I am working on a project that involes an inverter made with IGBTs. The device I selected for builing the H bridge is this: STGW60H65DFB. One of my roles in this project is also to select a suitable heat-sink for the transistors.
I have done all the calculation needed for the power losses and I found that a single device (STGW60H65DFB) dissipates about 60 W, in particular about 50 W are dissipated on the switch and 10 W on the antiparallel diode. About the thermal data, looking at the datasheet, it says:
RthJC Thermal resistance junction-case IGBT 0.4 °C/W
RthJC Thermal resistance junction-case diode 1.14 °C/W
Now my questions are: should I do the thermal calculations separately for the switch and the diode? Or can I assume an "average" thermal resistance of both?
If I should do separately, should I consider separated powers for diode and switch or use in both the cases the same power (the sum, so 60 Watts)?