AC/DC converter with medium frequency link for railway traction application. Evaluation of semiconductor losses and operating limits.

Nowadays, the typical railway traction chain, which operates under AC power supplies, includes a bulky and heavy transformer. In order to reduce the weight and the size 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 6.5 kV IGBT modules in soft switching conditions. Switching losses measurements are performed to determine the optimal switching frequency and the operating limits of the converter.