Series Connection of thermal networks

Question

Hi,

I'm trying to understand how 2 "Thermal Chains" connected in series are resolved

First, in red, is a thermal chain (Cauer type) and its equivalent network in Foster. Second part, in purple, is another thermal chain and its Foster equivalent. Third part, in black, is the series connection of the two thermal chains and their Foster equivalent.

Plot 1 shows how step responses of thermal chain and its Foster network are identical. Same happens in plot 2 for the second chain.

However, when I connect is series both thermal chains this is not true. Plot 3 shows how the series connection of Foster equivalent networks results in the sum of the individual step response (as I expected). But this doesn't happen for the thermal chain series connection.

Could anyone help me to clarify this?

BR

Answer 1

My understanding is that due to the nature of the Foster network, any changes to the system, such as to arbitrarily extend the network out from the junction, requires recalculation of all values. So I think this may lead to the discrepancy you are seeing in the synthesized Foster network. This resource may also be helpful for you: https://www.infineon.com/dgdl/Infineon-Thermal_equivalent_circuit_models-ApplicationNotes-v01_02-EN.pdf?fileId=db3a30431a5c32f2011aa65358394dd2

Comments

Yes, I think that you are right according to the app note you shared.

Many thanls for the feedback