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Electromagnetic force on iron plate

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Hello! I made a simple model with AD/DC Magnetic fields no current module. There is a cylindrical magnet and iron plate in it. Iron plate has relative permibility 4000 mur. I calculate the force with which magnet pull the plate. And I get a good result when there is a distance between magnet and the plate. But when the distance between them is 0 (that means that the magnet is in contact with the plate), I suddenly got wrong number. For example, with distance 0.1 mm I get the force about 30 N, but when the distance is 0 - the force is -5.8. How it can be explained? Thank you!

2 Replies Last Post 8 mars 2017, 10:30 UTC−5
Nirmal Paudel Tribhuvan University/Electrical Engineering

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Posted: 8 years ago 7 mars 2017, 10:42 UTC−5
Hi Andrey,

Please see "Magnetic Force/Torque" topic in this blog post:

www.comsol.com/blogs/modeling-magnetic-bearings-in-comsol-multiphysics/

The force calculation when magnet is touching the iron/permeable material is wrong. You would need to apply a thin layer of Thin Low permeability gap to get correct answer.

Hope this helps.

Best Regards,
Nirmal
Hi Andrey, Please see "Magnetic Force/Torque" topic in this blog post: https://www.comsol.com/blogs/modeling-magnetic-bearings-in-comsol-multiphysics/ The force calculation when magnet is touching the iron/permeable material is wrong. You would need to apply a thin layer of Thin Low permeability gap to get correct answer. Hope this helps. Best Regards, Nirmal

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Posted: 8 years ago 8 mars 2017, 10:30 UTC−5
Thank you! Now it's clear!
Thank you! Now it's clear!

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