关键词: 电动汽车；永磁同步电机；效率 MAP 图；等效磁路法

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