Quantitatively evaluation on the cogging torque of permanent magnet motor caused by stator and rotor defect

Cogging torque makes great attribute to the torque ripple and noise of permanent magnet motor. The causes to produce cogging torque are discussed in this paper. The cogging torques of two PM motors is computed by finite element analysis. Computed results show the effectiveness of pole-slot-pairing method to reduce ideal cogging torque. While in practical motor, there may be some defects caused by manufacture, such as magnet performance discrete, and the evaluation of stator inner surface. These defects can cause non-ideal cogging torque. Such cogging torque is quantificationally analyzed by finite element analysis.