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DAE is structurally inconsistent - Induced current in coil

Posted Jul 4, 2013, 2:45 p.m. EDT Low-Frequency Electromagnetics Version 5.0 6 Replies

Frédéric Maes
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Hello,

I am just starting to use COMSOL (4.3b) and I have encountered a problem while modelling. I am modelling two identical multi- turn coils where from one is excited by sinusoidal voltage source and I need to find the current generated in the second coil. For this I am using a 2D axisymmetric dimension, the Magnetic Fields (mf) and Electrical Circuit (cir) physics and a time dependent study. The circuit is a basic transformer circuit where the two inductors have been replaced by the coils (via the External I vs U component). When I compute, it displays this:

Errors during the multiphysics.

The DAE is structurally inconsistent.
-Variables:2
-Equation:1

Yet when I put an inductor in parallel with the coils, everything works and I don't see why.

Can someone help ?

Thanks
6 Replies Last Post Jun 21, 2016, 1:52 a.m. EDT
Andrea Ferrario COMSOL Employee

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Posted: 1 decade ago Jul 5, 2013, 10:34 a.m. EDT
Dear Frédéric,

The External I vs U features work (from the point of view of the circuit) as voltage sources, whose value depends on the applied current, so you cannot put them directly in parallel. The solution is typically to add a very small resistance in series.

Best regards,

--
Andrea Ferrario
Electromagnetics Group
COMSOL AB
Dear Frédéric, The External I vs U features work (from the point of view of the circuit) as voltage sources, whose value depends on the applied current, so you cannot put them directly in parallel. The solution is typically to add a very small resistance in series. Best regards, -- Andrea Ferrario Electromagnetics Group COMSOL AB
Frédéric Maes
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Posted: 1 decade ago Jul 5, 2013, 10:48 a.m. EDT
Thanks a lot! Now everything is working fine.

Best regards,

Frédéric Maes
Thanks a lot! Now everything is working fine. Best regards, Frédéric Maes
Frédéric Maes
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Posted: 1 decade ago Jul 11, 2013, 9:25 a.m. EDT
Hello Andrea,

Thanks again for the previous reply but I have a few other questions.

After using your tip (adding a small load to the induced circuit) I wondered if COMSOL takes into account the resistance of the inducing coil and of the induced coil ? If this is the case then it wouldn't be necessary to add the small load to the secondary circuit.

Another thing I noticed is that when I try to measure the impedance of the induced coil after a simulation (a load is in series with the induced coil), COMSOL evaluates the impedance of the coil as being the negative of the load ( for example if the load is 10 ohm then the impedance of the induced coil is (-10ohm). Is there an explanation to this?

Finally, set aside the electrical circuit, is there another way to evaluate certain coil parameters (impedance,induced current, emf) in the induced coil (for this I'm working in the frequency domain) ?

Thank you in advance,

Frédéric Maes
Hello Andrea, Thanks again for the previous reply but I have a few other questions. After using your tip (adding a small load to the induced circuit) I wondered if COMSOL takes into account the resistance of the inducing coil and of the induced coil ? If this is the case then it wouldn't be necessary to add the small load to the secondary circuit. Another thing I noticed is that when I try to measure the impedance of the induced coil after a simulation (a load is in series with the induced coil), COMSOL evaluates the impedance of the coil as being the negative of the load ( for example if the load is 10 ohm then the impedance of the induced coil is (-10ohm). Is there an explanation to this? Finally, set aside the electrical circuit, is there another way to evaluate certain coil parameters (impedance,induced current, emf) in the induced coil (for this I'm working in the frequency domain) ? Thank you in advance, Frédéric Maes
Abdul-Hadi Hassan
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Posted: 1 decade ago Jul 15, 2013, 4:03 p.m. EDT
hey Frédéric and Andrea,

i have the same problem in building the transformer could you please tell me where did you add the small resistance.

V/R
Abdul
hey Frédéric and Andrea, i have the same problem in building the transformer could you please tell me where did you add the small resistance. V/R Abdul
AH
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Posted: 1 decade ago Nov 18, 2013, 8:24 a.m. EST
Hello

I have the same problem even after insertig the mentioned resistors can you please attach your model, so that I can compare the procedures to my model

Thanks in advance
Hello I have the same problem even after insertig the mentioned resistors can you please attach your model, so that I can compare the procedures to my model Thanks in advance
Pratibha Garhwal
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Posted: 8 years ago Jun 21, 2016, 1:52 a.m. EDT
Greetings!
I am building an O core transformer and when I compute the results i got an error i.e.lambda is not defined.Please help me out in solving the problem.Kindly any help will be appreciated.
Thanks
Pratibha
Greetings! I am building an O core transformer and when I compute the results i got an error i.e.lambda is not defined.Please help me out in solving the problem.Kindly any help will be appreciated. Thanks Pratibha

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