Design and Analysis of Combined Magnetic Poles for the Rotor of a Less Rare-Earth Hybrid Permanent Magnet Synchronous Motor

Introduction: The non-renewable nature of rare-earth materials and their increasing demand have led to rising prices for rare-earth Permanent Magnet (PM) materials, thereby increasing the manufacturing costs of the corresponding motors. Reducing reliance on rare-earth materials while ensuring the operating performance of motors has attracted significant research attention, resulting in fewer rare-earth permanent magnet synchronous motors emerging in this context. This paper introduces a less rare-earth Permanent Magnet Synchronous Motor (PMSM) with a novel rotor permanent magnet structure, which has been designed, analyzed, and optimized. The primary feature of this motor is the stepped structure of the rotor, composed of neodymium iron boron, which enhances overall performance. Methods: The proposed motor is designed, simulated and analyzed by using the finite element analysis method using ANSYS Maxwell electromagnetic simulation software. Results: By improving the shape of the rotor neodymium-iron-boron permanent magnets, the motor offers the advantages of low cogging torque, low harmonic reverse Electromotive Force (EMF) at no load, and a more sinusoidal air-gap flux density waveform. This paper provides effective verification through simulation analysis. Discussion: The optimisation results of the motor are analysed in terms of rotor permanent magnet shape, main stage NdFeB angle, air gap length, NdFeB material, and number of motor coil turns. Conclusion: The proposed motor not only reduces the cogging torque and no-load back EMF harmonics, but it also makes the air gap flux density waveform closer to sinusoidal by optimizing the rotor structure while achieving the rated load torque requirement.