Discussion Forum

Hi,

i think you can start to learn comsol from the easiest modell from model library, in 2D. like this

www.comsol.de/community/exchange/74/

induced currents are named ussualy as rmm.Jiz or rmm.Ez for induced Voltage (i'm not very sure, but..something like that)

regard
akmal

Hallo everyone,

I'm still a newbie by working with comsol (in my terms Comsol 4.2). I've the same problem like mentioned in the topic and I can't find helpful informations. Is it really not possible to simulate voltage induction due to changing magnetic field? Or has anyone more experience by simulating voltage induction in Comsol?

I would be very pleased if anyone can help me!!

Best regards.

Hi

certainly you can simulate voltage induced in a coil by magnetic field variations, but you need to have a coherent model that respects the physical laws correctly (close loop current circuit, no spontaneous current source/sink appearing in free space, respecting ACDC frequencies and dimensions ...) I would suggest to start with a simpler model in 2D-axi.

But solving for A and V means ACDC MEF physics hence a complex coupled physics, it's somewhat heavy and needs often careful tweaking to get the solver converging. there are many examples (see Eddy current cases) in the model library, but I cannot rermember anything really like your image. A good occasion to make a new example and to propose it here so we might share :)

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Good luck
Ivar

Hallo Ivar,

first of all thank you very much for your response.
To go into detail my problem is not exactly the same like mentioned in topic. As you can see in the picture 'SpgsInduktionTestSim1.png' I'm feeding-in alternating current in a conductor to check the "induced" current density in a surrounding copper wire. This simulation still works well.
But I'm more interested in a construction like represented in picture 'SpgsInduktionTestSim2.png'. To state more precisely I'm interested in the voltage induced in the coil. As you mentioned, the main problem is certainly the unclosed current circuit of the coil. There arises the question whether it is possible to fix boundary conditions (or something like this) at the 2 coil contacts to get the voltage induced in the coil afterwards.

So I hope, everything was as far as understandable.

Thank you very much in advance for your answer.

Best regards

Stephan

Stephan,

if you are only interested in the voltage you can just probe it at the coil ends. There is no need to close the current loop. If you want to see a current you can close the coil with a circuit, e.g. with a resistor. Search the forum and you will find a very useful contribution by Ivar.

Cheers
Edgar

Stephan,

if you are only interested in the voltage you can just probe it at the coil ends. There is no need to close the current loop. If you want to see a current you can close the coil with a circuit, e.g. with a resistor. Search the forum and you will find a very useful contribution by Ivar.

Cheers
Edgar

Edgar,

thanks a lot for your answer.
Due to the fact that Comsol is almost new for my person, the main problem is how to probe the voltage at the coil ends.
I searched a long time yesterday but unfortunately I couldn't find helpful contributions. Maybe you can give me a hint or a buzzword to find the contribution made by Ivar.

Thanks a lot.

Best regards
Stephan

Hi,

I'm still busy with the specified problem. As you can see at the attachment I'm interested at the induced voltage between the boundaries (contacts) 15 and 16 of the coil (coil with only 1 winding). I've calculated the solution by hand but I'm not able to get the problem solved in Comsol correctly. I've read lots of topics but I couldn't find a solution how to solve this problem in 3D. As you can see in the file I tried to find a solution by line integration (Eds), but there is still a bug in it

It would be really great if someone could help me.

Thanks a lot in advance!!

Best regards,

Stephan

Hi

have you tried run it in 2D-axi with MF (and not MEF to start with, as adding the V of MEF changes things too and its quicker to debug in 2D-axi than 3D.) Thereafter you could try ina full 3D run

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Good luck
Ivar

Hi

have you tried run it in 2D-axi with MF (and not MEF to start with, as adding the V of MEF changes things too and its quicker to debug in 2D-axi than 3D.) Thereafter you could try ina full 3D run

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Good luck
Ivar

Hi Ivar,

thanks a lot for the reply.

Yes I've tried run it in 2D-axi. But for later applications I'm more interested in a 3D run. I really don't know where the bug is hidden. In my opinion it couldn't be as difficult as it seems to be, but I've my back to the wall.

