Analytical estimation of parasitic capacitances in high-voltage switching transformers

Abstract

Parasitic capacitances in transformers consist of three main groups: winding-to-winding, layer-to-layer, and stray capacitances. Stray capacitance is also made of turn-to-turn and turn-to-core capacitances. This study presents a novel analytical method for calculating the values of turn-to-turn, turn-to-core, and stray capacitances in each winding, and employs the results to calculate the equivalent parasitic capacitance especially for high-voltage switching transformers. The proposed analytical method introduces an explicit formula in terms of the winding and core dimensions. This formula can be applied in performance analysis and design optimisation methods. By utilising the proposed formula, calculation of the equivalent parasitic capacitance neither takes a great deal of time nor requires a particular computer system. The analytical results are verified by simulation results using the finite-element method and experimental results achieved by a practical prototype of a high-voltage switching transformer employed in a 390 W, 15 kV inductor-capacitor-inductor-capacitor resonant converter.