Analysis of EMI filter attenuation characteristics for a multi-converter system

A method is proposed for analysis of the attenuation characteristics of electromagnetic interference (EMI) filters for multiple power converters connected to same power line. The analysis results indicate that increase of the conducted EMI noise may occur, because the cut-off frequencies of the EMI-filter are varied according to the number of power converters. A mathematical solution for the cut-off frequencies is derived by simplification of the circuit configuration based on Thevenin's theorem. Finally, an effective design method of EMI filters is proposed to avoid such problem of a multi-converter system.