A Thermally Insulating Cryogenic Medium-Frequency Transformer for use in a Cryogenic GaN Dual Active Bridge

A key challenge in cryogenic applications is managing heat input from the warmer environment. This paper presents a novel Medium-Frequency Transformer (MFT) concept designed for converter integration as a thermal insulator at cryogenic temperatures. First, the basic idea of the thermally insulating transformer is outlined, followed by electromagnetic dimensioning and thermal design considerations. Detailed simulations illustrate the effects of critical design parameters on thermal and electromagnetic performance. Based on these insights, a prototype MFT is developed and integrated into a 20 kW/100kHz Dual Active Bridge (DAB) converter topology. Measurement results validate the functionality of the developed MFT in conjunction with the DAB, demonstrating its potential for efficient thermal management in cryogenic environments.