Analytical Modeling of Three-Winding Tunable Common-Mode Choke

The common-mode (CM) noise is generally addressed using a CM choke due to its simple design and reliability. However, the performance of the CM choke degrades and the CM impedance starts decreasing after the resonant frequency. Hence, tuning the CM impedance of the CM choke is widely adapted by inserting an auxiliary winding on the CM choke core to alter the resonant frequency. Thus, in this paper, the analytical approach to estimate the CM impedance of the tunable CM choke with known external circuit parameters connected to the auxiliary winding terminals and vice-versa is presented. In addition, the estimated CM impedance profiles and the auxiliary winding parameters are simulated in MATLAB/Simulink and are validated through experimentation.