Transcription of Common Mode Choke Analysis - Exality
1 Common Mode Choke AnalysisG. Barrere Exality CorporationCommon mode Choke with mutual inductanceM=k L1 = L2 = L, M is between 0 and L. Assume this is true, turns ratio N = any inductorvL=iLXL=iLsLso L=vLsiL(wheres=j )The effective inductance between 'a' and 'c' is then:Leff=v1si1=sL1i1+sMi2si1from transformer terminal equations=L1+Mi2i1 For Common mode signalsi2=i1soLeff(CM)=L1+MNote thatLeff(CM)=2 Lwhen coupling k = 1. For differential mode signalsi2= i1soLeff(diff)=L1 MNote thatLeff(diff)=0when coupling k = 1. This means that the Common mode Choke presents no inductance (and therefore no impedance) to differential mode signals.
