Abstract: The ever-changing operating conditions of electric vehicles require a wide speed-torque range and high efficiency range for the drive motor, and the motor efficiency MAP is the most intuitive tool to evaluate whether the drive motor satisfies the above requirements. However, the motor efficiency MAP usually requires bench testing to obtain, which wastes time and energy, and cannot satisfy the requirements of rapid verification and optimisation iteration in the current agile development process of electric vehicles. To address this problem, this paper calculates the electromagnetic parameters of the external rotor permanent magnet synchronous motor used in in-wheel motors using the equivalent magnetic circuit method. Then, the motor control strategy is introduced to calculate the losses in the entire speed torque range of the motor. Finally, the fast calculation of the efficiency MAP is programmed in MATLAB. Based on the method proposed in this paper and combined with genetic algorithm, the optimisation design of motor structural parameters can be achieved, thereby improving motor development process.

Key words: Electric vehicle; Permanent magnet synchronous motor; Efficiency MAP; Equivalent magnetic circuit method

摘要： 电动汽车复杂的运行工况要求驱动电机转速-转矩范围和高效率区范围宽，而电机效率 MAP 图是评估驱动电机是否满足上述要求最直观的工具。但是，电机效率 MAP 图通常需要 台架测试来获取，费时费力，无法满足电动汽车敏捷开发过程中进行快速验证和优化迭代的 要求。为解决这一问题，文章对轮毂电机中使用的外转子永磁同步电机，通过等效磁路法计 算电机电磁参数值，再结合电机控制方法对电机全转速-转矩区间损耗进行计算，最后在 MATLAB 中编程实现电机效率 MAP 图的快速计算。基于此方法，结合遗传算法，可以实现 电机结构参数的快速优化设计，进而提高产品开发效率。

关键词: 电动汽车；永磁同步电机；效率 MAP 图；等效磁路法