Multi-Point Optimization of High-Speed EV Traction Motors Considering Core Materials and Operating-Condition Sensitivity Under the WLTP Driving Cycle

This paper proposes a multi-point optimization method for a high-speed interior permanent magnet synchronous motor (HIPMSM) used in electric vehicle (EV) traction under the WLTP driving cycle. Representative operating points are first extracted from the WLTP speed–torque distribution, and their energy weights are determined according to the energy contribution of each operating region. The resulting operating points cover heavy-load climbing, frequent start–stop, normal cruising, and high-speed cruising conditions, providing a basis for multi-condition motor design. The characteristics of different stator core materials are then evaluated, and the amorphous magnetic alloy (AMA) motor is selected for further optimization. To link material characteristics and operating conditions with motor performance, four electromagnetic indicators are derived from the loss and torque formulations. Their sensitivities to structural parameters are evaluated under the representative conditions and mapped to efficiency, average torque, and torque ripple to identify key design variables for multi-point optimization. Response surface models and NSGA-II are then employed for multi-objective optimization. Compared with rated-point optimization, the proposed multi-point method increases the high-efficiency area from 64.5% to 69.2%. The average torque under the heavy-load condition is increased by approximately 6.5%, while the torque ripple under the high-speed condition is reduced from 17.9% to 12.6%. Finally, thermal validation further confirms that the optimized motor maintains acceptable temperatures under severe high-speed operation. The results demonstrate that the proposed method achieves a more balanced improvement in efficiency and torque performance over the WLTP operating range than conventional rated-point optimization.