Modeling and Analysis of Parasitic Capacitance of Secondary Winding in High-Frequency High-Voltage Transformer Using Finite-Element Method

A finite-element analysis (FEA) approach has been employed to predict the parasitic capacitance of the secondary winding of the multisection, multilayer, and multiturn high-frequency high-voltage transformer by a two-dimensional-axisymmetric model using the software of COMSOL. With the distribution of magnetic field and electric field, the energy method is used to calculate the lumped parasitic capacitance. The secondary winding of a 20 kHz, 40 kW transformer with the input voltage of 380 V and the output voltage of 25 kV has been designed. The parasitic capacitance of the windings with different number of sections, layers, and turns has been investigated. The optimal structure of the winding to minimize the parasitic capacitance has been derived, consisting of nine sections, nine layers, and four turns for each layer. The winding was manufactured and the parasitic capacitance was measured with the LCR meter using the frequency-sweeping method. Comparison of the FEA results with experimental results shows good agreement. The maximum relative error of the simulation in this paper is 12.4% smaller than the experimental results, whereas that of the classical analytical method is 70.8% and the existing FEA method is 19.4%.