Read amperes at top and volts at side, or vice versa.

31 .04156 .4156

32 .04290 .4290

2.145 2.681

4.357

4.692

5.027

40.22 48.26

8,000 10.724 107.2 9,000 12.065 120.6 10,000 13.405 134.1

.8579 1.287 1.716 2.145 33 .04424 .4424 .8847 1.327 1.769 2.212 34 .04558 .4558 .9115 1.367 1.823 2.279 35 04692 .4692 .9384 1.408 1.877 2.346 49 .05362 .5362 1.072 1.609 45 .06032 .6032 1.206 1.810- 2.413 3.016 50 .06703 .6703 1.341 2.011 2.681 3.351 55 .07873 .7373 1.475 2.212 2.949 3.686 60 08043 .8043 1.609 2.413 3.217 4.022 65 08713 .8713 1.743 2.614 3.485 70 09384 .9384 1.877 2.815 3.753 75.10054 1.005 2.011 3.016 4.021 80 .10724 1.072 2.145 3.217 4.290 5.362 6.434 7.507 8.579 85 .11394 1.139 2.279 3.418 4.558 5.697 6.836 7.976 9.115 10.26 11.39 12.53 13.67 90 .12065 1.206 2.413 3.619 4.826 6.032 7.239 8.445 9.652 10.86 12.06 13.27 14.48 95 .12735 1.273 2.547 3.820 5.094 6.367 7.641 8.914 10.18 11.46 12.73 14.01 15.28 100 .13405 1.341 2.681 4.022 5.362 6.703 8.043 9.384 10.72 12.06 13.41 14.75 16.09 200 .26810 2.681 5.362 8.043 10.72 13.41 16.09 18.77 21.45 24.13 26.81 29.49 32.17 300 .40215 4.022 8.043 12.06 16.09 20.11 24.13 28.15 32.17 36.19 40.22 400 .53620 5.362 10.72 16.09 21.45 26.81 32.17 37.53 42.90 48.26 53.62 500 .67025 6.703 13.41 20.11 26.81 33.51 40.22 46.92 53.62 60.32 67.03 600 .80430 8.043 16.09 24.13 32.17 56.30 64.34 72.39 80.43. 700 .93835 9.384 18.77 28.15 37.53 46.92 56.30 800 1.0724 10.72 21.45 32.17 42.90 53.62 64.34 900 1.2065 12.06 24.13 36.19 48.26 60.32 72.39 1,000 1.3105 13.41 26.81 40.22 53.02 67.03 80.43 2,000 2.6810 26.81 53.62 80.43 107.2 134.1 160.9 3,000 4.0215 40.22 80.43 120.6 160.9 201.1 241.3 4,000 5.3620 53.62 107.2 160.9 214.5 268.1 321.7 5,000 6.7025 67.03 134.1 201.1 268.1 335.1 6,000 8.0430 80.43 160.9 241.3 321.7 402.2 7,000 9.3835 93.84 187.7 281.5 375.3 469.2 214.5 321.7 429.0 536.2 241.3 361.9 482.6 603.2 723.9 268.1 402.2 536.2 670.3 804.3

2.574

3.003

3 432

2.654

3.097

3.539

4.022 4.692 5.362

4.424 5.161 5.898

3.740 4.156 4.571 4.987 3.861 4.290 4.719 5.148 3.986 4.424 4.866 5.308 2.735 3.190 3.646 4.102 4.558 5.013 5.469 2.815 3.284 3.753 4.223 4.692 3.217 3.753 4.290 4.826 3.619 4.223 4.826 5.439 6.032 6.032 6.703 6.635 7.373 8.110 8.847

5.161 5.630

5.363

5.898 6.434

6.635 7.239

7.373 8.043

4.826 5.630 6.434

7.239

8.043 8.047 9.652

9.584 10.46

Cost of Copper for Long-distance Transmission.

(Westinghouse El. & Mfg. Co.)

COST OF COPPER REQUIRED FOR THE DELIVERY OF ONE MECHANICAL HORSEPOWER AT MOTOR SHAFT WITH 1000, 2000, 3000, 4000, 5000, and 10,000 VOLTS AT MOTOR TERMINALS, OR AT TERMINALS OF LOWERING TRANSFORMERS. Loss of energy in conductors (drop) equals 20%. Motor efficiency, 90%Length of conductor per mile of single distance, 11,000 ft., to allow for sag. Cost of copper taken at 16 cents per pound.

