Thus diffrac-
tion gratings intended for use with visible
light (wave-lengths in the neighborhood of
10-5 centimeters) usually have a grating
space d of from 0.002 cm. to 0.0005 cm. Now
the wave-length of X-rays is in the neighbor-
hood of 10_0 centimeters. It is evidently
hopeless to attempt to rule a grating so fine
that the lines are only one hundred-millionth
of a centimeter apart.
G26
GENERAL ELECTRIC REVIEW
Haga and Wind* and Walter and Pohlf
tried to use a single narrow wedge in the
hope of overcoming this difficulty but they
did not achieve much success.
Fig. 1. Diagram showing production of a spectrum
of the 1st order
Fig. 2. Diagram showing production of a spectrum
of the 2nd order
/I
f
r
£ X'
^A
7
■
c
\^ 3™ofrorf?jf°£crfturr
To Prof. Laue of Munich belongs the
credit for the next great step in the diffraction
of X-rays. The atoms in a crystal are arranged
in a definite systematic formation and their
inter-atomic distances are of the same general
order of magnitude as the wave-lengths of
X-rays, as calculated from theory. Laue,
Lead 5crea
Lead. D'aphr-agmj
l\ Crysta
/PhotaO'-aph.c
' Plate
Fig. 3. Diagram showing production of a spectrum
of the 3rd order
Fig 4. Diagram of apparatus used by Friedrich Knipping
and Laue
therefore, was led to regard a crystal as a
ready-made natural diffraction grating for
use with X-rays. Such gratings are much
more complicated than those used with
♦Haga and Wind, Wied. Ann., pp. 884-895, 1899.
t Walter and Pohl, Ann. d. Phys., pp. 715-724, 19GS.
X-RAYS
627
ordinary light because of their three-dimen-
sional nature. Friedrich and Knipping *
verified experimentally Laue's conjecture.
Their apparatus is shown diagrammatically
in Fig. 4, and Fig. 5 shows diffraction patterns
which thev obtained.
It will be noticed from Fig. 4 that Friedrich
and Kipping used the crystal as a transmission
grating. The method was capable of showing
that X-rays could be diffracted, but was not
* Friedrich, Knipping and Laue. Ann. d. Phys.. pp. 971-1002.
1913.
C *£- 0.037*
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Fig. 5a. Through crystal of Zinc Blend.
Rays passed through crystal
perpendicular to 100 plane
Fig. 5b. Theoretical diagram showing
position of possible spots on Fig. 5a
Fig. 5c. Through crystal of Zinc Blend.
Rays pass through crystal
perpendicular to 111 plane
Fig. 5d. Same as Fig. 5c except that the
crystal has been slightly rotated
*u
Fig. 5e. Through Copper Sulphate.
Rays passed perpendicular
to 110 plane
Fig.
Fig. 5f. Same as Fig. 5e, except that
photographic plate is farther
from crystal
5. Spectra obtained by Knipping and Laue
Fig. 5g. Rays passed through
powdered Copper Sulphate
62S
GENERAL ELECTRIC REVIEW
well adapted to measuring the wave-length
of X-rays nor to a study of crystal structure.
W. L. Bragg conceived the idea of using a
crystal as a reflection grating (see Fig. 6).
This method possesses the advantage that
the results are very easy of interpretation,
which is evident at once by an inspection of
Fig. 7.
The distance MA P is the difference in
path-length of the two X-ray beams A\ and A2.
If this distance is an exact whole number of
wave-lengths, the two reflected waves are in
phase and the wave actually exists. Other-
wise, the waves are out of phase and interfere
destructively. There are thus only two
conditions to be met, (a) the angle of reflec-
tion must equal the angle of incidence,
(b) the wave-length of the X-rays must be
such that it is an exact divisor of the difference
in the path-length caused by reflection from
the various crystal planes. If the inter-atomic
distances and the angles between crystal
Taw z **.'<* •&*■•*'**•&*■*
Fig. 6. Arrangement of apparatus used by Bragg
Ca.
DE
71.
V
Cr
Mn.
; *
Co.
Mi.
Cu.
Brva-ss.
1 1
Increasing W<av« Length.
Fig. 7. Diagram showing reflection by atoms in a crystal
Fig. 10. Spectra obtained using various metals as reflectors
(1
1st Order
J
Rhodium Anticothode
Rock So it Reflector
2nd Order \
10'
IS'
Glancing Angles of Incidence of X frays
1
I
fc
«
1st Order
B,
Platinum Anticothode
Rock-Salt Reflzctor
3rd Order
S" . 10" IS" 20" 25° 30° 35° -40°
Glancing Angles of Incidence of X Rays
Fig. 8. Spectra obtained by Bragg
X-RAYS
629
planes are known, the wave-length of any
X-ray beam may be calculated from the
angle at which it will reflect. Conversely, if
the wave-length of the rays and the angle
at which they reflect from a given crystal
face are known, then from the angles between
the crystal planes the inter-atomic distances
may be calculated.
An attempt has been made in Fig. 7 to show
by lines drawn through the atoms that there
are many crystal-planes possible in different
directions in a single crystal. An inspection
of the diagram shows at once that the inter-
atomic distance is different for different
planes. By examining the various orders of
spectra from the various crystal planes, Prof.
Bragg has been able to assign a definite
arrangement to the atoms of a crystal. Fig. 8
shows two spectra obtained by reflection.
Fig. 9 shows the structure of a crystal of a
halogen salt of a monovalent metal. The
black spots represent metallic atoms, (Na,
K, etc.). The white spots represent the
halogen (F, CI, Br, I).
As a result of the work in X-ray spectra,
the Mendelejeff table of elements is to be
largely replaced by the Rutherford system
of atomic numbers (Table I) which is based
on the fact that, if the elements are arranged
in the order of their atomic weights, the
atomic numbers are proportional to the
reciprocal of the square roots of the wave-
lengths of the characteristic X-rays.
A striking instance of the interrelation of
the various branches of science is furnished
by the work of the physicist in X-rays which
has been found useful not only in physics but
THE RUTHERFORD SYSTEM OF
ATOMIC NUMBERS
m%3h
r«EH
**ee4
Fig. 9. Arrangement of atoms in a
crystal of sodium chloride
Atomic
Numbers
Symbol
Atomic
Weight
Atomic
Numbers
Symbol
Atomic
Weight
i
H
1.008
57
La
139.
2
He
3.99
58
Ce
140.25
3
Li
6.94
59
Pr
140.6
4
Gl
9.1
60
Nd
144.3
5
B
11.
61
6
C
12.
62
Sa
150.4
7
N
14.01
63
Eii
152.
8
0
16.
64
Gd
157.3
9
F
19.
65
Tb
159.2
10
Ne
20.2
66
Ho
163.5
11
Na
23.
67
Dy
Er
162.5
12
Mg
24.32
68
167.7
13
Al
27.1
69
Tm,
14
Si
28.3
70
Trrtj,
15
P
31.04
71
Yb
172.
16
s
32.07
72
Lu
174.
17
CI
35.46
73
Ta
181.5
18
A
39.88
74
W
184.
19
K
39.1
75
20
Ca
40.07
76
Os
190.9
21
Sc
44.1
77
Ir
193.1
22
Ti
48.1
78
P,
195.2
23
V
51.
79
Au
197.2
24
Cr
52.
80
Hg
200.6
25
Mn
54.93
81
Tl
204.
26
Fe
55.84
81
RaC,
210.
27
Co
58.97
81
AcD
28
Ni
58.68
81
ThD
208.
29
Cu
63.57
82
Pb
207.1
30
Zn
6.3.37
82
RaB
214.
31
Ga
69.9
82
RaD
210.
32
Ge
72.5
82
ThB
212.
33
As
74.96
82
AcB
34
Se
79.2
83
Bi
208.
35
Br
79.92
83
RaC
214.
36
Kr
S2.92
83
RaE
210.
37
Rb
85.45
83
AcC
38
Sr
87.63
83
ThC
212.
39
17
89.
84
RaA
218.
40
Zr
90.6
84
RF
210.
41
Nb
93.5
85
42
Mo
96.
86
Nt
222.
43
87
44
Ru
101.7
88
Ra
226.
45
Rh
102.9
88
Mes.Thi
228.
46
Pd
106.7
88
AcX
47
Ag
107.88
88
TUX
224.
48
Cd
112.4
89
Ac
49
In
114.8
89
Mes. Tha
228.
50
Sn
119.
90
Th
232.
51
Sb
120.2
90
Ux
230.5
52
Te
127.5
90
Io
230.5
53
I
126.92
90
RaAc
54
Xe
130.2
90
Rath
228.
55
Cs
132.81
91
Uxi
56
Ba
137.37
92
U
238.5
also in crystallography and chemistry. The
crystallographer is now able to measure in
centimeters the distances between the mole-
cules in crystals and is able in many cases
to assign a definite structure to them. The
chemist now knows that, at least as far as
crystals are concerned, there are no such
things as molecules in the sense in which the
word is ordinarily used in chemistry. The
whole crystal is a big complex molecule, and
630
GENERAL ELECTRIC REVIEW
the chemical formula only shows the relative
amounts of each element present. It is
reasonable to assume that in metals the
crystal (not the "molecule") is, next to the
atom, the unit to be considered. It has even
been suggested that it might be possible to
use the characteristic X-rays as a means of
identifying the various elements, so that a
measurement of the wave-length of the
characteristic X-ravs from a substance would
serveas a qualitative analysis of the substance.
Fig. 10 shows in diagram, spectra of the
third order obtained by Mosely.* They are
so arranged that the scale of wave-lengths of
each plate registers with the scale of the
plates above and below it. Table II which
is of approximate wave-lengths is given for
reference, f
* Mosely, Phil. Mag.. Dec. pp. 102-1-1031, 1913.
t See also General Electric Review, 1915. April, p. 263,
Table II.
TABLE II
VARIOUS ELEMENTS, THEIR ATOMIC WEIGHTS, AND WAVE-LENGTHS OF THEIR
CHARACTERISTIC X-RAYS
Element
Atomic Weight
Calcium 40.1
Titanium 48.1
Vanadium 51.1
Chromium 52.0
Manganese 54.9
Iron 5.5.9
Cobalt 59.0
Nickel 58.7
Copper 63.6
Wave-Length
3.36
xio-
"8 cm
3.09
xio-
"8 cm
2.76
xio-
'8 cm
2.52£
xio-
"8 cm
2.52
xio-
"8 cm
2.30
xio-
8 cm
2.30
xio-
8 cm
2.09
xio-
8 cm
2.11
xio-
8 cm
1.92
xio-
"8 cm
l.94£
xio-
8 cm
1.765X10"
"8 cm
1.80
xio-
8 cm
1.63
xio-
"• cm
1.66
xio-
~8 cm
1.50£
xio-
"8 cm
1.55
xio-
"8 cm
1.40
xio-
"8 cm
Remarks
Strong K
Weak
Strong K
Weak
Strong K
Weak
Strong K
Weak
Strong K
Weak
Strong K
Weak
Strong K
Weak
Strong K
Weak
Strong K
Weak
radiation
radiation
radiation
radiation
radiation
radiation
radiation
radiation
radiation
radiation
radiation
radiation
radiation
radiation
radiation
radiation
radiation
radiation
631
BALL BEARINGS IN ELECTRIC MOTORS
By Frederick H. Poor
Manager SKF Ball Bearing Company
The author has written an interesting article showing the advantages of ball bearings. It is likely that
some engineers will not fully agree with him in all of his claims, as it is difficult to make general statements of
the kind that can be broadly applied; but that many of his claims are perfectly justified is shown by the increased
use of ball bearings. It should be noted that some standard lines of motors manufactured without ball bearings
have their bearings sealed against leakage, and therefore this advantage can hardly be claimed as peculiar
to ball bearings. — Editor.
The motor manufacturer and the motor
user have in these days of active competition
come to realize the necessity of considering
those factors in design and construction
which affect cost of maintenance and at-
tention, as well as those which have a bearing
on overall mechanical efficiency; and at the
same time they cannot afford to overlook
features of compactness and reduction in
weight, and their resultant effects upon the
adaptability of motors to various industrial
conditions.
Improvements in electrical characteristics
are by no means at a standstill, but in con-
sidering them it may be stated that features
of mechanical construction taken in detail are
receiving a great deal of consideration. As
affecting the general progress in motor con-
struction, ball bearings are coming into
prominence, and their more general stand-
ardization in the electrical industry is assured,
both by reason of their extensive employment
in various industries, including textile mills,
paper mills, flour mills, mines, woodworking
plants, street railway service, etc., and the
abundant proof of their serviceability under
the exacting duties which these industries
demand, such as high speeds, heavy loads,
dusty mill conditions, and installations sub-
ject to neglect and possible abuse at the
hands of inexperienced workmen.
As an aspect of this progress we may take
for example the use of ball bearings on
mining locomotive motors, for here we have
operating conditions that are likely to be
subject to as little proper attention as will
be found anywhere. As indicating a few of
the advantages to be derived from the use of
ball bearings on this class of motors, a few
reports from users of ball bearing mining
locomotive motors may be cited. These
reports are in reply to a definite series of
questions submitted to a large number of mine
superintendents. Their reports are as follows :
In reply to a question as to what percentage
of time a locomotive with plain bearing
armatures is out of service due to the arma-
tures striking the pole pieces, one man gave
as his experience 20 per cent, with a further
statement that 30 per cent of these motors
give trouble. Another man answered: "We
have no plain bearing locomotives — don't
want any machinery with plain bearings."
A third replied: "Our data are in favor of
ball bearings, 50 per cent."
In reply to the question as to how much
the total motor repair bill is affected by the
use of ball bearings on motor armatures, one
man replied 60 per cent and another 50 per
cent. A third states: "We are sure there is
a large saving."
A third question was put up to the superin-
tendent: "How much have motor failures
due to grounds on brush-holders, cables and
other parts inside of the motors, been reduced
on account of ball bearing armatures?"
One electrical engineer said 80 per cent; a
general superintendent, 75 per cent.
Analyzing the foregoing replies as a whole
we see convincing evidence of, first, decreased
maintenance costs and fewer repairs, and
second, improvement in motor commutation,
a shortening of intervals of motor inspection,
freedom from lubrication troubles, etc.
Ball bearings must be lubricated, and in
the ball bearing motor construction which
has been in service in General Electric mining
locomotives for the past two years and a
half, a small grease cup within easy access of
the operator provides the sole source of
lubrication. A half turn a day on the grease
cup — possibly a refilling of the cup once a
week — is sufficient, because the double row
ball bearings are suitably encased within the
bearing heads with narrow sealing grooves
on each side of the bearings to prevent the
leakage of the lubricant into the motor frame.
With this protection, little or no overflow
into the armature occurs, the commutators
are protected against a conducting "slop"
of coal dust and oil, and good commutation is
maintained.
As affecting maintenance and repairs it
should be remembered that in a ball bearing,
hardened steel balls roll on hardened steel
bearing races, rubbing friction is eliminated,
G32
GENERAL ELECTRIC REVIEW
and accuracy is maintained. Added to this, the
self-aligning feature in the SKF ball bearings
allows them to accept, without binding, any
strains which might otherwise be developed
from slight shaft deflection due to the sudden
impulses of starting or shock loads. These
Mining Motor Heads. 1, Armature Shaft; 2, Motor Bearing Head ;
3, Outer Bearing Race; 4, Balls and Retainer; 5, Inner Bearing Race;
6, Lubrication Chamber; 7, Gland to Seal Lubrication Chamber; 8, Grease
Feed Pipe; 9, Outside Housing Cap; 10, Lock Nut to hold Inner Race
Securely on Shaft
factors insure the maintenance of the motor
air gaps and practically eliminate the danger
of armatures dropping onto the pole shoes.
Their effect upon the accuracy of gear
setting and the consequent greater life of
the gears is almost as pronounced.
Considering the conditions which surround
general industrial applica-
tions for induction motors
and direct current motors,
we find many cases which
require compactness. Some
motor manufacturers pride
themselves on their ability
to develop increased horse-
power out of a given sized
standard motor frame.
Their ambition is to obtain
larger output from a stand-
ard unit, a decreased weight
per unit of horse power ca-
pacity, maximum power in
a limited space condition,
etc. In striving to achieve
these ends, it is well to
consider features of mechanical compactness
in the bearings, as well as the electrical
characteristics which, with a possible stretch-
ing of the normal heating limits, permit the
motor to be used under exacting space con-
ditions and decreased costs of production.
As compared with a plain bearing, a
ball bearing, including a liberal lubricating
chamber surrounding it, will occupy approxi-
mately one-half to one-third the distance
along the shaft required by a babbitt bearing;
in some special cases the result being that a
ball bearing motor will be as much
as 20 per cent shorter than a plain
bearing motor of exactly similar
characteristics and capacity. This
feature is shown diagrammatically
in Fig. 3 and further in Figs. 4 and
5, where the plain bearing motor,
normally 40 in. overall length, was
reduced to 33 in. by the use of ball
bearings — a reduction of IS per cent.
The ball bearing heads are short,
compact and rugged, and in installa-
tions where space is at a premium,
where a consideration of aisle room,
floor space, machine arrangement,
etc., is necessary, the ball bearing
motor goes a long way toward solving
the problem. Where conditions of
high speeds are to be reckoned with,
the designer is confronted with the
problem of balancing the allowable
bearing pressure per square inch of surface
against the surface speed of the shaft in
babbitt bearings, i.e., he must seek a com-
promise between the allowable length of
bearings, as opposed to allowable bearing
pressures which different methods of lubri-
cation make possible. Oil rings must be used
Fig. 2. An SKF Ball Bearing Shown in Normal Sectional and Deflected Positions
for circulation, sometimes chains; in some
cases a simple wick will suffice, in others large
chambers for waste packing must be provided.
These considerations are all based upon the
presupposition that bearings in seivice will be
subject to frequent inspection, renewal of
BALL BEARINGS IN ELECTRIC MOTORS
633
the lubricant, or possibly occasional rebab-
bitting.
It is true that babbitt bearings as they are
at present being furnished in stock motors
occasion little complaint from the average
motor user, who quite expects to give to
them the normal attention now required;
but this same user is seeing the constantly
increased use of ball bearings on the machines
he is using in his shop, on machine tools, on
line shafting, grinders, buffers, and machines
mentioned previously in classified industries,
and is coming to a realization of the material
reduction in his shop maintenance costs as
a whole which results from their use.
In the flour milling industry, bearings
which are sealed against leakage prevent the
flour in process from becoming contaminated
with oil and they also reduce the risk from
fire. As bearing on this last statement, it is
of interest to read the report of Mr. John
Hoffa, Chairman of the Insurance Com-
mittee to the Pennsylvania Millers' State
Association, in which he states: "There has
been an aggregate fire loss, caused solely by
hot boxes in mills and elevators, during the
last three years, of over a million dollars."
A similar danger from fire exists in textile
mills, where there is frequently an accu-
mulation of oil-soaked lint, etc., around a
leaky bearing; and added to this is the pos-
sibility of ruining fabrics from dripping oil.
In the individual ceiling motor drive or the
four-frame drive, where direct connected
motors are employed, the possibilities of
dripping oil are a constant menace unless the
bearings can be sealed against leakage.
In vehicle motors, in motors for grinding
rooms, buffing rooms, cement plants or mill
installations where an abrasive dust or grit
is present, conditions are reversed. Here
is a case where abrasive material must be
kept out of the bearings in order to prevent
rapid wear and the consequent necessity
of frequent bearing renewals. Again the
bearings must be sealed in some manner.
It is only fair to the ball bearing to examine
into how the mounting adapts itself to the
conditions we have outlined, and a typical
motor mounting will suffice to make the
point clear. As will be seen from Fig. 7,
the inner race of the ball bearing is securely
locked in position against a shoulder on the
shaft so that the inner ball race is firmly
seated on and forms practically an integral
part of the shaft. The outer ball race has a
sucking fit in the end shield. On each side
of the bearing is a liberal lubricant chamber,
protected against leakage from within or
against the intrusion of grit, moisture, etc.,
from without, by small annular sealing
grooves in the end caps adjacent to the
shaft on each side. With the 'ubricant
chamber filled with oil to the level of the balls
in the lower part of the bearing head, with
Motor Equipped with
-2°£-i 5.K.F. Ball B6ar-*cs.
Motor. Usirxs A-1631
Babbitted Rim& Oiung Bearim<ss.
Fig. 3. Comparison of Motor Lengths
a suitable grease, the ball bearing is its own
lubricator, without the necessity of oil rings
or other auxiliary devices. Alignment is
taken care of by the spherically ground
surface of the outer bearing race, and a
compact, rugged mounting is obtained, free
from the inspection of curious and practically
proof against neglect. It will further be
noted that this arrangement is suited to
floor or ceiling use without the necessity of
reversal of the motor end shields.
A few words on the selection of the sizes of
ball bearings for motors may be of interest.
In selecting ball bearings for almost any type
634
GENERAL ELECTRIC REVIEW
of machine the power normally required for
the machine and the speed of the shaft are
usually established before the final details
of bearings are considered, and with this
data available the bearing loads may be
pretty closely determined.
Bearings on electric motors are liable to
excessive shocks, sometimes vibration, heavy
belt loads, and a variety of trying conditions
that will vary considerably with the shafting
or machines to which the motors are deliver-
ing their power. In making bearing selections
the designer must take into account the
extra strains which occur in the motor, such
as those due to vibration (which particularly
at great speeds and unbalanced motors can
In mounting the bearings, the inner race
should have a tight fit on the shaft and should
be permanently seated in a fixed position
against the shoulder on the shaft by means of
a lock nut or distance piece, the setting
being such that the inner race of the bearings
forms practically an integral part of the
shaft. A driving fit cannot always be relied
upon because the continued action of the
load on the bearing may tend to peen the
shaft, and greater security for the inner
bearing race is therefore obtained by locking
it securely in position.
When placing the bearing on the shaft,
the shaft should be slightly larger than the
bore of the bearing in all cases, inasmuch as
Fig. 4. A 40-h.p., 500-r.p.m., 230-voIt Shunt Wound
Motor equipped with Ball Bearings
Fig. 5.
A 60-h.p., 400-r.p.m., 230-volt"Shunt Wound
Motor equipped with Ball Bearings
cause a very considerable addition to the
load on the bearing), the extra thrust load
which may occur if the rotor is not well
adjusted in the magnetic field, and the
excessive load resulting from unnecessary
stretching of belting by inexperienced or
careless workmen. Experience has shown
that in selecting ball bearings for belt-driven
machines the proper bearing capacity may
be arrived at by assuming the belt tension
to be 350 pounds per inch width of belt, or
by adopting a bearing whose rated capacity
is approximately five times the predeter-
mined load.
On gear or chain drive, backlash, inac-
curacies in machining, and possible conditions
of shock which may come from frequent
reversals, usually call for ball bearings having a
capacity of three times the predetermined load .
the inner race will spring slightly and a
good driving fit can thereby be obtained.
The outer races of the bearings should
seldom, if ever, be held rigidly in the housing.
A slight clearance, i.e., a sucking fit within
the housing, will admit of the slow rotation
of the outer race when the bearing is in
operation, insuring a more perfect dis-
tribution of the load over the whole of the
outer race, thus obviating any undue fatigue
on one section of the outer race while the
other section remains entirely unloaded.
As a further requirement for the proper
mounting of bearingS on the motor it should
be pointed out that, where there are several
radial bearings on the same shaft, one bearing
only should be used to stabilize the shaft
against end motion, inasmuch as if an effort
is made to fix the outer races of both bearings
BALL BEARINGS IN ELECTRIC MOTORS
635
against end motion there is immediate
danger of cramping, entirely due to difference
in expansion of the shaft and the motor
frame with changes in temperature, etc.
On direct current motors both bearings
may be given lateral freedom in the housing
in many cases thereby giving opportunity
sulfation with the manufacturers of the
bearing, who by reason of their experience
are competent to give sound advice.
2. Care in mounting. This is a factor
which is very largely in the hands of the
manufacturer of the motor, for poor machine
work on those parts surrounding the bearing,
Fig. 6.
Sectional View of Ball Bearing Motor Head,
showing the Sealing Grooves
for end play and allowing the rotor an
opportunity to adjust itself in the magnetic-
field.
The housing surrounding the bearings
should be well tightened to prevent moisture
and dirt from getting in, as well as to prevent
the escape of the lubricant. The lubricant
should actually get down to the bearing, and
should be chemically neutral — free from acid,
alkali, or other rust-forming constituents.
Fig. 8
Mining Locomotive Motor, Disassembled, showing
the Ball Bearings
The factors which will in the largest degree
affect the successful operation of ball bearings
on motors may be briefly summed up as
follows :
1. Care in the selection of the bearings.
The use of a reasonable judgment, and con-
Fig. 7. Mounting of Ball Bearing Induction Motor
either on the shaft or in the bearing housing,
must be guarded against; and while this
cautionary statement may seem superfluous,
it may be stated that there are still a number
of ball bearing users who have not yet
recognized, or who have not become suf-
ficiently appreciative of, the fact that a high
grade ball bearing is an accurately finished,
carefully manufactured, and a precise mechan-
ical specialty, and a reasonable effort should
be made to finish the parts surrounding
the bearing with a proportionate degree of
care.
3. The third factor, which is none the less
important than the two first, is cleanliness.
The casings surrounding the bearings should
be free from casting sand; they should be
thoroughly cleared of all metal chips from
the machine work which is done on to
them, and if they are allowed to stand a
length of time that will develop rust, this
should be thoroughly cleaned out before the
bearings are mounted.
As a further precaution, it is well to
emphasize the fact that ball bearings
are normally packed in a preservative
grease, and if they are laid on shop
benches, containing dust, filings, or metal
chips, before they are installed in the
motor, there is grave danger of having
this grit work into the bearings in opera-
tion.
It is to be recommended, therefore, that
the bearings themselves should be thoroughly
cleaned out by gasolene or kerosene before
they are enclosed in the machine.
636
GENERAL ELECTRIC REVIEW
ELECTROPHYSICS
Part V
By J. P. Minton
Research Laboratory, Pittsfield Works, General Electric Company
This is the concluding article of this author's series on "Electrophysics." In our next issue we hope to
publish an article closely allied with this series by Mr. M. E. Tressler. The present contribution deals with
the characteristics of cathode ray tubes under two main headings, viz., their vacuum characteristics and the
electrostatic effect near the cathode. — Editor.
SOME CHARACTERISTICS OF CATHODE RAY TUBES
Introduction
Although the subject matter of this paper
is not strictly electrophysics, yet it is closely
related to this field, in that it deals directly
with an apparatus with which electrophysical
research can be carried out. For this reason,
this paper, dealing with some characteristics
of cathode ray tubes, will fit in nicely with the
series on electrophysics, and with an article
on the cathode ray tube and its application,
by Mr. M. E. Tressler, which is being pre-
pared for the August issue of the Review.
A number of interesting observations have
been made and some valuable information
gained concerning the cathode ray tube in
the work which this laboratory has conducted
along this line. In the present paper only
two points will be considered, because these
are the most important and reveal some
interesting facts regarding cathode ray tubes.
These two points will prove of value to those
who are engaged in work of this nature.
The first of the two subjects to be considered
is the vacuum characteristics of cathode ray
tubes, and the second one is the electrostatic
effects around the cathodes.
I. Vacuum Characteristics
In the literature on this subject, reference
is made to trouble encountered with "harden-
ing" and "softening" effects in these tubes.
The first is an increase and the second a
decrease of vacua in the tubes. The changes
in vacua may occur either during the opera-
tion of the tubes or at other times. If the
vacuum in a tube is originally adjusted to the
desired value, then any further changes in the
vacuum will be undesirable and in many
cases will cause the tube to be unfit for
further use. The "hardening" of the vacuum
usually occurs with continued use of the
tube and generally is of a gradual nature.
The "softening" effect, however, is usually
quite rapid and always occurs during .the
operation of the tube. If a tube is operated
heavily so that strong rays are produced, the
vacuum may be ruined within five minutes.
At other times, a tube may be strongly
operated for perhaps an hour or so, or even
six or eight hours, and then within a few
minutes the pressure will increase sufficiently
to make the tube of no further use. It
would seem that in the case of "hardening"
effects the tube acts as if it were exhausted,
while in the case of "softening" effects it
would appear that some air was suddenly
admitted into the tubes to increase the
pressure. Vacuum changes such as these
make the cathode ray tubes unreliable and
unsatisfactory for use over long periods of
time, perhaps several years.
Several suggestions1 have been made to
counteract or eliminate these effects. There are
four methods. The first an auxiliary side tube
made of platinum, or better still, palladium,
through which gas can enter the tube when the
metal is heated for a few seconds at red heat.
This is referred to in Air. Tressler's paper. This
method allows a reduction in vacuum but
it is useless for allowing an increase in it.
The second method is an auxiliary side tube
containing acid sodium carbonate. This
salt liberates a gas when a discharge of
electricity takes place through it. Conse-
quently, this auxiliary side tube is provided
with an electrode, and by parsing a discharge
between it and the anode the vacuum is
reduced. This scheme, therefore, allows
only a reduction in vacuum to be obtained.
A third method is to have a side tube con-
nected to the main tube through a stop cock.
If the pressure becomes too small, a little
gas is admitted from this side tube. Another
side tube containing platinum-black, which
readily absorbs large quantities of gases, is
also connected to the ' cathode ray tube
through a stop cock. If the pressure becomes
too great, the platinum-black is allowed to
absorb a sufficient quantity of gas to give
the desired vacuum. The fourth method
ELECTROPHYSICS
637
is to have the cathode ray tube connected
continually to a suitable exhausting system.
The vacuum can then be adjusted at any
time to any desired degree.
Evidently, the first two methods of vacuum
regulation are unsatisfactory for commercial
work. The third scheme is not suitable
because slight changes in pressure affect the
operation of the tubes greatly, and it is
difficult to obtain fine regulation by operating
stop cocks. Such a scheme as the third one
makes the construction of the tubes more
difficult. Likewise, the fourth method is
unsatisfactory for it is not expedient to have
suitable vacuum pumps installed where it is
desired to use the tubes.
These difficulties and objections lead to
the belief that, if satisfactory tubes were
made, it would be necessary to have them
maintain constant vacua of the desired
magnitudes under all ordinary conditions of
operation. In order to accomplish this, it
was necessary to first know why the vacuum
changes occurred. After this was known, it
would be possible to attempt to eliminate
them with some hope of success.
It is known that water vapor and other
condensable gases will be adsorbed on the
surface of glass. It was reasonable to believe,
therefore, that on the inside surface of a
cathode ray tube, a thin film of gas adhered
very tenaciously to the glass. The same kind
of a film would also adhere to the surface of
the electrodes, the fluorescent screen, the
diaphragm, and any other surface within the
tube. In addition to these adsorbed gases, the
metal electrodes, glass, etc., would tend to
absorb gases. Suppose then, that a tube had
been exhausted to the desired vacuum, there
would still be both adsorbed and absorbed
gases bound up with the glass, electrodes,
etc., within the tube. Now, if this gas was
liberated from the surfaces either during
operation of the tube or at any other time,
the pressure would increase and the "soften-
ing" effects described above would be
observed. On the other hand, if gas from the
interior of the tube was removed by absorp-
tion or adsorption, then the pressure would
decrease and the "hardening" effects would
be noticed.
With few exceptions, all the tubes showed
pressure-increases when they were operated.
Usually these occurred during the first few
minutes of operation. In several cases, the
tubes were operated heavily for perhaps 15
hours and exhausted at the same time. In
this way the liberated gases were removed
from the tubes as rapidly as they were freed.
Even this would not stop the "softening"
phenomenon and there appeared to be
almost an endless supply of gases from out of
and off of the surfaces within the tubes. It
was found, however, that if the tubes were
exhausted three or four hours, at perhaps
350 deg. C, sufficient gases were liberated
from the surfaces to maintain constant
vacua over long periods of time. One tube
has now maintained a constant vacuum for
almost two years and there is no indication
that it will not maintain this vacuum for a
number of years, although it is used almost
daily. Not one exception to this rule has
been found. Some tubes have been operated
about 10 hours continuously with such strong
rays that one could not touch the glass around
the cathodes without receiving severe burns.
Even in these most extreme cases, the vacua
remained constant. It may be said, therefore,
that when tubes are exhausted in this manner
they will maintain constant vacua over long
periods of time, thus requiring no regulators
of any kind. This improvement is of much
value and it insures reliable tubes for experi-
mental purposes.
Several questions now naturally suggest
themselves. Some of these are :
Were these vacuum changes due to the
portion of the tubes where the discharges
occurred or could they be partly due to the
large ends of the tubes in which the screens
were placed?
Were the vacuum changes of an adsorption
nature rather than an absorption one?
Were the changes due to moisture deposited
on the surfaces within the tubes?
Regarding the first question, it may be
said that the vacuum changes were not due
to the large ends of the tubes in which the
screens were placed. This was shown to be
true because the "softening" effects were
observed for small test-tubes containing
only a cathode and anode. When these
small test-tubes were exhausted at about
350 deg. C, they would maintain a constant
vacuum just the same as a regular cathode
ray tube would. It seems, therefore, that the
discharge will cause a film of gas to partially
disengage itself from the surface of the glass
and electrodes. This liberated gas will then
increase the pressure within the tube. Since
the temperature-rise of the glass is not over
a degree or so during' the time required for
"softening," it means that the film is partially
liberated by some means other than that of
heating effect. It is probably true that the
63S
GENERAL ELECTRIC REVIEW
cause of the "softening" effects is directly
due to a mechanical or electrical effect, as a
result of the discharge within the tube.
Regarding the second question, it is
probably true that the gas is adsorbed to the
surfaces within the tubes, rather than ab-
sorbed within the electrodes and glass walls.
This seems to be the case because of the
following observations :
Some tubes were exhausted for several
hours at about 350 deg. C. They were then
operated strongly for, perhaps, three hours,
and the vacua remained perfectly constant.
The pressure was then allowed to increase
quickly to atmospheric value by allowing
ordinary air to enter. After standing in this
condition for several hours, they were exhaus-
ted at room temperature. Then when they
were placed in operation, they would soften
within a few minutes, just as though they
had never been exhausted at a high tem-
perature. They could again be exhausted at
about 350 deg. C, and when operated the
vacua would remain constant. Allowing the
pressure to increase again to atmospheric
value and exhausting at room temperature,
the same "softening" effects were observed.
Even when the pressure increased to atmos-
pheric value for only a few minutes, the
vacua would "soften" as though the tubes
had never been exhausted at high tem-
perature. (There has been noted only one
exception to this characteristic of cathode
ray tubes.) These facts show that the gas if
adsorbed to the surfaces within the tubes for
absorption would require appreciable time.
Adsorption would require only a relatively
short time for as soon as the admitted gases
come in contact with the surfaces of the glass,
electrodes, etc., the gas film would begin to
form immediately on the exposed surfaces.
It was next shown that water vapor was
not responsible for the "softening" effects,
because the above phenomenon occurred
either when perfectly dry air or ordinary
moist air was admitted into the tubes. It
would seem, therefore, that ordinary air will
form a thin layer of air, the densitt' of which
is much greater than ordinary air, over the
surfaces of the glass and electrodes within
the tubes. A sufficient quantity of this film
should be removed, by exhaustion at about
350 deg. C, to eliminate any tendency for a
greater or less film to be formed either during
the operation of the tubes or at any other
time. If this condition is attained no trouble
will be encountered due to vacuum changes
within the tubes.
II. Electrostatic Effects near the Cathode
The second point to be considered is that
relating to the accumulation of electrostatic
charges' on the glass surrounding the alu-
minium cathode. Since the cathode is of a
negative potential, it means that the positive
ions will be drawn toward the cathode end
of the tube. Some of these positive ions will
strike the cathode while the others will
impinge on the glass surrounding it. These
positive ions then cause the glass to receive
a positive charge. In addition to this, the
negative cathode, which is charged to a high
potential, induces a positive charge on the
glass surrounding it. These two effects
continue so long as the tube is in operation.
When the potential difference between the
glass and cathode reaches a sufficient amount
a discharge will occur between them. Dis-
charges of this nature may start either from
the glass or the cathode, but they never
extend throughout the distance between the
cathode and the glass. The discharges may
occur several times a second, once every few
minutes, or not at all, depending on the
strength of the cathode rays and on the
initial conditions of the tube.
Such discharges always cause the cathode
ray stream to be unsteady and frequently
result in flash-overs within the tube between
the cathode and anode. The flash-overs were
prevented by the use of high resistances of
perhaps 100,000 ohms. High resistance
lightning arrester rods are especially suitable
for this work, and they should be connected
in the cathode lead adjacent to the cathode
itself. These resistances not only prevent
possible damage to the tube and vacuum,
due to the flash-overs, but they also cause the
tube to operate much more steadily. They
do not, however, prevent discharges from
occurring between the cathode and the glass
surrounding it. A number of investigators
have encountered this difficulty and have
tried to eliminate it in various ways. To
avoid this trouble. Dr. Zenneck2 surrounded
the cathode with glass formed into small cups
('"Hinterkleidungen") as illustrated in Fig.
1-a. Roschansky3, for the same purpose,
placed behind the cathode a metallic screen,
and filled the space between this and the
glass with ruffled tinfoil leaves. This scheme
is illustrated in Fig. 1-b where S is the
metallic screen and L the ruffled tinfoil
leaves. Grundelach, in his tube, made
the cross section of the cathode almost
large enough to fill the tube as illustrated in
Fig. 1-c.
ELECTROPHYSICS
639
A tube, made in Germany of Dr. Zenneck's
design, was tried but the glass "Hinter-
kleidung" did not prevent static discharges
between it and the cathode. It did, however,
prevent them from occurring between the
cathode and the glass wall of the tube. The
discharges between the cathode and the glass
"Hinterkleidung" caused unsteady rays, and
for this reason this scheme is not as advan-
tageous as one would wish. The size, shape
and position of the cathode, and the kind of
glass used, have a great deal to do with the
accumulation of these static charges and,
therefore, with the operation of the tubes.
For example, a cathode of the size and shape
shown in Fig. 1-d gives much trouble on
account of the frequency of the static dis-
charges between it and the glass. A cathode
of the form shown in Fig. 1-e is the most
satisfactory of any tried. This form of
cathode yields a fairly uniform field through-
out the cross section of the tube and permits
no concentration of the field at sharp edges.
Concentrated fields, due to sharp edges, are
quite effective in producing unsteady cathode
rays. Plane cathodes of a disk shape and of
large areas, are quite satisfactory; Fig. 1-c
represents such a cathode. It was found,
however, that none of the schemes, with the
possible exception of Roschansky's which has
not been tried, would prevent the trouble
due to the accumulation of static charges
on the glass surrounding the cathode.
In order to avoid this trouble the following
scheme of exhaustion was found to produce
the desired results. It was noticed that
tubes whose vacua "softened" during opera-
tion never gave any trouble due to electro-
static charges around the cathode. Tubes
which had been exhausted several hours at a
high temperature in order to eliminate
vacuum changes, were always unsatisfactory
because of difficulty with the charges. Since
the adsorbed gases are liberated from the
glass and electrodes during exhaustion at
about 350 deg. C, it would seem that the
reason why the charges accumulate during
operation of the tubes is on account of a film
of gas on the glass surface being necessary for
conducting away the charges. If a sufficient
film is present on the glass, the charges are
apparently conducted to the cathode and
there neutralized, but if the film is removed,
then the charges accumulate until they are
neutralized by discharges between the cathode
and glass. This phenomenon occurred with
any form of cathode and with any kind of
glass tried. The explanation, however, as here
given may not be the correct one. Trouble
due to electrostatic charges should not be
encountered in a tube whose cathode-end was
constructed as shown in Fig. 1-f; M is a
metallic screen fitting closely to the glass and
Fig. 1
extending down to the upper surface of the
cathode as shown. This construction, how-
ever, was not necessary for the following
scheme of exhaustion was found to eliminate
all trouble of this nature. The idea was to
remove a sufficient amount of the film of gas
by exhausting the tube at about 350 deg. C,
in order to allow a constant vacuum to be
maintained, and still leave enough of the film
to conduct away the charges, which collect
on the glass surface. After some experimenting
it was found that if the tube was exhausted
at about 350 deg. C. for perhaps half an hour,
the vacuum would remain constant during
several hours of continuous heavy operation,
and no trouble would be experienced on
account of charges on the glass surrounding
the cathode. Exhaustion at a high tempera-
ture for this time was sufficient to avoid
vacuum changes over long periods of time.
This method of exhaustion has been tried on a
640
GENERAL ELECTRIC REVIEW
number of experimental tubes and found
to be satisfactory. It would appear therefore
that why this trouble has been encountered
so much, is because the tubes have been
exhausted for too long4 periods at a high
temperature, in order to avoid vacuum
changes.
A word may be added as to the effect of the
kind of glass on the characteristics of cathode
ray tubes considered in the present paper.
It may be said that soft glass will give less
trouble on account of static discharges than
will hard glass. It is also easier to adjust the
time of exhaustion at a high temperature, in
order to eliminate static discharges around
the cathode and still maintain constant
vacuum characteristics, with soft glass than
it is with hard glass. Soft sodium glass is
satisfactory in every way, and it has the
advantages of being easily blown and of
yielding the characteristic greenish-yellow
fluorescence of this glass to help one judge
the character of the cathode ravs.
REFERENCES
(a) "A Power Diagram Indicator," by Harris J. Ryan,
A.I.E.E.. Vol. 30, P. 530. 1911.
(b) "Apparate und Verfahren zur Aufnahme und Darstellung
von Weckselstromkurven und Elektrischen Schwin-
gungen." Bv H. Hansrath; Helios. Fach-Zeitsehrift fur
Elektrotechnik. Zeite 527, 1914.
(c) Siehe Z. B., Fortschnitte auf dem Gebiets der Rontgen-
strahlen. Bd. 18, Heft 2. 1912. Heinz Bauer.
' Zenneck— Wied Ann. 69. P. 842, 1899.
3 Roschansky — Ann der Phys. 26, P. 281. 1911.
4 See for example Loc. Cit. 1 (b), P. 527.
CORRECTION TO "ELECTROPHYSICS, PART I"
Mr. Ralph Bown, Instructor in Physics at
Cornell University, has kindly called my attention
to a slight discrepancy which exists in Fig. 1,
Part I, on Electrophysics (see February, 1915,
issue of the Review) and which I overlooked in
preparing the figure. The quadrants QQ should be
sufficiently large to give a uniform electric field
as far as the screen 5. The magnetic field should
also be uniform over this same distance. The
text and equations were based on the assumption
of uniform electric and magnetic fields, but,
unfortunately, I neglected to say so, although it
was what 1 had in mind. It is to be hoped that this
modification in Fig. 1 will eliminate any difficulty
anyone may have encountered as a result of this
discrepancy. J. P. M.
641
HIGH-VOLTAGE DIRECT-CURRENT SUBSTATION MACHINERY
By E. S. Johnson
Railway and Traction. Engineering Department, General Electric Company
The rapidly increasing number of installations of high-voltage direct-current apparatus in railway systems
proves the commercial success of that method of operation. As a result, wide-spread interest has been aroused
in the design, operation, and characteristics of the equipment. The following article contains very interesting
information on the frequency, voltage, current, overload capacity, commutation, influence of short circuits,
etc., of the high-voltage direct-current machinery which is being used. — Editor.
The idea that the application of 1200 volts
or higher voltage direct current to electric rail-
way work constitutes a system radically differ-
ent from one employing 600 volts, and that the
difficulties attending the operation are greater,
has been shown to be entirely erroneous.
The design of higher potential direct-
current substation machinery follows a logical
advance in the design of 600-volt apparatus,
not a single good element being discarded or
replaced. The one feature that permitted
the use of higher voltages was the successful
application of the old idea of commutating
poles to motors and generators. This has
made possible the use of higher voltages per
bar and higher commutator speeds, which
result in greater output per pound weight, or,
as might be better stated, a reduction in the
cost per kilowatt capacity.
In the first 1200- volt and 1500-volt instal-
lations two 600- or 750-volt machines were
connected in series, the fields of both machines
generally being connected on the ground side.
The design of these machines was identical
in every respect with standard 600-volt
machines with the exception of the necessary
increase in insulation. Experience indicated
that the designs then adopted met every
condition of operation with marked success,
except it was found in a few cases that trouble
was experienced by flashing over on those
machines in which the brush rigging was
supported from the pillow block. In later
designs it has been the practice to support
the brush rigging from the magnet frame or
in some cases from a special yoke attached
to the base.
With the exception of 60-cycle synchronous
converters, it has become the usual practice
in designing substation apparatus (for oper-
ation up to and including 1500 volts) to
obtain the desired voltage from one machine.
Synchronous converters up to a frequency of
35 cycles can be designed to operate at any
voltage up to 1500. There are a number
of 33 cycle 1200-volt synchronous converters
in successful operation, two of the most
prominent installations being the 500-kw.
machines furnished to the Portland, Oregon,
Railway and the Michigan United Traction
Co. The latter machines are insulated for
2400 volts, being operated two in series, and
in a number of cases are arranged to supply
both 1200 and 2400 volts.
When it is desired to obtain a voltage
higher than about 600 volts and not above
about 1500 volts direct current from a
60-cycle power transmission system, motor-
generator sets are generally used because
the desired voltage can be obtained from one
machine and the synchronous motor can be
arranged to give power-factor correction. Two
synchronous converters connected in series,
however, give a higher efficiency.
On account of the cost and the construction
difficulties of the fields for self-excited gener-
ators having a voltage of 1200 or above, it is
found advisable to separately excite the
machines from a direct-connected 125-volt
exciter. Since a separately-excited generator
does not automatically drop its voltage on
short circuit, the same as a self -excited
machine, it is necessary to connect in series
with the generator field a resistance that is
normally short circuited by a contactor.
The contactor is so connected to an attach-
ment on the circuit-breaker that, when the
circuit-breaker opens, the contactor also
opens and thus the resistance is inserted in
the generator field. By this action the
voltage at the terminals of the generator is
reduced. This arrangement has been used
in a great number of cases and has met
every requirement for successful operation.
For all voltages higher than about 1500,
it is advisable to connect two machines in
series when synchronous converters are used
on account of the limitations of design; and
when motor-generator sets are used on
account of the cost. The machines furnished
the Butte, Anaconda & Pacific Railroad, and
the numerous interurban railways in Michi-
gan, all consist of two 500-kw., 1200-volt
generators or synchronous converters con-
nected in series for obtaining 2400 volts.
The series fields, commutating fields, and
compensating windings of all machines are
connected on the ground side. Where two
642
GENERAL ELECTRIC REVIEW
1200-volt synchronous converters insulated
for 2400 volts are connected two in series,
the low machine (the one on the ground side)
is self-excited and the high machine (the one
on the trolley side) is excited from the low
machine.
It has been found advisable from a cost
standpoint to build all high-voltage direct-
current apparatus to carry 200 per cent over-
load for one minute and sometimes in the
case of heavy traction work to design the
apparatus to stand 200 per cent overload for
five minutes and 100 per cent overload for half
an hour. Where direct-current generators
are required to stand 200 per cent overload
for accelerating a train, it is usual to design
them with compensating as well as commutat-
ing windings, thus almost entirely neutralizing
the armature reaction.
At the time of the general adoption of
commutating poles for 600-volt railway
apparatus, it was found necessary to use a
shunt in multiple with the commutating
field windings in order to provide a means
of adjustment for obtaining proper commuta-
tion. A simple resistance shunt was used with
the first machines. With such a resistance
shunt, it was found that the machines would
either spark very badly or flash over under
sudden large variations in load. An elaborate
and exhaustive series of tests were made
which demonstrated that it was necessary to
supply a shunt having inductance as well as
resistance in order that the current would divide
properly during rapid changes in load as well as
when the load was practically constant. Some-
times it is possible to design the commutating
field so that a shunt is not required. A small
amount of adjustment to obtain proper com-
mutation can be obtained by varying the
width of the commutating pole face slightly
or by inserting non-magnetic shims between
the commutating pole and the magnet frame.
The reluctance of the commutating magnetic
circuit can be changed by either of these
methods.
It is believed that the equalization of the
excitation, which will reduce the tendency
to flash over on machines having commutating
poles, will be obtained by bridging the commu-
tating poles. Recently a big improvement was
made in the operation of some commutating-
pole synchronous converters by the addition
of bridges. These machines are not provided
with shunts. As a matter of convenience,
it has been found advisable in general
operation to supply commutating poles with
a shunt winding which is excited directly
from the machine or from the separate
source of excitation, so that the commutation
of the machine may be adjusted while in
operation without being shut down.
Long years of experience have demonstrated
that it is not necessary to provide any
protection against short circuits, for 600-volt
substation apparatus, beyond that given
by the inherent impedance of the circuit and
the circuit breakers. It is a well known fact
that any 600-volt direct-current machine
will flash over on short circuit but the
resulting damage is not so great but that the
machine can again be placed in service after
the commutator has been cleaned up. There
are no records available which would indicate
the frequency with which short circuits occur.
In some cases they are very infrequent
and in others several occur each day. On a
line in which short circuits are liable to occur
quite frequently, it has been found that any
trouble that has been experienced can
generally be eliminated by extending the
feeder a short distance from the substation
before tapping it to the trolley. One case in
particular is known where a substation,
located adjacent to a car-barn, was subjected
to frequent short circuits due to the peculiar
overhead construction and the apparent
inefficiency of the car-barn employees. The
trouble was entirely eliminated by placing
the car-barn circuit on a separate feeder
in which was inserted a small amount of
resistance.
Due to the greater safety factor in the
design of all apparatus for 1200-volt operation,
to the care with which the apparatus has
been handled, or to the greater inherent
impedance of the circuit as compared with
600-volt circuits, short-circuits are of com-
paratively infrequent occurrence. No records
of any great damage being done are available
and it is a fact that the writer cannot find
that any serious complaints have ever
been made of trouble from short circuits on
any 1200- or 1500-volt substation apparatus.
It has therefore not been found necessary
to take special precautions to protect such
equipment against short circuits. If trouble
did occur, however, the natural step would
be to do the same as has been done for 600-
volt operation, i.e., to tap the feeder into the
trolley system a short distance from the
substation. In the initial operation of the
2400-volt Butte Anaconda & Pacific R.R.
the switching yards at Anaconda were tied
in directly with the main track. On account
of the substation being located near the middle
HIGH-VOLTAGE DIRECT-CURRENT SUBSTATION MACHINERY
643
of the yard, short-circuits, which were very
frequent, were very severe. The switching
tracks were placed on a separate circuit in
which the feeder was of considerable length;
thus, enough resistance was included to reduce
the severity of the short circuits. The opera-
tion since has been entirely successful.
The severity of short-circuits depends upon
the distance at which they occur from the
source of supply, i.e., they depend on the
amount of impedance in the circuit. A short-
circuit current near the terminals of a machine
will amount to about twenty-five times normal
current. However, as short-circuits near the
terminals are very infrequent (usually tak-
ing place at quite some distance from the
substation) there is enough impedance in the
circuit to reduce the short-circuit current to
from 12 to 15 times normal. Such values
will do no great amount of damage beyond
slightly burning the brush-holders and some-
what blackening the commutator. If short-
circuits are very frequent, it would probably
be necessary to tap the feeder into the
trolley at such a distance from the substation
that the current will be limited to eight or
ten times normal, as the damage to a machine
flashing over at this load would be slight.
Comparison of the short-circuits on 600-volt
apparatus with those on 1200- and 1500-volt,
shows conclusively that less damage done is
to the higher voltage apparatus. The damage
seems to be somewhat inversely proportional
to the voltage, i.e., it appears that the
damage done varies as the volume of the
current which is, of course, independent of
the voltage. In general, it might be stated
that high voltage apparatus is slightly more
susceptible to flashing over than 600-volt
apparatus, especially so where one machine
is used to obtain 1200 or 1500 volts because,
in the design of this apparatus, it is generally
necessary to use narrower commutator bars
and higher commutator speeds than are used
for 600-volt apparatus; thus the flashing
distances are shorter. As previously stated,
however, the consequences which result from
this increased tendency of higher voltage
apparatus to flash over need not be seriously
considered.
Very serious consideration has been given
to the question of introducing reactances in
feeder circuits to prevent the current from
rising to a greater value than eight or ten
times normal before the circuit breaker opens.
Calculations and a thorough study of this
indicate that the intentional introduction of
reactance is not advisable, on account of the
excessive cost and the space occupied and
because of the inductive kick which would have
a tendency to cause the arc to hold across the
breaker contacts. It is believed that it would
be preferable to introduce into the supply
circuit a resistance which will be normally
short-circuited by a quick-acting mechanism
that will automatically open and place the
resistance in circuit before the current
reaches a dangerous value.
644
GENERAL ELECTRIC REVIEW
THE 1500- VOLT ELECTRIFICATION OF THE CHICAGO,
MILWAUKEE & ST. PAUL RAILWAY
By W. D. Bearce
Railway and Traction Engineering Department, General Electric Company
The author gives a brief description of the 1500-volt electrification of the terminal line at Great Falls,
Montana, which will in all probability ultimately make connection with the 3000-volt installation of the
Chicago, Milwaukee & St. Paul Railway. The most interesting features of the substation and locomotive
equipment and the overhead line construction are described.— Editor.
GREAT FALLS TERMINAL
As a forerunner of the 3000-volt main
line electrification, the Chicago, Milwaukee
& St. Paul Railway has recently begun
electrical operation of the terminal line in the
city of Great Falls, Montana. This' city is
at present the terminal of the new 138-mile
feeder line from Lewistown, Montana, con-
necting with the main line transcontinental
division at Harlowton, the eastern terminus
of the 3000-volt electrification now under
construction. The Great Falls terminal
yards are located in the center of the city
and are connected by a cross-town line about
four miles in length, known as the Valeria
Way Line. There are about three miles of
additional electrified trackage, making a total
of seven miles. The terminal buildings
include a large freight house, round house,
power plant and passenger station.
The tracks connecting the Falls Yards and
the Terminal Yard pass through the business
part of the city and it is expected that con-
siderable benefit will be derived from the
elimination of steam locomotive smoke from
the center of the city as well as a reduction in
the cost of train haulage. The traffic includes
the transfer of both freight and passenger
trains from the Falls Yards to the terminal
station as well as switching service in the
terminals.
The electrical equipment is of sufficient
capacity to take care of 580-ton freight trains
operating at about 9J^m.p.h. on the maximum
grades of 0.65 per cent. Electric power is
supplied by the Great Falls Power Company
from the hydro-electric plant at Rainbow
Falls, about six miles from the substation.
Energy is transmitted at 6600 volts, three-
phase, 60 cycles, as generated at the power
station.
Substation
The substation equipment is located in the
power station operated by the railway com-
pany for heating the terminal buildings and
includes a two-unit svnchronous motor-
generator set with a two-panel switchboard
for controlling the alternating and direct-
current units. The motor is rated 435 kv-a.
(0.8 power-factor), 6600 volts, and operates
at 900 r.p.m. Provision is made for starting
as an induction motor through a compensator
which is operated from the alternating-current
panel. The generator is of the commutating
pole type, rated 300 kw. at 1500 volts. The
set is capable of carrying 200 per cent over-
load or 900 kw. momentarily. Excitation for
the a-c. motor fields and for the shunt fields
of the d-c. generator is furnished by a 10-kw.,
125-volt direct connected exciter.
The switchboard consists of two natural
black slate panels, one controlling the syn-
chronous motor and the other the direct-
current generator and feeder. The d-c. panel
is of the standard 1500-volt type and carries a
remote control, hand-operated switch and
circuit breaker mounted between slate bar-
riers at the top of the panel. The motor
Fig. 1. Part of the 1500-volt Substation Equipment
for the Great Falls Electrification of the
C. M. & St. P. Ry.
panel contains the usual instruments and
starting and operating switches for controlling
the motor. An aluminum cell lightning
arrester is also installed in the station for
protection against electrical storms.
1500- VOLT ELECTRIFICATION, CHICAGO, MILWAUKEE & ST. PAUL RY. 645
Locomotive
All trains are handled by a standard 50-ton
electric locomotive of the steeple cab type
designed for slow speed freight and switch-
ing service. The running gear consists of
two swivel equalized trucks carried on
semi-elliptic equalizer springs. The driving
wheels are of solid rolled steel, 36 inches in
diameter.
The motor equipment includes four GE-
207, 750-volt, box frame commutating pole
motors insulated for 1500 volts. Each motor
has a normal one-hour rating of 79 h.p. at
750 volts, and two motors are connected
permanently in series. All motors are venti-
lated by a blower direct connected to the
dynamotor in the cab of the locomotive.
The gear reduction is 64/17.
The control equipment is Sprague-General
Electric type M, arranged for operation from
either end of the cab. There are 10 steps with
the motors in series and seven steps in series
parallel. Control current for the operation of
contactors, lighting and other auxiliary cir-
cuits is furnished by a 1500/600-volt dyna-
motor. A multivane fan carried on an exten-
sion of the shaft furnishes air for ventilating
the motors.
The current collector is a sliding pantograph
similar to that being installed on the main
line 3000-volt locomotives. The slide is
Fig. 2.
1500-volt, 50-ton Locomotive on the
Great Falls Electrification
lifted into position by air pressure and is held
against the wire by steel coil springs. Pro-
vision is made for operating at trolley heights
varying from 17 to 25^ ft- above the top of
the rail.
Compressed air for operating air brakes,
whistles and sanders is supplied by two
1500-volt motor-driven air compressors.
Each of these units has a displacement of 27
cu. ft. of air per minute at 90 lb. pressure.
«s
gfc,
• b"[
lUirn^ffi
£=>=:
,|^^^^iH
I^^H
Fig. 3. Locomotive shown in Fig. 2 hauling freight train
The compressors are located in the cab of the
locomotive convenient for inspection.
A headlight is mounted on each end of the
locomotive provided with a concentrated
filament type Mazda lamp of about 100 c-p.
As a safety precaution no trolley wire is
installed inside of the round house. A con-
nection is made in the cab of the locomotive
for applying power to the locomotive through
a length of special flexible cable insulated for
2400 volts. A double-throw switch in the
locomotive cab allows connection to be made
either to the trolley or cable circuit.
Line Construction
The overhead line construction is of the
catenary type similar in a general way to
that installed on the Butte, Anaconda &
Pacific, 2400-volt railroad. Both span and
bracket construction are used, depending
upon local conditions. Poles are spaced
approximately 150 ft. apart on tangent
track supporting a 4/0 grooved trolley from
a three-point suspension. There is no feeder
copper installed.
The work was done by the Electrification
Department of the Chicago, Milwaukee &
St. Paul Railway, R. Beeuwkes, engineer in
charge, under direction of Mr. C. A. Goodnow,
assistant to the President. All of the elec-
trical apparatus including locomotive, sub-
station equipment, and line material was
furnished by the General Electric Company.
646 GENERAL ELECTRIC REVIEW
SOME RECENT DEVELOPMENTS IN SWITCHBOARD APPARATUS
By E. H. Beckert
Switchboard Sales Department, General Electric Company
Control and protective apparatus for electric power systems must of necessity undergo almost constant
change in design, owing to the ever higher voltages and larger capacities that are being employed. In some
cases a change in existing types will suffice to meet all requirements, while in others entirely new designs are
required. This article describes some of the more recent modifications and developments that have been
made in switchboard apparatus, including relays, oil switches, circuit breakers and instruments. — Editor.
As power and lighting systems become
more extensive, and operating voltages climb
higher and higher, as generators and generat-
ing plants grow in capacity, as new fields are
opened for the application of electricity and
the old fields are gone over and changes made,
it becomes necessary to develop new con-
trolling apparatus or change existing appa-
ratus to meet the new demands. At the
same time the buying public are becoming
more and more exacting in their requirements
in order to properly protect their financial
interests and safeguard against accidents.
The following paragraphs give a brief
description of some of the most interesting
developments in switchboard apparatus which
have lately come into existence, as a result
of the above conditions and the desire of
manufacturers to improve their product along
lines indicated by active original research
work.
Relays
Probably no branch of switchboard
apparatus has experienced more marked
advance than that of relays. Selective
relays of various sorts have become a neces-
sity in large systems in order to properly
protect operator and consumer. It means
much to each of these parties to reduce to a
minimum the loss due to short circuits,
grounds and overloads in different parts of a
system, and to insure continuity of service
as far as this is possible. Upon the relay
devolves this important duty.
On parallel transmission lines, on tie lines
between generating stations, and on generator
and motor-generator sets operating in parallel,
it is often desirable to provide means for
automatically cutting out lines or machines
in trouble due to a short circuit or ground
when a reversal of power is caused, and at
the same time not disturb the rest of the
system. The reverse power relay in several
forms has been developed to take care of this
situation. It is of the dynamometer type
with current and potential coils, the arrange-
ment of which is shown in Fig. 1 . With energy
flowing in the normal direction in the circuit,
the contacts are held in the normal position
by the pull of the relay, which increases with
increase of energy in the normal direction.
Consequently, no amount of overload will
cause the relay to operate as long as it is not
accompanied by a reversal of energy ; but the
relay may be relied on to operate on a reverse
Fig. 1. Reverse Power Relay
power short circuit even though the potential
is greatly reduced.
These relays are made in three forms, one
(form E) having single-throw circuit closing
contacts, another (form E-2) having single-
SOME RECENT DEVELOPMENTS IN SWITCHBOARD APPARATUS
647
Stot/a7/\b. /
Jo Otner Station
throw circuit opening contacts, and the third
(form E-3) having double-throw contacts and
requiring for its operation a pilot wire between
stations and a time delay low-voltage relay.
The application of the differ-
ent forms is as follows:
(1) For two generating
stations connected by one
line, with power normally
feeding in either direction.
To disconnect this line at
both ends in case of trouble
on the line, use E-3 at each
end of line.
(2) For two generating
stations connected by two
lines, with power normally
feeding in either direction.
To disconnect the line in
trouble, leaving the other
in operation, use E or E-2
at each end of each line,
the current coils of the
relays being interconnected.
The same scheme can be
used for more than two
lines by using additional relays and properly
interconnecting them. (The E-3 connected
at each end of each line could also be used,
but the arrangement given is less expensive
because of the fact that with the E or
E-2 no pilot wires between stations are
necessary.)
(3) For two or more generators con-
nected to one bus. To disconnect the
generator in trouble and not disturb the
others, use E or E-2 connected between
each generator and bus.
(4) For motor-generator sets or syn-
chronous converters. To prevent pump
back, use E or E-2 connected between
machine and bus.
(5) For two or more lines from generat-
ing station to substation only. To discon-
nect line in trouble without disturbing
others, use E or E-2 at the substation
and time limit overload relay at generating
station end of line.
Fig. 2 illustrates the connections of the
E-3 relay, using a single-phase diagram for
simplicity. With energy flowing in the
same direction at both ends of the line, all
the contacts of the relays will take a uniform
position. If the direction of energy should
change on the whole line, all contacts would
simultaneously reverse, bringing them again
to a uniform position. Under these circum-
stances, the circuits of the low-voltage time
delay relay will be unbroken, and the tripping
circuit will therefore be kept open. The
time limit feature is added to the low-voltage
relays simply to insure sufficient delay to
Station A/a S
'To Oder Station
Fig. 2. Connections of E-3 Relay
allow all relay contacts to swing to their
proper positions on the occurrence of a normal
reversal of energy in the tie line. In case of
trouble between stations, causing power to
flow from each end of the line, the relay
contacts at one end will remain normal, while
those at the other end will be thrown to the
opposite side. This will open the circuit of
the low-voltage relay and cause its contacts
to complete the circuit through the tripping
coil of the oil switch. The contacts of the
relay will remain in the position which caused
the oil switch to open on the occurrence of the
fault, and must be reset by hand before the
next operation. This is made possible by
the use of a knurled button at the front of
the relay. The relays should be set to operate
at some value above normal load on the cir-
cuit so that a reversal of power under normal
operating conditions will not cause the relay
contacts to be operated.
OIL SWITCHES
Improvement in Form H Oil Switches
Recently these oil switches have undergone
some structural changes to make the circuit
rupturing parts more accessible for inspection,
adjustment and repair. Also the cap on the
oil vessel as well as the lower oil vessel clamp
has been changed to allow metal straps to be
bolted between cap and clamp, as is very clearly
64.S
GENERAL ELECTRIC REVIEW
shown in Fig. 3. These straps have added
greatly to the security with which the caps are
fastened in position, a valuable feature when
the switch is called upon to open heavy
overloads or short circuits.
Fig. 3. Oil Vessels of Type F Form H6 Oil Switch
showing the easily removable parts
For ready inspection of contacts and oil
vessels, switches up to 35,000 volts inclusive
are provided with easily removable parts.
The construction is shown in Fig. 3, which
pictures one pole of the switch with one of
the oil vessels, the movable secondary con-
tact and fixed contact being removed. To
remove these parts it is necessary, after the
switch is opened, to remove the nut at the
top of the contact rod, loosen the clamping
nut on the crosshead, and push the contact
rod down into the oil vessel; then loosen one
swing bolt nut on the lower clamp on the oil
vessel and remove the unit, consisting of oil
vessel and fixed and removable contacts.
In order to supply the trade with a switch
which will most nearlv suit its needs and
Fig. 4. Bottom and Back Connected Type F Form H3
Oil Switch
Type F Form H6 Oil Switch with Poles
arranged in parallel
SOME RECENT DEVELOPMENTS IN SWITCHBOARD APPARATUS
649
which will give the engineer an opportunity
to work out the design of his station to the
best advantage, the line of motor-operated
oil switches has been extended, so that all
15,000-volt switches may be obtained with
studs so arranged that connection can be
made at bottom and back, as shown in Fig. 4.
The poles of the switch can now be obtained
either all arranged in parallel as shown in
Fig. .3, or all in tandem as shown in Fig. 6.
In the case of the tandem arrangement,
switches can be obtained either bottom-
connected as shown in Fig. 7, or back-
connected as shown in Fig. 8. From the
illustrations it is seen that a very complete
line is available, and the engineer should
have no trouble in choosing something that
will fit in with his station arrangement.
Type F Form K26 and K026
New 45,000-volt and 70,000-volt indoor
and outdoor oil switches have been developed
which can be mounted on a supporting frame-
work or on the floor as desired (Fig 8a). The
framework is provided to allow for the easy
removal of oil tanks by means of tank lifters.
The indoor and outdoor switches are similar
except for the necessary change in bushings.
The remaining features are practically the
same as in the type F form K21 oil switch,
the tanks being slightly larger in size and
the insulation increased. Fig. 8a shows the
indoor switch with the first tank entirely-
removed.
Fig. 8a. 45,000-volt Type F Form K26 Oil Switch
Fig. 6.
Type F Form H6 Oil Switch with poles
arranged in tandem
Fig. 7. Type F Form H6
Oil Switch with poles
arranged in tandem —
bottom connected
Fig. 8. Type F Form H6
Oil Switch with poles
arranged in tandem —
back connected
650
GENERAL ELECTRIC REVIEW
Type F Form K2 5 Oil Switches
Figs. 9 and 10 represent two capacities
in a new line of 600-volt oil switches, includ-
ing the 3000-, 4000- and 5000-ampere sizes.
In these switches laminated brushes very
similar to those of the larger capacity circuit
breakers are used to carry the main current,
although the final arc is always broken on
auxiliary contacts. In the 3000-ampere switch
these brushes are in the oil,
while in the larger capaci-
ties the brush is above the ^ j.
oil tank and the final break
is made on a set of auxili-
ary contacts under oil.
In all switches the tanks
are mounted on a frame-
work, allowing for their
easy removal and inspec-
tion of internal parts. The
3000-ampere switch may be
furnished hand-operated,
the others electrically oper-
ated onlv.
Type F Form K24 Oil Switches
A line of K24 switches
has also been introduced
having rupturing capaci-
ties somewhat lower than
the K21. These switches
are supported on pipe
framework and have tanks
and contacts similar to
those of the K21. They
are available in capacities
of 300, 500, 800 and 1200
amperes at 15,000 volts,
and 300 amperes at 35,000
volts. Fig. 11 shows a
35,000-volt switch of this
type.
of the tank, to the top of which are fastened
steel wire cables. These cables pass over pul-
leys and around a shaft operated by a worm
gear. The tank rests upon continuations of
the triangular supports bent at right angles to
fit over the rim at the bottom of the tank.
The pulley shaft is mounted on a casting
containing a triangular slot and can be moved
forward or backward on an arm which rests
Tank Lifters
To enable the station
attendant to more readily
and quickly remove or
attach oil switch tanks of
the form K switches, the
manufacturer has produced
several different designs of
tank lifters. Figs. 12 and
13 show the construction
as applied to the type F
form K12 switch.
The device consists of
separate triangular
supports, one for each side-
Fig. 9. 3000-amp. 600 volt Type F Form K25 Oil Switch
Fig. 10. 4000 amp 600-volt Type F Form K25 Oil Switch
SOME RECENT DEVELOPMENTS IN SWITCHBOARD APPARATUS
651
on the switch frame and also supports the
operating shaft, gear and handle.
The raising and lowering of the tank is of
course accomplished by turning the handle
operating the worm gear. The tank can be
lowered to the floor or can be suspended in
any intermediate position. The triangular
supports are removed from the tank by lifting
one end of the tank slightly and sliding the
support from underneath.
High Tension Series Trip
Series overload mechanisms which act by
direct mechanical means to trip open high
tension oil switches have often been the
subject of severe criticism on account of the
inaccessibility of the working parts. It has
been rather dangerous to inspect, clean or
adjust the mechanism which is in direct
connection with the high-voltage current.
To obviate these difficulties, a scheme has
been devised whereby the only portion of the
tripping mechanism alive at high potential
is a solenoid, constructed so simply and
ruggedly that it requires practically no
attention. As shown in Fig. 14, the solenoid
is supported on a post type insulator, the
plunger of the solenoid connecting directly
with the releasing mechanism of the oil
switch. Change in current setting is affected
by means of a calibrating mechanism at the
oil switch. The time limit feature is obtained
by employing an oil dashpot mounted at the
switch. If the switch and mechanism are
grounded, as is always recommended, either
the current or time setting can be accomplished,
if necessary, while the switch is alive, although
Fig. 11. 300-amp. 35,000-volt Type F Form K24 Oil Switch
it is recommended that the switch be entirely
disconnected from the line whenever this is
possible.
Fig. 12. Tank Lifter in position to lower tank
Fig. 13. Oil Tank partly removed by tank lifter
652
GENERAL ELECTRIC REVIEW
Employing practically the same principles
as before, a series overload relay has been
designed, the chief difference being that the
plunger of the solenoid, instead of acting
mechanically upon the tripping mechanism
Fig. 14. Time Limit Series Trips on a 35,000-volt Type F
Form K21 oil switch
of the switch, closes contacts which in turn
complete an auxiliary electrical circuit through
the trip coil of the switch.
Type F, Form P4 Oil Switch
Fig. 15 shows one of the latest designs in
oil switches for manhole service, having a
special bell chamber for entrance leads.
This switch is intended for service in locations
where there is danger of flooding, and all
current-carrying parts are entirely enclosed
in a compact cast iron frame oil tank, bell
chamber and cover. The leads are carried
to and from the switch through bell chambers
at the bottom of the frame. This bell chamber
is similar to the G-E interior end bells used on
incoming lines, and it is so constructed that
a triple conductor cable may be brought
entirely within the water-proof- compartment
before the lead sheath is removed. This
chamber affords ample room for separating
the strands of the cable and connecting them
to the switch terminals. The chamber may
then be filled with an insulating compound
and made entirely water-tight.
The bell chambers, as well as the oil vessel
and cover, are made of cast iron and
are securely bolted to the cast iron switch
frame. All these joints are made watertight
by the use of gaskets, and the switch
is tested totally submerged under water for
24 hours.
The operating handle is outside the frame
and is of such design that the switch can be
operated with a hook. The shaft to which the
handle is attached passes through the frame
in a water-tight stuffing box. These switches
are made single, double, or triple-pole,
single-throw, for use on currents up to 10,000
volts. The normal rating is 200 amperes.
LEVER SWITCHES
Automatic Throw Over Switch
A sudden failure of the source of power for
the lighting system in the power station is a
more or less frequent and troublesome
occurrence. To take care of such an emer-
gency and facilitate the reestablishment of
normal conditions where apparatus may have
been shut down due to the failure of power,
a switch for automatically throwing the lights
to an auxiliary or reserve source becomes
very handy. The switch shown in Fig. 10
accomplishes this result. The device consists
Fig. 15.
10,000-volt 200-amp. Type F Form P4 Oil Switch
with special bell chamber
of a special double-throw switch held closed
by a latch on one throw against a pair of
springs.
To close the lighting circuit with the normal
source of power in operation, the switch is
thrown in the lower set of contacts and latched
SOME RECENT DEVELOPMENTS IN SWITCHBOARD APPARATUS
653
in the closed position by hand. When a
failure of the source occurs, a low-voltage
release is caused to drop its armature, tripping
the latch free from the crossbar above it.
The springs on the hinge clips of the switch
then quickly force the switch into the upper
set of contacts, which are connected to the
reserve source of power. At the same time
an auxiliary switch at the top is thrown into
contact, causing a bell or other indicator to
operate to attract the station attendant's
notice. After the resumption of normal
conditions, the switch must be thrown by
hand into the lower contacts and latched.
These switches can be obtained in 100-,
200- and 300-ampere 250-volt capacities,
and either double or triple-pole. Besides
being valuable in power stations, this switch
finds a useful field in the lighting system of
large buildings, such as hospitals, office build-
ings and apartment houses, in which the
installation of a storage battery as a reserve
source is not likely to be too large an item
of expense.
Type L Form D16 Lever Switch
For starting six-phase synchronous con-
verters from the a-c. end, using taps on the
power transformers, two triple-pole double-
necessitating larger and larger starting
switches, until such a capacity has been
reached that it is next to impossible to operate
the switches by hand. The split lever con-
Fig. 16. Automatic Throw-over Switch
throw lever switches are necessary, the run-
ning throw of one switch carrying the full load
current of the machine. The capacities of
these converters have been steadily increasing,
Fig. 17. Synchronous Converter Starting Panel showing
split pole lever switch
struction was then resorted to. Fig. 17
shows a starting panel for a six-phase con-
verter, the switch on the left of the panel
being of 4000 amperes capacity. It has the
crossbars with separate handles, one-half
of the blade of each pole being fastened to
each crossbar. The upper contacts are
connected to the two-thirds taps on the
transformers for only a short time, and are
arranged to make contact only with that half
of the switch which must be thrown first to
the lower or running side. Half of the blades
readily carry the load until the operator
throws over the second section. Large
triple-pole switches such as this are easily
operated, whereas the alternative would be a
much more expensive set of large solenoid
operated circuit breakers. Converter starting
switches of this construction of 5000 amperes
capacity are in use and are operated without
difficulty.
CIRCUIT BREAKERS
20,000 Ampere Circuit Breaker
In Fig. 18 is shown a 500-volt d-c. auto-
matic solenoid-operated circuit breaker of
20,000 amperes capacity, a number of which
have recently been built. The breaker is
operated by two solenoids mounted below
the main contacts (which consist of three
brushes in one frame), which act in unison. It
G.34
GENERAL ELECTRIC REVIEW
will be seen from the illustration that the
breaker mechanism to the point where the
operating rods from the solenoid are con-
nected, is very similar to the toggle arrange-
ment of the large capacity hand operated
Pig. 18. 20.000-amp. 500-volt Circuit Breaker
breakers. Each solenoid consists of a closing
coil only, the automatic tripping of the
breaker being accomplished by its overload
armature striking the holding-in "latch
and the tripping of the breaker from the
control switch being effected by means of
closing the circuit through a shunt trip
coil whose plunger strikes the latch. It is
possible to close the breaker by hand, using
two handles which can be inserted in sockets
shown on the illustration. The breaker is
supplied with laminated studs.
High Voltage Circuit Breaker
The introduction of 2400-volt direct current
in the operation of electric railways has necessi-
tated the design of new apparatus, a problem
of some difficulty being the production of
an efficient automatic circuit breaker. After
considerable experiment and thorough tests
the design in Fig. 19 was completed. The
construction is similar to the lower-voltage
breakers, the chief difference being that the
2400-volt breaker is remote controlled, while
the secondary contacts and their adjacent
parts are changed. The carbon break has given
way to a magnetic blowout of an unusual
design. For the construction of this blowout,
two large flat barriers of a non-combustible
insulating material form an arc chute and
effectually confine the arc in a vertical plane.
On the outside of this chute there are iron
pole pieces which become magnetized when
the breaker opens under load. A strong
magnetic field is consequently produced
throughout the entire space between these
pole pieces. On account of the large mag-
netized area, the arc from the breaker will be
greatly extended and blown out and broken.
This breaker is mounted remote from the
panel and operated by a lever on the front
of the panel, the breaker being insulated from
the lever by a wooden rod. The breaker is
also insulated from the base upon which it is
mounted by porcelain supports. The illustra-
tion shows also the lever switch which is
connected in series with the breaker and
operated by a lever from the front of the
panel.
Fig. 19.
High Voltage Breaker used on 2400-volt
d-c. systems
Laminated Studs
For use on circuitsof heavy currentcapacity,
a line of rectangular laminated studs (Fig. 20)
has been developed, and it is recommended
that they be used on a-c. circuits of 3000-
ampere capacity and over, and on d-c. circuits
SOME RECENT DEVELOPMENTS IN SWITCHBOARD APPARATUS
655
of 5000 amperes and over. The advantage
gained is that the laminations of the connection
bar fit in between the laminations of the stud,
forming a joint which cannot work loose and
making it unnecessary to bend the bar or
to tighten a number of large nuts, and at
the same time greatly simplifying the arrange-
ment of connection bars at the back of the
panel. Studs can be obtained with the
laminations arranged in either a vertical or
horizontal plane.
INSTRUMENTS
Electrostatic Synchronism Indicator
Synchronizing on high tension lines, while
often desirable, has been out of the question
because of the excessive cost and space
required for installing the necessary potential
transformers for a secondary synchronism
indicator. A glow synchronism indicator is
now available for this purpose on circuits of
13,200 volts and above. The new indicator
depends for its operation upon the principle
of electrostatic discharge in a vacuum.
The instrument case resembles the ordi-
nary round pattern switchboard instrument.
Inside the case are receptacles for holding the
special glowers which project through holes
in the cover. Connections from the line to
the device are made through condensers,
which consist of suspension insulators having
an insulation equal to that used on the line.
Normally the glowers have the appearance
of ordinary spherical frosted incandescent
lamp bulbs. When, however, there is a
proper difference of potential across their
running fast or slow. When synchronism is
reached there will be no rotating effect, and
one glower will be dark while the other two
will glow at about half brilliancy. For syn-
chronizing two lines, the instrument is usually
Fig. 20. Laminated Stud for 6000-amp. circuit breaker
terminals they will glow with a reddish hue.
When the lines are not in synchronism, the
glowers will light up in succession, showing
the relative direction of rotation and indi-
cating whether the incoming machine is
Fig. 21. Electrostatic Synchronism Indicator and
disconnecting switches
mounted on a panel with disconnecting
switches as shown in Fig. 21. The equipment
can be made suitable for any voltage by
simply connecting in the proper number of
insulators.
Temperature Indicator
It is of great value to know the temperature
of certain parts of generator and transformer
windings that are inaccessible for ther-
mometer measurements. An instrument
known as the temperature indicator has been
produced to determine these temperatures.
Copper coils of known resistance are placed
in the parts whose temperature it is desired
to know. The changes in resistance are
shown on the scale of the indicator, which is
marked in degrees centigrade corresponding
to the change in resistance. The instrument
itself is a differential voltmeter with three
terminals. The connections are such that
one of the moving coil windings is in series
with a resistance coil which has a zero
temperature coefficient and a resistance
equal to that of the copper temperature
coil, and the other winding is in series with
the copper temperature coil. When the
temperature of the copper coil rises, the
current in that branch of the circuit decreases
656
GENERAL ELECTRIC REVIEW
and causes a corresponding deflection toward
a higher temperature on the scale of the
instrument. The reverse is the case when the
temperature falls.
Tuned Circuit Frequency Indicator
A frequency indicator with a large angular
deflection for each cycle variation becomes a
necessity where great accuracy is demanded.
Semi-Flush Type Instruments
To fill the demand for an inexpensive
instrument for small boards, there has been
put into production two new lines, which are
known as the semi-flush type (Fig. 22). The
two lines comprise ammeters and voltmeters
only for direct current and alternating current.
As the name implies, these instruments fit
into recesses in the panel which receive that
Fig. 22. Alternating-current Ammeter — Direct -current Voltmeter
An instrument known as the tuned circuit
frequency indicator has been produced, which
admirably fills this requirement with its
long scale and large movement of needle for
each small change in frequency. This new
frequency indicator differs from earlier types
principally in that capacity has been added to
the resistance and inductance common to
nearly all other indicators. The value of the
condenser is apparent when it is considered
that in instruments of the moving pointer
type, the entire operating force is obtained
by splitting up the single-phase potential
circuit in such a way that a change of fre-
quency affects one portion to a greater extent
than the other. Inductance is more imper-
vious to higher frequency, while capacity
has an action just the reverse. Therefore, by
combining both inductance and capacity in
proper proportion, it is possible to obtain
an instrument with a much greater movement
of armature and pointer for each unit change
in frequency than can be had with the older
resistance-reactance type.
The tuned circuit frequency indicators are
provided with scales approximately six inches
in length. Normal frequency is marked at
the center, the standard scale markings for a
60-cycle instrument being from 55 to 65
cycles. For special work they can be furnished
with a maximum deflection as low as one
cycle or as high as 10 cycles each side of
normal. The same principle can be applied
to the curve-drawing frequency indicator.
part of the case containing the mechanism,
the necessary holes in the panel being 4f^
inches in diameter. The d-c. instrument has
a D'Arsonval movement and the a-c. is of the
inclined coil magnetic-vane design.
Busbar Support
In stations of large capacity especial
precautions should be taken in supporting
buses in compartments, due to the great
Fig. 23. Busbar Support for Compartments
stresses which are exerted under short circuit
conditions. Fig. 23 shows a late design of
such a support. It consists of two porcelain
insulators, fitted loosely into the horizontal
compartment barriers as shown. Two alloy
clamps of similar design, held apart by four
THE SMALL CONSUMER, A PROBLEM
657
brass pillars fitting loosely into holes in the
clamps, form the support for the bars. The
top clamp has a threaded stud extending into
a hollow in the top insulator. By tightening
the nut on this stud against the top insulator,
the whole support is held firmly in place. By
loosening this nut to the limit of its travel
against the top clamp, it is possible to lift
the top clamp for the reception of new lamina-
tions of bus or to remove the top insulator,
there being just enough play to permit it to
clear the top stud. Subsequently the remain-
ing parts of the support can be easily removed
for repair or inspection. The individual
laminations of the bus are separated by
fillers, and the number of laminations can be
varied. at will by using pillars of the proper
length.
THE SMALL CONSUMER— A PROBLEM*
By A. D. Dudley
Commercial Agent, Syracuse Lighting Co., Syracuse, N. Y.
The small consumer offers a problem that is always present with Central Station managers. In many
instances, no adequate return accrues on investments for this class of consumers. Mr. Dudley discusses both
gas and electric small consumers and takes up the various phases of these problems. — Editor.
the
into
The small consumer problem confronts all
gas and electric companies and deserves
more serious consideration than it has been
given in many locations. Both the gas and
electric companies are interested in the
solution of this problem and, therefore,
subject is treated from both viewpoints.
The small consumer can be divided
two classes:
1. The consumer who is a small user of
gas and electricity and by nature of his
existence offers little, if any, possibility of
development.
" 2. The consumer whose monthly bill is
small because he has never been shown how
or through what medium more gas or elec-
tricity could be used to his own advantage
(as well as to the Company's).
The most striking example of the first class
or the consumer offering little, if any, pos-
sibility of development is found in buildings
having small offices. Even though elec-
tricity is used as much as is needed and in a
diversity of ways, the consumption will always
of necessity be small and in many cases
would be unprofitable without the minimum
bill charge which most electric companies are
allowed.
In such locations, the consumption of gas
is even smaller, in fact, is practically nothing
in many instances. The gas meter is retained
by the consumer for auxiliary or emergency
use and is a burden of expense to the majority
of companies for want of a monthly minimum
* Read before the National Electric Light A^s'n and the
Empire State Gas & Electric Ass'n, May, 1915.
or meter rental. This condition is without
doubt very serious at the present time. A
recent analysis of our ledgers disclosed the
fact that about ten per cent or some 3000 gas
meters yielded us less than 50 cents a month.
For the most part, these meters were located
in offices and rarely, if ever, were used or in
other places where effort to stimulate con-
sumption would be wasted. More serious
still is the fact that, as the use of electricity
becomes more general, the number of gas
meters installed for emergency use will
.materially increase and some provision where-
by the unprofitable consumer can be elimi-
nated, if not imperative, would, to say the
least, be most desirable.
Any company that has not already ana-
lyzed or classified its ledgers will be surprised
at the result. In no other way will the impor-
tance of the small consumer problem be
brought home more forcibly, and the data
thus obtained will give just the material
needed to apply practical methods for a
remedy.
As a result of our own analysis we found
that, in addition to the unprofitable con-
sumers previously named, there were many
more consumers who were using gas and
electricity in a limited way only; and our
total list of small consumers greatly exceeded
our expectations. We found, for instance,
that 1500 electric consumers were using less
than the minimum of $1.00 per month.
The field offers ample opportunity to
increase the yearly revenue and accomplish
the desired end of making the small consumer
658
GENERAL ELECTRIC REVIEW
more profitable. Efforts should be made in
this direction as no additional investment is
required in the way of line extensions, not
even a service meter is needed.
Inspection and maintenance, to a limited
extent, will do much to increase the con-
sumption on appliances now in use. A
consumer may be a small user because many
of his sockets are empty, the oven of the gas
range may be out of commission for the
want of new linings, and the electric iron may
have been laid on the shelf for six months
because of a burned-out element or a broken
plug. Until our sign flashers were placed
under a regular maintenance system for
which the consumer gladly pays, signs were
frequently out of commission and the con-
sumer constantly irritated. Bringing these
matters to the consumer's attention and
aiding him to have them remedied will
necessarily increase his consumption. In
a certain instance an extensive inspection
campaign was carried on in a large city and
it yielded a material increase in revenue.
Demonstration work is closely allied to
inspection work and may well be covered at
one and the same time. This work, covered
more advantageously by women, extends the
use of installed appliances. Many of the
pies, cakes and cookies now bought outside
would be prepared at home if the cook or
housewife understood better the operation of
the gas range oven. It is a well known fact
that thousands of broiling ovens have never
been used for lack of demonstration. The
uses of an electric grill are many. With the
different fittings of a vacuum cleaner, a
variety of work can be done. At the time an
appliance is sold, it may be explained fully
but a demonstration in the home after the
owner has used it very often assures a more
continuous use.
More important than maintenance and
demonstration is the sale of new appliances.
This is the surest way of developing the small
consumer. An analysis of this phase of the
subject should bring out plans and methods
which have been tried and proven effective
in the development of the small consumer.
The important considerations are as follows:
Are you selling the right appliances and
offering wide enough variety ? Is your selling
plan liberal enough to reach the small con-
sumer? Are your prices right? Have you
the right kind of a sales force and are you
paying the salesman enough to warrant your
expecting a more rapid development than
you are getting? These questions are asked
to present different views and ideas and to
learn how the " other fellow " has been success-
ful in making the small consumer a large one.
Whatever the sales plan adopted, it is
vital to know where one stands before he
start lest much time and money be wasted.
It is not only necessary to know what a
small consumer has, it is of greater importance
to know what he has not. No industry has a
better opportunity to keep in close touch with
its consumers. None come in personal
contact with them oftener. Granting that to
a certain extent the small consumer is unavoid-
able in our business as well as in every other
line, nevertheless we all have more than we
should because we allow that condition to
exist. The solution may be a matter of
maintenance or demonstration; the adoption
of an intensive sales plan ; the introduction of
a new appliance or perhaps only more cour-
teous treatment. In any event, there is no
reason why a policy of securing, developing
and holding cannot be adopted and followed
that will reduce to a minimum the number of
small consumers in the territories in which
we operate.
659
MODERN STREET LIGHTING WITH MAZDA LAMPS
By H. A. Tinson
Edison Lamp Works, Harrison, N. J.
The high efficiency Mazda lamp in the larger sizes is being extensively used for street lighting in
the smaller cities and towns, and in the outlying sections of cities of the first class. A number of installa-
tions are illustrated and described in this article, and some recommendations are made respecting the spacing
and height of units, and the reflector equipment for certain conditions of street lighting. — Editor.
Up until the year 1907 very few incan-
descent lamps were used for street lighting
purposes. Those that were employed for this
purpose operated at about ZYi watts per
mean horizontal candle-power, and could only
be obtained in low candle-power sizes. Eight
years ago tungsten filament lamps were
introduced and these marked the successful
application of incandescent lamps to street
lighting on a large scale.
The lamps were made to operate at an
efficiency about three times that of those
hitherto available, i.e., carbon filament lamps.
As a consequence of this development, a very
large number of incandescent lamps were
installed throughout the country. However,
owing to the fact that they were commercially
produced in sizes up to 350 candle-power only,
with the exception of ornamental cluster
lighting, they fulfilled the requirements where
only relatively low power light sources were
needed.
With the introduction of the Mazda tung-
sten filament lamp in high candle-power sizes
last year, a complete change in the field of
application of this lamp took place. The
results of this new development in street
illuminants will undoubtedly be far-reaching,
especially as there are likely to be still further
improvements in this type of lamp. It should
now be quite practicable to light the main
highways in the country districts and it might
be expected that considerable attention will
be given to this class of lighting in the near
future.
In this country most street lighting installa-
tions are operated on the series system and are
controlled by means of a constant-current
transformer or regulator. The Mazda lamp,
especially in the low candle-power sizes, can
be manufactured with a much higher operat-
ing efficiency when designed to use a relatively
high current at a low potential, and it is
therefore particularly suited to series opera-
tion. The current values generally adopted
follow those originally found most suitable
for the enclosed arc lamps, i.e., 6.6 or 7.5
amperes. Mazda series lamps made according
to these ratings offer the largest selection in
candle-power sizes, which range from 32 to
600. One-thousand-candle-power lamps are
made and some even higher have been pro-
duced, but as the filaments in these sizes
operate at a current of 20 amperes a suitable
device at the lamp is used to step up the
series line current to this value. In fact,
auto or series transformers are commonly
used with 400- and 600-candle-power lamps
in order to secure higher efficiency.
From the preceding it must not be assumed
that a series system is always to be preferred.
While series incandescent lamps operate at a
higher efficiency than those of the multiple
type, there are many other factors to consider
before it can be determined whether a series
system is to be preferred to a multiple one.
The multiple lamps are primarily designed to
be used for interior illumination; however,
many thousands of them find application in
street lighting — notably where Edison direct-
current three-wire systems exist, as in the
hearts of several of the larger cities.
Fig. 1 illustrates diagrammatically the steps
which have been made in the development
of the series incandescent lamp during the
last 15 years.
As might be supposed, the advent of Mazda
lamps in so wide an application to street
illumination has necessitated the development
of suitable fixtures and apparatus for their
use. Thus, there have been recently intro-
duced a large number of lighting units, which
may be classified as follows:
Heavy substantial pendent units for high
power lamps.
Light weight, low cost pendent units for
high power lamps.
Pole top units.
Open and enclosed units, mostly for low
power lamps, used on brackets or center
suspensions.
The accessories, such as reflectors, opales-
cent enclosing globes, refracting globes, auto-
660
GENERAL ELECTRIC REVIEW
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MODERN STREET LIGHTING WITH MAZDA LAMPS
661
m
Fig.
transformers, series transformers, cutouts,
sockets, etc., can be obtained in such variety
that there is now practically no class of street
lighting nor local condition that cannot be
adequately provided for when installing
Mazda lamps for exterior illumi-
nation. The fixtures and other
units cover a complete line for
use with multiple as well as with
series lamps.
Mazda series lamps in sizes
up to 250-candle-power, now
produced to operate at effi-
ciencies appreciably higher than
hitherto attainable, are rapidly
replacing the earlier types of
lamps. In the new construction
and method of mounting the
filament, the light source is
concentrated and is placed
lower in the bulb of the lamp.
It therefore becomes desirable
to use especially designed fix-
ture and reflector equipments
in order to insure the most
effective distribution of light.
The low candle-power sizes of
lamps find their greatest field of
application in the lighting of
residential streets and outlying
districts. Lamps of the inter-
mediate size (250-candle-power)
are very frequently used in the
lighting of the main and busi-
ness areas of small cities and
towns. If a suitable reflector
and globe equipment is used and
the units are properly spaced,
this intermediate size of lamp
meets the requirements of
moderate intensity lighting very
well. Figs. 2 and 3 show
examples of 100-candle-power
and 250-candle-power center
suspension units, as used in a
small Pennsylvania town. In
this particular installation , which Fig. 3.
is in many respects typical of
such a class, the smaller sizes of
lamps are used throughout the residential and
outlying sections and the 250-candle-power
lamps on the principal business streets. All the
units are equipped with concentric reflectors
and prismatic refractors, so as to distribute the
light as uniformly as possible throughout the
relatively wide spacings adopted. The spacing
of the lamps in this installation is not uniform,
due to the irregularity of the street intersec-
tions, the curved roads, and the hilly nature of
the streets. The average height of the units is
about 18 or 19 feet.
The new sizes of Mazda lamps (400-, 600-,
and 1000-candle-power in the series type, and
niiiHT
2. Day View of Washington Street, Sellersville, Pa., showing G-E eye
suspension fixtures equipped with concentric reflectors, prismatic
refractors and 100-c.p. 6.6-amp. series Mazda lamps
Day View of Main Street, Sellersville, Pa., showing G-E eye suspension
fixture equipped with concentric reflector, prismatic refractor
and 250-c.p. 6.6-amp. Mazda lamps
300-, 400-, 500-, and 750-watt in the multiple
type) are being employed for lighting city
streets in many places. In several cities,
where high power light sources have been
commonly employed in the illumination of
both business areas and suburban sections for
several years, the older illuminants have been
replaced, unit for unit, by high candle-power
Mazda lamps with excellent results.
662
GENERAL ELECTRIC REVIEW
When installing new
opportunity often
units, however, an
occurs to improve the
illumination at a small outlay. Suspension
heights can sometimes be made more uniform
and the spacings more regular. In tree-
Fig
4. Day View of Street in Carlisle. Pa., showing Novalux pendent units equipped
with 600-c.p. 20-amp. Edison Mazda lamps and prismatic refractors
Fig. 5. Night View of Street shown in Fig. 4
covered areas it is frequently advantageous
to mount the units lower than those they are
replacing. With lower mounting heights
smaller lamps should be used with closer
spacings. In this manner, the sidewalks can
be better illuminated and the lighting much
improved in uniformity. Figs. 4 and 5 show
day and night views taken in a city illuminated
by ( i0( i-candle-power Mazda series lamps.
The units used in this case are known as
"Novalux Form-2," which are of the pendent
type and are equipped with auto-transformers,
dome reflectors, and prismatic refractors.
The auto-transformers are contained in the
housings of the units and are
used to step up the line current
from 6.6 amperes to 20 amperes.
As will be noted in the night
view, Fig. 5, the illumination is
of high intensity and is uniform.
The spacings of the units are
not equal but varv between 300
and 400 feet.
A typical example of the
illumination afforded by Mazda
units in a large eastern city is
shown in Fig. 6. In this case
reflectors were not used on
account of the relatively narrow
spacing (200 feet), the appear-
ance of the unit, and the desire
for illumination on the faces of
the buildings. The lamps used
in these units are of the 400-
candle-power 1 5-ampere type
and are mounted IS feet 6 inches
above the sidewalk.
A good example of modern
bridge lighting by means of
pendent type Mazda units is
shown in Fig. 7. These units
are equipped with the radial
wave type of reflector. The
lamps used are of the 300-watt
multiple type, are suspended
about 16 feet high, and the
character of the lighting pro-
vided by these units is very
satisfactory with the spacings of
120 feet at which they are
installed.
The radial wave reflector is
quite effective and gives a fairly
wide distribution, but as it is
used without a diffusing globe it
is seldom applicable for use with
the higher power lamps. Some
installations are now in opera-
tion using this type of equipment with 250-
candle-power series lamps and 300-watt
multiple lamps.
The ornamental post type of lighting,
which originally was introduced through the
initiative of business men in many cities,
has now developed to j very considerable
proportions. The demand for such systems of
lighting is still unabated but single units are
MODERN STREET LIGHTING WITH MAZDA LAMPS
663
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G65
now preferred in place of the clusters that so
generally were favored before the advent of
the high power Mazda lamps.
It is now possible to avoid running the high
tension series line to the top of the ornamental
post. A small waterproof transformer may
be placed either in or near the base of the post
to step up the current and also to provide
insulation. Even on open circuit, the potential
at the socket does not exceed 100 volts with
the largest size lamp.
The advantages of the single light unit
over the cluster may be briefly summarized
as follows:
(1) Improved appearance in perspective
on the street, both by day and by
night.
(2) More effective distribution of the light.
(3) Large lamps operate at a higher
efficiency and give greater brilliancy
in appearance.
(4) Maintenance cost is considerably re-
duced both in respect to the number
of lamps and the enclosing globes.
An up-to-date example of this class of
lighting is shown in Figs. 8 and 9. Fig. 8 is
a daylight view of a business street in a small
town in western New York. The units used
are " Novalux Form-5," equipped with auto-
transformers and 600-candle-power 20-ampere
Mazda lamps operated from a 6.6-ampere
series circuit. The mounting height to the
center of the globe is 13 feet and the average
spacing along one side of the street is 134
feet. The staggered arrangement, of posts
was adopted and is very satisfactory for this
spacing. In this instance the lamps are
installed on two circuits, which permits of
somewhat more than half the units burning
all night and the remainder until midnight.
They are so arranged as to provide good
illumination at intersecting streets all night.
A double circuit is run to each post, so that
any particular lamp may be connected either
to the all-night or to midnight circuit. The
midnight circuit is controlled by a time clock.
Fig. 9 illustrates a night view of this installa-
tion with all the units burning.
Another example, similar in character to
that just described, is shown in Fig. 10.
This is in another town in western New York.
The average spacing, however, is somewhat
closer, being 100 feet, and four units are
placed at each street intersection. There are
74 of these units, using 400-candle-power
15-ampere Mazda lamps operated from a
6.6-ampere series circuit. The mounting
height is 13 feet 6 inches and the posts are
placed opposite one another. With the
closer spacing and lower candle-power lamps
in this case, the arrangement is well chosen.
In both the previously described instances
the property owners or business men bore a
large share of the cost of the installations,
the cities and lighting companies co-operating.
The ornamental lighting unit is also becom-
ing popular for the general lighting of resi-
dential streets. The Pacific Coast cities have
many examples of this class of lighting and
many cities in the East are rapidly following
suit. The illustrations given in Figs. 11, 12,
and 13 are typical of what has been done to
beautify the appearance of the avenues of a
progressive city in central New York. Fig. 11
depicts a residential street lined with heavy
foliage. In this case 100-candle-power Mazda
lamps are used, mounted about 10 feet high
and enclosed in opalescent globes. The
spacing varies according to the character of
the streets. The posts are of reinforced
concrete and the top fitter is of imitation
bronze. Not only is the illumination provided
by these units adequate, but it will be noted
that the foliage does not obstruct the light
from the roadway and sidewalk.
Figs. 12 and 13 show a day and a night view
of a main thoroughfare. While it is strictly
residential, the street is wide and traffic
relatively heavy, so that higher power units
are necessary for proper illumination. Mazda
lamps of 1000-candle-power are used. They
are enclosed in 18-inch opalescent globes,
mounted 14 feet 3 inches above the ground.
In this particular installation there are 57 of
these units spaced about 200 feet apart along
the street, in a staggered arrangement.
Space has permitted only brief descriptions
of a few installations. In spite of the short
time since these new lamps have been avail-
able, many installations are already in opera-
tion and these have been rendering excellent
service.
Thus the Mazda lamp is becoming a more
and more important factor in improving
all classes of street lighting.
666
GENERAL ELECTRIC REVIEW
PRACTICAL EXPERIENCE IN THE OPERATION OF
ELECTRICAL MACHINERY
Part IX (Nos. 47 to 50 inc.)
By E. C. Parham
Construction Department, General Electric Company
(47) THE WRONG SHUNT RATIO
Fig. 1 illustrates a method of increasing
the capacity of an ammeter so that it can be
used to measure currents that exceed its
range. The largest copper wire that can be
passed through the terminals is drawn
through them forming a loop in parallel with
the meter. The meter and wire are then used
as a single unit, and the value of the current
indicated by the meter depends upon the
loop length, which can be varied.
be multiplied by two in order to get the total
current flowing in the circuit.
Station ammeters and shunts are con-
nected in this manner (the meter carrying
only a small part of the current) but the dial
is marked as if the meter carried all of the
current. In portable work, milli-voltmeters
are used in conjunction with standard shunts.
Such sets have a stated maximum capacity
and several taps may be brought out of the
shunt as indicated in Fig. 2. The multiplying
a
Connect ingS/eeve
Fig. 1
Fig. 2
Using a steady source of current, the
calibration of the meter and shunt is carried
out as follows: It is desired to read 225
amperes on a 100-ampere ammeter, for
example. With only the meter in circuit,
adjust the current to 75 amperes; then close
the loop through the connector, tightening
the screws, and vary the loop length (by
drawing one end through a meter terminal)
until the reading is 25 amperes. (Each time
that an adjustment is made the binding-post
screw that is loosened for drawing through the
wire must be tightened.) A current of 75
amperes still flows; but, as the meter carries
only one-third of the current, the meter
reading must be multiplied by three in order
to obtain the value of the current in the
circuit. With an adjustment for example
such that the closing of the loop reduces the
meter reading to one-half, each reading must
factor to be used depends upon the tap that
is employed. Assuming that tap 1 is so chosen
that the meter reads 100 divisions when the
current is 100 amperes, the meter then
is direct reading and no multiplying factor
for the reading should be used. If another
tap, for example tap 2, includes twice as
much of the resistance of the shunt as tap 1,
a line current of 100 amperes will deflect
the needle through 200 divisions, and with
this connection the actual current will then
be but half of that indicated on the meter.
i An operator called in an inspector because
an exciter apparently was taking about twice
the amount of current that it should and
still was unable to furnish sufficient exciting
current to its alternator td maintain normal
alternating voltage. As is so often the case,
the exciter had no switchboard ammeter.
The operator was using a milli-voltmeter-
OPERATION OF ELECTRICAL MACHINERY
GOT
shunt combination that he had borrowed.
In connecting the milli-voltmeter to the shunt
he had used tap 2 instead of tap 1, thereby
making the apparent current twice the
actual current.
Upon increasing the exciter current, the
alternating voltage promptly became normal.
Had the tap been one such that the con-
nection would have caused the meter to
indicate but half of the current flowing, the
result might have been more serious had the
operator undertaken to load his exciter
according to the indication of the meter.
(48) REPULSION MOTOR HEATING
In Fig. 1, showing the internal connections
of a single-phase repulsion-induction motor,
the field coils brought to the terminals
outside of the motor are the main field coils
that correspond to the stator coils of an
ordinary induction motor. These connect
to the supply lines through a suitable switch.
In the actual motor, however, they are divided
into pairs and the pairs can be connected
in series or in parallel, accordingly as the
line voltage may be 220 volts or 440 volts.
The inner field coils are wound concentrically
with the main field coils and are called
compensating field coils because they oppose
and neutralize the armature reaction, thereby
preventing sparking. The compensating field
coils are connected to brushes 3 and 4 and
their exciting current is due to the rotation
of the armature. Since their polarity is the
same as that of the main coils and since
Fig. 3
their effect increases with the armature speed,
it is evident that they act to limit the speed
at very light loads. The brushes 1 and 2 are
short-circuited. These carry the current
which, being repelled by the main field,
causes the armature to rotate.
An operator complained that his repulsion
induction motor was heating too much. An
ammeter was connected into the stator circuit
and it indicated 30 per cent current overload ;
notwithstanding this overload, the armature
speed was about 200 r.p.m. too high. The
brushes sparked very little, but both the
brushes and the commutator ran hot. These
symptoms suggested a reversed compensating
field, which proved to be the case.
Upon reversing the compensating brash
leads, every sign of sparking disappeared,
the speed decreased about 150 r.p.m., the
current decreased from 8 amperes (30 per
cent overload) to about 2^ amperes (the
amount required for the load carried when
the motor was connected properly) and the
heating lessened correspondingly.
(49) VARIABLE-SPEED MOTOR ON
AN INERTIA LOAD
A variable-speed motor must commutate
satisfactorily at the comparatively high speed
that is incident to a weakened field, and this
requirement is sufficiently exacting without
imposing severe local conditions to aggravate
matters. It was necessary to diagnose a case
of bad flashing of a shunt-wound, variable-
speed, reversible motor that was connected
to a centrifugal drier. The motor was
operated from service lines that also supplied
several heavy motors which were frequently
started and stopped. The flashing did not
seem to depend so much upon what the motor
itself was doing, as it did upon what was
going on in other parts of the plant. The
motor would be operating with perfect
commutation, when suddenly there would
develop a tendency to flash-over between the
brush-holders, the brushes would spit a few
times, and then the operation would become
normal again.
The causes of these irregular actions were
about as follows. As long as the motor with
its connected load, which had a great deal of
inertia, was supplied by a constant line volt-
age it ran faultlessly; but as soon as the
starting of a heavy motor elsewhere pulled
down the line voltage, the motor (unable to
at once reduce its speed to a value correspond-
ing to the existing voltage) would act as a
generator and would "pump" into the line,
which additional load thus imposed would
slow the centrifugal motor. During the next
instant the throwing off of a large motor
elsewhere would suddenly raise the line volt-
age which would cause the slowed motor to
668
GENERAL ELECTRIC REVIEW
draw a heavy current that would always
cause sparking and which would sometimes
cause a flash-over. Owing to the fact that
the best position of the brushes for a motor
is not the best position when the machine is
operating as a generator, a change from motor
to generator would alone account for the
tendency to flash. Also, it is easy to account
for flashing without the generating feature;
for assuming a case in which the line voltage
was lowered so gradually that the speed of
the motor could respond there would then be
no generation, but the sudden increase in the
line voltage, incident to a sudden decrease
in the service load elsewhere in the mill,
would cause a flash-over because of the
increase in motor current.
Under ordinary conditions the installing of
overload devices and of reverse-current
devices would have helped matters, but in
the plant concerned it was undesirable to do
anything that would interfere with the
continuous operation of the motor. Should
the automatic devices have operated when
no one was near, considerable valuable time
would be lost. The problem was solved by
increasing the amount of copper in the dis-
tributing mains and by installing a com-
pensating voltage regulator to over-compound
the system for constant voltage at the center
of distribution.
(50) SERVICE VOLTAGE TOO LOW
Standard induction motors will operate
satisfactorily on voltages that are as much as
10 per cent greater or 10 per cent less than
that for which they have been designed.
A greater departure than this from the rated
voltage is likely to result in unsatisfactory
operation, especially if the connected load is
such as to require approximately the full
rated load of the motor. In practice, induc-
tion motors are more often subjected to
abusive conditions of low voltage than they
are to those of high voltage. When the volt-
age is abnormally low, unsatisfactory starting
characteristics result because the starting
power of an induction motor varies as the
square of the impressed voltage; in other
words, the starting power decreases much
more rapidly than does the impressed voltage.
Table I gives the percentages of full-load
torque that correspond to given percentages
of full impressed line voltage, and also the
percentages of torque decrease that cor-
respond to given percentages of decrease in
impressed voltage. For example, when the
applied voltage is 50 per cent of normal the
torque is only 25 per cent of the torque
corresponding to full voltage. Looked at in
another way, noting columns 3 and 4, a 50
per cent reduction in the applied voltage
causes a 75 per cent reduction in the resulting
torque. Many specific instances might be
cited wherein complaints of unsatisfactory
operation of induction motors have been
investigated and the source of all the unsatis-
factory operation found to be due to abnor-
mally low voltage. Perhaps the most trouble-
some condition for the operator to detect
is that in which a motor promptly starts its
connected load for some time after being
installed, but later begins to lose its starting
power on account of the line or the trans-
former from which it draws its energy
becoming gradually overloaded, as a result
of having further devices added from time to
time. Where the gradual overloading is due
to the addition of other motors in the same
service, the operator is more likely to suspect
the condition just named, but where the
overloading involves several plants that
draw their energy from the same trans-
former, or from the same mains, the cause is
not so evident.
TABLE I
Per Cent
Per Cent
Per Cent
Per Cent
Normal
Normal
Voltage
Torque
Voltage
Torque
Decrease
Decrease
100
100
0
0
90
81
10
19
80
64
20
36
70
49
30
51
60
36
40
64
50
25
50
75
40
16
60
84
30
9
70
90
ERRATA
In the article "Parallel Operation of Alternating-Current
Generators," General Electric Review, March. 1915. the
following changes should be noted:
Page 172. left-hand column, line 16, the word "different"
should be "definite."
Page 177, Table I:
Footnote (A) applies to the column headed "Longest
Torque Period."
Column C, Oil Engines, line 4, the formula 1.02X10*(K: +
0.45 P) should be 1.02 X10*(A' -0.45 P).
Same column, line 5, the formula 4.8 X107(A' +1.12 P) should
be4.8X10'(K-1.12 P).
Same column, line 2. the formula 2.4 X88P should be
2.4X10* P.
669
FROM THE CONSULTING ENGINEERING DEPARTMENT OF THE
GENERAL ELECTRIC COMPANY
TEMPERATURE COEFFICIENT FORMULAE
FOR COPPER
In the International Electro Chemical
Publication No. 2S, "International Standard
of Resistance for Copper," published in
March, 1914, this rule appears: "At a
temperature of 20 deg. C. the 'Constant
mass' temperature coefficient of resistance
of standard annealed copper, measured be-
tween two potential points rigidly fixed to
the wire, is 0.00393=1/254.45 per degree
Centigrade." Since this rule was written the
U. S. Bureau of Standards has used it in
Circular No. 31 as a basis of copper wire
tables and the rule has been formally stand-
ardized in the Standardization Rules of the
American Institute of Electrical Engineers,
Edition of December 1, 1914. The figure
given above should therefore be used in
temperature coefficient tables and formulae.
In the 1914 A.I.E.E. rules the necessity of
using a change of temperature coefficient for
a change of initial temperature is emphasized
in Paragraph 178.* The table included in that
paragraph shows the increase in the tem-
perature coefficient. The rule applying to the
increase follows:
"In the case of resistance measurements,
the temperature coefficient of copper shall be
deduced from the formulae ~„. . " where I
234.5 X J
is the initial temperature from which measure-
ments are made.
The above formula is a very convenient
one, accurate approximations can be secured
by its employment, and its natural sequence
of numbers allows it to be easily memorized.
For some time approximations have been
made by the well-known formula
Rh=Rc[lXa(Tb-Tc)] (1)
where
Rh = resistance at the hot or final tem-
perature.
Rc = resistance at the cold or initial tem-
perature.
7";, = hot or final temperature.
a = the temperature coefficient. From 0
deg. C, a has usuallv been taken as
0.0042, but under the 1914 rules should
be taken as 0.00427.
(Th—Tc), which is the temperature rise,
is often expressed as t.
* It is expected that a revised edition of the "Standardization
Rules of the A.I.E.E." will be distributed soon; in this edition
the quoted rule will appear unchanged but under a d-fferent
paragraph number.
The new values, a, la and the standard
reference temperatures are as follows :
Temp.
A" = l/„
0
234.5
0.00427
20
254.5
0.00393
25
259.5
0.00385
40
274.5
0.00364
Standard temperature of reference 20 deg. C.
Ambient temperature for water-cooled
machinery 25 deg. C
Ambient temperature of reference for air. 40 deg. C.
For general use it would possibly be better
to reconstruct the working formulas in order
to take care of any initial temperature without
having to introduce any numerical factor
other than the easily remembered 234.5
After revising formula (1) to take care of the
varying temperature coefficient for varying
initial temperatures, the formula becomes
Th-Tc • (2)
Rh = R,
r 7w,i
[1+234.5 + rJ
or possibly it may be more convenient to
memorize in the form
Rh = Rc
[SIS] <»
[234.5 + Tc
If it is desired to find the final temperature
for a given resistance we find
_23±.5 Rc + Th Rc
'' 234.5 + Tc
234.5 Rh+Tc K& = 234.5 Rc+Th Rc
234.5 fo-234.5 Rc+Tc Ri,
Rc
234.5 (Rh-Rc) + TcRh
Th
Rc
Solving for the initial temperature
234.5 (Rc-Rh) + T„Rc
Tc = '
Rh
and for initial resistance
r234.5+7V
Rc = Rh
[•234.5+ Tl
[234.5+ T h\
Rc = Ri
ri+-r-^-i
[i+234.5 + r*J
(4)
(5)
(6)
(7)
234.5+ 7\|
John D. Ball
670
GENERAL ELECTRIC REVIEW
QUESTION AND ANSWER SECTION
The purpose of this department of the Review is two-fold.
First, it enables all subscribers to avail themselves of the consulting service of a highly specialized
corps of engineering experts, or of such other authority as the problem may require. This service provides
for answers by mail with as little delay as possible of such questions as come within the scope of the Review.
Second, it publishes for the benefit of all Review readers questions and answers of general interest
and of educational value. When the original question deals with only one phase of an interesting subject,
the editor may feel warranted in discussing allied questions so as to provide a more complete treatment
of the whole subject.
To avoid the possibility of an incorrect or incomplete answer, the querist should be particularly careful to
include sufficient data to permit of an intelligent understanding of the situation. Address letters of inquiry to
the Editor, Question and Answer Section, General Electric Review, Schenectady, N. Y.
TEMPERATURE: KELVIN SCALE
(141) What is the basis and arrangement of the
Kelvin scale of temperature?
At constant pressure a given volume of a perfect
gas expands 1 ,'273 of its volume at 0 deg. C. for
each rise of 1 deg. C, and contracts at the same rate
for the same decrease of temperature. Consequently,
at —273 deg. C. the volume would apparently vanish,
if the gas laws were valid at this temperature. For
this reason, as well as those based on the second law
of thermodynamics, this temperature has been
chosen as the zero of the so-called Kelvin or absolute
scale. Temperatures on this scale are obtained from
the temperatures on the centigrade scale bv adding
273, i.e., T (Kelvin) =/ (centigrade) +273. (The
more accurate value of absolute zero on the centi-
grade scale is —273.1 . deg., hence in very exact
experimental work this value should be used rather
than the more commonly emploved value — 273.1
E.C.S.
THREE-WIRE SYNCHRONOUS CONVERTER:
CONNECTIONS AND UNBALANCED LOAD
1,142) Referring to diagrams Fig. 1 and Fig. la
which appeared in the article "The Edison
Three-Wire System," GENERAL ELECTRIC
REVIEW, March, 1914, will you please explain
the following points?
(1) Why is it necessary to have the middle
point of each transformer connected by a separate
switch to neutral?
2 What amount of unbalance will the con-
nection described take care of properly?
3 Kindly give an explanation of the division
of unbalanced current through the transformers
as indicated in Fig. la.
1 It is necessary to have. the neutral from each
transformer on a separate switch to neutral if the
synchronous converter is to be started by secondary
starting taps on the transformers. This will be
if one considers that the starting switch, when
connected to the half-voltage taps at the time of
start, would be short circuited by the neutral
-witch were this latter switch permanently i I
The usual method of starting from the alternating-
current side is by means of £j and % starting taps
in the transformer secondary. This would give the
same effect as the half-voltage starting, except that
there would not be a dead short circuit. Another
■ realize the n< if opening I
is to regard }4 of the secondary of each transformer,
or of each phase, considering the transformer as a
three-phase unit connected directly across the
synchronous converter. If, now, the neutral switch
is not open, the synchronous converter is short
circuited through }4 of the transformer winding.
Fig. 1. Complete Diagram of Connections for a Six-Phase
Three-Wire Synchronous Converter
(General Electric Review, March, 1914)
QUESTIONS AND ANSWERS
671
(2) The amount of unbalancing which this
connection will take care of properly depends
entirely upon the design of the synchronous con-
verter. With the straight synchronous converter,
that is, one having main poles only, an unbalancing
in neutral current up to 50 per cent of full load line
current is permissible; 25 per cent has been the
standard in the past. With a commutating-pole
converter the windings on the commutating-poles
must necessarily be split, and even under this
condition a heavy unbalancing may affect commu-
tation. It is seldom desirable, therefore, to attempt
to allow for more than 10 per cent unbalancing
unless the converter is especially designed for a
GENERATOR: INPUT AT 70 AND 100 PER
CENT POWER- FACTORS
(143) Does a Diesel engine or other prime mover
require as much fuel to drive a generator carrying
a 500-kv-a. load at 70 per cent power-factor as
it uses when the generator is under a load of 500
kv-a. at unity power-factor?
No; more fuel will be required when the generator
supplies 500 kv-a. at unity power-factor. The
copper loss (I„-R„) in the armature, the core loss,
and the friction and windage loss in the generator
are about the same for 500 kv-a. at 70 per cent power-
factor as at unity power-factor; but the copper loss
Fig. l-a. Simplified Diagram of the Connections Shown in Fig. 1
(General Electric Review, March, 1914)
Fig. 2-a. Simplified Diagram of Connections for Using a Three-Phase Core-Type Transformer
(Three-Phase Converter)
(General Electric Review, March, 1914)
greater percentage. (The above figures are not
necessarily guaranteed.)
(3) The current io (Fig. l-a), returning through
the neutral as the result of unbalanced load, will
divide into six equal parts as the transformer is
connected electrically at six equi-distant points
on the converter armature. This is similar to the
three-phase connection shown in Fig. 2-a, which
was explained in detail in No. 89 of the Question
and Answer Section of the same issue of the Review.
The principal difference between Fig. l-a and Fig.
2-a is that in Fig. 2-a the currents in the trans-
former legs are not neutralized, whereas in Fig. l-a
the currents in any one winding are completely
neutralized since they are equal and opposite to
each other.
R.TT.T.
(I/-Rr) in the field for 70 per cent power-factor
operation is greater than that resulting from unity
power-factor operation.
If the generating set referred to in the question is
of average speed, the total generator loss at 500
kv-a. output at 100 per cent power-factor m'ay be
assumed for convenience to be 30 kw. This loss
may be reasonably expected to increase to 35 kw.
when the generator furnishes 500 kv-a. at 70 per
cent power-factor.
Thus the output of the prime mover (the factor
determining the fuel consumption) is
For 500 kv-a. at 100 per cent p-f :
(500X1.00) +30 =530 kw.
For 500 kv-a. at 70 per cent p-f:
(500 X,'^,) +35 =385 kw.
inn
E.C.S.
IN MEMORIAM
The death of John P. Judge, Manager of the Baltimore
Office of the General Electric Company, which occurred on
January 26th, marks the passing of an old and valued
employee of the Company. Mr. Judge was first associated
with the Edison Company in October, 1890, and became
an employee of the General Electric Company in Novem-
ber, 1904, at which time he was placed in charge of the
power and mining business of the Baltimore territorv. For
the succeeding eighteen years his activities were responsible
JOHN P. JUDGE
for many of the most notable industrial applications of
electricity in that territory, and in November, 1912, he
was made acting local manager of the Baltimore office.
Mr. Judge was born in the City of Baltimore, where a
large part of his business career was spent. His death,
which occurred at the age of sixty-two years, was due to
apoplexy. He is survived by his wife, two sons and four
daughters. He was actively identified with church and
social betterment work, and his business acumen and
technical ability were combined with a personality which
make his loss keenly regretted among all those who came
in personal contact with him throughout the organization.
General Electric Review
A MONTHLY MAGAZINE FOR ENGINEERS
„ ., ~ t^t-^t, — ,., IAIIXI „ TT„_T___ Associate Editor, B. M. EOFF
Manager. M. P. RICE Editor, JOHN R. HEWETT . _,. ' _ n*„nnnr*
Assistant Editor, E. C. SANDERS
Subscription Rates: United States and Mexico. $2.00 per year; Canada, $2.25 per year; Foreign, $2.50 per year, payable in
advance. Remit by post-office or express money orders, bank checks or drafts, made payable to the General Electric Review,
Schenectady, N. Y.
Entered as second-class matter, March 26, 1912, at the post-office at Schenectady, N. Y., under the Act of March, 1879.
VOL. XVIII., NO. 8 tyG^eTd&ulLpany AUGUST, 1915
CONTENTS Page
Frontispiece 782
Editorial : The Paths of Progress 783
The Trend of Electrical Development 784
By Paul M. Lincoln
Economies in Operating Small Cars 790
By J. F. Layng
Radiography of Metals 795
By Dr. Wheeler P. Davey
Air Cleaning Apparatus for the Ventilation of Generators and Transformers . . .801
By William Baum
The Individual and Corporate Development of Industry 813
By Dr. Charles P. Steinmetz
The Cathode Ray Tube and Its Application 816
By M. E. Tressler
Law of Corona and Spark-Over in Oil 821
By F. W. Peek, Jr.
The Operation and Rating of the Electric Locomotive 828
By A. H. Armstrong
Emergency Transformer Connections 832
By George P. Roux
Parallel Operation of Frequency Changers 836
By G. H. Rettew
Principal Factors Governing the Choice of Method of Cooling Power Transformers as
Related to Their First Cost and Operating Conditions 839
By W. S. Moody
The Contact System of the Butte, Anaconda & Pacific Railway 842
By J. B. Cox
From the Consulting Engineering Department of the General Electric Company . . 860
Practical Experience in the Operation of Electrical Machinery, Part X . . . .861
Stations in Series ; Parallel Transformers ; Transformer Connections
By E. C. Parham
Question and Answer Section ... 863
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THE PATHS OF PROGRESS
We publish in this issue Mr. Lincoln's
presidential address before the American
Institute of Electrical Engineers delivered at
the recent annual convention held at Deer
Park, Md. Those reading this address must
be impressed anew with the wonderful
achievements of the electrical engineer —
The average efficiency of electric generators
and motors, when both small and large units
are considered, is 90 per cent; large trans-
formers may reach the extraordinarily high
efficiency of 99 per cent; and rotary converters
can approach 98 per cent efficiency. Such
accomplishments are hard to realize and
appreciate, but it must be constantly borne
in mind that it is these achievements that
have given electricity its unique position in
the industrial world.
There is still a large margin left for pos-
sible improvement in steam prime movers,
although the efficiency of large modern steam
turbines is something thought quite unat-
tainable but a few years ago. It is apparent
from Mr. Lincoln's address that our rate of
progress in the future must be slower than in
the past, but this statement only refers to
progress in attaining higher efficiencies in
specific apparatus.
In this connection it is interesting to try to
see in what directions we may look for future
progress even if we eliminate the possibility
of any great new discoveries that may make
as radical changes in our industrial life as
electricity has made during the last three
decades.
We feel that the extension of the applica-
tion of electricity is inevitable and that this is
true both in regard to applications already
attempted, with partial or full success, and
in a myriad of directions as yet unthought of.
That electricity is seriously contemplated for
the propulsion of large steamships and that it
is already extensively used on self-propelled
gas-electric railway cars goes to show that
the inherent features of electric control are
destined to play a part of ever increasing im-
portance in our future developments. In both
of these instances the prime mover is carried
as an essential part of the equipment whether
electrical apparatus is used or not. Elec-
trical apparatus is an addition which at first
sight would appear to complicate matters and
to add considerable weight to the equipment ;
but the addition of the electrical equipment
to the mechanical secures such a flexible
control of the energy used, and at the same
time eliminates large cumbersome mechanical
gearing such as speed-changing devices, etc.,
that the addition of both an electric generator
and motor leads to an added efficiency of the
whole equipment.
The same general principle with modifica-
tions is now being applied to the automobile
with every prospect of marked success; and
here again we look for wonderful develop-
ments which will be entirely due to the recogni-
tion of the fact that an electrical link in our
chain of energy conversion gives us refine-
ments in the control of energy that enable us
to obtain the maximum power at the essential
periods, a higher overall efficiency with a
minimum total expenditure of energy, and a
minimum total weight.
Over and above these opportunities for an
advancement in the art of electrical engineer-
ing there are the ever attractive fields of
electric lighting and electric heating, the
limits of which are not at present even con-
templated.
It is most interesting to review the past
progress as Mr. Lincoln has done in his able
address, but it is even a greater fascination
to anticipate some of the possibilities of the
future. The electrical industries are among
the most highly developed of the age and yet
the possibilities for the future of these same
industries seem to be absolutely limitless.
Each step of progress seems to lead us to new
possibilities and the electrical engineer is
constantly entering new fields and proving
that things can be done more economically
and more efficiently electrically than by any
other means.
784
GENERAL ELECTRIC REVIEW
THE TREND OF ELECTRICAL DEVELOPMENT
By Paul M. Lincoln
President of the American Institute of Electrical Engineers
In the presidential address before the American Institute of Electrical Engineers, Mr. Lincoln shows
among other things the progress made in the development of electrical machines. The average efficiency of
electric generators and motors, including both small and large, is given as 90 per cent, showing clearly that
small future progress can be made in this direction. The approach towards perfection is further emphasized
by stating the fact that some large transformers have an efficiency of 99 per cent and some rotary converters
approach 98 per cent efficiency. A statement of the room left for improvement in the development of water-
wheels and in thermo-dynamic engines forms an interesting part of the author's theme. He shows that our
rate of progress in the future must be smaller than in the past and substantiates his statements by quoting
from Mr. A. E. Kennelly's inaugural address delivered at Omaha in 1898. The author also shows in what
direction future progress may be looked for. We believe that our readers will get considerable pleasure from
reading this able address. — Editor.
An annual address by the President of our
Institute is more than a perfunctory affair.
It is a constitutional requirement. It is
enumerated specifically in our constitution
among the duties of the President — "He
shall deliver an address at the annual con-
vention."
It has occurred to me that in my address
on this occasion it might be well to trace the
progress of some of the developments and
practices that have marked the path that the
electrical engineer has traversed in the past
with a view of obtaining some idea possibly
as to whither these paths may lead us in
the future. Insofar as this method incor-
porates a review of the past it presents no
particular difficulty; but when it involves a
prognostication of what a continuation along
any particular line of development will finally
lead to, it delves somewhat into realms of
prophesy. I realize full well that anyone
who attempts to deal in prophesy among the
inventions and developments of this day and
age is running a grave risk, and I therefore
do not propose to wander far from what I
conceive that the trend of present develop-
ment will carry us in the future.
In the matter of efficiency, it has always
been recognized that electrical apparatus is
in a class by itself. Mechanical energy can
be converted into electrical by a generator,
or vice versa, by a motor at an efficiency
ranging up to as high as 97 per cent, or even
more in the most favorable cases. I think
it is a safe statement to say that the average
efficiency by which the conversion of mechan-
ical energy into electrical by generators or
electrical energy into mechanical by motors,
including all sizes under actual operation
conditions, will reach 90 per cent. There are,
of course, many cases where the efficiencies
are lower than 90 per cent. On the other
hand, there are many cases where the con-
version is carried on at much higher efficiencies
and I believe that the assumption of 90
per cent as an average figure is not far from
the truth. Owing to the fact that the size
of the average electrical generator is much
greater than that of the average motor and
that it is possible to operate the generator
at higher average loads than is the case of
the motor, it must be apparent that the
average efficiency for converting mechanical
energy into electrical is higher than the
reconversion of this electrical energy back
into mechanical. The average generator
efficiency is undoubtedly well above 90 per
cent while it is doubtful if the average motor
reaches so high a figure. However, the general
conclusion I would draw from these figures
is not modified by this difference between
generator and motor. This conclusion which
must be apparent to anyone is that no
development of a revolutionary character
can be looked for in this respect. Our ability
to convert mechanical energy into electrical
or vice versa has reached so high a value
that even if we could obtain perfection itself
we could add only a matter of 10 per cent to
what we have already accomplished. This
conclusion must hold unless the law of
conservation of energy is revoked and I am
not predicting any suspension of that law.
When we come to deal with the efficiencies
by which electrical energy in one form is
transformed into electrical energy of another
form, efficiencies are found to be still higher.
The efficiencies of some of our larger trans-
formers for instance exceed 99 per cent. The
rotary converter, in which alternating current
is changed into direct, attains efficiencies
approaching 9S per cent. It is evident that
perfection itself could not add greatly to
existing performances and hence nothing
revolutionary may be expected along this
line in the future.
When we come to consider the prime
mover, we find a marvelous improvement
THE TREND OF ELECTRICAL DEVELOPMENT
785
in recent years. Taking up first the water-
wheel, the early attempts to develop power
at Niagara Falls constitute a significant
commentary upon the status of the water-
wheel at that time (the late 60's and the
early 70's). About this time the building
of what is now known as the Schoellkopf
Canal at Niagara Falls made available a head
of about 215 ft. at the edge of the cliff below
the falls on the American side. Of this
215-ft. head these earliest wheels used only
some 15 or 20 ft. for. some of the least pro-
gressive and from there up to possibly
40 or -50 ft. for the more progressive. After
passing through the wheels under this head,
the water was then discharged at the face
of the cliff and fell uselessly for the remainder
of the distance, much to the detriment of the
scenic beauty of the bank. And not only
was it impossible at that time to obtain
waterwheels that would work under more
than these very limited heads but the effi-
ciencies of such as were used were very far
below those attainable now. Today, water-
wheels have no limit in head except that
imposed by the strength of available ma-
terials, and efficiencies ranging up to 90
per cent are expected as matters of course.
Improvements in waterwheel design will,
of course, continue, but perfection itself
would add but a matter of 10 per cent to the
best of our modern practice and not to exceed
20 to 25 per cent to the worst. Therefore,
in waterwheels, as well as in motor and
generator practice, we are approaching the
limits set by natural laws almost as closely as
human ingenuity can be expected to attain.
No startling or record breaking developments
need be expected along these lines so long as
the law of conversion of energy holds.
In thermo-dynamic engines, too, the last
few years have some marvelous improve-
ments. The reciprocating engine of Watt
has largely given place in recent years to the
steam turbine and the use of the turbine has
enabled us to attain efficiencies in thermo-
dynamic conversion that were out of the
question with the reciprocating engine of
Watt. In the thermo-dynamic conversion
the law of conservation of energy takes a
peculiar form. No conceivable method of
thermo-dynamic conservation can begin to
transform all the energy contained in a lump
of coal, for instance, into dynamic or mechan-
ical form. If the heat contained in the coal
is used to heat a fluid used in a thermo-
dynamic engine, the maximum mechanical
energy that can be taken from that engine
can bear no greater a ratio to the total heat
imparted by the fuel to the fluid than the
actual range of temperature used in the
engine does to the maximum absolute tem-
perature of the fluid as it enters the engine.
The efficiency which would result by the
use of this ratio of temperature ranges is that
which would result if what is known as the
"Rankine cycle efficiency" were 100 per cent.
Some of the best of our modern steam
turbines have attained to as high as 75 per
cent — or possibly a little more — of this
"Rankine cycle efficiency." In these most
perfect engines, therefore, perfection itself
would not add more than 25 per cent or such
a matter. It should be particularly borne
in mind that this statement is true only of
the best of modern practice. It is not true
that the average of modern practice attains
anywhere near this degree of perfection.
It is only with prime movers of the largest
size and most modern design and construction
that so close an approach to the ideal can be
attained. As capacity is reduced it becomes
rapidly more and more difficult to attain
the higher degrees of economy in thermo-
dynamic machines. This must always remain
one of the potent factors in the economics of
power supply. It is, and undoubtedly always
will be, one of the fundamental reasons why
central station supply of electric service
must prevail as against isolated plant supply
for the same service. The central station can,
of course, use units which are very large in
comparison, and can be worked at much
higher average loads than must necessarily
be the case with an isolated plant.
One means that has been suggested to
improve the efficiency of the thermo-dynamic
engine is to increase the temperature range
through which the working fluid is used.
When using water or steam as the fluid in
our heat engine, there are certain practical
limitations to the temperature range which is
available and the temperature range cannot
be materially extended over the best of
modern practice. The only two ways to
extend this temperature range when using
steam are to increase the super-heat or
increase the pressure. Increasing the super-
heat over the best modern practice does not
promise results commensurate with the ex-
penditure of heat to obtain this super-heat,
since increasing the temperature at one end
of the heat cycle simply involves a loss in the
efficiency at the other end. There is a rather
definite limit to superheating of stem beyond
which it is useless to go. Increasing the steam
786
GENERAL ELECTRIC REVIEW
pressure does promise results, and it is
probable that the tendencies for the future
will be toward these higher steam pressures.
Another promising method of increasing
temperature range is that to which attention
has been called during the last year or two
by Mr. W. L. R. Emmet of Schenectady.
He has called attention to the advantages
of using mercury as the working fluid in a
heat engine for temperature ranges above
those available with steam. After working
the mercury through a given temperature
range, the heat remaining in the mercury is
transferred to water and the steam thus made
available is again worked through a lower
temperature range. The advantages of this
are that the steam is in practically all respects
the same as in standard steam turbine
practice and the mercury cycle is closely
similar to the steam. Additional energy is
made available from the same amount of
initial heat due to the greater temperature
range obtainable by the use of the mercury.
The main disadvantage is the poisonous
nature of mercury vapor and the difficulty
of absolutely preventing its leakage at the
high pressures and temperatures of the
mercury boiler. These practical difficulties
make it too early to predict whether or not
this method will \\ork out as a feasible
solution of the thermo-dynamic engine prob-
lem. However, it can be said that, without
some such method or device, the future is
apt to bring no revolutionary improvements
in thermo-dynamic engines over the best
of modern practice. Improvements of course
will undoubtedly continue to take place, but
it cannot be hoped that the improvements
of the future will be of the same revolutionary
character as the improvements in the thermo-
dynamic engine which have taken place within
the last 10 or 15 years. Here again we are
approaching so close to the law of conservation
of energy that it is safe to make a prediction
of this nature.
In the matter of size and capacity of
generating units it can safely be said that
this is a consideration that will hereafter be
fixed by the conditions to be met and not
by any inherent limitation in our ability to
produce units of any desired outputs. We
now have units of 30,000-kw. capacity in
service and still larger ones projected, and
no limitations of design or material appear
of such a nature as to place a stop to further
progress along the same line.
At Omaha in June, 1898, the then president
of our Institute. Mr. A. E. Kennelly, made
an inaugural address upon the topic, "The
Present Status of Electrical Engineering."
This address constitutes a very convenient
milestone by which to judge our progress
since that time, and in this address I will
take the liberty of quoting freely from this
1898 address of Past President Kennelly.
In the matter of generator sizes, he says,
"In 1884 a 50-kw. dynamo was considered
a large machine while a 100-kw. Edison
steam dynamo was justly called a 'jumbo.'
At present the largest size of generator built
or building is of 4600-kw. capacity." In the
14 years from 1884 to 189S the maximum
size of generator therefore increased 46-fold,
while in the 17 years since that time, the
increase has only been about 7-fold. While
the increase in capacity therefore has been
a marked one, the rate of increase has not
been so rapid during the last 17 years as it
was in the previous 14 years, a result which
naturally might have been anticipated. The
future will undoubtedly continue to produce
larger and larger capacity machines, the limit
as to size being dictated by plant capacity
and economic considerations and not by any
inability to produce the larger sizes.
In the matter of selling price of such
apparatus the following extract from Kennelly
in 1898 may be of interest: "The price of
dynamos in 1882 was about 20 cents per
watt of output while dynamos of similar
running speed for comparatively small sizes
without switchboards now cost about 2 cents
per watt." The speed and size of these units
is not mentioned, but it may be said in
comparison that nowadays prices are fre-
quently quoted below x/i cent per watt. In
this respect again the improvement in the
last 17 years has not been so marked as it
was in the 14 years previous, a result that is
only to be expected. In the next succeeding
period it is probable that a still smaller degree
of improvement will occur. We are approach-
ing a saturation point in this respect.
It may be well to point out some of the
reasons for this approach to saturation in the
matter of costs. The two fundamental costs
of electrical apparatus are those of labor and
material. In regard to the item of labor, I
submit that it is safe to predict that the
tendency for the future will be for the cost of
labor to increase rather than decrease.
Economies in the use of labor will undoubtedly
take place by the introduction of the methods
of scientific management, etc., but these
need not be expected to be revolutionary in
character so far as cost of apparatus is
THE TREND OF ELECTRICAL DEVELOPMENT
787
concerned. The tendency of the labor item
will unquestionably be toward appreciation
rather than depreciation.
In regard to the item of material, modern
design has approached very close to the
physical limits of available materials. Take,
for instance, the property of permeability
possessed by irons. With higher permeability,
making available greater flux densities, the
cost of electrical apparatus might be consider-
ably reduced. That the future will bring
some improvement in this respect is un-
questionable but it is further highly improb-
able that this improvement will be of such
a revolutionary character as to cause any
sweeping change in the cost of electrical
apparatus.
The hysteresis and eddy current losses
that take place in irons and steels that are
subjected to varying magnetic fluxes is
another of the limits encountered in the
design of electrical machines. Marked pro-
gress has been made in this respect in recent
years. Our modern transformer steels in the
matters of losses and iron ageing qualities
show a vast improvement over those formerly
available. Unfortunately these improvements
have so far been accompanied by a decrease
in permeability which is highly objectionable
in rotating machinery. Unquestionably,
further improvements will be made in the
magnetic qualities of our irons and steels, but
these improvements will probably make no
revolutionary change in the costs of electrical
apparatus.
The conductivity of copper and other
metals is another physical property that sets
a limit to the output and cost of our electrical
apparatus. Apparently we have reached a
definite limit in this respect. The conductivity
of the copper of commerce is within an
extremely small percentage of that of pure
copper and we cannot expect to obtain a
higher conductivity in copper than that of
purity. There remains, of course, the possi-
bility of using some metal other than copper,
but at this present time there is very little
promise in that possibility. There is appar-
ently no metal that even approaches the space
and cost characteristic of copper that makes
it so essential to the construction of electrical
apparatus. Aluminum is a competitor only
when the volume of the conductor is not an
essential clement in design, as in transmission
lines and the like.
One of the most pressing of our existing
limitations to a reduction in cost of electrical
apparatus is that fixed byT temperature rise.
The output of a piece of electrical apparatus
increases with the temperature rise, and the
temperature rise in turn is dictated by the
point of balance between the rate at which
heat is put in and that at which it is taken
out. The rate at which heat is put in depends
largely upon such physical characteristics
as hysteresis and permeability of iron and
conductivity of copper, which characteristics
are already being crowded to the limit by our
modern designs. The rate at which heat is
dissipated depends upon the efficiency of the
ventilation methods used and in this par-
ticular there is a considerable opportunity for
improvement. The methods and devices for
taking heat out of machines are just as
important, when considering temperature
rise, as the prevention of heat from entering.
While there is unquestionably room for
considerable improvement in this particular,
there is a question as to whether it v/ill cause
any material reduction in the cost of such
apparatus. The additional costs of applying
the more efficient methods of dissipating
heat, will go far toward multiplying their
tendency toward a reduction of cost.
However, there is one line of development
that does promise some reduction in cost, and
that is the tendency toward higher operating
temperatures. In the past, the maximum
operating temperature has been fixed by the
disintegrating point of fibrous insulation, and
this point has placed a very definite and
logical limit to temperature rises in such
machines. However, when types of insulation
are used which do not have this definite
temperature of disintegration, this reason
for such a temperature limit disappears.
Just how far we can go in apparatus tem-
peratures without exceeding the safe limits
of these heat-resisting insulations is as yet
problematical. However, a limit to an
indefinite extension in this direction is set
by the temperature coefficient of copper
conductors, the property that causes the
resistance to rise with increasing temperature,
thereby causing still higher losses and in turn
still higher temperatures. If we go high
enough, we will reach a point of unstable
equilibrium in this temperature rise curve,
where the apparatus will literally and auto-
matically "burn out." This point is, of
course, far above anything that is projected
at the present time, but while we are looking
for limits, we might as well recognize that
such a one exists.
In the matter of power production, there-
fore, although we have steadily improved
788
GENERAL ELECTRIC REVIEW
in the past, both as to costs and as to per-
formance, and although we may expect to
continue this steady improvement in the
future, we must not expect that these
improvements will be of the same revolution-
ary character as they have been in the past.
Wie can see ahead of us a definite limit beyond
which it will be impossible to improve the
methods of power production now in use.
I do not mean to say that there will be no
new or revolutionary methods developed
in the future, but so long as we continue to
get our power from falling streams and burn-
ing coal we need not expect to see the same
radical improvements in the future as have
distinguished the past. To illustrate my
point more fully let us consider the nature
of a water power. Water is evaporated by the
action of the sun and is carried miles above
the earth into the clouds. Here it is precipi-
tated in the form of rain or snow and falls
on the earth. The streams carry this water
back to the ocean and it is then ready to
repeat the cycle. Our existing water powrers
utilize an almost infinitesimally small part
of this water over an almost infinitesimally
small part of the total height to which the
sun carried it. Insofar as is concerned the
water we use over the head through which
we use it, we do fairly well, but the part of
the sun's energy which we thereby realize
is so infinitesimally small that it puts us to
shame. Some Westinghouse or Edison of the
future will show us how to use the sun's
energy directly. The point I wish to make is
that the revolutionary improvements in
power production methods of the future must
come in a fundamental change of method
rather than in the continued improvement
of existing methods.
So much then for the methods of producing
power. In the matter of utilization of power
a few comparisons w'ith the past may not be
amiss. As indicated early in this address, the
modern motor has reached a stage, insofar as
efficiency is concerned, such that little
improvement may be.expected. We are within
a comparatively few per cent of perfection
in this respect. The progress of the future
will undoubtedly come from improvements
in methods of application and in this direction
the field is inexhaustible. For instance, the
problem of applying electrically the large
amounts of power which are demanded by
our modern railroad trains has not yet
received a solution which is satisfactory to all
concerned. That the problem will be solved
there is no doubt in my mind, but iust how,
is a question that I do not propose to discuss
in this address. However, this is only one of
the many problems that confront the electrical
engineer. The devising of methods for the
application of electricity to our modern
industries constitutes the occupation of no
small part of our fraternity; as witness the
many pages in our Proceedings that have
been occupied during the past years by the
activities of the Industrial Power Committee.
It is along this line that we may expect much
of what the future may have to offer us of a
revolutionary character.
In the field of electric lighting there have
been developments of importance. After
the telegraph, in point of time, the electric
light was the first practical application of
electricity.
Most of our modem development in
electrical engineering has taken its initiative
from the supply of electric lighting to our
communities. In this matter of electric
lighting let me quote again from Kennelly's
1898 address. He says; "The price of a
16-candle-power incandescent lamp 16 years
ago wras about .$1.00. Now it is about 18 cents.
The best lamps at that time, under laboratory
conditions, gave about 0.28 mean horizontal
British candle-power per watt, and under
commercial conditions about 0.20. The
highest pressure for which they could then be
obtained was about 110 volts. At the present
time, lamps are obtainable giving normally
0.4 mean horizontal British candles per wTatt,
while under commercial conditions the
average lamp normally develops about 0.25
candle per watt. They can also be obtained
(at 0.25 candle per watt) for pressures up to
240 volts, and are frequently installed on
220-volt mains."
Kennelly therefore records an improvement
in 16 years of about 50 per cent in cost of
lamps to the consumer and about 50 per cent
in efficiency. The introduction of the metal
filament lamp has enabled us today to record
a much greater rate of improvement in
efficiency than Kennelly did He reported
an improvement of about 50 per cent in
efficiency in the 16 years previous to 1898.
In the 17 years since Kennelly wrote, we have
improved our maximum efficiency about 1000
per cent, an advance which is truly marvelous.
But here is a field where we have a long way to
go yet without reaching a possible limit. It is
true that the melting point of the now
available materials seems to place the limit
of lamp efficiency at a point not much higher
than that which we have at present. However,
THE TREND OF ELECTRICAL DEVELOPMENT
789
when we come to compare the efficiencies of
even our best lamps with that attained by the
fire-fly it is evident that we still have a long
way to go before we have reached perfec-
tion.
In the matter of power transmission,
progress during the past few years has been
remarkable. In 1898 the record reads:
"The electric transmission of the power of
falling water is a branch of engineering that
has come into service since 1884, and is
making rapid strides, owing to the recent
successful employment of high voltages and
multi-phase alternating currents. It has been
estimated that about 150,000 kw. of this
class of machinery is installed in the North
American continent, commercially transmit-
ting power to various distances up to 85
miles, at various pressures up to 40,000 volts."
Since Kennelly wrote, 17 years ago, the
maximum transmission voltages have gone
up about 3j?-4 times; the maximum then was
40,000 and now is 150,000 volts. The maxi-
mum distance of transmission has gone up
about 3J/2 times, 245 miles as against 85, and
the installed capacity of water power plants
on the North American continent about
9 times, 1,350,000 instead of 150,000 kw.
Kennelly also mentions in his record that
"insulation testing sets have been made for
producing alternating pressures up to 160,000
volts effective." In this respect we can go at
least 10 times better than he reported,
1,000,000 volts from transformers having
been made available on more than one
occasion and in some cases the voltage
available from transformers has been pushed
even higher. This matter of power trans-
mission is a branch of our industry wherein
the progress of the last 17 years since Kennelly
made his record has advanced with probably
greater rapidity than in any other branch.
I feel very sure that the President of our
Institute who comes along 17 years hence
and compares the then conditions with my
record will not be able to claim any such
advance as that we may now claim over 1898.
This follows because we are approaching some
fairly well defined limits in these matters.
For instance, in the question of increasing
transmission voltages we are close to the
corona limit. The appearance of corona
in the transmission line means the continual
loss of power and therefore corona cannot be
tolerated to any appreciable degree. There
are, of course, methods of increasing the
voltage range somewhat before corona is
produced, such as increasing conductor diam-
eter, but it can be readily seen that the limits
of such remedies will be reached long before
transmission voltages have increased by the
same ratio as they have in the past 17 years.
Another limit that we are approaching
in the matter of power transmission is the
economic one. Transmitted power costs more
than that generated at the points of delivery
on account of the cost of and the losses in the
transmission line. There obviously is a limit
to the investment that can be made in
transmission lines and still be able to supply
power with the same economy as it can be
generated upon the ground. This considera-
tion, coupled with the rapid advance in
methods of generating power from steam,
has in my mind placed an economic limit to
the transmission of water power so that we
cannot expect any such advances in the
future as the past 10 or 15 years have given us.
That there will continue to be improvement
and advance, no one can doubt, but its rate
certainly will be diminished.
Transmission by high voltage direct cur-
rents has received some attention of recent
years. While there is no question but that
the problems of pure transmission are much
simplified by the use of direct currents, the
accompanying problems of the generation and
utilization are so much intensified that
nothing is to be gained in this manner. I
would predict no material advance for the
future in direct current transmission of
power unless some means, as yet undeveloped,
is found by which its generation and utiliza-
tion are made easier and safer than is possible
at present.
And so we might go on indefinitely and
draw comparisons with past practices. Always
we find progress ; always also we find that the
rate of progress is not so high now as it was
in previous years. This is but the working
out of a natural law. Electricity is no longer
the infant that it was formerly pictured, and
cannot be expected to continue the rate of
growth of the infant. It is attaining the vigor
and strength of manhood. It is contrary to
natural law that either a child or an industry
can have rapidity of growth and at the same
time strength and stability of character.
Unquestionably the rapidity of our develop-
ment is not so great .now as it was when
Kennelly spoke in 1898, and in this respect
we are following but a natural law. At the
same time, our vocation is acquiring a
stability and performance that are absolutely
incompatible with the rate of growth that
characterized our earlier vears.
r90
GENERAL ELECTRIC REVIEW
ECONOMIES IN OPERATING SMALL CARS
By J. F. Layng
Railway and Traction Engineering Department, General Electric Company
The author first outlines some of the disadvantages under which the modern street railway is operated.
He then analyses the expenses of electric railways, dealing specifically with general expenses, power, main-
tenance of ways and structures, maintenance of equipment and transportation, and shows the influence of
weight of car per passenger carried on each of these items. Finally he compares the present type of car seating
48 passengers with a proposed one-man car seating 32 people and emphasizes the economies that could be
effected by employing the lighter equipment. — Editor.
Railway managers have ever present before
them the problem of balancing their expen-
ditures with the receipts in the efforts to attain
the proper operating ratio of expense to
earnings. Of late years, due to general con-
ditions, this problem has been harder to
solve than formerly. It has been almost
universally impossible to secure a change in
the rate of fare, regardless of the advance in
the rate of change in the cost of producing
transportation. In past years it was pos-
sible to increase the total receipts by fare
zones, or by decreasing the transfer privileges,
but at the present time, in most cases, the
attitude of the public to the public service
corporation is that if reduction can be made in
the charge for transportation the public is
entitled to a reduction, but if for any reason
whatever the cost of producing transportation
is greater the public usually give the railway
companies very little consideration, and
generally the statement is made that the
management of the property is inefficient.
In nearly all cases for city service the fare
unit has remained the same, but it is also true
that the average passenger haul is longer and
the transfer privileges have had to be ex-
tended. The public have been educated to
expect more and more from the transportation
companies not only in the grade of trans-
portation given, but also they expect a lower
rate of fare. In the early days of electric
railways, small light weight single-truck cars
with longitudinal seats and non-heated cars
were looked upon as a luxury, but now the
public expect large double-truck cars with
comfortable transverse seats, and during the
winter time the ears must be kept at a uniform
temperature.
To meet the demand of the public and keep
down the expense of operation, it is best for
city service to run cars at the fastest practi-
cable schedule speeds. With the large double-
truck cars, naturally the total weights and
weight per seated passenger is increased.
These features naturally increase the wear and
tear on the track and special work, and also
increase the power consumption propor-
tionately. The heavier cars also naturally
require heavy roadbed construction with
heavy rails, and even with the larger first
expenditure for roadbed the heavier cars
greatly increased the maintenance of way
cost.
The rapid development of the automobile
and its continued increased use has greatly
cut into the receipts of both the interurban
and city roads. During the past two years a
large number of managers of interurban
properties found the receipts during county
and state fairs were greatly reduced when
compared with former years. This reduction
was attributed almost entirely to the increased
use of the automobile.
During mild seasons of the year the auto-
mobile is and will probably continue to be a
factor to be considered in the receipts of the
short hauls of the interurban road. The cost
of this method of transportation is higher than
that furnished by the electric road, but with
the class of person who owns and maintains
a machine, even though it costs a little more,
providing the expense is not continuous, it is
not considered serious, and the pleasure of
driving one's own car is considered to cover
the difference. To meet this form of com-
petition, many think the only thing to do is
to bring to the attention of the automobile
users the difference in the cost of the two
classes of service, and to make the car service
as attractive as possible. The city lines have
recently encountered much more serious
competition in the jitney. This service has
developed almost over-night, and within an
increditably short period of time many rail-
way companies have encountered a com-
petitor that reduced their gross receipts 5
per cent, and in some cases 20 per cent. The
jitney as operated at present in most cities
follows the lines which have the most traffic.
In a city where seven city lines are operated,
only two of these lines Were having jitney
competition. One of the lines during non-
rush hours gave a six-minute service, and
during the rush hours a three-minute service,
the other line gave a 10-minute non-rush hour
ECONOMIES IN OPERATING SMALL CARS
rgi
and a five-minute rush hour service ; the other
five lines gave a 15-minute service. With the
two lines having the dense traffic the gross
receipts dropped 20 per cent. Problems such
as this put the railway management in a most
serious position. The problem is not confined
to any local community, but is a general one
encountered from the New England States to
the Pacific Coast. The general consensus of
opinion regarding the jitney service is that
there are three things which influence the
public to use them; first, the high schedule
speed; second, the novelty of the ride, and
third, the direct delivery to the point of
destination. It is also generally believed,
from the experience of a large number of
people, that the jitney service as given at
present is not profitable, and that in its
present form the service will not continue and
is merely a passing fad. However, many
believe that some form of the auto bus carry-
ing possibly from 10 to 12 passengers will be
worked out, and may prove a really serious
competitor for the electric service as it is now
given .
The American railway men in the past have
proved progressive, ingenious and resourceful.
Every problem of maintenance and operation
is scientifically studied, and the results of
these studies are put into practice. There has
been more originality and progress in trans-
portation methods, car design and design
of apparatus for this class of work than in
any other business we have. With the art in
such able hands and with the assistance of the
technical press, which reaches us all at regular
intervals, there is every reason to feel con-
fident of the practical solution of the problem.
To get a proper perspective as to what is
involved, a study of the figures given by the
United States Census Bureau for the dis-
tribution of expenses of all the electric rail-
ways in the United States is of considerable
assistance. This table gives the following
ratio of costs to operating revenues:
General expense 9.53 per cent
Power 9.0 per cent
Maintenance of way and structure. . 8.17 per cent
Maintenance of equipment 7.06 per cent
Transportation 24.42 per cent
Total 58.18 per cent
In looking over these figures, it is but
natural that the largest figures should be
selected first for analysis; that is, the cost of
conducting transportation, which is 24.42
per cent of the gross receipts. Practically all
of this represents expenditures for platform
wages. With the present plan or system of
fare collections for the larger cities, and where
travel is heavier, there does not seem to be any
way of materially reducing these figures. All
of the progressive railway companies have
studied their local conditions and have in-
Fig. 1. Typical Schedule Speeds for 20- ton Car
Geared for 20 m.p.h. max. speed
Acceleration 150 lb. per ton
Braking 150 lb. per ton
Coasting 20 per cent power on period
's " -f-T
" **%i-^ ' : x _ - . .
* - iS>. ___ XX
*^£ - - -L- _£
>•« 55,.;..,
j - 3;;;=,, ±:p
j" - :: ""<;*;e;<^, I
»? t — '■* itf^^Se — ^— t-—
1 ■ — \££.o^TZ~ — ~^~~
a 1 *~~-~ — " - — „ — — — »
Jj ft "~"~ T~ ~~ " ~~ ~t~
*• X X 4
4- -t- -F-r-h-F
[-1 — ' — ' — 11 M 1 1 M — I ■ ] il 1 1 i 1 1 | J 1 1 l_i.lJ.Ml 1 M 1 1 11
Stopspar *tt*e
Fig. 2. Typical Schedule Speeds for 20-ton Car
Geared for 25 m.p.h. max. speed
Acceleration 150 lb. per ton
Braking 150 lb. per ton
Coasting 20 per cent power on period
creased schedule speeds to the maximum in
order to secure the lowest possible platform
expense per car mile. Cars have been designed
with entrances and exits especially adapted to
facilitate rapid loading and unloading, so
as to reduce the length of stop to a minimum.
In several cities skip-stop service has been
inaugurated to cut down the number of stops
per car on lines where a large number of stops
necessarily have to be made. Curves shown
in Figs. 1 and 2 illustrate the effect of increas-
ing the length of stop with different stops
per mile with cars geared to a free running
speed of 20 and 25 m.p.h. These curves
show the highest possible schedule speeds
that may be obtained on level track under
favorable conditions. When making cal-
culations and considering practical schedules,
792
GENERAL ELECTRIC REVIEW
it is best to increase the running time by 10
per cent to allow for the naturally slower
schedule speed which will be caused by curves,
grades, and obstructions by vehicles which
are encountered in actual service.
A practical example of what long stops
mean can be seen by referring to the schedule
speeds. Let us take for example a line having
a schedule speed of 12 m.p.h. with six stops
per mile and five-second stops. By increasing
the length of stop to 15 seconds the schedule
speed, is reduced to 10 m.p.h. This is a
reduction in schedule speed of 16% Per cent.
Of course, extending the length of stop to
15 seconds for city service is a larger value
than will be found normally, but it illustrates
the value of the efforts to keep down the
length of stop. By expending energy along
this line, we can secure true economies as the
increase in schedule speeds obtained in this
manner do not require increased power per
car-mile and will give us a greater number of
car miles per hour. All railway companies
have lines on which only one to five cars are
operated and give sufficient service, and in
some cases the combinations of the running
time and distance will not admit of much
change in present methods, but the cases
where some possible saving cannot be made
are comparatively rare.
The length of stops has been discussed at
considerable length as it directly affects our
problems of fare collection, general car
designs and schedule speeds. There are many
instances where one-man cars are now suc-
cessfully used, and there will no doubt be
many of these cars in the future. They will
probably ultimately be used for practically
all service, in cities having a population of
60,000 or less, and in large cities for lines on
suburban sections where the traffic is not
sufficient to warrant the use of the larger cars
such as are used for a heavily congested
traffic. In this class of work the light
weight one-man car should serve the public
equally as well as the larger cars.
With all of our present systems of fare
collections, it is necessary for the operator to
handle money, and as long as this is true, it
would hardly seem practicable to have the
cars in the larger cities operated by one man.
The additional time which would be consumed
by making change and giving transfers would
probably prove of too great a handicap.
These features with the larger number of cars
required would extend schedule speeds and
cause obstruction to traffic in the down town
' m. Therefore, unless we have some
radical change in our fare collection and
transfer feature for larger cities the only way
to change the traffic expense ratio is by having
each car operated so as to run the maximum
car miles per hour. However, in a small city
and on many suburban feeder lines, large
savings are possible with the small car. Those
who have made a study of the one-man car
deem it advisable to have all the possible
safety features, which includes "dead man's
release" on the controller, which when the
operator's hand is removed from the controller
handle, automatically cuts off current from the
motors, sands the track, applies the brakes,
and when the car comes to a full stop opens
the car door.
Again referring to our census figures, we
find that the next highest item is power,
which constitutes 9 per cent of the total . There
are three ways to reduce this figure, which are
reducing car weights, slowing down the
schedule, and more efficient operation. By
more efficient operation is meant savings that
can be made by operating at the proper rate
of acceleration, maximum coasting, and
proper rate of braking. The question of
saving power by lengthening the schedules can
hardly be considered, as the savings made by
this method for city service almost universally
are considerably less than is necessary to
balance the extra cost of transportation
expenses.
For the purpose of the present discussion,
it will be assumed that all possible savings are
being made by the proper application of
power and brakes. This will confine us
entirely to the question of car weights. The
influence of the actual cost of transporting
a given weight varies greatly. Some railway
officials say that it is a negligible figure and do
not consider that a few hundred pounds more
or less on the car affects the cost of operation ;
while others figure that it costs 30 cents
per year to carry7 an extra pound. The
generally accepted figure of five cents per
pound per year has a good deal of justifica-
tion. However, the only tangible figure is
that for power. All other elements enter-
ing into consideration are more indefinite.
Recently an analysis of the service of a large
city line where the maximum schedule speeds
are operated showed the power consumption
at the power house to be 170 watthours
per ton -mile, and the average miles for
a car owned is 40,000' miles per year.
Current costs this company 0.7 cents per
kw-hr. It can therefore be seen that
for current alone the cost of hauling
ECONOMIES IN OPERATING SMALL CARS
r93
one pound per year is 2.38 cents. There
are of course other expenses that increase
weight, such as larger investment for power
supply, feeders and extra cost of the mainte-
nance of right of way, due to the increased
weight to be carried.
When considering power alone, savings can
be made almost in proportion to reduction
in weights of cars.
When the successful storage battery cars
were put in operation, a great object lesson
in car body and truck construction and
electrical design was given to the equipment
designers in this country.
One of the next steps was the realization
that two-motor equipments will give satis-
factory service where grades do not exceed
five per cent and where trailer operation is
not required. However, there are many
American cities where grades exceed five per
cent, where two-motor equipments are far
from satisfactory.
One of the next greatest advances was made
by Mr. P. N. Jones and his assistants when
they put 24 in. wheel equipments in service
on the Pittsburg Railways. With these cars
and other cars of this character which have
since been built, the weight per seated pas-
senger was decreased to approximately 600
lb., while the preceding types of cars using
four-motor equipments had a weight equal
to 900 or 1000 lb. per seated passenger.
With the small diameter of wheel smaller
truck strains are obtained, which coupled
with the less weight of wheel gives us trucks
which are roughly speaking 33^3 per cent
lighter than the trucks which were formerly
used for this same class of service. Since the
Pittsburg Railways put in service cars with
24 in. wheels, a number of other com-
panies have also purchased the same class
of equipment, and all indications now are
that an entirely new field of development has
been started by the small diameter of wheel.
