Question

Which coil is shorted in commutation process?

(a) Coil under north pole

(b) Coil under south pole

(c) Coil lying in an interpolar region

(d) Cannot be determined

This question was posed to me during a job interview.

This question is from Commutation Process topic in portion Commutation Process & Excitation Methods of DC Machines

Answer 1

Right choice is (c) Coil lying in an interpolar region

The best I can explain: During the commutation period, the coil is shorted via the commutator segments by the brush. These brushes are located in interpolar regions electrically, and magnetically in neutral region. Thus, interpolar coil gets shorted.