How to set the parameter of the thermal resistance Rth(or Zth) between case and heat sink?

Question

Hello,

I am trying to simulate the temperature behaviour of a 2-level converter circuit. The IGBT module I used consists of a halb bridge and three of the modules are on one heat-sink.

I can set the thermal impedance from junction to case (Zth,jc) according to transient impedance curve from datasheet in the thermal description of PLECS, and thermal resistance from heat sink to ambient (Rth,sa) using a constant temperature block. But there is always a thermal resistance value between case and heat sink (Rth,cs) in the datasheet, how can I set this value in PLECS? Is what I have done in the attachment correct?

Thanks in advance!

Sara

Answer 1

Hello Sara,

Yes, from the image you attached, you have implemented a viable solution for defining Rth,cs. This is not necessary, but should you want to include the thermal capacitance of the case and/or heat sink you have two options. Either you will need to design a hierarchical structure of subsystems to define the thermal layers and use the Ambient Temperature component inside to connect to the nearest external layer (e.g., device sits on Case heat sink block, and via Rth,cs connected to ambient outside of subsystem, which is actually the true heat sink of the system), or directly place a Thermal Capacitor at each node in between.

Regards,

Kris