With single truck cars it is possible to have
a much longer wheel base with no greater
binding in curves than is obtained with a
relatively short wheel base with a large
diameter of wheel.
Recently the jitney competition has caused
operators to again review general car designs
to determine if it is feasible to develop a light
weight one-man car. Mr. J. M. Bosenbury,
Superintendent of Motive Power of the
Illinois Traction System, has designed a single
end and double-end one-man car; each of
these cars seating 30 passengers. The single-
end car completely equipped will weigh
10,000 lb. and the double-end car 15.000 lb.
These weights are equal to 333 and 500 lb.
respectively per seated passenger.
Mr. C. O. Birney of the Stone & Webster
Engineering Corporation has designed a
single-end one-man car which will weigh
completely equipped 9000 lb. and seat 29
passengers, which is equal to 310 lb. per
seated passenger.
In some cases these types of cars might
advantageously use motors smaller than we
are now considering standard for railway
service, but if there is a real demand for this
class of car, and if it is ultimately believed by
the transportation interests that such a car
is desirable, the manufacturers of apparatus
can be depended upon to supply equipments
which will meet the requirements in every
respect.
Again referring to the census figures, the
next item which we have to consider is S.17
per cent for maintenance of way and struc-
tures. Of course, with very light cars this
figure will be reduced, but as the amount of
the reduction is difficult of determination, a
direct answer could not be given to this
question as it would vary greatly with dif-
ferent localities and different conditions.
The next figure from the census report is
7.06 per cent for maintenance of equipment.
The maintenance figure would be reduced
with the small light weight cars from 10 to 20
per cent.
All that have been discussed previously in
this paper have been features which enter
into the design of our present cars and those
things which may be considered when design-
ing the small one-man car. From a purely
engineering standpoint there is not the
slightest doubt but that the small light weight
one-man car should be used for practically all
service. With the small car when compared
to larger cars used at present practically the
same service can be given with at least 18
per cent less expense; that is, when operating
a one-man car and in giving service that is
required in many cases.
For a direct comparison of power, with
different number of stops per mile and dif-
ferent car weights, a curve showing the
energy for an 8-ton and a 20-ton car is shown
in Fig. 3. The 20-ton car includes the live
load and therefore a four-motor equipment is
favoring the larger car to a considerable
extent, while the 8-ton car is showing the small
one-man car up in as unfavorable a light as
could be consistent insofar as power calcula-
tions are concerned. In order to help arrive
794
GENERAL ELECTRIC REVIEW
at an understanding of the advantages and
disadvantages of a one-man car, an example
has been taken of a line which is 10.6 miles
per round trip; the running time for the
round trip one hour, with six stops per mile.
Platform wages for the two-man car are
24
\
s
V
\
•s
S
^J-Sl/£
\
is -8
s
£ «,f
\
,«!«
k <
1
\
py?
Jj.
J<
^il
3.!
Hi
B f
*
£
11
gnJSL
/
jnerSJi
0 0
!
5
'
i
'
i
>
I
0
II
Stops per M//e
Fig. 3. Curves showing Energy Saving with Light Cars
for Various Stops
Free speed 25 m.p.h.
Four-motor, 20-ton car — friction 24 lb. per ton
Two-motor, 8-ton car — friction 30 lb. per ton
taken at 50 cents per hour, for the one-
man car 30 cents per hour, and the power is
assumed to cost one and one-half cents per
kilowatt-hour delivered to the car. The
present cars seat 48 passengers and the pro-
posed one-man car seats 32 passengers. The
power as shown by the curve for a 20-ton car
for this service would be 2.9 kw-hr. per car
mile at the car, and for the 8-ton car 1 .3 kw-hr.
The receipts for the present cars are assumed
to be 24 cents per car mile.
For the one-man car two grades of service
are analyzed, viz. : one in which the headway
during the non-rush hour is decreased from
the present service of ten minutes to six
minutes, and the second in which the
interval between cars is left the same as at
present, but giving during the rush hours
an increased service the same as would be
required with the one-man car frequent ser-
vice.
The above analysis shows the receipts the
same for all classes of cars. The smaller cars
in both cases give much more frequent
service, and it is but natural with this
increased service that the receipts should
be greater. With the large car the operating
ratio of expense to gross receipts is 56.5 per
cent while with the small one-man car with
cars at six-minute intervals instead of ten-
minute service, the operating ratio is 53.5
per cent.
Reviewing the figures of the one-man car
giving ten-minute service during the non-
rush hours and three-minute service during the
rush hours brings out several very prominent
facts. The first is that the operating ratio
has decreased to 46 per cent. The second is
that with this type car more seats per hour
can be furnished during the rush hour with
18 per cent decreased expense. Another fact
is that during the non-rush hours the larger
seating capacity of the larger cars is not
Present Proposed Proposed
Car One-man One-man
Seating Car Car
48 Seating 32 Seating 32
Head\
for 14 hours 10 min.
Headway for 4 hours 5 min.
Running time 60 min.
Cars required 14 hours 6
Cars required 4 hours. . . 12
Seats per hour 14 hours 288
Seats per hour 4 hours 576
Car miles per day 1399.2
6 min.
3 min.
60 min.
10
20
320
640
2332
Power $40.57 $30.31
Platform wages 66.00 66.00
Maintenance of way S.17 per cent 27.43 27.43
Maintenance of equipment 7.06 per cent 23.69 23.69
General expense 9.53 per cent 32.00 32.00
10 min.
3 min.
60 min.
6
20
192
640
1738.4
$22.60
49.20
27.43
23.69
32.00
Total expense $189.69 $179.43 $154.92
Receipts at 24 cents per car mile 335.80 335.80 335.80
Ratio of expense to gross receipts, per cent 56.5 53.5 46
RADIOGRAPHY OF METALS
795
required. In many cities the average load
does not require more than 50 per cent of the
seating capacity furnished. With the small
cars the seating capacity during the non-
rush hours is in the proportion to the logical
actual requirements and conforms to a natural
and proper saving.
It will be noted that expenses for traffic
other than platform wages are left the same
for the one-man car as for the proposed car
as it would hardly seem fair to the small car to
do otherwise. It is also assumed that the
extra car miles which are made by the small
car will offset any savings in maintenance
of equipment and track, and the same pro-
portions of expense have been used as have
been found by the average throughout the
country.
Certainly it would seem from these figures
that in the future many light weight one-man
cars will be purchased.
In many cities there are ordinances or
rulings of public service commissions which at
present prohibit the use of one-man cars, but
it is reasonable to assume that when the case
is properly presented, and if the light weight
car will serve the needs of a community, these
restrictions will be removed.
one of these, holes were drilled in such a way
that the axis of each hole was midway between
the faces of the steel and parallel to those
faces. The diameters of these holes are
listed in Table I.
Hole Number
Diameter
RADIOGRAPHY OF METALS
By Dr. Wheeler P. Davey
Research Laboratory, General Electric Company
Previous investigations by the author (insofar as these had been made) demonstrated the practicability
of employing X-rays to detect flaws in the interior of metal castings, etc. Naturally, the next steps undertaken
were the ascertaining of the limits of this new method of detection, the determination of the direction in which to
expect a possible extension of the limits, the derivation of the working formulae for the work, and the acquisition
of the necessary technique for its successful prosecution. In the following article the author describes these
latter investigations and records their results. — Editor.
In an article in the General Electric
Review, January, 1915, reference was made
to the X-ray examination of a steel casting t^
of an inch thick. Fig. 1 shows one of the
radiographs thus obtained. All these radio-
graphs showed plainly the tool marks on the
surface of the casting. All but one showed
peculiar markings which were of such shape
as to strongly suggest that they were indeed
the pictures of holes in the interior. A
cylindrical piece, one inch in diameter, was
punched from the casting at a point where the
radiograph, shown in Fig. 1, indicated that a
blow-hole should be found. (The location of
the sample punched out is indicated by a
circle.) Fig. 2 is a photograph of the side
of the punching and it shows the hole that
was found.
Since that article was written it has seemed
desirable (1) to obtain data from which the
exposure necessary for any thickness of steel
could be at once calculated, (2) to find the
thickness of the smallest air inclusion which
could be radiographed in a given thickness
of steel, (3) to find the direction from which
to hope for further progress, and (4) to find
the technique of radiographing metals.
In order to gain some preliminary data,
J4 inch
Y% inch
tV inch
T2 inch
6*1 inch
several pieces of H-in. boiler plate were
obtained, five by seven inches in size. In
Exposures were made on Seed X-ray plates
at a distance of 20 inches with Coolidge tube
X-117 which was operated on a Scheidel-
Western induction coil having a mercury
turbine break. The X-ray plate was placed
on a sheet of 2^-in. lead. The steel plate
was laid on this and a lead cover was placed
over the whole in such a manner that the
cover and backing made a complete lead-
shield for the X-ray plate. (See Fig. 3.) A
rectangular hole in the cover allowed such
X-rays as were able to penetrate the steel to
reach the X-ray plate. This afforded com-
plete protection against secondary rays.
796
GENERAL ELECTRIC REVIEW
Without such precautions, the effect of
secondary rays on the X-ray plate would
have been greater than that of the rays used
to take the picture. If the steel had been
two or three feet square, such precautions
would have been unnecessary. By placing
the pieces of boiler plate on top of each other
any thickness of steel desired could be
obtained. Exposures were made at 11-, 13-
and 15-in. parallel spark-gap between points.
An attempt was made to use a 17-in. spark
gap, but was abandoned due to flashing in the
tube. The results are tabulated in Table II.
Thick-
ness of
Steel
in In.
Plate
Spark
Gap
Exposure in
Milliampere-
minutes
Holes visible
v->
D
11
7
1-2-3-4-5
A
13
4
1-2-3-4-5
B
15
2
1-2-3-4-5
i
E
11
45
1-2-3-4-5
F
13
19
1-2-3-4-5
G
15
10
1-2-3-4-5
m
H
11
45
1-2-3 very faint
I
13
30
1-2-3 verv faint
K
13
90
1-2-3 faint
T
15
30
1— 2— 3— 4r-5 very faint
L
15
60
1-2-3-4-5 faint
This really means, of course, that at 13- in.
spark-gap 90 milliampere-minutes is suf-
ficient to enable one to notice the difference
in blackening between exposures through
1-rV in. and lj^ in. of steel, but is not sufficent
to enable one to detect the difference in
blackening between exposures through Iff in.
and 13^ in.
These results were necessarily incomplete,
since the plates were by no means all of the
same density. They served, however, to
demonstrate two facts.
(1) With the voltages which can now be
used, it is impracticable to radiograph through
more than 1}^ in. of steel with tungsten
target tubes because of the time required.
(2) The use of high voltages does not seem
to appreciably reduce the clearness of the
picture obtained. (It was to have been
expected from published data on scattering in
aluminum that enough scattered radiation
would have been produced to blur the pictures,
but plate B apparently shows as good detail
as does plate D.)
It remained to verify these conclusions by
data of a quantitative nature. Seed X-ray
plates were therefore exposed under the same
conditions as before except that none of the
slabs of steel used had been drilled. For each
thickness of steel, all the exposures at a given
Fig. 1. Radiograph of a Steel Casting showing Flaw within Casting. The circle shows where a piece was later punched out
RADIOGRAPHY OF METALS
797
spark-gap were made on the same plate.
Each plate, then, showed a series of steps
which increased in density from one end of
the plate to the other. Thickness of steel,
spark-gap, and milliampere-minutes were
recorded on each plate by means of lead
numbers. Data regarding these plates is
listed in Table III.
TABLE III
Plate No.
Thickness of Steel
Spark-gap
216
Vi
11 inches
217
XA
13 inches
218
y*
15 inches
221
l
11 inches
220
l
13 inches
219
l
15 inches
222
Wi
15 inches
A study of these plates showed the following
facts. Let Ey^ be the exposure in milli-
ampere-minutes necessary to produce a given
darkening of the plate through J^ inch of
steel, and let Ei and Eiy2 be the exposures
necessary to produce the same darkening
through 1 inch and \]4. inch respectively.
Then at 11-in. gap
£H:£i = l:ll
At 13-in. gap
Ey2 '. E\ = 1:8
At 15-in. gap
Ey^ '. Ei = E\ : E\y2 = 1 : 8
Also, through both J^ incn and 1 inch of steel
& 13-in. gap '• P" 11-in. gap = 1 ■ 4
and E 15-in. gap : E 13-in. gap = 2 : 3
of these conclusions is the more probable, but
it is the effect of the X-rays on the plate which
is of prime importance in this work, so that
from a radiographic standpoint we may say
that in any case the effective penetration of
the rays is a little, greater at 13-in. gap than
at 11-in. gap.
Fig.
2. Ordinary Photograph of one edge of the punching
from the plate shown in Fig. 2. Note flaw
In the same way we may conclude that the
effective penetration at 15-in. gap is the same
as at 13-in. gap. There is, however, a marked
decrease in the amount of exposure required
as the voltage^across the tube (as measured by
the spark-gap) is increased. This may be due
to one of two causes, either the efficiency -of
transformation from the kinetic energy of the
cathode stream into the energy of the X-rays
may be greater at high voltages, or there may
be some peculiarity in the wave-form pro-
duced by the induction coil such that a great
deal of energy is given off at a voltage cor-
responding to 13-in. gap when the coil is
operated -so as to give a maximum voltage
corresponding to a 15-in. gap. Investigation
Fig. 3. Diagram of the Method of Preparing Steel Sample, X-ray Plate, Lead Mask and Lead Backing for taking Radiograph
It is at once evident that either X-rays from
a tungsten target at 13-in. gap are more
penetrating than when produced at 11-inch
gap, or the X-ray plates used are more sen-
sitive to the rays produced at 13-in. gap.
There is other evidence to show that the first
work on crystal-reflection of X-rays will serve
to decide between the two hypotheses.
From the data at hand, it is easily possible
by well known means to construct formulae
for computing the exposure necessary for
radiographing steel at various spark gaps.
798
GENERAL ELECTRIC REVIEW
Let Q0 be the quantity of X-rays impinging
on the steel during the exposure.
■ Let Q be the quantity of the rays which pass
through the steel.
Let x be the thickness of the steel.
Let X be the coefficient of absorption of the
steel. Then, if the X-rays are homogeneous.
Where e is the base of natural logarithms.
£1 En /s
Now at 15-in.
gap we know that
Likewise for 15-in. gap
X = 4.16 inches-1 = 1.64 centimeters-1
Applying the same method for 11-in. gap
X = 4. SO inches-1 = 1.S9 centimeters-1
Now at 15-in. gap and 20-in. distance, 0.8
milliampere-minutes gives a good exposure
through x/2 inch of steel. A corresponding
darkening would have been produced on a
bare (unobstructed) plate by an exposure of
0.1 milliampere-minutes. This corresponds
Fig. 4a. Radiograph of Autogenous Weld in Steel. Sample
No. 1. Only the surfaces have been welded
Fig. 5a. Radiograph of Autogenous Weld in Steel.
Sample No. 2. Holes in center due to metal
not being thoroughly fused
Fig. 4b. Diagram of Section of Weld in Sample No. 1
The ravs given off at 15-in. gap are therefore
practically homogeneous. Since — = Vs at
Since -=- = XA
£1
13-in. gap, we may assume that these rays are
also practically homogeneous. Rays given
off at 11-in. gap are still sufficiently homo-
geneous, after having passed through the first
few hundredths of an inch of steel, to allow of
being treated as though they were actually
homogeneous. Calculations for exposures at
11-in. gap are to be considered as being only
good approximations.
For 15-in. gap we have
log s = i2\ = 2.079
X = 4.1(j inches-1 = 1.64 centimeters-1
Fig. 5b. Diagram of Section of Weld of Sample No. 2
to 0 in the formula. We may therefore write,
since 0o = £,
0A=Et
4.16 x
10 £=«*•«*
log* 10 £ = 4.16 x
login 10 £ = 1.80 x
£=l/10 1og-1.0 1.80*
where x is the thickness of the steel in inches
or
£=l/10log-110 0.71 x
where x is the thickness of the steel in cen-
timeters.
The corresponding formulas for 13-in. gap
are
E=3,20 log-1i0 ISO x (x in inches)
£ = 3/20 !og-1i0 0.71 x {x in centimeters)
RADIOGRAPHY OF METALS
r99
The approximate formulae for 11-in. gap are
£ = 3/5 log-1,,, 2.09 x(x in inches)
£ = 3/5 log-1,,, 0.82 x (x in centimeters)
It remained to find the thickness of the
smallest air-inclusion which could be radio-
graphed in steel at 15-in. gap. For this
purpose two plates of steel were taken. The
faces were machined flat and in one of them
a slot was cut, thus giving a wedge of air. The
slot and the faces of the steel plates were then
taking of pictures so that the technique of
radiography through metals might be worked
oat.
A record of a single example will suffice.
Four samples ot autogenous welds in steel
were obtained. The welding had been done
with an oxy-acetylene flame. The samples
were 3^ inch thick and about 4 inches square,
and their faces were fairly rough. Sample
No. 1 had only been welded on the surfaces.
(See Fig. 4b.) Sample No. 2 had been
Fig. 6a. Radiograph of Autogenous Weld in Steel.
Sample No. 3 Weld is porous
Fig. 7a. Radiograph of Autogenous Weld in Steel.
Sample No. 4. A good weld
Fig. 6b. Diagram of Section of Weld in Sample No. 3
I g
Fig. 7b. Diagram of Section of Weld in Sample No. 4
ground smooth. When completed, each plate
was % in. thick. The air wedge was 10 inches
long, 1 inch wide, and ^ inch thick at its
thick end. When the two plates were bolted
together, the air wedge simulated a blow-hole
in a casting. The wedge was then radio-
graphed at 15-in. gap. When the X-ray
plates were dry the place was noted at which
the outline of the wedge was barely visible.
In order to avoid error, only a small portion of
the wedge image was viewed at one time, the
remainder being blocked off with cardboard,
j, was found that an air inclusion 0.021 inch
, .ck could be detected in ] J4 inches of steel.
T % inches, an air inclusion of 0.007 inch
ln Id be detected.
C0Residrs the work that has been outlined
in much more has been done in the actual
ere
insufficiently heated so that there was incom-
plete fusion of the metal at the center. (See
Fig. 5b.) In welding sample No. 3 an excess
of oxygen had been used in the flame, which
caused the presence of oxide on the surface.
(See Fig. 6b.) Sample No. 4 was considered
to be a good weld. (See Fig. 7b.) One-half
of each face of the samples was machined off,
so that half the length of the weld was between
flat, parallel faces; the other half was left
under the original rough surfaces. As a
result, one-half of each sample was Y2 inch
thick and the other half was about % inch
thick. Radiographs were taken at 15-in. gap
under the conditions described above. Refer-
ence to the formula for exposure at 15-in. gap
shows that the exposures through the x/i inch
and ^ inch portions were in the ratio of 1
800
GENERAL ELECTRIC REVIEW
to 1.7. The resulting radiographs are shown
in Fig. 4a, 5a, 6a, and 7a.
Fig. 4a shows clearly the unwelded center
of sample No. 1 in both portions of the
picture. Fig. 5a shows, in both portions of
sample No. 2, the holes caused by the metal
not having been .thoroughly fused at the
center. That portion of Fig. 6a which was
taken through the machined end of the weld
of sample No. 3 would seem to indicate a
porous structure. Such a structure was
evident during the machining. The portion of
the picture taken through the unmachined end
of the weld did not show such a structure with
certainty. This was to have been expected, as
the inequalities in thickness due to the
uneven surface were at least as great as those
due to porous or frothy structure. Fig. 7a
shows that, as far as gross structure is con-
cerned, sample No. 4 was a good weld.
It is of course self-evident that a radiograph
gives only the gross structure of the metal,
and gives no information as to the "grain,"
crystal interlocking at the edge of the weld,
etc. A radiograph does, however, give
valuable information as to the presence of
blow-holes, slag inclusions, porous spots, and
defects of like nature which could not be
found otherwise except by cutting into the
metal. Unfortunately, no fluoroscopic screen
now known is sensitive enough for this work,
therefore all work in metals must be done
radiographically. An inspection of the for-
mula? that have just been derived demonstrates
that, for the present. at least, radiography of
steel is a commercial possibility only up to
thicknesses of Yi inch. For greater thick-
nesses, the time required is rather great.
The big saving in time which is gained by the
use of a 15-in. spark-gap instead of a 13-in.
gap makes it seem probable that a further
increase in the voltage across the tube would
allow one to radiograph still greater thick-
nesses of steel.
Fig. 8. A radiograph of a steel casting revealing a flaw in the interior of the plate
801
AIR CLEANING APPARATUS FOR THE VENTILATION OF
GENERATORS AND TRANSFORMERS
By William Baum
General Electric Company
In our last issue we published an article on "Tests for Dirt in an Air Supply." We now publish the follow-
ing comprehensive article on "Air Cleaning Apparatus." The author has gone into this subject so fully that
his treatment should be of great value to central station men. Dry air filters, wet surface filters, and air washers
of various designs are considered in detail and valuable comparative data and costs of operation are given.
This subject is of such live interest at the present time that we hope our article will fill the need expressed by
many central station men for such information. — Editor.
I. INTRODUCTION
The great importance of cleaning and
cooling the air used for the ventilation of
turbo-generators and air blast transformers
is well recognized.
The use of air for ventilating purposes
without any check on its purity results in the
rapid accumulation of dirt and oil with the
consequent risk of the breakdown of the
machine. Further, the accumulation of dirt
means rapid deterioration and frequent clean-
ing; to carry out the cleaning, the machine
must be shut down. These considerations
brought the question of air purification into
prominence.
The following is a study of air cleaning
apparatus which has been applied to the
ventilation of electrical machinery, and is an
attempt to arrive at a definite conclusion as to
the relative merits of the various apparatus
and their fields of application.
II. DRY SURFACE FILTERS
General
Modern dry surface filters consist of a
number of units or boxes suitably arranged
and fixed in a framework, the number depend-
ing upon the amount of air to be delivered to
the generator or transformer. Each unit
supports a filtering medium which permits the
passage of the air, at the same time obstruct-
ing the dust particles held in suspension. In
general, air filters should meet the following
requirements:
(a) Complete removal of suspended matter.
(6) Minimum loss in pressure due to air
passing through the clean and soiled filtering
medium.
(c) Minimum dimensions.
(d) Simple construction with means for
convenient removal and cleaning of the
filtering medium.
(e) Durable filtering medium which does
not require too frequent removal.
(/') Minimum fire risk.
In the following paragraphs these require-
ments are considered in detail :
(a) Complete Removal of Suspended Matter
Manufacturers of dry surface filters guar-
antee the complete removal of suspended
matter without giving, however, accurate
methods of determining the effectiveness of
cleaning. The degree of purification depends
upon the density of the woven material which
must be kept within reasonable degrees to
prevent excessive resistance to the passing
air.
(6) Minimum Loss in Pressure Due to Air Passing
Through
Fig. 1 relates to a dry surface filter which is
installed with a 6000-kw. A. E. G. turbo-
generator in the Berlin Electricity Works
and shows the resistance of the clean filter
and the increase of resistance as a function of
the hours of operation.
The filter started at a resistance of 5 m/m
(0.197 in.) of water column and rose to 26
m/m (1.02 in.) after 2000 hours of operation.
Then the filter was cleaned by means of
suction air and the resistance fell to 9 m/m
(0.354 in.), rising again to 28 m/m (1.1 in.)
after 2S20 hours of operation. A second
cleaning took place, the resistance falling to
10 m/m (0.394 in.) and rising again to 36 m/m
(1.417 in.) after 3600 hours of operation.
After a third cleaning, the resistance fell
again to 10 m/m (0.394 in.) and, as a maxi-
mum of permissible resistance had been
reached, the filter medium had to be replaced
by a new one after approximately 4000 hours
of operation.
The diagram indicates that the air resist-
ance after a cleaning process is always
higher than the resistance obtained after a
preceding cleaning and it is, therefore, neces-
sary to replace, with each cleaning process,
some of the units in order to keep the pressure
loss within permissible limits.
S02
GENERAL ELECTRIC REVIEW
i.ci Minimum Dimensions
An effective area of 0.2 square feet is
normally required for each cubic foot of air
per minute. The required area depends
so
I F,/ter /Verv
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Fig. 1.
Diagram showing the Air Resistance of an Air Filter in
connection with a 6000-kw. turbine
upon the nature of the filtering medium
which is spread on frames of wood or metal
in such a manner that a maximum of effec-
tive surface is obtained with a minimum of
space. The air velocity is in the neighborhood
of 6 to 10 feet per minute, according to the
amount of dirt in the air.
The filter medium is arranged in zig-zag
or in independent pocket form ; the latter type
is preferable as the individual pocket can be
easily removed, cleaned or replaced without
interrupting the filtering process. Cotton
rope filters require less space than cloth
filters.
d I Simple Construction with Means for Convenient
Removal and Cleaning of the Filter Medium
A great variety of dry surface filters has
been designed in Europe and their con-
struction will best be understood by referring
to the illustrations in this article. Cleaning
takes place by means of compressed air or
vacuum. Chemical cleaning cannot be recom-
mended, as practice has shown that the
fluffy parts of the filters are destroyed,
materially reducing the cleaning effect.
Further, the filters shrink and the stretching
on the frames becomes difficult. The success
of dry filters depends largely upon careful,
regular cleaning and handling.
e Durable Filtering Medium which Does Not
Require Too Frequent Removal
The life of the filtering medium depends
upon the grade of the woven material, the
amount of dirt in the air and the general
climatic conditions. In very damp localities.
the filter becomes covered with a coat of
slime and rapidly loses its cleaning capacity.
The filter medium consists usually of a cloth
made of cotton flannel or is made up of
cotton rope in the form of fluffy
strings.
(/) Minimum Fire Risk
If the filtering medium, consisting
of a combustible material, catches fire
it may cause the complete destruc-
tion of the power house. Air filters
should always be installed within
brick or concrete walls or be sur-
rounded by a strong fence wire. They
should be accessible only to con-
scientious attendants. Where pos-
sible, the air should be taken directly
from the outside. So-called "fire-
proof" filters, consisting of impreg-
nated cotton material, are useless
after the cloth is soiled. In the filter manu-
factured by the "Filterfabrik und Apparate
Bau Anstalt" the cotton has a tube shape and
is enclosed by wire gauze to prevent the
entrance of flames on the Davy lamp principle.
Often a sprinkler system is furnished similar to
those found in offices and factories. The filter
T-fl
7//ij/!M/////mmm/////////ww/\
•),f">>>:»miii>i»i)i>).
iillll)))ll)l)liillllimil))llllimillllllll/llll)Mllll)ii)ilililimr77rr7m
Fig. 2. Trap Door Arrangement in the Air Passages
to a Turbine
manufactured by '"Le Filtre A. R. " is con-
structed of sheet metal, the only inflammable
material being layers of cotton wool which are
fastened to those sheets. An efficient precau-
AIR CLEANING APPARATUS FOR GENERATORS AND TRANSFORMERS 803
tion is taken by the Allgemeine Elektricitats-
Gesellschaft in Berlin. A trap door is provided
which is kept open by means of a counter-
weight suspended by a "fuse rope." In case
of fire in the filter chamber,
the fuse melts (at 60 deg.
C.), the weight drops and
the door closes, due to its
own weight. This arrange-
ment, which protects the
power house against de-
struction by fire, is shown
in Fig. 2.
The objections raised
against the installation of
dry surface filters are the
fire risk, inefficiency of puri-
fication, frequent cleaning
and replacing of the filter
medium and the fact that
the air passing through the
filter cannot be cooled as is
the case with air cleaning
apparatus of the wet type.
Modern dry surface fil-
ters have proven satisfac-
tory in practice and, as will
be^shown later, there are
certain fields of application where this type
can be used with advantage. Table I indicates
the extent to which dry filters have been
installed in Europe. It will be seen that one
Fig. 4.
A Filter of Balcke Manufacture installed in the
basement of a power house
Fig. 3. General View of the Filter of Balcke Manufacture
company alone installed, in the years 1900-
1909, not less than 1264 filters with a total
capacity of 16,100,000 cubic feet of air per
minute. It can be concluded from this table
that dry surface filters are used for the ven-
tilation of comparatively small generators.
BRIEF DESCRIPTIONS
Filter Manufactured by Balcke & Co.
The construction of this filter is shown in
Figs. 3 and 4. The filter cloth is arranged in
zig-zag pocket form, sewed together at the top
and bottom and stretched tightly by means of
screws which draw or release the frames as
desired. These screws operate through springs
of tinned piano wire to avoid rupture of the
cloth and to take up unevenness.
Filter Manufactured by the "Deutsche Luft Filter
Baugesellschaft"
The design of this filter is very similar to
that mentioned above, the cloth being
arranged in zig-zag pocket form, and tightened
by means of screws. A complete Delbeg
filter is shown in Fig. 5, and the arrangement
of a walled filter chamber below the floor
surface in Fig. 6.
These filters are also furnished with inde-
pendent pockets as shown in Fig. 7. This
804
GENERAL ELECTRIC REVIEW
modern design has the advantage that any
soiled or damaged pocket can be cleaned or
replaced while the filter is at work. This
advantage cannot be claimed by the single
cloth filter, the cleaning of which is difficult
on account of its bulk and weight.
Filter Manufactured by K. Th. Moller
This type has probably found the widest
application, and is of the independent pocket
design illustrated in Fig. S. The pockets are
secured by means of bolts and nuts.
Filter Manufactured by G. A. Schutz
Details of this filter. are shown in Fig. 9,
and a general vie.w of the assembly before
shipment is given in Fig. 10. One of these
filters has been installed in the Lauchhammer
station in which each of three 5000-kw.
generators require 31,800 cubic feet of air per
minute or a total of 95,400 cubic feet. This
interesting installation is fully described in
the Zeitschrift des Vereins Deutscher Ingeni-
eure, 1913, page 272.
Filter Manufactured by Dr. Hans Cruse & Co.
The filter medium consists of cotton rope
arranged in independent pocket frames in
such a manner that the center line between
two strings on one frame is covered by the
E..< < «..««,««<!fr?Vi «»«»» l»HH'
.
TT>i|»»»»»»> »»»»<»» «t»»«»l
Fig. 5. The Pure Air Side of a Complete Delberg Filter
Fig. 6. Diagrams of a Walled Filter Chamber below the
floor surface
TABLE No. 1
INSTALLATIONS OF GERMAN DRY SURFACE FILTERS
Name of
Manufacturer
No
of Units
Tot
Capacity Cu.
per Minute
Ft.
Ay.
in
Capacity per Unit
Cu. Ft. per Min.
Generator Size in Kw. Determined by
Assuming Av. Requirements of 3.5 Cu.
Ft. of Air per Min. for 1 Kw. Output
Balcke
Delbeg
Moller 1900-1909
Schutz
Bollinger
Haberl
262
1264
257
100
1,440,000
16,100,000
783,000
1,700,000
5500
12700
3040
17600
3640
5030
Average Generator Output 4335 kw
AIR CLEANING APPARATUS FOR GENERATORS AND TRANSFORMERS 805
center line of a string on the next. A hori-
zontal filter of this type is shown in Fig. 11
and a vertical filter in Fig. 12. The danger of
rupture of the filter medium, due to high air
pressure, is avoided in this design. The air
will always pass through the filter medium,
even after the fluffy strings are soiled. This
filter, which is also exploited in this country,
requires less space than other dry filters.
Filter Manufactured by "Le Filtre A. R."
This apparatus is illustrated in Fig. 13
and is constructed of perforated sheet metal
to which the filter medium, consisting of
cotton wool, is fastened. The plates are
arranged in steel boxes supported by a steel
frame. This filter is of French design and is
practically incombustible, but has not as yet
Fig. 8. A Filter of Moller Manufacture
found application for the ventilation of
generators, due to its high first cost and heavy
maintenance charge.
III. WET SURFACE FILTERS
This class is represented by the "Heenan
filter" which is manufactured in England
where it has found considerable successful
application in connection with the ventilation
of generators.
The design is based on the principle of
utilizing large wet surfaces for the air to pass
through. The wet surfaces take up the dirt in
suspension, every particle of the air being
thoroughly rubbed against the surfaces,
which are washed clean by rotating in water.
Fig. 7. A Filter with Independent Pockets
On account of the evaporation, the heat in
the air is rendered latent and a cooling effect is
obtained.
The construction is shown in Fig. 14. The
wet surfaces are contained in special drums
consisting of a cast iron center on which is
wound, spirally, thin galvanized plates or a
special cloth. A space of about one-seventh
Fig. 9. Two Views of a Filter of Schiitz Manufacture
806
GENERAL ELECTRIC REVIEW
inch is left between each layer for the air
to pass through. The drums are driven by
electric motors at low speed; the lower part
of the drum revolves in a tank of water and the
air passes through the upper part.
The advantages claimed and guaranteed
for this apparatus are the thorough cleaning
(98 per cent), effective cooling of the air
(within 2 deg. of the wet bulb temperature),
simplicity of construction, operation and
handling, the absence of loose moisture in the
air leaving the filter and the small power
required to drive the drum. According to a
statement bv the manufacturer, 49 filters have
Fig. 10. A Complete Assembled Filter of the Type
shown in Fig. 9
Fig. 11. A Horizontal Filter
Fig. 13. A Filter of Le Filtre A. R. Manufacture
Fig. 12. A Vertical Filter
AIR CLEANING APPARATUS FOR GENERATORS AND TRANSFORMERS 807
been installed having a total capacity of
1,258,500 cubic feet of air per minute, and on
the basis of 3.5 cubic feet for each kilowatt,
an average generator capacity of 7350 kw.
would result. This would indicate that wet
surface filters are used for larger generators
than dry surface filters.
Where the water can be circulated in the
system and only enough added to make up
for the loss due to evaporation, the tem-
perature of the water and the air in the spray
will be within a few degrees of the wet bulb
temperature of the air. The following tabula-
tion may serve as an example :
Fig. 14. Diagrams of a Rotary Wet Surface Filter
IV. AIR WASHERS
General
All modern air washers operate upon the
same general principle. The air to be cleaned
comes into close contact with water in the
form of mist or spray. Dirt in suspension is
saturated with water whereby its weight is
increased. The air leaves the spray and passes
between "eliminator plates." The water
and wet dirt particles, having greater inertia
than the air, strike these plates and are
washed down to a settling tank. The air
leaves the washer clean and free from unevap-
orated moisture.
In passing through the spray, the air evapo-
rates water and the temperature of both the
water and the air is reduced. The reduction
of the air temperature depends upon the
humidity of the entering air and the latter is
subject to changes in various localities and at
different times of the day. If the entering
air is saturated, there will be no evaporation
and consequently no temperature reduction.
Tem-
perature
of Air
Before
Entering
1st example 25 deg. C.
2d example;35deg.C.
3d example!40deg. C.
Relative j Theoretical
Humid, of ^ Temp, of
Entering Leaving
Air Air
70%
60%
50%
21 deg. C.
28 deg. C.
30 deg. C.
Probable
Temp, of
Leaving
Air
22 deg. C.
30 deg. C.
33 deg. C.
It is evident from these figures that the
lower the relative humidity, the greater is the
quantity of water evaporated and hence- the
lower is the resultant air temperature. The
cooling effect of air washers can, therefore, be
based on the knowledge of the existing
atmospheric conditions only.
If the water, instead of being circulated in
the system is continually renewed, the air
can be cooled to the temperature of the water.
If an ample supply of cold water can be
obtained without the risk of freezing in winter,
808
GENERAL ELECTRIC REVIEW
this is the better method of cooling, as it is
independent of the humidity of the air.
A general discussion on air washers and the
operating conditions, with special reference to
the cooling effect, will be found in Edgar
Knowlton's article, "Ventilation of Steam
Turbine Engine Rooms," which appeared in
the General Electric Review, September,
1913, page 627.
The prime object in the installation of air
washers, or as they are often called, humid-
ifiers, is to clean the ventilating air. Advan-
tages due to cooling and consequent greater
capacity of generators or transformers are
incidental. In hot, dry localities, the cooling
effect of humidifiers may be appreciable but
the rating of generators or transformers
should never be established on this cooling
effect on account of the liability of accidental
interruption of the air washer and the con-
sequent possibility of dangerous overheating.
It has been claimed that the moisture of
the air entering the generator tends to increase
the cooling effect as water vapor has a higher
specific heat than air. Air. Knowlton has
shown in the above mentioned article that
the amount of water vapor, even in a saturated
mixture, is too small to have an appreciable
effect on the specific heat, the energy absorbed
by the saturated air being only 1J4 per cent
greater than the energy absorbed by perfectly
dry air.
As far as practical experience has shown, no
insulation troubles have been experienced due
to the effect of the saturated air upon gener-
ator windings. It is essential that the moist
air which comes in contact with the windings
be free of entrained water. As a matter of
precaution, the sprays should not be started
until the generator becomes sufficiently warm
to prevent condensation of the moisture; also,
the sprays should not be in operation after
the generator is shut down.
In some power houses, as for instance in
the Delray station of the Detroit Edison
Company, air washers are installed on the
roof and a fan is provided which draws the air
through the washer from which it is dis-
charged into the turbine room. With such
an arrangement, an even distribution of the
cleaned and cooled air throughout the room
is secured. The air leaving the washer is
heated to a certain extent by passing over
heated surfaces in the turbine room before
entering the generator. As a result of this, the
air is not in a saturated condition when it
comes in contact with the insulation, whereby
any effect upon the insulation of the windings
Fig. 15. Sectional View of the Carrier Spray Nozzle
Fig. 16. Sectional View of a Filter showing spray nozzles
and eliminators
Fig. 17. Motor and Pump furnished for use in connection
with the filter of the Carrier Company
Fig. 18. Self-Cleaning Rotary Strainer used in connection
with the filter of the Carrier Company
AIR CLEANING APPARATUS FOR GENERATORS AND TRANSFORMERS 809
is eliminated. The cooling effect, of course, is
offset as the air is heated before entering the
generator. However, the power house has the
benefit of the clean cool air. Finished metal
parts coming in contact with the moist air
corrode quickly.
Air washers operating on cold days in
winter may cause thick layers of ice to form
on the windows of the power house, but any
danger of water freezing can be avoided by
drawing the air from the power house through
the washer instead of taking it from the
outside.
Nozzles, strainer and settling tank should
be cleaned once a week.
The velocity of the air passing through the
humidifier is from 600 to 750 feet per minute,
in rare cases even higher. The pressure
developed by the centrifugal pump to force
the water through the nozzles is from 25 to 30
lb. per sq. in.
Where the air is directly discharged into
the generator, a fan is mounted on the rotor,
developing a static pressure of four to ten
inches of water, depending on the size of the air
passages through the machine. This includes
some margin for a drop of pressure in ducts
leading to the generator. A drop of 0.5 inch
may be allowed through air washers without
detriment to the ventilation of the generator.
Manufacturers of air washers usually
guarantee a cleaning efficiency of 95 to 98
per cent and a temperature reduction to
within 2 deg. of the wet bulb temperature of
the entering air.
A number of test methods for determining
the effectiveness of cleaning have been pro-
posed, but on account of the different nature
of such tests, none have been satisfactory for
practical purposes. The American Society
of Heating and Ventilating Engineers issued
a report in 1914 outlining standard methods
for testing air washers. Perhaps the best
method which gives fairly good results for
practical purposes is described in an article,
"Tests for Dirt in an Air Supply," by Sanford
A. Moss in the July, 1915, issue of the
General Electric Review. This method
relates to cotton covered wire screens which
are placed in the inlet and outlet of the
humidifiers until both screens appear to have
absorbed the same amount of dirt; the ratio
of the time exposed giving the efficiency of
cleaning.
According to available statistics, 58 air
washers have been installed in the United
States for the ventilation of generators,
giving an average capacity per unit of 36,582
cubic feet of air per minute. Assuming again
an average requirement of 3.5 cubic feet of
air for each kilowatt generator output, an
average generator size of approximately
10,000 kw. results.
Fig. 19. Interior of a Humidifier of the Carrier Company
It is thus shown that air washers are used
for the larger generators, dry surface filters
for the smaller, and wet surface filters for
medium sizes.
BRIEF DESCRIPTIONS
Air washers consist of the following essential
parts :
Spray chamber, spray nozzles and piping,
eliminator or baffle plates, strainer, settling
tank and water circulating system with
pump.
The difference in the various makes is
principally in the design and arrangement of
the nozzles.
Carrier Air Conditioning Company of America
The Carrier nozzle has a comparatively
large discharge opening, ranging from -j^g- in.
to -£2 in- and is shown in Fig. 15. The water
enters a circular chamber tangentially, receives
a whirling motion, and, as it approaches the
opening, an increase of velocity is caused by
the change in the shape of the passage until
it bursts into an atomized spray. This
atomizing effect, due to the centrifugal action
of the nozzle, is produced by a pressure of 15
810
GENERAL ELECTRIC REVIEW
lb., per sq. in. and is increased with greater
water pressure up to about 40 lb.
The eliminators, shown in Fig. 16, are of
galvanized iron or copper, and are to prevent
entrained water particles entering the gener-
ator or transformer. There is a second
arrangement of nozzles on top of the elimi-
nators to keep their surfaces thoroughly wet,
thereby adding to the washing of dirt down
to the settling tank. The pump, furnished
by the Carrier Company, is of the horizontal,
split-shell, centrifugal type, and is shown in
Fig. 17. A suction screen of No. 20 copper
wire, 14-mesh cloth, extends completely
across the tank to filter the water. A rotary
strainer with a self-cleaning arrangement is
furnished to prevent clogging of the nozzles
and is shown in Fig. IS.
The apparatus operates normally at an air
velocity of 600 feet per minute through the
eliminators. The resistance is 0.36 in. of
water column. The advantages claimed are
the combination of low water pressure, large
orifice in the nozzle and the self-cleaning
strainer, reducing the attention required for
the apparatus. A complete view is shown in
Fig. 19.
Spray Engineering Company
The apparatus shown in Fig. 20 differs
from the Carrier washer in the design and
arrangement of the nozzles. Fig. 21 and 22
illustrate the three parts forming the nozzle
and the section showing the direction and
flow of water. In passing through, the water
is given a rapid, rotating motion and a central
driving jet impinges on the rotating water at
the orifice and ejects it as a fine spray in a
solid conical formation. The fine mist pro-
duced by these atomizing nozzles is mixed
with the air which is again subjected to the
action of cross scrubbing sprays placed
beyond the first set of nozzles. The air then
passes through a screen and finally through the
eliminators. The apparatus is operated under
a comparatively high velocity, usually 720
feet per minute. The air resistance is never
more than 14 in. The sprays operate at 25
lb. per sq. in.
General Condenser Company
The arrangement of the nozzles is shown in
Fig. 23. The water entering the first set of
sprays is in the form of mist and is mixed
with the incoming air in a horizontal direction.
The draft effect of the first set of sprays is
neutralized by the opposing sprays of the
second set, the flow of air through the system
being maintained by the fan of the generator.
The object of this arrangement is to prevent
too much moisture and air passing to the
eliminators. The pressure at the nozzles is 30
lb. per sq. in. In almost every respect, this
apparatus is similar to others already men-
tioned.
There are a number of other types of air
washers manufactured in this country as well
as abroad. They have been used extensively
for the ventilation of public buildings, textile
industries and factories and are now being
applied to the ventilation of generators and
transformers. All these air washers work
upon the same general principle and differ
only in details of construction, and par-
ticularly in the arrangement and design of
Fig. 20. A Spray Engineering Company filter with
Motor and Pump
the nozzles. Among the best known builders
of air washers are the American Blower
Company, B. F. Sturtevant Company, Stuart
W. Cramer and Balcke & Company.
AIR CLEANING APPARATUS FOR GENERATORS AND TRANSFORMERS 811
V. COMPARATIVE DATA
A comparison of the approximate space
required by the different classes of air cleaning
apparatus is shown in Fig. 24, and a com-
parison of the approximate prices is indicated
in Fig. 25. The curves shown in these
diagrams are self-explanatory.
There are no operating costs for dry surface
filters, but the maintenance charges are
comparatively high in the medium sizes
and prohibitive in the larger sizes (above
5000 kw.). Expenses for labor and cloth
for a 3000-kw. generator requiring 15,000
Fig. 21.
Exploded View of the Spray Nozzle shown in
Fig. 22
cubic feet of air per minute would be approxi-
mately $400 per year. This expense depends,
of course, upon the amount of dirt which the
filter has to take up and also upon the damp-
ness of the atmosphere. An air washer of the
same capacity necessitates an expense of
approximately $300 per year for operation
and maintenance.
Wet surface filters have a very low cost
for operation and maintenance as the power
required to drive the pump is small and the
settling tank needs only occasional cleaning.
An estimate of the cost for operation and
maintenance of air washers is given in
Table III which is based on the assumption
that the cost of water is one cent per 1000
gallons and the cost of electric energy is one
cent per kilowatt-hour. The figures given
under the heading "operation" are based on
the requirements for water consumption and
Fig. 22. A Section of a Spray Nozzle. The dotted lines
show the direction of water flow
driving the pump motor, while the figures
under "maintenance" are based on the
assumption that the settling tank, screen,
strainer and nozzles are cleaned once a week.
This work is usually done by the man who also
attends to other auxiliaries.
An attempt is made to tabulate in a con-
venient form the advantages and disadvan-
tages of the three types of air cleaning
apparatus in Table IV in which "D" desig-
nates dry surface filters, "W" wet surface
filters and "A" air washers.
^V/V<£vIrV?/U CO/V2)^/VJf7? Co
—HotiTvN HlHtlUTOKS
Fig. 23. Complete Diagram of the Air Washer of the General Condenser Company
812
GENERAL ELECTRIC REVIEW
moo
/GOO
«
^1200
u
\1000
\J
t; BOO
\ *»
200
O
*•
^'
1 US'!-- ^ '
~J7«?f'
„?»<**-'' X--~~
_ --' ^wr^rrL--"
-•- D!2x3t5-h?;tei-
_,--■ ---~^kirWF
*■ ~^~ -^~v~-~~ ~*
"" --==r""
__..'5=-
-^P^T ± ± " ..
/A?<9? Z00OO -3G0OO aOOOO SOOO0 60000 7OOO0 3O000 SOOO0 /OOOOO
CojXJOtt^y met/tote f""*t ofo/r- per- r77in{jt&
Fig. 24. Curves showing the Approximate Space Required
by Air Cleaning Apparatus
if,
88-
r
\
rv
5$
J:\
i v\
A ^*
V ^s*.
\ "-*=^
. ±
^ = = = =
•;-^- _:.. —'.--.~ -~
'«»s4_
x-^
— ■ — > ,
1 1 1
T
rtf-MfosfTGr:*
:
»va^-fc. r,,
e/»
~X- %
X4-
i in:
/#**? aaaa? 30000 40000 joooo soooo 70000 &oo0o 90000 /0000O
Co&ac/ty /" cutec- feet ofotrper rr>i/->vce.
Fig. 25. Curves showing the Approximate Average
Prices of Air Cleaning Apparatus
VI. CONCLUSIONS
Dry Surface Filters
For generators up to about 5000
kw., dry surface niters may be
recommended on account of their
low first cost, and if the air is not too
dirty, thereby keeping down the
maintenance. Their application is of
advantage in dry, cold climates. Dry
surface filters require careful attention
and handling.
Wet Surface Filters
This type, which has found success-
ful application in England, has not
as yet been introduced in this
country. Its field of application is
for generators of medium size (above
5000 kw.). This interesting appa-
ratus has given satisfaction in various
electrical plants in England.
Air Washers
The tendency toward the installa-
tion of large turbo-generator units
will undoubtedly increase the applica-
tion of air washers or humidifiers
in preference to other types of air
cleaning apparatus. In dry, hot
localities, the cooling effect of air
washers is appreciable. Special pre-
cautions are necessary to prevent
freezing of the water in winter.
TABLE III
AIR WASHERS
Capacity
in Cu. Ft.
Approx. Yearly
Cost of Opera-
Approx. Yearly
Cost of Main-
Yearly Total
Cost
Cleaning
7,500
$165.00
$45.00
$210.00
10,000
200.00
50.00
250.00
20,000
300.00
50.00
350.00
30,000
360.00
55.00
415.00
40,000
400.00
60.00
460.00
.50,000
500.00
65.00
565.00
60,000
600.00
70.00
670.00
70,000
630.00
75.00
705.00
80,000
720.00
75.00
795.00
90,000
810.00
80.00
890.00
100,000
900.00
80.00
980.00
TABLE IV
Advantages
Type
Disadvantages
Type
Cleaning effect DWA
Fire risk :
D
W A
D
A
W A
Low cost of operation |D W
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813
THE INDIVIDUAL AND CORPORATE DEVELOPMENT
OF INDUSTRY
By Dr. Charles P. Steinmetz
Chief Consulting Engineer, General Electric Company
This contribution is of great human interest. The author shows that the growth of the corporation
schools and other " welfare work " activities was a natural process of evolution with the change from indi-
vidualistic to corporate industrial undertakings. He discusses the great problem of education to meet modern
industrial needs in an able manner and shows that the -industries themselves must give the technical training
after the schools have laid the foundations of a general education. The fact that the employee must be in
sympathy with the efforts of the employer to get the best cooperative results in all activities designed to
better industrial conditions is emphasized. This article was given as the author's presidential address to the
National Association of Corporate Schools, at Worcester, Mass. — Editor.
During the last generation a radical
advance in the efficiency of the industrial
system of our country has taken place
through the progress from the individualistic
production of the days of Lincoln, to the
corporate production of today. While the
corporation is proving the most powerful
and most efficient tool of industrial progress,
at the same time some defects have appeared,
and have led to the present rather wide-
spread antagonism against the corporation.
Nevertheless these defects are not inherent
in the nature of the corporation, but are
due to its newness and crudeness, which led
us to overlook too much the human element
in the industrial relation between corpor-
ations, employees and public. In the small
production of bygone days, personal relations
existed between the individual employer and
employee, which do not exist in the large
corporations, and must be replaced by
organized effort. That is, to the financial,
administrative and engineering or manu-
facturing activity must be added a fourth
activity, that dealing with the human
relation of the corporation with its employees
and the public at large, before the corporation
can socialogically justify its existence. The
beginning thereof is seen in the so-called
"welfare work" in attention to hygiene and
safety, profit sharing and service annuities,
etc., and in the educational work of the
corporation.
Amongst the first corporation schools were
the special apprentice courses established by
some industries to provide for their specific
educational requirements, which could not be
supplied by educational institutions nor by
practical experience. Such are the student
engineers' courses established twenty-five
years ago by electrical manufacturing com-
panies. In them college graduates are, by
one to two years' training in factory, testing
room and office, fitted for the higher positions
in the company. The early corporate develop-
ment of the electrical industry made this
possible, and also made it possible to exert a
considerable influence in shaping the curricu-
lum of engineering colleges towards the higher
efficiency of the graduates, and the superiority
of the electrical industry of the United States
is largely due to the educational work
carried on in co-operation with the engineering
colleges. Similar special apprentice schools
have been established by electrical operating
companies for the training of station opera-
tors, etc.
Intermediate between the special apprentice
schools and the general trade apprenticeship
are those dealing with new occupations
resulting from the corporate development,
such as salesmanship, business getting, office
work, etc. They represent activities suffi-
ciently broad to be undertaken by public
educational institutions, such as business
colleges, high school business courses, etc.,
in co-operation with, or preliminary to the
corporation school, and thus form a separate
class.
The most serious problem resulting from
the corporate development of the industry is,
however, the failure of the supply of skilled
workmen. In individualistic production, the
apprentice or helper learns his trade from
his employer, who was skilled in the trade.
To some extent this is still the case in some
trades. But within the field of the modern
corporation, with its subdivisions and increas-
ing specialization of work, very little chance
existed for the young man to learn a trade
and become a skilled workman. Immigration
from Europe for some time supplied skilled
workmen. However, European countries have
become industrial, and retain their skilled
men, and those who immigrate are directed
to European colonies, so that the supply by
814
GENERAL ELECTRIC REVIEW
immigration is vanishing, while the demand
of our industries is increasing.
Vocational training thus has become the
most important problem of the American
industries.
This is realized even more outside of the
corporation, by the general public. There it
appears as a problem of the parents, to find
a suitable occupation for their children, as
a problem of the young men and women to
find work without getting into a dead alley
occupation. Increasingly the general public
thus makes the demand on the public schools
to provide the vocational training which
the industry gave in former times, but which
now, in its corporate form, it fails to give.
So far, the output of the apprentice courses
of corporations is still very small compared
with the industrial demand.
The trade apprenticeship courses of corpor-
ations, and the industrial education of the
public schools, at first appear to be in compe-
tition with each other, but in reality the
problem of the trade apprenticeship can be
solved only by the co-operation of the
corporation and the public school, as was
proven by the experience in the profession.
Once it was customary for a young man to go
into an engineering office to learn engineering,
into a law office to study law, etc. Experience
has eliminated this as giving too narrow
and limited knowledge, and the engineering
college, the law school or medical school now
are the avenues of approach to the profession.
But experience also has shown that the
graduate of the engineering school is not an
engineer, the graduate of the law school or
medical school not a lawyer or physician, but
merely prepared to enter the practical part
of his professional education in the industry,
the law office or the hospital. Applying the
same to the trades, we see that the practical
trade training must be given in the industry
by the corporation apprentice course, but
the public schools must do the preparatory
work.
The field of the corporation school is the
industrial training of those fitted for the
industry. The field of the public schools is
the general education, that is, to supply that
minimum amount of knowledge which even-
intelligent citizen must have before he can
specialize in trade or profession, or at least
that part of general education which is
difficult to acquire afterwards. With increas-
ing civilization, the requirements of general
education also have increased. With increas-
ing population density and the growth of
cities, physical development, hygiene and
medical supervision become essential parts
of public education, and familiarity with the
use of the most common industrial tools,
such as the hammer, saw, etc., which formerly
was acquired in the home, has to be taught
by manual training in the schools. This
increasing general educational demand on the
schools precludes the possibility of industrial
training, that is, of teaching a trade, within
the limited time of mandatory school atten-
dance, and industrial or vocational training
thus must be a continuation of school work,
while manual training, giving a general
familiarity with the common tools of industry
such as every man should possess, belongs to
the grades as mandatory subjects. This sharp
distinction between manual training and
industrial education is not always realized.
Industrial training belongs to and can be
efficiently accomplished only by the industry,
by the corporation apprentice course taking
the place of the former individual apprentice-
ship or by co-operative systems of public
schools and corporations; vocational continua-
tion schools, technical high schools, etc., can
be of limited usefulness only, but the new
field of the public school is to establish an
intelligent system of vocational guidance,
based on the teacher's familiarity with the
pupil's characteristics, and especially on the
adaptability and interest shown in manual
training, so as to lead the pupils into those
trades and professions for which they are
adapted, and in which they can find the
satisfaction resulting from success.
With the heterogeneous population of our
country, where some States maintain fairly
good educational systems, many other States
practically none, and a large number of
immigrants, handicapped by unfamiliarity
with the American language, complicating
the problem, the general educational work
of the public school can not stop at the end
of the school age, but must be continued by
evening schools, language classes and other
educational efforts, and it is the duty of the
corporation to see that these educational
facilities are provided by the public schools,
and to exert its influence on their employees
to avail themselves of these educational
facilities.
The limitation of the corporation activities
in the educational and -similar fields neces-
sarily is that given by the limitation of the
corporation's purpose — to earn dividends for
its stockholders. No human activity can be
justified before the stockholders' meeting
THE INDIVIDUAL AND CORPORATE DEVELOPMENT OF INDUSTRY 815
which does not show a favorable financial
balance, however much the corporation
directors may desire philanthropic work.
This is often difficult, as the beneficial results
are largely intangible, and it must be proven
to the satisfaction of the administrative
heads of the corporation that these benefits
are very real, consist in the better relation
between corporations and employees, their
higher efficiency and better co-operation, the
lesser liability to interference by industrial
warfare, etc. Also, we must realize that the
right of existence of the corporation is
challenged by a considerable part of the
public, and self-defense justifies the expense
of activities bringing home to the public
the benefits which can be derived from
corporate industrial organization.
The human activities of the corporations
are co-operative with its employees, and the
favorable attitude and viewpoint of the
employees thus is essential for their success.
Herein lies the cause of many of the failures.
It is not sufficient for the corporations to
undertake such educational and welfare work
and other activities as are in the opinion of
the corporation managers for the best interest
of the employees, but the corporation actions
must be such that the employees and their
organization take the same viewpoint, other-
wise welfare work may be resented as charity,
educational work opposed by the suspicion
of an ulterior motive hostile to the employee's
interest, as an attempt of breaking down
their organization, safety regulation as an
attempt to evade responsibility, etc.
In the individualistic production of old,
employer and employee met on fairly equal
terms. With the close organization of
numerous employers, as stockholders of the
industrial corporations, organization of the
employees also appeared, as a matter of
course, in the labor unions. Theoretically,
the aims of both organizations, the organiza-
tion of employers as stockholders of the
corporation, and the organization of employ-
ees as labor unions, are the same: efficiency
of industrial production to increase the
return on the investment in labor and in
capital. Unfortunately, however, the relations
between the two organizations have fre-
quently been hostile industrial warfare over
the distribution of the returns rather than
co-operation for the increase of financial
returns of both parties, and as the result,
mutual suspicion and antagonism has arisen
making efficient co-operation for mutual
advantage of corporations and employees
difficult, while the obvious advantage of
organization, illustrated in the industrial
corporations, necessarily tends to lead to the
organization of the employees in some form
or another, and any attempt of substituting,
for the unions formed by the employees,
employees' organizations formed by the
corporation, give an apparent justification
to suspicion. On the other hand, there always
have been and always will be leaders, as the
majority of the people prefer to be led, and
the natural leaders in the co-operate human
activities of the industrial corporations would
be the leaders in its other activities, if once
the suspicion were removed by evidence
that suspicion is not justified any more, and
the leadership accepted.
This problem is still unsolved, and is most
serious, especially in a democracy, where
hostile masses, though incapable to recon-
struct, have the power to destroy, and are
beginning to use it, as the industrial history
of the last ten years has shown.
While under pressure of public opinion,
influenced by the dying remnants of former
individualistic production, and hostile
employees' organization, all political parties
profess hostility to the great industrial
corporations in the fulminations of the stump
speakers or soap-box orator at the street
corners, there is nothing in the principles of
the great political parties antagonistic to
corporate organization of the industries.
The principle of the republican party has
always been centralization, that is, to the
larger organization belongs what it can do
better than the smaller organization. This is
the principle of the industrial corporation.
The democratic party has been the party
of decentralization, of individualism, and
therefore was inherently hostile to the
corporations, but industrial laws, more power-
ful than party doctrines, are forcing it towards
centralization, and all the constructive work
of the present democratic administration has
been unwilling centralization.
The socialistic party can not be antagonistic
to the corporation principle, since its ultimate
aim, socialistic society, may be expressed as
the formation of the industrial corporation of
the United States, owned by all the citizens
as stockholders.
More serious appears the objection against
the industrial corporation, that it destroys
the individualistic development, on which all
progress, in invention, scientific research, etc.,
is based, and therefore is hostile to civilization.
It is true that in the early days of the new
816
GENERAL ELECTRIC REVIEW
country, when unlimited natural resources
gave everybody a good chance for success,
individualistic effort was most efficient for
progress. But these times have long passed,
and in the world today the fight for existence
has become so intense that the individual's
energy is wasted in the mere earning of a
living, without much chance of development,
and it is only in the comparative safety of the
industrial corporation, or the educational
corporation, the university, that the condi-
tions are favorable for such development of
individualism as leads to the world's progress.
It is significant that today practically all
scientific research, most of the inventive
and development work, is done within the
industrial corporations or the educational
institutions, and very little by the unattached
individual, showing that in the corporation
is found also the most efficient means of
making individual development possible in
our present state of civilization.
THE CATHODE RAY TUBE AND ITS APPLICATION
By M. E. Tressler
Research Laboratory, Pittsfield Works, General Electric Company
In the first section of the following article the mechanical construction and theory of operation of several
of the more successful cathode ray tubes is described. The second section contains a treatment of a subject
concerning which but very little has been published, viz., the use of the cathode ray tube as an oscillograph
and a wattmeter. — Editor.
The cathode ray tube in its simplest form is
a glass tube from which the air is exhausted to
a vacuum of 4 to S microns, i.e., to an air
pressure of 0.004 to O.00S millimeters of
mercury.
In one end of the glass tube is a small,
flat metal disk which is connected through the
glass to a terminal on the outside. This is the
cathode. At one side, or in the tube about
15 to 20 cm. away from the cathode, is another
metal electrode which is connected through
the glass to a terminal on the outside. This
is the anode. This is all that is actually
required to produce the cathode rays, but in
order to make use of them, the rest of the
tube must be formed to a particular shape and
several parts added.
The diaphragm is usually a glass or metal
disk just below the anode which closes the
tube with the exception of a small hole in the
center of this disk about 0.4 to 0.S millimeters
in diameter. About 35 cm. below the dia-
phragm is fastened the screen on which the
cathode particles strike. This screen is a
metal, mica or glass disk coated with some
salt which fluoresces when acted upon by the
cathode rays. This fluorescence may then be
observed visually or it may be photographed.
A sketch of the tube is given in Fig. 1.
C is the cathode, A anode. D diaphragm, 5
screen, R palladium tube regulator, F focusing
coil, 0 quadrants.
The tube is operated as follows: The
negative terminal of a high voltage (12,000
to 30,000 volts) direct current generator is
connected to the cathode and the positive
terminal to the anode, the anode being
grounded. The voltage to apply depends
upon the vacuum maintained in the tube, the
steadiness of operation desired, the position,
shape and connection of the focusing coil, the
intensity of the magnetic field of the focusing
coil and other minor influences. With this
voltage applied there is a stream of electrons
or negatively charged particles shot from the
cathode normal to its surface with a velocity
of 5000 to 60,000 miles (8 to 96 X 10s cm.) per
second, depending upon the vacuum in the
tube and the voltage applied. This discharge
of electrons is produced by the electric field
between the cathode and anode.
The attenuated gas in the tube is generally
understood to consist of a mixture of neutral
gas molecules, i.e., molecules where the
positive and negative charges are exactly
balanced; of gas molecules positively charged
because they have lost one or more electrons
or negative charges; and of free electrons
which have been separated from the gas
molecules, these being, of course, negatively
charged.
As soon as the electric field is set up the
positively charged molecules are attracted
toward the cathode and the electrons are
THE CATHODE RAY TUBE AND ITS APPLICATION
S17
repelled. By the time the positively charged
molecules have gotten to the cathode, they
have attained sufficient velocity so that the
force of the collision bumps off one or more
electrons. The positively charged molecules
in going to the cathode surface also run
against neutral molecules and electrons with
sufficient force to separate electrons from the
neutral molecules and even to lose electrons
themselves. The electrons, being negatively
charged and of very much smaller size and
mass than the molecules, are repelled with
much higher velocity from the cathode than
the molecules are attracted. These negative
particles from the cathode pass down the
tube to the diaphragm where most of them
are stopped, except a small beam which
passes through the central opening and strikes
the fluorescent screen. The diaphragm is
grounded so that the charge that would tend
to collect on it from the cathode particles is
neutralized.
Shunt.
^Condenser
Fig. 1
If the cathode surface was a perfect plane,
all of the cathode particles would start normal
to this plane, but, as compared with the size of
the cathode particles the unevenness of this
surface is very large, hence some of the
particles start off at an angle other than 90
deg. to the plane of the cathode surface.
This tends to make the cathode discharge a
diverging one, but even if this were not the
case there would be a spreading out of the
discharge, due to the repellant force between
negatively electrified particles. This spread-
ing out of the discharge is partially overcome
by the focusing coil which gives a longitudinal
magnetic field in the direction of the stream of
cathode rays, and which tends to concentrate
the rays and hence increase the intensity of
the beam passing through the opening in the
diaphragm.
The palladium tube regulator which is
connected opposite the anode is used for
regulating the vacuum when there is an
increase of vacuum due to a long continued
use of the tube at high voltage. The palladium
tube is sealed in the glass and closed at its
outer end. When heated to a red heat it
allows a small amount of gas to pass through,
and hence raises the gas pressure inside the
tube.
The diaphragm must be made of a suf-
ficiently dense, thick material so that the
cathode rays will not pass through it. A
platinum diaphragm 0.005 in. (0.127 mm.)
thick will allow the cathode particles to pass
through it. A brass cup with walls 0.030 in.
thick is commonly used and found satis-
factory.
The screen in order to be fluorescent is
coated with willemite, zinc sulphide or calcium
tungstate. The willemite gives a yellowish-
green fluorescent light when excited by the
cathode rays, which is very bright to the eye
but is not very active actinically, i.e., when
photographed it does not act rapidly on the
photographic plate. The zinc sulphide is
said to be very actinic, and is used by a great
many experimenters with the cathode ray
tube. Calcium tungstate has been found to
be the most actinic and best suited for our
work thus far. It gives a bluish-white fluo-
rescence which is quite brilliant, both visually
and actinically.
Other Methods of Producing Cathode Rays
There are several other forms of cathode
ray tubes where the electron or cathode
discharge is produced in a different manner.
Wchnelt's method of obtaining an electron
discharge is to coat a platinum strip with a
thin film of lime and then to heat the lime to
incandescence by causing an electric current
to flow through the platinum strip. He has
shown that the incandescent lime emits
copious steams of electrons in comparatively
weak electric fields. This discharge is also
largely due to the bombardment of the hot
818
GENERAL ELECTRIC REVIEW
lime by the positive ions or gas molecules, but
it is also due to the high temperature zone
into which these positive ions flow, the
electrons being much more readily separated
from them. Of course the velocity of the
electrons emitted from the hot lime is very
much lower than those which are repelled
under a very strong electric field.
j
1"
1
^G
If- -=1
1SH
o
1
Fig. 2
T
Fig. 2a
The latest and probably the best method of
obtaining an electron discharge in a cathode
ray tube is by means of the hot tungsten
cathode in a very highly exhausted glass tube
where the glass and all of the metal parts
have been kept in this high vacuum at a high
temperature for a sufficient time to get all
of the gases out of them.
When the cathode (which in this case is a
tungsten wire filament heated to high tem-
perature by an electric current flowing
through it) is connected to a high voltage,
there is a pure electron discharge from the
cathode with no accompanying positive ion
bombardment ; the tube having been exhausted
to such a high vacuum that there is an inap-
preciable number of positively charged mole-
cules or ions present. In this case the electrons
must come from the metal filament itself; the
number of electrons, or, in other words, the
current flowing depending upon the tem-
perature of the cathode and the voltage
applied, and the velocity of the electrons
depending upon the voltage only.
Uses
The cathode ray tube in practice has been
used as an oscillograph and as a wattmeter for
measuring very small amounts of power at low
power-factors and high voltages. In order to
use it as either one of these instruments it
requires some method of deflecting the beam
of cathode rays after it has passed through the
opening in the diaphragm and before it has
reached the screen. This is accomplished by
means of a transverse electric or magnetic
field applied a short distance below the
diaphragm opening.
The cathode particles carry a certain charge
or quantity of negative electricity and hence
when an electric field is applied at right angles
to the direction of travel of the particles they
are deflected parallel to the direction of the
field and if a magnetic field is applied they are
deflected at right angles to the direction of
the field. This is shown in Fig. 2 where the
circle is a section of the tube just below the
diaphragm and M is a set of magnetic quad-
rants and at £ a set of electric quadrants.
The deflection due to either field is in the
line a-b.
As accurately as can be measured from
photographs, it is found that the deflection of
the fluorescent spot on the screen due to the
field is directly proportional to the strength
of the field; that is, to the voltage applied or
to the current through the coil. This is so
because the angle through which the beam is
deflected is quite small, and therefore the arc
of the circle, whose radius is the distance from
the quadrants to the screen, through which the
spot would travel, is not appreciably different
from the distance on the surface of the screen,
which is the tangent of the angle. If an
alternating voltage is applied, the fluorescent
spot vibrates back and forth once per cycle,
which makes it appear as a line across the
screen.
In order to use it as an oscillograph, it is
necessary to have a photographic plate move
at right angles to the direction of vibration of
the spot which thereby will show the wave
shape.
When it is required to use the tube as a
wattmeter, two pairs of quadrants at right
angles to each other are required; on one
pair a voltage proportional to the current
flowing in the circuit is impressed and on the
other pair a voltage proportional to the total
voltage drop across the apparatus under test
is applied.
It will be noticed here that we have assumed
that an electric field is used for each pair of
quadrants, this being more convenient where
losses at high voltages and very small currents
are being measured.
The voltage for the current quadrants may
be obtained from the potential drop over a
capacity or resistance in series with the appa-
ratus or material under test. If a capacity is
used the area of the figure traced on the
screen will be a maximum when the power-
THE CATHODE RAY TUBE AND ITS APPLICATION
819
factor is 100 per cent, whereas, when a series
resistance is used the area will be a maximum
when the power-factor is 0 per cent. The
voltage for the voltage quadrants may be
obtained through a potential transformer or
from a capacity shunted across the line using
two plates of this condenser to step down the
The voltage across the condenser V is in
phase with that across the resistance R and
capacity C in series ; the wave is plotted as V
in Fig. 4, 90 deg. out of phase with the voltage
across the series condenser. This is not
exactly correct as the voltage across condenser
V is at a slight angle to the voltage across the
Fig. 3
voltage. The operation as a wattmeter is
shown in Figs. 3, 4 and 5.
Assume that it is desired to determine the
loss in a high resistance when subjected to
high voltage. The voltage drop over a con-
denser in series with the resistance is used to
produce the current deflection when connected
to the current quadrants and the voltage drop
over a part of a condenser shunted across the
^
107 C.
86 VPM
N. X. c IOTC.
" \ 139 VPM
<- I07°C.
190 VPM.
C 107 °C
2 18 VPM
277 VPM
Constant Voltage,
Variable Temperature
Fig. 6 Constant Temperature,
Variable Voltage
resistance and series condenser is used to
produce the voltage deflection when connected
to the voltage quadrants, as shown in the
circuit of Fig. 1. Taking the simple circuit
in Fig. 3, the current in C is in phase with the
current in R, but as C is a pure capacity the
voltage must be lagging 90 deg. behind the
current. This wave is plotted as Vc in Fig. 4.
resistance R, depending upon the voltage drop
over the condenser C. However, this is not
large, as the voltage over the condenser is
never greater than 15 per cent of the total
voltage across the condenser and loss together.
This slight phase angle is corrected for in
determining the true power-factor, by calcu-
lating the angular difference due to this series
condenser and subtracting it from the meas-
ured 6', where cos 0' is the measured power-
factor, leaving the angle 6 whose cosine
would be the true power-factor of the material
under test.
Now, if we take the line in which the
fluorescent spot vibrates, due to the voltage
across the series condenser, as the axis of
abscissa, and the line due to the voltage
across the shunt condenser as the axis of
ordinates, and plot instantaneous values of the
two waves in this co-ordinate system, it will
be seen that the fluorescent spot traces out
a closed figure, Fig. 5, on the screen which will
be a circle, ellipse or straight line, depending
upon the relative amplitudes of the two
voltages and the power-factor of the loss being
measured.
In order to know what this loss is in watts,
the voltage drop across the series condenser
is measured with an electrostatic voltmeter
and from the known capacity of this condenser
and the frequency and wave shape of the
voltage the current flowing in the circuit can
be calculated. The current and voltage are
now known and it becomes necessary to
obtain the power-factor, when the watts can
be calculated.
The power-factor is found to be the ratio
of the area of the figure as measured, to that
of the maximum area which could be obtained
with the separate measured deflections. This
820
GENERAL ELECTRIC REVIEW
is determined briefly as follows: The area
of the maximum ellipse is ir ab, where a is the
semi-major deflection and b is the semi-
minor deflection. The area of the ellipse,
x
-t-fc
+■ t
I
4= A
fl
ZJZ" " AJ&L-M
-12^ £y
/ Ap/
lS^ j
^P^ .'
-*^*^ -*^
=t= -
40 ao Volt-s perMll. i6o
zo 4o Temp.CX ao
200
ioo
240
120
aao
140
Fig. 7
which measures a loss whose power-factor is
cos 8' , would be 7r ab cos 8' .
„ ir ab cos 0' , ,
Hence - — ; = cos 8 , or power-factor,
7r ab
which is the measured area divided by the
maximum area calculated from the separate
deflections.
With a sine wave in both co-ordinates, the
maximum area would be w '4 times the prod-
uct of the length of the two co-ordinates VV
and CC. Then the measured area of the figure
divided by the maximum area gives the power-
factor. Hence we have measured the voltage,
current and power-factor and then can readily
calculate the loss.
In Fig. 6 is shown two series of losses; one
is the dielectric loss vs. temperature on black
varnished cloth at a given constant voltage,
and the other is dielectric loss vs. voltage at
a given temperature.
The law of variation of dielectric loss in
insulations with variation of temperature and
voltage has not yet been determined. If the
loss were similar to a resistance loss, we would
expect that it would vary as the square of the
voltage if the temperature could be kept
constant. However, there are several factors
which enter into the problem, such as the
thickness, area, thermal conductivity, specific
heat of and the amount of moisture in, the
material under test, the size and material of
the electrodes, length of time the voltage is
applied, etc., that make the calculation quite
difficult and unsolved as yet.
821
LAW OF "CORONA" AND SPARK-OVER IN OIL
By F. W. Peek, Jr.
Consulting Engineer, General Electric Company
The author shows that the mechanism of breakdown in gaseous and liquid insulations is very much the
same; the general laws which he has developed for air also apply to oil. These laws may be used in practice
in calculating the breakdown voltages in oil. Data on the various properties of oil for 60-cycle, high frequency
and impulse voltages are given. — Editor.
General Characteristics same as for air excepting the apparent
The most common liquid insulation is strength is very much higher,
transil oil. Its average characteristics are The dielectric strengths of oils are usually
as follows :* compared by noting the spark-over voltage
Flashing temperature
Burning temperature
Freezing point
Specific gravity at 13.5 deg. C
Viscosity at -10 deg. C. (Saybolt test)
Medium
180 deg.— 190 deg. C.
205 deg.— 215 deg. C.
-10 deg.— -15 deg. C.
0.865 — 0.870
100— 110 sec.
Light
130 deg.— 140 deg. C.
140 deg.— 150 deg. C.
-15 deg.— -20 deg. C.
0.845—0.850
40—50 sec.
Various other oils, mineral, animal and
vegetable, are insulators. All of these in the
pure state have more or less the same order
of dielectric strength.
Compounds made by dissolving solids in
oil to increase their viscosity are generally
S2C
zoo
ISO
160
i,ff0
0- /so
<y
60
ac
so
S 6 7 e 3
5jX7C/ng-<zm.
Fig. 1
unreliable unless used dry, e.g., varnish; under
the action of the dielectric stress the various
dielectrics of different permittivities tend to
separate. As in air, there is very little loss
in pure oil until local rupture occurs in the
form of brush discharge or corona.
Different Electrodes
In Fig. 1 are plotted 60 — spark-over curves
for different electrodes in good transformer
oil. The characteristics are very much the
J ! 1 1 1
1 1 1
/
'/25 cm <J/a a
ofteres
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'
/
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i
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S
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1 1 1
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A
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r?eef?s
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t
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5por/T-over Vo/£age5 &f
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r&r-/oess £/ectr
oefes
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t
*
'
between two parallel brass disks 1.25 cm.
in diameter, and 0.5 cm. (0.2 in.) separation.
The spark -over voltage for good oils used in
the investigation below tests 58.5 kv. maxi-
mum in the above gap.
Effect of Moisture
The slightest trace of moisture in oil
greatly reduces its dielectric strength. The
effect of moisture is shown in Fig. 2, for the
standard disk gap (test by Hendricks). Water
is held in suspension in oil in minute drops.
When voltage is applied these drops are
attracted by the dielectric field. Thus they
are attracted to the denser portions of the
field and may form larger drops by collision.
When attracted to, and after touching a metal
part, and thus having the same potential,
they are immediately repelled. If the field is
uniform the drops form in conducting chains
along the lines of force. It can be seen that
the effect of moisture should vary greatly
with the shape of the electrode, and with some
shapes the moisture may even be removed
from the space between the electrodes by the
action of the field, in which case its presence
would not be detected by low-voltage break-
downs. In transformers, moisture will gen-
erally be attracted to points under greatest
stress. The most effective way of removing
moisture is by filtration through blotting
paper. Dirt in oil may have an effect very
similar to moisture and the small conducting
particles may be made to bridge between the
electrodes by the dielectric field.
* Tobey — Dielectric Strength of Oil — A.I.E.E.. June, 1910.
S22
GENERAL ELECTRIC REVIEW
Temperature
Temperature over the operating range
has very little influence on the strength of
oil. The strength increases at the freezing
point; this is shown in Fig. 3; the insula-
tion resistance is also shown. The increase
|
Effect ofMo/stv re. on
D/a/ectr/c Strength
of Tr&nsform&rO//
(Henar/cks)
*;
$
■§50
4
8
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fti?
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£
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\
Sa
s
x
^
0 -
a
-
.
r
e
.
7
IZ
Water -ports in /OOOOhy volume.
Fig. 2
in strength with temperature seems only
apparent and is due partly to the decreas-
ing insulation resistance which allows more
current to flow through the oil, which tends
to even up the stress, but mostly to the
drying out of moisture particles by high
temperature. The hump at about 70 deg.
increases with poor oil, and decreases as the
quality of the oil is improved. The cooling
curve is generally higher, as shown in Fig. 3.
Evidently moisture and gas have been
removed by heating, when the strength
decreases with the density. The increase at
freezing should be expected, as an actual
change in dielectric properties results. For a
perfectly dry oil the strength generally
actually decreases with increasing tempera-
ture or decreasing, density.
Spark-over or "Corona" in Oil
A phenomenon similar to corona in gases
also takes place in liquid insulations such as
oil, due to a tearing apart of the molecules of
the oil or occluded gases. It seems probable
that occluded gases often take an important
part in supplying "initial ionization." (The
great effect of moisture must always be kept in
mind.) It will later be noted that the strength
of oil in bulk is not very much greater than air.
"Corona" in oil is not as steady or definite
as in air.* It appears to start quite suddenly
and to extend much farther out from the
electrode than a corona in air. It is much
more difficult to detect the starting point,
and unless the conductors are very small and
far apart (s/r large) corona does not appear
before spark-over. For instance, with an
outer cvlinder of 3. SI cm. radius and an
inner one of 0.0127 cm. radius
(?-»»)■
the
corona and spark-over voltages are practically
the same. (The condition for spark-over
before corona, for concentric cylinders of radii
R and r, is for an insulation of constant
strength — < e, (c = 2.718). " Corona " can
r
never occur when — < «.
r
The absence of corona
7?
in oil before spark -over when — < «, unless the
r
wires are very small or far apart, seems to
mean that the mechanism or breakdown in
oil is very similar to that in air; the apparent
strength is greater for small wires. This is
because energy is required to start a rupture, f
A rupture cannot, therefore, take place at the
s I
260 130
2*0 /SO
^ szo i/o
\
| zoo /oo
\'ao ^
\/eoT
IT
A) /SO ^ 60
% S
y /OO %so
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*e
60 30
oo so
so /o
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Specific fres.
X
03 /nc/? qo&
Tn Tr-&r75 1 / O//
\
d "7o so do *o so 60 to go so /oo //o ao
Te/rrpenziure C°
Fig. 3
conductor surface, but the oi! must be stressed
at or above the breakdown voltage over a
finite thickness. Thus, just before "corona"
* Corona may be considered as spark from conductor to space,
while spark-over is spark from conductor to conductor.
t Law of Corona I. II. III. A.I.E.E., June. 1911. '12, '13. '14.
Hi^h Voltage Engineering — Journal Franklin Institute.
December, 1913.
LAW OF "CORONA" AND SPARK-OVER IN OIL
823
occurs, the stress at the wire surface is higher
than the rupturing stress; at a finite distance
away it is the rupturing stress. This break-
down distance is called the energy distance
or rupturing distance. The energy distance is
much greater in oil than in air. Thus, as the
voltage is increased, "corona" rupture occurs
out to the energy distance ; this increases r to
the condition for spark-over
R
- — <e
»-iu(i+£)
/cm. max.
= lkv/cm. effective sine wave
1 J
The electron theory may also be very well
applied in agreement with experimental data.
When low potential is applied between two
conductors any free ions are set in motion.
As the potential and, therefore, the field
intensity or gradient is increased, the velocity
of the ions increases. At a gradient of g0 =
36 kv/cm the velocity of the ions becomes
sufficiently great over the mean free path to
form other ions by collision with atoms and
molecules. This gradient is constant and is
called the dielectric strength of oil. When
ionic-saturation is reached at any point, the
oil becomes conducting and glows, or there is
"corona" or spark. When a gradient g„ is
reached at the wire surface any free ions
are accelerated and produce other ions
by collision with molecules, which are in
turn accelerated. The ionic density is thus
gradually increased by successive collisions
until at 1.2V r cm. from the wire surface,
where g0 = 36, ionic saturation is reached, or
"corona" starts. The distance 1.2Vrcm. is,
of course, many times greater than the mean
free path of the ion, and many collisions must
take place in this distance. Thus for the wire
"corona" cannot form when the gradient of
go is reached at the surface, as at any distance
from the surface the gradient is less than g0.;
a finite thickness must be stressed at a gradient
of g0 or over or ionic saturation cannot occur.
r -(-energy distance oroken down (hence, conducting)
and spark follows. Therefore, the spark-over
voltages and corona voltages up to fairly high
ratios of — are the same, and may be used in
r
determining the strength of oil.
The strength of oil for different sizes of
wire from Table IV is plotted in Fig. 4. The
curve is similar to that for "corona" in air.
Fig. 5 shows that a straight line relation holds
approximately between —=. and g„. Values
Vr
are not used when R/r >3.5. Thus, as in the
case of air:
_
JL
yeo
It
±
Cor
rrcrr?&/lOft
L
in
\»c
<i/£0
\
Ss
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& SO
° ^S-
a
-H-.
■\~
so
40
zo
o .a-
& /z /e so £<■ se i
fi&dJ/US - CS77.
Fig. 4
,
COt
7r-ar?3i/Ot/
fr>
fc
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V.
*■
--£
Vj **'
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S an -
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-^J
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IS SO Z1 Z& 3S J6
Fig. 5
The gradient at the surface must therefore
be increased to gv so that the gradient a finite
distance away from the surface (1.2VV cm.)
is go- That is, energy is necessary to start
corona, as stated above.
When the conductors are placed so close
together that the free rupturing or energy
storage distance is interfered with, the
gradient g„ must be increased in order that
ionic saturation may be reached in - this
limited distance.
The gradient gv, as with air, should also
vary with the density of the oil — that is, with
temperature. When initial ionization is
caused by occluded gases it is probable that
the strength should increase for very high
pressure to a greater extent than would be
expected by the small increase in density
with the increase in pressure.
824
GENERAL ELECTRIC REVIEW
TABLE I
DIELECTRIC STRENGTH OF TRANSIL OIL— SPARK-OVER BETWEEN SPHERES— 60
RADIUS OF SPHERES. CM.
NEEDLES
0
Cm.
Kv.
Max.
Gradient
Max.
kv cm
Kv.
Max.
Gradient
Max.
kv cm
Kv.
Max.
Gradient
Max.
kv/cm
Kv.
Max.
Gradient
Max.
kv/cm
Kv.
Max.
Gradient
Max.
kv/cm
Kv.
Max.
0.129
44.6
449
48.0
394
47.1
364
0.198
50.5
360
0.264
59.2
365
73.9
333
73.5
310
74.3
288
74.8
289
0.322
65.0
360
0.378
71.1
364
90.0
295
0.508
81.0
368
99.0
222
105.0
220
107.0
214
0.650
....
41.6
(1.766
89.9
353
106.0
225
117.0
187
128.0
182
132.0
180
1.010
97.6
358
112.0
192
146.0
166
159.0
166
1.270
104.0
361
116.0
176
157.0
158
171.(1
158
177.0
147
57.0
1.780
111.0
384
131.0
171
165.0
143
203.0
137
214.0
130
2.540
124.0
416
149.0
174
185.0
130
240.0
122
245.0
110
84.0
3.810
145.0
470
172.0
184
206.0
131
266.0
103
280.0
90
108.0
5.080
168.0
542
191.0
192
231.0
133
124.0
7.620
166.0
10.150
■ ■ ■
203.0
TABLE II
SPARK-OVER BETWEEN PARALLEL PLATES IN TRANSIL OIL— 60 •
Kv.
Max.
34.6
52.3
71.0
113.2
155.5
212.
296.
X
£:■
Spacing
kv cm
Cm.
Max.
0.254
136.3
0.508
102.8
0.762
93.0
1.27
88.8
2.54
61.
5.08
41.7
7.62
35.
Remarks
10 cm. flat disks 0.5 cm. radius on the edge 25 deg.
58.5 kv. max. oil in 0.5 cm. std. gap.
TABLE III
•CORONA" IN OIL, WIRE AND PLATE— 60
(Distance of Wire from Plate = 16.5 cm. )
Kv.
eff. kv.
max. kv.
Eff.
Wire Cm.
g?,
cm
£' cm.
50
0.025
278
393
60
0.05
185
262
80
0.0635
201
284
100
0.152
122
173
oo
0.00508
615
870
LAW OF "CORONA" AND SPARK-OVER IN OIL
825
The rupturing distance is 1 .2\/r cm. or almost
four times that of air, indicating that a greater
amount of energy is required to rupture oil,
or a greater number of collisions are necessary
before ionic saturation is reached. g0 and a
vary to a considerable extent in oil. The
strength of oil or the disruptive gradient, or
the gradient required to bring the ions up to
sufficient velocity to produce others by
collision, seems fairly low. Oil should, there-
fore, have low strength in bulk (about 36
kv/cm maximum between parallel planes at
large spacings), but high apparent strength
when subdivided or confined to make use
of the large energy distance necessary to
rupture.
Spark-over voltages and gradients are given
for various sizes of spheres at various spacings
in Table I. The characteristics of the curves
between gradient and spacing, as shown in
Fig. 6, are the same as those for air. When the
spacing is so small that it interferes with
the rupturing distance, the apparent strength
of oil increases. At spacings above this the
gradient is constant until the separation is
so great that "corona" forms before spark -
over.
The rupturing gradient at the constant part
of the curve for various sizes of spheres is
given in Table V, and is shown in Fig. 7.
This may be written
gs = 28.31 H — p= lkv/cm max.
V VrJ
The energy distance is approximately 2.V r.
The spark-over voltages between electrodes
5, and for
for wires where — 7 10 or -
r r
<
3QO
360
5p/7e/-^s /it 7f~£?r?3//Of/
Tj
ir"
R
k
^~
■y
■ft
3
V. fSO
\
\
\
^
too
as>
&o
so
0o
.
J
4-
£
6
7
0
&
to
//
fs
/3
■a
ftoctius-csn
Fig. 7
spheres between 2V R and 3 R spacing on the
constant part of the curve, may be calculated
by substituting the proper gs in the voltage
formula.
700
& ?c/77 Gf/ometer 5/^eres
7r&r73t/Otf
600
fMU
0
5
i; too
JS
f
ti
zoo
/oo
--
..
&S-/00
0
20
Fig. 6
826
GENERAL ELECTRIC REVIEW
TABLE IV
SPARK-OVER VOLTAGES FOR TRANSIL OIL CONCENTRIC CYLINDERS — 60
R
Cm.
r
Cm.
Kv.
Eff.
Kv.
Max.
g-
Max.
kv/cm
l
*
r
Remarks
3.81
0.032
45.3
64.0
420.0
5.61
120.00
Tests made in dry cylinders
3.81
0.238
60.0
84.0
127.7
2.05
16.00
with belled ends. Oil
3.81
0.317
60.5
85.5
108.1
1.77
12.00
between std. disks 0.5 cm.
3.81
0.635
69.5
98.3
86.3
1.26
6.00
apart tested 58.5 kv.
3.81
0.794
75.0
106.1
85.5
1.12
4.80
(max.) 25 deg. C.
3.81
0.952
73.0
103.2
78.1
1.02
4.00
3.81
1.111
76.7
108.5
79.4
0.95
3.81
1.270
76.0
107.5
77.0
0.89
3.00
3.81
1.587
73.7
104.3
75.1
0.79
2.40
3.81
1.905
66.3
93.7
70.7
0.72
2.05
3.81
2.540
45.5
64.3
62.4
0.63
1.57
TABLE V
SPHERES IN OIL
Radius
Gradient
1
Radius
Gradient
1
Cm.
kv/cm Max.
Vr
Cm.
kv/cm Max.
\R
0.159
348
2.51
1.270
120
0.89
0.237
260
2.05
3.120
98
0.56
0.355
222
1.68
6.25
82
0.40
0.555
169
1.35
12.5
56
0.28
Gradient at constant part of the curve. 60 ~. Data from Table I.
TABLE VI
COMPARISON OF 60 CYCLE AND IMPULSE SPARK-OVER IN OIL
Gap
Spacing
Cm.
Kv.
60 Cycle
Max.
Kv.
Impulse
Max.
Standard disk
0.5
56.6
50.2
108.
37.2
111.2
170
2/0 needles
{ I
/ 0.25
1.02
103.3
2.54 cm. spheres
321.
117.3
337.
TABLE VIII
COMPARATIVE INSULATION STRENGTH FOR HIGH FREQUENCY IMPULSE,
OSCILLATION AND 60-CYCLE VOLTAGES
Temperature 30 Deg. C.
Transil Oil between Flat Terminals — Square Edge — 2.5 Cm. Diameter — 0.25_Cm. Space
60 CYCLES *
high frequency *
(alternator)
90,000 CYCLES
DAMPED OSCILLATION *
TRAIN FREQ. 120 SECONDS
200.000 CYCLES
SINGLE IMPULSE SINE SHAPE
CORRESPONDING TO HALF
CYCLE OF 200.000 CYCLES
Kv/cm (Max.)
Kv/cm (Max.)
Kv/cm (Max.)
Kv/cm (Max.)
170
•
67
300
390
* Voltages in columns 1, 2 and 3 brought up to breakdown in few seconds.
LAW OF "CORONA" AND SPARK-OVER IN OIL
827
Thus,
R
e = gs r loge — concentric cylinder.
5
e = 2 gs r loge — parallel wires, single-phase.
5
e= 1.73 gs r loge— parallel wires, three-phase.
e = gs y for spheres.
The spacings X and s, and the radii R and r,
are in cm., / is given below.
X
R
/
Non-grounded
/»
One Sphere
Grounded
0.1
1.03
1.03
1.0
1.36
1.42
2.0
1.77
1.98
3.0
2.21
2.60
4.0
2.62
3.21
Where the spacings are greater than the
upper limit, the voltage calculated is the
corona voltage.
In oil, the apparent strength can be
improved by limiting the "free energy
distance." This can be seen in Tables I and
II, where e/X is given for parallel planes, and
gs for spheres. It should be noted that the
strength between parallel planes decreases
with the spacing. It approaches a constant
value of 36 kv/cm. (max.) at about 10 cm.
spacing. For the small spacings, where the
free energy distance is limited, the apparent
rupturing gradient is very high, just as in the
case of air. Strengths as high as 700 kv/cm.
have been reached.
Permittivity
The permittivity of oil varies with its
density and, therefore, with its temperature.
It is 2.6 X the specific gravity of oil.
Barriers
The strength of oil may be greatly increased
by the use of barriers, by limiting the energy
distance. However, if the barriers have a
higher permittivity than oil, the stress on the
oil may be very greatly increased if the
thickness of the barrier is great compared
with the oil thickness. In this way the
breakdown voltage may be actually decreased
by barriers. Even under this condition,
however, there is a great gain, as the water
particles and dirt are prevented from lining
up, incipient sparks are prevented from
developing, etc.
Transient Voltages and High Frequency Voltages
Transient voltages, or impulse voltages of
short duration, greatly in excess of the low
frequency rupturing voltages may be applied
to insulation without rupture. In other
words, the rupture of insulation requires not
only a sufficiently high voltage, but also a
definite minimum amount of energy. This
means also that a definite but very small time
elapses between the application of voltage
and breakdown. This is called the "dielectric
spark lag." The rupturing energy seems to be
much greater for oil than for air, as indicated
by the large energy distance in the gradient
equation above. At low frequency a given
definite voltage is required to cause rupture
during the comparatively unlimited time of
application. This voltage is constant until
the application is limited to some small but
finite time, depending upon the initial
ionization, etc., when a higher voltage is
required to accomplish the same results in
limited time. Such transient voltages of
short duration, and impulses of steep wave
front, must not be confused with continuously
applied high frequency where breakdown
will generally take place at lower voltages,
due to loss, etc.
In Table VI, the relative breakdown
voltages of gaps in oil, at 60 cycles, and for
impulse voltages of steep wave front, are
given. An impulse voltage much higher than
the 60-cycle voltage is required to break down
a given gap.
Oil is an excellent insulation in combination
with proper barriers. On solid insulations the
effect of transient voltages is cumulative. A
partial break occurs which is enlarged by each
succeeding impulse, until dynamic energy
finally follows. With oil, such "cracks" are
closed up by new oil immediately.
The comparative strengths of oil for
impulse, high frequency, oscillatory and
60-cycle voltages are given in Table VII.
The author wishes to acknowledge in-
debtedness to Mr. B. L. Stemmons for
assistance in making tests.
S28
GENERAL ELECTRIC REVIEW
THE OPERATION AND RATING OF THE ELECTRIC
LOCOMOTIVE
By A. H. Armstrong
Assistant Engineer, Railway and Traction Department,
General Electric Company
The rating of electric locomoti\-es is a subject on which we need much education. The author who has
done so much work in giving rational ratings to electric railway motors in general gives some most useful data
in discussing the momentary, one hour and continuous capacity of some notable electric locomotives. Many
details of design including those of the locomotives for the Chicago, Milwaukee & St. Paul Railway are discussed.
This article is prepared from the author's discussion at the recent meeting of the Institute of Mechanical
Engineers in Chicago. — Editor.
The present articie touches upon the subject
of electric locomotive operation, what excuse
it has for existence, and draws some few
comparisons with the steam locomotive as
to its selection and rating.
Commencing with the New York Central
locomotive, we have a distinctive type
admirably adapted to high speed passenger
sen-ice. It is designed to deliver a moderate
tractive effort at a high speed, the first 47
locomotives of the "S" type giving a tractive
effort of 7100 lb. continuously at a speed of
56 miles per hour and a one-hour rating of
20,600 lb. The driving motors, four in
number, are thus able to give an output of
2200 h.p. for a period of one hour without
overheating. The later "T" type of loco-
motive, weighing approximately 130 tons, has
a capacity of 14.000 lb. tractive effort at a
speed of 53 ]/o miles per hour or a continuous
motor capacity of approximately 2000 h.p. For
the one-hour period the output is 2600 h.p.
Electric railway engineers talk about con-
tinuous and one-hour capacities and also
about starting tractive effort, and that brings
up one point that needs explanation to the
steam railroad man; that is. the time element
plays a very important part in the determina-
tion of the rating of an electric motor. In
a steam locomotive the tractive effort or
pulling power is determined by the diameter
of the piston and the steam pressure behind
it. and the locomotive can deliver this tractive
effort continuously provided it has sufficient
boiler capacity to supply the quantity of steam
demanded and the fireman is sufficiently
industrious to keep the grate covered which is
supposed to have sufficient surface. With the
electric locomotive, on the contrary, allowance
must be made for the fact that the insulation
used deteriorates if heated continuously
above a certain amount. It takes a con-
siderable time for the motor to heat up to
this dangerous point, thus giving rise to a
momentary rating or starting effort, a one-
hour rating and a continuous rating, the latter
being the output which the motors can give
continuously without injurious heating. In
other words, the steam locomotive engineer
is concerned in keeping his boiler hot, while
the effort of the designer of electric loco-
motives is to keep his machine cool.
In the early electric locomotive design
there was no such thing as continuous rating.
The service which it was called upon to
perform was of an intermittent character, the
runs between stops were short and the design-
ing engineers were concerned mostly with the
question of starting or accelerating, tractive
effort and commutation. Therefore, the
continuous rating of the early motors did
not affect its design. With the extension of
electrified lines and more especially with the
introduction of the electric locomotive on
main steam trunk lines, it was found that
the motive power was called upon to deliver
a continuous output for long periods at a
time, and it became necessary to introduce
air blown or ventilated motors as well as
fire-proof insulation in order to secure the
large output required without exceeding the
limitations of space and weight imposed by
standard gauge and reasonable diameter of
wheels, wheel-base and weight per driving
wheel. We are therefore designing electric
locomotives today suitable for the heaviest
class of freight and passenger service. Such
locomotives are entering into competition
with the steam locomotive with a full appre-
ciation of the phenomenal growth and possi-
bilities of the latter as developed during the
past few years, as well as a knowledge of the
growth in the demands placed upon the
motive power to take care of modern high
speed passenger and freight train service.
In designing such electric locomotives the
electrical engineer is fully alive to the fact
that a steam locomotive has been built
weighing 750,000 lb. on drivers and having
a total weight of 850,000 lb., and that nearly
90 per cent of the total weight of the loco-
motive and tender is now rendered available
THE OPERATION AND RATING OF THE ELECTRIC LOCOMOTIVE 829
for tractive purposes by the development of
the Mallet principle to include cylinders
placed upon the tender itself. It is also
known that the tractive effort of these loco-
motives has increased from the 40,000 lb., of
the early "Consolidation" engines weighing
200,000 lb. on the drivers, to values as high
as 160,000 lb. for the latest type of Mallet.
It is also known that the introduction of the
steel passenger car with the need of high
sustained speeds of between 60 and 70 miles
per hour, calis for the hauling of passenger
trains weighing over 1000 tons, and that
provision is made in the latest New York
Central electric locomotive to take care of
1200 tons at 60 miles an hour. Due apprecia-
tion is also paid to the results secured with the
combination of superheating and simple
engine which has so largely replaced the com-
pound. Also the increased capacity afforded
by the use of mechanical pushers, and fire
door openings with hand firing, have increased
the efficiency of the fireman so that it is now
possible for him to throw between 5000
and 6000 lb. of coal per hour where previously
4000 lb. might be considered good perform-
ance. Finally it is fully understood that
the modern steam locomotive has been so
improved as to fuel economy by the introduc-
tion of superheating, fire arch and other
developments that it is possible to get an
indicated horse-power with a consumption
of 15 lb. of steam and less than 2 lb. of coal
under the best conditions of operation, and
that with the use of mechanical stokers or with
oil fired boilers, locomotives are in operation
giving 3000 indicated horse-power or more.
Fully appreciating the above facts and the
magnitude of the problem confronting him,
the electric railway engineer nevertheless
offers in the modern electric locomotive a
type of motive power which can accomplish
results in transportation which are not
possible to obtain with the steam locomotive
as regards tonnage handled, speed on
mountain grades and general flexibility and
economy in operation. The first large loco-
motive built was placed in operation on the
Baltimore & Ohio Railway in 1895, and it is
worthy of note that this was a gearless loco-
motive and a forerunner of the highly efficient
gearless locomotives now in operation upon the
New York Central road today. The New York
Central locomotive, as developed in the later
"T" type, is capable of hauling the heaviest
overland passenger trains over any length of
track that may be electrically equipped, and
withal at a cost for upkeep, including all labor
and material spent in maintenance, of not
exceeding 33^ cents per mile run, as is shown
by the records of the New York Central dur-
ing the operation of the past seven years.
The first railroad in this country to adopt
electric freight locomotives having large
sustained output capacity is the Butte,
Anaconda & Pacific Railway. Some three
years ago the construction of 92 miles of the
total of 114 miles of track was commenced,
being completed for freight operation in May
of 1913 and for complete freight and passenger
operation in October of 1913. There are still
four or five steam engines in operation on
Butte Hill, but these will be replaced in the
near future, so that in a short time the entire
road, or 114 miles of track, will be in operation
electrically. The one motive inspiring this
installation was economy in operation, and
preliminary reports indicated that the savings
in electric over steam operation should be
sufficient to pay something like 18J^ per cent
upon the capital required to electrify. During
the first six months of operation of this road
careful detail figures were kept on the cost of
electric operation, every item of expense
being accounted for, with the result that
prorated over the entire fiscal year there was a
saving shown of $240,000 over the cost of
steam operation during the previous year
with practically the same tonnage handled.
The entire first cost of this installation,
including all material and labor and con-
tingent expenses as well as interest on money
during construction, was approximately
$1,200,000, so that the saving above indicated
results in a 20 per cent gross return upon the
capital required for electrification. This
makes no allowance for the scrap value of
more than 20 steam locomotives discarded.
On this road the heaviest class of freight
trains are operated electrically, regular opera-
tion calling for the movement of from 3500
to 4000 tons behind the locomotives from
the Butte Yards to Anaconda, and record
has been made of train weights as high as
4500 tons trailing against a gradient of 0.3
per cent. Each locomotive weighs 80 tons,
all on drivers, and two such units are coupled
together, operated by one engineer and com-
prise a complete locomotive hauling the above
tonnage. At the Butte end there is a gradient
of 2J^ per cent against the returning empty
cars, and at Anaconda a 1.1 per cent grade
against which one of the above locomotives
hauls 25 cars, or approximately 2000 tons.
This leads up to the subject of the rating
of an electric locomotive. The Butte loco-
830
GENERAL ELECTRIC REVIEW
motive, weighing SO tons, all on drivers.
will give a continuous tractive effort of
26,000 lb. at a speed of approximately 16H
miles per hour at full substation line voltage.
This corresponds to 16 1 i per cent of the
weight upon the drivers. Investigation of
the locomotive loading regulations on many
steam roads operating over ruling grades
indicates that it is almost universal practice
to assign to a locomotive a trailing load so
that the tractive effort at the rim of the
drivers, as required on a ruling grade, will
be equivalent to approximately 18 to 19 per
cent of the weight upon the drivers. In
other words, from 18 to 19 per cent coefficient
of adhesion between driver and rail is now
considered good steam practice, and the
electric locomotive rating is closely following
this same steam practice. The electric
motor, of course, gives a perfectly uniform
rotation to the driving wheels, and should
thus give something like 10 per cent more
tractive effort than the steam locomotive with
its reciprocating parts. Continued operation
will develop whether this additional 10 per
cent tractive effort can be utilized or not. In
the meantime steam practice is being followed
in the loading of electric locomotives.
In adopting a coefficient of adhesion of IS
or 19 per cent as the basis of determining the
tractive effort required on ruling grades, it is
evident that there is left for starting purposes
the difference between the above coefficient
of adhesion and the slipping point of the
wheels, whatever that may be, as determined
by the condition of the track. Tests on
electric locomotives have shown a coefficient
of adhesion as high as 35 per cent, or even
more under specially favorable conditions,
but it is fair to assume a maximum of 30
per cent as available in operation and even 25
per cent may be nearer the average. There
is therefore not much difference between
the tractive effort required on ruling grades
and that required for starting, and in order
to be "fool proof" and capable of meeting
the exacting demands of the heaviest kind of
sen-ice, the electric locomotive should be capa-
ble of delivering continuously a tractive effort
equal to from 16 to 18 per cent coefficient of
adhesion of the weight upon its drivers. The
Butte locomotive is therefore rated at 26,000
lb. or 16.25 coefficient of adhesion as its con-
tinuous output, and this capacity is sufficient
to meet all demands of operation on the Butte,
Anaconda & Pacific Railway.
Coming now to the latest type of trunk
line electric locomotive, the one designed
by the General Electric Company for the
Chicago, Milwaukee & St. Paul Railway, this
is a direct development of the Butte, Anaconda
&• Pacific both as to type of locomotive and
general system of electrification installed.
The weight of the locomotive is 260 tons, of
which 400,000 lb. are on the drivers. Each of
the eight driving motors has a continuous
rating of approximately 400 h.p., making the
sustained continuous output of the complete
locomotive 3200 h.p. at the rim of the drivers.
This locomotive, however, will give a con-
siderably larger output for short periods. For
example, it has a capacity of 3600 h.p. for one
hour and even greater than this for short periods.
The sustained tractive effort is 72,000 lb. at a
speed of 15^4 miles per hour at full substation
line potential. Compare this with the Mallet
engine of approximately the same weight now
in operation on the St. Paul road and we find
that the Mallet has 76,200 lb. tractive effort
corresponding to 23.5 per cent coefficient of
adhesion, but those of you familiar with the
performance of this beast of burden know
that it toils painfully at speeds seldom exceed-
ing 7 to 10 miles per hour when operating at
its full hauling capacity. It is in this matter
of higher speed for the same tractive power
that the electric locomotive excels. In fact
the question of speed is simply one of cost and
expediency, as the horse power output of the
electric locomotive can be raised to any value
desired without exceeding the limits of track
loading.
The St. Paul locomotive, weighing 70
tons, has a capacity to haul a 2500 ton trailing
load behind the locomotive on a 1.0 per cent
grade at nearly 16 miles per hour without any
assisting locomotive. The St. Paul road in
Montana and Idaho crosses three mountain
ranges, the Belt Mountains, the Rocky
Mountains and the Bitter Root Mountains.
From Lombard to Summit, in the Belt
Mountains, a distance of 49 miles, there is
an average gradient of 0.71 per cent and a
ruling grade of one per cent against which one
locomotive will haul a trailing load of 2500
tons without assistance. Between Piedmont
and Donald, a distance of 22 miles to the
summit of the Rocky Mountains, there exists
a two per cent grade against which two
locomotives will haul 2500 tons trailing, the
second locomotive being used at the rear of
the train as a pusher. A second pusher
division exists in crossing the Bitter Root
Mountains of Idaho making only two pusher
divisions in the 440 miles of electrified road
from Avery, Idaho, to Harlowton, Montana.
THE OPERATION AND RATING OF THE ELECTRIC LOCOMOTIVE
831
The general design of the St. Paul loco-
motive comprises a locomotive divided in
halves for facility in shop repairs, each half
being identical and equipped with four
driving axles and two guiding axles. The
design is identical with the Butte locomotive
except for the addition of the four-wheel
guiding truck at each end of the locomotive,
one of the reasons for its introduction being
that the same locomotive is thus made
available for both passenger and freight
service. This does not mean that any loco-
motive can be used interchangeably at will
in both freight and passenger service, but it
does mean that all parts of the locomotive are
identical whether used for freight or passenger
service with the single exception of the gearing
between motors and driving axles which has
a ratio of 4.56 for freight service and 2.45 for
passenger service. This adoption of a uniform
type of motive power for all classes of service
should result in effecting a great reduction
in the cost of maintaining the locomotives of
the four engine divisions electrified.
A second type of light locomotive for shift-
ing service may be introduced later, although
in this connection arrangements are being
made to operate independently, one-half of
the locomotive being equipped with draft
gear in place of the articulated joint joining
the two halves. This will provide a loco-
motive weighing 130 tons having 200,000 lb.
on the drivers and capable of doing one-half
the work stated above as the capacity of the
combined locomotive; this half locomotive
would require turning if used in passenger
service, as it has guiding axles at one end
only.
The installation on the St. Paul road will
use for the first time on such a large scale a
principle which should be of the greatest
advantage in the operation of mountain
grade divisions; that is, the utilization of the
motors on the locomotives to brake the train
on down grades and return the energy of the
descending train back into the trolley. The
efficiency of the locomotive, both electrical
and mechanical, is nearly 90 per cent as a
maximum, not taking into account the minor
losses in driving ventilating fans and air
compressors. When descending heavy grades,
therefore, the reversible feature of the loco-
motive, permitting it to transform mechanical
power received into electrical energy, suggests
by this means a considerable reduction in the
amount of power required to operate the road.
It is probable, however, that a power saving
of less than 10 per cent will result from the
regenerative braking feature of the electric
locomotives, and the principal advantage
resulting from the introduction of the electric
brakes will be to relieve brake shoes and
wheels from the dangers attending over-
heating. To those of you who are familiar
with the handling of trains on long and heavy
down grades this argument will appeal in full
force, as it is not an uncommon sight to see
brake shoes red hot as a result of sustained
application on down grades of long extent.
In conclusion it is well to comment on the
suitability of the New York Central gearless
type of locomotive for passenger service. This
is seen very plainly when the entire absence of
mechanical losses in the motor other than
the brush friction on the commutator is
considered. There are no bearings on the
motor of any kind as the armature is mounted
directly upon the driving axle and the field
structure is part of the frame which is carried
upon the journals. The electrical efficiency
of the motor and the frictional losses on the
commutator, due to the brushes, are therefore
the only losses to be considered, and the
efficiency of this locomotive in operation is
therefore between 93 and 94 per cent. In
other words, of the electrical input received
at the third rail shoes, from 93 to 94 per cent
appears as useful mechanical output at the
rim of the drivers. This in itself is a most
remarkable performance, but the value of
this high efficiency locomotive is rendered
more important when it is explained that the
maximum efficiency occurs at approximately
the free running speed between 50 and 60
miles per hour. In other words, the motor
has a drooping efficiency curve, being highest
at free running and lowest at overloads or
during acceleration, and in this respect being
just the reverse of the efficiency curve of
geared motors which reach their highest
point at practically the one hour load capacity
of the motors. The gearless locomotive is
therefore particularly adapted to operate on
fairly level profiles and could not be utilized
to such great advantage on roads like the
St. Paul which contains many heavy grades
sustained over a long distance. It is very
difficult to combine in one structure motors
capable of hauling 800 tons trailing over
heavy sustained grades, and also have the
characteristics required for good operation
on level track at 60 miles per hour, and in the
St. Paul locomotives recourse to gearing
between motor and driving axle appears
necessary to secure the greatest all round
advantages at the lowest first cost.
832
GENERAL ELECTRIC REVIEW
EMERGENCY TRANSFORMER CONNECTIONS
By George P. Rorx
Consulting Engineer, Philadelphia, Pa.
Emergency conditions, to be handled successfully, always require quick thinking and oftentimes ingen-
uous impromptu arrangements. Now while it would be entirely impossible to treat all the many sudden and
unexpected conditions that might arise in our various types of apparatus, it is certain that this article will
provide engineers and operators with such information as will be of greatest assistance to them when dealing
with emergency transformer connections. — Editor.
The constantly widening and almost un-
limited applications of electrical energy have
greatly increased the tasks of the engineer
and of the operating man ; they are very often
confronted with a variety of problems which
require almost instant solution. The origin
of these emergencies is either accidental, or
incidental, and due to the operating features
of all systems. In all instances they must be
met with prompt action, worthy of the
resourcefulness of the electrical engineer.
A very common kind of emergency engineer-
ing is found in transformer service where the
nature of the installation requires either an
unusual voltage or phase transformation not
easily obtainable from standard apparatus
generally on hand or available on short
notice; or else it is an interruption in the
service caused by the failure of some special
transformer not easily replaceable. In both
cases an emergency substitute is absolutely
necessary to resume service.
Transformer Taps
Transformers provided with special taps
other than the customary regulation taps are
not of standard construction and therefore
are not readily procurable from stock or from
the manufacturer: hence delay and expense
in obtaining them.
Special taps are objectionable for different
reasons, and to the designer and builder of
transformers they are in most cases a source
of great inconvenience. Some of the principal
objections are:
I 1 ) To locate the tap at the proper point
of the winding so that it can be brought
out without serious difficulties and without
impairing the dielectric strength of the insu-
lation or the internal balance of the apparatus,
thus affecting its degree of resistivity to
electrostatic and electromagnetic stresses.
(2) The additional expense in construction
entailed by special tap provisions is not
merely the cost of this extra connection,
which in itself would be unimportant, but the
expense involved in the special design and in
the provisions that must be made to conform
with the standard designs now adopted in all
improved types of transformers, which are
designed and built for the requirements of
the most strenuous services, with the view to
insuring continuity and reliability of opera-
tion.
(3) The greatest internal stresses occur in a
transformer at the extreme ends of its wind-
ings, and it is now the general practice to
reinforce the insulation at these points,
avoiding any taps or connections with the
exterior. In most modern types of trans-
formers the voltage regulation taps have been
removed toward the region of minimum
stresses, or at the center of the windings, as
shown in Fig. 1 .
It is evident that a special tap brought out
near the ends of the windings, as for instance
at C, requires an extension of the dielectric
reinforcement, or else a sacrifice of insulation
at the cost of security. Furthermore, the
transformer having its windings connected
to the line at C and B will have the balance of
its coil CA operating as an auto-transformer
open circuited at one end and with a voltage at
A in excess of the line voltage by an amount
corresponding to the ratio of turns in CA and
CB, thus causing an unnecessary strain on
the insulation of that part of the winding and
the terminal — a condition very objectionable,
especially with high voltage transformers.
Transformers with special taps must be
avoided as much as possible, except where it
VW\jvWWvWvfv1 MvfWWVWWWV
Vo/toge ffegu/at /or? Taps
/7 C
Fig. 1. Location of Transformer Taps
is physically impossible to dispense with such
provisions. In the majority of cases it is
possible to provide externally for the lack of
internal taps to a transformer, and yet secure
the same results without incurring the expense
and complication of specially constructed
EMERGENCY TRANSFORMER CONNECTIONS
833
apparatus, a feature more particularly appre-
ciated in the event of emergency connections.
Emergency T-Connection
It is entirely unnecessary to explain here
why an 86.6 per cent tap is required in the
teaser transformer, and a 50 per cent tap in
the main transformer to connect these two
pieces of apparatus according to the Scott
method of phase transformation : suffice it
to say that the Scott connection is used in a
great number of cases where voltage and
phase transformation are necessary. This
method would be used even more were it not
for the 86.6 per cent tap required. In many
instances two transformers are simply T-
connected in the absence of this special tap;
the 50 per cent tap being easily obtained from
nearly all transformers whose windings con-
sist of at least two coils. An attempt to
bring out an emergency 86.6 per cent tap is in
most cases fruitless, and no other course seems
possible but to use the T-connection. The
ill-effects resulting from this connection,
such as unbalancing of the secondary voltage
and phase angle distortion, are well known
and are always a source of trouble and com-
plaint.
Dealing first with the case of a three-phase
high voltage power which is to be transformed
to two-phase low voltage power, we find that
the absence of the 86.6 per cent tap in the
teaser transformer gives the conditions shown
in Fig. 2; that is, a difference of 13.4 per cent
in the voltages of phases A and B. Since
we have a difference of voltage of 13.4 per
cent between the voltages of each leg of the
two-phase system, it is only necessary to
e--86.6
/Twse /?
/^/-rose/3
-e=/O0-
Tn/ree-phose Side
Tyvo-^hose Sic/e
Fig. 2. Phase and Voltage Relation of T-connected
Transformers
boost one leg or buck the other to even-up
the potential of the phases. The solution of
this problem is therefore simplified, and is
reduced to the operation of connecting an
outside transformer in series with one of the
legs, in such a manner as to boost or buck the
voltage to the proper amount, as indicated
in Fig 3.
Assuming for instance that the low voltage
two-phase power is 2300 volts, we find 2300
volts across one leg of Fig. 2, but only 2300 X
0.866 = 1991.8 volts across the other leg
\W9S t>|
I 4 &-r'
F/Tasert
P'S-rasee
Ss conc/ar-y
Teaser
Buchirrg Secondary Mo/n
Fig. 3. Connections for Boosting or Bucking
which corresponds to the teaser transformer.
By taking two pole-type transformers, one
wound for 2200/220 volts and the other for
2200/110 volts with an aggregate kilovolt-
ampere capacity equal to at least 13.4 per
cent that of transformer A or B and connect-
ing these two transformers with their second-
aries in series-boost at the end of transformer
,4, it will be possible to balance externally the
voltage of phase .4.
This result is accomplished in this manner:
The primary of the first booster, being con-
nected across 1991.8 volts with a ratio of
10 to 1, will boost the voltage through its
secondary (in series with ^4) a value equal
1991 8
to - - = 199.18 volts, or from 1991.8 to
2190.9 volts. The primary of the second
booster, being similarly connected across
2190.9 volts, with a ratio of 20 to 1, will
again boost the voltage by 109.5 volts, making
a total voltage across phase A of 2300.48
volts. The voltage across phase .4 will then
be half a volt higher than that across phase B ;
that is theoretically, because in practice it will
be hardly detectable.
If it is found preferable to buck phase B
instead of boosting phase A, the same result
of voltage balance will be obtained with the
two pole-type transformers if we connect
them at the end of transformer B and buck
phase B by 308.6 volts, that is, reduce the
voltage from 2300 to 1991.4 by reversing the
834
GENERAL ELECTRIC REVIEW
primary connections of the pole type trans-
formers.
One objection that might be raised to this
method by the man of strict accountability
is the use of pole-type transformers (which we
have selected because they are generally
T
S300
-/3Z8Z5-
7isos er- (//orsno l)
- Z6S& 5
/323 ZS -
—//SO ~\~//5 — -Y6J£- -632+— //S —\> //SO
Afo//7 (Goosced)
Fig. 4. Equivalent T-connection, Boosting Main
available from stock), on the ground J that
the}- will be subjected to a voltage of 2.300
on the secondary windings and terminals.
To this objection we may state that all 2200-
volt transformers of modern design and con-
struction are so built as to withstand con-
tinuously a voltage of 5000 across either
winding, and between windings, terminals and
case, without injur}-. We may further point
out the fact that in our case there will be an
inappreciable difference of potential between
windings far less than when operating nor-
mally.
Where the conditions are reversed; that is,
where two-phase high voltage power is to be
transformed to three-phase power of lower
voltage, another system of connections, shown
on Fig. 4, can be used, which will increase
the voltage of the main transformer so that
the ratio of main to teaser windings will
be 100 to 86.6. This connection is somewhat
more complicated than the one previously
described and consists in splitting in half
both the primary and secondary windings of
the booster transformers and connecting the
teaser to the middle of the secondary winding
of the booster. It would be easier to reduce
the voltage of the teaser by bucking, again
using (in case of 2300-volt distribution)
the two pole-type transformers at the end
of the teaser winding, as shown in Fig. 5.
For high voltage ratio, the connection
shown in Fig. 5 is preferable, because the
extreme ends of the windings of the large
transformers are better protected by addi-
tional insulation against stresses, and in
emergencies of this nature it would be better
to connect the bucking transformers between
the lower end of the teaser and the middle of
the main transformer.
Where, for instance, a high voltage two-
phase power is to be transformed to a 6600-
volt three-phase power by the connection
represented in Fig. 5, the voltage impressed
on both main and teaser will be 6600 volts
respectively; whereas the voltage of the
teaser should be only 5715, or a difference of
SS5 volts. Two 6600/440-volt transformers,
connected with their secondary in series and
their primary in parallel but reversed, will
reduce the teaser voltage to 5720 volts.
There are of course limitations to the use
of these emergency connections when applied
to high voltages, and special attention should
be given to the matter of stresses imposed on
the insulation of the auxiliary transformers in
order to avoid accidents.
It will be found, however, that in the
majority of cases met with in practice the
connections described are of great help, at
least for temporary installations. The writer
has used these different styles of connections
on various occasions with excellent results,
7eoser- (Bached)
-
-3300-
~
-33O0 —
-6600-
AJa//7 (Aorma/J
Fig. 5. Equivalent T-connection, Bucking Teaser
and in a few instances for permanent opera-
tion now covering a period of three years.
Boosting Line Voltage
Very often it happens that a feeder requires
a higher voltage to compensate for an exces-
EMERGENCY TRANSFORMER CONNECTIONS
835
sive line potential drop, generally due to
an increased load, this condition indicating
an insufficient cross-section of conductor,
but because the additional load is only of a
temporary nature, or for some other reasons,
it may be policy to increase the voltage of this
particular feeder rather than add copper to
the line. Pending some ulterior decision
regarding an improvement, prompt action
involving the least possible expense is neces-
sary.
Immediate relief may be obtained by in-
stalling at a convenient point on the line one
or more booster transformers of the same type
as the transformers in use on the circuit in
question, and connected as shown in Fig. 6,
which is for a single-phase feeder. Using two
sooov
2300- Lood ■
3
£zoo*ar-'
no £
Fig. 6. Connections for Boosting Feeder Voltage
or more booster transformers and adjusting
their voltage regulation taps and connections,
it is possible to practically boost the line volt-
age by any value. The capacity of the booster
transformers must in all cases be sufficient to
carry in their secondaries the line current to
be boosted.
For two-phase and three-phase lines similar
connections can be used with equally^ satis-
factory results.
I
1
//OO y Loacf — -
J
Fig. 7. Step-up or Step-down Compensator Connection
for Ratio 1 to 2
Later, should it become unnecessary to
improve the voltage of the feeder, the booster
transformers can be removed and used some-
where else, as they are standard transformers.
Transformers can also be used as step-up
or step-down compensators, specially for a
ratio of 1 to 2. An installation made for such
service is shown in Fig. S. To reduce the
impedance between the primary windings, it
is advisable to connect the secondary coils in
multiple.
A great number of combinations of voltage
transformations and adjustments can be
effected with single-phase transformers prop-
erly connected. Multiphase and multivoltage
transformers can also be obtained by special
connections. In all cases some preliminary
studies must be made of the problem, as
several solutions are generally available, and
good judgment is essential in making the
final selection.
836
GENERAL ELECTRIC REVIEW
PARALLEL OPERATION OF FREQUENCY CHANGERS
By G. H. Rettew
Electrical Engineer, Potomac Electric Power Company
The author describes the difficulties sometimes met with in synchronizing frequency changer sets. The
problem of synchronizing such machines is increased when they are located in different stations. He describes
a concrete example of a system where continuous synchronous operation of two stations is only necessary during
certain periods, during the greater part of the time the load being carried by a main substation. The author
shows how all the difficulties were overcome and describes the successful method adopted. — Editor.
This article deals only with that form of
frequency changer consisting of synchronous
motor direct connected to a revolving field
alternator, that being the type generally
employed on the larger systems.
Not much difficulty is experienced in the
paralleling of alternators driven by any type
of engine, waterwheel, or steam turbine, as the
problems are 'well understood and such
difficulties as have manifested themselves
have been taken care of by proper designs.
All of these forms of prime movers have droop-
ing speed characteristics that assist in securing
satisfactory parallel operation of the alter-
nators driven by them, and the proper division
of load between units is easily secured by
regulating the amount of power supplied by
the prime movers.
In the operation of frequency changers in
parallel, difficulties arise which, while not
impossible to overcome, are not generally as
well known except to those who have such
apparatus in charge. These difficulties are
brought about partly by reason of the fact
that the motor is of the synchronous type and
hence does not have the drooping speed
characteristic which is desirable in driving
alternators which are to be paralleled, and
further by the fact that both the motor and
generator must be paralleled. An additional
trouble is that the division of load on the
generators cannot be accomplished by regulat-
ing the power supplied by the driving motor.
The last mentioned difficulty is overcome in
modern machines by mounting the stator of
either motor or generator in a cradle, thus
enabling the operator to give the various units
to be paralleled, such relation to their respec-
tive revolving fields, and to each other, as will
secure the desired division of load. With
units of similar characteristics, even though
there is considerable difference in capacity,
the load may be satisfactorily divided in
proportion to the respective capacities.
The paralleling of a unit of this description
on the motor end is readily accomplished by-
starting up through a compensator, but after
reaching synchronous speed the generator end
may or may not bear the proper relation to
synchronize with another unit which is already
carrying load, hence it is necessary to slip
poles by reversing the motor field. One or
more reversals may be necessary before the
proper relation is found.
The synchronizing of the generators without
a synchroscope is almost sure to lead to trouble,
hence synchroscopes are almost universally
used in connection with frequency changers.
It must be borne in mind that, as the load
increases on a unit such as we are here dealing
with, there will be a corresponding angular
displacement of the revolving fields, so that if
one machine is carrying a full load and a
second one is started, the scope will not show
true synchronism even though the proper
relation of the two machines has been estab-
lished. However, there is usually no serious
disturbance when two machines are thus
thrown together, provided they are in the
same station where the resistances of the leads
is small, and where automatic feeder voltage
regulators are used, such disturbances as there
are will usually not be manifest to the con-
sumer.
Where machines are located in different
stations, and where it is desirable to parallel
over a tie line, additional complications arise
due to the fact that the resistance of the tie
line tends to lower the synchronizing power of
the machines, and due further to the fact that
there is a drop in voltage in the tie line. Of
course the same conditions are also in evidence
that obtain where the machines are in the
same station, such as the angular displacement
due to load on one or more machines in one
station with an incoming machine in another
station having no load. These conditions are
so difficult to meet that where more than one
station has frequency changers, at least one
machine in each station is usually kept in
service, the tie line only coming into use for
transmitting part load from one station to the
other in order to hold a high machine load
factor, although in event of one machine
"kicking off," the tie line would prevent a
complete shut down.
The tie lines, where the above practice
prevails, must be capable of carrying con-
PARALLEL OPERATION OF FREQUENCY CHANGERS
■S3?
siderable load, perhaps the equivalent of one
machine, or say 500 to 1000 kw. Such tie
lines, at 2300 volts operating potential, become
rather expensive, particularly as they are
usually underground. In addition to the
matter of cost, it is not always desirable to
keep even one machine in operation in each
station.
A concrete example, which however repre-
sents the practice of one of the larger systems
in this country, will serve to illustrate some of
the difficulties referred to, and also to demon-
strate a method whereby, with relatively
small and inexpensive tie lines, the machine
load factor is held quite high, and satisfactory
synchronizing is secured. The system em-
ployed does not contemplate continuous
synchronous operation of two stations, but
rather to enable one main station to carry
the load, except during the peak, and thus
hold a high machine loading factor, and to
enable the transfer of load without appreciable
effect on the voltage regulation.
Referring to Fig. 1, the two substations
containing frequency changers are fed from a
common generator bus, some miles away;
hence by starting the frequency changers on
the motor side through compensators, they
must necessarily be properly paralleled on
that side. The two substations are practi-
cally three miles apart; the tie line is under
ground, and has a rated safe capacity of 450
kv-a. Owing to the voltage drop it cannot
carry more than 200 kv-a.
It should be noted that the four frequency
changers in the one station can be readily
paralleled, and from one to three machines
are always in use, depending on the load.
During the hours from midnight to approxi-
mately 5:30 p.m. the load on the smaller of
the two stations is about 100 kv-a. and is
carried by the larger of the two substations
over the tie line, the single unit in the second
station being idle. As the evening load
starts to come on, this single unit is started,
synchronized, and the tie line then cut out.
About midnight the tie line is cut in, and the
single unit shut down.
With a 1000-kw. unit in operation at the
larger station, with nearly full load on it, and
with approximately 100 kv-a. passing over
the tie line, there was formerly quite a nasty
" bump " at the instant when the unit was par-
alleled with the tie line at the smaller station.
As previously explained, the synchroscope
would never stand at the true synchronous
position due to the fact that the machine or
machines at the larger station were loaded
while incoming machine was unloaded, but
would stand at an angle of from 30 to 60
degrees fast, indicating that the incoming
machine was fast, or ahead, hence when the
machine was thrown in there was not only a
"bump," but surges, the character and
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Fig. 1. Diagram showing Two Frequency Changer Substations,
a Common Bus, a Tie Line, and Suitable
Resistances and Control Switches
extent of which depended on many circum-
stances, one of which was whether the switch
was closed on the peak of the wave or on the
increasing side of the wave, or whether on
the decreasing side, or at zero.
A very noticeable improvement in the con-
ditions has been made by installing a re-
sistance and suitable control switches, in
the station containing the single unit. Refer-
ring to the diagram, the disconnecting
switches are left closed except when repairs
are necessary. The cycle of operations is
as follows: Assume the tie line to be carry-
ing the load and it is desired to put the
frequency changer on load. Oil switches Nos.
S3S
GENERAL ELECTRIC REVIEW
1, 2, 3 and 4 and the generator oil switch
must be open. Start the machine and syn-
chronize. Close oil switch No. 4, then No. 1,
then No. 2, then generator. Open No. 4. close
No. 3, open the tie line switch, and No. 2,
open No. 1, open No. 3.
Assume the machine to be carrying the
load and it is desired to put the load on the
tie line. The tie line switch and Nos. 1, 2, 3 and
4 must be open. Close switch No. 3, then
No. 1, then No. 2, then the tie line switch.
Open Switch No. 3, close No. 4, open the
generator switch, then open No. 2, then No. 1,
then No. 4.
true synchronizing position to enable parallel-
ing with little or no "bump."
Practically the same result could be accom-
plished by putting an artificial load on the
incoming machine thus causing a mechanical
displacement in it which would bring it back
to the correct synchronizing position, and
this is virtually what is accomplished by the
method described.
The two recording voltmeter charts show
the "before and after" results, and demon-
strate the value of the method.
The number of operations involved in
putting the machine on load, or taking it
Fig. 2. Recording Voltmeter Chart taken before improvements
were made in the substation wiring. Note
wide fluctuations at "On" and "Off"
Fig. 3. Recording Voltmeter Chart taken after improvements
were made in the substation wiring. Note absence
of fluctuation at" On "and "Off"
The effect of these operations is to permit
the load to be shifted from the tie line to the
machine, or vice versa, in steps having a low
enough value to practically eliminate the
trouble previously experienced.
Assuming that the tie line is carrying the
load and that the machine is synchronized,
the synchroscope may stand at, say eight
minutes after 12, showing that the incom-
ing machine is approximately 48 degrees
ahead. As the resistance is thrown in cir-
cuit the incoming machine picks up part
of the load and the synchroscope will fall
back to say five minutes after 12 position,
or 30 degrees. Cutting out another step
of resistance will further reduce the angular
displacement, and on the last step the
synchroscope will be near enough to the
off, is considerable, but as the switches are
mounted on adjacent panels it does not cause
the operator a great amount of work, and the
time involved can be as little as ten seconds.
In practice the operator is required to count
three between one operation and the next to
give the machine time to overcome its inertia,
which is considerable, and adjust itself to the
new conditions, also to permit the automatic
voltage regulators to adjust themselves.
This method of operation has proved reli-
able and satisfactory and may be of service
to others in developing their substations
along the same lines, that is, to have one
main station with smaller stations carried
during the day over relatively inexpensive tie
lines, with units at these smaller stations to
take up the evening peak.
839
PRINCIPAL FACTORS GOVERNING THE CHOICE OF METHOD OF
COOLING POWER TRANSFORMERS AS RELATED TO THEIR
FIRST COST AND OPERATING CONDITIONS
By W. S. Moody
Engineer, Transformer Department, General Electric Company
The author shows in a few concise statements the different methods adopted for cooling transformers and
tells the relative merits, the limitations and suitable applications of each. The article is concluded with a few
interesting historical facts. — Editor.
The continuously increasing demand, dur-
ing the last few years, for the transmission
of energy over greater distances and for the
distribution of larger and larger amounts of
power, has necessitated the development of a
diversity of types of modern power trans-
formers, until they now may be had at
practically unlimited voltage and capacity.
In former days certain types were restricted
in size, as in the case of air-blast and self-
cooled oil-immersed designs, especially the
latter. Today, these limits have about
disappeared (excepting in the case of the air-
blast type which is still limited by voltage)
through advanced engineering acquaintance
with the laws of heat generation and dis-
sipation, gained by long experience and aided
by scientific progress in the art of designing.
Of all the features effective in modifying
the design of a static transformer, there is
none that so fundamentally affects it in every
way as does the method used for cooling,
which is also most intimately associated with
the first cost of the apparatus and with the
conditions of its operation.
The self-cooling, oil-immersed type of
transformer is desirable always whenever its
cost is not too high, because it has no auxiliary
cooling apparatus that requires attention. It is
especially applicable, therefore, for sub-
stations or where help or water is expensive.
The highest commercial voltages can be
supplied in this construction.
The cost varies from approximately 20 to 30
per cent more than for water-cooled trans-
formers. The interest on this extra cost must,
of course, be balanced against the cost of
attendance and auxiliary apparatus for the
artificially-cooled types. Oil-cooled trans-
formers should have ample ventilation around
and between the units. A variety of tanks is
required to cover the whole range in capacity,
but their choice is a matter only of efficiency
in heat dissipation and mechanical strength
and stability.
Water-cooled transformers are very exten-
sively used, owing to their being smaller and
cheaper per unit output than other types,
and because until recently self-cooled designs
were not available in sizes over 3000 or 4000
kv-a. capacity. Their voltage is limited only
by that of the transmission line, and their
capacity by transportation facilities.
In considering this type the question of
the availability of attendance must be settled.
Are attendants required for this particular
plant of transformers only or would they be
necessary for other apparatus that might be
installed there, and if not so needed, will the
transformer installation warrant it ?
Water-cooled units are practically inde-
pendent of the cooling effect of the air, par-
ticularly so in the larger sizes, and con-
sequently but one form of tank is used, that
is, a plain smooth case of sheet steel.
A combination self-cooling and water-
cooling design is becoming attractive in many
cases, particularly for conditions where long
and definite periods of light and heavy load
occur, such as in small winter and large
summer service.
Fig. 1. Probably, the First Oil-immersed, Self-cooled '
Transformer placed in commercial use (1890)
Such transformers are placed in the regular
sheet steel tanks of the self-cooled design,
excepting that they have smaller surfaces,
and are in addition provided with water
cooling coils to take care of the super-load.
Such transformers can easily be designed
to carry 50 per cent of the maximum load
S40
GENERAL ELECTRIC REVIEW
without water circulation and not exceed the
rated temperature rise. The increase in
cost over the water-cooled design is slight and
often will be found a good investment when
water for cooling has any appreciable value.
Fig. 2.
A 300-kv-a. Transformer Built in 1904. This type
of tank has become standard for units
of 100 to 1000 kv-a.
Forced oil designs were somewhat popular
a few years ago for reasons more academic
than real, but have now become essentially
obsolete, as there is no saving in the cost of
the transformer itself that is not usually
offset by the extra expense of auxiliary cir-
culatory apparatus.
Air-blast transformers owe their use to the
insurance restrictions and popular objections
against large oil-filled units in city districts.
Voltages are limited to 35,000 as a maximum,
on account of the difficulty in avoiding corona
and dielectric heating for potentials above
this voltage. While many thousands of
kilowatts of such transformers have operated
successfully on 30,000- to 35,000-volt cir-
cuits for many years, it is advisable to limit
their use to 25,000 volts or less. This type
has in general about the same cost as self-
cooled oil-immersed designs.
Outdoor transformers with both natural
and artificial cooling have now been proved
by the experience of the last few years
to be entirely successful, even for the high-
est voltages or capacity, in any type and
in any climate. The main difference from the
indoor type lies in certain simple details
relating to weather- proof ness. Precautions
against freezing must be taken with water-
cooled designs, while the oil-cooled units can
withstand cold weather if the oil does not get
below —20 deg. C. during idle periods. Air-
blast transformers have not as yet been used
outdoors, but there is apparently no reason
why they could not be.
Fig. 3.
The Form of Tanks used for units varying from
1000 to 1500 kv-a
The General Electric Company has always
been both active and conservative in its
transformer design, and the following brief
outline of its practices regarding methods of
cooling is one illustration.
.METHOD OF COOLING POWER TRANSFORMERS
841
In 1S90 it made its first commercial instal-
lation (probably the first ever made by any
manufacturer) of oil-immersed, self-cooled
transformers of the form seen in Fig. 1.
In 1893 the first air-blast transformers were
designed, and are still in successful operation.
The form of tank shown in Fig. 2 was
brought out in 1904 and has been the standard
for all manufacturers for self-cooled trans-
formers in sizes from 100 to 1000 kv-a. ever
since. That seen in Fig. 3 covers a range from
1000 to 1500 kv-a. The construction set
forth in Fig. 4 is used for transformers of
from 1500 up to 3000 kv-a. and larger.
As transportation facilities have always
been more restricted abroad than here,
The Form of Tank and the Radiators used for
units greater than 1500 kv-a.
Fig. 5. An outdoor installation of Transformers having
tanks of the type shown in Fig. 4.
Large self-cooled, oil-immersed designs,
requiring tanks having corrugated outlines
to give a sufficient radiating surface, were
at first made only with cast iron cases.
Later on, methods of welding were devel-
oped to admit the use of sheet steel
cases, in which all seams, as well as joints
between sides and base, could be thor-
oughly welded.
transformer tanks having detachable radiators
were first brought out there; although ship-
ping limits were soon reached here also. It is
now some three years since the General
Electric Company developed the first tanks
of this form used in this country. In Fig. 5
is shown a recent installation of transformers
in such tanks, located at one of the "outdoor"
substations of the Southern Power Company.
842
GENERAL ELECTRIC REVIEW
THE CONTACT SYSTEM OF THE BUTTE, ANACONDA 8b
PACIFIC RAILWAY
By J. B. Cox
Railway and Traction Engineering Department, General Electric Company
The main divisions of the following comprehensive article on "The Contact System of the Butte, Anaconda
& Pacific Railway" cover the following points: Reasons for selecting an overhead system, development of
the mechanical details of the pantograph to fulfill the local conditions, method of crossing trolley wires at
street railway intersections, sectionalization and layout of trolley wires, costs of material and labor, record of
progress during construction period, and difficulties encountered and the means employed in overcoming them.
— Editor.
A careful preliminary survey of the general
problems involved in the electrification of the
Butte, Anaconda & Pacific Railway had made
it evident that an overhead contact system
was unquestionably advisable; the two pre-
dominating reasons were that approximately
60 per cent of the tracks to be electrified con-
sisted of yards and sidings with numerous
switches and street crossings, and that a
great portion of these tracks were in localities
where it would be very difficult to protect
against trespass by the public.
An analysis of the general traffic conditions
had indicated that a locomotive unit with
approximately SO tons on the drivers and
equipped with an aggregate motor capacity of
approximately 2400 h.p., for maximum accel-
erating periods, would be the most economical
and best suited to the general service con-
ditions (two such units being operated in
multiple as a single locomotive for the heavier
freight trains) . Such a locomotive would thus
frequently have to collect from the trolley
from 3000 to 3600 kilowatts, which would
mean 6000, 3000 or 2500 amperes at 600,
1200 or 1500 volts respectively.
Trial estimates on the total initial costs and
the final operating expenses had indicated
that, for the general conditions, direct-current
motors operating two in series from a 2400-
volt trolley fed from two substations, one
located at each end of the line in existing
power supply buildings approximately 26
miles apart where no extra attendants would
be required, would be expected to yield the
most economic results. Higher trolley volt-
ages were considered but were not found to be
generally advantageous.
A double-unit locomotive with a capacity
as described would, therefore, be required to
collect from the 2400-volt trolley during
acceleration from 1400 to 1500 amperes or
700 to 750 amperes for each collector, there
being one collector for each unit.
While this was known to be well within the
capacity of a single 4 ,/0 trolley fed at frequent
intervals from both directions, the successful
collection of such a heavy current from a
single trolley wire was a more serious problem.
Sliding pantographs of various types had
been developed and made to operate fairly
successfully for the collection of currents up
to 150 or 200 amperes under similar operating
conditions, but none had given any hopeful
indications of collecting these heavy currents
with a reasonably satisfactory life.
Rollers of various kinds had been tried as
substitutes for the slider and one of these,
made from steel tubing, had been found to
give very satisfactory results.
On the whole this type of collector seemed
to give the most promising prospect at the
time, so that it was chosen for the moving
contact device on the locomotives.
A Shelby steel tube 5 inches in diameter and
24 inches long was used for making up the
roller. The thickness of this tube when
machined inside and outside was approxi-
mately i/g inch. Originally, a wooden lining
was forced inside the tube, which was expected
to hold the tube together until the sparking
had called attention to the necessity for its
removal, in case the metal wore through.
Removable bearing housings of aluminum
were fitted into each end of the tube, two
phosphor bronze sleeve bearings being in-
stalled in each housing and between these
was an oil chamber for containing the lubri-
cant. The complete roller revolved about a
% in. steel shaft which was fixed at each end
by clamps to the pantograph frame.
The completed roller with lining, bearings,
and spindle weighed approximately 31 lb.,
as against about 5 lb. for the corresponding
contact element usually adopted for the
sliding pantograph.
This comparatively heavy contact device
could not be expected to respond so readily or
so gently to hard or uneven spots in the
trolley wire as the lighter slider. Besides the
increase in weight, the rapid revolving of the
roller at high speeds would tend to increase
the difficulties unless the balance was almost
perfect. These difficulties were foreseen from
CONTACT SYSTEM OF BUTTE, ANACONDA & PACIFIC RAILWAY
S43
the beginning, and as it was realized that the
weight of the roller could not be materially
reduced it was decided to adopt practically
the standard pantograph frame with such
changes as were necessary for the substitution
of the roller and then turn to the trolley line
construction with a view toward removing
the most serious objections to the roller,
i.e., to eliminate the hard or uneven spots in
the trolley line which seemed to be its greatest
detriment.
The pantograph as originally installed on
the locomotives is illustrated in Fig. 1. One
such pantograph was mounted on each
freight locomotive unit, and two on each
passenger unit, though only one pantograph
is used at a time. The extra one was to be held
as a spare for use in case of trouble, thus
avoiding unnecessary delay. All main line
freight trains are operated by a double-unit
locomotive with both pantographs in contact
with the trolley wire. Both pantographs are
connected in multiple by means of a bus
line run on top of the locomotives, with a
jumper connection between the two units.
In case of accident to either pantograph on
these trains a single pantograph is capable of
collecting the current for both units for the
completion of the trip. The operation of this
pantograph in service is described in detail
later in this article.
In considering what might be done by way
of improving the design of the overhead line
construction, so as to make it more adaptable
to the satisfactory operation of the roller
pantograph, evenness and flexibility were
recognized as being the qualities most desired.
The introduction of catenary construction
with hangers at frequent intervals had accom-
plished much in these directions, especially
the first, and gradual improvements had been
made toward simplifying and cheapening
this type of construction, though perhaps the
Fig. 1. Pantograph Trolley
importance of flexibility had not been fully
appreciated until the heavier types of col-
lector became necessary.
Attention was directed to the redesigning
of all hangers, pulloffs and other line material
which tended to add unevenly distributed
weight or local stiffness to the trolley wire,
the result being the development of a new
line of this material.
The new hanger was made up of a % in.
by y% in. flat strap having a malleable iron ear
secured by a J^ in. by 1^ in- carriage bolt.
This hanger allows the greatest
possible vertical movement of
the trolley wire, or more than
the upward pressure of the two
pantographs of a double-unit
locomotive, operating with a
tension of 35 to 40 lbt each
against the trolley wire, will
normally raise it. No resistance
from the messenger wire will be
encountered even up to this
point, since the loop extends for
almost the entire length of the
hanger. The hanger is simple in
construction and is easily in-
stalled, since the loop is merely
thrown over the messenger and
the two ears carried by the loop
strap are secured by the single
at the same time clamps the
jaws into the groove of the
Fig. 2. 28-in.
Trolley Wire
Hanger
bolt which
self-aligning
trolley wire.
The design of the jaws gives liberal clear-
ance for the roller and would readily permit
the operation of a trolley wheel should such
for any reason be desired.
The weight of the complete hanger varied
from 14 Yi oz. in the case of the 8 in. to 1% lb.
for the 28 in. or longest hanger. Fig. 2
illustrates this hanger.
As a very large percentage of the trackage
to be electrified is of curve construction
varying anywhere from a tangent to 22 deg.
curvature, it was necessary to give most
careful attention to the design of a new
pulloff. The efforts in this direction created
an entirely new pulloff by means of which
the messenger and trolley wires are held in
position by separate clamps. From each
clamp runs an individual pulloff wire with a
strut between them that maintains the pull
parallel to the horizontal plane of the trolley
wire. This arrangement allows of a free
vertical movement independent of the mes-
senger, see Fig. 3.
The double pulloff used where there was
more than one track is shown in Fig. 4. This
pulloff, while an improvement in some
respects over former designs, was not as
satisfactory as the single pulloff, as it proved
to be heavier and less flexible than was desired
and caused a slight sparking when a single
844
GENERAL ELECTRIC REVIEW
pantograph passed underneath it at medium
speeds. The design has been revised and in
future construction will be considerably
improved.
Rigid pulloffs, as shown in Fig. 5, were used
at some points but were found to be subject to
Fig. 3. Flexible Pull Off for Pantograph Collector
much thesameobjections as the double pulloffs
because of the sparking due to similar reasons.
The splicing sleeve is made of sheet steel
with a malleable iron removable shoe which
gives a smooth underrun for the roller and
may be replaced when worn out before the
body of the holding member proper is injured.
The wire is securely held, without bending
the wire or diminishing its tensile strength, by
a drop-forged wedge with sharpened teeth.
Fig. 6 illustrates the form of wedge grip
clevis used for dead-ending the trolley and
messenger wires. This had double wedges
with sharpened teeth similar to that for the
splicing sleeve. These are readily installed
with a hammer; which fact, together with
their low manufacturing cost and ease of
adjustment in service, makes their use
economical as well as satisfactory.
The question as to the use of wood or steel
poles for the supporting structure was not a
difficult one owing to the general conditions
and the nearness to the best of markets for
good Idaho cedar poles which made their use
more economical when compared with the
cost of steel structures. Some consideration
was given to the use of steel structures in
some of the vard construction where as manv
Fig. 4. Double Flexible Catenary Pull Off
as eight tracks were to be spanned, but even
here it was finally decided to use the wooden
poles though the general advantages were not
so great as on the main line construction.
However, steel supporting structures were
used on the double track steel trestle running
from the concentrator yards up over the ore
storage bins alongside the concentrator build-
ings. These tracks are approximately ^/h. mile
in length. The steel supporting structure was
made up at the smelter and the cost of it is
included in Table I.
A further item of unusual character in
connection with the trolley line construction
was that required for about \i mile of track
alongside a slump pond from which the
sediment is taken by means of a drag-line
scraper bucket operated from a cableway
suspended between two traveling towers
mounted on rails on each side of the pond.
As the track in question on which empty cars
are placed for loading is located inside the
area covered by the cableway, a trolley wire
over the center of the track would interfere
with the loading. It was desirable to use a
standard locomotive for the handling of these
cars, so the brackets which supported the
Fig. 5. Rigid Catenary Pull Off
trolley and messenger wire were hinged at
the pole and a flexible wire cable, attached
to the outer end and passing over a pulley
anchored on top of the pole, was connected
to a hand-operated windlass by which
the brackets are swung upward carry-
ing the trolley line from over the
track and clear of the path of the
bucket. When the loading is com-
pleted the trolley is lowered to the
normal position while the loaded cars are
removed and replaced by. other empties.
The number of poles and costs will be found
in Table II.
The matter of insulation was not a serious
one as trolley voltage up to 11.000 volts had
CONTACT SYSTEM OF BUTTE, ANACONDA & PACIFIC RAILWAY
845
been in operation for a number of years and
insulation difficulties for such pressures had
been met quite satisfactorily. It was there-
fore simply a question of choice between wood
and porcelain, the decision eventually being
made in favor of wood as the dry climate in
the locality was favorable to
its satisfactory service with
greater general economy.
The wooden strain insula-
tors used are shown in Fig. 7
and the number employed
and the costs are given in
Table II.
Insofar as the general plan
of trolley construction is con-
cerned no decidedly radical
departures from some of the
later installations was at-
tempted, but every effort was
made to simplify and perfect
what had been done before
and to adapt the construc-
tion to the particular condi-
tions.
A very important item tend-
ing toward economy and sim-
plification was the omission
of the use of any form of deflector at all
special work. Some new departures were
made in the manner of arrangement of the
trolley wires at these points so as to insure the
pantographs picking up and dropping them
properly.
At switching points, in ordinary trolley
wire construction, frogs are employed to
make the trolley junction; and for use with
pantographs deflectors are generally required.
r
this usual type of construction the trolley and
messenger wires which were intended to
follow the switching track were started
several feet ahead of the switch, from a con-
venient point for dead-ending, and several
inches above the horizontal plane of the
Fig. 8. Pantograph in Contact with Six Trolley Wires at a Switching Point
4J
Fig. 6. Wedge Grip Clevis
Fig. 7. Wooden Strain Insulator
These deflectors prevent the pantograph,
when approaching such a junction toward a
trailing switch, from raising its wire above
that of the converging track, and thus avoid
the damage that would result to either the
pantograph or the trolley wire. Instead of
through wires and then gradually brought
down to that plane a short distance ahead of
the switching point from where they were
gradually carried away following over the
switching track. At some points in the
yards, where the parallel tracks left the
ladder' track at close intervals, as many as
six sets of wires are in the same horizontal
plane and all the trolley wires make contact
with the roller simultaneously. See Fig. 8.
This construction has proved entirely satis-
factory and there have been no instances of
trouble caused by the omission of deflectors.
The construction adopted not only lessened
the cost of the work but avoided much extra
weight at points where the supporting struc-
ture was most taxed. Fig. 9 is an illustration
of the construction described.
Air section insulation was used at all points
where it was practicable and has been found
to be advantageous from every point of
view. Instead of inserting wooden insulators
in the trolley line where sectionalization was
desired, the ends of the wires of each section
were made to overlap each other the length of
a pole spacing. The two sets of wires are
carried in approximately the same horizontal
plane but about 12 inches apart for a few feet
in the middle of the span, from which point
the dead ends of the trolley wire are gradually
S46
GENERAL ELECTRIC REVIEW
carried above the path of the collector to its
anchorage.
This construction avoids the use of heavy
insulators and prevents hard or heavy spots
in the line which are destructive to it and the
pantograph alike. With this construction
there is less objection to subdividing the line
into a number of short sections which, with
the elasticity provided by wooden poles and
catenary suspension, overcomes to a great
extent the difficulties arising from contraction
and expansion due to changes in temperature.
These sections are passed at full speed with-
out any noticeable effect on the line, or the
pantograph, or the least interruption of con-
tact.
Similar construction was used at all anchor-
ing points for both the trolley and messenger
and it has been found to be equally satis-
factory there. Undoubtedly this type of
sectionalizing will become much more general
in the future and means will be devised for its
adoption at points where it is now found dif-
ficult to install properlv.
Tests were made by cutting the current off
one section and running a locomotive from
the live section onto the dead section at slow
speed with heavy current to see if the arcing
between the pantograph and the live trolley
wire would be injurious. The arcing was
surprisingly small and not of a nature to
do serious harm to either wire or roller.
Fig. 10 shows the general method of installa-
tion.
The effect of such an operation in the case
of the wooden section insulators, used at
street railway crossings and other points
A
Fig. 10. The Arrangement of an Air Section Insulator
Fig. 9. View of the Contact System at the Stock Bin Yard
CONTACT SYSTEM OF BUTTE, ANACONDA & PACIFIC RAILWAY
847
where it was not found convenient to install
the air type, was quite injurious; and, though
such tests were not meant to be given them
and the insulators were not expected to stand
such treatment repeatedly, some of those
located at street crossings where considerable
switching was done received the test too
frequently and sooner or later broke down
under the treatment.
At these street railway crossings it was
necessary to use two such insulators about
75 feet apart in the 2400-volt line, the trolley
section in between being called the protecting
zone. This was made necessary on account of
the operation of double-unit locomotives with
a trolley of each in use and the two being
connected by a bus line.
As the first insulator was usually about 100
feet from the switch and the safety section
was not energized until a member of the
train crew ran ahead and threw a commutat-
ing switch located on a pole near the street
crossing (which cut off the commutating
section from the normal 600-volt connection
and energized it with the 2400-volt current so
long as the switch handle was held in the full
up position) it frequently happened in the
earlier period of electrical operation, before
the crews had learned from actual experience
the damage that might result, that the
member of the crew whose duty it was to run
ahead and operate the switch did not get it
thrown until the locomotive had passed under
the first insulator. As this was often done
with the power on the motors, the arcing that
occurred when the roller left the live section of
the insulator and ran onto the dead section
carbonized the wood of the insulator, and the
carbonization was extended with each repeti-
tion until the insulation was finally insuf-
ficient and the insulator had to be replaced.
The insulator originally used at these points
is shown in Fig. 11. These experiences
suggested the advisability of a change in the
design of the insulator so as to render the
arcing in such instances less destructive. The
overlapping metal contact strips which orig-
inally were attached directly to the bottom of
the wooden insulators were therefore replaced
by other strips which were carried out about
four inches from the wood insulation, thus
making the distance between the strips con-
siderably greater. These strips were attached
to the insulators by spring hinges, so as to
lessen the blow to both the insulator and
pantograph. The insulators were quite an
improvement over the original ones but even
they were not entirely free from injury when
heavy currents were broken under the con-
ditions heretofore described. Fig. 12 shows
the general arrangement of the electrical
connections for these street railway crossings.
The Butte, Anaconda & Pacific tracks
cross local street railway tracks at six points,
Fig. 11 Section Insulator for a Pantograph
Collector as Installed at a Cross Span
four of which are at street level in Butte.
Two are at the Anaconda end, but at these,
not being street crossings, it was possible
to avoid the use of the special switching
devices by arranging with the street railway
company to coast over the crossing. At two
of the crossings in Butte watchmen were
permanently employed to operate gates for
protecting the traffic. The electrical switches
for controlling the crossing at these points
were placed on poles near the watchman's
tower where he could operate them easily,
and they were interlocked with the gates so
as to make it impossible to energize the
crossing with the 2400-volt current until
the gates were closed or to open the gates
while the switch was in the 2400-volt position.
Practically no trouble was experienced at
these points after the watchmen became
accustomed to their new duties, but at the
less frequently used crossings where the train
crews operated the commutating switches
some troubles were experienced with the
switches in addition to that already noted
with the section insulators. These switches
were not expected to open heavy currents for
the operators were expected to hold them in
until the locomotive had entirely cleared the
protecting zone. Occasionally this was not
done or to aggravate matters the switch was
allowed to only partly open while the loco-
motive was still in the protecting zone, and
when arcing was noticed in the switch box the
handle was dropped and the switch badly
burned. These commutating switches are
shown in Fig. 13. At one point where this
trouble occurred a second time, electrically
s4s
GENERAL ELECTRIC REVIEW
Fig. 12.
General Arrangement of the Electrical Connections at a
Street Railway Crossing
operated contactors were placed in series
with the ordinary operating switch on both the
2400-volt and 600-volt circuits, the two sets
of contactors being so interlocked as to render
it impossible for both to be energized at the
same time. See Fig. 14.
Xo further troubles were experienced from
this cause after the installation of the con-
tactors. These switches have been redesigned
for future installations. After the men had
become familiar with the operation of the
switches there were very few instances of
trouble even with the original switches.
The trolley line was sectionalized at inter-
vals as shown in Fig. 15 which also shows the
final feeder arrangement. The sectionalizing
switches were placed in asbestos lined wooden
boxes and located on trolley poles well out
of reach from the ground. An operating
lever was located at a convenient point on the
pole, and at a suitable distance from the
ground for ease in handling. It is provided
with a standard track switch padlock so that
no extra key is required by trainmen for its
operation. The operating handle is connected
with the switch blade by a wooden rod which
provides adequate insulation.
In addition to the sectionalizing of the
main line these switches were used at all
yards and at most spurs and transfer tracks
to connecting lines, and at such of these
points as the service was infrequent the
switch was normally left open. Such transfer
connections were made with four other
railway lines, viz.. Great Northern, Northern
Pacific, Chicago. Milwaukee & St. Paul, and
the Oregon Short Line.
Eleven point suspension
with 28 inch deflection was
used throughout.
Approximately 10 per cent
of the 91 miles of track elec-
trified was bracket construc-
tion which was used on nearly
all tangent single track. These
stretches of tangent track were
so short comparatively and
the percentage and degree of
curvature so great that it was
unnecessary to make any
special provision for stagger-
ing the trolley wire. Approxi-
mately 38 of the 91 track
miles would be classified as
route miles leaving about 53
miles — or roughly 58 per cent
— of yards, sidings, spurs, etc.
These 53 miles were made up
principallv of 8 yards located at Anaconda,
East Anaconda, Silver Bow. Rocker. West
Butte, and Butte on the main line and the
Concentrator Bins, Storage Bins, and Butte
Hill Yards on branch lines. Fig. 16 shows in
Fig. 13. A Commutating Switch
CONTACT SYSTEM OF BUTTE, ANACONDA & PACIFIC RAILWAY
849
map form the relative location of these yards
and spurs as well as the number and arrange-
ment of the tracks, etc.
The East Anaconda Yards contained 12
tracks (including those of the main line)
aggregating approximately 5 miles. These are
the largest yards on the system . Eight of these
tracks run almost the entire length of the
yard which is approximately J 2 mile m length.
The eight tracks are spanned by double
messenger span wires supported from a pole
line on each side spaced approximately 110 ft.
apart. The details of this construction with
dimensions are given in Fig. 17.
At the western end of the yard there are
four additional stub end tracks where a third
pole line was erected to form the outside
support for the wiring. This eight track span
construction has stood up well and is quite
satisfactory. All the construction in the
yards and spurs is of the standard catenary
type and entire freedom from any kind of
trouble with it would seem to fully justify
any additional expense that this may have
required.
The construction work was practically
completed in October, 1913, though some
small extensions were made on Butte Hill in
1914.
Fig. 18 illustrates the form of weekly report
that was made to indicate the progress and
general condition of the work during con-
struction. As this was the last such report
made, it represents practically the completed
construction and indicates how nearly the
original estimates correspond with the final
results in addition to giving many other
details of useful interest relative to the nature
of the work.
Fig. 14. Diagram of Connections at a 600-volt Street Railway
Crossing showing commutating arrangement and protection
from 2400-volt System with Electrically Operated Con-
tactors in Series with Regular Commutating Switch
This report was not intended to cover
other than the regular construction and,
therefore, does not include the entire list
of all the items mentioned; some further
short extensions were made at a later date. 1
The total cost of the trolley and feeder
system inclusive of bonding and all changes
ANACONDA SUBSTATION
Panel No.lAII Smelter Hill Main Lines.
Panel No-2 ■ All Tracks West of East end of E. Ana. Yard
Panel No.3 • All Smelter Hill Yards.
Panel No.4 ■ Main Line to Butte from East end of E Ana. Yard
Bradley Spur
• Pood
T-Sr*CUJI lOCk CO Itiii SWItCO
lor cooveyor CI
SUBSTATION 3
BUTTE SUBSTATION
Panel Nol - Butte Hill Yard & Missoula Gulch Line.
Panel No. 2 - Main Line from West end West Butte Yard West to Anatonda
Pane! No.3- Mam Line 4 Yards from West end West Butte.Yard East
Panel No 4- Sp#re for Future use.
Section Insulator and Switch.
Section Insulator only.
Section Switch only.
Positive Feeder.
Negative Return.
Trolley and Track.
Note: Standard lock for Cutout Switch
is standard railway switch lock.
Fig. 15. Diagram Showing Sectionalization of Trolley and Feeder Systems
850
GENERAL ELECTRIC REVIEW
ANACONDA STA.
MAP
B.A.&P.RY.
SHOWING OfCTFlFlEO TRACKS
"~\
Fig. 16. Diagram of the Electrified Section of the Butte, Anaconda 8b Pacific Railway
TABLE I
COST OF DISTRIBUTION SYSTEM
ELECTRIFICATION OF THE BUTTE, ANACONDA & PACIFIC RAILWAY
Labor installing
Feeder copper
Work train service
Trolley wire
Cedar poles
Galvanized strand wire.
Copper bonds
Hangers.
Crosby clips
Wood strain insulators
Engineering and superintendence.
Tools
Anchor rods
Sectionalizing switches
Injuries and damages, etc
Fitting up work cars
Steel and iron from stock
Lumber and timbers
Rental on work cars
Shop expenses
Lightning arresters
Paints and oils
Feeder and messenger insulators.
Creosote and oil
Steel bond protectors
Splicing sleeves
Postage, car-fares, etc
Guards and signs
Wedge grips
Dynamite and fuses
Gasoline, solder, etc
Miscellaneous items
Total.
