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Modeling of a magnet

Posted Jan 14, 2011, 12:16 p.m. EST 4 Replies

Matthias Feser
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Hi all,

I want to model a cylindrical static magnet in Comsol 4.0a. From the manufacturer I obtained the following properties:
- magnetic flux density inside the magnet
- magnetic flux density on the surface of the magnet
- demagnetization (BH) curve (magnetic flux densitiy over external magnetic field)

My questions now is how to incorporate these properties into a model to run a realistic field simulation. A first attempt using the BH-curve property under 'Magnetic Flux Conservation' in combination resulted in a binary field distribution when putting the magnet in air surrounding (B max. inside the magnet, B zero in the air medium). Since this is obviously not the correct solution, hopefully you can give me a better approach to solve my problem.

Thanks in advance for helping me out.

Matthias
4 Replies Last Post Jan 17, 2011, 1:05 p.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 14, 2011, 2:58 p.m. EST
Hi

I must admit that to now, I have simply simulated my magnets as a constant Br or M (magnetisation) value devices. I have not really run a model where I study further the true behaviour of a magnet.

Most industrial magnets can be simulated this way, at least for first order approaches.

--
Good luck
Ivar
Hi I must admit that to now, I have simply simulated my magnets as a constant Br or M (magnetisation) value devices. I have not really run a model where I study further the true behaviour of a magnet. Most industrial magnets can be simulated this way, at least for first order approaches. -- Good luck Ivar
Matthias Feser
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Posted: 1 decade ago Jan 17, 2011, 10:38 a.m. EST
Thanks for your reply. When trying to simulate the magnet with Br, I get the same result as with the BH-curve, a binary distributed flux (Br inside the magnet, zero flux in air medium). Furthermore the solver throws an error that it cannot find a solution (relative error too large). Can you help me out with this issue ?

Thanks
Matthias
Thanks for your reply. When trying to simulate the magnet with Br, I get the same result as with the BH-curve, a binary distributed flux (Br inside the magnet, zero flux in air medium). Furthermore the solver throws an error that it cannot find a solution (relative error too large). Can you help me out with this issue ? Thanks Matthias
Matthias Feser
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Posted: 1 decade ago Jan 17, 2011, 12:38 p.m. EST
Here is the model file for the magnet. I played around with the mesh, without having any luck. Still getting the converge error. How can I get the parameters of the magnet into a working model (only B and BH curve are given) ?
Here is the model file for the magnet. I played around with the mesh, without having any luck. Still getting the converge error. How can I get the parameters of the magnet into a working model (only B and BH curve are given) ?

Attachments:

Matthias Feser
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Posted: 1 decade ago Jan 17, 2011, 1:05 p.m. EST
Managed to get rid of the converge error. In the attachment is the model file for the magnet including a linear BH-curve for simplicity. As mentioned before the flux distribution is binary. What can I do to get a closed flux around the magnet ?
Managed to get rid of the converge error. In the attachment is the model file for the magnet including a linear BH-curve for simplicity. As mentioned before the flux distribution is binary. What can I do to get a closed flux around the magnet ?

Attachments:

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