Impedance characteristics of a three-winding common mode choke

摘要

A newly proposed concept for CM impedance boosting has been developed and demonstrated. The impedance boosting is through a three-winding common mode(CM) choke with its auxiliary winding connected to an negative impedance circuit. However, in practical CM choke the imbalance of the windings will lead to impedance variations. The aim of this paper is to analyze these impedance variations. The DM and CM impedance characteristics of the choke are calculated and presented. Inductance of the auxiliary winding is proved to be unrelated to the main windings, which makes the design of the three-winding structure more flexible. Moreover, the imbalance of the two main windings is demonstrated to be beneficial for boosting up the DM impedance of the proposed CM choke mathematically.