Question

Cross-magnetizing effect of armature reaction can be reduced by __________

(a) Removing saturation in teeth and pole-shoe

(b) Making smooth pole shoes

(c) Chamfering the pole shoes

(d) Cannot be determined

I got this question in class test.

I need to ask this question from Ways to Reduce Effects of Armature Reaction topic in chapter Armature Reaction of DC Machines

Answer 1

The correct answer is (c) Chamfering the pole shoes

The best explanation: By chamfering the pole-shoes which increases the air-gap at the pole tips. This method increases the reluctance to the path of main flux in a DC machine but its influence on the cross-flux is much greater. This is because the cross flux has to cross the air-gap twice.