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Thermal chain foster or cauer

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Hello,

I am confused of the thermal chain difference between Foster and Cauer, though there is a brief explanation in plecsmanual. For example, when I directly use foster network from datasheet to calculate the junction temperature and heat flow, the temperature is quite high (between 85 and 110 ℃) and heat flow is circa 600W, which is the same as the total power loss, I think it makes sense, only the S5 and S6 IGBT also have a high temperature, which actually didn't work in the entire simulation, that confuses me a lot.

As for Cauer network, which I transfer from Foster network directly, it has significant results compared to Foster network. The junction temperature is quite low (between 25 and 43 ℃) and the junction temperature of S5 and S6 IGBT is circa 25 ℃, which also makes sense to my assumption. However the measured heat flow is almost 0 W, totally lower than the power losses of the system (600W), for that I can't understand.

So I would like to ask, which thermal chain should I use to calculate the temperature and which results are correct related to my simulation model? And why is there so a big difference between Foster and Cauer?

Btw, how can I upload pictures to the question box, it always shows that the word count is exceeded, but in fact I didn't write a lot. My simulation model is attached, firstly that is with Foster network, you can simulate it to see the results from the "thermal" display. Then you can change it to Cauer network and observe the results, that is totally different.

Thanks a lot for your help!

Regards

Joy
asked Aug 19, 2023 by Joy (16 points)

Hello, please see this other (related) thread and let me know if it is insightful to your simulation or you still have questions: https://forum.plexim.com/8183/issues-regarding-infinite-temperature-thermal-converter?show=8184#a8184

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