Question

How is the voltage related with the air gap density?

(a) air gap density is directly proportional to the voltage

(b) air gap density is indirectly proportional to the voltage

(c) air gap density is directly proportional to the square of the voltage

(d) air gap density is indirectly proportional to the square of the voltage

This question was posed to me during an interview.

My enquiry is from Synchronous Machines Output Equation topic in portion Design of Synchronous Machines of Design of Electrical Machines

Answer 1

Right choice is (b) air gap density is indirectly proportional to the voltage

To explain: The air gap density is indirectly proportional to the voltage. High voltage machine should have low air gap density, to avoid excessive values of flux density in the teeth and core.