A passive EMI filter for an adjustable-speed motor driven by a 400-V three-level diode-clamped inverter

This paper deals with a passive EMI filter designed for a 400-V, 15-kW induction motor driven by a three-level diode-clamped PWM inverter with a carrier frequency of 8 kHz. The EMI filter consists of a common-mode filter and a small-sized dv/dt reduction circuit. The common-mode filter is unique in terms of access to the motor neutral point. It can remove the common-mode voltage produced by the inverter from the motor terminals. This succeeds in eliminating both high-frequency motor shaft voltage and ground leakage current from the inverter-driven motor. The viability and effectiveness of the EMI filter is verified by experimental results even in the case that the motor is 100 m away from the inverter.