Evaluation of high voltage SiC diodes in a medium frequency AC/DC converter for railway traction

Nowadays, the typical railway traction chain, which operates under alternative power supplies, includes a heavy and bulky transformer. In order to reduce the size and the weight of the input transformer, a medium frequency topology, which involves switches in soft commutation mode, is proposed. A test bench, based on one elementary stage of the complete structure, was built. It allows characterizing new high voltage Silicon Carbide devices in soft switching conditions. Switching losses measurements are performed to determine the optimal switching frequency and the operating limits of the converter.