Question

How is the number of armature slots associated with the flux densities in iron?

(a) tooth ripples are increased, if the number of slots are increased

(b) tooth ripples are decreased, if the number of slots are increased

(c) tooth ripples are increased, if the number of slots are decreased

(d) tooth ripples are decreased, if the number of slots are decreased

I had been asked this question in an international level competition.

My enquiry is from Armature Design topic in division Design of Synchronous Machines of Design of Electrical Machines

Answer 1

Right choice is (a) tooth ripples are increased, if the number of slots are increased

To explain: The large number of slots a greater space is taken up by the insulation. This results in the narrower teeth giving flux densities which may go beyond acceptable limits.