In the domain of electric traction, the demand for medium voltage supply systems of high power, compact size and reduced weight is growing. Thanks to the new semiconductors (HV-IGBT, IGCT) with high voltage capability, the multilevel topologies with medium frequency transformer become very attractive. Several solutions based on this principle were proposed these last years. In this paper a 10 kVA, four stages multilevel converter is presented. This solution seems particularly well adapted to the different requirements (volume, weight, EMC, loss) of the electric traction domain