Reduction of Permanent Magnet Usage in Flux-Modulated-type Magnetic Gears using Optimization Methods

Magnetic gears provide non-contact power transmission, offering lower noise and higher reliability than mechanical counterparts. Among various types, flux-modulated magnetic gears are noted for their high efficiency and torque density. However, their requirement for large quantities of rare-earth permanent magnets remains a significant challenge for cost reduction and resource sustainability. This paper investigates a design methodology to reduce permanent magnet usage by combining topology and parametric optimization. First, a novel magnet geometry is explored through topology optimization to maximize the air-gap flux density per magnet volume, revealing that a trapezoidal geometry is suitable. Subsequently, parametric optimization is performed to determine the optimal dimensions of this shape for both inner and outer rotors. To verify the proposed design, a prototype magnetic gear was fabricated and evaluated. Experimental results demonstrate that the proposed trapezoidal magnets improve the stall torque per magnet volume by 1.39 times compared to parallel arrays and 1.15 times compared to Halbach arrays.