用于变频电机绝缘测试的PWM电压发生器

PWM voltage generator for insulation test of inverter-fed motor

在变频电机绝缘测试中,重复脉冲方波电压不能完全模拟变频器输出的PWM电压反映变频电机绝缘失效机理,并且同一实验中使用不同电源影响实验数据的一致性。文中设计了一台直接输出式PWM电压发生器,既可以输出模拟变频器实际的SPWM电压和SVPWM电压用于绝缘测试,又可以输出重复脉冲方波电压开展对比实验。设计了基于FPGA的脉冲信号发生器,产生基波频率、开关频率可调的SPWM、SVPWM触发脉冲以及频率、占空比可调的重复方波脉冲;研制了基于固态推挽开关的斩波器,在脉冲信号的触发下输出对应的双极性高压脉冲,使用该脉冲电压发生器开展了SPWM电压下变频电机绝缘局部放电实验,验证了系统的可靠性和实用性。

In the insulation test of inverter-fed motor, the repetitive pulse square wave voltage cannot fully simulate the pulse width modulation(PWM) voltage output from the inverter and reflect the insulation failure mechanism of the inverter-fed motor, and different power sources used in the same experiment affects the consistency of the experimental data. In this paper, a direct-output PWM voltage generator is designed, which can not only output the SPWM and SVPWM voltage of analog converter for insulation test, but also output the repetitive pulse square wave voltage to carry out contrast experiment. Firstly, a pulse signal generator based on FPGA is designed to generate the SPWM and SVPWM trigger pulse with adjustable fundamental frequency and switching frequency, repetitive square wave trigger pulse with adjustable frequency and duty ratio also can be generated. Then, a chopper based on solid-state push-pull switch is designed to output bipolar high voltage pulse under the trigger of pulse signal. Finally, the experiment of insulation partial discharge of inverter-fed motor under SPWM voltage is carried out with the pulse voltage generator, which proves the reliability and practicability of the system.