Menu

Discussion Forum

New Discussion
Filter

Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Time Derivation (or model in general) suddenly becomes unstable.

Posted Jan 31, 2012, 5:35 p.m. EST Low-Frequency Electromagnetics, Geometry, Materials, Modeling Tools & Definitions, Parameters, Variables, & Functions, Results & Visualization, Studies & Solvers Version 4.1 0 Replies

Norbert Bartscher
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hello everyone,

I am modelling electrical machines with the rotating machinery interface wthin the ACDC module.

This is my thread about the same model:
www.comsol.com/community/forums/general/thread/25702/

My problem is that the model won't solve when the permeability is non linear. Interesting is that after 2ms the simulation becomes very unstable and won't get to the 10ms mark.

In the attached pictures I want to show how unstable the time derivation of the flux linkage suddenly becomes.
You have an overview there and zoomed pictures.

Is it somehow possible to damp that derivation a litte? I'm afraid that this is causing my simulation to become unstable. Could it be that Comsol by default changes something at ca. 2ms that affects the derivation?


Here is a small overview about how I usually define my variables:

Psiges1 = 4*(intop2(mod1.Az))*...
e1 = -d(Psi1ges,TIME)
i2 = (u13+e1-e3)/4/Rsg/(-3)-...

Everything, including the derivations, is defined in the Definitions/Variables table.

Does anybody have an idea, why my model is so unstable? : (

Thanks in advance
0 Replies Last Post Jan 31, 2012, 5:35 p.m. EST
COMSOL Moderator

Hello Norbert Bartscher

Your Discussion has gone 30 days without a reply. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help.

If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content