Question

What is the ampere turns per pole for compensating winding in DC machines?

(a) (pole arc / pole pitch) * armature ampere turns per pole

(b) (pole pitch / pole arc) * armature ampere turns per pole

(c) (pole arc / pole pitch) * total ampere conductors per pole

(d) Cannot be determined

I have been asked this question during a job interview.

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

Answer 1

Correct answer is (a) (pole arc / pole pitch) * armature ampere turns per pole

The best explanation: The number of ampere-turns required for this purpose is ATcw /pole = ATa (peak) *(pole arc/pole pitch) = [IaZ/(AP2)]*(pole arc/pole pitch). The compensating winding neutralizes the armature mmf directly under the pole while in the interpolar region, there is incomplete neutralization.