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3d. Induction motors: 25 per cent for one-half hour, 50 per cent for one minute.
4th. Synchronous converters: 50 per cent for one-half hour.
5th. Transformers: 25 per cent for one-half hour; except in transformers connected to apparatus for which a different overload is guaranteed, in which case the same guaranties shall apply for the transformers as for the apparatus connected thereto.
6th. Exciters of alternators and other synchronous machines, 10 per cent more overload than is required for the excitation of the synchronous machine at its guaranteed overload and for the same period of time.
Efficiency of Phase-Displacing Apparatus. —
In apparatus producing phase displacement, as, for example, synchronous compensators, exciters of induction generators, reactive coils, condensers, olarization cells, etc., the efficiency should be understood to be the ratio of the volt-ampere activity to the volt-ampere activity plus power loss.
The efficiency may be calculated by determining the losses individually, adding to them the volt-ampere activity, and then dividing the volt-ampere activity by the sum.
1st. In synchronous compensators and exciters of induction generators, the determination of losses is the same as in other synchronous machines under Sections 10 and 11.
2d. In reactive coils the losses are molecular friction, eddy losses, and /Vloss. They should be measured by wattmeter. The efficiency of reactive coils should be determined with a sine wave of impressed E.M.F., except where expressly specified otherwise.
3d. In condensers, the losses are due to dielectric hysteresis and leakage, and should be determined by wattmeter with a sine wave of E.M.F.
4th. In polarization cells, the losses are those due to electric resistivity and a loss in the electrolyte of the nature of chemical hysteresis, and are usually very considerable. They depend upon the frequency, voltage, and temperature, and should be determined with a sine wave of impressed E.M.F., except where expressly specified otherwise.
In apparatus in which a phase displacement is inherent to their operation, apparent efficiency should be understood as the ratio of net power output to volt-ampere input.
Such apparatus comprise induction motors, reactive synchronous converters, synchronous converters controlling the voltage of an alternating-current system, self-exciting synchronous motors, potential regulators, and open magnetic circuit transformers, etc.
Since the apparent efficiency of apparatus generating electric power depends upon the power factor of the load, the apparent efficiency, unless otherwise specified, should be referred to a load power-factor of unity.
APPENDIX III. Power Factor and Inductance Factor. —
The power factor in alternating circuits or apparatus may be defined as the ratio of the electric power, in watts, to volt-amperes.
The inductance factor is to be considered as the ratio of wattless voltamperes to total volt-amperes.
Thus, if p = power factor, q = inductance factor,
p1 + q1 = 1.
„, r . • ., (energy component of current or E.M.F.)
The power factor is the - 5^— ^ ., „'
(total current or E.M.f.
and the inductance factor is the
(wattless component of current or E.M.F. — true power.
(total current or E.M.F., — volt amperes.
Since the power-factor of apparatus supplying electric power depends upon the power-factor of the load, the power-factor of the load should be considered as unity, unless otherwise specified.
The following notation is recommended : —
E, e, voltage, E.M.F., potential difference.
/, /', current.
*, magnetic flux.
<Sh magnetic density.
R, r, resistance.
X, x, reactance.
Z, z, impedance.
L, 1, inductance.
C, c, capacity.
Vector quantities when used should be denoted by capital italics.
Table of Sparking Distances in Air between Opposed Sharp NeedlePoints, for Various Effective Sinusoidal Voltages, in inches and in centimeters.
