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Tearing out my hair

Posted 18 ott 2013, 12:20 GMT-4 Low-Frequency Electromagnetics Version 4.3b 3 Replies

Matthew Aldous
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I am trying to model a very basic situation, but I have no idea what I'm doing and the error messages are no help (.mph file attached for Comsol 4.3.0.233).

The situation is just a single copper wire (current source at one end, ground at the other) in an air environment.

When I run the computation, it throws the error

"Failed to find a solution.
Singular matrix.

There are 1594 void equations..."

What am I doing wrong?

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3 Replies Last Post 18 ott 2013, 15:11 GMT-4
Sergei Yushanov Certified Consultant
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Posted: 1 decade ago 18 ott 2013, 12:28 GMT-4
Matthew,

Assign small conductivity to air, say, sig_air=1e-6[S/m].

Regards,
Sergei
Matthew, Assign small conductivity to air, say, sig_air=1e-6[S/m]. Regards, Sergei
Matthew Aldous
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Posted: 1 decade ago 18 ott 2013, 14:06 GMT-4
Ok thank you, that has helped an awful lot.

Now would you mind giving me some hints as to how I can modify this model to be able to view magnitude of the out-of-plane magnetic field generated by this simple wire? I have tried simple adding "magnetic field" physics to the study and it generates the surface plot but the value appears to be zero everywhere. I know I'm missing something obvious here, like the air conductivity thing, but I'm not sure what.
Ok thank you, that has helped an awful lot. Now would you mind giving me some hints as to how I can modify this model to be able to view magnitude of the out-of-plane magnetic field generated by this simple wire? I have tried simple adding "magnetic field" physics to the study and it generates the surface plot but the value appears to be zero everywhere. I know I'm missing something obvious here, like the air conductivity thing, but I'm not sure what.
Sergei Yushanov Certified Consultant
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Posted: 1 decade ago 18 ott 2013, 15:11 GMT-4
Matthew,

Not sure if I understand what you are trying to accomplish, but in 2D geometry wire must go in the out-of-plane direction, as shown in the attached image. Assumption is that current loop is closing at the infinity.

Regards,
Sergei
Matthew, Not sure if I understand what you are trying to accomplish, but in 2D geometry wire must go in the out-of-plane direction, as shown in the attached image. Assumption is that current loop is closing at the infinity. Regards, Sergei

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