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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.

APPENDIX I.

EFFICIENCY.

Efficiency of Phase-Displacing Apparatus. —

In apparatus producing phase displacement, as, for example, synchro. nous 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 1 ? r loss. 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.

APPENDIX II. Apparent Efficiency.

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-cur. rent 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, a = inductance factor,

p2 +q2 = 1.

(energy component of current or E.M.F.) The power factor is the le

(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.

APPENDIX IV.
The following notation is recommended : –
E, e, voltage, E.M.F., potential difference.
1, i, current.
P, power.
$, magnetic flux.
B, magnetic density.
R, r, resistance.
X, x, reactance.
2, 2, impedance.
L, I, inductance.
C, c, capacity.
Vector quantities when used should be denoted by capital italics.

APPENDIX V. Table of Sparking Distances in Air between Opposed Sharp NeedlePoints, for Various Effective Sinusoidal Voltages, in inches and in centimeters.

DISTANCE

DISTANCE.

KILOVOLTS SQ. RooT OF

MEAN
SQUARE

KILOVOLTS
SQ. Root OF

MEAN
SQUARE.

INCHES.

CMS.

INCHES.

CMS.

4.65
5.85

0.57
1.19
1.84
2.54
3.3

7.1

0.225
0.47
0.725
1.0
1.3
1.625
2.0
2.45
2.95
3.55

4.1

11.8 14.9 18.0 21.2 24.4 27.3 30.1 32.9 35.4 38.1

90
100
110
120
130
140
150

5.1
6.2
7.5
9.0

8.35
9.6
10.75
11.85
12.95
13.95
15.0

INDEX.

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PAGE

PAGE
Admittance . . . . . . . . . . . 1

Cables for Electric Lighting ...... 281
Ageing of Transformer Iron

. . . 155

Concentric . . . . . . . . . . 284
Alternating Currents ...
109 Callender System ... ·····

. . .2
Fundamental Waves . . . .

. . 112

Capacity ...........
Harmonic Waves · · · · ·

Of Cables and Conductors ...
Circuits, Calculation of ...

Effect on Current . · · · · ·
Power of . . . . . . . .

Formulas for .......
Systems of Distribution ... . . . 186 Means of Reducing ....

Wave, Form of .... . . . 112 Cardew Earthing Device .....
Aluminum as a Conductor ...

Circuit-breakers . .......

. .. 389
Angle of Lag ........ . . . . 117 Chapman Voltage Regulator ...

. . . 57
Arc, the Electric. · · · · · · ·

297 Cleats ............

. . . . 376
Lamps. . . . . . . . . .

.. . 329 Compound Dynamos, Regulation by.
Arc Lamp, Carbon of Direct Feed . 345 Composite Wound Alternator . . .
Cut-outs . . . . . . . .

Compensator for Voltmeter. ...... 199
Composition of the Light ... 313 Motor-Dynamo as ........ 99
Clutches , · · · · · · · ·

346 Compensated Field Alternator ...... 195
Dash Pots . . . . . . . . . .

Conductors, Current Capacity and Table , 13, 15
Differential Mechanism ....

Design and Economy in ... 10, 87, 226
Double Carbon . . . . . . . . .

Measurement of ......... 1
Focusing ...

Materials for .......... 3
Inverted .. ........ . 318 Overhead .......
Magnetic Circuits in Mechanisms ... 342 Underground .. .·· . . .262
Mechanisms of Typical Lamps. 336 to 351 Conductivity of Copper ....
Rod Feed ..

Coefficient of Change of Resistance
Shunt Mechanism ........ Copper Wire Table, . . . . . .
Arc Circuits, Incandescent Lamps on

Losses in Transformers . .
Arc Lighting, Series · · · · · ·

Conductors, Economy in ...
Brush System · · · · · · · ·

Constant Potential Regulator ......
Arc Light Globes ..

Current Transformer . .
Arc, the Alternating ......

Conduit, Cast Iron . . . . . .
Inclosed .........

Fiber .........

. . . . 273
Appearance of .......

Earthenware ....

269-277
Carbons for ........

Pipe .......

263, 267
Candle-Power of ......

Wooden ......

272, 273
Blowing-out of . ......

Edison Tube System . .
On Constant Potential Circuits.

Converter, Rotary . .
Inclosed...........

Cooling of Transformers . . .
Hissing of the · ... · · · · · ·
308 Core Losses in Transformers.

.. 154
Efficiency of the .
311 Cross Arms . . . . . . . .

... 247
Resistance of the ... · ·

Crompton System .....

. .279
Series Inclosed. ......... Cut-out, Thomson Film .. ... 176
Troubles that occur in the ...... 317 Cut-out, Cabinet ......... . 392
Short ............. 314
Unstable ............ 314 Delta Connection, of Three-phase Circuits , 145
Watts Consumed by the ... 308 Direct-Current Transformer. · · · · · · 97
Volts and Amperes Required for the, 303, 312 Distribution, Electrical ........ 1

Alternating Current Systems of . 186 to 223
Belknap Voltage Regulator ...... 57 From Underground Conduits . . . . . 291
Boosters . . . . .

