DIRECT-CURRENT DYNAMOS AND MOTORS. | 113 
about 12 inches for the shunt coil which is wound over the 
series coil. The total weight of the series winding is: 
Ws. = 21 X 3 X 4 X 1.87 X .0645 = 30.5 pounds. 
The size of the shunt wire is: 
6.420 XK 28 6 
en 
== 125 — 15 
=1,67O circular mils, or No. 18 wire. 
In Par. 79, the total cooling surface of two magnets of 
this machine is found 355 square inches; the power loss in 
the series winding is 4 X 105 = 52 watts per magnetic 
circuit ; hence, the shunt current : | 
« , 3 5 a, 
h= 5 X aa, es 1.04 amperes. 
Number of shunt turns: 
C; 
a — = 6,1'70 per circuit, or 3,085 turns 
per core, , 
The diameter of No. 18 wire is .045 inch; hence, there are 
34 + .045 = 77 turns 
in each layer, and the number of layers becomes - 
3,085 + 77 = 40, 
_ for which the winding depth is 
40 X .045 = 2 inches. 
The mean length of the shunt turn, therefore, is: 
1.” = (6 +2 x 4+ 2) Xx = 30.24 inches, or 2.54 feet. 
Resistance of shunt winding: aie 
Tan = 77 X 40 X 2.54 X .00638 = 50 ohms, at 20° C., 
or ran’ = 50 X 1.12 = 56 ohms, at 50° C. 
Actual shunt current: 
erin: sae 
ee a a ae ae 
= 1.04 amperes, '' 
ars 
Can 
