Conducted EMI simulation for a high power Ultra-precision PMSM driven by PWM converter

Abstract

The conducted electromagnetic interference (EMI) and overvoltage characteristics for a spindle permanent magnet synchronous motor (PMSM) driven by pulse width modulation (PWM) converter are comprehensively presented. The high power, ultra-precision PMSM is applied to a computer numerical control (CNC) grinding machine. The conducted EMI prediction model mainly includes multi-core shielded cable, high frequency (HF) converter and PMSM models. The multi-transmission line (MTL) theory is employed to establish the multi-core shielded cable considering their coupling effect caused by the control pairs. The parasitic capacitance for the PWM converter is calculated by using the analytical formula. The HF equivalent circuit model of the PMSM is obtained combining the methods of impedance measurement and vector fitting method. The influence of the rotor position on the PMSM impedance measurement is considered. The common mode (CM) and differential mode (DM) interference voltage and current both for the output of inverter and the input of PMSM terminals are conducted by using the prediction model. The parametric influence of the long multi-core shielded cables on the overvoltage for the PMSM terminal is discussed.