Torque Analysis of Interior Permanent-Magnet Synchronous Motors by Considering Cross-Magnetization: Variation in Torque Components With Permanent-Magnet Configurations

The variation in torque of interior permanent-magnet synchronous motors with driving conditions and magnet configurations is investigated by considering the cross-magnetization caused by magnetic saturation. The torque is decomposed into four components, i.e., the main magnet torque, main reluctance torque, cross-magnet torque, and cross-reluctance torque. It is revealed that the cross-magnet torque is always negative and this component reduces the total torque of the motor. This effect becomes large in the case of the V-type magnet configuration. The magnet configuration, which reduces the cross-magnetization effect, is also investigated by considering the mechanical strength against the centrifugal force caused by high-speed rotation. The validity of the calculation is confirmed by experiments.