280 



INDUCTION MOTORS. 



[Exp. 





Scale for power, (.vertical direction only) 



FIG. i. Circle diagram locus of primary current for predetermining the 

 performance of an induction motor. 





CURRENT. 



Primary current at no load = 7 = OA 



Added current due to load = 7< 2 ) = AP 



Primary current at any load = 7 : = OP 



Short-circuit or locked current = Is = OP" 



Power component of no-load current = OB = M N 



Power component of primary current = OC = MP 



POWER. (For scale see 10.) 



Power input = MP 



Power loss at no load = MN 



Added loss at any load = NK 



Total loss at any load = M K 



Power output = KP 



Primary copper loss (approx.) NS 



Secondary copper loss (approx.) = SK 



Secondary input = SP 





TORQUE. 

 Torque is proportional to secondary input, SP. 



In syn. horse-power = SP in horse-power -^ synchronous R.P.M. 

 In syn. watts SP in watts -f- synchronous R.P.M. 



In pound feet = 7.04 X SP in watts -i- synchronous R.P.M. 



