Comparative study of two types of high-frequency transformers in a 20-kW Phase-Shifted Full Bridge converter application

The paper presents a description of two types of high-frequency transformers with a power rating of over 20 kW - one made of planar cores and windings in the form of thin copper foil and the other built with E-type cores and Litz wire. Results of comparative tests conducted with the isolated phase-shifted full-bridge DC/DC converter are presented. The obtained results in the form of waveforms and electrical measurements with a precise power analyzer clearly indicate the advantage of the solution with the Litz wire winding. Due to the distorted current in the AC circuit and high frequency of the fundamental harmonic, a large part of the power loss in the transformer is the conduction loss. Possible causes of worse results in the case of windings made of copper foil are also indicated.