Common　mode　chokes　(CMCs)　are　key　components　in　electromagnetic　interference　(EMI)　filters,　and　accurate　modeling　of　these　components　is　critical　for　filter　design　and　EMI　noise　simulation.　This　paper　proposes　a　behavioral　model　and　parameter　extraction　technique　for　characterizing　three-phase　four-wire　common　mode　chokes　(4W-CMCs).　The　proposed　model　considers　the　inductance　nonlinearity　caused　by　the　nonlinear　permeability　of　manganese-zinc　ferrite　and　nanocrystalline　magnetic　materials,　as　well　as　the　asymmetry　and　local　symmetry　in　the　winding　distribution　of　4W-CMCs.　The　parameters　for　the　common　mode　(CM)　and　differential　mode　(DM)　models　are　extracted　using　a　parameter　extraction　program　and　a　simple　equation-based　method,　respectively.　For　the　DM　model　parameter　extraction,　this　paper　proposes　a　measurement　method　that　utilizes　the　local　symmetry　of　4W-CMCs.　The　equivalent　circuit　of　this　measurement　method　decouples　the　inter-winding　capacitance　(CW)　from　the　differential　mode　inductance　parallel　capacitance　(CD)　by　transforming　two-port　network　parameters,　greatly　simplifying　the　parameter　extraction　process.　The　accuracy　of　the　model　and　the　effectiveness　of　the　method　are　validated　through　experiments　using　several　4W-CMCs　with　manganese-zinc　ferrite　and　nanocrystalline　magnetic　cores.　　©　1986-2012　IEEE.