驱动电机用高性能钕铁硼永磁材料不可逆失磁扩散特性研究

Irreversible Demagnetization and Diffusion Characteristics of High Performance NdFeB Permanent Magnet for Drive Motor

由于钕铁硼永磁材料具有磁性能良好、价格低廉、力学性能优秀等优点,在电机行业得到广泛应用,但其较低的居里温度及热稳定性引起的不可逆失磁现象一直是永磁电机高可靠性设计及失磁故障管理的主要瓶颈。针对驱动电机用高性能钕铁硼永磁材料的磁通不可逆损失问题,本文研究了高温及高温与退磁场共同作用两种情况下,初始正常状态及初始已发生局部失磁状态的永磁体不可逆失磁现象的产生与演变规律。研究结果表明,钕铁硼永磁体的局部失磁扩散现象受磁体的磁性能状态、工作温度与退磁场强度影响,存在从磁体中心向四周演变的不可逆失磁扩散特性。高温作用下的局部失磁扩散随温度提高呈线性缓慢增加规律,高温与退磁磁场共同作用下,存在可使磁体发生大面积、快速失磁的拐点,磁体的局部失磁及反向充磁现象可同时发生。

NdFeB permanent magnet has been widely used in motor industry because of its good magnetic properties,low price and excellent mechanical properties.However,the irreversible demagnetization caused by its low Curie temperature and magnetic stability has always been the main bottleneck of high reliability design and loss of excitation fault management of permanent magnet motor.Aiming at the irreversible demagnetization of high-performance NdFeB permanent magnet materials for driving motors,the generation and evolution of irreversible loss of magnetic flux in the initial normal state and the initial partial demagnetization under the combined action of high temperature and demagnetizing field were studied by experimental methods.The results show that the partial demagnetization of NdFeB permanent magnet is affected by the initial magnetic property state,working temperature and external demagnetizing field,and there is an irreversible demagnetization diffusion characteristic from the center of the magnet to the periphery.The partial demagnetization diffusion under high temperature increases linearly and slowly with the increase of temperature.Under the joint action of high temperature and demagnetization magnetic field,there is an inflection point that can cause large-area and rapid demagnetization of the magnet,and the partial demagnetization and reverse magnetization of the magnet can occur at the same time.