This article deals with a 100 kW dual active bridge (DAB) DC-DC converter and a 20 kHz 3-phase medium frequency transformer (MFT). A computational fluid dynamics (CFD) model of the MFT is presented and compared with thermal measurements showing a good fit. The core hotspot is close to the thermal runaway limit. The maximum winding temperature in the normal operating mode results in a comfortable headroom to enable the operation in the degraded mode. Moreover, it is likely that the transformer may be loaded with higher power. The efficiency of the DC-DC converter was measured 99.2% at 100 kW.