Design of High-Speed Multilayer IPMSM Using Ferrite PM for EV Traction Considering Mechanical and Electrical Characteristics

This article proposes a design method of the high-speed multilayer interior permanent magnet synchronous motor (HSML IPMSM) employing the ferrite permanent magnet (PM). Since the maximum speed of the traction motor in this article is 15 kr/min, the mechanical stability must be considered. Additionally, in the case of the HSML IPMSM, as the number of the PM layers increases, the thickness of the PMs must be reduced to be mechanically stable. On the other hand, because the ferrite PM has a relatively low coercive force compared with the Nd PM, an irreversible demagnetization of the ferrite PM of the HSML IPMSM is likely to occur. Therefore, the mechanical stability and irreversible demagnetization must be considered at all design steps. As the irreversible demagnetization and mechanical stability can be confirmed only by the finite-element analysis (FEA), the proposed method in this article is a design method that considers the irreversible demagnetization and mechanical characteristics at all design steps using the FEA. After the design of the traction motor is completed using this design method, the designed motor is manufactured. To verify the validity of the design method, experiments are conducted on the manufactured motor, and the test results are compared with FEA results.