# Discussion Forum

## Magnetic field

 Topics: 4.3a, AC/DC Module, Physics
RSS feed   |   Turn on email notifications   |   7 Replies   Last post: January 26, 2013 3:26pm UTC

Martin Kandl

January 24, 2013 6:29pm UTC

Magnetic field

Hello

I created a simple model where the magnetic field and electric wire.

1 Why not spread outside the magnetic induction coil?
2 Why is not moving conductor in a magnetic field?

Thank you.
Goodbye.

Sergei Yushanov
Certified Consultant
AltaSim Technologies, LLC

January 25, 2013 1:59pm UTC in response to Martin Kandl

Re: Magnetic field

Martin,

It is difficult to understand what problem you are trying to solve. Seems that you want to model coil motion but velocity term is not defined in your model.

1. Magnetic field is not spreading out because you are imposing Magnetic Insulation boundary condition at the coil boundary. So, remove this BC.

2. You are using 2D geometry which is confusing. Is not your coil circular? Then, you need 2D Axisymmetric geometry instead of planar 2D.

3. Increase air domain size around coil and wire.

4. It is not clear why you are using Form Assembly feature?

Best regards,
Sergei

Martin Kandl

January 25, 2013 6:23pm UTC in response to Sergei Yushanov

Re: Magnetic field

Yes I have problem how simulate pohyb vire or coil in magnetic field.
1 What dos it mean BC? Magnetic insulation add automatic, how can I remove it?
2 How can I determinet velocity?

Thank.

By,

BTW I am new in comsol .can you antwort me to 29 jan 2013?
Thank

Sergei Yushanov
Certified Consultant
AltaSim Technologies, LLC

January 25, 2013 9:01pm UTC in response to Martin Kandl

Re: Magnetic field

Martin,

BC stands for “Boundary Condition”.

In order to help you, please, provide the description of the problem you are trying to solve along with the sketch of the system.

Regards,
Sergei

Martin Kandl

January 25, 2013 10:38pm UTC in response to Sergei Yushanov

Re: Magnetic field

In the picture there are 2 coils and electrical wire in the middle.

And I needed to know as I do that the geometry of the electrical conductor moving in the direction and strength of the magnetic field.
But so that the movement was visible and that each field to themselves really worked.

Rush preto.že 29 jan.2013 my license expires on the trial version.

Thank you very much for your help,

Martin Kandl.

Ivar Kjelberg

January 26, 2013 12:47am UTC in response to Martin Kandl

Re: Magnetic field

Hi

but are you in 2D (infinite long) or 2D-axi (but then where is the axis ?

Why not start with two magnets or just boundary flux values ?

--
Good luck
Ivar

Martin Kandl

January 26, 2013 7:49am UTC in response to Ivar Kjelberg

Re: Magnetic field

Good day.

It does not matter.
I need advice on how to achieve an electrical conductor or magnet is moved in a magnetic field according to the direction and size.

Goodbye.

Ivar Kjelberg

January 26, 2013 3:26pm UTC in response to Martin Kandl

Re: Magnetic field

Hi

First for you other quesion: the "Model Builder" that is a subject that interests me too, but I have not found enough time to understandand test how to use it correctly

---------------
Hey COMSOL developpers: what about an "advanced Model Builder" course 1-2 days, even in Stockholm, I expect I should manage to justify that to get on the list ;)
--------------- perhaps they will hear me, shouting out in the dark gives sometimes replies :)

Now back to your question about a moving wire in an magnetic field. I do not fully understand what you are after, with your model, to show the principle, or to test ALE meshing, or ...

The way you have drawn the N-S of your coils I do not se how you loop the current in 2D, and if your wire is vertical along Y and the current flow therein is vertical, then it's aligned with the flux lines, and you will have no forces on your wire.
But even if you had some forces, why should it move ?, it's position is governed by x,y or x=u+X, y=v+Y, but you are not solving for the displacement u,v, only for the magnetic vector potential Vm in ACDC 2D.

Furthermore ACDC is tricky, the Maxwell eqations with the curl mixes all 3 coordinates, even if you are studying only 2 such as x,y in 2D, you need to look into the "z" components, because of the curl terms.

You have the rotary motor example in the model builder. It's worth to modify it and make a linear motor in 2D-axi (moving along Z the vertical axis in 2D-axi, and then you could try the example with the wire in a field, but be sure you get your field as desired, and the current flow too ;)

--
Good luck
Ivar

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