Best regards,

Stephan

Hi

I have an example hereby in v4.2a it looks reasonable. In frequency domain you need some conductivity in air, its "just" that it must be kept sufficiently small to be realistic, it depends on the frequency to, which is rather obvious from the equations

I did it in MF as it's by far not so heavy to solve as MEF

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Good luck
Ivar

Hi

I have an example hereby in v4.2a it looks reasonable. In frequency domain you need some conductivity in air, its "just" that it must be kept sufficiently small to be realistic, it depends on the frequency to, which is rather obvious from the equations

I did it in MF as it's by far not so heavy to solve as MEF

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Good luck
Ivar

Hi Ivar,

thanks a lot. Unfortunately, I only have v4.2. Due to this I'm not able to open the file.

Btw. I considered the required conductivity in air.

Best regards,

Stephan

Hi
here is an image and the deailed reportyou might manage to redo it from here ;)

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Good luck
Ivar

Hi
here is an image and the deailed reportyou might manage to redo it from here ;)

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Good luck
Ivar

Hi,

first of all let me say thank you for the help.

I've still solved the problem by integrating the flux density over the cross section of the coil and furthermore multiply by 2*pi*f (like in the test example). But it's not really the way like I want to solve the problem.
However, the 2nd approach (Global Evaluation 3) could be more interesting for me. So I've to study this approach in more detail.

Okay, at first sight it seems to be the same approach, only defining a variable EMF first...
Is the only approach to solve this problem in comsol really to solve it with mf? No feasible way to get the induced voltage with emf?

Thank you very much Ivar!

Best regards,

Stephan

Hi

I would also suggest to start with MF, because of the ypprach of opening up a gap in the coil you will get a high voltage gradient between the two coil ends, this needs to be resolved and the solver takes extra time, and for what you ha vementioned so far I do not see any true reason to solve for V (at least not to start with)

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Good luck
Ivar

Hi

I would also suggest to start with MF, because of the ypprach of opening up a gap in the coil you will get a high voltage gradient between the two coil ends, this needs to be resolved and the solver takes extra time, and for what you ha vementioned so far I do not see any true reason to solve for V (at least not to start with)

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Good luck
Ivar

Hi,

sorry I was reading this message after editing my own. Yes, you are right, there is at the moment no true reason to solve for V. But in my opinion it couldn't be as difficult to get the voltage between the coil ends with emf (or in detail with Eds). Or I'm not right?

Best regards,

Stephan

Hi

it is trickier or more subtile that what one could first belive, that is why I only use MEF for induced Eddy curent cases or for Lorentz velocity cases, and then I loop the current on the ouside border of my model

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Good luck
Ivar

Hi

it is trickier or more subtile that what one could first belive, that is why I only use MEF for induced Eddy curent cases or for Lorentz velocity cases, and then I loop the current on the ouside border of my model

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Good luck
Ivar

Hi Ivar,

that means I should simulate the induced voltage only by using MF and in terms of eddy current (...) MEF can be used?
So the best way in my case is to integrate the flux density over the cross section of the coil and multiply it by N*2*Pi*f?

Thanks a lot again for your response!

Best regards,

Stephan

Hi

you get the voltage frm the integration of the time derivative of the B flux, or in harmonic development the integration ovcer a closed looped area of omega*B_normal where omega = 2*pi*freq. So you do not need to solve for the Voltage, you calculate it from B. It's different in MEF where any induced vltage is asumed to generate a current that will make a B field by its own and interact with the previous B field .

So if you do not need this feedback, as is the case for many studies, you are better off in MF (or if you do not even need any crrent flow, use MFNC, its simpler and quicker to solve)

Studying multiphysics with advanced tools, does not eman we should stop thinking and preparing our models correctly, one must still do the homework and all models must be validated and verified (or the other way around ;)

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Good luck
Ivar

I need documentation of model in which the Inductive coupling between two coils , to find inductances of both coils , magnetic flux density , mutual inductance , coupling coefficient ...

(1) I need to fix the distances between the coils , as distance increases how the various parameters increases ..

Please provide me this documentation
Thanks in advance , waiting for favourable reply
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kishore Naik Mude

Hi

Indeed I have noticed that is not readily in the model library of 4.2a, you have only single coils. This is something I havent tried in v4 yet, back in v3.5 I know I once integrated all the fields and coil sections to see how this behav w.r.t my ACDC cookbook.

I woulder if it has not been discussed already, have you tried to search the Forum, and the papers, there it must have been discussed, but there might not be a ready model, sometimes yes. And check the Model exchange too

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Good luck
Ivar