基于实测相电流的永磁同步电机转矩波动阶次来源分析及幅值预测

Order analysis and amplitude prediction of torque ripple in hub permanent magnet synchronous motors based on measured phase current

由于转子磁场非正弦分布、定子开槽及电流谐波等因素影响,轮毂永磁同步电机输出转矩中存在波动,驱动转矩波动将给轮毂电机驱动车辆带来振动噪声问题。为分析各因素对转矩波动的贡献及影响机理,通过转鼓倒拖试验实测了电机空载反电动势,进而确定了转子磁场分布情况及转子磁通系数;通过电机驱动转鼓试验实测了电机三相负载电流信号,发现电流中存在丰富的谐波成分并确定了谐波幅值及初始相位;考虑转子磁通和相电流谐波解析推导了电磁转矩表达式,分析了转矩波动阶次来源并根据电流谐波幅值和相位规律预测了各阶次幅值大小,进而确定了转子磁通谐波和电流谐波对转矩波动的贡献;通过实测的振动加速度信号间接验证了转矩波动阶次分析及幅值预测的准确性。结合试验和理论准确分析了轮毂电机转矩波动的全貌及其来源,为电动轮系统的振动优化提供了方向。

The electromagnetic output torque of a permanent magnet synchronous motor（ PMSM） has inherent ripples due to rotor flux harmonics,current harmonics and so on. Driving torque ripple brings NVH problems of hub motor-driven vehicles. Torque ripple in a PMSM was qualitatively and quantitatively studied based on theoretical analysis and test data. The no-load back-electromotive force（ EMF） of the motor was firstly measured through a drum towing test to determine rotor magnetic field distribution and rotor flux coefficient. 3-phase load current signals of the motor were measured through a motor driven drum test to find rich harmonics existing in current,and determine harmonics ＇amplitudes and initial phases. Electromagnetic torque expression in analytical form was derived based on rotor flux harmonics and current ones. The order source of torque ripple was analyzed,and each order＇s amplitude was predicted according to the law of current harmonics＇ amplitudes and phases to determine contributions of rotor flux harmonics and current ones to torque ripple. Finally,the actually measured vibration acceleration signals were used to indirectly verify the correctness of torque ripple order analysis and amplitude prediction. The full view and source of hub motor＇s torque ripple were analyzed with theory and tests here,the results provided a reference for optimal vibration control of hub motor driven vehicles.