Question

What is the formula for the flux density for the PM motors?

(a) flux density = residual flux density / 1 + (1.11/permeance coefficient)

(b) flux density = residual flux density * 1 + (1.11/permeance coefficient)

(c) flux density = residual flux density / 1 + (1.11*permeance coefficient)

(d) flux density = residual flux density * 1 + (1.11*permeance coefficient)

I had been asked this question in examination.

This question is from Design Preliminaries topic in chapter Design of Permanent Magnet (PM) DC Motors of Design of Electrical Machines

Answer 1

Correct option is (a) flux density = residual flux density / 1 + (1.11/permeance coefficient)

Easy explanation: The residual flux density is calculated first along with the permeance coefficient to obtain the flux density of the PMDC motor. The flux density is 0.85 times the residual flux density.