Brushless Direct Current Electric Motor Design with Minimum Cogging Torque

Abstract

Cogging torque is one of the factors that influence electric motor efficiency. Many methods have been used to reduce the cogging torque. One of the methods is the determination of the number of slots and poles fraction. This study was intended to determine the number of slots and poles fraction to get a minimum of cogging torque. Research was done by ANSYS software. By varying the number of slots and poles, the data cogging torque and torque ripple were observed. It was found that the lesser difference between the number of slots and poles produced lower cogging torque. More numbers of slots would reduce the cogging torque. The smallest cogging torque was produced at difference in the number of slots and poles of 1 and 2. For slots more than four, the cogging torque produced were irregular.

A Review of Torque Ripple Reduction Design Methods for Radial Flux PM Motors

“…When the right combination of slots and poles is selected, a substantial reduction in cogging torque is possible. Some reviewed articles dealt with cogging torque and tried to eliminate it or reduce it by experimenting with different slot/pole number combinations [22,24,[33][34][35][36][37][38][39][40][41][42][43][44]. One of those articles is [33], which showed the advantages of machines with fractional number of slots per pole and phase, not only in generating less cogging torque and torque ripple, but also having acceptable values of electromagnetic torque and copper losses, compared with machines with integer number of slots per pole and phase.…”