Question

What should be the length of pole with respect to the length of the armature and what should be the range of the length of pole?

(a) length of pole < length of armature, 10-15 m

(b) length of pole > length of armature, 10-15 mm

(c) length of pole > length of armature, 10-15 cm

(d) length of pole < length of armature, 10-15 mm

The question was posed to me in final exam.

My question is taken from Pole Design topic in section Thermal Design Aspects of Electrical Machines & D.C of Design of Electrical Machines

Answer 1

Correct answer is (d) length of pole < length of armature, 10-15 mm

For explanation: The length of the pole should be very much less than the length of the armature in order to permit the end play and t avoid magnetic centering. It should be in the range of 10-15 mm.