Novel Asymmetric Rotor Hybrid Interior Permanent Magnet Synchronous Machines for Torque Density and PM Utilization Ratio Improvement

This paper presents two novel hybrid interior permanent magnet synchronous machines (IPMSMs) that combine rare-earth PMs (RE-PMs) and ferrite PMs (FPMs) to enhance torque density and improve PM utilization ratio. One design features an asymmetric rotor, named AR-HIPMSM, while the other incorporates a consequent-pole asymmetric rotor, named CPAR-HIPMSM. The key innovation lies in the hybrid use of RE-PMs and FPMs, combined with a consequent-pole rotor that employs an asymmetric V-shaped PM arrangement. Finite element analysis (FEA) of the optimized AR-HIPMSM, CPARHIPMSM, and a conventional V-shaped IPMSM shows that both proposed machines achieve improved PM utilization. Specifically, AR-HIPMSM demonstrates the highest torque density, while CPAR-HIPMSM achieves a torque density similar to the conventional IPMSM. The enhanced torque density of both machines is attributed to the magnetic-field shifting (MFS) effect generated by the asymmetric rotor. Additionally, the improved PM utilization is due to both torque density enhancement and the reduced PM cost resulting from the use of hybrid PMs. Notably, CPAR-HIPMSM benefits significantly from cost reduction owing to its consequent-pole rotor, which results in the highest PM utilization, as confirmed by the magnetic circuit analysis. Experimental results of the prototypes validate the accuracy of the FEA predictions.