Cost per Item
Cost Per Mile
$129,027.56
$1417.89
89,697.00
985.68
64,268.31
706.25
58,213.60
639.71
27,739.21
304.83
26,807.47
294.59
20,564.20
225.98
7,596.27
83.48
5,396.17
59.30
5,385.22
59.18
5,289.30
58.12
3,811.30
41.88
3,403.73
37.40
3,097.05
34.03
3,036.56
33.37
2,292.61
25.19
2,043.87
22.46
2,013.61
22.13
1,716.50
18.86
1,418.59
15.59
1,271.02
13.96
901.32
9.90
842.15
9.25
637.00
7.00
570.00
6.26
294.00
3.23
238.62
2.62
234.08
2.57
130.01
1.43
121.36
1.33
100.46
1.10
33,629.50
369.55
$501,787.74
$5514.15
CONTACT SYSTEM OF BUTTE, ANACONDA & PACIFIC RAILWAY
851
made necessary in the way of clearance for
poles, wiring, etc. (such as relocation of
tracks, telephone, telegraph and light wires,
etc.) up to the fiscal period ending June 30,
1914, as reported to the Interstate Commerce
Commission was $501,787.74. This would
make the average cost of the overhead
system per track mile $5514.15 or per route
mile $13,381.00.
An itemized list of these costs is given in
Table I, while the amounts and unit costs
of the principal items involved will be found
in Table II. The total costs given are from the
official records of the railway company, which
are classified in accordance with Interstate
Commerce Commission regulations as appears
in Table III, which includes the entire cost of
the electrification.
The whole of Accounts Nos. 12, 16, 19 and
22 and such portion of No. 1 as was directly
in connection with the distribution system are
taken as the total cost of that system.
The listed items in Table I are approxi-
mately correct though in some instances there
was some question as to the proper allocation.
However, the general results are as nearly
correct as is practicable and even the slightest
variations in local conditions would easily
offset any likely discrepancy in the propor-
tioning of these costs. The sum of the listed
items was subtracted from the total cost
and the remainder listed as miscellaneous
thereby covering all items of materials and
labor, etc., not definitely specified, leaving
no question as to the total cost.
All this construction was done while the
road was under full operation and under many
conditions which tended to increase the cost
above normal.
2 Wrap, «rouAd f* W" *'* i">
■ Mc«urm IHookskyfV,
2 Chbyi tic" *»«
Fig. 17. Diagram showing Dimensions of a Cross
Catenary Span for eight tracks
The principal items tending to increase the
cost were the large percentage of curves and
special work, the high price of all labor, the
interference from foreign wires, the changes
in location of tracks, walkways, platforms,
buildings, trestles, bridges, etc., which was
made necessary on account of the electri-
fication, extra heavy traffic on the main line
due to the use of fifteen miles of it by a trans-
continental line for all traffic while a con-
necting link for this section was being built,
strike of electrical wiremen, cold weather,
variation of ground condition, number of
street railway crossings, etc.
Remarks:
Great Northern work held up on account of moving freight
house.
Construction work finished except:
Wiring of Great Northern Yard at Butte.
Foundry tracks at Anaconda,
Installing new lightning arresters.
Installing signals at railway crossings.
6 8 MJ«i (o Smeller* -?
PROGRESS REPORT FOR WEEK EN DING OCTOBER 25, 1913
Poles
Pole
bracket
Cross
arms
Pole
anchors
Posi-
tive
feeder
Negative
feeder
Trolley and
messenger
Spans
Back
Bonds
Earth
Rock
600 M.
and
300 M.
600 M
4/0
Run
out
built
Bone
■ 0"
36"
48"
Cross
Bond
Long
at
Frog
Rock
Pole
42.50
4846
370
270
1600
140R
4600
5303
300
187
miles
55
SI 05
miles
0 89
miles
19 IS
miles
.4
98 56
miles
94
98 56
1700
25S0
4
miles
32 2)
780C
7927
2450
2408
22800
19893
450
175
300
362
Holes
513
Guys
7038
Total previously installed ........
Installed durinc currciU week.. . . .
19
7C57
4846
270
187
Fig. 18. A Tabulated Progress Report
852
GENERAL ELECTRIC REVIEW
It is not likely that the average steam road
would encounter so many obstacles of this
nature in undertaking the electrification of its
lines, for seldom would there be found more
complications than in this case where the
nature of the work (being required for a
mining and smelting industry of large mag-
nitude) calls for many varieties of structures
and conditions not usually to be encountered
in ordinary railway electrifications.
The work was begun in the summer of 1912
and was just reaching a state of efficient
organization when the electrical wiremen
went on strike tieing up the entire work from
June to October, about three months of the
most favorable part of the year for such work,
thus bringing the heavy part of the work in
the winter when the weather at times was
20 degrees below zero. During the three
months cessation of work the engineering and
supervision force was continued at a very low
percentage of efficiency and this delay con-
tributed in various other ways to an increase
in the cost of the construction.
Some of the items of expense in connection
with changes made in existing construction
and charged against the distribution system
are shown approximately in Table VI. The
new telephone lines listed in this tabula-
tion were run on the trolley line poles and
were for the purpose of enabling the train
crews to communicate with the dispatcher
from any locomotive on all of which telephone
instruments were installed, together with a
standard rod for making electrical connec-
tions with the wires at any point along the
line.
Table VI is by no means complete, though
it gives an indication of the various items
represented in the total costs of the sys-
tem.
Combining eleven pay rolls gives the
classification of labor, see Table VII. These
eleven payrolls represent the principal items
of labor in connection with the erection of the
trolley and feeder wires, and are those for the
regular forces engaged in this work and
charged against account No. 22, Table III.
TABLE II
TABLE SHOWING AMOUNTS AND COSTS OF PRINCIPAL MATERIALS REQUIRED FOR
BUTTE, ANACONDA AND PACIFIC DISTRIBUTION SYSTEM
Feeder copper, lb
Trolley copper, lb
Cedar poles
Galvanized steel strand, feet.
Copper bonds
Crosby clips
Wood strain insulators
Anchor rods
Splicing sleeves
Wedge grips
Total
Total Units Units Per Mile Costs Per Unit
Total Cost
507,055
5,572
17.69 cents
$89,697.00
343,030
3,770
16.97 cents
58,213.60
4,869
53.5
566.00 cents
27,739.21
1,553,750
17,074
1.73 cents
26,807.47
32,260
355
63.74 cents
20,564.20
61,911
680
8.72 cents
5,396.17
15,850
175
33.97 cents
5,385.22
6,123
673
.55.57 cents
3,403.73
265
3
111.00 cents
294.00
680
7.5
19.13 cents
130.01
$237,630.61
TABLE III
COSTS OF THE ELECTRIFICATION OF THE BUTTE, ANACONDA & PACIFIC RAILWAY
CLASSIFIED IN ACCORDANCE WITH INTERSTATE COMMERCE REGULATIONS
Account No. 1 — Engineering and superintendence (including general preliminary report) $10,937.15
Account No. 12 — Roadway tools (used for construction 19 and 22) 3,851.74
Account No. 16 — Crossings, fences, guards and signs, mostly for signs 234.08
Account No. 17 — Interlocking and signal apparatus, new system required account of
electrification ' 22,367.62
Account No. 19 — Poles and fixtures (approximately 91 miles track) 135,263.98
Account No. 22 — Distribution system (approximately 91 miles track wired) ., 357,009.45
Account No. 2.5 — Substation building (existing building used) ' 191.15
Account No. 31 1 Electrical Equipment (five 1000-kw. motor-generator sets and 17 loco-
Account No. 36 J motive units) 671,764.78
Account No. 41 — Interest 9,975.80
Total $1,211,595.75
CONTACT SYSTEM OF BUTTE, ANACONDA & PACIFIC RAILWAY
853
Time and a half was allowed for all over-
time and double time for Sunday work in
the case of electrical workers.
Wages and perhaps most materials were
somewhat higher in the locality of Butte
than in any place east of it or in most places
in the western states.
The operation of the overhead system as a
whole has been quite satisfactory in every
respect for there have been practically no
troubles or delays to traffic on account of it.
There were two instances of wires slipping in
the splicing sleeves due to the wedges not'
being properly driven up. One of these
instances was in connection with the trolley
wire and the other with the messenger. In
both cases the results were negligible for, in
the first instance, the trolley hangers slid
back along the messenger much as the rings
hanging a curtain slide along the supporting
wire until the tension was evened up, the
trolley being held clear of the ground by the
messenger; while, in the second instance, the
messenger slid back through the loop of the
hanger until the tension was relieved but
was supported clear of the ground by the
trolley wire so that no harm resulted. All
that was necessary to remedy the trouble on
TABLE IV
COST OF MAINTENANCE AND DISTRIBUTION SYSTEM, OCTOBER, 1913, TO
MARCH, 1915, INCLUSIVE
POLES AND
FIXTURES
Labor
Ma-
terial
Labor
Ma-
terial
Labor
Ma-
terial
MISCEL-
LANEOUS
Labor
Ma-
terial
Labor
Ma-
terial
Labor
Ma-
terial
Labor and
Material
Oct.
Nov.
Dec.
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Jan.
Feb.
Mar.
1913.
1913.
1913.
1914.
1914.
1914.
1914.
1914.
1914.
1914 .
1914.
1914.
1914
1914.
1914.
1915.
1915.
1915.
$599.95
219.65
251.50
172.10
105.10
134.90
115.55
152.95
163.55,
$14.43 $449.25
15.09 446.50
26.98
.13
6.12
2.47
6.58
98.70
389.15
165.30
103.45
186.95
135.15
141.15
Total 18 months
Rate per year
Rate per mile per year
1915.35
1276.90
14.03
71.80 2115.60
47.86 1410.40
.48 15.50
$9.32
.48
19.36
3.08
.50
$334.65
32.40
150.95
23.15
26.95
70.90
9.20
49.10
63.45
67.05
Cr
235.64
320.57
2ii<; !•:.
55.86
4.64|
42.96
45.41
91.04
$60.50
65.95
64.95
37.65
40.20
24.00
104.65
47.40
24.05
Id. 'in
43.10
30.85
94.90
39.20
58.40
$291.85
431.20
426.35
390.30
286.25
570.55
313.65
526.75
473.65
32.74
21.83
.22
827.70
551.87
6.06
601.09 746.70
400.72 497.80
4.40 5.47
$66.22
64.57
94.54
99.68
97.55
66.02
488.58
325.72
3.58
3710.55
2473.70
27.18
$7.50!$291.S5
264.47, 431.20
114.74 426.35
88.72; 450.80
784.21 686.85
808.51: 667.90
34S.95 351.30
628.36 566.95
972.08 497.65
11304.80
.... , 736.70
! 374.35
367.94 599.10
384.40
278.40
446.50
390.75
430.15
4385.48
2923.65
32.13
$7.50
264.47
114.74
88.721
784.211
Nl IS :, I
348.95:
628.36!
972.08:
Cr.221.2l|
335.66;
308.77;
423.80!
69.34
144.101
119.04
218.51
164.14:
9316.00
6210.69
68.25
5579.69'
3719.79;
40.881
$299.35
695.67
541.09
539.52
1471.06
1476.41
701.25
1195.31
1469.73
1082.59
1072.36
683.12
1022.911
453.74
422.50
565.54
609.26
594.29
14895.69
9930.46
109.13
TABLE V
SMELTER HILL SERVICE
EAST ANACONDA TO CONCENTRATOR
Train
No. 1
No. of cars in train . . . .
Gross wt. tons
Ton-miles, gross
Schedule speed. .
Avge. amperes-total. . . .
Avge. volts
Avge. kilowatts
Max. amperes
Maximum volts
Max. kilowatts
Total kilowatt-hours . . .
Watthours per ton-mile
Minimum volts
Max. drop per cent. . . .
Avge. drop per cent. . . .
18
1420
9940
16.1
580
2327
1350
860
2456
1951
580
61.4
2250
8.4
5.3
Train
No. 2
21
1580
11060
16.2
583
2277
1327
640
2419
1500
560
50.6
2119
12.4
5.9
Train
No. 3
25
1910
13370
14.2
667
2276
1518
800
2456
1733
746
55.82
2100
14.5
7.3
Average
21.3
1633
11431
15.5
610
2293
1398
767
2444
1728
629
55.02
2156
11.8
6.9
MAIN LINE SERVICE
ROCKER TO EAST ANACONDA
Anaconda
to Rocker
64
1335
26700
20.1
366
2325
852
624
2475
1368
852
31.91
2175
12.1
6.0
Rocker to
Anaconda
57
4150
83000
20.1
380
2345
891
640
24.35
1510
654
7.87
2175
10.7
3.6
Average
60
54850
20.1
373
2335
872
632
2455
1439
753
13.73
2175
11.4
4.9
854
GENERAL ELECTRIC REVIEW
both occasions was to pull the parted wire
back into position and properly wedge it into
the sleeve. There have been two instances of
the trolley wire parting due to the improper
welding of the metal in manufacture and other
similarly negligible instances common to such
installations.
TABLE VI
New telephone line on trolley line poles. 87,850.64
Changing light, power, telephone and
telegraph lines 4,273.15
Changing street railway crossings 1,546.65
Relocating railway tracks 815.90
Raising drip sheds 785.54
Changing station platforms 693.29
Raising wagon bridges 361.52
Total $16,326.69
The most serious interruption that occurred
was originated by the blasting out of some
old bridge piles by the section men of a
paralleling railway. A fragment of the pile
was blown against a telephone wire carrying
it across the 2400-volt trolley. This telephone
wire ran through the switching board in all
the stations along the line, some of which had
not then been provided with the proper
protecting devices. The result was that the
arc set fire to some of the boards and in one,
where the operator happened to be tem-
porarily absent at the time, the building was
burned setting fire to adjacent poles and part-
ing both the trolley and messenger wires.
At the other stations involved, where the
operators were present and could give prompt
attention to putting out the arc, no serious
damage resulted.
The maintenance men who took charge of
the trolley system were put on October 1,
1913, and consisted of a foreman and two
linemen who could requisition other assistance
when an occasion demanded it. The cost
of maintenance from this date up to and
including March 31, 1915, covering the first
IS months operation, is given in Table V.
Beginning with July, 1914, these accounts
were kept more in detail. These expenses
include some rearrangements of feeder, etc.,
and the cost of some special instruments for
bond testing, and tools. The average cost of
maintenance of the distributing system
inclusive of the track bonding for the 18
months has been at the rate of $109.13 per
track mile per year.
Taking the last nine months during which
the costs were segregated more completely
gives the data listed in Table VIII.
To ascertain the rate of wear on the trolley
wire, measurements were recently made on the
Smelter Hill line where the traffic is heavier
than at any other point and where the electric
service has been in operation longest (just
about two years).
The original diameter of the wire vertically
was supposed to average about 0.482 of an
inch. The minimum diameter found where
the measurements were made was 0.470 of an
inch. The average of a number of measure-
ments was 0.475. It is usually considered safe
to allow a 4/0 trolley wire to wear down to
0.350 thus allowing a wear of 0.132. If the
maximum wear of 0.012 as found for the two
years is taken as the average during the
useful life of the wire, which is at the rate of
0.006 per year, the wire can be expected
to last 22 years. At this portion of the line
there has been an average of approximately
50 passages of pantograph rollers per day
which for two years would be an aggregate
of 36,500 passages or 18,250 per year indicat-
ing 3041 passages per thousandth of an inch
TABLE VII
Davs
Avge. Approx.
Per Day
Total
Blacksmiths and helper .
Boilermakers and helper.
Carpenters and helper .
Machinists and helper . .
Electricians and helper. .
Pipefitters and helper. .
Laborers
Teamsters
Electrical foremen
Foremen
Clerks
Totals .
27
26
17
15
3,580
2
3,035
35
835
665
500
13,737 days
$3.08
$110.58
3.76
97.78
4.40
75.56
433
64.91
5.71
20,544.09
3.80
7.69
3.56
28,611.53
3.25
106.96
• 6.35
5,300.62
6.06
4,030.82
3.35
1,670.42
$4.41 ave.
$60,620.96
CONTACT SYSTEM OF BUTTE, ANACONDA & PACIFIC RAILWAY
855
It is perhaps questionable as to whether the
first few months wear on the trolley wire
would be at the same rate as after the con-
tact surface had become greater. The out-
side surface of the wire might be slightly
harder than the interior and thus the wear
be less at the beginning, while on the other
hand when the wire is new the contact area
with the roller is quite small and the pressure
per unit area together with the increased
current density might cause more rapid wear.
From such data as are at hand, it would appear
that the rate of wear on the trolley is greater
at the beginning and decreases as the contact
area is increased. Extensive tests with a
sliding contact, where the operating con-
ditions were varied as to the amount of
tension against the trolley wire and current
collected, almost invariably indicated that the
spot or groove which rendered the roller unfit
for further service (if not detected at an early
stage).
This sticking was first due to the imperfect
alignment of the clamping jaws which held
the ends of the spindle passing through the
roller and on which the bushings revolved.
As the bearings consisted of four bushings
\y<l in. long, being arranged in pairs one at
each end with a space of 1 in. between the two
bushings of each pair, thus making each
lining substantially 4 in. in length, it was
possible to clamp the ends of the spindle so
tightly as to spring it out of line and cause
it to bind in the bushings until it did not
revolve with the ordinary friction offered by
its contact with the trolley wire. This trouble
was overcome by more care in the adjustment
of the clamps. A little later the caps in the
TABLE VIII
Poles and
Fixtures
Trolley
Feeder Bonding
Misc. Total
Labor
Material
$1915.35
71.80
$2115.60
32.74
$460.75 $453.45
601.09 488.58
$0.00 $4945.15
367.94 1562.15
Total
$1987.15
2649.53
29.12
96
4
31
$2148.34
2864.45
31.48
98
2
33
$1061.84 $942.03 $367.94 $6507.30
1415.79 1256.04 490.59 8676.40
Rate per year per mile of track
15.55 13.80 5.39 95.34
43 48 76
57 52
16 15
100 24
Per cent of total
5 100
rate of wear decreased as the area of contact
increased; and there seems no reason to
suppose that the same would not be true in the
case of the roller collector so that the average
life of the trolley wire in this service should not
be less than 20 to 25 years.
The roller collectors adopted for the service
and described in the beginning of this article
have performed their work in general equally
as well as had been expected of -them, though
at the beginning of the electrical operation
a number of minor improvements were found
desirable. The rollers were operated against
the trolley with an upward pressure of
approximately 35 lb., the practice being not
to readjust so long as the tension was not
above 38 or below 33 lb., at the average
operating height.
The first difficulties experienced with these
rollers was from the sticking of the roller
in the bearings, which resulted in their
sliding along the trolley wire causing a flat
bearing heads began to loosen until they
bound the roller between the clamps and
caused them to slide as before. A set screw
was provided which prevented the unscrewing
of the caps and no more trouble from the
sliding of the roller was experienced until
extremely cold weather came and heavy
frost accumulated on the trolley wire
which, on being knocked off by the roller,
lodged on top of the 23/2 in. iron brace or
hooker frame supported underneath the roller
(having about -^g in. clearance) piled up and
finally clogged the roller causing it to slide
with the same results as heretofore.
This difficulty was met by increasing the
clearance of both the brace and the roller and
inverting the T so that the web was on the
bottom and thus did not offer so large an
area for the collection of the frost.
Another defect that threatened trouble at
an early stage was the removable cast iron
wearing plates screwed to the pantograph
856
GENERAL ELECTRIC REVIEW
head at each end of the roller and intended to
guide the trolley wire smoothly from the
horn onto the roller.
It was found quite difficult to keep this
plate in proper alignment with the roller
owing to the wearing down of the bushings
and the increase in the end play of the roller,
which allowed the trolley wire to hang in the
gap between the wearing plate and the end of
the roller. When this condition was not
remedied promptly a groove was soon worn
at this point which often made the replace-
ment of the plate necessary and sometimes
m.p.h., the bushings wore out very quickly
which allowed the oil to be carried out along
the spindle and thrown off. It fell on the roofs
of the locomotive and cars and made it
necessary to replenish the oil at the beginning
of each trip.
When the bushings became worn the roller
vibrated considerably, causing more sparking
at the contact with the trolley wire and often
breaking the truss rods used for bracing the
pantograph frame. In some instances these
bushings were badly worn before they had
made 200 miles.
Fig. 19. A Pantograph Folded showing Revised Wear Plate
that of the roller tube as well. This difficulty
was removed by the application of a new
type of wearing plate which extended out
slightly over the roller with a prong on either
side gradually dropping below the line of the
top of the roller so that the wire passed from
one to the other so gradually that there was
no point where the wire was inclined to catch.
The lower end of this wearing plate extended
out over the upper end of the horn in a similar
manner and avoided the necessity of such
careful fitting as had been required with the
old type where butt joints were used. The
new wearing plate is shown in Fig. 19.
The sleeve bearings with oil lubrication
were fairly satisfactory in the freight service
where the average speed was from 15 to 30
miles per hour but when the passenger service
was started, requiring a schedule speed of 26
m.p.h. with maximum speeds of 45 to 50
Experiments were made with grease lubrica-
tion, which gave promise of good results and
which led to some slight modification of the
bearings and to a general substitution of
grease for oil as a lubricant.
In the meantime tests were being made with
Hyatt roller bearings and the results had been
so encouraging that it was decided to sub-
stitute these for the sleeve bearings in all
the rollers as fast as the latter wore out and
required to be renewed. Fig. 21 shows their
installation in the later rollers designed for
this purpose.
The total locomotive miles made by the
electric locomotives up to the end of March,
1915, was 927,234. The number of roller
tubes received by the Railway Company up
to that date was 123 including those that
came on the locomotives and extra panto-
graphs bought for spares.
CONTACT SYSTEM OF BUTTE, ANACONDA & PACIFIC RAILWAY
857
On this data the roller tube stock was as
shown in Table IX :
TABLE IX
5 new rollers complete in pantographs
29 new tubes in stock
20 partially used tubes on locomotives
10 partially used tubes in stock
Total 64 tubes used and unused, 34 of which are new
and 30 partially worn, leaving 59 tubes
that have been replaced.
The master mechanic estimates that the
30 partially used tubes are, on the average,
about half worn out, on which basis the
average miles per roller would be ' — =
11,750 or supposing that these tubes were
two-thirds worn out the average mileage per
927,234
tube would be — — — = 1 1,030 miles.
84
In this connection it should be noted that
eleven of the 59 abandoned tubes were
removed before they had been in service
many miles on account of the rollers sticking
and sliding along the trolley until a groove was
cut in them as shown in Fig. 22. Some of
Fig. 20.
Original Pantograph Roller Housing Modified
and Fitted with Roller Bearing
these tubes were thus injured during the
commencement of electrical operations before
the defect had all been remedied, but most of
them were caused by the frost freezing the
roller to the T iron brace underneath, pre-
viously mentioned.
A large percentage of the above mileage was
made before all the sleeve bearings were
replaced by roller bearings or the clearance of
the roller above the T iron had been increased.
Comparatively few rollers that were fitted
with the roller bearings when new have yet
Fig. 21.
Latest Type of Pantograph Roller Designed
for use with Roller Bearing
had to be replaced. One roller which had
been in the passenger service, where the
average current collected is not so great as in
the case of the freight service, though the
speed is considerably higher, ran 26,880 miles
before it was replaced. The average mileage
of all tubes with roller bearings at the present
time is approximately 16,000 miles which
indicates that roller bearings are responsible
for an increase of about 35 per cent in the
average life of the rollers.
The old sleeve bearings with grease lubrica-
tion had to be renewed about each 5000 or
6000 miles, thus requiring about two sets of
bushings during the life of a tube. The roller
bearings after making 26,880 miles were
in perfect condition and it is difficult to judge
as to what mileage they will make but, from
present indications, it is reasonable to expect
that they will make at least 100,000 miles
per set. It cost approximately $2.92 in
labor and material to renew a set of the old
bushings.
The cost of substituting the roller bearings
for the bushings was approximately $2.20 for
material and $2.25 for labor or $4.45 per
roller. It will thus be apparent that the
change was even more important from the
point of saving in maintenance of bearings
than from increased life of the rollers. The
roller bearings require comparatively little
attention, a small quantity of fresh grease
being inserted at each regular inspection of the
engine.
The general repairs to the entire pantograph
have been likewise affected as the decreased
S.-.S
GENERAL ELECTRIC REVIEW
vibration has stopped almost all pantograph
troubles.
The repairs to other parts of the pantograph
during the past six months consisted of renew-
ing six wearing plates; the replacing of two
horns and one cross bar.
Fig. 22.
View of Pantograph Rollers showing Injuries
that have developed from sliding
The average cost of maintenance of the
original pantographs with the sleeve bearings
was about $185 per month or approxi-
mately S3. 20 per 1000 locomotive miles.
The present corresponding cost of this main-
tenance is about $35 per month or 62 cents
per 1000 locomotive miles which shows a
decrease of approximately 81 per cent in this
item.
It was found in practice that the wooden
lining originally pressed inside the tube was
unnecessary and this was omitted when the
new bearings were installed.
The operation of these roller pantographs
is, therefore, considerably more efficient than
had originally been expected.
Two 500,000 feeder cables in multiple for
the trolley and one 4/0 cable for the track
circuits were run on the trolley line poles
between the two substations; the other
trolley feeder running to the yards which
were fed separately or in pairs.
Voltmeter and ammeter readings were
taken on a number of trains to ascertain the
drop in voltage and energy consumption; a
summary of these is given in Table V from
which it will be seen that the maximum drop
in voltage obtained was 14.5 per cent while
the average drop for all readings was 5.6
per cent.
The readings making up the averages given
were taken at 30 second intervals for the
entire trips on the locomotives in regular
service hauling normal trains under average
operating conditions and are, therefore,
fairly representative of general results. How-
ever, there has been a gradual increase in the
weight of the trains which might slightly
affect the average drop in voltage.
Fig. 23. Section of Tangent. Track, showing Pantograph Trolley Suspension as sketched in Fig. 17
CONTACT SYSTEM OF BUTTE, ANACONDA & PACIFIC RAILWAY
859
It may be of interest to note that repair
work on the 2400-volt trolley line is done from
an ordinary wooden work car without special
insulation with full voltage on the line. There
has been no serious cases of shock to the
workmen.
In wet weather it is not considered safe to
work from this car with full potential on the
line but there should be little difficulty in
constructing a tower car which would make
it quite safe under any ordinary conditions.
The writer wishes to thank herein Mr. C. A.
Lemmon, Chief Engineer and Mr. C. H.
Spengler, Master Mechanic of the Butte,
Anaconda & Pacific Railway, Mr. R. E. Wade,
(now Ass't Electrical Engineer of the Chicago,
Milwaukee & St. Paul) who had personal
charge of the construction of the Butte,
Anaconda & Pacific distribution system, and
Mr. C. J. Hixson and staff for assistance
kindly rendered in obtaining the data con-
tained in this article.
Fig. 24. West End of East Anaconda Yard
860
GENERAL ELECTRIC REVIEW
FROM THE CONSULTING ENGINEERING DEPARTMENT OF THE
GENERAL ELECTRIC COMPANY
A CURSORY ACCOUNT OF THE FIRST
LIGHTNING STORM OF THE SEASON
AS GIVEN BY THE RECORDS OF
THE MULTI-RECORDER
This information is given to emphasize
the importance of making exact records of
interruptions and the beneficial effects in
avoiding interruption of service which may be
obtained therefrom.
The data are taken from a multi-recorder
operating on a large transmission system and,
in the limited space allotted, it is possible
only to give a cursory account of the record
of the storm during the first hour.
The first indication of the storm occurred
at 4 p.m. when the dense gathering clouds
caused it to grow dark. A surge recorder gave
the first record on the multi-recorder of a
lightning stroke which affected the line 17
minutes and 41 seconds after four o'clock.
This surge recorder is a coherer actuated
device which is connected to the line through
specially arranged condensers so that the
surges on the line cause the coherer to operate.
There occurred then no further disturbance
for seven minutes when five records were
made in nine seconds, showing almost a
continuous surge. There was then another
interval of twelve minutes of no disturbance
and the record of a single instantaneous
surge at the end of it.
There was no further disturbance for two
minutes but after this time there began a
succession of instantaneous surges. There
were ten of these records in all, scattered
over a minute and a half. The records show
that the time between discharges first
increased and then decreased. The time
between successive discharges was as follows,
all given in seconds: 9, 14,41,4,6,3,3, 1, l.and
2. These momentary surges then developed
into a continual surge which lasted 17 minutes.
During this period of 17 minutes of continual
surges there were a number of extra heavy
surges which caused four distinct operations
of a surge recorder connected to one phase of
a parallel line.
It is interesting to note that up to this time
no arc had yet occurred between the line and
ground. This is known because there is a
relay which makes a record of a ground. The
surges were apparently caused by the pre-
liminary "spitting " or corona discharge which
often precedes the arc-over of a string of
insulator disks.
The end of this long succession of surges
occurred at four o'clock, 57 minutes, 34
seconds. It was seven minutes before the
disturbance recurred. The disturbance then
lasted twenty seconds. Apparently it dif-
fered somewhat from the previous disturbance
in that it brought into operation several
times a surge recorder on the adjacent phase
of the same line.
There was then another period of no dis-
turbance for one minute and 38 seconds
(6 minutes, 14 seconds past 5 p.m.) when an
arcing ground took place.
The recorder shows that the oil switch did
not open and disconnect the line until eight
seconds after the arcing ground took place.
This time is too brief to allow of any appreci-
able number of definite visual observations
but the recorder made. twelve records. Most
of these were of surges, but one record was
that of the opening of a circuit breaker which
disconnected one transformer of a bank of
four that were in service at this time. The
surges started some trouble inside the trans-
former which caused smoke to blow out at one
of the leads. It is a favorable comment on the
watchfulness of the operator that he switched
out this transformer seven seconds after the
accidental arcing ground started and one
second before the oil switch was opened.
As an answer to the very pertinent ques-
tion a practical operator might ask "Of what
use are these hair-splitting detailed records?"
further intermediate records are taken from
the multi-recorder.
There were four circuits in operation when
the storm first started. Twenty-four minutes
and no seconds after the continuous surge
ended the recorder shows that three of the
circuits were separated from the one in trouble
by the opening of a circuit breaker which
sectionalized the bus. No interruption
occurred on these three circuits. The operator
did this two minutes and 16 seconds before
the arcing ground took place. There is a
parallel circuit to the one on which the arcing
ground developed and there was plenty of
time to switch on this parallel circuit if it
had been free. Unfortunately some mechan-
ical damage had previously been done to
this circuit and the linemen were repairing it
at the time, otherwise it would have been
possible to have avoided entirely an interrup-
tion of service by the use of the multi-recorder
and its auxiliarv devices.
OPERATION OF ELECTRICAL MACHINERY
861
During this one line trouble the recorder
had shown to the second of time the passage
through the arresters of lightning strokes as
they occurred. It had also picked out the
circuit and the phase on which the trouble
was developing and gave the operator plenty
of warning and, as it happened, plenty of
time to perform the necessary switching in the
station.
If one were asked " Is this apparatus worth
while?" the answer is a similar question:
"Is it worth while to know when and where
trouble occurs and avoid all the interruptions
that do not develop instantaneously? Also,
is it worth while to know how troubles occur
with the probability of making arrangements
to avoid an interruption when troubles of
the same kind occur subsequently?"
E. E. F. Creighton.
ERRATA
General Electric Review, July. 1915, p. 669. "Temperature
Coefficient Formulas for Copper."
Left-hand column, line 1: "Electro Chemical" should read
"Electrotechnical Commission."
Equation (1): R,; = R< [1 X a (T/t-T,)] should read
R/,=Rc[l+a(T/,-T,)].
Right-hand column, line 15: "any numerical factor" should
read "any tabulated values or numerical factor."
PRACTICAL EXPERIENCE IN THE OPERATION OF
ELECTRICAL MACHINERY
Part X (Nos. 51 to 53 inc.)
By E. C. Parham
Construction Department, General Electric Company
(51) STATIONS IN SERIES
Instances of power stations or of sub-
stations operating in parallel are numerous;
instances of stations operating in series are
comparatively few.
Two electric railroads, the tracks and lines
of which abutted at their terminii, had
initially been operated independently. Later
these were merged under a single management
and the two developments were converted into
a continuous right of way. The trolley wires
were made mechanically continuous but
electrically they were insulated from each
other by means of a section-insulator. One
of the insulated sections was supplied from a
power-station and the other was fed from
a substation having a single 600-volt syn-
chronous converter. One day the converter
apparently "blew up." At first the machine
appeared to be badly damaged but a complete
examination showed it to be in a much
better condition, and it was soon qualified
for service again.
In the meantime a report was received to
the effect that, simultaneously with the
trouble of the converter, the generator in the
distant power-station had given trouble also,
but of a lesser degree because it was larger
than the converter. Subsequently it developed
that the converter had "come up" with the
wrong polarity, thereby placing the opposite
ends of the section insulator at a potential
difference of about 1200 volts, instead of
one of 50 or 100 volts as normally existed.
The first car that ran past the section breaker
with its controller on an operating notch had
dragged an arc, which resulted in placing the
power-station and the substation in series
with each other. The resistances of the track,
the line, and that of the two machines acted
as the only limit to the value of the short-
circuit current due to the 1200 volts.
The source of the trouble was a voltmeter
of the type that gives a positive reading
irrespective of whether the current through
it is flowing in a positive or in a negative
direction. So long as the converter operated
independently, its polarity was a matter of
no consequence; but if the same voltmeter
had been used for paralleling that converter
with another, the result might have been
much more serious than the one described.
(52) PARALLEL TRANSFORMERS
The secondary coil of a transformer may
be considered as a source of voltage in the
same manner as the armature of a generator.
In either case any number of independent
sources supplying independent loads will
affect each other only insofar as load excesses
or load fluctuations may affect the amount
of line drop or may affect the speed of the
prime movers upon which the generators or
the transformers depend. Where two gener-
ators are to supply current to the same
circuit, however, certain conditions must be
fulfilled or the two units will not divide the
total load proportionally. Similarly, if the
S62
GENERAL ELECTRIC REVIEW
secondaries of two transformers are connected
to the same service line, the two units require
that certain conditions be fulfilled or they
will not divide the load proportionally. It is
not sufficient that the internal characteristics
of the transformers be similar: the external
conductors bv means of which the trans-
A
Ml
3
mm
mm
Load
rr
Fig. 1
formers are connected to the load must have
resistances that are inversely proportional
to the ratings of the respective units, and
furthermore there should exist no local
conditions capable of greatly modifying the
reactance of the external circuit of either
secondary.
The full lines in Fig. 1 illustrate an instance
where two transformers of equal size, of the
same rating, and of similar characteristics
failed to divide the total load equally,
because the leads from one transformer to
the load buses were approximately ten times
as long as the corresponding leads of the other
transformer. In permanent installation work
the matter would have been rectified by plac-
ing the two transformers beside each other.
The installation under discussion, however,
was only temporary; therefore, in order to
relieve the condition the load lines were
simply shifted to the positions indicated
by the dotted lines in the diagram. This
change equalized the lengths of the leads.
The main objection to an unequal division
of the load is that at the full-load capacity
of the heavier loaded unit the lighter loaded
one is not fully loaded. This results in an
uneconomical investment for a considerable
transformer capacity has to be purchased
that is not used.
(53) TRANSFORMER CONNECTIONS
If a three-phase service voltage is derived
from the delta connected secondaries of three
single-phase transformers, the secondaries
would not be adapted for Y connection to the
same service. With the delta connection, the
service voltage equals the voltage per coil;
in the case of the Y connection, however, two
of the coils connected in vector series add their
individual voltages and thereby produce a
resultant voltage that is less than the arith-
metical sum of the component voltages, but
which exceeds the value of the service voltage.
In Fig. 2 a primary voltage of 100 and
a 1 to 1 ratio between the primary and the
Fig. 2
secondary have been assumed, also the
voltage per phase and the voltage per coil
have been indicated for several secondary
and primary combinations. It will be seen
that the service voltage produced by a
primary voltage of 100 varies from 173 to
57 according to the connection used. It is
of great importance, therefore, to specify the
primary and secondary voltage and also the
standard connections that are to be used,
when ordering single-phase transformers for
three-phase service.
Fig. 3
Fig. 3 illustrates the condition that was
found to exist in two sets of transformers
which would not operate together but would
blow the fuses. The secondary of one was
connected in delta and the secondary of the
other was connected in Y.
863
QUESTION AND ANSWER SECTION
The purpose of this department of the Review is two-fold.
First, it enables all subscribers to avail themselves of the consulting service of a highly specialized
corps of engineering experts, or of such other authority as the problem may require. This service provides
for answers by mail with as little delay as possible of such questions as come within the scope of the Review.
Second, it publishes for the benefit of all Review readers questions and answers of general interest
and of educational value. When the original question deals with only one phase of an interesting subject,
the editor may feel warranted in discussing allied questions so as to provide a more complete treatment
of the whole subject.
To avoid the possibility of an incorrect or incomplete answer, the querist should be particularly careful to
include sufficient data to permit of an intelligent understanding of the situation. Address letters of inquiry to
the Editor, Question and Answer Section, General Electric Review, Schenectady, New York.
PHASE RELATION AND ROTATION: DETERMINATION
(144) (a) What is the difference between phase
relation and phase rotation?
(b) Describe a method of testing out both the above
with lamps (with and without potential trans-
formers) when a three-phase alternator is to be
connected to the bus for the first time.
(c) What is considered the best method of determin-
ing whether a synchronoscope is indicating
correctly?
(a) The best means of showing the difference
between phase relation and phase rotation is to
define each.
Phase relation is expressed as the difference in
angular-position between the maximum alternating
voltage and current in the same circuit or between
the alternating voltages in two circuits (or between
the currents in those circuits).
First example: The phase relation between the
alternating voltage and the current in the same
circuit is ordinarily expressed by the value of the
angle between the voltage vector and the current
vector. For sine waves of current or electromotive
force, the phase relation between the voltage and
the current determines the available power in a
given circuit and the power-factor is equal to the
cosine of the angle which represents their difference
in phase. In the case of waves of non-sinusoidal
form as well as for sine waves the power-factor is
the ratio of the available power, as determined by
a wattmeter, to the volt-amperes. From the watts
and the volt-amperes in the above relations, the
cosine of the angle of phase displacement can be
determined and from this the angle which expresses
the phase relation. The phase angle then refers
to the position of two vectors, one of current and
one of voltage, each of which would be that corres-
ponding to "equivalent sine waves" by which the
actions in the circuit may be represented. It is
convenient to regard most circuits as- being rendered
active by simple sine waves which are the "equiva-
lent sine waves" corresponding to actual conditions.
The actual waves are usually more or less complex.
Second example: The phase relation between the
alternating voltage (or the current) in one circuit
and the corresponding voltage (or current) in another
circuit is expressed by the angular distance between
the vectors representing them. This phase relation
from time to time, if the circuits are not
synchronized and consequently have frequencies
differing to a greater or less degree. If the maximum
voltage in circuit A is displaced from that of
circuit B by 60 deg., the phase relation between
Itages is 60 deg. (Phase relation is considered
in this sense when synchronizing two lines.)
Phase rotation is that angular direction which
in a polyphase system represents progression of the
maximum value during a sequence of time. (It will
be noted that "phase relation" is a phenomenon
considered fixed at any time, and that "phase
rotation" is one considered as progressing with
5*viLch
Lamp
Potent/a/ vW
-P i=l
Fig. 1
cyclic speed.) Phase rotation is ordinarily defined
as being "clockwise" or "counter-clockwise." The
designation which is applicable to a particular case,
e.g., in a three-phase line with its conductors located
geometrically (at the apexes of an equilateral tri-
angle) is theoretically determined by the observer
imagining that he is looking end-on at a cross-section
of the line and determining whether the crests, or
the valley points, of the current or the electro-
motive force in the conductors pass from conductor
to conductor in a clockwise or in a counter-
clockwise direction. (Phase rotation must be
considered when synchronizing two lines, and when
connecting any polyphase motor for a definite
direction of rotation.)
(b) There are two methods of employing lamps
for synchronizing an alternator with a bus. These
are called the "dark" and the "light" methods.
The former is the one customarily used since its
connections are the more simple; consequently
this method will be described.
Depending upon what would be the value of twice
the normal voltage of the alternator connect one
lamp, several lamps, or a potential transformer (with
a lamp in its secondary circuit), across the terminals
of each switch. (Fig. 1 shows the connections for a
potential transformer and one lamp per switch.)
S64
GENERAL ELECTRIC REVIEW
Run the alternator at normal speed and excite it to a
voltage equal to the bus voltage (measured by
voltmeter). Observe the periodic increase and
decrease in the brilliance of the lamps.
If the three lamps brighten and darken simul-
taneously, the phase rotation of the voltage in the
leads that are brought to one side of the switches is
the same as that brought to the other side. If the
lighting does not take place simultaneously in all
three lamps but assumes a "see-saw" action, the
phase rotation of the alternator is unlike that of the
bus. To correct this condition it is only necessary to
transpose the leads (interchanging two) coming
to one side of the switches until the lamps act
together. (Like phase rotation is necessary, but
it is immaterial so far as this general discussion is
concerned whether it is clockwise or counter-
clockwise.)
Then, increase or decrease the speed of the
alternator (whichever is necessary) until the fre-
quency of the light fluctuation decreases. When
the periodic variations in the light are very slow, the
y/9e<7Cfo/7ce£ox
J?7Si'/'<y/ffe/7?
Fig. 2
alternator is running at very nearly the frequency
of the bus. At the instant that the three lamps are
at the mid-point of the dark period, the phase
relation of the alternator voltage to that of the bus
is one of coincidence, i.e., the phase relation is
zero, and the voltages are in phase. The connecting
switches should be closed at this instant and the
alternator will be ready to take on load.
If desired, the lamp around one of the switches
may be dispensed with after the leads to the switches
have been correctly arranged for like phase rotation.
(It is the modern practice, however, to install a
synchronism indicator rather than to continue to
use lamps after the connections to the switches
have been properly made.)
(c) The best method for completely testing the
accuracy of the connections made to a synchronism
indicator is first to connect a set of lamps (or set of
potential transformers with lamps if necessary)
across the switches as described in the foregoing and
shown in Fig. 1. Then observe if the indications of
the synchronism indicator are in accordance with
those of the lamps. If they are in coincidence, the
indicator is registering correctly. If this is not the
case, attention should first be given to checking the
wiring to the indicator since it is most probable
that the mistake will be found there. If it is only
desired to check the location of the needle at syn-
chronism, a test more simple, convenient and
accurate than the lamp method will supply "this
information. Connect the indicator and its react-
ance box, as shown in Fig. 2, to a single-phase line
of the normal voltage for the instrument. If the
needle is mounted correctly, it will point to the
neutral or synchronism index on the dial; if it does
not assume this position, it should be made to do so
by changing its setting on the spindle that rotates it.
E C.S.
INDUCTION MOTOR: CHANGE IN
NUMBER OF POLES
(145) When it is desired to increase the normal
speed of a squirrel-cage induction motor by recon-
necting the stator windings to give a fewer number
of poles, what are the limiting factors that
determine if such a change is possible? If the
reconnection is possible what would be the effect
on the motor's characteristics?
The principal factors limiting a change in the
number of poles of a squirrel-cage induction motor
are these:
(a) The number of turns in series per phase.
These must remain the same sinpe the
applied voltage is to be unchanged.
(b) The insulation between the conductors of
different phases. Of this there must be
sufficient to not reduce the factor of safety
against breakdowns after the regrouping
of the conductors has been carried out.
(f) The saturation of the iron. It is often inad-
visable to use a magnetic density much
higher than normal.
Because the designs of induction motors vary
widely with different manufacturers and also in the
product of each maker (for the purpose of supplying
motors for various types of service), it will be
impossible to make other than very general state-
ments regarding the expected change in character-
istics of the motor when running at the higher speed.
Furthermore, the following statements must not
be expected to hold true when the number of poles
has been decreased sufficiently to raise the normal
speed more than say 25 per cent.
After the reconnection,
(a) The normal speed will be equal to approxi-
mately the original normal speed times the
original number of poles divided by the
new number of poles.
(b) There will be a somewhat higher torque per
pole exerted, due to the slightly increased
flux per pole that arises from the shortened
pole pitch, so that the total motor torque
might be expected to be decreased but
little by the change,
(r) The running-light current will be slightly
lowered.
(d) The starting torque will probably be slightly
decreased.
(e) The power-factor might be expected to be
somewhat higher.
(/) When the power-factor is higher the rating
of the motor can be increased about in
proportion to the square root of the
increase in speed with the same heating.
(g) The efficiency will be practically the same as
before the change. A.E.A.
General Electric Review
A MONTHLY MAGAZINE FOR ENGINEERS
Editor. JOHN R. HEWETT — £ »£ J £ »™ERS
Subscription Rates: United States and Mexico. $2.00 per year; Canada, $2.25 per year; Foreign, $2.50 per year, payable in
advance. Remit by post-o3ice or express money orders, bank checks or drafts, made payable to the General Electric Review,
Schenectady, N. Y.
Entered as second-class matter, March 26, 1912, at the post -office at Schenectady, N. Y., under the Act of March, 1879.
VOL. XVIII.. No. 9 iyG.nlTE&ic9cLtany SEPTEMBER, 1915
CONTENTS Page
Frontispiece: Dr. Fred S. Pearson .... 866
Editorial : The Paths of Progress . 867
The Relation of Research to the Progress of Manufacturing Industries .... 868
By Dr. W. R. Whitney
The 45,000-kw. Synchronous Converter Substation of the Aluminum Company of America
at Massena Springs, N. Y 873
By J. L. Burnham AND R. C. Muir
Protective Coatings for Metal 87S
By H. B C. Allison
The Iron-cobalt Alloy, FeoCo, and its Magnetic Properties . 881
By Trygve D. Yensen
Control and Protection of Electric Systems 887
By Charles P. Steinmetz
Current Supply for Motion Picture Machines 895
By H. R. Johnson
Proper Construction of Earth Connections 904
By G. H. Rettew
Methods of Removing the Armature from Box Frame Railway Motors . . . 908
By J. L. Booth
A Ten-to-one Ratio for Comparing Precision Resistance Standards 915
By C. A. Hoxie
Some Problems in Burning Powdered Coal, Part I 920
By Arthur S. Mann
A Review of the N.E.L.A. Lamp Committee Report 925
By G. F. Morrison
Practical Experience in the Operation of Electrical Machinery, Part XI 928
Field Connection Error; Motor Would Not Start; Adjusting Single-phase Motor
Clutches
By E. C. Parham
In Memoriam: Dr. and Mrs. F. S. Pearson 930
From the Consulting Engineering Department of the General Electric Company . . 934
Question and Answer Section 935
THE LATE DR. F. S. PEARSON
On page 930 we publish a memorial to Dr. and Mrs. Pearson, who were lost with the
sinking of the Lusitania, on May 7, 1915
THE PATHS OF PROGRESS
We publish in this issue a memorial tribute
to a great American engineer who has left
behind him monuments which will testify
for long years to come of his usefulness to
mankind. The contemplation of such a man
and especially of his life's work must make
many a seriously minded man wonder wherein
lav his special power to accomplish so much
in the brief span of human life. No amount
of energy, unless perpetually guided by a
fixed purpose, can account for such a career.
Energy is often misguided. No amount of
specialized study will lead to such results.
The lives of many most learned men are sadly
lacking in accomplishments that benefit
mankind and lead us further along the paths
of progress. The secret does not lie in the
physical strength of the body or in stature,
this is too apparent to need comment or
qualification. We know of many men that
left the world the gainer by their lives through
thinking great thoughts and recording these
for the benefit and guidance of the world
at large, but these are literary men. An
engineer can never become great by writings,
however eloquent, and it is with the abstract
greatness of an engineer that we are par-
ticularly interested.
This greatness cannot be traced to energy
alone, nor to the material body which is
matter, but must be traced to the greatest
attribute of life — mind. The energy and
matter are both essential parts of ,the mani-
festation of greatness, but each is equally
impotent of accomplishing results unless
perpetually guided and controlled by the
mind.
The more we contemplate the greatness
of an engineer who converts nature's forces
and materials to the use of mankind, the
more fully we realize that there are but three
fundamental essentials that we can consider —
mind, energy and matter. That these three
must work in harmony we think is apparent.
Of these three essentials the mind must ever
be the greatest. A great man need have no
greater store of energy than one of lesser
caliber, and stature is of still less importance,
but a great and active mind he must have.
Tracing backward from the accomplished
work to the source from which it emanates we
are forced to a realization of the fact that
each great engineering work must first have
originated in a thought and that it is by
thoughts, properly controlled and tempered
by an imagination which can produce results,
and that can guide both physical energy and
materials, or matter, that great men become
great.
Again a great man with great thoughts
would hardly be reckoned great if his
thoughts guided and controlled physical
energy and matter alone. The genius of
most great men must be attributed to the
additional faculty of, by thoughts, controlling
or guiding the minds of other men. Indeed
it seems that the highest function of the great
mind is to influence and guide the thoughts
of other men less gifted. And so the function
of the great engineer, and in fact, of all great
men in all walks of life, is to guide and control
mind, energy and matter, and their success
in this direction is a measure of their great-
ness.
Of course, there are many who attribute
success to luck and who think that most
successful careers are the playthings of
fortune, and that all that is essential is to be
a mediocre man, in the right place at the
right time. Some also seem to think that
most men might be great if opportunity had
presented itself, but we are rather inclined
to think that more men fail to become great
by not taking the opportunities when they
present themselves than are kept back in the
ranks of mediocrity by lack of opportunity,
For—
There is a tide in the affairs of men
Which, taken at the flood, leads on to fortune ;
Omitted, all the voyage of their life
Is bound in shallows and in miseries."
S6S
GENERAL ELECTRIC REVIEW
THE RELATION OF RESEARCH TO THE PROGRESS OF
MANUFACTURING INDUSTRIES
By Dr. W. R. Whitney
Director of the Research Laboratory, General Electric Company
The author shows the great value of a knowledge of every fact concerning nature. A knowledge of the
most trival fact has often led to developments of most vital importance. He shows that utility is the prime
factor of modern research work, but that purely academical research has led to some of our greatest develop-
ments. The spread of scientific knowledge is traced to the publications of scientific societies and it is pointed
out that some of the best work has been done by poorly paid services. The whole address demonstrates clearly
thai the nation that is to advance commercially must do so by the aid of scientific knowledge. This address
appeared in The Annals of the American Academy of Political and Social Science, Philadelphia, May, 1915.
— Editor.
We humans can never quite appreciate the
incredible applicability and utility of new
facts of nature. We are repeatedly shown by
our experience, but each new example only
augments our stock of wonderment or be-
wilderment. A very few months ago a
certain well-known scientific investigator
(Lord Rayleigh) found a slight difference in
the density of nitrogen taken from air and
nitrogen derived from other sources. He
felt obliged to know about this little difference.
In co-operation with Sir William Ramsay, he
discovered argon. This was present in the
atmospheric nitrogen and had always escaped
detection. It formed less than one per cent
of the air. It was discovered to be entirely
inert and chemically inactive. This was an
apparent promise of great chemical use-
lessness. At that time it was also exceedingly
difficult to separate it from the air, and
except for its scientific interest, it seemed
destined to be left inactive. Newly dis-
covered methods of liquefying air and of
combining nitrogen for fertilizer, as in the
cyanamid process, have just made the argon
available commercially. Other pure scientific
research had shown the value of such a gas in
incandescent lamps, and it is just at this
time being used to produce the most efficient
incandescent lamps of our knowledge. It
was the recently discovered differences be-
tween this gas and other gases which made
this lamp possible. When its existence and
properties were known, its application was
relatively simple and easy.
Our American people are quick to see the
value of new things where value exists. They
are given, in this era, to actively utilizing
every scheme which means better health,
greater safety, greater pleasures, greater
profits, and greater economies. We can
hardly conceive of a people devoting their
lives to inactivity and idleness. To better
living conditions, to improve and extend
manufacturing industries, and to conserve
resources is quite generally the life aim of our
ablest men.
A nation or a race does not stand still.
It either advances or falls behind its neighbors.
Knowing more has been the means of every
nation's advance.
Research is a convenient word which covers
the pioneer work upon which advances are
founded. It is significant that as life becomes
more and more complex, it is ever less possible
for advances to be made by accident or by the
designs of an individual working for short
periods on different subjects. The day of that
inventor is past who discovers an animal
carrying a new hide, who modifies the shoe
machinery or devises a new button or button-
hole. Each of these and a thousand other
such details are now the fertile fields in which
groups of trained experts are at work. We
want shoes badly and there are many of us.
We want them to wear well, even to the
enamel on the brass eyelets. The fact that
we are collectively willing to pay hundreds of
thousands, or even millions of dollars for some
slight improvement in a shoe or additional
economy in the manufacture, indicates not only
that we are many, but that we want actively
every possible improvement and economy.
A Benvenuto Cellini lived and left the
impression that he did all the work of an
army of artists, inventors, soldiers, politicians,
murderers, and — I may as well add — biog-
raphers. Besides his autobiography, he
wrote books on the goldsmith art, sculpture
and bronze, foundry practice, architecture,
and poetry. There are none extant like him.
A Franklin wrote equally advanced dis-
courses on electricity, on coal stoves, on the
recently united states of America which he
represented, on economy, on philosophy, and
many other subjects. We have few Franklins
and Cellinis to day.
Today the research chemist, with his
analytical methods, the metallographist, with
his microscope, the physicist with his pyrom-
RESEARCH AND THE PROGRESS OF MANUFACTURING INDUSTRIES 869
eter, the mechanical engineer with his tensile
strength apparatus, and the coke, gas, oil
and electric furnace experts are each sep-
arately working on the still wonderfully
complex cast iron of which a stove is made.
Certainly they will not be satisfied, nor will
we, the people, be satisfied, with any final
state, so long as we can conceive of a better
one. Iron must cast better, must rust less, be
stronger, be permanent in the grate bar, be
cheaper, keep an unaltered color, and so on.
The entire work involved in developing
such new devices and processes may be called
research, but there is a part of it which
deserves more careful attention than the rest.
This part is sometimes called pure research.
Most people mean by this term the search
after new knowledge, without reference to its
utility. Others mean the search for new and
useless knowledge. There certainly are
searchers after new truth who do not wish to
see the usefulness of their disclosures. But
facts of nature or true principles of science live
forever and are sure to be useful. The attempt
at worship of pure research for its own sake, as
is often done, is merely the tipping backward
of those who wish to stand erect, unbent by
sordid aims in their search after truth.
Bergson points out that the essential object
of science is to enlarge our influence over
things. He says:
"Science may be speculative in its form,
disinterested in its immediate ends; in other
words, we may give it as long a credit as it
wants. But however long the day of reckoning
may be put off, some time or other payment
must be made. It is always then, in short,
practical utility that science has in view."
A fair example of scientific research lies in
the history of our talking at a distance.
First, we called out as loudly as we could
and the strongest voice was the best tele-
phone. The use of some new knowledge
which was not immediately or obviously
connected with the voice was later put to use,
and a tin or iron pipe was used for short
distances as a speaking tube. After this idea
was disclosed, plumbers, tinsmiths, or pipe
fitters could do the rest. Then, later, the
possible application of formerly entirely
undreamt of principles to the increase of the
speaking distance was tried. Those to which
I reter were the electromagnetic principles
which, in short, produced the telephone
transmitter and receiver. These changed the
short, thick pipe into a long, thin wire. I
regert that I cannot go into detail to point out
the extended researches which, without the
slightest premonition of telephony, had to be
made before the knowledge was at hand to
enable Bell to contribute his part. Joseph
Henry, for example, studying in the basement
of an Albany school, had to wind wires with
insulation and study the properties of the
magnet, and this had to be followed by the
studies of many others for half a century.
To the early art, in the pipe stage, the tele-
phone wire may have looked merely like a
more refined pipe of the same material, but
it was not. There were entirely new, and
what I may call remote, principles, brought
into play and added to the metal of the pipe.
These were discovered by patient scientific
research of the highest order. The outcome
could not have been foreseen from any
knowledge of pipes or piping. In a practical
treatment of the subject of Research and the
Industries, this point must be made clear.
The final gathering of the fruits of the labor of
research often seems as little anticipated by
the real planting done by search for new
knowledge, as the picking of the fruit of a
tree seems anticipated by burying a seed in
the ground. Nevertheless, the developments
are the same in the two cases. It may be for
this reason that the President of the Carnegie
Institution, in his 1914 report, referred to the
work of the Institution in the words :
"The general reader must take it for
granted (provisionally, at least) that these
investigations are in the main worth under-
taking . . . for in proportion as such investiga-
tions are fundamental, and hence worth
carrying on, they will be difficult of exposition
and more difficult of comprehension."
Of the lines of activity of that Institution,
the farmer sees value in the studies in heredity
in cattle, but wonders why anyone should
want to synthesize rocks ; the glass maker who
sees value in the geophysics work, wonders
why the sun spot work is of use, while the
naturalist* says: "The sublime ideas of
infinity of space and time, and the beauty of
the simple laws of planetary motion, have had
a value to mankind far transcending that of
any so-called practical application of stellar
science." Thus, those who have had the
broadest comprehension have generally most
highly valued pure research.
So we are now in our day apparently seeing
our telephone wire grow finer and longer.
Talking from New York to San Francisco is
a thing of every day commercial experience.
This, in turn, was due not alone to the use
* R. G. Harrison, President of the American Society of Nat-
uralists, Philadelphia. 1913.
870
GENERAL ELECTRIC REVIEW
of longer wire or lower resistance or more
delicate instruments (what Bacon calls an
increase in the efficient), but involved new,
remote ideas, the result of research. Such
is the Pupin loading coil, for example,
which has made long distance telephony
possible. We are also aware that to all
appearances the telephone wire is now being
drawn so fine that it is altogether disappear-
ing, and wireless telephony is an accomplished
fact. This becomes possible not through
finer wire drawing, but by the application of
newly discovered laws or principles of nature.
It was not even done by those who were most
industrious in construction of telephones, any
more than the tin speaking tube was really
displaced by the tinsmith. The work was
done by those already trained scientific
investigators, who were learning new facts of
physics or electricity which, at some stage of
their work, seemed applicable to telephonic
use. This new work, this pioneer obtaining
of facts which never revert to the undis-
covered state, constitutes research.
Our government, among others, has schemes
for the promotion of research. One of them is
the patent law. If a discoverer will disclose
his discovery to the public, he may exercise a
monopoly of it for seventeen years. In some
cases this is very encouraging, but it seems to
have at least one serious defect. The dis-
covery, besides being new, must be, at the
same time, useful. With many great dis-
coveries this is not the case. It may seem
ridiculous to favor useless discoveries, but it
is quite the reverse. The thing to encourage
is the search and finding of new facts, prin-
ciples, laws, and habits of nature; i.e., addi-
tions to our knowledge without reference to
immediate value. These are the surest
guarantees of ultimate utility. The process
of making knowledge useful is not half so
difficult nor so rare as is the production of the
knowledge itself. But the rewards usually
go to the man who shows us the utility.
For this reason we must plan better ways of
encouraging scientific research. To emphasize
this is the only object of this paper. It is
being done to some extent. Many of those,
living and succeeding under our system of
advance, have realized the way the seeds have
first to be sown. They have usually selected
some special field where the utility to be
expected from newly disclosed facts would be
of greatest public good. In this spirit have
been established many of those research insti-
tutions which are devoted to the health of the
people, the cure of disease, etc. These are starts
in the right direction and are naturally made
where the need is most painful.
Of a little more remote benefit is such
research work as is being carried out by the
Research Corporation, from whose minutes
the following abstract was made :
"This far-sighted and patriotic conception
found its realization through the 'Research
Corporation' which for administrative reasons
was substituted for the Smithsonian Institu-
tion as the custodian of Dr. Cottrell's endow-
ment. The objects of the Research Corpora-
tion as stated in its Charter are :
' To provide means for the advancement
and extension of technical and scientific
investigation, research and experimentation
by contributing the net earnings of the
corporation, over and above such sum or
sums as may be reserved or retained and
held as an endowment fund or working
capital, to the Smithsonian Institution, and
such other scientific and educational institu-
tions and societies as the Board of Directors
may from time to time select in order to
enable such institutions and societies to
conduct such investigations, research and
experimentation. '
"Organized in 1912 as a stock corporation
but precluded by its charter from paying
dividends and capitalized by a group of
gentlemen desirous of furthering Dr. Cottrell's
objects, without personal profit, the Research
Corporation undertook and successfully ac-
complished the installation of the Cottrell
processes in various industries throughout
the country, with the result that in two years'
operation its surplus has provided the capital
of twenty thousand dollars required by its
charter, and a fund of over one hundred
thousand dollars for scientific research."
A few such steps as this one would soon
build up a fund of new knowledge. I think
it is safe to say that most of our new knowl-
edge of physical, chemical, and electrical
phenomena has come to us through the
publications of various scientific societies.
The work was largely done as a by-product of
poorly paid services in colleges and univer-
sities of the world. Let me illustrate this
point. The general field of colloid chemistry
is open for investigation. There is surely
no more fertile field. It touches all the
reactions of living organisms and most of
those of organic and inorganic chemistry,
from the growth of cells through immunity
to disease in animals, to the decay of metals,
from the coloring of glass and dyeing of
fabrics, to the production of a river delta
RESEARCH AND THE PROGRESS OF MANUFACTURING INDUSTRIES 871
or the manufacture of an automobile tire.
It is being largely done as the by-product or
hobby of a few teachers in their spare time.
As the principles governing this part of
chemistry are made known, the applications
in useful processes will be rapid, but there
are many men ready to perform the latter
operation compared to the few who are mak-
ing known the laws involved. For every
investigator who might point out from his
experiments the possibility that the antitoxic
action of immunized blood serum might lie
in the magnitude of the electric charges on
the colloids concerned in the reactions, there
are hundreds of others who will ably test the
hypothesis when it is advanced. For every
chemist whose experiments go to clarify the
laws of tensile strength and the wear and
friction of colloidal materials, for example,
there are hundreds who will test his con-
clusions in new aero-metals and automobile
tires. We in this country are particularly
active in putting the "useful" into the inven-
tion, but we are less active in the study for
the "new." For this reason it is necessary
to encourage research of the advanced type.
Anyone who has followed the subject knows
that, during the past ten or more years, the
amount of research work in connection with
the industries has greatly increased. Large
manufacturing companies in many lines have
groups of men who devote all their time to
advancing the methods of manufacture by
more or less pure research. They are never
expected to become part of the production
department, but are always kept on the
exploring line in laboratories. There are
now research laboratories connected with
almost every art and profession. The
American canners and the American dentists
have them, as well as the companies making
powder and shot, and those making armor
plates. There are laboratories devoted to
research on paper and others on paint, some
working on cements and others on soils,
some on gas lights and others on electric
lights, some on fertilizers, others on sterilizers,
and some on almost everything. They could
all use more knowledge to advantage if they
could get it. If there were no way to increase
the rate of our acquisition of knowledge,
then this argument would be useless, but we
have had a lesson from Germany during the
past forty years which shows one way of
increasing the world's stock of knowledge.
It is by encouraged or endowed research.
Germany did it through her universities.
Ever}- year there were turned out one or two
thousand men with the degree of doctor of
philosophy. This meant that each one had
done a couple of years' research work and,
in most cases, freely published it. The stock
of investigators in the country was rapidly
increased. The industries and the arts felt
the effects. In 1912 there were 1703 of these
doctorates conferred there, 705 were on
science and 355 in chemistry. How could
such a country stand still in industry? Last
March, Lord Haldane, addressing a teachers'
meeting in London, said:
"We are behind the level which has been
reached by several of our competitors, a
level which will put us in peril. We cannot
dissociate national progress from the basis of
knowledge, even when it comes to the question
of making money."
This conclusion is only a year old, but it is
being proved.
In addition to the very helpful and impor-
tant university methods of Germany, there
should continue in America, beyond what is
done by government laboratories and bureaus,
the natural extension of the ideas exemplified
by the cancer research laboratories and
hospitals, the Rockefeller Institute for Med-
ical Research, the Carnegie Institution, the
Smithsonian undertakings and others.
Here also a start has been made in such
work as Dr. Duncan inaugurated in the Mellon
Research Laboratory at Pittsburgh and at the
University of Kansas, in the very recent Brush
endowed fellowships at the Nela Park labora-
tories, and in the Mayo brothers endowment
at the University of Minnesota.
Dr. Woodward, President of the Carnegie
Institution, has recently said: "Successful
research requires neither any peculiar con-
formity nor any peculiar deformity of mind.
It requires rather peculiar normality and
unusual patience and industry." This cer-
tainly applies as well to the researches of an
Edison, devoting his life to the immediate
utilities, as to the abstract researches of the
mathematician. It is for this reason that
research ought to and does succeed in its
applications in the case of many industries.
In the industrial research laboratories, nor-
mality, patience and industry are apt to be
encouraged. Interruptions are there at a
minimum. Equipment, power, facilities and
the rest are made a matter of some one's
business. On the other hand the universities
and colleges, which are forced to combine
with short hours and short years the teaching
of science and the methods and habits of
research, are still our foremost organized
872
GENERAL ELECTRIC REVIEW
research institutions. It seems possible that
manufacturing companies may offer in the
future nearly as great assistance to the
increase of useful knowledge. Co-operation
between laboratories of research in univer-
sities and industries has already been the
subject of considerable study. There is a
committee of one hundred of the American
Association for the Advancement of Science
which was appointed to encourage it. Natur-
ally, with so great an undertaking, the
progress may be slow. It is certainly possible
for industrial laboratories to economieally
add to scientific knowledge and to grow in the
process. This fact is being recognized.
It is unfortunately true that most of what
we may call the new knowledge in physical
science of the past decade has had to cross
the Atlantic for us. No one knows this
better than those Americans who make the
most use of it. The fundamental knowledge
behind almost every utility which Yankee
ingenuity has assisted, grew on older soil
than ours. The list is almost discouraging to
an American. The encouraging view to take
is that we have it within our power to force
the future to write different history. It is
unfortunately quite safe to predict, for
example, that just as most of our technical
advances of the past can be traced to early
fundamental discoveries in academic fields in
Europe, so also we will have to see here
future applications of still more modern
European scientific thought. A wonderful
list of useful results, processes, products,
conveniences, cures and economies are sure to
be produced by applications of the new
knowledge of such things as radium. X-rays,
wireless waves, electrons, crystal structure,
atomic numbers, canal rays, none of which
"made in U. S. A."
In physical science there is but little chance
that our country will do its full share for
years to come. If the wisdom of attempting
it, rather than confining attention to short-
sighted application of research to pressing
commercial problems can be gradually recog-
nized, the future is assured. It is surely the
duty of our American research laboratories to
contribute effectively in the advance of
knowledge, and particularly is this true of
those richly endowed with men, new materials
and appliances.
And so I return to the cardinal point in any
suitable consideration of research in its
relation to our industries. Search for new
knowledge is the insurance for the future of
the industries. .Many of them will later be
manufacturing things not even conceivable
today. The past has proved it. Most of the
present products will, like the ox-yoke and
flail of our grandfathers, be replaced in our
factories by utilities more fitting to our new
needs and less exhaustive of our energies
and assets. This change is practically con-
tinuous. Technical complacency is like the
mercuric chloride tablet taken internally — it
means a lingering suicide. The incandescent
lamp business will serve me for illustration,
because I am more familiar with it than with
others. I have seen whole factories entirely
overhauled a number of times in the past few
years, in order to make the newest lamps.
Not only have entire floors of complicated
and expensive machines for making carbon
lamps been thrown out and new machinery
for making metal filament lamps installed,
but before packing cases containing new
machines could be opened and unpacked in
the factory they have been thrown out as
useless, as the advance from squirted metal
filaments to drawn wire filaments proved the
better way. Before the limit of factory
efficiency on vacuum lamps could be reached,
the introduction of nitrogen into the lamps
brought the factories an entirely new factor,
and now, before the consumers have more than
commenced to feel the effects of the nitrogen-
tungsten lamps, the manufacture of argon
and its introduction into the incandescent
lamp becomes a reality. If the research
laboratories which discovered the means for
bringing about these changes, with their
corresponding economies, could tax the con-
suming public a cent for every dollar thus
saved to the public, the laboratories would
receive over a million dollars a year to spend
for further research. This is not written in a
spirit of dissatisfaction at all, but rather to
point out what is probably true in many
fields. The people are the ones most interested
in research , though they may not know it. It is
easier seen in therapeutic and curative research,
but even there the more ignorant fail to realize
the great lasting value of such work.
Bacon wrote:
"For man, being the minister and inter-
preter of nature, acts and understands so far
as he has observed of the order, the works and
mind of nature, and can proceed no further:
for no power is able to loose or break the
chain of causes, nor is nature to be conquered
by submission: whence those twin intentions,
human knowledge and human power, are
really coincident; and the greatest hindrance
to workers is the ignorance of causes."
S73
THE 45,000-KW. SYNCHRONOUS CONVERTER SUBSTATION
OF THE ALUMINUM COMPANY OF AMERICA
AT MASSENA SPRINGS, N. Y.
By J. L. Burnham
Direct Current Engineering Department, General Electric Company
AND R. C. MUIR
Power and Mining Engineering Department, General Electric Company
The installation described in this article is of special interest for the large kilowatt rating of the individual
units and the large total capacity coupled with the extraordinarily high amperage distinguish it from any
we have previously described. The authors give many interesting details concerning the construction and
operation of the synchronous converters, transformers, and circuit breakers, in addition to other important
data. — Editor.
The cost of electrical energy represents
such a small part of the total cost of manu-
facture in most industrial products, that a
factory location favorable to raw products
and the market is often more important than
a location where cheap power can be obtained.
In the reduction of aluminum, however, each
pound produced represents an energy con-
sumption of approximately 15 kw-hr., which
makes it essential to locate the reduction
plant where electrical energy can be obtained
at a very low figure. For this reason the
Aluminum Company of America first located
one of their large plants at Massena Springs,
New York, where a hydro-electric develop-
ment of considerable size was possible. As
soon as the full capacity of this development
was utilized arrangements were made with
the Cedars Rapids Manufacturing and Power
Company for the provision of an additional
60,000 h.p. from a large development on the
St. Lawrence River, about fifty miles distant.
The Cedars plant was completed and put
in operation the first week in January, 1915,
and since that time power has been trans-
mit fed to the receiving substation at Massena.
The receiving substation at Massena is
particularly noteworthy in that it is the
largest rotary converter substation in exist-
ence; the synchronous converters are the
largest 60-cycle units ever built, the trans-
formers involved unusual construction diffi-
culties, the combined ampere rating of the
circuit breakers totals over one-half million
amperes and the arrangement of apparatus
from the incoming high tension lines to the
outgoing pot lines is unique in many ways.
The design has been carried out with one
predominant idea, directness of connections.
The current passes through the station in
practically a straight line, the apparatus being
arranged in the following order, starting
from the high tension buses: disconnecting
switches, oil switches, transformers, alter-
nating current circuit breakers, synchronous
converters, direct current circuit breakers,
direct current busses, pot line circuit breakers.
The substation is composed of two parallel
buildings separated by a court 30 ft. wide
and connected only by the walls at the end
and a passageway at the center. One building
contains the high voltage transformers and
oil switches and the other contains the
synchronous converters, circuit breakers and
controlling switchboard.
Incoming Lines
The voltage is stepped up at Cedars from
6600 volts by two 24,000-kv-a. banks of
transformers connected delta-delta.
Power is transmitted at 110,000 volts,
three-phase, 60 cycles over a single steel
tower double-circuit transmission line. Each
circuit consists of three aluminum cables of
500,000 cm. with a steel core of 114,110 cm.
A 7-strand, J^-in. galvanized steel grounding
cable is also supported by the towers. The
insulators are of the 10-in. disk suspension
type, seven units being used on the top and
bottom cross arms of the suspension towers
and eight units at all other attachments.
Electrolytic lightning arresters are installed
in the yard adjacent to the substation. The
ends of the transmission lines are anchored
on the roof, one at each end of the substation.
Connections are dropped down to cross wires
supported by strain insulators between the
two buildings and from there entrance is
made through wall entrance bushings into
the transformer room.
High Voltage Connections and Switches
The following description can probably be
followed more easily by referring to the one-
line diagram of connections shown in Fig. 1
and to the photograph of the high tension
room shown in Fig. 2. The incoming lines, one
at each end of the transformer room, pass
874
GENERAL ELECTRIC REVIEW
y- Z"** Positive Bus
Circuit BreoHer , , .
Solenoid Operated Automatic
DC. Buses
Stortingr Bui
Circuit Breaker
Solenoid Operated Non-Automatic
Circuit Breaker ,
Solenoid Operated Automatic
Vo'tmeter Bus
Receptacle
Ammeter
Voltmeter
Rotary Converter
Synchronism Indicator
® Potential Transformers
Synchronizing 3us
Wattmeter
Ammeter
Wattless Component Indicator
Circuit Breaker
Solenoid Operated Automatic
Power Tronsfor/ner
Oil Switch (Automatic)
Current Transformer
Disconnecting Switch
High Tension Bus
Disconnecting Switch
Oil Switch
Inverse Time Limit Relay
Disconnecting Switch
Choke Coil
Fig. 1. A One-line Diagram of the Connections for three transformers and six converters in the substation.
The connections for the other machines are similar
45,000-KW. SYNCHRONOUS CONVERTER SUBSTATION
875
through choke coils and then through parallel
disconnecting switches, oil switches, and
disconnecting switches to the high tension
bus. Parallel switches are used simply to
guard against interruptions, either switch
being of sufficient capacity to carry the full
load of the line.
The high tension bus is
composed of aluminum rods
supported from the ceiling by
suspension insulators. It runs
the full length of the station
but provisions are made be-
tween transformers 2 and 3,
4 and 5, 5 and 6, and 7 and 9
to open the bus by means of
disconnecting switches. The
disconnecting switches are all
arranged to be operated from
the floor, the three poles open-
ing simultaneously. A sec-
tionalizing oil switch is also
placed between transformers
5 and 6.
The high tension connec-
tions to the transformers are
made in a rather novel way.
The connections first pass
from the high tension bus
through a disconnecting
switch mounted on the wall
then out over the transformer
to an oil switch mounted on
steel framework and wheels
(located adjacent to the trans-
former) and thence to the
transformer leads. The object in mounting the
oil switches on an elevated framework was
to keep all high tension connections a con-
siderable distance above ground, to shorten
the connections, to make the arrangement
compact and to facilitate repairs. The mini-
mum clearance between the high tension
connections is 4 feet 7 inches, the same
distance as is allowed between the high
tension transformer terminal and the con-
nection passing from the disconnecting switch
to the high tension oil switch.
The oil switches are solenoid operated and
are controlled from the benchboard in the
machine room. Inverse time limit relays,
which operate from bushing type current
transformers, are provided for all of the
high voltage switches.
Transformers
There are nine transformers, each rated
5000 kv-a., with a 40 deg. C. temperature
rise. They are 110,000-volt "Y" connected
(ungrounded) units with three-phase pri-
maries, with two secondary windings each of
377 volts, and with six-phase diametrical
connections. The high tension winding is
furnished with taos so that with a potential
Fig. 2, General View of the High-Tension Room showing transformers, oil switches,
and 110,000-volt connections
of 110,000 volts there can be obtained on the
total low voltage winding the following
voltages: 396, 377, 366 and 356 volts.
Each of the twelve low voltage connections
have a normal current carrying capacity of
2210 amperes and the problem of bringing
out the necessary connections involved many
difficulties in the design and construction
of the transformers. It was impossible to
arrange the connections inside the transformer
in such a manner as to provide convenient
connections to the rotary converters, there-
fore, a system of copper bar cross connections
were provided just outside each transformer,
whereby all the leads could be run directly
to the converters without further crossing.
The fact that it required a ton of copper to
make these bar connections for each trans-
former gives some idea of the difficulties
involved.
The transformers are of the shell type,
water-cooled. A central oiling system is
876
GENERAL ELECTRIC REVIEW
provided from which the transformers and
oil switches can be filled with filtered oil.
Provisions are made for draining the trans-
formers and oil switches to the central
reservoirs, a complete system of piping being
installed in passageways under the floor.
Fig. 3. The Direct-Current End of One of the 2500-kw.
Synchronous Converters used in the substation
Synchronous Converters
The illustration on the cover of this issue
of the Review shows the interior of the syn-
chronous converter room, with seventeen of
the eighteen 2500-kw. machines in operation.
Not man)- years ago the 60-cycle rotary con-
verter attained a reputation for sensitiveness
in operation which was usually manifested
by flashing at the commutator. Pulsation and
alternating or direct current line disturbances
frequently caused flash-overs and shut-downs.
These troubles have now been practically
eliminated by better line construction and
protective devices and by the more uniform
speeds of prime movers, as well as by improve-
ments in the design of the rotary converter.
This largest installation of synchronous
converters thoroughly establishes the reli-
ability of the 60-cycle converter operating
under reasonably good conditions.
Each of the eighteen units is rated at
2500 kw., at 500 to 525 volts. Thev will
operate at 5000 amperes with the voltages
reduced to 300. With a higher temperature
rise, they will carry 3125 kw. continuously,
giving a total station output of 56,250 kw.
As the load is held continuously at the
rating for long periods, all parts were more
liberally designed, to insure low heating and
good commutation, than would be necessary
for usual services with lower load factors.
On account of the large amount of energy
available on short circuit, which might be
caused by errors in operation, etc.. the
protection of the commutator and its brush
rigging was made unusually complete. Each
brush-holder is fitted on the trailing side with
a moulded asbestos piece to prevent burning
in case of such accidents as would cause
flashing. The leading side of each group of
brushes is protected by a one-piece barrier
and another barrier, extending entirely around
'the commutator next to the armature, com-
pletes the enclosure of all the brush-holders.
*
Fig. 4. The Direct-Current Ends of the Converters
as installed, showing the moulded asbestos
pieces on the brush-holders
A severe short circuit with flashing has
occurred without any damage by burning to
the brush-holders or other parts.
Fig. 3 shows the barriers on the trailing
side of the groups of brushes and the one
extending around the commutator next to
45,000-KW. SYNCHRONOUS CONVERTER SUBSTATION
877
the armature. Fig. 4 shows the moulded
asbestos protection on each brush-holder.
In other respects the construction is
standard for 60-cycle commutating pole
converters. The balance of the armature
circuits is assured by the use of equalizers
that connect to every slot of the winding.
The construction of the equalizers, which
are mounted on the collector side of the
armature, is shown in Fig. 5. It will be seen
that they are supported by U-bolts, which
take all of the strain and are adjustable
for any shrinkage of insulation. The dampers
in the pole faces are of grid construction
with copper rods passing through the pole
face close to the surface. The through rods
are accurately fitted on a taper into the side
bars to insure a permanently good contact.
The brushes on both the commutator and
collector rings are self-lubricating and thus
greatly reduce the labor of operation. Two
of the machines are provided with a brush
Fig. 5. The Alternating-Current End of the Converter
shown in Fig. 3
raising device in order that the brushes may
be quickly raised to avoid sparking when
starting from the alternating current side.
The other sixteen machines are always
started as direct current motors and syn-
chronized.
Circuit Breakers
The alternating current circuit breakers
are located along the transformer house side
of the synchronous converter room and the
direct current breakers are located along the
pot house side of the room, as is shown in
the cover illustration.
Fig. 6. One of the 20.000-ampere Direct-Current
Circuit Breakers that are installed
in the substation
The alternating current breakers are
three-pole units of 2300 amperes capacity
and the direct current breakers are of
1000, 5000, 10,000 and 20,000 amperes
capacity; the various breakers being
used for starting, running, bus section-
alizing and pot lines respectively. All
the breakers are solenoid-operated, designed
for 500 volts and are rated at their normal
continuous current carrying capacity. On
overloads the breakers open automatically by
means of a direct acting trip which releases
the locking latch when the plunger of the
GENERAL ELECTRIC REVIEW
tripping coil is raised. The 5000-ampere posi-
tive breakers are also equipped with reverse
current relays.
Fig. 6 shows one of the 20,000-ampere
breakers. It represents the most recent
construction for solenoid-operated breakers
of unusually large capacity. The compactness
and neatness are especially noticeable.
Switchboard
All the switches and circuit breakers are
controlled from a gallery type of benchboard
located in the center of the machine room
on the transformer house side .
The synchronous converters are started
automatically from the direct current side
and then synchronized across the alternating
current circuit breakers. A starting bus and
two automatic starting panels are provided
for this purpose.
Control wires are all run in iron conduits
directly to the various switches. The control
circuit is fed by a small storage battery.
Two 35-kw. motor-generator sets, one alter-
nating current driven and the other direct
current driven, are provided for charging
the battery. These sets are provided with
automatic starters and are started from the
main control board.
While there is nothing unusual about this
benchboard, except its size, it is thoroughly
modern and in keeping with the remainder
of the apparatus.
The engineering and construction was
carried out under the supervision of the
engineers of the Aluminum Company of
America and the apparatus was furnished
by the General Electric Companv, Schenec-
tady, N. Y.
In view of the size and importance of the
undertaking, it is particularly gratifying to
those concerned that the substation was
completed - and started up on schedule
time and has since operated continuously
in regular service in a most satisfactory
manner.
PROTECTIVE COATINGS FOR METAL
By H. B. C. Allison
Research Laboratory, General Electric Company
The author has compiled a very valuable resume^ of the most effective processes of forming protective
coatings for metals. Each process is dealt with in such a brief and concise manner that will make this contri-
bution paiticularly useful for the purpose of reference. — Editor.
Introduction
This brief review of some of the processes
at present in use for protecting metals from
oxidation will be confined to two types:
firstly, that in which the metal itself is made
more resistant, usually by some chemical
treatment; and secondly, that in which
another metal is used as a surface coating.
In the first instance a coating is formed
which must possess the following properties,
if it is to be successful: It must be homo-
geneous, continuous, resistant to attack by
acids or alkali, firmly attached to the base
metal and must have a similar expansion
coefficient. The ideal metal coating should
also be homogeneous and continuous, but
should be strongly electropositive to the base
metal and should form electropositive alloys
with it, so that in case of oxidation the coating
will be attacked and the base metal protected.
As iron is the metal most commonly used
as the base, the processes chosen will be
those used for its protection, although some
may be applicable to other metals.
Protection by Oxide Coatings
It was known for a considerable time
before any process was devised that the black
or magnetic oxide formed on iron, under
certain conditions, was a very fair protective
coating. Attempts to control and improve
this coating have led to a number of patented
processes, of which two may be taken as
typical.
Bower-Barff Process
The pieces to be treated are heated to a
temperature of 900 deg. C. in a closed retort.
When this temperature has been reached,
superheated steam is admitted for 20 minutes
and a coating consisting of a mixture of
red and black oxides is formed. Producer
gas is then substituted for the steam and
allowed to act for the same length of
time. After cooling somewhat, the pieces
are oiled and a smooth, green-back coating
is produced, which affords efficient protection
from sea water, acid fumes, etc., and will
stand a wide variation in temperature.
PROTECTIVE COATINGS FOR METAL
879
Gesner Process
This is a further development of the
above process. The pieces to be treated are
maintained at 600 deg. C. for 20 minutes,
after which steam at low pressure is let in
at intervals for 30 minutes. The steam, on
entering, passes through a red hot pipe at the
base of the retort, and is thus partially
decomposed into hydrogen and oxygen. After
this treatment a small quantity of naphtha
or hydrocarbon oil is introduced and allowed
to act for 15 minutes to reduce any red
oxide, and also to carbonize the surface. The
coating is said to be a compound of iron,
hydrogen and carbon, and analyses have
shown that a minimum of 2 per cent hydrogen
is present.
It is an improvement on the Bower-Barff
process in that the danger of warping, due to
high temperature, is removed, the size of the
piece is practically unaltered, and the ten-
dency to scale is much less.
Both of these processes are quite expensive,
but users have usually found the protection
afforded of sufficient benefit to warrant the
added expense.
Protection by Chemical Means
There is one process which may be of
interest in this connection, known after its
inventor as "Coslettizing."
The pieces to be coated are first cleaned
as usual, either by pickling or sand blasting,
and are then placed in a boiling water solution
of phosphoric acid, in which iron or zinc
filings are always present. The period of
treatment is from one-half to three hours,
depending on the thickness of the coating
desired. After drying, the pieces are usually
oiled. By this treatment a very slight amount
of the surface of the article is converted into
certain phosphates of iron, but most of the
coating comes from the solution itself.
This coating has been found to be particu-
larly useful in the tropics, and is used in one
instance for typewriters. It is not a compli-
cated process or an expensive one and the
finish is very durable. It is, however, subject
to patent restrictions.
Protection by Another Metal
The agent used in the majority of cases
for protecting iron is the metal zinc. Zinc is
strongly electropositive to iron and so are
its alloys, if free from impurities. It is also
readily available and may be applied by a
number of processes.
Hot Galvanizing
The oldest process is that of hot galvaniz-
ing, which consists simply of cleaning the
piece, coating with a suitable flux and then
dipping in the molten zinc. The piece is
usually wiped after this to improve the coat-
ing. This process has the disadvantages of
limiting the thickness of the coat, of plugging
any small holes, of the composition of the
coating being variable, and the possibility of
including injurious and corrosive substances
in the coating, which may cause early failure.
Lohman Process
A modification of this process is known as
the Lohman process. After cleaning, the
article to be coated is dipped in the Lohman
bath, which is a solution of hydrochloric
acid, mercuric chloride and ammonium
chloride; it is then dried before immersing
in the molten metal, which may be any one
or a mixture of a number of metals such as
lead, zinc, and tin. The chief point in its
favor seems to be that the junction between
the iron and the protective alloy is kept
free from all oxide, and, therefore, the alloy
will fill all the pores and no corroding agent
can be included.
It is claimed by its backers that a graduated
alloy is formed so that the protective coating
cannot be completely broken through except
by breaking the sheet itself.
Cold Galvanizing
Another process which is being used more
and more as it is improved is that of wet
galvanizing or electroplating. In this case
the article to be coated is suspended as a
cathode in a suitable bath and is subject to
easy control. It provides a coating of high
purity and uniform thickness in general, but
recesses and corners cause some trouble. It is
liable to be more or less porous and may
contain acid which will eventually cause
failure. In both of these processes, hot or
cold, the coating does not become intimately
connected with the base metal through deep
alloying.
Sherardizing
The latest process of this type is sherardiz-
ing, and it is undoubtedly the most perfect
as a protection. The object to be sherardized
is placed in an iron drum which is filled with
a mixture of finely powered zinc and zinc
oxide, in varying proportions, and is heated
in a reducing or inert atmosphere for a period
of time, the length of which depends on the
880
GENERAL ELECTRIC REVIEW
thickness of coating desired. The coating so
obtained consists of four protective layers.
Next to the pure iron is an alloy "C," rich in
iron, upon which is another definite alloy " B,"
containing more zinc. Then there is a layer
containing a number of more or less unknown
alloys, and finally a layer of pure zinc. This
makes a coating which is not easily broken
down and which is continuous. The principal
objections to its use are the high temperature
to which the piece must be subjected and the
increase in size which may be caused.
The theory which has been advanced to
explain this process is interesting in that
it may be considered as a distillation process.
The zinc dust which is obtained from the
zinc smelters is said to be in a state of
unstable equilibrium, so that in contact
with the hot iron it undergoes a change
tending to restore it to the normal con-
dition. During this change some of it alloys
with the iron, thereby lowering the vapor
pressure for zinc in that region. A slow
distillation then begins from the zinc nearest
the object to the object itself. As the alloy
becomes richer in zinc the difference in vapor
pressure becomes less and less and then
finally becomes zero. This is found to be the
case in practice. The deposition becomes
slower as the time is extended.
Calorizing
This recently developed process makes use
of aluminum as the protective metal and is
of particular advantage in preventing oxida-
tion at high temperatures. The protective
action is due to the oxide formed by the action
of heat on the protecting metal, rather than
to any electrolytic relations between the alu-
minum and the base.
It has been found very useful in the case
of iron utensils subject to direct contact with
flames at temperatures up to 1000 deg. C.
and also in the case of boiler tubes, for the
life is increased many times by this treatment
and the saving in the cost of replacments is
much greater than the additional initial cost
of calorizing.
Schoop Process
One of the most recent processes, and one
of the most promising, is the Schoop process.
This is applicable to the deposition of metals
or alloys on any sort of an object. The
apparatus consists of a pistol into which the
coating metal is fed as a wire. It passes
through a straightening and centering device
into the nozzle, where it is fed through a
burner whose temperature mav be regulated
from 700 deg. to 2000 deg. F. The molten
metal is carried a short distance by the gas
current and is suddenly caught by a powerful
blast of compressed air which shoots it out
of the nozzle with a velocity of 3000 feet per
second, directly on the object to be coated,
which is held a short distance away. The
coating is homogeneous, continuous, and of
any desired depth, and is also exceedingly
intimate.
The following explanation of the theory
is given by the inventor:
"The theory is that the gaseous medium
used is much larger in volume at any moment
than the drop it has pulverized and is carry-
ing, and the gas is expanding so rapidly that
its temperature is far lower than that of the
spray. A rapid exchange of heat, therefore,
takes place between them, which consolidates
the molten particles and gives them a tem-
perature far below the melting point. If the
particles arrived in a liquid state at the base
with the observed velocity of 3000 feet per
second, they would simply splash on the
surface and largely rebound. As a matter of
fact they impact and inter-penetrate freely,
and the later bombarding particles unite
with the earlier ones to form homogeneous
compact bodies. In accounting for the
observed action of the Schoop spray at the
receiving base, it is supposed that the cooled
particles of the metal, just before impinging
with great velocity on a hard surface, are in
an abnormal physical condition. Due to the
heat of collision they pass directly into a
vapor which condenses and solidifies on the
relatively cold receiving body, penetrating
by osmotic pressure the superficial pores of
the base when an affinity for the latter exists,
and otherwise driven in by the pressure
behind it. In either case it condenses and
solidifies after penetration, and is effectively
dovetailed into the base. The hammering
and bombardment of the solidified first coat
by the minute succeeding particles is practi-
cally a process of cold working. The entrained
particles liquidity and solidify so rapidly that
the metal has not time to return to its
natural crystallized state."
In conclusion it should be stated that there
are many other processes in use which could
not be mentioned in a brief review of this
type. Those processes outlined were chosen
as representative of the various different
means used to obtain the desired protection
because of their prominence, -or of some new
feature which thev contain.
881
THE IRON-COBALT ALLOY, FE2CO, AND ITS MAGNETIC
PROPERTIES
By Trygve D. Yensen
Engineering Experiment Station, University of Illinois
The author first briefly refers to the work of earlier investigators in preparing pure iron and iron cobalt
and in testing these substances. He next describes the preparation and testing of his own samples, and records
by tables and a summary the conclusions derived from the tests, viz., the magnetic properties and apparent
usefulness of the iron-cobalt alloy. — Editor.
During the last four years experiments
have been carried on by the writer in the
Engineering Experiment Station of the
University of Illinois on the magnetic prop-
erties of pure iron and iron alloys1. Elec-
trolytically refined iron has formed the basis
of these experiments, and, in order to prevent
contamination, the melting has been done in a
vacuum furnace. On account of the high
permeability and low hysteresis loss obtained
by the vacuum method of melting, it was
suggested to the writer by Dr. Jacob Kunz
that an iron-cobalt alloy of the composition
Fe2Co, melted in vacuo, might show some
interesting properties. This alloy was pro-
duced by Dr. P. Weiss2 of Zurich in 1912, who
found that it had a saturation value of
magnetization 10 per cent higher than that of
pure iron. ' Previous to that time the magnetic
properties of iron in intense fields had been
investigated by Ewing and Low3, Du Bois4,
Gumlich5, and by Hadfield and Hopkinson6.
The intensity of saturation, Is, obtained by
these investigators for pure iron ranged from
16S0 to 1750, and, until Weiss produced his
FcoCo alloy, it was generally accepted that no
alloy had a higher saturation value than pure
iron.
This article gives the results obtained for
pure iron and for the alloy, Fe2Co, melted and
annealed in vacuo. For the sake of com-
parison a sample of FejCo, obtained from Dr.
P. Weiss, was tested both in the original state
as forged, and after being remelted in vacuo.
Furthermore, the following commercial grades
of iron were tested and the data included
here:
No. 1 Magnetic and Other Properties of Electrolytic Iron
Melted in Vacuo, 'Bulletins Nos. 72 and 74, Engineering
Experiment Station. University of Illinois, 1914.
No. 2 The Effect of Boron upon the Magnetic and Other
Properties of Electrolytic Iron Melted in Vacuo, Bulletin
No. 77,1 915.
"Compt. Rend. 156, 1970-72. 1913.
3Proc. Royal Soc. 42. p. 200, 1887.
Phil. Trans. 180A, p. 221. 1889.
<Ph.l. Mag. 29, p. 293. 1890.
'Elektrotech. Zeitschr. 30, p. 1065. 1909.
«Journ. Inst. Elect. Engrs., Dec. 1910.
1. Ordinary cold rolled steel
2. Standard transformer steel
3. 4 per cent silicon steel
4. Swedish charcoal iron.
Numbers 2 and 3 were received from the
manufacturers and had received their standard
heat treatment.
The results include the magnetic properties
in low, medium and intense fields, the elec-
trical resistance, the mechanical properties,
chemical analysis and microstructures.
Materials, Apparatus and Methods
As already mentioned, the iron for this
investigation consisted of doubly refined
electrolytic iron containing 0.02-0.03 per cent
impurities. The melting was done in an
Arsem type vacuum furnace, capable of melt-
ing 600 grams of iron at a pressure of 0.5 mm.
of mercury. The charge was left in the furnace
until cold, and the resulting ingots were then
forged into rods Yi in. in diameter. From
these rods the test pieces were machined into
the proper form.
The magnetic testing in low and medium
fields was done by means of the Burrows
compensated double bar and yoke method
using rods 14 in. (35.5 cm.) long and 0.392 in.
(0.966 cm.) in diameter.* The saturation
values were obtained by Dr. E. W. Williams
of the Physics Department. He employed
for this purpose an electromagnet with
conical pole pieces between which a field of
10,000 gilberts per cm. could be obtained.
The test pieces consisted of ellipsoids about 1
cm. long. After testing as forged the magnetic
test pieces were annealed at 900 deg. C, and
then at 1100 deg. C. The annealing was done
in a vacuum furnace to prevent oxidation.
Results
The results of the investigation are shown in
the following tables and figures. In Table 1
* For details regarding the magnetic testing as well as other
matters concerning the investigation the reader is referred to
Bulletins Nos. 72 and 77 of the Engineering Experiment
Station of the University of Illinois.
S82
GENERAL ELECTRIC REVIEW
(upper Curves) Magnetaing Force-H-qilberts per cm.
300 400 SOO 600 700 BOO
I00O
3 4 5 6
Magnet/zing Force H gilberts per cm.
Fig. 1. Magnetization Curves for Various Grades of Iron and Iron Alloys. Annealed
the various specimens are listed,
together with the chemical
analysis in case this was made.
These specimens did not all
receive the complete set of tests,
however, because test pieces
were lacking in some cases. The
iron-cobalt alloys, although
forging and machining readily,
were quite brittle when cold,
and on that account the rod
forged from specimen No. 3Co01
broke in the lathe due to the
carelessness Of the machinist.
This specimen, therefore, could
not be used for magnetic tests
in low and medium fields. The
only specimens for which com-
plete sets of tests were obtained
are the pure iron specimen- —
which is an average representative of a large
number— and specimen No. 3Co02, but suffi-
Permeobil'LyyU
IZOOO I60O0
la
\
\
£?—
/
V
\
X
4
I
Z -1
t
f t
-
4
r t
' 6
<
A
7 /
1 /
7 1
3 A
t /.
r /e
Fig. 2a
tfognetiztng force -h ' ?//6e/~ts per cm
Hysteresis Loops and Permeability Curve for Iron-Cobalt (Fe:Co)
Melted in Vacuo. Annealed at 900 deg. C.
cient data are available for the rest to allow
definite conclusions to be drawn.
THE IRON-COBALT ALLOY, FE,CO, AND ITS MAGNETIC PROPERTIES 883
TABLE 1
SPECIMENS TESTED
Electrolytic iron, melted in vacuo,
C— 0.01 per cent. Si— 0.01 per
cent.
No. 3Co01, iron-cobalt, melted in
vacuo, at a pressure of about 3.0
mm. Hg. Co — 33.36 per cent.
No. 3Co02, iron-cobalt, melted in
vacuo, at a pressure of about 1.0
mm. Hg. Co — 33.33 per cent.
No. 3Co03, iron-cobalt, melted in
vacuo, at a pressure of about 0.5
mm. Hg.
Iron-cobalt, forged from a casting
obtained from Dr. P. Weiss.
Same as above, remelted in vacuo
at a pressure of 0.5 mm. Hg.
COMMERCIAL GRADES
Cold rolled steel
Standard transformer steel of com-
mercially high permeability
4 per cent silicon steel for trans-
former cores
Swedish charcoal iron C — 0.163 per
cent, Si — 0.032 per cent, 5 —
0.0002 oer cent. .
The magnetic properties are
shown in Tables 2 and 3 and
in Figs. 1 and 2. The mag-
netic properties in the forged
state are not included, as they
are of interest merely to show
the vast improvement obtained
by annealing*. The electrical
resistance is recorded in Table 4,
and the results of the mechani-
cal tests are given in Table 5.
Figs. 3 to 5 inclusive show the
microstructure of some of the
specimens tested.
Discussionjof Results
From the chemical analysis it
appears that the iron-cobalt
alloys contain 33.33 per cent
cobalt and may thus be said to
conform quite closely to the for-
mula Fe2Co.
Before discussing further the
iron-cobalt alloy, it may be of
interest first to give some atten-
tion to the pure iron specimen
with which it is compared. In
the results published by the
writer about a year ago on
Permeabz/ityfj
8000 12000 /6000
Fig. 2b.
8 9
Magnetizing Force H gilberts per en
Hysteresis Loops and Permeability Curve for Pure Iron Melted in
Vacuo, Annealed at 900 deg. C.
0
PermeaOtZ/ty/u
4O0O GOOO HQOO
1
■
BH
i
4*
\
>*>
i
J
'S
I
f
//
71
r
t
I
A
-
^
1 c
) j
r
i
t
T I
•
' t
i
1 10 11 12 /J /4 /S /6
Fig. 2c.
Magnet/Zing Force -H-g'/QertS per cm
Hysteresis Loops and Permeability Curve for Commercial
4 per cent Silicon Steel, Annealed
PermeQ6///£yyu
0 4000 8000 IZOCO
I.
I
TJ 6
\
8
H
^*"
_y
/
/*
1
' f°
/
1
/
/
i
1
1
y
*
!
1
i j !
i i 1 1
Fig. 2d.
pure iron
melted in vacuo, 19,000 was given as the
* The reader who is particularly interested in this phase of the
investigation is referred to Bulletin No. 72 of the Engineering
Experiment Station of the University of Illinois.
I Z 3 4-5 6 7 B 3 IO II 12 13 14
Maynet izing Force -H gilberts per cim
Hysteresis Loops and Permeability Curves for Commercial
Transformer Steel, Annealed
maximum permeability obtained. By im-
proved apparatus and refined methods of
testing, this figure, instead of being an excep-
tion, has been shown to be below the average
ss4
GENERAL ELECTRIC REVIEW
TABLE 2
/.-SATURATION INTENSITY OF MAGNETIZATION
Specimen
As Forged
Annealed at 900 deg. C. Annealed at 1100 deg. C.
Pure iron — melted in vacuo3
1798
1803
1803
Fe^Co — Xo. 3Co01 — melted in vacuo1
1977
1967
1967
FejCo — No. 3Cc02 — melted in vacuo2
21 136
2039
2039
FejCo — Xo. 3Co03 — melted in vacuo3
2057
2048
2048
Fe2Co — obtained from Weiss
1977
Same, remelted in vacuo3
2038
As rolled
Cold rolled steel
1750
'At a pressure of about 3.0 mm. Hg.
:At a pressure of about 1.0 mm. Hg.
'At a pressure of about 0.5 mm. Hg.
TABLE 3
MAGNETIC PROPERTIES
Specimen
Maximum
Permeability
Density for
Maximum
Permeability
Gausses
HYSTERESIS
LOSS ERGS PER
MX PER CYCLE
COERCIVE
FORCE
GILBERTS PER
CM.
RETENTIVITY
GAUSSES
for
Bmax.
= 10000
for
Bma*.
= 15000
for
Bmax.
= 10000
for
Bmax.
= 15000
for
Bmax.
= 10000
for
Bmax.
= 15000
Pure iron — melted in vacuo
Fe;Co — melted in vacuo
22,800
13.200
10,000
8.000
820
1.460
1.700
3,200
0.27
0.48
0.33
0.65
9.250
9.100
14,000
12,000
COMMERCIAL GRADES
Standard transformer steel
4% silicon steel
Swedish charcoal iron
3,850
3.400
4.850
7.000
4.000
6.500
3.320
2.260
2.490
5.910
3.030
4.530
1.20
0.88
0.88
1.33
0.88
0.95
7.700
5.400
6.900
9,900
5,400
s.
Pure iron — melted in vacuo
Fe<Co — melted in vacuo
24.300
8.800
8,500
S.000
686
2.230
1.655
4.400
0.22
0.75
0.26
1.00
9,300
9,300
13.000
12.300
Heat treatment
lo'nnn } Annealed at 900 deg. C.
Received manufacturer's
standard heat treatment
Annealed at 900 deg. C.
■ Annealed at 1100 deg. C.
TABLE 4
ELECTRICAL RESISTANCE
Microhms per CC. at 20 Deg. C.
Specimen
As Forged
Annealed
at 900 deg. C.
Annealed
at 1100 deg. C.
Remarks
Pure iron — melted in vacuo
Fe2Co — Xo. 3Co02 — melted in vacuo
Fe-jCo — Xo. 3Co03 — melted in vacuo
COMMERCIAL GRADES
Standard transformer stee!
4^ silicon steel
Swedish charcoal iron
9.90
9.55
9.25
9.85
10.15
9.72
11.00
51.00
10.57
10.10
9.60
] Received manufacturer's
/standard heat treatment
TABLE 5
RESULTS OF MECHANICAL TESTS
Specimen
AS FORGED
Stress
at Yield
Point
lbs/sq.
in.
Ulti-
mate
lbs/sq.
in.
Elonga-
tion
%
Reduc-
tion
of
Area
Pure iron — melted in vacuo
Fe;Co — No. 3Co01 — melted in vacuo
Fe?Co — No, 3Co02 — melted in vacuo
Swedish charcoal iron
40.600 42.630 5.5
73.400 97.500 < 1.0
4n,
32.0
3.0
71.0
3.0
36.0 57.0
ANNEALED
Stress
at Yield
Point
lbs/sq.
m.
Ulti-
mate
Stress
lbs/sq.
Elonga
tion
%
in
. 1
Reduc-
tion
of
— Area
-
16.100 35.500 25.0 49.0
30.800 30.800 -=1.0 <1.0
29.450 29.450 < 1 .0 < 1 0
1. Elongation before specimen has commenced to" neck.'
2. Ultimate elongation.
78.0
< 1.0
■= 1.0
Av'ge for several spec.
As cut from plate
THE IRON-COBALT ALLOY, FE,CO, AND ITS MAGNETIC PROPERTIES 885
Fig. 3a.
as obtained today. The
magnetization curve and
hysteresis loop for pure
iron as shown in Fig. 1
and Fig. 2b, represent aver-
age results recently
obtained, giving a maxi-
mum permeability of
23,000 at a flux density of
8000 gausses. The hystere-
sis loss for B,nax= 10,000
and 15,000 is 764 and 1610
ergs per cc. per cycle,
respectively.
With regard to the satu-
ration values, it is seen
from Table 2 that the
results obtained in this
investigation show that the
iron-cobalt alloy, Fe2Co,
has a saturation value
about 13 per cent higher
than that of pure iron,
irrespective of the method
of melting. However, the
saturation values both for
pure iron and for the iron-
cobalt alloy are raised
about 3 per cent by melting
the substances in vacuo.
While the saturation value
is primarily of scientific
interest, Fig. 1 shows that
the iron-cobalt alloy may
be of practical importance
in the electrical industry.
While its magnetization
curve is 13 per cent above
that for pure iron at satu-
ration, it is 25 per cent
higher in medium fields,
such as H = 50 to H = 20t).
It crosses the pure iron
curve at H = 7.5 and
remains below at lower
densities. However, its
maximum permeability is
13,500, which is much
higher than is obtained for
the best grades of trans-
former iron at the present
time. Its hysteresis loss,
too, is as low as or lower
than that in commercial
grades of iron. Its chief
importance, however, lies
in its high magnetic permeability at high
densities. An increase here of 25 per cent,
Pure Iron, Melted in Vacuo.
As forged. 50 diam.
Fig. 3b.
Pure Iron, Melted in Vacuo.
Annealed. 50 diam.
Fig. 4a. Iron-Cobalt. FeiCo, No. 3 CoOl ,
Melted in Vacuo. As forged.
50 diam.
Fig 4b. Iron-Cobalt, FeiCo, No. 3 CoOl.
Melted in Vacuo. Annealed.
50 diam.
Fig. 5a. Iron-Cobalt, Fe:Co, No. 3 Co02,
Melted in Vacuo. As forged.
50 diam.
Fit. 5b. Iron-Cobalt, Fe:Co, No. 3 Co02
Melted in Vacuo. Annealed.
50 diam.
when coupled with a low hysteresis loss, is a
highly desirable characteristic, for instance,
886
GENERAL ELECTRIC REVIEW
for the teeth of the armatures of dynamo
machinery, where the density is always very
high. Without going into detail, a few con-
siderations will make this apparent. By
increasing the density in the teeth 25 per cent
— which is allowable by using the Fe2Co
alloy — the armature may be shortened a
corresponding amount. As the increased
density in the teeth necessarily means . an
increase in the density of the air gap, the
latter may be shortened so as to keep the
field ampere turns for the air gap and the
teeth the same as before. Furthermore, the
inside diameter of the armature core may be
increased so as to give a smaller core cross-
section. The shortening of the armature also
shortens the pole pieces and if a high per-
meability alloy is used in the field magnetic
circuit as well as in the armature, the cross
section of the field core and yoke may also be
reduced. From the above reasoning it
follows that the armature, besides requiring
less iron, will also require less copper; and the
field spools, while containing the same number
of ampere turns as before, will also require
less copper. The total reduction of iron and
copper may thus amount to as much as 25
per cent each. Passing from the amount of
material needed to the energy losses in the
machine, it is readily seen that the PR loss
is reduced in direct proportion to the reduction
in copper used. Furthermore, as the hysteresis
loss is lower per pound for the Fe2Co alloy
than for ordinary iron, and as the eddy cur-
rent loss is about the same, the total core loss
should be considerably less than with ordinary
iron, in spite of the increased density. Thus,
it would appear possible with this iron-cobalt
alloy to construct dynamo-machinery con-
siderably lighter than at present, and with a
higher efficiency.
The mechanical properties of this iron-
cobalt alloy, as seen from Table 5, are not
particularly advantageous. In the forged
state, while rather brittle, it is considerably
stronger in tension than pure iron. After
being annealed at 900 deg. C, however, its
tensile strength has decreased to about one-
third, and it is even more brittle than in the
forged state. It may be that the alloy could
be annealed at a lower temperature than
900 deg. C, and retain some of the strength
that it exhibits in the forged state, at the same
time acquiring the magnetic properties obtain-
able by annealing 900 deg.
The electrical resistance of the Fe2Co alloy,
as seen from Table 4, is about the same as
for pure iron, and makes the alloy unsuitable
for use in places where the eddy current loss
is of chief importance.
Annealing the Fe2Co alloy at 1 100 deg. C, as
seen from Tables 2 and 3, reduces the per-
meability and increases the hysteresis loss
considerably, although the saturation value
remains "the same as before.
Summary and Conclusions
The results settprth in the previous pages
relating to the iron-cobalt alloy, Fe2Co, may
be summarized as follows:
1. The iron-cobalt alloy, Fe2Co, has a
saturation value of magnetization 13 per cent
higher than that of pure iron. However, the
values for the vacuum product, both for pure
iron and for the Fe2Co alloy, are about 3 per
cent higher than for the corresponding grades
melted under ordinary conditions.
2. When melted in vacuo its maximum per-
meability is above 13,000 at a density of
8000 gausses. While this is considerably
lower than the maximum permeability found
for pure iron, melted in vacuo, its permeability
in medium fields such as H = 50 to H = 200 is
25 per cent higher than that for pure iron or
for commercial grades of iron.
3. Its hysteresis loss at densities of 10,000
gausses or below is considerably less than for
the best grade of commercial transformer iron.
At densities of 15,000 or above the hysteresis
loss is about the same as for this commercial
iron, at the same densities.
4. Its specific electrical resistance is about
10 microhms, or about the same as for pure
iron.
5. Mechanically it is brittle but fairly
strong. Annealed, the ultimate tensile strength
of the Fe2Co alloy and of the pure iron is
about the same, while in the forged state
the alloy is more than twice as strong as
pure iron.
In this iron-cobalt alloy, Fe2Co, is thus
found a substance that is suitable for use in
places where the magnetic density is very
high, such as armature teeth of dynamo
machinery. While its electrical resistance
is low, there is reason to believe that this may
be raised by the addition of other alloying
elements.
The cost of cobalt prohibits the general use
of this alloy at the present time, but there are
indications that the price of cobalt will be less
in the future.
It is the writer's intention before long to
make a more systematic study of the iron-
cobalt series, as it may reveal alloys with
CONTROL AND PROTECTION OF ELECTRIC SYSTEMS
887
even more desirable properties than the ones
recorded in this article.
In conlusion the writer wishes to acknowl-
edge his indebtedness to Dr. Jacob Kunz for
suggesting the possibilities of the investiga-
tion, to Dr. Elmer H. Williams for the
saturation values of magnetization, to Pro-
fessor E. H. Waldo for criticizing the manu-
script, and to Mr. W. A. Gatward for assist-
ance with the magnetic testing.
CONTROL AND PROTECTION OF ELECTRIC SYSTEMS
By Charles Proteus Steinmetz
Chief Consulting Engineer, General Electric Company
We have from time to time published quite a number of articles dealing with the many problems involved
in the Control and Protection of Electric Circuits, but none covers the complete subject so fully as the present
paper. The clearness and simplicity with which the subject is handled are typical of the author; meters, trans-
formers, circuit-breakers, reactances, grounds and short circuits, arcing-grounds, time-limit devices, relays,
lightning, surges, impulses and stationary waves are all taken into consideration. This paper was presented
before a joint meeting of the Electrical Section of the Franklin Institute and the Philadelphia Section of the
A.I.E.E.— Editor.
When the first commercial electric circuit
issued from a station the problem of control
and of protection arose. It was a simple
problem at first: an ammeter and voltmeter
to measure current and voltage ; a knife-blade
switch to send the current into the desired
path, or withdraw it; the fuse to open the
circuit in emergencies; and if the wires
became crossed and fuse and switch failed,
generator and engines stopped and not
much harm was done.
With the extension of the circuits into the
suburbs some lightning troubles were felt
and led to the introduction of lightning
arresters — in the early days based mainly
on hope and trust in providence rather, as
very little was known of lightning phenomena.
Since these days, less than a generation
ago, enormous changes have taken place,
and the electric systems have increased in
size, in voltage, and in extension.
Where 100-horse-power machines were large
once, now steam turbine alternators of
40,000 horse power and more are in com-
mercial operation. The steam engine has
made room for the steam turbine, and the
steam turbine does not stop when the wires
are crossed and a short circuit occurs, and
the momentum of the turbine disks, revolving
at velocities of 300 to 400 miles per hour,
can supply ample energy for the destruction
of any part of the system.
Feeders of 10,000 horse power or more,
generators of 40,000 horse power have to be
controlled by switching: an attempt to open
such a circuit by the knife-blade switch of
old would lead to the destruction of the
switch — and probably its operator.
Instead of small machines operating
separately on independent circuits, huge
generators now feed in parallel into the
system of busbars, on which is concentrated
all the power of the station or the group of
stations which are tied together. Numerous
stations and systems of interconnected sta-
tions of 100,000 to a quarter million horse
power and over are in operation, and the
half-million horse power mark has been
reached.
Anywhere on the busbars of the station or
in the feeders near the station there is
available, destructively in case of an accident,
as a short circuit, not only the entire power
of the station, of perhaps half a million
horse power, but the far greater power which
the station generators can give momentarily.
Short-circuit currents of forty to fifty
times normal full load current may momen-
tarily flow from some turbo-alternators,
representing ten and more times full load
power.
Such a station, or group of closely inter-
connected stations, of half a million horse
power full load capacity, may momentarily
send into a short circuit at the busbars over
five million horse power. This is the power
of Niagara : for Niagara is estimated variously
at from 5,000,000 to 15,000,000 horse power.
It is obvious that no switch or circuit
breaker can be built to safely open such
power, to suddenly stop Niagara, especially
when considering that many hundreds of
feeders issue from the busbars, that in any
one of these feeders a short circuit in the
cable may let loose the power of the entire
system, and every feeder thus requires such
a circuit breaker.
With half a million horse power station
capacity, a momentary overload capacity
ten times as high, assuming that we could
NS.S
GENERAL ELECTRIC REVIEW
build a circuit breaker to open this short
circuit power as quickly as in three to four
cycles, or one-eighth second: this would
require to dissipate in the circuit breaker the
energy of over 200,000,000 foot-pounds — the
destructive energy of 1000 tons dropping
from a height of 100 feet. This is about the
energy of a projectile of 2000 pounds weight
leaving the cannon at the velocity of 2500
feet per second. It is the destructive energy
of two heavy railway trains, of 400 tons each,
going at sixty miles per hour, and meeting
in head-on collision. It is the energy of the
explosion of thirty pounds of dynamite.
Equally great has been the increase of
voltage: where once 2000 volts were high-
voltage distribution, in circuits of a few
miles length, now circuits of hundreds of
miles length are in operation at voltages of
100,000 to 150,000. Such voltages jump
toward any object for over a foot distance,
and will maintain arcs of practically unlimited
distance; that is, with 100,000 volts and
practically unlimited power back of it, an
arc can extend for hundreds of feet. Thus
no simple switch will open such voltages
under power.
Transmission systems at high voltages have
been interconnected with each other into
networks, which spread and extend, and
already today often represent thousands
of miles of interconnected high-voltage lines,
covering tens of thousands of square miles,
and picking up every lightning, every atmos-
pheric disturbance within this entire area.
Thus the lightning protection also has
become a far larger problem than in the
small circuits of old.
But far greater than the energy of any
lightning stroke is the energy stored as
magnetic field surrounding the conductors,
as dielectric field radiating from the con-
ductors of these big transmission systems,
and if this internal energy of the system is set
surging, its effects are far more destructive
than those of lightning, and the effects may
not be merely momentray, as those of
lightning, but continual, as machine energy
continually replaces the stored internal
energy which -causes the destructive surge.
And, in addition hereto, far greater relia-
bility and continuity of service is today
demanded from the electric systems than was
in the early days, and that at a lower cost of
electric energy; and it must be remembered
that, with the increasing cost of living,
electricity is one of the few commodities
which has steadily decreased in price.
The foremost problem of control of electric
systems thus is that of controlling enormous
powers; the foremost problem of protection
is that against self-destruction by its own
power.
Current and voltage have grown beyond
the values for which instruments can be
built, and current transformers and voltmeter
transformers are interposed between the
circuit and the instruments measuring it.
With the general introduction of parallel
operation, power-factor indicators are required
to insure the division of load without excessive
waste currents; frequency indicators and
synchronizing devices to safely connect
machines into the system.
With hundreds of feeders radiating from
the generating station, the office of the load
dispatcher has become essential, and the
necessity of keeping exact records of all
operations and of all accidents and incidents
is of the greatest importance. Automatic
recording devices thus have been developed,
as the multi-recorder, to record, within
fractional seconds, all important events, as
opening and closing of switches, starting and
stopping of generators, surges, lightning
disturbances, etc. Such automatic devices
afford a valuable check on the operating staff,
but more important still is their record in
emergencies, where a number of things happen
almost at once, where the attention of the
operators is detracted from accurate observa-
tion by the necessity of action, and the record
thus could be made only afterwards from
memory, which is not very accurate in such
a period of excitement. It is just in such
abnormal conditions where the most complete
and accurate record is of greatest importance,
to enable the engineers to determine with
certainty what happened and why it
happened, so as to take steps to guard
against its recurrence.
Oil circuit breakers have been developed,
which can safely and without disturbance
close and open the feeder circuits of over
10,000 horse power, the generator circuits of
40,000 horse power and more, with an ample
margin of overload capacity. In these the
circuit is opened under oil with such mechani-
cal arrangement of contacts and oil vessel
that in the moment of circuit opening the
current is extinguished at the end of a half
wave by the rapid expansion and chilling
of the oil vapor which is produced by, the
opening arc, and which in the first moment
is under high compression, due to the momen-
tum of the oil, which has to be set in motion.
CONTROL AND PROTECTION OF ELECTRIC SYSTEMS
SMI
The most serious danger, in the growth of
electric systems, was, however, the possibility
of self-destruction by the power let loose
under the short circuit, and there were
anxious years for the operators and managers
of these large electric systems before the
industry devised the means of safely control-
ling unlimited power. More than once, when
a serious short circuit occurred and a disaster
was averted only by luck, the system was cut
into two or three sections and these operated
independently, to limit the power. But
when months passed without further acci-
dents, invariably, due to the requirements
of economy and reliability of operation, the
sections came together again and parallel
operation of the entire system was restored.
This, the most serious problem of the
high-power electric system, was solved by the
development of the power limiting reactances.
In the generator leads, between generators
and busbars, are inserted reactances, capable
of standing enormous overloads, of a size
sufficiently small not to interfere with the
normal flow of power at full load or any
overload which the generator may be called
upon, but large enough to materially limit
the generator current and power at short
circuit. Usually the generator reactances
limit the momentary short-circuit current to
about ten to twelve times full-load current;
that is, the momentary short-circuit power
to about two and one-half times full-load
power. This solved the problem for medium-
sized stations. Thus in a 60,000-horse power
station, instead of a possible short-circuit
power of over half a million horse power, the
power is limited to 150,000 horse power.
However, even with generator reactances,
with increasing size of station, the power
which may be let loose under short circuit
becomes large beyond control; with a 400,000-
horse power station, with generator power
limiting reactances, a million horse power
may still be concentrated at a short circuit.
Busbar reactances then were introduced;
that is, the busbars divided into sections by
reactances sufficiently small not to interfere
with the interchange of power along the
busbars, and thereby retaining the advantage
of parallel operation, but large enough to
limit the flow of power, which, in case of a
short circuit on one busbar section, can
flow into it from the adjoining sections.
With. such reactances in the busbars and
in the tie feeders between the stations, the
system is divided into sections of about 60,000
horse power each. A short circuit then can
seriously involve one busbar section only,
and the destructive power of a short circuit
is limited to that of one section, plus the
limited power which can flow from the two
adjoining sections, a total of 150,000 to
200,000 horse power, and this is within the
emergency limit of the modern oil circuit
breaker of moderate size. It still represents
a terrific energy, nearly 10,000,000 foot-
pounds, and is a severe strain on the circuit
breaker.
These busbar reactances permit an unlimi-
ted extension of the system, and the short
circuit on a section of a half-million-horse
power system is no more severe than a short
circuit on a 100,000-horse power system, and
there is now no limitation to the future
increase to electric systems of many millions
of horse power capacity, operating in parallel
on one set of busbars.
With hundreds of feeders radiating from
the busbars, the probability of a short circuit
in feeders is far greater than in the busbars,
and a material advantage, therefore, is given
by feeder reactances; that is, reactance inter-
posed between the feeder or a group of feeders
and the busbars, so that a short circuit in
the feeder is still more limited than a short
circuit in the busbars.
By the development of generator reac-
tances, busbar reactances, and feeder reac-
tances, the problem of the power control of
large systems for protection against self-
destruction by short circuit has been solved
and unlimited extension of systems without
any increase of danger has been made
possible, and experience has shown that after
the introduction of such power-limiting reac-
tances dead short circuits have occurred at
the busbars of very large systems v/ithout
even interfering with the operation of most
of the synchronous apparatus on the system.
Not all three classes of reactances are
always necessary: in systems of moderate
size busbar reactances may not yet be
needed. In low-head water-power plants,
with slow-speed multipolar alternators of
inherently limited short-circuit current, gener-
ator reactances may be unnecessary and only
busbar reactances required. Such, for
instance, is the case at the Keokuk plant on
the Mississippi River. Again, with a perfect
system of generator and busbar reactances,
feeder reactances may be dispensed with — -
though they are even then an advantage.
In high-voltage transmission networks,
even of very high power, power-limiting
reactances sometimes may not be required or
890
GENERAL ELECTRIC REVIEW
are less essential. With a considerable number
of medium-sized water-power plants feeding
into a transmission system, the power of
each individual generating station may not
be sufficient to give destructive values under
short circuit, and the impedance of the lines
between the generating stations may be
sufficient to limit the power which can feed
into the short circuit at one station. In
transmission networks, therefore, power-
limiting reactances are necessary only in very
large generating stations, such as the Keokuk
station, or where several fairly large stations
are close together, and also, as generator
reactances, in turbo-alternators connected
into the system as steam reserve.
To cut off a disabled line or feeder with the
voltages and powers of our modern systems
is beyond the capacity of the fuse or simple
blade switch, and automatic oil circuit
breakers are generally used. However, the
problem has become more difficult by the
increasing demand for reliability and con-
tinuity of service.
The two main sources of troubles in lines
and cables are grounds and short circuits
between phases. In transmission lines a
ground on one phase is the most frequent
trouble, and short circuits are rare except
in lines in which the design was faulty, or
reliability had been sacrificed to cheapness,
and the spacing between conductors chosen
too small, so that they swing together during
wind storms, etc. A short circuit is far more
serious than a ground, as in the former the
current is limited only by the generator
capacity, while with a ground the current
has no return — except if the neutral is
grounded, and then over the resistance of
the neutral — and the current, and with it the
shock on the system, is therefore very much
less, especially if safeguards against the
occurrence of high frequency by arcing
grounds are installed. In a well-designed
transmission line a short circuit usually
occurs only as the result of two simultaneous
grounds. A ground on one conductor, how-
ever, raises the voltage against ground of
the other two phases, from the Y voltage
to the delta voltage of the system, and
thereby increases the strain on the insulation
of the other two phases. It thus either
introduces the danger of a second ground,
causing a short circuit, or requires a higher
grade of insulation.
This has led to two methods of operation
of transmission systems. In one the neutral
of the transformers is grounded, frequently
through a resistance where the resistance
of the ground is not high enough to limit the
current. Then a ground on one phase is a
partial short circuit to the neutral, and causes
a large current to flow, and thereby opens the
automatic breakers and cuts off the circuit
before the ground has developed to a short
circuit. However, this method, the "grounded
Y system, ' ' means a shutdown at every ground,
even' flashover of an insulator by lightning,
etc. In the other the neutral of the system
is not grounded, the insulation of the circuit
being made good enough to safely stand the
increased strain put on it by a ground on one
phase, and by an arcing ground suppressor,
etc., care is taken not to continue an arcing
ground — leading to high frequency distur-
bances— but convert it into a metallic ground.
In this case, the "isolated delta" system,
service can be maintained on the circuit,
even if one phase grounds, until arrangements
are made to take care of the load, or the
fault found and remedied, and the continuity
of service thus is not interfered with. How-
ever, the cost of line construction is higher,
due to the better insulation required. The
relation between grounded Y and isolated
delta thus is that of cheapness versus relia-
bility and continuity of operation, and, as a
rule, we find grounded Y systems where
lowest cost of development is considered
essential and occasional interruption of service
not considered objectionable, while the iso-
lated delta is generally preferred in systems
in which reliability and continuity of service
are considered as of first importance, such
as in the extension across the country of the
great Metropolitan Edison systems — systems
which are proud of their record that the
voltage has not been off their busbars for
ten years or more.
Different are the conditions in underground
cable systems. In a cable the three con-
ductors are so close together that a ground
on one conductor quickly reaches the other
conductors and becomes a short circuit. A
grounded cable, therefore, cannot be kept
in service, but has to be cut out as promptly
as possible. In these systems it therefore is
customary to ground the neutral through
a resistance sufficiently low, in case of a
ground on one conductor of a cable, to allow
sufficient current to flow to open the circuit
breaker and cut off the cable, but sufficiently
high not to give a severe shock on the system.
Or, where grounding of the neutral is con-
sidered undesirable, an arrangement of relays
is made to give the same effect. With under-
CONTROL AND PROTECTION OF ELECTRIC SYSTEMS
891
ground cables such cutting off of a disabled
feeder does not interfere with the continuity of
service, as a number of feeder cables are
always used in multiple for every important
substation.
However, the problem of cutting off a
disabled feeder by the operation of the circuit
breaker, due to the large current taken by
the grounded feeder, is not so simple. Assum-
ing that three cables feed in multiple into a
substation, and one of these feeders grounds:
a large current then flows from the generating
station into this cable to ground, and the
circuit breaker at the generator end of this
feeder opens. This, however, does not stop
the current rush, but a large current still flows
through the damaged cables into the ground,
coming back from the substation, and flows
to the substation from the generating station
through the two parallel feeders, which are
undamaged; that is, short-circuit current
feeds back through these two cables over
the substation, and these two cables also
open their overload circuit breakers, cutting
off and thereby shutting down the substation.
If the substation is connected by tie feeders
to adjoining substations, current feeds back
into the faulty cable over these tie feeders
from adjoining substations, and these tie
feeders, and the cables feeding the adjoining
substations from the generating station, open
their circuit breakers by overload, and in
this manner a ground in one cable may shut
down a number of substations, possibly the
entire system. Time-limit devices in the
circuit breakers are insufficient to protect
against such extended shutdowns resulting
from a single fault in a cable. A permanent
time-limit is not permissible in large systems,
as with a dead short circuit the circuit
breakers must open instantly before extensive
damage is done by the large power of the
short circuit. Therefore, so-called ''inverse
time-limit" circuit breakers are generally
used; that is, circuit breakers in which the
time limit of their operation decreases with
increasing overload. Such circuit breakers
would first cut off the cable carrying the
greatest excess current — that is, the faulty
cable — and then those of less excess current;
but, as with the cutting off of the faulty
cable — at both ends — the excess current
stops, other cables should not be interfered
with. However, the inverse time-limit circuit
breaker necessarily must be practically instan-
taneous under short circuit, and therefore,
while the time limit discriminates between
100 or 200 or 300 per cent overload, it cannot
discriminate between short circuits of various
severity; that is, not only the faulty cable,
but its parallel undamaged cable, and the
tie cables to other substations, etc., would
open, and, while the extent of the shutdown
would be somewhat limited, it is still far
beyond the extent permitted by reliability of
service.
Thus devices become necessary to select
a disabled feeder and cut it out without
cutting off its parallel feeders or the tie
feeders to the substation served by the
faulty feeder, regardless of what excess
currents these may carry. This is a problem
which has not yet been completely solved.
As the result, in general in high-power
systems of high standard of reliability the
radial system of substation supply is used;
that is, each substation is fed by a separate
set of cables, and the substations are not
interconnected into a network by a system
of tie feeders. This radial system, however,
is materially less economical in feeder copper
than the interconnected network, since the
radial system requires for each substation a
feeder capacity equal to the maximum power
demand of the individual substation, while
in the network, by cross-feeding between
the substations, the feeder capacity is reduced
to that required by the average maximum
demand of the substations.
To avoid a shutdown of the substation
by a fault in one of its feeders, the different
feeders of the same substation are not con-
nected in parallel in the substation, but feed
separate translating devices, as transformers
and converters, and are paralleled in the
substation only on the secondary side of
transformer or converter. In case of a faulty
feeder, the current feeding back into the
fault over the other feeders of the same
substation, therefore, has to pass through
two sets of translating devices, and this limits
it sufficiently to allow the time limit relay
of the circuit breakers to operate and cut out
the faulty feeder without opening the other
feeders; that is, without shutting down the
substation.
However, the economic disadvantage of the
radical system remains, and an effective
selective feeder relay, which could be relied
upon to pick out the faulty feeder and no
other, would offer material advantages.
Such a selective device is afforded by the
use of pilot cables. Each cable or feeder is
duplicated by a smaller low-voltage, three-
phase cable, which joins the secondaries of
current transformers connected into the two
892
GENERAL ELECTRIC REVIEW
ends of the main cable. If the main cable
is undamaged, the same current comes out
of it as flows into it, and the connections to
the pilot cable are such that in this case the
secondary currents would be in opposition;
that is, neutralize each other. If, however,
the main cable grounds, current flows into
it from both sides, the secondary currents
in the pilot cable then add, and the current
flowing in the pilot cable operates the relay
which opens the circuit breaker. This
arrangement is very perfect in operation,
capable of cutting out the damaged cable
whether feeder cable or tie cable, without
interfering with any other cable, but it has
the formidable disadvantage of doubling
the number of cables required in the system,
and, while the pilot cables are small and of
low voltage, they occupy room in the under-
ground ducts which carry the electric circuits
in American cities. Thus this method of
control by pilot cable is, due to its high cost
of installation, very little used in this country.
Another method is that of the "split
conductor" cable. Every cable conductor is
made of two parts, of which the one surrounds
the other concentrically, with some insulation
between them. Normally there is no potential
difference between the inner and the outer
half of the conductor, as they are connected
with each other at the ends of the cable.
If, however, a ground occurs on the cable,
this ground can at first reach only the outer
half of the conductor, and a potential differ-
ence and current appears between the inner
and outer half of the conductor and operates
the circuit breakers, through a relay connected
between the two halves of the conductor,
at either end of the cable.
This method also works very satisfactorily,
but has the same economic disadvantage,
though to a lesser degree than the method
of pilot cables, in that the split conductor
cable is materially larger and more expensive
than the standard cable. It is therefore used
to a limited extent only.
The usual method of taking care of the
problem, at least in most cases, is by the
so-called "reverse power relay," also wrongly
called "reverse current relay."
When a cable grounds, the current at its
end reverses; that is, flows into the cable
( "feeding back") instead of coming out of it.
However, this reversal of current by itself
can do nothing, as it is an alternating current,
and as such has no direction of its own, but
only a relative direction to other alternating
waves, as that'of the voltage. Installing then
a wattmeter relay at the end of the cable — ■
that is, a relay operated by the action of two
coils upon each other, the one coil energized
by the current, the other by the voltage:
if the current reverses, the voltage remaining
the same, the pull of the relay reverses, and
thereby closes the operating circuit, which
opens the circuit breaker which disconnects
the cable.
Such reverse power relay operates perfectly
so long as there is any voltage for the reverse
current to act upon. If, however, a short
circuit occurs at or close to the substation, the
voltage vanishes, and with it the reverse
power relay looses its pull. To guard against
this, the installation of reactances is recom-
mended between cables and substations to
give a sufficient voltage drop to operate the
relay. However, this is an additional compli-
cation.
The reverse power relay is not adapted to
guard tie feeders between stations, as in these
the current reverses in direction with the
change of the distribution of load between
the substations.
Thus the reverse power relay does not make
the operation of interconnected networks of
substations possible, but in the radical
system of operation, which is generally used,
it is the only device which is generally
available economically, and is very satis-
factory, with the only exception — which must
be realized — that it cannot operate where
there is no voltage left.
In overhead transmission systems and
networks the problems of selectivity are
essentially the same as in underground cable
systems, except that in interconnected net-
works of distributed generating power the
high impedance of the lines often gives an
automatic partial selectivity, which cannot
exist with the low impedance of cable systems.
Interference by lightning with high-poten-
tial transmission lines has rather decreased
with increasing line voltage, and this is very
fortunate when considering the enormous
extent of these systems and the resulting
certainty of lightning effects. In the present
high-potential transmission lines voltages
have been reached comparable with the
voltage of lightning disturbances; possibly
not with the voltage of the direct lightning
stroke — but direct strokes into lines are
rare — but few lightning-induced voltages
reach beyond the insulation strength of
modem high-voltage lines. In 100,000-volt
lines the insulators are tested for one minute
at 200,000 to 250,000 volts, and stand
CONTROL AND PROTECTION OF ELECTRIC SYSTEMS
893
momentarily, for the very short time of
lightning, over half a million volts. Thus
it is rare that lightning flashes over or
punctures the suspension insulators of our
very high -voltage transmission systems. A
flashover, with the grounded Y system, shuts
down the circuit, often without any damage,
while with the isolated delta system it may
not even shut down the circuit, but is taken
care of by the protective device against
flashovers, the arcing ground suppressor in
the station. Most lightning voltages incapable
of destroying the line insulation run along the
line until their energy is dissipated or they
reach a station, and there they often do
serious damage. The most important problem
of lightning protection thus has become the
rapid damping out of line disturbances
caused by lightning, so as to make them
harmless before they reach the station. The
most effective method heretofore is the
overhead ground wire. By its screening
effect it lowers the voltage which lightning
can induce in the line, but far more important
is its powerful damping effect on the line
disturbance, the travelling wave caused by
lightning, which runs towards the station.
As short-circuited secondary to the line wire,
the ground wire absorbs and dissipates in its
resistance the energy of the travelling wave,
and causes it to die out at a rate several times
more rapid than is the case in a line which
is not protected by ground wire.
Far more destructive than the energy of
lightning may be the internal energy of the
system. While a lightning stroke may amount
to millions of horse power, at a duration of a
millionth of a second, this means only
thousands of foot-pounds. In a transmission
network of thousands of miles extent a
surge of the system may amount to many
thousands of horse power. But even a surge
of a hundred horse power only is liable to be
very destructive, as it may be continual, the
generator power continually replenishing the
surge energy, and a hundred horse power,
during one hour, means 200,000,000 foot-
pounds.
Thus the foremost problem is again the
protection of the system against destruction
by its internal energy, and lightning is
dangerous mainly by letting loose the internal
energy.
Against damage by breakdown to ground,
by over-voltages, effective and complete
protection is given by the aluminum cell
lightning arrester, so "that the problem of
over-voltage protection resolves into the
economic question, how far the cost of
lightning arresters is warranted by the
elimination of the danger of breakdown to
ground.
Impulses, high-frequency oscillations, and
stationary waves are the most common
other dangers.
An impulse is an electrical effect in which
voltage and current rise rapidly — with a
"steep wave front" — and then gradually
taper down and die out. Such impulses are
produced by switching operation, by flash
over the insulators, by induction from
lightning flashes, etc. The danger from
impulse voltages lies in the local piling up of
voltage due to its steep wave front. Thus,
for instance, when a switch is closed and
100,000 volts put onto a line at the moment
of closing the switch, 100,000 volts suddenly
appear in the line at the switch, while perhaps
five feet away the line voltage is still zero.
Gradually — with the velocity of light, or
188,000 miles per second — the voltage spreads
over the line as an impulse. Suppose now
such impulse reaches the terminals of a
transformer near the source of the impulse,
where its wave front is till very steep. When
the full impulse voltage reaches the first
transformer turn the second transformer
turn is still at zero voltage, and the full
voltage of 100,000 comes on the insulation
between the first two turns. While the
transformer winding is insulated to stand
200,000 volts to ground for one minute, and
momentarily still much higher voltage, nor-
mally the voltage between adjacent turns
may be only ten volts, and with all the extra
insulation between the end turns, even if we
make this insulation to stand 1000 times the
voltage to which it is normally exposed, it
would be far below standing 100,000 volts.
Thus the danger from impulses is that they
produce voltages across small parts of the
circuit, single turns or coils, which are often
many thousand times the normal voltage
existing in this part of the circuit; thus they
may be far below the total circuit voltage,
and thus would not discharge over the over-
voltage protective devices or "lightning
arresters."
Fortunately such steep waves fronts rapidly
flatten out in the progress of the wave along
the circuit, so that their danger is largely
limited to the immediate neighborhood of
the origin of the impulse.
Assuming now that we would, by a con-
denser in shunt to the circuit, bypass the
energy of the impulse for only one-millionth
894
GENERAL ELECTRIC REVIEW
of a second. During one-millionth of a
second the impulse travels about 1000 feet,
and such a very small condenser would
flatten the wave front to 1000 foot length.
With such a flattened wave of 1000 foot front,
before full voltage appears at the transformer
terminals, the beginnings of the impulse is
passed over ten or more turns, and the
impulse voltage thus distributes over the
insulation of a number of turns, and no
difficulty exists to give the end turns an extra
insulation sufficient to stand the voltage.
The foremost cases of high-frequency
oscillations are spark discharges from the
line, arcing grounds, etc. Their danger also
is the piling up of voltage in reactive devices,
such as current transformers, end turns of
power transformers, etc. While a current
transformer may take only a few volts at the
normal frequency of sixty cycles, at 10,000
times this frequency it would take 10,000
times the voltage, and then break down
between turns and between terminals. Induc-
tance to reflect the high-frequency oscillation
back into the line — which can stand it — with
shunted capacity, and a non-inductive, or
preferably, a capacity bipath to the inductive
device such as the aluminum cell, offers
protection against the danger from high-
frequency oscillations. The best guard
against interference by high-frequency oscil-
lations is, however, to avoid all causes which
may produce them, and the foremost cause
is the arc. Thus arcs, arcing grounds, spark
discharges, open-air switches, etc., should be
carefully avoided in transmission systems,
as introducing the dangers of high-frequency
disturbances. This is to a large extent a
designing problem.
In apparatus capable of electric oscillation
— that is, apparatus of high inductance,
considerable capacity, but very low energy
losses, such as high-potential transformer
windings — under certain conditions stationary
waves may occur; that is, high-frequency
impulses or oscillations, coming from the
outside, built up by resonance to higher and
higher voltages. Such stationary high-
frequency waves are extremely destructive,
as their energy is practically unlimited; is
given by the low-frequency power of the
system. Their frequencies usually are fairly
low, between 10,000 and 100,000 cycles, and
therefore it is more difficult to deal with
them than with the oscillations of many
hundred thousands or millions of cycles.
The best protection against them is not
to allow them to build up. This is done by
designing the apparatus so as to give the
least ability to stationary oscillations, and
by dissipating their energy, and thereby
limiting their voltage, by shunted resist-
ance. To avoid excessive waste of power in
such shunted dissipating resistances, a con-
denser of moderate capacity is connected in
series with them. Such condensers practically
cut off the flow of power at the low machine
frequency, but permit the flow of large
currents through them into the dissipating
resistance at the much higher frequencies
of the standing waves.
In considering the protection of modern
electrical systems it must be realized that the
various sources and kinds of interference or
danger require correspondingly different pro-
tective devices: it would be just as unreason-
able to expect a standard type of "lightning
arrester" to protect an electric system
against all possible troubles as it would be
to call for a single-standard "safety device"
which would protect a railway train against
all possible dangers, from a broken rail or
a washout of the roadbed to a collision or
a boiler explosion.
895
CURRENT SUPPLY FOR MOTION PICTURE MACHINES
By H. R. Johnson
Small Motor Department, General Electric Company
The popularity of motion picture displays has increased at a phenomenal rate. In contradiction to the
early predictions that this form of entertainment would be short-lived, the "movies" have secured a permanent
place in our list of public amusements. While this solidarity of establishment is largely due to the efforts of
the producers, there are grave doubts that motion pictures would have remained in public favor had not
great improvements been made in the projecting apparatus. The following is a comprehensive article that
furnishes data on the present-day illumination and operation requirements of projection and describes the
commercial electrical apparatus that fulfills these requirements. — Editor.
The cinematograph or moving picture
exhibition has apparently permanently estab-
lished itself as a part of our national life. This
is evinced not only by the ever increasing
number of show houses offering moving
pictures as the principal form of entertain-
ment but, even more surely, by the ever
widening scope and variety of subjects
presented. The popularity of moving pictures
did not decline, as was sometimes predicted,
as soon as the mere novelty of pictures in
motion ceased to be a strong attraction,
because the producers have realized and met
their opportunity to adequately present a
class of spectacular and news subjects scarcely
attempted or possible hitherto, for which
this new art is a peculiarly valuable medium.
Improving standards in the matter of
seating accommodations, attendance, music,
ventilation, and projection have kept pace
with the increasing popularity of this form
of entertainment The day of shadowy,
jumpy projection is passing; and, as the
business of motion picture exhibiting settles
down to a solid and permanent basis, the
development of standard electrical equipment
to meet the varied conditions of operation is
the next logical step.
Developmental Steps
It may be interesting to trace very briefly
the history of electric apparatus for supplying
and controlling the current used in the
projecting arc. It is essential to remember
that the voltage required for direct current
carbon arcs is approximately 55 volts, and
for alternating current arcs approximately
33 volts; the current of course depends upon
the amount of light demanded, the actual
amperes required for the same illumination
being three to four times as great with
alternating as with direct current. It should
also be remembered that the carbon arc is
characteristically subject to sudden and
extreme variations of current when operated
directly from a constant potential circuit.
When a sufficient resistance (or reactance) is
connected in series with the arc, satisfactory
stability can be obtained because the change
in voltage drop over the resistance tends to
instantly counteract any variation in the
current. With a sensibly constant potential
supply circuit, the direct current arc requires
sufficient steadying resistance to give a
voltage drop of at least 15 to 20 volts which
makes the required supply voltage about
70 to 75 volts. If the supply voltage has a
sufficiently drooping characteristic, due to
the special design of the generator, no
steadying resistance will be needed and a
normal voltage of 55 is sufficient.
The first installations naturally took their
current directly from commercial alternating
or direct current power circuits, using adjust-
able resistances or reactances to reduce the
standard line voltage to that required at the
arc. More than enough such resistance or
reactance to give the necessary stabilizing
effect was required for voltage reduction,
so that the results were quite satisfactory
in that respect. When direct current circuits
of voltages higher than 110 had to be used,
the waste of power was tremendous and the
heat generated in the grids made the operating
rooms very uncomfortable in warm weather.
The excess voltage of alternating-current
circuits was cut down with much less loss by
means of reactances ; but the use of alternating
current was strictly limited by the candle-
power that could be obtained from a current
of 60 to 70 amperes and also it was rather
unsatisfactory on account of the color of the
light produced. The economy of the alternat-
ing current projector was soon further
improved by the development of adjustable
voltage transformers, such as the alternating
current "Compensarc."
With the growing demand for better and
more brilliant projection a means was required
for economically converting alternating cur-
rent, often the only kind available, into
direct current. This demand was early met
in a very satisfactory manner by the standard
moving picture rectifier outfit.
The rectifier well combines the principal
advantages of both alternating and direct
896
GENERAL ELECTRIC REVIEW
current, i.e., better quality of light, smaller
current in the arc, economical reduction
and regulation of voltage by means of
transformer, compensator, or reactance. In
addition to a good efficiency, the absence of
moving parts, noise or vibration and the
fact that it may be neglected for long periods
as far as oiling, cleaning, etc., are concerned
have contributed to the popularity of the
mercury-arc rectifier. The rectifier may be
made to start automatically by simply
bringing the arc-lamp carbons together for
an instant and then separating them the
required distance. In this way the rectifier
runs only during the operating time of the
arc. and all losses due to running idle are
that have been mentioned are shown approxi-
mately in Fig. 5.
Optical System of the Projector
Before considering in greater detail the
performance, characteristics, and choice of
sizes of the compensarc, or other apparatus
used for supplying current to the projecting
lantern, it will be interesting to briefly discuss
the fundamental conditions and requirements
to be met. Fig. 1 shows diagrammatically the
optical arrangement of a typical projection
apparatus.
The arc is so placed that the maximum
intensity of light shall be directed upon the
condenser lens, which in turn concentrates
aperture '
aperture piateJ
Revolving
Shutter
^— Condenser Lense
Fig. 1. Diagram of the Optical Arrangement of a Typical Motion Picture Projection Apparatus
eliminated. Due to the small space occupied
and to the entire absence of vibration, the
rectifier can be installed in almost any
convenient space without the necessity of
providing a special foundation.
Dynamo-electric alternating to direct cur-
rent translating devices, e.g., motor-generator
sets, and rotary converters, have always
been close competitors of the rectifier, and
many operators claim for them the advantages
of better quality (whiter) light and greater
freedom from interruptions in service. A
more important advantage of the motor-
generator or the rotary-converter is the
ability to provide a single machine whose
characteristics will permit a second arc to be
started and warmed up without interfering
with the continuous projection of a picture.
This is especially desirable in the higher class
establishments where successive pictures are
dissolved into one another. Most equipments,
however, are handicapped in the matter of
economy because of the usual necessity for
using continuously a certain amount of ballast
resistance. In the specially designed genera-
tors used with the a-c. — d-c. and d-c. — d-c.
compensarcs, this handicap is overcome and
the efficiency is fully as good as that of the
rectifier.
The essential points in the comparison
between the economy of the different devices
the rays which it receives into a very intense
beam or "spot" that slightly overlaps the
opening in the aperture plate. Each picture
in the film pauses for an instant, directly
beyond this rectangular "aperture," which
defines the illuminated area of the film and
so fixes the outline of the picture thrown
upon the screen. An image of the intensely
illuminated section of film is magnified and
reproduced upon the screen by the objective
lens.
Aside from technical problems in the
construction of film handling mechanisms,
lenses, and shutters, the fundamental require-
ment for satisfactory projection is to secure
an illumination on (or more exactly reflection
from) the screen of good chromatic quality
with a suitable minimum intensity. This
required intensity of screen illumination
is most conveniently considered in terms of
the horizontal candle-power of the electric
arc, or other light source. It is to be remem-
bered that the results depend upon:
(1) The size of the picture.
(2) The density or tinting of the film.
(3) The kind of screen surface.
(4) The ratio between periods of darkness
and light caused by the action of the shutter.
(5) The size and quality of the condenser
lens and its consequent ability to use a larger
or smaller fraction of the available light flux.
CURRENT SUPPLY FOR MOTION PICTURE MACHINES
897
(6) To a less extent upon such factors as
the size of "spot" run, size and position of
carbons, amount and arrangement of house
lighting, etc.
Size of Screen
First in importance in determining the
amount of light required is the size of the
screen to be illuminated in square feet. One
can readily appreciate that with a certain
quantity of light available at the arc, the
intensity at the screen will decrease in
exactly inverse ratio to the area over which
it is dispersed — in other words, the larger
the surface for a given amount of light
available, the thinner it must be spread.
Since the number of square feet surface
may vary rapidly with changes in dimensions,
the effect in illumination is very marked.
For example, a 12 by 9 foot screen represents
an area of 108 square feet which is approxi-
mately one-half that of a screen with only
a two-foot wider margin, that is, a 16 by 12
foot screen which has an area of 192 square
feet. For the same light available at the
arc, the two screens would have an illumina-
tion intensity in the ratio of 1 to 0.56.
Although there are no set dimensions for
projection screens, the actual proportions
of the illuminated area are fixed by the shape
of the "aperture" of the projection machine
which is ordinarily jf inches wide by fi inches
high. Accordingly, the width of the picture
will always bear a ratio to the height of
15 to 11. When the picture is spoken of
in one dimension only, the width is meant.
Probably the most common size is a 12-foot
wide picture, which is considered "life size."
In a small hall a picture as narrow as 9 feet
is sometimes used. With a hall of seating
capacity from 1000 to 1500, the picture is
usually 12 to 16 feet wide; with a still larger
seating capacity it may be necessary to run
a picture as much as 18 to 22 feet wide.
About 20 or 22 feet is the limiting width,
however, since all defects in the film are
magnified in like proportion and a larger
picture will have a general fuzzy outline.
The 12 by 9 foot or " life size " picture, appears
clear and fairly satisfactory, although rather
small, at a seating distance of 75 to 100 feet
from the screen.
Another factor that tends to keep down
the size of pictures is the increasing use of
expensive screen surfaces. As a rule mirror
screens are not over 12 to 16 feet wide. Also
there are optical troubles with pictures whose
width runs more than a quarter of the
projection distance, e. g., the necessary wide-
angle lens gives a distortion at the edge of
the picture that cannot be corrected.
Density of Film
There is a marked difference in the density
of the films supplied by various manufac-
turers. Pictures taken outdoors in a Western
atmosphere where the air is particularly clear,
or in interiors with light backgrounds taken
with artificial illumination rich in actinic value,
will as a rule require considerably less light
for proper projection than will pictures taken
in a smoky humid atmosphere. The various
brands of films vary widely in density; some
films due to the use of heavy backgrounds
and silhouette lighting effects are very dense
requiring a considerable increase in the
current at the arc, while other films are of
the exact opposite type being so thin that
the current at the arc must be cut down to
keep from bleaching the detail from the
picture. Alternating thin and dense sections
of film to secure the effect of moonlight,
cloudy or bright atmosphere, smoke, etc.,
do not necessarily need to be corrected
by altering the arc adjustment. It is evident
that projecting outfits must be provided with
a light powerful enough for the densest
make of ordinary black and white films.
Tinted films, or the use of color screens as
in the Kinemacolor machines, may require
two or three times as much light as the
ordinary film.
Screen Surface
Screens for motion-picture projection may
be roughly divided into four classes: Plain
muslin, plaster, semi-reflecting and mirror
screens.
The plain muslin screen requires the
largest amount of light for proper brilliancy
of projection, due to the low reflecting value
of its surface. At one time used only by the
cheap traveling show or vaudeville house
in which pictures were a minor part of the
program, the muslin screen has been found
to give exceptionally soft, artistic pictures,
rich in detail and free from harsh contrasty
black and white effects, so that it is now found
in some of the most pretentious theaters, in
spite of the high current required at the
arc. Sometimes the muslin surface is slightly
starched, which tends to reduce the light
required, but it more often presents a plain
freshly laundered white surface.
Plaster screens, usually coated with cal-
cimine or a flat paint preparation, are found
S9,s
GENERAL ELECTRIC REVIEW
in all classes of moving picture theaters.
They require somewhat less projected light
than a muslin screen to secure the same
brilliancy. The present tendency, largely due
to the increasing size of theaters, is toward
a plaster finished screen of some kind which
will combine the softness and pleasing detail
of the muslin screen with reflecting qualities
that reduce the high current consumption
of the arc.
Semi-reflecting metallic screens such as
mirroride, radium, gold-fiber, etc., give rather
harsh, contrast}- pictures but these require
considerably less light for a given brilliancy
than either the muslin or the plaster screen.
The characteristics of these screens vary
between those of the plaster and the mirror
types.
Mirror screens are the most economical of
current for a given brilliancy, but the sizes
are at present limited to 18 feet and their use
is further limited by the high initial cost,
particularly in the larger sizes.
The comparative degrees of illumination
required by the different classes of screens
in order to produce approximately equivalent
brilliancy of illumination at various observa-
tion angles are recorded in Table I, taking
the plain muslin surface as the standard of
comparison.
TABLE I
Material
REQUIRED
ILLUMINATION FOR
OBSERVATION
ANGLES
15 Dec. 45 Deg. 60 Deg.
White muslin 100 107 110
Magnesium oxide 73 88
Plaster of paris 77 83 94
White lead 83 93
Century white 82 90
Zinc pa'int 87 96
Aluminum paint on card 35 408
Zeiss metallic screen, smooth . . 54 526
Mirror screen 37
Shutter Motion
In the operation of the projecting mecha-
nism, a revolving shutter cuts off all light from
the screen from the instant just before the
film starts to move from one position to the
next until the film has come to rest in that
next position. The interval of movement
of the film in ordinary projectors occupies
approximately one-sixth of the complete
cycle, there being, on the average, a new
picture shown every one-sixteenth of a
second. It has been found that if the alter-
nations of light and darkness take place too
slowly, or in other words if the intervals of
darkness are too far apart, the eye catches an
impression of "flicker." To prevent this
effect from becoming noticeable, ordinary
shutters have two or three "wings" instead
of one which introduce one or two extra dark
intervals during the time the film is actually
at rest and the picture is being projected.
The two-wing shutter is still largely used
where 60-cycle alternating current is supplied
to the arc, and also by a few managers who
prefer to economize on current at the expense
of a slight impression of flicker. The tendency
to flicker is increased by more brilliant
projection whether by improved types of
screens or by increased illumination, hence
the present tendency to standardize the
three-wing shutter. The three-wing shutter
cuts off approximately 50 per cent of the
light, whereas the two-wing shutter cuts off
only about 35 per cent; the type of shutter
must therefore be considered in choosing the
capacity of the illuminant required.
Lenses
Although the size and focal length of the
condenser lens might theoretically have a
very important effect upon the amount of
light required at the arc, it is believed that
the differences between ordinary outfits in
this respect are not nearly as important as
are several other factors in respect to which
no standardization can be effected, as for
instance the management of the arc, the
size and setting of the carbons, the arc
voltage, the size of "spot," etc.
Size of "Spot"
As already explained, the function of the
condenser lens is to concentrate all the light
that it receives into an intense and fairly
uniform beam, which covers the opening in
the aperture plate, Fig. 1. The usual con-
denser, being an uncorrected lens, possesses
a certain amount of chromatic aberration
(tendency to separate light into the primary
colors). This fault occurs largely at the edge
of the "spot"; and therefore the beam is
always spread enough so that the light
delivered to the aperture shall be substantially
pure white in quality. The larger the spot,
within certain limits, the purer and more
uniform will be the quality of the illumination
on the screen. In practice, this size is de-
termined by making the spot just large
CURRENT SUPPLY FOR MOTION PICTURE MACHINES
S99
enough to prevent any noticeable weakness
in the illumination at the corners of the
picture, so that any variation in the size
of the spot (and consequently waste of light
at the aperture) is usually not very great.
Distance
It is the general consensus of opinion that,
within the ordinary limits of 50 to 150 feet,
the distance from the screen to the projector,
or the "throw," has no direct effect on the
quantity of light required.
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Screen Area in Sq ft
Fig. 2. Curve showing the Candle-power
Size Plain Muslin Screens. Black
Required for Various
and white film
House Lighting
An important factor in determining the
required brilliancy of the screen illumination
is the amount and arrangement of the house
lighting. The present tendency is more and
more to have the auditorium lighting sufficient
for patrons to readily see their way about
and even to read programs while pictures
are being shown. Although any stray light
from this source which falls upon the screen
makes necessary a considerably more brilliant
projection, it has been found that by care-
fully _ screening auxiliary light sources a
surprisingly good general illumination can be
maintained without materially interfering
with the exhibition of the pictures.
Size and Setting of Carbons
The actual amount of light obtained from
the arc depends to a great extent upon the
kind, size, and setting of the carbons. Each
make of projection carbons has its good
qualities and, in the hands of operators
familiar with the particular brands, will give
good results. While most operators use two
cored carbons of the same size for a direct
current arc, others prefer using a smaller solid
carbon for the negative. Probably the most
common combination, and one that will give
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Amperes
Fig. 3. Curve showing the Candle-power of Projection Arcs
for Different Arc Currents
good results, is two ^-inch cored carbons
for 25 to 40 amperes and two %-inch cored
carbons for 40 to 60* amperes. The most
satisfactory setting is to incline the carbons
backward about 15 to 30 degrees, which
brings the white-hot crater of the upper
carbon directly opposite the condenser. The
upper carbon is generally pulled back from
iV-inch to j^-inch behind the lower carbon,
which forces the crater away from the back
edge of the upper carbon. The carbons should
be separated to a sufficient distance so that
the negative carbon cannot cast a shadow
due to its being in front of the crater. Ordi-
narily the length of the arc will be approxi-
mately %-inch to i^-inch.
900
GENERAL ELECTRIC REVIEW
Required Candle-power
Assuming the use of a plain muslin screen,
a three-wing shutter, and other average
conditions, it is believed that the required
horizontal candle-power delivered by the
arc for different size pictures will be approxi-
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f 20 AO 60 SO IOO IZO 140 160 /SO ZOO Z ZO Z^O ZOO ZSO ZCJ
j/ze of Picture m So Ft-
Fig. 4. Curves showing Relation Eetween Size of Picture
and Necessary Arc Current
mately in accordance with the curve given
in Fig. 2. Theoretically, the required candle-
power should increase in direct ratio to the
screen area; it appears, however, that in
practice the larger pictures do not require
quite so great a brilliancy of illumination.
In using the curve in Fig. 2 it is particularly
necessary to make due allowances for the
kind of screen surface and the ratio of area
of dark and light sectors in the shutter. A
two-wing shutter is almost always used with
an alternating current arc. The expression
'"maximum candle-power" refers to the
candle-power measured toward the lens,
which should be the direction of maximum
intensity.
Required Current Supply
The curve in Fig. 3 shows the approximate
maximum candle-power of direct and alter-
nating current arcs for different arc currents
when using .the arrangement of carbons
previously described. Fig. 4 combines in a
more convenient form the data shown in
Figs. 2 and 3. The current from a mercury-
arc rectifier may be considered as giving
practically the same candle-power as that
obtained from ordinary continuous-current
sources. Alternating current is much inferior
on account of the reddish quality of light
obtained and the high current required for a
given intensity of illumination.
Summarizing the foregoing. 35 amperes
direct current is usually great enough for a
12-foot picture, and an obtainable range of
30 to 50 amperes at the lamp will meet all
except extreme conditions.
Dissolving
When one picture is to immediately follow
another in the program it becomes necessary,
in order to avoid a delay of several minutes,
to have a second machine ready to start at
the instant the first stops. By this means the
delay may be cut down to a very few seconds.
It is generally considered necessary, however,
to warm up the second arc for 3 to 5 minutes
before showing the picture, thus giving it
time to become steady. Moreover, in the
better class of show houses, it is coming to
be the accepted method of operation to
"dissolve " one moving picture or stereopticon
view into another, thus eliminating all delay.
This necessitates the use of ballast resistances
when the second arc is struck and while the
two are operating in parallel, as well as extra
switching equipment, rheostats, etc., the
arrangements varying considerably with
different apparatus.
5 6 7 3 9 10 II IZ t3 /< 15 /6 17
Cand.'epower (xtooo)'
Fig. 5. Curves Comparing the Approximate Economy of
Different Methods of Current Supply
Apparatus for Moving Picture Houses
A complete line of standard apparatus
suitable for practically all requirements of
large or small moving picture establishments
has been developed and placed on the market.
It includes the alternating-current "compen-
CURRENT SUPPLY FOR MOTION PICTURE MACHINES
901
sarc" (transformer) for operating an alternat-
ing-current arc from a lighting circuit; the
d-c. — d-c. and a-c. — d-c. " compensarcs "
(motor-generator sets) for obtaining perfectly
regulated direct current from commercial
lighting or power circuits, of any voltage
or frequency, alternating or direct current;
the mercury arc rectifier for obtaining
approximately continuous current from single-
phase commercial circuits; the "Transport-
arc" (spot-light transformer) for alternating
current; a spot-light, as well as efficient
transformers for low-voltage sign or house
lighting.
AC. — D-C. and D-C. — D-C. Compensarcs
The d-c. — d-c. compensarc is built in
three sizes, viz., 35, 50 and 75 amperes for
one lamp only; or, with proper switching
arrangements, the 50-ampere outfit can be
used for the operation of two 35-ampere
lamps alternately, and the 75-ampere outfit
for two 50-ampere lamps where two picture
machines are used to obtain a dissolving
effect upon the screen. These sets are of the
two-bearing construction and have their
armatures electrically interconnected in such
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Ampere at Arc
Fig 6. Typical Volt-ampere Characteristic Curves of a
"Compensarc" for Two 35-amp. Lamps Alternately
A— Normal operation, one 35-amp. lamp, change-over switch
closed.
B — Normal operation, two 35-amp. lamps in use for short
period, change-over switch open, grid resistance in circuit.
C — Normal operation, compensarc connected for one 50-amp.
lamp.
D — Minimum load, field rheostat all in, change-over switch
closed.
E — Maximum load, field rheostat all out. change-over switch
closed.
F — Maximum load, same as "E" except change-over switch
open.
a way as to give an improved operating
efficiency. The volt-ampere characteristics
of the generator end are similar to those
of the a-c. — d-c. compensarc.
A-c. — d-c. compensarcs are built for opera-
tion on single-, two-, or three-phase commer-
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Fig. 7. Diagram of Connections for a Two-lamp
A-c. — D-c. Compensarc
cial power circuits, and in three ratings, as
follows: — 35 amperes, one lamp; two 35-
ampere lamps alternately, or one 50-ampere
lamp; two 50-ampere lamps alternately or
one 75-ampere lamp. The generators are
specially designed machines and have a high
armature reaction. The two-lamp (alter-
nately) machines are equipped with a series-
field winding so arranged that, for a short
period of time, two lamps can be carried
simultaneously while generating the addi-
tional voltage consumed by the necessary
stead ying resistance. This allows the second
lamp to be heated up and prepared 'for use
while the first picture is being shown, thus the
second reel may be dissolved into the first.
