This article investigates the time-dependent demagnetization behavior of NdFeB permanent magnets used for electrified vehicles. A mathematical model of magnetic viscosity was derived using maximum-likelihood estimation based on the test data. This magnetic viscosity model was then used to predict the magnet demagnetization behavior over time. A demagnetization test fixture and a programmable dc power supply were used to apply a constant demagnetizing field to N48H magnet samples. A hall-effect sensor was used for online measurement of the magnetic field under a constant demagnetizing field over a wide time range. A buck converter was used to generate a pulsed demagnetizing field in the timescale of milliseconds. The results of this article will help understand the demagnetization behavior of NdFeB magnets caused by overcurrent faults in permanent-magnet synchronous machines.

中文翻译：

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直流和脉冲磁场下 NdFeB 磁铁的时间相关退磁

本文研究了用于电动汽车的 NdFeB 永磁体的随时间退磁行为。使用基于测试数据的最大似然估计推导出磁粘度的数学模型。然后使用该磁粘度模型来预测磁体随时间的退磁行为。退磁测试夹具和可编程直流电源用于向 N48H 磁体样品施加恒定的退磁场。霍尔效应传感器用于在很宽的时间范围内在恒定退磁场下在线测量磁场。降压转换器用于产生毫秒级的脉冲消磁场。