# Thermal Package Description :Error evaluating parameter 'Thermal description' **URL:** \ **Category:** PLECS\ **Tags:** model, thermal, impedance, coupling, package\ **Created:** [June 13, 2023, 11:01am UTC](https://forum.plexim.com/t/thermal-package-description-error-evaluating-parameter-thermal-description/1245 "2023-06-13T11:01:23Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![mr\_naidu](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@mr\_naidu](https://forum.plexim.com/u/mr_naidu)\ **Post date:** [June 13, 2023, 11:01am UTC](https://forum.plexim.com/t/thermal-package-description-error-evaluating-parameter-thermal-description/1245/1 "2023-06-13T11:01:23Z")
Hii, I am trying to model the half bridge power module using discrete IGBT and Diode. While implementing thermal package impedance , i am getting the error in thermal description evaluation. I have attached the error and plecs model. Thank you. Manikandan Raju [SKM100GB12T4\_IGBT.xml](https://forum.plexim.com/uploads/short-url/r8JWRy9T19wL0HUiDfROTvcOau3.xml) (136 KB) [Test.plecs](https://forum.plexim.com/uploads/short-url/bqMsotAq9LHRJxkWmBfLLCY3MhH.plecs) (83.6 KB) [SKM100GB12T4\_R2.xml](https://forum.plexim.com/uploads/short-url/l8Oz3zIcpwsPPiHulJID1sSITPn.xml) (475 KB) ![Error.JPG](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/1X/11e846fbd4f5327e44e90054882443f9cbbf6c2a.jpeg) ![Thermal Description.JPG](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/1X/66915e630975a2d562528ce3ea8bbe28d189fec9.jpeg) ---
**Author:** ![Kris\_Eberle](https://dub1.discourse-cdn.com/flex006/user_avatar/forum.plexim.com/kris_eberle/32/6_2.png) [@Kris\_Eberle](https://forum.plexim.com/u/Kris_Eberle)\ **Post date:** [June 13, 2023, 2:01pm UTC](https://forum.plexim.com/t/thermal-package-description-error-evaluating-parameter-thermal-description/1245/2 "2023-06-13T14:01:09Z")
Hello, Actually you do not need the Thermal Package Impedance component in this case and can remove it from the three PM leg subsystems like so: ![3](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/1X/46b15bb261c04cbf9e506610d68ac5f1d2f8d659.png) Each of the six IGBT/diode pairs are all connected to the heatsink via their individual Rth\_ch interfaces. The Thermal Package Impedance is an advanced option and is only necessary if you are using Thermal Package Descriptions for the semiconductors (this isn’t the case for these Semikron devices) _and_ you include in that description a package impedance state-space system (such as to describe the interdependent heating between the IGBT and diode in the packaging). Here is a screenshot of that interface just for some further context: ![3](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/1X/cebb528618e33ff11724cf8e41d3febd3d8a4ab4.jpeg) One other thing I noticed in your model is that you are averaging the instantaneous switching and conduction losses with multiple averaging schemes- you should use only the Periodic Impulse Average for the switching loss as the Periodic Average block is intended for averaging conduction losses. Anyway, I hope this helps, but let me know if you have further questions or doubts. ---
**Author:** ![mr\_naidu](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@mr\_naidu](https://forum.plexim.com/u/mr_naidu)\ **Post date:** [June 14, 2023, 12:26am UTC](https://forum.plexim.com/t/thermal-package-description-error-evaluating-parameter-thermal-description/1245/3 "2023-06-14T00:26:33Z")
Hii Kris, Thanks for your reply. I would like do package level modelling for the SEMIKRON half bridge power module. As you mentioned I already created the thermal package description in the name of SKM100GB12T4\_R2.xml for the SEMIKRON power module(screenshot attached). I facing problem while including this thermal description in the thermal package impedance. Plz check it. Also let me know proper steps to be followed for thermal modeling of SEMIKRON power module as subsystem. [SEMIKRON\_DataSheet\_SKM100GB12T4\_22892020.pdf](https://forum.plexim.com/uploads/short-url/na7Anen2SYNZACIIKHFpCmuJPNU.pdf) (476 KB) ![Thermal package description.JPG](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/1X/8dfe841d66b89c112f2851f8171099abe7c44d5c.jpeg) ![Thermal package description1.JPG](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/1X/386aa1cbe8a522f55996dad98466680e41008651.jpeg) ---
**Author:** ![Kris\_Eberle](https://dub1.discourse-cdn.com/flex006/user_avatar/forum.plexim.com/kris_eberle/32/6_2.png) [@Kris\_Eberle](https://forum.plexim.com/u/Kris_Eberle)\ **Post date:** [June 14, 2023, 3:34pm UTC](https://forum.plexim.com/t/thermal-package-description-error-evaluating-parameter-thermal-description/1245/4 "2023-06-14T15:34:39Z")
Attached is a basic subsystem that will allow you to use the thermal package impedance along with the …\_R2.xml file you provided (which has the necessary information for the thermal network and correct variable names). Let me know if this is clear. [example.plecs](https://forum.plexim.com/uploads/short-url/6IjYS5QP7W6r82TYTl5ktWbpeAz.plecs) (83.6 KB) ---
**Author:** ![mr\_naidu](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@mr\_naidu](https://forum.plexim.com/u/mr_naidu)\ **Post date:** [June 15, 2023, 12:34am UTC](https://forum.plexim.com/t/thermal-package-description-error-evaluating-parameter-thermal-description/1245/5 "2023-06-15T00:34:28Z")
Thanks Kris, I will try this.