Fig. 6 shows the volt-ampere character-
istics of the two 35-ampere lamp (alter-
nately) set, the corresponding wiring con-
902
GENERAL ELECTRIC REVIEW
nections are shown in Fig. 7. It will be noted
that, when one lamp is being run and the
change over switch is closed, no ballast
resistance grids are used, thus securing the
best possible economy; and the rapid change
of voltage with a slight variation of the
Fig. 8. The Ballast Resistance Grid Used with an
A-c. — D-c. Compensarc for Two Lamps Alternately
current results in maintaining an extremely
steady and elastic arc that will not rupture
even though the carbons are fed very irregu-
larly. The grid steadying resistance is used
only when changing from one arc to the
other and during a brief period for warming
up the second arc while running the first
machine. The voltage drop through this
resistance prevents the first arc from being
put out at the instant the second is struck.
It should be particularly noted that, with
the change-over switch closed, it is impossible
to overload the generator at any particular
rheostat setting, since the voltage drops
"over the bend" and the machine protects
itself from injury when the carbons are
brought together or "struck." The com-
paratively low current on short-circuit makes
these sets much superior to ordinary constant
potential circuits with which, even though a
series resistance is used, "striking" the arc
results in a very high rush of current that
often blows fuses or destroys the ' ' crater ' ' of
the positive tip (thus resulting in poor
illumination until a new crater is formed).
Figs. 8 and 9 show the compact, self-
contained grid rheostat and control panel
developed for use with the two-lamp (alter-
nately) a-c. — d-c. compensarc set. Fig. 10
illustrates the simplicity and compactness of
the generating set itself, as well as the
specially designed control panel and arrange-
ment of a typical one-lamp installation for a
small theater.
The mercury-arc rectifier has been in use
in moving picture theaters and elsewhere
for so many years that a description of it
seems hardly necessary. The rectifiers are
built in three current capacities, viz., 30, 40,
and 60 amperes, and they are interchangeable
on either 1 10 or 220 volts. Rectifiers are made
for various frequencies, the 60-cycle rectifiers
being satisfactory for 50 cycles and above,
the 25-cycle rectifiers being suited to fre-
quencies up to 50 cycles. A rectifier is shown
in Fig. 11. This is one of the latest type; it is
equipped with a dial switch for regulating
the current without any loss in resistance
Fig. 9. The Control Panel Used with an A-c — D-c.
Compensarc for Two Lamps Alternately
and with two link connections just below the
triple-pole switch for connecting to 110 volts
(in position shown) or on the two outside
binding posts for 220 volts. The rectifier
can be furnished either with or without an
ammeter, or with an ammeter and a volt-
CURRENT SUPPLY FOR MOTION PICTURE MACHINES
903
meter. All rectifiers are equipped with a
triple-pole, double-throw switch, so that
in case of trouble with the rectifier the switch
can be immediately thrown to the lower
position and the arc operated from the
rectifier as an alternating-current compensarc.
Motor Lead To
1 10 von A C Line
balance against relative power consumption,
maintenance cost and convenient regulation,
while duly considering portability, class and
patronage ot the house, daily hours of
operation, etc.
The curves in Fig. 5 give an approximate
comparison of the power con-
sumption of different apparatus
and arrangements for supplying
current. Different makes of the
same class of apparatus natu-
rally vary slightly in efficiency.
Single-phase, a-c. — d-c. compen-
Fig. 10. Diagram showing Installation Arrangement for a
One- lamp A-c. — D-c. Compensarc
Fig. 11. A Single-phase Mercury Arc
Rectifier Equipped with Dial Switch
and Change-over Switch
An additional feature which is just
beginning to be used with the rectifier is an
auxiliary equipment whereby two pictures
can be faded one into the other by a very
simple and almost automatic process.
Each of the previously described methods
of current supply has its own peculiar field
of usefulness. The use of alternating current
often saves a great deal in first cost of instal-
lation. Between the different sources of direct
current, initial investment must be set in the
sarcs have a slightly poorer and d-c. — d-c.
compensarcs a slightly better efficiency than
indicated by the curve. Although a small
synchronous converter might be expected to
have a better efficiency than a motor-gener-
ator set for supplying direct current, those
available at present apparently have not;
and, furthermore, the specially designed
"Compensarc" is one of the few types of
direct-current apparatus that has the neces-
sary characteristics to maintain a steady
904
GENERAL ELECTRIC REVIEW
arc without the use of ballast resistance,
even when running only one lamp at a time.
Other generators and converters require
various amounts of series resistance, con-
suming from 5 to 20 volts in order to
secure the necessary stability. It will be
noted that this is a particularly important
point because, as shown by the curves, any
economy of power to be secured by the
motor-generator or converter, as compared
with current taken directly from a light-
ing circuit using the cheaper series resist-
ance or transformer, depends largely upon
the ability to dispense with ballast resist-
ances during the period of normal or one-
lamp operation.
PROPER CONSTRUCTION OF EARTH CONNECTIONS
By G. H. Rettew
Electrical Engineer, Potomac Electric Power Co.
The necessity that ground connections be of permanently low resistance is obvious; yet most engineers
give but meager attention to the construction and periodic testing cf these protective connections. As the
result of an extensive investigation, which included the resistance measurement of grounds, the author coop-
erating with the Bureau of Standards learned that many ground connections are of such high resistance as
to entirely vitiate their worth as a protection. The development of a permanently effective and cheap type
of ground connection constituud the remainder of the investigation, the results cf which with tests form the
basis of the following article. — Editor.
Those grounds, or earth connections, which
are installed for protective purposes are
important as by such means danger to life
and property is materially reduced, hence
any method of constructing such grounds
which reduces the resistance is worthy of
study.
Grounds are used for the neutrals of trans-
former secondaries, for lightning arresters,
for cases and frames of apparatus, and for
the neutrals of transmission systems, and,
while all operating companies do not use
grounds for all of these purposes, they all
must necessarily use them to some extent at
least.
On account of this wide usage it would
naturally be supposed that the best methods
of making effective grounds would have been
the subject of much study and experiment by
the engineering and construction departments
of the companies using and installing grounds,
but it is surprising how little attention has
been paid to this important matter. In fact
little information is available to assist those
companies who do not have an engineering
force to study such problems, and many
engineers have neglected to make a study of
this supposedly unimportant detail.
It is hoped that this article will be of
some assistance to those who are not informed
on the subject, and to those operating com-
panies who have not given the matter the
consideration it rightfully deserves.
Something like three years ago the atten-
tion of the writer was called to this matter
by certain occurrences on the system of one
of the largest companies in this country.
Upon invi ion it was learned that a
number of different forms of earth connections
were in use, but none of these forms had been
standardized and in fact no tests were recorded
to show the effectiveness of any of the large
number of grounds that were in use.
A test was accordingly made of different
forms of earthing devices, such as plates,
cones, rods, and pipes of various sizes, the
conclusion being finally reached that pipes
were the most desirable form owing to the
fact that they can be readily driven to a
sufficient depth to reach permanent moisture,
while plates or cones require considerable
excavation and resulting cost. No ground of
any form is effective unless placed at a depth
of seven feet or more, hence the value of a
deep driven pipe.
A test was then made of 100 grounds of
different forms, in scattered locations, and
of various ages, the average resistance being
found to be approximately 200 ohms. It is
quite certain that these grounds were installed
with average care and under approximately
the same conditions that obtain in other
cities, and thus we conclude that, where the
matter has not been made the subject of
investigation, the same conditions would
exist, or even worse conditions found. It is
needless to state that an earth connection
having a resistance of 200 ohms is of no value
in protecting transformer secondary mains
in event of a leak from the primary, hence
any manager who does not definitely know
the resistance of his grounds would do well
to investigate. Even a lightning arrester
connected to such a ground is of doubtful
value, so there is more than one reason for
careful construction.
PROPER CONSTRUCTION OF EARTH CONNECTIONS
905
Having finally determined on using pipe
grounds, tests were made of different sizes,
and of the same size driven to different
depths. It was finally decided that a single
% -in. galvanized pipe driven ten feet would
meet the requirements, except at power
houses or substations at which points a num-
ber of such pipes in multiple are to be used.
The first 250 such grounds which were
installed showed an average resistance of
15.68 ohms. Each of these had a mate
driven nearby and the test was made by
means of a 2300/115-230-volt transformer of
2.5-kw. capacity, this being carried on the
tool wagon. Temporary connections were
made to 2300-volt lines, current was passed
into the two grounds in series with an am-
meter in circuit, the drop of potential taken,
and the resistance of two grounds in series
was calculated. The resistance of each of the
two grounds was assumed to be equal to that
of the other, hence the resistance of the
permanent ground was taken at half the
resultant resistance of the two in series.
Some thousands of these pipe grounds are
now in use, hundreds of older types having
been replaced, or reinforced by a new one
installed close thereto and the two connected
together. During the progress of such work
it was not unusual to blow a primary trans-
former fuse when a new ground was connected
in, and an investigation would disclose a
ground on the interior wiring, the resistance
of which in series with the poor ground would
not permit enough current to flow to blow
even a 6-ampere branch fuse; however, it
would cause some meter registration, and
the constant flow of even a small amount
of current would tend to bake out the ground
and make it just so much worse.
During the latter part of 1914, the Bureau
of Standards, in connection with a compre-
hensive investigation of the subject of earth-
ing and earth connections, co-operated with
the writer in making tests of grounds of the
form referred to in order to determine not
only the effectiveness at the time of installa-
tion but also to ascertain what deterioration,
if any, took place with lapse of time. This
investigation is still in progress. For the
purpose of the tests just mentioned five
standard grounds were installed by men
regularly engaged in line work, no effort
being made to secure better results than in
regular practice. These were located as
shown in Fig. 1. The numbers shown are
used for identification purposes in the tables
and descriptive matter which follow, much
of which is taken directly from notes on the
tests which were submitted by the Bureau
of Standards.
The measurements were made in various
combinations by means of ammeters and
voltmeters at 110, 220, and 1100 volts, the
Na.l No.2 No.3 Na4
o o o o
(♦ /'•)» — *' 4* 104.5' *|«—
No. 5
Fig. 1
first measurements being made immediately
after the grounds were installed, that is, before
the soil had a chance to settle and pack
around the pipes, and before the electrolytic
agent which is part of the pipe form of ground
had a chance to diffuse through the surround-
ing soil.
The result of first test is shown in Table I :
TABLE I
TEST AUGUST 15, 1914, 110 VOLTS
Number of
Resistance of
Calculated
Grounds in
Grounds in
Resistance of
Series
Series
Each Ground
1 and 2
12.2 ohms
No
1 -12.4 ohms
1 and 3
21.4 ohms
No
2-11.2 ohms
3 and 4
23.1 ohms
No
3 — 15.4 ohms
2 and 4
18.7 ohms
No
4 — 7.6 ohms
1 and 4
20.0 ohms
No
5 — 16.7 ohms
3 and 5
32.1 ohms
2 and 5
28.0 ohms
1 and 5
29.1 ohms
4 and 5
24.3 ohms
It should be noted that the resistance
between two earth connections increases to a
maximum as they are moved apart, the maxi-
mum being reached at from 6 to 10 feet.
This is shown to some extent by the measured
resistance between No. 1 and No. 2 in Table
I, which is 12.2 ohms, although the sum of
the individual resistances is 23.6 ohms.
The method by which the individual resist-
ance was calculated may be of interest;
Nos. 1 and 2 being so close together, it was
thought preferable to calculate Nos. 3, 4 and
5 individually, and later to calculate Nos. 1
and 2 by testing in series with one of the others
whose resistance had been found.
From Table I it may be noted that
Resistance of No. 3 + No. 4 = 23.1 ohms
Resistance of No. 3 + No. 5 = 32.1 ohms
Resistance of No. 4 + No. 5 = 24.3 ohms
906
GENERAL ELECTRIC REVIEW
If we substitute X
3—4 — 5, then
X+Z = 32.1
X+Y = 2ZA
Z-F = 9.0
F+Z = 24.3
Y—Z respectively for
2Z = 33.3
Z= 16.65 or 16.7 as per Table I, Z
being No. 5.
Having thus determined Nos. 3, 4 and 5,
Nos. 1 and 2 were tested against those
already known and their resistance deter-
mined.
The same tests as indicated by Table I,
which was based on 110 volts pressure, were
repeated using both 220 and 1100 volts. .4*
the higher voltages the resistances were almost
uniformly less than when tested at 110 volts,
probably due to the fact that the temperature
of the earth was raised by the quite con-
siderable amount of energy consumed.
It should be here noted that 1100 volts was
impressed directly on Nos. 1, 4 and 5, im-
mediately after first test, and continued for a
sufficient length of time to thoroughly bake
them out, the idea being to determine
whether this would permanently impair their
effectiveness.
On November 18th, the tests were repeated,
this being three months after the first test.
The result of the resistance measurements
is shown by Table II, from which it may be
noted that the baking had not caused per-
manent impairment, but on the other hand
that the resistance had materially decreased.
TABLE II
TEST NOVEMBER 18, 1914, 230 VOLTS
Number of
Resistance of
Calculated
Grounds in
Grounds in
Resistance of
Series
Series
Each Ground
1 and 2
2.8 ohms
Xo
1 - 6.42 ohms
1 and 3
6.2 ohms
No
2 - 6.50 ohms
1 and 4
10.25 ohms
Xo
3- 8.80 ohms
1 and 5
17.8 ohms
Xo
4- 3.83 ohms
2 and 4
10.3 ohms
No
5-11.39 ohms
2 and 5
17.9 ohms
3 and 4
12.7 ohms
3 and 5
20.2 ohms
4 and 5
15.2 ohms
A third test was made March 4, 1915, the
results appearing in Table III. For a week
or ten days prior to this test there had been
no rain, consequently the ground was rather
dry. The resistances were, however, quite
low, in fact much lower than is generally
considered necessary, although a ground for
the protection of life or property cannot be
too low in resistance. In any event there is
not manifest any deterioration such as might
have been expected, particularly after the
grounds had been baked out on more than
one occasion.
TABLE III
TEST MARCH 4, 1915, 230 VOLTS
Number of
Resistance of
Calculated
Grounds in
Grounds in
Resistance of
Series
Series
Each Ground
1 and 2
7.52 ohms
Xo
1 -8.72 ohms
1 and 3
11.24 ohms
No
2-8.08 ohms
3 and 2
9.26 ohms
Xo
3-8.96 ohms
2 and 4
15.88 ohms
No
4 — 7.78 ohms
1 and 4
16.46 ohms
No
5-9.89 ohms
3 and 4
16.78 ohms
1 and 5
18.66 ohms
2 and 5
17.96 ohms
3 and 5
18.81 ohms
4 and 5
17.68 ohms
After this test Nos. 1 and 5 were baked
out by impressing 1100 volts on them for
40 minutes. The average current during this
period was 60 amperes, or roughly 66 kw.
Feeling that earth connections of this form
are highly desirable, as they are of low
resistance, easy to install, do not require
expert workmen, are apparently permanent,
and moreover are relatively inexpensive,
there is appended a complete description of
the methods which have been standardized
for the particular system with which the
writer is connected :
A 2-in. pipe is driven 5 feet deep and then
pulled out ; the hole thus formed is then filled
with rock salt; a piece of %-in. galvanized
iron pipe 12 feet long is then driven through
the 5 feet of salt and 5 feet further into the
ground; the hammering naturally batters
the top of the pipe, which is then cut off and
threaded, and an additional length of 10
feet, more or less, screwed on. As grounds
of this character are usually placed at the
base of poles, it is necessary to locate the
pipe IS inches or 2 feet from the pole so that
the three-wheel pipe cutter and the stock can
be operated. A trench is dug from the pipe
to the pole, the pipe is bent into the trench,
and the projecting length cleated to the pole.
This brings the top of the pipe approximately
10 feet above ground; it is cleated at intervals
as it passes up the pole to a brass coupling.
PROPER CONSTRUCTION OF EARTH CONNECTIONS
907
The brass coupling is specially made for the
purpose and is readily obtainable on the
market. It is similar to an ordinary pipe
coupling except that a lug is cast on the side
and drilled to receive the wire, which is
sweated in. This method is far superior to
using a cap on top of the pipe, as the coupling
being open permits rain to enter the pipe and
thus get down where it effectively increases
the conductivity of the soil, for quite a large
quantity of salt is inside the pipe and the
entrance of water gradually dissolves this
and permits this excellent electrolytic agent
to permeate the soil.
The salt is an essential feature of any low
resistance earth connection; or at least some
electrolytic agent is necessary, salt being
preferable as it has little or no destructive
action on the pipe.
Experience with this form of ground has
demonstrated that it is durable, as after three
years' use the pipes show little or no deteriora-
tion. The majority are painted to harmonize
with the pole and this undoubtedly assists
in preserving the pipe at the ground line.
In concluding it might be well to note that
the wire need not be carried down into or
through the pipe. The writer has frequently
seen weather-proof wire carried through a
protecting pipe to an earthing device, which
was intended to carry off charges induced by
lightning. The reactance of the pipe to high
frequencies when surrounding a conductor is
considerable, and in some cases the charge
will jump from the wire through the insula-
tion to the top of the pipe, the insulation
being frayed out by the discharge. Such a
ground is not only lacking in protective power
but is actually a source of danger.
The pipe ground as described has as little
reactance as any form that could be placed
in practical use, as well as having the other
desirable characteristics which have been set
forth.
It is believed that the Bureau of Standards,
at the conclusion of its investigation, will
publish a treatise on the subject of "Earthing
and Earth Connections"; if so, it will doubt-
less be a valuable addition to the present
knowledge of the subject.
908
GENERAL ELECTRIC REVIEW
METHODS OF REMOVING THE ARMATURE FROM BOX FRAME
RAILWAY MOTORS
By J. L. Booth
Railway Motor Engineering Department, General Electric Company
We hope to be able to publish a number of articles dealing with some of the more important features of
car barn practice. This first article after showing the advantage of the box frame design of railway motor
describes several different methods of removing armatures from such motors of different capacities. The
illustrations are especially valuable as showing the processes in great detail. — Editor.
The box type of frame for railway motors
was originally developed in order to meet the
demand for motors capable of giving the
large outputs required for heavy service on
interurban, elevated and subway lines. In
addition to possessing many advantages from
Fig. 1. Small Light-Weight Motor with box frame for
small wheel cars
a mechanical point of view, it enables the
designer to obtain a considerable increase
in capacity for a given weight and space,
when compared with the split frame. As the
advantages of this type of frame became more
widely known and recognized among operat-
ing engineers, the demand for box frames
increased until at the present time they are
being used for motors of all sizes from the
largest to the smallest, and have almost
entirely superseded the split frame. From
SO to 90 per cent of the railway motors now
being made are of the box frame type, and
many of the most recent designs of motors are
being built wTith this type of frame only.
Advantages of the Box Frame
For a given space and weight, a larger out-
put can be obtained than with a split frame,
or for a given output the motor can be made
both smaller and lighter. It also possesses
greater structural strength and durability,
and there is less chance of breakdowns due
to the mechanical failure of parts of the
machine, or the breakage of bolts. The
lower half of malleable iron gear cases may
upported in a more substantial manner
rendering them better able to withstand the
severe stresses to which they are frequently
subjected. The elimination of the joint in the
frame, in addition to giving an unbroken
magnetic circuit, prevents oil from working
into the interior of the motor from the axle
bearings, which is always liable to occur
through the joint in a split frame.
From the absence of this joint, which is
usually horizontal, a greater freedom of
design is generally obtained for the armature,
pole pieces, and coils, and for the same reason
a better axle preparation and design of axle
bearing housings is made possible.
With a ventilated motor, in which air is
drawn through the frame and armature core,
a greater space is available in the frame for
the passage of the cooling air around the
field coils. This allows unrestricted ventila-
tion with a corresponding increase in the
service capacity of the motor. Better pro-
tection is afforded to the field coil connections
which, in the box frame motor, are all inside
the frame. By removing the motor from the
truck repairs are effected, bearings seated and
connections made under favorable conditions
to insure good workmanship, while with the
Fig. 2. 160-H.P. Motor with box type of frame
split frame the work is often done from the
pit in a cramped position and under poor
lighting and working conditions.
There are also a fewer number of parts
which are liable to work on each other and
which ultimately require liners to take up
REMOVING ARMATURE FROM BOX FRAME RAILWAY MOTORS
909
wear. This together with the increased relia-
bility of the box frame motor gives a low
maintenance cost.
A typical example of a small box frame
motor is shown in Fig. 1 . This motor has
been especially developed for use with light
cars having small wheel trucks. It is built in
the box frame type only and although of
35 h.p. rating weighs only about 1500 lb.
Even in this size of motor it is possible to
provide openings, both on the top and suspen-
sion side of the motor, of sufficient size to
permit the thorough inspection of the com-
mutator and brush-holders.
A larger motor is shown in Fig. 2. This
motor which rates at 160 h.p. weighs, com-
plete with all parts, approximately 5720 lb.
Methods of Removing Armatures
When the box frame was first advocated
it was felt by some operating engineers that
the necessity of dismounting the motor from
the truck in order to remove the armature, for
repairs, would take so much time and keep
a car out of service so long that the cost
of repairs would largely offset the advantages
of the box frame. Experience, however, has
shown this not to be so, and by the provision
of various simple appliances to facilitate the
removal of armatures, repairs to box frame
motors are today being executed just as
rapidly as with split frames. Indeed, in the
opinion of some operating engineers of roads
where both types are in operation, inspection
and repairs can be effected in less time with
the box frame, due to the superior working
conditions which exist when the motor is off
the truck. In many cases the time necessary
to have an armature "on the floor" after the
car has been run in has been cut down to
something very small, and the systematic
inspection of motors at regular intervals of
time or of distance run is materially reducing
the cost of maintenance and repairs. It has
been urged that for small roads operating
single-truck cars, and not provided with the
equipment for easily lifting the car body from
the truck, the split frame can be more easily
handled and should be used. The removal of
the box frame motor, however, without
taking out the truck from under the car,
presents no great difficulty and is recom-
mended for this type of car. The axle caps
and bolts are first removed and the gear case
taken down. The motor is then supported
from the pit by a jack bearing against the
center of the motor frame. The suspension
bolts are next taken out (if of the bolted bar
type) and the suspension bar unbolted from
the truck. The motor may then be raised by
the jack and moved away from the axle
sufficiently far to allow the portion of the
axle bearing housing that projects over the
axle to clear it. The motor may then be
T^^^aih
Fig. 3. Removing a 65-H.P. Box Frame Motor from the Truck.
This operation takes fifteen minutes to perform
lowered into the pit. If preferred, the axle
may be used as a fulcrum and the motor
swung down around the axle until the bearing
housings are clear. In any case, the motors
generally used on single-truck cars are small,
and the weight to be handled is not great.
No elaborate equipment is required for remov-
ing a truck from a double-truck car. In most
car barns, two pairs of chain blocks can be
arranged to lift one end of the car while the
truck is being removed, and it is not necessary
to send the car to the main shops for the
removal of an armature. Some examples are
given here of the methods employed on various
roads. Figs. 3, 4 and 5 show how GE-242
motors are being handled on a large system
in the middle west. This motor is rated at
65 h.p. on 600 volts, and weighs with gear,
gear case, pinion and axle linings approxi-
mately 3045 lb. The truck is run out from
under the car, and the suspension bolts, gear
910
GENERAL ELECTRIC REVIEW
case, axle caps and linings removed, the dust
guard coming away with the axle caps.
The motor is then lifted out by means of the
bails and an ordinary pair of chain slings
(see Fig. 3). The four bolts securing the
pinion end frame head are next removed and
the head started by jack screws.
A lever, having a collar at one end which
fits over and is clamped to the pinion, is used
to support one end of the armature which is
then pulled out sufficiently far to enable a
wide lifting strap to be placed in position as
shown in Fig. 4. The length of the bearing
at the commutator end is sufficient to support
that end of the armature until the lifting
strap is in place.
By bearing down on the end of the lever,
the weight of the armature can be balanced
while being removed from the frame. Fig. 5
shows the armature clear of the frame, with
the man's weight still on the lever, balancing
the armature in the sling.
Fig. 4.
Removing Armature from a 65-H.P. Box Frame Motor. Lifting strap in position. From the
time the motor is off the truck until the armature is on the floor is twenty minutes
Fig. 5. Armature of a 65-H.P. Motor Removed. Man's weight on lever balances weight of armature.
To replace armature and remount motor on truck takes twenty-five minutes
REMOVING ARMATURE FROM BOX FRAME RAILWAY MOTORS
911
Fig. 6. A 140-H.P. Box Frame Motor removed from truck
and turned on end preparatory to lifting out armature
It will be noticed that the pinion has not
been removed, and that it is only necessary to
remove the four bolts in the pinion end arma-
ture head, also that in this method, which
avoids turning the motor on end, it is not
necessary to remove the oil from the oil boxes.
The time necessary to remove and replace
an armature after the truck has been taken
out from under the car body is as follows:
To perform the first operation, that is,
the removal of the axle caps and suspension
bolts and raising the motor frame from the
truck, takes 15 minutes.
The second operation, covering the removal
of frame head bolts, forcing off frame head,
Fig. 7. Lifting out Aimature of a 140-H.P. Box Frame Motor
with scissors-like clamps which fit under pinion
Fig. 8. The clamps are replaced by a light chain before
laying the armature flat on the ground
clamping lever to pinion, placing lifting strap
in position, removing armature and laying it
on floor, requires 20 minutes.
The third operation, picking up armature,
replacing it in shell, bolting up frame head,
lifting motor and placing it on truck ready for
service, takes 25 minutes.
This makes a total time of one hour from
the time the truck is taken from -under the
car, until the motor is remounted and the
truck ready to be replaced under the car
body. This is, however, an average time
and, under extraordinary circumstances, the
work could and has been done in 45
minutes.
912
GENERAL ELECTRIC REVIEW
. 1 1 -- ^3
Fig. 9. Removing an armature by means of an extension of the armature shaft supported
by a roller in a bracket bolted to the frame
Handling a Large Motor
Photographs are reproduced in Figs. 6.
7 and 8 snowing the method adopted by
another road for removing the armature from
GE-222 motors. This is a 140-h.p. motor
weighing complete with all parts 4260 lb. In
this case, the motor is turned on end, after
having been removed from the truck by-
slings in the usual manner. To turn the
motor on end, the air intake pipe is removed,
and a sling with hooks is attached to one of the
bails on the motor frame, and to an eye bolt
screwed into one of the axle cap bolt holes.
For removing the armature the chain slings
for taking the motor out of the truck, and for
turning it on end, are replaced by scissors-
like clamps which fit under the pinion teeth.
The armature is then withdrawn, and stood
vertically on blocks, while the clamps are
replaced by a light chain before laying the
armature flat on the ground.
A road operating a large number of GE-200
box frame motors is using an extension of the
armature shaft to support one end while the
latter is being dismounted. The pinion end
frame head is removed, and the head at the
commutator end replaced by a malleable
iron bracket which fits the bore of the frame
and is held in place by two tap bolts. This
bracket carries a machined roller of such a
diameter that the extension of the armature
shaft, see Fig. 9, is kept in the center of the
frame. This extension is a steel tube machined
on the inside to just slip over the armature
shaft . The shaft at the other end is supported
by an oak pole 3 inches in diameter having a
steel tube at one end of it that fits over the
armature shaft. The armature is moved out
Fig. 10. The other end of shaft than that shown in Fig. 9
supported by an oak pole with a steel tube
fitting over the shaft
horizontally and is supported at one end by
the roller until it is clear of the frame.
Two somewhat similar methods are in use
on another road for handling GE-210 motors.
In one case the frame is stationary and the
armature moved. An iron pipe having one
REMOVING ARMATURE FROM BOX FRAME RAILWAY MOTORS
913
11
3 3
si
CO CO
*s
Xi CO
•o S
4J —
n
"1
3 j:
s «
E n
CO *J
V O
SE
2 -o
« 5
E a
bS
■o =
■S 2
914
GENERAL ELECTRIC REVIEW
Fig. 15. A special machine for removing armatures from Box Frame Motors. Motor in place
Fig. 16. Frame-head bolts withdrawn and frame moved partially along the bed of the machine by
means of the handwheel
Fig. 17. Armature clear of frame and in a convenient position for examination and for
effecting minor repairs
RATIO FOR COMPARING PRECISION RESISTANCE STANDARDS
915
end bushed with brass, to avoid injury to
the armature shaft, is used to support one
end of the shaft. The armature is lifted by
slings and moved out of the frame horizon-
tally by an overhead traveller, see Figs. 11
and 12. The illustrations show the pinion
and pinion end frame head removed from the
shaft, though this is not actually necessary
for the removal of the armature.
With the second method in use on this
road, the armature is held stationary and the
frame moved. Figs. 13 and 14 show this.
The armature is supported by jacks, a bushed
pipe being used at one end as before. The
jacks can be readily adjusted to take the
weight of the armature off the pole pieces,
and the truck with the frame is moved along
until the armature is clear.
This method is similar to that employed
with the special machine shown in Figs. 15,
16 and 17. Although this involves the use of
a special tool, it is simple and inexpensive to
make and has many advantages.
The machine consists of a pair of centers,
one of which is adjustable, mounted on a base
which may be either a casting or built of
channel bars. By using a long center instead
of the pipe fitting over the armature shaft,
the removal of the commutator frame head is
avoided.
The table may be moved along the base
by means of a hand wheel, and each of the
supports on which the motor rests can be
adjusted vertically by a lever.
The motor is supported by the machined
bosses on the. bottom of the frame. The
method of removing the armature is made
evident by the photographs. It is unneces-
sary to remove the oil from the armature
bearing oil boxes, and the armature and
frame are in a very convenient position for
inspection and making minor repairs.
These examples illustrate some of the means
employed for the removal of armatures from
box frame motors. Other appliances may be
used where better suited to individual shops.
A TEN-TO-ONE RATIO FOR COMPARING PRECISION
RESISTANCE STANDARDS
By C. A. Hoxie
Standardizing Laboratory, General Electric Company
The main object of this article is to describe a method of establishing a ten-to-one ratio by which preci-
sion resistance standards of either higher or lower denomination than the standard of reference may be com-
pared with practically the same accuracy as those of equal nominal value. — Editor.
A piece of apparatus (which will be de-
scribed later) for accurately determining a
ratio of ten-to-one (Fig. 1), together with a
bridge designed for the comparison of pre-
cision standards (Fig. 2), has been recently
built and is now in use at the Standardizing
Laboratory of the General Electric Company
at Schenectady. This ten-to-one ratio is a
modified form of a similar device in use at the
Bureau of Standards at Washington to check
the accuracy of another ratio with which their
precision standards are compared.
The modification consists of an arrange-
ment by which an adjustment of the special
ratio set may be made, thus permitting a
direct comparison of the standards.
The determination of the relative values of
resistances having the same nominal value
presents small difficulties compared with those
encountered when the ratio is 10:1.
One of the first methods that might occur
to us would be to form the ratio arms of
eleven units that have been adjusted to an
equal value, ten in one arm and one in the
other; or to place the ten in parallel, using the
odd one for the high side. But this, although
employed for several years, is not entirely
satisfactory, owing to the fact that there is
no convenient way of checking the result-
ing measurements by interchanging the ratio
coils.
We can, however, establish a ten-to-one
ratio that possesses this advantage and puts
it very nearly on a par with the even ratio
method as to accuracy.
In the ordinary commercial electrical
instruments the accuracy required is seldom
greater than 0.1 per cent; but where such
instruments of precision as potentiometers
and resistance standards are manufactured
916
GENERAL ELECTRIC REVIEW
the resistances should be known to within
0.01 per cent.
The standard of reference is the inter-
national ohm, defined as that resistance
offered to an unvarying electric current by a
column of mercury at the temperature of
Fig. 1. Ten-to-One Ratio used in Connection
with Precision Resistance Bridge
melting ice, 14.4521 grams in mass, of con-
stant cross sectional area and of a length of
106.3 centimeters.
The results of several de-
terminations of this value
by different physicists, to-
gether with the comparison
with wire standards, have
agreed to within about two
parts in 100,000 (0.002 per
cent). If we add to this
an estimated change of not
more than 0.002 per cent
in the reference wire stand-
ards, it probably would be
difficult to certify to the
absolute value nearer than
about five parts in 100,000.
Relative values, however,
between suitably con-
structed standards under
favorable conditions can be determined to
within one or two parts in a million.
There can be obtained resistance standards
of approved design constructed of resistance
material which will not vary more than 30
in a million per degree C. and adjusted
to within 0.01 per cent of its nominal value.
These standards are provided with heavy
copper terminals projecting beyond the case
by which they can be supported in mercury
cups.
Having one of these standards, it is possible
by means of a suitable precision bridge to
determine the relative value of other stand-
ards.
In order to explain in the simplest way the
10:1 ratio, it seems advisable to refer in detail
to a 1:1 comparison carried out according to
ordinary well known means.
Let the standard S, Fig. 3, and a resist-
ance of the same nominal value to be com-
pared Si be placed in two adjacent arms
of a Wheatstone bridge and a set of even
ratio coils, A and B, form the other two arms.
If now the ratio coils and the resistance Si be
adjusted until the bridge is balanced and this
balance be not disturbed by a reversal of the
relative position of the ratio coils, it is evident
that A=B and Si = S. The adjustment of the
arms S and Si may be accomplished by shunt-
ing one or the other, depending on which is
the higher, with a comparatively high resist-
ance a. If then the ratio coils are equal and
the standard S be the one shunted to obtain
a balance;
S,=
aS
a+S
or if Si, then Si :
aS
-S
In practice .4 seldom equals B exactly, but
it can be shown that if A differs from B not
Fig. 2. Precision Bridge for Comparison of Resistance Standards
more then 0. 1 per cent, the value of S obtained
by taking the mean of two measurements, one
with .4 and B in their normal position and one
with their positions reversed, will not be
affected by this difference more than one part
in a million. This error in the result, however,
10:1 RATIO FOR COMPARING PRECISION RESISTANCE STANDARDS 91'
varies as the square of the difference between
A and B. For example, if A differs from B
1 per cent, the result would be in error about
one part in 10,000, or 100 times that of the
first case.
Example 1. Let A = 100 ohms and 5 = 99.9
ohms (0.1 per cent lower) 5 and Si=l ohm
each. In order to balance the bridge, if
arranged as shown in Fig. 3, the shunt a
would equal - '- ■ ■ =999 ohms.
Result obtained from 1st reading
_aS_ = 999 XI
a-S 999-1
Result obtained from 2nd reading
aS 999X1
-Si-
= 1.001002.
5l" a+S 999 + 1
Mean of 1st and 2nd
1.001002 + 0.999
= 0.999.
1.000001.
z
When the 2nd measurement was made the
positions of A and B were reversed and S was
shunted to balance the bridge.
Example 2. In this case let B be 1 per cent
lower than .4 . .4 = 100 ohms, B = 99. , a would
equal 99 ohms. 1st reading,
5: = ™—= 1.010204.
99 X 1
2nd reading, 5j =jgxi = °-99-
Mean of 1st and 2nd =
1.D10204+0.99
2
= 1.000102.
In the first case the error in the final result
was one part in a million; in the second, one
part in 10,000, one hundred times that of the
first.
The principal objection to this method of
shunting the standard of reference, 5, or the
standard being compared, Si, in order to
balance the bridge, is the very large range of
shunt values that are required. For example,
if the nominal value of the standards were 10
ohms each, it would require a shunt of one
million ohms if only a reduction of one part in
100,000 were necessary; and if 100-ohm
standards are being compared, ten times this
shunt value, or ten megohms, are required to
obtain the same result, while on the other hand
one ohm shunted across a standard of 0.0001
ohm would onlv reduce its value one part in
10,000.
For this reason it is better to shunt a
portion of the ratio coils .4 or B. If the
nominal value of A and B is 100 ohms, let
this portion be, say one ohm. If this part be
selected to within an accuracy of 0.2 per cent,
the resulting calculated value of the reduction
in /I or B due to the shunt will be in error
not more than two parts in a million, if this
reduction be not more than 0.05 per cent of the
Fig. 3
total, which will seldom be the case when
comparing precision standards.
For example, let the ratio coils equal 100
ohms each and the shunted portion, y, equal
1.002 ohms; let the reduction in the ratio coil
be 0.05 per cent, which in this case would be
0.05 ohm. In order to make this reduction,
7 (y-C)
the shunt a =
when C = amount of
y — (y—C)
reduction. Substituting,
1.002X (1.002-0.05)
1.002- (1.002-0.05)
= 19.07 ohms = resistance of shunt. This
value shunted across exactly 1 ohm would
19 07X1
reduce it 1 — ' = 0.049S3 ohm instead
of 0.05 as in the first case — a difference of only
0.00017 ohm, which is less than two parts in
a million when A and B = 100 ohms.
The shunting resistance under these con-
ditions would not exceed 10,000 ohms to show
a change of one part in a million, nor lower
than 20 ohms to reduce the ratio 0.05 per
cent, the resistance of this shunt being
independent of the nominal value of the
standards under comparison.
In the foregoing we have dealt entirely with
comparing resistances of the same nominal
values, determining the accuracy of our ratio
by a reversal of position.
In order to establish a 10:1 ratio we. may
select a suitable resistance, the value which
need only be known approximately, and by
intercomparison as before described adjust
six others to the same value. Place three of
these in parallel and adjust a seventh unit to
the resultant value. We have now six units
91S
GENERAL ELECTRIC REVIEW
of equal resistance and one that is one third
of this.
If we now form two adjacent arms of a
bridge by placing in each arm three of the
six units in series, arranged so that either
group of three can be connected in parallel,
Fig. 4
a nine-to-one ratio can be established. This
is the ideal condition, as the ratio can be
reversed by simply placing the groups of
these in parallel first on one side and then the
other, of course leaving the units on the
opposite side in series. In this case there will
be an actual reversal of the relative position
of the standards under comparison with
respect to the resistance units forming the
ten to one ratio, thereby obtaining a check
equal to that of the even ratio condition.
(Note. — The parallel or series condition is
made possible by assembling the seven coils
in a suitable case and connecting the terminals
of each to mercury cups located on the top,
which can be joined by copper links of negli-
gible resistance. (See Fig. 1.)
But unfortunately it is not a nine-to-one
but a ten-to-one ratio that is required, which
makes the problem somewhat more com-
plicated.
However, by adding another resistance we
can produce a ten-to-one condition that will
still permit of a check that will assure very
nearly the same accuracy in the final result.
If we connect the unit "g" that was adjusted
to % the resistance of the others, between the
two groups as shown in Fig. 4 and place the
three units in the B arm in parallel by links m
and «, the resistance of the A arm will equal
ten times that of B, and reversing these condi-
tions by removing the links from 5 — 6 and 7 — 8
and placing them across 1 — 2 and 3 — 4 and
changing the galvanometer connection from
5 to 2 will result in making B ten times that
of A, provided all the resistances have been
adjusted correctly.
This arrangement permits of a check on
the accuracy by taking the mean of two
measurements, as in the case of the even
ratio condition, one with the relative positions
of S and Si reversed with respect to the resist-
ances forming the A and B arms (with the
exception of the portion g, which will always
be on the higher side of the ratio). For this
reason any error in the value of g will cause
an error equal to one-tenth of this in the
final result. Therefore a check should be
made to determine the relative value of g
with respect to the mean value of the two
groups of three in A and B, in order to be
able to apply the necessary correction.
This check can easily be made by letting 5
and Si form an even ratio (Fig. 4) and placing
a copper link of negligible resistance from 2
to 3, leaving the galvanometer connection at
5 and the coils in B in parallel.
After noting the difference in per cent
between g and the coils in B, reverse the
conditions (being careful to reverse the
relative position of S and Si also) and compare
g with the coils in the A arm. The mean
of these two results will be the per cent that
g is different from the mean value of the two
groups; one-tenth of this difference being the
correction that should be applied to the arm
containing g when comparisons of ten to one
ratio are made. This relative value of g can
readily be determined to within one part in
100,000; then by applying this correction the
measurement will not be affected by more
than one part in a million.
It can be shown as was the case with the
even ratio condition that the relative value of
the six other resistances forming the A and B
arms can be in error 0.1 per cent without
affecting the final result more than one part
in a million if the mean of two comparisons of
a standard having a normal value of ten times,
or one tenth that of the standard of reference,
be taken, letting A form the high and B the low
side in one, and with these conditions reversed
in another as before described. This added to
the estimated error introduced by the resist-
ance g amounts to about two or three parts
in a million.
In order to balance the bridge in the even
ratio condition it was convenient to shunt a
small portion of the A or B side, depending on
which was the higher with respect to S and S\.
In the ten to one ratio the only portion
that permits of adjustment in this manner is
10:1 RATIO FOR COMPARING PRECISION RESISTANCE STANDARDS 919
the resistance g, which is always on the high
side. If, however, g is left about 0.5 per cent
high (which is equal to 0.05 per cent of the
total value of the arm) and a suitable portion
be shunted until it is correct when compared
with the remaining coils in A and B, as
before described, it is evident that a balance
can be obtained if the relative value of the
standard being compared varies not more than
0.05 per cent either way from the standard of
reference.
To illustrate, let the resistance forming g
be a little larger than its true value. Select
a small portion 7, across which can be shunted
a variable resistance a. Compare the resist-
ance g with the remaining coils in both A and
B, adjusting in each case its resistance by the
shunt a. If ai be the mean of the two shunt
values required to bring the bridge to balance,
then 7 —
Qi 7
ai+7
will equal the amount that the
resistance g exceeds that of its true value.
For example, we will take some actual data
obtained in the Standardizing Laboratory in
connection with the ten-to-one ratio now in
use. The coils of equal resistance that form
the large part of the A and B arms were
adjusted to 150 ohms each. The values of
150
g were —^- =50 ohms. The high side was
then equal to (150X3) + 50 = 500 ohms, and
150
the low side — =50 ohms.
o
The resistance of the coil g was made approxi-
mately 0.5 per cent large. The portion 7,
across which a variable resistance a was
shunted, was adjusted carefully to 15 ohms.
When comparing g with the three coils in
parallel on the A side, it was necessary in
order to obtain a balance to shunt 7 with 945
or 961 ohms, depending on the relative
positions of S and Si (S and Si in this case
equaled approximately 100 ohms each), the
mean of which was 953 ohms. When com-
paring g with the B side, the shunt values
were 942 and 958, the mean being 950 ohms.
T, .... 953+950
Ihe mean of the two means was - =
951.5 ohms. Let this = a': then the amount
that the resistance g exceeded that of its true
value = 7-
Pi7
2+7
= 15
951.5X15
951.5 + 15
= 0.232S
ohms. Therefore under these conditions,
when making ten to one comparisons if less
than 951.5 ohms is required for a balance, the
resistance of the high side is smaller than ten
times that of the low side, or vice versa.
This is, of course, strictly true only when the
coils on the A side exactly equal in value
those in the B arm. For this reason a mean
of two measurements made under reverse
conditions should be taken. If this is done,
practically the same accuracy should be
obtained as with the even ratio measure-
ments, i.e., within two or three parts in a
million. This, of course, only refers to rela-
tive values.
For example, let a standard Si having a
nominal value of 100 ohms be compared with
a standard S of 10.0012 ohms.
Let the value of the shunt necessary to
secure a balance be 875 ohms and under the
reverse conditions 878 ohms.
In the first measurement the reduction of
the 15 ohms by the shunt of 875 ohms
=15-ioTi!=0-252Sohm'
500 - (0.2528 - 0.2328) = 499.9800, which is 40
parts in a million low.
In the second measurement the reduction
=i5-P^!!=o-25i8ohm'
8/8 — 15
500- (0.2518-0.2328) =499.9810, which is 3S
parts in a million low.
The results obtained from the first reading
S1= (10X10.0012) -0.0040 = 100.0080 ohms.
The results obtained from the second reading
Si = (10X 10.0012) -0.0038 = 100.0082 ohms.
The mean of the first and the second
= 100.0081 ohms = the true relative resistance
of Si.
It has not been the intention of the writer
to discuss the merits of the different bridge
methods best adapted for the various resist-
ance values under comparison.
In this article only the Wheatstone bridge
was mentioned, but the principles brought
out apply equally well to other types. In
fact, the general practice is to employ the
Kelvin double bridge for all comparison? or
measurements of precision standards of ten
ohms or less, using the Wheatstone bridge
for all resistances over that value.
920
GENERAL ELECTRIC REVIEW
SOME PROBLEMS IN BURNING POWDERED COAL
Part I
By Arthur S. Mann
General Electric Company, Schenectady, N. Y.
The author writes from a wide experience in this most interesting subject; this experience has been gained
first hand from his experimental work at the Schenectady plant of the General Electric Company. In the
present article he deals in considerable detail with the apparatus employed and includes data on the nature
and behavior of powdered coal. We hope to publish in our next issue a report of the tests made. — Editor.
Powdered coal has been burned for years.
It is more difficult to burn it beneath a
boiler than it is in a forge furnace or in a
cement kiln.
It seems simple enough to drop coal down
a pipe by a screw feed, to pick it up with a
cross current of air which carries it along
to a furnace; and it is simple, provided the
rules are obeyed. But such a plan is not very
economical; the mixture is not good and
some of the coal is long in burning; the fire
may do the work required of it if there is
room, but it will not give a high initial
temperature; it will not have completed its
burning in fifteen inches or so, perhaps not
in fifteen feet.
Coal acts like other dust. Some of it is
picked up on an eight-mile breeze but it will
not stay in suspension at that speed: double
the velocity to 1500 feet per minute and
most of it will stay up, though 2000 feet is
none too high for general work.
It is not good practice to send such a
current at such a speed into a furnace. The
combustion of carbon compounds is best
at high temperature ; the sooner it is over the
better, and it requires a perfect mixture.
A particle of coal speeding along parallel
with an air stream has no inducement to
mix with 10,000 air volume units, which it
must have for its combustion. Such stream
lines should be broken up.
A Burner
There are many ways of stirring things up.
In one case we let the stream make a sharp
turn with fair results: but more than one
turn is needed and such turns take up room.
One general rule may be stated: it is easier
to make the mixture (it must be done in
one-third second or less) if all those ten
thousand volumes are not put in at once.
Two, three, even five divisions are much
better if the quantities are great. A pail of
meal and water is better intermingled if the
meal is added in small quantities; time is
lost if all of both elements are brought to-
gether at once.
A device which is being used successfully to
perfect a mixture and at the same time reduce
high velocities is shown in Fig. 1. It consists
of a cast iron cylindrical box eight inches in
diameter with five openings beside its dis-
charge mouth. Either opening 5 or T is used
for coal and its primary air, or carrying air
(40 to 60 cubic feet per pound of dust).
Either X or Y is used for the combustion air
and sometimes air is admitted at the end U.
The first four of these openings are tangential,
causing the currents to take irregular spiral
forms, and they are used for short burning.
For an ordinary forge furnace, say five by
four feet, S, Y and U will be piped up. A fire
is started by using combustion air through Y
alone, for through its use a short complete
mixture can be dropped right upon burning
kindling, and so long as this arrangement is
preserved the high heat will be near the
tuyere, and perhaps twelve inches in front
of it. It sometimes happens that with short
work it is not necessary that a furnace be
hot all over and fuel will be saved if there be
a high local temperature only. If a complete
and uniform heat is wanted additional com-
bustion air is admitted at U and there is an
immediate change in the character of fire.
The flame is no longer local: the mixture is
not so good and burning calls for more
time. Coal that can find adequate air near
the tuyere burns there; other coal waits till
it finds air, and there is a long flame in
consequence. By manipulating the air valves
at Y and U the range of regulation is great
and it is possible to make a very long flame,
even thirty feet under certain conditions.
The same is true of an oil fire. If mixtures are
only poor enough and oil is sent from the
burner in chunks large enough, a flame of
great length is attainable; it is only requisite
that the fuel and air travel in parallel streams,
whatever the nature of a suspended fuel.
Such long flames are not economical; good
mixture gives good economy. It must be
remembered that the velocity of the stream
passing along the axis of the burner must not
be low enough to drop the coal, so a burner
SOME PROBLEMS IN BURNING POWDERED COAL
921
must not be too large if a short fire is wanted.
When two air streams (as at S and Y)
rotating in counter directions meet, the
rotation becomes nil and the axial speed
must be enough to keep the coal in suspension
and preserve the mixture already made.
It will be noted that the
rotary motion within this
burner is just the motion
used in a centrifugal sepa-
rator to draw moisture out
of steam, or in a dust col-
lector to separate air from
solids. In these devices
either the body diameter is
large enough to keep the
two elements apart, or
baffles are provided to trap
the heavier material. Then
there are separate and
guarded outlets for the two
components, all of which
are not true of the burner.
That the device does pro-
duce a mixture is shown in
its operation; for even
when openings S and X are
used, causing both sets of
air to swirl in the same
direction, the flame is only
about twenty-four inches
long, and as the combus-
tion air at A' is reduced and
the air at U increased, the
flame length is increased
and combustion becomes
slower, showing a less per-
fect mixture. Some of our
furnaces are piped in just
that way and though the
range is not so great it is
ample for most forging
work.
600 turns per minute, or more if required.
With so wide a speed control it is possible to
carry a fire that shows just a visible red : by a
simple movement of a rheostat handle this
same fire will spring up vigorously and shortly
give a heat high enough for any forge work.
Fig, 1. Elevation and Sectional Drawings of an 8-inch Powdered Coal Burner
A Feeder
While there are several designs of feeders
in use and no doubt many more are to be
invented, we have found that a simple screw
will answer every purpose. The feeder draws
coal from a supply tank and delivers it in
definite amounts to a cavity in which it can be
picked up by the primary or carrying air ; and
therefore more than one speed is required. In
the plant under consideration the feeder is
driven by a little motor which can turn at
1800 r.p.m., 600 r.p.m., or any intermediate
speed, and is geared down only once. We
therefore made a screw that will feed at 300 or
There is a feature of the plain screw feed
that makes it very convenient in many
situations; viz., it can stand a little back pres-
sure so that discharge distances may be long.
In the installation under consideration the
coal is being fed across a shop, that is,
the supply tank with its feeders and motors
is fixed to the shop wall, out of the way.
A two-inch pipe is led along underground
for 90 feet or more, then up to a furnace and
its burner. The distance could be much
greater, even a few hundred feet, and the
control would be just as convenient and exact
because the switch and rheostat are located
922
GENERAL ELECTRIC REVIEW
at the side of the furnace, and the operator
has no occasion to come over to the supply
tank. In all these long transmissions there
will be a little back pressure at the screw.
Primary air is introduced on the eductive
principle, using the fitting shown in Fig. 2.
Fig. 2.
The Special Pipe Tee in which the powdered coal is picked up
by the primary air
The resistances on the discharge side increase
with distance. If the distance is short, we
have a negative pressure in the pipe leading
from the end of the screw to the opening A,
see Fig. 2. Eight inches of vacuum, by water
column, is easily attainable. As the discharge
distance increases with addition of elbows
and crooks this vacuum falls and we may
have even five inches pressure. A plain screw
is little affected by these changes, for the
throat fit at A Fig. 4 is machined and gives a
certain force to the coal. We have, however,
so proportioned our long transmission that
static pressure is usually negative, say
one inch or so.
The screw and its feeder box are shown in
Figs. 3 and 4 respectively. While usually
only a small amount of power is needed to
turn the screw (it can be turned with the
finger fast enough to carry a moderate fire)
there are times when considerable power
is required. Normally the coal is light
and fluffy, but under certain conditions of
long standing coal can pack so tightly that
no mechanical device can move within it.
The screw is cut in a lathe
with spaces proportioned to the
quantity required. A 23^-in.
diameter screw, as shown, will
feed 700 pounds per hour, and
with slight modification much
more. The bottom of the thread
is tapered so that after the screw
has taken its bite the volume
increases as a threadful ad-
vances, and the flow to the pipe
is free and easy in consequence.
The weight of a cubic foot of
coal may be anything from 20 lb.
to 50 lb. As coal lies on a feeder
screw it will not reach 20 lb. per
foot. When delivered by a con-
veyor screw to a tank seven feet
deep and measured immediately
it weighs 31 Yi pounds per foot.
In 24 hours it will reach 35
pounds, and increases in density
till in six weeks without jarring,
it will weigh 38H pounds. Now
these changes will take place in
a container with smooth sides,
or in one with a diameter equal
to half its depth. In a piece of
6-in. vertical pipe 10 ft. 6 in.
long, it was found that there
was little settlement in two
months. The pressure in the
tanks, however, is computed at
35 pounds. Sometimes the coal flows as freely
as a liquid and will spread out its top surface
nearly level in the tank. At other times it
„„ ,<r2"P/tCh
7-*-
-/4". ^
* Bote om o f Thre ad
Topers From ThisPo/nt.
Fig. 3. The Feeder Screw
won't even flow down hill, though it always
moves freely enough unless it has stopped for
48 hours or longer.
This tendency to pack and clog is due to the
physical arrangement of the particles through
SOME PROBLEMS IN BURNING POWDERED COAL
923
Sect/on T/ircugh Y-Y
|« — 4 — H *, /
These Fits Are Babbitted.
Section Through r-Jf
Fig 4. The Feeder Box in which the feeder screw is located
settlement rather than to moisture. The
powder will absorb microscopic water, but
it cannot be made wet by throwing water
upon it. We tried to make a paste once by
using sticks to stir and squeeze the coal into
the water ; but it did not work. The only way
that we could make a mixture was to take a
little of each between thumb and finger and
knead the two together. After the game was
over we left our playthings in the sun. In a
day or so the water had evaporated, leaving
our coal clean and dry.
It isn't hard to dry the coal to one-half
per cent moisture or less, but there is always
some small portion that contains moisture
in excess. It is a little surprising to find an
eight-ton bin of coal that has been nicely
dried dripping with water twelve hours
afterwards; but it does so, and it is not an
uncommon thing to find a pulverizer frozen
Fig. 5.
A Front View of a Forging Furnace that uses
powdered coal for fuel
Fig. 6
View of a Forging Furnace similarly equipped
to that shown io Fig. 5
924
GENERAL ELECTRIC REVIEW
up with this water in the morning. The
source of such water is not hard to find. When
coal is in a dryer it is hot and so is its con-
tained air. The air is saturated with moisture
at the temperature of the dryer and when
the coal and air cool the moisture is precipi-
tated, and in cold weather makes its presence
felt. It thus appears that coal cannot be
made thoroughly dry through the agency of
heat.
A Furnace
A question often asked is: Can I use my
present oil furnace for a powdered coal
furnace? The answer is yes, in the average
case, though the writer believes it will pay to
rebuild a furnace when its fuel is changed.
As a rule two oil burners, if they be of the
If all gases are allowed to escape in this way,
the heat distribution is not perfect, and there-
fore we like a chimney vent at an appropriate
point. It is good practice to run this chimney
up through the roof over each furnace and to
cut into a 45 deg. Y to which the hood vent
is attached and in which an upward draft is
induced by the chimney draft. Figs. 5 and
6 are photographs of such connections. It
pays to provide a nicely fitted damper
which can be adjusted with precision: if
the damper works on a screw thread the
tips can be moved 1/50-inch, though such a
fine adjustment is not needed. It also pays
to preheat the combustion air. The saving in
fuel greatly exceeds that represented by the
heat imparted to this air. It was found that
a saving of 35 per cent was secured in one
Sect/oo&S
Jeet/o/j /*-A
Fig. 7 Fig. 8
Sectional Drawings of a Forging Furnace that burns powdered coal
atomizing type, are required on an average
furnace. An oil burner of the globular type
needs a combustion chamber of some sort.
A coal furnace needs but one burner and
calls for no combustion chamber. In every
other respect the coal furnace is more complex
than its oil counterpart. An oil fire makes
no visible smoke and there is little or no
odor from its products of combustion, so
there is no reason why there should be a
chimney or in many cases even a furnace
vent. Flame and hot gases can be brought
up to and passed out of the door, keeping
the fronts hot. A coal fire yields no black or
colored smoke, though the gases contain
some small particles of white ash, but it
does have a decided and disagreeable odor.
It is better then to provide a hood over the
furnace door, enveloping it, if heat is wanted
right at the door as it is in most forge work,
and this hood must have an outdoor vent.
case with air heated to 334 deg. C. while the
heat contained in the combustion air was
only 16 per cent of that in the coal. Only a
moderate air temperature was used, as it is
preferable to install only such surface as can
be readily cleaned, and the low temperature
prevents burning out the preheating surface.
It is good practice to allow 15 feet of surface
in a furnace that burns 100 pounds of coal
per hour, with an inside temperature of 1355
deg. C.
The preheater is made of 3-in. cast iron
soil pipe, six lengths being rusted into a header
at either end and placed beneath the hearth
in the path .of the waste gases.
Two vertical .-sections of a furnace in the
Schenectady Works are shown in Figs. 7 and S.
The hearth is 43 inches long and 24 inches
deep though this same, design is being used
for furnaces having twice the area.
(To be Continued)
925
particular voltages, it has been necessary to
broaden the voltage limits of lamp speci-
fications.
"Development work on the incandescent
lamp has been principally along the lines of
increasing the number of sizes of Mazda lamps
Domestic lnc<wdesce/if Lamp So/es
1307-1)14
A REVIEW OF THE N.E.L.A. LAMP COMMITTEE REPORT
By G. F. Morrison
Edison Lamp Works, Harrison, N. J.
The report of the lamp committee of the N.E.L.A. is always looked forward to with great interest by the
lighting industry. This year the committee has rendered a particularly interesting report and throughout
the year has kept the members of the electric lighting industry informed on developments and progress in
the incandescent lamp field. The increase in the number of gas filled lamps manufactured is significant as
showing the rapidity with which research work is leading to industrial results.- — Editor.
The comprehensive report presented at the
San Francisco Convention is an excellent
record of the present status of the incan-
descent lamp with relation to the central
station business. It is enhanced with numer-
ous illustrations, curves, diagrams and
tabulations, giving data not elsewhere avail-
able. As might be expected, in view of the
rapidly increasing use of the Mazda C lamps,
a considerable portion of the report is devoted
to their development and application, especial
attention being given to the question of
providing suitable fixture equipment. Besides
following out and bringing up to date the
report of last year, it contributes much new
and important information in line with the
broadening policy of the Committee.
The lamp sales for 1914 fell a little below
those of the preceding year, being slightly
less than 100,000,000. The trend toward the
use of the Mazda lamp continues to increase,
so that 70 per cent of all lamps sold were of
the Mazda type as against 56 per cent for
1913. In the same period, the sales of Gem
lamps decreased from 31 to 22 per cent and
the carbon from 12 to 7 per cent. Fig. 1.
The distribution of lamp sales among the
various sizes shows that about 41 per cent of
all multiple Mazda lamps were of the 25-watt
size or below; 27 per cent were of the 40-watt
size; 17 per cent were of the 60-watt size;
and 6 per cent were of the 100-watt size.
Notwithstanding the recent extensive use
of low wattage lamps, the average candle-
power of all incandescent lamps sold annually
during the last eight years has risen from
18 to 38.2, while the average wattage has only
fallen from 53 to 48. Especially during the
past year the high power lamps have been
influential in raising these averages.
The falling off in the sales of Gem lamps
and the irregularity of the demand as pre-
dicted last year by the Committee made it
seem necessary to warn the member com-
panies to anticipate their requirements, on
account of the impracticability of furnishing
such lamps in large quantities on short
notice. For a similar reason, together with
the tendency of the demand toward a few
I
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Fig. 1
available, embodying the gas-filled principle.
Lamps of this type will be referred to as
Mazda C lamps to distinguish them from
vacuum lamps. They are now made for
multiple service in the following sizes: 100,
200, 300, 400, 500, 750 and 1000 watts. All of
926
GENERAL ELECTRIC REVIEW
these lamps are primarily unit illuminants,
that is, it is customary to use them in indi-
vidual reflectors, and your Committee
emphasizes the importance of seeing to it,
so far as may be possible, that these lamps
are introduced and used as unit illuminants.
"The popularity of lamps embodying the
gas-filled principle is illustrated by the fact
that in the neighborhood of a million were
sold during 1914.
lamps designed for operation in an inverted
position (tipup) but such lamps must be
ordered specially for this purpose."
In order to secure the best result, it is
important that lamps be used in suitable
fixtures which for the high power lamps
should provide ample ventilation, and for
outdoor service protect the bulbs from
moisture. Rule No. 35 of the National
Electric Code prescribes the conditions to be
1907 1908 1909 '9i0 1911 15^ 1913 1914 1915
Fig. 2
Improvements in these lamps have been
principally along the lines of securing a more
uniform product * * * * .
"The principal change in their design has
been to adopt a new line of bulbs in all
standard sizes, with the exception of the low
candle-power street series. The new bulbs are
pear-shaped with extended glass necks * * * .
"It is customary to insert a mica disk
deflector between the stem and the filament
of this lamp, thereby deflecting hot gases
from the glass seals and base.
"The usual practice in the design of these
lamps is to construct them for but one
position of burning, namely, tipdown. Manu-
facturers are, however, in a position to supply
met by fixtures and installations. A list of
the principal types of fixtures and reflectors
indicates the classes of service for which
each is suited.
In connection with the greater economic
value of the Mazda C street series lamps over
the vacuum type or Mazda B, it should be
noted that the 60-c-p. Mazda C consumes
slightly less wattage than the 40-c-p. Mazda
B, and but little more than the 32-c-p. The
Committee recommends the policy, as gener-
ally adopted by the larger companies, of
substituting the 60-c-p. Mazda C for the
old 40-c-p. and 32-c-p. sizes and thus stand-
ardizing it as a minimum size. Likewise in
the higher powers it recommends replacing
A REVIEW OF THE N.E.L.A. LAMP COMMITTEE REPORT
927
the 80-c-p. with the 100-c-p. Mazda C, and
the 200-c-p. with the 250-c-p. Mazda C.
"Last year it was stated that the practice
of introducing chemicals to delay the dis-
coloration of the bulb of the Mazda B lamp
had been extended to include the 40- and
25-watt sizes. This practice has been still
further extended to include 20-, 15- and
10-watt lamps and has permitted the opera-
tion of all vacuum lamps at higher efficiencies
with improved maintained candle-power."
These improvements in quality have resulted
decreased 60 per cent and the cost of electric
light 85 per cent.
This economy, together with the increasing
range of sizes, not only makes it desirable to
intensify the use of incandescent lighting in
present fields, but opens up many new
applications which may be exploited with
profit to the central station. Some of the
important classes of lighting worthy of such
attention are the semi-indirect and indirect
lighting of large interiors, the lighting of
photographic studios, lighting of streets,
"*ilH
^^
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—-wort
i Per
CeyaM
tower
"£&»• c
'Li'/ecn
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^\
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Fig. 3. Curves showing Decrease -in Cost of Electric Light
in increases of from 7 to 10 per cent in the
efficiencies of sizes below 150 watts.
A table shows the improvements in
efficiency of each size of Mazda lamp since
its introduction, while a chart which is here
reproduced as Fig. 2 indicates the very
considerable price reductions which have
been made in the corresponding period. These
reflect the remarkable strides made in the
manufacture of lamps since the introduction
of the tungsten filament, both as to the
quality of lamps and the economy of manu-
facture. From Fig. 3 it will be seen that
since 1896 the cost of electric energy has
bridges, parks, etc., and the lighting of
outdoor areas for athletic events such as
tennis courts, court golf and trap shoot-
ing.
The new focusing type of Mazda C lamps
(concentrated filaments) also opens up new
uses for electric current. Prominent among
these are the flood lighting of building fronts,
billboards, etc., which are very desirable loads
to the central station on account of' their
excellent load factors. The focusing type
lamps are also used to advantage in stereop-
ticons, spot lights and small moving picture
machines.
928
GENERAL ELECTRIC REVIEW
In regard to lamp policy, the Committee
urges the member companies to maintain
supervision of the size, quality and rating
of lamps used on their circuits. This is
becoming more and more important, as
inferior tungsten filament lamps, both in
vacuum and gas-filled types, are making their
appearance on the market in increasing
numbers. Their use is likely to result in
unsatisfactory service and a disadvantage
to the lighting industry. Appended to the
report are the series of articles published
during the year in the Association Bulletin
under the auspices of the Lamp Committee.
PRACTICAL EXPERIENCE IN THE OPERATION OF
ELECTRICAL MACHINERY
Part XI (Xos. 54 to 56 ins.)
By E. C. Parham
Construction Department, General Electric Company
(54) FIELD CONNECTION ERROR
Single-phase repulsion-induction motors
van,* in the number and in the disposition
of their brushes according to the size of the
motor, according to the number of poles, and
according to whether the motor is reversible,
is of variable speed, or is of variable speed
and reversible also. Irrespective of the type,
every repulsion-induction motor has at least
two sets of brushes — one set of energy
brushes and one set of compensating brushes.
•Supply
Main Field
Comp.
'^Brushes
Energy Brushes
Fig. 1
On the constant-speed motors the energy
brushes are short-circuited within the motor
and the compensating brushes are connected
directly to the compensating field winding
which is an extra field winding, one purpose
of which is to limit the speed of the armature
at light loads. The speed limiting property
depends on the fact that an increase in
armature speed increases the e.m.f. available
at the compensating brushes, therefore the
compensating field current becomes stronger.
The circuits of a constant-speed repulsion-
induction motor are indicated in Fig. 1.
Since the rotation of the armature is due
to the current of the energy circuit, if that
circuit is opened, for example, by a poor
contact, the armature cannot rotate. Further-
more, since the speed is limited by the
compensating field, which concurs in direction
with the main field, if the compensating field
circuit is opened or is reversed not only will
the armature speed be higher for a given
load condition but the current will be corres-
pondingly high at all load values because
the counter e.m.f. of the armature will be
lower.
The full lines in the diagram indicate the
correct connection, the dotted line indicates
an incorrect connection that caused heating,
sparking, and high speed of a repulsion-
induction motor that was applied to driving
a printing machine. The trouble was caused
by the fact that the operator when reversing
the direction of rotation of the armature by
shifting all the brushes to the opposite
running mark, had not followed the instruc-
tions properly. He reversed the compensat-
ing field terminals correctly but instead of
fastening both of the field leads onto the
compensating brushes again, he connected
one of them to a compensating brush and the
other to an energy brush.
(55) MOTOR WOULD NOT START
When a motor fails to start on closing the
starter and there is no evidence of current
flowing, a "dead" line or an open-circuit is
suggested; if there is an evidence of current
flowing, a short-circuit or a wrong connection
is generally sought. In the case of a polyphase
OPERATION OF ELECTRICAL MACHINERY
929
motor, however, symptoms are not as well
defined because current may flow in one phase
and not in the others. If a polyphase motor
does not start but simply hums when voltage
is applied, it is reasonable to assume that only
one of its phases is energized.
An operator installed a three-phase induc-
tion motor to operate a "skull-cracker" in an
iron foundry. The motor ran continuously
but the skull-cracker was operated by means
of a clutch. On applying voltage for the first
time, the motor started but ran in the wrong
direction. Two of the stator leads were then
reversed, after which the motor just hummed
instead of starting. On throwing the compen-
sator to the running position, the fuses blew.
The renewal of the fuses and restoration of
the stator leads to their original connection
did not correct matters. On removing the
bottom and front of the compensator to look
at the contacts, it was noticed that one of the
three coils showed no evidence of heating.
The switch was then opened and a magneto
used for ringing from the fuses to the bottom
contacts 1, 2, 3, 4, 5 and 6. With the switch
on either side, the bell rang from fuses a
and b to contacts 2 and 3, respectively, but
fuse c would ring to contact 6 only when the
compensator switch was on the running side.
Supply
Start
Transformer
Fig. 2
The compensator was then disassembled and
a burned off flexible wire was located at the
place marked with a cross in Fig. 2. The
wire did not appear to be parted because its
insulation held the ends in line. Most of the
strands had been parted for a long time but
three of them showed recent burning. This
explained why the motor had started once
and why it could not be started again.
From the diagram it will be seen that the
2, 4 and 6 contacts rang to the fuses with the
compensator on the running side, because in
this position the starting wires to the bottom
fingers are by-passed by the paths that lead
through the fuses, the switch, the trans-
former taps, and the upper sections of the
coils.
(56) ADJUSTING SINGLE-PHASE MOTOR
CLUTCHES
On one very successful type of self-starting
single-phase induction motor, the armature
core is free to turn on the armature shaft up
to a certain predetermined speed, at which
value the centrifugal force causes clutch
fingers, that are integral with the core, to
engage a clutch shell that is integral with the
shaft. The shaft and its connected load are
then started and accelerated to practically
synchronous speed. The speed at which the
clutch members engage is adjustable by
means of springs that oppose the effort
caused by centrifugal force. The advantage
of this construction lies in the fact that the
limited torque afforded by split-phase starting
devices is not required to start the con-
nected load.
The clutch springs are usually so adjusted
as to permit the centrifugal force to overcome
the opposing clutch tension at about two-
thirds synchronous speed. At this speed
value, the momentum of the core together
with the rapidly increasing single-phase
synchronizing effort of the motor will be
sufficient to start the connected load and
bring it to speed, unless the connected load
has a great inertia such as that due to a fly-
wheel, for example. If under conditions of
great inertia or of low voltage the clutch is
adjusted to throw in too soon, the motor will
not have acquired sufficient synchronizing
power at the time that it is required to take
up the connected load. Under this condition
the core will either partially slow down or it
will stop entirely in accordance as to whether
the starter is on the starting notch or is on the
running notch. The obtaining of the correct
clutch adjustment for particular loads is a
matter of trial, adjustment and trial again.
The standard factory adjustments will cover
most of the operating conditions ordinarily
met, but occasionally the adjustments must
be modified to suit local special conditions.
930
GENERAL ELECTRIC REVIEW
IN MEMORIAM
DR. AND MRS. F. S. PEARSON
It is always difficult to write a befitting
eulogy of a great man whom we admire
and respect, and the task is harder when,
as in the case of Dr. Pearson, his activities
have extended back almost into another
generation, and his energy has been of
such a versatile nature as to lead him to
many widely distant fields of activities.
There are some few men whose energy and
genius seem to lead to their being considered
rather as citizens of the whole world than as
belonging to any one particular nation.
Such was the case with Dr. Pearson, for while
his early activities were confined largely to
the United States, latterly he undertook
many great schemes in foreign countries,
notably in Mexico, South America and Spain,
and he drew upon the financial resources of
England, France and Belgium to carry out
his many ambitious undertakings.
Dr. Pearson was first and foremost an
engineer in the fullest and best sense of the
word; he was a builder, a constructor, a man
who carried through great schemes to a suc-
cessful conclusion ; he was one who met many
different kinds of difficulties and obstacles,
both technical and financial, and overcame
them all. His whole life was spent in con-
verting the forces of nature to the useful
service of man.
Both Dr. and Mrs. Pearson were lost
in the most tragic of modern disasters —
the destruction of the Lusitania by a sub-
marine on the high seas on May 7, 1915 — a
disaster that shocked and horrified the whole
civilized world as none other has done in the
memory of man. It is not our intention,
though, to dwell upon this tragedy, but rather
to try to give our readers some conception
of the work, life and character of Dr. Pearson.
Perhaps the best way that we can accomplish
this purpose is to quote, in extenso, from
some of the addresses made by his friends
at the memorial service held in New York
on June 23, 1915.
On this occasion Dr. E. W. Rice, Jr., said:
I first made the acquaintance of Dr. Fred S.
Pearson over 25 years ago in connection with the
electrification of the West End Street Railway of
Boston.
I have a very distinct recollection of the strong
and altogether favorable impression which he
immediately made upon me. He was the engineer
of the Street Railway Company, and the Thomson-
Houston Company, with which I was connected,
furnished the electrical apparatus.
The problems presented were new, difficult and
without precedence for guidance. Courage, per-
severance, versatility and optimism were in constant
demand, the situation was frequently critical, but
Dr. Pearson's confidence in the ultimate success
of the enterprise never flagged for a single instant.
He had a ready solution for every difficulty, a
courage that was contagious, and optimism not
blind to immediate .shortcomings but nevertheless
full of the vision of the more perfect future.
He showed at this early date those qualities
which characterized his whole after life. While
tremendous energy was the dominant note in his
character, he was also patient, studious and practi-
cal, careful but bold, painstaking enough in details
which seemd important, yet possessed with a
breadth of view that encompassed the whole prob-
lem.
After the successful electrification of the street
car system of Boston he came to Brooklyn, and
as engineer was responsible for the introduction of
the electric street cars of that city, designing and
erecting in connection therewith what was then the
largest and most modern of electric power stations.
He then turned his attention to New York City.
The problem presented here was exceedingly
difficult because the overhead trolley was not
permitted. It was due to his courage and engineering
ability that the underground conduit or trolley was
brought into successful operation in this city; it
still remains practically as he left it.
In connection with this work in New York, he
designed and erected the 96th Street power house
of what was then the Metropolitan Street Railway
Company. This was the first of New York's mam-
moth power houses, and was at the time (1896) the
largest in the country, with a total generating
capacity of 70,000 horse power. It remained for
some years a model for the guidance of the rapidly
expanding industry.
During this period his services were in great
demand as consulting engineer for many electrical
enterprises in Providence, Toronto, Montreal,
Xiagara Falls, Winnipeg and other places.
His health failed after such tremendous exertions
and it was necessary to seek rest, but after a short
vacation he resumed his strenuous life. From this
time on his interest was largely in foreign countries.
In Mexico, he built up the great engineering
works which supply the City of Mexico with light
and power. In Sao Paulo, Brazil, he developed a
similar enterprise, and again as the result of his
labors in Rio de Janeiro, Brazil, it is said, that "in
place of several lines of mule cars, an antiquated
gas plant and a telephone service where one could
walk to the one he desired to talk with quicker than
telephone, Rio de Janeiro now enjoys the highest
type of modern electric railway service unexcelled
anywhere in the United States or Europe, an electric
lighting system which makes it the best lighted city
in the world, a new and modern gas plant and a
regular Bell telephone service which is now being
extended all over the United. States of Brazil."
IN MEMORIAM
931
Between frequent trips to Brazil and Mexico
he found time to plan and superintend the hydraulic
installation of the Electrical Development Company
at Niagara Falls, a plant of 160,000 horse power,
supplying electric light and power to the city of
Toronto 100 miles away.
His last great enterprise is located in Spain and
involves the building of works for the utilization
of the water power of the Ebro river and the supply
of such power to the city of Barcelona for the opera-
tion of electric lights, general power and the city
tramways. This great enterprise he had nearly
completed at the time when the war burst upon the
world and interrupted his work because of the
general dislocation of finances.
Dr. Pearson then returned to this city and we
were glad to renew our friendship of so many years.
I was again impressed by his splendid courage and
quiet defiance of misfortune. Anarchy in Mexico
had for the time paralyzed his great creation in
that country and the European war had forced a
sudden stoppage of the Barcelona enterprise, but
with his characteristic energy and ability he soon
succeeded in overcoming all obstacles and arranged
the necessary finances to give assurance that his
latest enterprise would soon go ahead to a final and
successful completion.
I have only mentioned a few of his achievements
in electrical engineering, but as is well known his
energy and activity were so great that he found
time to engineer and direct many other important
enterprises entirely outside the electrical field, such
as mining and railroading, lumbering and irrigation,
and as if these were not enough he found leisure
to indulge his love of nature by developing and
managing a beautiful estate of thousands of acres
in the hill country of western Massachusetts.
While Dr. Pearson was a loyal American he was
in every sense a citizen of the world; his work
kept him abroad much of the time and he was
equally at home in England and Spain, in Mexico
and Brazil, as in the United States.
The features of Dr. Pearson's personality, which
appealed to all those who met him, were his great
energy and activity, as ceaseless as the running
water of the many rivers he so loved to turn to
useful purposes; his thoroughness which permitted
no necessary detail to be neglected and which led
him to personally visit and study at first hand the
site of every water power or other engineering pro-
ject in which he was interested, no matter where
located. This was perhaps one of the reasons for his
success and the secret of the astounding amount of
work accomplished because it enabled him to go
ahead at full speed with that confidence which
follows a definite and accurate knowledge of the
road to be traveled.
He also possessed to an extraordinary degree a
mind capable not only of conceiving the largest
plans but the courage and optimism to put such
plans into execution and the ability to interest the
necessary financial assistance.
He was always leading his profession in the
demands which he made upon the manufacturers
for increase in size of engine, dynamo or trans-
former, for the highest practical efficiency, for the
highest operating pressure; in fact, he was always
pushing everything and everybody to the limit, and
yet his judgment was so well balanced that I cannot
remember a single instance of failure of any of his
engineering works in any important part. His work
was permanent and reliable, and eminently practical
and successful.
In a very real and literal sense his works are his
monuments; in the mountains of Brazil, on the
plateau of Mexico, at Necaxa, and on the Ebro
river in Spain, are solid concrete dams and electrical
power houses, great and permanent engineering
structures created by his genius and energy for the
perpetual service of man. It is said that Caesar
dammed the rivers of Spain for the purpose of war
to enable him to destroy his enemies; Pearson
dammed the same rivers for the purpose of peace,
to save life and to make it better worth living.
In the entire course of his busy life, in which he
had the most complicated business and engineering
relations with numberless men of many types,
professions and nationalities, and involving financial
obligations of millions of dollars, there was never
any question as to his absolute honesty and in-
tegrity, not only of word and deed but of that
uprightness of mind which permits no deception of
itself and which makes straight thinking and honest
dealing with others a matter of second nature.
I have tried very hard to keep my thoughts from
contemplating the tragic ending of this benefactor
of his own country and of the people of foreign
lands, but it is impossible, I cannot keep it out of
my mind. We, his friends, cannot helping thinking
of the frightful needless sacrifice of such a valuable
life, cut off in the prime of its vigor and usefulness.
He was actually engaged on an errand of peace when
he met his tragic fate. He was then on his way to
England to help complete arrangements which
would start anew the wheels of industry and give
employment to thousands of men.
It is impossible to think of his sacrifice and that
of the sweet and noble partner of his life, and those
other unoffending men, women and innocent babes
without feelings of horror.
If, as we hope, the aroused conscience of the
civilized world, acting through our country, succeeds
in restoring the practices of humane civilization,
then his sacrifice and that of so many others may
not have been wholly in vain.
Whatever may happen, however, we, his friends,
have the solace that although cut off in his prime,
Dr. Pearson had lived a great life, that this work
was so well done that the industries which he
established will live on, that many of his incom-
pleted plans will be taken up and continued by
others who have been stimulated by his example
and inspired by his personality. He will continue
to live in the hearts of his friends as long as they
live, and we may all take comfort and inspiration
from our belief that this world is and will continue
to be a better world as the result of his life and
work.
Mr. C. A. Coffin, who was unable to be
present at the service, communicated the
following tribute:
It is with a certain sad satisfaction that I am
able to send you my personal tribute to the memory
of my friend of many years, Dr. Fred S. Pearson.
It is with deep regret that I am unable to be present
at the memorial service in honor of him and his wife.
I came into close personal and business relations
with Dr. Pearson some thirty years ago, and during
all the intervening time I have never ceased to hold
him in high and affectionate regard. His ability,
his openness and frankness, his loyalty, his sim-
plicity and truth, his untiring industry and earnest-
ness, were striking attributes of a most unusual
932
GENERAL ELECTRIC REVIEW
character, which won for him universal esteem
and admiration.
In his untimely death, all those associated with
him must feel his loss as a personal sorrow. For
myself, it is as if a warm and cheerful light had been
extinguished, because of which the world in which
we move became darker. One of the finest spirits
in the brotherhood of men has been taken from us,
but we shall ever cherish his memory as an un-
common and lasting heritage.
Professor Elihu Thomson wrote as follows:
I can only say now that I always had the highest
esteem for Dr. Pearson. He was an example of a
very able engineer, of great courage, always ready
to act up to his convictions. He was such a man as
was needed in the early inception of street railway
electrification on a large scale, such as the West
End Street Railway system in Boston. He was
engaged in this work when we first met. His great
ability, altogether exceptional, and his personal
earnestness and integrity always impressed me.
His quiet modesty was not the least of his qualities.
Those who were privileged to know him as a friend
must deeply mourn his loss and deplore the circum-
stances which brought to an untimely end the
work of a great man; for that he was a truly great
man is shown simply by the list of activities in
which his talent was demanded.
He shrank from no task, however formidable,
which fell upon him and achieved remarkable
success due to hard work and unflinching devotion.
I am glad of the opportunity to testify to his great
worth but with all others of his friends deeply
mourn his loss.
Mr. W. B. Potter's tribute was:
Our lives are not unlike a road which, day by day,
we build into the wilderness of a far country. We
seek only to build, and only at the last call from
labor are our hands withdrawn — whither the road
leads and how constructed is a mark of the builder,
and its route and foundation are an inheritance
to those who follow after.
Dr. Pearson was a builder of roads and of men, a
pioneer in undertaking, an engineer of construction
and a master of opportunity.
His work will endure and his example long be
an inspiration to other workers in the world's
welfare. He brightened many of the world's dark
places and eased the weary travel of multitudes.
But he will no longer direct and guide, and why it
thus should be, only in the infinite wisdom of God
is the answer. He was, with all, a man among men
and with whom it was a privilege to be a friend.
The loss is more than ours, but to those of us who
knew Dr. Pearson, there is an intimate realization
of one who has gone before.
Professor William L. Hooper, who knew
Dr. Pearson from his early manhood gave
the following address:
It is my privilege to speak of Dr. Pearson as
one who knew him well during his early manhood
and who had watched his subsequent career with
keenest interest and with profound admiration.
We became friends in the Spring of 1883 when I
began to teach in, and he was to about graduate
from, Tufts College; and during the succeeding
three years, while he was Walker Special Instructor
in Mathematics, we taught and sometimes worked
together.
Even in his college days young Pearson displayed
that restless, tireless energy, that love of work for
work's sake, that has always seemed to me his
chief and distinguishing characteristic. Though,
of course, an excellent student, he was not content
to follow tamely the lead of his professors, but was
impelled to gambol by the wayside. First we saw
him absorbed in chemistry, then buried in
philosophy, and again delving into the mysteries of
Hamilton's quaternions and the higher mathe-
matics. And, strange to say, each thing that he
touched he seemed to absorb and master as though
endowed by nature with special aptitudes in that
one branch of learning. I have never known another
with Dr. Pearson's versatility of intellect.
As a teacher he is remembered by his former
pupils in various ways. To his more brilliant
students he was a delight and an inspiration; the
more slothful remember only an illuminated mist
that their dimmer vision could not penetrate. It
soon became apparent that the career of a college
professor, which some of us had predicted for him,
offered an entirely insufficient field for his super-
abundant activity; for before his term as Walker
Instructor had expired, he was already engaged in a
number of commercial enterprises. Then or shortly
afterwards he visited and investigated mining
enterprises in Texas and Brazil. He was one of the
founders of the Somerville Electric Light Company
in Massachusetts; he assisted in organizing com-
panies in Woburn, Massachusetts; Halifax, Nova
Scotia, and elsewhere.
The first field adequate for the display of Dr.
Pearson's genius was presented when Henry M.
Whitney having consolidated the various street
railway companies of Boston and vicinity, called
upon him in 1888 to take charge of the electrification
of the West End Street Railway. Hardly anyone
then, and few even now, can fully appreciate all
that was involved in that undertaking. It had been
shown that cars could be successfully propelled by
electric motors; in several places a few cars were
being so run; but a great system of electric traction
had as yet to be created. Among the problems he
met and solved in the West End were those of
adequate insulation for overhead construction,
better track construction and bonding, better
engines and larger generators, improved switchboard
equipment, and the prevention of electrolysis in
underground pipes and cables. Some years ago
the late George Westinghouse stated that the
specifications for the first large West End generators
marked an epoch in the development of the dynamo.
Mr. Whitney once said to me that in the electrifi-
cation of the' West End no difficulty ever arose, and
difficulties were the common experience, for which
Dr. Pearson did not soon devise an effective remedy.
Dr. Pearson found in the West End electrification
the crude beginnings of an experiment; he left it
with two large power houses well advanced in
construction and equipment, a thousand cars in
successful operation, and the plans for the complete
electrification of the road nearly finished.
As I have already said, cars had been run by
electricity before, but here was the first great system
of electric traction the world had ever seen and for
years afterwards the West End was the model for
all who sought to equip electric railways.
I leave to another better qualified than I the task
of speaking of Dr. Pearson's subsequent professional
IN MEMORIAM
933
career, but I cannot let pass this opportunity of
paying my tribute of affectionate admiration to the
characters of Dr. Pearson and his devoted wife.
With Mrs. Pearson I was never intimately
acquainted, but I knew her well enough to appreciate
that she was a loving and devoted wife, his constant
companion on his travels, watching over him and
guarding him as a mother does her child. To her
devotion and self sacrifice it seems to me the
Doctor owed the strength that enabled his not too
robust frame to be sustained under the strain of
his Herculean labors.
I have spoken of Dr. Pearson's indomitable
energy and his versatility of intellect. To these
must be added a wonderful power of imagination,
not merely the susceptive imagination of the poet or
the artist, though he had that too, but the construc-
tive, the creative imagination of the scientist.
This power of picturing in his mind a whole compli-
cated course of events and seeing clearly what the
ultimate outcome should be accounted for an
audacity of execution that frequently astounded
others. This power of imagination and audacity
in execution are well illustrated in the Necaxa
Hydraulic Development in Mexico. Who but a
Pearson could have seen in the brooks of Northern
Puebla the possibility of a great power generation?
Who but he would have had the courage to under-
take its realization?
One of the qualities that most endeared the
Doctor to others was his simple, kindly manner and
entire absence of ostentation. He was always
ready to receive a suggestion and if that suggestion
seemed to him to possess merit he was ready to
adopt it. Coupled with this kindly disposition was
an almost too ready confidence in the faith, good
intentions and ability of others. This confidence
generally was well bestowed, but I have sometimes
thought that had it always been deserved the
Doctor's troubles and perplexities would have been
reduced. Like a thread of gold through a fabric
of sober hue ran a keen sense of Yankee humor,
which sometimes even in the midst of grave and
mighty transactions would set the table in a roar.
His humor, however, was never low, never vicious;
it left no sting.
To Dr. Pearson's untiring energy and impartial
appreciation, to his tremendous grasp of principles
and mastery of details, to his wonderful memory
and vivid imagination, to his versatility, his kindly
disposition, and his faith in others were due the
immediate source of his successes, the unswerving
loyalty and devotion of his staff. Without such
loyalty and devotion it would have been impossible
for any man to have conducted such great and
widely scattered enterprises.
Dr. Pearson's name will always occupy a high
place in the history of engineering. One of the
world's great engineers has said of him, and still
another has said to me, that Dr. Fred Stark Pearson
was the world's greatest engineer.
We believe that the above tributes to
Dr. Pearson's memory by some few of his
many friends and admirers express better
than anything that we could write the
admiration and affection with which he was
esteemed, and give a better idea of his genius
and of his work than any short compilation
that we might make from them. But in
concluding there is one thought which we
wish to express — that it is upon just such men
as Dr. Pearson, who have their genius
fortified with courage and indefatigable
energy, that the progress of nations depends —
it is by such men that empires have been
founded, and we feel that we, one and all of
us, benefit by their work. Dr. Pearson was
a great American — and America mourns his
loss, as does the rest of the civilized world
that knew him through his works.
934
GENERAL ELECTRIC REVIEW
FROM THE CONSULTING ENGINEERING DEPARTMENT OF THE
GENERAL ELECTRIC COMPANY
HIGH FREQUENCY
. The term "high frequency" is at present
very loosely used; under it are generally
included high frequency voltage from an alter-
nator, oscillations with varying unknown
damping factors and train frequencies, steep
wave-front impulses of various unknown
shapes, etc. The effects of these on insulation
are naturally not the same. There are, conse-
quently, many apparent discrepancies result-
ing from the "same" cause — "high fre-
quency." In "high-frequency" tests the
wave shape has not been exactly known.
In the following table is a comparison of
the breakdown values of oiled pressboard
insulation for known continuously applied
and transient voltages.
The same general relative effects also occur
in air and oil. Such data has already been
given.| Oil, and especially air, are however
not affected to as great an extent by
continuously applied high frequency. The
total range in puncture voltage in the data
given is 10 to 1. By reducing the damping
and increasing the train frequency, the effect
of oscillatory voltage may be made to
approach that due to high frequency. At high
frequency the losses are very great and
puncture results from heating or even burning.
The high puncture voltage for the impulse
is due to the limited time of application.
The effect of impulse voltages higher than
the 60-cycle puncture voltage is cumulative;
each one locally "cracks" or "shatters" the
BREAKDOWN VALUES OF OILED PRESSBOARD
60 CYCLES
KV. (MAXIMUM)
Time of Application
high frequency
(alternator)
90.000 CYCLES
(KV. MAXIMUM)
Time of Application
DAMPED OSCILLATION
200,000 CYCLES
(train frequency
120 per second)
(kv. maximum)
Time of Application
SINGLE IMPULSE
CORRESPONDING TO
SINGLE HALF CYCLE
OF 200.000 CYCLE
SINE WAVE Thickness
(KV. MAXIMUM) Qm
Time of Application
Rapidly One
* App. Minute
Rapidly
App.
One
Minute
Rapidly
App.
One
Minute
Single
Impulse
89 87
200 185
24
30
18
20
95
210
73
120
180 0.25
0.50
* Brought rapidly up to breakdown value in a few seconds.
An examination of these data shows that
the impulse puncture voltage is approximately
double the 60-cycle puncture voltage, while
the high-frequency (alternator) puncture
voltage is only about 30 per cent of the
60-cycle voltage. These data are sufficient to
emphasize the importance of knowing the
exact conditions under which tests are made.
t A.I.E.E.. June. 1913 — Discussion by author at Detroit.
F. W. Peek. Jr. — "The Law of Corona and Spark-over in
Oil." General Electric Review. August. 1915.
F. W. Peek, 'Jr. — " Dielectric Phenomena in High-Voltage
Engineering."
insulation. The puncture voltage may be
180 kv. for one impulse and 95 kv. for a
thousand impulses. This, to a certain extent,
is shown in the table above by the single
impulse puncture voltage and the damped
oscillation puncture voltage. The damping
is so high that the oscillation roughly repre-
sents a single impulse. There were approxi-
mately 1000 oscillations in the "rapidly
applied" damped oscillation test; the damp-
ing and train frequency were such that appre-
ciable heating did not result.
F. W. Peek, Jr.
935
QUESTION AND ANSWER SECTION
The purpose of this department of the Review is two-fold.
First, it enables all subscribers to avail themselves of the consulting service of a highly specialized
corps of engineering experts, or of such other authority as the problem may require. This service provides
for answers by mail with as little delay as possible of such questions as come within the scope of the Review.
Second, it publishes for the benefit of all Review readers questions and answers of general interest
and of educational value. When the original question deals with only one phase of an interesting subject,
the editor may feel warranted in discussing allied questions so as to provide a more complete treatment
of the whole subject.
To avoid the possibility of an incorrect or incomplete answer, the querist should be particularly careful to
include sufficient data to permit of an intelligent understanding of the situation. Address letters of inquiry to
the Editor, Question and Answer Section, General Electric Review, Schenectady, New York.
REACTANCE COILS: PRACTICABILITY FOR
SEGREGATING TROUBLE
(146) The accompanying "one-line" diagram
(Fig. 1) represents the layout of the alternating-
current distributing circuits of a direct-current
trolley railway system. Two nominally indepen-
dent high-tension lines connect the stations.
If a short circuit takes place on one of these lines,
say on line No. 1 at y-z (1) it is found that all the
connected lines feed into the fault, which opens
all the breakers back to the main station. Could
not reactance coils be designed so that, when
placed one in each station bus between the
tapping points of lines No. 1 and No. 2, (at the
points marked - X-), they would prevent the good
line from feeding sufficient current into the faulty
one to cause trouble? If such an installation is
possible, the stations, in the event of a short
circuit crippling one line, could continue to draw
power from the other line which might suffice
until the damaged line could be placed in service
again.
Commenting upon the proposed scheme of insert-
ing reactance coils in the bus at the generating
station and at each substation, it should first be
said that such reactances could be arranged to take
care of the conditions mentioned. That is, short
circuits in certain lines could be prevented from
affecting lines in tandem with them, which are
arranged on the other side of the bus reactance.
U-U-(t)
(T-Xd)
bus at both ends of the reactances are liable to
fall out of step.
(3) The system as a whole will be benefited
but very little by having short circuits paralyze
one side of the system all the way back to the main
station, even if the other side is left in good working
order.
Continuity of service, as it is understood at the
present time, demands that a disturbance of any
one line be localized and that only the line in trouble
be cut out (this without affecting any of the other
lines either in parallel or in series with it).
The whole situation is one that should be met not
by the introduction of additional new devices, such
as reactances, but by a change in existing arrange-
ments. The selection and distribution of relays
on the various transmission lines, as described,
denote rather an old-fashioned practice. Un-
fortunately, in the past, very little attention
was frequently given to the selection of relays, with
the result that it was impossible in a great many
cases to localize trouble and confine it to its own
circuit. Instead of disturbances being limited to
the circuit of the line in which they started, they
were not prevented from running back throughout
the whole network and opening up circuit-breaker
after circuit-breaker, through which they passed
on their way to the main source of power. Only
recently has there been developed a regular fine
art in diagnosing the characteristic needs of each
x-yd)
Substation
Main Station
Substation
Fig. 1
Y Z
Substation Substation
R = Rotary Converter; G = Generator; -0-0- =Bus Switch; - X- Proposed Reactance.
Transmission lines No. 1 B. and S., three-phase. Y-connected, neutral grounded.
Lines u-v (1) and (2) are protected at U by instantaneous relay on middle leg only.
Lines u-v (1) and (2) are protected at V by time-limit relay on all three legs.
Lines v-x (1) and (2> are protected at V by time limit relay on all three legs.
Lines v-x (1) and (2) are protected at X by instantaneous relay on middle leg only.
Lines x-y (1) and (2) are protected at A' by instantaneous relay on all three legs.
Lines x-y (1) and (2) are protected at Y by instantaneous relay on middle leg only.
Lines y-z (1) and (2) are protected at Y by instantaneous relay on all three legs.
Lines y-z (1) and (2) are protected at Z by instantaneous relay on middle leg only.
However, the use of reactances has the following
objections:
(1) Considerable expense.
(2) Bus reactances always have the disadvan-
tage that synchronous apparatus connected to the
individual circuit in order to fit it with relays
sympathetic only to those troubles starting within
their own radius, and not to be affected by
outside disturbances, no matter how near nor
how great.
936
GENERAL ELECTRIC REVIEW
It is easy enough to equip a power system such
as that described with a line of relays, which will
combine reliability of operation with dependable
selective action, s:> that the trouble referred to will
be eliminated; that is, to prevent short circuits
from going back to the main station and throwing
out of commission every station between it and the
seat of the trouble. The main features of such a
scheme would be to employ reverse-power relays
at the incoming ends and selective time-limit relays
at the outgoing ends of the lines, the time element
increasing the nearer the relays are to the main
station. DB-
HARMONICS: DEFINITION AND TEST
(147) What is a harmonic current?
What designates it as being of the first, second,
or third, etc., degree?
How can its presence be detected?
" A harmonic current (or harmonic electromotive
force) is a current the value of which, at each
instant of time, is proportional to the sine or the
cosine of an angle that is increasing at a constant
rate."* In practical work, an alternating voltage or
current is seldom a simple harmonic function of
time for it contains one or more of the so-called
"higher harmonics." In fact, an alternating wave of
even very irregular shape may be resolved into
several component waves which act according to
the harmonic law. The wave having the greatest
length (lowest frequency) is generally called the
"fundamental" or "first harmonic," and all the
others are referred to it. A wave having a periodicity
or frequency twice as great as the fundamental is
called the "second harmonic"; one having a fre-
quency three times as great is the "third har-
monic," etc.
A simple means of obtaining an indication of the
presence or the absence of higher harmonics in an
alternating voltage wave is to place an electrostatic
condenser of accurately known capacity in the
circuit and measure its charging current. If the
measured value is greater than that calculated
from the formula
Current =2 X frequency X capacity Xe.m.f .
it can be safely assumed that the voltage wave
contains harmonics higher than the fundamental
frequency.
The best method of testing waves for higher
harmonics (although somewhat more elaborate
than that just described) is based upon the use of
an oscillograph. This method, in addition to
furnishing positive and accurate data, possesses
the following advantages over the condenser method;
it is equally applicable to examining current waves;
and, besides merely indicating the presence or the
absence of higher harmonics, it permits the number
and degree of all the harmonic waves that may be
present to be determined. The scheme consists of
taking an oscillogram of the wave, enlarging the
photograph, and subjecting it to some method of
analysis. There are several of these methods, a
simple one being described in Bedell's "Direct and
Alternating Current Manual," Chapter 11. Another
is the so-called "point-to-point" method. This
and other methods of wave analysis are described
in Karapetoff's "Experimental Electrical Engineer-
ing," Vol. II, Chapter 31. S.T.
* From "Elements of Electrical Engineering" by Franklin
and Esty.
CABLES: CARRYING CAPACITY
1 148 We have an underground, 60-cycle, 6600-
volt, three-phase line 85 feet long, between
generators and their oil switches made up of
nine, 500,000 cir. mil, cambric-insulated, lead-
covered cables laid in groups of three in fiber
ducts. The three cables of each group are con-
nected in 'parallel with each other, comprising
one leg of the three-phase line, and are drawn
into one duct It was impossible to use three
equivalent single-conductor cables because of
sharp bends in the ducts. The current per phase
varies from 1000 to 1250 amperes and is often
higher for short periods.
(a) What is the approximate cable loss?
(b) What would be a reasonable temperature
rise to expect?
(c) What is the eddy current loss in the lead
covering of the cables?
(d) Would the loss be increased or decreased if
the cables were reconnected so as to have a
cable pe: phase in each duct, i.e., have three-
phase current in each duct?
(e) Assuming it to have been possible to have
used only three single-conductor cables I instead
of nine, three per phase) of equivalent section
and with the same thickness of lead sheath
would the loss have been decreased?
(a) The loss would be approximately 10 watts
per duct foot.
(b) The loss given in (a) would be expected to
cause a rise in the cables of 30 to 40 deg. C. above the
temperature of the floor or surrounding earth.
(c) We know of no recent tests that have been
made of the eddy-current loss in the lead sheath of
alternating-current cables. Early ones have shown,
however, that it is small compared to the PR loss,
and in single-conductor cables carrying 60-cycle
alternating current (when the lead on the different
legs of the circuit is insulated so that there are no
cross currents between the sheaths) the lead loss
is about 10 per cent of the I2R loss.
(d) The loss would be greater.
(e) It is doubtful if alteration in the arrangement
of the lead covering would cause any further change
in the losses than to slightly increase the skin effect
due to the greater diameter of the cable. W.S.C
AN OMISSION
Through oversight we failed to give credit to the
American Institute of Electrical Engineers for the
article, The Contact System of the Butte, Anaconda
and Pacific Railway System, by J. B. Cox, published
in our August issue. This was a paper presented at
the Annual Convention of the A.I.E.E., Deer Park,
Md., June 29, 1915.
INSERTION
July Review, The Periodic Law, page 618. Following third
paragraph read: We shall consider the thorium series as typical
of the three series. The atom of thorium disintegrates with the
expulsion of an alpha <„> particle and yields Mesothormm L
The radiation emitted during the transition from Mesothormm
I to II is extremely weak; but a study of the properties of the
other members of the series leads to the conclusion that these
radiations are most probably beta (0) particles of very low
penetrating power.
1V
General Electric Review
Manager, M. P. RICE
A MONTHLY MAGAZINE FOR ENGINEERS
Editor, JOHN R. HEWETT
Associate Editor, B. M. EOFF
Assistant Editor, E. C. SANDERS
Subscription Rates: United States and Mexico, $2.00 per year; Canada, $2.25 per year; Foreign, $2.50 per year; payable in
advance. Remit by post-office or express money orders, bank checks or drafts, made payable to the General Electric Review,
Schenectady, N. Y.
Entered as second-class matter, March 26, 1912, at the post-office at Schenectady, N. Y., under the Act of March, 1879.
VOL. XVIII, No. 10
Copyright, 19ir,
by General Electric Company
October, 1915
CONTENTS
Frontispiece
Editorial : The Paths of Progress
The New Advanced Course in Electrical Engineering at Columbia University
By W. I. Slichter
Power Consumption of Railway Motors
* By H. L. Andrews and J. C. Thirlwall
The Kinetic Theory of Gases, Part I
By Dr. Saul Dushman
Some Problems in Burning Powdered Coal, Part II ... .
By Arthur S. Mann
The Theory of Lubrication, Part I. ...
By L. Ubbelohde
Translated from Petroleum by Helen R. Hosmer
Relation Between Car Operation and Power Consumption
By J. F. Layng
Automatic Railway Substations
By Cassius M. Davis
Protection and Control of Industrial Electric Power ....
By Dr. Charles P. Steinmetz
Sprague-General Electric PC Control .
By C. J. Axtell
General Notes on Grounding ... ....
By H. M. Wolf
The Volume Resistivity and Surface Resistivity of Insulating Materials
By Harvey L. Curtis, Ph. D.
Water Rheostats ....
By N. L. Rea
Practical Experience in the Operation of Electrical Machinery, Part XII
Crane Troubles; Motor Stopped and Reversed; Unstable Voltage
By E. C. Parham
History of the Schenectady Section of the A. I.E. E
By S. M. Crego
From the Consulting Engineering Department of the General Electric Company
Page
938
939
940
944
. 952
959
966
973
976
979
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996
1001
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1006
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THE PATHS OF PROGRESS
In the issue of the Review which appears
about the time that the American Electric
Railway Association hold their annual con-
vention we usually try to publish some
material that will be of special interest to
electric railway men. So in this issue we
publish several articles on railway subjects,
one of which is written to show the pos-
sibilities of securing greater economies by
studying every detail which enters into
schedule making and the proper selection of
equipment. Such a study is timely. Electric
railways in common with all other public
sendees are finding it increasingly harder
to balance the ratio between receipts and
expenditures in a manner that will give
satisfaction to the stock holders. With the
constantly increasing demands of the public
for better, and incidentally more expensive
service, the earning power of the railways is
being reduced rather than increased and at
the same time, through too numerous regula-
tions, the responsibilities of the operating com-
panies are being enlarged rather than curtailed.
During the past year the electric railways
throughout the country have had to face the
jitney problem which has materially added to
their embarrassment, and while some relief
may possibly be looked for from legislation —
which should protect as well as regulate — the
problem of lost traffic caused by privately
owned cars other than jitneys is more likely
to increase than to decrease.
In addition to these problems it must be
borne in mind that all, or almost all railways
are operating under unfavorable conditions.
They have to provide facilities that could be
operated profitably if the load were uniform
over the entire 24 hours, but in most instances
conditions compel them to operate at a very
poor load factor. Handicapped by such
conditions, profitable operation, if possible at
all, is only to be attained by a scientific study
of every factor entering into the industry.
Three main factors enter into every
industry — labor, energy and material. The
cost of labor is steadily increasing and for
many reasons it is not susceptible of the same
close regulation as the other two factors.
The cost of electrical energy has steadily
decreased during the last quarter century.
For these reasons it is profitable to sub-
stitute electrical energy for human energy
wherever possible on a railway system and to
adopt labor saving devices wherever such
are possible consistent with safety. That
this factor is recognized is evident by the very
extensive adoption of electrical apparatus in
railroad shops, car barns, etc.
The third factor, material, which among
many other items in railway undertakings
includes powerhouse, substation and car equip-
ments, has also been considerably reduced in
price during recent years; and coincident
with this decrease in cost there have been
far reaching improvements in efficiency and
adaptability to service requirements.
The manufacturers of electrical apparatus
and the operators of electric railways jointly
have done wonders in producing cheap
transportation, and undoubtedly improve-
ments in apparatus and economies in operat-
ing methods will be effected in the future as
they have been in the past ; but it would seem
that there must be some limit as to how much
transportation can be sold at a profit to the
public for a nickel.
The operating companies and the manu-
facturers have called to their aid in the fight
for the production of cheaper and ever cheaper
transportation all that engineering skill and
a scientific knowledge can provide, but on
the last analysis there must be some limit
to the character as well as to the amount of
service that can be given for a nickel. When
this limit has been reached it seems only
reasonable to suppose that the public will
have to pay more for the transportation they
are receiving, and whether the operating
companies will earn more substantial returns
by being permitted to institute a zone system
of fares or some such scheme must be left for
the future to determine.
940
GENERAL ELECTRIC REVIEW
THE NEW ADVANCED COURSE IN ELECTRICAL ENGINEERING
AT COLUMBIA UNIVERSITY
By W. I. Slichter
Head of Department of Electrical Engineering, Columbia University
As an answer to the mooted question, "How many years are required to furnish the most serviceable
college engineering education?" Columbia University is about to make a departure from the previouslv
existing four-year standard. The reason for this change has been the conclusion on the part of the management
that the average four-year course, because of an insufficiency of time, does not allow of following a curriculum
that is well balanced between cultural and technical studies. The tendency has ever been to minimize the
time devoted to the study of broad cultural subjects and to utilize this for the further pursuit of specialized
technical subjects. — Editor.
In September of this year all the engineering
courses at Columbia University will be placed
on a graduate basis, that is, will require a
college course before admission. This is the
first instance in this country of an educational
institution putting its engineering work on a
graduate basis; but in making this change
the engineering school is only following the
example of the schools of Law and Medicine.
Thus the three professional schools at
Columbia — law, medicine and engineering
are placed on the same basis.
The Engineering School at Columbia, being
a part of a large university having a very
large teaching staff including specialists and
authorities in almost every branch of human
knowledge, has an advantage in intellectual
resources not possessed by independent tech-
nical schools which only teach engineering
subjects. To make the best use of these
resources the faculty of Columbia has
arranged the new advanced courses in
engineering with the object of furnishing a
training which will produce engineers of
broad and liberal education, capable of
filling the highest positions in the professions
and in society.
The system of instruction in engineering
in the technical schools of this country has
for many years past consisted uniformly of
four years of technical training beginning
immediately upon the student's completion
of a high school course. It is attempted in
these four years to give the prospective
engineers a reasonable amount of general or
cultural education, such as English and
another modern language, philosophy,
political economy and as much science and
professional training as the time allows.
Some institutions realized that it was
impossible to accomplish much in the pro-
fessional line if the general subjects were
given as completely as they should be, and
have recognized this by giving only a
bachelor's degree, and not the professional
degree. Others have included a more thorough
technical training and given a professional
degree, but it has been pretty generally
recognized that these graduates were lacking
in some very important qualifications, particu-
larly the ability to express their ideas in
speech and writing in a clear and forceful
manner, and partly in the broad attitude of
mind which comes from a good liberal
education in the humanities.
The professions of law and medicine have
had the same experience and the more
important law and medical schools have
recognized this and met the difficulty by
requiring a college education and a bachelor's
degree for admission to the professional school.
This broad qualification (a bachelor's degree)
does very well as a preliminary for the
education of a lawyer or a doctor, as all that
is required is a mental training that has
developed the intellectual powers, but as a
preparation for an engineering career this
preliminary work must include a definite
amount of training in mathematics, physics
and chemistry, which are as necessary to the
engineer as tools are necessary to a carpenter
or a mechanic.
For this reason the preliminary collegiate
education of those men anticipating a
graduate engineering course must be carefully
planned to include a proper amount of these
fundamentals and a reasonable amount of
cultural courses such as English, history,
philosophy, economics and foreign languages
as given in most colleges. The equivalent
of three years of this work is specified for
entrance to the Columbia School of Engi-
neering, and whether this is increased to
cover the requirements for a bachelor's
degree depends upon the tastes or resources
of the student.
The course, therefore, consists of three
years spent in any college giving these
fundamental scientific subjects (and most
colleges offer these courses but do not require
them) and three years professional work at
Columbia. During these six years it is
possible to obtain by extra work (as at
Columbia College) both the B.S. degree and
the E.E. degree, although the former is
not necessary.
ELECTRICAL ENGINEERING AT COLUMBIA UNIVERSITY
941
By this arrangement a student is expected
to begin his preparation for professional
study at an age one or two years earlier than
he would for the standard four year technical
course, and as a result he will finish possibly
at the same age or one year later than with
the old four year course. Thus the change
from four years to six years does not mean
that the student will be two years older
when he graduates but that the School of
Engineering will endeavor to direct his training
two years earlier. Foreconomy of the student's
time it is desirable that he should decide on the
scientific career earlier in life, although he need
not decide any earlier on which branch of engi-
neering he desires to follow.
Object of the Course
The objects of the advanced professional
course are: First, by means of a study of
applied science to cultivate judgment in the
student by teaching him to analyze problems
and reason from cause to effect; second, to
give a broad engineering education which
will be of value in any line of activity whether
electrical or other branch of engineering or
even in commercial work; and third, to give
the student a preparation in the specialized
knowledge of one profession in order that he
may immediately understand practices and
methods, and thus the sooner be of value to
an employer, and eventually master the more
complex problems which would qualify him
as a specialist in Electrical Engineering.
Preparation for the Course
The requirements for entrance into the
first year of the new advanced course are
briefly as follows :
Mathematics. Algebra through determi-
nants, complex numbers, the theory of
equations and partial fractions. Analytical
Geometry through conic sections and the
elements of three dimensional geometry.
Calculus, differential and integral.
Physics. Heat, Light, Electricity and
Magnetism, with one year of laboratory
work. Mechanics, through harmonic motion,
resonance, hydrostatics and coplanar statics.
Chemistry. General chemistry and quali-
tative analysis.
Drafting. Engineering drafting, topography
and descriptive geometry.
Surveying. Theory of plane surveying and
triangulation.
General Cultural. English, History, Philoso-
phy, Economics, Mineralogy and two modern
languages.
A special course has been arranged in
Columbia College in which a student may
complete this work in three years after
leaving high school. On the completion of a
small amount of extra work (about 15 per
cent more in time) in electives, such as
advanced English or modern languages, the
student will obtain the degree of B.S. This
extra work may be done any time during the
six years and the first year of the advanced
course is arranged so that he may have an
opportunity then.
Description of the Professional Course
The advanced course in Electrical Engineer-
ing comprises, in addition to the electrical
subjects, a group of studies in civil, mechani-
cal and chemical engineering and metallurgy,
in order that the graduate will be primarily
an all-round broad engineer, and along with
this general engineering education a little
less than half the total time is devoted to
purely electrical subjects. The student of
electrical engineering will spend 46 per cent
of his working time for three years on elec-
trical subjects, 27 per cent on mechanical
engineering subjects, 10 per cent on chemistry,
9 per cent on physics, and the balance, 18
per cent, on miscellaneous subjects.
The courses in electrical engineering, in
accordance with the established policy of the
department, are designed to teach the
principles rather than the details. They may
be divided into three general classes, theoret-
ical, technical and practical. The theoretical
courses are given mostly by the Department
of Electro Mechanics of which Dr. M. I.
Pupin is the head. These courses give the
student an insight into the application of
mathematics to the fundamental principles
of electrical phenomena. These courses are
usually the most difficult for the student but
are of the greatest importance as they are
not easily acquired after leaving college.
There is at least one of these courses in each
term throughout the whole three years.
Closely in parallel with the theoretical
courses are the technical courses which point
out the application of the principles laid
down in the theoretical courses and show the
use of those principles. They are intended
to familiarize the student with the terms,
practices, instruments and appliances 'of the
profession by a description of the apparatus,
a discussion of their principles and a descrip-
tion of their operating characteristics and
applications. Problems are given in these
courses which involve a concrete application
942
GENERAL ELECTRIC REVIEW
View in the Direct Current Machine Laboratory at Columbia University
View in Standardizing and Instrument Laboratory at Columbia University
ELECTRICAL ENGINEERING AT COLUMBIA UNIVERSITY
943
of the principles learned. Of this class of
courses are electrical machinery in the first
graduate year, alternating current engineering
and electrical communication in the second
year, and alternating current machinery,
applications of electric motors and electric-
railways in the final year.
The practical courses are those of the
laboratory and drafting room which are in
their chronological sequence: direct current
laboratory, design of direct current machinery,
standardizing laboratory, photometric labor-
atory, alternating current laboratory and
design of alternating current machinery.
These courses are always preceded by a
preliminary lecture and are arranged in
parallel with lecture courses treating the
same subjects in detail. Among the various
experiments performed and investigations
undertaken in these courses are the following
which are of more than ordinary interest:
Testing and location of faults on a generator;
complete tests on a railway motor equipment ;
parallel operation of alternating current
generators as operated in power stations,
including measurement of all variables such
as circulating current, power-factor and phase
shift; complete tests of polyphase circuits,
including the study and measurement of
upper harmonic currents and voltages in
various connections; practical experience in
the use of curve-tracing apparatus, such as
the ondograph and oscillograph for the
study of transient phenomena in alternating
and direct current circuits; adjustment of
radio telegraphy apparatus; calibration and
standardization of instruments; measurement
of the distribution of light and the economy
of different forms of lamps; the design of a
direct current generator and motor and of an
alternating current generator, motor and
transformer. These practical courses serve
to keep up the students' interest in the
theoretical courses as well as to teach their
own particular lessons.
In addition provision is made for each
student to spend eight weeks during one
summer at actual work in the shops of one
of several large manufacturing concerns
with whom arrangements have been made.
Here the student will obtain a practical
experience of great value and his time will be
efficiently used as each group will be under
the careful supervision of an instructor
assigned to the purpose.
The Department of Electrical Engineering
of Columbia acts as electrical laboratories
and consulting engineer to the government
View in the Alternating Current Machine Laboratory at Columbia University
944
GENERAL ELECTRIC REVIEW
of the City of New York, which involves the
investigation of many live questions and the
testing of many new pieces of apparatus.
This gives students a touch with the actual
work of the profession while they are still
at their studies.
Columbia has granted the degree of E.E.
to 394 men in the 25 years that that degree
has been granted. Of these many have of
their own accord availed themselves of an
optional seven year course, comprising three
years in the college and four years in the
engineering school for which they were
granted both the Bachelor's and Engineer's
degrees. These men have generally shown
a marked superiority over the regular four
year men and this noticeable difference has
been in part the reason for the change about
to go into effect.
For the past two years a graduate course
in electrical and mechanical engineering has
been given at Columbia to officers of the U. S.
Navy. The men were assigned to this course
by the Navy Department after graduation
from Annapolis and five or six years active
service at sea. These classes have averaged
about eighteen men a year and the men
chosen were those who had given evidence
of a particular fitness for and interest in the
engineering side of naval work.
POWER CONSUMPTION OF RAILWAY MOTORS
By H. L. Andrews and J. C. Thirlwall
Railway and Traction Engineering Department, General Electric Company
The authors deal with a subject that is of great importance to all those interested in operating electric
railways. They show that operating economies may be secured by selecting the equipment best suited to the
service and by designing schedules on a scientific basis. The characteristics of the motor, weight of car and
equipment, the adoption of two or four motor equipments, frequency of stops, amount of coasting, gear ratio,
rate of accelerating and rate of braking, and the type of control are all considered in their relation to power
consumption and their general effect on operation. The curves included in the article add greatly to its
value. — Editor.
The increasing cost of electric railway
operation, due to higher wages of employees
and the general advance in the price of
materials and supplies, makes it more and
more imperative that the operators look for
economies in every direction where it is
practicable to secure them. On every road
the cost of power is one of the major items of
expense, running from 10 to 20 per cent of the
entire cost of operation in city service and
averaging about 17 per cent of the total.
Of this, by far the greater part is consumed by
the car motors. Any material decrease
that can be secured in this item, either by
the use of more efficient equipment or by
better methods of operation will be of material
assistance in keeping the ratio between
expenditures and receipts down to a point
where a profit can be shown.
It is the. purpose of this aiticle to point out
the essential factors entering into the power
consumption of the motive equipment of
electric cars, and to indicate where economies
can be secured either in existing equipments
or those that may be purchased in the future.
To move a car of given weight a certain num-
ber of miles per hour on a level track requires
the application of a certain definite amount of
power through its motors. The obvious
factors which determine the minimum energy
necessary to make any schedule are: the
weight of the car plus its load; the distance
to be covered and the time in which the run
is to be made; the number of stops and their
average duration; and the number of slow-
downs. Given these, and an approximate
curve of the car's resistance, it is a simple
mathematical calculation to determine what
average kilowatt input is the least that will
do the work. The effect of grades and of
curves on the power consumption can also
be accurately determined if a correct profile
and contour of the line is available.
But in actual service, these minimum
values are always considerably exceeded, due
in part to the equipment itself and in part to
the way in which the car is handled. In
addition to the factors mentioned above,
there are several others which modify the
power calculation. These are: the character-
istics of the motor used; the diameter of the
car wheels; the gear ratio; the scheme of
control; the amount of coasting ordinarily
done by motormen; and the rates of accelera-
tion and of braking employed.
A number of curves have been plotted to
illustrate the effect of these various factors
on the power; that is, what variations in each
POWER CONSUMPTION OF RAILWAY MOTORS
945
factor may be looked for and what can be
done to secure the greatest efficiency in
operation.
Characteristics of Motors Used in Calculation
Comparisons of power consumptions of
two equipments are affected by the relative
shapes of speed curves and the relative
values of motor efficiencies. In order to
eliminate any effect of the shape of speed
curves or motor efficiencies in this compari-
son, the motors used were selected with
identical speed curves and efficiencies. Motor
" A " in Fig. 1 is a standard motor, rating 35
h.p. on 600 volts. Motor "B," which is a
65-h.p. machine on 600 volts, is assumed to
have the same speed and the same efficiencies
as motor "A" at a current input corresponding
to the increased duty imposed on the motor.
Motor "A" requires 73 amperes for
acceleration of a 32,000Tb. car at 1.5 m.p.
h.p.s., and at this input has a speed of 11.2
m.p.h., a tractive effort of 1315 lb. and an
efficiency of 79.5 per cent. In order to
accelerate the 42,000-lb. car with the "B"
motor there is required 171 1 lb. tractive effort,
and, as the car must be accelerated to the
same speed as the lighter car with motor "A,"
30
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on 500 volts with 30-in. wheels
the 1711-lb. torque point must be obtained
at 11.2 m.p.h. and the motor efficiency must
be the same. It is then a simple calculation
to obtain the new current scale for the "B"
motor and to calculate a new torque curve
using the new current scale.
By using these characteristics, the time
spent on the controller and the speed on the
last point of the controller is the same in each
case, and the motor efficiencies are the same
for the relative duty imposed on each motor.
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Current C" Motor-
Characteristic Curves of G.E. Railway Motors
on 500 volts with 30-in. wheels
The characteristic curves given in Fig. 1
were used for the calculations illustrated in
Figs. 4 and 5.
In making the calculations in Fig. 6 the
characteristics given in Fig. 2 were used.
These characteristics were obtained in the
same manner described above and give the
same speed and the same motor efficiencies.
Car Friction and Coasting Friction
The car friction and coasting friction used
in these calculations are taken from the curves
shown in Fig. 3.
The values of friction used in plotting these
curves were obtained from numerous tests
made on cars of approximately the weights
assumed, and represent an average of the
friction values obtained throughout the
country.
Weight
Figs. 4 and 5 illustrate the effect of a
difference in weight alone on the current and
power values. Fig. 4 is based on a schedule
of 9.9 m.p.h. making 7 stops per mile of 10
seconds each, and Fig. 5 is based on a
schedule of 16.75 m.p.h. making' l.S 10-
second stops per mile. In both figures cars
weighing 32,000 lb. and 42.000 lb. are con-
sidered.
The motors are properly geared for the
cycle of duty assumed and perform the
schedule with a reasonable amount of coasting.
946
GENERAL ELECTRIC REVIEW
In Fig. 4 it will be noted that the speed
time curves practically coincide, the slightly
higher speed of the heavier weight car being
due to a lower car friction. The current curve
is considerablv higher for the " B " motor and
the 42.000-lb. car. The 32,000-lb. car is
JU ' /
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Fig. 3. Car Friction and Coasting Friction Curves
for 16-ton and 21-ton Cars
23.8 per cent lighter than the other; and its
power consumption per car mile is 2.185
kw-hr. as against 2.795 kw-hr. for the heavier
car, or a saving of 21. S per cent. In other
21
22
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Fig. 4. Speed-time and Current-time Curves illustrating
the Effect of Weight on Energy Consumption
words, the difference in power is nearly in
direct proportion to the difference in weight.
The efficiency of the lighter car, due to dif-
ference in car friction being lower than that
of the heavier car, accounts for the energy
not varying in direct proportion.
In Fig. 5, making 1.8 stops per mile, the
relative power values per car-mile become
L.585 kw-hr. for the heavier car and 1.27
kw-hr. for the lighter car, or, a difference of
19. S per cent. The savings due to weight
reductions are therefore of greater relative
importance in frequent stop city service than
in infrequent stop suburban or interurban
service. The total saving is also greater.
For instance, the city cars would run 178
miles in an lS-hour day and the suburban car
297 miles. The reduction in power of 0.61
kw-hr. per car mile with the city car equals
108 kw-hr. per car daily, while the saving of
0.315 kw-hr. per car mile in the suburban run
equals 93 kw-hr. per car daily. In interurban
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Fig. 5. Speed-time and Current-time Curves illustrating
the Effect of Weight on Energy Consumption
service, with stops of one per mile to one in
ten miles, the saving becomes even less.
Two- or Four-Motor Equipments
Aside from questions of traction on exces-
sive grades, or when pulling trailers, or other
local conditions, the selection of a four-motor
equipment instead of a two-motor equipment
for city cars is inadvisable. Under ordinary
conditions of single-car operation rates of
acceleration and braking as high as passenger
comfort will permit can be secured with a
two-motor equipment and with an appreci-
able reduction in weight. There are in service
today, in cities all over the country, cars
which weigh 44,000 lb. or more equipped with
four GE-S0 or four W-101 motors. The
POWER CONSUMPTION OF RAILWAY MOTORS
947
electrical equipment on these cars weighs
approximately 13,000 lb. If this same car
were equipped with two motors of recent
design, of sufficient capacity to do the same
work as the GE-SO or W-101 motors, a saving
in weight of 6000 lb. could be made. If
maximum traction trucks were used, a further
reduction of 3000 lb. could be made, or a
total reduction of 9000 lb., with two motors
and maximum traction trucks.
Considering motors of recent design in
each case, the saving in weight is less and
with the weight of car assumed would amount
to 21 10 lb., i.e., between a modern four-motor
and a two-motor equipment.
Fig. 6 illustrates the power differences
inherent in two-motor vs. four-motor equip-
ment.
The two-motor equipment will take 2.795
kw-hr. per car-mile and the four-motor
equipment 2.935 kw-hr. per car-mile, or, a
reduction in power of approximately 4.76
per cent. On the basis of 40,000 car-miles
per year, the two-motor equipment would
take 5600 kw-hr. less than the four-motor
equipment annually. This comparison is
made on the same schedule and stops as in
Fig. 4. The cars assumed in each case are
the same — the car with two motors weighing
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Fig. 6. Speed-time and Current-time Curves illustrating
the Effect of Two-motor Equipment vs. Four-motor
Equipment on Energy Consumption
42,000 lb. complete, and the car with four
motors weighing 44,110 lb. complete — the
difference in weight of the two cars being due
entirely to the difference in weight of a two-
motor "B" equipment and a four-motor
"C" equipment. This difference in weight
amounts to 4.78 per cent which indicates that
the reduction in power varies directly with
the weight. Since there is very little dif-
ference in car weight, the car efficiencies are
approximately the same.
1 1 1 I 1 1 1 I [
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Fig. 7. Speed-time and Current-time Curves illustrating
the Effect of Stops on Energy Consumption
In Figs. 4, 5 and 6 the power consumption
is given at the car on the basis of 500 volts.
At the station, due to line losses, the relative
values would be 20 per cent to 25 per cent
higher, and the savings due to weight would
be correspondingly increased.
When allowance is made for the difference
which exists between maximum traction
trucks and the M.C.B. type, the total power
reduction of two-motor over four-motor
equipments would be close to 17,000 kw-hr.
per car per year. This is a considerable
item and would on most roads save the
company at least $150 per car annually.
Frequency of Stops
For any given schedule speed, power will
vary with the number of stops in the run,
Figs. 4 and 5 show that even with a con-
siderably faster schedule speed a car making
but 1.8 stops per mile requires only about
57 per cent as much energy as one making
seven stops per mile. To reduce stops in
city service to two or less per mile would be
impracticable. To bring them down to five
per mile by the use of the skip-stop plan is in
many cases feasible.
Fig. 7 illustrates the savings made possible
by such a change. With the same car making
9.9 m.p.h. in each case, the power drops from
2.185 kw-hr. per car mile to 1.41 kw-hr., a
948
GENERAL ELECTRIC REVIEW
decrease of 35 per cent. Of course, in practice
the excessive amount of coasting shown here
for the five stop run would probably not be
obtained, but this would permit of a faster
schedule being run. thus reducing the number
of cars required and still leave a lower power
load on the station.
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Fig. 8. Speed-time and Current -time Curves illustrating
the Effect of Schedule on Power Consumption
in the number of cars required on the given
run. and thereby a reduction in platform
expense can be secured. That is, assume
a line 6 miles in length, with a schedule speed
of S m.p.h. and with 15-minute headwavs.
The round trip time is 90 minutes and 6 cars
are required. To increase the speed to any-
thing less than 9.6 m.p.h. (which would cut
the round trip time to 75 minutes and allow
5 cars to be used instead of 6) would be worse
than useless to the operator. If, however, by
decreasing stops or by faster running the
speed can be brought up to 9.6 m.p.h., a
saving of over $3000 annually could be made
in platform wages which would more than
offset the increased power cost.
Gear Ratio and Wheel Diameter
Gear ratio and wheel diameters have the
same effect on the speed of a car and con-
sequently on its energy consumption. A
change in gear ratio is equivalent to a change
in wheel diameter.
Fig. 9 illustrates the effect of a change in
gear ratio on the energy consumption of the
car. The car, schedule and motor equipment
used is the same as used in Fig. 4, the only
change made being in the gear ratio.
Slowdowns will affect power in the same
manner as stops, the effect depending upon
the number of slowdowns and the speed to
which the slowdown is made.
Coasting and Schedule Speed
Fig. S illustrates the effect of coasting on
schedules and on power consumption. The
weight of car, stops and motor equipment are
the same as used in Fig. 4. When coasting
the short distance the equipment makes a
schedule of 9.9 m.p.h. and has an energy
consumption of 2.185 kw-hr. per car mile.
When coasting the longer distance the
schedule drops to 9.05 m.p.h. and the equip-
ment has an energy consumption per car mile
of 1.825 kw-hr.
It is pointed out that by holding the power
on for the longer period the schedule is
increased 9.39 per cent, while the power con-
sumption is increased 19.72 per cent. The
increased schedule obtained is only approxi-
mately 50 per cent of the increase in energy.
To secure the greatest economies in opera-
tion, both the foregoing factors should be con-
sidered, in connection .with the headwavs
which arc used. There is no object in increas-
ing schedule speeds at the expense of power
unless the increased speed enables a reduction
,'rtj//L/r7e-32OOO/ec0/--ZMotor^,-3S9
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Fig. 9. Speed-time and Current-time Curves illustrating
the Effect of Gear Ratio on Energy Consumption
The higher speed gearing gives a free
running speed of 25 m.p.h. and an energy
consumption per car mile of 2.36 kw-hr. The
lower speed gearing gives a free running speed
of 23 m.p.h. and an energy consumption of
2 L85 kw-hr. per car mile, or, a reduction of
POWER CONSUMPTION OF RAILWAY MOTORS
949
7.42 per cent in power. On the basis of an
18-hour day the car will make 178 miles per
day, equalling a saving of 31.2 kw-hr. per
car per day. This power consumption is at
the car and due to line losses would be 20 per
cent to 25 per cent higher at the station.
This comparison is made with a 15-tooth
pinion against a 17-tooth pinion on 30 in.
wheels. There are, however, many equip-
ments in the country running on a schedule
very nearly the same as that assumed and
using a 22-tooth pinion on 33 in. wheels, which
would give a free running speed of over 33
m.p.h. In this case the saving in energy for
the lower speed gearing would be much higher
than given above.
Rate of Acceleration and Braking
The rate of acceleration and braking
influences to a large extent the power con-
sumption of a given weight car. With a
moderately low rate of acceleration, i.e., one
m.p.h.p.s., it requires a much longer time on
the controller than with a higher rate, i.e., 1.5
m.p.h.p.s., which is an average rate through-
out the country for city service.
In frequent stop service where rheostatic
losses and losses during acceleration are a
Large percentage of the total, it is essential
:
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Fig. 10. Speed-time and Current-time Curves illustrating
the Effect of Rates of Acceleration and Braking on
Current Consumption
for low energy consumption that the rate of
acceleration and braking be as high as per-
missible without discomfort to passengers.
Fig. 10 illustrates the effect of low accelera-
tion and braking on the power consumption.
The weight of car, stops and equipment used
is the same as used in Fig. 4, but the schedule
has been decreased to 8.5 m.p.h.
With one m.p.h.p.s. acceleration and brak-
ing, there is required 12.8 seconds for accelera-
tion. During this time the average current
input per car is 114 amperes, or 14(30 ampere-
seconds. The energy consumption per car-
mile for this rate of acceleration and braking
is 2.27 kw-hr. With the rate of acceleration
and braking increased to 1.5 m.p.h.p.s., the
time required for acceleration is decreased
to 7.46 seconds. The average ampere input
per car is increased to 146 during this time,
but the ampere-seconds are decreased to 1090.
The energy consumption per car mile is
decreased to 1.853 kw-hr. a reduction of
18.35 per cent, 13.4 per cent of which is saved
during acceleration.
Schemes of Control
The most economical control from a power
standpoint is dependent upon the class of
service in which the equipment is to be used.
Tapped field control shows a slight saving
in energy in frequent stop city service. In
congested districts where the stops per mile
are very frequent, the saving will be higher
than in suburban or interurban service where
the stops per mile are less frequent. The
saving in power with tapped field control is
accomplished by the use of a slower speed
motor, or a slower speed gearing during
acceleration, which decreases the time and
current during acceleration. With frequent
stop city service where the time on the con-
troller is a comparatively large proportion
of the total time, this saying will become
greater. As the length of the run increases
and the percentage of time on rheostats to
total time decreases, the saving in energy
will become less.
In a mixed city and interurban service
where an equipment must run at low speeds
in the city and- comparatively high speeds in
the interurban portion, a tapped field equip-
ment can sometimes be used advantageously.
The low speed in full field position permits
making the city service without resorting to
running on resistance points, while the tapped
field position gives what is equivalent to a
change in gear ratio for the higher speed
interurban running. An equipment of this
kind, however, is used for flexibility only and
not from any energy standpoint.
It is obvious that an equipment properly
geared for a given service should not have a
higher speed when running on tapped field
than a full field equipment of the proper speed
950
GENERAL ELECTRIC REVIEW
for the service. The equipments used for
this comparison were selected with this point
in mind and have the characteristics as shown
in Fig. 11. The characteristics of the full
field motor and of the tapped field motor on
tapped field are identical. The tapped field
to 20 30 <*-o so eo 70 eo so /oo //o izo
Fig. 11. Characteristic Curves of G.E. Railway Motors
on 500 volts with 30-in. wheels
A — Tapped Field Motor; B — Full Field Motor
motor does, however, have a lower speed and
corresponding higher torque for the full field.
By using these motors any saving due to
different speed motors or different shape
speed curves is eliminated and the saving in
energy shown is due entirely to the use of the
tapped field permitting lower current inputs
and shorter time during acceleration.
Tests have been made by a number of
operators between cars using tapped field
control and other cars using ordinary control,
where there were inherent differences in
motor characteristics, needlessly high speed
gear ratios, greater weight, or a combination
of all these factors operating to the disadvan-
tage of the full field equipment. Reports of
such tests have led in some cases to an exag-
gerated idea of the inherent value of tapped
field control.
Fig. 12 illustrates the effect of tapped
field on energy consumption. The speed
time curves coincide and each equipment
does the same amount of coasting and dis-
sipates the same amount of energy in the
brakeshoes. The cycle assumed is 9~9 m.p.h.
with 7 ten-second stops per mile. The weight
of car is assumed as 40,000 lb. complete.
The tapped field equipment requires an
energy consumption per car mile of 2.42
kw-hr. while the full field equipment has an
energy consumption of 2.62 kw-hr. per car
mile, or, a reduction in energy of 0.2 kw-hr.
per car mile, equivalent to 7.63 per cent.
From the current time curves it will be noted
that all the saving in current is made during
acceleration and that as the percentage of
time on the controller to the total time
decreases, the percentage saving in current
and in power will decrease, or, as the length
of run increases the saving in power will
decrease.
Three speed control for four-motor equip-
ments affords a small power reduction due to
the elimination of a large part of the rheostats
and of the time spent on resistance. This
saving will not exceed 5 per cent of the total
in frequent stop city service and will be much
less in infrequent stop suburban or interurban
service.
Handling of the Equipment
Probably the most important point for a
road to consider, when power reductions are
sought, is in the handling of its cars by the
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Fig. 12. Speed-time and Current-time Curves illustrating
the Effect of Tapped Field t'S. Full Field Control
of Energy
motormen. The growing use of coasting
clocks, and of car watthour meters or ampere-
hour meters is a proof of the value of their
records in demonstrating what a tremendous
difference there is between the methods of
operation of different men; many roads
POWER CONSUMPTION OF RAILWAY MOTORS
951
without any change in equipment or schedules
have reduced their power consumption from
10 to 20 per cent or more, simply by proper
instruction of motormen. Without such
instruction and supervision, the average man
is apt to either overrun his schedules, in order
to increase his layover time at a terminal, to
run an excessive amount of time on resistance
points or to use extremely slow rates of
acceleration or of braking.
This last point is very common. So much
motor and controller trouble in the earlier
days of electric operation was attributed to
"fast feeding" that it became a fetish on
most roads to instruct motormen to notch
up their controller at a very slow rate, and
rates of acceleration of 1 m.p.h.p.s. or less
became and are still very common. This
never was good practice, and with motors
designed within the past ten years, par-
ticularly those having commutating poles,
rates of acceleration up to 2 m.p.h.p.s. would
in many cases impose no injurious strains on
the machines. But the result was, in a very
large proportion of cases, that, due to the slow
rate of acceleration, unnecessarily high free
running speeds were required to make the
schedules, as shown in Fig. 10. This led to
a wide adoption of higher speed gearing than
was advisable, with the result of high power
costs and to a large extent high maintenance
due to overloading of the motors, thus defeat-
ing the very object which the operators
sought to obtain by the slow feeding. There
is hardly an urban railway of any size in this
country on which a large proportion of their
motors do not have improper gear ratios for
the service performed. Some roads have
experimented with slower speed ratios and
then abandoned the idea because the motor-
men, not being instructed to accelerate faster,
complained that the cars were slow, after the
change was made.
A very frequent occurrence and one hard
to prevent, except by some form of graphic
record on the car, or exceptionally close
supervision, is for motormen to seek to
obtain a layover at a terminal where none is
listed, or to increase the length of his nominal
layover, by fast running. This is very com-
mon practice, and results in a power increase
such as is illustrated in Fig. 8.
In conclusion, it is strongly recommended
that roads, seeking economies in their operat-
ing costs to meet the conditions of reduced
earnings so universally prevalent, devote
some time to the study of their power, bearing
the points in mind which are touched on
above, and we venture to say that they will
find the manufacturers of their electrical
equipments glad to co-operate with them
both in making such investigations and
suggesting remedies for wrong conditions
found.
■
J
Fig. 13. Photographs of the 600-volt, 35 h.p. Railway Motor upon which the calculations in this article were based
952
GENERAL ELECTRIC REVIEW
THE KINETIC THEORY OF GASES
Part I
By Dr. Saul Dushman
Research Laboratory, General Electric Company
The kinetic theory of gases has often been referred to in the Review. The following article is the first
of a series in which the author elucidates this theory in an elementary manner, and discusses the principal
conclusions that have been deduced from it and their bearing upon different problems in physics and
chemistry. — Editor.
Atoms and Molecules
A consideration of the composition and
properties of substances and of the changes
which they undergo has led to the view that
matter is discontinuous. According to this
view all substances are regarded as consisting
of atoms and molecules. The latter are the
ultimate units of the physicist, while the
chemist, seeking a representation of the
manner in which the elements combine to
form different substances, conceives the
molecule as consisting of still smaller units —
the atoms.
Various phenomena, such as evaporation,
solution and diffusion and the behavior of
gases in general, lead to the assumption that
the molecules of gases and liquids are in
constant motion. The evolution of this idea
along the line of applying the laws of ordinary
mechanics to the molecules in the gaseous
and liquid states has led to a number of
interesting and very important generaliza-
tions that are comprised under the heading
of "Kinetic Theory of Gases."
Kinetic Theory
According to this theory the molecules of
a gas when in a diffused state are assumed to
be in constant motion in all directions, and
except in more condensed states the mole-
cules are so far apart that they exert no
attractive or repulsive forces whatever on one
another. Furthermore, the collisions of these
molecules with one another or with any
enclosing wall are assumed to be perfectly
clastic; that is, there is no loss of energy of
motion in such encounters, merely the direc-
tions and relative velocities are altered.
Since the total energy of a given mass of gas
is proportional to the temperature, it follows
that the average energy per molecule is pro-
portional to the temperature only, and heat
added to a mass of gas is used up in increasing
this average molecular energy.
Fundamental Laws of Gases
The first essential of any theory of gases
must be the possibility of readily deducing
from this theory the simple laws which
govern the behavior of gases The laws of
Boyle, Gay-Lussac and Avogadro may be
combined in one statement by the formula :
P V=n RT
(1)
Here P indicates the pressure at the
absolute temperature T of a mass of gas
occupying a volume V; n denotes the number
of mols,* that is, it corresponds to the mass
divided by the molecular weight; and R is a
universal constant which has the same value
for all gases.
If «=1, V denotes the molar volume, or
volume occupied by the molecular weight in
grams of any gas at pressure P and tem-
perature T .
The value of the constant R is derived from
experimentally determined values of V, the
volume of 1 mol of an ideal gas at given values
of P and T. In this article we shall consider
as normal pressure, a pressure of 1 megabar.
This is a much more logical unit than the
conventional 760 mm. of mercury, and its
use as standard is being adopted in all recent
publications.
By definition, 1 megabar is equal to 106
dynes per square centimeter, and corresponds
pretty closely to 750 mm. mercury at 0 deg.
C, latitude 45 deg., and sea-level, f
At 7 = 273.1 (0 deg. C.) and P=106 dynes
per cm2, V = 22,708 cm3.
Hence, i? = S3.15X 106 ergs per deg.
Since 4.1S4X107 ergs = 1 calorie f
R= 1.988 cal. per deg.
mean
calorie
)
* The molecular weight in grams is known as a "mol."
t The approximation is correct tq 1 part in 5000. The con-
ventional unit. 760 mm. mercury at 0 deg. C. =1.0132X10
dynes per cm.-.
THE KINETIC THEORY OF GASES
953
Velocity of Molecules
We shall now consider the meaning of the
term " pressure " from the point of view of the
kinetic theory, and then show that this
interpretation leads to a method of calculating
the molecular velocities.
A gas exerts pressure on the enclosing walls
because of the impact of molecules on these
walls. Since the gas suffers no loss of energy
through exerting pressure on the solid wall
of its enclosure, it follows that each molecule
is thrown back from the wall with the same
speed with which it struck it, but in the
reverse direction, that is, the impacts are
perfectly elastic.
Suppose a molecule of mass, m, to approach
the wall with velocity G. Since the molecule-
rebounds with the same speed, the change of
momentum per impact is 2 mG. If n0 mole-
cules strike unit area in unit time with an
average velocity G, the total impulse exerted
on the unit area per unit time is 2 m n0 G.
But the pressure is defined as the rate at
which momentum is imparted to a unit area
of surface.
Hence.
2mn„G = P (2a)
It now remains to calculate n0. Let n
denote the number of molecules per unit
volume. It is evident that at any instant we
can consider the molecules as moving in six
directions corresponding to the six faces of a
cube. Since the velocity of the molecules is
G, it follows that, on the average, — G mole-
cules will cross unit area in unit time.
Equation (2a) therefore becomes
n G--
(2b)
From equation (2b) it is possible to deduce
the three fundamental laws of gases that have
been mentioned.
Since the product mn corresponds to the
density, it follows that at constant tempera-
ture the pressure varies directly as the
density, or inversely as the volume. This is
known as Boyle's law.
Again, from equation (2b) it will be seen
that the kinetic energy of the molecules in a
volume 1* is:
i mnGW = ~ PV
(3a)
Now we know that if we mix two different
gases that were previously at the same tem-
perature there will be no change in tempera-
ture; this holds for all temperatures. Con-
sequently, the average kinetic energy of the
molecules (i mG2) must be the same for all
gases at the same temperature and must
increase at the same rate for all gases. We
can therefore define temperature in terms of
the kinetic energy of a gas. If we write
1
in G2V --
RT
(3b)
where R is a constant, it immediately follows
that
PV=RT
which is the law of Gay-Lussac.
Lastly, let us consider equal volumes of any
two different gases at the same pressure and
temperature. Since P and V are the same
for each, and A mG" is constant at constant
temperature, it follows that n must be the
same for both gases. That is, equal volumes
of all gases at the same temperature and pressure
contain an equal number of molecules. This
was stated as a fundamental principle by
Avogadro in 1811, but it took chemists about
fifty years to understand its full import.
TABLE I
THE MEAN VELOCITY OF MOLECULES
OF DIFFERENT GASES AT 0 DEG. C.
AND ROOM TEMPERATURE
(20 DEG. C.)
Molecular
Weight
MEANVELOCITY
X10_iCM. SEC-1
Gas
at 0 deg. C.
at 20 deg. C.
H2
2.016
1.838
1.(104
Ot
32.00
0.4613
(1.4778
N,
28.02
0.4928
0.5106
Air
28.96
0.4849
0.5023
Hg
200.6
0.1842
0.1908
CO*
44.0
0.3933
0.4076
H20
18.016
0.6148
0.6368
A
39.88
0.4133
0.4282
NH,
17.02
0.6328
0.6554
CO
28.00
0.4933
0.5109
If we let V denote the volume correspond-
ing to the molecular weight, the value of the
constant R is that defined on page 952.
Instead of mn V we can write M, the molec-
ular weight, and (3b) becomes
}-mc?=Irt
(3c)
Equation (3c) enables us to calculate the
so-called mean velocity of the molecules.
Substituting for R the value given above, we
can write equation (3c) in the form:
yj3x
83.15 XWX
M
15,800
\K'
(3d)
9.54
GENERAL ELECTRIC REVIEW
In Table I are given the values of G at
0 deg. C. and 20 deg. C. for some of the more
common gases.
Application to Efflux of Gases
An evident consequence of the last equa-
tion is the law that, at constant tempera-
ture, the rates of flow of different gases
through a narrow opening must vary in-
versely as the square roots of their molec-
ular weights. This law was confirmed
experimentally by Graham and has been
applied to determine molecular weights in a
number of cases where no other method could
be used. The case of the radio-active emana-
tions and still more recently the isolation of
meta-neon, a gas of molecular weight 22,
which is an isotope of neon, furnish interest-
ing applications of the relation between rate
of efflux and molecular weight.
Ratio of Specific Rates at Constant Pressure and
Constant Volume
One of the most important deductions in the
kinetic theory of gases is that regarding the
specific heats of gases.
According to the kinetic theory we con-
ceive a gas to be constituted of molecules
which are in constant agitation and we
furthermore assume that these molecules are
constituted of atoms which may be more or
less rigidly held together. Energy added to
the gas may therefore be absorbed in the
following operations:
(1) In overcoming the external forces when
the gas performs work during expansion.
(2) In increasing the translational kinetic
energy of the molecules.
(3) In increasing the rotational energy of
the atoms in the molecules.
(4) In increasing the energy of vibration of
the atoms.*
(5) In overcoming attractive forces between
the molecules.
In a "perfect" gas there are no attractive
or repulsive forces between the molecules,
and the gas obeys Boyle's law rigidly t- For
the present therefore we shall neglect the
term in the specific heat due to this cause.
Let C-, denote the specific heat at constant
volume and Cp that at constant pressure,
both being referred to the molecular weight
as the unit of mass.
* This phase of the subject will be discussed later.
t At high pressures and very low temperatures all gases
deviate to a large extent from the laws of a "perfect" gas. By
introducing certain assumptions regarding the nature of the
forces acting between the molecules. Van der Waal has deduced
an equation which is in good accord with the observed data.
A further discussion of this equation will be found in the second
if this series.
The heat absorbed in raising the tempera-
ture of the gas at constant volume from T\
to 72 is C, (T2 — Ti). The increase in trans-
lational energy of the molecules as deduced
from equation (3b) is
E, = Y2M (GS-GS)
= 3,2 7? (Tt-TJ.
We shall denote the energy absorbed in the
other ways by Er. We can therefore write,
C, ( r2-7Y) = 3/2 R (To-TO+Er (4a)
During expansion at constant pressure, the
gas performs work. Therefore,
CP (r, - r,) =3/2 R(Tt - T:) +Er+P( Vt- \\)
= 3/2R{Ti-T1)+E,+R(Ti-T1) (4b)
Now in the case of monatomic gases, where
we can reasonably assume that the atoms
possess the simplest possible structure, it is
actually found that
G = 3,2 Rand Ct/Cl=b 3.
This leads to the conclusion that for such gases
there is no absorption of energy in any other
manner than in the form of increased transla-
tional energy of the molecules.
On the other hand, the fact that for poly-
atomic gases CP Cv is less than 1.667 indicates
that in the case of these gases heat is absorbed
in increasing both the rotational and vibra-
tional energy of the molecules.
Table II shows that in case of monatomic
gases the relations
C:=3/2 R = 2.982 cal.
Cp = 5 2 # = 4.970 ca!. (5a)
are in splendid accord with the results of
experimental observations.
Degrees of Freedom. Specific Heats of Polyatomic
Gases
According to the principles of dynamics,
any velocity can always be resolved into three
component velocities in directions at right
angles to each other, so that the sum of the
squares of the component velocities is equal
to the square of the resolved velocity. We
can therefore consider any swarm of mole-
cules as constituted of three streams which
are travelling at any instant in directions at
right angles to each other. On the average,
there will be just as many molecules travelling
in one direction as the other and, since the
kinetic energy is proportional to the square of
the velocity, it follows that the average kinetic
energy of the molecules for each of the three
directions of motion is V2 'R T, that is, 0.994 T
cal. per gram molecular weight.
THE KINETIC THEORY OF GASES
955
Now let us consider two different gases in
temperature equilibrium, one of these gases
being monatomic and the other diatomic.
From the laws of dynamics, it can be de-
duced that under these conditions the energy
resolved along each of the three directions
of motion must be the same for each gas;
furthermore, the same considerations show
that if the molecules of the diatomic gas
possess a rotational energy, due to the
rotation of their atoms about an axis per-
pendicular to the line joining their centers,
the average rotational energy must also be equal
to ]/2 R T for each of the degrees of freedom of
rotation. Now if we assume that the two
atoms constituting the diatomic molecule are
at a fixed distance from each other and are
capable of rotating only on an axis per-
pendicular to the line joining their centers,
we limit their rotational motion to two direc-
tions. We thus conclude that for diatomic
gases,
C,. = 5/2 R = 4.970 cal.
Ct = 7/2 R = 6.958 cal.
CtIC, = 1.40 (5b)
This conclusion is also in good accord with
the experimental data, as shown in Table II.
■Maxwell and Boltzmann deduced these con-
clusions as particular cases of a more general-
ized conclusion which they stated as follows:
The average energy content of any system of
molecules or atoms is always equal to } 6 R T
for each degree of freedom .
This is known as the Principle of Equi parti-
tion of Energy. It is true that the principle
has been shown to be not quite as valid as was
originally thought to be the case*; but,
nevertheless, the generalization remains as
one of the most important deductions of the
classical theory of gases.
For triatomic and more complex gases the
calculation of Cv becomes quite difficult, but
we can conclude this much as certain, that
Cp/C-, must be less than 1.40.
It is, however, necessary to point out some
respects in which the original form of the
kinetic theory has failed to account for some
of the actually observed facts.
The specific heats are found to vary with
the temperature, while according to the above
considerations they should remain constant.
This has led riot only to a lengthy discussion
among physicists as to the validity of the
principle of equipartition, but has also led to
various attempts to modify the classical
theory in such a manner as to account for the
new observations.
The absorption spectra of gases in the
infra-red region led to the suggestion that the
molecules probably possess a certain amount
of vibrational energy due to oscillations of the
atoms about mean positions of equilibrium.
At ordinary temperatures this is negligible
but, as the temperature increases, the atoms
begin to vibrate with greater and greater
amplitudes until at a high temperature
they break apart, i.e., the .molecule disso-
ciates.
* See "Recent Views on Matter and Energy," General
Electric Review. Sept.. 1914. where the author has discussed
this question at greater length.
TABLE II
SPECIFIC HEATS AT CONSTANT PRESSURE AND CONSTANT VOLUME
Gas
ct
c:.
cp/cv
Temp.
Value
Temp.
Value (4)
Temp.
Value
•
20-90
4.908 (])
0
2.98
0
1.667 (1)
He
0
2.976
310 .
1.667 (1)
1.63 (1)
H,
•V,
0
CO
16
20
20
18
6.860 (2)
6.983 (2)
6.980 (2)
7.006 i2l
0
0
II
0
4.76
4.95
4.96
4.35
16
20
2(1
18
1.407 (2)
1.400 (2)
1.399 (2)
1.398 (2)
f CO.
ILo
MI.
l'ii
100
23-100
8.88? (1)
8.374 (I )
8.84 (1)
0
0
0
6.60
6.16
6.60
0
100
0
1.315 (3)
1.305 (1)
1.317 (3)
( 1 i Kaye & Laby, Physical Constants, pp. 58-9.
(2) Scheele & Heuse, J. Chem. Soc. 103, 11, 183-4.
(3) Icllinek, Lehrbuch d. Physik. Chem. I, 1, 191, etc.
(4) Eucken, Phys. 14, 324, (1914).
956
GENERAL ELECTRIC REVIEW
By bringing in the additional assumption
that the energy from the hot source is
absorbed by the molecules, in multiples
of a unit amount which is proportional to
the frequency of vibration*, N. Bjerrum has
been able to account quantitatively for a
number of the discrepancies that have been
hitherto observed f.
The theory of energy quanta has been
applied not only to the vibrational energy but
also to the rotational and even translationa!
energies, and it looks at present as if these
views will be able to account for all the
variations in the specific heats over the range
of temperatures 250 deg. C. to 2000 deg. C.
Maxwell's Distribution Law of Velocities
Equation (3c) shows that the value G of the
velocity of the molecules may be defined to be
such that it corresponds to the mean energy
of the molecules which strike against the wall.
In other words, "with this equalized dis-
tribution of velocities the gaseous medium
retains the same energy and exerts the same
pressure as with its actual unequal distribu-
tion."
It is evident that even if all the molecules
in a given volume actually possessed the same
velocity at any initial instant, the constantly
occurring collisions between them would
disturb this equal distribution of velocities
and a non-uniform distribution would be
established.
Can we calculate the distribution of
velocities amongst an infinitely large swarm
of molecules' Maxwell showed that-the laws
of probability could be applied to answer this
problem and the result at which he arrived is
known as the law of distribution of velocities.
It may be stated as follows:
''The possible values which the components
of the molecular velocities can assume are
distributed among the molecules in question
according to the same law as the possible
errors of observation. are (by the method of
least squares) distributed among the observa-
tions."!
The curve shown in Fig. 1 represents
graphically . the distribution of velocities
among a large number of molecules which
* This is the fundamental assumption of the theory of energy
quanta. If v denotes the frequency of vibration, the energy is
absorbed by the oscillating atoms in multiples of the unit
quantum h where h is a universal constant. See "Recent Views
on Matter and Energy," General Electric Review, Sept.,
1914. The value of 0 is derived from measurements of the
absorption spectrum in the infra-red.
+ Z. F. Elektrochemie, 17. 731 (1912).
I Meyer. Kinetic Theory of Gases, p. 44.
have a given mean velocity. The equation
of this curve is
Y = \-x*t-* (6)
V7T
where Y denotes the probability of a velocity
whose magnitude is x, the most probable
velocitv beintj taken as unit v.
1.0
.
V
7t
,
t^
\
~4
\
1
\
't
>■
\
1,
1
, i>
S
?
>
V
■
i
5
■^
\
1
S
S
V
*
*
\
8
r
<
>*
f
1
-ffl
»
<
--
'
~ H
/
-*
— 1
—
-J-
c
/
A'
>
X
Fig. 1
The most probable velocity is usually
denoted by W. The value of the mean
velocity, G, is greater than II", while the
value of average (arithmetical) velocity
which is denoted by 0, lies between G and 11".
The distinction between G and 9. is analogous
in certain respects to the difference between
the readings of alternating current and direct
current meters on a pulsating direct current
circuit (such as is obtained by rectifying an
alternating current without introducing
inductance or capacity). The alternating
current meter reads the root mean square
value of the current, corresponding to G in
our velocity diagram, while the direct current
meter reads the average value of the current,
corresponding to P..
The curve in Fig. 1 may also be interpreted
as follows: Consider the molecules with
velocities ranging between OA and OB, the
total fraction of the molecules which will have
velocities in this range is given by the area
under the curve which is comprised between
the ordinates A D and BC.
Relation between W, G and '..'
From the equation of the curve in Fig. 1,
it can readily be shown that
G = W ^3j2 = 1.225 W (7)
and
Q = W \ 4 7r = 1.128 w
(8)
THE KINETIC THEORY OF GASES
957
Substituting for
follows that :
G from equation (3c) it
n = V S RT/ttM = 14551 V TIM (9)
The ordinates corresponding to each of
these values of the velocity of molecules
have been indicated in Fig. 1. Table III gives
the values of fi in centimeters per second for
different gases at various temperatures.
Importance of fi in the Consideration of Evaporation
and Kinetics of Chemical Reactions
It was shown by Meyer* that the number
of molecules of a gas at rest as a whole which
in unit time strike unit area of the enclosing
tion leads to the results o>= 13.8 g. per sq. cm.
per second.
While equation (10a) has been more or less
familiar to physicists ever since its deduction
by Meyer, it remained for Dr. Irving Langmuir
to point out its importance in the considera-
tion of rates of evaporation and of the kinetics
of heterogeneous gas reactions.
We shall quote from the paper on ' ' The
Vapor Pressure of Metallic Tungsten. "f
"Let us consider a surface of metal in
equilibrium with its saturated vapor. Accord-
ing to the kinetic theory we look upon the
equilibrium as a balance between the rate of
evaporation and rate of condensation. That
TABLE III
VALUES OF THE AVERAGE (ARITHMETICAL) VELOCITY
S2X10-
AT T =
M
273
293
373
1000
1500
3.970
2000
2.016
1.696
1.755
1.980
3.241
4.583
17.02
0.583
0.604
0.681
1.115
1.367
1.57/
18.016
0.566
0.587
0.662
1.084
1.317
1.533
28.00
0.454
0.471
0.531
0.870
1.065
1.230
28.02
0.454
0.471
0.531
0.869
1.064
1.229
28.96
0.447
D.463
0.522
0.855
1.047
1.209
32.00
0.425
0.440
0.497
0.813
0.996
1.150
39.88
0.381
0.395
0.445
0.729
0 892
1.030
44.00
0.362
0.376
0.434
0.694
0.850
0.981
96.0
0.469
0.575
0.664
184.0
0.339
0.416
0.480
200.6
0.170
0.176
0.199
0.325
0.398
0.459
XII,
H,0
CO
X.
Air
o2
A
CO,
Mo
w
Hg
wall is J4 n Q, where n denotes the number of
molecules per unit volume. (This is the
signification to be attached to n in the
remainder of this article.)
Denoting the mass of gas that strikes unit
area per unit time by co, it follows that
, = i
I n m 0
i p a
(10a)
P=V
u-
Q
(10b)
where p denotes the density of the gas.
Since
M MP
''RT
MP
RT
Substituting for Q. the value deduced in
equation (7) above, and also the value of R,
co = 43.74 XIO"6 \ .1/ T . P (10c)
Here w is expressed in grams per square cm.
per second, and P is in bars.
For air at normal pressure (P = 106 bars)
and room temperature (7 = 293), this equa-
ls, we conceive of these two processes going
on simultaneously at equal rates.
"At temperatures so low that the vapor
pressure of a substance does not exceed a
millimeter, we may consider that the actual
rate of evaporation of a substance is inde-
pendent of the presence of vapor around it.
That iss the rate of evaporation in a high
vacuum is the same as the rate of evaporation
in presence of saturated vapor. Similarly
we may consider that the rate of condensation
is determined only by the pressure of the
vapor."
It is therefore possible, according to
Langmuir, to apply equation (10) to calculate
the vapor pressure of a metal like tungsten
in vacuum from the observed rate of evapora-
tion (loss of weight at constant temperature) .
Thus, at a temperature of 2800 deg. K.,
the observed value of co, the loss in weight of
a tungsten filament is 0.43 X10~6 gms. per
* Meyer, Kinetic Theory, p. 83.
t Phys. Rev., 2. 329, 1913.
958
GENERAL ELECTRIC REVIEW
square cm. per second. Substituting in
equation (10c) we find for P, the value, 2S.oX
10~6 nuns, of mercury, or 38 .1 X10~s bar.
In this manner Langmuir and Mackay
have obtained the vapor pressure curves of the
metals tungsten, molybdenum and platinum
over a large range of temperatures.
The application of the same considerations
to the study of chemical reactions between
gases and heated filaments has also been pro-
ductive of intensely interesting and important
results.*
One of the simplest cases is that of the
dissociation of hydrogen into atoms, f
Measurements of the heat lost by convec-
tion from tungsten wires heated in hydrogen
showed that the losses increased at an
abnormally high rate when extremely high
temperatures were reached. In explanation
of this it was suggested by Langmuir that the
increased loss is due to the heat absorbed
in the dissociation of hydrogen molecules as
they strike the filament, and a comparison
of the actual results with the deductions based
on this hypothesis has led to a striking
confirmation of the latter.
Of special interest is the application of
equation (10) to the calculation of the heat of
dissociation of hydrogen molecules.
At extremely low pressures the rate at
which hydrogen molecules strike the surface
of the tungsten may be calculated by means
of equation (10), and knowing the heat
loss from the surface, the energy carried away
by each molecule may be determined. Now
at very high temperatures the heat loss tends
to reach a constant value. Hence, if it be
assumed that under these conditions every
hydrogen molecule which strikes the filament
becomes dissociated, then those experiments
must lead to a direct determination of the
heat absorbed in the dissociation of hydrogen
molecules. That is, it is possible by applying
equation (10) to the observed results on the
heat losses from tungsten wires in hydrogen
* The work in this field has been summarized by Dr. Langmuir
himself in a paper presented at the Xew York Section of the
American Chemical Society. March 5. 1915. on the occasion of
his receiving the tXichols medal. (Chemical Reactions at Low
Pressures, Journ. Am. Chem. Soc. ST, 1139).
t Journ. Am. Chem. Soc. 37, ill (1915)
at low pressures to calculate a lower limit for
the heat of the reaction :
2H±»H2.
Another interesting illustration is the
reaction between oxygen gas at very low
pressures and a heated tungsten filament in a
lamp bulb. The tungsten is attacked and
forms the oxide, WO3. At sufficiently high
temperatures, this oxide volatilizes; the mole-
cules of WOz travel directly to the walls of
the bulb and condense there, so that the
surface of the filament remains clean. Now
the rate at which oxygen molecules strike
the surface can be calculated by means of
equation ( 10) . When we compare this with the
rate at which the filament is actually attacked,
we find that only a fraction of all the molecules
that strike the filament react with it.
The value of this fraction in the case of the
reaction between oxvgen and tungsten varies
from 0.00033 at 800" deg. C. to 0.15 at 2500
deg. C. In other words, at the latter tem-
perature, about one out of every seven mole-
cules of oxygen that strike the surface of the
tungsten react with it. It would take us
beyond the scope of the present paper to
discuss the interesting conclusions which
Langmuir deduces from this result ; but it may
be pointed out in what respect such cal-
culations are of importance.
