Analysis of Current Resonances due to Winding Parasitic Capacitances in Medium-Voltage Medium-Frequency Transformers

This paper presents the analysis of the current resonances on medium-voltage, medium-frequency transformers due to the parasitic capacitances of the windings. Converter performance is affected by these high-frequency current resonances; therefore, the winding arrangement of high-voltage high-turns ratio transformers must be carefully considered during the building process. Three different windings arrangements are built for a 5-kV-to-400-V, 10-kHz transformer for a high-power dual-active-bridge (DAB) converter. Open-circuit and short-circuit impedance response of the three windings are compared. Experimental results include open-circuit test on each of the three different winding arrangements and a 10 kW load test to illustrate the effect of the parasitic capacitances.