Design of Asymmetric Permanent Magnet Rotor for Efficient Material Use in a PMSM for High Performance Automotive Applications

In this paper, a design procedure of an asymmetric permanent magnet synchronous machine is introduced. The purpose of the design is to improve the material utilization while maintaining and/or improving the performance and efficiency of the machine. Two different machine designs are shown where the degree of design freedom in terms of magnet size is the only varying factor. The proposed designs are compared to two reference machines, one being a conventional high performance permanent magnet synchronous machine and the other being a lower power machine intended for lower performance passenger cars. The main design procedure is described, starting with the electromagnetic optimization and then moving to the mechanical design of the machine. The proposed designs are analyzed presenting how the torque is affected by the asymmetric rotor and how the material utilization is improved. The final designs are compared with the reference machines, and it is shown that the asymmetric design can reduce the required magnet mass of a high-performance machine to the level of a low power machine while slightly improving the performance compared to the high-power reference machine. It is also shown that the asymmetric machine can improve the efficiency of the powertrain and therefore providing overall system improvement without requiring significant investment.