Error: Thermal state derivatives are infinite or NaN.
- [Gesamt_Modell_RC/4xMobilab Inverter/Sub2/GeneSiC SiC MOSFET5/MOSFET:Cth1]. Where can I find this Cth parameter as I am not able to find it. Or is there any other error?
You can find the values for the thermal impedance junction-to-case in the thermal description. So simply open the thermal description and go to the “thermal impedance” tab.
Regarding the error, in my experience I have received that error when the thermal losses in the semiconductor tend to infinity, which then makes the junction temperature tend to infinity as well. This happens when your junction temperature increases beyond the highest temperature data curves in the thermal description. In this scenario, when the temperature is higher than the maximum value provides, PLECS will extrapolate the losses. Commonly the curves show higher losses for higher temperature values, this means that the extrapolation will increase the semiconductor loss. Then a positive feedback loop is created, higher losses, means higher temperature, which then creates higher losses, which then increases the temperature again.
Then solution to this is either make sure that the semiconductor is operates within its limits (even in transient scenarios), or you can add extra curves, to the thermal description, for a higher temperature value with the same loss values as the previous maximum temperature curves (so you avoid the extrapolation).