A study of an active EMI filter for suppression of leakage current in motor drive systems

High-frequency leakage current in PWM inverter-fed AC motor drive systems is a major cause of the EMI problems, which can affect the operations of nearby equipments. This paper presents a study on leakage current mitigation by the use of an active EMI filter. This filter has simple structure, composing of only two parts, a common-mode current transformer for leakage current detection and an amplifier circuit for injection of compensation current into drive system. The proposed active filter is very small and inexpensive as compared to the conventional passive filter. Therefore, it is an alternative for industrial applications. The theoretical concepts can be verified by the experimental results on a real drive system.