Medium/high-frequency transformer (MFT/HFT) is an essential device in solid-state transformer (SST), connecting the medium and low voltages for flexible power distribution network application. Tremendous heating generated by significant power loss in MFT is one of the key issues for high voltage and high power SST operation. This paper focuses on the influence of heat dissipation structures on the temperature rise in a 10kW/10kHz MFT used for a 10 kV SST prototype. A newly interpolated structure using an aluminum sheet with fins or a water-cooling panel was proposed. Power losses from the core, windings, and insulation were calculated using finite element method simulation by considering high frequency and harmonics. After that, the thermal heating, combined with the fluid dynamics was simulated to obtain the temperature distribution in the MFT. It pointed out that the temperature is reduced by 25℃ by interpolating the aluminum sheet with fins, especially for the forced air-cooling. Water cooling structure exhibits a better effect for decreasing the temperature rise. An enhancement of heat conduction near the water entrance is ascribed to the temperature gradient and the vortex effect. It can be concluded that the interpolated aluminum sheet with fins presents great potential application due to its simplicity.

MFT; heat dissipation structure; power loss; hot spot temperature; heat flux.