Question

Inequality in brush arm currents caused due to different emf induced in different parallel paths may give rise to copper losses. These effects can be avoided by using _________

(a) Compensating windings

(b) Interpoles

(c) Equalizer rings

(d) Cannot be determined

This question was addressed to me during an interview for a job.

My doubt stems from Ways to Reduce Effects of Armature Reaction in chapter Armature Reaction of DC Machines

Answer 1

The correct option is (c) Equalizer rings

To elaborate: The armature coil in lap windings have equal to or more than 2 parallel paths. Under the influence of pole pairs there may arise asymmetry in various paths resulting in different parallel path voltages. So, equalizer rings are connected in order to achieve symmetry again.