The effects of the distribution of residual magnetization on the cogging torque and switching signals in permanent magnet (PM) motors

A novel cogging torque reduction method is presented for permanent magnet (PM) motors. The key idea of the method is optimizing the distribution of residual magnetic flux density of the PM by putting auxiliary slots on the pole face of the magnetizing yoke. Through the three-dimensional (3-D) finite-element simulation with edge elements and nodal force method for the motor having eight PM poles and six winding slots, the effectiveness of the presented method is proved. The effects on the switching signal are also investigated.