主绝缘劣化对变频电机宽频开关振荡特性的影响

为研究主绝缘劣化对变频电机开关瞬态宽频振荡特性的影响，建立了计及功率器件开关暂态过程和主绝缘状态的变频调速系统宽频域模型，分析了宽频开关振荡电流的主导模态及其传导路径，探索主绝缘电容变化对开关振荡电流幅频响应特征的作用规律。仿真和实验结果表明：开关振荡电流主要包含高频差模、高频共模和中频共模3个主导模态分量。开关振荡中频共模分量电流可以渗透进电机绕组内部，其幅频响应特征与主绝缘电容参量有关：共模串联谐振频率随主绝缘电容增加而减小，靠近串联谐振点的幅值特征随主绝缘电容增加而增加，从而为变频电机绝缘在线状态监测提供了一种新的思路。

Impact of ground-wall insulation degradation on broadband switching oscillation characteristics of inverter-fed machine

To study the impact of the ground-wall insulation degradation on the broadband switching transient oscillation characteristics of the inverter-fed machine, a broadband model of the inverter-fed machine system considering the switching transient process of the power device and the ground-wall insulation condition is established. The dominant modes of the broadband switching oscillation current and its propagation path are analyzed, and the effect of the ground-wall insulation capacitance variation on the amplitude-frequency response characteristics of the switching oscillation current is explored. Simulative and experimental results show that, there are mainly three dominant modes in switching oscillation current, including HFDM(High-Frequency Differential-Mode),HFCM(High-Frequency Common-Mode) and MFCM(Medium-Frequency Common-Mode). The MFCM switching oscillation current can penetrate into the stator windings, and its amplitude-frequency response characteristics are related to the ground-wall insulation capacitance. The common-mode series resonant frequency will decrease with the increase of ground-wall insulation capacitance, while the amplitude characteristics close to the series resonant frequency will increase with the increase of ground-wall insulation capacitance. The study may provide a new solution for online insulation condition monitoring of the inverter-fed machine.