COST OF COPPER REQUIRED TO DELIVER ONE MECHANICAL HORSE-POWER AT MOTOR-SHAFT WITH VARYING PERCENTAGES OF LOSS IN CONDUCTORS, UPON THE ASSUMPTION THAT THE POTENTIAL AT MOTOR TERMINALS IS IN EACH CASE 3000 VOLTS.

Motor efficiency, 90%. Cost of copper equals 16 cents per pound. Length of conductor per mile of single distance, 11,000 ft., to allow for sag.

Systems of Electrical Distribution in Common Use. I. DIRECT CURRENT.

A. Constant Potential.

110 to 125 and 220 to 250 Volts.-Distances less than, say, 1500 feet.

For incandescent lamps.

For arc-lamps, usually 2 in series.

For motors of moderate sizes.

200 to 250 and 440 Volts, 3-wire.-Distances less than, say, 5000 feet.

For incandescent lamps.

For arc-lamps, usually 2 in series on each branch.
For motors 110 or 220 volts, usually 220 volts.
500 Volts.-Distances less than, say, 20,000 feet.
Incidentally for arc-lamps, usually 10 in series.
For motors, stationary and street-car.

B. Constant Current.

Usually 5, 6, or 9 amperes, the volts increasing to several thousand, as demanded, for arc-lamps.

II. ALTERNATING CURRENT.
A. Constant Potential.

For incandescent lamps, arc-lamps, and motors.
Ployphase Systems.

For arc and incandescent lamps, motors, and rotary con-
verters for giving direct current.

Ployphase-2-and 3-phase-high tension (25,000 volts and over), for long-distance transmission; transformed by step-up and step-down transformers.

B. Constant Current.

Usually 5 to 6.6 amperes. For arc-lamps.

References on Power Distribution.-Abbott, Electric Transmission of Energy; Bell, Electric Power Transmission; Cushing, Standard Wiring for Incandescent Light and Power; Crocker, Electric Lighting, 2 vols.; Poole, Electric Wiring.

ELECTRIC RAILWAYS.

Space will not admit of a proper treatment of this subject in this work. Consult Crosby and Bell, The Electric Railway in Theory and Practice; Fairchild, Street Railways; Merrill, Reference Book of Tables and Formula for Street Railway Engineers; Bell, Electric Transmission of Power; Dawson, Engineering and Electric Traction Pocket-book.

ELECTRIC LIGHTING.

Arc Lights. Direct-current open arcs usually require about 10 amperes at 45 volts. or 450 watts. The range of voltage is from 42 to 52 for ordinary arcs. The most satisfactory light is given by 45 to 47 volts. Search light projectors use from 50 to 100 amperes at 48 to 53 volts.

The candle power of an arc light varies according to the direction in which the light is measured; thus we have, 1, mean horizontal candle-power; 2, maximum candle-power. which is usually found at an angle below the horizontal; 3. mean spherical candle-power; 4, mean hemispherical candlepower, below the horizontal.

The nominal candle-power of an arc lamp is an arbitrary figure. A 450watt arc is commonly called 2000 c.-p. and a 300-watt arc is 1200 c.-p. These figures greatly exceed the true candle-power. Carhart found with an arc of 10 amperes and 45 volts a maximum c.-p. of 450, but with the same watts 8.4 amperes, and 54 volts he obtained 900 c.-p. Blondel, however, found the c. p. a maximum usually below 45 volts. Crocker explains the discrepancy as probably due to a difference in size and quality of the carbons.

Current for are lighting is furnished either on the series, constant current, or on the parallel constant potential system. In the latter the voltage of the circuit is usually 110 and two lamps are connected in series. currents with higher voltages more lamps are used in series; for instance 10 with a 500-volt circuit.

In

Enclosed Arcs -Direct current enclosed arcs consume about 5 amperes at 80 volts. or 400 watts. The chief advantages of the enclosed arcs, on constant potential circuits are the long life of the carbons, 100 to 150 hours, as compared with 8 to 10 hours for open arcs; simplicity of construction, absence of sparks, agreeable quality and better distribution of light.

Alternating-current enclosed arcs usually take a current of 6 amperes at 70 or 75 volts. With 70 volts and 6 amperes, in a 104-volt circuit, the apparent watts at the lamp terminals are 625 and at the arc 420, the actual watts being 445 and 390 respectively. The watts consumed in the inductive resistance average 35 to 45.

