盘式永磁同步电机永磁体内涡流的有限元分析

FEM Analysis of the Eddy Current in the Permanent Magnet of Disc Type Permanent Magnet Synchronous Machines

钕铁硼是采用最多的永磁体材料,虽然性能令人满意,但电导率高,耐热性差;并且由于转子散热能力差,涡流会使永磁体发热升温,从而导致部分不可逆的退磁,因此很有必要对永磁体内的涡流进行分析。针对盘式永磁同步电机自身的特点,通过二维电磁场有限元法分别求解了空载和负载时电机内的磁场和永磁体内的涡流,其中包括有铁心电机由于齿槽的存在而引起的涡流和不同电机运行速度下的涡流。为了考虑电机的运动效应和使计算结果更加精确,采用了瞬态分析,同时在划分单元时考虑了磁场的透入深度。最后根据瞬态计算出的数据绘出了磁矢位和涡流波形。波形分析得出了影响永磁体内涡流的因素以及应采取的措施。

NdFeB is mostly used permanent magnet. Despite of its satisfactory performance, it suffers from high electrical conductivity and poor heat resistance. Moreover, due to the relatively poor heat dissipation from the rotor, eddy current losses may cause significant heating of the permanent magnets, and result in partial irreversible demagnetization. Therefore, it is necessary to study the eddy current in the permanent magnet. Based on the actual structure of disc type permanent magnet synchronous machines, the magnet field of the machine and the eddy current in the rotor respectively in the condition of load and no-load are solved by two-dimensional finite element method, which also includes the eddy current caused by the teeth of the stator and the different eddy currents under different running speed conditions. Considering the motion effect of the motor and ensuring the accuracy of the results, this paper utilizes transient analysis and takes the skin depth of magnetic field into account when the model is meshed into finite elements. After solution, the magnetic vector potential waveforms and the eddy current waveforms are drawn according to the result data. Some influencing factors on the eddy current in the permanent magnet and some effective measures are concluded by the analysis of the waveforms.