Novel Parallel Hybrid Rare-Earth and Ferrite Magnets in V-Spoke Interior PM Synchronous Machine

Abstract

This paper introduces a novel interior permanent magnet synchronous machine (IPMSM) using a parallel configuration of hybrid rare-earth and ferrite permanent magnets (HPMs) and V-shape arrangement of spokes. Aiming at the same torque with lower volume of rare-earth PMs (REPMs) than a double V-shape IPMSM for EV application, the proposed parallel HPM V-spoke IPMSM is designed and optimized by genetic algorithm. In addition, the electromagnetic performance, mechanical strength at high speed and demagnetization withstand capability of ferrite magnets are analyzed using finite element analyses (FEA). It is shown that at the same torque, the REPM volume can be reduced by 37% leading to about 30% reduction of total PM cost. Although the total mass of PMs is almost doubled, the introduced verge and gap in the proposed parallel HPM V-spoke design can significantly reduce the maximum von-mises stress on ribs and keep it close to that of the benchmark. In addition, the demagnetization withstand capability of ferrite magnet proves a high tolerance against irreversible demagnetization except a small region close to the REPM. A scaled prototype is made and tested to verify the FEA.