Accurate Capacitance Calculation of Multi-layer Foil Windings in a Medium/High-frequency High-power Transformer

In the literature, capacitance calculation of foil windings in a high-frequency transformer is reported but it assumes a simple foil winding configuration, consisting of a single turn only in each of the primary and secondary windings. It, therefore, does not consider the effect of layer-to-layer potential difference present in a multi-layer foil winding. This paper presents an accurate capacitance calculation of a multi-layer foil winding transformer where the turn-to-turn and layer-to-layer capacitances are differentiated and calculated based on the conductor and insulation geometry. It also incorporates the effect of actual layer-to-layer voltage difference based on the types of winding connections i.e. standard and flyback winding methods. Accordingly, it calculates the effective winding capacitance using the principle of energy equivalence method. Case study of a 10 kW, 0.5/1.5 kV, 25 kHz transformer is carried out with the help of 2-D FEM analysis in ANSYS Maxwell to validate the theoretical analysis and discuss in detail the effects of different winding strategies on the winding capacitances. Close agreement is noted between the analytical and FEM results, which verify the modeling accuracy and aptness of the proposed capacitance calculation of multi-layer foil winding transformer.