Research on the Design of a Medium-Frequency Transformer Employing an Amorphous Alloy Hybrid Core

To address the issues of high core loss, elevated temperature rise, and limited thermal stability in medium-frequency transformers (MFTs) used in three-port isolated DC/DC converters, this paper proposes a hybrid magnetic core composed of amorphous alloy and ultra-thin silicon steel. The magnetic permeability, loss characteristics, and saturation behavior of the two materials are experimentally evaluated, forming the basis for building a design model of a three-winding MFT. A multi-objective optimization method is employed, targeting minimized total loss, enhanced power density, and compliance with thermal and insulation constraints. Core dimensions, winding arrangements, and insulation distances are jointly optimized. A multiphysics finite-element model is then developed to analyze the magnetic flux distribution, loss separation, and thermal field of the hybrid core, revealing the different magnetic and loss characteristics contributed by the amorphous and silicon-steel sections. A prototype hybrid-core MFT is subsequently fabricated and integrated into a three-port full-bridge isolated DC/DC converter for experimental validation. The measured voltage ratios, current waveforms, and loss performance are consistent with the design targets. Results demonstrate that the proposed hybrid-core structure significantly reduces iron loss, improves thermal stability, and ensures reliable operation under rated conditions. This confirms the technical feasibility and practical value of the hybrid-core MFT in multiport isolated power conversion applications.