Thermal design considerations for medium voltage power converters with 15 kV SiC IGBTs

Medium Voltage (MV) Silicon Carbide (SiC) devices such as the 15 kV SiC IGBT have better thermal handling capability compared to Silicon (Si) based devices. These devices also have lower switching and conduction losses, at high switching frequencies and high power levels, respectively. The maximum safe operating junction temperature for the 15 kV SiC IGBT is 175 °C. This enables high power density design of the MV converters using this device. Heat sink with forced air cooling is sufficient for dissipating the heat generated during converter operation. In this paper, the thermal design of 3-phase MV converters based on 15 kV/40 A SiC N-IGBT is discussed. The design is carried out based on experimental loss data and the continuous heat-run test of the device. It is supported by analytical calculations and FEM simulations in COMSOL Multiphysics simulation software. Hardware prototypes of the converters are developed and experimental results are given.