Improvement of Torque Capability of Permanent-Magnet Motor by Using Hybrid Rotor Configuration

Abstract

This paper proposes a novel hybrid rotor permanent-magnet (HRPM) motor to improve torque capability, including average torque and torque ripple. The key of the proposed motor is that it can utilize high PM torque of surface-inserted PM (SPM) rotor module and high reluctance torque of interior PM (IPM) rotor module at the same time. Meanwhile, the shifting angle of SPMs and open angle of air barriers are introduced to improve the average torque and reduce the torque ripple, respectively. The two variables are employed to create circumferential asymmetry of the rotor for generating an angular difference of the electromagnetic torque between adjacent N-pole and S-pole, thus minimizing torque ripple. In order to evaluate the proposed motor, an IPM motor and a SPM motor with the same dimension and volume of PM are used as benchmarks. Through theoretical analysis and experimental test, it is verified that the proposed HRPM motor can offer higher torque density and lower torque ripple simultaneously.