Wideband Mechanism Model and Parameter Extracting for High-Power High-Voltage High-Frequency Transformers

The high-power high-voltage high-frequency transformer (H3T) is a key equipment to develop the isolated high-power dc–dc converter. In this paper, a wideband mechanism model is proposed to analyze the external behaviors of the H3T. This model is characterized by elaborate considerations on magnetic and capacitive effects of the H3T, including electrostatic couplings between windings, magnetic core, and the enclosure, with parameters which have explicit physical meanings. In terms of large number of turns and racetrack windings of the H3T, a finite-element method based on weighted algorithm is used to extract model inductance and capacitance parameters. To verify the proposed model and corresponding parameter extraction method, impedance characteristics of an H3T prototype under open circuit, short circuit, and load conditions are measured and simulated over a wide frequency band. The results show that the proposed model is valid up to 300 kHz. Besides, when one or two windings of the H3T are grounded, the proposed model may be reduced to traditional six or three capacitance models due to changes of winding-to-ground capacitances, which may account for shift of resonant frequencies. The proposed model and corresponding analyses are helpful to electromagnetic design and external behavior investigations of the H3T.