Question

Calculate the number of conductors on each pole piece required in a compensating winding for a 6-pole lap-wound dc armature containing 286 conductors. The compensating winding carries full armature current. Assume ratio of pole arc/ pole pitch = 0.7.

(a) 6

(b) 8

(c) 9

(d) 7

I had been asked this question by my college professor while I was bunking the class.

Question is taken from Ways to Reduce Effects of Armature Reaction topic in section Armature Reaction of DC Machines

Answer 1

Right answer is (a) 6

The explanation: The number of ampere-turns required for compensating winding is ATcw /pole = ATa (peak) *(pole arc/pole pitch) = [IaZ/(AP2)] * (pole arc/pole pitch).

Ncw/pole = (Z/2AP) * (pole arc/pole pitch) = [286 / (2*6*6)] 0.7 = 2.78.

Compensating conductors/pole = 2 * 2.78 = 6 (nearest integer).