Analysis of EMI Filter Attenuation under the Influence of Parasitic Elements of Components and their Mutual Couplings

Attenuation of EMI filters strongly depends on the mutual couplings among filter components and their parasitics. This paper explains and analyzes such effects of filter components. Analytical, numerical, and experimental methods are used in a systematic way, considering single- and three-phase EMI filters as examples. It is shown that several paths of couplings and parasitics reduce the filter performance significantly. A separate discussion of the impact on differential- and common-mode behavior is shown in detail, showing further potential in the methods for filter improvement.