Question

How many coil sets undergo commutation simultaneously in a wave winding?

(a) 1

(b) 2

(c) 4

(d) 3

The question was asked during a job interview.

My doubt stems from Commutation Process in section Commutation Process & Excitation Methods of DC Machines

Answer 1

Right answer is (b) 2

Easy explanation: Commutation takes place simultaneously for P coils in a lap-wound machine (it has P brushes) and two coil sets of P/2 coils each in a wave-wound machine (electrically it has two brushes independent of P).