Revisiting Models of Common Mode Inductors to Include the Magnetized Capacitance Effect

Common mode (CM) inductors are filter components that are key to achieving electromagnetic compatibility (EMC) in power electronics systems. Their design depends upon comprehensive system models, which require the best knowledge of parasitic effects. Typically, a filter design is based on equivalent circuits, and the quality of the component models defines the outcome and applicable design safe margins. Thus, high-accuracy models of every filter component are desirable. Past works proposed models for CM inductors. However, recently, the notion of magnetized capacitance has been proposed to model the effect of the energy stored in a magnetic core of power inductors and the consequent generation of electric fields that also store energy. The impact of such an effect on CM inductors has yet to be reported. Thus, this work addresses the question of how significant this effect is in the modeling of CM inductors. The method used here incorporates state-of-the-art models for the well-known electromagnetic effects occurring in CM inductors, including the magnetized capacitance model. Experimental results on inductors built with different Mn–Zn and Ni–Zn ferrite cores are compared with the presented theoretical models. It is found that the magnetized capacitance improves the parallel capacitance modeling for Mn–Zn, with reduced errors in experimental results. However, it has less effect on Ni–Zn cores. A critical evaluation of the results is presented.