Small-Signal Calculation of Common-Mode Choke Characteristics Using Finite-Element Method

This paper presents a finite-element (FE) method approach to calculation of the common-mode choke (CMC) impedance over a wide frequency range. The proposed method involves a 3-D electrostatic FE calculation of each turn-to-turn and turn-to-core capacitance, and their usage as electric circuit lumped parameters in the 3-D time-harmonic magnetic FE calculation of the CMC impedance. It also takes into account the variation of the nanocrystalline core permeability and losses with frequency up to 100 MHz. The proposed methodology is used for calculation of the common-mode, open-mode, and differential-mode impedance characteristic for single-phase and three-phase CMC. Results are compared with measurements.