Online monitoring of AC motor grounding insulation based on switch oscillating current
In the variable frequency drive system,the high dv/dt and transient overvoltage generated by the high-speed switch of the power device will make the motor insulation parts withstand high electrical stress,accelerate the aging of the motor insulation materi-als,and then increase the probability of insulation failure and harm the overall reliability of the drive system.Compared with the tradi-tional offline monitoring method,online monitoring of motor insulation states can improve the real-time monitoring performance and re-duce the loss of shutdown maintenance.Therefore,this paper presents a method of online monitoring of AC motor grounding insulation based on inverter switch oscillating current.First,the authors established an AC motor insulation equivalent circuit,analyzed the influ-ence of insulation aging on the impedance of AC motor,and simulated the insulation aging process by connecting external capacitors in parallel.Then,the influence of the motor grounding insulation parameters on the switch oscillating current under pulse width modulation(PWM)was analyzed,and proposed an online monitoring method with the frequency domain deviation of switch oscillating current as the aging characteristic index.This test shows that this method can effectively monitor the aging state of the motor grounding insulation without affecting the normal operation of the motor.
AC motorinsulation agingonline monitoringcurrent responseinverterhigh-speed train
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