异步起动永磁同步电机非正常工况退磁分析

为了研究异步起动永磁同步电机非正常工况运行时的退磁磁场对永磁体的影响,通过建立有限元模型,计算分析了包括三相突然短路、缺相运行、过载运行、降电压运行、失步运行和堵转运行6种常见非正常工况运行时定子电流、转速和永磁体工作点磁密的变化。结果表明,起动过程电流均大于非正常工况运行时的冲击电流,直接影响了作用在永磁体上的去磁磁动势,定、转子合成磁动势作用在永磁体上,将使得永磁体工作点磁密最小,退磁风险最大。当电机在同步状态运行时,永磁体工作点磁密为恒定的值;当电机在失步状态运行时,转子导条产生感应电流,定子电流和转子导条电流产生的合成磁场使永磁体工作点磁密做周期性波动。

Analysis of Demagnetization of Line Start Permanent Magnet Synchronous Motor under Abnormal Operation Conditions

To study the influence of demagnetizing magnetic field on permanent magnet of line start permanent magnet synchronous motor under abnormal operation conditions, the changes of armature current, speed and magnetic density of permanent magnet are calculated and analyzed under 6 kinds of common abnormal operation conditions, including three-phase sudden short circuit, missing phrase operation, overload operation, voltage-reducing operation, out-of-step operation and locked operation by setting up finite element model. The results show that the starting current is greater than the impact current under these abnormal operation conditions, which affects the demagnetizing magnetomotive force acting on the permanent magnet. When the combined magnetomotive force of the stator and rotor acts on the permanent magnet, the magnetic density of the working point of the permanent magnet is the smallest and the demagnetization risk is the largest. When the motor is running in the synchronous state,the magnetic density of the permanent magnet working point is a constant value. When the motor is running in the out-of-step state, the induced current is produced by the rotor bar, the magnetic field produced by the stator current and the composite magnetic field produced by the rotor bar current fluctuate the magnetic density of the permanent magnet working point periodically.