There is no doubt that the chemistry of the
future will be largely a study of the actual
mechanism of chemical reactions. The chem-
istry of the past has been distinguished by
the applications of the first and second laws
of thermodynamics. But such applications,
no matter how brilliant the success attained,
have necessarily been limited to systems in
equilibrium. When, however, we come to
consider the kinetics of chemical reactions, all
such considerations fail; the kinetic theory
in its manifold applications is the only means
by which we can hope to attain a better
understanding of this phase of chemical
reactions and manifestly the simplest con-
ditions for such a stud}' are present when we
are dealing with very low pressures where
we can. as it were, follow up the history of
each individual molecule.
(To be Continued)
! I.V.i
SOME PROBLEMS IN BURNING POWDERED COAL
Part II
By Arthur S. Mann
General Electric Company, Schenectady, X. Y.
In Part I of this article, which was published in the September Review, the author describes a highly
successful system which he has developed for burning powdered coal and illustrates its application to firing
furnaces. In the present installment he narrates how the same equipment has been applied to firing boilers
and, in addition to stating the peculiarities in burning powdered coal, he includes the records of tests on forging
furnaces and boilers which demonstrate the value of this type of firing. — Editor.
Furnace linings have been burned out by
powdered coal fires. Sometimes a wall looks
as the rocks in a turbulent stream after ages
of wearing. You can see where the brick
has been cut away, and it was all done in a
few weeks. Coal may be awful in its action,
but it need not be. A hot stream of coal and
air driven at high speed against a wall will
cut it out. A low fusing point brick is melted
down : a refractory brick is cut away mechan-
ically. We have cut away carborundum
brick by misdirecting a fire which did not
approach the melting temperature of the
brick. But such action is unnecessary. Except
at the burning tuyere brick need not meet a
destructive flame, and the tuyere itself can
be so shaped that repairs are minor and
infrequent. The remedy is to avoid high
velocity along the brickwork. If a wall
must take the full force of a current, we
protect it with loose brick or pass a current
of combustion air along its face, which both
deflects and protects. An arch can always
be treated in this way. Some of the com-
bustion air is cut off from a burner and sent
along on top and over it. The total volume
of air used is not increased and a reducing
fire can still be carried; heat distribution is
noticeably good.
The designing and building of furnaces is
an undertaking that calls for engineering skill.
Speeds, volumes and currents must all be
considered; sizes and areas influence heat
generation and distribution; the position of
egress ports, if many, may defeat the purpose
of a furnace. To be sure, all the elements at
hand involve only the simple laws of nature
and the problems are susceptible of simple
mathemetical solution. But it will not do to
build a furnace in a haphazard way — apply
a burner somewhere and if it does not work
squirt in enough fuel to make it work. Per-
haps there is no fuel so sensitive to correct
use as coal dust.
Some fuels can be burned without care on
the part of an operator: gas is one and oil
virtually another. There is no economy in
such ways, but the furnace is undeniably hot.
We recall an instance where an oil man wanted
a really good fire and had no oil to waste.
He watched that fire all the time and kept it
right; if he eased off his oil a trifle he cut
down his air too and did not forget to look at
the chimney, top and bottom. Such work
always pays, whatever a fuel may be.
Powdered coal is not a fuel that can be left
for half a day to itself while the fireman goes
to grind his knife and pare his apple. We
have fires that run all day with no change in
adjustment whatever, but somebody always
knows they are right and the fire is looked at
every half hour or so. There is always slag
and some fine ash forming: it is well to know
where these are going. On the other hand a
wrong adjustment of either coal or air makes
itself apparent. Powdered coal burns best
with 200 cu. ft. of air for each pound. It
can burn, and burn clearly, with 160 ft. and
even less, but the extra air pays. As the
supply exceeds 200 ft. efficiency begins to
fall. There is even a noticeable loss at 208
ft. The eye cannot discriminate between a
200 ft. and a 208 ft. fire, but it can recognize a
250 ft., or even a 220 ft. blaze. There is a
marked change in its appearance and unless
a cutting fire is really wanted, there is no
excuse for such bad mixtures.
This is not true of other fuels. Coal on a
grate is not doing its best at 200 feet, and it
takes a remarkably close observer to note the
difference with a 240 ft. fire. With oil this is
even more pronounced. It is the usual thing
to find an oil fire with air greatly in exeess, .
and the fact not known. The average operator
will not even try to find out whether he is
wrong, for in order to do so he must, reduce
his air little by little till things go wrong, and
all that takes time. Firemen are not paid to
save fuel. The powdered coal fire begins to
spark and wheeze when it has too much air.
An interesting problem in furnace con-
struction presented itself eighteen months ago
960
GENERAL ELECTRIC REVIEW
It was desired to heat certain metals very
slowly and uniformly, the furnace to be
charged when cold, that is, at room tem-
perature, and brought up to 900 deg. C. in
six hours, the rate of temperature rise not to
exceed 200 deg. C. per hour at any time.
After reaching 900 deg. the heat was to be held
for the rest of the day. Perhaps this can be
done with other fuels but it was done very
easily with powdered coal, and there would
have been no trouble in holding a temperature
increase ot 20 deg. per hour had it been
and the five cold ones put in. The hot
billets were dropped in a tank of cold water
and kept there till they were stone cold. So
these charges were heated alternately all day.
Fuel was weighed, furnace temperatures
were measured, and in order to allow for the
metal burned away it was weighed at begin-
ning and close of trial to give an average.
The procedure in boiler testing was followed
as closely as possible with these two dif-
ferences; the furnaces were cold when a trial
began and not all the metal was heated that
6 Motors and Feeders used
across face of Boiler
This pipe can be any length .
(!p0ft.ormore)Maybe run vacuum Tec
uhderqround or overhead.
It needj-iot be straight /
l-Burnzr
6 Burners used
across face of Boiler
Floor Line
'////////////
//////////////////////A SlQg
Y////////7
Fig. 9. A diagrammatic longitudinal section of a boiler and powdered coal burning equipment
required. This was true of the first hour too,
which, by the way, presents the greatest
difficulty.
It may be of interest to note thr results of
trials upon furnaces built to heat metal for
forging purposes. There is no standard
of comparison as there is in the case of a
boiler trial, so we had to make one. We had
eleven billets 4 in. square and about 20 in.
long weighing approximately 91 lb. each,
which were to be melted down for scrap.
The two furnaces selected could each heat
one-half of them at a charge, five at one
time and six at the next, so the hearth was
covered to 50 per cent of its area and
4 in. deep. As soon as six of these billets were
1 to a smart forging temperature just
short of dripping they were hauled out
could have been heated. If each charge had
been twice as great the output per pound of
fuel and the working efficiency would have
been nearly twice as large for only about 10
per cent of the fuel in a furnace goes toward
heating the charge; one quarter of the rest
goes to heat up brickwork and the balance
goes out the chimney.
Table I gives results of these trials.
The first was upon No. 4 furnace with cold
combustion air and coal dust for fuel; the
second upon No. 0 furnace with hot air and
coal dust. The third trial was with oil on No. 0
furnace. No. 4 furnace is somewhat larger
in area than No. 0. The first and the second
trials may be compared to show effect of
preheating air; the second and third to show
input of coal and oil.
SOME PROBLEMS IN BURNING POWDERED COAL
961
The temperature of the heated air was
apparently higher in the case of coal than in
that of oil; but all the air was preheated for
oil, while primary air, or say 25 per cent of
the air for coal, was not heated at all. In any
event the same air heater and same furnace
were used in the two cases.
The heats in this class of work are unques-
tionably better with coal. They were notice-
ably brighter and softer; to express the dif-
ference as a forgesmith would, it is stated that
coal heat is more penetrating, and in a given
furnace more work can be done, and more fuel
can be well burned with coal than with oil.
Columns 2 and 3, Table I, show a 10 per cent
greater output with coal than with oil. It
can be noted, however, that efficiencies are
virtually the same, less than three-tenths of
one per cent difference. We have found the
same thing true in comparing coke with oil
in a large oven, and in general it may be
stated that efficiencies will be equal if fuel is
properly burned, and this will cover coal upon
a grate too. If burning conditions are right,
if fires are carefully and intelligently watched,
efficiencies will be high and will be essentially
equal. When fires are not understood, when
conditions are wrong and results poor, there
is no use in trying to draw conclusions from a
trial. The speed of two race horses cannot be
gauged by a trial when they are half starved.
If a fire beneath a boiler cannot turn 75 per
cent of itself into steam, have 75 per cent
efficiency, either the operator is untrained or
the burning arrangements are wrong. A skill-
ful man will obtain better than 75 per cent.
Some time ago we fitted up a boiler furnace
to burn coal dust. It was a single 474 horse-
power (10 sq. ft. rating) unit that had been
fitted with an extension front, making a 4-ft.
Dutch oven, for burning oil. We used the
same oven, the same front, for a coal furnace,
but the internal arrangements were made
quite different. Fig. 9 shows a longitudinal
section of this furnace, Fig. 14 is a photo-
graph of the front, and the illustration on the
cover of this issue shows the front and side.
Fig. 11 is a diagram of the front.
The same feeders and same driving gear
are used as those shown in Figs. 3 and 4.
In order to perfect mixtures and to supply
both air and coal in small quantities, six
burners and six feeders were used. Air is
admitted at six separate ports, that is, each
particle of coal encounters six air currents
before it passes on to the heating surface,
and every air current is pointed across, or
at an angle to the burning current, to make
the stirring action perfect. In consequence
combustion is virtually complete in eight feet
of travel even with 200 per cent or more load.
Five hundred and twenty pounds per front
foot of furnace has been burned with only
seven feet between header and floor line.
The boiler has carried 265 per cent load long
enough to show that such loads are possible,
and 220 per cent or more can be carried
indefinitely, for there are no cleaning periods.
TABLE I
RESULTS OF FORGE FURNACE TRIALS
Kind of fuel
Duration of trial
Temperature of furnace at start
Temperature of furnace at finish
Average furnace temperature
Time to end of first heat, including bringing up furnace
Number of heats
Average time each heat, neglecting first
Temperature combustion air
B.t.u. per lb. fuel '
Total fuel, including kindling
Total steel heated
Hourly Quantities
Pounds steel heated per hour
Pounds fuel per hour
No. 4
Furnace
Economic Results
Pounds steel per pound of fuel
B.t.u. per lb. steel in fuel
Powdered Coal
7 30/60 hr.
Cold 16 hr.
1370 deg. C.
1300 deg. C.
94 min.
8
51 min.
16 deg. C.
14000
1042
4288
573
139
4.11
3406
No. 0
Furnace
Powdered Coal
7 37/60 hr.
Cold 16 hr.
1355 deg. C.
1301 deg. C.
85 min.
HI
41 min.
S34 deg. C.
14000
790 lb.
5015
659
104
6.35
2203
No. 0
Furnace
Fuel Oil
7 34/60 hr.
Cold 16 hr.
1350 deg. C.
1270 deg. C.
98 min.
9
44 min.
240 deg. C.
19400
518 lb.
4563 lb.
604
69.5
8.8.3
2196
962
GENERAL ELECTRIC REVIEW
Bin for Six Feeders and Six Burners
Coal does not pack in this bin for the
six descending columns work upon each other
Us» Us*
Fig. 10. Diagram of the powde.ed coal bin, feeders and motors on a boiler front
The six burners across our furnace front are
so arranged that the air currents issuing from
them revolve in counter direction with respect
to each pair. The diagram, Fig. 12, shows
this relationship and the currents act as do a
train of toothed gears at the tuyere mouth
and so tend to preserve a path of travel
normal to the general gas curreat. These
swirling masses proceed a little way only,
when they meet with air from the arch ports.
Fig. 13 shows this movement. The swirls
move onward in a corkscrew path, and are
met with hot air from A. The result is the
curve D, and the whole volume follows the
path and can be seen plainly at lighter loads
making its turn beneath the arch. There are
six curves like D, one for each burner, and
each curve is a corkscrew at least part way.
The side wall currents help to prolong the
mixing action.
One difficulty presents itself in burning
powder that is not met in burning coal by
usual processes. Powder is burned in sus-
pension, and as it travels at 40 or 50 ft. per
second it must be consumed in one-sixth
second or so. If it isn't, it will not be com-
pletely oxidized. During this brief time
interval there is only one-fifth pound burning,
even at heaviest loads, and at no instant is
there a greater quantity of coal on fire. With
a grate no coal particle must bum in a short
time, the average time for all particles being
half an hour, for there is a ton and a half or so
on the grate burning slowly. This seeming
disability really works to the good of powdered
coal.
■ DOT
Line
7777777//.
'
o
Przl-iizatar in !
Arch «-j
Arch
WOO O O QO
-J ^-A FO ii~
6 Burners'
77777777
Sloq Pit
/
7
7777?
V777Z7,
Fig. 11. Diagram of a'boller front showing location of burners and air passages
SOME PROBLEMS IN BURNING POWDERED COAL
963
When the morning for starting a first fire
beneath this boiler arrived, an armful of
kindling was placed at the mouth of one
burner and lighted; then secondary air was
admitted at this burner followed by primary
air. A switch started a motor and its feeder
Fig. 12. Diagram showing the direction of rotation of the
powdeied coal and air as they leave the burners
sending down coal; a puff of smoke and the
fire was going. The next burner caught from
the first and so two more, making four in all,
were set at work. The memorandum taken
at i he time was:
8:26 a.m. light fire, four burners % on
8:33 a.m. 10 lb. pressure
8:46 a.m. 14(1 lb. pressure
At 8:46 a.m. the fireman checked his coal
feed and went up overhead to open the stop
valve, and in two more minutes our boiler
had load.
This fire was started in a new cold furnace
beneath a boiler full of cold water. With
half the coal-burning capacity in use, pressure
was up in twenty minutes.
Our first boiler trial gave us 68 per cent
efficiency with 131 per cent load. Efficiencies
are calculated by dividing heat in steam by
heat in coal (laboratory test) that produced it.
That is, if we had 10 lb. equivalent evapora-
tion per pound coal and 14,000 coal we multi-
ply 10 by 966 and divide product by 14,000,
giving 69 per cent efficiency. Successive trials
gave the results shown in Table II.
Since the last and best trial the boiler has
given as good or better efficiencies for a week
at a time including coal for all purposes,
with railroad weights for coal, the fire being
put out at 5 p.m. and kindled fresh at 7 :30 a.m.
every day.
The earlier experiments show nothing
remarkable in economy, but in the beginning
we knew neither how much air to admit nor
where best to admit it. We wrorked in the
dark till we made experiment No. 5, when
our observations began to coordinate. Nos.
7 and 8 taught us much, but we had to make
some mistakes before we brought out No. 11,
and this is not final. We can do better with
Fig. 13. Diagram showing the path of the powdered coal
and air currents immediately after entering boiler
less air, though perhaps there are some fires
not giving 75.7 per cent efficiency with 205
per cent load.
We experimented chiefly with air dampers,
noting air volumes, flue temperatures and
color of smoke. Each air supply has its
TABLE II
RESULTS OF BOILER TRIALS
Load percentage. . .
Efficiency per cent.
Air per lb. coal c.f.
Flue temperature.
131
68
210
553
186
63.8
178
684
3
4
5
6
7
8
212
119
97
136
154
154
65.8
68
71.8
65.5
71
69.4
150
190
250
181
200
226
786
583
568
652
693
685
9
10
11
141 164 ■ 205
66.1 63.7 j 75.7
216 168 j 208
628 678 ' 724
964
GENERAL ELECTRIC REVIEW
damper, and these were adjusted inde-
pendently. With a given coal feed, if it was
found that changing points of application of
air enabled us to reduce air volumes, with an
accompanying rise in flue temperature with
no smoke, we concluded we were making an
improvement.
Fig. 14. Front view of a bciler equipped with powdered coal
burning apparatus
In this way we found it best to admit as
little air at .4 and B as possible, a lot at C,
some at D, and a little at E (F is used only on
heaviest loads, that is above 210 per cent).
In general it may be suited that as the air
supply departs from 200 cubic feet per pound
of coal efficiency falls.
We have supplied the operator with some
gauges which give him the heights of water
column for a definite air volume. Each
gauge is marked with its number of coal
in feeder rheostats, for example,
16-20-24 and so on. He then makes the water
column fit his coal feed. Dampers are marked
and results are definite.
It is to be observed that measuring air
volume is much better than measuring CO->
in chimney gases. Two hundred feet of air
gives a C02 of about 15.3 per cent: 208 feet
gives 14.7 per cent, and this small change
I which no C02 apparatus can be sure
of) gives a marked change in evapora-
tion. The same change in air volume
makes our water column move V£ in.
Furthermore, the fireman knows of
any change here instantly. He
measures it and he measures all the
air. The CO? content is judged from
a minute sample and is half an hour
behind the time.
It will pay to so arrange air piping
on any boiler that air volumes can be
measured instantly, and this is true
whether a chimney or a fan produces
the draft. A nozzle plug is used in
the pipe, though perhaps a Pitot tube
might do : however, the nozzle plug
acts well and it is liked. If a fireman
sees his water column go up he knows
that a hole is coming in his fire and
he knows it right away. This knowl-
edge would be of more value to him
than any other information of the
sort he could have.
We are for the present conducting
no more boiler trials. Those already
recorded point the way to improve-
ment. There is enough heat in flue
gases to warrant the placing of heat-
ing surface in its path. Everything in
the shape of tar has been burned out
of the fuel, so we are putting about
600 ft. of 1}4 in- tubing in the breech-
ing and will send feed water through
it. The stack is clear. All soot drops
in the gas chambers long before reach-
ing the stack, so that all troubles
commonly met with on this surface
are absent. More trials will be conducted
when this addition is ready.
There are three difficulties to be overcome
in burning powdered coal, which are greater
as quantities and temperatures are greater.
These are slag, ash and burned brickwork.
None of these are serious with light loads, say
140 per cent or less, but heavy loads are so
easily and economically carried that the three
problems call for care in designing furnaces.
Furnace temperatures are high; 2700 deg. F.
or more is not uncommon and most of the ash
will slag when hot. We aimed to slag as
SOME PROBLEMS IN BURNING POWDERED COAL
965
much as possible, for it can be drawn off at
intervals. Fine ash passes on among the
tubes. The slag weighs 5.72 per cent, and the
soot 3.41 per cent of the coal that made it.
This coal gives 11.26 per cent ash in the
laboratory, so that 2 per cent must have gone
out the stack. This 2 per cent is a very fine
white powder, scarcely visible at the chimney
top. The slag (114 lb. per ton) contains no
carbon whatever. For a moderate load, say
ISO per cent, it is drawn out once during the
day to a concrete pit containing water. The
pit is cleaned out with pick and shovel the
next morning. This is not the easiest way
to handle slag. If there were a cellar beneath
the boiler room there would be less labor, but
even as it is the work is not difficult. Water
in the pit is essential, however.
With heavy loads some particles of slag
travel with the gas current and cling to the
first cold surface they meet — the bottom row
of tubes. If this slag is allowed to accumu-
late, say for ten hours, it will choke off enough
of the gas passage to make reduction of load
necessary. This seemed a great difficulty at
first, but it has been overcome. It can be
blown off with a steam jet once during the
forenoon and again in the afternoon for heavy
loads. It does not call for much time and
is not laborious. However, we have greatly
improved this condition by admitting a
little steam at the inlet end of the pas-
sages. This steam travels with the hot
air, mingling with it and altering the
character of the fire; it makes slag run more
freely, softening and decreasing the quantity
that clings to the tubes. We have found
that 145 lb. per hour is enough for l(i()
per cent load, or 24,000 lb. of steam per
hour.
It pays to blow tubes once a day and we
follow that practice. Most of the soot goes
over through the second pass and drops
nicely in the back chamber. The bottom of
that chamber has been paved giving it a
pitch, with tile pipe leading to a pit, and all
this material is washed out every second day
by merely opening a valve. The soot, how-
ever, is a loss for 60 per cent of it is carbon ;
that is, 60 per cent of 3.41 per cent or 2 per
cent of our coal is unburned. The soot is
light and fluffy, weighing 18 lb. per cubic
foot but we have found no good use for it
thus far.
Other losses are not great. Radiation from
the furnace is small, for the furnace is virtually
surrounded with air passages and heat that
gets into them is returned to the furnace.
These air passages, and the deflecting air
currents C, D, E and F do much toward
protecting furnace walls. We have burned
out one arch, melted it down from nine inches
to four inches when it fell, but it stood up
nearly six months. It did not run every day
with heavy load and did not run nights at
all; but it was made of common fire bricks
which arc not intended for high temperatures.
The new arch is of better material, costing
$37.00 per thousand. We may find it will
pay to use carborundum.
Somebody will ask how much it costs to
make powdered coal. The answer is that it
depends upon how much is made. Coal has
to be crushed, elevated, dried and distributed,
whatever burning system is used. There are
two elevations and the pulverizing additional
for powdered coal. So the question of real
interest is how much more does it cost to
make and burn pulverized coal than it costs
to make and burn coal by the usual process.
Our pulverizer is small, and the cost with
motor installed was about $1000 per ton
pulverized per day. If it were to run only
five hours per day, leaving ample time for
repairs, fixed charges come to about 7c. per
ton, allowing 10 per cent per year.
Our current costs, in cents per ton, are as
follows: Driving dryer, 1 .95; two elevations,
0.77; pulverizing, 14.8; which makes 17.52c.
per short ton for current and 24.52c. includ-
ing fixed charges. This total is reduced by a
third with larger pulverizers.
The pulverizer calls for some attention, but
it is in the coal house with other machinery
and whatever labor it needs is more than
made up in decreased labor of firing. Our
blower at the furnace gives a pressure of three
ounces, which is ample, so that 25c. per ton
is all that can be charged against pulverized
coal. We have not run long enough to say
what the repairs will be, but our two years
have shown that they are nominal, at least no
greater than is rr.et with in all coal-handling
machinery.
966
GENERAL ELECTRIC REVIEW
THE THEORY OF LUBRICATION
By L. Lbbelohde
Translated for the General Electric Review from Petroleum
By Helen- R. Hosmer
Research Laboratory, General Electric Company
Part I
This article is the first installment of a valuable and exhaustive treatise on the subject of " Lubrication."
The present section deals with the fundamental physical principles and its subdivisions treat of the subjects —
capillarity, general characteristics of friction, definitions, physical and technical units and the interrelation of
these, external friction, and the characteristics of oil. The following installments will take up the "Laws of
Friction in Lubricated Machine Bearings" and the "Failure of Oil Testing Machines." — Editor.
In the following article are briefly recorded
the results of investigations, some of them
completed years ago, upon the important
problems of friction in lubricated machine
parts and the testing of lubricants. Time
has been lacking to publish this material in
detail, as was originally intended.
I. FUNDAMENTAL PHYSICAL PRINCIPLES
Before entering upon a consideration of the
phenomena of lubrication, there are several
underlying principles, such as capillarity and
friction between solid bodies, and within
fluids, which may well be recalled.
(a) Capillarity
It should be noted in the first place that
the wetting of a journal and bearing and the
angle of contact due to surface tension are the
factors controlling the lubricating power of a
fluid. The phenomena of capillarity thus
enter directly into the problem under con-
sideration.
Oil forms a thin layer between a bearing and
journal, the action of which may be studied
as follows: If a drop of oil be placed upon a
watch glass and a second glass, slightly more
curving, be laid upon it, the oil layer between
the glasses may be made as thin as desired by
pressure. But if this experiment be repeated
with mercury, it will be found very difficult
to retain this fluid between the glasses, for
it tends constantly to slip out at some point
from the narrow space, allowing air to enter
from the other side.
In explanation of this behavior let us con-
sider the surface tensions at a and b (Fig. 1),
and assume that by chance the mercury is
not evenly distributed about the narrowest
constriction, so that the space at b is some-
what narrower than at a. Since at both
places the liquid-solid angles of contact are
approximately equal, there must be at b a
smaller radius of curvature, and therefore a
sharper curve than at a. Consequently the
surface presses harder upon the liquid at b
and the meniscus at b pushes the mercury to
the left, overbalancing the surface tension at
a", until the narrow space is free from mercury.
With a liquid such as oil, which wets the
walls, the converse phenomena appear. In
Fig. 2 the more curved surface at b sucks the
oil drop to the right until it is distributed
uniformly about the narrow space.
A wetting fluid always seeks the narrowest
space, and with a force, under certain con-
ditions, sufficient to prevent the coming in
contact of the two surfaces. If there are air
bubbles in the fluid they will behave in the
opposite sense from the fluid itself; in oil they
will move toward the place where the layer
is thickest, in mercury toward the narrowest
point.
As the force of capillarity becomes very
great in very thin layers, on account of the
small radius of curvature, it follows that if a
non-wetting fluid be used for a lubricant, one
can never be sure that there is any present
between the bearing surfaces at the points
where they approach most closely. The
contrary condition is much more to be
expected, and this is indeed the reason why
fluids which do not wet are unsuited for
lubrication ; no power can retain them between
the rubbing surfaces3.
It is the general impression that water is not
applicable to the lubricating of machine
bearings. This is to be traced back to the
fact that tests have been made with bearings
which had not previously been completely
freed from fat, and so water would not wet
them. The conclusion should be corrected.
However, there is never any demand in
practice for so thin a lubricant4.
(') See introduction to "Tabellen zum Englerschen Vis-
cosimeter." S. Hirzel. Leipzig, Absatz 4.
(2) This manifestation of surface-tension in non-wetting
fluids, which can be appropriately termed "abhorrence of narrow
spaces" is turned to account in mercury joint packing. The
mercury will not flow, in spite of gas pressure, into the extremely
narrow spaces between the ground and packed surfaces.
Ji Not even in pressure lubrication by means of especially
constructed pumps, unless extremely high pressures be used.
(*) I have known of instances where water was used for
'lubrication, but in these cases the bearing consisted of a wooden
bracket. Such bearings are the "Sternbuch" bearing, or the
outside bearing of a ship's propeller. The lubrication of metal
bearings with emulsions of oil and water (soap solutions) will
not be considered here.
THE THEORY OF LUBRICATION
967
lb) General Characteristics of Friction between
Solid Bodies and in Fluids
(1) Definition of Friction
Although there are many good contribu-
tions on the subject of friction, one who has
kept track of the publications upon the subject
of the testing of lubricants will not consider
a repetition of the general laws superfluous,
as preliminary to a consideration of the
subject of the internal friction of fluids.
By the simple term "friction" is always
understood a force (which the engineer there-
fore measures in kilograms), which we shall
always denote in the course of this article
by R. A related term is frictional work A
(measured in meter kilograms) which equals
the frictional force times the distance over
which it is overcome. A third term is fric-
tional power, L, which is the frictional work
per unit of time (measured in meter kilograms
per second, horse power, kilowatts, or calories
per hour).
Therefore .4 =R s (1)
and L = -==R~
■■Rv
(2)
where T denotes time and v the velocity of
the rubbing bodies. The frictional power is
obtained by multiplying the frictional force
by the velocity. There are also in use the
further expressions ' ' specific frictional work ' '
a, and "specific frictional power" /, meaning
the total frictional work A or frictional power
L divided by the size of the surfaces in contact.
These values may be measured in m. at.
(meter atmospheres) and in m. at. sec.
All frictional phenomena are accompanied
by the production of heat, that is, the temper-
ature of the rubbing bodies rises until as
much heat is given off per second by con-
duction and radiation as is produced. It is
said that the bearing has then reached con-
stant temperature.
From these considerations it appears that
frictional work and frictional heat are
identical, and hence the terms are often used
interchangeably. It is specially to be noted
that the frictional work is usually expressed
as meter kilograms, but the frictional heat
as calories.
(2) Friction of Solid Bodies (Dry Friction)
Under the designation friction is under-
stood, for the case of solid bodies, that force
which must be applied to the sliding bodies
in order to maintain them in uniform motion.
The dry friction of solid bodies is expressed
by the law of Coulomb
R = lxN
where N equals the force pressing the bodies
together and /x a constant dependent upon the
nature of the rubbing surfaces.
Fig. 1
Fig. 2
(3) Friction in Fluids
(a) Viscosity or Internal Friction
Of far greater importance for lubricated
bearings than dry friction is the internal
friction of the lubricating oil, so that for one
who would make a thorough investigation of
the conditions of bearing friction an absolutely
clear understanding of the laws of fluid
friction is indispensable.
Newton stated several laws applying to fluid
friction which are expressed by the formula :
«-,/* (3)
Here R is the frictional force (in dynes)
which is necessary to shove over each other
two fluid layers of / cm2 surface separated
from each other by dn centimeters at the rate
of dv centimeters per second; 77 is the viscosity
of the fluid. (See below.)
In connection with Newton's law it should
be stated that the coefficient rj, which accord-
ing to Newton should depend only upon the
fluid and the temperature, is also influenced
to a slight extent by the pressure5 and free
surface.6 Neither of these effects need be
(6) Warburg and von Babo, Wied. Ann. 17, 290, 1882; see
also the graphical representation in work of R. Biel, Fprschung
a.d. Geb. d. Ing.-Wes. 44, 5. 1907; other articles upon the effect
of pressure: Rontgen, Wied, Ann. 22, 510, 1884; Cohen, Wied.
Ann. 45, 666, 1892; G. Tammann, Wied. Ann. 69, 771. 1899;
Hauser, Diss., Stuttgart 1900, Beibl. 1900, p-1253; Drudes Ann .
S. 597. 1901.
(«) Plateau. Mem. de l'Acad. de Belg. 1843-63; Statique
des liquides soumis aux seules forces molecoulaires; Gand et
Paris 1873, T. 2. p-261 ff; Pogg. Ann./ 14, 604. 1861; see also
Plateau, Pogg. Ann. 141, 44, 1870; see also: Stables and Wilson,
Phil. Mag. IS, 406—1883; Beibl. 7, 884.
968
GENERAL ELECTRIC REVIEW
taken into consideration, however, in general
in connection with bearings. Only in the case
of very thin layers of lubricant (insufficient
lubrication) would the effect of adhesion
upon the density of the oil become significant.
This condition will not be gone into here.
The present day theory of the friction of
lubricated machine parts is based upon
Newton's law. whose mathematical expres-
sion is free from error only under the condition
that the sliding of the separate fluid layers
consists of pure translation, that is, when
there is no eddy. Such eddy occurs under
otherwise similar conditions with higher
velocities, wider tubes, or lower viscosities.
The expression "critical velocity" is used to
indicate that velocity at which under the
conditions existent the straight line move-
ment just ceases and the circular motion
begins. It would take us beyond the limits
of this paper to discuss the matter further
here. When, as the result of exceeding the
critical velocity, eddy movement sets in, it
produces a greater resistance, and the effect
is to give 7] a higher value in the quoted
formula.
[a) DETERMINATION OF VISCOSITY IN
THE SYSTEM OF UNITS USED IN PHYSICS
The absolute value of the viscosity can be
determined from the amounts flowing through
capillary tubes, by the formula:
7T prl t
where p = the pressure necessary to overcome
the resistance. / and r are the length and radius
of the capillary tube, V the volume of liquid
which has flowed out, and t the time of flow.
This viscosity has, then, the dimensions
cm~'g sec-1 (c.g.s. system) and can be called
the absolute viscosity. Frequently the vis-
cosity is referred to that of water at 0° = 1, and
the value thus obtained is called the specific
viscosity. The absolute viscosity of water at
0° = 0.(11 797 c.m_1g sec.-1. The value of the
specific viscosity multiplied by 0.01797 gives,
therefore, the value for the absolute vis-
cosity.
' J TECHNICAL UNITS
Besides the units of measure used in physics
there are employed for technical purposes
other systems, which, in contrast to the above,
are derived from certain conventional testing
machines. These units differ, therefore. En >m
those used in physics, not alone in that they
have a different fundamental unit (as, for
instance, do absolute viscosity and specific
V =
(4)
viscosity) but the numerical values them-
selves are:
1. Not proportional to the viscosity (i.e.,
an oil of the Engler number 2 is not twice as
viscous as one with the number 1).
2. Not always comparable among them-
selves.
3. Not capable of being referred back
directly to the c.g.s. system. See under (7).
Nevertheless the easy manipulation of the
technical testing apparatus entirely justifies
its use. But the technical units must not be
used in hydrodynamic or hydraulic com-
putations. This would, and indeed has,
already led to grave errors. (See below.) For
such cases the methods given under (7) may
be used for conversion into absolute values.
The types of conventional apparatus are
many, and only the principal ones will be
named, such as the Engler, the Saybolt
(America), the Redwood (England), and
the Barbey (France) viscosimeters. In
Germany the Engler viscosimeter is used
exclusively for testing lubricants, and the
same instrument is also much used in other
European countries. The so-called "Engler
numbers" or "Engler degrees" are defined
as the ratio of the time taken for the discharge
of 200 cc. of oil to that taken by the same
amount of water at 20° = 1 , using this par-
ticular apparatus under the specified con-
ditions. The values thus obtained average
34 to l/i the specific viscosities as defined
above. The relation is, however, entirely
different below 5 of the Engler scale, and is
very dependent upon the specific gravity
of the oil (see formula 6). Engler expressly
pointed out that the relative values obtained
from the viscosimeter are dependent upon the
adjustment; hence they have no absolute
definition.
(7) COMPUTATION CONNECTING THE
PHYSICAL AND THE TECHNICAL
SYSTEMS OF UNITS
An easily applicable relation between these
two systems of units has been worked out by
Ubbelohde", giving the following formula,
which is derived theoretically but has been
experimentally confirmed. Using this, the
so-called viscosity factor can be calculated
from the Engler degrees.
Z = 4.072£-^ (5)
Here E is Engler degrees and Z the viscosity
factor. The viscosity factor of Ubbelohde
[ libelohde. Tabellen zum Englerschen Viskosimeter,
Leipzig 1907.
THE THEORY OF LUBRICATION
969
approaches very closely to the specific
viscosity (see formula 6) and can be used as
a technical value. With the aid of the vis-
cosity factor there can be determined:
1.
from the
2.
(6)
(7)
The specific viscosity
formula z = Z s
The absolute viscosity in the c.g.s.
system from the formula 77 = Z s
0.01797 cm._1g sec.-1
In these formulae 5 is the specific weight of
the fluid at the temperature of the experiment
and the numerical factor 0.01797 is the vis-
cosity of water at 0° in the c.g.s. system.
Fig. 3 represents in a rough way the relation
of the specific viscosities at the various densi-
ties of the oil to the Engler numbers. However,
as it is impossible from such a table to get the
specific gravity corresponding to a certain
Engler value with sufficient accuracy, a table
has been drawn up, with the help of the above
mentioned formula?, for the Engler viscosi-
meter5 from which may be obtained with
great accuracy the viscosity factors corres-
ponding to all Engler values. (For further
information concerning this, see introduction
to the table.)
The viscosity factor is of special value for
international use, as it makes possible the
comparison of the results from all technical
viscosimeters, as soon as the relation of each
to the viscosity factor has been established,
as has already been done for the Engler
viscosimeter. The national section of the
International Petroleum Commission (Karls-
ruhe in Baden) is at this time occupied in the
preparation of the necessary tables9. In
conclusion it may be suggested that the
viscosities of oils be given as viscosity factors,
whereby two advantages will be obtained:
1. The value can be determined upon any
viscosimeter at choice.
2. The values obtained are very nearly
proportional to the real viscosities and can be
recomputed directly into specific or absolute
viscosities by means of the formulae given
above. •
(b) External Friction
Having explained the methods for the
determination of viscosity, we will return to
the problem of the friction of lubricated
machine parts.
Besides the internal friction (or viscosity)
of the fluid, there must be taken into con-
sideration its "external friction." that is, the
friction between the fluid and the bounding
solid bodies. Concerning this latter phenom-
enon there is still a division of opinion, and
among non-physicists, a great deal of con-
fusion.
It has been supposed that the outer layer
of fluid, which is in immediate contact with
the solid boundary, does not cling thereto,
Specific Gravity
0,6 0,7 0,6 0.9 1,0
o 100 aoo 300
Specific y/sco-sity Compared To
Water- /it Zero Deg. Cent.as One
Fig. 3
but slides, and the friction which opposes
this movement, with certain materials, is
proportional to the velocity of sliding, and
hence can be expressed by the equation:
R=\fv0 (8)
in which v0 is the sliding velocity, X is an
experimental coefficient, the "coefficient of
external friction," corresponding to y) and
dependent, besides the material of the
boundary, only upon the nature of the fluid
and the temperature.
From experiments upon the flow of liquids
from capillary tubes of different diameters it
can be shown, however, that the fluid immedi-
(s) See (9). See also R.v. Mises, "Ueber den Englerschen
Flussigkeitsmesser." Phys. Ztscher. li, S12-814. 1911; the
author cannot have been acquainted with the "Tabellen."
(9) Sec Ubbelohde. "Die Internationale Petrolemkom-
.ni, ion," Zcitschr. Petroleum 7, 398. (1912). Also Dr. W.
Meissner "Internationale Vereinheitlichung der Zahigkeits-
bestimmungen." Zeitschr. Petroleum ~, 405. (1912). Also
the report of Committee D upon lubricating oils. (Chairman:
A. H. Gill of the American Society for Testing Materials)
contains comparative data on the time of flow of the following
viscosimeters: Saybolt. Saybolt Universal, Redwood and Engler;
the investigations can not. however, be considered as finished
and will not be described in more detail here, as within a short
time the standardization will be given out by the Intern.
Petroleum-Kommission in Karlsruhe (Drugs. Oils, and Paints 26.
Nos. 6 and 7. 1910: Petroleum Berlin 6. 2029. 1911).
970
GENERAL ELECTRIC REVIEW
ately against the wall has an infinitely small
velocity, or. in other words, clings to it.
The opinion has been repeatedly expressed
that when a fluid does not wet the solid
surface, sliding will be more likely to occur.
Poiseuille expected, on the other hand, to
find that for the flow of mercury through glass
capillary tubes his experimental formula
(formula 4) would no longer hold. Careful
investigations by Warburg10, however, showed
that even in the case of mercury and glass
no slipping occurred. Moreover, water clings,
whether it wets or not. Coyette performed an
experiment in 1890 in which water flowed
through paraffin capillaries, and assuming
adhesion obtained a very accurate value for 77.
Yet more convincing perhaps, is a fact
which I happened upon. During the above
mentioned determination of specific viscosity
of oils, a glass capillary was used for a long
time in testing mineral and fatty oils, and
when with it the water value was again tested,
the water would not wet it, in spite of careful
cleaning with benzol, alcohol, and ether, but,
upon removing the pressure, would still form
a convex head in the capillary. A test of the
flow, carried out in spite of this condition,
gave exactly the same value as was found
earlier, when the water was wetting the capil-
lary. For confirmation, the test was repeated,
after wetting had been produced by cleansing
most carefully with nitric acid. But this time
also, as in a fourth test in which again there
was no wetting, exactly the same time for
flow was obtained. The following table gives
the observations :
TABLE
1
Xo. E\pt.
TIME
(WATER
1 1 ij,
AT
FLOW
20°. p
IN SEC.
= 60 G .„,;,
Wetting
Not Wetting
1
2
3
4
5
6
510.8
510.6
510.4
510.9
510.5
510.4
Average
510.6
510.6
The variation of the single observations is
very small, and shows no dependence of the
time of flow upon the circumstance of wetting
or non-wetting of the capillary by the water.
The mean values agree exactly.
From all these facts concerning external
friction, it can be assumed, at least so long as
no investigations indicate the contrary, that
the external friction is independent of the
degree of wetting and also of the angle of
contact, and that all fluids adhere to all
solid substances, and that hence the external
friction can be taken as infinitely great.
Under these conditions, in the derivation of
the hydrodynamic resistance in lubricated
machine bearings the external resistance
should be neglected. Hence only the viscosity
appears as a constant of the lubricant, in the
formula in Section IP1. That wetting, however,
is of the greatest importance in another
respect, in connection with lubricating phe-
nomena, and is to a certain extent a necessary
condition has already been shown above.
(4) Other Characteristics of Oils, Alleged to be
of Especial Concern to the Subject of
Lubrication
The recently derived laws of friction
in lubricated machine bearings take into
account, as a constant of the lubricant, only
the viscosity or internal friction, and this is
generally recognized as correct by the physi-
cists of today. In the voluminous literature
concerning methods of lubrication and its
relation to the characteristics of oils originat-
ing in other circles are to be found, however,
a number of other characteristics of lubricat-
ing oils of alleged importance. There appear
such terms as lubricating power, lubricity,
durability, layer forming power, adhesion,
etc., but without especially clear definition
of the characteristics named. In general,
however, the external friction discussed above
plays a part in the definition. The obscurity
is increased to a superfluous degree by the fact
that very erroneous conceptions exist con-
cerning well defined terms such as internal
friction, surface tension, wetting and the like.
This all but inscrutable confusion will only be
mentioned, for it is impossible here to clear
up all of these errors.
But for just this reason it seems desirable
to prove, with the aid of a well known experi-
mental investigation, that for the behavior
of lubricating oil between bearing and journal
only the viscosity of the lubricating oil is of
significance. Work has been done by Klaudy,
from which, up to this time, quite the opposite
conclusion has been drawn.
The apparatus used by Klaudy was of the
following form: Into a vessel filled with the
lubricant to be tested, so arranged that it can
be heated, and furnished at the top with a
ring neck 44 mm. high and 40 mm. internal
diameter, can be sunk a freely moving piston
weighted with iron weights, the diameter of
the piston being several hundredths of a
millimeter less than the bore of the ring. At
each test 100 cc. of lubricating oil is pressed
('») Warburg. Pogg. Ann. 140, 367, 1870.
(") Section II will appear in the next installment of this
article.
THE THEORY OF LUBRICATION
971
out through the narrow ring channel, and the on the piston. This time is divided by that
time is measured which is necessary for the observed for water under the same con-
flowing out of this amount with a known ditions, and this gives a value called the
thickness of layer, temperature, and weight "capillary viscosity" for that thickness of
TABLE II
Materia!
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
a at 20 deg. C.
Ether
Benzine
Methyl alcohol
Benzol
Toluol
Cumol
Chloroform
Pyridin
Xylol ft
Water
Soap, 68 g/1
Salt solution 174 g/1
Petroleum
Ethyl alcohol
Amyl alcohol
Aniline
Gas oil
Velocite
Vacuum oil (Floridsdorf). .
Cleaning oil
Spindle oil (Wagenmann) .
Spindle oil II. (Floridsdorf).
Olive oil
Spindle oil I. (Floridsdorf).
Arachisol
Bakuol III. (Floridsdorf) . . ,
Riibol
Knochenol
Etna
Vulkanol
Glycerine
Transmission oil (Wagen
mann)
Bakuol II. (Floridsdorf)...
Bakuol I. (Floridsdorf)
Russian Petroleum
J at 50 deg. C.
37. Cylinder oil (Floridsdorf) .
c at 75 deg. C.
38. Paraffine
39. Pressed tallow
40. Vaseline
41. Natural wool fat
42. Valvoline
VALUES DEJERMINED BY KLAUDV
Capillary
Viscosity
A'
0.15- 0.21
0.31-
0.41-
0.47-
0.39-
0.62-
0.39-
0.69-
0.45-
1
1.35-
1.27-
1.17-
1.20-
3.31-
4.16- 4.50
9.99-13.7
13.3 -15.0
15.5 -20.3
18.7 -22.2
37.5 -42.5
54.7 -66.9
86.0
83.8
77.3
91.5
124
181
112
139
0.46
0.57
0.71
0.76
0.89
0.53
1.06
0.68
1.53
1.61
1.53
1.59
3.69
65.4
74.0
53.9
71.6
93.2
75.9
87.3
134
171-231
206-250
138-213
140-193
233-381
248-405
574-757
9.94-13.8
45.0 -59.4
163-174
355-602
317-419
Engler
Degrees
E>
1.40 +
0.94**
0.94
0.94
0.98
0.98
1.00 +
1.00
l.OOf
1
1.00
1.00
1.08
1.10
1.30
1.40t
2.21
2.80
3.10
3.50
5.80
8.40
9.00
10.5
10.7
10.9
12.6
12.7
13.0
16.7
21.0
23.5
24.2
27.5
35.7
43.0
18.9
1.30
2.90
9.06
9.68
10.0
Adhesion
Factor
k
°=E
0.15
0.49
0.60
0.75
0.77
0.91
0.53
1.06
0.68
0.11-
0.33-
0.43-
0.50-
0.39-
0.63-
0.39-
0.69-
0.45-
1
1.42-
1.27-
1.05-
1.09-
2.55- 3.04
2.97- 3.21
4.52- 6.18
4.75- 6.32
5.00- 6.50
5.35- 6.35
6.47-
6.51-
7.26-
7.04-
5.03-
6.63-
7.39- 8.95
5.98- 7.99
6.71- 8.58
8.00- 8.40
8.14-11.00
8.81-10.66
5.70- 8.79
5.06- 7.03
6.52-10.68
5.77-10.41
30.40-40.06
7.65-10.62
15.80-20.50
18.02-19.80
36.70-62.20
31.70-31.90
1.61:
1.61
1.46
1.45
7.32
7.96
9.56
7.98
7.22
8.39
5 6 7 8
VALUES CALCULATED BY UBBELOHDE
Sp. G. 1 Sp.
7 Viscosity
in g 'cu.cm3 z*
Variations
ki : ki » s : k 4
0.72
0.7
0.80
0.884
0.88
1
1.49
1.00
0.87
1
1.13
0.8
0.79
0.81
1.03
0.83
0.82
0.85
0.85
0.89
0.90
0.90
0.90
0.90
0.91
0.91
0.91
0.91
0.92
0.92
1.24
0.92
0.92
0.92
0.92
0.90
0.9
0.9
0.9
0.89
0.9
0.23 1
0.59f
0.646f
0.58f
0.7
0.56f
1.00
0.61 +
1
1.1
1.6
1.8
3.8
4.45f
.11
.15
.16
.20
.37
.55
.58
.68
.70
.72
83
84
86
111
141
211
163
184
240
"XX
218
11
45
151
164
172
1.40
1.48
1.39
1.51
1.95
1.43
1.36
1.54
1.51
1.27
1.31
1.33
1.11
1.18
1.37
1.13
1.31
1.19
1.13
1.22
1.32
1.13
1.43
1.28
1.33
2.38
1.27
1.04
1.35
1.22
1.54
1.38
1.64
1.6.3
1.32
1.39
1.32
1.06
1.70
1.32
1.09
1.0**
1.03
1
1
1
1.06
1
1
1
1
1
1.03
1
1
1
1
1
0.96
1
0.89
0.92
1
1
0.89
1
0.99
0.83
0.83
1
0.38?
1
1
0.93
0.46?
0.54?
1 Round numbers. At a layer thickness of 0.03 to 0.075 mm. a Capillary viscosities of column 2.
2 Round numbers. * Specific viscosity computed from the nearest capillary viscosity.
* Referred to water at the same temperature as that of the liquids in column 1.
** In the article quoted this is given as 9.94. apparently a misprint.
*** This number is the ratio of the given Engler value (0.94) to that obtained by recalculating the nearest capillary viscosity to specific
viscosity. _ This procedure is necessitated by the fact that for such thinly fluid substances almost identical Engler values are obtained for
liquids which in reality have very different viscosities (see also in this connection " Tabellen Zum Englerschen Viskosi meter" by Ubbelohde).
t These viscosities, as well as the values for ether, chloroform, xylol, and aniline, are taken from Landolt-Bornstein's tables, since the
Engler viscosities given in Table II for the former appeared to be incorrect, and viscosities cannot be deduced from the Engler values for
such thin fluids as the latter. (See my article " Die Zahigkeit des Leucht petroleums und ein Apparat zu ihrer Bestimmung," Zeitschrift
"Petroleum" IV, Nr 15.)
tt The viscosity given is that for metazylol.
972
GENERAL ELECTRIC REVIEW
layer. Four different sizes of piston inserted
within the bronze ring determine four dif-
ferent layer thicknesses. 0.03, 0.04, 0.05, and
0.875 mm.1-. The pressure can be increased
up to two atmospheres above normal, and
the temperature to 100 deg. C. and a bronze
piston may be substituted for the steel.
The investigation shows that this capillary
viscosity does not agree with the Engler
viscosity (Engler degrees), but is sixty times
as large for many fluids, and a tenth as large
for others. This fact led Klaudy to the natural
but erroneous impression that he was dealing
with a new property of the lubricant which he,
in accord with the conception then in vogue,
connected with the effect of the walls upon
the fluid. As in general the capillary vis-
cosity was considerably greater for viscous
lubricants than for non-viscous, and as this
difference far exceeded and so masked the
variations mentioned above in the Engler
viscosity (Engler degrees), it seemed desirable
to distinguish between them. For this
purpose, the measured capillary viscosity was
divided by the Engler viscosity, and the result,
which should accentuate this wall effect and
reduce that of viscosity, was called the
"adhesion factor."
In controversion of this line of reasoning
should be mentioned the following facts:
It is evident that the conditions under
which the fluid flows out between the piston
and the ring neck are such that the time con-
sumed by the flow of a specified volume under
a certain pressure is exactly proportional to
the viscosity of the fluid.
Therefore, the above determined "capillary
viscosity" is nothing more than the viscosity
of the fluid in question referred to the viscosity
of water at the same temperature. This may
be proved as follows :
In Table II are brought together capillary
viscosities and specific viscosities (arranged
in the order of increasing viscosity), the latter
having been determined in the following
manner: In Klaudy's work were given.
besides the capillary viscosities, the Engler
degree of each of the fluids investigated. For
each of these Engler measurements I have
taken from the tables supplied with the
Engler viscosimeter the corresponding vis-
cosity factor (see above), and using the
specific gravities in column 5 of Table II
have computed by equation (6) the specific
sity (referred to water at 0°=1). In
(l:) See Bericht iiber die Ziele und den Stand der Arbeiten
des Schmiermaterialkomitees im Xiederosterreichisehen Gewer-
beverein in Wien vom 11 Dezember. 1S99. Abo Allgemeine
Oesteireichische Chemiker — und Techmker-Zeitung 16. No. 12,
898 .r.,i i:. No. i I, L8!
order to refer the specific viscosities to that
of water at the temperature of the test, they
were divided by the specific viscosity of water
at the experimental temperature, the latter
having been also reduced to 0 deg., and the
quotients thus obtained, which therefore are
identical with the capillary viscosities k of
column 2, according to my assertion, are
recorded in column 6 of the table.
To make the variations existing yet more
apparent. I have added columns 7 and S.
Column 7 contains the ratio of the values of
k given by Klaudy. which ratio must theor-
etically always equal /, and whose variation
from / is sufficiently explained by experi-
mental error, as is shown below. Column S
similarly contains the ratio of the specific
viscosity z to the capillars' viscosity. When
the former lies between the two given values
of the last , the ratio is taken as /, otherwise it is
divided by that of k which comes nearest to it.
In considering columns 2 and 3, it must not
be overlooked that the Engler measure and
the capillary viscosity are not identical.
Hence the values of a in column 4 differ
markedly from unity. On the other hand, the
values of z in column 6 accord decidedly
better with k. This is especially easy to see
in column S, whose numbers show no note-
worthy variation from unity; only a few
fluids appearing, as it were, to form an excep-
tion. In general, the values in column 8
differ from unity less than do those in column
7, which indicates that the specific viscosities
agree better with Klaudy's capillary vis-
cosities than do the latter among themselves.
In other words, if, in place of the Engler
numbers of Klaudy, the specific viscosities be
substituted, the adhesion factor disappears
wholly. All the phenomena are therefore
explained completely by the specific viscosity
of the lubricant. That the specific viscosity
was not substituted by Klaudy is easily
explained by the fact that at that time it
was not recognized that such extremely
great differences existed between the Engler
numbers and the specific viscosities. This
was first shown by the computation of Engler
degrees over into specific viscosity. This
explains the above error in connection with
the adhesion factor. According to the new
interpretation, the work of Klaudy acquires
very positive value, in that it shows experi-
mentally, by means of an apparatus similar
to the common journal bearing, that no spe-
cific property of the lubricant, beyond the
viscosity, is of significance in considering the
behavior of oil between bushing and journal.
itinued)
973
RELATION BETWEEN CAR OPERATION AND POWER CONSUMPTION
By J. F. Layng
Railway and Traction Engineering Depariment, General Electric Company
The results of a series of tests are shown graphically m this article to illustrate the saving in power which
can be effected by increasing the amount of coasting for a given length of run. With a set of assumed con-
stants the difference in energy consumption is shown for varying rates of acceleration, varying rates of
braking, varying duration of stops and, finally, varying schedule speeds. It is evident that appreciable
savings in power consumption can be made by giving the motormen proper and uniform instructions. — Editor.
Since the early days of electric railroading
it has been known that in test runs there are
great differences between power used, even
when the conditions of service are the same.
With the same car over the same route, with
the same number and length of stops, the
power consumption will vary more than
30 per cent when operated by different motor-
men. This is a case where the difference
between individuals is strongly emphasized.
It is also recognized that with the same motor-
man on different days the power used will
vary greatly. If he feels strong and in a good
humor the motorman accelerates fast and
saves power, but if he feels otherwise he will
accelerate slowly and consequently waste
power in starting resistors. Weather con-
ditions, of course, will cause variation in the
amount of power used, but with reference to
the remarks just made, it is assumed that
weather conditions are normal. The dif-
ference in power consumption in the different
runs is caused by the relative amount of
coasting and rate of braking by the different
men. The maximum amount of coasting is
obtained when a car is accelerated at a max-
imum rate and decelerated at a maximum rate.
When a car is accelerated rapidly instead of
slowly, the starting resistor is in use for a
proportionately shorter length of time and
consequently the difference in the energy
consumption is transferred from rheostatic
losses to useful work.
A few years ago there were a number of
investigations made to determine some
systematic method of securing the maximum
coasting at all times, and as a result the coast-
ing clock was designed and is now very
extensively used throughout the country.
Two other methods that have been used in
a number of instances to obtain the maximum
coasting consist in employing wattmeters and
ampere-hour meters. With these two instru-
ments it is of course necessary to make
proper allowance for the difference in the
weight of cars when making an analysis.
Recently there has been considerable data
published regarding the methods of obtaining
the maximum amount of coasting, and it
would therefore seem advisable to make an
analysis of the fundamentals which will
illustrate in curve form just what can be
expected in energy savings by accelerating
and decelerating as rapidly as possible.
To illustrate these points, calculations and
curves have been made on cars weighing 18
tons complete with load, and equipped with
two motors. It is assumed that the car is
geared to have a free running speed of 22
m.p.h., a 1000 ft. run, a schedule speed of
10.65 m.p.h., 7-second stops, and 20 lb. per
ton friction. As has been previously stated,
with maximum rates of acceleration and
deceleration the maximum amount of coast-
ing is obtained. The curves shown in Fig. 1
^1
■§^oo
* iso
- 120 <
* (1*
■ft lOO^
t Hi
a *
l. 60
* o
-i
1
SO lb. Fer Ton Friction
tOOOrt.Rvn. 7 Sec Stop,
in GJi MPH Schedule.
rZMPHPS..,
s
\
l'>"*
ff?HPSx£
\
z-
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V
/
/
z
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~l£ MPH.P^S.
-/ M PH PS
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J
1 IO SO SO 40 SO 60
Time In Seconds
I 2 3
M.PH Per- Second deceleration.
Fig. 1. Decease in Energy as Rate of Acceleration is. Increased
illustrate the amount of power which will be
required per ton mile when accelerating at
different rates, that is, %, 1, lj^, \y2 and
2 m.p.h.p.s. The amounts of current are
also plotted on these curves.
974
GENERAL ELECTRIC REVIEW
A stud\- of the amounts of energy required
for the different rates of acceleration is very
interesting. When acceleratingat^m.p.h.p.s.,
it is found that the power consumption is
110 watthours per ton mile. When accelerat-
ing at 1 m.p.h.p.s. this is reduced to 90 watt-
/OOOfl Pun
Constant Schedule
?OLb. Per Ton Friction
/^ m.Ph.P S. Acceleration
ib.65 M PH. Schedule
7Sec Shop
^ ZOO ZO
8!
^■130 /8
•3I6O 16
•C
^140 /4
§
\ °
X'Ou^/O
I •
G 60 SJ. <3
^ !?
# 60% 6
%
S- 20
\
X 1 n
vO IO 20 30 40
Times in Seconds
O i I 'i 2 ?Z
M.PH.P S. Bra King
Fig. 2. Decrease in Energy Consumption as Rate of Braking is
hours per ton mile, and when accelerating at
1J4. ^Vi and 2 m.p.h.p.s. the energy required
will be 83, 79, and 76 watthours per ton mile
respectively. The difference in energy saving
is considerably less between the higher rates
of acceleration than between the extremely
low rates; it will be noticed that the dif-
ference between the 110 watthours and 90
watthours is 19 per cent, while the difference
between 90, 83, 79 and 76 will be 7, 5, and
3.8 per cent, respectively. Therefore it will
be appreciated that while there is some con-
siderable saving between accelerating at \}A
m.p.h.p.s. and 2 m.p.h.p.s. still at the same
time the saving is considerably less than in
rates of acceleration lower than this value.
Fig. 2 has been made to illustrate the
value of braking or decelerating at different
rates, and is based on the same data as given
in Fig. 1. This curve is made up on the basis
of accelerating at \y2 m.p.h.p.s The rates
of deceleration chosen are 0.S25, 1, \}4 and
2 m.p.h.p.s. The additional amount of
coasting which is obtained will enable current
to be cut off from the motors sooner than when
braking at some relatively lower rate, and a
greater amount of coasting will be
obtained. The energy required for
the different rates of deceleration are
respectively 100, 85, 79 and 76 watt-
hours per ton mile. The difference
between 100 watthours per ton mile
and 85 watthours per ton mile is 15
per cent, and the difference between
the other values are 7.5 per cent
and 4 per cent respectively. It will
therefore be seen that the difference
between decelerating at the most
rapid rate on the curve and the
lower rate on the curve gives a saving
of 24 per cent in energy. The dif-
ference in accelerating from the lower
to the higher rate, as shown in Fig. 1,
gives a saving of 31 per cent. These
values when considered separately can
actually be obtained, but there are
points between the lowest rate of
acceleration and the lowest rate of
braking where the lines cross.
It is generally accepted that the
proper rate of acceleration and braking
is in the neighborhood of 1 ^m.p.h.p.s.
However, there are some cities in
the United States where, due to
exceptional conditions, it is deemed
advisable to accelerate and decelerate
increased at- 2 m.p.h.p.s. This of course gives
the highest possible schedule speeds,
which of necessity give the largest number
of car miles per hour which can be obtained,
and in this manner the greatest use of a
car is obtainable. It has also long been
recognized that by carefully following up
the motorman's instruction with the assist-
ance of coasting clocks, ampere-hour meters
or wattmeters, the motorman will realize the
advantages which will accrue from coasting,
and in this way great savings will be made in
power, brake shoes, and wheels. Coasting
records also show whether it is possible to
decrease the number of cars on a given line,
and give a direct indication of how much lee-
way there is in schedules. There are other ways
in which power can be saved, that is, by
decreasing the length of stop and also slightly
extending the schedule speeds. Analysis of
many conditions will show that in some
cases by very slightly extending the running
RELATION BETWEEN CAR OPERATION AND POWER CONSUMPTION 975
time considerable power can be saved.
Fig. 3 illustrates the amount of power
which can be saved when making the
same schedule as has been previously
outlined in Figs. 1 and 2. With 4, 8
and 12 second stops the energy
required to propel the car will be 74.
81, and 105 watthours per ton mile
respectively, which shows a saving in
energy of 22.8 per cent between the 8
second and 12 second stop. To
maintain the same schedule with a
12.3 second stop will require 41.8 per
cent additional energy when compared
with a 4 second stop.
Fig. 4 illustrates what can be done
by extending the schedule speeds.
With an actual running time of 52
seconds, 115 watthours per ton mile
are required. By extending the
actual running time of this run to 53
seconds, there is a power saving of
22^2 Per cent. Of course, it is not
practicable to operate a schedule
with absolutely no coasting, such as
the 52 second run, but these figures
illustrate the value of a small working leeway
in running time. It will be noted that the
actual running time, not including stop, is
extended to 80 seconds, and that the energy
is reduced to 54 watthours per ton mile, but
the schedule has been reduced from 11.7
/ooon. Run
SO Lb- Per Ton Flat Friction.
Is M.R H. Per Second
A cceleraiion And Brakinq.
IO. 65 M PH. Schedule.
o
/O PO 30 40
Time In Seconds
50 SO
o
1 Z34S6789
7/rne Of Stop In Seconds
10 II 12
Fig. 3.
Increase of Energy Consumption for a given Run and Schedule
as the Time of Slop is Increased
m.p.h. to 7.8 m.p.h. when considering the
entire range which is covered by the curve.
The last two sets of curves which have just
been discussed are entirely separate from the
first two curves. The first curves illustrate
certain fixed conditions with reference to
no
100 200 ZO
90 180 18
"5 SO ISO 16
| 70^/40^14
5; eo^iso is
I »- i
u> SO*ilOO IO
\ » s
u 40 y eo\ e
* .* *
v> 30 60 6
%
SO 40 4
IO SO 2
O O O
I I I I ! I I I I I I I I I I I I I I
I I I I I I I I I I M I | I I I
- /on
I
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4
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S
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6
y
k
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sO
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ffy.
V
-V*
**.
to
N,
\
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\-
K
=?-
{
A
\
»&
£V
£■
v
V
\\
^
\
&
~/r.
1
\
\
*■
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~1
!2z J
fair,
\
\
\
<s
V
1
S
v,
\
\"
S2£
uc
£,
w
\
•v
1
,
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\
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w
\
1
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\
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v
>
1
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IO SO 30 40 SO 60 70 6
7/me of l?unr Excluding Stop. In Seconds
Fig. 4. Decrease in Energy Consumption, Current Input, and Schedule Speed by
Increasing the Coasti .g in a I000 ft. Run
976
GENERAL ELECTRIC REVIEW
schedule speed, length of run and length of
stop, while the last two curves assume the
operating conditions to be changed, that is,
by changing the length of stop or extending
the schedule speed.
After reviewing the four series of curves
given, there can be but two conclusions, viz. :
the effort to keep track of power con-
sumption and to instruct the motorman is a
very profitable undertaking, and that there
is as much reason for following up and keeping
tab of the energy used by individual motor-
men as there is for keeping record of any other
expenditures on the property. By keeping
these records and following them up properly,
savings in power of 20 to 25 per cent can
reasonably be expected. In many cases a
study of the local conditions will show how
schedules can be slightly rearranged and
either less cars used for a given service, or
the running time can be very slightly
extended and the power savings made
which are illustrated in the curves of
Fig. 4.
AUTOMATIC RAILWAY SUBSTATIONS
By Cassius M. Davis
Railway and Traction- Engineering Department, General Electric Company
The present article revives an old subject that has been food for thought and fuel for inventions for a
number of years. Many engineers have been cognizant of the financial possibilities of the automatic substa-
tion, but few have considered it very practical. The author points out that such railway substations are a
commercial possibility and that several are or are about to be placed in regular operation on interurban sys-
tems. He shows what reductions in operating expenses may be made and discusses the fields of application.
— Editor.
General Remarks
Automatic substations have been proposed
a great many times and a large number of
schemes have been devised, some of them
dating back many years, but it is only
recently that the question has assumed any
commercial significance. This is due largely
to the willingness of the management of the
Elgin & Belvidere Electric Railway to
install automatic equipment on their system
near Chicago. This road, in endeavoring
to reduce the operating expenses to a mini-
mum, thought it advisable to adopt some
method not only of operating the substations
without attendants but of operating them
in such a manner that would practically
eliminate the light load and no-load losses
in the apparatus.
A scheme of automatic operation was
devised and an experimental installation put
in service about December 1, 1914. This
equipment worked so satisfactorily that the
Elgin & Belvidere Electric Railway decided
to equip all three of its railway substations
for automatic operation. These have since
been placed in commission.
The forerunner of the automatic substation
was the remote-controlled substation, notably
the type installed on the Edison System in
the city of Detroit. In the remote controlled
substation, the equipment operates without
an attendant but the starting up and shutting
down is controlled manually from a distant
point. The automatic substation, on the
other hand, starts up and shuts down without
attention on the part of any operator, and
then only when the load conditions require its
service. The function of the remote-controlled
substation is to reduce the expense of atten-
dants. That of the automatic substation
is to not only reduce the expense of attendants
but to eliminate light load and no-load
losses.
Saving in Operating Expenses
The first saving which can be secured by
automatic control is the item of expense for
attendants. The regular operators can be
replaced by a few inspectors. It is estimated
that a road operating, say, four substations
could eliminate the day and night operators
in each substation and in their place employ
one day inspector and one night inspector
for all substations whose duty would be
merely looking after the equipment, keeping
it in proper adjustment, oiling, polishing
commutators, cleaning, etc.
The saving that can be made in power is
quite appreciable; this depends upon the
number of units per substation necessary
to carry the maximum load and upon the
frequency of the train service on the road.
The saving will of course become greater the
less frequent the train service.
As an example of the saving which might
be possible, the following may be of interest.
AUTOMATIC RAILWAY SUBSTATIONS
977
Headway between trains
Number of substations
Capacity of each substation
Actual time machines operate per day
No load losses per substation
No load energy losses per day per substation . . .
Cost of energy at substation
Value of energy saved per day per substation . .
Value of energy saved per year per substation . -
Number of operators or inspectors
Wages of each operator or inspector per month .
Total wages per year
Value of wages saved per year
Value of energy saved per year
Total saving per year
It should be understood that the above
figures are not based on the actual operation
of any road. They are based, however, on
conservative assumptions such as would
apply to a road operating cars on an infre-
quent schedule.
The significant fact brought out in the pre-
ceding tabulation is that over $1600.00 per
substation can be saved per year. This
amount would pay for a large part of the
automatic apparatus during the first year.
The automatic feature should therefore appeal
strongly to many operating companies.
Where cars are run under shorter headway
the saving would not be quite so large but
even then it is possible to secure a marked
economy during the early morning and late
evening when fewer trains are running. Dur-
ing these hours the substation may be shut
down for a considerable portion of the time.
When the cars run under such short
headway as to require the continuous opera-
tion of some of the substation equipment,
an appreciable reduction can be secured
by the automatic operation of other ma-
chines in the substation, which are required
only during the rush hours. For example,
it is common practice during the morning
and evening peaks to operate additional
units for a period of two or three hours. It is
seldom, however, that the additional machines
are needed continuously during this time;
therefore all machines in the station operate
at partial load and consequent poor effi-
ciency. As a definite example of this condition
we may take the case of a substation contain-
ing two 300 kw. converters, one of which is
in continuous operation from 6 a.m. until
2:30 the next morning, and the other machine
from (i to 7:4.3 a.m. and again from 3:45 to
9:30 p.m. The service assumed on the road
calls for trains each way every half hour with
extra cars during the morning and evening
rush hours. Under this condition it is esti-
mated that the first machine when running
Hand Operation
Automatic Operation
120 min.
120 min.
4
4
300 kw.
300 kw.
18 hr.
7 hr.
12 kw.
—
132 kw-hr.
—
lc. per kw-hr.
lc. per kw-hr.
—
$1.32
—
$482.00
8
2
$65.00
$65.00
$6240.00
$1560.(Mi
—
$4680.00
—
$1928.00
—
$6608.00
alone operates at no load for a period of
3.4 hours. The no-load loss of the converter
and transformers is approximately 12 kw.
Therefore, the energy loss per day is approxi-
mately 41 kw-hr. or a total of 14,965 kw-hr.
per year, which at 1 cent per kw-hr.
means approximately $150 per year. During
the time the two machines are operating it is
estimated that there is no load on either
machine for a period of 18 minutes per day
which represents a no-load loss of approxi-
mately $15 per year. Furthermore, during
the time the two machines are operating,
it is estimated from a typical load curve that
the second machine could be shut down a
total of at least two hours when it is not
required to carry load peaks. The no-load
losses during this time would amount to
24 kw-hr. per day, which represents approxi-
mately $88 a year at 1 cent per kw-hr.
This station could therefore save at least
S253 per year in power alone. There would
also be a slight additional saving during
the time when the two machines are running,
due to the fact that under automatic operation
when two machines were necessary, both
would be operating at a high efficiency.
In addition to the saving in power and
expense for operators, the maintenance
charges on the substation equipment should
be materially reduced.
Scheme of Operation
As mentioned earlier, there are a variety
of ways by which automatic operation can be
accomplished. The scheme which has been
placed in operation on the Elgin & Belvidere
line represents the latest application and this
has been the basis for other equipments about
to be placed in operation.
The station is started up when the potential
on the trolley falls to 450 volts, or below.
This low voltage causes a contact-making
voltmeter to close various relay circuits
which start a motor-driven drum controller.
978
GENERAL ELECTRIC REVIEW
The contact fingers and segments on the
drum controller energize the operating coils
of the starting and running alternating current
switches, the field switch, and the direct
current line switch. As soon as the converter
reaches full speed and full voltage the drum
controller comes to rest, and the station then
operates until the current which it supplies
to the trolley circuit falls below some pre-
determined value at which time a current relay
drops out and shuts down the station.*
One novel feature which has been intro-
duced is a series resistance placed between
the positive brush of the armature and the
bus, which is automatically cut into circuit
at predetermined overloads. This resistance
has the effect of limiting the output of the
substation and thereby obviates the necessity
for providing a means for repeatedly closing
the feeder and direct current converter
circuit-breakers for the purpose of "trying
out " the circuit as is done in hand operation.
It is possible to modify the equipment to
accomplish practically any desired result.
For example, the Elgin & Belvidere equip-
ment will start up on a dead trolley. Where
this feature is not desirable, it can be arranged
to start only when the trolley voltage comes
between certain specified limits; or, the
station may be made to start when the
current at some part of the system reaches a
certain value. It may be made to start by
means of a clock mechanism at certain
definite times; or, it can be made to start its
initial operation each day from some remote
point by means of pilot wires, or upon the
excitation of the incoming transmission line,
etc. In fact, there are an almost unlimited
number of arrangements which can be made
to suit practically every operating condition.
Field of Application
The chief object of installing automatic
substations is to eliminate the light load and
no-load losses, to reduce the number or to
largely eliminate substation operators (and
therewith the expense of their wages), and,
incidentally, to lower the substation main-
tenance costs.
On railway systems where the service is
so frequent as to require the continuous
operation of part of the substation equipment,
it is usually possible to improve the load-
factor, and therewith the station efficiency,
by so arranging the apparatus that additional
equipment is cut in only when the load
conditions require it. It is common practice
in a substation containing, say, two converter
• For a detailed description of this equipment see a paper by
Allen and Taylor in Proc. A.I.E.E., September. 1915.
or motor-generator equipments to keep one
machine running throughout the entire work-
ing day and to start up and shut down the
other machine at specified times. The second
machine is usually operated for an hour or
two in the morning and again three or four
hours in the late afternoon and evening.
During both the morning and evening rush
hours the load conditions are usually such as
to require the second machine only for
intervals of a few minutes, or at most half an
hour at a time, and during the remainder of
the time the second machine as well as the
first are operating under reduced load and
low efficiency conditions.
A material saving should be possible,
under the conditions that have been outlined,
by making the second machine autoinatic
in its operation. During the early morning
and late evening hours the infrequent schedule
usually requires the first machine only a
portion of the time, and therefore a saving
can be made by having the first machine
also automatically controlled.
In a station having two machines, both
automatically controlled, it is very easy to
provide a change-over switch which will
cause No. 1 machine to operate continuously
and No. 2 machine to carry the overloads
for one day, and then No. 2 machine to
operate continuously and No. 1 machine to
take the overloads on the next day. This
switch could be thrown by the inspector while
making his regular rounds.
It is possible to carry out the automatic
features for stations having any number of
machines which would automatically be cut
in and out to take care of fluctuating load
conditions.
The field where automatic operation seems
particularly applicable is in connection with
railway substations located at or near the
ends of main or branch lines, and especially
on branch lines feeding summer resorts
and picnic grounds. Such substations carry
their heaviest load for a few hours in the
morning and evening and very light loads
during the remainder of the day. The
advantage of automatic operation in such
locations is so obvious as to need no further
discussion.
It may be said in general that the automatic
operation of substations will produce the most
efficient results where hand operation is least
efficient.
While the discussion in this article has been
applied more particularly to railway work,
it should be borne in mind that equally
attractive results may be obtained in lighting
and power substations.
979
PROTECTION AND CONTROL OF INDUSTRIAL ELECTRIC POWER*
By Dr. Charles P. Steinmetz
Chief Consulting Engineer, General Electric Company
This article considers briefly the disturbances that the modern high tension transmission system, with its
distribution system, is subject to, such as destructive current rushes on short circuit, lightning strokes, and
high frequency surges, and the devices that have been produced to protect the system against each, such as
power limiting reactances, the aluminum cell lightning arrester, and high frequency energy absorbing choke
coils. vSome interesting information derived from the operation of the multi-recorder is also given. — Editor.
For industrial power application, from the
small isolated motor to the huge steel plant,
electric energy offers advantages over all
other forms of energy, which are leading to
its rapidly extending use. The foremost
advantages of electric power are the high
efficiency and the simplicity of its conversion
into any other form of power, so that in most
cases no special skill of the operator of electric-
devices is required; and the possibility of
almost unlimited transmission and distribu-
tion at high efficiency and reliability, which
permits concentrating the power generation in
one station and subdividing the power applica-
tions by attaching the motor directly to the
driven machine, thus eliminating mechanical
transmission losses.
The concentration of the power generation
in one large station — which very often is
interconnected, for reserve, with the network
of electric trunk lines, rapidly spreading over
the country — introduced two serious prob-
lems, not existing before. At any place of the
wide ramification of the distribution system,
the entire power of the system is available and
may be let loose destructively in case of
accident, and any accident anywhere in the
wide extent of the system may involve the
whole system and shut down the entire plant.
The two problems thus are: to limit the
power, which may be let loose destructively
by an accident in any part of the system,
without interfering with the normal flow of
power, and to protect the system against
being involved bv any accident in anv part
of it.
For this purpose, switches, fuses and cir-
cuit breakers, either automatic or hand
operated, have been developed to cut off
any disabled apparatus. However, they solve
the problem to a limited extent only, for, no
matter how quick acting switches, fuses
and circuit breakers may be, they operate
only after the concentration of power at the
place of accident, and in a very high power
system much of the damage has then already
been done, and furthermore, these devices
also are limited in capacity and fail, or have
*A paper read before the Association of Iron and Stee^
Eleetrcal Engineers, Detroit. Mich., Sept.. 9, 1915.
to be built of a commercially impracticable
size if they have to deal with the concen-
trated power of a large system. The problem
thus became, by power limitation inherent
in the system, to eliminate the possibility of a
dangerous power concentration at a place of
accident, rather than to permit it to occur
and then attempt to open the circuit at
unlimited power.
This power limitation is accomplished by
reactance in the generator circuits. Slow
speed steam engine or gas engine driven
generators usually have sufficient inherent
reactance to limit their power under short
circuit; but not so in steam turbine alter-
nators. The latter thus either have to be
specially designed for high internal reactance
— which makes them larger and less efficient
— or reactors are inserted into the generator
leads. Experience has shown that the most
economical method is to build the generators
with as high internal reactance as feasible,
without interference with economical design,
and to add the rest of the limiting reactance
in the generator leads.
As the safety of the system from self-
destruction depends on the absolute reli-
ability of these power limiting reactances, any
attempt to economize in them is greatly to be
deprecated. They should be able to stand
enormous overloads without danger of self
destruction by heat or mechanical forces;
the distance between the turns should be
large and no metal near them, to escape
danger from short circuit by high frequency;
and they should not contain any inflammable
material. Fig. 1 shows an illustration of such
a power limiting reactance, consisting of
bare copper wire cast into concrete, with the
layers arranged V shaped, so as to give
maximum distance between the extreme
turns of successive layers.
In very large power plants with numerous
generators feeding into the busbars, power
limitation in the generators still gives a
dangerous power concentration in the bus-
bars, and then power limiting reactances are
used also for sectionalizing the busbars.
Such busbar reactances are designed so as
to practically limit a short circuit on the bus-
9S0
GENERAL ELECTRIC REVIEW
bars to the section on which it occurs, without
under normal operation interfering with the
power transfer along the busbars, required by
parallel operation.
Still further the power concentration in the
•7i is limited by feeder reactances, and as
Fig. 1. "Cast in Concrete" Power Limiting Reactance
short circuits in the feeders are more frequent
than in the busbars or generators, feeder
reactances are of material assistance, though
not essential if the power is limited by
generator and busbar reactances.
In transmission and distribution circuits,
whether overhead lines or underground cables,
two or more lines are used in multiple to all
the more important distribution centers, so
that with one line out of service from a
ground or short circuit, the others maintain
the service This requires selective cut-out
devices. With a short circuit on one feeder,
excess currents would flow also in all parallel
feeders to the substation, from there feeding
back into the disabled feeder, and overload
circuit breakers would thus shut down the
good feeders as well as the disabled one.
Thus selective devices are necessary which
do not open the undamaged feeders, even
if overloaded. The most satisfactory type of
such devices is the reverse power relay. The
alternating waves have no direction of their
own. thus there is no reversal of current
when feeding back into a disabled feeder, as
would be the case in a direct current circuit.
But the direction, or phase of the current
with regard to the voltage, that is, the power,
reverses in feeding back, and a wattmeter
relay thus is selective. Its limitation, however,
is that it depends on the voltage, and while
usually built so as to operate on very low
voltage, if by a dead short circuit near the end
of the feeder the voltage entirely vanishes,
the relay fails. Other methods, based on the
use of pilot wires, of split conductor cables,
etc.. have been devised which are operative
under all conditions, but are of limited applica-
tion due to their complication and corres-
ponding cost.
In a similar manner, where a number of
transformers are connected in parallel between
high and low tension busbars, in case of one
transformer being disabled, it is disconnected
without interfering with the others, though
the others feed back into the disabled one:
a relay is energized by primary and secondary
current so that the two currents neutralize
each other's action as long as they are pro-
portional to the ratio of transformation.
Such a relay would not operate from any over-
load, but would be operated if there were a
short circuit in the transformer, which would
disturb the ratio of primary to secondary cur-
rent. The same interlocking relay between
the primary and secondary of a transformer
also discriminates between the transformer
and line, that is, in case of a short in a circuit
consisting of a line and transformer, it shows
whether the fault is in the transformer or in
the line connected to it.
Whenever overhead lines of any appreciable
extent exist in the system, troubles from
atmospheric disturbances such as lightning
may be expected. These consist of over
voltages, of high frequency discharges and of
impulses. But even without any overhead
lines exposed to lightning, in any extensive
system, the same class of phenomena of
over voltage, impulsfe or high frequency not
infrequently occur, produced in the system by
internal disturbances such as arcing grounds,
spark discharges, switching, connecting and
disconnecting lines and transformers, etc.,
and these internal disturbances, while usually
of lower voltage than lightning, often are
recurrent, that is, repeat continually for
minutes, hours and even days, and then may
be far more destructive than lightning.
Against over voltages, experience has proven
as the most satisfactory protection the
aluminum cell lightning arrester in the station,
together with high insulation of the line.
Photographs of such a'n aluminum cell
arrester are given in Figs. 2 and 3. Abnormal
PROTECTION AND CONTROL OF INDUSTRIAL ELECTRIC POWER 981
frequencies may vary from a few hundred
cycles, in some arcing grounds, up to millions
of cycles in spark discharges over insulators.
The most dangerous frequencies, however,
seem to lie between 10,000 and 100,000 cycles,
as these are sufficiently high to give de-
structive voltages across inductive parts of
the circuit, such as current transformers,
regulators, end turns of generators and
transformers etc., and sufficiently low to
have considerable power behind them: the
energy of a high frequency discharge in a
system usually is the lower the higher the
frequency, and as the resonance frequency of
high potential transformer windings usually
is within this range the aluminum cell light-
ning arresters can not protect against high
frequency, unless the high frequency voltage
is so high as to jump the arrester gap, which
is rarely the case. In the transmission line,
the most effective protection is the overhead
ground wire. This, as short circuited second-
ary, rapidly dissipates the high frequency
energy and thereby localizes the disturbance,
and relieves the station, that is, the high
frequency energy is dissipated in the line,
and little if any reaches the station. A small
reactance at the entrance of the station
affords considerable protection against high
Fig.
2. Three-phase 44,000-volt Lightning Arrester
Installation
frequency entering it from the line, by reflect-
ing the high frequency back into the line,
where the line insulation can stand it. Such a
lightning protective choke coil, however, intro-
duces a considerable danger, for if the high
frequency discharge is produced in the station.
by the switching arc, etc., the choke coil as
a barrier reflects it back into the station,
where it may build up to destructive volt-
ages, from stationary oscillations in apparatus
capable thereof, such as transformer high
potential coils. The danger introduced by
To Horn Gap'^
Porcelain^
Bushing
Wooden
Rod
Support—
E/ectro/y/e
Cones in
Cross
deer/on
Aluminum
Cones
Comp/ete -
Centering
Contact
Spring
Metal
Base
Fig. 3. Cross-section of a Tank of Cells for a
25,000-volt Aluminum Lightning Arrester
the lightning protective choke coil, of reflect-
ing the high frequency back into the station,
is eliminated by retaining the barrier action
given by its reactance, but instead of reflecting
the high frequency energy, cause it to dis-
sipate this energy. Such a coil, having a
moderate inductance and capable of dissipat-
ing considerable high frequency energy —
without consuming appreciable energy at
normal line frequency — is illustrated in Fig.
4. By energy absorption, it greatly reduces
the energy of the reflected wave, and thereby
guards against building up by resonance, to
stationary waves.
Coming now beyond the line and the step-
down transformer into the receiving circuit,
to the control and protection of the motors
and other apparatus, which are the purpose
of the power system, we are in the field of
industrial power applications, which is vastly
9S2
GENERAL ELECTRIC REVIEW
beyond the possibility of even a general
review within the limits of this article.
First class installations, high insulation
and effective controlling and protective
devices are the requirements of efficient and
reliable, and therefore economical operation.
Fig. 4. Choke Coil for Dissipating Energy of High
Frequency Surges
However, they are only half the require-
ment, and equally important is the operating
staff. This is not always realized, and some
first class installations give rather unsatis-
factory operation, due to false economy in
the selection of the operating staff, while
some rather poor installations give good
service. A proof of this we see occasionally,
when one of the large high class central
station organizations acquire some second
rate local plant: even before any recon-
struction is made, the improvement of service
by the high quality of the operating staff
often is marked.
Reliable and economic operation thtis
depends on a first class operating staff. It
requires system and organization of the
operating staff, and requires that accurate
records be taken of all operations and all
occurrences in the system, not only to control
the reliability of the individual operators,
but more still is this important in those cases
where unusual incidents occur, as in emer-
gencies and in case of accidents. Reliable
and complete records then are essential to
get the exact facts, find what happened and
how it happened, so as to guard against its
recurrence. This, however, requires auto-
matic records. In the operation of the system,
we use automatic devices as far as possible.
Equally then, in recording the operation,
automatic devices are essential for the com-
pleteness and reliability of the records. This
at present is done to a limited extent only:
we have a few curve-drawing voltmeters and
ammeters, etc., but in the record of switching
operation, etc., we rely on the operator's
notes. The result is, that when any accident
or other emergency occurs, the record as a
rule is practically worthless: when a number
of circuit breakers open rapidly after each
other, practically simultaneously, lightning
arresters discharge, and the generators and
other apparatus require the operator's imme-
diate attention, it is impossible to observe
accurately all the occurrences, still less the
sequence of incidents, and their exact time,
and records can be taken only after the trouble
is over, from memory, and during the time
of excitement memory is an entirely unreli-
able guide. This is the reason why so little
is known of the nature and cause of troubles
in electric systems; in most cases, we have
to so largely guess what happened, and how
it happened, that it is remarkable that we
have advanced so far in our knowledge.
Fig. 5. Fifty -point Multi Recorder
Automatic records of all the operations and
occurrences in a larger electrical system thus
are of most valuable assistance in securing the
safety and reliability of operation, and for
discovering the causes' of many troubles
before they have led to the loss of apparatus.
PROTECTION AND CONTROL OF INDUSTRIAL ELECTRIC POWER
983
Such an automatic recording device has
been developed by Professor Creighton in
the multi-recorder, shown in Figs. 5 and (5.
It has been described in Human Accuracy:
Multi-Recorder for Lightning Phenomena
and Switches, by Prof. E. E. F. Creighton,
H. E. Nichols and P. E. Hosegood, Trans.
A. I. E. E., Vol. XXXI-1912 pp. 825-849.
The multi-recorder essentially consists of a
number of stamps — in the usual size 50 — oper-
ated by clockwork and printing the time,
within fraction of seconds, of the event to
which they are relayed. Thus some of the
"points" may be connected to the switches
and circuit breakers, and record the opening
and closing of these switches, others record
lightning discharges, or excess currents, etc.;
in short, the time of anything whatever may
be recorded, by connecting it by a proper
As illustration, the following records may
be given:
1. The following report was made by the
inspector of the multi-recorder, in a high
power system feeding a railway converter
substation :
"We got a very interesting record Friday,
December 18th, at 11:29:31 p.m. One of
the rotaries at the X street substation arced
over and its oil switch blew open, showering
everything near with oil.
"The operator at the power house claimed
he threw no switches at that time. X street
could find no cause of the trouble. All
trolleys were OK and no short on any of the
feeders.
"Immediately after the trouble the oil
switch at the power house on the X street
line was carefully inspected. It was closed
J» 1 SO b5
» 1 49 4fi
V 1 49 37
» 1 49 33
V 1 49 01
t> 1 <S 44
27 1 48 20
n 1 48 1)9
2> 1 48 09
V 1 48 09
2P 1 48 (15
?< 1 47 58
V 1 47 45
V 1 47 30
if 1 47 27
» 1 47 !4
i 2 — 4 — 1
1 3 3 G ■
O J -
-12-15-17- 13-
31— S3 — S52627'
ji —3 ;•<! — , ~394c
8 9;.
11
— 13 — 15 — 17 — 19 —
11—21 -'723 — Zi
31 — "■-31- 37 — 394C
CTZ
11
-13-15-17- 19-
■><— ?- — — -- -■
31 34 — '— 37 — 394<
'.T~
3 : ...
11
15 — 17— 19 —
->1 —23— 25262°
31 — —31 37 — 394C
A7 "J
8 9i.
11
15 — 17 — 19 —
31 — 35--
31 31 37— 39«
67 «
8 9. ■
11
— IS — 17— 19-
31—23— "262;
31 31 37 — 394C
3 9 "
11
— 13 — 15 — 17— 19 -
312223— 2529— 23— 30
:(1 34 57— 394C
- ■■-.-..
47 es
is::
- 13- T- 17-19-
--3325 — Zj-.r — S3— 5:
31 34 3' — 1 941
4744X'
— U— -.-— 7— 19-
::r^--T3— I:
J! 34 37 — 394C
47£--7
s s ..
1!
— 13 — 15— ,7— 19-
312223— 2529— £3— w(
.11 34
■-• ■
f?'Z
3 S ; .
11
-13-15-17- 19-
312223-
3J — — 134— -
-:
8 9 1.
11
-13 — 15— '7— 19-
■
31 51 !
'T".
8-1.
11
— 13 — 15 — 17 — 19 —
- 23— 3C
31 — — 34
CT3
3 - ,.
:i
r-13 — IB — 17— 19 —
312223—
31 34 37 - 4?4C
46
t.T2-
8 - ..
ii
— 13 — - — 7 — 19 —
P12223— 252S- 23 — 31
31 3435- a •- <rj,
4748-
8 — ]~
11
— 13 — I"—/— 19 —
31— 33 — a*?-:--::- -
31 343C — »4C
- - .
Fig. 6. Record Sheet made by a 50-point Mu!ti Recorder showing four records made in one second
relay to the multi-recorder. By using one of
the 50 points to record standard time, the
events in different stations, hundreds of
miles apart, may be compared with each
other in their exact sequence within a second,
by the multi-recorders.
At present, multi-recorders are used to
record the following events, through relays
devised for the purpose:
Opening and closing of switches and circuit
breakers.
Recording when lines are made alive, and
when killed.
Recording grounds or short circuits, on
which line, and on which phase of the line
they occur.
Excess currents.
High frequency in lines, in which line and
which phase.
Lightning discharges over the arresters,
which line and which phase.
Operation of protective devices.
Approach of thunderstorms, etc.
and in perfect condition. This left the
whole matter in the dark. When inspecting
the multi-recorder record the following morn-
ing, I saw that X street line No. 4 was taken
off at 11:29:30 p.m. and thrown back on at
11 :29:31 p.m. This was shown on the record
as contact No. 7, which is located on the Hs
500-amp. 10,000-volt oil switch on X street
line No. 4, opening and closing as shown
above.
"I inquired the cause and was told they
thought perhaps it was blown open due to
the overload caused by a rotary at X street
arcing over, as the two incidents were
simultaneous.
" I then looked at the multi-recorder record
to see if the excess current relay on X street
line No. 4 had operated before the oil switch
had blown and found that it had not, but
operated when the oil switch was thrown
back in. This seemed to prove quite con-
clusively that the oil switch was opened at the
power house, causing X street to fall out of
984
GENERAL ELECTRIC REVIEW
phase and then closed. This of course would
account for the trouble. This is also borne
out in another way. The oil switch at the
power house is set to trip out at about three
or four times the current required to open the
oil switch at X street or the excess current
relay. Since the excess current relay failed
to operate before the oil switch at the power
house opened, it is evident the switch did
not open due to overload.
"Since, after the trouble was over, the oil
switch at the power house was found closed
and the operator claimed to know nothing of
its operation, we would never have known of
its operation had it not been for the multi-
recorder.
"As fortunately no material damage was
done by the incident, the matter was not
further followed up."
2. Another record of the same system,
operating a large steam turbine plant in
parallel with a hydraulic station over a long
distance transmission line, is given in the
following report:
"One incident showed the utility of the
multi-recorder. At 3:04:10 the discharge
alarm recorded a lightning stroke. Several
observers saw the transmission line No. 2
arc over; whether from line to line or line to
ground could not be accurately told, although
the supposition is that it occurred between the
upmost line and the middle one on the first
tower across the canal. The operator has
standing orders to clear the board in a con-
tingency like this. He waited, however,
over two minutes as the electrostatic relays
showed the line was energized from the steam
turbine station until 3:06:24. Just 8 seconds
later the water power station came on — if
the operator had been just a little bit slower
the system would probably have been badly
bumped."
3. As the record of the disturbances caused
by a thunderstorm in a large 100.000-volt
Date and Time
MR. Com. No.
X = closed
— =open
MR.
No.
Probable Cause of Operation
May 4, p.m.
There was a thunderstorm over toward X that caused a very severe bump on the 100-kv. lines.
2:25:00
11, 16. 20, 22X
2
Lightning struck line Xo. 2 grounding same, causing the excess
31-
2
current relavs in ground leg of transformer, contacts, 41, 42,
41, 42, 43, 45X
2
43 and 45 and high frequency relays 11, 20, 22 to operate on line
Xo. 3 due to the verv high induced voltage or may be from direct
2:25:01
11, 20, 22, 33-
2
stroke on line and Xo. 16 high frequencv relay on phase 3 of
2:25:01
16, 32-
2
line Xo. 2.
41, 42, 43, 45-
2
May 4, 1915, p.m.
Voltage was pulled down so low the electrostatic relays on line Xo. 2 (contacts Xo. 31, 32, 33) dropped
open. Horn gaps to lightning arrester did not arc over at this time.
May 4, p.m.
2:25:02
11, 12, 16, 20
22, 23, 26X
2:25:02
11, 12, If.. 2ii
22, 23, 26 -
2:25:11
45, 4ii, 47 -
2:25:12
16X
2:25:12
16-
2:25:13
45, 46. 47 X
16, 23 X
31. 32, 33 X
2:25:15
13X
- 25:15
13-
2:25:16
16,23-
A heavy surge came at this time arcing over horn gap to both the
live line Xo. 2 and the dead line 3. This was a single heavy
surge lasting only a part of one second.
Lint- oil switch on line Xo. 2 opened.
Xo. 2.
Due to switching off line
Put line Xo. 2 back on 100 kv. bus. Horn gap to lightning arrester
arced over on line Xo. 2 and high frequency relay on phase 3
operated. When voltage came on the line electrostatic relays
picked up instantly as shown by 31, 32, 33 closing in the same J4
second that the line was charged.
It seems there was some stray high frequency going to ground on
phase 3. This coherer is about 300 ft. from the roof wrhere arc
was, and would hardly work at all due to wireless I'm quite
sure.
Horn gap arced over continuously for 3 seconds as shown by con-
tacts 16 and 23 remaining closed from 2:25:13 to 2:25:16.
Lines now seem to be OK. again.
SPRAGUE-GENERAL ELECTRIC PC CONTROL
985
transmission system, the following report on
the operation of the multi-recorder is given.
The system contains two multi-recorders
located in the hydraulic generating system,
and connected to show the operation of all
the switches, line voltage, excess current,
lightning arrester and high frequency absorber
operation, high frequency disturbances in lines
and in stations.
" (The data in the table do not include the
regular switch operation, which also were
recorded, but are omitted here.)
"It is interesting to note that 53 different
things occurred and were recorded in their
sequence, within 16 seconds. Fortunately,
possibly due to the protection afforded by the
high frequency absorber, no damage was
done to any apparatus. We can realize how
utterly impossible it would be, even for a
large and well trained operating staff, to
observe and record some 50 different
occurrences, together with the sequence in
which they occurred, within 16 seconds, or
even a small fraction of them, and how dif-
ficult, if not hopeless, it therefore would be
without the multi-recorder, if any damage
had occurred, to ascertain the exact cause and
protect against its recurrence."
SPRAGUE-GENERAL ELECTRIC PC CONTROL
(THE ELECTRO-PNEUMATIC SYSTEM)
By C. J. Axtell
Railway Equipment Engineering Department, General Electric Company
A detailed description of the mechanical construction and pneumatic operation of this new type of car and
train control forms the body of the following article. This system of control combines elements which give
extreme simplicity in operation and compactness in design which particularly adapts it to the many varying
conditions of wheel diameter and minimum space requirements. — Editor.
Probably few, if any, branches of electrical
engineering have developed more rapidly
during the past few years than the electric
railway. This is particularly true in the large
cities where the demands for rapid transit
facilities are constantly ahead of the facili-
ties provided. Not only a greater carrying
capacity of cars and trains is required, but
also an increased schedule speed is demanded.
These increases tax the equipment ; not only
to care for the additional load imposed by the
car service, but, also to operate upon a system
on which the power station and distributing
lines have grown to tremendous proportions.
Such demands necessitate control equipments
on cars to handle the increased capacity, to
be capable of opening heavy overloads and
even short-circuits under the above conditions
and to provide for a reliability that has never
before been obtained, while at the same time
the cost of maintenance must be kept at a
minimum. Due to the present day tendencies
in car design to lower the car floor, to use
small wheels, etc., the space available under-
neath a car for control equipments has been
growing smaller instead of larger.
It is to meet these conditions that a new
type of control, known as the Sprague-
Gcncral Electric Type PC Control, has been
developed and recently placed upon the
market. This system of control embodies
all the essential characteristics for the simple
and satisfactory operation of electric railway
cars either singly or in train. The complete
control of the car movement is possible from
any car in the train, the equipments operating
on the well-known multiple-unit principle,
viz., all main or motor controllers on the train
operate synchronously, their movement being
governed by the master controller. The
control equipment for a car consists essentially
of a main or motor controller, a master con-
troller, and motor resistor, together with
such auxiliary apparatus as is common to all
car equipments.
The principal piece of apparatus is the main
or motor controller. Exterior views of a
typical controller are shown in Figs. 1 and 2,
and the front and rear views with covers
removed are shown in Figs. 3 and 4. The
particular controller shown in these illustra-
tions is suitable for operating two 220 h.p.,
600-volt, tap-field motors. One hundred and
twenty-four of these controllers will shortly
be in use for operating trains on the lines
of the Interborough Rapid Transit Company,
New York.
The controller contains in one box the line
breaker, the overload relay, the contactor
elements for making the various motor and
resistor connections, the reverser, and the
operating mechanisms. The line breaker
9S6
GENERAL ELECTRIC REVIEW
elements, of which there are two in the
equipment illustrated, are electro-pneumati-
cally operated contactors provided with
extremely powerful magnetic blowouts. The
power for operating these line breakers is
obtained from the compressed air supply
Fig. 1. Type PC Motor Controller
Front view with covers
F13. 2. Type PC Motor Controller.
Rear view with covers
of the air-brake system. Air admitted
through a small magnet valve to a cylinder
located underneath the operating mechanism.
forces up an air piston and closes the main
contacts of the line breaker element against
a powerful spring. These line breaker
elements function to open the motor circuits
under all normal conditions as well as under
overload conditions. This possesses the ad-
vantage of rupturing all arcs in that part
of the equipment particularly designed for
such sen-ice; which part was formerly used
as a circuit-breaker, opening only under over-
load or short-circuit conditions. Extensive
investigation and development has recently
been made to produce the most efficient
magnetic blowout, the results of which have
been incorporated in this new control both in
the line breaker and in the contactor units.
The current carrying parts of these line break-
ers are similar to those used on the contact-
ors of the Sprague-General Electric type "M"
control and consist essentially of a main
contact, series coil with magnetic blowout,
and arc chute. Fig. 5 shows a partially
disassembled view of one of these break-
ers. The construction of the element in
a unit form and the assembly of it on a
moulded compound base makes the removal
or replacement of any element very simple.
for it is only required to detach the two cable
terminals and loosen the two nuts holding the
unit in position. The operating levers are so
designed that the contact tips when closing
and opening are given a "wipe" or rolling
motion which prevents them from "freezing"
or weldir g together.
Included as a part of the main controller
is an overload relay consisting of a series coil
through which passes the line current taken by
the car, an armature that operates contacts
in the control circuits of that equipment, and
a mechanical latch having an electrical reset.
This latch is arranged to hold the relay in an
open position, in case it is tripped by an over-
load current, until the reset coil is energized
by a small switch in the motorman's compart-
ment. The armature of the relay is held in
the normal position, that is, with the contacts
closed, by means of a tension spring, which
spring also affords a means of calibrating and
setting the relay to trip at any desired over-
load current value, depending upon the equip-
ment and service conditions.
The reverser used on this type of controller
is, like the line breakers and main contactor
units, operated electro-pneumatically. The
form of reverser is that of the well-known
cylinder type such as has been used for many
years on the standard "K" type of platform
controller. On account of the severe service
and increased capacity of motors, which this
controller is designed to handle, the parts of
the reverser must be very large and rugged
which is made possible by locating them under
the car body. The operating mechanism of
the reverser consists of two air cylinders with
a magnet valve directly attached to each cylin-
der. The pistons of the air cylinders are con-
nected to an arm on the shaft of the reverse
cylinder that carries the contact segments.
The energizing of one of the reverser magnet
valves admits air to its cylinder and rocks
the reverse cylinder to the opposite or reverse
position. Control fingers, as well as the main
current fingers, are also placed upon the
reverse cylinder, the function of which is to
commutate the control circuits as the reverser
is thrown. The control circuit energizing the
reverse magnet valve passes through an
interlock on the control cylinder of the cam
shaft, which connection is made only on the
"off" position of the main controller, thus
positively preventing the throwing of the
reverser until power is cut off from the motor
circuit. After one of the magnet valves of
the reverser is energized and the reverse
cylinder thrown over to the reverse position,
the control fingers on this cylinder transfer
SPRAGUE-GENERAL ELECTRIC PC CONTROL
987
Fig. 3. Type PC Motor Controller. Front view with arc-chute unit swung down
this control circuit from the magnet valve of
the reverser to that of the line breaker. This
transfer of control circuits gives the safety
feature of insuring that the reverser is thrown
to its final position before the line breaker
magnets can be energized and any current
applied to the motors. It also cuts off the air
from the reverser air cylinder, as the air
pressure is required only for throwing and not
for maintaining the reverser in position.
The fourth and principal part of the main
controller consists of the cam operated con-
tactors or magnetic blowout switches which
function in the proper sequence to make the
series and parallel connections of the motors
and to cut out the resistance sections used to
accelerate the car. These contactors are
constructed very similarly to, but smaller in
size than, the line breaker elements for they
are not required to have as great an arc
rupturing capacity as the line breaker. They
are, however, of sufficient capacity to open
the motor circuit, even under abnormal con-
ditions, if for any reason the line breaker
should fail to do so. One of the contactor
units without arc chute is shown in Fig. 6.
The arc chute for the entire group of con-
tactor elements is made up as a unit, that is,
the individual arc chutes are rigidly fastened
together and are hinged on the lower side, the
construction being similar to that of the
platform type of controller. By simply
loosening two spring thumb nuts, the entire
arc chute can be lowered as shown in Fig. 3,
thereby affording free access for inspection
or repair of the moving parts of the contactor
units. In any method of connecting up the
motors and resistors of the control equip-
ment certain of the contactors, due to their
location in the circuit, operate under more
severe conditions than others, which causes
a greater burning of the tips and arc chutes.
In the arc chute of such contactors there is
introduced a small auxiliary arc chute to
Fig. 4. Type PC Motor Controller. Rear view with covers removed
988
GENERAL ELECTRIC REVIEW
take this burning. This arc chute is revers-
ible and is readily renewable, it being easily
detached in a few seconds without tools and
without disturbing any other part of the con-
tactor.
Fig. 5. Line Breaker, with One Arc Chute Removed,
for PC Motor Controller
The movement of these contactor units is
effected by means of cams mounted upon a
rotating shaft which is located underneath
the contactors and which bears upon the
rollers of the contact levers. The construc-
tion is illustrated in Fig. 4. This shaft is
rotated by a pinion and rack, the rack being
actuated by the piston of two air cylinders.
The air pressure against the piston of the '* on "
cylinder tends to rotate the cam shaft to give
full parallel connections of the motors, while
the air admitted to the "off" cylinder pro-
duces a rotation in the opposite direction.
To each air cylinder is attached a magnet
valve which governs the admission of air
to that cylinder. The magnet valve attached
to the "off" cylinder is so arranged that
when the valve is in the normal or unener-
gized position the "off" cylinder is charged
with air from the supply reservoir, and when
this valve is energized the cylinder is con-
nected to the atmosphere. The magnet
valve governing the "on" cylinder has the
reversed function, that is, when in the normal
or deenergized position it connects the
cylinder to atmosphere while in the energized
position it admits air to the cylinder. It will
thus be seen that when neither of these
magnet valves are energized the air pressure
will be against the piston of the "off" cylinder
only, which will turn the cam shaft to the
"off" position. In order to advance the cam
shaft through the successive steps of the con-
trol, it is necessary to first energize the "on"
magnet and to admit air to the "on" cylinder.
This equalizes the pressure in both cylinders,
and the advancement of the cam shaft is then
obtained by reducing the air pressure in the
"off" cylinder. As this reduction is governed
by the magnet valve, it follows that the entire
control of this cam shaft from the first series
to the last parallel position of the motors is
obtained by the energizing or deenergizing
of a single valve.
On the cam shaft is also mounted a con-
trol cylinder with the segments and fingers
necessary to make the required control con-
nections for each step, and to insure the
proper functioning of the line breaker ele-
ments, the reverser, and the cam operated
contactors. Xo interlocks are used on the
contactor units themselves, as in the case of
other multiple unit controls; this control
cylinder takes the place of such interlocks
and thus gives not only a much less com-
plicated control connection but a greatly
reduced number of parts. Fig. 7 shows the
control and motor circuit connections for an
equipment suitable for four, 130 h.p., 600-volt
motors. This controller gives five series and
four parallel steps and is operated by nine
control wires in the train line. The con-
nections shown are for a hand control but,
by the addition of a series relay in one of the
motor circuits and one finger on the control
cylinder of the main controller, the equip-
ment can be made automatic with current
limit. This series relay opens up the control
Fig. 6. Contactor Unit for PC Motor Controller
circuit of the "off" magnet, thus preventing
the "notching up" of the motor controller
when the motor current is above a pre-deter-
mined value.
The master controller is provided with a
"slip ring" attachment which closes the
SPRAGUE-GENERAL ELECTRIC PC CONTROL
989
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990
GENERAL ELECTRIC REVIEW
trollev circuit to the control when the master
controller is moved from the "off" to the
first position. This contact remains closed
with any forward movement of the master
controller handle, but it immediately opens
if the handle is turned backward and it can-
not be closed again without returning the
handle to the "off" position and again ad-
vancing.
Line breaker element No. 1 is so inter-
locked that it can close only when the cam
controller is in the " off " position, and the cam
controller cannot advance from the "off"
position to the first position until this element
No. 1 is closed. Therefore, the control has
been made, as far as possible, proof against
abuse, improper, or unsafe operation.
The control current required to operate the
magnet valves is approximately 0.3 amperes
per car on a 600-volt circuit. Only a part of
the energy represented by the above current
is used in operating the magnet valves; con-
sequently, the control is particularly adapted
for use where the control current is to be
taken from a small batten- on the car.
A prominent feature of this control is that
the sequence of operation of these contactors
is positive as they are closed by the cam and
opened by a stiff spring. This feature effec-
tively eliminates the trouble found in using
individually operated contactors, viz.. that
due to the time lag of opening and closing
which varies with the electrical connections,
voltage, air pressure, etc. This controller has
also the advantage of insuring that, regardless
of the rapidity with which the motorman
advances the master controller handle, the
main controller must advance through all
the successive steps exactly the same as does
a drum controller, which not only protects
the motors from abnormal rushes of current
but also avoids improper circuits in the con-
troller itself.
This type of control contains, therefore,
in one piece of apparatus what was formerly
located in three separate boxes, that is, the cir-
cuit breaker, the contactors, and the reverser.
As will be seen from Fig. 2, all the conduit
inlets are at the back, the cables going into the
box and directly to the terminals thus elim-
inating much of the interior wiring that was
necessary on former types of equipments.
The cable inlets are located on a hard wood
strip to insulate the box from the conduit,
as it is recommended that the controller be
insulated from the grounded framework of the
car. Due to the combination of these pieces
of apparatus in a single box, this new type of
control equipment is considerably lighter in
weight than other types of multiple-unit
control of equal capacity, and occupies much
less space under the car.
This control system is applied to either two
or four-motor equipments for 600-volt or
higher voltage systems, and for motors of any
capacity. It is also applicable where tap-field
motors are used. When used on a line of
higher potential than 600 volts, a dynamotor
is not required as the small amount of energy
necessary for operating the control magnets
can be obtained by the use of a control
resistor.
991
GENERAL NOTES ON GROUNDING
By H. M. Wolf
Capital Electric Company, Salt Lake City
This article, which treats of the subject of grounds in a strictly practical manner, contains information
which should be very useful to those engineers who are concerned with grounded circuits. The author after
describing the various types of grounds, discusses their relative merits, the proper methods of installation,
the effects of various soil conditions, and the different methods of applying electrical tests. — Editor.
This article will deal only with the practical
side of grounding, i.e., the making and testing
of grounds; the history or necessity for
grounding will not be discussed. It has been
the general practice to make use of treated
surface grounds, i.e., ground elements placed
only a few feet in the earth and then treated
with some sort of solution, usually salt water.
The writer has attacked the grounding
problem from a different angle, and the
following are the different types of grounds
arranged in what he believes to be the order
of their relative importance. The series is
arranged on the basis that the most satis-
factory ground is the one that gives the best
results with the least expense and trouble.
(1) Grounds to water systems, where
proper conditions permit, are the cheapest
and best type. (These will be discussed later
in the article.)
(2) Grounds located at a permanent water
depth.
(3) Grounds located at a permanent mois-
ture depth.
(4) Treated surface grounds.
(5) Untreated surface grounds.
Relative Value of Different Types of Grounds
It has been truly remarked that a poor
ground is worse than none ; and an untreated
surface ground is absolutely worthless in
most cases, for the contact resistance is too
high, varying possibly from 12 ohms where
the permanent water strata is close to the
surface to 250 ohms in dry season where
water is not close to the surface.
Omitting, for the time being, consideration
of grounds to water systems, there remains
the choice between the ground placed at
permanent water or permanent moisture
depth and the treated surface ground. The
ground element placed at permanent water
or moisture depth will be under uniform
conditions throughout the year, and will
require no upkeep or testing until sufficient
years have elapsed to wear away the pipe.
The ground element placed at permanent
water depth will offer a constant resistance of
from 12 to 20 ohms, and the ground element
placed at permanent moisture depth will
cause a resistance of from 18 to 40 ohms.
The cost of placing these ground elements
will vary over a wide range, depending upon
the depth to which the pipe must be driven
and upon the nature of the soil; but an
average cost for placing about 800 of these
grounds at a possible average depth of 27
feet, under varying soil conditions, was about
$.5.00. This figure includes labor and material,
and placing wire on the pole, and testing the
resistance of the ground.
When a pipe is placed at permanent water
or moisture depth, the current discharged
to the ground cannot dry out the earth
surrounding the pipe because of the excess
amount of moisture present; but with the
treated surface grounds, where the soil is dry,
it is possible for the current to dry out the
soil surrounding the pipe, thereby causing a
rise in the contact resistance.
The treated surface ground is subject to
varying qualities as a ground; and it requires
systematic and regular testing until the
variables can be determined and the condi-
tions of maintenance and upkeep standardized
for each kind of soil. The life of the pipe is
shorter where grounds are treated than
where they are not treated, and it is believed
that the difference in life is quite noticeable.
To maintain a reasonably constant contact
resistance, one ground will require more salt
than another and will require the replacement
of the salt more often than another, due to
differences in the compactness of the soil
and the amount of moisture it contains. A
heavy rainfall with a loose earth soil will
wash a considerable quantity of salt away
from the ground element; and, when the soil
again dries out, the contact resistance will
show an appreciable increase. The change
of the seasons will affect the contact resistance
due to the fact that frozen soil is of higher
resistance than that which is not frozen.
For this reason it is desirable to sink surface
ground elements to a depth of at least 8 or 10
feet; a greater depth will be productive of
good results. These ground contacts might
vary in resistance from 1 to 5 to 40 ohms, and
992
GENERAL ELECTRIC REVIEW
even up to 2.50 ohms if not kept properly
salted.
Proper Grounding
For ordinary grounding purposes it is
believed that a ground contact resistance of
not more than 20 ohms is satisfactory; but
lower contact resistances are desirable in
connection with abnormally heavy currents or
large station equipments. The average
contact resistance where one pipe is placed
at permanent water depth is between 12 and
20 ohms, depending upon the size of the
ground element, its depth in the ground, and
more especially upon the kind or nature
of the soil. If the necessary expense is
justified, this resistance can be lowered to
one ohm or even less by placing additional
ground elements in multiple or by treating
the earth directly surrounding the ground
element with solutions to increase its con-
ductivity.
It is generally conceded that the earth has
no resistance except the contact resistance
which is generally taken as the resistance
between the ground element and the earth
directly surrounding the ground element.
The grounding problem then resolves itself
into one question, that of what is the allow-
able ohmic resistance of contact. This will be
determined by the requirements of the
particular case and the cost of obtaining the
desired results under the existing soil condi-
tions.
It would seem apparent from the data
already given that a satisfactory ground
could be obtained at any place under any soil
conditions, but this is not always possible.
Where rock is within a few inches or a few
feet of the surface, or where the soil is of
boulders as in old river beds, it is impossible
to get low contact resistances and a wire will
have to be run to some point where a proper
ground can be made.
The earth crust is made up of rises and
depressions in the stratified layers of soil
and these depressions are generally filled with
loose soil which, from all outward appear-
ances, seems to offer a satisfactory ground;
and in many instances seepage water is held
in these depressions. These conditions some-
times give satisfactory grounds, but it is
necessary to test to another ground suffi-
ciently removed to determine the actual
grounding value of such an earth contact.
The following facts are generally agreed
upon by those having made extensive ground
tests.
(1) Assuming a uniform soil and moisture
condition, the contact resistance is not
materially lowered by increasing the depth
of the pipe in the ground after the pipe has
reached a depth of about 8 feet. Placing the
pipe 16 feet deep, instead of S feet, would
likely lower the contact resistance only
6 to 12 per cent.
(2) The size of the pipe to be used should
be determined from the mechanical conditions
of driving and the possible saving due to the
longer life of a larger pipe, but not from the
difference in contact resistance due to
increased surface, for doubling the size of the
pipe gives only 6 to 12 per cent lower contact
resistance.
(3) Driving pipes near together, say a few
inches or a foot apart, is equivalent to driving
one pipe of the larger size; pipes driven not
less than 6 feet apart, when connected in
multiple, will give a combined resistance
inversely proportional to the number of
pipes placed.
(4) Ground elements can be tested with
either direct or alternating current with equal
accuracy, for there is no inductive or capacity
effects introduced.
Peculiarities of Special Interest
There are no doubt many peculiarities
connected with the process of grounding.
The. following have come to the writer's
attention and are of interest :
(1) When testing three grounds by alge-
braic applications of three equations with
three unknown quantities, it is noted that
if one of the contact resistances is very high
with respect to the other two, say five or
more times as high, the values determined
by the equation may be in error possibly
2 to 5 per cent. The writer's belief is that
while the resistance of the earth is generally
not considered, the earth does have a resist-
ance and the difference in values is due to the
resultant obtained by combining the earth's
resistance with the sum of the contact
resistances of the elements under test.
It is the belief of the writer that the earth
has a specific resistance, which depends upon
the nature of the soil, but that the resistance
is constant for different amperages unless the
contact is of such a nature that the increased
current can dry out the moisture in the soil
and change the nature of the surrounding
earth.
(2) If two pipes are driven into the earth
within a few feet of each other, either of the
GENERAL NOTES ON GROUNDING
993
pipes will show a lowering of its contact
resistance of from 2 to 5 per cent due to the
presence of the other pipe which is not
electrically connected in any way with the
pipe tested. This apparently is due to the
auxiliary pipe tending to tie the earth
together between the upper and lower strata
and offering a point of increased current
density.
Relative Value of Copper Plates and Iron Pipes
( 'op per Plates
I 1 ) Costly to place at any great depth.
(2) Cost of placing copper plates G or 8
feet is greater than cost of placing iron pipes
to the same depth, and the cost of the copper
itself is greater than the cost of the pipe.
(3) Have a short life in the ground.*
(4) Large contact surfaces are readily
obtainable with copper plates, but increased
surface within closely defined areas gives but
little decrease in contact resistances.
Iron Pipes
(1) Easy and cheap to place, even to a
considerable depth.
(2) Comparatively long life in the ground —
galvanized pipe will last from 10 to 25 years,
possibly average 15 to 18 years.
(3) Satisfies all the requirements of a good
ground element.
Value of Charcoal or Coke
Charcoal or coke has no value where
ground elements are placed at permanent
water or permanent moisture depth, as they
are not of especially low resistance and only
serve to hold moisture. With treated surface
grounds the charcoal or coke serves a useful
purpose when placed around the ground
element. Probably the best results can be
obtained by using charcoal or coke of about
one inch size and, after mixing it liberally
with some sort of loamy soil, filling it in
about the ground element to a depth of
possibly 6 or 8 inches. The use of charcoal
or coke with an untreated ground is not
productive of good results, and it does not
materially add to the value of the untreated
surface ground.
Water Systems for Grounding Purposes
Where the water system is of metal pipe,
this usually offers a very satisfactory ground-
ing medium, under certain restrictions; but,
where the mains are of wooden pipe and only
* There are still some adherents to the use of copper plates.
To those it is suggested that a piece of iron be buried with
the copper, as the iron (being more electro-positive than the
copper) will eat away before the copper will begin to depreciate.
the laterals or services are iron, the water
system should not be used as a ground.
The restrictions that were referred to are
as follows: First, where a water system is
to be used as the ground, the attachment
should be to one of the main pipes and it
should be made by means of an iron band or
clamp fitted around the pipe so that local
electrical action will not take place between
the copper fastening wire and the water
main but between the wire and the clamp.
Second, the copper or iron wire running
from the pole to the water main should be
encased in a galvanized iron pipe to (a)
mechanically protect the wire from being
broken, and (b) in the case of copper wire
being used, to increase the life of the copper
by offering a more electro-positive surface
than the copper. Third, an emergency ground
element of reasonable grounding quality
should be placed so that the opening of the
water mains at any point will not relieve the
circuit of a ground or endanger the workman
on the mains.
Soil Conditions and the Type of Ground
Assuming that it is desired to place a
ground element, the procedure should be as
follows :
First, determine insofar as is possible these
features concerning the character of the soil;
its depth, formations at different depths,
depth to either surface or live water, different
height of surface or live water at different
seasons of the year, and the amount and
depth of permanent moisture. It is surprising
how much information there can be obtained
on these subjects as the result of effort in
asking a few questions and making a small
amount of careful observation. There are
usually wells in most places that give con-
siderable data; then, also, well drillers and
city or county engineers are usually more or
less liberally supplied with data along this
line.
The writer has made considerable use of a
5-inch diameter auger post-hole digger and
has drilled holes 30 and 40 feet deep to study
the soil conditions. This is not a tedious
process by any means for holes have been
drilled 20 feet deep in one hour, and the
information obtained was readily applicable
to other locations which saved considerable
time in placing grounds elsewhere.
It is recommended that the intention of
driving a pipe to a permanent water depth
be held until it is satisfactorily shown
that this cannot be done. If permanent
994
GENERAL ELECTRIC REVIEW
water is readily obtainable, a pipe can be
driven to the necessary depth in most cases
without difficulty.
As the result of investigating the soil as
just described one will also have determined,
by the amount of moisture near the imper-
vious stratified layers, whether a permanent
moisture ground is possible in case there is an
absence of abundant water. If sufficient
moisture be found at 12 feet or deeper, a
satisfactory ground can be made by driving
a pipe to this depth; and, if the contact
resistance of one pipe is too high, a second
pipe can be placed (not closer than 6 feet)
and tied-in in multiple with the first pipe,
which combination gives one-half of the
resistance first obtained.
Careful investigations have indicated that
it is usually possible to place a pipe to
permanent water or permanent moisture
depth; but assume that in this case neither
of these could be accomplished. The investi-
gation already made will give sufficient data
to determine whether a treated surface
ground would secure the proper results, but
it is safe to say that a treated surface ground
would be satisfactory if the soil was of loose
earth formation. At least it would be worth
while to place this ground and make the
necessary7 tests, as the cost would be small
and the experience very valuable.
Several small towns, where solid rock
varied from a few inches to a few feet from
the surface, would necessitate a common
ground system with the ground elements
specially and advantageously placed ; perhaps
wells or other open water sources might be
available.
Placing Ground Elements
Driving a pipe to permanent water or
moisture depth offers unusual difficulties only
when a considerable depth must be reached.
The general practice is to drive the pipe with
a hammer, the lineman swinging the hammer
from the pole; but the writer has made up a
special hammering ram by attaching a guide
pipe to a weight and operating the device
by means of a rope through a pulley attached
to the top of the pole or a cross-arm. A
complete hammer of this kind can be made
up for about SS.00 and will prove a great
saving in time and labor. A 50-lb. hammer
is used with ?4-inch pipe for all grounding
purposes, except for special soil conditions
where the 34-inch pipe bends too easily and
a 1 J 4 -inch pipe is used. This latter is driven
with a 100-lb. hammer. This standard has
been arbitrarily chosen and has given good
results.
Where a pipe longer than SO feet is to be
placed, it will be necessary to couple lengths
of pipe together and this coupling is liable
to prove bothersome. Considerable difficulty
has been experienced from pipes breaking at
the coupling, until a proper standard was
developed which made the joint stronger
than the pipe itself. Many grounds 30 to 35
feet deep have been placed, quite a number
40 to 50 feet deep, and one 60 feet deep.
Undoubtedly, under favorable conditions,
pipes can be driven to 100 feet depth.
In placing treated surface grounds, it is
recommended that a hole about S inches in
diameter be drilled to at least 8 or 10 feet
depth, and if possible to 15 feet depth. A gal-
vanized iron pipe not smaller than 1 inch
diameter (preferably I1 4 or 1}A inches in
diameter) should be placed in the center of
this hole and a mixture of charcoal or coke
with loamy soil tamped in about this pipe
for at least 6 feet in height. The rest of the
hole can be filled with the earth that was
removed. To treat the pipe with salt, pour a
liberal amount of salt water around the pipe
and, after the ground has dried out on the
surface, sprinkle a reasonable amount of
salt on the ground in a ring about the pipe,
allowing possibly 18 or 24 inches clearance
from the pipe to protect it from a concen-
trated chemical action at the surface. The
salt will then be carried into the ground
with the rainfall and will maintain a low
resistance contact. The salt will have to be
replenished from time to time and tests
should be made to determine the average
varying conditions, from which a practice
can be established in accordance with the
requirements.
Testing Grounds
Algebraic Method
The most accurate method of determining
the value of a ground is to measure its contact
resistance in ohms. This can best be done
by applying the algebra of three equations
with three unknown quantities, which is a
very simple process. It is necessary to have
three ground elements to make this test, but
the resistance need not be the same; so that
two pipes can be driven temporarily into the
ground and removed after the test is made.
Because of the accuracy and ease of appli-
cation, this method is strongly recommended
for all experimental and "standardizing testing
purposes.
GENERAL NOTES ON GROUNDING
995
Ammeter Test with Two Grounds
It is a common practice to test, with an
ammeter, the current flow between two pipes,
and take a voltage reading across the pipes
at the same time. This method is accurate
only when the pipes are of the same resistance.
If the two pipes are of equal ground qualities,
each is responsible for one-half of the total
resistance of the circuit; but if the grounds
are not of the same value, it is absolutely
impossible to determine what is the resistance
of each.
Fuse Test
It has been established as a standard in
some localities that a satisfactory ground
will cause the blowing of a 5-ampere fuse.
Tests of fuses have shown that a 5-ampere
will sometimes melt at from 7 to S amperes in
5 minutes with a room temperature of about
70 degrees Fahr. The fuses were 24 inches
long and were supported horizontally on small
metal contacts. In other tests a 5-ampere
fuse carried 12 amperes indefinitely without
warming up perceptibly to the hand.
It is evident that the range of variation of
melting point of a fuse is wide and 25 amperes
may perhaps be required to blow a 5-ampere
fuse instantly. It is believed that the point
at which a fuse will blow instantly can be
standardized within close limits, but that the
time limit at which a fuse will be melted
cannot be standardized due to the radiation
of heat which is dependent upon several
factors that are usually uncontrollable.
Assume two pipe grounds under test, each
having 12 ohms contact resistance, or a
combined resistance of 24 ohms. At 1 10 volts,
110 divided by 24 equals 4.0 amperes which
will not even melt the 5-ampere fuse.
Assume one pipe of 12 ohms contact
resistance against a water system ground of
say one ohm resistance. At 110 volts, 110
divided by 13 equals 8.5 amperes which would
require some little time to melt the fuse:
perhaps it would not melt at all.
These tests were made with open string
fuses, but later tests were made with enclosed
fuses. The results, however, were not satis-
factory owing to the time factor. If it is
possible to make up a fuse that will blow
instantly within well defined limits, a fuse
that is rated at 5 amperes will prove of
value.
Because of the inability to blow 5-amperc
fuses on 110-volt circuits, and to avoid the
time element, the writer made 5-ampere fuse
tests with the primary distributing voltages,
1100, 2300 and 6600 volts. As a matter of
economy, the tests were made between two
independent and permanent grounds, rather
than to cause the placing of a temporary
ground at great cost for testing only. This
made the testing cost but a very small per
cent of the total cost of securing satisfactory
grounds. The distance between the grounds
was usually not less than 14 mile which
insured good grounding.
General Testing Practice
The depth to water should be known and
the pipe driven to the desired depth. In such
cases it is only necessary to know that the
pipe is intact and that it has not broken at a
coupling. This can be readily determined by
running a wire down the pipe to the distance
the pipe was driven. If the pipe point has
been flattened, but not welded, water will
rise in the pipe and the end of the wire should
show moisture.
Assuming any given resistance between two
grounds, a given capacity fuse will act with-
in closely defined limits of performance under
any similar tests (if the fuse is blown instantly)
and a standard practice can be established
for different voltages so that the fuse will
blow with about the same amount of force.
When testing with a 5-ampere fuse about
24 inches long on 2300-volt circuits, the fuse
had to be completely destroyed to prove the
ground to be satisfactory. On 6600-volt
tests, a 2-ampere fuse was put in series with a
5-ampere fuse, and if the 5-ampere fuse blew
it did so with considerable force which showed
that the rush of current was great and the
ground was satisfactory.
To test a pipe while driving it, connect
one side of a 110-volt circuit to a well (if
one is nearby or if not to a pipe temporarily
driven in the earth), connect the other side
of the 110-volt circuit to an ammeter so
arranged that contact can be made at will
from the ammeter to the pipe being driven.
When the pipe is started into the ground the
ammeter will show a deflection which will
be very small but which will increase as the
pipe is driven into the earth, until a certain
fixed point is reached. This will be the
greatest deflection that will be read until
thoroughly wet soil is reached, when the
deflection will show a marked increase
suddenly. The pipe should then be driven
four to eight feet farther. This method has
been used with excellent results in determining
water depth.
996
GENERAL ELECTRIC REVIEW
THE VOLUME RESISTIVITY AND SURFACE RESISTIVITY OF
INSULATING MATERIALS
By Harvey L. Curtis, Ph. D.
Associate Physicist, Bureau of Standards, Washington, D. C.
After naming the factors which affect the volume resistivity and the surface resistivity of an insulating
material, the author describes the influences which these factors exert. Then he furnishes tables listing the
values of resistivity for a large number of the more common insulators and gives an example of the method for
applving these data to calculating practical problems. — Editor.
It has long been known that the insulation
resistance between two conductors which are
insulated by a solid dielectric depends upon
leakage over the surface of the insulator as
well as conduction through the material.
Very little quantitative data has been pub-
lished, however, by which the resistance of the
two paths can be computed in any given
case. To procure more data upon this sub-
ject, different kinds of solid insulating ma-
terials (mostly hard rubber substitutes) have
been collected and their surface and volume
resistivity measured under different condi-
tions of temperature, humidity, and applied
voltage.
The volume resistivity, p, of a material is
the resistance between two opposite faces of
a centimeter cube of the material. It may be
/? A
expressed by the equation p = —j- where R
is the resistance in ohms of a specimen of
uniform cross-section .4 and length /. To
measure the resistivity of the insulators a
specimen approximately 10X10X1 cm. was
employed. This was floated upon mercury,
and three short concentric copper tubes were
placed on the upper surface. Sufficient
mercury was then poured into the inner tube
and between the two outer tubes to cover
the bottom, while the two inner tubes were
carefully insulated from each other. The
resistance was measured between the mer-
cury on which the specimen floated and the
mercury in the inner tube. The outer ring of
mercury was maintained at the same poten-
tial as that in the inner tube and hence served
as a guard ring to prevent leakage over the
surface.
The volume resistivity of a material may
depend upon its temperature, upon the applied
voltage, and upon the amount of moisture
absorbed by the material. The resistivity
decreases with increasing temperature. The
resistivity of most materials at 30 deg. C. is
from one-half to one-third of the resistivity
at 20 deg. Most materials show no change in
resistance with change in the voltage until
the breakdown voltage is approached. How-
ever, if a porous material such as marble or
slate has water absorbed in its pores the
resistance will decrease with increasing voltage
at comparatively low voltage. With 50 volts
it is often found to be two or three times that
with 500 volts. Most materials do not absorb
enough moisture from the air to change the
volume resistivity appreciably, but with
porous materials such as marble, slate and
unglazed porcelain, the absorption of moisture
is sometimes sufficient to make the resistance
in very humid air only one one-hundredth of
that in very dry air.
Values for the volume resistivity of various
materials are given in Table I. These are, in
most cases, the mean of the measurements
upon two or more samples. They were taken
at 22 deg. C, using 200 volts. The measure-
ments were made when the samples were dry.
The leakage over the surface of insulators
is best determined by measurements of the
surface resistance. The surface resistivity a
is the resistance between two opposite edges
of a square centimeter of the film of water or
other liquid which is condensed on the surface
of the material. It may be expressed by the
equation
R'b
where R' is the resistance of a film of length
I and breadth b. While for purposes of
definition it is desirable to use a square
centimeter, yet the equation shows that the
size of the square is immaterial, since the
resistance of a square inch or a square foot of
a uniform film is the same as the resistance
of a square centimeter.
There is no method by which the surface
resistance alone can be measured. If two
long metal strips are pressed upon the surface
of a thick slab of insulating material so that
their inner surfaces are one centimeter apart,
the resistance per unit length of the strips due
to the flow of current through the material
is about three times the volume resistivity.
Since this is in parallel with the surface
VOLUME AND SURFACE 'RESISTIVITY OF INSULATING MATERIALS 997
resistance, the total resistance T is given by
the formula
*~h£ ■■-7^-K+(S,+-]
Hence if T/3p is small, 0" = T approximately.
For most materials T /3p is negligible, except
when the material is in a very dry atmosphere.
The surface resistance of most materials
is very much higher at low humidity than at
high humidity. The exceptions are waxy
materials such as paraffin and beeswax. For
these any condensed moisture collects in drops
70 per cent humidity, however, the surface
resistance decreases rapidly. New hard rub-
ber maintains its high insulating properties
only to 50 per cent humidity, while the
resistance of glazed porcelain and old hard
rubber decreases from the very lowest hu-
midities. With the exception of paraffin the
changes are very large. The resistance at
high humidities of amber, glazed porcelain,
and new hard rubber is about one-millionth
of that at low humidities, while old hard rub-
ber changes by a factor of 1011, or 100 trillion.
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Relative Humidity
Fig. 1
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Relative Humidity
Fig. 2
Curves showing the relationship between surface resistance and relative humidity for some common insulators
and docs not spread over the surface. With
other materials the surface resistance is not
infrequently a million times as great at low
humidity as at high humidity. In one case
the resistance changed by a factor of IO11. To
be able to show such enormous changes upon
a curve it has been necessary to plot the
logarithm of the resistance rather than the
resistance. Three sets of curves are shown,
covering materials of general interest. To
facilitate comparison they are all plotted to
the same scale.
The curves of Fig. 1 are grouped to show the
very different behavior of some common
insulators. They are all very good insulators
at low humidity. Paraffin maintains its
insulating properties at the highest humidities.
Amber is an excellent insulator so long as the
humidity is less than 70 per cent. Above
In Fig. 2 are grouped some materials which
are good insulators. The G.E. 55R is one of
several very similar moulding compounds
which are being prepared by the General
Electric Company. It compares very favor-
ably with new hard rubber. Also it deterio-
rates very little, if at all, on exposure to light,
which is in marked contrast to the behavior
of hard rubber. Shellac was measured by
coating a surface of glass. Also a number of
compounds were measured in which shellac
was used as a binder. In every case the
curve was nearly identical with that shown.
Evidently the shellac coated the other par-
ticles and the condensation was that caused
by the shellac alone. The curve for mica is
that for a very clear piece. A number of
samples were examined and they showed
great variability.
998
GENERAL ELECTRIC REVIEW
In Fig. 3 are given curves for some of the
poorer insulators. The marble was a piece
of clear Italian marble. The upper curve
shows the effect of impregnating with paraffin.
A piece was boiled in paraffin until bubbles
ceased to come off. It was then sandpapered
Iff I7|
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Relative Humidity
Fig. 3. Curves showing the relationship between surface
resistance and relative humidity for some
of the poorer insulators
to remove any paraffin which did not pene-
trate the marble. Experiments show that
coloring materials do not materially affect the
surface leakage of celluloid. Slate is very
variable, and it would require many tests to
fix an average value. It is one of the few
insulators in common use where the current
flowing through the volume of the material
is usually greater than that flowing through
the surface film.
Besides humidity there are other conditions
which may affect surface leakage. Tem-
perature produces an effect which is insig-
nificant compared to the effect of humidity.
However, exposure to light, either sunlight or
ultra-violet light, may produce chemical
changes at -the surface which will greatly
affect the surface resistance. Changes w^hich
may take place in hard rubber are indicated
in Fig. 1. At 90 per cent humidity the newr
hard rubber had a resistance nearly 10,000
times as great as the old hard rubber which
had deteriorated by exposure to sunlight.
Other materials showed a slight deteriora-
tion, while some showed none at all.
Materials which are used in such places
that they are either in constant service or
must be available for service under all con-
ditions must be judged by their poorest
performance. Therefore in considering the
surface leakage it is necessary to take the
highest humidity to which the material is
likely to-be subjected. Within buildings the
humidity occasionally is as high as 90 per
cent. Hence insulators which are subjected
to the normal fluctuations of humidity and
which must be available for service at all
times can best be judged by the value of the
surface resistivity at 90 per cent humidity.
For this reason the values of the surface
resistivity at 90 per cent humidity are given
in Table 2.
It should be noted that the surface resistance
may be affected by very minute traces of
foreign matter upon the surface. In the case
of carefully cleaned quartz, the surface
resistance corresponds very closely to that
which is computed from the thickness of the
water film* and the resistance of distilled
water. But. it requires only one one-hundredth
of a milligram of common salt per square
meter to lower the resistance by a factor of a
thousand. With well cleaned glass, however,
the resistance of the water of the film is much
less than distilled water, corresponding quite
closely to the resistance of water which has
been thoroughly digested with pulverized
glass. This shows that the water of the film
dissolves material from the glass, so that a
small amount of impurity on the surface will
Section of Porcelain Insulator between the
electrodes, as assumed in example
not materially affect the surface resistance.
In this same way the surface resistance of
insoluble materials like rosin and amber will
*This was determined by Ihmori by weighing thin plates of
quartz firit in dry air and then in humid air. Wied. Ann. 31
p. 1006; 1887.
VOLUME AND SURFACE RESISTIVITY OF INSULATING MATERIALS 999
be greatly decreased by small amounts of
soluble salts on the surface, while the surface
resistance of soluble materials like mica and
marble will be but slightly affected by their
presence.
The above facts show that very slight
differences between two samples will make
marked differences in the surface resistance.
A factor of 10 has often been observed between
two samples which were supposed to be
identical. The results which are given must,
TABLE I
VOLUME RESISTIVITY OF MATERIALS
Material
Ceresin
Paraffin, special
Quartz, fused
Hard rubber, new
Mica, clear
Sulphur
Amberite
Rosin
G.E. No. 55 R
Bakelite No. L 558
Electrose No. 8
Halowax No. 5055 B
Glyptol
Paraffin (Parowax)
Shellac
Glass, Kavalier
Insulate No. 2
Sealing wax
Duranoid
Murdock No. 100
Beeswax, yellow
Khotinskv cement
G.E No. 40
G.E. No. 55 A
Moulded mica
Porcelain, unglazed
Stabalite
Glass, plate
Halowax No. 1001
Dielectrite
Wood, paraffined mahogany .
Gummon
Tegit
Volume Resistivity
Bakelite No. 1
Wood, paraffined poplar.
Condensite
Wood, paraffined maple .
Celluloid
Lavite
Hemit
Marble, Italian
Fiber, red
Marble, pink Tennessee .
Marble, blue Vermont . . .
Ivory
Slate
Megamegohms*
Over 5,000,000
Over 5,000,000
Over 5,000,000
1,000,000
200,000
100,000
50,000
50,000
40,000
20,000
20,000
20,000
10,000
10,000
10,000
• 8,000
8,000
8,000
3,000
3,000
2,000
2,000
1,000
1,000
1,000
300
30
20
£0
5
4
3
2
Megohms
200,000
50,000
40,000
30,000
20,000
20,000
10,000
10,000
5,000
5,000
1,000
200
100
therefore, be considered as giving the order of
magnitude rather than exact values.
In order to facilitate the use of the results
given in Tables 1 and II, Table III has been
compiled. In it the materials are arranged in
alphabetical order, and the volume resistivity
and surface resistivity at 90 per cent humid-
ity are given.
TABLE II
SURFACE RESISTIVITY OF MATERIALS
AT 90 PER CENT HUMIDITY
Material
Ceresin
Paraffin, special
Paraffin (Parowax)
Bakelite No. L 558
Beeswax, yellow
Rosin
Sulphur
Sealing wax
Halowax No. 1001
Amberite
Electrose No. 8
Glyptol
Khotinskv cement
Halowax No. 5055 B
Insulate No. 2
G.E. No. 55 R
G.E. No. 40
G.E. No. 55 A
Shellac
Wood, paraffined mahogany
Mica, clear
Moulded mica
Murdock No. 100
Wood, paraffined maple ....
Wood, paraffined poplar. . . .
Celluloid
Condensite
Glass, Kavalier
Hard rubber, new
Porcelain, glazed
Gummon
Hemit .
Duranoid
Bakelite No. 1
Fiber, red
Quartz, fused
Lavite
Porcelain, unglazed
Tegit
Dielectrite
Ivory
Stabalite
Marble, pink Tennessee ....
Glass, plate
Marble, Italian
Marble, blue Vermont
Slate
Surface Resistivity
at 90 per cent
Humidity
Megamegohms
Over 100,000
Over 100,000
7,000
900
500
200
100
80
70
6
2
2
Megohms
700,000
600,000
400,000
100,000
10,000
10,000
10,000
7,000
5,000
3,000
2,000
2,000
2,000
1,000
1,000
1,000
1,000
600
400
400
300
200
200
200
100
60
50
40
40
40
30
20
20
10
10
*A megamegohm is a million megohms.
1000
GENERAL ELECTRIC REVIEW
As an example of the method of using the
results for the estimation of resistance, the
resistance between two electrodes insulated
by a porcelain insulator of the form shown in
cross-section in Fig. 4 will be computed.
The resistance may be taken as that of two
circuits in parallel; viz., that through the
insulator and that over the surface. The
TABLE III
VOLUME AND SURFACE RESISTIVITY
OF MATERIALS
resistance R through the insulator will be
Material
Volume
Resistivity
Ohm-Cms.
Surface
Resistivity
at 90 Per Cent
Humidity
Amberite
5X10'6
6X10'=
Bakelite Xo.l
2X10"
2X108
Bakelite Xo. L 558
2X1016
9X10"
Beeswax, vellow
2X1015
5X10"
Celluloid
2X1010
1X109
Ceresin
Over 5X1013
Over 1 X1017
Condensite
4X10
1 X10'«
Dielectrite
5X10'-
4X107
Duranoiil
3X10'5
3X108
Electrose Xo. 8
2X1016
2X1012
Fiber, red
5X109
2X108
G.E No. 40
1X1015
1X10'°
G.E. No. 55 A
1X1015
1X10W
G.E. No. 55 R
4 X 1016
1 X10"
Glass, Kavalier
8X1015
1X109
Glass, plate
2 X 1013
2X107
Glvptol
1 X1016
2X1012
Gummon
3X101-
4X108
Halowax No. 1001. .
2X1013
7X10"
Halowax Xo. ,505.5 B.
2 X 1016
6X10"
Hard rubber, new . -
1X10"
1X109
Hemit
1X1"
4X108
Insulate No. 2
8>
4X10"
Ivory
2X10'
4X10'
Khotinskv cement . .
2X1015
7X10"
Lavite
2X10'°
IX 10s
Marble, Italian
1 X10"1
2X107
Marble, pink Tennessee
5> 10
3X107
Marble, blue Vermont
1X109
1X107
Mica, clear
2X1"::
5X109
Moulded mica
1X1015
3X109
Murdock Xo. 100. . .
3X10
2X108
Paraffin (special)
Over 5X1018
Over 1 X 1017
Paraffin i Parowax i
1X10'6
7X1015
Parcelain, glazed
6X108
Porcelain, unglazed. . .
.3X10"
6 X 10'
Quartz, fused
i )ver .5 X 101S
2X108
5X1016
2X10"
8X1015
8X1013
Shellac
1X10'6
1 X 10'°
Slate ;
1X108
1X107
Stabalite
3X10"
4X10'
Sulphur
1X10"
1 X10H
Tegit
2X10'2
5X10'
Wood, paraffined
mahoganv
4X10IS
7X109
. paraffined maple
3X1010
2X109
Wood, paraffined
poplar
5 X 10">
2X109
R = p-l =
Pt
-r—'Pi t~, m approximately, where
,4 2tt ad+w d-
t ■ is the thickness of the porcelain, and a
and d have the values indicated. The surface
resistance between the outside electrode and
the lower rim can be found by the following
method. Let P be any point on the surface.
The resistance of a circular element of the
surface of width ds and circumference 2irr is
. The total surface resistance R' is
2irr •
R'
= fe
ds
2 w r
But
s = — : where 5 = OP
COS 6
ds = dr cos 8
log—
Hence R'=277e7iJa T1 =27757^ =2V7o71
The resistance of the inside surface will be the
same, so that the total surface resistance
between electrodes is
2.3 o- , c
—i log -
it cos o a
To find a numerical value, assume
i = 1 cm
a =5 cm
d =5 cm
c =20 cm
8 =45°
a = (3 X 10s the value at 90 per cent humidity
p =3X1014
The value of p is taken as that of unglazed
porcelain, since that under the electrodes is
seldom glazed.
Then R=\XW2 ohms, the resistance
through the porcelain, and i?' = 4X108 ohms,
the resistance over the surface. But the
current through R is negligible in compar-
ison with that through R', so that the resist-
ance between the electrodes is 4X10* ohms
at 90 per cent humidity.
If the relative humiditv is 40 per cent
a will be 2X1013, and R'~ becomes 1X1013.
The total resistance T is
RR'
= 9X10l
R + R'
which is only slightly less than R. At lower
values of the humidity, the surface resistance
becomes of less importance, so that for a
WATER RHEOSTATS
1001
porcelain insulator of this form the leakage
over the surface at humidities below 40 per
cent is negligible.
These results show that the surface resist-
ance must always be considered where the
resistance of a solid insulator is being meas-
ured. The surface leakage may become
negligible at very low humidities. In other
cases it becomes necessary to estimate its
amount. For a considerable part of the
cases which occur in practice the surface
resistance is so much lower than the volume
resistance that the latter does not need to be
considered.
WATER RHEOSTATS
By N. L. Rea
Construction Department, General Electric Company
A water rheostat is of great service in making heat runs and other tests on large generators. Below 2300
volts salting is necessary and a tank must therefore be used; although it is usually possible to step up the
voltage and thus avoid this nuisance. With hydro-electric plants it is customary to suspend the rheostat
electrodes in the forebay or tail race, preferably in running water to get rid of the gases. The results of some
tests on rheostats of this kind are given. A number of wrong principles in design and construction of tank
rheostats are mentioned, with recommendations fcr correcting the faults. — Editor.
It is often necessary to make heat-run
tests on large generators after installation,
which usually necessitates some form of
artificial load. Many experiments have been
made to devise a cheap, reliable, and satis-
factory form of temporary water rheostat.
For voltages below 2300, salt must be
used to lower the water resistance and
therefore it is necessary to build a tank to
hold the electrolyte. In the majority of
cases, however, it is possible to step up the
voltage and to connect the artificial load to
the high-tension side of the transformers.
Water rheostats have been used satis-
factorily for voltages as high as 45,000.
Water rheostats for hydro-electric plants
are usually installed either in the tail-race
or in the forebay; and many experiments on
spacing, type of electrodes, etc., have disclosed
some surprising results. For use as electrodes,
the following have been tried: spheres, copper
bar or rods, carbon rods, iron plates, and
iron pipes. The two latter give very good
results and are usually available in a power-
station. Rectangular plates are used which
are hung from one corner by a rope to a
strain insulator, or the rope may be tied to a
standard line insulator installed horizontally.
With this latter arrangement, it is, of course,
necessary to disconnect the rheostat when
making adjustments.
It has been found that the spacing of the
plates (the distance between them) has very
little, if any, influence on the load capacity.
The surface contact resistance is the governing
factor, for the same electrode surface passes
practically the same current whether the
plates are five or fifty feet apart. In a three-
phase circuit, plates arranged in a straight
line with uneven spacing give apparently
the same degree of balanced load as is fur-
nished by a carefully arranged equilateral
triangle.
When it is necessary to use more than one
electrode per phase, more current will be
transmitted if the connected plates are
separated several feet than if they hang close
together. If possible, the electrodes should
be hung in running water to carry away the
steam and gases which form on their surfaces;
otherwise, arcing may be caused by this gas
blowing the water away from the electrodes.
In some cases the rheostat has been placed
in the tail-race, and protected from waves
by a hollow square of timbers. These timbers
;,-«.- ^'j.- e»
&G— 9
eve—a*" 9o*f3
Fig. 1. Arrangement of Pipe Electrodes for Water Rheostat
must, however, be kept at some little distance
from the electrodes or they will be carbonized
by the current flowing over them and even-
tually take fire. It is rather astonishing to see
a log apparently blazing under several inches
of water. If the electrodes are installed inside
1002
GENERAL ELECTRIC REVIEW
the building, care must be taken to eliminate
the possibility of accidental shocks to oper-
ator.
It is advisable that all adjacent metal parts
of the building be connected together with
cables as a protection to persons and to
JJ^ III Mil
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TWo &rn Pipes •* ft Long In Parallel
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.ong 3 ft. From Center of Other- Pipes
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On Each Electrode All In Line But
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Fig. 2. Tests on Water Rheostat shewn in Fig. 1
prevent burning between the iron and
concrete. Any iron embedded in concrete
seems to cause a concentration of current
at that point.
Where rheostats are installed in running
water a large number of fish are usually
killed. When the plates are comparatively
close together, a large fish lodged between
them seems to offer less resistance than
water and it carries enough current to burn
it to a crisp.
A series of tests was recently made at the
Cedars Rapids Manufacturing & Power
Company. Fig. 1 is a sketch showing the
arrangement of pipe electrodes used in this
particular case, and Fig. 2 gives the curves
resulting from the test. This water rheostat
was located in the head-race and arranged
as shown in Fig. 1. About 1000 cubic feet of
water flowed through each bay per second
while the rheostat was being tested. A large
part of the surface of the steel headgates is
always under water, so that these gates and
all other iron in the water around the rheostat
were connected together by cables as shown
in the sketch. A loose connection showed
that considerable current was carried by
these cables. The steel gates themselves are
connected by shafting. No trouble, whatever,
was found in keeping the load balanced with
the same length of pipe electrode in each bay ;
there was no steaming at the pipes, and one
could not tell by looking
at them when the load was
on or off the rheostat.
The curves were taken
while experimenting on the
number and length of elec-
trodes necessary for this
series of tests.
, Under some conditions it
is impossible to secure sat-
isfactory results with a tem-
porary arrangement such
as just outlined; or again,
it may be desirable to have
a permanent rheostat as
part of the power-station
equipment.
The first cost and main-
tenance of a permanent
rheostat is small and the
expenditure is usually war-
ranted by the advantages
offered by the equipment.
This is especially true for
hydro-electric stations of
any considerable size, or
for those which contain several units. A good
rheostat gives a ready and convenient means
for testing machines or adjusting governors
without interfering with the commercial opera-
tion of the power-station.
Much thought, time, and money have been
expended in the past on various schemes
( >f water rheostat design, and the same ground
has been covered many times by different
engineers. The natural way of approaching
the problem is to construct some form of
tank provided with an overflow and with a
pipe for admitting fresh water at a point
opposite the overflow. Then electrodes of
pipe or iron plates are hung in the tank
with ropes and strain insulators. This
arrangement has the same capacity limi-
tations as has the temporary rheostat, for
satisfactory service is impossible when violent
gassing (and consequent arcing at the elec-
trodes) takes place. This arcing usually occurs
at lower capacities in tank rheostats than in
temporary outfits, due to the smaller amount
and the poorer distribution of the fresh water.
Errors are frequently found in the design
and construction of tanks, in the arrangement
OPERATION OF ELECTPICAL MACHINERY
1003
of electrodes, and in the manner of admitting
cooling water. Some of the more common
errors will be named, and the remedies
developed by experience with various types
will be described.
Wooden tanks have been constructed
using the iron hoops common to stave
construction, only to find that the current
came through between the staves to the iron
hoops and quickly burned many holes. This
trouble can be overcome by several inside
bands of flat bar iron against the inside
surface of the tank. These bars must be
firmly secured in place by bolts and vertical
iron straps connecting the several bands
together.
Many of these tanks have been carefully
insulated from the ground which is unneces-
sary as the rheostat operates as well, and is
much safer, with the tank grounded. Boiler
plate or concrete construction is preferable
to wood. It is advisable that metal reinforcing
be omitted from concrete tanks, due to the
lack of definite data on the effect of current
on this reinforcement.
It has been found that a more intelligent
use of cooling water will overcome arcing at
the electrodes and allow of a much higher
load capacity. Two schemes have been used
successfully. Both of them have, as a basis,
a false bottom in a portion of the tank with
some means for admitting the cooling water
under pressure to this space.
The first rheostat constructed along these
lines had three vertical wooden posts attached
to the bottom of the tank and the pipe
electrodes were slid over the posts. Several
small holes were drilled in this false bottom
around these posts. The pipes were kept from
swinging and the jets of water played over
the electrode surface, cooling and sweeping
away any gas or steam.
In a later rheostat, the posts were made
one-half inch smaller in diameter than the
pipes and a large hole was drilled through
them into the cold water space under the
false bottom. The electrodes were capped
to compel the cooling water to flow down
between the outside of the post and the
inside surface of the pipe.
With this arrangement the tank can be
liberally salted, and loads up to 15,000 kw.
at 13,000 volts have been carried without
the least trouble from arcing.
PRACTICAL EXPERIENCE IN THE OPERATION OF
ELECTRICAL MACHINERY
Part XII (Nos. 57 to 59 inc.)
By E. C. Parham
Construction Department, General Electric Company
(57) CRANE TROUBLES
Fig. 1 shows diagrammatically the con-
nections of the limit-switch of a hoist induc-
tion motor and of that section of the con-
troller which is connected to the motor
stator. The object of the limit-switch is to
open the motor circuit if the operator should
forget and allow the motor to raise the hoist
too far. Under this condition a ball carried
by the hoist rope interferes with a lever, the
consequent movement of which separates
contacts a and c from contacts b and d, respec-
tively. The opening of these contacts inter-
rupts the Ll and L2 line wires that pass
through the controller before going to the
motor. On the down side of the controller
a by-pass is provided to short-circuit the
limit-switch contacts. This provision is made
in order that, after the ball has opened the
contacts of the limit switch, the controller
may be used for lowering the hook but not
for raising it. Of course if the limit-switch
contacts fail to touch for any local reason,
the raising motion will become inoperative
but the lowering motion will not.
An operator had run the hook too high and
had tripped the limit-switch. Upon throwing
the controller to the down side, the motor
would hum and the electric brake would
release but the hook would not lower. Ring-
ing out with a magneto proved that all the
wire parts of the lowering circuit were intact.
Upon testing the controller cylinder, however,
no ring could be obtained through strip e
which was used to connect two cylinder
segments together. An inspection disclosed
the fact that a screw had worked loose in this
strip so that finger/ represented one side of a
break in the circuit. This instance is cited
because, out of a total of twenty or more
controllers that had been subjected to un-
usually exacting service for over a year, this
11)04
GENERAL ELECTRIC REVIEW
simple defect was the only one that had given
the local electrician trouble to locate. The
same symptoms would have been caused by a
loose finger /, also by excessive burning of
that finger. A poor connection of tap t would
have interrupted the stator circuit thereby
Dcvvn
(SMMJU
Brake
Coil
Limit
Switch
Fig. l
the
crane inoperative m
both
them on all
c and d are
respectively,
them on all
rendering
directions
It will be noticed that contacts a and b are
connected to fingers 3 and 2, respectively,
and that strip g short-circuits
dowx positions; also contacts
connected to fingers / and 1
and that strip e short-circuits
down positions. Therefore, the hoist can be
lowered whether the limit switch is closed or
not. but it cannot be raised if either member
of the switch is open because each member
is in series with one of the raising circuits.
In many cases where it is practicable to lower
on all positions but impracticable to raise on
any, inspection of the limit-switch will likely
disclose a bad contact that may not be
evident to the eye. Contact failure of fingers
1 . 2, 3 or/, possibly on account of the cylinder
having become eccentric, its shaft bent, or
its bearings loose, will give the same symptoms
for under any of these conditions the fingers
may make contact only on certain positions
of the cylinder.
On a similar crane that had just been
installed, the line fuses would blow as soon as
the controller handle was put on the first
notch in either direction. This was found to
In1 due to the connecting of limit switch wire
a to the L3 stator wire instead of to the L2, as
in the diagram. On another occasion the
crane could be made to lower a load on all
positions but could not be made to raise the
load on any position. This was found to be
due to a blown fuse; the open-circuit really
disabled both the raising and the lowering
circuits but the weight of the load was suf-
ficient to lower it and there was too much
noise to permit of noticing that the motor was
not operating.
(58) MOTOR STOPPED AND REVERSED
When two alternators of the same voltage
and frequency are driven by separate engines
and are operated in parallel, the electrical
interaction between them tends to keep them
in step. This interaction consists of a local
synchronizing cross current that always
flows to the machine of lower frequency
during the motor part of the cycle. The
motor action of the lower frequency machine
and the simultaneously increased generator
duty of the higher frequency machine tend
to equalize the frequencies.
Where the two alternators are not operated
in parallel, however, this synchronizing action
cannot exist; and in such a case a slight
difference of speed will continuously and
progressively change the phase relations of the
two machines. This happens because the
frequencies will be slightly different, and
under this condition the higher frequency
cycle will, at regular intervals, lead, coincide
with, and fall behind (in regard to the relative
speed of phase rotation) the cycle of the
lower frequency.
A certain power-station equipment included
two quarter-phase alternators; they were
driven from different engines and were elec-
trically isolated. A contractor installed a
10-horse power, three-phase motor at some
distance from the station. The motor was
[CTO1
Motor Gen No. I Gen. No. Z
Fig. 2
connected to its compensator and trials
proved the direction of rotation to be as
desired.
A few days later the contractor was called
in and was told that the motor was heating,
although it had never been connected to the
OPERATION OF ELECTRICAL MACHINERY
1005
load; and he was further informed that at
that moment the motor was operating in the
direction opposite to that in which it had
run in its trial. He thought, of course, that
some one had tampered with the wires; but
this proved to be untrue. The key to the
situation was suggested by the fact that, when
the inspector got there, the motor was hum-
ming but not running. This action indicated
single-phase operation and, as the operator
could not recall having seen the motor stall
before, an inspection was started in order
to locate an open-circuit in one of the line
wires. The humming of the motor was due to
single-phase operation, but this was not
caused by an open-circuit in the ordinary
sense of that word. The action resulted from
one of the quarter-phase generators having
been shut down.
The wireman, who had tapped the motor
line to the station service wires, had connected
one phase of the motor to the conductors
from one generator and the other phase to the
conductors from the other generator as is
indicated in Fig. 2, instead of connecting
both phases of the motor to the same gen-
erator. The reversal of the motor's rotation
had been due to phase rotation reversals
incident to the frequency differences of the
two alternators. The excessive heating had
been caused by prolonged overloads that were
incident to the motor being repeatedly
retarded, stopped, reversed, and accelerated
in the opposite direction.
Had the motor been loaded, it probably
would have burned out for its circuit included
no fuses or other automatic circuit breaking
devices.
(59) UNSTABLE VOLTAGE
In Fig. 3 is illustrated the rise in the no-
load voltage of an armature when the field
current of the generator is gradually increased
from zero to the value that corresponds to the
practical saturation of the magnetic circuit.
When the field current is small an increase
a in its value produces an' increase b in the
value of the armature voltage. When the
field current is large, however, an increase a
in its value produces a much smaller increase
b' or b" in the voltage, because the field core
is saturated, i.e., a given increase in the
magnetizing current cannot add as much to
the magnetism. Similarly, if the magnetizing
current be gradually decreased from a high
a
a
a
a
value to zero, as soon as a value which cor-
responds to the steep part of the voltage curve
is reached, a small decrease in the field current
will produce a comparatively large decrease
in the armature voltage. Practically, this
means that when a generator is operated
<»....
»
g»6
rigid Current
Fig. 3
with a weak field, the field will be unstable
and so will be the dependent armature volt-
age. This takes place because a slight change
in speed, in load, in brush contact, or in
armature reaction will affect the voltage
that is applied to the field circuit and there
will result a disproportionate change in the
armature voltage, thereby again affecting the
value of the field current.
An operator complained that the voltage
of his alternator varied so much that he could
not operate the dependent motors satis-
factorily. An inspector found that almost
all of the voltage regulation was being effected
by means of the exciter field rheostat, the
alternator rheostat usually being entirely cut
out. As a result of this procedure, the 125-
volt exciter was being operated at voltages
from 50 to 70 volts under the average con-
ditions; and as there was no automatic voltage
regulation, it was necessary to keep a man at
the switchboard.
By gradually increasing the exciter voltage
by means of the exciter rheostat and at the
same time maintaining the alternator voltage
by means of the alternator field rheostat, the
exciter and the alternator were both adjusted
to operate at their respective normal voltages ;
and the operation was greatly improved.
On the other hand, many instances of poor
commutation of the exciter have been traced
to the practice of operating with a consider-
able resistance in the alternator field rheostat,
thereby necessitating an abnormal exciter
voltage in order to obtain the required excit-
ing current.
1006
GENERAL ELECTRIC REVIEW
HISTORY OF THE SCHENECTADY SECTION OF THE
A. I. E. E.
(THE LARGEST SECTION OF THE INSTITUTE)
By S. M. Crego
The Schenectady Section of the American
Institute of Electrical Engineers grew from
a small engineering club fostered by the
General Electric Company and limited to its
employees. Thus was the General Electric
Engineering Society, organized in the summer
of 1898 at a meeting of engineers at which
Mr. W. J. Clark, now Manager of the Trac-
tion Department of the General Electric
Company, presided.
Mr. W. H. Buck, now of the firm of Viele,
Blackwell & Buck, was elected President of
the new society and Mr. J. H. Jenkins, now
Supply Manager of the Foreign Department
of the General Electric Company, Secretary.
Succeeding Mr. Buck two years later, Mr.
Jenkins held the office of President for the
next two years, and during his term of office
the Society had grown to such size that it
was necessary to secure new quarters for its
monthly lectures.
A constitution and set of by-laws were
adopted on June 1, 1S9S. A copy of these
is still extant.
The Club's activities were not limited to
the electrical field but embraced subjects of
general engineering interest. Electrical
subjects, however, were naturally given
most attention, and the following list of
speakers and subjects may be taken as
representative :
Mr. E. W. Rice, Jr., Problems of Modern
Central Station Design.
Prof. Elihu Thomson, Lightning and Light-
ning Arresters.
Dr. W. R. Whitney, Electric Chemistry.
Mr. W. J. Foster, Design of Alternators.
Mr. A. H. Armstrong, Current Railway
Problems.
The General Electric Engineering Club
soon recognized the advantages to be derived
by merging with the American Institute of
Electrical Engineers, and on January 26,
1903, it became known as the Schenectady
on of the A.I.E.E., Dr. C. P. Steinmetz
being elected its first Chairman. Dr. Stein-
metz officiated for three successive years and
was followed by Mr. D. B. Rushmore, who
held the office for two years. The following
members in the order named have held the
Chairmanship for one year:
Mr. E. J. Berg,
Mr. M. O. Troy,
Mr. E. A. Baldwin,
Mr. E. B. Merriam,
Mr. J. B. Tavlor,
Mr. G. H. Hill.
Mr. H. M. Hobart.
In the season of 1913-14 the Section was
fortunate to be able to establish permanent
and commodious headquarters in the building
just then completed for the Edison Club.
The auditorium of this building has a seating
capacity of 500. The Edison Club has also
placed at the disposal of the Section an
office in the building for the purpose of
committee meetings. This also serves as the
Secretary's office.
The Schenectady Section was the ninth to
be recognized by the Institute, and it is now
the largest of the Institute's thirty-one
Sections. Its activity and membership
standing are indicated in the following table
which shows statistics of the seven largest
sections :
Number of
Rank
Number of
Meetings Held
Members
During
Past Season
1
Schenectady
791
18
2
Lynn
528
14
3
Chicago
450
7
4
Boston
392
10
5
Pittsburgh
378
9
b
Philadelphia
298
13
i
Pittsfield
275
11
The Schenectady Section has been excep-
tionally fortunate in being able to secure for
its meetings speakers of authority in their
respective spheres. That this has been the
rule from the inception of the organization
is in some measure an indication of the
influential position which the Section occupies.
