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Voltage dependent resistor

Posted Jul 5, 2011, 10:34 a.m. EDT Low-Frequency Electromagnetics, Materials, Parameters, Variables, & Functions, Studies & Solvers Version 4.2 4 Replies

Sebastian Heß
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Hello,

I am trying to calculate the current at a resistor (a simple cylindrical volume) whose conductivity dependents on the applied voltage, the simulation should be time dependent. To prevent circular relations I think it is necessary to compute the voltage first and after that calculate the conductivity for the next time step. Is that thought right?

Could someone tell me how I could realize such a stepwise calculation?

Best regards
Sebastian

PS I'm using Comsol 4.2
4 Replies Last Post Jul 6, 2011, 10:11 a.m. EDT
Edgar Kaiser
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Posted: 1 decade ago Jul 5, 2011, 11:14 a.m. EDT
Hi,

I think it should be possible to directly use a conductivity term which is a function of the voltage (or a function of electrical field strength) without doing it stepwise.

Cheers
Edgar

Hi, I think it should be possible to directly use a conductivity term which is a function of the voltage (or a function of electrical field strength) without doing it stepwise. Cheers Edgar
Sebastian Heß
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Posted: 1 decade ago Jul 6, 2011, 3:12 a.m. EDT
Hi Edgar,

Thanks for your quick response, I've already tried your suggestion but unfortunately it doesn’t work, I only get an error-message (“undefined value found”). I think that message occurs because the voltage cannot be calculated without the conductivity and vice versa. I don’t know if there is a possibility to circumvent this problem apart from the stepwise calculation. But I'm always open to suggestions.

Best regards
Sebastian
Hi Edgar, Thanks for your quick response, I've already tried your suggestion but unfortunately it doesn’t work, I only get an error-message (“undefined value found”). I think that message occurs because the voltage cannot be calculated without the conductivity and vice versa. I don’t know if there is a possibility to circumvent this problem apart from the stepwise calculation. But I'm always open to suggestions. Best regards Sebastian
Edgar Kaiser
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Posted: 1 decade ago Jul 6, 2011, 3:37 a.m. EDT
Sebastian,

I think you need to define an initial value for the voltage or define it by a boundary condition or a port. And the conductivity must be defined as a function of voltage for the whole range of voltages that can happen.

Cheers
Edgar
Sebastian, I think you need to define an initial value for the voltage or define it by a boundary condition or a port. And the conductivity must be defined as a function of voltage for the whole range of voltages that can happen. Cheers Edgar
Sebastian Heß
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Posted: 1 decade ago Jul 6, 2011, 10:11 a.m. EDT
Hi Edgar,

Thanks for your support, I completed the simulation successfully.

Best regards
Sebastian
Hi Edgar, Thanks for your support, I completed the simulation successfully. Best regards Sebastian

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