Design and Analysis of a High-Torque-Density Brushless Hybrid Magnet Vernier Machine With Reduced Rare-Earth Material

Permanent magnet Vernier motors demonstrate high torque density characteristics, making them a promising candidate for low-speed direct drive applications. However, achieving high torque density and power factor requires excessive consumption of permanent magnets. This article investigates the topology of a Vernier motor with the combination of both rare earth and ferrite magnets, to achieve the goal of significantly reduced rare earth material. The working principle is modeled by using the combined subdomain and analytical method. Various slot/pole combinations are investigated and compared for optimal performance metrics. A comprehensive comparison is conducted between the proposed topology and conventional counterparts with rare-earth magnet. By using parallel magnetization for rare-earth and ferrite magnets, the proposed topology achieves high torque density of 32 N·m/L, high power factor of 0.87 and high torque per unit of rare-earth magnet volume of 730 N·m/L. A prototype is fabricated to verify the proposed assumption.