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Current due to induced charges in frequency study

Posted 23.03.2015, 07:27 GMT-4 Low-Frequency Electromagnetics Version 5.0 5 Replies

Jan
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Hi, I'm trying to find the currents (and resistive heating) in a metal object (e.g. a sphere) placed between a capacitor's plates, which has an AC current running through. The environment should be vacuum (i.e. conduction = 0).

As electric field induces a charge distribution in the studied object, an oscillating E field should induce a changing charge distribution, i.e. currents.

I tried to model this with the electric currents physic, but without specifying a potential in the object, the solution won't converge. I could use a floating potential BC on the objec's surface, but in that case I would have to leave out the insides of the object and I wouldn't get to study the currents inside it.

Any ideas how to solve this?

I also attached the model I currently tried; don't mind the magnetic field interface (Eventually I would like to couple that in also, but not right now.)

Attachments:

5 Replies Last Post 26.03.2015, 17:15 GMT-4
Edgar J. Kaiser Certified Consultant
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Posted: 10 years ago 23.03.2015, 09:27 GMT-4

Jan,

I would recommend using a direct solver instead of the iterative one. Then ec needs some small conductivity everywhere, also in the vacuum. You have to try how small you can go.

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Jan, I would recommend using a direct solver instead of the iterative one. Then ec needs some small conductivity everywhere, also in the vacuum. You have to try how small you can go. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
Jan
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Posted: 10 years ago 23.03.2015, 11:20 GMT-4
Thanks for the reply, Edgar.

When I give the air/vacuum a small conductivity, there will be current going through it and then the vacuum will have resistive heating (much higher than the metal parts) which isn't physically correct. And as that is what I want to study, I feel like this isn't the best solution.
Thanks for the reply, Edgar. When I give the air/vacuum a small conductivity, there will be current going through it and then the vacuum will have resistive heating (much higher than the metal parts) which isn't physically correct. And as that is what I want to study, I feel like this isn't the best solution.
Edgar J. Kaiser Certified Consultant
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Posted: 10 years ago 23.03.2015, 11:53 GMT-4

You don't need to couple the heat production in the air domain into the thermal part of the model.
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
You don't need to couple the heat production in the air domain into the thermal part of the model. -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
Jan
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Posted: 10 years ago 26.03.2015, 13:57 GMT-4
I've been thinking about this and your idea doesn't work.

When I want to find magnetic fields due to the currents I will need to input the ec physic currents as external currents to magnetic fields physic. I can not do that when the nonphysical current is running through the air/vacuum. (I need only the displacement current from vacuum and the total current in the metal parts.)
I've been thinking about this and your idea doesn't work. When I want to find magnetic fields due to the currents I will need to input the ec physic currents as external currents to magnetic fields physic. I can not do that when the nonphysical current is running through the air/vacuum. (I need only the displacement current from vacuum and the total current in the metal parts.)
Edgar J. Kaiser Certified Consultant
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Posted: 10 years ago 26.03.2015, 17:15 GMT-4
Couldn't you just couple the displacement currents from ec into mf for the air domain and the total current for the metal domains?

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Couldn't you just couple the displacement currents from ec into mf for the air domain and the total current for the metal domains? -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com

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