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Current induced by a magnet

Posted 25 ott 2011, 16:45 GMT-4 Low-Frequency Electromagnetics, Mesh Version 4.2a 2 Replies

Marco Fontana
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Hi.
I'm really new to COMSOL Multiphysics and I think I need some help.
I have a single turn coil and a permanent magnet, same radius and parallels, in 3D. I know that moving the coil, i can change the magnetic field in the coil, and so i can obtain an induced current. But I don't know how to do this in COMSOL.

Moving the magnet depends on "moving mesh" (I think); so I put my magnet in "Free Deformation". Moving the magnet, the magnetic field (ploted in a 3D slice) doesn't move...Why? What's wrong? Otherwise, putting air and magnet in that node, the MF plotted moves too, but my magnet change its geometry.

I read various threads looking for a hint without succes.

I can also change my system using a MF time dependent. In this way nothing moves. But how can I evaluate the magnetic flux (B) and obtain a voltage? ( V=-d flux(B)/dt ) How many B involves my coil? Between them there is about 2/3cm.

I think it's a simple problem, but i read here ( www.comsol.se/community/forums/general/thread/18617/ ) that maybe this problem can't be solved using COMSOL.

Thanks in advance for any suggestions.

MF
2 Replies Last Post 13 mag 2013, 12:02 GMT-4
Andrew Chou
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Posted: 1 decade ago 25 ott 2011, 23:20 GMT-4
Hi everyone,

I'm facing some similar issues as well.

In my model, I have a permanent magnet (13.2 Tesla remanant flux density) moving back and forth and a fixed copper coil right next to it and I want to have the moving magnet induce a current and voltage into the fixed coil.

I initially based my model off of a CFD tutorial model for a fluid damper that has similar geometry to what I want and also uses the "Moving Mesh (ale)" module in order to move the damper piston (in my case, the magnet). I altered the tutorial model by removing the CFD physics and replacing it with MF physics and adding ampere's law to the magnet portion, as well as editing all the material properties. However, after running the simulation, I ran into some issues. With the fixed coil area part of the "Prescribed Deformation 1" for ale, I get a decent looking plot for the current density in that area (although I believe the values are a few orders of magnitude too large). If I don't select the fixed coil area as part as "Prescribed Deformation 1", I get a zero value for the current density in the coil. Is my approach to this problem correct?

Also, any suggestions on where I should put a cut point/line in the model to measure things going on in the coil (eg current density, electric field, etc)? Right now I'm using a cut point on the boundary between the coil and the magnet. My results change if I move the point just slightly to the right into the middle of the coil....

I'd like to attach the model file to clarify but the forum says its too big. What is the max size I can post and any tips on making my file smaller? I'm running 4.0a

Thanks!
-Andrew
Hi everyone, I'm facing some similar issues as well. In my model, I have a permanent magnet (13.2 Tesla remanant flux density) moving back and forth and a fixed copper coil right next to it and I want to have the moving magnet induce a current and voltage into the fixed coil. I initially based my model off of a CFD tutorial model for a fluid damper that has similar geometry to what I want and also uses the "Moving Mesh (ale)" module in order to move the damper piston (in my case, the magnet). I altered the tutorial model by removing the CFD physics and replacing it with MF physics and adding ampere's law to the magnet portion, as well as editing all the material properties. However, after running the simulation, I ran into some issues. With the fixed coil area part of the "Prescribed Deformation 1" for ale, I get a decent looking plot for the current density in that area (although I believe the values are a few orders of magnitude too large). If I don't select the fixed coil area as part as "Prescribed Deformation 1", I get a zero value for the current density in the coil. Is my approach to this problem correct? Also, any suggestions on where I should put a cut point/line in the model to measure things going on in the coil (eg current density, electric field, etc)? Right now I'm using a cut point on the boundary between the coil and the magnet. My results change if I move the point just slightly to the right into the middle of the coil.... I'd like to attach the model file to clarify but the forum says its too big. What is the max size I can post and any tips on making my file smaller? I'm running 4.0a Thanks! -Andrew
Mario Andres Kovacs
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Posted: 1 decade ago 13 mag 2013, 12:02 GMT-4
Hi

Its a really late answer, but there is a good model in the comsol library:

www.comsol.com/showroom/gallery/14163/

good luck!
Mario


Hi Its a really late answer, but there is a good model in the comsol library: http://www.comsol.com/showroom/gallery/14163/ good luck! Mario

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