Holistic approach to three-phase EMI filter improvement

摘要

The design of passive EMI filters demands simultaneous consideration of multiple aspects, including the manufacturing costs, especially crucial for industry applications. In this article the stray components of the filter elements, the electromagnetic couplings, the circuit layout and the magnetic materials are taken into consideration. Impact of every aspect on the insertion losses (IL) is analysed step-by-step. Relevance of the impact from different contributors on degradation of IL is assessed. Simulations and measurements show that most of the stray coupling effects inside of a commercial three-phase EMI filter do not have a presentable impact on IL and are negligible. Simple replacement of the core material for a common mode choke (CMC) does not bring expected enhancement and requires more advanced analysis. An equivalent circuit is used for parasitics assessment and simulated results shows a good agreement with measurements. Four different methods of filter improvement are evaluated.