钕铁硼永磁材料在过热失磁条件下的磁滞损耗测试与分析

以钕铁硼为代表的稀土类永磁材料因其磁性能好、价格低、力学性能好等特点广泛应用于永磁电机，电机中的谐波磁场又会使永磁体产生损耗，严重时会导致永磁体过热失磁，影响到电机的稳定运行。通过设计的永磁综合磁特性测试装置定量施加交流磁场，发现在低频下，饱和充磁的钕铁硼会出现明显的磁滞现象。对钕铁硼材料在过热失磁条件下进行了磁滞损耗的定量测试与磁特性分析，发现过热失磁的钕铁硼会产生明显的磁滞损耗。测试结果表明：永磁体在高温状态下长时间运行时会逐渐失去磁性，永磁体的磁滞损耗会逐渐增加，甚至在一定条件下磁滞损耗会高于涡流损耗。这说明永磁体的磁滞损耗会加速永磁体的失效，而且在某些情况下是失磁的主要原因。

Measurement and Analysis of Hysteresis Loss of Nd-Fe-B Permanent Magnet under Superheated Loss of Magnetism

Rare earth permanent magnet materials, such as NdFeB, are widely used in permanent magnet motors because of their good magnetic properties, low price and good mechanical properties. The harmonic magnetic field in the motor will cause permanent magnet loss, which will lead to permanent magnet overheating loss of excitation and affect the stable operation of the motor. In this paper, through the design of permanent magnet comprehensive magnetic characteristics test device, quantitative application of AC magnetic field, it is found that under low frequency, saturation magnetization of NdFeB will appear obvious hysteresis phenomenon. In this paper, the hysteresis loss of NdFeB material under the condition of overheating loss of excitation is measured quantitatively and the magnetic characteristics are analyzed. It is found that the NdFeB with overheated loss of magnetism will produce obvious hysteresis loss.The test results show that the permanent magnet will lose its magnetism when it runs at high temperature for a long time, and the hysteresis loss of the permanent magnet will increase gradually, and even the hysteresis loss will be higher than the eddy current loss under certain conditions. This shows that the hysteresis loss of the permanent magnet will accelerate the failure of the permanent magnet, and in some cases is the main reason for the loss of excitation.