Design to Reduce Cogging Torque and Irreversible Demagnetization in Traction Hybrid Motor Using Dy-free Magnet

Abstract

The PMSM (Permanent Magnet Synchronous Motor) is being studied a lot in traction motors for high efficiency and high performance. Usually, magnets containing rare earth elements are used. However, since rare earth elements are not suitable for future industries due to their limited reserves, many studies on magnets excluding rare earth elements are being conducted. Magnets excluding rare earth elements have a low coercive force and are vulnerable to irreversible demagnetization, so their design must be robust. Additionally, the design used for reducing the cogging torque, which is a major variable of traction motors, is also important. Therefore, in this study, a design process for reducing irreversible demagnetization and cogging torque is proposed. There are three methods for this process. The first one is the application of the tapering structure, and the second one is the tapering skew structure. The third one is the application of an asymmetric air hole. As a result of these methods, the target irreversible demagnetization ratio was satisfied and the cogging torque was reduced. This was proven through FEA (Finite Element Analysis) and verified by comparing and analyzing the experimental results and simulation results of actual manufacturing.