A method for reducing cogging torque by magnet shifting in permanent magnet machines

Cogging torque is one of the important issues for permanent magnet machines. Due to the interaction between the permanent magnets and slotted armature lamination, there exists cogging torque in slotted permanent magnet machines, which may cause noise and vibration. To reduce the cogging torque, the expression of the cogging torque was studied based on the Fourier analysis in this paper. Based on the analytical expression of cogging torque, a method of permanent magnet (PM) shifting to reduce cogging torque of PM machines was presented. The new method to obtain the PM shifting angles was achieved. At last the method is verified by finite element method. The results verify that the method to obtain the PM shifting angles is very simple, and with this method the cogging torque can be greatly reduced.