A Fully-Isolated Robust Common-Mode Hybrid Filter

Abstract:
A common-mode noise filter is presented, that comprises a small passive filter and an active filter covering the low frequency range. The filter ensures high level of safety by being galvanically isolated from the mains. The architecture and the design of the filter allow compliance with the most stringent requirements for leakage current yet presents an extended frequency range, catering for the rich harmonic content generated by SiC devices. The filter is also stable for any set of terminal impedances and cable lengths. The design trade-offs are presented and the key topological and component choices are discussed. The operation of the filter is validated by in-situ measurements of a 4 kW/3-phase inverter.