Question

Calculate the shaft power developed by a motor using the given data: Eb = 404V and I = 25 A. Assume frictional losses are 444 W and windage losses are 777 W.

(a) 8879 W

(b) 2177 W

(c) 8911 W

(d) 8897 W

This question was posed to me in examination.

Origin of the question is DC Motors in chapter Characteristics of DC & AC Motors of Electric Drives

Answer 1

Right choice is (a) 8879 W

To explain: Shaft power developed by the motor can be calculated using the formula P = Eb*I-(rotational losses) = 404*25- (444+777) = 8879 W. If rotational losses are neglected, the power developed becomes equal to the shaft power of the motor.