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

Posted 31 gen 2012, 17:35 GMT-5 Low-Frequency Electromagnetics, Geometry, Materials, Modeling Tools & Definitions, Parameters, Variables, & Functions, Results & Visualization, Studies & Solvers Version 4.1 0 Replies

Norbert Bartscher
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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 31 gen 2012, 17:35 GMT-5
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