Question

What is the pole arc/pitch ratio, if 360 AT compensating winding is used where 1960AT is peak value?

(a) 0.7

(b) 0.8

(c) 0.9

(d) 0.6

This question was posed to me during an online interview.

Asked question is from Ways to Reduce Effects of Armature Reaction in portion Armature Reaction of DC Machines

Answer 1

Correct answer is (d) 0.6

For explanation I would say: The ampere-turns required for compensating winding in a DC machine is ATcw /pole = ATa (peak) *(pole arc/pole pitch). If compensating winding of 360AT is used the, 360/1960 will give ratio of pole pitch /pole arc, equal to 0.6.