Design and performance of a passive EMI filter for use with a voltage-source PWM inverter having sinusoidal output voltage and zero common-mode voltage

This paper deals with integrating a small-sized passive EMI filter with a voltage-source PWM inverter. The purpose of the filter is to eliminate both high-frequency common-mode and normal-mode voltages from the three-phase output voltages of the inverter. A laboratory system consisting of a 5-kVA inverter, a 3.7-kW induction motor, and a specially-designed passive EMI filter was constructed to verify the viability and effectiveness of the filter. As a result, both line-to-line and line-to-neutral output voltages look purely sinusoidal as if the inverter were an ideal three-phase variable-voltage, variable-frequency power supply, when the inverter is viewed from the motor terminals. This results in a complete solution to serious EMI issues related to high-frequency common-mode and normal-mode voltages produced by the PWM inverter.