22 ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
473. Short Cireuit Characteristic.—In Fig. 99 the 
short circuit characteristic OA, is given by the line passing 
through the zero point and the point which represents 
72.5 amperes armature current on the abscissa of 2,300 
ampere turns. The latter value has been obtained by 
multiplying the normal back ampere turns per pole by the 
48 x 13 X 72.5 
3X16 
short circuit constant, and is eaual to 2.12 x 
x 1,15 = 2,300. 
474. Overload Capacity.—Fig. 99 clearly indicates that 
the specified overload capacity is obtained, because the 
ratio between the short circuit current, which corresponds 
to the normal excitation and the normal current, is sat 
= 1185. : 
4475. The V Curve.—tThe V characteristic of the motor is 
determined in the manner described in Pars. 440 and 
441 and Fig. 99 indicates that for the condition of 
normal full load and the supply of a leading current with - 
cos p=0.9, the field excitation must have the value of 
- 6,050 ampere turns. The form and course of the V curve 
is very satisfactory and may be considered as standard. 
4746. Field Winding.—tThe field winding is to be determined 
for a maximum pressure of 120 volts, and a maximum of 
6,050 ampere turns per pole. Assuming a winding depth 
of 1.6 inches, the length cf mean turn is found to be 38 
inches. Assuming a current density of 1,600, e= 
(2x C,)xX2px LD, 
a q; 107’ 
area of g, equal to 0.0245 sq: inch. 
| The nearest size to this will be a No. 7 S.W.G. wire of 0. 0243 
‘it sq. inch, in which the current will be equal to 0.0243 x 
‘1600=39 amperes. The maximum excitation requires 
» 6050 
a. 39 
in the pole winding amounts to 120 x 39=4,680 watts. 
. from which we find a sectional 
—q = 155 turns per pole. The maximum energy utilized 
