Novel Hybrid Rare-Earth and Ferrite Magnet Asymmetric V-Shape and U-Shape IPMSMs Accounting for Demagnetisation Withstand Capability

This paper presents two novel hybrid rare-earth and ferrite permanent magnet (HPM) asymmetric V-shape and U-shape interior PM synchronous machines (IPMSMs) with high ferrite PM (FEPM) torque contribution accounting for the enhanced demagnetisation withstand capability of FEPM at both open circuit and overload conditions. The proposed topologies are designed and compared with a rare-earth PM (REPM)-based symmetrical V-shape baseline in terms of electromagnetic performances, mechanical strength, demagnetisation withstand capability, and PMs cost. All machines are optimised for the same torque with the minimum volume of high-cost REPM at the same specification and size as a commercialised electric vehicle (EV) IPMSM. It is shown that the synergies of magnetic field shifting effect and HPM utilisation have improved the torque per REPM usage in both proposed machines. However, the magnetic field shifting of the proposed HPM asymmetric U-shape IPMSM is twice of that in the V-shape IPMSM counterpart along with a slightly better FEPM demagnetisation withstand capability. Meanwhile, the results show that the proposed HPM asymmetric V-shape IPMSM would be cheaper than the U-shape counterpart as the former and latter topologies require ∼31% and ∼23.5% less REPM volume than the baseline, respectively. Finally, two small laboratory size prototypes are made and tested to verify the finite element analyses.