Initial IGBT temperature using Foster network

Question

Hello Users

I'm using an IGBT switch with thermal model and connected to a reference temperature (e.g. Ambient) via an RC foster network. I want the IGBT to start from higher temperature than the ref. I tried to let the "initial temperature" parameters of the Thermal capacitances in Foster as blank and initialize the IGBT temp to e.g. 125. But in the end still the IGBT temperature still starts from Ambient. Any recommendations ?

Thanks

Anastasios

Answer 1

Are you sure it truly starts at the ambient temperature (did you zoom in at t=0+? Can you post the model if the problem still exists.

Comments

Hello Kris

Here I attach a simple representation of the circuit. In general, I want to be able to start the simulation from an initial component temperature and not from Ambient/reference in order to speed up the simulation time until reaching steady state. In the model I can't see the temperature to start from T_initial even in the very first samples.

Best regards

Anastasios

---

Hello,

I have taken a look at your model and I believe it runs as expected since the heat sink has no thermal capacitance set. Note that simply adding capacitance will cause a state/source dependence since the thermal chain is a Foster network and the capacitors are directly connected to the temperature source. You would then need to either use a Cauer network or simply add a series thermal resistance to the chain to break this direct ideal source-ideal capacitor connection. If you make these changes, the heat sink and IGBT junction temperatures do indeed start at your initial value of 125C. Let me know if you are able to see this.

Best,

Kris