不等极弧结构永磁同步电机噪声和转矩特性

对转子采用表贴式不等极弧结构的车用永磁同步电动机的转矩和噪声特性进行综合分析.通过试验测得其在有风扇和无风扇负载运行时的噪声频谱，诊断噪声源的主要频率成分.根据离散傅里叶分解理论，推导出单极极弧系数不等和相等2种结构下转子磁动势的谐波分布，得到单极极弧系数不等结构电机主要电磁力波的幅值和频率.结果表明，单极极弧系数不等结构虽然有效地降低了齿槽转矩幅值，但同时引入了更多的转子磁动势谐波分量；当转子结构对称时，转子永磁体磁场只存在奇数次谐波，而当转子结构不对称时，不但会产生偶数次谐波分量，还可能会出现分数次谐波分量，使径向电磁力波幅值增大，从而导致电机振动噪声特性变差.通过有限元计算证实了理论推导的正确性，并总结了原方案电机电磁噪声较大的原因.

Noise and torque characteristics of permanent magnet synchronous motor with unequal pole arc structure

The torque and noise characteristics of surface mounted permanent magnet synchronous motor (PMSM) for electric vehicle with unequal pole arc structure were analyzed. The noise spectrum was measured within fan and fanless conditions respectively to diagnose the main noise frequency components. The rotor magnetomotive force (MMF) harmonic distribution was deduced by the theory of discrete Fourier decomposition with the pole arc coefficient of equal and unequal, and the amplitude and frequency of the main electromagnetic force wave with the structure of different monopole pole arc coefficients were obtained. Results showed that although the monopole pole arc unequal structure effectively reduced the amplitude of the cogging torque, it also introduced more harmonic wave components of the rotor MMF. When the rotor structure was symmetrical, only some odd harmonics existed in the magnetic field of the rotor permanent magnet. When the rotor structure was asymmetrical, not only even harmonics but also fractional harmonics may appear, which increased the amplitude of the radial electromagnetic force and made vibration and noise characteristics worse. The correctness of the theoretical deduction was confirmed by the finite element calculation, and the reason for the large electromagnetic noise of the prototype motor was summarized.