Ageing of Transformer Iron 155
Alternating Currents 109
Fundamental Waves 112
Harmonic Waves 112
Circuits, Calculation of 224
Power of 119
Systems of Distribution 186
Wave, Form of 112
Aluminum as a Conductor 3, 238
Angle of Lag 117
Arc, the Electric 297
Arc Lamp, Carbon of Direct Feed .... 346
Composition of the Light 313
Dash Pots 356
Differential Mechanism 339
Double Carbon 343
Magnetic Circuits in Mechanisms . . . 342
Rod Feed 344
Shunt Mechanism 338
Arc Circuits, Incandescent Lamps on ... 24
Arc Lighting, Series 21
Brush System 22
Arc Light Globes 332
Arc, the Alternating 318
Appearance of 298
Carbons for 302, 329
Candle-Power of 308
Blowing-out of 314
On Constant Potential Circuits . . 315,325
Hissing of the 308
Efficiency of the 311
Resistance of the 306
Series Inclosed 323
Troubles that Occur in the 317
Watts Consumed by the 308
Volts and Amperes Required for the, 303, 312
Belknap Voltage Regulator 57
Induction Type 206
Method of Feeder Regulation .... 67
Bus bars, Auxiliary 64
Cables for Electric Lighting 281
Callender System 280
Of Cables and Conductors 136
Effect on Current 121
Formulas for 138
Means of Reducing 138
Cardew Earthing Device 176
Chapman Voltage Regulator 57
Compound Dynamos, Regulation by . . . 53
Composite Wound Alternator 193
Compensator for Voltmeter 199
Motor-Dynamo as 99
Compensated Field Alternator 195
Conductors, Current Capacity and Table . 13, 15
Measurement of 1
Materials for 3
Conductivity of Copper 4
Coefficient of Change of Resistance .... 6
Copper Wire Table 8
Losses in Transformers 153
Conductors, Economy in . . . 10,87,226
Constant Potential Regulator 57
Current Transformer 176
Conduit, Cast Iron 267
Edison Tube System 273, 279
Converter, Rotary 96
Cooling of Transformers 167
Core Losses in Transformers 154
Cross Arms 247
Crompton System 279
Cut-out, Thomson Film 170
Cut-out, Cabinet 392
Delta Connection, of Three-phase Circuits . 145
Direct-Current Transformer 97
Distribution, Electrical 1
Alternating Current Systems of . 186 to 223
From Underground Conduits 291
D. C. Transformers 93
Parallel Systems of 28
Polyphase Svstems of 200
Single-phase Systems of 186
Distribution, Scries Systems of 17
Dobrowolsky Three-wire System 77
Donshea Method of Field Excitation ... 00
I >ouble-Current Generator 215
On Mains, Calculation of 38
On Net Works 103
I)rawing-in of Conductors 288
I >ynamotor .93
Dynamo, Compound 53
Economy in Conductors 10, 87,220
Edison Tube System 273
Eddy Current Losses 15G
Efficiency of Transformers 159, l0l
All Day.TabL- 1£5
Effective Value of A. C. Volts and Amperes . 114
Regulation t , 195
Flashing Filament; 197
Filaments of Incandescent I.,mips .... 395
Resistance of 110
Sizes of Ill
Fished Wiring .»1
Five-wire Systems 86
Fixtures for I^imps 192
Flux Densities in Transformer Cores . . . 157
Frequency Changer 218
Choice of 224
Foucault Current Losses i66
Fuse Blocks for Transformers 179
Grounded Shield for Transformers . . .177
Grounding the neutral of 3-wire system . .
S4 and A pp. I
of Transformers .... 177 and App. I
Guard Wires and Hooks '-17
Guying Pole Lines 246
Harmonics in A. C. Waves 112
High Voltage D. C. Distribution 100
Holophane Globe 334
Hysteresis Loss in Transformers ..... 155
of Parallel Circuits 126
Due to Resistance and Inductance . . . 116
of Series Circuits 126
Incandescent T-tmps 39.>
Incandescent Lamp Bases and Sockets 401
on Arc Circuits 24
Light Distribution 407
Target Diaenm 417
Voltage, Candle-Power, Efficiency and
Inductance . , 114
Effects, Means of Reducing 332
Lag of Current due to 117
Table of 130
Induction Motor 147
Induction, Self and Mutual 115
Interior Conduit 379
Iron Losses in Transformers 154
Joints in Cables 285
in Line Wires 253
Kelvin's Law 11
Kennedy's System 280
Knob and Tube Wiling 378
Lag of Current 117
Lag Due to.Inductance . 117
Lead of Current 121
Leakage Current in Transformers .... 158
Magnetizing Currents in Transformers . 158
Magnetic Leakage in Transformers .... 1C0
Mains, Calculation of ;i8
Mains and Taps £83
Matthiessen's Standaid of Conductivity . . 6
Mershon Compensator 190
Mesh Connection. See Delta.
Meters ... 432-451
Motor-Dynamo . 93
Motor' Dynamos as Boosters ...... 99
as Compensators 99>
Motor, Induction 147
Synchronous . . 147
Municipal Lighting Circuits 15
Mutual Induction • 15, 134
Inductance of Circuits 131
Naked Conductor Underground Systems . 279-
Networks of Conductors 103
Current and Drop in 103
Design of 106
Neutral Conductor, Grounding of , 84 and App. I
Over-Comuound dynamos, regulation by . 53
Overhead Conductors 237
Insulators for 248
Materials for 237
Poles for 243
Sag and Stress in 241
Specifications for 237
Psnel Board 392
Parallel Svstems of Distribution 28
Regulation of 5t