Due to the continuous development of semiconductor technology, the operating frequency of medium-voltage DC systems has been increasing, resulting in a reduction in the size and weight of medium-frequency transformers(MFTs). However, the increase in frequency and the decrease in size have brought many challenges to the design of MFTs. Finding a trade-off between insulation, cooling system, losses, and electrical parameters has become the key to achieving high power density and high efficiency. In this thesis, a structure of medium-frequency transformer with toroidal core and foil windings for high-current, high-power applications is presented, for which analytical models from the literature have been adapted in order to achieve an optimal design. The final results are experimentally validated.