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Different current at two ports

Posted Jul 21, 2013, 12:17 p.m. EDT Low-Frequency Electromagnetics, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.3 5 Replies

Ruochen Lu
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I am simulating a device in electrical currents model, and find the currents in the only two port are not the same.
And what is more, the current in the electrode with higher voltage is confusing. I do not know what is wrong with my model. Is it because I am using the wrong model?

Thank you very much.
5 Replies Last Post Jul 22, 2013, 9:59 a.m. EDT
Ruochen Lu
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Posted: 1 decade ago Jul 21, 2013, 2:49 p.m. EDT
Hello everyone,

I have tried these for some time, then I find that if I change the boundary condition of the input port from 5V to 2e-10A, The result is better and the input voltage is about 4.8V.
I just do not know if there are any difference between these two conditions since the voltage is very same but the result looks different. I am really confusing about these two kind of conditions.
Thanks in advance.

Regards,
Ruochen
Hello everyone, I have tried these for some time, then I find that if I change the boundary condition of the input port from 5V to 2e-10A, The result is better and the input voltage is about 4.8V. I just do not know if there are any difference between these two conditions since the voltage is very same but the result looks different. I am really confusing about these two kind of conditions. Thanks in advance. Regards, Ruochen
Ruochen Lu
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Posted: 1 decade ago Jul 21, 2013, 3:04 p.m. EDT
I finally find out what happened.
These conditions can get two result, a good one and a bad one. After I solve the answer to the voltage one on the base of the current one, the problem solved.

Thanks for some discussion in this forum I just read, I cannot remember the exact page. Thanks a lot.
I finally find out what happened. These conditions can get two result, a good one and a bad one. After I solve the answer to the voltage one on the base of the current one, the problem solved. Thanks for some discussion in this forum I just read, I cannot remember the exact page. Thanks a lot.
Ruochen Lu
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Posted: 1 decade ago Jul 21, 2013, 3:12 p.m. EDT
And one more physics question, is it any chance that the input and output current are different? Then where does these current go?
And one more physics question, is it any chance that the input and output current are different? Then where does these current go?
Eric Lämmel
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Posted: 1 decade ago Jul 22, 2013, 9:25 a.m. EDT
Hello Ruochen,

no offense, but I really think if you ask that question about electric currents, you better should delay the simulation work and repeat some studies of electromagnetics/electrical engineering instead.

Regarding the different currents at the two terminals: this is a normal inaccuracy of the finite element method, check www.comsol.com/support/knowledgebase/973/ for a dicussion of the matter. In general, if you refine the mesh at the respective boundaries, the error should decrease.

Bye
Eric
Hello Ruochen, no offense, but I really think if you ask that question about electric currents, you better should delay the simulation work and repeat some studies of electromagnetics/electrical engineering instead. Regarding the different currents at the two terminals: this is a normal inaccuracy of the finite element method, check http://www.comsol.com/support/knowledgebase/973/ for a dicussion of the matter. In general, if you refine the mesh at the respective boundaries, the error should decrease. Bye Eric
Ruochen Lu
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Posted: 1 decade ago Jul 22, 2013, 9:59 a.m. EDT
Hello Eric,

Thank you very much! I have fixed this problem by changing the mesh. And you are right. I should think more about this device. ^_^

Regards,
Ruochen
Hello Eric, Thank you very much! I have fixed this problem by changing the mesh. And you are right. I should think more about this device. ^_^ Regards, Ruochen

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