When SiC pn diode modules and 4.5 kV class Si-IGBTs are combined，reduction of the size of cooling system can be expected. We produced a SiC diode module made by the metal package for 100kVA class SiC inverter and measured the switching characteristics for that module in combination with the 4.5 kV class Si-IGBT in the chopper circuit. Based on the measurement results，we estimated losses and presumed the size of cooling fin. We calculated losses at various junction temperatures and carrier frequencies and we clarified that power density in case of junction temperature 100℃ is superior to the value in case of 80℃. We revealed that the volume ratio of the cooling fins is minimized at a certain junction temperature.

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