Comparative study of Mechanical and Electrical Characteristics on High-Strength Steel and Conventional Steel for EV Traction High-Speed Multilayer IPMSM Using Rare-Earth Free PM

In this article, the electrical and mechanical characteristics are compared with multilayer IPMSM (ML-IPMSM) using ferrite permanent magnet (PM) when driven at high-speed according to electrical steel. In high-speed operation, in the case of ML-IPMSM, the mechanical and electrical characteristics change depending on the number of PM layers, PM shape, the number of bridges, and bridge thickness. In addition, ferrite PM has a lower coercive force than Nd PM, therefore irreversible demagnetization (ID) must be considered, and it is affected by the number of layers and PM shape of ML-IPMSM. Therefore, when designing a multilayer IPMSM using ferrite PM for electrical vehicle (EV) traction, all the characteristics must be considered. Compared to conventional electrical steel (CES), High-strength electrical steel (HSES) has advantages in mechanical properties, allowing the ML shape to be relatively free. Accordingly, it is possible to design a shape that is advantageous in electrical performance compared to CES by adjusting ML shape. In this article, all characteristics of each ML-IPMSM applied with HSEC and CES are reviewed through finite element analysis (FEA), and the advantages of HSEC applied motors for high-speed driving motors are presented. To verify the validity of the review contents of this article, experiments are conducted on the manufactured motor, FEA results are compared with the test results.