Analytical Capacitance Calculation for Transformers with Grounded Core

Silicon carbide (SiC) semiconductors enable more and more medium voltage (MV) applications, but their fast switching transients lead to undesired effects as e.g. oscilla-tions in transformer windings due to parasitic capacitances. In order to consider these effects/parasitics in the design process, this paper presents an analytical model of the electric energy/capacitance per unit length within the winding window of foil-wound transformers. The model is based on calculating the electrical energy within basic regions using Schwarz-Christoffel (SC) transformations. It also considers the potential distribution introduced by the voltage-drop between different turns and achieves an error below 3 % compared to FEM simulations. The model can be used for calculating comprehensive lumped element equivalent circuits and is based on computationally efficient analytical equations.