PWM逆变器高频脉冲输出对电机的负面效应及其对策

NEGATIVE EFFECTS OF HIGH-FREQUENCY PULSE OUTPUT OF THE PWM INVERTER ON MOTOR AND ONE WAY TO RESTRAIN THEM

基于传输线理论 ,讨论了PWM脉冲对过电压的影响。在利用有限元分析法获得电机绕组分布参数值的基础上 ,得到绕组电压分布不均的根本原因是输入脉冲的dv/dt太大。由于分布电容的存在 ,定子绕组和轴承形成电压耦合回路 ,PWM脉冲输入时 ,电机轴承电流存在dv/dt电流和EDM电流两种基本形式 ,导致电机轴承过早损坏。文中就此进行了理论和仿真分析 ,设计了一种滤波器用于抑制过高的电压上升率dv/dt。

Based on transmission line theory, this paper analyzes phenomena of generating the over voltage at the terminal of the motor fed by PWM pulse. By use of the finite element method, the values of distributed parameters of the motor windings are obtained, which reveals the root cause of asymmetry winding voltage distribution is the excessively high d v /d t of the input pulse. Meanwhile,due to the distributing capacitance, a coupling voltage loop is composed between the winding and the bearing. When the PWM pulses reach the motor, two types of bearing current, the EDM current and d v /d t current, may occur, and these will result in premature bearing failure. The simulation and theoretical analyses of the shaft voltage and bearing currents are described. Furthermore, a filter is designed to restrain the d v /d t .