Question

What is the value of pole pitch (in SI unit) for mean air gap radius= 0.5mm and P=4?

(a) 0.785* 10^-6

(b) 0.785* 10^-3

(c) 0.785* 10^-2

(d) 0.785* 10^-4

This question was posed to me in unit test.

Query is from EMF and Torque Production in division Circuit Model, Emf and Torque of DC Machines

Answer 1

Correct option is (b) 0.785* 10^-3

The best explanation: Pole pitch is called as center to center distance between two adjacent poles. When measured in electrical degrees one pole itch is equal to 1800. Pole pitch can be calculated as ratio of 2πr/P.

Pole pitch= 2*3.14* 0.5* 10^-3 / 4= 0.785* 10^-3 m.