Cogging torque analysis in disc-type permanent magnet motors with fractional-slot windings

SHANGGUAN Jing-shi1， FAN Lei2， WANG Xiu1， FAN Cheng-zhi1
（1. College of Electrical Engineering， Zhejiang University， Hangzhou 310027， China；
2. Yuhang Electric Power Bureau， Hangzhou 311100， China）

Abstract： Force ripple caused by cogging torque is one of the important issues which prevent the motor from acquiring high performance. Aiming at reducing the cogging torque，an analytical method based on the energy method and the Fourier series was applied to obtain the expression of cogging force. Based on the expressions，a method of weakening cogging torque by adopting fractional-slot windings combined with slot opening optimization was proposed. The results acquired by finite element analysis show that the proposed method of combination of fractional-slot winding and slot opening optimization can effectively reduce the cogging torque in disc-type permanent magnet motors.
Key words： disc-type permanent magnet motors； cogging torque； fractional-slot windings； slot opening； 3D finite element