Capacitance of UR-Core and C-Core Common Mode Inductors

An important aspect of all power processing equipment is common-mode current generation. Common-mode current leads to electromagnetic noise and potential equipment malfunction. Common-mode inductors are often used to reduce common-mode current. However, their effectiveness is limited by their capacitance. In this paper, common-mode capacitance models of two related classes of common mode inductors are set forth. These models include an improved method of calculating the layer-to-layer capacitance. Means of reducing capacitance by use of multiple inductors is discussed. The methodology for calculating capacitance is experimentally validated using several common mode inductors. Finally, the use of the model in a multi-objective optimization-based common mode inductor design algorithm is demonstrated.