脉宽调制电压激励下电机永磁体涡流有限元计算的比拟等效方法

Analogy Method for Finite Element Method Calculation of Eddy Current in Permanent Magnet with PWM Voltage Excitation

永磁体涡流损耗计算是永磁电机热分析的关键问题之一。运用电机学基本理论与电磁场解析法提出一种比拟方法,使得高脉宽调制开关频率下的永磁体涡流问题可以用低开关频率模型进行比拟。在相同过渡过程时间内,比拟模型可以减少时步有限元法的计算步数,使永磁体涡流有限元分析的时间得以缩短。以表贴式永磁电机为例,对所提出的比拟等效方法用有限元算例进行检验,比拟比例取为3。计算结果表明,比拟等效模型的计算时间减少到原问题的1/4以下,比拟等效模型与原问题电机电流谐波幅值相对误差小于2.36%,永磁体涡流损耗相对误差小于0.48%。

Calculation of eddy current loss in permanent magnet is a key issue in thermal analysis of permanent magnetic synchronous machine （PMSM）. With fundamental theories in electrical machinery and analytical method in electro-magnetic field, an analogy criterion for equalizing an eddy current problem with high pulse width modulation （PWM） frequency to one with lower switching frequency was proposed, hence lessens the calculation steps and shortens the calculation time under similar transient process. An example of finite element method （FEM） analysis for surface-mounted PMSM was used to validate the proposed analogy method with the analogy proportion being 3. The result showed that the proposed method could reduce the calculation time to less than 1/4 of the original problem, whereas the relative errors in harmonic amplitude of machine current within 2. 36% and eddy current loss in permanent magnet within 0.48% .