The frequency of the meetings has varied
somewhat in different years, but even during
HISTORY OF THE SCHENECTADY SECTION OF THE A.I.E.E.
1007
the past season, when an unprecedentedly
large number of meetings were held, no
difficulty was experienced in securing the
desired speaker for each of the eighteen
meetings.
The Season's activities are varied by
occasional meetings of a purely social nature,
two of these, in the form of smokers, having
been held last year. The season is usually
ended by a dinner.
Fig. 1 shows the yearly increase in the
membership of the American Institute of
foremen, and others of the General Electric
Company's factory organization, with the
hope that these men would be interested in
securing the advantages of the Section by
becoming active members.
The Apparatus Committee was assigned the
duty of obtaining and installing apparatus
needed by lecturers for experimental demon-
strations.
The Classes Committee was formed to
determine whether the Section members
desired to organize classes and study subjects
1
eooo eoo
(•>.',
© Membership offll £ £
<&/9/££ members, of Loco/ Sec
® Local 'members of Locaf 5ec
@To£a/ membership of Loca/ Sec
/
/
£ sooo < eoo
i \
§ <U}00 &4-00
\ ^
V
,
/
/
/
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/
/
,/
/
i
/
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i
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/
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IB
39
18
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■9
01
.9
7£
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tS/3
1399 /S03
S&asor>s
Fig. 1
Electrical Engineers and of the local organiza-
tion. The Section now has 791 members.
Of this number 336 are National members
and 455 are Local members. It will be seen
from the curves that during the present
season the total number of members has
increased by 156. The Treasurer reports the
financial standing as excellent.
As an innovation, special committees, on
Factory Co-operation, Apparatus and Classes
were appointed during the past season.
The Factory Co-operation Committee
issued complimentary tickets for one or more
meetings to the factory superintendents and
of general interest to members. Two classes,
one in geology and one in photography, are
now holding regular meetings.
For the coming season the Chairman is
Mr. L. T. Robinson, the Secretary Mr. F. W.
Peek, Jr., and the Treasurer Mr. W. S.
Bralley. The Section is now in a very
flourishing condition and has every promise
for a future of continued usefulness and
success.
The first meeting of the tenth season is
scheduled for Oct. 12th (subject to change),
at which Mr. J. J. Carty, Chairman of the
A.I.E.E., expects to be present.
ioos
GENERAL ELECTRIC REVIEW
FROM THE CONSULTING ENGINEERING DEPARTMENT OF THE
GENERAL ELECTRIC COMPANY
INSULATION TESTING
The development of insulating materials
has reached such a stage that radical changes
in the standard materials are not to be
expected. Improvement then lies in the
treatment and application of these materials
and a closer study of their electrical character-
istics. At present little is known, for instance,
of the relative importance of moisture, non-
homogeneousness, ionization, temperature
changes, etc., insofar as they affect the
electrical characteristics. A study along these
lines is analogous to the study of magnetics
and there is every reason to hope that the
resulting improvement of insulating materials
will be as pronounced as was the case with
iron and steel.
It has often been asserted that dielectric
strength measurements give sufficient
information concerning the electrical behavior
of insulating materials. Dielectric strength
measurements simply show an ultimate
effect and in this respect are a valuable help
in the study of dielectrics. What takes place
before breakdown occurs can only be de-
termined by energy loss measurements. These
measurements are, then, just as indispensable
as dielectric strength measurements, for in
the study of any subject the object aimed at
is to discover both cause and effect.
There are a number of methods developed
for measuring dielectric energy loss but most of
these are limited to comparatively low voltages.
The two high voltage methods that have proved
the most practical make use of the cathode ray
tube and the dynamometer wattmeter.
The cathode ray tube and its application
are fullv described in a paper read before the
A.I.E.E., July, 1915, page 1115, by Mr. J. P.
Minton of the Pittsfield Laboratory. This
paper gives also a clear and concise summary
of the progress made in the study of insulating
materials.
A phase shifting method, making use of
the dynamometer wattmeter, is being
developed in the Consulting Engineering
Laboratory. It will greatly increase the
accuracy of these readings, especially at
very low power-factors.
The behavior of insulating materials under
high frequency stress is now receiving the
attention it deserves. When you consider
that a large percentage of insulation failures
are due to high frequency surges, it seems
unusual that more attention has not been
paid to this subject in the past. Materials
that are superior to others under continued
low frequency stress are not necessarily
superior under transient high frequency
stress. Comparative low and high frequency
breakdown tests give very interesting results
and are of considerable help to the designer
of high voltage apparatus in selecting the
most suitable insulating material.
The high frequency test is also a valuable
aid in studying designs. As a rule, the weakest
spots of a design under low frequency stress
are the hot spots, where accumulative effects
can cause final breakdown. Under high
frequency stress the end turns of windings
must bear the greater burden and it is here
that trouble usually occurs. In studying
high voltage designs, then, it is necessary
to make tests at both low and high fre-
quency.
There is one other development in insu-
lation testing that is quite promising. Direct
current voltages comparable in value with
alternating current testing voltages can be
obtained by the use of the new high voltage
kenotron. This makes it possible to investi-
gate the behavior of commercial insulations
under equivalent values of direct current and
alternating current stresses.
The kenotron has also proved of practical
value in testing out long lengths of under-
ground cable. The large capacity and
consequent charging current often makes an
alternating current test impractical.
G. B. Shanklin
General Electric Review
A MONTHLY MAGAZINE FOR ENGINEERS
«j «» n dt^u cj-t ,nnv d urnTTT Associate Editor, B. M. EOFF
Manager, M. P. RICE Editor, JOHN R. HEWETT . „,,,,,..,,
Assistant Editor, E. C. SANDERS
Subscription Rates: United States and Mexico, $2.00 per year; Canada, $2.25 per year; Foreign, $2.50 per year; payable in
advance. Remit by post-office or express money orders, bank checks or drafts, made payable to the General Electric Review,
Schenectady, N. Y.
Entered as second-class matter, March 26, 1912, at the post-office at Schenectady, N. Y., under the Act of March, 1879.
VOL. XVIII., No. 11 ,,v cJrT^i'9cLpa,,> November, 1915
CONTENTS Page
Frontispiece, Dr. W. R. Whitney ... 1010
Editorial : The Paths of Progress . .1011
Research 1012
By Dr. W. R. Whitney
Electrical Equipment of the Vermont Marble Company . . . . . .1015
By John Liston
The Thury System of Direct Current Transmission 1026
By William Baum
The Kinetic Theory of Gases 1042
By Dr. Saul Dushman
Electrical Characteristics of Solid Insulations 1050
By F. W. Peek, Jr.
Isolated Power-House for Factories 1057
By W. E. Francis
Mechanical Effects of Electrical Short-Circuits 1066
By S H. Weaver
The Theory of Lubrication, Part II 1074
By L. Ubbelohde
Translated from Petroleum by Helen R. Hosmer
Practical Experience in the Operation of Electrical Machinery, Part XIII . . 1082
Armature Threw Solder; Load Was Unbalanced; Stator Coil Connections
By F. C. Parham
From the Consulting Engineering Department of the General Electric Company . . 1084
Question and Answer Section 1085
Copyright, 1915. by General Electric Review
DR. W. R. WHITNEY
Recently Appointed a Member of the U.S. Naval Consulting Board
A short article by Dr. Whitney on "Research" is published in this issue
( a«
THE PATHS OF PROGRESS
The Panama-Pacific Internationa] Exposi-
tion has been the occasion for many gatherings
of engineering and scientific societies at San
Francisco during the summer and autumn of
L915, and a great amount of work has been
accomplished. The subjects dealt with at
these Conventions and Congresses are too
many and too varied to permit of even a
brief review. Most of these meetings were
exceedingly well attended and were, beyond
doubt, highly successful.
But, as is usual with such gatherings, the
full benefit of the technical papers and dis-
cussions will only be felt by each individual
after he has selected, read, and digested
those papers in which he is particularly
interested. The great mass of useful and
interesting data presented precludes any one
individual from attempting to even read
one-half of the papers prepared.
The personal element always enters largely
into the usefulness of such meetings, and we
feel in this special instance that the personal
element played an unusually important part.
The fact that so many notable meetings
were held on the Pacific Coast this year will
have a beneficial effect upon the engineering
community throughout the country, as it
has led to so many visiting the West that
otherwise might never have taken the oppor-
tunity.
In the past the West has learned much
from the East, and we feel that the East has
still a great deal to learn from the West.
This latter is especially true in those cases
where the East is catering for Western
business. A thorough understanding of each
other's problems and requirements is essential
to both parties for the best results, and this
year's meetings in the West should materially
help in this direction.
The developments on the West Coast are
something of which the whole nation may
justly be proud, and the future of the West-
ern states may be looked forward to with
utmost confidence and satisfaction. The
same spirit that has developed the natural
resources of the West to their present stage
can be depended upon to produce still more
wonderful results in years to come.
The further development of the West is to
be the work of the Engineer, in even a more
marked degree than in any other section of the
country. The greatest essential is a plentiful
supply of energy. Much has already been
developed; indeed we have noted some
instances where more power has been
developed than is at present used, and many
cases where much more power can be
obtained from sources already tapped. The
problem will resolve itself largely into one of
distribution ; this is especially true for mining
and agricultural work in districts that are not
closely settled.
In a country where so much land must lie
fallow until the Engineer brings water to the
soil, distribution over large areas becomes the
vital problem. The cost of such distribution
is high; it is sometimes even prohibitive.
Consequently, we sincerely trust that no
unnecessary restrictions will be placed in the
way of the Western Engineer in this great
development work. In the construction of
the necessary distribution systems it will be
impossible to use the same class of work as
is used in many more closely settled com-
munities. Some cheaper form of construction
is essential and any burdensome laws and
regulations will only retard progress.
1012
GENERAL ELECTRIC REVIEW
RESEARCH
By Dr. W. R. Whitney
Director of Research Laboratory, General Electric Company
It is pointed out in the beginning of this article that the processes of the world's work, or improvements
in them, are made possible only by attaining an increased knowledge relative to them. Such knowledge can
only be secured from research. It is also called to attention that while the result of a research may show that
the" desideratum is not to be attained along the line investigated, the resulting knowledge is almost certain to be
of great value in some other direction. The present war has brought a number of nations to a startling realiza-
tion of the need for extensive research to strengthen their national defence. — Editor.
from the battle ax. Someone invented the
coulters, and then came the moldboards of
all shapes and sizes, and the wheel. Some
Americans produced the light chilled plow,
and others discovered that a man could ride
and still plow. Then, before the plow business
stopped growing, the double Michigan plows
came along (a little one in front of a larger
one), and then two large ones in echelon
(for making a double furrow), next, multiple
plows drawn by rope or windlass with steam
power, then steam tractors and then gasolene
tractors with twenty or thirty units, and
perhaps then just dynamite, — who knows"'
How simple and familiar they all look up to
the last one, and how difficult to see just
beyond that point.
Confine yourself to your own day. Do you
remember the big one-cylinder gasoline
engine you put into that boat? It was easier
and safer to row the boat than to start the
engine. It was largely the love of the risk
involved that made you use the engine. It
weighed one or two hundred pounds per horse
power. The ignition system was an engine
by itself, and when it was operating it made
you feel like a locomotive engineer, it had
so much useless motion. Recall how perfect
some of those little improved yacht engines
looked and how natural it seemed to go to a
two-cylinder engine ? The next gas engine
you saw was a four-cylinder, costing about
the same as your first single cylinder, but
quite a different animal. Of course the
improvements need not consist of merely
added cylinders and you laughed when some-
one suggested more, but sixes, eights, and
even twelves are making the fours look a
little old already. You guess now that from
twelve the advance will be to twenty or more,
or to a turbine type with many blades to
take the thrust, or even infinite blades which
means the plain rotating disks already de-
scribed in the newspapers. No matter what
you guess, the changes will come and always
in one direction: "More for the money."
Paradoxical as it may look, when we stand
still we are going backward. If we want to
stay we have to go forward.
The president of a manufacturing company
who was hesitatingly considering the possible
recovery of valuable waste solvents from a
chemical process said: "You know we are
making photographic paper and are not
interested in the solvents. We buy them,
use them and make a profit on the product."
In other words, the existing condition was not
unsatisfactory. It seemed, in fact, perfectly
satisfactory. Nevertheless, he realized that
this view was not foresighted and he corrected
it to his advantage. A process or product
susceptible of economical improvement, as
are all of them, cannot be looked upon as an
entity, enduring and unalterable. It changes
like everything else. What this man wanted
was that his process instead of continuing
as it was, the best among its contemporaries,
should become as it was not, the best among
its future competitors. He really wanted
continuing profit. Perhaps it is the impos-
sibility of actually seeing what is not which
accounts for our faith in what is: but who can
name a product, a process, or even a faith
which does not alter with time? One might
almost say that the most typical impossi-
bilities of one decade often become the live-
liest realities of the next. Darius Green and
Captain Nemo certainly taught us something.
Rather than suppose that we will ever reach
a stationary state of perfection in anything,
it is more interesting and probable to assume
that for some reason, either highly complex
like the union of heredity and environment,
or simply mechanical like the grain size in
our gray matter, we cannot really conceive
a physical impossibility. A good working
hypothesis is: If it can really be conceived,
then it may be made. If one deliberately
analyzes the history of any manufactured
article he is struck with its active mutation.
This ought to jar one's feeling of complacency,
but usually it does not. The things laboriously
made in units by hand today will be made in
dozens by machines or assembled on endless
conveyors tomorrow.
Even in the oldest business of the world the
continuous order of change is evident. The
wooden plow was displaced by one forged
RESEARCH
1013
That Allegheny Indian who first rubbed
the rock oil on his aching bones started the
line of research which now lets us run about
so easily in automobiles. The petroleum
industry has always been and ever will be a
living, moving, growing thing. If we want to,
we shall probably eat modified vaseline and
wear clothes colored with modified paraffin,
but it will not be done by being satisfied with
what is, afraid to try what is to come.
Nature does not supply us with baskets
and a sunny spot to place them so that we
can catch the falling futures, but she shows us
that swimming may be learned almost entirely
by getting into the water, or at least by
adding some push and a little kicking.
It was not my intention to discuss prepara-
tion for national defence, which is only a
single one of those fields in which, when we
want to advance beyond others, we shall
probably have to excel in our efforts. Nor do
I care to devote too much of this note on
research to a comparison of the industrial
situations in such leading countries as England
and Germany. But, a few words chosen from
modern English literature seem very perti-
nent. More on this point may be found in an
editorial in the Journal of Industrial and
Engineering Chemistry for October, 1915,
from which I quote:
"The attitude of the government toward science
was well illustrated during the debate of British
Dyes, Ltd., when the Parliamentary Secretary of
the Board of Trade stated that:
'A man conversant with the science and
practice of dye manufacture was unfit to go
on the directorate because, as he would know
something of the business, the whole of the
other directors, being but business men, would
be in his hands.'
As Prof. Meldola points out:
'One feature of the new scheme which the
chemical profession can view with favor is the
distinct recognition of research as a necessity
for the development of the industry. The
Government will, for ten years, grant not more
than 100,000 pounds for experimental and
laboratory work. That is certainly a eon-
cession which marks an advance in official
opinion. It will be for the satirist of the future
to point out that it required a European war
of unparalleled magnitude to bring about this
official recognition of the bearing of science
upon industry.'
According to Sir Ronald Ross:
'The war now raging will at least demonstrate
one thing to humanity — that in wars at least,
the scientific attitude, the careful investigation
of details, the preliminary preparation, and the
well thought out procedure bring success, where
the absence of these leads only to disaster. So
also in everything. After all, the necessity for
research is the most evident of all propositions.'
As S. Roy Illingworth puts it:
'The inexorable law of the survival of the
fittest is as true of nations as of animals and
only those nations that are the most efficient
in industry can have any chance of maintaining
their entity.'
Dr. J. A. Fleming writes:
'A few days ago an eminent electrical engineer
was sitting in my room here, and said to me, — I
am too old to enlist or even do manual work in
the manufacture of shells, but I have a con-
siderable scientific knowledge which I am just
yearning to employ in the service of the country,
yet I cannot find any person in authority who
will tell me how to do it.
'This sentence expressed concisely not only
my friend's feelings, but my own, and I am
confident that of hundreds of other scientific
men as well. At the present moment, after
10 months of scientific warfare, I myself have
not received one word of request to serve on any
committee, co-operate in any experimental
work, or place expert knowledge, which it has
been the work of a lifetime to obtain, at the
disposal of the forces of the crown.'
Sir William Ramsay says:
'It is bad policy to regret what might have
been; it is much better to try to devise plans to
make up for lost time; and the first essential is
organization. It is notorious that there is
little intercommunication between the various
Government Departments: many of them are
confronted by the same difficulties; many of
these difficulties would be overcome if scientific
advice were asked for; and the prime necessity
at the present moment is a central body of
scientific men to whom the various Govern-
mental Departments should be compelled to
apply for advice and assistance.'
In July Mr. Henderson, successor to Mr. Pease as
President of the Board of Education, issued a
White Paper outlining a 'Scheme Designed to
Establish a Permanent Organization for the Pro-
motion of Industrial and Scientific Research by the
establishment of a single responsible body entrusted
with the disbursement of a considerable fund. This
consists of a Committee of the Privy Council with
' a small Advisory Council composed
mainly of eminent scientific men and men
actually engaged in industries dependent upon
scientific research, which shall be responsible
to the Committee.'
The first members of the Council wili be Lord
Rayleigh, Messrs. Beilby, Duddell, McCormick,
and Threfall, Profs. Hopkinson, M'Clelland, and
Meldola, and the Committee of the Privy Council
consists of Lord Haldane and Messrs. Ockland and
Peasi
In this way does the English Government an-
nounce at last a change of policy and propose to
retrieve its past inaction. Of this scheme Nature
remarks:
'By its inception and publication the Govern-
ment acknowledges and proclaims its apprecia-
tion of the work of science and by this acknowl-
edgment alone gives scientific workers that
encouragement and prestige in the eyes of the
country which has too long been withheld.'
1014
GENERAL ELECTRIC REVIEW
'Thus England has awakened after the most
costly delay to a situation which she must probably
work for years, at the best, to remedy, a situation
which threatens not only her future supremacy but
even her present existence.'
Research is not a word to conjure with.
As a magic it is exactly like a grindstone.
You can tie it around your neck or you can
work it. The dictionary says that "Research
is diligent protracted investigation especially
for the purpose of adding to human knowl-
edge." The dictionary is right. The man
who investigated boron was diligent; he
observed all its peculiar qualities and
measured its quantities. When it failed to
make a suitable incandescent filament as
had been hoped and the "addition to human
knowledge" of its low melting-point was
made, his protracted diligence had already
taught him that it was a great oxygen-eater.
It would take oxygen even from aluminum
oxide. So it happened that it was inves-
tigated in connection with copper castings.
It took oxygen from copper. It made a
perfect electrical and physical product of
what had before been a failure. At that
time magnesium was used in the manufacture
of boron. The war came on and the price
of magnesium rose. It was made only in
Germany. Another research, or "diligent
investigation" was started and for 5 or (>
months the "protraction" continued until
a manufacturing method using American raw
materials was devised. There is now little
probability that this metal will ever cease to
be made in America. This illustration is
given because it is fairly typical of research.
The point attained is not always that par-
ticular spot aimed at, so far as knowledge is
concerned. A yield is obtained, nevertheless,
and the knowledge acquired is a perpetually
enlarging accretion, so long as the diligent
investigation is under way.
The impossibility of foreseeing the applica-
tions of a research and the certainty that all
knowledge is of use might be illustrated by a
thousand cases. No one fact, well known,
can exist without reacting on the remainder
of knowledge. In 1895 and 1S9S the first
discoveries of X-rays and radium rays were
made. The facts as they were disclosed fed
every science. Chemistry was given a jolt
it had thought could never occur. Physics
went back to the consideration of dimensions
thousands of times smaller than before.
Electricity's views of conduction were
enlightened and the phenomena of electrical
insulation of gases and oils were clarified.
Medical diagnosis and surgery were given
additional eyes and therapeutics a new
reagent. From the man who today sees the
gas holes in iron castings to the one who
studies heredity by exposing eggs and sperms
separately to the rays, all have to thank
those who carried out the necessary researches
on these rays. Few or none of these applica-
tions could have been predicted prior to 1895.
What could have been predicted, however,
with certainty was that some uses could be
made of such disclosed facts.
1015
ELECTRICAL EQUIPMENT OF THE VERMONT MARBLE COMPANY
By John Liston
Publication Bureau, General Electkic Company
The quarrying and finishing of marble by modern methods involves the use of an extensive mechanical
equipment, the essential elements of which are clearly indicated in this article. The writer has outlined the
operating conditions in quarries, mills and shops and their relation to electric drive, and by specific reference
has analyzed the factors which have influenced the selection of the electrical equipment. — Editor.
While the discovery of marble deposits in
the State of Vermont occurred more than a
century ago, only sporadic efforts were made
to develop the industry along commercial
lines prior to 1870.
The succeeding years, however, witnessed a
marked expansion; new quarries were opened,
mill and shop buildings erected, and the equip-
ment of the various plants added to and
improved to meet a constantly increasing
demand, until the Vermont Marble Company,
with about 4000 employees, attained an
annual output in excess of a million cubic
feet and became the largest producer of
marble in the world. The timber, farm and
quarry lands acquired, cover more than
2.3,000 acres and include about 75 quarries.
In the early days the quarrying operations
were carried on very largely with manual
and animal labor, while the mills and shops
were operated at first by directly applied
water power, which was later, in some cases,
supplemented by steam drive.
Subsequent to 1870 there ensued a com-
prehensive and consistent improvement in
the methods of power application, paralleling
the commercial development of the company,
and today practically all of the various
properties are interconnected by an efficient
modern electric distribution system, the
energy for which is derived from four hydro-
electric power stations, supplemented by two
steam-driven generating stations, normally
held in reserve. Electric motors are utilized
for the operation of all forms of machinery
in quarries, mills and shops.
The plants referred to in this article are all
located in the State of Vermont, and in order
adequately to indicate the character and
extent of the electrical equipment provided,
the following analysis will be divided roughly
into three sections, viz. :
Various motor applications in the quarry,
where individual drive is the rule.
Methods utilized in operating mill and shop
machinery, with typical examples of both
individual and group drive.
A general survey of the generator, trans-
mission line and substation arrangement, and
the operating conditions imposed by the
linking together of widely separated plants,
with fluctuating energy demands, into a
homogeneous system having a high power-
factor with ample safeguards to insure an
uninterrupted current supply.
There are at present in service a total of
about 570 motors, ranging in capacity from
2 h.p. to 250 h.p., with an aggregate rating of
approximately 14,000 h.p. Direct current
units are in many cases applied to hoists,
cranes and locomotives, and constitute about
25 per cent of the total motor equipment;
the remainder being polyphase induction
motors operating at 220, 440 or 2300 volts on
three-phase 60-cycle circuits.
An interesting example of the reliability of
electric motor drive is found in the group of
double lever channelers, some of which are
shown in Fig. 1. These machines are pro-
vided with a gang of long chisels set on either
side of a strong framework and actuated
through gearing by a 12-h.p. railway type
direct current motor. The vertical recipro-
cating motion of the chisel gangs, combined
with the slow forward movement of the
machines, forms narrow channels or slots of
the desired length and depth, usually at
right angles to the "rift" or natural cleavage
line of the marble strata, and cross channels
are then cut or holes drilled at right angles to
the main channels in order to secure blocks
of the desired size.
It is obvious that the motors, which are
mounted directly on the channelers, must be
unavoidably and continuously subjected to a
considerable amount of vibration when the
channelers are in action; but in spite of these
severe conditions the original outfits, which
were installed in 1896, are today regularly
applied on flat cutting and are operating with
unimpaired efficiency after an active service
of nearly two decades.
Owing to the diverse arrangement encoun-
tered in marble strata, it is frequently neces-
sary to operate channelers at various angles to
the horizontal, and, as the mechanical design
of those shown in Fig. 1 limits their effective
use to surfaces which are practically level,
101G
GENERAL ELECTRIC REVIEW
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ELECTRICAL EQUIPMENT OF THE VERMONT MARBLE COMPANY 1017
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1018
GENERAL ELECTRIC REVIEW
another type (see Fig. 2) has been developed
which can accomplish both flat and slope
channeling as required.
This machine is equipped with only one
chisel gang, which is given a positive recipro-
cating motion by means of compressed air.
This is in turn supplied in a closed circuit by
a motor-driven compressor; the entire outfit
comprising a self-contained and adaptable unit.
The operator can secure all necessary speed
adjustments through the motor controller.
There are in all about 100 electric chan-
nelers used in the Vermont quarries, including
about two dozen of the old double lever type,
which are driven by direct current motors,
whereas the electric-air machines are uni-
formly equipped with 12-h.p. Form M in-
duction motors. These motors have phase
wound rotors and external resistance con-
nected through slip rings, and are specially
adapted for conditions requiring frequent
starting under load with a relatively low
current demand.
Supplementing the channeling process, the
bottom of the block of marble is perforated by
means of drills ; the holes being usually driven
either along, or parallel to, the "rift" or
natural cleavage line, thereby rendering it
possible to loosen the block by means of
levers or wedges. No blasting is required
as the actual work of quarrying marble is
performed entirely by machinery.
About 70 electric-air drills are available
for this work and operate on the same principle
as the electric-air channelers, but the drill
proper, and the motor-driven air compressor,
are separate portable units connected only
by flexible air tubing, as shown in Fig. 3.
The load conditions are not severe and the
compressor is direct geared to a two-speed
53^-h.p. induction motor.
While most of the quarries are open work-
ings from which the detached blocks of marble
can be removed with the aid of derrick
hoists, some of them extend for a considerable
distance underground, have heavy pillar
supports for the roof or hanging walls, and
in some respects entail work similar to that
encountered in mining.
An example of this is the West Rutland
quarry in which the workings have been
carried to a depth of about 300 ft.; the open-
ing at that level exceeding 2000 ft. in length.
In this quarry electric lighting is required, and
an electric haulage locomotive (Fig. 4) is
used to haul the blocks of marble from the
working face to the base of a slope hoist,
which in turn elevates them to the surface.
The locomotive is operated on direct
current, 230 volts, supplied through a motor-
generator set to a guarded feeder wire running
along one side of the track about 18 inches
from the ground. In spite of the limited
radius of action of this small tractor, it has
proved to be a valuable addition to the
quarry equipment.
As a rule, the natural ventilation and
lighting of the quarries produces favorable
working conditions, but at West Rutland
the underground galleries extend a con-
siderable distance from the open shaft, and
an artificial circulation of air is therefore
necessary. This is amply provided for by a
6-ft. upcast fan located on the surface and
belt-driven by a 40-h.p. induction motor,
and 250-watt Mazda lamps are used at
all points where the daylight is inade-
quate.
From the nature of the work it is evident
that underground water in varying volumes
may frequently be encountered in quarrying,
and as the quarry shafts are practically
unprotected, a certain amount of surface
drainage and seepage must also be provided
for. The pumping sets used for unwatering
the quarries include both reciprocating and
centrifugal types, driven by induction motors.
Small portable pumps driven by 2-h.p.
motors are available for temporary use, and
stationary units do not in any case require
more than 35 h.p., as the operating head in
no instance exceeds 350 ft. and the load
demand is not heavy.
The flexibility of motor drive is well illus-
trated by the quarry installations already
referred to, for while it would be possible
to' operate the isolated machines by means of
air or steam, fed from a centrally located
compressor or boiler at each quarry, the
difficulty, of installing air or steam pipe lines
in the quarry, maintaining them in good
condition to avoid pressure losses, and extend-
ing or relaying them to take care of the shift-
ing of channe'ers and drills involved in pro-
gressive work, would entail installation and
maintenance costs greatly in excess of those
of the electric system. The efficiency of the
latter is unaffected by temperature changes,
which must always be considered with steam
or air lines, and the laying of additional wire
or cable to supply current to new machinery
or to meet changes of location of any existing
machine can be safely, easily and rapidly
accomplished without interfering in any way
with the operation of the remainder of the
quarry equipment.
ELECTRICAL EQUIPMENT OF THE VERMONT MARBLE COMPANY 1019
With individual motor drive the energy
consumption of each machine is limited to its
period of actual operation and the generating
equipment need only be designed for the
average maximum demand of the entire
system. With steam or air, however, the
compressors or boilers at each quarry would
have to maintain full pressure throughout
the working day, with a consequent low load
factor during the time required for relocating
machinery or for changing or adjusting tools
on individual machines.
The conditions in a quarry are not by any
means ideal for the operation of motors, due
to the difficulty of completely protecting them
from moisture, mechanical injury, or vibration
strains; but many years' experience in the
numerous quarries of the Vermont Marble
Company shows that enforced stoppage of
work, even of individual units, is exceedingly
rare, and that the repair expense for well
designed open type modern motors, in con-
stant use over long periods, is confined
largely to the rewinding of the smaller pump
and drill motors. For the larger units it is
practically negligible.
While a few slope hoists are used in handling
the quarried marble, a large percentage of
Steel derrick masts with steel girder booms
are largely used, and more than 20,000 blocks
averaging about 20 tons in weight are handled
annually, the largest blocks weighing about
55 tons. The maximum derrick lift at present
does not exceed 325 feet.
Fig. 5.
Hollister Quarry — showing two typical quarry shafts
and two motor -operated derricks
the blocks are brought to the surface by means
of simple derrick hoists similar to those shown
in Fig. 5. There are in all about 80 of these
derricks and the hoisting motors are rated at
from 25 h.p. to 165 h.p. with smaller motors,
usually about 6 h.p., for swinging the derrick.
Fig. 6. Hoisting Equipment for Derricks~shown in^Fig. 5 —
main hoist motor, 165-h.p., derrick swinging motor, 6-h.p.
The detail arrangement of the hoisting
machinery for these derricks varies somewhat
at different quarries, but in Fig. 6 a typical
outfit is shown. At the right is a Form M
slip ring induction motor
direct geared to the main
hoist, while on the wall at
the rear is a panel board
supporting a switch, circuit
breakers and the contactors
through which the motor
resistance is controlled. The
resistance units and the motor
controller are located on the
floor near the panel board and
the small derrick swinging
motor may be seen at the
left.
It is evident from the nature
of the work at the quarries
that the derrick operation
must ordinarily be intermit-
tent, as the average service
for the entire battery of der-
ricks is less than one 20-ton
block hoisted per day. Many
of the derricks are of course
utilized with greater fre-
quency, while in other cases they are idle
for considerable periods; but with electric
drive they are at all times available for
instant use and consume power only while in
operation and in direct proportion to the
amount of work performed.
1020
GENERAL ELECTRIC REVIEW
When the blocks have been hoisted to the
surface they are deposited on flat cars and
hauled either directly to the mills or to storage
yards where they are piled for future use:
In the latter case the blocks are removed
from the flat cars by means of electrically
the blocks are run off onto the sawing beds.
The crane is equipped with travel, hoist
and turning motors and has also a motor-
operated winch for pulling the block-carrying
cars onto the transfer car after the sawing
operation is completed.
Fig.
Electrically-operated Gantry Crane serving block pile at West Rutland, Vt.
operated cranes in the manner shown in Fig
7, and are later transferred to the mills as
required. The amount of marble thus held in
reserve is usually sufficient for about one
year's output of the mills and shops.
Direct current motors are utilized for
storage yard cranes, the one in Fig. 7 being
equipped with five motors, viz., one bridge
motor of 35 h.p.. two hoist motors each 30 h. p.,
and two trolley motors each 7}/£ h.p. The
crane has a bridge span of 160 ft. and a
capacity of 50 tons. Its load conditions are
not exceptional and it does not differ materi-
ally from the cranes used for the other block
piles, or in other industries; it is referred to
merely as a connecting link between the
quarry and the mill.
When the blocks of marble are transferred
to the mill for sawing they are delivered to the
gang saws or "gangs" by a specially designed
trolley type locomotive crane (see Fig. 8) which
travels on tracks running lengthwise through
the mill building between two rows of gangs.
The process of delivery is as follows: The
overhead yard crane removes the blocks
from flat cars in the yard and deposits
them on a short heavy car, which is in turn
placed on the tracks of the small transfer
car, shown in Fig. 8 immediately in front of
the crane. The transfer car is then moved
into the mill by the crane and the car carrying
The sawing process and the method of
adjusting the saws can be readily understood
by referring to Figs. 9 and 10, which show-
two typical "gangs" at work. The saws
are toothless and are made of soft iron }/% in.
Fig. 8. Electric Locomotive Crane especially designed for deliv-
ering blocks to sawing beds at mills
thick and 4 in. wide when new. Small pumps
deliver a mixture of sand and water to the
saw cuts and the rigid framework containing
the saws is given a horizontal reciprocating
motion, the sand doing 'the cutting. There
are more than 300 of these electricallv
ELECTRICAL EQUIPMENT OF THE VERMONT MARBLE COMPANY 1021
operated "gangs," and they are in every
case driven in groups which comprise from
12 to as high as 43 gangs; the driving motors
ranging from 75 h.p. to 250 h.p. Average
conditions require about 100 h.p. for every
14 gangs, including the necessary sand pumps.
As the "gang" saw drive re-
quires approximately 2500 h.p.
in motors, it constitutes a large
percentage of the total load.
Constant speed squirrel cage
motors have been adopted for
this service, although a few
wound rotor motors have also
been utilized in some cases for
starting duty.
The motors drive through
overhead countershafts and,
while in some cases they are
direct connected in the line
shaft, as shown in Fig. 11, as a
rule they are belt connected.
Extreme fluctuations may occur
both in the starting and operat-
ing loads on individual " gangs,"
varying with the number of saws
in each "gang" and the dimen-
sions of the blocks of marble,
and it might appear from this
that "gang" saw drive would
cause a very irregular demand
on the power supply, but, the
equalizing effect of the group
arrangement of the "gangs" is
such that a very steady load is
imposed on the motors, and
they do not adversely affect the
power-factor of the system,
which is normally maintained
at from SO to 85 per cent.
From the mills the marble
passes to the finishing shops
where all remaining operations
are performed. The rough sur-
faces, left after the sawing pro-
cess, are smoothed on rubbing
beds, which consist of large steel
disks rotating in a horizontal
plane, on which a flow of water
and sand is maintained.
There are about 65 electri-
cally operated rubbing beds in
the different shops and the older
installations consist of groups of
five or six machines driven through counter-
shafting by 50-h.p. motors. Later, there
developed marked tendency toward an indi-
vidual drive svstem, with its inherent economy
in current consumption, and the more recent
additions to the shop machinery provide
a 25-h.p. motor, belt-connected to each
pair of rubbing beds (see Fig. 12). The
squirrel cage induction type of motor
was adopted as a standard for this
Fig. 9. Block of Marble being cut into slabs of varying thickness by gang saws
Fig. 10. Block of marble after sawing has been completed
work and for practically all finishing shop
drives.
Some hand work is necessary in finishing
marble products of intricate shapes, but most
1022
GENERAL ELECTRIC REVIEW
of the polishing on flat surfaces is performed
with the type of machine shown in Fig. 13.
It consists of a heavy two-part hinged bracket,
linked together by two driving belts, at the
end of which is a vertical shaft with a polishing
disk at the lower end. The workman, by
Fig. 11. 250-h.p.. 240-r.p.m., Form M Induction Motor direct
connected in line shaft — driving gang saws
at Proctor Mill
grasping a large iron loop, controls the move-
ment of the machine and guides the revolving
polishing disk over the surface of the marble;
the hinged bracket construction permitting
the movement of the disk in any direction in
a horizontal plane. The polishing disks or
plates, like the saws and rubbing beds,
utilize a copious supply of water, but do not
require sand as they constitute in themselves
the necessary abrasive. In the order in
which they are utilized, they employ the
following materials: carborundum, brown
emery, fine hone; while the last operation
utilizes a plate covered with felt in con-
nection with a polishing putty. There are
about 100 of these machines in use, but, as
they individually constitute a light and
variable load, they are always driven in
groups.
A number of turning lathes of considerable
capacity are employed in producing marble
columns, and blocks more than 30 feet long
can be handled by the largest lathe. In spite
of their impressive size, these lathes do not
at any time impose a heavy demand on the
power system as they rotate very slowly when
cutting, and large columns are usually turned
at less than 5 r.p.m. For individual drive
or for running two lathes with a single motor,
not more than 10 h.p. is ordinarily required.
Two unique auxiliaries to the standard shop
equipment are shown in Figs. 14 and 15.
The first is a 6-ft. circular saw employed in
cutting and trimming marble slabs. It is
provided with two motors, one rated at 25 h.p.
for rotating the saw, and a 3-h.p. unit driving
the feeding mechanism. The periphery of the
saw has inset diamond cutting tools and very
rapid sawing is possible, but it is not intended
to perform the work ordinarily done by the
gang saws or rubbing beds.
The second is known as a carborundum
machine, and in Fig. 15 it is shown cutting
grooves in two pieces of marble. The bed
plate has a slow reciprocating travel similar
to that of a planer, and the adjustable grind-
ing elements are carborundum wheels of
various sizes and shapes. Like the saw, it is
independently driven, a 20-h.p. induction
motor driving both tools and bed plate.
In the foregoing the references have been
confined largely to those features of the
equipment peculiar to the marble industry,
but in general it may be stated that motor
drive is utilized throughout all departments of
the Vermont Marble Company, including
the various machine shops, repair shop,
carpenter shop and to some extent in saw
mills. More than 6,000,000 sq. ft. of lumber
is required annually for boxing and shipping
marble but a large part of this is the product
of steam-driven saw mills.
Several hundred pneumatic hand tools are
used in the shops, and air is supplied to them
at from 50- to 60-lb. pressure, by motor-
driven compressors. Overhead electric travel-
ing cranes of the usual types are found in
both shops and yards, while those yards
where the finished marble is stored or shipped
are served bv cranes constructed as shown in
Fig. 16.
As previously mentioned, current is supplied
to the various plants from four hydro-electric
stations having a total capacity of 5525 kw.,
and two steam stations having an output of
1250 kw. Distribution is made through
eleven substations, over transmission lines
aggregating more than seventy miles in
length.
The hydro-electric stations are all located
on Otter Creek, a small stream which rises
in Bennington County, Vermont, flows
through Rutland and Addison Counties, and
enters Lake Champlain near Vergennes
For many years prior to the adoption of
electric drive it supplied the power require-
ments of some of the mills by means of simple
waterwheel drives. Its total drainage area
is less than 1000 sq. miles and above Proctor,
where the first and largest generating station
ELECTRICAL EQUIPMENT OF THE VERMONT MARBLE COMPANY 1023
c
a
a
to
3
S
1024
GENERAL ELECTRIC REVIEW
was installed in 1906, the drainage area is only
about 150 sq. miles, but a dependable water
supply is insured by storage reservoirs of the
Rutland Railway, Light & Power Company
which are back of the falls at Proctor and
an operating head of 120 ft. is available.
Fig. 16.
A Typical Three-Motor Swinging Crane used in handling finished marble
for storage or shipment
K The station contains three 750-kw. 4S0-volt
514-r.p.m. three-phase 60-cycle alternators,
each direct connected to a waterwheel.
About 30 miles down stream the second
station was located in 1911, at Huntington
Falls (see Fig. 17), with an operating head of
40 ft. The generators here consist of two
750-kw. 2300-volt 300-r.p.m. units with belt-
driven exciters, as shown in Fig. 18. About
two miles above this station is a third power
plant, at Beldens, which was
completed in 1914 and is
practically a duplicate of the
Huntington Falls station,
having the same generating
capacity and operating under
the same hydraulic head. The
drainage area above this point
is approximately 6 15 sq. miles.
Four miles up stream from
the Proctor is the fourth
generating plant at Center
Rutland, where, in 1915, a
275-kw. 460-volt 300-r.p.m.
generator replaced an old
direct waterwheel drive; the
operating head here being
30 ft.
In addition to these four
hydraulic plants are the two
steam generating stations
already referred to, which are
normally held in reserve, but are placed in
service during low water periods. An ample
emergency supply is also available through
the inter-connection of the transmission sys-
Fig. 17. Huntington Falls Power Station with concrete dam giving operating head of 40 ft.
ELECTRICAL EQUIPMENT OF THE VERMONT MARBLE COMPANY 1025
tern of the Vermont Marble Company with
that of the Rutland Railway, Light & Power
Company.
Three transmission potentials are used on
the different sections of the system, which
includes 56 miles of 44,000-volt conductors,
and 10 miles at 11,000 volts, all single circuit,
while the connection with the railroad system
referred to above is obtained by a 4}-2-mile
13,200-volt line. Wooden poles are used on
all lines, with spans varying from 150 to 300
ft., excepting at railway crossings, where
they are replaced by steel towers. The pole
lines are not equipped with a guard wire, but
protection is afforded by ten sets of aluminum
cell lightning arresters.
When we consider that the present dis-
tribution system with its eleven substations
has been a gradual growth during the past
nine years, to meet increasing demands for
power in widely separated plants which were
successively electrified, the necessity for the
various transformer ratings and voltages
used can be readily understood.
Both single-phase and three-phase oil-
cooled and water-cooled transformers, aggre-
gating over 5000 kv-a., are installed in the
substations; the largest unit being rated at
1250 kv-a. three-phase, and the smallest at
33 kv-a. single-phase. The potentials also
range from 44,000 to 2300 for high voltage
windings, and from 11,000 to 230 for low
voltage windings. By means of this diversity
in substation voltages there is secured a
uniform operating voltage for each class of
motor drive throughout the entire system.
Where the motor loads are of such a
character that the voltage and capacity of
the system is adversely affected, partially
loaded synchronous motors are used to supply
a compensating leading current, and the
power-factor is thereby normally maintained
at from 80 to 85 per cent — a very satisfactory
result in view of the exceptional operating
conditions existing for a large percentage of
the motors.
The water supply can be relied on during
a large part of the year and the hydro-electric
stations ordinarily carry the entire load. The
records for 1914 show that 16,600,600 kw-hr.
was supplied by water power stations, while
somewhat less than 1,000,000 kw-hr. was
required of the steam plants.
The generators and motors supplied by the
General Electric Company constitute about
65 per cent of the total electrical equipment.
Fig. 18. 750-kw., 2300-volt, 300-r.p.m. Waterwheel-driven Generator in Huntington Falls Power Station
1026
GENERAL ELECTRIC REVIEW
THE THURY SYSTEM OF DIRECT CURRENT TRANSMISSION
By William Baum
This article forms a valuable work of reference. The author gives a very complete description of the
Thury system of direct-current transmission and deals at considerable length with the advantages and dis-
advantages of its applications in numerous fields of work. It should be remembered that these advantages
are features of the line construction and. as such, become only of great importance in connection with long-
distance high-power developments of, say, 50,000 to 100,000 kw. capacity. The installations of the Thury
system now in operation do not come in this class; consequently, experience with it is lacking in this field.
Moreover, estimates made from the best available data covering long-distance high-power transmissions, using
duplicate circuits and steel supporting structures, show that the first cost of the complete installation, including
hydro-electric station, transmission line, and substation, is considerably greater for the Thury system than
for the present type of three-phase alternating-current system as used in this country. Furthermore, when
transmission voltages of the order of 150,000 are considered, one can be sure that difficulties in connection
with the insulation of generators and motors to ground and between coupled machines will be greatly increased,
and although the arrangement may be simpler there will be introduced construction complications involving
considerable life hazard to the operating force. Consequently, from available data, there seems to be no reason
for considering direct-current transmission for propositions where the present type of alternating-current
transmission can be successfully and economically used. — Editor.
I. INTRODUCTION
The problem of transmitting direct currents
in series is not a new one, the well known
Brush and Wood series arc lamp systems
being the forerunners of what is today called
the "Thury system." This constant current
scheme has found but a limited application in
Europe, having replaced the well established
polyphase constant potential systems in
exceptional cases only. The reason for this
is to be found in the fact that the direct
current system is not a distribution system.
but essentially a transmitting scheme posses-
sing, for this particular application, a number
of advantages of considerable interest to
transmission engineers.
II. THE PRINCIPLE
In the usual transmission system one or
several generators in parallel feed the line
at a potential which is kept constant as far as
possible, and the current varies with the load.
The Thury system of direct current trans-
mission is a series system in which the gener-
ators supplying the power and the motors
absorbing the power are all connected in
series in a single closed circuit. In this system
the voltage varies with the load and it is the
current which is kept constant.
Fig. 1 shows the closed ring and the con-
nections of the generators and motors. This
diagram is a simple representative of the
Thury system. Fig. 2 shows the short cir-
cuiting switch by means of which the gen-
erators and motors can be switched in or out
of circuit and disconnected from the line.
In the Thury system the current is con-
stant and exactly the same in the whole of the
circuit. The loss due to ohmic resistance
in the line and in the machines is. therefore,
constant and independent of the load.
The maximum power obtainable in this
system is determined on one hand by the
strength of the constant current, circuits are
in operation with currents from 50 to 450
amperes; on the other hand, for a given
current the power is limited by the maximum
voltage which is permissible with regard to
the insulation from earth. Plants of 100,000
volts and higher have been installed.
The Thury system permits the trans-
mission of power from the generators directly
to the motors without the help of any inter-
mediary such as transformers, and at the
same time leaves the generators and motors
as independent units. Fig. 3 gives examples
of a Thury series system showing the closed
ring principle without any switch, apparatus
or machine capable of breaking the circuit.
In 1SSS when the transmission of power by
direct current in series was first employed
(Genoa, distance 27 kilometers [16.8 miles]
12,000 volts, constant current 45 amperes)
polyphase current .was still unknown from an
industrial point of view and the series system
appeared at the time to be the solution of the
problem of long distance transmission. During
the following years, however, three-phase
transmission developed and its rapid and
successful progress limited the further applica-
tion of the direct current series system to a
few exceptional cases. In these years interest
was detracted from the Thury system, due to
the fact that engineers were then almost
entirely occupied with distribution for com-
bined power and lighting purposes for which
constant voltage was necessary.
In later years when it became necessary to
arrange for transmission of power over great
distances for which high voltage was required,
certain disadvantages arose in adhering to
transmission at high alternating voltage. Due
THE THURY SYSTEM OF DIRECT CURRENT TRANSMISSION
1027
to these difficulties, interest was again
awakened in the direct current series system
because it avoids all effects due to induction,
phase displacement, capacity and leakage
to a certain extent.
Table I, page 1028, represents a list of the
more important installations carried on upon
the Thury principle and under the leadership
of its inventor, Mr. R. Thury. The list is
taken from Mr. Highfield's paper in the Jour-
nal of the Institution of Electrical Engineers
(1913, part 222, vol. 51, page 640).
III. ADVANTAGES
(a) General
One of the chief practical advantages of
the direct current series system is the fact
that high tension underground cables can be
used in which losses in the dielectrics are
practically eliminated. Experience shows
Liqhtnmq Arrester
Short Circuiting
Snitch
L iqhtntnq Arrester
Fig. 1. Diagram of a Series Circuit for the Generation, Trans-
mission and Utilization of High-Tension Direct Current
Of nam i
out Of Circuit
~j^rr
Fig. 2. Diagram of the Short Circuiting Switch employed in
the Series Circuit shown in Fig. 1
that it is possible to employ cables of one
conductor at high voltages in densely pop-
ulated centers, across rivers, estuaries, etc.
In papers presented by Highfield before the
Institution of Electrical Engineers (England)
in 1907, 1912, and 1913, the series system,
with special reference to the plant of the
London Metropolitan Electrical Supply Com-
pany, is described. Highfield discusses in
detail the cable system which is for operation
at 100,000 volts and a load of 12,000 kw„
and these papers are valuable and interesting
contributions to the subject.
40 fv -|
Total Electromotive Power of Generators
200000 Volts
Amperooe 3O0 Poiver 60000 ff~
Majiimum Voltaae 80000 Volts, t'lot is
-r or - 40000 Volts
Total Electromotive Poiver of"Generators ZOOOOO Volts
Hiqhest Tension petiveen Earth and Line JOOOO Mts
Fig. 3. Typical Examples of Series Circuits with Kilowatt
and Kilovolt Data
Another point of interest is the use of the
earth as a return circuit. In the above
mentioned papers Highfield refers to experi-
ments which Thury made on the Lausanne-
St. Maurice line and reports in detail upon
his work on the London line to prove the
feasibility of using the earth as a return or as a
reserve in case one cable breaks down. These
experiments have proven that, owing to its
constancy, direct current can be transmitted
through the earth with only a small loss.
The current density being relatively small
(50 to 500 amperes) electrolytic effects upon
pipes, etc., are localized to the proximity of
the earth terminals.
The Thury system offers several further
advantages of which the following should be
mentioned. A higher voltage can be used
than for alternating current with the same
insulation, the great simplicity of the central
stations on account of the absence of step up
1028
GENERAL ELECTRIC REVIEW
and step down transformers, the absence of
complicated switch gear such as circuit
breakers and the usual breaking switches, and
the impossibility of a great excess of current
in case of damage to machines. Where
desired, advantage can be taken of the fact
that the motors on the Thury system have
the property that the torque is independent
of the speed.
This system of transmission allows the use
of any natural source of power, great or small,
which happens to exist in the regions through
which the lines run. Individual central
stations connected in series are entirely
independent of local overloads or lack of
demand, whatever the relative importance
of these stations ma)- be or whether the
distance is great or small from the points of
consumption. Their simultaneous running
is absolutely independent of the distances
covered by the primary circuit, that is,
independent of the resistance of the lines.
When the series system is combined with
alternating current distributing plants there
is no difficulty in linking together several
lines fed by alternating stations of different
frequency. Series motor-generators thus
acting as a link form a valuable, elastic
coupling for correcting both the variations of
load and the differences of voltage caused by
the load on the lines.
Highfield studied this question thoroughly
with the object of connecting the twenty-
four principal London stations. There exists
no unity of system in London and lines are
found one beside the other of 42, .50, 60, 80
and 100 cycles per second, or three- and
single-phase, besides other sections fed by
TABLE I
Description of Undertaking
Soc. Acquedotto de Ferrari-Galliers
(Italy), Genes, 1889
Wasserwerke Zug (Switzerland)
Papetries de Biberist (Switzerland)
Communes du Val de Travers
(Switzerland)
Soc. d'EclairageElectrique (Brescia, Italy )
Soc. Romande de Electricite (Switzerland)
Commune de la Chaux de Fonds et du
Locle (Switzerland)
Usines Electriques d'Eisenbourg (Hun-
gary) Ikervare Steinamanger
La Papelera Espanola Renteria (Spain)
Soc. Industrielle d'Electricite (Italy) . . .
M. V. J. Dunand a Batoum (Russia).. . .
Usines Electriques d'Eisenbourg (Hun-
gary) Ikervar Sopron
Mines de Plomb Linares (Spain)
*St. Maurice-Lausanne
t Moutiers- Lyons First Stage:
Station at Moutiers
JSecond Stage:
Station at LaBridoire
iThird Stage:
Stations at Moutiers and LaBridoire
coupled in series
^Fourth Stage i
Station at Bozel
Year of
Start-
ing up
Line
Cur-
rent
Amp. 1
1889
1891
1893
45
50
40
1895
65
1895
50
1895
50
1896
150
1896
65
1896
65
1896
1899
30
50
1899
1900
1902
40
60
150
1906
75
1911
150
1911
150
1912
150
Total
Length of
Circuit
Miles
74.6
14.9
23.0
21.7
32.3
22.4
32.3
40.4
17.4
37.3
12.4
74.13
37.3
69.6
223.7
PART. MACHINE UNITS
Xo. Volts
18
5
2
{?
[3
12
4
Kw.
1,600
3,400
2,600
1,300
1,500
3,000
3,500
1,800
6 1,500
3 2,600
2 2,740
4 3,000
2 1,300
4 2,500
3 3,500
6 4,500
89
186
93
288
112
186
194
112
238
675
§5 14,400 1,080
4 9,125 1,368
§3 18,250 2,737
R.P.M.
Total Total Line
Output Pressure
320
260 1
450
300
260
320
300
300
428
428
630
400
272
590
525
525
700
585
865
865
360
130
400
630
4,000
4,300
3,600
14,000
S.000
6,800
9,100
10,500
10,500
14,000
1,890 12,600
9,000
13,280
13,280
12,000
2,600
10,000
10,500
27,000
57,600
24,000
8,400 56,000
: aight transmission of 34.8 miles.
tStraight transmission of 112 miles, consisting of 106 miles of overhead wire and 6 miles of underground
cable, the latter being at the extremity of the line and working at the full pressure.
:So far the total line pressure has not exceeded 75,000 volts, but it will subsequently be raised to 100,000
volts with a line current of 150 amperes.
SEach unit consists of two double generators coupled to one water turbine.
li Each unit consists of one double generator coupled to one water turbine.
THE THURY SYSTEM OF DIRECT CURRENT TRANSMISSION
1029
direct current, and the harmonizing of these
various systems is only possible with the aid
of the series system.
The five different three-phase stations of
the line belonging to the "Societe Generale
de Force et Lumiere" (Grenoble-Lyon) are
coupled and sustained by the Moutiers-Lyon
series transmission, of which 28,000 h.p.
is used for the general control of the three-
phase line (46,000 h.p.) and for feeding the
principal center of consumption in the town of
Lyon. In this case the advantages gained by
this combination of the two systems are
important and interesting. It happens daily
that two of the principal generating stations
of this Company's distribution system are
unequally loaded with reference to the capac-
ity of the respective three-phase stations
which feed them. The Bellegarde station
generally has spare power, but that of
Grenoble is not able to satisfy the consumers
and at times of overload the speed of the
turbines decreases slightly. Running in
parallel with Bellegarde then becomes prac-
tically impossible, but at Lyon, the point of
contact of the two lines, at least 100 km.
(62 miles) from Bellegarde and about the
same distance from Grenoble, the series
system intervenes and reduces the load of
Grenoble, thereby raising the frequency to
that of Bellegarde. The latter can then be
directly coupled in parallel with Grenoble.
Each of the three big stations can thus be
proportionately loaded in spite of the dispro-
portion of available power and consump-
tion.
This multi-circuit feature, which makes the
constant direct current system especially
efficient for inter-connecting a number of
stations, systems or networks, can be applied
to long distance railroading, as trans-con-
tinental lines where the stations feeding the
railroad and all available sources of power
near the railroad would be inter-connected
by a series direct current system, resulting
in economy of installation and operation
together with a very high degree of reliability.
(b) Absence of Induction Effects /
The absence of phase displacement and
effects due to the capacity in the lines is
advantageous to the transmission and to the
central stations which are no longer exposed
to the effects of resonance. At the same time
running under small loads is facilitated by the
absence of charging current due to the elec-
trostatic capacity of the line at very high
tension.
The reduction of corona effect as against
alternating current, and the possibility of
greatly reducing this effect by using equipo-
tential lines either in case of return by earth
or in case of the closed circuit, constitutes
still greater advantage over alternating cur-
Fig. 4. Conductor Cable used in the Lyon High-Tension
D-C. Transmission System. Its cross-section is
75 sq. m.m. (148,500 cir. mils). Full size
rent. The suppression of all induction
effects permits the use of underground cables.
(c) Absence of Transformers
To obtain very high tension alternating
current with constant voltage, step up trans-
formers are necessary. Each of these trans-
formers, if it is to be capable of producing a
tension of, say about 100,000 volts, represents
a considerable expense. The same high
tension can be obtained with the direct
current by connecting in series several units
at reduced voltage without any machine
having to stand more than 5000 volts between
the frame and the winding. This subdivision
of the tension has not only the advantage
that intermediate transformers are unneces-
sary, but greater safety in working is effected
and also simplicity of the installation.
(d) Transmission by Cable
The difficulties resulting from an overhead
arrangement due to storms, etc., are elimi-
nated in an underground transmission when
such is possible; at the same time the cost of
supervision and upkeep is reduced. The
value of underground transmission for high
tension is recognized especially in crowded
centers so that expensive intermediate trans-
formation is avoided.
1030
GENERAL ELECTRIC REVIEW
A high tension alternating current rapidly
fatigues the dielectric of the cable, heats it up
and ultimately renders it unserviceable. The
result is that one can only use underground
cables for alternating current when the tension
is relatively low and the distance not very
great.
Cables with one conductor have been
manufactured for tensions of 100,000 to
150,000 volts direct current between the
conductor and the earth.
For nearly ten years a single conductor
underground cable 9 km. (5.6 miles) in length
has connected the central station of Vaulx
en Velin with the station of the Cie. des
Omnibus et Tramways de Lyon in the
Moutiers circuit, and has formed the line to
the interior of the town of Lyon. This
cable was designed to work normally at
100,000 volts direct current, 150 amperes, but
actually works at a tension of 70,000 volts
and although it is connected with an overhead
line of 200 km. (124 miles) often exposed
to atmospheric disturbances, it has not
suffered from any accident since it has
been in use. Fig. 4 shows a section of this
cable full size which has been in sendee since
1906.
In England the Thury system has been
adopted by the Metropolitan Company for
general distribution in the West of London
297 sq. mi.). As the transmission had to be
underground, the adoption of alternating
current suitable for underground cables led to
an estimate out of proportion to the economy
of the project and it was that which led to the
direct current being adopted. The first sec-
tion of this distribution has been in service
since 1911 and the scheme has fulfilled in
evenT way what was expected of it.
The transmission over great distances by
means of underground or submarine cables is
an economic proposition with high tension
direct current at 100,000 to 150,000 volts
between the core and the earth, that is,
200,000 to 300,000 between the extreme
conductors.
The losses, except those due to ohmic
resistance, are negligible.
(e) Earth Return
The Thury direct current system permits
the practical use of the earth as an active
conductor. The use of the earth as a con-
ductor presents considerable industrial
advantages as it permits a reduction of 75
per cent in the necessary weight of copper for
the same tension.
The Federal Government of Switzerland
has made tests on the transmission scheme
installed between St. Maurice and Lausanne
(5000 h.p., 2200 volts, 150 amperes, 56 km. or
34.7 miles). One of the two overhead lines
was replaced by the earth and the whole
town service, traction and light was served
during a period of 450 days by a single con-
ductor. No accident caused by lightning or
troubles on the earth connections and the
numerous telegraph and telephone lines have
become known.
The resistance of the two earth terminals, if
they are well established, ought not to exceed
one ohm. This resistance is only local, the
distance separating the two earth terminals
being of no influence. The earth can be used
in two ways, as a neutral or as an active
conductor. As a neutral the earth transmits
no current, but only limits the difference of
tension between the extreme conductors and
the earth to half the total tension. In case of
an accident on one of the lines, it permits the
other to transmit at least half the energy.
IV. DISADVANTAGES
(a) Transformation
Whereas alternating current can be trans-
formed by static transformers, the transforma-
tion of direct current requires rotative
machines which are more expensive, require
greater up-keep and are less efficient. This
and the impossibility of subdividing the
constant current are the two principal reasons
which limit the use of direct current series
transmission.
However, with alternating current the
transformer must take the full voltage and,
therefore, requires elaborate protecting
apparatus whereas the machines of the direct
current series system only take a part of the
total tension. For instance, a motor of 1000
h.p. in series on a circuit of 300 amperes and
100,000 volts is calculated and insulated only
for 3000 volts which is the maximum it
can absorb, including 15 per cent overload.
A motor for an output of 100 h.p. and fed by
the same circuit would be calculated for
300 volts.
(b) Insulation from Earth
All machines on the Thury direct current
system forming part of the high tension
transmission circuit must be specially insu-
lated from the earth and in such a way that
the insulation can withstand the full line
voltage without excessive strain. This special
insulation is necessary for tensions over 10.000
THE THURY SYSTEM OF DIRECT CURRENT TRANSMISSION
1031
volts or plus or minus 5000 volts between the
extreme poles of the station and the earth.
This insulation considerably increases the
cost of the installation of the machines. It
is necessary to insulate the bed plates of the
machines, and as a precaution for the safety
of the men, to insulate the ground around
the machines and to avoid having any un-
insulated objects around for some distance.
Originally the bed plates were mounted on
a number of porcelain insulators. To prevent
any accident, due to the splitting of an
insulator, the concrete block underneath the
insulators is insulated by arranging a number
of insulating blocks underneath it. These
insulating blocks are set in a pit which is
afterwards filled up with an asphalt com-
pound. With alternating current, insulation
between the machine frames and the ground
is not necessary, but on the other hand, a
partition work is indispensable for all sections
of the switch gear.
Where the Thury system is used, no general
switchboards are required which may be said
to reduce the danger to the operators. The
necessary instruments are fitted on the
machines and are, therefore, insulated by the
machine insulation. Only a panel with the
controlling instruments is installed at some
distance from the machines and if an earth
return is not used the panel must be insulated
from the ground. This panel may carry a
wattmeter, a voltmeter, a standard ammeter,
and, if required, a registering voltmeter;
these instruments being at the same voltage,
can be manipulated when working without
any danger. Their winding insulation must
be the normal insulation of the correspond-
ing machine.
When the machine has two armatures
mounted on the same shaft there must be a
specially strong insulation between the shaft
and the punchings. This arrangement has
been adopted for the Moutiers-Lyon line.
The machines are calculated to give a normal
tension of 9130 volts, but are frequentlv
working at 10,000 volts.
(c) Commutation
In the Thury series system the commutators
are a weak point as they must be very care-
fully made and generously proportioned, and
this considerably augments the cost of the
machines. Great attention must also be
paid to the commutators during running,
in which respect alternating current machines
with slip rings have an advantage. This
is undoubtedly the most serious difficulty
encountered in the production of satisfactory
powerful units at high voltage with low
amperage.
The first series machine made in 1890 was
designed for a voltage of 1200 volts per
commutator. In 1893 machines were made
for a voltage of 3500 volts per commutator,
and later 5000 volts per commutator. A
higher voltage than 5000 volts has, up to the
present time, not been exceeded in practice
and this sets a limit to the size of the unit.
With 5000 volts per commutator, twenty
commutators are necessary to produce 100,000
volts. With four commutators per unit,
which is the case in the La Rosiere station of
the Moutiers-Lyon line, five generator units
are necessary for the tension of 100,000 volts
at a constant current intensity of 150 amperes.
The power thus available in this circuit is
15,000 kw., each unit of four commutators
giving 3000 kw. With 300 amperes the power
of each unit would be 6000 kw. and with 600
amperes 12,000 kw., this latter giving a total
power of 60,000 kw.
It is evident from the above that the present
day limit of 5000 volts per commutator
means that the number of units to give a
total high voltage is relatively great. This
disadvantage, however, has one good point.
In case of break down at any part of the plant
it will only be necessary to shut down
a small section. In a Thury installation
erected in Zory in 1891 the generators in this
station have been working for eight years at
a rate of 18 hours per day at full load without
having to change the carbon brushes, and
during the 24 years of service not a single
commutator has had to be removed. The
voltage of these units, however, was not as
high as 5000 volts, but something like 1600
volts per commutator.
(d) Constant Loss in the Mains
In the Thury series system the line is fed
by a current of constant intensity and the loss
in the line is, therefore, independent of the
load. The efficiency of such a line is con-
sequently low for small loads and then rises
proportionately with the load. With rela-
tively constant load this is not disadvan-
tageous, but with a varying load the average
efficiency of the transmission is considerably
lowered.
When the prime movers used are heat
engines or hydraulic machines using large
reservoirs, the voltage and copper section of
the line is important in order to obtain a
suitable daily efficiency. On the other hand,
10.32 GENERAL ELECTRIC REVIEW
when water power is used without reservoirs power can be utilized at any point of the cir-
the quantity of waste water during hours of cuit whatever the distance or the resistance
small load is of little or no importance. Again, between the two points may be.
when the transmission line has several central
Stations in series as is the case in the Moutiers- ^ Excessive Voltage Due to Open Circuits
Lyon line, and one of the stations makes use As it is dangerous to interrupt a constant
of the river without any reservoir, the con- direct current, it is necessary to use all means
stant loss is then of no importance. If any of in order to prevent the circuit from being
the other stations wish to profit by economiz- entirely broken thereby eliminating a danger-
ing their water or their fuel, they can do so ous rise of pressure,
bv allowing the station which makes use of
the river without any reservoir to work under v- GENERATORS AND MOTORS
full flood. Each kilowatt added to the loss A description of the Thury generators and
in the line is thus completely utilized at the motors has frequently been given in technical
other end without additional loss. literature. According to the Elektrotech-
Thus in the series circuit, power can be nische Zeitschrift, 1906, page 1091, the gener-
added to the circuit at any point and this ators of the Moutiers-Lyon plant have cast
TABLE II
SPECIFICATIONS OF THURY GENERATORS
Output 270 kw.
Speed 300 r.p.m.
Tension 3600 volts
Current 75 amperes
Number of poles 6
Bore 1250 mm. (49.21 in.)
Diameter of armature 1232 mm. (48.50 in.)
Axial pole length 300 mm. (11.81 in.)
Ventilating ducts 4 ea. 10 mm. wide (0.4 in.)
Number of armature slots Ill
Number of coils 332
Number of turns per coil 3
Number of commutator bars 996
Diameter of commutator • 1100 mm. (43.30 in.)
Width of commutator 75 mm. (2.95 in.)
Number of brush spindles 6
Number of brushes per spindle 2
Cross section of brushes 8X30 mm. (0.31X1.18 in.)
From this data the following characteristics would result :
Induced voltage at full load 3,736 volts
Air density at full load 59,000 lines
Maximum tooth density at full load 172,000 lines
Armature density at full load 73,000 lines
Magnet core density at full load 97,000 lines
Yoke density at full load 93,000 lines
Peripheral velocity of armature 3,820 feet per minute
Peripheral velocity of commutator 3,410 feet per minute
Maximum tension between two adjacent commutator bars 34 volts
TABLE III
SPECIFICATIONS OF THURY MOTORS
Output 360 h.p.
Voltage 3820 volts
Current 75 amperes
Number of poles 4
Bore 1262 mm. (49.68 in.)
Diameter of armature 1232 mm. (48.50 in.)
Axial pole length 300 mm. (11.81 in.)
Ventilating ducts 4 ea. 10 mm. wide (0.4 in.)
Number of slots Ill
Number of armature coils 333
Number of turns per coil 3
Number of commutator bars 666
Diameter of commutator 750 mm. (29.52 in.)
Width of commutator 110 mm. (0.43 in.)
Number of brush spindles 4
Number of brushes per spindle 3
Cross section of brushes 8X30 mm. (0.31X1.18 in.)
THE THURY SYSTEM OF DIRECT CURRENT TRANSMISSION
1033
steel frames with six cast-on poles. The
armatures and commutators are fitted on the
shaft with bosses. The drum windings con-
sist of form-wound coils laid in slots. The
main particulars of the individual machines
are given in Table II.
Fig. 5 illustrates a typical Thury generator
with an automatic regulator built by the
Compagnie de l'lndustrie Eleetrique et
Mecanique, Geneve, Switzerland. This
machine is designed for 170 kw., 375 r.p.m.
3400 volts, 50 amperes.
Thury motors are practically of the same
design as the generators. The station at
Rue d'Alace of the Moutiers-Lyon plant has
five series motors each of 720 h.p., coupled to
500-kw. direct current machines giving 600
volts and supplying the tramway circuit in
Lyon. These motors are arranged as double
machines, each bed plate carrying three
bearings and two four-pole frames of cast
steel. The poles are screwed on to the frame,
and according to the Elektrotechnische Zeit-
schrift, 1906, the specifications are as given in
Table III.
Fig. 6 is an illustration of a series motor for
220 h.p., 320 r.p.m., 3400 volts, 50 amperes,
with an automatic regulator, built by the
Compagnie de l'lndustrie.
Fig. 5. A D-C. Series System Generator of 170 kw., 375 r.p.m.,
3400 volts, 50 amperes capacity with Automatic Regulator
VI. REGULATION
(a) Generators
In the Thury series system each generator
and each motor must have its governor; the
generators to maintain the amperage constant
on the line and the motors to maintain the
speed constant, except in special cases. Two
methods of governing the generators are
employed, (a) by varying the speed of the
generator groups or (b) by varying the
position of the brushes should the speed be
constant. In the first method one governor
alone automatically adjusts the speed of the
generator groups according to the tension of
Fig. 6. A DC. Series System Motor of 220 h.p., 320 r.p.m.,
3400 volts, 50 amperes capacity with Automatic Regulator
the circuit. It works on the turbine nozzles
by means of a ratchet and pawl device or
is actuated by oil under pressure. The
generators are then series wound with fixed
brushes and without any regulating device.
This method of governing is chosen when
hydraulic turbines capable of running at low
speeds with half the available flow of water
produce the necessary power. To avoid the
speed being reduced too far for small loads
when the output varies greatly, it suffices to
keep only the number of units running which
the service actually demands.
Governing by moving the brushes is used
when the construction of the turbine requires
a constant speed or when the efficiency of
the turbines at small load is of importance.
In such cases a double control is necessary,
one for the speed and one for the current
intensity.
Speed governors are those generally used,
but they are not required to fulfill the con-
ditions which are demanded of governors
controlling alternators; thus in the series
system the control of the speed can be approxi-
mative, the division of the load between
several units being independent of the speed.
1034
GENERAL ELECTRIC REVIEW
The groups of the central stations can run at
speeds varying 10 per cent one from another
without any inconvenience and the division
of the load suffers in no way. These con-
ditions permit the best use of the inertia of
flywheels.
This is very important when the inertia of
the water in the pressure pipes plays an
important part and could produce dangerous
hvdraulic recoil or surges. The fact that
synchronizing is not required renders the
governing of turbines or other prime movers
with the series system much easier.
The equal distribution of the load between
several groups might seem difficult to realize,
but the use of powerful governors with a
sensibility of 0.2 per cent has made the
satisfactory distribution of the load possible.
The chief point in the question of regulation,
which is in favor of the Thury system, is
that all synchronizing troubles are avoided.
b) Motors
To prevent the speed of the motor varying
with the load, a special speed governor is
employed. As each motor on the Thury
svstem requires a governor, this is a serious
drawback in comparison with the usual
alternating synchronous and asynchronous
motors. This constitutes a great objection
to using the Thury system as a means of
distribution.
VII. APPARATUS AND ACCESSORIES
In the series system the amperage being the
same in all parts of the circuit, the necessary
apparatus is the same for all the machines
whatever their individual power may be.
The windings of the different machines bear
a great similarity and a uniform section of
conductor can be employed. This is also an
advantage from a manufacturing point of
view.
For each unit the apparatus consists
chiefly of a general control switch and an
auxiliary switch. The former is mounted on
arms fitted to the bed plate of the machine
and provided with an ammeter and volt-
meter. The object of the latter switch is to
isolate any particular unit when cleaning or
dismantling is necessary in which case the
unit is properly connected to earth. When
the rotation of the generators is reversed,
they are automatically short circuited through
a relay which acts upon the switch. The
motors are similarly fitted with safety con-
trivances. General switchboards are not
necessary.
The generators can be started up in a few
seconds. In the case of a generator controlled
by varying the speed, the attendant opens
the turbine valve, the generator being short
circuited. Owing to the poles being connected
in series their effect is felt after the first two
or three revolutions and the amperage rises
according to the rate of starting until the
normal intensity is reached. By opening
the switch, the machine is brought in circuit
and this occurs without any sparking.
In the case of a constant speed generator,
the machine is brought up to its normal speed,
the brushes are moved until the normal
current intensity is reached and then the
switch is opened. In order to shut down a
variable speed generator, the turbine valve is
closed and the generator is short circuited as
soon as the voltage becomes zero. If the
speed is constant, the governor is cut off, the
brushes brought to the zero position, and the
switch is then closed. The turbine can also
be cut off and the switch closed as soon as the
turbine stops. Starting-up and shutting-
down generators is, therefore, a simple process
and no breaking switch is required. There is
no trouble as regards synchronizing or adjust-
ing and this is particularly important in case
of overload or accidents as synchronizing is
in such cases often difficult and the cause of
delay just when this delay is very undesirable.
One feature of great importance in connection
with generators on the Thury system is that
automatic circuit breakers become unneces-
sary. Circuit breakers are not required owing
to the fact that a damaged generator does
not cause an increase of current but on the
contrary the total current is decreased. The
precaution taken consisis in providing a
relay for each governor which automatically
shifts the brushes to the zero position in case
of accident. The attendants have then only
to short circuit and stop the machine. This
same relay brings the generator brushes back
to zero when the transmission line is acciden-
tally cut or short circuited and prevents any
subsequent re-excitation without the inter-
vention of an attendant. A broken line is
thus immediately rendered harmless unless
doubled by any other line in parallel. In this
case the broken line can be automatically cut
off without interrupting the general circuit.
VIII. COST COMPARISONS
The cost of a d-c. transmission line is less
than that of a line of similar capacity for
alternating current, more particularly where
underground cables are employed, and
THE THURY SYSTEM OF DIRECT CURRENT TRANSMISSION
1035
1036
GENERAL ELECTRIC REVIEW
further, the use of the earth as one of the
conductors results in a very large saving.
In addition to this the switch gear is simpler
and cheaper. Against this, however, the cost
of the necessary governors must be set, the
commutator construction of the machine, the
special insulation to earth, in short, the
costly d-c. generating station.
The Swedish and Danish governments
carried out investigations in regard to a trans-
mission line between Trollhalten, Sweden,
across the strait to Copenhagen, Denmark.
and comparative costs were made up of a
generating equipment and a 200 mile line for
90,000 volts. In this particular case the
existing generating station is 2.3 cycles, and
50 cycles is required at Copenhagen, thus
necessitating frequency changer sets.
The investigations resulted in favor of the
Thury system, the d-c. generation and trans-
mission using wooden pole line construction,
a submarine cable across the strait and ground
return being considered the most economical
one and possessing favorable operating fea-
tures. So far as known, this installation has
not been made.
IX. MOUTIERS-LYON TRANSMISSION
SCHEME
(a) General
The "Societe de Force et Lumiere" owns
a three-phase distribution network covering
an area of about 9000 to 10,000 sq. km.
(3474-3860 sq. mi.) in the French districts
of the Rhone, Isere, Savoie and the Loire.
This network was originally fed by four
hydro-electric stations distributing three-
phase current at 40,000 volts, 50 cycles per
second and was completed by three stations
on the Thury series system. A steam plant
also producing three-phase current formed
the reserve at Lyon. The total power of the
three-phase stations is 40,000 h.p. and at the
present time the Thury stations generate
28,000 h.p. but they are capable of pro-
ducing twice this power. The three-phase net-
work was installed some years before the
Thury section, the latter dating from 1906.
It is interesting to note the reasons which
led the Societe Generale to install the Thury
system when it would have appeared at first
sight to be more logical for the sake of
uniformity to equip the three stations at
Moutiers, Luzerne and LaBridoire with
three-phase current. The choice of direct
current made it necessary to build a sub-
station at Lyon containing rotary con-
verters for transforming direct to three-phase
current. This meant not only greater cost,
but a lower efficiency than that obtainable by
alternating current.
The direct current series line from both
Bozel and Lyon is 200 km. (124 miles) in
length. For a great part of its course it runs
through mountainous country where storms
and hurricanes frequently occur. Fig. 7
show's the complete transmissions, the dotted
line represents the Thury transmission and
the full line the three-phase transmission.
A three-phase line would have been much
more costly and more difficult to construct
than a direct current line consisting of two
conductors. Further, the company had to
penetrate into the heart of the town of Lyon
in order to furnish the tramway station with
the necessary power. It was only possible
to enter the town in this way by using under-
ground cables and to do this with alternating
current, the transmission tension would have
had to be lowered. The application of the
direct current series system made it possible
to enter the town by means of a cable with
full line voltage, thus making any trans-
formers on the outskirts unnecessary.
A further consideration which led to the
adoption of the Thury system was that it
Fig. 8. A Column carrying a Switch. Voltmeter, and
Ammeter as employed in the d-c. series system
dispensed at once with all the inherent
difficulties of running the different three-phase
lines in parallel and its adoption meant the
perfect control of the voltage and frequency
in the heart of the most. important center of
consumption.
THE THURY SYSTEM OF DIRECT CURRENT TRANSMISSION
1037
The first section of the Thury installation,
erected in 1906, consisted of a single generat-
ing station situated on the Isere (Savoie) at
a distance of ISO km. (112 miles) from Lyon.
This station had four units, each of 1600 h.p.
at 57,000 volts, 75 amperes; a fifth unit was
added later. The current was transmitted
to Lyon by an ordinary transmission line
erected chiefly on wooden poles and fed the
tramway station (an average of 2500 to 3000
kw.) and also the three-phase network of
Grenoble and Bellegarde.
Later the three-phase network of Lyon
rapidly developed and it became necessary
for 150 amperes as a test and raised in power
to 900 kw. instead of 500 kw., the total
generating power being thus increased to
18,000 kw. including reserve. The Moutiers
station and also that at Bozel has a period of
low water in winter. The LaBridoire station
was installed with the object of maintaining
a total production of 15,000 kw. (100,000
volts, 150 amperes) all the year round. The
power is obtained from a natural reservoir
formed by the lake of Aiguebillette working
under a double head of water of 120 meters
(394 feet). The stations at Moutier and
Bozel usually work under the fullest load
Fig. 9. A Double, Series. DC. Generator of 2000 h.p.. 428 r.p.m., 150 amp.. 2 X4565 volts with Regulator
for the Moutiers-Lyon Transmission located in the Bridoire and Rosiere station
to considerably increase the help given by the
Thurv svstem and two new stations were
established in 1909, one at Bozel (12,000 h.p.,
150 amperes, 57,000 volts) at a distance of
200 km. (124 miles) from Lyon, the second
at LaBridoire (S000 h.p., 150 amperes,
36,000 volts).
These new stations were connected in
series with the Moutiers station; the arma-
tures of the Moutiers generators (75
amperes) being coupled in parallel to obtain
the 150 amperes of the new circuit. At Lyon
the first motors were also supplied for 150
amperes and seven new converter groups of
200 h.p. were put into service on the Grenoble,
Bellegarde and Lyon three-phase network.
The two first converter groups were rewound
that the available water can produce. The
LaBridoire station bears all the fluctuations
and either maintains the control alone or
jointly with the Bozel station. The station
rarely works at night time, the water being
economized as much as possible for the period
of low water.
(b) Moutiers Plant
There are five units each of 3600 h.p.
running at 300 r.p.m. The turbines have
neither flywheels nor individual governors.
A general governor regulates all the units in
use simultaneously by means of a contrivance
which acts upon the nozzles of the turbines.
This governor is less sensitive than those of
the Bozel and LaBridoire stations; it is only
103S
GENERAL ELECTRIC REVIEW
brought into play when these two stations
reach the limit of their control. In practice
the governor is rarely in use, the load always
being greater than the capacity of the station.
The dynamos have no governors and, being
excited in series, their brushes are stationary.
Each unit is fitted with a column carrying
a switch, a voltmeter and an ammeter, shown
in Fig. 8. A small switch attached to one of
the bearings is used for short circuiting the
dynamo. The machine is shut down by
simply closing the turbine. This having been
Pelton wheels develop a maximum power of
4400 h.p. with a head of 720 meters (2362
feet). Each group forms a complete unit
having its own control by means of an electric
oil pressure regulator. This device shifts the
brushes, thus obtaining a variable voltage
from 0 to 4500 volts for each commutator.
The current is 150 amperes and there are
no signs of sparking under any conditions
of load. The regulators, unlike those at
Moutiers, are very sensitive and show varia-
tions of 0.2 per cent. The load is auto-
Fig. 10. D-C. Three-phase Converters, each group including 2000-h.p. series motors 2 X4565 volts,
140 amp., 428 r.p.m., Vaulx en Velin
done, the column is short circuited, thus
disconnecting the dynamo from the circuit.
There is no general switchboard but a small
panel is used on which a meter, a general
voltmeter and a standard ammeter are fixed.
A recording device plots the daily fluctua-
tions of voltage. No rheostats are necessary
and the station is in charge of a superin-
tendent and mechanics.
(c) Bozel Plant
This station contains three groups each of
4000 h.p. at 18,000 volts under normal con-
ditions with a margin of 10 per cent. The
speed of 428 r.p.m. is maintained by Piccard
governors with the help of flywheels. The
matically distributed between the groups
within a margin of 10 per cent. The apparatus
is the same as in the Moutiers plant. The
dynamos are connected in series by means of
a single cable with single core which passes
directly from one machine to another.
(d) LaBridoire Plant
This station contains four groups each of
2000 h.p. at a normal voltage of 9000 volts,
428 r.p.m. The station is equipped in exactly
the same way as that at Bozel. The gener-
ators are shown in Fig. 9.
(e) Insulation
Each pair of dynamos is mounted on a
carefully insulated bed of cement. The
THE THURY SYSTEM OF DIRECT CURRENT TRANSMISSION
1039
insulators which support this bed are packed
in a thick composition of asphalt and bitumen
tested up to 100,000 volts alternating cur-
rent. The control panel is mounted in the
same way.
(f) Couplings
The couplings are of the Raffard type mod-
ified on account of the large power which
they have to transmit and the insulation
which they have to provide between the
turbines and the dynamos. The coupling
are isolated by a series of circuit breakers and
the connection of one section with the earth
can thus be effected should any accident
happen or any particular combination be
necessary.
For a distance of 40 km. (25 miles) the
line is carried on the same poles which carry
the three-phase current at 40,000 volts. The
rest of the line is supported on wooden poles,
or uprights made of reinforced concrete.
The length of the overload section is about
19G km. (120 miles).
Fig. II. D-C. Three-phase Converters including double, series, motors 2000-h p., 2 X4565 volts, 428 r.p.m. with
Oil-pressure Regulator, Vaulx en Velin
is connected up by means of a belt, the two
halves being at a distance of about 0.40
meters (1.3 feet) apart.
(g) Transmission Line
The constant current is 150 amperes at
100,000 volts. The line is 200 km. (124 miles)
in length and consists of four conductors
9 mm. (124,740 circ. mils) in diameter. The
total resistance is 5.3 ohms, including the
underground cable which enters the town of
Lyon. The loss under full load is S per cent
and the weight of copper for the 800 km.
(497 miles) is 456 tons. This works out at
30 kg. (66 lb.) per kilowatt. The two wires
of each line form a mutual reserve. These
The overhead line runs into the trans-
mission station of Vaulx en Velin which is
about 4J/2 km. (2.S miles) from the town
center. From this point the power is carried
into Lyon by the underground cable in order
to feed the tramway station which latter has
its converters giving 3000 kw. at 600 volts.
(h) Vaulx en Velin Plant
This station takes two three-phase lines at
40,000 volts and distributes the current to
Lyon at 10,000 volts. It also takes the
current from the steam plant at Lyon. In this
station the greater part of the series current
power is converted into three-phase current
at 10,000 volts by means of seven converters,
1040
GENERAL ELECTRIC REVIEW
each giving 1400 to 1500 kw., and two con-
verters of 500 to 700 kw. These converters
are shown in Figs. 10 and 11. There is thus
about 11,000 kw. available for increasing the
general three-phase distribution, maintaining
the voltage and frequency of the three-phase
current. From this distributing station the
secondary network which is entirely under-
ground, feeds the chief industries of Lyon,
which it is expected will absorb later a further
50,000 h.p. The extension of the Thury
system is being studied and it is probable
that a new line for 15,000 kw. entirely under-
ground will be laid.
The converters in the Vaulx en Velin plant
consist of series motors 2000 h.p. driving the
above mentioned generators of 1400 L500
kw. three-phase, 10,000 volts, 50 cycles per
second at 428 r.p.m. The motors are identical
with the Bozel and LaBridoire generators.
They are also fitted with an oil pressure
regulator which shifts the brushes. These
regulators, in order to maintain a constant
speed, are fitted with extremely sensitive
tachometers and the speed can be adjusted
at will. Thus a converter can be coupled to
one or other of the three-phase networks
(Lyon, Bellegarde or Grenoble) in spite of a
slight difference of frequency which occurs
daily when one or other of the lines is over-
loaded. In this way it is possible to couple
an overloaded line having a low frequency
to another having a frequency slightly too
high. Once the lines are coupled in this way,
the frequency of the overloaded line is raised
by the energy from the line which happens to
be under low load. In this way the Thury sys-
tem divides the available energy proportion-
ately amongst the five three-phase stations.
The steam reserve only comes into play in
case of accident or when the hydraulic power
fails. This power can, however, be used to
the last drop of water and each line can work
even when its own station becomes insuf-
ficient to supply the demand.
(i) Lightning Protection
The three generating stations at Bozel,
Moutiers and LaBridoire and the converter
station at Vaulx en Velin are all equipped
with protective apparatus against lightning.
This consists of a condenser connected to the
terminals of each station, an inductive resist-
ance of iron and a metallic resistance linked
to the earth for electrostatic discharges and
to choke oscillations caused by lightning.
Conductors insulated with "paper on the
Herthoud Borel principle have given entire
satisfaction and so far no accidents have
happened. Storms have only been indirectly
the cause of disturbances, due to lines broken
by falling trees, broken insulators or short
circuit, probably caused by branches of trees
blown on the wires by the wind. These
troubles are partly due to the fact that a
considerable portion of the line is only about
5 to 7 meters (16.4-23 feet) above the level
of the ground. The security of the line would
be considerably greater if underground trans-
mission were used and it is more than prob-
able that the next extension will be carried
out underground.
X. CONCLUSIONS
The Thury direct current system is a trans-
mission, and not a distribution scheme. The
possible applications are much more limited
than those of the polyphase system. The
two systems are mutually complementary
instead of competitive, each having its own
sphere of application and both are suitable
to work side by side. The Thury system
possesses certain important advantages, par-
ticularly where power in bulk is to be trans-
mitted from one point to another over a long
distance, and for interconnecting a number of
stations for the transfer of power and for
power systems of networks covered by means
of a single wire closed-ring circuit.
With the usual overhead construction the
Thury system can claim the advantage
inasmuch as only two wires are required and a
given insulator will withstand a much higher
direct current tension than alternating current
tension. One of the prominent advantages
of the Thury system is that underground and
submarine cables can be, and have been
successfully employed with very high tension.
There are no inductive losses, phase dis-
placements and capacity troubles; corona
losses are reduced and losses in the dielectrics
are practically eliminated.
A further important feature is the employ-
ment of the earth as an active return con-
ductor which has been found practical with
only small losses.
Owing to the saving which can thus be
affected in the line, the fact that trans-
formers are not necessary, and the absence
of all elaborate switchboards, the cost of a
transmission scheme on the Thury system
may be lower in certain cases than the cost of
an alternating current system. As several
power stations on the Thury system can be
put in series with the utmost simplicity, the
svstem can be used for transmitting and trans-
THE THURY SYSTEM OF DIRECT CURRENT TRANSMISSION
1041
forming into any desired frequency and volt-
age, thus enabling one alternating current
station to assist another which may be unable
to cope with its load, even though the two
stations may not have the same frequency or
voltages.
Although the Thury system plants are
simple in construction and operation, there
are several disadvantageous features; namely
the large number of comparatively small
machines necessary, the presence of high
tension commutators as against slip-rings for
alternating current, the difficult and expen-
sive insulation necessary to insulate the
machines from earth, and the rather com-
plicated regulating apparatus.
It is usual for distribution purposes to
transform the high tension direct current into
alternating current and to do this rotary
converters are necessary, as against static
transformers in alternating current trans-
mission schemes. Another point in the con-
sideration of the Thury system is that the
losses in the line are constant whatever the
load may be.
In conclusion, the author desires to ex-
press his appreciation to Mr. R. Thury for
the valuable assistance rendered to him in
the study of this interesting transmission
scheme.
XII. REFERENCE LIST
Journal of the Institution of Electrical Engineers
1907, vol. 38, page 407
1912, vol. 39, page 848
1913, vol. 51, pages 443, 040
Electrical World
1912, vol. 60, pages 1093, 1144
1913, vol. 61, pages 294, 759
National Electric Light Association, 36th Con-
vention, Chicago 1913, Hydro-electric and
Transmission, page 96
Elektrotechnische Zeitschrift
1902, Heft 46, pages 1001-1005
Heft 47, pages 1016-1021
Heft 48, pages 1038-1042
1905, Heft 24, page 571
1906, Heft 47, page 1091
1908, Heft 28, page 679
1913, Heft 39, page 1115
Zeitschrift des Vereins Deutscher Ingenieure
1913, page US
Bulletin et Comptes Rendus Mensuels de la
Societe de I'Industrie Minerale
March, 1910, page 233
Distribution de la Force A Grande Distance par
F Electricite par H . Cuenod, Paris, Cauthiers-
Villats, 1900
Die Gleichstrommaschine von E. Arnold,
Zweiter Band, 1907.
1042
GENERAL ELECTRIC REVIEW
THE KINETIC THEORY OF GASES
Part II
By Dr. Saul Dushman
Research Laboratory, General Electric Company
In the present installment of this series of articles on "The Kinetic Theory of Gases" the author discusses
the deductions from the theory of molecular collisions. It is shown that, according to the kinetic theory, the
coefficients of heating conductivity, viscosity, and diffusivity are quantitatively connected with the length of
the free path and molecular diameter. Tables of values are given of the average free path and molecular
diameter for some of the more common gases. — Editor.
Free Path
In Part I we showed that gas molecules
possess very high velocities, ranging as high
as IS, 000 meters per second in the case of
hydrogen gas at room temperature. This is
apparently in contradiction with the common
observation that gases actually diffuse very
slowly. Hydrogen sulphide gas generated
in one corner of a large room will not be
detected at the other end for quite a long
time. Under normal conditions heat is
conducted by gases at an extremely slow rate,
yet if the gas molecules traveling from the
hotter region possess high velocities, they
should reach the colder region in an inap-
preciably small interval of time.
It is evident that if the molecules were
mere point centers with no forces acting
between them, there would be no chance of
collision among them; on the other hand, if
the molecules have definite dimensions, or
exert attractive forces on each other, it is
possible for such collisions to occur, and the
molecules will therefore not be able to travel
very far in a direct line. Thus we obtain an
explanation of the fact that, while individual
molecules travel with extremely great veloc-
ities, molecules of one kind actually diffuse
into molecules of another kind at a very slow
rate.
The use of the term "collision" naturally
leads to another concept — that of free path.
Ordinarily this is defined as the distance
traversed by a molecule between successive
collisions. Since, manifestly, the magnitude
of this distance must be a function of the
velocities of the molecules, we are further led
to the use of the expression "average free
path ' ' (denoted by L) , which is defined as the
average distance traversed by ah the mole-
cules between two successive collisions.
Mathematically, it is the sum of the free paths
of all the molecules at any instant divided by
the total number of paths.
However, this definition assumes that the
molecules actually collide like billiard balls;
that is, the molecules are assumed to be rigid
elastic spheres possessing definite dimensions
and exerting no attractive or repulsive forces
on each other. This, however, can certainly
not be in accord with the facts. We have
every reason to believe that the structure of
atoms and molecules is exceedingly complex.
It is probably impossible to state definitely
what is the diameter of a hydrogen atom or
molecule. Also there is no doubt that the
molecules exert attractive forces on each other
for certain distances and repulsive forces when
they approach exceptionally close. Other-
wise how could we explain surface-tension,
discrepancies from Boyle's law, and a host of
related phenomena? To speak of collisions
among molecules such as these is impossible.
What meaning, therefore, shall we assign to
the free path under these conditions?
It is readily seen that the most essential
idea at the back of the term "free path" is
this : We imagine it possible to take a cinema-
tograph picture of the molecules in a given
portion of space; we then consider their
velocity components in a given direction and
find that at the end of a certain distance L
the average value of the velocity components
of all these molecules taken in the same direc-
tion has decreased by a certain amount; in
other words, the average number of molecules
traveling in the given direction is less after
they have traversed the distance L. On this
basis, the term free path has a physical
meaning which is independent of all ideas that
we may form of the actual structure of the
molecules or of the nature of the inter-
molecular forces.
Another method of overcoming the same
difficulty is to investigate the relations
between the free path and the other prop-
erties of a gas, assuming rigid spherical
molecules with or without attractive forces
THE KINETIC THEORY OF GASES
1043
and then considering the case of any actual
gas in terms of this hypothetical gas.
Methods of Calculating Mean Free Path
Evidently the mean free path must depend
upon the molecular diameter, and simple
considerations indicate that the length of the
mean free path must vary inversely as the
total cross-sectional area of the molecules per
unit volume. Again, the magnitude of the
coefficients of viscosity, heat conductivity
and diffusivity of gases are intimately bound
up with the length of the free path; whether
it be transference of momentum from one
layer to another as in viscosity, or trans-
ference of increased kinetic energy of the
molecules as in heat conductivity, the rate
of this transference must depend upon the
number of collisions which each molecule
experiences as it passes from point to point.
We thus obtain relations between the mean
free path, the coefficients of viscosity and
heat conductivity on the one hand, and on
the other hand, equations that connect the
mean free path with the molecular diameter.
In the following sections we shall discuss
these relations under the following headings:
(1) Relations between mean free path
and coefficients of viscosity and heat con-
ductivity.
(2) Relations between mean free paths;
molecular diameter and coefficients of vis-
cosity and heat conductivity.
Relation Between Coefficient of Viscosity and Mean
Free Path
A gas streaming through a narrow bore
tube experiences a resistance to flow, so that
the velocity of this flow decreases uniformly
from the center outwards until it reaches
zero at the walls. Each layer of gas parallel
to the direction of flow exerts a tangential
force on the adjacent layer tending to decrease
the velocity of the faster-moving and to
increase that of the slower-moving layers.
The property of a gas (or liquid), in virtue
of which it exhibits this phenomenon, is
known as internal viscosity.
As a simple working hypothesis we may
assume, as Newton did, that the internal
viscosity is directly proportional to the rate
of decrease of velocity in the different gas
layers. Furthermore, the viscosity must
depend upon the nature of the fluid, so that
in a more viscous fluid the tangential force
between adjacent layers, for constant rate
of decrease of velocity, will be greater than
in the case of a less viscous fluid. We thus
arrive at the following definition of the
coefficient of viscosity:
The coefficient of viscosity is defined as the
tangential force per unit area for unit rate of
decrease of velocity.
With this definition we are in a position to
deduce the approximate form of the relation
between the coefficient of viscosity and the
free path.
Fig. 2
Let u denote the velocity of flow of the gas
at a distance d from a stationary surface.
In the case of uniform flow along a surface,
the velocity will decrease uniformly to zero
as the surface is approached. We can there-
fore represent, as in Fig. 2, the velocity at
distance OA=d by the ordinate AB = u and
velocities at intermediate distances by the
corresponding ordinates below the line 0 B.
We shall imagine the gas divided into
layers parallel to the surface, each having a
depth equal to the free path, L.
Let us denote the tangential force per unit
area between adjacent layers by B. By
definition :
B = r]X velocity-gradient
(11)
where r\ denotes the coefficient of internal
viscosity.
But according to the kinetic theory, the
tangential force per unit area is measured by
the rate at which momentum is transferred
per unit area between adjacent layers.
Owing to the relative motion of the layers,
the molecules moving from a faster into a
slower moving layer possess more momentum
in the direction of flow than those moving in
the opposite direction.
1044
GENERAL ELECTRIC REVIEW
Let us consider any layer, CE or EH of
thickness equal to L. We have chosen this
particular value of the thickness so that we
may be justified as a first approximation in
assuming that the molecules starting at
either of the planes CD or EF reach the
opposite plane without suffering collision,
that is, without change of momentum.
The momentum, parallel to the surface, of
any molecule reaching the plane EF from the
plane CD is m{u'-\-G), where u' denotes the
velocity of flow at the plane CD and G is the
mean velocity of the molecules.
The momentum, parallel to the surface, of
a molecule reaching the plane EF from the
plane HK is ml h'-\-G+2—t
The number of molecules that cross unit
area per unit time in any direction in a gas
at rest is equal to — n G, and this must be the
H 0
same for the molecules traveling in a direction
perpendicular to the plane EF, for the
velocity of flow is assumed to be so small that
the density remains constant throughout the
different layers.
Hence the net rate of transference of
momentum across unit area of the plane EF
is equal to
>
1 uL
B = — m n G —r-
6 a
(12)
From equations (11) and (12) it follows
that
r] = -m n C L= —p G L
MP
where p = -== = densitv
Kl
(13)
G=15,S00 VT/M cm. seer1
In deducing this equation it has been
assumed that the molecules all possess the
same velocity G and the same free path L.
It is evident therefore that the equation thus
derived cannot be accurate. Introducing
Maxwell's law of distribution of velocities,
Boltzmann deduced the equation
77 = 0.3502 pOL (14)
where 9 = average velocity
= 145.3 1\ T M cm. sec.-1
and L is defined as the average free path.
Meyer in his "Kinetic Theory of Gases"
used a different method of calculation and
derived a relation of the form.
17 = 0.3097 pUL' (15)
This is the relation usually adopted in text
books on physics. On the other hand, the
more recent publications, such as those of
Jaeger1, Millikan and Fletcher2, prefer Boltz-
mann's formula. Following the latter author-
ities we have made use in the following cal-
culations of equation (14) to determine the
so-called mean or average free path.*
From equation (13), (14) or (15) an interest-
ing conclusion may be deduced regarding the
dependence of viscosity on pressure. As
has been mentioned above, it is evident
from very simple considerations that L
varies inversely as the number of molecules
present per unit volume. Consequently the
product pL is constant and independent
of the pressure. The velocity, 9, depends
only upon the temperature and molecular
weight. It therefore follows that, for any
gas at constant temperature, the viscosity is
independent of the pressure, and must increase
with the temperature. The confirmation
of these two deductions has been justly
regarded as one of the most signal triumphs
of the kinetic theory of gases. As is well
known, the viscosity of all ordinary liquids
decreases with increase in temperature. That
the viscosity of gases must increase with
temperature was therefore regarded as a
remarkable conclusion.
At both extremely low pressures and very
high pressures, the conclusion is not in accord
with the observations, but this is due to the
fact that the same derivation as has been
used above is not valid under those conditions
where either attractive forces between the
molecules come into play or the pressure is so
low that a molecule can travel over the whole
distance between the walls of the enclosure
without suffering collision.
According to the above equations, it is
therefore possible to calculate L for a gas
under given conditions from data on the
viscosity. In Table IV are given the values
of L = t] (0.3502 pQ.) calculated for different
gases at 0 deg. C. and 20 deg. C. and 106 bars.
The values of p have been calculated from
the molecular weights, while the values of
9. have been taken from Table III.
Fort, der Kinet. Gastherorie.
P) Phys. Rev., 4, 440 (1914).
* In German text-books, L is referred to as "roittlere freie
Weglange." The term "mean free path" is used by English
writers, most of whom adopt Meyer's formula. In view of the
fact that we may have several different "means," we prefer the
unambiguous designation "average free path."
, , ,. , 0 3502 . ._ ,
L' i Meyer) = L (Boltzmann)
; =1.131 L (B)
THE KINETIC THEORY OF GASE.S
1045
In choosing values of r]0 (the viscosity at
0 deg. C.) from the large amount of data
available in the literature, an attempt has
been made to choose the most recent and
most accurate values in each case. The
authorities for the different data are given
in footnotes. For 7720 (the viscosity at 20 deg.
C.) the experimentally observed value has
been used in the case of air, while in all other
cases use has been made of Sutherland's
equation.*
S273A + C\ /2931l\f
7720 -^y^J+c) ymx)
where C is a constant for each gas.
(Hi)
* The derivation of this equation is discussed on page 1048.
Collision-Frequency
From the values of L and 0 we obtain the
collision-frequency, il/L, that is, the average
number of collisions per second. These are
given in the last column of Table IV for room
temperature. Thus, a molecule of nitrogen
under ordinary conditions suffers over 5000
million collisions per second. It is not sur-
prising, therefore, that gases diffuse relatively
slowly.
Direct Determination of Average Free Path
The magnitude of the average free path
under normal conditions is extremely small.
As seen from Table IV it is about 10~5 cm, or
— - mil. But as the pressure decreases the
2o0
TABLE IV
COEFFICIENT OF VISCOSITY AND AVERAGE FREE PATH AT NORMAL PRESSURE
u
(Boltzmann's equation)
0.3502p,fy
V (according to Meyer's equation) =1.131 L (according to Boltzmann's equation)
Gas
1,i xi°7
c
»Mxl0'
»,xi»
LX10S (0°C.)
LX10= (20°
C.) SVL10X^(20°C.)
Air
1711 (1)
1809
1277
8.560
9.376
4940
H,
843 (2)
76.5
(3)
886
88.72
16.00
17.44
10060
He
1870 (4)
75.8
(5)
1964
175.7
25.25
27.45
4545
NH3
919 (6)
352
(7)
999
760.8
5.916
6.600
9152
H20
904 (8)
548
(9)
[1320 (10)]
[606.0]
[9.40]
CO
1660 (11)
102
(12)
1752
1234
8.459
9.2.32
5101
N2
1670 (13)
111
(14)
1764
1234
8.500
9.287
5072
0,
1905 (15)
130.3
(16)
2018
1414
9.046
9.931
4432
-4
2107 (17)
162
(18)
2239
1758
8.982
9.879
3998
COi
1375 (19)
249
(20)
1472
1951
5.560
6.148
6115
Hg
1620 (21)
[5320 (22)1
[4200]
[14.67]
References to Literature on Determination of i\
The literature on this subject is very extensive.
Fortunately most of the data have been summarized
by Fisher, [Phys. Rev. 24, 385 (1904); Chapman,
Phil. Trans. A. 811, 433 (1911), and Gilchrist,
Phys. Rev. /, 124 (1913). The latter's determi-
nation of the coefficient of viscosity for air is
probably the most accurate value available of this
constant, and has been used by Millikan in his
precision measurement of the charge on an ion.
According to Millikan [Ann. Phys. 41, 759, 1913],
the most accurate value for the coefficient of
viscosity of air is
r,, =0.00018240 -0.000000493 (23-0
(23>/>12)
According to this relation,
nso = 0.0001809
For ijo, Prof. Millikan quotes three values, see (1),
whose average 0.0001711 we have used as probably
the most accurate value.
Vogel [Ann. 43, 1235, 1914] has carried out
similar measurements in the case of other gases.
As he referred his results to 770 for air = 1724 X 107,
we have re-calculated them to correspond with
the above value. These are referred to as Vogel's
corrected values.
The other authorities to whom reference has
been made are:
Kaye and Laby's Tables of Constants (K & L.).
Jellinek's Physikal. Chem. I, 1, p. 305-7.
Markowski, Ann. Phys. 14, 742.
In the following references, C, F and V denote
Chapman, Fisher and Vogel respectively.
(1) Breitenbach, 1708.7; Fisher, 1709.2; Holman,
1715.7.
(2) V, 844; C, 854; Markowski, 841.
(3) F. (4) V, 1862; C, 1885. (5) F, 76.2; C, 75.3.
(6) V. (7) V. (8) Jellinek. (9) V. (10) K. & L.
The values in square brackets are for 100
deg. C. (11) V.
(12) F. (13) V, 1666; C, 1672; Markowski, 1674.
(14) F, 110.4; C, 111.7; V, 110.6.
(15) V, 1905; C, 1900.
(16) C, 1303; F, 131.1; V, 133.
(17) C, 2107; V, 2100. (18) C. (19) V, 1370; F,
1387.
(20) C, 249; V, 277; K. & L. 240. (21) K. & L.
(22) K. & L. The values in square brackets are
for 300 deg. C.
-
GENERAL ELECTRIC REVIEW
1 bar. -which is
t the degree of vacuum attained in
isting or - :.:andescent lamps, the
I
and 10 cms. A molecule -:n evapo-
m the filar: [ers very
-lis of
the bulb, i m the sharp boun-
dary OS.
he only inves-
bo have made any direct determina-
tion of th . nard1. Robinson2,
and Franck and Hertz::.
; the
: determining the average dis-
i by a gaseous ion between
A charged molecule
b a sufficiently high velocity,
is capable of producing other ions by collision,
sible to measure the mini-
mum distance at which two plates must be
- in order that it may be possible
for the ions passing from one plate to the
other to produce fresh ions by collision.
Franck and Hertz obtained the following
resii! '
L CiLC it =30 DE
Pressure
He
4.5
■
'_ bars
9.43*
. ' ■ cm.
0.14
0.014 cm.
256 em.
-. g cm.
243 cm.
0.130 cm.
0.012 cm.
_ " ' cm.
■•
0.215
0.115
0.011
U.221
The r i values of L appear to agree
h the values calculated according to
Meyer's equa: - " The experimental
i .^sufficient to be able
-m from it a definite conclusion
which equation is - /.ore satisfactory.
Relation Between Coefficient of Viscosity, Heat
Conductivity and Diffus
The theory gases achieved a
- ;mph when it led to the conclusion
that ■ ■;• is independent of the
[1 i I U -till further important
ied the existence of
t perties of
nd diffusivity.
: view it is
the same r the molecules transfer
i
i
,'5.373
momentum from one layer to another or
translational energy. The equations are
quite analogous.
As in the case of viscosity, we consider any
two layers CE. EH (Fig. 2), each of thicknes's
L. between two plates whose temperatures
are Tj and Tj and distance apart d. Let c,,
denote the heat capacity per unit mass. The
relative temperature drop between the planes
CD and HK is equal to
- ■ - I- I k
a
Hence the heat transferred per unit area is
Q=-nG.
D
= g P G C,.
(T,-T,) L
- -Tt).
Therefore the coefficient of heat con-
ductivity.
k = — pGc, L.
(17)
From equations (13) and (17) it follows
that
77 = ■ (18a)
A more acturate calculation of the heat
conductivity shows that this equation is not
quite correct, and should be written
r) = Bkc- (18b)
where B is a constant (greater than unity),
whose value depends upon the nature of the
forces that are assumed to exist between the
molecules and the structure of the molecules
themseh
Similarly it can be shown that the diffusion
constant of a one gas into any other is propor-
tional to the coefficient of viscosity. The
relations are. however, quite complicated.
According to Jeans, the value of the con-
stant B in equation (ISb) is 1.6207. This is,
however, not in accord with the facts. Chap-
man4 has shown that for monatomic gases the
value of the constant must be very closely
equal to 2.5. while for polyatomic gases the
value must be lower but not as low as 1.62*.
These conclusions have been confirmed experi-
mentally by Eucken5.
Table V taken from Eucken's paper gives
the values of k (experimentally determined by
« S. Chapman. the Kinetic Theory of a Gas Constituted of
Sphencallv Symmetrical Molecules- Phil. Trans A. £11. 433
* This value has been so generally accepted that even Kaye
and Laby have used it m their tables, p. 33.
s Eucken. Phys. Zeit. 14. 324. (1914).
THE KINETIC THEORY OF GASES
1047
Eucken), 77 (Vogel's data*) and cv together
with the observed values of B at T = 273.
TABLE V
Gas
*X10;
,xio;
<":
BObs.
B Calc.
He
3360
1876
0.746
2.40
2.50
A
390
2102
0.0745
2.49
Hi
3970
850
2.38
1.965 1
1.905 1
«i
566
1676
0.177
ot
570
1922
0.155
1.913 y
1.90
CO
542.5
1672
0.177
1.835
NO
000
1794
0.1655
1.870 J
cot "
337
1380
0.1500
1.628
mo
(429)
1006
0.342
1.25
Xlh
513.5
926
0.388
1.43
According to Chapman, if it is assumed
that the molecules are absolutely spherical
and possess rotational as well as trans-
lational energy (see Part I). 5 = 1.90 for
diatomic gases, and 1.75 for triatomic gases.
The results tabulated above would indicate
that in at least the case of monatomic and
diatomic gases this assumption must be in
very good accord with the facts.
Relation Between Molecular Diameter and Mean
Free Path
As mentioned previously, recent specula-
tions on the structure of the atom lead to the
conclusion that atoms and molecules are far
from being the rigid elastic spheres postulated
by the founders of the kinetic theory. If
Rutherford's views are correct, and all the
evidence points in that direction, we must
conceive of the atom as consisting of a posi-
tively charged nucleus surrounded by one
or more rings of electrons. The diameter of
the nucleus is extremely small (less than
1 100,000) compared to the diameters of the
electronic orbits, so that it is possible for the
alpha particles, which have the same dimen-
sions as helium atoms, to pass right through an
atom of a heavy metal like gold. It is there-
fore certain that in the case of chemical com-
binations the atoms have inter-penetrated to
form the molecule. The evidence deduced
by Richards on the compressibility of atoms
is also in accord with these views. On the
other hand, it may be reasonable to speak of
the diameter of a molecule if we think of it as
the smallest distance apart to which the
centers of two molecules can approach. Even
this definition may not be accurate, but we
can make use of it as a physical basis for
mathematical relationships.
Denoting the number of molecules per
unit volume by n and the molecular diameter
by dm, it was shown by Clausiusf that in the
case of spherical molecules all possessing the
same velocity, G, the length of the free path is
L=. 3 . , (19)
4 7T n dm-
If we take into account the fact that the
molecular velocities vary according to Max-
well's distribution law, it can be shown that
the average free path
L= ~ (20)
V2 -k n dm°-
Jeans has, however, pointed out that this
equation cannot be accurate, since it takes no
account of the persistence of velocities after
collision1. "On the average, a collision does
not reverse the velocity in the original direc-
tion of motion, or even reduce it to rest, but
there is a tendency for the original velocity
to persist after collision." Jeans shows that
in the case of two similar molecules colliding
with relative velocities that may vary all the
way from 0 to <*> , the average value of the
2
persistence is very nearly equal to -= of the
value when the molecules collide with equal
velocities. That is, on the average, the mole-
cules traveling in a given direction will after
collision have lost sixty per cent | '— J of their
©
velocity component in that direction.
Hence, according to Jeans, the equation
should be written
1.319 I
L-
\ 2 7r n d„
(21)
* No correction has been applied to any of the data given in
Table V, as the intention was merely to illustrate the variations
in the value of B.
t See Jellinek. pp. 2S7-292.
Meyer's Kinetic Theory, pp. 161-3.
1 Jeans, Dynamical Theory of Gases, p. 236, etc.
X This manner of defining the free path could obviously be
extended to the case of molecules obeying any other law of
force, where no collisions (according to the literal meaning of
the word) occur. It has already been observed in a previous
paragraph (p. 1042) that we might define L in terms of the ratio
of the molecules traveling in a given direction at one point to
the number traveling in the same direction at a point further
along in the same direction. Jean's concept of persistence of
velocities ieads us therefore to the following definition of average
free path which would hold in all cases except that of unlike
molecules. We can define the average free path as being twice
the distance which the molecules traveling at any instant in a
given direction will pass over before losing sixty per cent of their
velocity component in that direction. The factor 2 is required
because, at any instant the molecules have, on the average,
covered one-half the distance between collisions.
This definition has been suggested to the writer by Dr.
I. Langmuir and although it may not be the usual definition, the
latter is so vague that a scientifically correct definition would
certainly help to clear the prevailing mistfadeTstanding about
the whole subject of free paths.
104S
GENERAL ELECTRIC REVIEW
According to Chapman. Jeans' formula is
not quite correct. He has shown that for
the case of rigid elastic spheres with no
attractive forces.
0.4909
r\ =—7= (22)
\ 2 w n dm-
It will be observed that this equation differs
quite radically from Meyer's or Boltzmann's
equations for rj. Comparing equation (22)
with equation (14) it is seen that, according
to Chapman.
0.4909
0.3502 V-2 x n d„
1.402
\ 2irndm-
< 2:; I
This formula is true only for rigid elastic
spheres with no attractive forces. Assuming
the existence of such forces, the effect
obviously must be to shorten the free path.
and Sutherland* has shown that in this case,
L =
1.402
2TTndrni\l + -f\
(24)
where C is a constant for each gas whose
value may be determined from the tem-
perature coefficient of the viscositv.
This equation, combined with equation
i 1 4 i leads to the following expression for the
variation with temperature of the coefficient
of viscositv:
/273+CV /TV
= ri»\-T+c) (ITS)
(IB)
Sutherland's equation has been found to be
in excellent agreement with the experimental
data. The assumption therefore appears to
be justified that the molecules approximate
fairly closely to rigid elastic spheres sur-
rounded by attractive fields of force.
Equation (24) combined with equation (14)
and a knowledge of n enables us to calculate
the molecular diameter from the coefficient of
viscosity.
Relation Between Molecular Diameter and Van der
Wall's Constant, b
At very high pressures or temperatures so
low that the gases can condense, it is observed
that Boyle-Gay-Lussac's equation
PY = RT
is no longer applicable.
* Phil. Mag. 3*. 507 (1893).
Van der Waals found that the behavior of
gases near their critical temperature and
pressure** could be expressed quantitatively
by a modified form of the above equation as
follows :
(***) (' -o-
■R T
(25)
In this equation, a \'~ is a correction term
added to P. which takes into account the
attractive forces exerted by the molecules
upon each other. The constant b denotes a
small volume whose magnitude compared to
\ ' becomes of importance when we are dealing
with gases near their critical state. Accord-
ing to Van der Waals. — is equal to the total
volume of the molecules.
That is,
b i- w A 3
- = ;; 1 . 77 dm3
4 b
d 3 =
3.6
2 n Vtc
(26)
The value of the constant b may be deter-
mined for each gas from the critical tempera-
ture [Tc) and pressure {Pc) by means of the
relation :
b = RT, 8P, (27)
There is still a third method by which the
molecular diameter may be calculated. Ac-
cording to Clausius and Alossotti, the volume
actually occupied by the molecules may be
calculated from either the dielectric constant
D or the refractive index i by means of the
equations:
n6dm=(p+i
9
(28)
(29)
Table VI gives the values of the molecular
diameter calculated for different gases by
each of these methods. The first column
gives the values of dm calculated from the
average free path, L. according to the equation
(24,
L =
\ 2 TT H d„-
0+9
The values of C and L have been taken
from Table IV.
The second column gives the experimentally
observed values of Tc and Pc. and the values
** "The Absolute Zero,'
ary and April, 1915.
General Electric Review, Febru-
THE KINETIC THEORY OF GASES
1049
of b and dm, calculated from these by means
of equations (26) and (27).
The last column gives the values of dm
calculated bySackur1 from the refractive index
for the D line. These data have been cor-
rected for the difference between the values
of n used by Sackur and by the writer. For
1 Ann. Phys., Ifi, 97 (1913). The values for argon and helium
are given by Eucken. Phys. Zeit.. 14, 324 (1913).
n, the number of molecules per unit volume,
at 0 deg. C. and 106 bars, we have adopted
Prof. Millikan's value,
iV = wV = 6.062X1023
that is, m = 2.G696X101h
A discussion of the different methods by
which n has been determined is reserved for
the next issue.
(To be Concluded)
TABLE VI
MOLECULAR DIAMETERS*
From Coeff. of Viscosity; Van der Waal's Constant, b, and Refractive Index
Gas
108 Xd„, from
Equation (24)
Critical
Temp.
in Deg.
Absolute
Critical
Pressure
in
Megabars
b
Equation (27)
\0'Xd„, from
Equation (26)
108XJ», from
Refractive
Index
H,
2.403
22.2
14.15
16.28
2.341
1.914
He
1.905
5.25
2.29
23.53
2.646
1.177
NIh
2.967
405.9
113.8
37.1(1
3.080
H2D
647.0
220.4
30.52
2.887
2.276
CO
3.190
133.5
35.97
33.79
3.121
2.52
N2
3.146
127.0
33.4
39.50
3.146
2.414
0,
2.975
155.0
51.1
31.56
2.919
2.316
A
2.876
150.7
48.63
32.22
2.939
2.358
CO?
3.335
304.0
73.80
42.83
3.231
2.782
Hg
1543.0
462.0
35.67
3.013
* The critical data have been taken from Landolt and Bornstein's TabelVen and Jellinek, loc. cit., p. 444-5.
per molecular weight.
The value of b is in cm'
1050 GENERAL ELECTRIC REVIEW
ELECTRICAL CHARACTERISTICS OF SOLID INSULATIONS
By F. W. Peek, Jr.
Consulting Engineer, General Electric Company
Three types of insulation are in general use in practice, gaseous, liquid and solid. The author has shown
in previous articles in the General Electric Review that the mechanism of breakdown in gaseous and
liquid insulation is very similar; the general laws which he has developed for air also apply for oil.* These
laws are used in practice in calculating the breakdown voltages of air and oil.
The present paper treats of solid insulation, the electrical characteristics of which are quite different from
those of the other two types. The laws of breakdown, etc., developed from experimental data, as well as sug-
gestions for their practical application, are given. — Editor.
Gaseous and liquid insulations may be
electrically stressed very close to the ruptur-
ing point without appreciable loss or heating.
Considerable loss occurs only in corona or
local brushes when some part is stressed above
the breakdown point. Great loss in air and,
to a less extent, in oil is thus a phenomenon
which follows local breakdown after some
critical voltage has been reached. Loss
occurs in solid insulation as soon as the volt-
age is applied and increases rapidly with
increasing voltage. Due to this loss the
temperature of solid insulation increases
after the application of voltage. The prop-
erties of the insulation, such as resistance,
dielectric strength, etc., change with this
change in temperature. The rupturing volt-
age of solid insulation will thus van* with the
rate of application of voltage. For instance,
a given piece of insulation may withstand a
very high voltage for one minute, but break
down at a low voltage applied for one hour.
Insulation Resistance
Among the solid insulations used in practice
are varnished cambric, oiled and varnished
pressboard, treated paper, treated wood,
mica, micanite, soft and hard rubber, syn-
thetic resins, glass and porcelain. The actual
resistance of the insulating material is very
high. Practically all solid insulating material,
however, absorbs moisture to a greater or less
extent. The capillary tubes and microscopic
interstices, etc., in the structure become
filled with moisture and gases. These afford
conducting paths through the insulation,
or part way through the insulation. The
result is, in effect, a complicated arrangement
of resistances and capacities in series and
*F. W. Peek. Jr.. "The Limiting Effect of Corona on the
Electrical Transmission of Energy at High Voltages," October.
F. W. Peek. Jr.. "Further Investigations into the Nature
of Corona and Dielectric Strength of Air." December. 1912.
F. W. Peek. Jr.. " The Sphere Gap as a Means of Measuring
High Voltages." May, 1913.
F. W. Peek. Jr.. "The Electric Field." December. 1914.
F. W. Peek. Jr., "The Law of Corona and Spark-over in
Oil." August. 1915.
multiple. This may be illustrated in Fig. 1-
(a) and (b), where (a) represents a very
much enlarged section of insulation, and (b)
is a diagrammatic arrangement of connections.
Thus, ti may represent the resistance of the
insulation itself and rt, r» and r3 the moisture
or air paths. It can be seen by reference to
(b) that direct current will pass through, and
therefore measure, n, rx and r4. Alternating
current will, in addition, pass through r3 to
a greater or less extent depending upon the
frequency. The effective resistance must,
thus, vary with the frequency. It must also
vary with the applied voltage if the insulation
contains considerable occluded moisture or
air. The d-c. resistance is very high in good
insulation. For instance, for varnished cam-
bric it is 20,000 to 50,000 megohms per cm.
cube.
Insulation Loss
In oil, and particularly in air, there is very
little loss until local brush or corona break-
down gradient is reached. The loss then
increases directly as the square of the excess
voltage above "the critical voltage. With
\lnsaJotJOrr& 4-
1
f°)
Fig. 1
solid insulations loss appears as soon as the
voltage is applied. The loss may be due to :
(1) The so-called dielectric "hysteresis" or
lag of the flux behind the electromotive force
due to some molecular action.
(2) Conduction. Practically all solid insu-
lations absorb moisture to a greater or less
extent. The capillary tubes and microscopic
interstices, etc., in the structure become filled
ELECTRICAL CHARACTERISTICS OF SOLID INSULATIONS
1051
with moisture and gases. In the non-homo-
geneous structure this makes a complicated
arrangement of capacities and resistances in
series and in multiple as shown diagrammati-
cally in Fig. 1, and already discussed.
The losses due to (1) should
vary as the square of the volt-
age and approximately as the
frequency
pxZfafe* (1)
The loss due to r3 must vary
as the square of the voltage
if the resistance is constant.
The variation with the fre-
quency will depend upon the
relative values of the resist-
ance and capacity reactance;
the range will be all the way
from
2 to 15 for Oiled Pressboard — depending
upon the quality or kind.
5 for Glass
7 to 10 for Varnished Cambric.
The values for varnished cambric were
pi = faP e-
(2)
Fig. 2.
(4)
to
p 2 = fa e*
The loss due to rit r2 and rit
Fig. 1 (b), must vary as the
square of the voltage, if the
resistance remains constant,
but is independent of the
frequency
p3 = fae- (3)
The total loss may thus con-
tain the terms
P = pi+p2+ps = ai eH+a2e°f+a3 e
In poor insulation, or in insulation containing
moisture, the loss may increase at a greater
rate than the square of the voltage as the
resistance will decrease with increasing volt-
age.
In homogeneous insulations in good con-
dition the last two terms are small and the
expression for loss becomes*
p = ae*f (5)
and for certain insulations
p = ac-(f+c) (6)
Deviations from the square law are
generally due to the conditions of the insula-
tion. From examination of a considerable
amount of experimental data it is found that
p = ae*f (5)
is generally followed, or, putting in this the
gradient, g, in kv./min, in place of e.
P = b g2 / 10~6 watts per cu./cm. (7)
At 25 deg. C. b is
K
. /
g
: I-
£
023 $
7
'
'jo'<
/Vo.
'/
'
/
/
„„ *
*"*
/
: / ~
/ 74*C.
/
^ or*
/
A/ £
*
\ a/6 *o
'
/
/
s*
z
, » /
■a «/*
<
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£ a/2 30
/
/
±^
/
: '
' es"c
'
s
V *t d£'
O.IO
s
°J{
t*\
90'r
OOB 20
s
,.'
:+'
!
Q04 /O
\c6
. ■ ■ -
-
- -
1 1
Ifi/eyolta Per- M ill, meter (E ffccl ive)
Curves of Insulation Loss and Power-factor vs. Kilovolts (Oiled pressboard
5 mm. between parallel planes with rounded edges in oil)
Curves Nos. 1, 2, 3 and 4 — watts per cu. cm.
Curves Nos. 5, 6, 7 and 8 — power-factor
10~26 for Varnished Cambric.
obtained for 60 cycles and 40,000 to 100,000
cycles, f
The loss, and therefore b, increases with
increasing temperature in the form
b = kf (8)
Where
/ is the absolute temperature in degrees
centigrade.
6=1.2 f°
or,
p=\.
This
mate.
In some cases for insulations like varnished
cambric the equation takes the form
P = bf(f+c) (9)
Where the insulation contains occluded
moisture the losses become very great and
2g2 /io 10-32 watts cu
relation, however,
/cm.
is only approxi-
* F. W. Peek, Jr., " Dielectric Phenomena in High Voltage
Engineering," page 185.
t The author analyzed considerable data taken at high fre-
quency by Mr. Alexanderson published in the Proceedings of the
Radio Engineers, June, 1914. It was found that this data
followed equations (5) and (6) very closely. The constant b
checked with the 60 — curves. See — F. W. Peek. Jr., " Dielectric
Phenomena in High Voltage Engineering." pages 186-187.
L052
GENERAL ELECTRIC REVIEW
the square law is not followed. It is of the
utmost importance to keep insulation dry.*
Fig. 2 gives 60 ~ loss and power-factor
characteristics of solid insulation at various
temperatures. Fig. 3 gives a 60 ~ loss curve
£aoa
0)006
%o.os
0
!
f
eo~/
i
/
-,Q-
/
<r
/
/
/
/
,'
J -■
p/ Z 3 4 S 6 7 S 9 IO // /2
Gradient k/mn/E frect/ro)
Fig. 3. Curves showing Loss in Varnished Cambric 4 mm.
thick between parallel planes at 25 deg. C. Data
from "Dielectric Phenomena in High-Voltage
Engineering" p. 186
\
o+o
XI
■y
O30
^
y"
° I 2 3 4 S 6 7 S 9 IO II 12
Gradient ""/mm.fc ffectlve)
Fig. 4. Curve showing Loss in Varnished Cambric.
Data from Fig. 3, plotted with \l p. Straight line
shows that loss varies as square of voltage
gradient
for varnished cambric. This data is plotted
between y/p and g in Fig. 4. The fact that
the points are on a straight line shows that
the square law.is followed. Figs. 5 and 6 show
that the same characteristics obtain at very-
high frequency as at 60 ~. For these dif-
ferent samples the constant b is 7.5 for the
high frequency tests and 9 for the 60 ~ tests.
* J. P. Minton — Measurement of Dielectric Losses with the
Cathode Ray Tube. A.I.E.E.. June. 1915. This interesting
paper contains considerable data on dielectric losses for various
insulations under various conditions.
This variation would be expected in different
samples.
Dielectric Strength vs. Time of Application
The mechanism of breakdown is quite
different for oil or air, and solid insulation.
In oil or air a local breakdown may take
place as corona or brush discharge; when
voltage is removed the broken down dielec-
tric is replaced. In solid insulation a local
breakdown means charring or cracking and
generally develops progressively into com-
plete rupture.
The puncture voltage of solid insulations
varies greatly with the time of application.
This variation is due principally to heating
where the time of application is comparatively
long. The effect of loss is cumulative; the
insulation becomes warm and while the loss
§
MINI
^
p-7.S33ftO~e
--
&
"1
13
■ij
5
1
£
1
H.
r
I.OO
j
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OSO
1
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l
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y
O 0 2 0 4 0.6 OS IO 12 14- 16 LB 2.0
Gradient /n ffiloi/o/ts Per mm. (Effective.)
Fig. 5. Curves showing High Frequency Loss in Varnished
Cambric at 25 deg. C (Tests by Alexanderson.)
Tests made between parallel planes, 21 sheets
of insulation, thickness 5.9 mm.
increases with the temperature, the dielec-
tric strength generally decreases with increas-
ing temperature. The ultimate strength
then depends upon the rate at which heat is
conducted away.
The strength of insulation vs. time of
application in a uniform field is best illus-
trated bv the curve for varnished cambric in
ELECTRICAL CHARACTERISTICS OF SOLID INSULATIONS
10.33
Fig. 7. Where the time is not over a few
seconds heat is not a factor. The strength
of insulation, however, still
rapidly increases with de-
creasing time of application.
The reason for this, in the
case of impulse voltages, will
be discussed later. In practice
certain arbitrary comparative
tests, to include the effect of
time, are made on insulations;
the "Rapidly Applied Test,"
the "One Minute Test," and
the "Endurance Test."
The Rapidly A p plied break-
down voltage is found by
applying a fairly low voltage
and rapidly increasing until
breakdown occurs. The volt-
age is increased at about 5
kv. per second.
The Minute Test is made
by applying 40 per cent of the
Rapidly Applied voltage, and
increasing this voltage by 10
pel cent steps at one minute
intervals. The total time is
usually 3 to 5 minutes.
The Endurance Test is made by applying
40 per cent of the Minute Test voltage and
^ 60
i-
■*
0 30
i
« 20
I
-o
"*> /S
■o
<b S
.»
Q
I
V
.
x
"~~.
1
Lc3y&r~.
Thickness ■
= 03
mm^
1
\
\
/O Ldt/crs. Thickness =3. 0 rnm.
0 20 40 60
Fig. 7.
1 1 1 1
90O0Or^j
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'
O OS o.-» oe OS I.O /.Z /.4 1.6 /.3 2C
Qr-ac/ ient . H~lloi/o/ts/m m.(t free tire)
Fig. 6. Curves shoeing High^Frequency Losses in Varnished
Cambric*at,25 deg. C. Tests'made^between parallel planes,
21 sheetsTof insulation, thickness 5.9 mm. plotted
with V /> from data in Fig. 5. Straight line
shows'that "square|law" holds
SO IOO /20 /dO /<50 /30 200 220 240 260 28 O 300
77rnc of*/4pp/icotl'orr /ft Seconc/^s .
Curves of Dielectric Strength vs. Time of Application. Varnished cloth
between 10 cm. disks with rounded edges; 60 cycle; 25 deg. C.
increasing 10 per cent every hour or half hour
until puncture occurs. These tests may be
made at any given temperature. The tests
are made in oil between 10 cm. diameter
electrodes slightly rounded at the edges.
The one minute dielectric strength for the
3.0 mm. insulation, Fig. 7, is 12.5 kv/mm., the
rapidly applied 26. kv/mm.
The strength-time curve follows the law'
Where
a = constant for a given insulation.
gs = constant for a given insulation of given
thickness, temperature and frequency.
r = time of application in seconds.
g = strength in kv/mm.
Strength vs. Thickness
The apparent strength of insulation varies
greatly with thickness. One minute strength-
— thickness curves for varnished cambric at
25 deg. C. and 100 deg. are given in Fig. 8.
The author has found that strength-
thickness curves follow the general law
It VLAl V C 1U1K
V */7V
g = S
•0-vO
(11)
* F. W. Peek. Jr., "Dielectric Phenomena in High Voltage
Engineering," Chapter VII.
105-4
GENERAL ELECTRIC REVIEW
Where
g = unit strength in kv mm.
gs = constant = unit strength at infinite
thickness.
oc = constant depending upon the insulation.
/ = thickness in mm.
it
is'*
V
\\
\
\
s
S
s
\
V.
es°c
~~/oo°c
.S I.O 1.5 20 25
Thickness In mm
3.0 3.5 AO
Fig. 8. Curves of Dielectric Strength vs. Thickness of
Varnished Cambric. One minute; 60 cycles;
between 10 cm. disks in oil
The constants gs and <x will vary with the
material.
Examples
For Porcelain, 60 ~ , 25 deg.C. one minute test
(0-9A , „ .
1+- r= I kv,mm. effective.
VtJ
The puncture voltage is,
e = gt
For Varnished Cambric,
60 ~, 25 deg. C. one minute
test.
0 \ kv mm
1 = 7.5
(1.20\
i+7t)
effective.
For irregular fields, as those
around wires or cables, the
apparent breakdown gradient
of solid insulation is higher
around small conductors than
large ones.
Reliability of Solid and Lami-
nated Insulation
The structure of most insu-
lations is not homogeneous.
If a given insulation is tested
with terminals of varying area
it is found that the average
puncture voltage becomes
lower as the area is increased,
and thus the chance of it
covering a weak spot is
increased. As would be
expected the strength-area curve approxi-
mately follows the probability law.
An insulation built up of laminations is
much better than a solid insulation as the
weak spots in the laminations are not likely
to line up. It is also much easier to make
better and more uniform insulation in thin
sheets.
Tests are useless for comparing insulation
strengths unless made upon some standard
basis.
Transient Voltages and High Frequency
The term "high frequency" is generally
used in such a way that no distinction is made
between sinusoidal high frequency from an
alternator, undamped oscillations, damped
oscillations, impulses of steep wave front, etc.
Naturally the effect of continuously applied
undamped oscillations is quite different from a
single high- voltage impulse of extremely short
duration. As the effects are attributed to the
same cause — ' ' high frequency ' ' — apparent
discrepancies must result. (See comparative
tests, Table I.)
High Frequency
It takes energy and therefore time to
rupture insulation. For a given potential a
given number of cycles of very high frequency
voltages, where heating does not result, are
f
<o
?
|
\
\
1-
>
v
1-
\
g-tay+y^,
\
7 '*
<
\
<$
G 7 e s /o
Th/cKness In m m.
II IB 13 14 IS
Fig. 9.
Curves of Dielectric Strength vs. Thickness of Porcelain.
60 cycles; between disks at 25 deg. C
One minute;
ELECTRICAL CHARACTERISTICS OF SOLID INSULATIONS
1055
therefore much less injurious than the same
number of cycles at low frequency. This also
applies to impulse voltages of steep wave
front. Continuously applied high frequency
is, however, generally very injurious for two
distinct reasons:
( 1 ) On account of the very great loss at high
frequency from an alternator or undamped
oscillations the insulation may be literally
burned up in a very short time even at low
voltages. This condition does not result in
practice from surges, etc., on low frequency
lines, but in high frequency generators, and
transformers, etc. In such apparatus it is
important to use very smooth electrodes to
prevent local concentration of stress and
charring of insulation. This is especially so
to produce the same results in the limited
time. Impulse voltages of steep wave front
many times in excess of the rupturing voltage
may be applied to insulation without rupture
if the application is very short — measured
in microseconds. They may be caused in
practice by lightning, switching, etc. If such
voltages are sufficiently high, complete
rupture may result at once. In any case if
these voltages are much in excess of the 60
cycle puncture voltages the insulation will be
damaged. As an example, an impulse voltage
equal to three times the 60-cycle puncture
voltage may be applied to a line insulator.
During the very small time between the
application of the voltage and the arc-over
through the air, the insulator is under great
TABLE I
COMPARATIVE STRENGTHS OF INSULATION AT 60 CYCLES, HIGH FREQUENCY,
AND TRANSIENT VOLTAGES
Varnished Cambric
60 CYCLES BREAKDOWN GRADIENT
kv/mm. MAX.
DAMPED OSCILLATIONS
HIGH FREQUENCY (ALTERNATOR) 200.000 CYCLES
90.000 CYCLES (TRAIN FREQUENCY 120 PER
KV/MM. MAX. SEC.)
kv/mm. MAX.
SINGLE IMPULSE
CORRESPOND-
ING TO SINGLE
HALF CYCLE OF
200.000 CYCLE
SINE WAVE.
kv/mm. MAX.
THICKNESS
Time of Application
Time of Application Time of Application
Time of App.
Single Imp.
108
78
70
60
Rpdly. App.
One Min.
Rpdly. App.
One Min. Rpdly. App.
One Min.
53
42
37
33
46.5
31
28
27.5
19.5
13.5
10
17.6
10 55
7.3 49
41
56
41
30.5
.06
.15
.25
.36
where contact is made with the air. If a
local brush starts, on account of the great
loss, it becomes very hot and extends out a
considerable distance.
(2) In certain apparatus containing induc-
tance and capacity very high local potential
differences may be produced by very low
applied voltage, by resonance and thus cause
rupture by overpotential. The high fre-
quency thus does not cause the rupture
directly but makes it possible by causing
overpotential. Local concentration of stress
may also result in non-homogeneous insula-
tion, as across the condenser and resistance
combinations in Fig. 1.
* Impulse Voltages
If the time of application is limited below a
definite value, higher voltages are necessary
* F. W. Peek, The Effect of Transient Voltages on Dielec-
trics, A.I.E.E. Aug., 1915.
F. W. Peek. Jr.. "Dielectric Phenomena in High Voltage
Engineering." Chapter VII.
stress. It may be that up to the ninth applica-
tion of such a voltage there is no evidence of
any injury while on the tenth application
failure results. Each stroke has contributed
toward puncture. It is probable that each
application adds to or extends local cracks.
Cumulative Effect of Overvoltages of Steep Wave
Front
Voltages greatly in excess of the "rapidly
applied" 60-cycle puncture voltage may be
applied to insulation without rupture if the
time of application is sufficiently short. All
such overvoltages injure the insulation, prob-
ably by mechanical tearing, and the effect is
cumulative. A sufficient number will cause
breakdown. Incomplete breakdown or local
"cracking" can often be observed in glass.
For example: A piece of oiled pressboard 3.2
mm. thick has a rapidly applied breakdown
at 60 cycles of 100 kv. maximum. If sinusoidal
impulses reaching their maximum in 2.5 micro-
1056
GENERAL ELECTRIC REVIEW
seconds are applied, the number of impulses
to cause breakdown is as follows:
KV. MAXIMUM OF APPLIED
NUMBER TO CAUSE
IMPULSES
BREAKDOWN
100
OO
140
100
150
16
155
2
165
1
If the impulses are of still shorter duration,
a greater number are required to cause break-
down at a given voltage. Insulations, and
line insulators, are often injured and gradually
destroyed in this way by lightning.
When very high impulse voltages are
applied to insulation explosive effects result;
porcelain may be shattered, or cambric torn
apart.
Damped Oscillations
By comparing columns 1 and 3, in Table I,
it will be noted that the breakdown strengths
of insulation for 60 cycles and for the damped
oscillation used in this test do not greatly
differ. The oscillation was sufficiently damped
so that dielectric heating was not the main
factor. This insulation was in good condition.
If the insulation were allowed to absorb mois-
ture to some extent, however, the 60-cycle
strength would be greatly decreased; the
strength for this particular damped oscilla-
tion would, however, not be greatly changed
— the moisture wTould not be readily detected.
The reason is a conduction or thermal one. A
knowledge of many such factors is necessary
when insulations are compared by "High
Frequency Tests."
Operating Gradients and Temperatures of Insula-
tions
Great caution is necessary in the use of
tabulated values of insulation strength in
design. On account of the variable quality
of solid insulations, tests must be con-
tinually made to see that the product does
not change. Vacuum treatment is necessary
before use to remove moisture. Even when
all of the test conditions are known, experience
is necessary to- judge the proper factor of
safety. Aside from this, stress concentra-
tions due to the shapes and spacings of the
conductors must always be considered and
allowed for. It is generally not possible to
do this with mathematical exactness, but
approximation must be made with all factors
in mind. Care must be taken that the solid
insulation is below the rupturing gradient at
any local point. If such a point is broken
down locally the flux becomes still further
concentrated. The puncture voltage will
also decrease with frequency, etc.
It must be remembered that in design only
a fraction of the gradient corresponding to the
"one minute" breakdown voltage is per-
missible for continuous operation, the par-
ticular per cent depending upon the design,
the rapidity at which heat may be radiated,
or conducted away, etc. It is generally not
more than 10 per cent; it is often as low as
5 per cent, sometimes as high as 30 per cent.
The maximum operating temperature of
insulation is not definite. For low voltage
apparatus, temperatures not high enough to
cause electrical failure may cause mechanical
failure, etc. With fibrous materials, as cloth
and paper, the life of insulation will generally
be greatly shortened if the operating tem-
perature is above 100 deg.; for asbestos and
mica in binders this limit is about 150 deg.
Often the electrical properties will limit the
temperature much below these values.
Mechanical Consideration in Design
It is of great importance to arrange designs
in such a way that local cracking, or tearing
is not caused by high localized mechanical
stresses. This is especially so with porcelain,
as in the line insulators. Expansion of a
metal pin, localized mechanical stress due to
sharp corners, expansion of improper cement,
etc., will cause gradual cracking of the por-
celain. The so-called deterioration of line
insulators is often caused in this way. It is
also often due to moisture absorption.
Permittivity
A knowledge of the permittivity of insulat-
ing materials is of as great importance as a
knowledge of the dielectric strength.* If
insulations are combined in design without
this knowledge, concentration of stress and
breakdown may result.
Insulations, such as dry paper, with low
dielectric strength and low permittivity, are
impregnated with oils or compounds of
high strength and permittivity. The result
is a dielectric of greater strength and per-
mittivity. If the impregnating is improperly
done, for instance so as to leave oiled spots
and unoiled spots, the dielectric strength may
be less than the dry paper alone. This is due
to the difference in permittivities of the dry
* For data on dielectric strength, permittivity, etc.. see
"Dielectric Phenomena in High Voltage Engineering." Chapter
VII.
ISOLATED POWER-HOUSE FOR FACTORIES
1057
and oiled spots, which cause a concentration
of stress on the electrically weak dry spots.
When a given number of sheets of several
insulations of different permittivities are
combined to form a plate, the dielectric
strength of the resulting plate will vary with
the method of combining. It will make con-
siderable difference whether the different
kinds of sheets are piled alternately, or
otherwise.
Dielectric Field
Undoubtedly insulation is sometimes placed
in apparatus in such a way that the stresses
at local point are many times greater than
necessary. To prevent such conditions the
dielectric field must be considered. It is
more satisfactory, for instance, to reduce
stresses to one tenth by proper design than
to seek an insulation of ten times the strength
for improper designs.
ISOLATED POWER-HOUSE FOR FACTORIES
By W. E. Francis
General Electric Company
This article is a compilation of thoroughly practical and useful information to apply in the design, con-
struction and operation of an isolated power-house. All sections of the power plant are treated under their
respective side-headings. The information presented has been gathered from actual practice, and therefore
it should prove to be well worthy of favorable consideration by the designers and operators of this type of
power-house. — Editor.
In designing a plant for the supply of power,
light, and heat it is first essential to obtain an
intelligent survey of the field to be supplied,
so that no mistake will be made when later
selecting the apparatus that is to be the most
suitable for the plant. It will be necessary
not only to secure an accurate knowledge of
the total energy required for present con-
sumption but also to estimate, as closely as
possible, the probable requirements of the
future. Due regard also must be given to
securing a spare outside source of power
supply and adequate spare apparatus to use
in case of breakdowns. The amount of steam
that will be required for heating and other
manufacturing purposes must also be con-
sidered.
Many firms have spent unnecessarily large
sums of money on a power-house building
but have failed to provide space in the
building to properly install the machinery
which, in reality, is the most essential part.
A building for a power-house need not be
ugly because it is built of iron girders and
concrete instead of fancy brick with elaborate
facings; and the machinery will operate just
as well if the floors are of nicely laid concrete
and cement as though they were of mosaic
blocks.
The location of the power-house should be a
central one; also it ought to be near a railway
siding so that a cheap method of conveying
the coal from the cars can be employed. One
example of locating a power-house at a short
distance from a railway siding is that of a
certain station which pays $1.00 a ton for coal
and $1.85 per ton freight charge, but which
has to spend 25 cents additional a ton for
handling the coal after it has arrived. This
high additional expense is due simply to the
fact that the power-house was built across
the street from the railroad. It might just as
well have been "placed with its boiler room
next to the siding, which arrangement would
have facilitated handling the incoming coal.
It can easily be seen that if 6000 tons of coal
were used per annum the extra charge for
handling it on arrival would amount to $1500.
In laying out a proposed new plant it is
best to consider each item separately; there-
fore the following discussion will be treated in
sections.
Boiler Room
A well equipped boiler room should contain
the following apparatus: boilers, solidly con-
structed boiler mountings, forced or induced
draught equipment, damper regulator, econo-
mizer, automatic stokers, ash exhauster,
filters, feed-water heaters, feed pumps, feed-
pump regulators, and boiler flow meters.
Type of Boilers
If the power-house is to be subjected to
heavy overloads periodically, water-tube
boilers offer a great advantage because of the
rapidity with which steam can be generated
to meet the peak loads; but, if it is ascertained
that the load will be constant, boilers which
hold a larger volume of water and steam
would be very suitable since these can be
worked uniformly day and night.
1058
GENERAL ELECTRIC REVIEW
It is recommended that all the boilers be
of the same manufacture and rating. The
practice of purchasing cheap or second-hand
boilers is to be condemned on the ground that
it is false economy.
Fig. 1.
An Installation of Flow Meters Measuring the Steam
Output of the Individual Boilers of a Battery
Number of Boilers and Cleaning
An important point, which is often over-
looked, is that in addition to ample boiler
capacity to carry the heaviest load there
should be one or two additional boilers, so
that this number can always be laid off for
cleaning. Many firms have learned to their
cost that the hasty cleaning of a boiler at the
week-end does not pay. As a matter of fact
the boiler usually receives only a "lick and a
promise." Frequently, it is blown down in a
hurry and then cooled by pumping in cold
water to permit the fireman to enter after it
has been drained. The scale is then removed
in the most get-at-able places, while in those
other parts where perhaps its removal is more
necessary it is allowed to accumulate until a
cracked tube-plate or a leaky tube develops.
This lack of thoroughness may endanger
lives. It certainly will necessitate shut-downs
and expensive repairs, to say nothing of the
fact that even a scale yg in. thick on the heat-
ing surfaces demands an excessive coal con-
sumption.
Boiler Arrangement and Mounting
A straight line arrangement of the
boilers should be adhered to if possible.
There should be an adequate drain to a
river, or to a sewer that is beneath the
boilers; and plenty of head-room should
be allowed for taking off manhole doors
and for inspection. On no account
ought any part of a boiler be buried in
brickwork, otherwise corrosion may start
and continue without being noticed. A
double set of blow-offs should be installed,
consisting of an approved cock placed in
such a position that it can be easily turned
with a key without having to get beneath
the boiler; and beyond this cock there
should be a screw-down valve having a
soft metal seat which can be renewed from
time to time; and the ends of the blow-off
pipe ought to be led to some position
where any leak can be immediately
detected. The blow-off pipe should not
be rigidly fixed, i.e., allowance should be
made for vertical and horizontal expan-
sion and contraction.
Safety Valve, Gauge Glass, and Whistle Alarm
The main safety valves should be fitted
with rods connected to a screw and wheel
which occupy an accessible position, so
that the fireman can ease the valves
occasionally and thus prevent the possi-
bility of their sticking. There should
always be two safety valves fitted to each
boiler, and they ought to be of ample capacity
to allow the excess steam to escape so fast
that the boiler pressure will not increase
more than 10 per cent when the furnace con-
tains a bright fire.
The gauge-glass mountings should be fitted
to a column from which one pipe leads to the
steam drum or steam space, and another to a
point near the bottom of the boiler. This
method of piping results in a more accurate
indication of the water level (because allow-
ance is automatically made for difference in
temperatures) than when both the steam and
water are taken from points just above and
below the gauge glass.
Approved whistle alarms are satisfactory,
if kept in order, but visual observation is best
since accidents have happened because the
ISOLATED POWER-HOUSE FOR FACTORIES
1059
fireman relied on such an automatic con-
trivance.
Feed-water Regulator
If the water level in the respective boilers is
to be kept at the proper height, otherwise
than by hand, it will be necessary to select
and install the most efficient and reliable
feed-water regulators on the market. These
should never be bought under any other con-
dition than those of the "kill or cure system,"
under which they are installed by the makers
and paid for after they have "made good."
Furthermore, only those devices which have
been approved by the leading boiler insurance
companies should be selected. One has only
to look around or to inquire to find how many
useless or practically useless articles for this
purpose there are on the market. A good
feed-water regulator is both essential and
economical, and a regularity of boiler feed is
one of the^ principal requisites for boiler
economv.
Fig. 2. An Indicating, Recording. Integrating Flow Meter
Automatic Stokers
Mechanical stokers when supplied with
uniform size coal, that has been especially
prepared for them by a crusher, and when
operated by an intelligent and capable person
will produce excellent results. Unless this
type of stoker is given constant attention,
however, the neglect allows of a big loophole
for carelessness which results in waste. Any
automatic device for firing coal is liable to
make and leave holes in the fire bed unless
checked by careful observation. More money
will be wasted by an inefficient mixture of
gases in the combustion chamber than can be
saved by decreasing the manual labor.
Unfortunately, it is not always realized that
a cheap man in a boiler room is expensive.
Fig. 3.
A Typical Boiler Room with Steam Flow Meters
Mounted on the Fronts
Actually, the brains of the operators should be
centered in this part of the plant for it is here
that the economy of the whole plant is deter-
mined.
The principal benefits to be derived from a
mechanical stoker are :
(1) Regularity of firing, i.e., the mainte-
nance of a regular supply of coal moving across
the bars at an even and desired thickness.
(2) Reduction in cost of labor.
(3) Reduction in the amount of clinkers
formed, thereby causing better and steadier
combustion of the coal.
These economies soon disappear with
carelessness on the part of the engineers or
firemen. For this reason a steam flow meter
and a CO* recorder should be installed, the
first to immediately show the fireman that
his fires are not in proper condition and the
second to give the engineer an absolute
record of the percentage of carbon dioxide
in the chimney gases.
Assume a battery of boilers in which each
boiler is fitted with a steam flow meter.
Should holes occur in the fire of any particular
unit, the index finger on the flow meter will at
once begin to travel toward zero which shows
that an excess of cold air is rushing through
the fire grate and is cooling the tubes or other
heating surfaces. Again, should all the boilers
1060
GENERAL ELECTRIC REVIEW
be apparently working to the same degree
and should there be a leakage of air through
the boiler setting, the CO* recorder will
indicate this condition by the percentage of
carbon dioxide in the chimney gases.
The composition of the chimney gases also
shows the working of the furnaces under the
boilers. When the fuel is properly consumed,
the furnace gases should contain only nitrogen,
oxygen, steam, and carbon dioxide. To secure
this result an excess of air is required, but
this excess must not be greater than a certain
amount, otherwise there will be too great a
volume of air heated and this heat wasted.
The percentage of COi in the chimney gases
indicates the amount of excess air entering the
furnace. The relationship between the per-
centage of CO? and the amount of air is given
in Table I.
TABLE I
Per cent of Carbon
Dioxide Found in
the Chimney
Gases
Number of Times the Theoretical
Amount of Air which Should be
Admitted to the Furnace as
Indicated by the Per Cent
of Carbon Dioxide
4.0
4.9
5.0
3.5
6.0
3.0
7.0
2.5
8.0
2.3
9.0
2.0
10.0
1.7
12.0
1.5
17.11
1.0
Experiments tend to show that per cents of carbon
dioxide from 1(1 to 14 give the most profitable
combustion in the furnace as a general rule.
An inspection visit to a boiler room that is
not equipped with these indicating devices and
where the fireman is "taking it easy" will
almost always disclose large holes in the
furnace fire or leaky flues or settings. The
elimination of these faults has oftentimes
permitted a reduction in the number of
boilers required to be in service.
Boiler Feed Pumps
The boiler feed pumps should be of an
approved type, and each ought to be capable
of supplying the battery of boilers for which
it is intended without having to run at undue
speed. In addition to these, there should
always be a spare pump in readiness to con-
tinue the work should one on the line fail.
These feed pumps are to be fitted with pump
regulators and also with by-passes for hand
control. Care must be taken, when the
pumps are working in conjunction with a
feed-water heater, that the water is able to
flow from the heater through the suction pipe
to the pump below. Feed-water pumps
should be situated in such a location that the
fireman can observe their operation, for manv
unat tended pumps have been wrecked by
running away.
Economizer
By using an economizer a saving in coal of
about 10 to 15 per cent can be made. Kent
states that for a given quantity of chimney
gases passed through it, its economy will be
greater :
(1) The higher the temperature of the
gases.
(2) The lower the temperature of the
water fed into it.
(3) The greater the amount of its heating
surface.
From (1) it is evident that an economizer
will save more fuel when added to an over-
loaded boiler than to a boiler working at its
normal rate.
From (2) it appears that a smaller saving
can be expected from an economizer in a
power-plant in which the feed-water is heated
by the exhaust steam from auxiliary engines
than can be looked for when the feed-water
entering it is taken directly from the con-
denser hot-well.
For the efficient working of an economizer,
it is very essential that the outside of the
tubes be kept thoroughly clean by means of
mechanical scrapers; and it is especially
necessary that the tubes should be peri-
odically inspected, all scale removed, and any
pitting or corrosion stopped. If this practice
is not followed the economizer will become
useless and will be an impediment to the
chimney draught. Economizers must be
fitted with ample cleaning doors underneath
and large doors at each end for inspection
and cleaning. All baffle doors and dampers
should be made with ample clearance to allow
for warping and expansion when hot. It has
often happened that an economizer has been
started before the brickwork has had time to
dry, which has caused distortion due to
rapid expansion and resulted in consequent
trouble with dampers.
The use of an economizer introduces an
additional element of danger. The apparatus
can be and often has been as dangerous as a
boiler; therefore during its manufacture it
should be inspected and thoroughly tested,
and its safety valves tried out before placing
it in service. Also, it should be fitted with
easilv get-at-able blow-off cock^. Another
ISOLATED POWER-HOUSE FOR FACTORIES
1061
fact to be remembered, and a very important
one, is that the designer of the chimney must
be informed as to whether an economizer is
to be included in the plant or if the use of
one is contemplated. It has often happened
that an economizer has been purchased as an
afterthought, or has been added to an already
existing plant, consequently an additional
fifty feet or so has to be added to the stack
or an induced or a forced draught system
installed. This it is almost needless to say
creates much annoyance for the owners.
Feed-water Heaters
There are various feed-water heaters on the
market probably the best of which for most
purposes is the open heater. This type uses
the exhaust steam from auxiliaries in the
power-house and in some cases steam from a
steam-extraction device on a turbine. Most
of these heaters are supplied with an internal
float arrangement; but it is a good plan to also
add an external float chamber on a separate
water supply, that this may be used should
anything go wrong with the former. The
heater should be located above the feed
pump; and the water-gauge, thermometer and
pressure gauge must be placed so that the
operator can easily see them, for an increase
in temperature above normal or a decrease in
water level below normal will cause the pumps
to "kick," probably resulting in damage to
them.
Main Stop Valves
The main stop valves should have outside
threaded spindles and should be tested before
leaving the factory. Where more than one
boiler is installed approved non-return valves
are to be fitted between the boiler and the
main stop valves. Many accidents have
occurred through this necessary precaution
being disregarded. Not only is a non-return
valve a safeguard against steam from other
boilers entering a boiler in which a burst tube
has developed or in which a manhole has
blown out, but when raising the steam pres-
stire in a boiler (which has been laid off for
cleaning) with the other boilers in the battery
working this non-return valve opens auto-
matically when the pressure attains that of
the others. Thus the fireman has no trouble in
cutting in his boiler on the line. Feed check
valves should be strong and well made, and
the feed-water piping be made of brass, and
approved for the purpose.
Check Valves
Check valves should be bolted to the
boilers or to some short and rigid connection;
but on no account must the valves be fastened
to long lengths of pipe that are merely screwed
into the boiler and thus might easily become
broken off. The internal extension of the feed
pipe into the boiler is generally placed in a
position where it will not retard circulation.
This location varies according to the particular
kind of boiler. It has been found in practice
that the jet of feed water should not be
directed so as to impinge on any plate that is
in contact with the fire, nor should the pipe
discharge its contents (which often contain
sand and mud) toward one place only; the
flow should be as distributed as possible.
Meters
A well equipped power-house should be
furnished with the latest steam flow meters
and water flow meters. These instruments
have long passed through the experimental
stage, and can no more be dispensed with than
can the pressure gauge or safety valve.
Powerhouse Operators
A power-house must be operated on a
methodical and intelligent basis if it is to be
run economically. At its head must be a
man who not only knows his work, but who
also has at heart the interest of the company.
Too often the men in charge of power-houses
are subject to the whims and caprices of
superiors in rank who have not the slightest
idea of the rudiments of engineering. Such
a practice may produce so disastrous a result
that, at the end of a working year, it will be
found that the isolated plant is not a paying
investment.
Power-house Book-keeping
The power-house should be isolated, it
should always be ready to supply power,
light, and heat, and be ready for overloads;
but, it should sell these commodities to the
factory. No man can run a power-house
efficiently unless he either has control of the
power, light, and heat when it leaves the
power-station or can send a monthly bill of
them to the factory. When the superintendent
receives these bills — so much for "power,"
"heat," and "light," — he will give them
attention and will issue instructions for
repairs or renewals which will effect a saving
wherever possible in order to lower the
expenses of his manufacture.
This satisfactory method of billing can be
put into practice through the use of steam
flow meters. The power-house staff can
determine (by a series of readings from the
power and the light steam flow meters, which
should be separate) the price to charge per
1062
GENERAL ELECTRIC REVIEW
kilowatt-hour for power and for light. The
amount of steam that is used in the factory
can be arrived at by placing a recording and
integrating steam flow meter in the steam
lines. The cost can be determined and a fair
rate charged per thousand pounds of steam
used, to insure that there will be no waste
of steam through leaky steam traps, or by
exhausting into rivers, creeks, or sewers.
The amount of return condensate should be
registered and if it is not up to normal the
factor}' should be penalized by charging a
small percentage more for power, light, or
heat, or some immediate arrangement can
be entered into with the superintendent or the
master mechanic to have the matter remedied.
Too often the loss is blamed on the generating
apparatus and operating engineers instead of
on the carelessness and waste of the factory.
Ash Chutes and Ejectors
There are several makes of ash chutes and
ejectors on the market and very little trouble
is experienced with them provided care is
taken not to choke them by too hasty feeding
of clinkers or ashes. On no account should the
ash pipe or bin bottom outside the power-
house be exposed to the weather more than is
necessary. Such parts as are exposed should
be thoroughly lagged with some heating
insulating material. If this is not done the
damp ashes may become frozen daily in
winter and more time and money be spent to
thaw them than would be required to wheel
them out with a barrow. For cleanliness and
dispatch, however, an ash ejector when
carefully installed and given attention is
highly recommended.
Coal Bunkers
Local conditions primarily determine the
location of the coal bunkers. Frequently
these are placed directly over the furnaces, so
that the coal can regularly be fed through
large sheet-iron feed pipes to the mechanical
stokers. Wherever the coal bunkers are
placed, however, there should be a means
provided for weighing the coal to each boiler
when desired. This system in a boiler room
soon pays for itself by the increased economy
it secures. Desirable results are not obtained
from forced tests that are run over a period of
only a few hours. These give information as
to what the boiler can do, but not what it
does do in daily service from which latter the
proper prices to charge the consumer should
be determined.
Water Supply
The water supply to a power-station should
be the best and cleanest procurable (not
necessarily from the city water supply, but
preferably from a river or lake if unpolluted).
There should be two distinct sources of supply
to prevent a possible shut-down with the
attendant danger of burning or exploding the
boilers. Chemical compounds should be
avoided if possible. However, if some chemical
must be used, soda ash will probably be
found to be the most effective and least
injurious. In some cases a judicious amount
of lime may be found useful. Graphite when
applied in reasonable quantities is also highly
recommended as a medium for scale preven-
tion and elimination. A good mechanical
means for cleaning and maintaining cleanliness
is, however, conceded by many to be more
effective than any chemical means.
Engine or Turbine Room
The power-generating room should be well
lighted day and night, and also should be well
ventilated. If the window space is large
but the room is not properly ventilated, a
sweat and mist will cause much trouble in
winter due to the difference in the temperature
within and without. In some cases where the
ceiling is high and there is but a small amount
of window space, it is necessary to install an
exhaust fan in the roof to take out the
hot air and vapor and at the same time draw
in air from the basement wherein it has had
an opportunity to warm up somewhat before
entering the engine room. Proper ventilation
is most important because, among other
reasons, if it is ignored valuable recording
instruments may be ruined.
The skylights of the boiler room should be
solidly constructed and be composed of
sections not exceeding three feet in width so
that they can be lifted easily. The hinges
should be at the upper edge, so that when a
skylight is lifted on its hinges and brought
into a horizontal position rain will be pre-
vented from falling on the boilers and spoiling
the asbestos lagging, etc. (This is the position
of the hinges used on the skylights of a ship.)
If, on the other hand, the hinges are placed at
the lower edge of the skylights, the boilers
will be exposed to the sky at times. Such sky-
lights are also difficult to fasten closed and are
in danger of being blown to pieces by the wind.
Switchboard
The switchboard should be placed in a dry
and well-lighted location and plenty of room
ISOLATED POWER-HOUSE FOR FACTORIES
1003
should be allowed at the back for replacing
fuses, etc. A door having a lock should be
fitted to the back, so that no unauthorized
person can enter. Simplicity is the keynote
of a successful switchboard.
The switches should be of ample capacity
and be well-constructed ; small cheap switches
should never be used. The switchboard
should be equipped with recording watt-
meters for power and light in addition to the
customary indicating instruments; and when
the generators may be required to run in
parallel, even while only changing over,
not to unnecessarily cool the condensing
water which can be used as warm water for
factory purposes and, second, to extract
steam from say between the first and second
stages of the turbine for heating and other
purposes. Table II shows the amount of
steam which can be extracted with a steady
extraction pressure of 5 lb. or 10 lb. as
required from a 750-kw. machine carrying
400 kw. The operation of the device is
entirely automatic and it will maintain con-
stant extraction pressure regardless of the
mechanical load on the turbine. A device
Fig. 4. A 750-kw. Curtis Steam Turbine equipped with an Automatic Steam Extraction Device
synchronizing gear and indicators should be
installed. A good rubber mat should be
placed in front of the switchboard for the
safety of the operators.
Turbine
Turbines are rapidly coming into favor,
especially in those cases where they can be
coupled direct to high-speed generators.
Turbines in which the number of wearing
parts is reduced to a minimum, such as the
Curtis, are recommended. Machines of this
type are now available in sizes ranging from
100 watts to 35,000 kw. The best compromise
in the economy of steam consumption and
relative cost of upkeep and repairs determines
the most suitable machine.
In equipments calling for a daily running
load of 500 kw., two machines should be
installed and run alternately. It has been
found economical, first, to use a condensing
turbine with a vacuum of sav 26 inches so as
TABLE II
Load Kw.
