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Failure in modelling magnetic field of a current carry wire

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Hi all,

I am new to Multiphysics and now trying to model a magnetic field of a current carrying wire with a limited length. So I used a cylinder to simulate copper wire. I made two attempts where I used a cylinder and a sphere to simulate surrounding air. However, I got totally different results and these results are all different from theoretical values.

I could not come up with solutions to this problem. Please find the attached files and make some suggestions.

Thank you very much

Kind regards
Junjie Tu


3 Replies Last Post 09.11.2015, 08:45 GMT-5
Nirmal Paudel COMSOL Employee

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Posted: 9 years ago 06.11.2015, 09:56 GMT-5
Hi,

It is not possible to model a finite length of a current carrying coil by terminating the conductor in the air region. You must have a close loop or extending to touch the outer boundary (magnetic insulation boundary) which acts as a return current path.
For more information about this refer to the following blog post:
www.comsol.com/blogs/computing-the-inductance-of-a-wire/

Best Regards,
Nirmal
Hi, It is not possible to model a finite length of a current carrying coil by terminating the conductor in the air region. You must have a close loop or extending to touch the outer boundary (magnetic insulation boundary) which acts as a return current path. For more information about this refer to the following blog post: http://www.comsol.com/blogs/computing-the-inductance-of-a-wire/ Best Regards, Nirmal

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Posted: 9 years ago 07.11.2015, 12:32 GMT-5
Hi,

Thank you for your reply.

I read the web page you provided and added magnetic and electric field interface to my modelling, but I couldn't find terminal and ground boundary condition in this interface. So should I include electric current too? I failed to calculate magnetic field by applying current in electric current interface. Is it because I didn't couple this two interface? If it's so, can you please tell me how to do this?

Many thanks
Junjie Tu
Hi, Thank you for your reply. I read the web page you provided and added magnetic and electric field interface to my modelling, but I couldn't find terminal and ground boundary condition in this interface. So should I include electric current too? I failed to calculate magnetic field by applying current in electric current interface. Is it because I didn't couple this two interface? If it's so, can you please tell me how to do this? Many thanks Junjie Tu

Nirmal Paudel COMSOL Employee

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Posted: 9 years ago 09.11.2015, 08:45 GMT-5
Hi,

The "Terminal" and "Ground" boundary features are available under "Magnetic and Electric Fields -> Magnetic Insulation 1" in MEF physics interface.
See the following example:
www.comsol.com/model/inductance-of-a-power-inductor-1250

Best Regards,
Nirmal Paudel
Hi, The "Terminal" and "Ground" boundary features are available under "Magnetic and Electric Fields -> Magnetic Insulation 1" in MEF physics interface. See the following example: http://www.comsol.com/model/inductance-of-a-power-inductor-1250 Best Regards, Nirmal Paudel

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