Torque Improvement of a Flux-Reversal Permanent-Magnet Motor Based on Harmonic Oriented Design

The flux-reversal permanent-magnet (FRPM) motor is known for its robustness and suitability for harsh environments. However, the use of rare-earth permanent-magnet (PM) material makes it costly. In this paper, a less rare earth FRPM (LRE-FRPM) motor with PM arranged in slot opening is proposed to improve rare earth PM utilization. The operation principle is analyzed by flux-modulation effect. By maxwell tensor method, the torque generated by each harmonic is calculated. It is found that even static harmonics can generate effective torque. In addition, based on the harmonic characteristic and torque components, the harmonic oriented design methods are used to improve the torque density. By finite element analysis (FEA), the improvement effect of the proposed methods is verified.