Extraction in
lb. per hour
Flow to
Condenser
Flow at Throttle
for 160 lb. -26
in. -100
5-lb. Gauge Extraction Pressure
400
2,00(1
7,650
9,650
400
4,000
6.500
10,500
400
6,000
5,400
11,400
400
8,000
4,200
12,200
400
110,000
3,100
13,100
400
12,000
1 ,900
13,900
400
14,000
800
14,800
10-lb. Gauge Extraction Pressure
400
2,000
8,250
10,250
400
4,000
7,250
11,250
400
6,000
6,100
12,100
400
8,000
5,100
13,100
400
10,000
3,950
13,950
400
12,000
2,950
14,950
400
14,000
1,950
15,950
1064
GENERAL ELECTRIC REVIEW
which has proved to be successful in com-
mercial operation for the extraction of steam
from a turbine is shown in Fig. 4. It works
automatically by means of a steam cylinder
operated by a piston-type pilot valve, which
has an adjustable setting for maintaining
constant pressure. In conjunction with
this steam extracting device a multiport
back-pressure valve should be fitted because,
being spring loaded, it opens and closes
more gently than any valve operated by
weights and levers. This insures a greater
regularity in the operation of the extractor.
It has been found that the extractor and
relief valve system is more economical than
that which uses exhaust steam direct from
the turbines.
Exciters
In a power-house having two 500-kw.
turbines there should be two motor-generator
exciter sets and one turbine-driven exciter
set; also an exciter can be coupled directly
to the shaft of one of the turbine-generators.
This last is a great advantage as it obviates
the necessity of starting up the small set
except at week-ends, and the big machines
and exciters can be synchronized when chang-
ing over at night or morning. The small
direct-current exciter set (turbine-driven) can
be arranged for lighting the offices, power-
house, and one or two rooms or warehouses
when necessary; or there can be a turbine-
driven alternating-current generator with an
extension direct -current exciter. In the latter
case it is a good plan to install a turbine of say
50 or 100 horse power that is to operate non-
condensing (non-condensing, because when
the large machines are not running the
exhaust steam, boosted with some live steam
to say 5 or 10 lb. pressure, can be used for
heating the building and also for heating the
feed water).
Condenser
The condenser room should be well lighted
and the condenser pumps, traps, etc., easily
accessible for attention and repairs.
In choosing a condenser the machine that
is to be purchased is one that is well designed,
and will stand up to the work. There are
condensers which give daily trouble through
inherent weakness of design, and others which
give no trouble at all. A condenser should not
be purchased simply on its merits to produce a
high vacuum, but because of its simplicity
and freedom from requiring continual repairs.
Miscellaneous
Great uncertainties attend the selection of
steam traps as there are so many types on the
market. Perhaps the simplest and best are
those which for their operation depend on the
displacement of a copper-sheathed float con-
taining water-logged wood, and not those
which use hollow floats that are liable to
become punctured. Every well-equipped
power-house should have racks for wrenches
which ought always to be in their places
ready for emergencies. The wrenches should
be of standard sizes to suit the apparatus to
which they are to be applied, i.e., not shifting
wrenches. There should also be convenient
vises and hand tools for making the small
repairs that are so often neglected. All back
pressure and reducing valves should be by-
passed and isolated by means of stop valves
so that they can be repaired readily, and
these should be placed in an accessible posi-
tion. The piping arrangement should be a
simple one, and the most careful attention
should be given to the layout to prevent a
tangle of steam and exhaust pipes. Plenty
of room for tightening up joints should be
allowed around the pipes that are run in
trenches. This is most essential if the mainte-
nance expenses in the power plant are to be
kept at a minimum.
Keeping of Records
There are various methods of keeping
power-house data and the one that is to be
used depends largely upon the size of the
station. Generally speaking, simplicity should
be the guiding factor for a complicated
system that involves too much time on the
part of the operating engineers is apt to
defeat its own end. Weekly records of coal
consumption and evaporation (when the
power-station is equipped with scales over each
boiler and water flow meters for measuring
the water or steam flow meters for measuring
the steam) are really necessary for efficient
working. Records of carbon dioxide should
be kept to safeguard the proper consumption
of the fuel, flow meter readings should be made
of the steam supplied to the factory, and
light and power readings ought to be taken
twice in 24 hours. A simple loose-leaf log-
book can be procured for filing this data, and
a copy of each page sent to the President of
the company and to the Superintendent.
This systematic recording of data will be of
great assistance in securing economy in the
power-house, with the result of a low charge
for power, light, and heat for the factory.
ISOLATED POWER-HOUSE FOR FACTORIES
1065
Purchase of Coal
There are various kinds of coal — anthracite,
bituminous, semi-bituminous, run of mine,
and slack. To believe each salesman, one
would conclude that the particular company
he represents furnishes a better grade of
any one of these coals than can his com-
petitors. The heat-unit system, however, is
the best salesman. Prompt coal analyses
are now made at a reasonable price by reliable
firms; and the coal should be bought on the
system of so many heat units at one cent, not
so many tons at a fixed price. Samples are
to be taken from each car, as it is being un-
loaded. These are then carefully mixed,
quartered, and ground until reduced to a
quantity sufficient to fill an air-tight can
which is say four inches in diameter and
seven inches high. This can is then dis-
patched to a reputable fuel engineering
company, and the price fixed according to the
number of heat units found per pound of
coal. This system of purchase automatically
causes coal dealers to refrain from supplying
poor coal, but regardless of the quality which
is supplied the purchaser receives full value
for his money.
A rough and ready means of determining
the number of B.t.u. in a pound of coal is
given in Table III.
TABLE III
To Calculate the number of British Thermal Units in Coal from an Analysis of its Percentages of Moisture,
Volatile Matter, Fixed Carbon, and Ash.
(Accurate within 100 B.t.u.)
Rules
(1)
(2)
(3)
(4)
(5)
(6)
Deduct sum of the per cent Moisture and Ash from 100.
Divide the result into the percentage of Fixed Carbon.
Multiply this result by 100.
Consult table below and find B.t.u. opposite this number.
Multiply this "B.t.u. figure" by the figure found by Rule 1.
Divide by 100, and the result is the number of B.t.u. sought.
Per Cent
B.t.u
Per Cent
B.t.u.
Per Cent
B.t.u.
Per Cent
Per Cent
B.t.u
50
51
52
53
54
55
56
57
58
59
12240
12600
12840
13100
13320
13560
1.3800
14040
14220
14400
60
61
62
63
64
65
66
67
68
69
14580
14760
14940
15120
15210
15290
15360
15420
15480
15540
70
71
72
73
74
75
76
77
78
79
15590
15630
15660
15690
15720
15750
15780
15800
15820
15830
80
81
82
83
84
85
86
87
88
89
15840
15840
15830
15810
15780
15750
15710
15660
15600
15540
90
91
92
93
94
95
96
97
98
99
15480
15390
15300
15210
15120
15000
14880
14760
14670
14580
1066 GENERAL ELECTRIC REVIEW
MECHANICAL EFFECTS OF ELECTRICAL SHORT-CIRCUITS
By S. H. Weaver
Drafting Department, General Electric Company
There has been but little data available for satisfactorily determining the stress that will be set up in the
mechanical parts of a generator when it is suddenly short circuited. The following article admirably supplies
this lack for it contains the desired information and presents it in such a simple and practical form as to be
readily applicable to design problems. — Editor.
Torque on the Shaft Between Two Units
In sets composed of two or more units, an
electrical short-circuit on one unit will place
a strain on the shaft connecting the units.
The short-circuit dissipates electrical energy
and this energy can only be obtained from
the mechanical store in the rotating parts
and is given out by the deceleration of the
machines. The unit that is not short-circuited
can give out its energy only through the
shaft. The unit that is short-circuited has to
absorb the electrical torque by deceleration
and it receives torque sent through the shaft
by the other unit.
Consider the connecting shaft of elastic
material. The shaft to transmit torque
must then be twisted through a torsional
angle and the torque is proportional to that
angle.
The mechanical action in the simplest form
at the instant of short circuit is as follows:
Unit No. 1 (the short-circuited machine) only
gives out torque, for the shaft has not been
twisted by the new load. As unit No. 1 is
retarded, unit No. 2 begins to take load
proportional to the shaft twist. When both
units are giving up their proportional share
of the energy the shaft twisting does not stop
(because of the different angular velocities
of the units) but continues until unit No. 2
may take all the load. When the large twist
has equalized the angular velocities (zero
relative to each other) the torsional forces
in the shaft tend to bring the units back to
the position where each gives up its pro-
portion of energy, but the new angular
velocities attained carry them beyond this
point and a cycle of operations is completed.
Thus the inertias of the units, connected by
an elastic shaft, cause a mechanical torsional
vibration between the machines and produce
shaft strains higher than the proportional
share of the load. This is called the "free
torsional oscillation."
Alternating current gives an oscillating
power or torque whose instantaneous values
must be considered. Even with a low power-
factor and small effective power, the pul-
sations of the torque are very great. The
vibrating electrical torque is the "forced or
impressed torsional oscillation."
The forced electrical oscillation causes a
disturbance when impressed on a mechanical
structure that has free oscillating properties.
The mechanical frequency of oscillation
depends upon the shaft dimensions and upon
the inertias of the units. The amplitude of
the mechanical vibration depends upon the
amplitude of the forced electrical oscillation
and upon both frequencies. It is possible to
have a condition which the electrical engineer
calls "resonance"; but the larger the ratio
of mechanical to electrical frequencies the
smaller will be the forces on the shaft.
The mathematical work detailing these
general statements and simple formula? re-
duced to predetermine the maximum torque
on the shaft are given in Figs. 1 to 3. The
considering of the current transient as being
constant for the first cycle makes the formulae
average 10 per cent high for commercial
machines. The single-phase electrical power
at short-circuit for a power-factor of 0.2 is
shown in Fig. 4. Figs. 5 to 7 show the instan-
taneous value of the shaft torque for different
ratios of mechanical to electrical frequency,
and show that the maximum stress occurs in
the first cycle except in the case of resonance.
As the power does not divide between the
two machines in proportion to the inertias,
the ratio must be multiplied by the value C,
given in Fig. 8. These data show that the
double frequency of power in a single-phase
machine causes two points of resonance,
and that while a three-phase machine has
only one point of resonance it can be short
circuited single-phase with about the same
destructive effect. Fig. 9 shows that at
resonance the torque increases with the
time for a number of cycles until the power
dies away.
The practical importance of this article is
in the formulas that enable the mechanical
designer to proportion the shaft so that the
high stress and resonance points can be
avoided.
MECHANICAL EFFECTS OF ELECTRICAL SHORT-CIRCUITS
1067
Description of Mathematics
Equation (1), Fig. 1, is the mathematical
statement that the torque on the shaft
equals the decelerating torque of unit No. 2
which, in turn, is equal to the torque of the
angular twist in the shaft. Equation (2)
states that the mechanical decelerating torque
of unit No. 1 plus that of unit No. 2 must
always equal the electrical torque. All the
equations are written with the assumption
that the short-circuit occurs at zero time
so that the integration constant can be
Short Circuit Torque on Shaft
El
Unit No. I
Short Circuited
D
rr
L
Unit No. 2
H
r(t)= Shore circuit Torque on Unit No. I
F(o) = F(t ) When t=0 t = Time
a:, onc/az = ongulor distance
I, and 1 2 = inertias
K, = Maximum Instantaneous Torque f Electrical)
K= 1,300.000 °4/l For Steel Shaft.
T = Torque on Shaft
The Two Torque Equations are
I'~aT? 1~ h
d'ec.
z~dTT
F(t)
(I)
(2)
Both Distance (ar) and Velocity (^f)are Zero at t ~o Integrat i ng
(Z) Twice and combining witn (I) gives
<Q±fbza2=E where £-fe[ffF(t)-tfF(o)-JfF6>)] (3)
The General Solution of (3) is
a2= C, cos. at t Cz sintt tfz -^0 1 pg£- &$f. +
(4)
Determine value of C, and C2 and subsitute in (I ) for T
Example :- Let F(t)=K, a Constant as in ideal continuous current.
^-Electrical Torque K,
Mechanical
(*f \ Tor-que of ,
__ W _ 1 NO-l
V
Torque of NaZ
F(t)-K, jF(t)'K,t fF(0)-0 JfF(t)-^tz
ffna-o
HK, t'
zr,z?b*
Time ^
Equation (5)
Cr
K,
a^Ccosbt+c^sinbt +
dec.
dt
*" J,Iz Z
At t=0 ar? and -^2*=c
'b* (I it I*)
c2-0
K, T> .. , t* 1 7
■J^TzK'[l-C05-bt]
' l2 dtz
'max Z
Iz
I, til
K, If I, =I2
Tmax. r\i
1068
GENERAL ELECTRIC REVIEW
determined by making both distance and
velocity zero, thus measuring only the effect
of the disturbance. Equations (1) and (3?)
can be reduced to (3) which is the elemental
form of an equation for a forced vibration,
the left-hand side representing a free system
while E gives rise to the forced system. The
solution of equation (3) is equation (4),
wherein the trigometric functions represent
the complementary solution or free oscillation,
b equals 2 ir times the mechanical frequency,
and the remaining series part of the right-hand
Electrical Equations.
a-ZK Frequency
For single -phase <z, =]/2~ E sin (at f c)
is = V2~I sin (at -he ~<t>) Sym metrical
it = -Y2 I sin (c-0) Transient
it = is + it = l/2 I [sin (at tc-0) -sin(c-<t>j]
p, = e, i, =2 EI '[sin (at t c-0) -sin(c-0)jsin (at -he)
p, -EI [cos <t>-cos(2at + 2c- <p)-tcos(at+2c- 0)- cos(ot+4>)J Mbx.atC=^ i-0
p = EI [cos tp + cos (2ot + 0)-2cos (at + 0)J *
Let % = Percent Reactance per Phase
KVA = Kilovo/t-ampere rating of Machine ™)
N = Revolutions per Minute
F(ty
7040
'P'
-704C KVA.
<V
yc-'/bos 0 f cos (2a t + 0) -2 cos (at + 0)j
,7*
Polyphase Power :-m = no. of phases > i
x =any given phase
V2~Esm(at+c-Tm\) i*=Y2l[sin(ot+c-0- t£ x)sm(c-0 - t£ x)l
p=T.e*ix~EIiI[cos<t> -Y_cos(2ati-2c-cp- j^r x)-[cos (at t0)tYcos(at 1 2c-<p- rn x)*t
= m EI /cos 0 -cos (at +0)1= -^— cos 0 -cos (at +0)1 , »
(ot+0)]
, . 7Q4Q KVA r
(tr -77- ~^r[cos 0
casl
Torque for Single-phase short circuit :-
Inserting (6) m(4) finding CiQndCz and subsituting (I) gives
I-z 7040 KVA. r-20z(b1!T 2ax)cos 0 cos bt i-6osb sin<p sin bt ,
~7j ^-/ f**-*„,)/H2-„*) -+CO30 +
T-
I+Iz
(b2-4o*)(t>z-az)
cos (2ot + <p) _ 2t>zcos(at t4>)l
bz-4a- bz-0'
If n = & and Tan £ = rT*Tz Fan <p
_ U T040 KVA f z]/9n 2t(n* -■4)(n~-l)C0S*<t> , .
T~L7I* fV~ ~%-t (n<-*)(n*-0 C0S(nat + £)+«>S0i- 0
l&L±*L] (9)
(8)
nscos(2ot t<j>)
2nz cost
Tor the greatest possible Maximum, add the Amplitudes (cos20 = o )
It 7Q4Q KVA.p_ = ^ x 6n j- 3 n* fnz - 3)1
INUKX. — ,
!tlz n WLCOS * + ~'(n*-4)(h>-0fJ °°)
Bracket value decreases for the large n toward the /imit/3+cas 0]
-fcc5<fi+cos(zot t &)- Zco.' r:* t $)J is Maximum at c t =K~ § ^ ancf equals 4 cos $
Fig. 2
MECHANICAL EFFECTS OF ELECTRICAL SHORT-CIRCUITS
1069
side is the portion which provides for the
function E. The values C\ and C2 must be
determined under the condition of angular
distance and velocity equaling zero at zero
time and substituting in equation (i) for the
torque.
A simple example is worked out for F (t)
equal to a constant, which is the ideal case
resulting from equation (5) and plotted in the
curve adjacent.
The section headed "Electrical Equations,"
Fig. 2, shows the structure of the instan-
taneous torque equations for electrical short-
circuits. A constant c is used because the
short-circuit occurs at zero time. This is a
mathematical expression for the ideas on
short-circuit given in Steinmetz's "Electric
Discharges, Waves, and Impulses," except
that the transient value of the current is
taken as constant instead of logarithmatic
for the sake of simplicity and dealing only
with the first cycle for maximum values.
The general expressions for polyphase
circuits are not true for the so-called two-
phase or 90 deg. displacement, but it can be
shown by the same process that the equations
Torque for Polyphase Short Circuit :-
Placing (l) in (4) Pinding CiandCz subsitutinq in (i)gives
It 7040 kva. bz fa* _, _Li <*_.__, _. ,_., bz-Oz
T=
l-tlz
N
-yT ' p^i /p cos <p cos bt - frS/'n <t> sin bt t -[prcos <p -cos(ot t<j>j] (uj
Por a=n and Ton 6=n Tan 4>
fjj2 ^T ^r/ras <p +fjci (Vn*-(n*-/)co524> cos(natte)-n>cos(ot t0)}J
7"=
Por the greatest possible Maximum add the Amplitudes
,. Iz 7Q4Q KV*/4./~ , Ljnz-(nz-l)cosz0 +n*l
T»«*=l~Fl, ~* %-[cos(i>-h 7^-7 J
Brocket value decreases for large n toward the limit [itcos <pj
(iz)
03)
Polyphase Generator '- Ratio of one phase short circuited to all
phases short drcuited=^ = mftco°sQ for m='J mio = '!+Zs<t>
(14)
Resonance .- Special 'solution of (4) when P(t)^6)and d= b or n=l
Kt racos& . 7sin</> ,st* ii \ .,3t.. cosfzot+t). t _. r,..Cf
CC2~It +IZ[ 3o* cas at~ ~3a*~sin ot M z -Ja*)005* fZa 3in<P t iza* ^a5in(at f^)J
_ ., Iz rsin0sinot z-*.^. + cos(Zati<t>) 2cos(at+<t>)T ,lC>i
T= K, i~TT;/ 3 ot sm(ati<t>)+cos <t> 3 5 -y (15)
t in the Amplitude of one term increases Torque with the time
Special solution of (4) when P(t)=(6) and b=2a or n = 2
K, T zcosd , . ,l75in<t> . __ /t*z\ ^ ,3t ■ t ■ , . , .x 0cos(at+<$
T-K, jj= l-£Sin<i>sin 2at tcos <t>+§cos(2ot+Q)+at si n(2at+ <}>)-§ cos(at+<t>)\ (16)
Special solution of (4) when P(t)=(j)ond a=b or n =/ (Polyphase)
CCz=lfI2L^~ c°5ot' z -oT5,nati-{z -Q')cos<t>i-5,n(t> t- sm(at t<t>)j
ot
T-K,z-f^ F-^j^sin at-^sin(at+<p)tcos 0 -cos(at+$
(")
Fig. 3
1070
GENERAL ELECTRIC REVIEW
satisfy this condition after the summations
have been made.
Introducing the electrical torque equations
(6) and (7) in general equation (4), then in
(1) for the shaft torque T gives (8), (9) and
(10) for the single-phase short-circuit, and
(11), (12) and (13) for the polyphase short-
circuit.
Maximum values for T are obtained by
adding the amplitudes. This is the safest
method as the maximum values plotted
against n is a wave-like curve with high and
low point in every variation of 2 in value of n.
Equation (14) shows the relative effect of
short-circuiting one phase in a polyphase
generator. It also demonstrates that if a
short-circuit occurs between one leg and the
neutral of a three-phase generator the effect
is as destructive to the shaft as though all
phases were short circuited.
At the points of resonance special solutions
of equation (4) are required, these giving (15)
and (16) for single-phase and (17) for poly-
phase short-circuits. In each solution one
of the coefficients or amplitudes contains (t)
thereby showing an increase of vibration
f/ectr/co/ Poiver Of Short C/rcu/t
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Fig. 5
MECHANICAL EFFECTS OF ELECTRICAL SHORT-CIRCUITS
1071
with the time. Equation (15) is plotted in
Fig. 9, wherein the radiating straight lines
show the limit of the resonance factor of the
equation. Actually, there would be an increase
of vibration with the time for a number of
cycles until the power died away.
Finally, curves for a short-circuit power-
factor of 0.2 are shown in Fig. 8 plotted from
the formula combined with values of C and
reduced to a practical form.
PART II. PULL ON STATOR FOOT-BOLTS
When a horizontal electrical unit is sub-
jected to a short-circuit, the torque produced
is usually so great that the resulting lever
action would lift one side of the stator from
Shaft Torque Due To Short Circuit
Mechanical Frequency 3 . „
Clectricol Frequence/ ~2 ?„*. f -a~
{,
s
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Efectrical Degrees From Short C/rcy/C
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Fig. 6
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Shaft Torque Due To Short Circuit
5
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Mechanical Freouenc
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Fig. 7
1072
GENERAL ELECTRIC REVIEW
1
II
II
N-Rerolution*.
Per Minute
Pond L In Inches
1 1
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i\lsE/ectrical Cucle<s
! I
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7
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5
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AfoMtmum Shaft Torque in Pounds
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Electrical Frequency
Fig. 8
1
Shaft Tor<?ue Due 7b Short Circuit
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Fig. 9
MECHANICAL EFFECTS OF ELECTRICAL SHORT-CIRCUITS
Stress Or? Stat or foot ffo/ts
1073
fifJOCL
Force on the /eft side = %+P = %+?
= »/ -p = Vj - T
2 P 2 I
ri,
T\w
ant
<fl>
the force ts a pu// on the Oo/ts
7040 KV-A
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, 0
x4cosJ j
//? inch pouncfs =*3737°x '
N
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XCOS J 3
T^ox forpo/yphase = ^^x ^^ [l+cos0]
Maximum pu// on£>o/£s 0/7 one s/de = Tax ~ j
5tator fbot-Bo/ts
fforizonta/ Machines
W=We/'aht of st at or /n pounds
I - D /stance between 00/t rows /'n /nches
A/=f?evo/ut/ons per m/nute
/Ci/-A=K//ovolt- ampere ra£/n<? of mach//7e
ty - Percent reactance p er phase [percent
vo/taae drop w/th rated current]
e ana/ t - Rated iro/t s ana1 amperes per phase
y = Res/stance per phase
(is)
(19)
(20)
(21)
COS0 =?L
Tm =
337970 KI/-A.
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A/
S44-SO
/V
%
KV-A.
cosJ-j fors/na>/e-phase
[/+cos<p] for po/yphase
Max/mum pu// /n pounds on a// oo/ts on one s/de
of stator=T-f&-f
t/ert/ca/ AAach/nes
Max/mum shear/na force /n pounds orr a// bo/ts
eoua/s 7^ d/y/ded i?u rad/us of 00/t c/rc/e /n /nches
Fig. 10
1074
GENERAL ELECTRIC REVIEW
the base if these were not bolted together.
In many cases, as in large turbine-generators,
etc., this pull on the bolts is excessive and
determines the size of bolts required. The
mechanical designer should know the maxi-
mum pull on the stator foot-bolts so that he
can proportion the feet, their supports, the
size of the foot-bolts, the foundation bolts,
and the twist on the base itself.
The forces on the holding-down bolts can be
easily determined by the simple principles of
mechanics. Consider first the influence of the
stator weight W shown in Fig. 10a. Assume
the stator to be a "free" body held in equi-
librium only by the forces acting upon it.
It is evident that a symmetrical stator is
held in equilibrium by the forces shown in
Fig. 10a. Next consider the electrical torque
T acting on the stator in Fig. 10b. T is a
mechanical couple and must be opposed by
introducing an opposite couple, or forces,
whose moment equals T. Thus, placing the
two forces P at the foot-bolts, T must equal
PL Now, if both the weight 11', Fig. 10a and
torque T, Fig. 10b, act at the same time,
there is on the one side the forces given by
equation (18) and on the other side by
equation (19). The latter equation represents
the pull on the foot-bolts.
All is known in equation (19) except the
value of T which is obtained from equations
(6) and (7) of Part I of this article, but
changed to inch-pounds instead of foot-
pounds and given as equations (20) and (21).
The remaining part of Fig. 10 gives the
formulae in a practical form.
The bolts connecting the stator to the base
in a vertical machine are subjected to a
shearing force instead of to a tensional force as
in a horizontal machine. This shearing force
on all the bolts combined can be calculated
by dividing equations (20) or (21) by the
radius of the bolt circle in inches.
Any movement of the stator has not been
considered, for the smallest movement would
carry the bolts beyond the elastic limit and
also the inertia of the stator would enter
and reduce the force. Furthermore, at a
failure in a horizontal machine, the foot-bolts
would be permanently elongated and loosen
one side of the stator; and in a vertical
machine the stator would move around so as
to partially shear the bolts and they would
have to be drilled out.
THE THEORY OF LUBRICATION
By L. Ubbelohde
Translated for the General Electric Review from Petroleum
By Helen R. Hosmer
Research Laboratory, General Electric Company
Part II
II. LAWS OF FRICTION IN LUBRICATED MACHINE BEARINGS
The first installment of this article appeared in the October issue and dealt with the "Fundamental
Physical Principles of Lubrication." The present installment covers the subjects of "The Laws of Friction in
Lubricated Machine Bearings" and "The Failure of Oil Testing Machines." Later installments will treat of
"Combined Oil and Graphite Lubrication" and "Investigations of the Future." — Editor.
(a) General
The process of lubrication consists of the
bringing between the moving surfaces, as
for instance between the surface of the bush-
ing and the journal, a fluid which prevents
the surfaces ■ from coming in contact, and
whose internal friction is less than the dry
friction when the surfaces are in direct con-
tact.
Petroff11, who first treated the problem
of lubricated journal bearings from the
theoretical point of view, has distinguished
between internal friction and external friction
of the lubricating material. This internal
" Petroff, Neue Theorie der Reibung. Hamburg, 1888.
friction (or viscosity) is that friction which
acts between the particles of the fluid itself.
See page 967. As external friction Petroff
designates that which exists between the
fluid on the one hand, and the two solid walls
on the other. As a matter of fact Petroff
pointed out that the external friction was
really of very little significance (that it is,
in fact, of no importance was shown on page
968). This limitation of Petroff 's has, how-
ever, not been given sufficient weight by
many of the later interpreters, so that the
conception of external friction (see formulae
12) is the real cause of the obscurity con-
THE THEORY OF LUBRICATION
1075
cerning frictional phenomena, and has led
especially to the testing of lubricating
materials by entirely false methods, as is
done in technical circles today.
It is not possible to take up these errors
in detail, but they will be mentioned in
general. In the course of time there has
grown up the following point of view, from
which indeed individual authors1'2 differ
more or less. The external friction is con-
sidered to be the property of the lubricant
through which it is able to produce a stable
and lasting layer of oil between the bearing
and the journal. The external friction should,
accordingly, prevent the oil from being
squeezed out from between the journal and
the bushing by pressure on the journal. It
would seem important, therefore, that the
oil should have as great an external friction
as possible. On the other hand, the internal
friction of the lubricant must be as small as
possible, since the internal friction must be
continually overcome during the turning of
the journal. Therefore, those oils are con-
sidered the best which have the most favorable
relation of external to internal friction, that
is, in which the external friction is large in
proportion to the internal. It is assumed that
this relation is very different for different oils,
and that they should be evaluated accord-
ingly.
It will be demonstrated below, on the
contrary, as it has been in an earlier section,
that in reality it is the internal friction of the
oil that is of importance, and all the effects
in the bearing are to be traced back to it and
to the property of capillarity, now appearing
for the first time in connection with the
problem.
For the purposes of this inquiry into the
laws of friction in lubricated machine bearings,
it is necessary to go back to the laws men-
tioned in section I-(b), page 967.
Coulomb's law for dry friction, (page 967)
and Newton's law (page 967) for fluid friction
are as different as possible. The dry friction
is independent of the velocity and propor-
tional to the total pressure P. The fluid
friction, on the other hand, is independent of
the pressure P and proportional to the
velocity. It is especially to be noted that by
constantly increasing the sliding velocity
the fluid friction approaches zero ; but the dry
friction does not, but approaches a maximum
Ha, where fj.0 is the coefficient of friction at rest.
Although in practice a lubricant is indis-
pensable the technical man ordinarily uses
without hesitation Coulomb's law, and writes
accordingly for the moment of friction
M = n-r.P (9)
where P is the journal pressure, and r the
radius of the journal, n is here designated the
coefficient of friction, but at the same time
it is not identical with the coefficient of
friction for the dry friction of the journal
material against the material of the bushing,
but must be especially determined by test
for each case.
(b) Hydrodynamic Theory
On the other hand, Petroff has shown that
the phenomena incident to bearing friction
are governed by the laws of the internal
friction of the lubricant. If it is assumed that
the lubricant clings both to the revolving
journal and to the stationary bushing (see
page 970) and that the journal rests con-
centrically in the bearing, then the velocity
in the lubricant
1-)
can be written, where U is the velocity of the
journal surface and & (presupposed to be
small and uniform) the thickness of the
lubricating layer. According to Newton's
law, the moment of friction on the journal,
if F represents the area of the inner wetted
surface of the bearing, can be expressed by
the following formula:
M = r. r,. Fj (11)
For the case where the lubricant does not
cling to the journal and bearing, but slides,
the computation gives, if Xi and X2 are the
coefficients of external friction on the journal
and bearing:
M = rr]F — (12)
Xi Xj
As a matter of fact this relation stated by
Petroff does not come into consideration,
since, as mentioned above (page 970), the
lubricant does not slide. While, therefore,
according to equation 9, the friction should
be proportional to the journal pressure P and
independent of the related specific pressure
p in the lubricant, and while according to
equation 11 it should be proportional to the
velocity U, it should, according to equation
9, so far as the coefficient of friction can be
regarded as a constant, be independent of U.
Experience shows that neither formula 9
nor formula 1 1 holds for all cases.
11 See. for instance, A. Martens. Mitteilungen aus den Kgl. techn. Versuchsanstalten Berlin 1888 Erganzungsheft III. S. 7, 8 und 23;
ferner ebenda 1900 S. 1 IT. — Post, Chem. — techn. Analyse. Braunschweig, 2. Aufl. 1S81 — Grossmann, Die Schmiermittel, Wiesbaden
1909, S. 75, 77, 78, 80, 108 — 110 und 250. Pierre Breuil, Bulletin du laboratoire d'essais du conservatoire nationale des arts et metiers,
Paris 1906. No. 6, Tome 1 (1905-06). Rupprecht. Zeitschrift fur Dampfkessel und Maschinenbetrieb 1905, No. 4 u 5; 1907 No. 48 u. 49;
1908 No. 1 u. 47; 1909 No. 9. — Benedikt-Ulzer, Analyse der Fette und Wachsarten. 5, Aufl. 1908, S. 369 ff. — Rakusin, Die Untersuchung
es Erdols, Braunschweig 1906, S. 144.
1076
GENERAL ELECTRIC REVIEW
The hydrodynamic theory of lubrication
derived by Petroff provides, however, a
general formula for the moment of friction,
which, at sufficiently great velocities, becomes
identical with equation 11, and at sufficiently
small velocities with equation 9.
U min.
Fig. 4
The statement of the theory of lubrication
of loaded bearings was not consummated at
one stroke, but is the product of a number of
students, who divided the work with the
already mentioned Petroff somewhat as
follows: In the years 1S83-4, were published
the investigations of Tower, from which it
became apparent that the laws of fluid
friction are involved in bearing friction.
In the same year (1884) was put forth simul-
taneously by three different investigators.
Lord Rayleigh, Stokes, and an unknown
third (according to Reynolds, page 160),
the fundamental differential equation for the
theory of friction. Two years later appeared
Reynold's article, "Concerning the Theory
of Lubrication and Its Application to the
Researches of Tower," in which he integrated
the above mentioned equation, but by means
of development of series, which are not at all
easy to analyse. Under the inspiration of
Striebeck's investigations (see below) ap-
peared in 1904 the work of Sommerfeld13.
who solved the integral in the finite form, and
applied the results to enclosed and half
enclosed bearings. Further, several general
laws, as for instance the existence of a transi-
tion velocity, were first stated by him.
\\ e must forego examining the derivation
of these formula; more closely, as this would
lead us far beyond the limits of this article.
The results of the theory in the form of several
curves made by Sommerfeld will be discussed.
But it must not be overlooked that the
deviation of the exact theory from the formula
of Petroff has its cause in the fact that the
journal does not lie in the center of the bear-
ing, as Petroff assumed, but deviates side-
ways according to the velocity, and this
" Sommerfeld. Ztschr. f. Mathematik u. Phys. 1904, S. 97.
displacement is greater the smaller the
velocity and the higher the pressure. This
idea of Reynold's has been further developed
by Sommerfeld.
In the following figures and formula?
U = velocity
M = moment of friction
fj. = coefficient of friction (coefficient of
friction fi is defined bv the equation
M = H r P).
P = pressure
t] = viscosity (or internal friction) of the
lubricant.
5 = difference of radii of journal and
bushings
r = radius of journal
In Fig. 6 are plotted as abscissa; the
velocities U and as ordinates the coefficients
of friction /jl. For each curve the pressure P
is constant.
The numbers on the curves are proportional
to the pressures. The viscosity 77 is the same
for all curves.
Now it is apparent that the coefficient of
friction for the velocity zero has a certain con-
stant value for all pressures, jiio (coefficient of
friction at rest //0=-)- With increasing
velocities the coefficient of friction decreases
for all pressures down to a small value, and
then rises again. The minimum value for the
coefficient of friction /ilm,„i is the same for
all the curves (line b) and amounts to about
M(m«)=0.943 /i„. It depends, therefore,
just as does the coefficient of friction, at rest,
only upon the dimensions of the bearing, is
about 6 per cent smaller than the coefficient
of friction at rest, and independent of journal
H
P mm.
Fig. 5
pressure and velocity. In certain parts of
the curve there is apparent, however, a
marked effect of pressure and velocity. The
higher the pressure, so much the greater is
the velocity at which the minimum coefficient
of friction is attained. The velocitv at which
THE THEORY OF LUBRICATION
1077
this occurs is designated as C/(m,„), and is
called the "transition velocity." The pres-
sure corresponding to the transition velocity,
P(min) (see also Fig. 5) is called the "transi-
tion pressure." The value of the transition
velocity is obtained from the following
formulas :
rr _ &"'P
15.1 r] r
7] r2
vidual curve is constant, the numbers on the
curves being proportional to the velocities.
The viscosity r/ is the same for all the curves.
It should be noted that P(min) increases at
the same rate as U, as was also indicated
by Fig. 4.
0030
U
',«,-„) = 15.1^—^- (13)
0"
The value of the transition velocity,
according to this equation, increases with
increasing journal pressure P, and with
increasing fluidity of the lubricant, that is,
with decreasing tj. Since, as is well known, the
value of r; is markedly lowered by a rise in
temperature, we can also say that the transi-
tion velocity increases with rising temper-
ature. The converse holds for the transition
pressure.
At high velocities the several curves
approach asymptoically lines passing through
the origin whose equation is:
2-K-qrU . .
M = — fp~ (14)
' For £/(m,-„) this straight line has the ordinate
2w8
0020
O.QIO
= 0.416 ix0
(15)
15.1 r
At 0.416 yUo is drawn a line c parallel to the
axis of abscissae. If the intersection of this
line with the ordinate through L'r(mi„) be
Fig. 7
(c) Comparison between the Hydrodynamic Theory
and Practical Tests
Sommerfeld has. for purposes of comparison
with the computed curves of Figs. 4 and 5,
prepared two series of experimental curves
from data in a very valuable article by R.
Striebeck14. The first series of Striebeck's15
curves has as abscissae the velocity U in
meters per second, and as ordinates the
coefficient of friction fx. The abscissae of
the second series of curves'6 are quantities
proportional to the journal pressures per
unit length; to be exact, the journal pressure
per unit of surface of the projection of the
bearing upon a plane perpendicular to the
p
journal pressure (in our symbols ^-). The
ordinates again are the coefficients of friction
ix. The numbers written upon the curves
indicate in the first figure journal pressure per
unit surface kg/cm2, in the second the number
of revolutions per minute.
It cannot be overlooked that there is a
general similarity in the forms of the theo-
retical and the observed curves. There is
indicated, for instance, the existence of
transition velocity or transition pressure, the
increase of the transition velocity, in pro-
portion to the journal pressure or the increase
of the transition pressure in proportion to
the journal velocity, and further, the fact
that the value /xlmin) is independent of the
pressure or of the velocity, as is shown by
the fact that all the curves in Figs. 4 and 5, as
well as in Figs. 6 and 7, rest upon the same
straight line. The difference in scale, as well
as the difference in journal pressures, and the
velocities of revolution, are to be expected;
" Striebeck. Die wesentlichsten Eigenschaften der Gleit und Rollenlager. Ztschr. des Vereins Deutscher Ingenieure 46. 341 1902,
abstracted in Mitteil liber, Forschungsarbeiten, Heft 7, Berlin 1903.
16 Figure 7a by Striebeck.
16 Figure 6 by Striebeck.
0.008
o.5m/sec
Fig. 6
connected with the origin of co-ordinates we
will obtain the asymptote for our curves.
In Fig. 5, the pressures P are taken as
abscissae and the coefficients of friction /j,
as ordinates. The velocitv U for each indi-
1078
GENERAL ELECTRIC REVIEW
an effect upon the form of the curve. More-
over the variation of temperature and the
resulting alteration of viscosity must be
taken into consideration. The difference
between the theoretical and practical curves
can not, however, be completely explained
by these several causes.
EXPERIMENTAL PROOF
The advocates of the view that yet other
properties of lubricants (lubricity, specific
lubricating power, external friction, layer
forming power, etc., see page 970) besides
viscosity, exert a real influence upon the
frictional resistance, can find good reason
for their belief in the failure of agreement
between the experimentally determined and
the calculated curves.
It is therefore of interest to bring forward
yet one more experimental proof. If the
statement is correct, that the only property
of the oil affecting the coefficient of friction
is the viscosity, then all oils of the same
viscosity should give the same coefficient of
friction in a given bearing. The experimental
proof of this fact may be taken from an
investigation which was undertaken prin-
cipally for other purposes.
The Marten oil testing machine for the
testing of the frictional resistance of oils in
journal bearings was used in the experiment.
This machine, like all testing machines, is
equipped for measuring the pressure, the
velocity, and the temperature. The details
of this equipment do not interest us at
present18.
On this machine were tested 24 oils of
entirely different viscosities, of different kinds
and sources, at several pressures and veloc-
ities, and at entirely different temperatures.
Besides the coefficient of friction of the
oils, there were also determined on this
Marten machine, the viscosities, at the same
temperatures which occur in bearings during
friction tests. This is necessary, since the
viscosity of oils is very markedly affected by
the temperature. All the viscosity results
are expressed as specific viscosities, not in
Engler numbers, for as mentioned above on
page 968 the Engler numbers are not pro-
portional to the viscosities, and hence could
not be used for our purposes.
The values are given in Table III, which
will now be explained.
Columns 4 to 12 contain the coefficients of
friction determined at various rotating veloc-
ities and bearing pressures on the Marten
machine. All the tests from No. 1 to No. 15
" Sommerfeld 1. c. S. 137.
ts Marten's machine and tests therewith have been described in detail in the Mitteilungen aus den Technischen Yersuchsanstakten
(now the Konigl. Material-prufungsamt) Berlin 1888 and 1889, Ergansungsheft 3 and 5. also same 1900. p. 1 ff.
but it follows from these that the curves in
Figs. 6 and 7, and those in Figs. 4 and 5,
indicated by the same numbers, are not
directly comparable with each other. (Fig. 6.)
On the other hand, it must not be over-
looked that there are important differences
between the theoretical and the observed
curves. Especially should it be noted, that
of the curves in Fig. 6 none approach a
straight line through the origin, but all bend
back a little behind the minimum, as the
velocities increase, and then rise much less
steeply. Moreover, while the ordinate of the
starting point /z0 in Fig. 4 is only about 6
per cent larger than the smallest value of
fj., in Fig. 6, the ordinate is twenty-five times
larger than the last named value. (It should
be noted that the ordinates in Fig. 6 have
been verv much shortened bv omission of a
strip between 0.012 and 0.138.)
According to the observations of Striebeck
jlio = 0.14. According to the Sommerfeld
theory it should equal — , which in normal
operation of the bearing may be less than
0.005. However, there exists a certain
qualitative agreement even in regard to this
value, for in both the theoretical and the
observed curves all start from the same point
in the axis of ordinates.
The cause of the higher range of the values
determined by Striebeck may be traced, in
the opinion of the author, in the left side of
the curves, which indicate that in all, and
especially at the lower velocities, no pure
fluid friction existed, but that on account of
faulty finish the surfaces of the journal and
bearing were in direct contact throughout,
so that dry friction also played a part, and
raised the total frictional resistance very
considerably. The theory provides for the
appearance of negative pressures17 and also
for a definite end point of the same, since at
small velocities the layer of lubricant may
become broken. The increase in this co-
efficient of friction after a period of rest of the
journal is especially large. That direct con-
tact of journal and bearing occurs can be
shown by the fact that there is electrical
connection between journal and bearing.
The higher resistance caused by this dry
friction may be diminished considerably by
mixing graphite with the oil. This method
will be considered below under the subject
of "Oildag." At high velocities, on the
other hand, disturbing resistances in the oil
layer may arise from exceeding the critical
velocity (see page 967) and this would have
THE THEORY OF LUBRICATION
1079
(column 1) were carried out at the same
temperature, that is, 75 deg C. (see column
3). The viscosity was therefore the same for
every oil (column 3) in all the tests in the
same horizontal line (that is, at all the dif-
ferent pressures and velocities).
The tests numbered 16 to 23 were made
at different temperatures, which are given in
the last horizontal line of the table. The
viscosity of each oil consequently varies in
the test recorded on the same line, and is
written in parenthesis each time under the
corresponding coefficient of friction in the
columns 4 to 12.
Several of these oils had equal viscosities:
oils 3 and 4 at the temperature of 75 deg.
for instance. In accordance with our state-
ment the coefficients of friction of these oils,
determined on the Marten machine, should be
equal. Inspection shows that this is the case
to a high degree of accuracy. We find the
same for oils 7 and 8. Moreover, those oils
whose viscosities are approximately the same
also agree very closely in the coefficients of
TABLE III
10
COEFFICIENT OF FRICTION y. ON MARTEN MACHINE
Specific
Vis-
Initial velocity in
m/sec.
Nature of Oil
0.6
1.2
2.3
at 75°t
Bearing
pressure r.
in atm.
7
18
33
7
18
33
7
18
33
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
17.8
0656
0320
0231
0820
0410
0294
1050
0591
0387
2. 'Amer. unrefined
19.9
0676
0348
0256
0849
0421
0299
1090
0570
0401
3. Gal. refined
26.6
079
0396
0276
0980
0510
0382
1440
0761
0526
4. Rum. distilled
26.6
080
0385
0264
0961
0510
0384
1575
0767
0561
5.
27.3
0782
0390
0253
0991
0530
0382
1381
0781
0573
6.
31.1
0798
0399
0271
1179
0560
0373
1451
0773
0526
7.
32.7
0851
0470
0328
1183
0630
0441
1643
0863
0641
8.
33.1
0799
042
0290
1137
0551
0440
1581
0840
0611
9. Amer. raw oil dis-
tilled to 180°
34.4
0853
0423
0296
1086
0598
0433
1590
0838
0637
10.
37.2
0798
0429
0299
1120
0621
0436
1818
0935
0650
11. |Rum. distilled
39.8
0817
0439
0319
1239
0651
0451
1778
0928
0663
12. Rum. distilled
41.1
0890
0430
0326
1231
0621
0490
1853
0961
0650
13. Rum. distilled
41.2
0910
0440
0337
1340
0602
0502
2061
1000
0653
14. ;Residue refined
49.6
0979
0499
0346
1450
0731
0559
2034
1070
0741
15. Residue refined
54.4
0890
0550
0387
1448
0790
0531
2151
1100
0823
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
16. Amer. refined
M*
0641
0331
0221
0760
0350
0240
0841
0410
0275
Z**
(11.3)
(11.1)
(10.7)
(10.7)
(9.5)
(8.4)
(7.9)
(6.8)
(6.1)
17.
0699
0351
0245
0880
0426
0273
0956
0460
0313
z
(18.5)
(18.0)
(17.3)
(17.3)
(14.9)
(12.9)
(12.4)
(10.5)
(9.3)
18.
0840
0426
0306
1139
0490
0326
1273
0598
0386
z
(33.0)
(31.6)
(30.3)
(30.3)
(26.0)
(22.0)
(20.8)
(17.3)
(14.8)
19.
IX
0876
0445
0316
1170
0550
0351
1357
0620
0393
z
(37.6)
(36.0)
(35.3)
(35.3)
(29.4)
(25.0)
(23.7)
(19.7)
(17.0)
20.
0980
0483
0333
1191
0571
0371
1390
0710
0467
z
(45.4)
(43.0)
(41.4)
(41.4)
(34.0)
(28.5)
(26.8)
(22.1)
(20.0)
21.
1230
0601
0441
1631
0763
0526
2016
0953
0608
z
(91.4)
(86.6)
(82.7)
(82.7)
(66.5)
(54.0)
(51.1)
(40.9)
(33.8)
22.
1221
0603
0451
1716
0823
0517
1901
0864
0566
z
(99.4)
(93.8)
(89.7)
(89.7)
(71.5)
(57.0)
(52.8)
(40.9)
(33.9)
23.
Wagon oil, refined. . .
M
1389
0785
0568
2128
1029
0698
2394
1140
0713
z
(150)
(140)
(132)
(132)
(102)
(82.7)
(77.6)
(62.5)
. (49.7)
Temperatures at which tes
ts No.
16-23 were made
22°
23°
24°
24°
27°
30°
31"
35°
38°
* ft = coefficient of friction on the Marten machine.
** z= specific viscosity,
t Referred to water at 0° = 1 -
1080
GENERAL ELECTRIC REVIEW
friction. As a third example may be taken oils
12 and 13 ; here again the coefficients of friction
agree very closely. The above mentioned
oils were all tested upon the machine
at the same temperature. This concordance
of values is not found where oils have equal
cozs
f
aozo
aois
0 010
0005
0000
P'
7ul
9m
p
—
lot
1st
X*
O 10 20 30 40 SO 60 70 60 90 100 I/O ISO 130 HO ISO I60IT0
-z
Fig. 8
viscosities at different temperatures. This
is noticeable if we compare oil No. 1 with oil
No. 17. The former has a viscosity of 17. S
at 75 deg. and a coefficient of friction of
0.00231 at a rotary velocity of 0.6 and a bear-
UViS
1
P*'>
'at
*
O.OIS
y
0.010
1
P°
Wi
7t
/.
A
•<
p=33at
0.005
nnoo
■
-
•
O 10 20 30 4C JO 60 70 60 90 100 110 IZO ISO 140 150
Fig. 9
ing pressure of 33 atmospheres. Oil 17 has
at 24 deg. (see last line of table) almost the
same viscosity, 17.3, and a coefficient of
friction of 0.00245. A whole series of such
examples can be taken from the table.
We may note from the table, moreover, that
with increasing viscosity the coefficient of
friction increases. If these results are plotted
in the form of a curve with viscosities as
abscissas and coefficients of friction as
ordinates, the curve will rise continuously
with increasing Z. This actually happens,
as is shown in Figs. S to 10.
In one table are brought together the tests
with the same rotary velocities. It is to be
noted that the individual tests so group
themselves that it is possible to draw con-
necting curves for all the tests which were
made with the same bearing pressure or with
the same velocity. The separate values lie
very nearly upon this intersecting curve and
the small deviations therefrom, generally not
more than 5-10 per cent, can be accounted
for by the error of the machine, which, how-
ever, is superior to most oil testing machines
in regard to accuracy. Should any particular
oil lubricate better or worse than another of
the same viscosity, then the position of its
coefficient of friction should fall quite outside
the group, and so lie markedly higher or
lower than the curve on our table. This,
however, does not occur, and consequently
the continuity of our curves proves that all
oils of the same viscosity have the same
coefficient of friction.
DEDUCTIONS CONCERNING THE
EVALUATION OF LUBRICATING
OILS
From these tests may then be drawn
correct conclusions concerning the relative
value of oils.
The oils investigated were of very different
kinds. Among them were: American, refined
and unrefined ; Galician, refined and unrefined ;
Rumanian distillate; American crude oil,
which had been distilled up to 180 deg. C.
and was therefore a residue; also other
residues, refined and unrefined. In other
words, very expensive and very cheap oils
were tested' side by side. Nevertheless, there
can be found in the table of curves no par-
ticular sort of oil which gave better results as
to the coefficient of friction than another.
It is therefore erroneous to assign to an oil
from any special region, or prepared or
refined in any special manner, very much
greater lubricating value than another, for
it is only the viscosity of the oil in which one
is interested from the purely mechanical
point of view.
Of course this statement holds without
restriction only for those cases where it is of
no importance whether the oil contains
asphalt or other material subject to decom-
position under hard usage. But the restric-
tion does not apply to by far the greatest
r»
THE THEORY OF LUBRICATION
1081
number of uses, where the oil is not raised to
a higher temperature. It is quite otherwise
for hot cylinder oils, compressors, etc. Then
the oil must be as free as possible from decom-
posable substances and so should be carefully
refined, but only because carelessly refined
oils are subject to easy decomposition and
formation of residues. Hence certain oils are,
for secondary reasons, to be preferred.
III. THE FAILURE OF OIL TESTING
MACHINES
The tests in Table III have yet another
significance which leads us to a consideration
of routine lubricant testing on the so-called
oil testing machines.
The mechanical testing of lubricants is
accomplished at present by determining on
such a machine the coefficients of friction
for any oil in question under the most diverse
conditions of pressure and velocity according
to a scheme similar to that indicated by the
tests recorded in Table III. Now my investi-
gations have shown that the coefficients of
friction are dependent upon the viscosity
of the oil alone. If, therefore, a number of
oils of different viscosities be systematically
tested, as I have done, and the coefficient
of friction corresponding to each viscosity be
determined once for all, for the particular
oil testing machine in use, then these co-
efficients of friction will apply, without
further experimentation, to all oils of the
same viscosities. Hence all coefficients of
friction on this machine could be predicted,
and the continual testing of individual oils,
which is nowadays the practice in various
testing laboratories, would be unnecessary.
The reason that this relationship has not
previously been recognized is to be found in
the fact that the viscosity and hence the
value upon which everything depends has
not been expressed in a system of units that
is proportional to the viscosity, i.e., not as
specific viscosity, but as technical units
which cannot be used in computations as
proportional to viscosity (see page 968).
Moreover, the relation of the viscosity to
the temperature has not been sufficiently well
determined.
It is safe to say that this simple relationship
has not even yet become recognized, in spite
of the thousands of tests of friction which
have been made on oil testing machines, and
although a few simple experiments would
have demonstrated the close and reasonable
connection, and in so doing proved the
superfluity of the many routine tests.
Another thing should be noted. It can be
seen from the explanation of the laws of
friction in lubricated machine bearings (for-
mulae 13 to 15) that not only the viscosity
of the lubricant, the pressure, and the velocity
affect the magnitude of the coefficient of
friction, but also the form of the bearing.
Especially important is the difference in
diameter of bushing and journal. The oil
testing machine does not take into considera-
0.02S
f
0 02C
O.O/S
O.OIO
o. oas
o.ooo
7at.
•
/
1
/
1
^p=/8ot.
,/•
1
/
fj^
/
««
'
-p=33at.
p
ao>^
/ ,
/
IO So JO to SO 60 70 SO SO /OO
— »-z
Fig. 10
tion the effect of the form of the bearing at
all. The machines which are in most general
use differ in the form of the surfaces of friction
entirely from the bearings used in practice.
Thus the Marten machine uses for ordinary
tests only three narrow studs instead of a bush-
ing. The hydrodynamic action in the bearing
is very much affected by this, and the value of
the coefficient of friction entirely changed. It
is therefore quite incorrect to apply the coeffi-
cients of friction thus obtained to actual oper-
ating conditions. The machine is for this
reason quite worthless for routine oil testing.
The usefulness of almost all the other oil
testing machines should be regarded from a
similar point of view. The machines of
Fein-Kapf19 and of Kirsch have, for instance
step bearings. Wilken 's'2" machine has only
a winged wheel which revolves in the oil
container, and the resistance of which is
measured. Dettmar's machine21 does not
operate at a constant velocity.
(To be Concluded)
" Dinglers Polyt. Journ. 1900, 608 und Ztschr. d. Vereins deutscher Ingenieure 1901, 343.
» Elektrotechn. Zeitschrift 1904, Heft 7.
H Made by Lahmeyer & Co., Frankfur|> a.M., s.a., H. Dettmar, Neue Versuche uber Lagerreibung. Dingl. Polyt. Journ. 1900, S.
1082
GENERAL ELECTRIC REVIEW
PRACTICAL EXPERIENCE IN THE OPERATION OF
ELECTRICAL MACHINERY
Part XIII (Nos. 60 to 62 inc.)
By E. C. Parham
Construction Department, General Electric Company
(60) ARMATURE THREW SOLDER
The most difficult troubles to diagnose are
those that are due to two or more causes;
especially is this likely to be true where an
irregularity, which generally produces two
or more symptoms, apparently produces only
one of those symptoms. Any condition which
will cause a continuous-current motor to
spark will cause it also to heat, even if the
heating is due directly to the sparking. Any
irregularity that will cause a non-commutating
pole motor to heat will generally cause it to
spark; but that the sparking may be insuf-
ficient to suggest the cause of the heating is
illustrated by the following instance:
A motor gave evidence of throwing solder;
since the brushes sparked and since the
armature heated excessively, overload was
suspected and the suspicion was confirmed
by applying an ammeter. The connected
load was decreased; this relieved the heating
and reduced the sparking, but the com-
mutator was evidently too rough to permit of
sparkless operation. Consequently, the com-
mutator was then turned down and this
resulted in sparkless commutation. The
motor continued to operate with apparent
satisfaction for several months. Then it
was noticed that the commutator was
gradually roughening and that the bars were
becoming pink on those areas that the brushes
did not wipe. It was then recalled that the
same pinkish tint had characterized the bars
before the commutator was turned down.
As the motor seemed to be doing its work
properly no further attention was paid to it
until there was noticed a line of solder on the
inner surfaces of the end-shield bracket arms
just in line with the armature end connec-
tions. An inspection of the connections
disclosed that they had been throwing solder.
The armature was removed for resoldering.
As the throwing of solder on the first occasion
had been attributed entirely to overload and
as the resoldering then had been done with
very soft solder, it was decided to resolder
the connections with tin solder for this would
not melt at low temperature. The hard
solder idea was not carried out, however,
because, when the armature was sent to the
lathe to have its commutator turned, it
developed that the man who did the turning
had had considerable experience in such
work and he noted at once that the mica was
high. After undercutting the mica no further
trouble was experienced.
The unusual part of the experience was
that the mica, although raised enough to
cause heating which was sufficient to melt
the solder from the end connections, failed to
produce the sparking that usually character-
izes high mica.
(61) LOAD WAS UNBALANCED
One disadvantage of operating a polyphase
motor from a service line, the phase voltages
of which are unbalanced, is that the full
load rating of the motor cannot safely be
realized. Unbalanced impressed voltages
cause unbalanced currents in the windings
of the motor; and a condition can easily be
obtained in which one winding of the motor
is heavily overloaded while the other windings
(or the other winding in the case of a quarter-
phase motor) are correspondingly under-
loaded. This unbalancing effect can be
better appreciated in connection with a
quarter-phase motor since it has only two
windings and those are parts of entirely
independent circuits. Another, and perhaps
more serious, effect of unbalanced line volt-
ages (hence of unbalanced motor currents)
is the liability of the motor to be subjected
to single-phase operation as the result of a
fuse blowing in the heavier loaded phase.
The operation of a certain quarter-phase
motor was so much hampered by frequent
blowing of its fuses that the owner reported
the trouble and asked that a man be sent to
examine it. It was stated that no particular
pair of fuses gave all the trouble; sometimes
one pair would blow, sometimes the other
pair, and sometimes both pairs. When the
inspector arrived the motor had been operat-
ing continuously for several hours and it
seemed in no way distressed.' The application
OPERATION OF ELECTRICAL MACHINERY
1083
of a voltmeter and an ammeter, however,
disclosed that both the voltages and the
currents were unbalanced. The interchang-
ing of the supply leads proved that the
unbalancing was due to the supply circuit and
not to the motor.
The cycle of conditions that was responsible
for the fuses blowing apparently without
selection was about as follows: With one
phase carrying more current than the other,
the motor would operate normally as long as
the connected load demand did not exceed
the capacity of the fuses of the overloaded
phase. At times the load demand did exceed
this capacity and then the two overloaded
fuses would blow. This would throw all of
the load onto the remaining phase, the fuses
of which would then blow. This sequence
is accountable for the apparently non-selective
blowing of the fuses. Actually, all the fuses
blew at so nearly the same time that no
positive difference in sequence could be
detected. That the motor occasionally would
run continuously for hours without blowing
a fuse was due to the fact that during such
periods the load demand never became suffi-
cient to heat the fuses to their melting point.
(62) STATOR COIL CONNECTIONS
The free speed of an induction motor
depends on the number of poles of the stator
and on the frequency of the supply circuit.
One familiar with the windings of such motors
can usually judge how many poles the stator
has by observing the appearance of the end
connections. If, however, inspection fails to
give this information conclusively, it can be
determined indirectly by measuring the free
speed of the rotor and calculating the number
of poles from this speed and the known
frequency of the circuit by means of the
formula : The number of pairs of poles equal the
frequency divided by the number of revolutions
per second. For example, if the speed were 1 200
revolutions per minute, the revolutions per
second would be 20 and, at a frequency of 40
cycles per second, the number of pairs of poles
40
would be — = 2; therefore the number of
poles would be 2X2 = 4.
The number of coils per group, that is,
the number of coils per phase per pole, can
generally be determined by inspecting the
stator winding. The insulation between
groups is heavier and, therefore, is more
prominent than the insulation between
individual coils (as a matter of fact the armor
of the coils themselves is usually sufficient
for the individual insulation). On all wind-
ings excepting those that have two coils per
group, in which case the coils will be adjacent
and their windings continuous so that their
connecting jumper may be on the under side
where it can not be seen, the number of coils
per group can be ascertained by counting the
number of short jumpers between coils: the
number of coils per group will be one greater
than the number of connecting jumpers.
If the number of slots in the stator is not
exactly divisible by the product of the number
of poles and the number of phases and the
number of coils per group, it does not neces-
sarily mean that the stator can not be con-
nected both for three-phase or for quarter-
phase operation; but if the number of stator
slots is divisible by the product of the number
of poles and the number of phases and the
number of coils per group, it does mean that
the stator can be connected both for three-
phase or for quarter-phase operation.
A quarter-phase motor which had been
heavily overloaded for a long time finally
broke down and rewinding was necessary.
Since the quarter-phase supply was even-
tually to be converted to three-phase it was
decided to rewind the stator for three-phase
service (the rotor was adaptable equally well
for both services). Examination of the dam-
aged winding showed that there were three
coils in series for each group which gave the
correct coil spread. The stator had 24 slots,
24
therefore the number of poles was ^75 = 4.
As the speed of the motor was to be kept
the same, it was necessary that the number
of poles be unchanged. Therefore, for the
three-phase winding, the number of coils per
24
group had to be =2. This grouping was
oX4
observed in the rewinding. On the quarter-
phase winding the reinforced insulations
included three coils and two short jumpers;
on the three-phase winding reinforced insula-
tion was placed between alternate coils and
included one jumper which could not be
seen because it was underneath the coils.
In this particular combination of slots,
poles, phases, and coils per group, the number
of coils included between insulations might
have been misleading to the novice, because
the insulations of the three-phase motor
included two coils while the insulations of the
quarter-phase motor included three coils, such
an appearance inviting a hasty conclusion.
1084
GENERAL ELECTRIC REVIEW
FROM THE CONSULTING ENGINEERING DEPARTMENT OF THE
GENERAL ELECTRIC COMPANY
METHODS OF OBTAINING HIGH-POTENTIAL DIRECT CURRENT
Occasions often arise where it is desirable to
obtain high-potential direct current, such as the
precipitation of smoke, the testing of long high-
voltage cables, corona investigations, etc. It is
thought that a brief review and discussion of the
various methods which are available for obtaining
such a current will be of interest.
(1) The Static or Influence Machine
This is one of the oldest electrical devices and
makes use of electrification by friction. The volt-
age which can be obtained is limited only by the
insulation of the machine, or the leakage due to
corona, and is probably in the neighborhood of
200,000 volts. The effective current is extremely
small, not more than 0.005 amperes, even in a
large machine. Owing to this limitation the machine
is of use in making tests only where the loss is very
small. The voltage wave-shape is, of course,
perfectly flat.
(2) Storage or Primary Batteries in Series
A direct current of very high voltage can be
obtained by connecting a great number of small
battery cells in series. Assuming a voltage of 2 per
cell, 50,000 cells would be required to give a potential
of 100,000 volts. Even with small cells, it would be
possible to obtain a current of as much as 5 amperes
for a short time. Storage batteries would be con-
nected in parallel groups for charging. The cost
of the apparatus, however, is so high as to make it
commercially impossible.
(3) Corona Rectifier
In this device a pulsating direct current is obtained
by the rectifying effect of a gap, across which an
alternating voltage high enough to produce corona,
is applied. The voltage available is practically
unlimited, but thus far 0.030 amperes is the greatest
current which has been obtained. It has been
found practically impossible to operate two or more
of these gaps in parallel, owing to the difficulty of
adjusting them so that the current divides uniformly,
except by the use of high series impedance. This
apparatus has never been carried further than the
experimental stage, and is hardly worth considering
for commercial use.
(4) Spark Rectifier
Rectification occurs when sparks are caused to
pass across a gap consisting of a point and plane
or point and sphere. A device of this kind has been
built in France for testing cables with direct current.
(5) The Synchronous Switch or Mechanical Rectifier
In this device the voltage wave from a high-
tension transformer is rectified by a mechanical
device which makes contact at the maximum points
of the positive and negative half cycles. Thus
intermittent pulses of direct current are obtained
once at every half cycle of the alternating current.
A current of 1 or 2 amperes can be obtained at
200,000 volts. It has been used to some extent in
Germany for testing cables (E.T.Z., October 22,
1914). An improved device of this type has been
used in which a polyphase current of a large number
of phases is rectified by mechanical means. A
moderately pulsating voltage wave can be obtained
having an average variation of about 20 per cent
from the mean.
(6) Dynamo-Static Machine
This device contains, in addition to a mechanical
rectifier similar to the one described, a means for
charging a number of condensers in parallel and then
connecting in series for discharge. This scheme
enables a moderate alternating-current voltage to be
used on the mechanical rectifier and still offers a
very high direct-current voltage. The current
capacity of the apparatus depends upon the capacity
of the condensers used, but it is necessarily much
less than that of the simple mechanical rectifier.
(7) Mercury-Arc Rectifier
This apparatus gives a moderately pulsating
voltage wave which can be smoothed out by a series
reactance. The approximate limit of a single tube
is 10 amperes at 10,000 volts. The operation of a
number of tubes in series to give very high voltages
has been suggested, but insulation difficulties have
prevented the practical carrying out of this idea.
(8) Cathode Rectifier or Kenotron
This apparatus has been developed in the
Research Laboratory of the General Electric Com-
pany, and is described in the General Electric
Review, March, 1915. It gives a pulsating direct-
current wave which can be made practically smooth
by the use of a series reactance and shunted capacity.
Thus far the maximum output for a single tube is
about 0.25 amperes at 100,000 volts. Any number
of tubes can, however, be operated in parallel.
(9) Direct-Current Generator
A moderately high-voltage direct current can
be obtained by connecting a large number of
machines in series; but not more than 5000 volts
can be obtained from a single commutator, and this
only on machines of large kilowatt capacity. The
insulation problems are difficult and the cost high
when the total voltage is greater than 15,000 or
20,000. More than 100 amperes of current can be
obtained with a wave-shape as flat as desired.
Summary
For direct-current voltages, not greater than
10,000, the mercury-arc rectifier, or the series con-
nection of direct-current generators, is probably
the most practical. For higher voltages the choice
would be between the mechanical rectifier and the
hot cathode rectifier.
Stuart Thomson
1085
QUESTION AND ANSWER SECTION
The purpose of this department of the Review is two-fold.
First, it enables all subscribers to avail themselves of the consulting service of a highly specialized
corps of engineering experts, or of such other authority as the problem may require. This service provides
for answers by mail with as little delay as possible of such questions as come within the scope of the Review.
Second, it publishes for the benefit of all Review readers questions and answers of general interest
and of educational value. When the original question deals with only one phase of an interesting subject,
the editor may feel warranted in discussing allied questions so as to provide a more complete treatment
of the whole subject.
To avoid the possibility of an incorrect or incomplete answer, the querist should be particularly careful to
include sufficient data to permit of an intelligent understanding of the situation. Address letters of inquiry to
the Editor, Question and Answer Section, General Electric Review, Schenectady, N.Y.
TRANSFORMERS: NEUTRAL FROM DELTA
CONNECTED SECONDARIES
(149) Is it possible to operate transformers in delta
if they have center secondary taps connected
to a common neutral? The object in making this
connection is to obtain two voltages from the
secondaries, i.e., 220 volts between secondary
phase wires, and 110 volts between any secondary
phase wire and the neutral.
Fig. 1 illustrates diagrammatically the scheme of
transformer connections proposed in the question.
Such a plan of connecting a neutral is impossible,
for short-circuits in the windings would result
when the middle points of the secondaries were tied
together.
Fig. l
for doing this would tie together the tap points of
the secondary windings as effectively as in Fig. 1,
and consequently the same short-circuits as de-
scribed would take place in the windings.
The second feasible scheme for obtaining two
voltages from delta-connected transformers is
shown in Fig. 3; in this case the primaries must be
delta connected. This method possesses an advan-
tage over the one shown in Fig. 2 in that the neutrals
may either be ungrounded, Fig. 3 (a), or grounded,
zeov. H
Fig. 3 (a)
Fig. 3 (b)
There are, however, two other schemes which
could be satisfactorily employed to obtain both
normal voltage and half voltage from the secondaries
of transformers connected in delta relationship.
The first is shown in Fig. 2, wherein three separate
neutrals are used, one from the center of each sec-
ondary. This using of three separate neutrals will
not cause short-circuits in the windings. It would
not be possible to ground these neutrals, however,
Fig. 3 (b). In either the ungrounded or grounded
scheme of connections, however, six phase wires are
necessary while only three are required for the
method shown in Fig. 2. Furthermore, the full
secondary winding voltage cannot be obtained
between all pairs of phase wires in the methods
shown in Figs. 3 (a) and 3 (b) ; it can only be secured
between those wires constituting three particular
pairs, viz., a-b; c-d; and e-f. E.S.
10S6
GENERAL ELECTRIC REVIEW
RAILWAY MOTOR: SHORT-CIRCUITED FIELD COILS
(150) Can supposedly defective railway motor field
coils be tested for short circuits without removing
them from the pole pieces?
We know of no method which can be applied by
a factory or repair shop to reliably determine
whether a short circuit exists in a railway motor
field coil while the coil is mounted on its pole core.
Many schemes toward this end have been tried but
they have afforded uncertain results. The principle
employed in most of these trials has been that of
measuring the resistance of the suspected coil and
comparing this value with that of a normal coil.
The information in regard to possible short circuits
as gathered from the results of such tests can by no
means be regarded as reliable, because greater
differences in resistance than would be produced by
a short-circuited turn, or few turns, can easily arise
from other causes in perfectly good coils.
So far as we know the only commercially success-
ful method of detecting short circuits in those field
coils is one in which the coil is first removed from
the motor and then placed around the core of a
special transformer which passes such a heavy
alternating flux through the coil that the heavy
current generated in a short-circuited turn, if there
is one, will cause the insulation to smoke.
The alternating current supplied to this testing
transformer can be purchased at a suitable voltage
from a lighting or power company (ordinarily rail-
way companies have no alternating-current gen-
erating apparatus) or it can easily be secured by
means of a home-made inverted rotary converter.
For constructing such a converter an old railway
motor is very adaptable. Two of the diametrically
opposite field coils (series) should be removed and
replaced with shunt coils; and two slip rings should
be mounted on the end of the armature that is
far from the commutator. These slip rings are to be
connected to two diametrically opposite taps made
to the end connections of the armature (similar to
the connections employed in a single-phase rotary
converter). Power for the converter can then be
supplied from a trolley circuit, and the machine will
be enabled to furnish alternating current to the
transformer from the slip rings.
The transformer, though necessarily of special
design, can easily be constructed in a repair shop.
It merely consists of a primary exciting coil and a
split core which can be opened up to pass through the
railway motor field coil that is to be tested and then
closed upon it. While the coil is being tested it
should be under rrechanical pressure, the same as
when clamped in the motor.
The field coil will then act as the secondary of the
transformer (the induced alternating voltage in the
coil need not exceed three or four volts per turn);
and if the insulation on the coil is in good condition
no visual evidence of action within the coil will be
observable, but if any turns are short-circuited the
insulation will soon begin to smoke.
H.L.A.
KW, APPARENT KV-A., WATTLESS KV-A..
P-F.: RELATIONSHIP
(151) It possible please show by a curve the relations
between the equivalent values of apparent power,
actual power, and wattless power at various power-
factors.
It would be impractical, perhaps impossible, to
represent the desired relationships by a single curve.
However, by using one curve for each power-factor
the very clear and useful curve sheet shown on
page 1087 can be constructed.
The theoretical construction of the chart is based
upon the fundamental and familiar vector right-
triangle of which the hypotenuse represents the
apparent power (apparent kv-a.), one leg the true
power (kw.), the other leg the wattless "power"
(wattless kv-a.), and the cosine of the angle between
the true power leg and the apparent power hypot-
enuse the power-factor.
The reproduction of the chart on page 1087 is of
a size that will prove to be directly useful. If it is
desired, however, to construct the chart in a different
size, the following geometric directions will be found
to be simple and absolutely accurate.
(1) Lay off 10 equal divisions on the horizontal
axis.
(2) Lay off 16 divisions on the vertical axis of
the same length as those on the horizontal axis.
(3) With the origin as center describe an arc
which will cut the horizontal and vertical axes at
the tenth division.
(4) At the 9.5, 9, 8.5, and 5-point divi-
sions on the horizontal axis erect perpendiculars to
intercept the 10-unit radius arc named in (3).
(5) From the intersections of these perpen-
diculars with the arc draw straight lines to the
origin and label these, which are per cent power-
factor, 95, 90, 85, and 50.
(6) Divide the distances 5 to 6, 6 to 7,
and 9 to 10 on the horizontal axis into 10 equal
divisions each. Without actually drawing in the
perpendiculars erected on the horizontal axis at
these points, mark the points on the 10-unit radius
arc which would be the intersections of that circle
and these perpendiculars if they were drawn.
(7) Describe the remaining arcs for apparent
power using the distances from the origin to the
divisions on the horizontal axis as radii.
It is particularly worthy of note that the chart
when constructed as described is applicable over a
limitless range of true power, apparent power, and
wattless "power." This feature is secured by laying
out all the scales (except that for power-factor
which is a ratio) as multiples of 10. The scales
that are given enable accurate readings to be taken
from half a watt to 10,000 kilowatts. By shifting
the decimal point uniformly on all the scales (except
that for the power-factor which is to be held un-
changed) readings may be taken on either side of
the range just quoted if the necessity should arise.
The chart is so simple that a description of the
method of applying it will be unnecessary.
E.C.S.
QUESTIONS AND ANSWERS
1087
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True Power- (Waits or M'/owotts)
GENERAL ELECTRIC REVIEW
~3
The Trade Mark, oi3 the Largest Eleetpical Aanufac-tupep in The Wopld.
Sales Offices
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tric Review. To insure correspondence against avoidable delay, all communica-
tions to the Company should be addressed to the sales office nearest the writer.
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Boston, Mass., 84 State Street
Buffalo, N. Y.. Electric Building
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Cincinnati, Ohio, Provident Bank Building
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For Michigan business refer to General Electric Company
of Michigan
Detroit. Mich., Dime Savings Bank Bldg.
For Texas. Oklohama and Arizona business refer to South-
west General Electric Company (formerly Hobson
Electric Co.)
Dallas, Texas, 1701 No. Market Street
Houston, Texas. Third and Washington Streets
El Paso, Texas, 500 San Francisco Street
Oklahoma City, Okla., Insurance Building
For Hawaiian business address
Catton Neill & Company, Ltd., Honolulu
For all Canadian business refer to
Canadian General Electric Company, Ltd., Toronto,
Ont.
For business in Great Britain refer to
British Thomson-Houston Company, Ltd., Rugby, Eng.
FOREIGN OFFICES OR REPRESENTATIVES:
Argentina: Cia. General Electric Sudamericana, Inc., Buenos Aires; Australia: Australian General Electric Co., Sydney and
Melbourne; Brazil: Companhia General Electric do Brazil, Rio de Janeiro; Central America: G. Amsinck & Co., New York,
U. S. A.; Chile: International Machinery Co., Santiago, and Nitrate Agencies, Ltd., Iquique; China; Andersen, Meyer &
Co., Shanghai; Colombia: Wesselhoeft & Wisner, Barranquilla; Cuba: Zaldo & Martinez, Havana; England: General Electric
Co. (of New York), London; India: General Electric Co. (of New York), Calcutta; Japan and Korea: General Electric Co.
and B agnail & Hilles, Yokohama; Mitsui Bussan Kaisha, Ltd., Tokyo and Seoul; Mexico: Mexican General Electric Co.,
Mexico City; New Zealand: The National Electrical & Engineering Co.. Ltd.. Wellington, Christchurch, Dunedin and Auck-
land; Peru: W. R. Grace & Co.. Lima; Philippine Islands: Frank L. Strong Machinery Co., Manila; South. Africa : South
African General Electric Co.. Johannesburg, Capetown and Durban.
General Electric Company
General Office: Schenectady, N. Y.
Member of the Society for Electrical Development, Inc.
"DO IT ELECTRICALLY"
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' .
ID
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(c
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General Electric Review
Manager, M. P. RICE
A MONTHLY MAGAZINE FOR ENGINEERS
Editor, JOHN R. HEWETT
Associate Editor, B. M. EOFF
Assistant Editor. E. C. SANDERS
Subscription Rates: United States and Mexico, $2.00 per year; Canada, $2.25 per year; Foreign, $2.50 per year; payable in
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Schenectady, N. Y.
Entered as second-class matter, March 26, 1912, at the post-office at Schenectady, N. Y-, under the Act of March, 1879.
VOL. XVIII., No.
Copyright, 1915
by General Electric Company
December, 1915
By Jesse W. Lilienthal
By W. L. R Emmet
By W. B. Curtiss
CONTENTS
Frontispiece, W. L. R. Emmet
Editorial : The Paths of Progress
Welfare Work
Engineering in the Navy
Depreciation of Property
A Model X-Ray Dark Room
By Wheeler P. Davey
The Production of Damped Oscillations ....
By Leslie O. Heath
The Theory of Lubrication, Part III
By L. Ubbelohde
Translated from Petroleum by Helen R. Hosmer
A Modern Acid-Dipping, Electroplating and Japanning Plant ....
By Horace Niles Trumbull
Protection of Railway Signal Circuits Against Lightning Disturbances
By E. K. Shelton
Growth of Current in Circuits of Negative Temperature Coefficient of Resistance
By F. W. Lyle
Electrically Heated Enameling Ovens .
By C. W. Bartlett
The Electric Motor in the Printing Industry
By W. C. Yates
The Possibilities Open to the Central Station in Solving the Freight Terminal Problem
By Jas. A. Jackson
Portable Searchlights for Fire Departments ...
By L. C. Porter and P. S. Bailey
Practical Experience in the Operation of Electrical Machinery, Part XIV
Crossed Resistance Wires; Motor Reversed; Elevator Trouble.
By E. C. Parham
Theory of Electric Waves in Transmission Lines
By J. M. Weed
The First 3000- Volt Locomotive for the Chicago, Milwaukee & St. Paul Railway Company
By E. S. Johnson
The Kinetic Theory of Gases. Part III
By Dr. Saul Dushman
Question and Answer Section
In Memoriam: George Crellin Cartwright
From the Consulting Engineering Department of the General Electric Company
Page
1090
1091
1092
1097
1099
1107
1110
1118
1121
1127
1129
1130
11 30
1142
1144
1140
1148
1154
1159
1168
1170
1171
W. L. R. EMMET
Recently Appointed a Member of the U. S. Naval Consulting Board
A^short article by Mr. Emmet on Engineering in the Navy is published in this issue
Ulf
— 1,
-H
FTT*
THE PATHS OF PROGRESS
We publish in this issue a short article by
Mr. W. L. R. Emmet, who has recently been
appointed to serve on the U.S. Naval Consult-
ing Board; in our last issue we published
an article by Dr. W. R. Whitney, who has had
the same honor conferred upon him.
The appointment of these and many other
prominent men to a Board where their
services and experiences will always be at
the command of the government will, we
hope, only be a first step in organizing
the technical and scientific knowledge of
the country for its permanent good. The
method adopted for selecting the most
suitable men to be the recipients of this
signal honor is to be highly commended, as
leaving their selection in the hands of the
various responsible and representative scien-
tific and technical bodies avoids the possi-
bilities of political influences, which, if they
entered into such selections, would defeat
the object sought.
The existence of such a board will supply
an imperative need if government work is
at all times to be kept up to the usually
high standard of commercial work, as by the
very nature of things government employees
cannot keep constantly informed on all
phases of commercial developments and
commercial developments are likely to always
lead every other field of activities.
Any department of the government that
can secure the best talent available in every
branch of its work will be immeasurably
stronger than when entirely dependent on
its own resources.
With this good beginning in one depart-
ment is it too much to hope that this same
general idea will expand till the scientific
and engineering talent of the whole country
will be organized in such a manner that
it will be available to every department
of the Federal Government, and perhaps,
in part, to the several State governments?
Such a development might lead to the estab-
lishment of what would, in effect, become a
National Privy Council of Scientists and
Engineers.
The advice and experience of such a council
would always be available to help in the
framing of technical laws and regulations and
would, we believe, largely reduce opposition,
and, indeed, the cause of much opposition,
to many phases of the government regulation
of industries.
It would surely have been of great service
if some such properly constituted body of
technically trained men had been available
to co-operate in the preparation of the
proposed Code of Safety Rules for Electrical
Practice as is being prepared by the National
Bureau of Standards.
We believe that if such a Council were
established it would be a potent factor in
raising the engineering profession to the
plane where it properly belongs and in
putting the status of the Engineer on an
entirely different basis. In addition to other
advantages it might well lead to establishing
more harmonious relationships between indus-
trial and commercial concerns and the gov-
ernmental departments that are responsible
for their regulation.
1092
GENERAL ELECTRIC REVIEW
WELFARE WORK
By Jesse W. Liliexthal
President of the United Railroads, San Francisco. Cal.
This quite remarkable address was read before the thirty-fourth annual convention of the American
Electric Railway Association. It is based on actual experience and deals with "Welfare Work" in its very
broadest phases: we feel that it will be read not only with interest, but with much profit by a large number of
our readers. The author's "code of commandments" to govern the public utilities of which he is president is
well worthv of a close studv. — Editor.
The subject of this paper was not of my
own selection, so that I am not certain to
have understood it in the sense in which it
was intended. It may have been meant to
have reference to what an employer does for
his employees or to what the utility does for
the public at large, or both. I shall assume
in its treatment that welfare work for any is
for the welfare for all. I am not sure that you
will all concede the point, but it represents
my own profound conviction, not shaken by
some conflicting experiences, that it will be
the purpose of this address to narrate.
When at college I submitted to my pro-
fessors for their approval as the title for a
proposed Commencement Day oration the
subject "Revealed. Abstract and Legislative
Morality." I was assured that if I could do
justice to the theme the oration would be a
notable one. If I ever had any doubt as to
the soundness of their comment, that doubt
has been removed since I have assumed the
presidency of a public utility. In other words,
we have three possible standards of morality,
namely, the one that is supposed to have been
announced to us by an all-wise and all-
knowing Supreme Being, the very conception
of whom implies infallibility and beneficence.
Then we have an abstract morality, that is to
saw the one that, irrespective of any dictates
on high, is prescribed to us by our own
individual inner consciousness and by the
stress of actual personal experience. And
finally we have a legislative morality, that
is to say, the one that our law-givers prescribe
from year to year, with appropriate sanctions,
in congress, state legislatures and city coun-
cils. That certainly makes morality an un-
certain entity. The right and wrong of
things, therefore, must as a practical ques-
tion be a fluctuating quantity, depending
upon the particular faith or standard of the
one assuming to judge or the law which he
deems controlling.
I have learned that in a similar way and
very generally for similar reasons public
welfare is a varying quantity and very often
an elusive quantity. For one thing, public
welfare may mean what is actually for the
public weal or it may mean what the public
believes to be for its own welfare. And it
may mean one thing at one time and another
thing at another time, or one thing in one
place and another thing at a different place.
So it may be, as it has now become the
fashion to proclaim, that what is best for the
public is best for the utility. But even with
this conceded, we shall still find ourselves
always brought back to the question of what
is really best for the public. It sounds
Machiavellian to declare that for all practical
purposes that should be assumed to be for
the public's greatest good which for the
moment it deems to be for its greatest good.
It may be that something of this sort was in
the mind of President Wilson when, during
his campaign for the presidency, having been
charged with inconsistency on the subject of
the initiative and referendum, he is reported
to have justified himself by saying, in sub-
stance: "I was able to demonstrate to my
pupils at Princeton that the initiative and
referendum would not work, and I can
demonstrate to you now that the initiative
and referendum will not work; but they do
work." That is to say, it may be that there
was nothing more in his mind in making
that statement than that there was growing
such an insistent demand on the part of the
people for the right, without the inter-
position of any representative body, to them-
selves make and repeal laws that we should
give them the chance to learn from actual
experience that the thing would not work.
However, I do not wish to leave this
incident without conceding that, our presi-
dent being a man of conscience, it may very
well be that he was finally "persuaded that
representative government has proven a
failure.
At all events, to the man of conscience,
with no ambition other than to do the best
by his fellow men of which he is capable,
t here is something repugnant about a doctrine
that requires the people to feel the rough
places before they are permitted to reach the
WELFARE WORK
1093
stars ; that the child must be allowed to burn
its fingers so that it may understand the
importance of shunning fire.
In this man of conscience the feeling is
strong that he wishes to guide the people
into the right path; that it is not necessary
that they must first stumble and fall and
bruise themselves before they can find the
right path. I know from my own experience
that we are not all agreed as to this and that
in truth this is a very practical question that
those of us charged with the duty of managing
public utilities ought to endeavor to solve
correctly, because I believe that on its correct
solution depends the success of our manage-
ment— depends the right standing before the
bar of public opinion. We certainly cannot
succeed with the public if there be any ques-
tion in its mind of our absolute good faith,
whatever the merit or lack of it, in the things
that we offer to it.
One of the things making up the so-called
public welfare program of the United Rail-
roads was the establishment of a monthly
magazine, distributed to each of its 3500
employees, as a means of communication
between the men and the company. I con-
tribute in each number a short talk to the
men over my signature as president. A little
while ago I received a very bright, well
written letter from the wife of a motorman,
in which, among other things, she said that
she judged from my articles that I often felt
"lonesome." I have been taking a long time
to weigh that statement. I may not yet have
caught her meaning. Was it that, notwith-
standing the earnest effort made to pro-
pitiate the public, it had turned the cold
shoulder? And yet we have been doing those
things that were intrinsically right under
every code of morals and that also appeared
to be the things demanded by the existing
state of public sentiment. It also happened
that a very brilliant journalist, who had
read one or more of these messages to the
men which were intended to remind them of
our duty to the public and of what we were
doing in the performance of that duty, in one
of which I asked why we had apparently not
overcome the popular ill will towards us,
said that I was striking a false note. I was
told that I was furnishing excellent gun
wadding for the fertile agitator ; that I should
not lose sight of the fact that the company,
whether willingly or unwillingly, was a prize
participant in a rising economic battle; that
armed peace was the best we could hope for;
that the only way to make popular what was
undoubtedly an unpopular corporation was
to grant to employees all that they wanted
and whenever they wanted" it; to do the same
thing for the city for the benefit of its com-
peting municipal lines; to surrender to the
jitney for love of the little fellow; to extend
service whenever asked for; to equip and
operate regardless of expense and to reduce
fares to the Cleveland basis.
I am still smarting under that criticism.
This doing your duty by the public costs
money, and if it breed resentment rather than
good will, or even if it only fail to eliminate
existing ill will, had not the expense better
be withheld? I am speaking from actual
experience, and you are entitled to the benefit
of whatever lesson it inculcates. I do not
forget the exceptional circumstances under
which our particular utility is operating.
We have a successful and growing municipally
owned and operated system, all of it com-
petitive to our own, and consequently our
company is constantly a thorn in the city's
side. They pay wages and provide conditions
that we cannot afford, and this makes it
necessary for us to take the ordinarily inde-
fensible position of preventing, while we can,
the organization of our men. This in turn
makes us anathema with organized labor and
its sympathizers. Then the public accepts
it as an undoubted fact that we have secured
valuable franchises through the bribery of
public officials, and the press does not allow
it to forget that the so-called graft prose-
cution failed to secure more than one con-
viction. It is with this state of the public
mind that our company has had to deal.
I accepted the presidency of the United
Railroads only because I thought that I saw
an opportunity to render public service. The
years were advancing, so that it seemed my
last opportunity, if any, to do so. I meant
to start right with the public, and to that end
began my administration with a formal
statement — a sort of confession of faith — in
which I made the acknowledgment that I
conceived it to be the primary duty of a
public utility to serve the public adequately
and considerately. I pledged the company to
scrupulously keep out of politics and promised
that, if an attempt were ever made to influence
public opinion, it would be done openly and
in the name of the company. I declared it as
my only motive for taking office that I was
ambitious to improve the relations between
the people and the company and invited the
frankest criticism and the most cordial co-
operation on the part of the public to that
1094
GENERAL ELECTRIC REVIEW
end. Finally, in recognition of the strong
sentiment in favor of municipal ownership
that had been very markedly manifested in
a recent election held to provide money for
the extension of the city lines, I declared
that I had no fault to find with the advocates
of municipal ownership even of street car
lines, but believed that if such ownership
should obtain the properties themselves
could be operated with the greatest good and
with the largest profit to the public if en-
trusted to private management under public
regulation.
Then, with the desire to treat the employees
as generously as the revenues of the company
would permit and at least as well as they
would be treated by impartial arbitrators in
case of an organization, demands made and
refused and a strike threatened, we volun-
tarily granted a substantial increase of wages.
Let it be remembered that the men were not
organized and the increase was granted with-
out any compulsion whatsoever. We devised
a plan for insuring the lives of all employees
in our service for a period of three years and
upwards, without any physical examination
on behalf of the insurance company and with-
out any cost to the men for premium or other-
wise ; the families of the three-year men getting
$250 in case of death in the service, of the
four-year men $500, and of those having
served five years or upwards $1000. Each
employee was allowed to select his own
beneficiary arbitrarily. This insurance was
giving to the men something that many of
them, quite apart from the expense of
insurance, could not give themselves. The
men with tuberculosis, with cancer, with
B right's disease or with a weak heart was
insured along with those who were organically
sound. And this was better than an increase
of wages, as to which there is no assurance
that any of it would be husbanded.
Then, realizing as a paramount duty that
as far as possible we must stop killing and
maiming people and that to accomplish this
we must depend on the vigilance, the loyalty
and intelligence of the platform men, we said
that, taking the sum paid in the previous
year by way of damages for injury to persons
or property as a basis, we proposed to give
the entire amount that might be saved over
this sum in succeeding years to these platform
men in the exact proportion represented by
the time contributed by them respectively
to the service
Finally it appeared upon investigation that
many of our employees had gotten into the
hands of loan sharks and were paying as high
as ten per cent a month for the loans which
they had obtained. Many of these were men
with the best of records, with excellent
characters, but who through stress of cir-
cumstances, sickness in the family, financial
distress of those having claims upon them, or
otherwise, had found their wages inadequate
for this abnormal condition and had nothing
to take to the pawnbroker or remedial loan
association as collateral. We say to these:
"We will lend you the money that you need,
without any security, taking from you simply
your own promissory notes, payable in such
installments as you may yourself determine
to be practicable, considering other demands
upon you, and bearing interest at the rate
of five per cent per annum." Our files are
full of grateful acknowledgment for what we
have done in this direction, testifying elo-
quently to the good that has been accom-
plished.
When this program was announced we felt
that the new management was keeping faith
and looked for grateful response on the part
of the public. There was a good deal of
commendation, to be sure, but I am not
certain that the true sentiment of the people
at large was not voiced by a prominent and
influential local newspaper, which said edito-
rially in double-leaded type : "The Street Car
Workers are Men; They are Not Children to
be Coddled. President Lilienthal and his
directorate should have heard what Lincoln
Steffens and Austin Lewis told the New Era
Club about welfare work the other day.
Welfare work: The United Railroads might
as well save its time and money. 'The only
way to help labor,' said Lincoln Steffens, 'is
to help labor to help itself.' " In other words,
employees want nothing from employers
that they do not demand and demand in a
position where they can enforce their demands.
I have always believed in labor unions.
Perhaps I do not believe in them as much as I
used to. It is of course an indefensible
position to maintain that employees shall not
be permitted to organize. Even advocates
of the open shop stop short of that. But
sometimes, and, as already said, such is the
situation in San Francisco, it is a condition
and not a theory that confronts you. Organ-
ization of the men of the United Railroads
would mean inevitably and logically a demand
for the same wages, hours and other con-
ditions that are conceded by the municipal
lines, under the terms of the city charter, to
men working on a track literally alongside
WELFARE WORK
1 1 1!).")
of our own. A demand would mean a refusal,
because the company cannot concede the
demand, and a refusal would mean a strike,
which would be a calamity for the company,
the public and the men. We have therefore
been placed in the incongruous position of
having to discharge men whose only fault
may have consisted in joining the union,
because the alternative was inevitable dis-
aster.
I have of course had the experience that
all of you have had and that may have
hardened some of you — that it is not enough
to be good 364 days in the year; you must be
good the whole 365 and you must be good
in the sense that the public chooses to use
the term; that is to say, you must do the
things that the public wants you to do and
refrain from doing those things to which it
objects. We have tried, in the interest of
peace and good feeling, to meet that view too.
I said at the outset of my administration that
I would always grant to the city anything that
it wished, but that I had no right to forget
that, just as officials of the city were trustees
of the people, I was a trustee for the creditors
and stockholders of the company and there-
fore must exact a reasonable equivalent for
any property rights surrendered. We dis-
covered in a recent experience that we had
been sowing the wind. Such an equivalent
for a right proposed to be surrendered was
recently asked by the company and promptly
conceded by the Board of Supervisors. Their
ordinance, however, carrying out the terms
of the agreement was vetoed by the Mayor,
a majority but not a sufficient number of the
supervisors voting to override the veto, and
the right in question was exercised without
giving the equivalent. Upon an appeal to
the courts the company's motion for an
injunction to restrain the exercise of the right
was granted. Unfortunately, however, this
has proven to be a case of being good only
364 days in the year, and apparently in
consequence of our legal victory the company
is once more under the ban of excommunica-
tion, and the injunction, at this time of
writing, is being violated, and boastingly
violated, forcing the company to contempt
proceedings.
What moral shall we deduce from all this?
What is the public welfare ? And what should
be the course of conduct of a public utility?
It is of course axiomatic that in things done
or omitted the presumption is in favor of a
popular public utility, assuming that any
such exists, and against the unpopular public
utility. When the latter takes a step for-
ward in a matter that should win popular
approval it is apt to be charged with moving
from fear and not from public spirit or the
desire for public welfare. And the usual
result or absence of result follows where an
act, even though undoubtedly praiseworthy
on its face and in itself and done from a
proper motive, is said to have been done under
compulsion, that is to say, from fear. Is that
a reason for not making the effort to propitiate
the public? Shall you refrain from taking
this step forward because your motive in so
doing may be impugned?
I realize that this paper is taking on a very
personal aspect, but I apprehend that these
conventions derive at least some of their value
from the exchange of personal experiences.
Nothing seems to drive home like actual
occurrences. Should we not look upon these
gatherings somewhat like revival meetings,
where in response to the exhortations of the
Billy Sundays we are impelled to take the
platform and speak of the things of which
we know, because they have happened to us?
That, at all events, must be my excuse. And
this is my story. When I was offered the
presidency of the United Railroads, I had
come to a time and condition of life where I
had no financial, political or social ambitions.
In dealing with the public, therefore, I at
least as an individual have been in an excep-
tionally favorable position, because there
have been no conflicting motives — none at
least except possibly in having the one
ambition to deserve and obtain the esteem of
my fellow-men. And with this purpose and
no other I have laid down for myself the
following code of commandments to govern
in the conduct of the public utility that has
been entrusted to my management :
1 . Accept loyally and without reservation
the now universally proclaimed doctrine that
a public utility is the servant of the people.
Our courts of last resort have so declared,
and the public utilities have bowed their
heads in meek submission. Whatever the
resources or lack of resources of the utility,
we acknowledge that we must render ade-
quate service The requisite capital must
somehow be provided, the matter of adequate
return being irrelevant, except in the sense
that the right exists to appeal to the rate-
making bodies to provide for reasonable
compensation for the service rendered. This
requirement of adequate service existing, let
us not wait until pressure is brought to compel
this service. Anticipate the public demand.
1096
GENERAL ELECTRIC REVIEW
Keep your door wide open to every complaint,
so that you may not overlook the existence of
such a demand. Forestall criticism by
inviting recommendations, and in all close
cases give the public the benefit of the doubt .
2. Give the affairs of the utility the widest
publicity. The public is entitled to know
what you are doing and how you are getting
on. Conditions may be unfavorable, and you
may fear that publicity might affect your
credit, but you should not ask for credit that
you do not deserve, and perhaps your mis-
fortunes, when frankly told, may beget the
public sympathy and good will which you so
sorely need. I never knew anything so engag-
ing as complete candor, and I shall not
quarrel with the saying of the late Mr.
Hawley that honesty is the best policy, even
though he bade us accent on the word
"policy." When I have been interviewed
by the reporter of a newspaper however
unfriendly I have answered every question
directly and fully, and it has happened to
me at least once that when such candor has
not changed the tone of the unfriendly
newspaper the reporter has insisted that this
attitude be changed or that someone else
be assigned to his task. I have gone to men
who have assailed me and sought to explain
to them my reasons for doing the things that
they have criticized, and this has sometimes
led to a change of front or, as in the case of
at least one newspaper editor, to a statement
that my position was justified, but that in
order that his newspaper should hold its
circulation it must continue to print the news
in the form which his patrons expected. The
abuse of the power of the press, however,
involves a discussion that is foreign to my
subject, and I shall keep away from it.
3. Treat your employees fairly and, as
far as your resources will permit, generously.
I believe that the man who is well fed and
well clothed, who has a reasonable amount
of time for play and recreation, who is in a
position to save a little for a rainy day or
towards the owning of his own home, who
feels that the doors of his superiors are always
open to receive suggestions or to redress real
or imaginary grievances, who is not exposed
to nagging and hectoring by officious subal-
tern officers, who is given the right of appeal,
who is made to feel that all of the employees
of the company, from the president down, are
members of one family, each having the same
paramount duty to serve the public and the
employer, will give the best results, and there-
fore this is the ideal to be attained or at least
approximated as closely as conditions will
permit.
It might be well, in furtherance of this
idea, to have a council, composed of represen-
tatives of the men and the chief executive
officers of the company, meet, say, once a
month to consider measures for the improve-
ment of the service and in the interest of
efficiency. The representatives of the men
should, I think, be selected by secret ballot —
one, say, from each barn, where the utility
is a street railroad company — the man
receiving the largest number of votes to be
the representative of that barn for the time
being. In that way the most popular man
would be chosen and through him all the
employees of that barn would feel that they
had a mouthpiece. A new election should
perhaps be held every six months or year.
This will at least furnish a sort of safety valve
without providing much, if any, of a nucleus
for agitation or organization.
4. Keep out of politics. I realize how
great the temptation is to do just the con-
trary. The public utility is the target for
the politician. That one of them who is not
venally dishonest has, at least in recent years,
found that attacks made upon it is the short
cut to popularity. That one who is venal has
found the strike bill the most lucrative source
of revenue. It has seemed necessary to go
into politics to keep such men out of office,
and where the only purpose of the utility in
so doing has been to eliminate such as these
the motive is of course ethically justifiable.
But we all know to what abuses this has led.
The utility, to effectually accomplish prac-
tical results, has had to build up a political
machine, and then having through this
machine acquired the power not only to
defeat injustice, to stifle bad bills and prevent
biased judgments, the temptation to use that
power for affirmative selfish ends generally
proves irresistible. Then the people feel
themselves throttled, and they are driven to
rebel and are themselves then led into excesses
by the desire for revenge, and it is from these
excesses that we are now suffering.
5. The alternative remedy involves the
next commandment — the appeal to the public
for fairness and justice. Deem it your right
and duty to influence public opinion. Com-
plain of the wrongs that are done to you.
Expose the methods of corrupt or unfair
politicians. Combat the arguments of muck-
rakers and pseudo-reformers. Never allow
an untrue charge to remain unchallenged.
Circularize the public. Buy space in the
ENGINEERING IN THE NAVY
1097
newspapers. Participate in public discussions.
But above all remember that whenever you
do anything along these lines you must do it
openly and in the name of the company.
Do not hide behind reading notices. Do not
have paid agents masquerading as inde-
pendent gladiators. Let it be your fight, con-
ducted in your name, as an appeal to the
justice and reason of the people and based
upon the trustworthy assumption that, ap-
proached in the right way, with patient and
constant endeavor that appeal will ultimately
not prove in vain.
I realize that I am proposing to you noth-
ing that has not been suggested before in a
form much more attractive and convincing
than I have been able to give. But at least
you have the picture of an actual personal
experience acquired under circumstances of
special interest, the recital of which may
teach something and inspire some course of
action that I trust may prove of some prac-
tical value. I do not mean to be sacrilegious
or visionary when I quote from the Scriptures
in saying that "I do set my bow in the
clouds." I place my confidence in the ulti-
mate good sense and fairness of the people.
Our salvation must be worked out through
them, because after all, under our system of
government, the power to deal with us in the
last analysis rests in them, and we shall not
have won our battle until we make the people
feel that w - re doing our duty by them.
We must De politic enough to recognize our
masters and public-spirited enough to be
willing to make every effort to deserve the
good will of the people.
The task will not be so difficult, if, as we
should, we cultivate a frame of mind that
makes this a labor of love.
ENGINEERING IN THE NAVY
By W. L. R. Emmet
Consulting Engineer, General Electric Company
This article is of special interest as coming from the pen of one who has just been appointed to the V. S.
Naval Consulting Board at a time when so much attention is being focused on "preparedness." The author
shows some of the difficulties that those responsible for government work have to put up with; the sum total
of these difficulties is usually labelled "red tape." — Editor.
While the navy has accomplished much in
the direction of constructive engineering,
most engineers and manufacturers who have
been connected with naval work have felt
that they labored under great difficulties and
have desired some change of practice or
organization which might render such efforts
more effective and more expeditious.
New developments in engineering generally
entail much labor and expense, even where
the objects are very simple. There is scope
for much thought in every construction if it
is to be brought to a state of ideal fitness, and
much experience has shown that new things
do not pay unless they are done with great
care and thoroughness.
The navy is in constant need of inventive
development and much of its need relates to
things which have no appropriate application
outside of the navy itself. Improvements for
the navy must come from within or from
outside sources. If they are to come from
within the navy itself, means must be pro-
vided for the necessary expenditure of time,
study, experimentation, and construction,
and if they are to come from outside, incen-
tives must be affoided to those who have the
facilities for doing such work. It would seem
that the present conditions do not fully meet
either of these requirements. Some conditions
may be suggested as possible reasons for these
difficulties.
The first of these is the lack of authority
and scope for continued effort afforded to
engineers in the navy. Few officers other than
the naval constructors are permanently
engaged in engineering work and few are so
detailed as to be able to devote themselves
to one thing long enough to establish the
influence and grasp of conditions necessary
in the putting through of difficult under-
takings. Executive and financial men in or out
of the navy can seldom form sound judgment
about engineering matters, particularly new
ones, and engineers must be trusted and given
ample authority in connection with such
undertakings if the best progress is to be
expected. In private industries, certain well
tried men are so trusted after experience has
shown that their judgment is dependable.
The navy system does not tend to sufficiently
establish the influence of such men. There
109S
GENERAL ELECTRIC REVIEW
are many bright men, but it would seem that
they lack scope for effective continuous effort.
Another difficulty is that the law and the
vearly acts of Congress only allow certain
specific expenditures, and it is hard to get
money from Congress for activities which
cannot be made to appear attractive to lay-
men in a paragraph of an appropriation bill.
The navy should be organized to do research
and development work as great corporations
do it, funds should be provided for it, and
at least a few men of the highest type should
be kept on it without frequent and unneces-
sary changes of duty.
If the navy desires to render the study of
its problems attractive to private manu-
facturers, it must modify the system of price
competition upon which it now operates and
must do as great private purchasers of
machinery do, that is, it must have expert
men in positions of influence and authority
who can be trusted to purchase for reasons
other than price, and whose positions are such
that their good faith can be depended upon
not only by the government but by those
who do work for the navy. The great differ-
ence which generally distinguishes private
business from public is that the former is
largely governed and expedited by individual
trust and judgment of character, while the
latter is governed mainly by law and formula;
but while this limitation of government
business is common, it is not invariable and
there seems to be no good reason why the
navy should not be, to a great extent, relieved
from a condition which interferes so seriously
with constructive activities in engineering
lines.
It would be interesting to know whether
such men, for example, as Sir William White
have not enjoyed in foreign navies a scope
and permanence of engineering authority
which is superior to that afforded to the many
fine engineers who have served our navy.
It would seem that the accomplishment of
such objects as are here suggested would
necessitate some change in the organization
of the personnel of the navy or in the customs
governing its use. In the opinion of the writer,
the present practice of using experienced
sea-going officers for much of the important
engineering work of the navy is a very good
one, which should be continued. It is believed
that every department of technical work in
the navy, including that of construction and
repair, will be benefited by the services of
such men. It is believed, however, that the
activities of these men should be supple-
mented by a moderate number of first class
experts, who, as a permanent engineering
corps, can devote their lives to the practice
of engineering, Such a corps should not be
recruited from newly graduated cadets. It
has been often proved that success as a
student affords little indication of value as an
engineer. Its numbers had better be taken
from experienced officers and civilian
employees of the navy who have reached the
age of thirty and have shown the ability and
character necessary to usefulness in such
work. The members of this corps should hold
positions of influence and importance in
departments of the navy where engineering
work is done. Their activities should gener-
ally be of a purely engineering rather than of
an executive character, although they should
not be entirely excluded from executive
positions.
The possibility of making improvements
in the equipment of existing vessels in the
navy affords a very ready and practical
means of making experimental development
of new methods and devices, but such changes
if they involve much expense can generally
not be undertaken without authority from
Congress It may be quite as desirable to
bring an old ship up to a higher standard of
efficiency as it is to improve the design of a
new ship, but under existing conditions it
would seem that new methods must generally
await their opportunity until new ships are
authorized. In the opinion of the writer it
would be desirable to provide an ample fund
which could be used at the discretion of the
Secretary of the Navy in developmental work,
cither through purchase of machinery or
through manufacturing and experimenting
in navy yards. Where these developments
resulted in permanent improvements to
vessels, the fund could be dulv credited.
1099
DEPRECIATION OF PROPERTY
By W. B. Curtiss
Appraisal Division of Accounting Department, General Electric Company
This article on Depreciation is the first of a series on Accounting and Finance that is being written especially
for the Review. Depreciation is a very important factor to consider when dealing with property, yet its
various phases are often but vaguely understood. The author has prepared a well arranged, intelligible article
which will make interesting reading and serve the purpose of a work of reference. The principal subdivisions
are: Explanation of depreciation, fluctuation, and amortization; Classes of depreciation; Methods of providing
for depreciation; Methods of showing depreciation on the books; and the Necessity of proper provision for
depreciation. — Editor.
The general subject of depreciation of
property is quite complex and volumes
have been written upon it by expert account-
ants, engineers, and others. While all
authorities are in substantial agreement upon
the fundamentals of the subject, their views
differ on some of the questions related to it.
The treatment of depreciation may, in a
general way, be compared with the medical
treatment of a sick person. In neither case
can the treatment be described as coming
within the domain of exact science. The
physician diagnoses the case of the sick
person and prescribes the treatment which
his knowledge and experience lead him to
believe will produce beneficial results; but
if the patient does not respond to the treat-
ment, the physician tries something else.
So it is with the treatment of depreciation.
It is known that several causes give rise to
depreciation; and while no set rules can be
laid down to determine exactly the total rate
of depreciation or the rate due to any particu-
lar cause, these items can be determined
within reasonable limits of accuracy by
closely studying local conditions and applying
the knowledge and experience gained along
similar lines.
Definition of Depreciation
A dictionary definition of depreciation is —
"the act of lessening or bringing down value."
One authority defines it as "the loss, arising
from years of service, in the value of the
investment in perishable property." Various
authorities have coined differently worded
definitions, but in the sense here used the
interpretation of them all is that depreciation
is the deterioration of anything by use or time.
Depreciation VS. Fluctuation
The terms depreciation and fluctuation
are sometimes confused, although they
refer to conditions that are quite different in
character. Depreciation is always a decline
in value, due to the use of property or to its
age regardless of whether it is in or out of
actual service. If the property is in use it
wears, if it is not used it rots or disintegrates;
in either case it tends to become obsolete in
addition. Furthermore, a combination of all
these factors may exist to a more or less
extent. Fluctuation in value may be either
up or down but unlike depreciation it is not
due to the operation of the plant or the
business. Fluctuation in the value of a plant
and equipment is due to causes entirely apart
from the operation of the plant, and among
them may be mentioned the changes in the
market price of labor and materials entering
into the cost of buildings, machinery, etc.
It is a well known fact that the cost of almost
all classes of labor and material has advanced
rapidly in recent years, and it requires but
little thought to arrive at the conclusion
that a building erected in the prosperous
period of a couple of years ago, or a tool
purchased in the same period, cost more than
a building or tool of the same specifications
erected or purchased ten or fifteen years ago.
Changes in value due to fluctuation are not
usually considered as affecting the operating
profits, because they are influenced by
considerations quite apart from the business
and may be upward or downward. Generally
they may be considered as temporary only,
the increases of one period balancing the
decreases of another period. On the other
hand, when a plant is appraised the current
costs of labor and materials (or the average
costs over a term of years) must be taken into
consideration, and thus the value of the prop-
erty at the date of appraisal will be affected.
Depreciation VS. Amortization
Depreciation has been clearly defined. The
term "amortization" has sometimes been
used incorrectly when referring to deprecia-
tion; but it refers more properly to the
accumulation of funds, by setting aside
annually some stated amount at a fixed rate
of interest, which are ultimately to be used
in replacing capital investment in such items
as franchises, mortgages, bonds, etc. It is
important to make this distinction between
the two terms.
1100
GENERAL ELECTRIC REVIEW
Classes of Depreciation
Broadly speaking, depreciation may be
divided into three general classes, as follows:
(1) Current repairs and renewals of a
minor character to buildings, machinery, and
equipment, including the replacement of
small parts, all of which should be charged
to the expenses of the year in which the)'
occur.
(2) Repairs and renewals of larger and
more costly parts or units, the cost of which
may either be charged to the expenses of the
year in which they occur, as in (1) or the
cost may be distributed over a number of
years.
(3) The gradual renewal of the plant
part by part necessitated by the fact that.
even after the repairs and renewals covered
in (1) and (2) have been made, the plant
will gradually age and tend to become
obsolete.
Each of these general divisions is in reality
the summary of a number of component
parts which it will be necessary to consider,
for although depreciation is usually expressed
as some fixed per cent or rate for a given
class of property, it actually represents the
total depreciation from all causes, as deter-
mined by local conditions and experience.
Wear and tear is the most obvious tvpe of
depreciation, as its effects can be readily
seen and it can be measured to some extent
by the cost of repairs necessary to keep the
machine or other property in good working or
usable condition. This class of depreciation
results from use. It is extremely doubtful,
however, that the use of a piece of physical
property ever wears it out completely, except
in the case of very short-lived items, such as
small tools and small shop fixtures. Certain
parts of a machine will wear more rapidly
than other parts and certain parts of a
building, such as the floors, stair treads, roof,
etc., will wear more rapidly than other parts;
but, as time goes on, these parts will be
wholly or partially renewed with the result
that, from the viewpoint of wearing value,
the property is maintained in a thoroughly
good condition.
Age or physical decay goes on in spite of
repairs and renewal of parts; and it may be
said that practically all physical property,
that has a normal life extending over a
number of years, will eventually reach a
stage where maintenance will be so extensive
and costly as compared with the original cost
that abandonment will be much more advan-
tageous than repair. With some kinds of
property, the passage of time is directly
responsible for depreciation, whether the
property is in or out of use. A good example
of this condition is the insulated wires and
cables that transmit electricity. Such wires
and cables are wrapped or covered with one
or more layers of cotton, silk, rubber or other
insulating material, and such materials will
deteriorate with age or with exposure to the
weather. The rubber will become dry and
will crack and the fabric will rot if the wires
are in use or not. The horse is frequently
mentioned as an ideal illustration of deprecia-
tion caused by age. He has a certain number
of years of useful life, just as machine tools,
locomotives, or buildings have certain terms
of useful life, such terms varying with the
character of the property, the amount of
repair work done upon it, the kind and amount
of service exacted, etc. As applied to a horse,
depreciation exists largely in the natural
process of aging. Although his hoofs wear
more or less, depending upon the character
and location of his work, such wear can be
minimized by shoeing at proper intervals;
but the main cause of permanent depreciation
in his case is age, and this condition cannot
be offset by repairs. He must eventually
be replaced because of physical decay. The
conclusion to be drawn from these and other
typical examples is that substantially all
physical property, except land, begins to
deteriorate from the moment it is put into
use, and that, despite repairs made upon it,
the time will surely come when it must be
replaced.
Inadequacy is the term used to designate
the depreciation that is specifically due to the
growth of business In the case of public
utility corporations, such as street railways,
electric light and power companies, gas
companies, etc., inadequacy is frequently
the result of public demands for better
service. A review of the trolley system growth
in almost any city offers a good example of
inadequacy. Some twenty years ago a city's
electric transportation service was usually
furnished by small single-truck cars running
over light weight tracks. The growth of the
city and the consequent demand for better
transportation facilities made it necessary
for the railroad to add to its equipment from
time to time. Naturally, the new equipment
was of the type that was modern at the time
of installation and gradually replaced the
older equipment, not because the old was
worn out but because it 'had become inade-
quate for the service demanded. If any of
DEPRECIATION OF PROPERTY
1101
the first cars be in existence at this date, they
have outlived their usefulness as passenger
cars and have become hopelessly inadequate
to take any substantial part in the transporta-
tion problem as it exists today.
Obsolescence is the term used to designate
the depreciation that is due to the develop-
ment of newer and more economical machines
or other property. It may also be designated
as the depreciation due to changes or advances
in the art or method of manufacture. It is
similar to inadequacy in that it may result
in the abandonment of property long before
it is worn out and it may also, in some cases,
result from public demands for better service.
However, it is distinct from inadequacy and
usually results from different causes. For
example, when a progressive city legislates for
the removal of all overhead telephone and
electric light wires in the streets of the business
district, the owners of the wires are compelled
to place them in underground conduits. In
those particular streets, the overhead con-
struction has become obsolete and has to be
completely replaced. In other sections of the
city, however, the overhead construction is
permitted and is the standard practice in
those localities. It is probably true that
obsolescence and wear and tear rank as the
two chief causes for the enormous charges
to depreciation in the past, although wear
and tear can largely be made good by repairs.
In some classes of property, such as electrical
machinery, advances in the art of manu-
facture and design have been so rapid that
machinery in great quantities has had to be
replaced, long before it was worn out, by
other machinery of newer and more eco-
nomical types.
Deferred maintenance is the term used to
designate the depreciation resulting from
neglect in the way of repairs and general
upkeep. In providing for depreciation, it is
customarily assumed that the property will
be maintained in an efficient operating
condition and that the expense to be provided
for is represented by the sum of the actual
loss in value and the cost of repairs. Recog-
nition is given to the fact that, in spite of
adequate repairs, the property is constantly
lessening in value. Deferred maintenance
represents the expenditure that must be
made upon any piece of property to put it into
the best possible operating condition at any
given time. It is not a class of depreciation
that is taken care of in the depreciation
account, as it represents expenditures for
maintenance which are properly chargeable
to expense at the time the repairs are made.
In any factory, for example, it will be readily
understood that, at any given date, there
would be many items of equipment needing
repairs in order to bring them to their maxi-
mum efficiency. These repairs could not all
be made at one time and it is, therefore, a
fact that there is always more or less
work to be done at all times. The condition,
known as deferred maintenance, is only taken
into account when property is appraised or
sold. A purchaser naturally expects the
owner to put the property in first class
condition before the transaction is concluded,
or insists upon an adjustment in price equiva-
lent to the estimated cost of the necessary
repairs.
Accidents sometimes result in very sudden
depreciation. While accidental destruction
of property should not perhaps be classed
with the various classes of depreciation
previously described, it is, nevertheless, a
factor that cannot be entirely ignored. In a
locality subject to earthquakes, a building
or other structure may be badly damaged or
even destroyed by a heavy shock. A bridge
over a river may be carried away by flood.
Such cases result in quick destruction of
property values much in excess of the amount
normally chargeable to maintenance. Prob-
ably no concern engaged in ordinary business
makes provision for such accidental destruc-
tion of property by means of charges to the
depreciation account, although there may be
special hazards that are so handled. There
are numerous kinds of insurance that can be
purchased which will be applicable, such as
those covering breakage of plate-glass win-
dows, bursting of boilers, damage due to
earthquakes, cyclones, floods, lightning, etc.;
and insurance is probably the best medium
through which to provide against such
destruction of property.
The foregoing paragraphs explain the
several classes of depreciation; and deprecia-
tion must be provided for out of income before
any profits can properly be taken.
The annual charges to income for this
purpose are to meet the eventual complete
renewal of the plant (not all at once, but
parts of it from time to time as become
necessary). They are represented simply by
the estimated yearly proportion of the loss
in value that cannot be made good by current
repairs and maintenance — a loss for which
necessary provision must be made in advance
against the time when the plant, or any
portion of it, shall be entirely worn out.
1102
GENERAL ELECTRIC REVIEW
inadequate, obsolete, or for any other reason
will no longer be useful to serve the purpose for
which it was provided. Before discussing the
methods that may be used for providing funds
to cover depreciation, consideration should
be given to those kinds of depreciation that
are of a current character and that are taken
care of in the expenses of the month or the
vear in which the expenditures occur.
Maintenance, Repairs and Renewals
As here used, maintenance, repairs, and
renewals are practically synonymous terms.
The term "maintenance," as generally used,
includes the cost of current repairs, replace-
ment of small parts, and general upkeep,
including the labor and material involved.
Such expenditures form a part of the general
operating expenses of a plant and should be
charged to expense in the period in which
they were made. As used in this article, the
term "renewals" refers particularly to the
replacement of small parts or of certain
classes of small tools and devices which have
but a short life, less than one year for example.
Such renewals are quite properly chargeable
to expense; but, in the case of a renewal of a
large and expensive part that would last for
several years, it would be proper to distribute
the cost over a number of years or it might
all be charged to maintenance in the year
in which the expenditure was made. The
complete renewal or replacement of property
of importance, however, is not usually
charged to maintenance, because it would
result in abnormal drains upon the treasury
and would destroy the comparisons that
could otherwise be made of the cost of
maintenance from year to year.
Useful Life of Plant
It is now clear that the depreciation of a
plant must be provided for out of income
each year during the life of the plant. It
would not be possible to provide for the
complete replacement of the plant out of the
earnings of a single year, therefore, it must
be provided for in annual installments. The
next step of importance is to determine as
accurately as possible the terms of useful life
that may reasonably be expected of the
several classes of property. This will require
the exercise of skill and judgment, the
knowledge of the local conditions, and a
general familiarity with the art in which
the property is employed. As an example, let
us assume that the total wearing value (wear-
ing value being the difference between the
cost and the scrap value) of a small plant is
S125,000, exclusive of land. The problem
now is to determine the approximate useful
life of each class of property comprising the
plant, with the exception of land as the land
cannot be worn out or destroyed for plant
purposes. After a thorough investigation,
let it be assumed that the value and life of
the several classes of property are as follows:
$10,000 useful for 5 years
$30,000 useful for 10 years
$45,000 useful for 15 years
),000 useful for 20 years
$125,000
On considering these items, it will be seen
that if annual provision is to be made for
their replacement at the expiration of their
useful lite it will be necessary to set aside
each year one-fifth or 20 per cent of $10,000.
one-tenth or 10 per cent of $30,000, one-
fifteenth or 6% per cent of $45,000, and
one-twentieth or 5 per cent of $40,000. These
can be tabulated as follows:
$10,000X1/5 (or 20%) =
$30,000X1/10 (or 10% ) =
$45,000X1/15 (or 6%%) =
$40,000X1/20 (or 57„) =
$125,000
$2,000
$3,000
$3,000
$2,000
$10,000
This indicates that, if the estimated terms
of useful life be conservative, the amount
realized annually by the application of the
rates of depreciation (20, 10, 6% and 5 per
cent) against their respective property values
will be sufficient at all times to provide funds
for the complete replacement of worn out
property with new property of equal cost.
The "mean life" of the plant may also be
used to produce the same result. "Mean
life" may be defined as the number of years
that will be required to accumulate an amount
equal to the wearing value of the plant as a
whole, which in this case is 12J^ years. In
the foregoing assumption certain predeter-
mined portions of the plant will wear out in
5, 10, 15 and 20 years respectively, but it
has been shown that the setting aside of an
annual depreciation fund of $10,000 will
suffice to completely replace these portions
as they wear out.
This can be shown in another way. It is
obvious that certain portions of the plant will
wear out before other portions do; e.g., that
portion which has the relatively short life
of 5 vears will wear out four times while that
DEPRECIATION OF PROPERTY
1103
portion which has a 20-year life wears out
once. Using the life (20 years) of the most
permanent portion of the plant as the basis
for calculation, the following figures are
obtained:
that while the fixed apportionment for
depreciation is the same in the first year as
in the last year of the life of the property,
the repairs, etc.; are relatively small in the
first years and much more extensive in the
T •* No. Times
Wearing Installed
v™ Value in 20
^ears Years
Total
Investment v.,-,-,. Dollar
in 20 Y ears Years
Years
5 $10,000 4
10 30,000 2
15 45,000 1H
20 40,000 1
$125,000
$40,000 X5 = $200,000
60,000 X10 = 600,000
60,000 X15 = 900,000
40,000 X20 = 800,000
$200,000 $2,500,000
The "mean life" is determined by dividing
the dollar years by the total investment
required during 20 years, which gives 12J^
years. The annual amount necessary to cover
depreciation during the "mean life" is
determined by dividing the total investment
required by the number of years (20) during
which the investment has been made, which
gives $10,000.
Methods of Providing for Depreciation
Authorities have written volumes on the
subject of providing for depreciation and
many individual viewpoints can be obtained
by reference to published works on "Audit-
ing," "Accounting" and "Appraisal of Prop-
erty." It is also discussed in engineering
publications. However, all authorities agree
that the following three methods are in more
general use; therefore only these will be
considered.
( 1) Straight line method.
(2) Diminishing value method.
1 3 ) Sinking fund or annuity method.
In all of these methods it is the usual
practice not to include maintenance charges
in the fund in addition to depreciation.
The straight line method provides for
setting aside each year an equal proportionate
part of the cost (less scrap value) based upon
the life of the property. If a certain portion
of the plant cost $10,000 and its life be
estimated as ten years with a scrap value of
$1000, the annual depreciation by the
straight line method will be 10 per cent of
$9000 or $900. This method is in most general
use in manufacturing plants; but it is fre-
quently argued that the combined charges
to income for depreciation and maintenance
increase as the years go by, for the reason
latter years. The effect of this would no
doubt be noticed in the first fifteen or twenty-
years of the life of an entirely new plant, but
after it had been in operation for a long
period it would be comprised of units of all
ages from new to worn out and consequently
the criticism mentioned would be eliminated.
The diminishing value method provides for
the setting aside each year of a fixed rate first
applied to the cost and then to the diminishing
value, such rate being based upon the life
of the property. By this method the property
is depreciated to scrap value at the end of its
estimated life. If a certain portion of plant
cost $10,000 and its life be estimated as ten
years with a scrap value of $1000, the annual
depreciation by the diminishing value method
will be 20.57 per cent of $10,000 or $2057 for
the first year and in decreasing amounts in
the following years as will be illustrated later.
It is claimed for this method that the com-
bined charges to income for depreciation and
maintenance are more uniform as under it
the charges for depreciation are heaviest in
the early years and constantly decrease as
the years go by, whereas the maintenance
charges are lightest in the early years and
heaviest in the later years.
There is also another form of the diminish-
ing value method that might be called the
"false diminishing value method," which
is a combination of the straight line and
diminishing value methods. It is not to be
recommended, however, unless in addition
to the yearly charges for depreciation a
further amount be set up out of the income
to be carried as a special reserve for plant
depreciation. The fallacy of this method is
that while the rate of depreciation is based
upon the life of the property, as in the
1104
GENERAL ELECTRIC REVIEW
straight line method, it is applied, not to the
cost (less scrap value), but to the diminishing
value. The results will be illustrated later.
The sinking hind or annuity method provides
for setting aside each year such a sum that,
invested at a certain rate of interest com-
pounded annually, it will equal the cost of the
property (less scrap value) at the end of its
life. If a certain portion of the plant costing
$10,000 has a life of ten years, with a scrap
value of $1000, and it is desired to set aside
such a sum that, at 5 per cent interest com-
pounded annually, will accumulate an amount
equal to the cost (less scrap value) at the end
of the life period, it will be found by referring
to an annuity table that $9000X0.0795 will
of the ten years of life are identical in each
case and that the capital investment has not
been impaired. The fourth column, however,
shows the operation of what has been termed
the "false diminishing value method" and
it is clear that, if the property is actually
worn out in its assumed life of ten years, the
capital investment in plant is impaired to the
extent of $2486.78, which is the difference
between the total depreciation (plus scrap
value) and the original cost.
Where the depreciation funds or reserves
are invested in extensions to the plant, as is
the usual practice in manufacturing enter-
prises, either the straight line or the diminish-
ing value method is the proper one to use ; for
TABLE I
Year
Straight Line
Method
10 Per Cent on Cost.
Less Scrap Value
$900.00
900.00
900.00
900.00
900.00
900.00
900.00
900.00
900.00
900.00
Diminishing
Value Method
20.57 Per Cent on
Dimin. Value
$2,057.00
1,633.87
1,297.78
1,030.83
818.78
650.36
516.58
410.32
325.92
258.88
Sinking Fund
Method at
5 Per Cent Comp.
Interest
False Dimin.
Value Method
10 Per Cent, on
Dimin. Value
1
2
3
4
5.. ...
6
$715.50
715.50
715.50
715.50
715.50
715.50
715.50
715.50
715.50
715.50
1,845,00
$1,000.00
900.00
810.00
729.00
656.10
590.49
7
8
531.44
478.30
9
430.47
10
5 per cent compound interest . .
387.42
Total depreciations
Scrap value
$9,000.00
1,000.00
$9,000.32
1,000.00
$9,000.00
1,000.00
$10,000.00
$6,513.22
1,000.00
$10,000.00
$10,000.32
$7,513.22
produce the required amount, $715.50. The
sinking fund or annuity method is more appli-
cable to public utility properties that have
reached their full development than to manu-
facturing properties, as it usually provides for
investing the accumulations in outside securi-
ties at from 3 to 5 per cent interest.
The results obtained by the use of the three
methods of providing for depreciation are
given in Table I. As a basis for the calcu-
lation, a $10,000-portion of a plant has been
assumed, its estimated life is to be ten years,
and it will have a scrap value of $1000.
The few cents excess in the total depreciation
obtained by the diminishing value method
is of course due to not using the exact decimal
in the rate of depreciation. This tabulation
shows clearly the yearly amounts provided
by the three recognized methods, and it will
be seen that the net results at the expiration
on the assumption that a given enterprise is
profitable, it can earn more money on its funds
in its own business than it can by investing
the same amount in outside securities.
Methods of Showing Depreciation on the Books
There are three methods in more or less
general use :
(1) A general account for depreciation
reserve is credited with the depreciation on
all classes of property and an equal amount
is charged to income.
(2) Individual reserve accounts for each
class of property are credited and an amount
equal to the total of these credits is charged
to income.
(3) The value of each class of property
is written down and an amount equal to the
total of these reductions in property values
is charged to income.
DEPRECIATION OF PROPERTY
1105
A combination of (3) with either (1) or (2)
may also be used where it is desired to set
aside special reserves in addition to the
regular scheduled depreciations for the pur-
pose of providing against extraordinary
contingencies. The method that shall be
used in showing depreciation on the books
must, of course, be governed by each enter-
prise. Of the three methods, the first
is quite objectionable for the reason that, in
crediting a general reserve account with the
depreciation on all classes of property, it is
impossible to determine the carrying value
of any item or class of property without a
detailed analysis of the general reserve
account. Either (2) or (3) will be quite
satisfactory if individual records are kept of
the items comprising each class of property.
The proper classification and recording of
property is of great value. Unless individual
records are maintained of the items comprising
buildings, machinery, etc., there will be no
closer reference to individual items than the
total of the class of property in which such
items are carried, and this will result in
losing sight of the original cost and the
carrying value. Thus the proper classification
and recording of property will be found to be
of great value.
Graphic Representation of Depreciation
Fig. 1 is a graphic representation of the
trend of depreciation. Three of the series of
seven curves are intended to illustrate the
ways in which depreciation actually takes
place, and the remaining four are intended
to indicate the methods that have been
explained for providing the necessary depreci-
ation funds. These curves are similar to
others that appear in Henry Floy's "Valua-
tion of Public Utility Properties." In Fig. 1.
however, one of Floy's curves has been
omitted and one of the writer's has been
added in order. that the example of graphic
representation of depreciation will be in
agreement with the discussion herein. The
explanation of the curves also closely follows
Floy's text wherever the latter may be used
to advantage.
Now assume that any piece of property
cost an amount represented by the ordinate
OC, and that it has an estimated useful life
of a number of years represented by the
abscissa OD, also that it has a scrap or junk
value of an amount represented by the
ordinate 0.4. As the scrap or junk value will
be constant throughout the life of the prop-
erty, except for the fluctuation in market value
of the materials which may be up or down,
the horizontal line AB will represent the
scrap value, below which there should be
no depreciation. The ordinate OA will then
represent the value at the beginning of the
life period and the ordinate DB the value^at
the end of the life period.
1
5
3
-^
— »
\
\M
^\
4>
.7
2^
LS
5crop Va/ue
, Y .
Life in Years
Fig. 1
In general there are two factors affecting
values through depreciation, (a) the sale
price that can be obtained if the property
be sold before it is worn out, (b) its value as a
working unit when used for its original
purpose throughout its life.
Curves 1 and 2 may be used to represent
the values of most pieces of property during
any period of life as determined from the
sale price for use elsewhere. As is well known,
the depreciation of new apparatus or equip-
ment, from the viewpoint of salable value,
is very rapid from the time the apparatus
is installed; but after depreciating rapidly
in salable value in the early period of life,
it only gradually depreciates to scrap value
during the remainder of its life. The values
thus illustrated are independent of the
service for which the apparatus was purchased
and installed.
Curve 1 represents the value of special
machinery, tools, etc., which would be of
very little value on any work other than that
for which they were intended. It might also
represent the value of any kind of property,
the cost of removing which would be rela-
tively high compared with its inherent value.
Curve 2 represents the sale value of
readily movable property in general, i.e.,
1100
GENERAL ELECTRIC REVIEW
property that can be moved and used to
advantage in other locations and for other
purposes than those for which it was originally
provided.
Curve 3 represents depreciation due only
to wear and tear until just before the end of
the life at which time other classes, such as
inadequacy and obsolescence, may have an
important bearing upon the value. The
assumption is made that the property in
question will be kept in first-class repair and
that if kept in that condition will be just as
useful at all times throughout its life for its
original purpose. Curve 3 therefore indicates
a high continuous value, the loss representing
a certain amount of depreciation through
deferred maintenance and age.
These first three curves represent what may
be termed "absolute" depreciation They
indicate very rapid rates of depreciation
either in the earlier or in the later period of
useful life, and it has been necessary for
accounting purposes to fix upon some method
of providing for this deterioration in some
logical and uniform manner. The "straight
line" method, the "diminishing value"
method, the "sinking fund or annuity"
method, and what may be termed the "false
diminishing value" method will each provide
a means for the accumulation of depreciation
funds The merits and demerits of each
have been briefly mentioned. It is a fact
that depreciation does not proceed at an
even or uniform rate during the life of
property, but for practical accounting pur-
poses it is necessary to devise methods that
will provide out of income, at a relatively
uniform rate, the necessary funds to offset
deterioration in value. The rates used in
connection with these methods may therefore
be termed the "theoretical" depreciation,
and curves 4. 5, 0 and 7 come under this
designation. The curves shown in Fig. 1
have been plotted from the values given in
Table I.
Curve 4 represents "straight line " deprecia-
tion, in which a uniform rate of reduction in
value goes on during life.
Curve 5 represents depreciation by the
"diminishing value" method, in which more
rapid reduction takes place in the earlier
than in the later years of life.
Curve 6 represents depreciation by the
sinking fund or annuity ' ' method ; in
drafting this curve, the compound interest
values have been added to each year's
accumulation. Here the reduction in value
is more rapid in the later years of life than
in the earlier.
Curve 7 represents depreciation by the
"false diminishing value" method; and, as
was pointed out, there would be a loss to
capital account of about $2500 under this
method, unless an adequate reserve in
addition to the regular depreciation had been
set up for such emergencies.
Necessity of Proper Provision for Depreciation
While this article relates to the depreciation
of the permanent plant investment of manu-
facturing plants, it is equally applicable to
physical property of all kinds, with the
possible exception of land. It is a certainty
that depreciation in one or more of its phases
is an ever present factor in connection with
all physical property, except land; and even
in the case of land, farm land for example,
depreciation exists if the land is not properly
fertilized and cultivated after each crop.
It is further evident that adequate provision
must be made out of income against the time
when the natural wearing or aging of the
property will render it useless for the purpose
for which it was obtained.
It is a self-evident truth that the capital
account of any business must not suffer
impairment for any reason, and as the per-
manent plant investment is usually an
important part of the capital account, it is
obvious that such safeguards must be
established as will maintain this important
asset at its proper value.
Generally speaking, capital is frequently
impaired in manufacturing concerns by inade-
quate provision for depreciation and by
charging to investment those expenditures
which should be charged to maintenance.
These errors in accounting methods result
in the showing of false profits that are not
earned; and if dividends be distributed to the
stockholders, based on these false profits, the
capital is impaired to the extent of such
distribution.
In conclusion, it may be stated as an axiom
that any business enterprise which has an
investment in permanent plant and which
does not make adequate provision for the
depreciation of its plant, by setting aside
from its earnings each year a sufficient amount
to insure the replacement of the property at
the end of its useful life, will sooner or later
find itself in financial difficulties.
1107
A MODEL X-RAY DARK-ROOM
By Wheeler P. Davey
Research Laboratory, General Electric Company
The author describes and illustrates both a small and a large dark room specially suitable for X-ray work
and as he has had much experience in this work the article should prove of considerable value to Roentgen-
ologists.— Editor.
Anyone visting the offices of a large number
of X-ray practitioners is impressed by the
small number of first-class dark-rooms. Men
enjoying a large practice as X-ray specialists
have had occasion to fit up rooms very well
adapted to the purpose, but those with smaller
practice, or those who use X-rays as an aid
to diagnosis in their own general practice
do not seem to have been so fortunate. It
is with the hope of aiding such men in plan-
ning an efficient and convenient dark-room,
that this article is written.
In planning a dark-room for X-ray work,
space must be provided for the following:
(1) Stock solution of developer; (2) Develop-
ing shelf; (3) Sink; (4) Hypo bath; (5) Wash-
tank; (6) Drying rack; (7) Racks for holding
envelopes; (8) Interval timer; (9) Ventilating
fan; and (10) Necessary lights and switches.
In addition to the above it is usually
desirable to provide room for a moderate
supply of plates and for a stock of chemicals.
A small viewing screen in the dark-room is a
great convenience but not a necessity. If
frames are used for fixing, washing, and
drying the plates (and the author believes
that they should be), then space should be
provided for them on the walls of the room.
The room should be planned so as to make
everything as compact as possible, and so that
it is never necessary to allow a plate, wet with
hypo, to drip on the floor. The two dark-
rooms described in this article have been
found satisfactory enough to warrant them
being called " Model" dark-rooms. One is in
the Research Laboratory of the General
Electric Company. Space was at a premium
and the room was built out like a closet in one
of the rooms. The other is in the office of a
well-known surgeon whose X-ray practice is
large enough to require the constant services
of a trained Roentgenologist. In this case
compactness was not as essential as the ability
to handle a large number of plates quickly.
Both dark-rooms were planned with the
idea of developing plates entirely by time.
With the Coolidge tube the penetration and
exposure can be made so definite that this
method is by far to be preferred. Tank
development was considered, but was thought
not to be economical enough of developer
because of the large size of plates used in
stomach and chest work. It is possible,
however, to combine the convenience of the
tank -method with the economy of the tray-
method if the following technique is followed.
(1) Fill the tray quarter-full of fresh
developer at some standard temperature
(say 65 deg. F.).
(2) Insert plate.
(3) Shake tray vigorously from end to end
and from side to side to remove air bubbles.
(4) Cover tray with a light-tight cover and
leave undisturbed for ten minutes, as shown
by the interval-timer. (Adjust the exposure
so that this is the proper time of develop-
ment.)
(5) After using, pour developer at once into
an air-tight bottle just large enough to hold
it, and put in water bath to keep cool. If
care is taken not to use stale, discolored devel-
oper, this method has been found to be quite
as satisfactory as tank development.
As soon as the plate comes from the devel-
oper it is put in a frame, washed in the sink
and at once put in the hypo tank. After
fixing it is washed in the wash-tank and hung
on the rack to dry. The use of the frames will
be found to keep the gelatin from being
marred by finger prints.
A glance at the plan of either dark-room
will show that (1) a plate is never brought
near the developer after having once left it;
(2) lights are turned on and off from the
floor, — there are no switches covered with
hypo to spread hypo-dust into the developer;
(3) the sink is between the h/po and the
developer so that in passing from one to the
other the hands may be washed; (4) the
running water of the wash-tank is in contact
with the hypo tank, thus insuring cold hypo;
(5) a plate can never drip hypo on the floor,
even wher being viewed on the viewing
screen.
In planning the viewing screen, a great
deal of experimental work was done to find
the best possible source of illumination for
negatives. Every style of incandescent lamp
known has been tried and compared with
north-sky and with the mercury arc.
1108
GENERAL ELECTRIC REVIEW
IDrt/tnq
XacX
Fig- 1. Ground Plan, Dark Room No. 1
Treadles
Fig. 2. Back Wall, Dark Room No. 1
Rack for
5 i "V-. e'Of es
Deve/optnq
8 *
§ I
f?ac* fat
SkIO'p* ve lopes
Lead-Lme\ drawer
for x-ffai) Plates
lb"
Fig. 3. Right Wall, Dark Room No. 1
Fig. 4. Left Wall, Dark Room No. 1
Fig. 5 Fig. 5a
Method of Hanging Curtains in Doorway of Dark Room No. 1
A MODEL X-RAY DARK-ROOM
1109
As a result, it was found that the "Blue
Photographic Mazda" is by far the best
source of illumination for viewing X-ray
negatives. The viewing screens were there-
fore designed to be used with these lamps.
Plans of the smaller of the two dark-rooms
are given in Figs. 1 to 6. This room was
designed for use with plates not to exceed 10
by 12 inches in size. There is no reason why
it could not have been designed for use with
plates of any size. The walls were built of
dry matched sheeting. The developing shelf
was covered with lead partly to make it
water-proof and partly to better protect the
plates in the drawer from X-rays. Care must
be taken to have plenty of overlapping of
3oz for
R
Fig. 6. Roof Plan, Dark Room No. 1
— fe Pine.
/ns/efe ortaovt
c?na //neef mrtlfi
'de/Bad
Fig 7. Side View of Hypo and Wash Tanks and
Drying Racks, Dark Room No. 2
-/4 ■
12'
o
Fig. 8. Top View of Hypo and Wash Tanks,
Dark Room No. 2
*- 7"
8
>H
4
Fig. 9. End View of Drying Rack, Dark Room No. 2
Treadle for Treadle for Treadle for
V/ewmq Jcreen J?ed hqhl White liqht
Fig. 11. Wall of Dark Room No. 2
1110
GENERAL ELECTRIC REVIEW
lead so that the rays may find no open crack
through which to enter. The rheostat, Fig.
2, is a 300-ohm rheostat, and has all the range
needed for dimming a 50-watt red light. The
use of light during development is, however.
not as necessary with "time development"
as with the ordinary method. It is the
practice of the author to dim the lamp as
much as possible, using it merely as a point
of reference in locating things in the room.
Attention is called to the use of curtains
in the doorway as a means of economizing
space. Two curtains are hung on separate
rods as shown in Fig. 5. The outside edges
are fastened permanently to the door way.
The inside edges are fastened to sticks about
one inch square. These sticks act as weights
and prevent the curtains from blowing in and
causing light-leaks. Each curtain is wide
enough to stretch completely across the
doorway. A suitable housing, see Fig. 5a,
painted black on the inside prevents light-
leaking over the top of the curtains. The
curtains are made of double thicknesses of
galatea.
Plans of the larger dark-room are shown in
Figs. 7 to 11. Attention is called to the
method of drying the plates with the fan.
The arrangement of the red lights is also
worthy7 of notice. Instead of using a rheostat,
two 10-watt red lamps were connected in
series. This made them both burn dimly.
In accordance with the suggestion made
above, they are used, not as a source of light
for watching the development of the plates,
but merely as marks to guide the operator in
his movements about the room. One lamp
is olaced at the extreme end of the developing
table, the other is placed over the sink.
The dimensions of the hypo and wash tanks
and of the drying rack are given in Figs.
7 to 9 in some detail as a guide to any who
care to have similar work done. In Fig. 11
the switches governing the various lamps are
not shown. The treadles will, however, indi-
cate where these switches should be placed.
THE PRODUCTION OF DAMPED OSCILLATIONS
By Leslie 0. Heath
Research Laboratory, Pittsfield Works, General Electric Company
Damped high frequency oscillations are playing an increasingly important part in the testing of certain
forms of electrical apparatus and of insulation. The author describes the three most important ways of pro-
ducing such damped oscillations; viz. the "simple," the "coupled" and the "quenched-spark" methods. He
treats the subject clearly and comprehensively and the valu_* of his contribution is materially increased by the
illustrations and diagrams. — Editor.
Within the past few years a certain amount
of work has been done in testing protective
apparatus, power transformers and various
forms of insulation with damped high fre-
quency oscillations. It is probable that in
the future such work will be considerably
extended and that some lines of investigation
will require high frequency apparatus for pro-
ducing oscillations of certain characteristics.
In view of this situation a consideration of
the various methods of producing damped
oscillations and a comparison of the different
types of oscillations produced by these
methods may be of value in predetermining
the effectiveness of any given type of high
frequency system in any particular line of
high frequency investigation.
A study of the various methods of produc-
ing damped waves points out certain advan-
tages for each method; but in every method
the oscillations are produced primarily by
discharging a condenser through an induc-
tance. There are in use three general systems
for producing damped waves, which may be
termed the simple, the coupled, and the
quenched-spark, which is a modification of the
ordinary coupled system. It is well to con-
sider these systems in the order given, as
they were developed in this sequence.
Probably the most familiar example of the
simple system is that shown in Fig. 1. The
oscillating system itself is drawn in heavy
lines. At each break of the interrupter in
the primary circuit of the induction coil the
condenser is charged to a high potential and
is discharged across the gap through the
inductance. The frequency of these oscilla-
tions when the resistance of the circuit is
low, as it is in most practical cases, is given
bv the equation
/= 1
■IttVlC
where L = the inductance in henrys; and C
the capacity in farads. In many cases it is
more convenient to measure the frequency
THE PRODUCTION OF DAMPED OSCILLATIONS
1111
by means of a wavemeter. These oscillations
can be shown graphically by means of a
Gehrcke tube1 and rotating mirror, pro-
vided that the oscillations are sufficiently
steady and the mirror is driven at the proper
speed. The Gehrcke tube is a glass tube
filled with a rarified gas having two polished
aluminum electrodes in the form of round
wires or flat strips which project inward from
the ends of the tube and nearly touch at the
middle. See Fig. 2. When a voltage is applied
to the tube a glow starts at the middle and
extends toward the ends along the electrodes
a distance depending on the value of the volt-
age. If an oscillating voltage is applied
across the terminals, at each oscillation the
glow extends along the tube a distance
roughly proportional to the voltage, so that
if the tube is viewed in a rotating mirror,
instead of a steady band of light, a series of
bands of decreasing amplitude is seen, giving
a fairly accurate representation of the wave
train. A somewhat similar method of show-
ing sustained oscillations by means of the
cathode ray tube has been used by Ernst
Ruhmer in experiments with the high fre-
quency arc2.
When such apparatus is not available it is
usually practical for purposes of illustration
to construct a low voltage oscillating circuit
whose frequency comes within the range of
ID
<h
ing the wave train shown in Fig. 3 consisted
of some paraffine paper condensers and an air
cored inductance. The condenser was charged
on a 125 volt direct current circuit and dis-
charged through the inductance, the oscil-
lations being recorded by an oscillograph
Fig. 2. A Gehrcke Tube
connected across a shunt which was inserted
in the circuit.
The decrement of the oscillations is the
difference of the natural logarithms of two
successive oscillations in the same direction,
and can be calculated from the equation
8- R
2/L
where i? = the total resistance of the circuit:
/ = the frequency; and L the inductance in
henrys.
The decrement of the oscillations shown in
Fig. 3 as determined from wave micrometer
measurements is 0.103 per complete period, a
value which checks very well with the value
calculated from the measured inductance and
resistance of the circuit, taking into account
the losses in the condensers.
In the case of the high frequency circuit,
Fig. 1, the determination of the decrement
Fig. 1. Simple High-frequency Compound System
Fig. 3. Low-frequency Wave Train and Tuning Wave
the ordinary oscillograph. Fig. 3 shows a
damped wave train of 265 cycles as a
theoretical example of a wave train produced
at a very much higher frequency by the system
shown in Fig. 1. The lower wave in Fig. 3
is a timing wave. The apparatus for produc-
from the constants of the circuit is not so
easily accomplished on account of the resist-
ance of the spark, which is usually a very
considerable part of the total resistance.
Furthermore the resistance of the spark
varies throughout the wave train, being
1112
GENERAL ELECTRIC REVIEW
relatively low at the start and increasing
toward the end. As a result of this variation
of spark resistance the oscillations decay
more nearly according to a linear than a
logarithmic function3. Dr. Chaffee of Har-
vard has experimentally shown by means of
jLi
Fig. 4. Ordinary Coupled System
the cathode ray tube the linear damping
characteristic of a high frequency spark4.
When oscillations of any very great amount
of power are required the method of exciting
the high frequency system, Fig. 1, by means
of an induction coil is unsatisfactory, and a
power transformer operating on a commercial
supply system is substituted. With the
high frequency system supplied by a power
transformer special precautions are necessary
to prevent the formation of a power arc at
the gap, and to prevent the occurrence of a
large number of discharges of varying initial
voltages during one alternation of the low
frequency supply voltage. To eliminate
these troubles and to maintain a greater
constancy of the oscillations various methods
have been devised for rapidly extinguishing
the spark, such as turning an air blast on
the gap or placing the gap in the field of a
powerful magnet; but probably one of the
most effective methods is to replace the
ordinary spark electrodes with a pair of
heavy discs which are rotated by a suitable
motor so that a spark occurs at a fresh place
on the disk at every discharge.
Maintaining the regularity of the spark is
greatly assisted by placing a suitable induc-
tance in the low tension circuit of the trans-
former which charges the condenser; but this
feature will be considered in more detail in
connection with the quenched-spark system.
Fig. 4 shows the connections of an ordinary
coupled oscillation system. The main con-
denser A is charged by the power transformer
E, as in the simple system, and is discharged
across the gap B, through the inductance C,
which is the primary of an oscillation trans-
former, the secondary of which is in series
with the condenser D. An equivalent auto-
transformer can be substituted for the oscil-
lation transformer without basically altering
the operation of the system. The primary and
secondary circuits must be in resonance or
nearly so.
The practical advantage of the coupled
system is that very high voltages can be
produced in the secondary high frequency
circuit without having a high resistance
spark in the circuit. The spark, being in the
primary, can be of a very moderate voltage.
Thus where high voltages are required the
coupled system is more efficient than the
simple and oscillations of a lower decrement
can be produced.
Ordinary Spark
Primary
Secondary
Primary
Secondary
Fig. 5.
Comparison of Ordinary and Quenched-spark
Excitation of a Coupled System
The plain coupled system has one very
serious defect. The oscillations produced by
this method are split up into two frequencies,
the wave trains being similar to those
theoretically shown in Fig. 5. These oscil-
lations of a coupled system can be shown by
THE PRODUCTION OF DAMPED OSCILLATIONS
1113
means of the Gehrcke tube in the same man-
ner as the oscillations of a simple system5.
The two frequencies are theoretically given by
the equation
-K l+/v
and ft = -
K
2ttV LC""~J* 2tV LC
where K is the coefficient of coupling of the
primary and secondary circuits.
M
Vl7T2
Where M is the mutual inductance of the
circuits; L\, the primary inductance and L2
the secondary inductance. In practice the
foregoing equation for the two frequencies
in a coupled system is only approximate
since the damping characteristic of the spark
in the primary circuit is not a negligible
factor. The existence of these two fre-
quencies in a coupled system is most easily
shown by a resonance curve obtained by
means of a wavemeter. Curve B, Fig. 6,
shows a curve taken on an experimental
coupled system at the Pittsfield laboratory.
Oscillations of this type are hardly suitable
for use in many high frequency investigations
1 1 1 1 1 1 1 1 II 1 1 1 1 1
A-Quenchea- Spark Excitation
B-Ord/nary • 5partr Excitation
140
130
j
1.
\
4
IFO
110
IOO
\ so
% eo
1
% 70
\
/
1
? 60
/
\
\ 50
i
\
I
.
10
1
1
\
J
1
\
30
/
^
I?
'
i
/
i
V
J
.
S
eo
S
\
\
/
IO
s
,_
'
o
c
'
It
-1
ec
0
f?
3,
<0
4C
9
96
c
ic
0
Fig/6. Resonance Curves with Ordinary Spark and
Quenched-spark Excitation
where any great accuracy is required, since
wave trains of this complex nature would
produce results of questionable value.
An interesting modification of the coupled
system, producing single wave but operating
on a different principle from the quenched-
spark system consists of the insertion of an
atonic circuit between the ordinary primary
and secondary circuits of a coupled system6.
See Fig. 7. It is claimed that the use of this
third circuit between the primary and second-
ary eliminates ■ the coupling wave. This
w
Fig.
7. Modified Coupled System^fbr Producing Single
Frequency
system is not so efficient as the quenched
spark system but is claimed to be well suited
for producing very powerful oscillations.
Since it appears that the spark persists
throughout the duration of the wave train in
the secondary, it is probable that the oscil-
lations have a linear damping characteristic
similar to that of the oscillations produced
by a simple system.
The oscillations produced by the quenched-
spark system are of a single frequency and of
characteristics which are determined almost
entirely by the constants of the high tension
high frequency circuits, which is circuit IV
of the experimental quenched-spark system
shown in Fig. 8. It will be noted that the
only apparent difference between the con-
nections of the ordinary coupled system and
the quenched-spark system is the sub-
stitution of a special form of gap for the
ordinary type of spark gap.
The type of oscillations produced by the
quenched-spark method is shown theoretic-
ally in Fig. 5.
It was noted by Wien7 in 1906 that short
spark gaps between metal surfaces very
quickly recovered their resistance after the
1114
GENERAL ELECTRIC REVIEW
passage of a spark. It has been found that a
short gap, or series of short gaps, put in the
place of the usual gap of the ordinary coupled
system will extinguish the primary spark at
the first node of the coupling wave (see Fig.
5) provided that the coupling between the two
Fig. 8. Experimental Quenched-spark System
circuits is of a certain value, so that in effect
the primary circuit III is open throughout
the rest of the high tension wave train in
circuit IV, Fig. 8. The purity of the wave
produced in practice by the quenched-
spark method is shown by the resonance
curves secured by means of a wavemeter in
the usual manner on an experimental system
at the Pittsfield laboratory. See Curve A,
Fig. 6 and Fig. 9. Each resonance curve in
Fig. 9 was taken with a different value of
resistance inserted in circuit IV, Fig. S. The
addition of resistance shows no change in
frequency over the range covered, the only
change being an increase in the decrement of
the oscillations which is shown by the fiat-
teningof the resonance curves. All the curves
in Figs. 6 and 9 would be much sharper had
the damping factor of the wavemeter been
lower.
An interesting point in connection with the
quenched-spark system is that the power in
the high tension high frequency circuit IV,
Fig. 8, is constant over a considerable range
of damping, the alternator voltage and fre-
quency being held constant. This fact can be
shown in two ways. If the resistance of the
high tension high frequency circuit IV, Fig.
8, is increased the effective current decreases
as would be expected from theory, and the
primary current remains constant. See Fig.
LO. If the power varied in circuit IV, the
current would vary in circuit III. The gap
therefore quenches uniformly over quite a
range of damping in the high tension circuit
IV. If the resistance inserted in circuit IV
is varied in known amounts and the cor-
responding value of effective current noted, a
curve can be drawn such as is shown in Fig.
11. The total resistance of the circuit is the
sum of the resistance added plus the inherent
resistance of the circuit, which includes
copper losses, condenser losses and radiation.
The power at any point in the curve is given
by the equation
P = F(RH+RL)
where I equals the effective current; Rh, the
inherent resistance; and Rl, the added resist-
ance. If the power is first assumed constant
over the range explored,
P = IS(RH+RL1)=IS (Rh+RlJ
In this manner a series of simultaneous
equations can be developed and the value of
Rh determined. It is usually satisfactory
to take the average value Rh as determined
from a number of these equations since values
derived from any given pair of equations may
differ somewhat from the value determined
from another pair, the difference being due to
slight variations in the oscillations which
affect the value of the effective current. The
value of Rh determined by this method, and
the added resistance multiplied by the square
of the effective current gives the power at any
point in the curve.
In this particular case the value of Rh was
found to be 2.73 ohms and the power 476
watts. If a theoretical curve is plotted with
a power of 476 watts with varying resistance,
ISO
no
ISO
iao
no
I 1 1 1 1 1 III
! 1 : ! |
_| | t it I it J_
ittt II
^ it t
f
+ tr ' -f
I / \ 1
11 \\
MM
// 1 \
if/ 111 \
ttj \t Tj
/ ffj l\l
/// \\\ .
/ Iff \\\ \
/ ill \\\ \
izmi^a: ; It
252izsr\- Li j i_
,' // '5\\ 1 |
y /A vK. \
j *ZZ#L ^5ii^
sSI II §5 Jib,., it
t?3_:t it s5>-,._
±1 ± tst-
soo
600
o too eoo soo -too
Frequency in Kilocycles
Fig. 9. Resonance Curves with Quenched-spark
Excitation
the result is the curve shown in Fig. 12. The
points observed in Fig. 1 1 plus the value of 2.73
ohms determined for the inherent resistance
fall along the curve in Fig. 12 very well. A con-
stant power of 476 watts is'thus demonstrated
with an inherent resistance of 2.73 ohms.
THE PRODUCTION OF DAMPED OSCILLATIONS
1115
If the oscillations in circuit IV, Fig. 8,
reached their maximum value during the
first cycle of the wave train, which would be
the case were the coupling between the high
frequency circuits equal to unity, the maxi-
mum voltage in circuit IV would be given
quite accurately by the equation, which
applies directly to the simple system, Fig. 1.
:\/v
P
NC
where P equals the power in watts; N the
spark frequency; C the capacity of the con-
denser; and E the maximum voltage to which
the condenser is charged.
Since in all practical cases the oscillations
in circuit IV, Fig. 8, do not reach their maxi-
mum amplitude during the first cycle of the
wave train (see Fig. 5) it follows that there
is a loss in the resistance of circuit IV during
the first few alternations while the oscillations
are building up, so that the measured maxi-
mum voltage at high decrements is appreci-
ably less than that given by the equation
: = \1
P
NC
But at low decrements where the effective
values of that portion of* the wave train
before the maximum are small as compared
with the effective values succeeding the
maximum, the calculated maximum voltage
and the observed should check very closely.
This is found to be the case in practice.
' X - -P ■
>o A
L
V "r
\
t
' i
V/5 5
? z;=±!s- -=- = 3
-;:::: ::: :3s:::
h* ^ : "=_-
\ ^„
- -r 4
~4- ~"t—
i -
~~*~~ — — ~
S3 3.? 36 40 44 43 5e 56 60 64 63
Fig. 10. Current in High and Low Tension Circuits
of Quenched-spark System vs. Resistance
For satisfactory results and smooth opera-
tion of the quenched-spark system it is
necessary that the coupling between primary
and secondary high frequency circuits III
and IV be of a certain value, and that the low
frequency supply circuit be of a certain
critical reactance. The reactance of the low
frequency system is adjusted by means of a
variable inductance B in the low tension
circuit of the power transformer C, Fig. 8.
The required value of inductance in the low
tension circuit of the power transformer is
12
n'X -- -
V
10 r
*9 \
39 5
I8 S
$7 V
T ^s
S NkN
*6 ^z
£5 -,
~~ k
$4
"■--.. M
S
Z
1
n
Ohms fpes'stance eaaaed
Fig. 11. Current-resistance Curve of Experimental
Quenched-spark System
given approximately by the equation for
resonance
U w2CV2
where L is the inductance in henrys; measured
in the low tension circuit /, Fig. 8; w, 27T
times the alternator frequency ; C the capacity
of the main condenser in farads; and r, the
ratio of the power transformer. The value
of L to produce resonance at any given
frequency can be very readily determined
12
\
\
\
lO
*>
\
£ 3
S
i
f"5
r '
*.
N
r u
* r
■
'
'
c
4
I
i
It
7/
C
■
■
-r-
J
/r
0
t
?r
3
t
B
8
3
a
Fig. 12. Current vs. Total Resistance of Experimental
Quenched-spark System
experimentally by measuring the current in
the high tension circuit of the power trans-
former for different values of inductance with
a given excitation of the alternator, care being
taken that no discharges of the condenser
occur during the measurements. Fig. 13
1116
GENERAL ELECTRIC REVIEW
shows a resonance curve obtained in this
manner with a quenched-spark system con-
nected with a 420 cycle alternator. In the
same manner it is possible to obtain similar
curves for other frequencies. When the low
frequency system is adjusted for resonance,
f,n - -*£^^
1 V
; h x
l j
X v
t %
% t i
S *L
k"0^ t X
K \ t \
%. t V
*«-,- J s
* X/ ^
« ' ^
!!
j --,
f°
4 X
JO
o
305 .006 .007 DOa 009 .0/0
Henrys /nctuctance Measured in Low Tension
of Transformer
Fig. 13. Resonance Curve of Low-frequency System
with no discharges occurring, the voltage
across the condenser E, Fig. 8, has a phase
angle of 90 deg. in respect to the alternator
voltage. Under these circumstances if a
discharge occurred at the maximum voltage of
the condenser it would bridge the gap D at
zero voltage of the alternator and no power
arc could occur, a condition which is neces-
sary for satisfactory operation of the quenched
gap. In practice it is found that a value
of inductance somewhat in excess of the
value required to produce resonance under
stead}' conditions gives the best results. With
proper adjustment of the system there is no
difficulty in causing the discharges to occur
with absolute regularity. Fig. 14, an oscil-
logram of voltage taken in the low tension
circuit J, Fig. 8, shows one discharge per
alternation occurring with a 420 cycle supply.
The cleft in the top of each voltage wave
denotes the occurrence of a discharge. The
same thing can be shown at other supply
frequencies.
The same general rules govern the adjust-
ment of the inductance in the low frequency
circuits of the simple system, Fig. 1, and the
coupled system, Fig. 4; but in these cases
there are certain other factors to consider.
With the quenched-spark system the primarv
spark may last onlv 11X10"6 seconds at an
oscillation frequency of 360,000 cycles and
the power transformer is short-circuited
through the gap only a very small fraction of
time. With the simple, or plain coupled
system, the spark for the same oscillation
frequency persists for a very much longer
time unless the damping is extremely high,
so that the time during which the power
transformer is short-circuited may not be a
negligible factor. This point is particularly
important in case high spark frequencies are
desired.
In order to maintain a satisfactory con-
stancy of the oscillations produced by the
quenched spark method it is important that
the surfaces of the discharge electrodes should
be affected by continual use as little as pos-
sible. The previously described method of
"resonance working" reduces the wear to a
minimum with any given metal used as
electrodes; but the metal itself is of the
utmost importance. Experiments have shown
zinc to be quite unsatisfactory. Aluminum
probably gives somewhat better results9,
copper gives good results with stationary elec-
trodes, if frequently cleaned, but silver is
very much more satisfactory and will last
under much more severe conditions than
copper. Platinum10 is probably superior to
silver; but the writer has found tungsten
electrodes to wear the least of any. Tungsten
has also been used to some extent for this
purpose in wireless telegraphy11.
Fig. 14. Voltage Wave at 420 Cycles showing the
Occurrence of One Discharge per Alternation
The high efficiency of the quenched-spark
system is of considerable importance in some
cases. The power in circuit IV, Fig. 8, may be
70 to 80 per cent of the power supplied by the
alternator in circuit I.
THE PRODUCTION OF DAMPED OSCILLATIONS
1117
In conclusion it can be said that the simple
system, Fig. 1, is the most convenient to use in
high frequency work where no great accuracy
of measurements is required. On account of
the resistance of the spark it is not suited for
producing oscillations of low decrement,
especially at high voltages. The frequency
of the system can be readily varied by chang-
ing either or both the capacity and inductance
of the circuit. If the system is supplied by a
power transformer operated on the principle
of the resonance transformer it is more
satisfactory to change the value of the high
frequency inductance than the capacity,
since a change in the capacity would neces-
sitate a corresponding change in the
inductance of the low frequency system if
the low frequency system is to be operated at
resonance at the alternator frequency.
. With the ordinary coupled system, where
the high and low tension high frequency
circuits, see Fig. 4, are tuned to the same,
or about the same frequency, the oscillations
are of such a complex nature as to be of
questionable value in very extended high
frequency investigations. As in the simple
system, the frequency of the oscillations
produced by the coupled system can be
varied by changing the values of the constants
of the high frequency -circuits ; but where such
a change is made with the coupled system,
it is usually necessary to also vary the cou-
pling between the two high frequency circuits,
so that, if changes in frequency are to be made
very often it is usually best to provide an
oscillation transformer designed especially
to meet these conditions.
