High-frequency modeling of a current transformer by finite-element simulation

Abstract : This paper depicts a method to elaborate a high-frequency (100 kHz to 50 MHz) model of a current transformer. The method uses finite-element analysis to determine the values of the parameters of the circuit model; all electrostatic and magnetic couplings are taken into account and calculated. The paper shows how parasitic capacitance and flux leakage alter the transformer frequency response. These effects are deeply modified by the primary conductor position, by an air gap in the core, and by the presence of a shielding case around the transformer. The paper compares simulation results with experimental ones to show the accuracy of the models.