PWM逆变器驱动异步电动机采用长线电缆时电压反射现象的研究

RESEARCH OF VOLTAGE REFLECTION OF PWM INVERTER-FED INDUCTION MOTOR WITH LONG MOTOR LEADS

PWM逆变器驱动的异步电动机 ,在逆变器和电动机之间采用长线电缆传输时 ,会产生电压反射现象 ,导致在电动机端产生过电压、高频阻尼振荡 ,使电动机绝缘老化 ,造成电动机在短期内绝缘击穿等事故 ,这是PWM逆变器驱动异步电动机采用长线电缆所产生的负面效应。文中首先分析了长线电缆传输时由于长线电缆的分布参数所产生的电压反射现象及其所造成的过电压等负面效应 ,分析表明电动机端产生的过电压与逆变器输出PWM脉冲上升时间和电缆长度有关 ,PWM脉冲上升时间愈短 ,电缆愈长 ,反射现象愈明显。采用低成本无源滤波技术可消除这种负面效应 ,文中分析和设计了一种一阶RC电动机端滤波器 ,用于接在异步电动机的接线端上 ,实验结果表明该滤波器可有效地减小电动机端过电压等负荷效应 ,从而提高系统的可靠性。

When long motor leads are used between inverter and motor on PWM inverter-fed i nduction motor, there will be resulted in voltage reflection which contributes o ver-voltage and damped high-frequency ringing at motor terminals and further s tresses the motor insulation, even leads to insulation breakdown in premature pe riod. This is an adverse effect on PWM inverter-fed induction motor due to long motor leads. In this paper, voltage reflection due to distribution parameters i s analyzed, which indicates that over-voltage at motor terminals depends on the more apparent reflection phenomenon. The adverse effect can be solved by low co st passive filtering techniques. A first-order RC motor terminal filter whi ch i s installed at motor terminals is analyzed and designed, experimental results sh ow that the filter can effectively reduce the over-voltage at the motor termina ls and improve reliability of the whole system.