The point of greatest importance in connec-
tion with the quenched-spark system is that
very regular oscillations of a single frequency
can be produced at decrements of the order
of 0.03-0.04 per complete period with an
efficiency of 70 to SO per cent. In cer-
tain cases somewhat lower decrements
can be maintained. The decrement can be
varied by inserting a damping resistance in
the high tension high frequency circuit IV,
Fig. S. The system is very well suited for
operation at high spark frequencies, and can
also be run at relatively low spark frequencies.
More skill is required in operating an experi-
mental quenched-spark system than the
simple system, especially if changes in the
oscillation frequency or spark frequency are
to be made often, but with apparatus designed
especially for such changes the system would
require considerably less attention.
REFERENCES
i E. Gehrcke, Verhandl, Physik Ges. 6, 176. 1904. Zeitscher.
1. Instrumentenkunde 15, 33, 278, 1905; also J. Zenneck —
Lehrbuck der Drahttosen Telegraphic p. 5.
2 Ernst Ruhmer — "Wireless Telephony" — p. 168.
» J. Zenneck, Ann. der Physik, March, 1904, Vol. 13, p. 822;
or Science Abstracts, July, 1904, Vol. 7, A.
4 E. Leon Chaffee — Journ. Franklin Institute — Vol. 173, p.
466, May. 1912.
' H. Diesselhorst. Ber Deutsch, Physik. Ges. 5.320, 1907—
6,306, 1908— E.T.Z. 1908, 703.
6 Lumiere Electrique, July 11 and July 18, 1914.
7 M. Wien, Physikalische Zeitschrift, No. 23, December,
1906. p. 872.
* H. Rau, Jahrb. 4, 52. 1910.
• M. Wien. Jahrb. 1, 469, 1908. 4. 135. 1911. Ann. Phys. 25.
625. 1908. Phys. Zeitschr, 11, 76, 311, 1910.
10 H. Boas— Deutsch, Phys. Gesell.. Vehr. 13. 14 pp. 527-
539— July 30, 1911.
11 H. Boas — Deutsch. Phys. Gesell., Vehr 15. 21, pp. 1130-
1149, Nov. 15, 1913.
ins
GENERAL ELECTRIC REVIEW
THE THEORY OF LUBRICATION
By L. Ubbelohde
Translated for the GENERAL Electric Review irom Petroleum
By Helen R. Hosmer
Research Laboratory, General Electric Company
Part III
IV. INVESTIGATIONS OF THE FUTURE
This installment concludes the series on "Lubrication." The former sections covered "Fundamental
Physical Principles," "Laws of Friction in Lubricated Machine Bearings," and "Failure of Oil Testing
Machines." The following section treats of the "Investigations of the Future" and describes very completely
"Combined Oil and Graphite Lubrication." — Editor.
Although mechanical oil testing according
to the present day usage will be done away
with in the future, yet systematic investiga-
tions of friction can bring about an important
advance in another direction. In illustration
of this I will go back again to the curves of
Fig. G, and recall the fact that the frictional
resistance in bearings depends upon the
relative velocity of the rubbing surfaces, the
pressure per unit area, the difference in
diameter of bushing and journal, and the
viscosity of the lubricant, as is shown also
by equation (13). If it is a question, then, of
choosing a lubricant for a certain bearing
whose velocity, pressure, and difference of
diameters are known, an oil should be taken of
such a viscosity at the temperature of the
bearing that it will stand at the lowest point
of the curve (see Fig. 6), and in this way the
optimum lubrication will be obtained. Under
conditions otherwise similar, oils of increasing
viscosity should be chosen as the pressure
increases or the velocity diminishes, and oils
of decreasing viscosity as the pressure dim-
inishes and the velocity increases22.
Hence the lubricant par excellence in a
mechanical sense does not exist. For each
case there is a most suitable lubricant which
can only be characterized in this regard by
its viscosity. At present it is not known
what viscosity will give the smallest coeffi-
cient of friction for each of the individual
combinations of pressure and velocity. Hence
systematic investigations of friction must be
made for this purpose23.
Types of bearings used in practice, with the
most accurate definition possible of bearing
and journal, as well as the determination of
the difference of diameter, must be employed
in these investigations, and not the oil
testing machines, whose friction bearings
differ entirely from the typical bearing. By
such investigations would be rendered possible
a comprehensive orientation of conditions
such as is now entirely lacking. They would
constitute an effective advance and render a
great service to technology. Similar sys-
tematic investigations could produce a like
enlightenment as to conditions in other
machine parts, such as the pistons of steam
engines, valves, etc. The many difficulties
of these investigations are yet to be overcome.
So much for simple oil lubrication. A
wholly new and very important aspect of the
matter is opened up by a method of oil and
graphite lubrication recently made known.
This will be considered in the following
section.
V. COMBINED OIL AND GRAPHITE
LUBRICATION
It has already been shown in Section II,
(page 1078) that in the practical operation
of machines one must take into consideration
not only the fluid friction in the bearing but
also the dry friction between the bushings
and the journal, especially at low velocity, or
at high pressure, or with both of these con-
ditions existing simultaneously. The entire
predominance of the dry friction over the
fluid in this case can be seen by comparing
the experimentally determined curves in
Fig. 6 (page 1077) with the computed curves
in Fig. 4 (page 1076). The fluid friction alone
can produce only a slight increase of frictional
resistance on the left ascending branch of
the curves, in fact, only about 6 per cent in
Umin- (See page 1076.) The increase found
in practice is, however, 500 times larger than
this, and raises the coefficient of total
friction at Uo to nearly 25 times /um,-„
Under the conditions this extraordinary
n The author has previously pointed out 'this relation in
"Post Chem.-techn. Analyse, Braunschweig 1906-7, Bd. 1. Heft
2, p. 327.
33 This has already been begun at the Karlsruher Technischen
Hochschule.
THE THEORY OF LUBRICATION
1119
increase must be attributed to dry friction
as well as fluid playing a part, and making up
a greater or less fraction of the total fractional
resistance according to circumstances.21
Now in order to obtain the optimum lubri-
cation, the dry friction should be avoided as
far as possible by using a lubricant of high
viscosity. However, this presents very great
difficulties in practice. The attainment of
the optimum depends upon the following
points:
1. Maintenance of a constant velocity.
2. Maintenance of a constant pressure.
3. Availability of a -constant viscosity in
the oil.
4. Dimensions and high polish of the
bearings and journals.
But in practical machine operation it is not
possible to fulfill all these conditions con-
tinuously, for the following reasons:
1. The velocity varies greatly; consider
for instance, rolling stock on a rail-
road.
2 The load varies, as, for instance, in
case of belt pressure, concussion,
deflection of the shaft, etc.
3. The viscosity of the oil changes with
the temperature.
4. The character and dimensions of the
bearing alter, because of the tem-
perature, wear, etc.
All of these causes work together in pro-
ducing the result that dry friction enters into
almost all cases, not only increasing the
frictional resistance tremendously, but also
at length altering the bearing by wearing and
grinding, and thus constantly supplying
further cause for dry friction.
The means must be sought, then, not to
avoid dry friction, but to decrease it as much
as possible.
We know that in Coulomb's law
R=H.N,
which refers to dry friction, the constant is
dependent upon the character of the surfaces,
and is large when the surface exhibits large
inequalities. The coefficient of friction for
machine bearings is therefore noticeably
higher when the journal and bearing have
not been sufficiently well ground, and smallest
when they have a high polish. Nevertheless,
there are always some inequalities, and dirt
in the bearing produces more as time goes on.
But there has been available for some
time a means of reducing dry friction, viz.,
the so-called graphite lubrication. Finely
divided graphite has the property of levelling
up the hollows in the surfaces, thereby
diminishing the coefficient of friction.
Yet simple graphite lubrication cannot in
most cases be substituted for oil lubrication,
since the coefficient of dry friction even then
would be many times greater than that for
fluid lubrication; and moreover the applica-
tion of the powdered lubricant to the sliding
surfaces presents difficulties. A combination
of graphite and oil lubrication is, however,
of the greatest advantage, since the graphite
reduces very considerably^ that part of the
total friction due to direct contact of journal
and bearing (dry friction), while the advan-
tages of oil lubrication are all retained.
The use in practice of this combination
has formerly been subject15 to the difficulty
that it was not possible to obtain a mixture of
graphite and oil of sufficient uniformity.
An important advance came about through
the discovery of Edward G. Acheson, described
below :
An artificial graphite26 made according to
the well known Acheson process in the
electric furnace and already used in large
quantities for various purposes is employed,
For the purpose under consideration two
properties are of especial significance: first,
Acheson graphite consists of almost pure
carbon, while natural graphites contain vary-
ing amounts of other constituents which
corrode the bearings and make their use for
lubricating processes always uncertain;
second, and specially important, is the fact
that the Acheson graphite, because of the
special method of preparation, is extremely
finely divided, so much so that the particles
exhibit Brownian movement. According to
the measurements of M. Alexander27 with
the ultra microscope, the particles are of the
order of magnitude of 100 jjl (x.
If this powdered graphite without further
treatment be combined with water, it forms
a temporary emulsion which settles out after
a short time. Moreover, the graphite can be
filtered off from this water emulsion without
difficulty. Acheson produced, however, per-
fectly stable emulsions, which could not be
separated by filtration, by treating28 the
(24) In general the part due to dry friction will be large, for" it
would appear that thin lubricants are used in most cases. The
viscous oils are too expensive.
(") See B.D.R., 140, 882. April 22, 1902. In this patent are
proposed, besides graphite, mica and talcum.
(!1) See M. F; Fitz-Gerald, Kunstlicher Graphit, Mono-
graphien uber angew. Elektrochemie 15, (1904): see also P.
Werner, Ueber Acheson-Graphit als Schmiermittel. Ztschr. f.
Chemie u. Industrie der Colloide 7, 161 (1910).
(=') See DeBocculation. Jour. Ind. Eng. Chem. 4, No. 1 (1912).
(a) Jour. Soc. Chem. Ind. »9, 244 (1910). also Jour. Ind. Eng.
Chem. 4. No. 1 (1912). The process has been patented in all
countries since 1907. D.R.P. 191, 840, April 4. 1907.
1120
GENERAL ELECTRIC REVIEW
specially prepared and powdered graphite
with tannin.
For the details of the process, see the patent
and publications of the inventor29. It may be
mentioned, however, that the effect of the
tannin is to be accounted for by its well known
and powerful effect upon the surface tension.
.1&.OS
Go 04
o, . 'o 30 SO 30 /So /SO /30 z/o s-to
CJ^ T/me /n MinuCes
Fig. n
This graphite is on the market as a paste
in two forms, as "Aquadag" and as "Oildag30."
The former contains, besides the graphite,
water, and is for preparing water emulsions;
the latter contains oil, and is suitable for
making graphite-oil emulsions.
Mixtures of "Oildag" and any oil desired31
are used for lubricating. Only small quanti-
ties, about 3^2 Per cent °f Oildag, are added,
and mixed by stirring. The resulting emulsion
may be used like the ordinary lubricants.
According to the investigation of L. Archbutt32,
it will pass through wick lubricators, etc.,
without any separation33.
Several investigations concerning the reduc-
tion of friction by the Oildag-Oil mixture,
have been published. Prof. C. H. Benjamin
of Purdue University34 has found that with
a bearing pressure of S.7 kg. per sq. cm. and
500 revolutions per minute, the frictional
resistance of a bearing lubricated with a
mixture containing }/£ per cent of graphite
in the oil is only 60 per cent that with oil
alone. After an hour the frictional resistance
becomes 50 per cent.
Exhaustive researches by Prof. Charles F.
Mabery35 have shown that the coefficient of
friction with the mixture of Oildag and oil is
markedly lower than with simple oil lubrica-
tion. Especially interesting are these inves-
tigations of Mabery's which prove that even
after an addition of only 0.35 per cent of
graphite, the lasting qualities of the oil are
significantly greater, and the amount of oil
may be reduced one-half and still have the
coefficient of friction smaller than before.
This is illustrated by curves determined with
a Carpenter Machine.
The tests shown in Fig. 11 were carried
out with a pressure of 150 lb. per sq. in. and
a velocity of 445 revolutions per minute.
As abscissa is taken time in minutes, and
as ordinates coefficients of friction. The oil
used was spindle oil.
Curve 1 is oil alone, supplied at a rate of 6
drops per minute.
Curve 2 is oil alone, supplied at a rate of 8
drops per minute.
Curve 3 is oil with 0.35 per cent graphite,
at a rate of 8 drops per minute.
Curve 4 is oil with 0.35 per cent graphite,
at a rate of 4 drops per minute.
After 120 minutes the oil supply was shut
off for all cases.
It should be noted on curve 1 that oil
alone, supplied at a rate of 6 drops per
minute, was quite inadequate.
Eight drops per minute (curve 2) was suffi-
cient, but shortly after cutting off the supply
the coefficient of friction increased very
rapidly.
In curve 3 (with 0.35 per cent graphite) it
is shown that not only with this last rate of
supply is the coefficient of friction lower, but
the oil lasts about four times as long after
stopping the supply, as does oil without
graphite. The graphite mixture at half this
rate of supply (curve 4) produces a smaller
coefficient of friction, and twice as long a
retention of the lubricant after stopping the
supply.
Fig. 12 shows very high pressure,
1200 lb. per sq. in., and a velocity of 444
revolutions per minute. As particularly
suitable to the high pressure, a viscous
American cylinder oil was used with bronze
bushings. After 120 minutes the oil supply
was shut off. It can be seen that the coeffi-
cient of friction with oil alone is considerably
higher than that with oil to which 0.35 per
cent of graphite has been added. The latter
also lasted six times as long after the oil supply
was cut off.
Oildag appears to have operated well in
the cylinders of steam engines. The reports
of comprehensive tests on the Government
railways are favorable. Moreover, a con-
siderable saving of oil in hot vapor cylinders
is indicated.
(■s) See preceding footnote.
(30) Furnished by Deutschen Acheson Oildag Company,
Berlin, Friedrichstr. 61.
(31) The lubricating oil must contain no acid constituents, as
otherwise the graphite will not stay completely emulsified.
(") Journ. of the Society of Chemical Industry. Dec. 30. 1911,
No. 24. Vol. XXX.
(M) There are also other trade products. These are, of course,
made from natural, non-emulsified graphite, which, as men-
tioned above, does not exhibit the same lubricating properties.
(M) According to Nach Ztschr. d. Bay. Revisions- Vereins
1908. S. 5-7.
(w) Charles F. Mabery of the Case School of Applied Science
of Cleveland, Ohio. Presented at the" January, 1910, meeting
of the American Society of Mechanical Engineers.
A MODERN ACID-DIPPING, ELECTROPLATING AND JAPANNING PLANT 1121
From all these investigations it appears
that, in accordance with the theory, graphite
properly prepared produces an extraordinary
reduction of the coefficient of friction. Apart
from this reduction in the coefficient of
friction, which is extremely important from
an economic point of view, the diminished
wear of the bearing and cylinder materials,
as well as the reduction in the amount of
lubricant required, is very important in
lowering the cost of operation. All of these
factors increase considerably the coefficient of
safety during operation, so that with oildag
lubrication the machine parts can be much
more safely overloaded than in other cases.
This is of especial importance in light motors,
aeroplanes, automobiles, etc.
c;c:
0/7 with
Of/ <4/one \35% Graph </te\
■3o so so /.?<? /so /do e/o
T/rne /n M/notes
Fig.
A MODERN ACID-DIPPING, ELECTROPLATING AND
JAPANNING PLANT
By Horace Niles Trumbull
Switchboard Sales Department, General Electric Company
It has been so universally true that electroplating rooms are unhealthful that one has almost come to
accept the belief that they must be so. Therefore it is of particular interest to read the following article which
describes a recent establishment that offers its workers hygienic conditions equally as good as those existing
in a well designed and operated factory. The article describes in detail the heating and ventilating of the
building, and the mechanical and electrical equipment which is used to carry on the work of acid dipping,
electroplating, and japanning. — Editor.
The various practical considerations
involved in the production of manufactured
articles require that the factory manager be
ever on the alert to obtain whatever advan-
tages may accrue from the use of the most
efficient machinery and methods available.
Under present day conditions, he must con-
tinually strive for both increased output and
lower manufacturing cost. There is thus con-
stantly before him the problem of determin-
ing whether to continue under existing
conditions or to retire some or all of the
present equipment in favor of other apparatus
more recently developed.
The human factor must be considered also.
There is a general agreement among thought-
ful and experienced minds that, based on
utilitarian principles alone, the environment
of the workman is of great importance and
worthy of careful attention.
In the case of perhaps the majority of
electroplating establishments the general con-
ditions in vogue certainly leave much to be
desired from several standpoints. A des-
cription of a modern plant, which in com-
pleteness of working equipment and means
of safeguarding the health of employees is
unsurpassed, will be of interest.
This plant is a part of the Switchboard
Department of the General Electric Company
and is centrally located with regard to
the various manufacturing sections of the
department from which it receives its work.
The building is a one-story brick structure
as shown in Fig. 1 and is divided into three
rooms; one for acid dipping, one for electro-
plating, and one for japanning and enameling.
It is lighted through a large amount of window
space located both on the sides and top of the
building. To aid the lighting system the
interior of the building, with the exception of
a five-foot border around the wall at the
floor line which is treated with asphaltum,
is finished with ecru paint.
The floors are of concrete and are kept
dry by draining into sewer inlets. The floors
of the dipping and plating rooms are, in
addition, treated with asphalt and granite
dust to make them acid proof.
The means of heating and ventilating these
rooms is quite unique. For heating, what is
known as the direct-indirect system is
employed. Air enters the building through
the several openings seen in Fig. 1 near the
ground line and then passes up through steam
radiators, which are of course heated in cold
weather only. The radiators, one of which is
shown in Fig. 2, are located in the interior
of the building against the wall and above the
air entrances.
The vitiated air is removed by a 35 h.p.
motor-driven fan through a particularly
effective system of hoods, flues, and ducts.
Over the dipping tank (Fig. 3) and over the
1122
GENERAL ELECTRIC REVIEW
cleaning tank (Fig. 4) a specially designed
hood extends out from the wall at an angle
of 60 degrees. Gases, fumes, and steam
from the tanks, together with air from the
room, are drawn up into the hoods through
slots 12 inches long, ranging from 134 to *M
Fig. 1. Acid Dipping, Electroplating and Japanning Plant
inches wide. These hoods are divided into
six sections, corresponding to the six sections
of the tanks, and each section of hoods is
provided with five slots or vents. From the
vents the air is drawn through flaes into the
main duct which leads to the intake of the
fan. Any section of the hoods may be shut
off from the main duct by slides in the flues,
to economize power when all sections of the
tanks are not in use. The fan is located
outside the building, rotates at a speed of
800 r.p.m., and develops a pressure of 3J4
oz per sq. in. It forces the exhaust of the
building up a steel stack, which is higher
than the surrounding buildings. This stack
may be seen in Fig. 1. The fan, motor, and
stack are treated with acid-proof paint.
The combined volume of the two rooms is
51,100 cu. ft.; and the ventilating system
removes the steam and acid fumes above
the dipping and cleaning tanks immediately
and completely changes the total volume of
air once every minute and a half. Thus the
atmosphere in the room is kept fresh and pure,
so that all danger to occupants from breathing
impure air is avoided.
The painting and baking room is heated by
radiation from steam pipes and is ventilated
by means of tilting-sash windows in the
cupola.
The work of acid dipping is carried on in the
usual manner, the dipping solutions being in
removable earthern vats placed in reinforced
concrete tanks along the wall (Fig. 3) . Run-
ning water and steam is
piped to these tanks
which are connected to
sewer drains.
Next to the dipping
room is the plating room,
a general view of which
is shown in Fig. 5. On
a balcony or platform
overhead will be noticed
three motor-generator
sets. These furnish cur-
rent at 5 or 10 volts for
plating. Two of these
sets are of 837 amperes
capacity. They are sup-
plied with double com-
mutators which may be
connected in parallel for
5 volts or in series for 10.
The third set has a 600-
ampere, 10-volt gener-
ator. The generators
are separately excited
from the factory power system.
Below the balcony is the three-panel
switchboard (Fig. 7) which controls the
motor-generator sets and the three main
Fig. 2. Direct-indirect Steam Heating Unit
feeder lines. The feeders carry current at
either 5 or 10 volts, depending upon the
position of the three lower switches on the
right-hand panel. On the lower section of
each panel is a twin pull-button control
switch which controls contactors for starting
A MODERN ACID-DIPPING, ELECTROPLATING AND JAPANNING PLANT 1123
or stopping the motor-generator sets. A
circuit breaker is provided for each motor
armature circuit and each generator field
circuit. In case of overload, series overload
relays in the generator circuit trip the gener-
ator field breakers. The switchboard is so
arranged that all generators may be operated
in multiple or any generator may supply any
feeder.
Instead of obtaining the desired voltage by
means of bulky rheostats mounted at each
plating tank, sets of contactors are used,
these being mounted on pipe framework
suspended from the ceiling. One set is pro-
vided for each tank. At the tank is a pedestal
(Figs. 8 and 9) on which are mounted a
voltmeter, a clock dial, and a series of push-
button switches. These push-button switches
operate the contactors. For each tank there
are six contactors, with resistances arranged
in parallel, which give a control equal to a
dial rheostat of thirty-six contact points.
In the plating room (Figs. 5 and 6) silver,
nickel, copper, brass, and zinc plating and
oxidizing are done. The equipment includes
cleaning tanks, two spiral conveyer plating
machines, four rotary-barrel plating machines
and four still plating tanks. All plating
machines are motor driven, the motor being
run from the factory power system; all
plating tanks are made of reinforced concrete.
The tanks for the two spiral conveyer
plating machines are each three feet wide,
three feet deep, and twenty-four feet long
(inside dimensions) . The walls are four inches
thick and the top surface of the tank is thirty
inches above the floor level. These two tanks
are equipped with spiral conveyer plating
machines. By referring to Figs. 6 and 8,
an idea of the operation of this machine may
be gained. A worm in the casing, extending
along the end of the tank, is belted to a
motor. This worm is geared to two long
spiral conveyers which extend the length of
the tank above the solution. These conveyers
are connected at the farther end by a U-shaped
rod over which rotates a disk with fingers
that slide on the rod (Fig. 6). The work to
be plated in this machine is hung on the
lower end of S-shaped hooks. The upper end
of each hook is hung on the continuous groove
of the conveyer. As this conveyer revolves,
the hooks advance along the groove or thread
and draw the work through the plating
solution. When the hooks reach the end of the
first conveyer they are mechanically trans-
ferred to the beginning of the second conveyer,
by being pushed along the U-shaped rod by
the fingers on the rotating disk. The work
is thus moved through an arc of 180 degrees,
then caught by the thread of the second con-
veyer, and in time is returned to the starting
end of the tank. Work may be continuallv
supplied to and removed from the machine
by one man, and a large quantity completed
in a short time. As this plating machine is
run by a variable speed motor, the time of
travel through the solution may be regulated
to suit the conditions of various kinds of
electroplating, the time to complete the
travel varying from half an hour to an hour
and a half.
There are two large and two small rotary
plating barrels to accommodate work so
shaped that it cannot easily be hung on con-
veyer hooks. The rotary plating barrel
(Fig. 9) consists of an octagonal cage on a
shaft and a concrete tank. In Fig. 5 the cage
is shown raised and ready to be loaded.
After loading, the cover is replaced and the
cage lowered into the tank where its support-
ing shaft fits in bearings. The cage is then
revolved in the plating solution by a motor
located outside the tank. As the cage revolves,
the work is tumbled which facilitates the
plating. For assistance in loading and
unloading the plating barrels, two air hoist
equipments are provided. Very large or
special work is plated in the still tanks.
No hot plating solutions are used, as
baths have been developed which, when
cold, plate as quickly as the old hot processes.
All water used for plating solutions is distilled.
All water used for cleaning is filtered. The
still and filter are mounted on the wall above
the cleaning tanks (Fig. 4).
The cleaning tanks are similar in con-
struction to the acid dipping tanks. The
cleaning compounds that are used hot are
heated by steam coils. In place of the old
method of stirring cleaning solutions by means
of flappers run by rods from eccentrics on
a line shaft, the solutions are agitated by
admitting jets of compressed air into the
bottom of the tanks from a pipe having a
number of small holes. The air bubbles up
through and thoroughly agitates the solu-
tion, giving excellent results. An air com-
pressor furnishes air for the agitators and the
air hoists.
The third section of this building is devoted
to painting and baking. The sanding necessary
on filled castings, and the painting are done
on the bench along the wall shown in Fig. 1 1 .
Openings on this bench are connected by
gooseneck pipes under the bench to exhaust
1124
GENERAL ELECTRIC REVIEW
S =
0 fc
1
= t
O £
-j. z
— ^
■ss
1> —
o
a.
IS
c E
1*
ft! S
A MODERN ACID-DIPPING, ELECTROPLATING AND JAPANNING PLANT 1125
fans which effectively remove all dust when
sanding and paint motes when spraying.
Articles to be japanned are dipped in the
tanks shown in the foreground in Fig. 11,
and then placed on adjustable shelves or
hung from racks in the electrically heated
revolving bake oven.
This oven consists of a square brick room
open on part of one end and lined with non-
pareil insulating brick which is sprayed on
the exposed surface with silicate of soda.
In the oven is a motor driven turntable on
which is built a steel cylinder ten feet in
diameter and nine feet high, containing two
opposite compartments with openings cor-
Fig. 7. Switchboard in Electroplating Room
responding to the opening in the brick wall.
In the space between the brick wall and the
steel cylinder there are placed a sufficient
number of electric heaters, consisting of
resistance grids, to bring the temperature of
the oven to 500 degrees F. When, the turn-
table is in such a position that one of the
openings of the cylinder is in line with the
opening of the brick wall, that compartment
of the cylinder may be loaded with the
material to be baked. After this is done,
the turntable is revolved through ISO degrees.
The loaded compartment is then in the baking
position. The other compartment of the
cylinder has now swung round to the position
Fig. 8. End View of Spiral Conveyer Plating Machine
showing Pedestal for Regulating Plating Voltage
and Speed of Conveyer
where it may be unloaded and reloaded. If
the turntable is turned 90 degrees instead of
180 degrees, both compartments will be in
the baking zone.
The wire mesh gate shown raised in Fig. 1 1
is a safety device, and when in this position
allows access for loading and unloading. It
is necessary for the gate to be in the lowered
Fig. 9. Motor-operated Rotary Plating Barrel in
Operating Position — Air Hoist Above
112G
GENERAL ELECTRIC REVIEW
Fig. 10. Switchboard for Controlling the
Heating of the Baking Oven
position before the driving
motor circuit can be com-
pleted, thereby preventing
movement of the turn-
table when the gate is up
but allowing the table to
be revolved at the proper
time without danger of
accident to the operator
or others.
A means taken to con-
serve heat consists of two
vertical doors or flaps along
the edges of the oven open-
ing, which press against
the revolving cylinder and
close to the outer air the
zone between the oven and
the cylinder. When the
cylinder is revolving the
flaps are drawn to one
automatical!-..
Clock dials, conveniently located, are used
to show the time of placing a load in the oven.
A dial thermostat located under the clock
dials indicates the inside temperature of the
oven. Behind the oven is located the switch-
board (Fig. 10) which controls the heating of
the oven. On the switchboard are mounted
an ammeter, a circuit breaker, a relay, a lever
switch for each bank of heating resistances
and two single-pole contactors which are
controlled either by a lever switch or an
automatic time switch. By use of the
automatic time switch, which has a resetting
device, the current may be automatically shut
oft from the heating resistances at a pre-
determined time and turned on again when
desired. Thus the work can be safely left
baking when the attendant goes home at
night, and when he arrives in the morning the
oven will be at the required temperature and
ready for the next load.
The oven and equipment are unique in
design, and very efficient in operation. The
objects accomplished by this revolving oven
are; (a) continuous baking may be obtained
without having to bring the temperature
from that of the room to the baking tempera-
ture at each loading, (b) there is no fire risk
as with gas-heated ovens, and (c) the turn-
table feature allows the work to be handled
close to the oven so that floor space is econo-
mized and the distance necessary to earn-' the
parts reduced to"a minimum.
Fig. 11.
Painting and Baking Room showing Paint Bench and Electrically
Heated Revolving Oven — Oven in Loading Position
1127
PROTECTION OF RAILWAY SIGNAL CIRCUITS AGAINST
LIGHTNING DISTURBANCES
By E. K. Shelton
Lightning Arrester Engineering Department, General Electric Company
The subject matter of the following article is well explained in its title. The author first classifies the
various types of automatic block and interlocking signal systems and their circuits, and then classifies the
apparatus that is to be protected on each circuit. Following these are statements of the locations where trouble
is likely to occur due to disturbances, and descriptions of how the troubles can be eliminated by properly select-
ing and installing lightning arresters. — Editor.
The modern systems of railway signaling
in this country all operate on the well-known
automatic block and interlocking principle.
They can be classified in three types or groups,
viz., the mechanical, the electro-pneumatic,
and the all-electric. The successful operation
of the second and the third types is largely due
to the effectiveness of the apparatus that pro-
tects their electrical elements against lightning
disturbances. Consequently, a description of
this protective apparatus and its operation
should be of interest.
In studying the protection of these systems
against lightning there are three main factors
to be considered : first, the nature of the circuit
and the importance of the service; second, the
disturbances that are to be experienced; and,
third, the nature and the type of the apparatus
that is connected to the circuit.
The all-electric system of railway signaling
can be divided into two general classes
(dependent upon the method of operation)
and these into further subdivisions in accord- .
ance with the detail circuits.
Automatic Block Signals and Interlocking Signals
I. D-C. Operated
(1) Primary batteries
(a) Track circuits
(b) Signal mechanism circuits
(2) Portable storage batteries
(a) Track circuits
(b) Signal mechanism
(3) Stationary storage batteries
(a) Track circuits
(b) Signal mechanism circuits
(c) Battery charging circuits
II. A-C. Operated
(1) Generating or power supply stations.
(a) Power supply line fed direct from
generators used entirely for that
service.
(b) Power supply line fed through
step-up transformers or direct from
another commercial system.
(2) A-c. supply transmission circuits and
line sectionalizing equipment — 1100 to
11,000 volts.
(3) Step-down transformers at signal sta-
tions supplying 110 and 220-volt signal
mechanism circuits,
(a) Secondary transformers or low-
voltage taps on main transformers
supplying 6-volt track and 15-volt
lighting circuits.
In these circuits are located the various
pieces of electrical apparatus upon the reliable
operation of which the success of the signal
system depends. By an intelligent and proper
application of lightning arresters to these
circuits a high degree of reliability is secured.
The classification of the signal apparatus
connected in the circuits follows:
Apparatus to be Protected
I. D-C. Operated Systems
(1&2) Track relays and signal control
relays, contact points, signal motors,
and lights.
(3) Same as under (1) and (2) with the
addition of the battery charging
circuits, including the generator and
rectifier.
II. A-C. Operated Systems
(1) Generators and transformers with
controlling switchboard.
(2) Transmission lines, sectionalizing
oil switches, and primaries of step-
down signal transformers. (These
in general are under 1.5 kv-a.)
(3) Low-voltage secondary circuits:
Track relays, signal relays, contact
points, signal motors and lights.
These various circuits and the apparatus
connected thereto are usually exposed, in
a greater or lesser degree, to lightning dis-
turbances. The amount of trouble that is
experienced depends primarily of course upon
whether tile system is operating in a lightning
zone, for the majority of disturbances are the
result of lightning. Other types of trouble
than those arising from direct lightning
influences have occurred in some installations.
For instance, there have been cases of static
accumulations on the transmission circuits
due to peculiar climatic conditions and, what
1128
GENERAL ELECTRIC REVIEW
is more frequent, of surges on the main trans-
mission circuits due to badly balanced loads.
An example of this latter type of case is that
in which a single-phase power supply for
signal purposes is taken from a three-phase
circuit that is carrying a badly regulated
power load on the other phases.
As the signal control and operating
apparatus is of the same general type for
both direct-current and alternating-current
circuits, and as the lightning arresters are
the same for both services, consideration of
the protection of both systems can be made
under one common heading.
Generally speaking, it would seem that
these low-voltage circuits ought to be quite
well protected by the very nature of their
installation but experience has shown that
much damage can be done to their connected
apparatus by lightning. Relay and instru-
ment coils have been burned out, grounded
or short-circuited between turns, and con-
tact points have been arced over and fused
together. For adequate protection against
such troubles (which are severe because the
insulations involved are rather delicate and
therefore cannot withstand the strains to
which general power apparatus may be
subjected successfully) a discharge path
having a low spark potential is necessary,
and at the same time the path must be one
which will not permanently ground or short-
circuit. The vacuum-tube lightning arrester
admirably fulfils both requirements. At all
points on these low-voltage circuits where
protection is desired this type of arrester
should be employed, it being installed as
near as possible to the terminals of the relays,
coils, motors, lights, contact points, etc.,
that are to be protected. The single-pole
vacuum-tube arresters designed for this
service assure both satisfactory operation in
themselves and the fulfilment of the signal
circuit requirements.
The manner of grounding these arresters is
of the same importance as that with other
types of arresters, and perhaps more depends
upon this feature than upon any other. At
each signal station a good reliable earth
ground of permanent value should be in-
stalled, to which must be connected the
ground leads from the various arresters at the
station.
The transformer secondary circuits of low-
voltage alternating-current systems should be
fused to their full capacity ; this will prevent
the fuses being blown when discharges occur
over the arresters.
Aside from the actual signal circuits there
are several auxiliary circuits involved where
protection is of vital importance. Included
in the third class of direct-current operated
systems there is a charging circuit which is
usually of from 350 to 600 volts and is supplied
either from a motor-generator set or rectifier.
Its lines are carried either overhead or under-
ground along the track and tap into the signal
stations for the purpose of charging the spare
storage batteries. If this circuit is an over-
head one and is subjected to only mild dis-
turbances, a magnetic blowout arrester in-
stalled at the supply station will furnish
sufficient protection, but additional arresters
should be also applied at the signal stations
if severe disturbances are experienced.
Instead of the magnetic blowout arrester,
the direct-current aluminum arrester could of
course be applied but, since the circuit is
non-grounded, the aluminum arrester would
necessarily have to be a special one in that
it must be made up of three units (two in
series between lines and one from the middle
connection of these two to ground) and, in
addition, a special charging switch would be
required so that the film could be formed on
both plates of the ground cell.
In alternating-current operated systems
the continuity of service depends almost
entirely upon the reliability of the supply.
The possibility of failure of the generating or
transmitting apparatus, and the consequent
endangering of life and property, demands
that only the best equipment be employed.
Considering the various parts of this supply
system in order we have, first, the generating
station feeding the supply line either directly
or through step-up transformers. For an
overhead distribution system the supply
station should be protected by alternating-
current electrolytic arresters and choke coils
in the outgoing power lines. The step-down
transformers which feed a signal station
should be protected by graded-shunt resist-
ance multigap arresters, or compression-
chamber arresters, and it is also desirable to
have choke coils in the taps to the trans-
formers. If the signal stations are located at
considerable distances apart and the overhead
transmission line is exposed to frequent
lightning disturbances, line arresters should be
installed at frequent intervals between the
stations to relieve the stresses on the line.
These arresters should be of the same type as
those at the transformers and should be
connected directly to the line without choke
coils.
1129
GROWTH OF CURRENT IN CIRCUITS OF NEGATIVE TEMPERATURE
COEFFICIENT OF RESISTANCE
By F. W. Lyle
Research Laboratory, Lynn, General Electric Company
This article was prompted by the contribution in our January issue on the Infinite Duration of Transients,
which dealt with the growth of current in circuits of positive coefficient of resistance. The author takes the
formula derived in the preceding article and shows how it may be applied to the consideration of the growth of
current in circuits of negative coefficient of resistance; and for the critical and larger voltages, where this
modified formula becomes inapplicable, a new formula is derived which will give the time required for the
current to reach an indefinitely great value in circuits that are virtually non-inductive. — Editor.
The steady state representing the complete
evanescence of transients is given by -r, — o
hence
a-\-bi+ci2 = o (3)
The limiting value of current i for the steady
state is obtained by solving this for i and is
In the January, 1915, number of the Gen-
eral Electric Review, Mr. Chas. L. Clarke
discusses, in a very interesting note, the effect
which a positive temperature coefficient of
resistance has on the time that is taken by
an electric current in a conductor to rise to
its full value.* As conductors, pure metals
and most alloys show a positive temperature-
resistance coefficient, but there are many
conductors which display a negative co-
efficient. For instance, the negative char-
acteristic is possessed by the pure metalloids
— carbon, silicon, and boron — and by most
chemical compounds.
Since such conductors do exist and have
many rather unusual properties, a considera-
tion of them and of their relationships may
prove to be interesting when viewed in the
light of Mr. Clark's equation.
In the circuit of constantly applied e.m.f.
and simple non-inductive resistance, as
treated in the article above mentioned, the
relation between current and time is derived
from an equation
Edi Edi
[\Sr,E-\Sr,ra(.\+ahi)-aUr»EP)i (a+bi+cp)i K
where a = temperature coefficient of resist-
ance; E = applied e.m.f.; i = current; £ = time;
and the other quantities are physical constants
which do not relate to the present question.
This equation is directly applicable to a
circuit of negative temperature coefficient by
simply changing the sign of a from plus to
minus. By so doing, it is found that the
sign of c changes, while those of a and b do
not, and that the form of the solution depends
upon whether the quantity Vo2— \ac which
is derived from the term in parenthesis in
(1) has been made imaginary in the result.
If Vo2 — 4ac is still real, the solution remains
as given by Mr. Clark's equation; if it has
become imaginary, the solution takes on the
entirely different form that will be given below.
Upon turning again to equation (1) it will
be apparent that by simple transposition it
can be written
jg=(a+K+«*)« (2)
^-fczpA/fc2-
■4ac
2a
(4)
It is at once noticeable that when a is nega-
tive — 4ac is negative and that under certain
circumstances 4ac may be greater than b2
under which conditions the equation will have
imaginary roots and there will be no real
value of i which gives a steady state of current.
The significance of the change of form in
the solution of (1) when \/b2 — Aac is unreal
is now apparent, for it represents an unstable
circuit. As such, it should possess con-
siderable interest and its general properties
be worthy of investigation.
The solution here found represents the
conditions frequently met in circuits of nega-
tive temperature-resistance coefficient. Boron
and silicon conductors and many of their
alloys with carbon produce these circuits, as
do also many chemical compounds such as
the oxides composing the Nernst glower.
The phenomena observed in such circuits
may be illustrated as follows: On applying
to the circuit a small constant voltage, a
current flows starting at the value corre-
sponding to the cold resistance of the circuit.
By this flow the latter is heated slightly and
the current increases. If the voltage is not
too high, the current soon reaches a sensibly
steady value and equilibrium is attained.
As successively higher and higher voltages
are applied, the current increases in a .ratio
somewhat greater than the first power of the
voltage until a small further increase of volt-
age causes a very sudden current rise, and
the rise will continue at an always accelerat-
ing rate until the circuit is ruptured by the
overload. This unstable equilibrium exem-
* An errata note, applying to the article referred to. appeared
in General Electric Review, Feb. 1915, p. 152.
1130
GENERAL ELECTRIC REVIEW
plifies the case where equation (4) has unreal
roots.
The effect which the negative temperature
coefficient of resistance has on the rate at
which the current rises in value will now be
explained.
As long as a voltage less than the critical
is applied to the circuit, the value of b- — 4 ac
is positive as in Mr. Clark's equation and the
current will vary with time according to the
statement of value given in his article, viz:
-S— l0g T.
•j-coiist.
Eb
"2a
vV
(1 2ci + b-
\ I- -la. '' 2ci+b+y/&
-iac )
and the current will be an exponential func-
tion of the time.
When the breakdown voltage is exceeded,
this formula involves imaginary numbers and
cannot be directly applied.
An integral in the form
E, P F.h( i -i_2ri+ft_\
'= Ta '°g a+bi+cp— J\ ^ Vac --b-- ""' % AaT^b'-)
gives the relationship of current and time in-
volving only real quantities.
For very great values of current i the" first
term of the right-hand member of (6) ap-
E 1
proaches the value — loe — and the second
~>n r
term the value
la
Eb
a viae
=*G>
The lapse of time / that is required for the
current to reach an indefinitely great value
is therefore finite and is equal to
l^1- ^ 1
£[*
for the ideal circuit of zero inductance
treated herein. It is practically equal to
this value for actual circuits which are vir-
tually non-inductive. The necessarily in-
creasing rapidity of the growth of current is
sufficiently evident from the above con-
sideration.
ELECTRICALLY HEATED ENAMELING OVENS
By C. W. Bartlett
Industrial Control Supply Department, General Electric Company
Wink- it is true that heat units in the form of electricity cost more than the same amount in the form of
gas or oil, it does not always follow that heating by gas or oil is the cheaper or better method. Among the
several fields of heating in which electricity has been proved superior to chemical fuel is that of enamel baking.
A description of the types of electric baking ovens used and a contrasting of the advantages of electric heating
against the disadvantages of fuel heating summarizes the contents of the following article. — Editor.
The recent action of a prominent auto-
mobile manufacturing concern in converting
all its gas heated enameling ovens to electric
service, together with the addition to its
baking plant of a number of new ovens
designed originally for electric heating, has
served to concentrate on the electric type
of oven the attention of others interested
in the economical production of baked
enamel parts.
The installation above referred to comprises
twenty ovens, having a total content of more
than 50,000 cu. ft., and the aggregate con-
nected load will be approximately 6000 kw.
This large installation was not determined
upon until the superiority of the electrically
heated oven over others heated by oil, gas,
or steam had been thoroughly demonstrated
by numerous and drastic tests; therefore,
an analysis of the conditions developed and
results obtained ought to be of interest.
Briefly stated, it was found that the electric
type of oven insures a greater production,
with a lower unit cost, than do other types;
it permits of utilizing a positive heat control,
eliminates the danger of explosions, and in
addition it produces a notable improvement
in the quality of the finished enamel.
In regard to the first point, i.e., increased
production, it was estimated that enamel
could be baked from 30 to 40 per cent faster
with electric heat than with either gas or oil
heat, but actual tests made later in a number
of ovens showed that the time required with
the electrically heated ovens was in many
cases 60 per cent less than that required
by other types. These data were secured in
tests of ovens that were formerly operated
by gas or oil, as well as of those originally
designed for electrical operation.
The remarkable production increases are
due largely to the fact that practically all
the available thermal energy of the electric
current is directly applied in useful work,
whereas with gas or oil-fifed ovens the flame
must be baffled or mufHed in order to secure
ELECTRICALLY HEATED ENAMELING OVENS
1131
Fig. 1. A View of an Electrically Heated Japan Baki
ng Oven and its Controlling Equip
, '
Fig. 2. A View showing a Loaded Elect™
cally Heated Drying and Baking Oven
1132
GENERAL ELECTRIC REVIEW
an approximation to uniform heating and
for this reason the convection currents,
which are the drying agents, are retarded.
The electric heating elements give a uniform
heat" radiation and, therefore, muffling is
unnecessary.
Furthermore, in comparing the costs of gas or
oil-fired ovens with those of the electrically
heated type, the latter must also be credited
with a saving in the insurance rate, on
account of the lessened fire risk.
In quality, the enamel baked by electric
heat surpasses that by gas or oil. The work
done by an electric oven is readily dis-
tinguishable from that of a gas oven by its
finer finish and brighter gloss, which is
accounted for by the fact that all combustion
gases (which tend to dull the finish) are
absent in the electric oven.
In lacquered work, especially, it has often
been found that the products of combustion
of the gas-heated furnace produce dis-
colorations.
In the electric oven, with the correct
arrangement of units, the heating is uniform
and all parts of the work are baked to the
same degree of hardness, whereas when
done with gas it is often found that the
work is baked much harder at the top of the
oven than it is at the bottom.
Fig. 3. A Set of Electrically Heated Drying and Baking Ovens
In addition to this factor of muffling, there
is a very considerable loss of thermal efficiency
in gas or oil-fired ovens due to the fact that
considerable ventilation is required in order
to take care of the combustion gases. As an
instance of the improved oven efficiency
rendered possible by electric heating, it was
found that in a battery of gas ovens provided
with eight 10-in. by 28-in. vents each, to
carry off the gases, it required only one of
these vents (and this one but partially
opened) after the adoption of electric heating.
Thus the thermal loss entailed through
ventilation was reduced to practically
nothing. With electric heat there are no
combustion gases and ventilation is required
only for the purpose of permitting the escape
of the vapors produced during the baking
process.
While in some cases the gross cost of heating
ovens by means of electric current is greater
than when using gas or oil, the improvement
in production. is such that a greatly increased
output is insured for a given oven equipment .
This feature may well be considered
important, aside from the economy in time,
in plants where floor space is limited or
valuable. Where the enameling equipment is
of considerable size, it will be found that the
labor cost per unit is considerably reduced
when electricity is employed for heating.
Fig. 4. Combined Steam and Electric Oven for Baking Japan,
one compartment being loaded and the other baking
In order to bake colored enamel properly,
the temperature must be constant, for a
variation of a few degrees may change the
color of the enamel. For example, a white
japan that bakes properly at 150 deg. may
ELECTRICALLY HEATED ENAMELING OVENS
1133
turn to a cream at 165 deg. F. In the electric
oven the temperature is more easily con-
trolled than in the gas or oil oven; and the
electric system adapts itself very readily to
automatic control so that a uniform baking
temperature can be maintained.
In all gas and oil installations there is
always danger from fire and explosion. So
long as these types are used, there is a con-
stant and unnecessary, risk which involves
possible material damage, loss in production,
and even loss of life. The use of electricity
for heating eliminates this fire and explosion
hazard.
Work is heated in an oil or gas furnace
almost entirely from convection; the flame
offering very little chance for radiation. With
electric heaters the units are close to the
work and heat is given off partly by con-
vection currents but mainly by radiation.
The radiating heat travels in straight lines,
as do the rays of the sun, and is transmitted
much more rapidly to the work and pene-
trates more completely and rapidly than
does heat from convection currents.
The final operation in enameling is the
oxidation of the surface of the enamel which
gives finish and gloss to the work. In the gas
or oil fired oven a large part of the oxygen is
used in combustion, while in the electric oven,
it remains in its free and uncontaminated state
to do its work in oxidizing the enamel.
Electric heat is superior to steam heat as
it is more easily controlled and as steam heat
cannot be used except for low temperatures:
For example, 400 deg. F. would require a
steam pressure of 250 lb. per square inch,
which is not to be desired.
Conversion of Gas or Oil Ovens to Electric Heat
Any oil or gas-fired oven can be adapted
to electric heating with very little trouble.
It is merely necessary to remove the oil or gas
fixtures and to place the electrical units
in the proper position in the oven. This
position will depend upon the kind and
shape of the work, and upon the size of the
oven. If the old oven is effectively heat
insulated and its interior walls are of low
thermal capacity, this part of the oven may
be left unchanged; but, if it is not so con-
structed, economy will demand that it be
redesigned so as to obtain the greatest advan-
tage of electric heat.
Arrangements should be made to cut off
practically all ventilation when the work has
reached a certain temperature as this will
greatly increase the efficiency of the oven.
Ovens Especially Designed for Electric Heat
There are several different kinds of ovens
especially designed for electric heat. These
are thoroughly heat insulated and are most
efficient for the class of work to which they
are adapted.
Fig. 5. An Electrically Heated Drying Oven
Revolving Type
The revolving type of oven is so arranged
that work can be put in or taken out half of
the oven while the other half of the oven is
baking. The oven is revolved by a motor
and worm gear at the top. When the safety
door in front of the oven is open, the motor
is automatically disconnected from the line,
which makes the outfit absolutely safe. This
type of oven has several advantages.
(1) The space taken up is small compared
with the output.
(2) The baking can go on while work is
being put in and taken out.
(3) It is not necessary to cool down the
oven every time a charge is put in, which
makes the oven very efficient.
Drawer Type
In this type of oven the work is placed on
a carriage and pushed into the oven. Y/hen
one charge is baking a second carriage may
be loaded and in this way the oven is never
without a load. This type has an advantage
over an oven where the work is hung on
1134
GENERAL ELECTRIC REVIEW
internal supports in that it never has to be
cooled down to take out and put in work,
thereby giving a larger output from the
same size of oven.
Enamel Characteristics
Different classes of work require different
grades of enamel; and the enamels or japans
be dried and hardened in an oven at 160
deg. F. in three or four hours with much
better results.
There are other enamel-japans that can
be baked on at high temperatures. The
advantage of these enamels is that at a high
temperature the enamel can be baked on a
great deal quicker than at a low temperature,
Fig. 6. An 11-Kw., 440-Volt Air Heating Unit
made by different manufacturers for the
same kind of work may vary greatly in their
constituents and in their baking treatment.
It is imperative, therefore, in order to obtain
the best results, to follow the instructions
of the enamel manufacturer closely when
using his particular product.
Some work, owing to its construction and
material, will not stand a temperature of
over 300 deg. F. for baking. For instance,
any piece of work that is soldered will be
and a much larger production is therefore
possible in the same amount of space. For
example, an enamel that required four or five
hours baking at 300 deg. F. can be baked
on at 500 deg. F. in three-quarters of an hour.
The heater units are so designed that their
resistor temperature will be considerably
under the flash point of the enamels which
are being baked, when the oven is running at
its maximum baking temperature. In this
way, absolute protection is afforded against
Fig. 7. A 5-Kw, Ribbon-Wound Air Heating Unit
injured at a temperature of 370 deg. F. On
account of this fact, baking enamels have
been manufactured which harden at a low
temperature.
Some air drying japans which require
twenty-four hours to harden in the air can
ignition of the oven vapors, whereas in the
gas oven with an open flame there always
exists a possibility of ignition from the gas
flame which may result in a fire or explosion.
The advantages of baking electrically
increase as the baking temperature is
ELECTRICALLY HEATED ENAMELING OVENS
1135
increased; and the greatest economy, in
general, is secured through the use of a high
temperature baking enamel — for example,
an enamel that bakes at 500 deg. F. Among
the reasons for this fact are the following:
The temperature of an oven may be raised
to a high value in much less time through
the application of electric heat than through
the use of oil or gas, and at the same time
electricity offers a greater safeguard against
overheating of the oven contents. By
bringing up the oven temperature rapidly
the baking is done in much less time, and
convection and radiation losses are reduced
in proportion, thereby giving a greater
thermal efficiency than is possible with gas
or oil-fired ovens. It is due to this lessening
of time that from 40 to 50 per cent greater
production can be secured from a given
electrically heated oven than from an equal
size gas or oil heated oven.
Location of Heating Units
The position of the units in the oven
depends upon the size of the oven and the
shape and quantity of the work. In some
classes of work it may be desirable and even
necessary to mount the units on the wall
while in other cases the units will work to
better advantage on the floor.
Units on Jloor,
sides and end
ire ^£-7- f?eo*£-
S '£?£■& S*?*0 £-sv^>
W V .
T — X
XI
H 3T
x — X
x — X
i1 V
B
W4
n
rT^~F
X~l
x~x
r^
x—x
X — X — £ — T
u n (j
Fig. 8. Wiring Diagram for an Oven having Heating Units on the Floor, Sides and Ends
1136
GENERAL ELECTRIC REVIEW
THE ELECTRIC MOTOR IN THE PRINTING INDUSTRY
By W. C. Yates
Industrial Control Department, General Electric Company
The author makes an interesting review of the application of the electric motor to the printing industry.
Statistics are cited to show the importance of the printing press and the general advantages of the electric drive
are discussed. The motor and control requirements of job, flat bed, lithographing, rotary, magazine and news-
paper presses are given. This article is an amplification of a written discussion given at the annual convention
of the A.I.E.E. at Deer Park, Md. — Editor.
The claims of the electric motor found
early recognition in the printing industry and,
likewise, the requirements peculiar to that
industry have long been given thorough
consideration by the manufacturers of elec-
tric motors and controlling appliances. Some
of the earliest specialized types of controllers
used with industrial motors were those
designed primarily to afford features of
control essential to the proper operation of
the printing press. As most noteworthy
of such control equipments may be men-
tioned the full automatic type by means of
which the operation of a large newspaper
press can be completely controlled from a
small group of push button switches. This
full automatic remote control equipment for
the printing press was in use in many news-
paper plants at a time when practically all
other electric motors applied to industrial
service were equipped with manually operated
controllers; the chief exceptions being self-
starters installed with pumps and the control
for electric elevators.
The importance, therefore, of the electric
motor to the ideal drive of the machinery of a
printing establishment, especially the presses,
was determined years ago, and has been
taken for granted ever since. It should not,
■however, be taken for granted that no new
features have been introduced or that no
improvements have been made. The amazing
progress during the past several years in the
art of electric motors, and especially their
control, is naturally reflected in all motor
installations including the printing plant.
The magnitude of a business is the largest
factor in determining to what extent it may
profitably be specialized upon. In this con-
nection a few facts bearing on the size and
rapid growth of the printing industry may
be of interest.
The following statistics are extracted from
the United States census reports of 1909
showing the condition of the printing industry
at that time :
The foregoing figures indicate not only the
rapid growth of the industry, but also the
much more rapid increase of power used
which has come to be, for the most part,
electric power.
The census reports show further that the
printing and publishing industry stands
sixth in the gross value of products among the
manufacturing industries of the United States.
It is interesting to note that the value added
by manufacture to the raw material is over
72 per cent of the ultimate total value, which
percentage is approached by few other
industries.
It can be assumed that the census statistics
cover the printing industry as represented by
the establishments devoted entirely or pri-
marily to that business. These are chiefly:
Job printers, book and magazine publishers,
newspapers, photo-engravers, electrotypers,
stereotypers, lithographers, book binders.
Figures are not available covering the
large number of printing plants which are
adjuncts to other industries. Private plants
are to be found in many large manufacturing
establishments and their value is no doubt
credited by the census takers to the industries
represented by those establishments. As
examples of such private printing plants are
those which are a part of the equipment of
manufacturers of food products and of
proprietary articles.
The census report tells us further that the
value of products of the printing, publishing
and allied trades totalled for 1909 the sum of
$878,000,000. The manufacture of paper
goods, including boxes, bags, and wall paper,
may find credit in that total, but it can be
taken for granted that the printing of silk,
other cloth, and leather, although neces-
sitating the use of machinery very similar to
that employed in the printing of paper, is con-
sidered as belonging to those particular trades.
Newspapers, as can well be appreciated,
comprise no small part of the printing
industry. There are today published in over
10,000 towns in the United States and ter-
ritories, approximately 2400 daily papers and
20,000 newspapers issued weekly or at other
periods.
The greatest center of the printing industry
in the United States is New York City where
THE ELECTRIC MOTOR IN THE PRINTING INDUSTRY
1137
that industry stands third in the list as
regards the number of employees. The two
industries which rank it are first the clothing
industry followed by the aggregate of the
various metal trades.
Enough has been said to indicate the
magnitude and importance of the printing
industry, in which industry the electric motor
finds a most important field of application.
In fact, the motor is indispensable as it
furnishes the ideal drive for the various
machines in a printing plant which in no
modern establishment or one of any con-
all machines with the exception of the presses
and folders the selection of a suitable motor
is a relatively simple matter and no special
features of control are involved. For the
most part, constant speed motors are employed
and the control may be an ordinary hand
starter or in cases where remote control is
desired, a self starter may be used which is
operated from one or more push button
stations. Where the work necessitates the
use of an adjustable speed motor, a manually
operated speed controller will usually answer
the purpose.
PRINTING AND PUBLISHING ESTABLISHMENTS
Number of establishments
Total persons engaged. . . .
Value of products
Capital
Total horse power
Electric horse power
Electric power purchased.
1899
23,814
$395,000,000
333,000,000
119,775
41,413
33,582
1909
31,445
388.446
$738,000,000
588,000,000
297,763
229,312
197,692
Per Cent Increase
32
87
76
148
450
490
sequence are operated by any other means.
The chief factors favoring motor drive as
compared to any other driving means are:
No obstruction to light by overhead
belting and shafting.
Cleanliness.
Quietness.
Convenience of location.
Saving of floor space and headroom.
Economy of power.
Wide range of speeds.
Convenient control.
Protection to the operator.
Economy of time.
Reliability.
These factors may be recognized as apply-
ing to almost any kind of machinery equipped
with individual motor drive. There are no
machines, however, to which the speed range,
convenience of control, and reliability of the
electric motor are of greater importance than
to a printing press— especially one producing
a daily newspaper.
In the general book, pamphlet and job
printing industry motors are applied to
composing machines, printing presses, folders,
cutters, stitchers, and binding machinery.
In newspaper printing plants, motors are used
on composing machines, matrix and plate
making machines, printing presses, paper
hoists and conveyors and exhaust fans. For
The advantageous characteristics offered
by the electric motor apply to all the power-
driven machinery in the printing plant but
especially to the presses, which require
features of drive and control that nothing else
can offer. In the following are taken up the
several broad classes of printing presses,
with a brief discussion of the types of motors
applicable in general to each class and of the
features entering into the proper control of
the motors.
The various types of printing presses fall
into three general classes:
Small platen presses, ordinarily called job
presses.
Flatbed cylinder presses.
Rotary presses.
Job Presses
These, used for printing cards, circulars,
small jobbing and commercial work, have a
type bed and impression platen which are
both flat surfaces. The type form is held
stationary, and approximately vertical, while
the platen on which the paper is placed
swings up to meet it. Hand sheet feed is
the rule, though automatic feeds are some-
times used.
The general ran of job presses requires
motors ranging in capacity from y§ to 1 J^ h.p.
The motors are generally best mounted on the
floor and arranged for belt drive to a fairly
1138
GENERAL ELECTRIC REVIEW
large press pulley. Friction drive, using a
friction pulley bearing against the flywheel,
is also used.
The control requirements are simple. On
direct current circuits a shunt motor is
employed usually controlled by a no-voltage
Fig. 1. Job Presses Equipped with Controllers and
Push Button Stations
release speed regulating rheostat in the
armature circuit. The small sizes of the
motors used make permissible control of
speed by armature resistance as the wastage
of power is inconsiderable, especially as the
motors are usually run at or near the normal
speed.
There are applications, where the speed of
production is of prime importance, where a
push-button operated controller, providing
predetermined speed setting, gives the best
results. See Fig. 1.
On alternating current circuits the best
results are obtained by the use of a com-
mutator type single-phase motor. Such
motors are available designed for speed
control by brush shifting and with the shift-
ing mechanism arranged for foot operation.
See Fig. 2.
Flatbed Presses
These have the type forms carried by a
heavy, rigid platen sliding back and forth in
"ways," similar to the bed of a metal planing
machine. At each pass the type passes under
the impression roll at one end of its travel, and
under the inking rolls at the other extreme
There are several classes of flatbed presses
differing in the relative motions of the cylinder
and platen, although in all types the impres-
sion cylinder always revolves in the same
direction.
Flatbed presses are employed for sheet
printing and are generally used for color work.
The feed may be either hand or automatic.
The ideal location for motors is within the
frame of the press, on brackets. Belt drive
is preferable to gear or chain drive as the
slipping of the belt serves as a protection
against shocks to the motor and machinery.
The motors required range in capacity, for
different makes and sizes of presses, from 1J4
to 15 h.p., and must be capable of exerting a
strong starting torque, for which reason the
direct current motors are usually compound
wound with about 20 per cent series field.
The alternating current motors used are for
two- or three-phase circuits and are of the
slip ring type.
The ordinary requirements of speed varia-
tion are met by providing the d-c. motor with
50 per cent reduction by armature resistance,
and with field control giving a 25 or 50 per
cent speed increase above normal. In the
case of the a-c. motor, a regulating resistance
is furnished which permits of a speed range
down to 50 per cent of normal. Ordinarily
only the higher speeds are in requisition, the
lower speeds being required for occasional jobs
where an extra high grade of work is involved.
Fig. 2. A Job Press Driven by a Single-phase Motor,
Foot Control and Friction Drive
The ideal control equipment provides for
push-button starting and stopping and for
predetermined speed control. The ability to
start or stop the press from stations at both
the feeding and delivery, ends makes for
greater convenience and safety to the operator
THE ELECTRIC MOTOR IN THE PRINTING INDUSTRY
1139
fa
•§
3 E
a, S
•a o
C °
I8
< O
a. -o
1140
GENERAL ELECTRIC REVIEW
and is an important factor in the saving of
time. The predetermined speed feature
makes possible the proper setting of the
ultimate speed for the work in hand so that
when the press is producing it will run at that
speed. Thus is avoided the wasting of time
by reason of running too slow, as also the
spoiling of work by reason of running too fast.
Furthermore, it becomes possible to work to
a definite schedule of production which is of
great importance to the printer.
Other features of the control equipment are :
No-voltage protection to motor and to
operator.
Overload protection to the motor.
Dynamic brake or solenoid brake for quick
stopping.
"Jogging" or "inching."
Reverse for emergency conditions only.
In Fig. 3 is shown a modern installation of
flatbed presses with direct current motors and
with control equipments including all of the
above mentioned features.
Recent developments in control equipments
for use with alternating current motors
incorporate all of these advantageous features.
The essential difference is that dynamic
braking is, in the nature of things, out of the
question, and a solenoid brake is used. The
results, however, are identical.
Lithographing Presses
The lithographing press differs from the
ordinary flatbed press in that it prints from
an engraved stone instead of from type. In
its various makes and sizes it takes motors
ranging in capacity from 2 to 10 h.p. The
requirements as to the types of motors, speed
range, and control features are the same as for
the general run of flatbed presses.
Rotary Presses
Rotary web presses, used largely for
magazine or newspaper work, employ curved
stereotype, electrotype, or zinc printing plates,
attached to the cylinders. They print a
continuous roll or "web" of paper, which
allows a much faster speed than even the
automatic feed applied to flatbed presses.
Due to this feature, and also to the elimina-
tion of heavy reciprocating parts, this type of
press is superior in point of speed.
Small rotary presses, which may print either
on a continuous roll or on automatically
fed sheets, are used for work similar to that
performed by job presses and flatbed presses.
The motors required range in capacity from
2 to 15 h.p. and the types of motors and the
control features are essentially the same as for
the job and flatbed presses doing similar
work. Fig. 4 illustrates a small rotary sheet-
fed "offset" press driven by a 7}^-h.p.
induction motor and operated from push-
button stations and a predetermined speed
controller.
Rotary Magazine Presses
The sizes of rotary presses used for maga-
zine printing require motors ranging in size
from 5 to 35 h.p. The direct current motors
employed are compound wound and of the
adjustable speed type with a speed range by
field control of 2:1, although occasionally a
speed range as high as 3:1 is of advantage
where the work which the press turns out is
of widely varied quality. When alternating
current motors are used they are of the slip
ring type with speed control by resistance in
the secondary circuit.
A suitable control equipment may be either
"full automatic" or "semi-automatic," al-
though the former is the more convenient to
the press operators. By "full automatic"
is meant entire control from push button
stations. Each complete master station,
of which there may be one or more, contains
push buttons for "jog," "fast," "slow,"
"stop" and a two-button operated snap
switch for "safe — run." Partial stations, of
which there may be several, usually comprise
"jog" and "safe — run."
The various contactors and other remotely
controlled switching mechanisms actuated by
the push buttons are mounted on a panel
together with the knife-blade line switches,
fuses and whatever instruments may be
desired. The panel and resistances connected
thereto may be placed in any available space
as the complete control of the press is accom-
plished from the stations and the only devices
on the panel ever manually operated are the
line switches.
Pressing the "jog" button will cause the
press to run at a very slow speed as long as
the button is held closed. When the button
is released the press instantly stops. Pressing
the "fast" button will start the press off at
the lowest speed and gradually accelerate it
toward the highest running speed as long as
the button is held down. When the "fast"
button is released the press will run at what-
ever speed it has attained. Pressing the
"slow" button causes the press to decrease in
speed. The "stop" button is used to bring
the press to a quick stop. The "safe — run"
THE ELECTRIC MOTOR IN THE PRINTING INDUSTRY
1141
buttons permit of opening the control cir-
cuits at any one station so as to prevent the
starting of the press from any other station.
Whether the press be stopped by release of
jog" button or operation of "stop" or
safe" buttons, the brake comes instantly
into effect and quickly brings the machinery
to rest.
A ' ' semi-automatic ' ' control equipment
differs from the "full automatic" in having
a manually operated device for bringing the
machinery up to running speeds. The "jog,"
"stop" and "safe — run" features are, how-
ever, controlled by push buttons exactly as in
the "full automatic" equipment.
The equipments for induction motors
accomplish much the same results as those for
d-c. motors. The advantage in favor of the
d-c. motor lies in economically producing
speeds over a wide range. When the pro-
ducing speed is to be at or near synchronous
speed the induction motor offers no disad-
vantage whatever.
tion. A speed range of 2:1 by field control
and 50 per cent reduction by armature con-
trol is usually in the large motor of the d-c.
combination. The running speed range of the
induction motor combination is from normal
down to about one-third normal. In either
Fig. 6. A Two-Motor Alternating Current Driving Equipment
Rotary Newspaper Presses
The great advantages of motor drive as
compared to any other drive in the case of
rotary presses lie in :
Economy of space. — Crowded conditions
usually prevail in a newspaper plant.
Convenience of control. — From several sta-
tions and by quickly operated devices.
Safety. — All is hurry and bustle and the
press operators must be protected against
carelessness.
Delicacy of control. — The web of paper
must be slowly fed in while making ready
and gradually accelerated to the full
running speed.
Reliability. — The loss of an edition is a
serious matter.
Some small newspapers are produced by
•single motor-driven rotary presses in which
case the equipment is the same as described
for the rotary magazine presses. See Fig. 5.
The larger newspapers, however, are run
•off from rotary presses which have a two-
motor drive. A small motor is used, driving
the press through gearing to obtain the make-
ready slow speeds. A large motor is used to
■obtain the high producing speeds. Fig. 6
shows a combination of two induction motors.
When the large motor takes up the work the
small motor is electrically and mechanically
automatically disconnected.
The motors required range in capacity
from a 3 to 25-h.p. to a 10 to 100-h.p. combina-
case the ordinary producing speed is usually
figured at about 75 per cent of the ultimate
possible speed in order to allow for con-
tingencies of delay.
The control equipment for the two-motor
drive is almost always of the "full auto-
matic" type and the same features of control
are incorporated as already described. The
push button stations are the same as for
single motor drive, but the control panel
naturally contains a larger array of devices by
reason of the fact that both the small and
large motor must be controlled and in proper
sequence.
Fig. 7 illustrates a modern newspaper press
room. The equipment is a two-motor a-c.
drive. The illustration shows a quadruple
or double 16-page unit, capable of printing
30,000 16-page papers or 15,000 32-page
papers per hour. Some large newspapers
necessitate two, four, six, and even eight
press units. Producing speeds vary from
20,000 to 36,000 papers per hour, of 12 pages
per paper up 32 pages. Presses even larger
and faster have been built.
The Electrical World of June 19, 1915,
contained a very pertinent article describing
the motor and control equipment of the
New York Times as recently installed in the
Times annex. From that article the following
data have been taken :
The main presses are four double-sextuple,
and one double-octuple. These will print
372,000 24-page papers in an hour under
114:
GENERAL ELECTRIC REVIEW
ordinary operating conditions. When all are
in operation, paper is used at the rate of a ton
a minute. A ton of ink is consumed in the
run of a single edition.
The main presses are operated by a total
of ten SO-h.p. and ten 7)4-h.p. d-c. motors,
the drive being of the two-motor type and the
control being full automatic.
There are three rotogravure presses, two
of which are operated by a 14 and 2-h.p. two-
motor drive, the other being driven by a
single 10-h.p. motor. There are also 2 Cot-
trell presses, one driven by a 15-h.p. motor,
the other by a 10-h.p. motor. These five
presses print the pictorial supplement and
the midweek picture number.
A certain New York publishing house
which may be considered as typical of the
largest up-to-date plants engaged in the
production of magazines, color work, pat-
terns, etc., utilizes a total of 310 motors of
which 237 drive machines which are directly
connected with the printing and allied work.
The plant includes 31 rotary presses driven
by motors ranging from 5-h.p. to 25-h.p. and
45 flatbed presses driven by motors ranging
from 2-h.p. to 10-h.p. in size. The total
connected load is 440 h.p.
A summary of the entire motor equip-
ment of the Times annex follows:
Machinery
Printing presses
Elevators
Conveyors and lifts
Fans, blowers, compressors . . .
Pumps
Autoplate machines
Linotype and monotype ma
chines
Machine tools
Folders and cutters
Miscellaneous
Total 292
No. of
Total H.P.
Motors
of Motors
31
946
o
265
72
95
37
86
11
82
5
50
61
20
14
19
8
17
48
38
1 1 ; i s
THE POSSIBILITIES OPEN TO THE CENTRAL STATION IN
SOLVING THE FREIGHT TERMINAL PROBLEM
By Jas. A. Jackson
Power and Mining Engineering Department, General Electric Company
This article is specially opportune at this time, when we are daily reading of the congestion of freight at
the large railroad terminals and of the resulting car shortage that is entailed by the delay in unloading. While
the present conditions may be largely due to the fact that most of this freight is for shipment abroad, and to the
difficulty of securing bottoms, the situation would be greatly relieved were the terminals equipped to expedi-
tiously handle the freight from freight car to ship's hold. The electric motor as adapted to a number of con-
veyances now on the market would seem to afford the most satisfactory solution of the difficulty. — Editor.
possible reduction in cost during the hauling
period would be of but a fractional value.
However, just the opposite condition prevails
at the terminals and transfer stations. Here,
the "gang" and the hand-truck still rule
supreme, which means that the cost per
ton for handling at these locations has
actually increased due to the higher cost of
labor and to the increase in overhead expense,
including interest, depreciation, etc.
Here, then, is the opportunity for the
central station to reduce transportation
charges and at the same time to increase its
profits by the sale of power. In order to
induce terminal managers to make purchases
of improved freight handling equipment, the
central station power solicitor must make a
thorough study of the freight handling
business so that he may be in a position to
recommend the particular type and size of
machinery that will best fulfill the customer's
requirements, and be able to tell him approxi-
In these days when the problem of how
to reduce the high cost of living is uppermost
in everyone's mind, many very satisfactory
reductions could be made if business men
and corporations would seek out methods
for conducting their business in such a
manner as would directly assist in lowering
the cost of production without lessening the
profits or, better yet, actually increasing
them. Concerted action of this kind would
undoubtedly produce good results and could
not adversely affect the business of the
country. Many situations present oppor-
tunities along, this line wherein marked
improvements can be brought about.
Among these it would seem as though the
most fruitful field is in the reduction of
transportation charges. Little remains to be
done in reducing the cost of hauling freight
for the rolling stock, roadbeds, vessels and
harbors have been developed to such a
high state of efficiency that any further
SOLVING THE FREIGHT TERMINAL PROBLEM
1143
mately how much will be saved by its use.
The power salesman is in the ideal position
to make such recommendations for, being
interested only in the sale of power, he can
give an unbiased opinion as to what machin-
ery will be most successful.
To show what are the possibilities of this
field a brief analysis of the present situation
will be made, and to it will be added a short
list of the types of machinery involved,
together with a few facts that will show the
benefits to be derived from the adoption of
improved methods for handling freight.
While no figures are at hand, it is probably
not far from true that at least one-third of
the amount which the ultimate consumer pays
for his goods is due to transportation charges
in one form or another. An analysis of
transportation charges, based on the average
haul, shows that about 50 per cent of the
freight charge is accountable to the high
cost of handling in terminals. A few figures
will suffice to prove this statement. The
average length of freight haul on railroads
is something less than 250 miles, and the
average cost per ton-mile for hauling package
freight (which this article particularly con-
.cerns) is about three miles. Thus, the hauling
cost for one ton over the average distance is
75 cents.
Now, consider the cost of handling at the
terminals. The average railroad shipment
goes through at least two terminals and often
one or more transfer terminals as well.
However, to be conservative only two termi-
nals will be considered, one at each end of the
haul. Variable conditions and classes of
freight make the cost per ton for handling
difficult to determine accurately, but the
available figures indicate that a safe average-
would be about 37 cents per ton per terminal.
This figure does not include interest, depreci-
ation, and fixed charges on the terminals.
In the two terminals, then, the cost of
handling will be 74 cents or approximately
50 per cent of the cost of moving the ton of
freight from the time of its delivery at one-
freight house to its departure from the other.
In the case of water-borne freight, the
terminal percentage of the cost is still greater,
for the cost per ton-mile in this case is from
six to seven-tenths of a mill; and although
the average haul is longer than on railroads,
it is not sufficiently long to make the cost
per ton per average haul equal to that on a
railroad.
A saving of only one cent a ton per terminal
on the miscellaneous freight handled in the
United States would result in a saving of
approximately $20,000,000 per annum, assum-
ing that each ton goes through two terminals.
A saving of 10 to 15 cents a ton is well within
reason.
Now, turn attention to the machinery with
which this saving can be accomplished. No
one type of machinery will suit the require-
ments of all terminals because of the variety
of freight to be handled and of the varying
local conditions. In many places, a combina-
tion of two or more radically different types
of machines working in conjunction with
each other will be necessary to produce
the best results. A partial list of apparatus
that is adaptable to freight handling work
will be educational:
Storage battery operated trucks and truck
cranes.
Portable and stationary conveyors.
Piling, tiering, and stacking machines.
Winches and hoists.
Locomotive, gantry, portal, and travelling
cranes.
Elevators, escalators, and ramps.
Telphers and monorail systems.
Industrial railways and cable-ways.
This list is of course incomplete, but it
gives a general idea of the line of apparatus
involved.
The installation and proper use of machin-
ery will result, in part, in
1st: Decreased cost per ton for actual
handling.
2nd: Increased terminal capacity.
3rd: Decreased cost per ton in interest,
depreciation and overhead charges due to
the larger tonnage handled for a small
increase in investment.
4th: Increased storage capacity due to
utilization of hitherto useless height.
5th: Increase in handling capacity with
reduction of labor, due to greater unit loads
and greater speeds.
6th: Decrease in length of time to unload
and load, thereby increasing the earning
power of vessels and cars due to the larger
number of trips per year.
7th: Increased prestige of the port since
freight will naturally follow the line of least
resistance and lowest cost.
It would seem that the possibilities are so
great in this field that power companies
could afford to assign a wide-awake solicitor
to study this problem in all large port cities
and probably in large railroad centers as well.
Electricity is undoubtedly the only form of
1144
GENERAL ELECTRIC REVIEW
energy that is sufficiently flexible and safe
to be applied to meet the conditions, and
at the same time it is readily adaptable to
all the machinery involved.
In conclusion, it might be well to mention
that the efficient lighting of piers, freight
houses, warehouses, etc., could also be
considered a part of this work, and even
ornamental and decorative schemes could be
taken up. There is one case where a large
municipal wharf has illuminated its entire
water side with large tungsten units installed
primarily for decorative purposes, but which
incidentally have practically put a stop to all
thieving from the water side by harbor
thieves.
PORTABLE SEARCHLIGHTS FOR FIRE DEPARTMENTS
By L. C. Porter and P. S. Bailey
Harrison Lamp Works and Lynn Works, General Electric Company
This article gives a brief description of a portable searchlight set equipped with a gas-filled incandescent
lamp and a storage battery. The beam of light can be concentrated or spread as occasion demands. Besides
describing the apparatus the author recites its various uses. — Editor.
In several cities the fire departments are
supplied with one or more searchlights. There
are, however, thousands of places where such
equipment is not available. To meet this
condition there has been developed at the
laboratory of Thomas A. Edison, in co-
operation with the General Electric Company,
a portable storage battery searchlight outfit.
It consists of a waterproof 20-in. projector
on a trunnion mounting. The projector
In many cases much valuable material
has been lost by fires that occur at night
through the lack of sufficient illumination
to permit its removal from the buildings. It
not infrequently happens that the electric
light or other sources of illumination are put
out of commission ; or the supply may be shut
off as a safety measure, and the work of
fighting the fire is seriously handicapped
thereby.
Fig 1. Front and Rear Views of the Portable Searchlight Truck
PORTABLE SEARCHLIGHTS FOR FIRE DEPARTMENTS
1145
contains a special 35-volt 750-watt, focus-type,
Edison Mazda C lamp.
The searchlight is equipped with a hand-
wheel focusing device, thus enabling the
beam to be quickly and easily concentrated
into a narrow shaft of light for long distance
work and for smoke penetration, or spread
out into a fan shape for close range operation.
With the beam concentrated, its strength is a
little over one million candle-power; suffi-
ciently powerful, under ordinary conditions,
to "pick up" a man half a mile distant.
The searchlight is mounted on two large
wheels, from the axles of which is hung a
150-ampere-hour, 35-volt Edison storage bat-
tery. There is a switch with which to turn
the light off and on. The projector, battery
and carriage are completely self-contained
and can be easily and quickly operated by
one man. The beam may be thrown in any
direction, spread out or concentrated at
will.
It is claimed that the battery is particu-
larly appropriate for this equipment, that
it may be left standing unused for long
periods of time, be roughly handled, given
a high rate of overcharge or otherwise abused,
without serious harm. The battery will
operate the lamp continuously for seven
hours on one charge.
The complete outfit is approximately
5 feet high, 3 feet wide and 3 feet long; it
weighs about 600 lb. It should find a wide
application not only for municipal fire
departments, but also for factory fire depart-
ments. It would be particularly valuable
to factories, as it can be used for many
purposes other than fighting fires. Night
construction work can be carried on under its
light. It can be effectively used on special
occasions for advertising purposes to illumi-
nate a sign, a flag, or in fact, flood-light the
entire face of a building, in much the same
manner as is being done by permanent
installations of flood-lighting projectors.
The outfit should also be of service to
military and naval organizations as well as
for spectacular lighting at resorts, etc.
Fig. 2. Section of a Building Illuminated at a Distance of 210 Feet by a
750-watt Portable Searchlight
1146
GENERAL ELECTRIC REVIEW
PRACTICAL EXPERIENCE IN THE OPERATION OF
ELECTRICAL MACHINERY
Part XII (Nos. 63 to 65 inc.)
By E. C. Parham
Construction Department, General Electric Company
63 CROSSED RESISTANCE WIRES
The crossing of resistance wires is here
meant to be the interchanging of two or more
wires that are used for connecting a rheostat
to a controller. When a controller has many
notches, an interchange of wires of adjacent
resistance sections may have no noticeable
effect; unless, for example, an exact value of
motor speed or an exact value of generator
voltage is desired and the controller position
that ought to give the result desired happens
to involve the interchanged connections. In
Fig. 1
Fig. 2
the case of a motor it means, however, the
loss of at least one speed adjustment.
The other extreme of crossed wires occurs
through the interchange of the first and the
last rheostat wires. In such a case, if the con-
troller cylinder segments are just wide enough
to maintain contact on one notch, the motor
will start on short-circuit (if it does not blow
a fuse or breaker) and on the last notch all of
the rheostat resistance will be cut in. Between
these extremes, various degrees of jerkv
acceleration will take place and the violence
of the impulses will depend on the serial
number of the displaced wires and on the
degree to which they are displaced.
Fig. 1 indicates the connections of a two-
section series resistance, and Fig. 2 those of
the corresponding two-section multiple re-
sistance which is not as generally used. In
both cases, the full lines indicate the correct
connections, and the dotted lines the inter-
change of two adjacent resistance wires. As
the controller has only three steps, the cross-
ing of even adjacent wires will have a marked
effect. In Fig. 1, if the cylinder segments are
narrow ' so that the first finger to engage
breaks contact just after the next finger
engages, the motor will start on only the
3-4 section and will jump violently; on the
second notch the whole starting coil will be
cut in and the motor speed will decrease ; and
on the third notch the whole coil will be cut
out and the motor will again jump. Thus,
in this case, not a single notch produces a
normal result. If the cylinder is so con-
structed that any contact, when once made,
is maintained throughout the sweep of the
cylinder, the motor will jerk on the first notch,
as before ; on the second notch' no change will
take place because No. 2 finger is still active;
and on the third notch normal acceleration
will occur. In this case, the characteristics of
only the first notch have been changed.
In Fig. 2, if the cylinder has narrow
segments, the motor will jerk on the first
notch because only section 3-4 will be in; on
the second notch 3-4 will be open-circuited
and the higher resistance section 2-4 cut
in, causing the motor to slow; and on the
third notch the cutting out of 2-4 will cause
another jerk. The characteristic of every
notch therefore has been changed. With
wide segments, the motor will jerk on notch
No. 1 as before; the second notch will intro-
duce no change; and on the third notch
normal acceleration will occur.
Ordinarily, the advancement of a controller
changes the previously existing circuit to a
circuit of lower resistance. This tends to
prevent arcing of the fingers. The crossing
of resistance wires, however, causes at some
stage of the advancement a change to a
circuit of higher resistance, thereby causing
the fingers and segments (if of the narrow
type) to burn and blister on their "off" sides.
OPERATION OF ELECTRICAL MACHINERY
1147
In hundreds of cases of jerky acceleration,
especially of car equipments, the trouble has
been traced to an interchanging of resistance
wires either at the rheostat, in which case
operation will be affected on both controllers,
or in one controller, in which case operation
from only that controller will be affected.
(64) MOTOR REVERSED
Fig. 3 indicates the connections of the
three-phase compensator that is used for
starting a squirrel-cage induction motor.
The particular motor dealt with in this section
operated a stone crusher.
The quarry foreman complained that the
fuses were being blown too frequently.
Ordinarily, compensator fuses are installed
on a small panel that is mounted above the
compensator, and, as all leads are brought out
of the compensator in a regular order that is
maintained by the bushings through which
they pass, the chances of confusing the leads
are remote.
In this particular case, however, the instal-
lation was a temporary one and the com-
pensator had been handled so roughly that
there was but a little left of whatever order
might have originally existed. Two of the
fuse wires had become confused as indicated
in Fig. 3, in which the full lines show the
connections as they were and the dotted lines
indicate the connections as they should have
been. It is to be noted that with the dotted
Supp/y
indicated by the full lines, however, the line
wires a, b and c are connected to the motor
wires a, b and c, respectively, only when the
compensator is in its starting position. On
throwing the switch to the running position,
the line wire c is connected to motor wire c
as in the first case, but line wire a is now
connected to motor wire b and line wire b is
connected to motor wire a, thereby reversing
one phase of the motor. As the result of
closing the compensator the motor would
start in one direction, and on throwing the
compensator to the running side the motor
would stop and start in the opposite direction.
The fuses had blown each of the several
times that an attempt had been made to
start the motor; and, if the fuses had not
blown, the probabilities are that the rotor
would have developed a sprung shaft or some
of the stator coils would have been pulled
out of their slots. The attending help was
not qualified to notice such a detail as the
stone crusher turning in the wrong direction.
(65) ELEVATOR TROUBLE
In addition to the regular floor-limit stops,
operation of which opens the motor circuit,
motor-driven elevators have additional safety
stops that open an auxiliary circuit-breaker
should the car for any reason get past the
top or the bottom floor stops. Fig. 4 shows
one type of auxiliary circuit-breaker operating
mechanism. Rope R passes round a grooved
wheel W. The ends of the rope carry inter-
ferences that will be engaged by dogs on the
car should it pass the top or the bottom
limits. Wheel W turns with shaft 5; arm A
is free to turn on shaft 5 as a center and it
connections the line wires a, b and c are
applied respectively to the motor wires a, b
and c; and this holds true irrespectively
of the position in which the compensator
switch may be. With the connections as
Fig. 4
carries at its upper end a trigger T, the
forked end of which normally straddles pin P
which turns with wheel W. Lug L, when up,
holds the circuit-breaker closed. The ball B,
which is fastened to the rope, rests in a
114S
GENERAL ELECTRIC REVIEW
hemispherical depression in the groove of
wheel W. It should be noted that in the
positions indicated in the diagram all centers
are vertically in line; pin P is in its highest
position and lug L bears upward against the
circuit-breaker mechanism. A pull on either
end of the rope R will turn the wheel 11" and
will thereby move the pin P to a lower point
and break the toggle-joint setting of the parts.
The breaking of the toggle-joint permits a
heavy weight mot shown) to knock down the
whole construction, thereby withdrawing lug L
from under the circuit-breaker mechanism and
causing the circuit-breaker to fly open.
An operator complained that the emergency
trip had developed a tendency to operate at
any time, thereby stalling the loaded elevator
between floors. An investigation disclosed
that at some previous time an employee
had operated the trip with a crowbar, to
see how the mechanism would work. In
resetting the mechanism, he had failed to
restore the centers to a stable position. The
jarring incident to the handling of heavy
barrels on the same floor would shake the
construction loose and release the circuit-
breaker. The mechanism would then again
be improperly set and again would be jarred
down.
After properly resetting and aligning the
parts as indicated in the diagram, there was
no more trouble.
THEORY OF ELECTRIC WAVES IN TRANSMISSION LINES
By J. M. Weed
Transformer Engineering Department, General Electric Company
This article, the first of a series on the above subject, is devoted to a theoretical study of the behavior
of transmission lines and connected apparatus with respect to the traveling waves which result from switching
operations, arcing-grounds, short-circuits, etc. The present article presents a theoretical conception of the
propagation of these waves and of their reflection from the open end of a line. The fundamental voltage,
current, and energy equations are developed, and also those for the velocity of propagation and for the natural
frequency of oscillation of the line. — Editor.
If we consider a generator of zero impedance
and of voltage E connected instantaneously
to a pure inductance by the switch of Fig. 1,
the result is a gradual growth of current, such
that
lr«
(i)
The current which enters the inductance
at one end is leaving it at the other end at
the same instant, since there is no capacity
within the inductance for storing up current.
The value of L involved in equation (1)
is therefore the total inductance, and since
there is no resistance the growth of current is
uniform and continuous.
If the same generator is thrown suddenly
onto the end of one wire of an indefinitely
long transmission line of zero losses by closing
the switch of Fig. 2, the capacity of the first
element of the line is instantly charged, but
current must .flow through the inductance
of this element to charge the second element.
After the second element is charged there is no
further growth of current in the first element.
since there is no difference of potential applied
to this element. The current set up at the
first instant merely continues to flow, sup-
plying the necessary charging current for
successive elements of the line, and current
grows in but one element at a time, this
growth being by an instantaneous change
from i = 0 to i = I. The current I and the
electrostatic charging of the line to voltage E
advance together with an abrupt or sheer
wave front, so that the total voltage of the
circuit appears at the front of the wave.
Equation (1) may be written in the form
<%-'
(2)
and for the transmission line; since we have
an instantaneous growth of current from zero
to a constant maximum value in successive
elements of inductance, we may say that we
have constant current with gradual increase
of inductance, so that equation (2) becomes
'£-«
(3)
If L = the inductance per unit length of line
this becomes
or
*■*-*
IL dx = Edt
(4)
where dx is an element of length.
If X = the total length -of the line, and T
= the time required for the charging wave to
THEORY OF ELECTRIC WAVES IN TRANSMISSION LINES
1149
traverse the line, the integration of equation
(4) gives
IXL = ET (5)
Considering now the relation between
current, voltage, and the capacity of the line,
we find the equation
EC dx = Idi (-6)
•a
X
( )
Jl_.
Fig. 1
where C is the capacity per unit length of the
line. The integration of this equation gives
EXC = IT (7)
From equations (5) and (7) we find the
time required for the charging wave to traverse
the line
T = XX/LC (S)
and since the velocity equals the length of the
line divided by the time, we have,
Vlc
(9)
Substituting (8) in (5) or (7) we obtain
y/Ll = y/CE (10)
whence
LP- = CE*
2 '' : 2
Equation (11) shows the equality between
the electrostatic energy and the electro-
magnetic energy of the advancing wave,
(11)
-St
-/ -i
>>
_l
Fig. 2
since the first member represents the elec-
tromagnetic energy per unit length, and
the second member the electrostatic energy.
This condition of equality between electro-
static energy and electromagnetic energy is
a characteristic of all pure traveling waves.
The total energy per unit length of the charg-
ing wave thus is
W = ~+^ = LP = CE^
(12)
2 ' 2
This energy per unit length multiplied by
o_
/-/
J
Fig. 3
the velocity of the wave gives the power
absorbed from the generator. Thus
P=T T* — =~ = J- V-
VLC \c
and
1 £2
p=CEi ~vm= j
Mr,
So far as the generator is concerned, with an
indefinitely long transmission line this power is
lost, just as much as though it had been con-
sumed bv a resistance of the value ,. |_ ohms.
Mr
(13)
(14)
C
L,
The quantity .. _ has been called the "natu-
ral impedance" of the line. It has also been
called the "wave resistance." "Wave impe-
dance" seems a more suitable name than the
latter since the energy absorbed by the line
exists in it as electrical energy and is trans-
mitted and may be returned to the source as
such. For this wave impedance the symbol
HI (15)
is used.
From equation (12) we have also
E E
Mr
Thus Ohm's law may be applied to a trans-
mission line with respect to traveling waves,
giving the amount of current which will flow
into the line with a given voltage applied. This
must be restricted, however, to the initial
period of charging the line.
1150
GENERAL ELECTRIC REVIEW
If we examine a point in the line after the
wave front has passed, we find the constant
current / flowing at the constant voltage E
(which is the generator voltage) supplying the
power
P = EI = V-Z=y (17)
&-£-"
Fig. 4
Now, if the generator voltage be suddenly
reduced to zero, current ceases to enter the line
from the generator. One might, at first
thought, expect the current to begin to flow
back from the line into the generator. This,
however, is not the case. The wave of current
and voltage continues to progress in the line
(see Fig. 3). The rear end of the wave is
similar to the front end, except that the
voltage E existing in the line here acts in a
direction toward the generator, instead of
away from the generator, and we have here
a counter e.m.f. which is away from the
generator, due to the cessation of current in
that inductance from which the rear end of the
wave is passing, whereas the counter e.m.f.
at the front of the wave is toward the gen-
erator, occasioned by the current entering
the inductance which is in advance of the
wave. Kirchoff's law for voltage is satisfied
at both ends of the wave, as expressed for the
front end by equation (4). The same equa-
te i = t*e)c.
<*i) = i*6 j (*v)
Fig. 5a
This equation for the rear end of the wave
may be looked upon as belonging to a wave
front of opposite polarity, the front of a wave
of negative current and negative voltage,
superposed upon the former wave of positive
current and positive voltage, and thus reduc-
ing both current and voltage to zero (see Fig. 4) .
That a wave with both current and voltage
reversed, i.e., with negative current and
negative voltage, always travels in the same
direction along the line as one with positive
current and positive voltage is seen by an
inspection of Fig. 5.
Thus, in the wave of Fig. 5-a, with volt-
age E the charge per unit length of line is
Q = EC (19)
Since the wave is traveling in the positive
direction (toward the right) at velocity V,
we have the positive current
I = QV (20)
That is, with positive voltage and positive
current the wave is moving in the positive
direction.
Again, in the wave of Fig. 5-b, with voltage
(-E) the charge per unit length of line is
{-Q) = (-E)C (21)
this being a negative charge.
Since this wave also is traveling in the
positive direction, the current is negative, or
(~D = (-Q)V (22)
Thus, the wave with negative voltage and
negative current is also traveling in the posi-
tive direction.
In other words, in Fig. 5-a, with positive
voltage, the positive current, by transferring
positive charge from the rear end of the wave
to the front end, is seen to advance the wave
in a positive direction, and in Fig. 5-b, with
negative voltage, the negative current is seen
to advance the wave in a positive direction,
by transferring positive charge from the front
(-/;-- {-a )(*v>
(-0 ) = (-£>c
Fig. 5b
tion may be used for the rear end, but the
opposing e.m.f.s are reversed with respect to
the positive direction in the circuit. If we
change signs on both sides of the equation to
account for this, we have
-ILdx=-Edt (IS)
end of the wave to the rear end, i.e., by trans-
ferring negative charge from the rear end
to the front end.
A similar inspection of Fig. G shows that
a wave with positive voltage and negative
current, or with negative voltage and positive
THEORY OF ELECTRIC WAVES IN TRANSMISSION LINES
1151
current, is advancing in the opposite or
negative direction.
The wave of Fig. 6-a, with voltage E, is
moving in the negative direction (toward the
left). The velocity, therefore, is negative, or
c-g ) M*f)C
Fig. 6a
In Fig. 2, if we assume that the earth is a
perfect conductor, the distribution of the
electrostatic flux lines at the surface of the
earth will be similar to that at the neutral
plane midway between the wires of a two-
(*i)-- [-o )(-r)
Fig. 6b
— 1 ". Although the charge per unit length is
positive, the current is negative, or
-I = Q{-V) (23)
We thus see negative direction of travel with
positive voltage and negative current.
The wave of Fig. 6-b, with negative voltage,
is traveling in the negative direction. Both
the charge and the velocity are therefore
negative, so that the current is positive. Thus
I-(-OX-V) (24)
That is, with negative voltage and positive
current the direction of travel is also negative.
The diagram of Fig. 2 represents a single
wire transmission line connected to one
terminal of a single-phase generator, the
other terminal being grounded. In an actual
two-wire single-phase line, with grounded
neutral or symmetrical potential with respect
i*i'=o
Fig. 7
to ground, the closing of the double-pole
switch would at the same time send out a
positive wave on one leg of the line, and a
negative wave on the other leg. These may,
in fact, be considered the positive and nega-
tive phases of one and the same wave.
wire line, and the waves which we consider
in connection with the single wire line are in
every respect similar to that part of the wave
of a two-wire line which exists between one
wire and the neutral plane. The condition,
so far as the single wire is concerned, is the
same as with a two-wire line, of which the
earth's surface represents the neutral plane.
The discussion with respect to a single wire
has been adopted because it is simpler, and
the results can be applied directly to a two-
wire line. It is only necessary to remember
that with the two-wire line the signs of both
voltage and current are in one wire the
reverse of what they are in the other, the
direction of travel being the same in both.
In a three-phase, three-wire line, due to
various causes we may have waves between
individual wires, waves between one wire and
the other two, waves between one wire and
the ground, or waves between all three wires
and the ground. The principles involved,
however, are the same as with the single
wire, considered with respect to ground. The
general problem will be simplified by con-
tinuing to consider various cases with respect
to a single wire. It must be borne in mind,
however, that where ground is spoken of, or
shown in the figures, it may be taken as
representing the neutral plane, or surface, and
that where the wave phenomena exists
between wires, only one-half of it is considered
in this discussion, the other half being the
image or counterpart of that considered.
Also, where the line is shown as grounded, the
counterpart line would also be grounded, so
that the condition is similar to that of short
circuit for a two-wire line. Where the line is
grounded at the end farthest from the gen-
erator, therefore, it will be spoken of as a
line with closed end, as distinguished from
the line with open end.
If we consider the generator, of voltage E,
connected to the transmission line of length
11.52
GENERAL ELECTRIC REVIEW
X, which is open at the end, the charging
wave advances as in Fig. 2, until it reaches
the farther end of the line. The line is then
fully charged to the voltage E, with the
current I flowing throughout its length.
The voltage immediately builds up to a higher
value in the last element of the line, on account
of the current, I, which is still flowing into
it after it has reached the voltage E. With
the building up of this excess voltage, E',
in the last element, current must cease in
next to the last element, otherwise the voltage
E' would continue to build up indefinitely.
Just how this occurs is seen when we con-
sider that E' will act in the negative
direction in the line, or toward the generator,
while the cessation of current flowing in the
positive direction produces an e.m.f. in the
positive direction. Applying Kirchoff's law
again, we have similar to equation (4)
IL{-dx)=-E'dt (25)
This equation applies to a wave front of
excess voltage and current cessation which
now travels back toward the generator
(see Fig. 7).
A comparison of equation (25) with equa-
tion (18) shows the difference that while in
equation (18) both current and voltage are
negative, in equation (25) the current is
positive, the negative sign belonging to the
differential of length of the line. This may be
interpreted as signifying a wave of negative
voltage and positive current which is traveling
in a negative direction in the line, and super-
posed upon the static condition of voltage
with zero current. We will obtain an equiva-
lent interpretation, if we change signs on
both sides of the equation, making voltage
positive and current negative, thus referring
the equation to the other side of the wave
front. This gives
-IL(-dx)=E'dt (26)
This equation represents a wave of positive
voltage, E', and negative current, I'=—I,
which we may cail the reflected wave, travel-
ing toward the generator and superposed upon
the advancing wave of voltage E and current
/, which is still coming from the generator.
Deductions similar to those made with
respect to the advancing wave, to determine
the current which will flow into the line
with a given voltage applied, will now show
the excess voltage, E', which will be built by
the current /. Thus, similar to equation (6),
we have,
Integrating (26) and (27), and solving for E',
we obtain
E' = Iyj^ =IZ (28)
whence, from equation (16)
E' = E (29)
That is, the end of the line is at a voltage
E+E'=2E (30)
and the current is zero.
That the reflected current is equal and
opposite to the advancing current may be
more explicitly shown by applying Kirchoff's
law for current to the end of the line. The
current beyond the end of the line must be
zero. Therefore, the sum of the currents in
the line adjacent to the end must be zero.
If /' be the reflected current, we have
whence
/' + / = 0 (31)
/'=-/ (32)
It is instructive to note that the electro-
static energy of the superposed reflected and
advancing waves is equal to the sum of the
electrostatic and electromagnetic energies of
both the advancing and reflected waves.
Thus, for the advancing wave we have the
total energy per unit length of
T 7-2 (7/72
(12)
and for the reflected wave
J T'2 CF'-
W' = ==~ + ^=- = CE'- = CE2 (33)
whence
W = W
(34)
Xow, with the waves superposed, we have
the voltage 2E and the current zero, so that
the total energy per unit length is
W"=C(2P~ =2CE2
whence
ir" = 2ir = ir+ir
E'C <-dx= -Idt
(27)
(35)
(36)
This relation will always be found true, for
the superposition of oppositely moving waves.
In this case, the energy XW in the total
length of the line was received from the gen-
erator during the time that the charging
wave was traveling from the generator to the
end of the line, and the equal amount XW
was also received from the generator during
the equal time that the reflected wave was
returning to the generator.
THEORY OF ELECTRIC WAVES IN TRANSMISSION LINES
1153
When the line has become completely
•charged to double voltage, there is no current
flowing in any part of the line, and no longer
.any counter e.m.f. due to cessation of current,
to neutralize the excess voltage E' . Since
the voltage of the generator is only E, while
that of the line is IE ( = £ + £') the voltage
E' will produce a current from the line into
the generator, resulting in a wave of dis-
charge traveling forward into the line (see
Fig. S). Negative current is produced
which, as the wave advances, engages with
more inductance at a rate sufficient to produce
a counter e.m.f. equal to E' . Equation (18)
applies here.
When, with advancing positive wave, the
generator was shut down, resulting in the
superposition of an advancing wave of nega-
tive current and negative voltage upon the
former wave of positive current and positive
voltage, the resultant current and voltage in
the line were zero. The present case is the
same, except that the wave of negative current
and negative voltage are superposed upon a
condition of double voltage and zero current,
the resultant voltage being the generator
voltage E, and the resultant current — I.
This voltage and current exists in the entire
1=0
IL-ft = -E-
Fig. 8
JT\
line when the wave of negative current and
negative voltage, or discharge wave, reaches
the open end of the line. This discharge
wave is then reflected in a manner similar
to that of the charging wave (see Fig. 9)
with the result that the line is entirelv dis-
charged, leaving it in its initial condition,
at the end of a period of time 4T, four times
as long as that required for the initial wave
to traverse the length of the line. The cycle
of operations thus traced would be repeated,
ad infinitum, in an ideal transmission line,
?r
-(-")
1=0
'"U
Fig. 9
with zero losses, and a generator with zero
impedance.
The frequency of this oscillation, which is
called the natural frequency of the line, is
the reciprocal of the period, which is AT.
Thus
1
n = if
whence, from equation (8)
1
4X VLC
and from equation (9)
V_
:-LY
(37)
(38)
(39)
Now, for an ordinary transmission line, V is
approximately the same as the velocity of
light, or about 1S6.000 miles per second.
Hence, for a line open at one end, and with a
generator of zero impedance at the other end,
which is the same as though it were short
circuited, or grounded, the natural frequency
is
46500 . , m.
n = — y— cycles per sec. (40)
The natural frequency of a line 100 miles long,
for instance, is about 465 cycles per second.
1154
GENERAL ELECTRIC REVIEW
Fig
1. The First 3000-volt, C, M. & St. P. Locomotive shown Coupled to the "Olympian,'
the famous transcontinental train between Chicago and Tacoma
Fig. 2.
The First 3000-volt, 282-ton, C, M. &. St. P. Locomotive on the Erie Test Tracks
of the General Electric Company
1155
THE FIRST 3000-VOLT LOCOMOTIVE FOR THE CHICAGO,
MILWAUKEE 8b ST. PAUL RAILWAY COMPANY
By E. S. Johnson
Railway and Traction Engineering Department, General Electric Company
The trip of the first 3000-volt electric locomotive from Erie to the West attracted such wide attention
that it is worthy of special note in the Review. Beside recording the interest displayed en route the author
cites interesting data concerning the locomotive. The regeneration of power is a feature that will attract
world wide attention. — Editor.
Interest in the approaching electrical opera-
tion of the transcontinental lines of the
Chicago, Milwaukee & St. Paul Railway has
been greatly increased by the exhibition tour
of the first locomotive over the railway
company's lines. The "big motor" as it is
called by the railway men was taken in charge
by the railway company at Chicago and
has been exhibited at all the principal cities
on the system between Chicago and Tacoma.
The great interest displayed indicates popular
approval of the electrification project from
every quarter. The contract made on
November 25. 1914, called for the delivery
of the first locomotive in ten months and
it is worthy of record that this date was
promptly met, shipment being made on
September 25, 1915. That this quick
delivery is remarkable can be appreciated
when it is understood that the design is
entirely new, that the capacity exceeds that
of any electric locomotive ever built, that
the voltage of the system is higher than any
direct current system for commercial opera-
tion, and that the system of control is entirely
new, being designed for regenerative brak-
ing. Since the first delivery several addi-
tional locomotives have been shipped so that
electrical operation of the first division be-
tween Deer Lodge and Three Forks is
expected to begin about December 1st.
These locomotives may be properly termed
the first transcontinental type, since no
electrification now in operation involves such
continuous heavy service over long distances.
The lines now being electrified include 440
miles of route, carrying both freight and
passenger traffic over three mountain ranges
all within the territory known as the Great
Continental Divide. It is also intimated that
electrification to the Pacific Coast is con-
templated, which will give a continuous
electrified stretch of S50 miles. Trans-
continental electric train operation has never
before been undertaken on so large a scale.
Exhaustive tests were made by the manu-
facturing company's engineers before ship-
ment and the locomotive performance easily
exceeded the expectations of the designers.
Tests made on the regenerative braking
equipment were especially gratifying to the
engineers and the hauling capacity of the
locomotives was demonstrated to the satis-
faction of all concerned.
Fig. 3. The Locomotive on a Trip from Butte to Durant
and Return on the B., A. & P. Rwy. with the
C. M. & St. P. President's Special
Fig. 4. The Locomotive and Train on the B.. A. & P. Rwy.
at Silver Bow
On account of the very general interest in
the new locomotive the officials of the railway
conceived the plan of making an exhibition
tour in order to explain the various novel
features to both the engineering fraternity
and the general public. In all cities where an
exhibit was planned a three column advertise-
ment was inserted in the local papers for a
week or ten days prior to the date of exhibi-
1156
GENERAL ELECTRIC REVIEW
Fig. 5. The Locomotive on Exhibition near the Union Station, Chicago
Several thousand visitors inspected the locomotive
Fig. 6. Another View of the Locomotive while on Exhibition near the Union Station, Chicago
FIRST 3000-VOLT LOCOMOTIVE FOR C, M. & ST. P. RWY. CO.
1157
tion. The newspapers were also furnished
with an abridged description of the locomotive
for use in their news columns.
The famous transcontinental trains "Olym-
pian and "Columbia" will be hauled electri-
cally through the Missoula and Rocky
Mountain Divisions and the conditions of
travel will be greatly improved by the
elimination of smoke, gases and noise incident
to steam operation, making a trip over this
beautiful scenic route a very delightful
experience.
The first public inspection was held in
Chicago at Fulton Street near the Union
Station on October 6th, from 12 noon to
4 p.m. It was estimated that 10,000 people
gathered to see the great machine and 5000
visitors actually passed through the interior.
So great was the popular interest that several
"Movie" operators were on hand and made
films at different points which are now being
exhibited throughout the country. Several
photographers secured pictures, one of which
shows the electric locomotive coupled to the
luxurious through train Olympian. .See Fig. 1-
Prominent among these visitors were many
railroad officials located in Chicago and
university professors; particularly those inter-
ested in engineering work at the University
of Chicago and at Northwestern University.
A number of students were dismissed from
class work in order to give them an oppor-
tunity to examine the locomotive. Superin-
tendents of motive power, street and steam
railway officials, consulting engineers and city
officials from Chicago and points within 200
miles took advantage of the opportunity to
inspect the first transcontinental locomotive.
Public men of every profession and city
officials of Chicago were especially interested
on account of the agitation in favor of electri-
fication of the railway terminals of Chicago.
Visitors evinced great interest in the
characteristics of the locomotive such as its
capacity, speed, operation in cold weather,
regenerating equipment, etc.
The equipment of the freight locomotive
is sufficient to handle a 2500-ton trailing
train on a 1 per cent grade at 16/m.p.h. and
with passenger gearing an 800-ton- train can
be handled on the same grade at about
30 m.p.h. It weighs 282 tons and the length
is 112 feet over all. Each of the eight motors
has a one hour rating of 430 h.p. and a con-
tinuous rating of 375 h.p., thus providing a
total of 3000 h.p. continuously. Each motor is
geared to an axle by twin gears thus equalizing
strains on the driving axles. The available
tractive effort at the one-hour rating is
85,000 lb., but for starting trains approxi-
mately 135,000 lb. is available at 30 per cent
coefficient of adhesion.
The locomotive is equipped with two
pantographs, one at each end, but one of these
^An
*pect
/THE WORLD'SV
MIGHTIEST
LOCOMOTIVE/
\ I (electric) /
Dn Public Exhibition
Union Passenger Station
ST. PAUL
Tuesday, Oct. 12, 12 noon to 4 p. m.
rr>HE FIRST AND ONLY ONE OF ITS KIND—
more powerful than any steam locomotive — weight
260 inns— eight pahs of drive wheels — J 12 feet long
•—every inch works— direct current 3000 volts — over-
head trolley— uses no coat, requires no water, carries
no leader, has no boiler— will handle uniform tonnage
irrespective of weather conditions. By regenerative
braking on down grades returns large part of power
used on climb up grade. Will be used to haul pas-
senger and freight trains over the Rocky Mountains.
This is one of the most revolutionary sights in railroading—
the world's mightiest electric locomotive on its way to the
greatest project in railroad elect rificat ion, that of the main
fine of the Chicago, Milwaukee & St Paul Ry. for 440 miles
through the Rocky Mountains in connection with its trans-
continental service between Chicago, Milwaukee, St. Paul,
Minneapolis and the Pacific North Coast.
The public are cordially invited to enter and thoroughly inspect the
locomotive. Attendants will be on hand to explain details.
Chicago, Milwaukee & St. Paul
RAILWAY
Fig.
7. A Typical Newspaper Notice Inviting the Public
to Inspect the New Locomotive
is sufficient to collect the necessary current
should occasion demand.
The most novel feature of the locomotive
is the regenerative braking which enables the
locomotive to hold back the heaviest trains
on the long descending grades — at the same
time returning power to the line. The air
1158
GENERAL ELECTRIC REVIEW
brakes are thus used only for emergency
service or in making the final stop. Regenera-
tion is controlled by the engineer through an
auxiliary handle on the master controller
which causes the motors to return power to
the trolley in the proper amount to maintain
Fig. 8. One of the Eight, 430-h.p., 3000-volt Motors
Used for Driving a C, M & St. P. Locomotive
any desired speed. This feature was very
thoroughly tested on the General Electric
Companv's experimental track at the Erie
Works.
The general public showed much interest
in the fact that cold weather offers no ob-
stacles to electric locomotive operation as
is the case with steam engines. It was pointed
out that steam locomotives are usually in
difficulties in the winter time, necessitating
extra leeway in the time table to take care
of delays and that there will be no delays for
fuel or water or cleaning fires and that the
electric engine will always be ready at a
moment's notice. With electric operation
trains will move exactly as scheduled so the
meeting and passing points may be figured
to the minute. Fuel trains will be eliminated
in the mountain districts thus giving room
for additional trains handling revenue freight.
At Milwaukee an accurate count was kept
and 5010 people went through the locomotive.
As many more inspected the locomotive
from the outside and either did not have the
time or the opportunity to make an examina-
tion of the interior. Especial interest was
displayed by the employes of the railway
company, practically the entire office and
shop force taking occasion to visit the
machine.
In St. Paul 2550 visitors passed through
the locomotive and in -Minneapolis nearly
0000 people. Opportunity was also afforded
the faculty and students of the Railway
Engineering Course of the University of
Minnesota to make a careful examination
at a special hour.
On the trip west over the Chicago, Mil-
waukee & St. Paul lines stops were made at
Aberdeen, Miles City, Butte and Missoula
with 2000 to 3000 visitors at each stop.
At Butte, the President's special car was
attached and a trip made over the lines of
the Butte, Anaconda & Pacific Railway to
Durant and return. It is noteworthy that
the locomotive was operated under its own
power as a demonstration to these officials
the day it arrived at Butte after being hauled
more than 2000 miles. Among the officials on
the trip to Durant were President A. J.
Earling; Vice President H. B. Earling;
Assistant to the President, C. A. Goodnow
in charge of electrification work, R. M.
Calkins, Traffic Engineer at Seattle; A. M.
Ingersoll, Assistant to the Vice President;
R. Beeuwkes, Engineer in charge of electri-
fication; Mr. H. A. Gallwey, General Manager
of the Butte, Anaconda & Pacific Railway,
and many others.
Final exhibitions were made at Ellensburg,
Spokane (10,000 first day), Seattle and
Tacoma. The number desiring to inspect the
Fig. 9. One of the Driving Trucks for i
C, M. & St. P. Locomotive
locomotive at both Spokane and Seattle was
so large that it was necessary to allow two
days at each place for the exhibition. From
Tacoma the locomotive was started on its way
back to Butte where it will be placed in opera-
tion about December 1st.
1159
THE KINETIC THEORY OF GASES
Part III
By Dr. Saul Dushman
Research Laboratory, General Electric Company
In this concluding issue of the series, the author discusses the different methods which have been used for
determining the number of molecules per unit volume of a gas under standard conditions. A table of atomic
and electronic constants has been added at the end of the paper. — Editor.
In Parts I and II it has been shown that
according to the kinetic theory of gases, the
molecules possess velocities which range
around 5.104 cms. per sec. at room tem-
perature, that is, around 1600 feet per sec.
From measurements of the coefficient of
viscosity we were furthermore led to the
conclusion that at ordinary pressures the
molecules travel between successive colli-
sions a distance which has about the same
magnitude as the wave-length of red light.
Finally we attempted to obtain some con-
ception of the size of the molecules them-
selves. By assuming a definite value for n,
the number of molecules per unit volume
under standard conditions, we deduced the
conclusion that the diameter of the mole-
cules is about 2 to 3 X 10-8 cm. In the present
issue, we shall discuss the different methods
which have been used to determine the value
of this constant, n, which is one of the most
important fundamental constants in physical
science. The product nV, the number of
molecules per molecular weight is known as
Avogadro's constant and will be denoted
by Ar.
I. FROM THE FREE PATH AND VAN DER
WAAL'S CONSTANT, b
It has been shown that the average free
path L, and molecular diameter, d„„ are
related by an equation of the form.
1.402
L =
V2 irn d-
'(1+f)
(24)
On the other hand, the molecular diameter
may also be calculated from Van der Waal's
constant b, by the equation
2tt nV
By eliminating d,„ from these two equa-
tions, it is possible to calculate n in terms of
L and b.
It must be observed, however, that not only
is there a certain amount of doubt regarding
the validity of the assumptions on which
these equations are based, but even if these
assumptions are granted, the conclusions
derived from them are strictly true only for
monatomic gases. The values of n obtained
by this method, and given in Table VII, can
therefore be regarded as only a first approxi-
mation to the correct value, even in the case
of a monatomic gas like argon, while greater
and greater deviations are to be expected as
the structure of the molecules increases in
complexity.
TABLE VII
Number of molecules per cm3 at 0 deg. C. at 106 bars
Calculated from values of b (Table VI) and L
(Table IV)
Gas »X10""
Argon 2.34
Nitrogen 2.67
Oxygen 2.99
Carbon monoxide 3.90
II. FROM INVESTIGATIONS ON BROWNIAN
MOVEMENTS
A drop of water containing some fine
particles in suspension when seen under a
powerful microscope presents an intensely
interesting phenomenon. Under the high
magnification of an achromatic lens we see
that the small particles arc in constant motion
hither and thither. Each little particle
describes an extremely irregular path. (See
Fig. 3.) The motion is the same no
matter what the external conditions may be,
the same, day after day; "eternal and self-
maintained." This phenomenon is known as
Brownian movement — after the name of the
English botanist, who first observed it (1872).
The Brownian motion is exhibited by all
kinds of suspensions and emulsions. An
emulsion of gum arabic or mastix in water; a
cloud of extremely fine dust particles in a gas ;
a suspension of clay in water; all these, when
observed under the miscroscope, show the
same irregular motions of the extremely
small particles in suspension.
1160
GENERAL ELECTRIC REVIEW
The similarity of this motion to that
postulated by the kinetic theory for the
invisible molecules led to the suggestion that
the spontaneous motion of the Brownian
particles is due to the continual collision with
molecules of the medium in which the par-
Fig- 3
tides are suspended, that is, that the par-
ticles are really "large molecules," and there-
fore subject to the same laws as the much
smaller molecules constituting gases. This
theory was first formulated by Einstein (1905)
and mathematically developed so that its
conclusions could be tested out quantita-
tively by experiments. For our present
purposes the great value of this theory con-
sists in the fact that it has led to four dif-
ferent methods of determining the so-called
Avogadro's constant, N, from which n may
be calculated for any desired pressure and
temperature.
For the mathematical derivation of the
different relations, the reader may be referred
to the literature mentioned in the footnotes.
It has not been' considered necessary to go into
the methods more fully because most of this
literature is readily accessible in English.
(1) Equilibrium Distribution of Suspended Par-
ticles in a Vertical Cylinder
Assuming that the Brownian particles obey
the same laws as gas molecules, it follows that
they must exert a pressure P, which is given
by the relation
RT. n
A
Now let h represent the mean height of any
layer in a vertical cylinder containing an
emulsion or suspension of fine particles in
some liquid, and let n denote the concentra-
tion of particles at this height. Owing to
the force of gravity, there will be a tendency
for the particles to settle to the bottom, while
owing to thermal agitation, that is, the
Brownian motion itself, the particles will
continually tend to move in other directions.
The result of these two opposing forces is
that in the equilibrium state, the distribution
of the suspended particles decreases expo-
nentially with the height. Einstein shows
that under these conditions the following
relation ought to hold true:
, n o N m'e h
In — =
(31)
n RT
where
«0 = number of particles per cm3 at h = 0,
m' = " apparent mass" of the particle*
g = gravity constant.
ln = natural logarithm
A similar relation is found to hold for the
rate of decrease of density in our atmosphere
with increase in height above the earth's
surface. Owing, however, to the much greater
mass of the particles in suspension as com-
pared with the molecules of air, the actual
rate of decrease of density is infinitely greater
in the case of a suspension; Fig. 4 illustrates
this very well. Each cylinder contains the
same total number of molecules; the rate of
decrease of density is, however, much greater
in the case of oxygen than in that of hydrogen.
Thus, in order that the pressure at 0 deg. C.
may decrease to half value, we must rise to
a height of 3.4 miles in air, whereas if our
atmosphere were constituted of hydrogen
1 14.5 times lighter than air), we would have
to rise to a distance of about 50 miles.
Equation (31) evidently furnishes a method
of determining N with a high degree of
accuracy. For this purpose it is necessary
to count the number of particles present in
different layers of the suspension and also to
determine m'.
The most accurate method of determining
the mass of a small particle in a suspension
* The term "apparent mass" is use4 to denote the difference
between the actual mass and the buoyancy of the medium in
which the particles are suspended.
THE KINETIC THEORY OF GASES
161
The coefficient
allows for the
involves an application of Stokes' law.
According to this law, the velocity u of a
particle under the influence of a force X is
given by an equation of the form
X = 6wa-qu (32)
where
a = radius of particle
and
i\ = coefficient of viscosity of medium.
In the case of a particle falling freely under
the action of gravity,
X = m'g
Consequently,
m'g = 6ir a i) u (33)
If A denote the density of the particles and
p that of medium,
4
m = - 7T a3 (A — p)
= -(lf) (34)
where m is the actual mass of each particle.
0-i)
buoyancy of the particles in the medium.
By observing the rate of fall of the par-
ticles and determining both p and A, it is
therefore possible to calculate m'g in equation
(31) and thus obtain a value for N.
Determinations of N by this method have
been carried out in the laboratories of Perrin
and T. Svedberg, both of whom have carried
out a number of investigations on the laws of
Brownian movements.*
The rate of decrease in n was found to obey
an exponential law according to equation (31),
and the values of NX10~23 observed by
Perrin in preliminary investigations varied
from 6.5 to 7.2. A very careful investigation
was carried out, using a fine suspension of a
gum in water. The particles were centrifuged
and a suspension obtained containing par-
ticles of as nearly the same size as possible,
the average diameter being about % p. (p =
10-4 cm). The value of m' was determined
accurately by three different methods and n
was counted in 70 cases. In this manner
Perrin obtained the value iV = 6.8X1023
which he considers to be accurate to within
3 per cent.
(2) Intensity of Brownian Motion
The irregular motion of the Brownian
particles has this property, that for any
given suspension the mean square d2 of the
displacements during an interval of time t is
a constant, that is:
— = constant (35)
The value of this constant expresses, there-
fore, the intensity of motion of the particles
HZ
He Oz
Fig. 4
in any suspension. The word Lebhajtigkeit,
that is, "liveliness" may perhaps serve as a
synonymous designation.
Fig. 3 represents the horizontal projections
of the irregular path, described by three
different particles of a mastix emulsion during
a certain period of observation. Each space
corresponds to 3.125 p., and the dots record
the successive positions at 30 second intervals.
The values of the distances travelled during
these intervals are of course distributed
according to Maxwell's distribution law; but
from a large number of such observations, it
is possible to calculate the value of the mean
of the squares of the displacements.
Qualitatively it can be seen that the more
"lively" the Brownian movements in any
emulsion, the greater the rate at which this
emulsion will diffuse into the pure medium.
Einstein showed that the value of the dif-
fusion coefficient D is given by the equation
H?
(36)
It can, however, also be shown that in
accordance with Stokes's law,
D =
1
RT
N ' 6tt a rj
(37)
* Jean Perrin. Die Beweise fur die wahre Existenz der Mole-
kule, Abhandlungen Bunsengesellschaft, Nr. 7, 124-20/ (1913).
T. Svedberg, Untersuchungen uber die Brownsche Bewe-
gung, Jahrb. d. Radioakt. u. Elektronik, 10, 467-515 (1913).
1162
GENERAL ELECTRIC REVIEW
It therefore follows that
d1 RT
t~N3irav (38)
This equation gives us a method of deter-
mining A* from the intensity of the Brownian
movement .
Experimental observations have not only
confirmed the validity of equation (35) but
have also led to values of N of the same order
of magnitude as those obtained by the first
method.
Perrin using emulsions of rubber and mastix
in water has obtained a value of 6.9X10",
while Svedberg working with colloidal solu-
tions of metals has obtained the lower value.
6.2 X1023.
Attempts have also been made to apply
equation (37) directly to determine N from
measurements of the diffusion constant. In
this manner Brillouin, working under Perrin,
has obtained a value 6.9 X 1023, while Svedberg
has obtained values ranging between 5.S and
6.2 X1023.
So far we have spoken only of the trans-
lational motion of Brownian particles; but
particles in suspension also suffer a rotational
motion, and N may be determined by measur-
ing the magnitude of the angular displacement
of any particle at constant intervals of time.
Denoting the mean value of the square of the
average angular displacement in time / by
A", it has been deduced bv Einstein that
A*=RT 1_3__
t A ' 4 7T a*V (ay)
This method of determining A* is not
susceptible of great accuracy, although from
observation on mastix emulsions Perrin has
derived a value of 6.5X1023.
Fletcher1, working with Prof. Millikan,
made a determination of A" from measure-
ments of the Brownian movement of small
oil-drops suspended in air In this case,
however, he did not measure the mean square
displacement, but the average arithmetical
displacement da, which, as both he and
Einstein have shown, is related to the mean
square displacement (d2) in the same time, by
the relation-:
V!^
(40)
Bv this method, Fletcher derived a value
Ar"=5.75X10*».
More recently3 he has made more accurate
determinations of N under similar conditions,
from observations of the law of distribution
of times of fall of oil-drops through a constant
distance. He thus obtains a value of (6.03 ±
.12)X1023 which must be considered one of
the most accurate determinations that has
been made of Avogadro's constant.
III. From Spontaneous Variations in Density
At first sight there appears to be little in
common between the Brownian movement,
and the opalescence observed in gases at the
critical point or the blue color of the sky, but
it has been shown that each of these observa-
tions can be used to calculate at least an
approximate value for Avogadro's constant.
The fact that all gases near the critical
point exhibit opalescence indicates that
under these conditions there are large varia-
tions in density, occurring throughout different
parts of the substance. Smoluchowski has
shown that this is to be expected as a result
of molecular motions; for just as we have
variations in molecular velocities from instant
to instant, so we can expect spontaneous
variations in density at any point. That is,
there will be liable to occur at irregular
intervals a congestion or rarefaction of
molecules. The theory developed on this
basis shows that it is possible to calculate AT
from observations of the degree of scattering
of the light by a gas at the critical point, and
the value obtained, about 7.5 X 1023(4), is fairly
close to those obtained by other methods.
In a similar manner it has been shown by
Lord Rayleigh that the blue color of the sky
is due to an actual scattering of the light by
molecules of the atmosphere which are
distributed irregularly in space. Observations
of the relative intensities of the light coming
directly from the sun and that coming from
other parts of the sky lead here also to a
determination of A". Lord Kelvin thus arrived
at values for A'XIO-23, ranging between
30 and 150, while more accurate determina-
tions since then have led to values ranging
between 45 and 75 (5).
IV. From Measurements of the Unit Electric Charge
According to Faraday's law, it requires
the same number of coulombs to liberate or
decompose by electrolysis amounts of different
substances that are chemically equivalent.
The Faraday constant, F, is defined as the
number of coulombs required to decompose
or deposit by electrolysis that weight in
grams which is equivalent to 16 gms. of
(■) Phys. Rev. 33, 81 (1911).
(*) See also T. Svedberg, loc. cit.. p. 496.
(■) Phys. Rev.. 4, 440 (1914)
i<) Perrin, loc-cit., p. 182.
(*) Perrin, loc. cit. p. 185.
THE KINETIC THEORY OF GASES
163
oxygen (or 1.00S gms. of hydrogen). Very
accurate determinations of this constant have
been carried out at the Bureau of Standards
and the values obtained are (3) :
F = 96,515 coulombs (Iodine = 126.92),
= 96,494 coulombs (Silver = 107.88).
The value 96,500 is therefore recommended
by the Bureau.
Denoting the unit charge of an ion by t,
it follows that
Nt = F (41)
Thus the value of N may be determined
from accurate measurements of the funda-
mental unit of electricity.
Instead of measuring the charge on an ion
in solution, all the investigators in this field
have worked with charged Brownian particles
or ions in gases. That however the unit
electric charge has the same value for all
charged bodies, whether they be ions in
solution or charged Brownian particles was
first demonstrated by Townsend.
The method used consisted essentially in
comparing the average velocity of ions in a
gas under the influence of an electric field
with their diffusion coefficient. From Stokes'
law, equation (36), it follows that the velocity
u of particles having a charge e, in a field of
strength H must be proportional to H t,
so that
H « = 6 7T a 7] it (32)
Combining this with equation (37) for the
diffusion constant, D, there results the
relation
iV t =
RT 1
(42)
D 6 7T a 7]
Fletcher(4) and Eyring(5) have used a
somewhat similar method to measure N for
oil drops in ionized air and ionized hydrogen
respectively.
Instead of determining D, they found it
more convenient to observe d-, the mean
square displacement, which is related to D
according to equation (36). In both cases
the values of N e obtained were very nearly
equal to 96,500 coulombs or 2.95X10"
electrostatic units (e.s.u.) thus showing that
the value of N e is the same for ions in gases
as for ions in solution.
The two principal methods which have been
used for the determination of the charge on
an ion are those of H. A. Wilson and R. A.
Millikan.
(») Bull. Bur. Stand. 10, 425 (1914).
(4) Phys. Rev. 3S, 81 (1911).
ts) Phvs. Rev. S, 412 (1915).
(<) Phil. Mag. 5. 429 (1903).
METHOD OF H. A. WILSON
A gas exposed to X-rays, or to the radia-
tions from a radioactive substance undergoes
ionization, that is, some of the molecules are
made to give up one or more unit negative
charges (electrons) and the residues thus
become positively charged. The electrons
themselves do not remain detached, but
combine with neutral molecules to form
negatively charged ions. The gas is said to be
ionized. If the gas contains microscopic
particles in suspension, such as exhibit the
Brownian movements, the ions attach them-
selves to the particles which thus become
charged in their turn, and by successive-
collisions with charged molecules the particles
will receive or give up part of their charge
until finally a stationary state is obtained.
It is a matter of common observation that
a gas freed of dust particles can contain large
concentrations of water vapor in a super-
saturated state. C. T. R. Wilson observed
that if a gas containing supersaturated water
vapor is ionized, each ion acts as a nucleus for
the condensation of a drop of water, so that
from a determination of the number of water
drops and their total charge, it is possible to
calculate the charge on each drop. The
results obtained by J. J. Thomson and
Townsend were of the right order of magni-
tude but extremely inaccurate.
H. A. Wilson(4) also used charged water
drops but measured their rate of fall under the
influence of gravity alone and under the com-
bined effect of gravitational and electric fields.
Let m! denote the apparent mass of a
water drop (see page 1160) ; u and u' the rate
of fall before and after applying the electric
field of strength H. Assuming that the
velocity of the drop is in each case propor-
tional to the applied force, it follows that
H e—m' g _ u'
m g
or
H \ u )
(43)
The apparent mass m' was deduced by
means of Stokes's law according to equations
(33) and (34). The results obtained indicated
the existence of ions with more than one
unit charge, but the lowest value observed
was about 3.1 X lO"10 e.s.u.
The experiments of H. A. Wilson were
subsequently repeated by other investigators.
Working under much more improved condi-
tions their results have led to values ranging
from 4.5 to 4.7X10-10 e.s.u.
1164
GENERAL ELECTRIC REVIEW
METHOD OF R. A. MILLIKAN
Undoubtedly the most accurate results up
to the present have been obtained by Prof.
MillikanO) at the University of Chicago.
Whereas all the other workers in this field
"had deduced the elementary charge from
the average behavior in electrical and gravi-
tational fields of swarms of charged particles
while the equations used by them hold true
only for individual particles, Millikan avoided
this source of error. A single oil drop sus-
pended in air was isolated "and its speed
measured first in a vertical electrical and
gravitational field combined, then in a
gravitational field alone." The equations
used are therefore those given above. The
result obtained in 1911 was e = 4.891X lO"10
e.s.u. Subsequently more accurate data were
obtained regarding the coefficient of viscosity
of air, which led to the value e = 4.774X 10~10
e.s.u. This is considered by Prof. Millikan as
accurate to within 0.2 per cent.
In the course of these investigations, Prof.
Millikan also arrived at the conclusion that
"Stokes' law for the motion of a small
sphere through a resisting medium breaks
down as the diameter of the sphere becomes
comparable with the mean free path of the
molecules of the medium."
As pointed out by him, the simple form of
this law involves the assumption that there is
no slip at the bounding surface between the
medium and the drop. The existence of such
a phenomenon would tend to counteract the
frictional force otherwise exerted on the
suspended particle. These considerations
therefore led Millikan to suggest the following
modified form of Stokes' law, which was
found to be in good accord with the experi-
mental results.
X
6 ir a t] u
1+A L/a
(44)
where
L = mean free path (see Part II).
A = constant.
The results obtained by Prof. Millikan
form a direct demonstration of the view
"that all electrical charges, however produced,
are exact multiples of one definite elementary
electrical charge; or, in other words, that
an electrical charge, instead of being spread
uniformly over the charged surface has a
definite granular structure, consisting, in fact,
of an exact number of specks or atoms of
electricity, all precisely alike, peppered over
the surface of the charged body."(2)
On a single oil drop it was possible to hold
under observation for any desired length of
time one ion or any definite number of such
ions up to 150. In all cases, the charge was
observed to be an exact multiple of the unit
charge, e = (4.774 ± .009) X 10~10 e.s.u.
Substituting this value in equation (41) it
follows that according to Millikan
iV = 6.062 ±. 012 X1023
N
n =y = 2.6696 X1019 at 106 bars and 0 deg.
C.
= 2.7048 X1019 at 1.01323 X106 bars and
0 deg. C.
V. From Radioactive Phenomena
As well known, a number of radio-active
elements emit so-called alpha particles during
the process of disintegration. It has also been
shown that these particles possess the same
mass as helium atoms and differ from these
only in being positively charged. Upon these
observations have been based four different
methods for determining A', which are
extremely interesting because they furnish an
additional check, as it were, on the values ob-
tained by the other methods described above.
1. Electric Charge on Alpha Particle
Rutherford and Geiger(3) carefully meas-
ured the rate at which alpha particles are
emitted by a given weight of radium, and
also the charge due to a known number of the
particles. Observations of a somewhat
similar character were made by Regener(4),
but instead of using an ionization method of
counting the alpha particles, he observed the
scintillations produced by each particle on a
diamond. It was found in this manner that
the charge carried by one alpha particle was
9.3 X10"10 e.s.u. according to Rutherford and
Geiger, and 9.58X10-10 e.s.u. according to
Regener. On the other hand, other lines of
evidence have led to the conclusion that this
is twice the unit charge. Thus, measurements
of the charge on an alpha particle lead to a
value of the unit charge, ranging from 4.65
X10"10 to 4.79 X10-10 e.s.u.
2. Number of Alpha Particles in a Given Volume
of Helium
Since both the rate at which alpha particles
are emitted and the rate at which helium is
(i) Phys. Rev. Si, 1911).
Phys. Zeit. 14, 796 (1913); Phys. Rev. 2, 140 (1913).
(2) Millikan. Phys. Rev. SB (1911). The italics in all the
quotations are the writer's.
(») Proc. Roy. Soc. 81. 141, 162 (1908). Rutherford.
Radioactivity, p. 135.
(«) Rutherford, loc. cit. p. 52; 137).
THE KINETIC THEORY OF GASES
1165
formed by the same weight of radioactive
element can be readily determined, we are
obviously able to determine N directly.
Dewar observed that 1 gm. radkim evolves
164 cubic millimeters helium in one year.
Combining this with Rutherford's observation
that 1 gm. radium emits 3.4 X 1010 helium
atoms per second, it follows that N = 6.0 X 1023.
Boltwood and Rutherford repeated these
measurements and deduced the result NX
10-23 = 6.24 to 6.4; while Mme. Curie, working
with polanium obtained the value N X 10-23 =
6.50).
3. Period of Radium and Rate of Emission of
Alpha Particles
The period of radium is about 2000 years,
that is, at the end of this interval of time,
half of the radium will have been transformed
into helium and the other disintegration
products. That is, each second there dis-
appear ArX1.09X10~u atoms of radium.
But this must be the same as the number of
atoms of helium produced per second by one
atom of radium. Since the atomic weight of
radium is 226.5 and 1 gm. emits 3.4 X1010
helium atoms per second, we obtain the
relation
1.09X10-nX7V = 226.5X3.4X1010
Hence
N = 7.1 X1023
4. Kinetic Energy of an Alpha Particle
It has been shown in Part I that the
average kinetic energy per gram molecular
3
weight of any gas is equal to- RT. Denoting
the kinetic energy of a molecule by Kt, it
follows that
T , 3 R ~ 1
Ar=2A7T=2W
G2
(45)
where w=mass of molecule, and G = square
root of mean squares of velocities (Part I).
The constant R/N is usually denoted by k
and is known as Boltzmann's constant.
This kinetic energy is converted into heat
owing to bombardment of the radium by the
helium atoms. Hence by measuring the rate
at which heat is emitted by 1 gm. radium, it is
possible to deduce still another value for N.
Rutherford obtained in this manner the
result Ar = 6.2 X1023.
VI. From Radiation Laws for Black Body
From theoretical considerations of a rather
complex nature, Planck arrived at the
following equation expressing the relation
between intensity of unpolarized mono-
chromatic radiation from a black body and
the temperature of the latter.
r 2 tv c2 h X-5 ....
z»=— 5T (46)
ek\T— 1
where
I\ = intensity of monochromatic radiation
of wave-length X at temperature T.
c = velocity of light.
k = Boltzmann's constant (see above).
h = universal constant; so-called "Wirkung-
squantum. "
ch
The coefficients 2 w c- h and -r are usually
denoted by ci and Ci respectively.
From the form of this equation it can be
shown that the intensity of the radiation at
any temperature possesses a maximum value
at a wave-length Xm such that
Xm T = 4.9651 Xk = 4^51 (48)
This is known as Wien's displacement law.
Again, it was shown by Stefan and Boltz-
mann that the total radiation varies with the
temperature according to a relation of the
following form :
■-£■
(47)
/=JoiWX = (7(P-7V)
where
cr = Stefan constant.
T = temperature of radiating surface.
T0 = temperature of absorbing surface.
Integrating equation (46) from X = 0 to
X = °° , and comparing the result with the
above equation, it can be shown that
12 7rX1.0S23fc4 ....
* = -?h>- (49)
From (48) and (49), h may be eliminated
and k = R/N calculated; that is, k can be
calculated from accurate determination of
<s and Xmr.
According to the results obtained up to the
present, the best values of the Stefan-
Boltzmann constant and Xm T appear to be
X,„ 7 = 0.29 cm. deg.
<r = 5.63X10-5 erg. cm.-2 sec.-1 deg.-4
Substituting these values in (48) and (49)
it follows that
AT = 6.06X1023.
While this method has been discussed
rather briefly, it is in reality one of the most
important methods for obtaining an accurate
value of N. Owing to the fact that the
(') Perrin, loc. cit., p. 200.
1166
GENERAL ELECTRIC REVIEW
development of all the above equations has
been discussed very fully in another con-
nection*, the writer has felt that a more
lengthy discussion is unnecessary.
Summary
When we consider that by about, a dozen
totally independent methods, we obtain
approximately the same value of X, the
coincidence must appear more than acciden-
tal. Not only does this result represent the
best deductive evidence for the belief in
the existence of molecules and atoms, but the
phenomena of Brownian movements may be
considered as splendid visible evidence for
believing that the kinetic theory is much
more than a "theory" — that it represents
a reality. There are indeed some doubts
about certain phases of the theory, but the
general point of view appears more justified
today than it did twenty years ago.
In view of the results given above, it is
evident that Prof. Millikan's statement is
quite justifiable that ' ' today we are counting
the number of atoms in a given mass of
matter with as much certainty and precision
as we can attain in counting the inhabitants
in a city. No census is correct to more than
one or two parts in a thousand," and there is
little probabilit3r that the number of mole-
cules in a cubic centimeter of a gas under
standard conditions (106 bars and 0 deg. C.)
differs bv more than that amount from
2.67X1019.
Let us now see what this means. The
highest vacua obtainable range from 10~3 to
10-4 bar. Even at this lowest pressure, the
number of molecules per cubic centimeter is
still 2.67 X109, or 2,670,000,000.
It has been shown in Part I that the
number of molecules striking unit area of a
surface is 34 n 0. For air at 20 deg. C. and
106 bars, this corresponds to 2.8SX1023.
In other words, each square centimeter of a
surface is being struck by this number of
molecules per second. The pressure in an
ordinary tungsten lamp is about 0.1 bar, the
residual gas being probably all nitrogen.
I nder these conditions, each square centi-
meter of the bulb is being bombarded by
about 3X1016 molecules per second.
APPENDIX
It has been felt that a paper on the Kinetic
Theory of Gases would be incomplete without
a table of the most accurately available values
a number of the constants to which refer-
ence has been made above. The table at the
end of the paper contains the values of a
number of atomic and electronic constants,
such as are being constantly used by physi-
cists and chemists. References to literature
and further explanations will be found in the
main part of the paper.
A few remarks are, however, added in
connection with some of the values given.
The number in front of each of the following
sections corresponds to a reference in the table.
(1) The values for V, F, e, e/m0; c; and h
are the fundamental experimental data from
which all the other constants have been
calculated, by means of the relations indi-
cated in each case.
(2) Bull. Bur. Stand. 10, 42b (1914).
(3) R. A. Millikan, Phvs. Rev. 2, 140
(1913).
(4) The values of e ;m0 obtained in recent
vears are as follows:
Classen
(190S)
1.776X107 e.m.u.
Bucherer
(1908)
1.763
Wolz
(1909)
1.707
Malassez
(1911)
1.769
Bestelmeyer
(1911)
1.766
Alberti I
(1912)
1.756
Alberti II
(1912)
1.766
Neumann
(1913)
1.765
Schaefer
(1913)
1.767
The best average of these values is L766
X107 e.m.u.
(5) Direct determinations of h have been
carried out in Prof. Millikan's laboratory
during the past two years. For this purpose
the Einstein photo-electric equation (see
General Electric Review, October, 1914)
was tested for the case of the alkali metals
over a large range of frequencies. The values
observed were h = 6.561 X10"27 (K and Na)(l)
and 6.585 X10-27 (Lf)(2).
(6) The values of a obtained by different
observers(3) range all the way from 5.45 X 10~5
to 6.51 X 10~5. Taking the weighted mean of
all the observations to 1913, Coblentz arrived
at the result ct = 5.70X10~5 erg. cm.-2 deg.-4.
In a more recent paper he considers the
value 5.61 X10-5 as more accurate(4).
* See Recent Views on Matter and Energy. General Elec-
tric Review. July. September, October, and December, 1914.
Attention ought to be drawn in this connection to the fact that
in the above paper, the distribution law was derived for the
case of monochromatic polarized radiation, thus leading to the
omission of the coefficient 2 v in the expression for ci. Thus /^
in the equation given above is equal to 2jt £^. where Ex -=
intensity of polarized monochromatic radiation- On the other
hand, in the equation for the Stefan-Boltzmann law. E=I
according to the above notation.
0) Phys. Rev. .{. 73 (1914).
(!) Phys. Rev. 6, 55 (1915).
{') See the summary by Coblentz, Jahrb. d. Radioakt 10,
340. (1913).
(<) Bull. Bur. Stand. It. 97 (1914).
THE KINETIC THEORY OF GASES
11G7
(l)
(2)
(3)
(4)
(5)
(6)
General Electric Review, December, 1915
Compiled by Research Laboratory, General Electric Company
ATOMIC AND ELECTRONIC CONSTANTS
Volume per gram-moleeular weight of ideal gas.
At 0 deg. C. and 1.01323 X106 bars (760 mms. Hg) K = 22,412 cm3.
At 0 deg. C. and 1 X106 bars (750 mms. Hg) T/ = 22,708 cm.3
Gas constant PVIT = R =83.15 X106 ergs/deg.
= 1.987 cal/deg.
Faraday constant F = 96,500 coulombs.
Unit electric charge c =4.774X10-10 e.s.u.
= 1.591 X10"20 e.m.u.
Number of molecules per gram-molecular weight F/e = N = 6.062 X 1023
Number of molecules per cubic centimeter
At 0 deg. C. and 1.01323X106 bars NjV = n =2.7048 X1019 cm."3
At 0 deg. C. and 1 X106 bars =2.6696X10" cm."3
Boltzmann gas-constant R/N = k = 1.372 X 10-16 erg. /deg.
3
Kinetic energy of a molecule at 0 deg. C =—k X273.1 =5.621 X10~14 erg.
Mass of hydrogen atom 1.008/7V = »nH = 1.663 X10-24 gm.
Ratio of charge to mass of electron «/»io = 1.766 X 107 e.m.u. gm.-1
Mass of electron m0 = 9.01 X 10"28 gm.
Velocity of light c =2.9986 X1010 cm. sec."1
Constant of quantum theory h— 6.585 X 10~27 erg. sec.
Potential difference in volts for X-rays of wave-length X cm V\ = hc/e = 1.241 X10~4 volt. cm.
Fundamental frequency (Rydberg's constant according to Bohr) .. 2 tt- m0 e4 h~3 = v0 = 3.235 X 1016 sec.
Planck's Distribution Formula.
Ci X-6 For radiation from "Black Body" surface. . .ci=2 tt c2 h
Exponent in Wien-Planck equation c2 = chk~1.
Wien's displacement constant \mT =
I\
-1
(6)
Intensity at max. wave-length /„
Stefan-Boltzmann Law
4.9651 k
2 7r&5(4.9651)5r5
= c3 hl "(>•»«« -1)
Total energy radiated from surface = I I\ d X = <r(T4 — To*) ; <r =
12 ttX 1.0823 k*
c2 h3
CORRESPONDING VALUES OF RADIATION CONSTANTS BASED ON PLANCK'S EQUATION
AND MILLIKAN'S VALUE OF k
log a =21.75202 +log h; log c, =26.33950 +log h.
log o- = 83.20626—3 log h log (X,„ T) =25.64364 +log h.
log (ImT~h) =109.38057— 4 log h.
hX 10"
c.XlUb
CI
tXIO*
x,„r
/».7'-5X10<
(erg. -sec.)
erg.-cm.2-sec._1
cm. -deg.
erg.-cm.~2-sec-l.-deg.-*
cm. -deg.
erg.-cm.-3-sec~l.-deg.-i
6.40
3.616
1.399
6.134
0.2817
1.432
6.45
3.644
1.410
5.992
0.2839
1.388
6.50
3.672
1.421
5.855
0.2861
1.346
6.55
3.700 ■
1.432
5.722
0.2883
1.305
6.585
3.7203
14392
5.6310
0.28986
1.2776
6.60
3.728
1.442
5.593
0.2905
1.266
6.65
3.757
1.453
5.468
0.2927
1.228
Numbers in italics are recommended as probably the most accurate values.
MOLECULAR DATA
Hi
Molecular weight (H = 1.008)
Mean velocity at 0 deg. C.
Unit = cm. X 10s sec."1
Average velocity at 0 deg. C.
Unit = cm. X105 sec.-1
Average free path at 0 deg. C. and
10$ bars. Unit = cm. X 10"6
Molecular diameter (viscosity)
Unit = cm. X 10-s
Mass of molecule
Unit = gm. X10"24
2.016
• 1.838
1.696
16.00
2.403
3.326
He
3.99
1.307
1.205
25.25
1.905
6.582
NH,
17.02
0.633
0.583
5.92
2.967
28.08
H*.0
18.02
0.615
0.566
2.9
29.73
CO
N,
0!
A
28.00
28.02
32.00
39.88
0.493
0.493
0.461
0.413
0.454
0.454
0.425
0.381
8.46
8.50
9.05
8.9S '
3.190
3.146
2.975
2.876
46.20
46.23
52.78
65.79
CO:
44.0
0.393
0.362
5.56
3.335
72.59
Note. — For references see General Electric Review, October, November and December, 1915.
llliS
GENERAL ELECTRIC REVIEW
To c2 and \mT, Coblentz assigned in his
earlier paper, the values 1.4420 and 0 2905
respectively, while in a later paper he gave
the values 1.44G5 and 0.2911 respectively (').
On the other hand, Warburg and his
associates at the Reichsanstalt(2) arrived at
the results c2 = 1.4370 ±0.0004 and \mT =
0.2S94 ±0.0008.
Taking into consideration these data, it
would seem that the values given in italics in
the Table are in best accord with both the
experimental observations and the deductions
from the Planck equation. For those, how-
ever, who prefer to choose any other values
of h, C\ or c2, the table of corresponding values
will be found useful. In each horizontal line
are given the corresponding values of h, C\, c2,
a, \mT and Im. It is therefore very easy to
perceive at a glance the effect of slight
changes in the value of each constant on the
values of all the other constants.
The last table summarizes molecular
data which
I and II.
have been published in Parts
(») Bull. Bur. Stand. 10. 1 (1914).
(*) Ann. Phys. 40, 60S (1913).
QUESTION AND ANSWER SECTION
The purpose of this department of the Review is two-fold.
First, it enables all subscribers to avail themselves of the consulting service of a highly specialized
corps of engineering experts, or of such other authority as the problem may require. This service provides
for answers by mail with as little delay as possible of such questions as come within the scope of the Review.
Second, it publishes for the benefit of all Review readers questions and answers of general interest
and of educational value. When the original question deals with only one phase of an interesting subject,
the editor may feel warranted in discussing allied questions so as to provide a more complete treatment
of the whole subject.
To avoid the possibility of an incorrect or incomplete answer, the querist should be particularly careful to
include sufficient data to permit of an intelligent understanding of the situation. Address letters of inquiry to
the Editor, Question and Answer Section, General Electric Company, Schenectady, New York.
CABLE. MULTIPLE-CONDUCTOR:
AERIAL SUSPENSION
(152) Would it be inadvisable to use multiple-
conductor cable hung from a messenger wire for
light and power distribution at 2300 volts and 60
cycles?
The scheme outlined in the question can be suc-
cessfully carried out provided properly constructed
cable, hung in an approved manner, is employed.
Multiple-conductor cables suspended from mes-
senger wires have been used to transmit power at
voltages up to 13,000. Two types of cable are
suitable for this purpose; one is of either varnished
cambric or paper insulation and leaded (being
suspended by hangers at least every 18 inches)
and the other is of varnished cambric armored on
the outside with band steel and made up without
lead. Obviously, a voltage of only 2300 can be
handled successfully by either type of cable. The
varnished cambric cable with band steel armor and
no lead possesses the advantage of being lighter in
weight than the leaded cable, and therefore does not
require such short spans, heavy messenger wire, or
heavy pole construction. W.L.C.
INDUCTION MOTOR: QUARTER-PHASE
TO THREE-PHASE
(153) Can standard quarter-phase motors be changed
to three-phase by reconnecting the stator coils?
In a rather limited number of cases it is possible
and practical to make this change in the manner
described.
Concerning a particular motor it is first necessary
to have data regarding the winding and magnetic
densities, and also the condition of the insulation
between phases. (It is obvious that the flux per
pole after the regrouping of connections should be
approximately equal to the original flux per pole,
and that the insulation between phases after the
regrouping should be amply sufficient to withstand
the voltage strain that will be present under the
new conditions.)
It is usually practicable to reconnect a 220- or a
440-volt quarter-phase motor to 550 volts three-
phase; but, outside of this combination, each
individual case would have to be considered
separately. A.E.A.
REACTANCE COILS: PROTECTION
(154) (a) Would it be practical to build a react-
ance coil for directly protecting a 110,000-vo!t
transmission line?
(b) Could not a reactance coil be so arranged
that during normal operating conditions it
would not be in circuit but could immediately
be placed in the circuit by automatic switches
in time of trouble? Thus, under ordinary condi-
tions its reactive voltage drop in the line would
be eliminated.
(a) There are serious design and cost limitations
that would apply in constructing a 110,000-volt
current-limiting reactance coil. So far as we know
there has none been built for as high a voltage.
It has usually been found possible to secure an
equal degree of protection for these high-voltage
lines by inserting a reactance coil in the low-tension
side, which practice permits of a more economical
and substantial coil construction.
(b) The proposal to automatically insert a
current-limiting reactance coil in a line has been
considered on several occasions. It is the general
consensus of opinion, however, that such a scheme
would seriously lack the certainty of the coil
accomplishing its purpose, viz., giving protection.
In order that a reactance coil may be infallibly able
to give instantaneous protection against short-
QUESTIONS AND ANSWERS
1169
circuits or arcing-grounds, the device should
remain permanently in circuit. The greatest damage
(mechanically) occurs during the first iwo or three
cycles. It is almost impossible to build a switch
that can be relied upon to operate quick enough to
cut reactance coils into a line before the system
has been subjected to the heavy strains incident
to the first two or three current peaks. It is entirely
possible, however, that such an arrangement might
be feasible for an installation wherein protection
against arcing-grounds is more to be desired than
protection against short-circuits.
C.M.D.
TRANSFORMER: BOOSTING
(155) Would it be feasible to use an ordinary
single-phase transformer for boosting the voltage
near the end of a line?
Theoretically, the scheme outlined in the question
is thoroughly applicable, and it can be successfully
used in practice provided the following conditions
are fulfilled.
(a) The frequency of the boosting transformer
should be the same as that of the line.
(b) The voltage of the high-tension winding
should be nominally the same as that of the line.
(c) The voltage of the low-tension winding
should be approximately equal to the desired
voltage boost of the line.
(d) The current-carrying capacity of the trans-
former's low-tension winding should not be
exceeded, in order that overheating will not result.
The current-carrying capacity of the low-tension
winding is equal to the volt-ampere capacity of the
transformer divided by the low-tension voltage.
This value should not be less than the amperes
current that is furnished directly to the load.
Load <Q~04<*v
Po>v*n-foctor-OS
Lco*g$-?*St,r-e
^iSO^otips
Fig. 1
Line load of 40 kw. at 90 per cent power-factor = — =44.5 kv-a.
. . t 44.5X1000 ,„
Load current = — — =18.4 amps.
18 4 X220
Booster transformer load = — '—— — =4.05 kv-a., which it will
be noted is less than the transformer capacity, 5 kv-a.
4.05 X1000
Booster transformer primary current :
2200
= 1.84 amps.
(e) The insulation between the transformer's
low-tension winding and the ground should be
strong enough to withstand (with a reasonable
factor of safety) the boosted line voltage. This is a
requisite because if the "through" line (the one in
which the boosting winding is not inserted) should
become grounded the stress of the boosted voltage,
instead of only half the boosted voltage, will be
applied to the insulation named: the insulation of
this winding will be subjected to the same stresses
as the high-voltage winding, inasmuch as it is
electrically connected to it. (Whether the trans-
former selected will be suitable in this regard can
be determined from the following rule which is
taken from the "1915 A.I.E.E. Standardization
Rules," paragraph 500. "The secondary windings
of distributing transformers shall be tested with
twice their normal voltage plus 1000 volts.)
Fig. 1 is a diagram in which a 40 kw. load at
90 per cent power-factor has been assumed, the
voltage for which is being boosted by a 5 kv-a.
transformer. For the purpose of furnishing a guide
in making calculations the instantaneous directions
of the currents and values of the voltages and
currents are indicated on the diagram.
E.C.S.
CABLES: POT-HEADS
(156) In running an underground 2200-volt, three-
phase, 60-cycle, lead-covered cable with rubber
insulation is it necessary or good practice to use
pot-heads where connections are made to trans-
formers in manholes or in transformer vaults in
buildings?
Are pot-heads more necessary with varnished
cambric insulation than with rubber?
It is not considered good practice to terminate
either rubber insulated or varnished cambric 2200-
volt cable in a manhole without the use of a pot-
head which would properly seal the end of the cable.
Pot-heads are also considered equally necessary for
both rubber insulated and varnished cambric cables
carrying higher voltages than 2200.
w.s.c.
GENERATORS, LOW -SPEED: FORCED VENTILATION
(157) Why is not forced-draft ventilation applied
to cool low-speed (75 to 120 r.p.m.) electric
generators?
A current of air at low pressure is produced most
conveniently and efficiently by a fan which is
inherently a high-speed device. It would be imprac-
ticable, however, to apply this practice to low-speed
machines (such as are named in the question) because
the fan, operating at low speed, would be inefficient
and would have to be so large in order to pass the
necessary volume of air that it would prohibit a
compact mechanical and electrical generator design.
While the system of self-contained-fan ventilation
is inapplicable to low-speed units for the reasons
stated, the method of forced air cooling that is used
with air-blast transformers could be successfully
adopted. This plan, however, would entail the
addition of a separate motor-driven fan set and
air ducts to the generator. Although this system
would be thoroughly practical and would present
no engineering difficulties, it has seldom been used
because of an aversion on the part of central-
station men to adding auxiliary apparatus if it
can reasonably well be avoided.
E.C.S.
1170
GENERAL ELECTRIC REVIEW
IN MEMORIAM
CAPTAIN GEORGE CRELLIN CARTWRIGHT
Captain George Crellin Cartwright, Royal
Warwickshire Regiment of England, who
was killed while gallantly rallying a company
which had suffered the loss of nearly all its
officers in "the great advance" of September
26th, was born in London in March, 1SS2,
and graduated from the Central Technical
College of the City and Guilds of London
Institute. He served in the 2nd Scottish
Horse in the Boer War, receiving the Queen's
Medal with four clasps.
Captain Cartwright
came to New York after
the Boer War and joined
the student course at the
Schenectady Works of
the General Electric
Company. After com-
pleting the course in the
shops, he took a position
in the Foreign Depart-
ment of the Company.
He was sent to Japan by
the General Electric
Company where he re-
mained three years,
returning to New York
in 1910. He then went
to Rio de Janeiro to
represent the General
Electric Company in
Brazil for about a year.
While in Rio he met the
late Dr. F. S. Pearson of the F. S. Pearson
Engineering Co-operation and President of
the Sao Paulo & Rio de Janeiro Electric
Light and Tramway Company's. Dr. Pear-
son offered Captain Cartwright a position
in the F. S. Pearson Engineering Co-opera-
tion London Office in charge of engi-
neering and purchasing work, which was
accepted.
He returned to London in 1911 and from
that time until the outbreak of the war he
was associated with the F. S. Pearson Engi-
neering Co-operation — in particular in work
in connection with the Barcelona (Spain)
Power Transmission — the Ebro Irrigation
& Power Company.
At the outbreak of the war, Captain Cart-
wright applied for a commission and was
gazetted to a second lieutenancy early in
November, 1914. He was promoted to
lieutenant in April, 1915, and to Captain in
July last. Shortly before his death he was
attached to the staff of the 22nd Infantry
Brigade as a machine-gun officer.
On the morning of the attack, on the 26th of
September, Captain Cartwright, as Brigade
Machine-Gun Officer, was in the front line
trenches with his guns, observing the English
advance.
A certain regiment in front had suffered
the loss of nearly all its officers, and Captain
Cartwright, seeing that the men needed
assistance, immediately left the security of
his trenches and rallied
the men and started to
lead them forward again
to the attack. He had
hardly begun the ad-
vance when an unfortu-
nate shot struck him
about two inches below
the right breast and
came out at his back.
He was carried to the
rear and a doctor was
brought and every pos-
sible aid given to him,
but he lingered only two
hours.
It will be seen there-
fore that he sacrificed
himself by a voluntary
act of bravery. As staff
officer in charge of
machine guns, his posi-
tion was in the trenches observing the ad-
vance and directing his gun fire, and report-
ing the results to headquarters. As soon,
however, as he perceived that the men in the
advancing line in front had lost practically
all their officers and needed a leader, he
unhesitatingly and fearlessly rushed into the
open and rallied the men and died leading
them forward. He thus died the death of a
true soldier, noble, brave and self-sacrificing.
Captain Cartwright's untimely death is a
great loss to the service and to his country.
He was an extraordinarily keen, able and
efficient soldier, and most highly regarded by
all his fellow staff officers. He was a capable
and exceedingly well informed engineer — a
man of brilliant mind, a student of art with a
full appreciation and understanding of all
that is best in life. He had many staunch
friends who were endeared to him by the
unusual personal qualities of his strong,
high-minded character.
1171
FROM THE CONSULTING ENGINEERING DEPARTMENT OF THE
GENERAL ELECTRIC COMPANY
A STANDARD IN REFRIGERATION
The need of some method of producing
artificial cold was felt centuries ago and
various crude methods were used to obtain it.
But it was only with the introduction of the
shipment of large quantities of meat over
long distances that it became imperative to
develop some satisfactory method of cooling
to prevent heavy loss from spoiling.
Apparatus making use of air as the cooling
agent was first tried because the principle
involved was best understood at the time and
also because air was cheap.
A gradual evolution has taken place, during
which different refrigerating agents have been
brought into use, along with improvements
in the apparatus employed.
From the first use as a means of preserving
large cargoes of meat we have seen the number
of applications for artificial refrigeration
multiply until at the present time it has
assumed a large commercial scale, and in the
future will undoubtedly be considered as
essential to comfort in large public buildings
and homes as are our present heating systems.
The significance of refrigeration, then, as a
branch of engineering must not be questioned.
Quite noticeable is the fact that there is
at present no standard unit of refrigeration or
standard cycle.
The determination of these is necessary
from a scientific and practical standpoint, as
considerable misunderstanding exists among
engineers, manufacturers and users as to the
rating and capacity of different refrigeration
apparatus of different types, as well as
difference in the same types among different
manufacturers.
The settlement of this problem has been
taken .up in our country as well as abroad,
and engineers and manufacturers are striving
for a standard which will be universally
adopted. A joint committee from the Ameri-
can Society of Refrigeration Engineers and
the American Society of Mechanical Engineers
have been working on the problem for several
years. In their early consideration of the
subject the committee found that the con-
stants employed in the refrigerating industry
varied as to value and it would be necessary
to definitely determine their value before a
refrigerating unit could be proposed.
A serious handicap, however, was the lack
of suitable laboratory equipment and finally
Congress was induced to make an appropria-
tion to permit the Bureau of Standards to
take up these investigations. Their determina-
tion shows that the latent heat of liquefaction
of ice is 143.4: B.t.u. per pound instead of the
old determination of 142 B.t.u. This value
is so near 144 that it is considered safe to use
the latter.
From this determination, the joint Com-
mittee has proposed a value for the unit ton
refrigeration equal to 144X2000, or 288,000
B.t.u. per day of 24 hours, or 200 B.t.u. per
minute. In England the ton refrigeration is
considered equal to 322,600 B.t.u. per day
based on the metric ton of 2240 lb. These
values are also modified by a specified range
of temperature on the machine, which is
different in the two countries.
The British Institution of Mechanical
Engineers also appointed a committee which
recently reported on their work. In their
opinion the most simple and unambiguous
form of statement would be to express the
cooling effect of a machine in calories per
second, the calorie being the amount of heat
necessary to change the temperature of 1
kilogram of water by 1 deg. C.
One calorie is 2.2046X9/5, or 3.968 B.t.u.
One calorie per second is equivalent to
3.968X60X60X24 or approximately 342,860
B.t.u. per day. This value is little larger
than the suggested standard unit of 288,000
B.t.u. per day in the United States and
322,000 B.t.u. "in England.
The following recommendations have also
been made by the British engineers:
1. Definite temperature range in con-
denser and brine end of machine.
2. That the refrigeration produced under
standard condition be called the rated
capacity of the machine; thus, a machine
producing a refrigeration effect of 2 calories
per second would have a rated capacity of
two units.
It is the intention of the interested societies
on both sides of the water to further consider
the problem and come to an agreement as
to the value of the standard unit under
standard conditions and a standard theoret-
ical cycle of operations for comparison.
The following recommendation for a stand-
ard unit of refrigeration has been made by
Dr. C. P. Steinmetz and is very interesting:
"The calorie has been the standard energy
unit in mechanics and in chemistry, until the
1172
GENERAL ELECTRIC REVIEW
last decade, when the Joule was adopted in
chemistry as the unit of energy. The Joule
is the International Electrical Unit of Energy,
and as such offers advantages over all other
energy units in other fields of engineering.
1 cal+4.186 kilojoule. It would, therefore,
appear preferable to adopt the Joule also
as the unit of refrigeration, just as it is the
energy unit in chemistry, in electrical engi-
neering, etc. One Joule per second then is one
watt, and the adoption of the Joule as
refrigerating unit would permit to express
the output of the refrigerating machine in
watts or kilowatts. The only practical
objection, which might be raised against this,
is, that with electrically driven refrigerating
machines, due to the extremely low efficiency
of the cycle (less than 10 per cent), the use of
the same energy unit for output as for input
would show up the low efficiency, which is
inherent in the process."
L. A. Simmons.
TK General Electric review
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