Question

What happens to the armature diameter and the volume of air gap and magnet when the angle is lower in value?

(a) volume of air gap and magnet increases, armature diameter increases

(b) volume of air gap and magnet increases, armature diameter decreases

(c) volume of air gap and magnet decreases, armature diameter decreases

(d) volume of air gap and magnet decreases, armature diameter increases

The question was asked in quiz.

My query is from Design Steps and Considerations in section Design of Permanent Magnet (PM) DC Motors of Design of Electrical Machines

Answer 1

Correct choice is (d) volume of air gap and magnet decreases, armature diameter increases

To explain I would say: The lower values of angle, reduces the volume of air gap and magnet. The reduction of volume of air gap and magnet, increases the armature diameter.