. . . . . 93

D. C. Transformers .......93
Induction Type ......... 205 Parallel Systems of ........ 28
Method of Feeder Regulation ....

Polyphase Systems of ....... 200
Bus bars, Auxiliary . . . . . . . . . .

Single-phase Systems of ......
503

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· 114

HAGE

PAGE
Distribution. Series Systems of ..... 17 Inductance ...........
Dobrowolsky Three-wire System . . . . . 17 Effects, Means of Reducing ....

132
Donshea Method of Field Excitation ... 60 Lag of Current due to .....
Double-Current Generator .....

Table of .....
Drop .... ........

Induction Motor ......
On Mains, Calculation of ..

Induction, Self and Mutual. ..
On Set Works . ...

Insulation . . . . . . . . .
Drawing-in of Conductors.

Interior ( onduit . ......
Dynamotor . . . . . .

Wiring .........
Dynamo, Compound ...

Iron Losses in Transiormers . . . . . . 134
Double ........

Joints in Cables ...
Economy in Conductors . . . .

in Line Wires ..
Edison Tube System · · · · · · · · ·
Eddy Current Losses . . . . . . . . . 156. Kelvin's Law . . . . . . . . . . . 11
Efficiency of Transformers .... . 159, 161 Kennedy's System .......... 230

All Day, Table .......... 113 Knob and Tube Wiring ........ 378
Effective Value of A. C. Volts and Amperes. 114 1
Exciting Current in Transformers . . . . . 125 Lag of Current . · · · · · ·

Lag Due to Inductance......
Parad .............. 20 Lead of Current ...
Feeders . . . . . . . . . . . . . 84 Leakage Current in Transformers ...
Regulation .

.
.

.
. .
. .
.

.
.

.
.

.
.

. 195
.
. .

Leakage, Magnetic in Transformers ...
Flashing Filamenti ....... 197 Lightning Arresters ........
Filaments of Incandescent Lamps .. 395
Anchored ......

Magnetizing Currents in Transformers
Re istance of ...

Magnetic Leakage in Transformers ....
Sizes of . . .

Mains, Calculation of ......38
Fished Wiring ......

Mains and Taps . . . . . . . · · · *85
Five-wire Systems ...

. . . . . . . 86

Manholes . . . . . . . . . . . . . 286
Fixtures for Lamps . . . . . . . . . . 52

Matthiessen's Standard of Conductivity .. 6
Flux Densities in Transformer Cores ..157 Mershon Compensator ..... 199
Frequency Changer . . . . . . . . . . 218

Mesh Connection. See Delta.
Frequency ............. 111 Meters ............ 432-451
Choice of . . . . . . . .

Motor-Converter .......... 93
Foucault Current Losses ....... 156 Motor-Dynamo .......... . . 93
Fuse Blocks for Transformers . . . . . . 179 Motor-Dynamos as Boosters ...

as Compensators ...
Grounded Shield for Transformers . . . 177

Motor, Induction .....
Grounding the neutral of 3-wire system .

Synchronous · · · · ·
84 and App. I

Transformer . . . .
of Transformers .... 177 and App. I

Municipal Lighting Circuits . . . . . .
Guard Wires and Hooks . . . . . . . . 217

Mutual Induction . . . . . . . . .15, 134
Guying Pole Lines . . . . . . . . . 246

Inductance of Circuits ....... 131
Harmonics in A. C. Waves ....112

Naked Conductor Underground Systems . 279
Henry . . . . . . . . . . . ...

Networks of Conductors ....... 103
High Voltage D. C. Distribution ... . 100

Current and Drop in. ....... 103
Holophane Globe ..

Design of ............ 106
Hysteresis Loss in Transformers, ... 155

Neutral Conductor, Grounding of . 84 and App. I

115

334

Impedance . . . . . . . . . . . 131

of Parallel Circuits ....... 126
Due to Resistance and Inductance . . 116

of Series Circuits . . . . . . . . . 126
Incandescent Lamps .........
Incandescent Lamp Bases and Sockets. , 403

Globes . . . . . . . . . . . 399
on Arc Circuits ......... 24
Light Distribution ........ 407
Target Diagram ... ..... 417
Voltage, Candle-Power, Efficiency and

Life . . . . . . . . . .

Over-Compound dynamos, regulation by . 53
Overhead Conductors . . . . . . . . . 237

Insulators for .......... 248
Materials for ... . . . . . . . 237
Poles for. . .

. . . . . 243
Sag and Stress in . . . . . . .
Specifications for ........

| Panel Board ............
Parallel Systems of Distribution. ...

Regulation of ...........

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