电机绝缘在线监测用高频电流传感器设计

Design of High Frequency Current Sensor for Online Monitoring of Motor Insulation

逆变器开关激励产生的高频振荡电流可用于电机绝缘状态监测,但开关振荡电流的频域分布宽,且混杂在基波和纹波电流中,幅值微弱。针对开关振荡电流传感器带宽和灵敏度设计需要准确获取传感器寄生参数的问题,此处提出一种基于脉冲频率响应的寄生参数提取方法,通过有限元电磁仿真提取自感参数,根据脉冲响应谐振频率提取分布电容参数,并在此基础上对终端电阻进行合理选择。最后,设计了一个小尺寸、少匝数的高频电流传感器并在3 kW永磁电机系统中进行验证。实验结果表明所设计的传感器能够准确地从电机运行电流中提取开关振荡电流分量,可为电机绝缘非侵入式在线监测提供技术支撑。

The high frequency oscillating current generated by inverter switching excitation can be used to monitor the insulation of the motor,but the switching oscillating current has a wide frequency domain distribution,mixed in the fundamental and ripple current,and has a weak amplitude.Aiming at the problem that the bandwidth and sensitivity design of switching oscillating current sensors requires accurate of parasitic parameters of the sensor,a method of extracting parasitic parameters using impulse frequency response is proposed,extracting self-inductance parameter through finite element electromagnetic simulation,and extracting distributed capacitance parameter through impulse response resonance frequency.On this basis,the terminal resistance is selected reasonably.Finally,a small sized,small number of turns high frequency current sensor is designed and verified in 3 kW permanent magnet motor system.The experimental results show that the sensor can accurately extract the switching oscillating current component from the motor operating current,which can provide technical support for non-intrusive online monitoring of motor insulation.