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switching electric AC voltage

Posted 2014年1月28日 GMT-5 10:26 Low-Frequency Electromagnetics, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 4.3b, Version 4.4 4 Replies

Edwin Lok
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Hi, I'm rather new to COMSOL. Is there a way to model a switching AC field between two electrodes? That is, both electrodes are always applying an AC field of the same frequency, but one side is high and the other is lower but periodically, they switch potentials?

In the past, I've used the electric currents model and frequency domain to solve, but I need to include this switching effect in the model, which I'm not sure how to.

Also, why is there such a huge difference when I'm defining the electrodes as floating potentials versus terminals? The E-field map I got when using the floating potential resulted in no gradient in potential and thus the E-field was zero everywhere.

Any suggestions would be helpful.

Thanks,
Ed
4 Replies Last Post 2014年1月30日 GMT-5 01:16
Edgar J. Kaiser Certified Consultant
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Posted: 1 decade ago 2014年1月28日 GMT-5 12:59
Ed,

in this case you need a time dependent study. You must define the waveforms at the electrodes explicitely as functions of time.
If your model only consists of floating electrodes without terminal or potential BCs you won't get any non-zero field. But I am not sure if I understand this issue correctly.

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Ed, in this case you need a time dependent study. You must define the waveforms at the electrodes explicitely as functions of time. If your model only consists of floating electrodes without terminal or potential BCs you won't get any non-zero field. But I am not sure if I understand this issue correctly. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
Edwin Lok
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Posted: 1 decade ago 2014年1月29日 GMT-5 10:17
Hello Edgar,

Thank you for your response. I basically have a very basic geometry setup: a sphere with certain dielectric properties, and a pair of opposing electrodes (thin cylinders) placed on the surface of the sphere. Both electrodes are always producing a periodic wave with a particular frequency where one of the electrodes is producing a higher amplitude wave than the other and every couple of seconds, the electrodes switches outputs. I'm not sure how to set up the problem in time dependent mode. I've only been using stationary and frequency domain. I simply defined the electric properties for the 3 geometries, used the electric currents model and defined both electrodes as floating potentials.

Any suggestions?

Thanks in advance!
Hello Edgar, Thank you for your response. I basically have a very basic geometry setup: a sphere with certain dielectric properties, and a pair of opposing electrodes (thin cylinders) placed on the surface of the sphere. Both electrodes are always producing a periodic wave with a particular frequency where one of the electrodes is producing a higher amplitude wave than the other and every couple of seconds, the electrodes switches outputs. I'm not sure how to set up the problem in time dependent mode. I've only been using stationary and frequency domain. I simply defined the electric properties for the 3 geometries, used the electric currents model and defined both electrodes as floating potentials. Any suggestions? Thanks in advance!
Edgar J. Kaiser Certified Consultant
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Posted: 1 decade ago 2014年1月29日 GMT-5 12:39

You can find examples how to set up time dependent studies in the model library, the knowledge base and you can search the forum and check the documentation.

Cheers
Edgar
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
You can find examples how to set up time dependent studies in the model library, the knowledge base and you can search the forum and check the documentation. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
Edwin Lok
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Posted: 1 decade ago 2014年1月30日 GMT-5 01:16
Hello Edgar,

I've successfully defined a piecewise function to describe the switching effect between waves. I explicitly defined the units as per the documentation. However, when I type in "pw1" or "pw1(t)" for the terminal voltage, I get an "unexpected unit of input" even though I explicitly gave the unit of V to the function.

Also, I'm going to make an attempt to solve for the electric field using the time dependent study, ranging from 0 to 2 seconds in intervals of 0.5 seconds.

Any suggestions on the first part, anything wrong with the approach I've taken to the 2nd part?

Please let me know.

Thanks!
Hello Edgar, I've successfully defined a piecewise function to describe the switching effect between waves. I explicitly defined the units as per the documentation. However, when I type in "pw1" or "pw1(t)" for the terminal voltage, I get an "unexpected unit of input" even though I explicitly gave the unit of V to the function. Also, I'm going to make an attempt to solve for the electric field using the time dependent study, ranging from 0 to 2 seconds in intervals of 0.5 seconds. Any suggestions on the first part, anything wrong with the approach I've taken to the 2nd part? Please let me know. Thanks!

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