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Modelling admittance in Comsol V4

Posted Jun 28, 2010, 10:13 a.m. EDT 5 Replies

David Smith
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Hi,

I have a model which uses conductivity and permittivity as the parameters for a dielectric material. This dielectric is placed between a HV supply (modelled as terminal and ground), using 'electric currents' mode. In the previous version, v3.5a using 'quasi-statics' mode, it was the case of evaluating the admittance (then converting to resistance and capacitance). v4 doesn't seem as simple, I've tried 'derived values, global evaluation' - I can get a resistance, but no capacitance.

Has anyone managed to do something similar in v4?

Regards, David.
5 Replies Last Post Jul 12, 2011, 7:14 a.m. EDT
David Smith
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Posted: 1 decade ago Jul 9, 2010, 8:27 a.m. EDT
I've found the problem.

When v3.5a frequency dependent models are brought across into v4 the freqency domain needs to be re-activated in advanced settings. Once this is done the admittance becomes available as a variable.
I've found the problem. When v3.5a frequency dependent models are brought across into v4 the freqency domain needs to be re-activated in advanced settings. Once this is done the admittance becomes available as a variable.
Nidhi Maheshwari
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Posted: 1 decade ago Jul 3, 2011, 4:07 p.m. EDT
Dear David,
I am also trying to simulate impedance for a parallel plate capacitor with water as a dielectric. I do not see a change in the value of impedance/admittance with frequency. Can you shed some light on this. Do we need to define permittivity and conductivity of the solution as a function of frequency. If you can share your model which can give a fair idea about the variables defined and the boundary conditions, it will be of great help. I have tried simulating in both version 4.0 and 3.5, so model in any of the versions would be of help.
Thanks in anticipation
Nidhi
Dear David, I am also trying to simulate impedance for a parallel plate capacitor with water as a dielectric. I do not see a change in the value of impedance/admittance with frequency. Can you shed some light on this. Do we need to define permittivity and conductivity of the solution as a function of frequency. If you can share your model which can give a fair idea about the variables defined and the boundary conditions, it will be of great help. I have tried simulating in both version 4.0 and 3.5, so model in any of the versions would be of help. Thanks in anticipation Nidhi
David Smith
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Posted: 1 decade ago Jul 6, 2011, 8:17 a.m. EDT
Dear Nidhi,

Thanks for your interest in this work.

You should see a change in admittance (capacitive component) with changes in frequency without specifying frequency dependent material properties as Xc=1/(2*pi*f*C), where C=ep*A/d.

The model should be set-up as follows:

- Electric currents application mode
- Frequency domain study

- The energised boundary should be a 'terminal'
- The grounded boundary is of course 'ground'
- The open boundaries are 'electric insulation'

I have attached a basic model for reference.

Meshing is critical and you may need to use the 'adaptive mesh refinement' tools for an accurate solution.

I hope this had been of assistance.

Regards,
David.
Dear Nidhi, Thanks for your interest in this work. You should see a change in admittance (capacitive component) with changes in frequency without specifying frequency dependent material properties as Xc=1/(2*pi*f*C), where C=ep*A/d. The model should be set-up as follows: - Electric currents application mode - Frequency domain study - The energised boundary should be a 'terminal' - The grounded boundary is of course 'ground' - The open boundaries are 'electric insulation' I have attached a basic model for reference. Meshing is critical and you may need to use the 'adaptive mesh refinement' tools for an accurate solution. I hope this had been of assistance. Regards, David.

Attachments:

Nidhi Maheshwari
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Posted: 1 decade ago Jul 7, 2011, 5:02 a.m. EDT
Thanks David for sending the information across. Can you please let me know which version of comsol you have used for the model. I have not been able to open the file in Comsol 4.0, it says that an advanced version has been used to make the model. If possible can you send a 4.0 compatible version of the model?

Regards,
Nidhi
Thanks David for sending the information across. Can you please let me know which version of comsol you have used for the model. I have not been able to open the file in Comsol 4.0, it says that an advanced version has been used to make the model. If possible can you send a 4.0 compatible version of the model? Regards, Nidhi
David Smith
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Posted: 1 decade ago Jul 12, 2011, 7:14 a.m. EDT
Hi Nidhi,

I am using COMSOL 4.1 and do not have any older versions installed on my computer.

Have a read of the example (tunable capacitor) in the COMSOL model library as it will help when setting up your model.

Regards,
David.

Hi Nidhi, I am using COMSOL 4.1 and do not have any older versions installed on my computer. Have a read of the example (tunable capacitor) in the COMSOL model library as it will help when setting up your model. Regards, David.

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