Cogging Torque Reduction of Interior Permanent-Magnet Synchronous Motors by Finite-Element Method

The cogging torque of a permanent-magnet motor is an oscillatory torque that always induces vibration, acoustic noise, possible resonance and speed ripples, and its minimization is a major concern for electric motor designers. This paper presents an effective approach for the cogging torque reduction of interior permanent-magnet motors by modifying the magnet span angle of the rotor and the shoe depth and shoe ramp of the stator. The cogging torque is calculated by employing a commercial finite-element analysis software Ansoft/Maxwell. The results show that the peak value of the cogging torque for the modified design decreases 50% in comparison with that of the original design.