Comparative Studies of Wire-Wound and Planar Transformers in a PSFB Converter for Welding

This paper presents comparative studies between conventional wire-wound and planar magnetics, typically used in the isolation transformer of a phase-shifted full-bridge (PSFB) converter for low voltage (LV), high current (HC) applications such as welding. The design considerations of planar magnetics for a desired application are provided at first. The detailed design of both the transformers and the winding configurations are also presented. Standard commercially available finite element software packages have been used to simulate the transformers and validate them against analytical calculations. To compare the performance of the transformers, experiments have been performed on a laboratory-fabricated SiC-based phase-shifted inverter (PSI) with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$380\ V$</tex> DC Bus and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$500\ kHz$</tex> switching frequency, feeding a current doubler synchronous rectifier (CDSR) circuit with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$24\ V,60\ A$</tex> DC output. The equivalent circuit of the transformer comprising the winding AC resistance, leakage inductance and the inter-turn, inter-winding parasitic capacitance is presented here. The values of parasitic capacitances are evaluated analytically from the experimental data. Different aspects of comparison between both the transformers are carried out and presented to comment on their advantages and disadvantages for the proposed application.