Estimation of EMI Filter Performance for the "Worst Case" System

Abstract

This paper deals with the performance problem of the EMC filters. The core of this problem in EMC filter is the uncertainty of impedances that are connected to the input and output of a filter. In addition, an estimation technique is presented that gives approximate insertion loss of the filter. The performance of this technique was tested on several filters and the data obtained were checked by insertion loss measurement. The heart of the matter is based on the L C equivalent circuits, which are described by Y parameters. The estimation gives pretty good results for the 0.1 Ω/100 Ω and vice-versa systems and also for other systems. Also discussed are system configurations with the Δ (delta) and (Y) star topologies of terminating impedances which better approximate the real situation on the input and output terminals of filter.