Series Hybrid Rare-Earth and Ferrite Magnets Delta-Shape IPMSM with Split Ferrite Spoke

In contrast to the parallel hybrid permanent magnet (HPM) configuration, the main feature of a series HPM counterpart is to have a higher demagnetization withstand capability at the cost of a lower electromagnetic performance. Although a series HPM delta-shape IPMSM can compromise the low electromagnetic performance by an improved reluctance torque component, the FEPM contribution remains low as a low volume of ferrite PMs can be used due to the structural limitations. To address this issue, a novel series HPM delta-shape IPMSM with split ferrite spoke is proposed and compared to a series HPM delta-shape counterpart without split ferrite spoke and a REPM-based benchmark using frozen permeability method. It is revealed that the proposed machine benefits from the higher ferrite PM torque and reluctance torque contributions by 35% and 6% compared to those of the other HPM machines without split ferrite spoke, which lead to a less required rare-earth PM (REPM) torque component. As a result, this machine needs only 52.14 cm3 REPM which is less than that of the latter topology with 112.85 cm3 and much less than that of the benchmark with 249.4 cm3. Therefore, at the same torque and size, the PM cost of the proposed series HPM delta-shape IPMSM with split ferrite spoke is ∼37% less than that of its HPM counterpart without split ferrite spoke and ∼67% less than that of the benchmark. In addition, open-circuit and onload performances, demagnetization withstand capability, von-mises stress distributions and PM cost are also investigated using the finite element analysis (FEA). A laboratory size prototype is built and tested to validate the FEA investigations.