Incandescent Lamps.-Candle-power of nominal 16 c.p. 110-volt

lamp:

Mean horizontal 15.7 to 16.6

Mean spherical 12.7 to 13.8

Mean hemispherical 14.0 to 14.6

Mean within 30° from tip 7.9 to 10.9

Ordinary lamps take from 3 to 4 watts per candle-power. A 16 candlepower lamp using 3.5 watts per candle-power or 56 watts at 110 volts takes a current of 56+ 110 = 0.51 ampere. For a given efficiency or watts per candle-power the current and the power increase directly as the candlepower. An ordinary lamp taking 56 watts, 13 lamps take 1 H.P. of electrical energy, or 18 lamps 1.008 kilowatts.

Variation in Candle-Power, Efficiency, and Life.-The following table shows the variation in candle-power, etc., of the General Electric Co.'s standard 100 to 125 volts, 3.1 and 3.5 watt lamps, due to variation in voltage supplied to them. It will be seen that if a 3.1 watt lamp is run at 10 per cent below its normal voltage, it may have over 9 times as long a life, but it will give only 53 per cent of its normal lighting power, and the light will cost 50 per cent more in energy per candle-power. If it is run at 6 per cent above its normal voltage, it will give 37 per cent more light, will take nearly 20 per cent less energy for equal light power, but it will have less than one third of its normal life.

The candle-power of a lamp falls off with its length of life, so that during the latter half of its life it has only 60 per cent or 70 per cent of its rated candle-power, and the watts per candle-power are increased 60 per cent or 70 per cent. After a lamp has burned for 500 or 600 hours it is more economical to break it and supply a new one if the price of electrical energy is that usually charged by central stations.

Specifications for Lamps. (Crocker.) The initial candle-power of any lamp at the rated voltage should not be more than 9 per cent above or below the value called for. The average candle-power of a lot should be within 6 per cent of the rated value. The standard efficiencies are 3.1, 3.5, and 4 watts per candle-power. Each lamp at rated voltage should take within 6 per cent of the watts specified, and the average for the lot should be within 4 per cent. The useful life of a lamp is the time it will burn before falling to a certain candle-power, say 80 per cent of its initial candle-power. For 3.1 watt lamps the useful life is about 400 to 450 hours. for 3.5 watt lamps about 800, and 4 watt lamps about 1600 hours. Special Lamps.-The ordinary 16 c.-p. 110-volt is the standard for interior lighting. Thousands of varieties of lamps for different voltages and candle-power are made for special purposes, from the primary lamp, supplied by primary batteries using three volts and about 1 ampere and giving 1⁄2 c.-p., and the 34 c.-p. bicycle lamp, 4 volts and 0.5 ampere, to lamps of 100 c.p. at 220 volts. Series lamps of 1 c.-p. are used in illuminating signs, ampere and 12.5 to 15 volts, eight lamps being used on a 110-volt circuit. Standard sizes for different voltages, 50, 110, or 220, are 8, 16, 24, 32, 50, and 100 c.-p.

Nernst Lamp.-A form of incandescent lamp originated by Dr. Walther Nernst, of Göttingen, is being developed in this country by the Nernst Lamp Company, Pittsburg, Pa. It depends for its operation upon the peculiar property of certain rare earths, such as yttrium, thorium, zirconium, etc., of becoming electrical conductors when heated to a certain temperature; when cold, these oxides are non-conductors. The lamp comprises a "glower" composed of rare earths mixed with a binding material and pressed into a small rod; a heater for bringing the glower up to the conducting temperature; an automatic cut-out for disconnecting the heater when the glower lights up, and a "ballast" consisting of a small resistance coil of wire having a positive temperature-resistance coefficient. The ballast is connected in series with the glower; its presence is required to compensate the negative temperature-resistance coefficient of the glower; without the ballast, the resistance of the glower would become lower and lower as its temperature rose, until the flow of current through it would destroy it. Fig. 171a shows the elementary circuits of a simple Nernst lamp. cut-out is an electromagnet connected in series with the glower. When current begins to flow through the glower, the magnet pulls up the armature lying across the contacts of the cutout, thereby cutting out the heater. The heater is a coil of fine wire either located very near the glower or encircling it. The glower is from 1/32 to 1/16 inch in diameter and about 1 inch long.

The

The material of the glower is an electrolyte, so that this type of lamp is not well adapted for operation on direct-current circuits because of the wasting away at the positive end end the deposition of material at the negative end.

Line

Cut-out

Cut-out

Coil

Heater

Glower

FIG. 171a.

Ballast

The lamps are made with one glower, or with two, three, or six glowers connected in parallel, and for operation on 100 to 120 and 200 to 240 volt circuits.