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Permanent Bar Magnet
Posted Oct 29, 2012, 5:36 p.m. EDT Low-Frequency Electromagnetics Version 4.3 1 Reply
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Dear
I am completely new to comsol multiphysics. I am trying to visualise the magnetic field of a permanent bar magnet. I will be using grade n35 neodyium magnet having a magnetic flux density of 1.3 tesla. The geometry will be width 10mm, height 5mm, depth 5mm.
I have no idea how to add the north pole and south pole of the magnet and add the material.
I am using version 4.3. Any help will be much appreciated.
I am completely new to comsol multiphysics. I am trying to visualise the magnetic field of a permanent bar magnet. I will be using grade n35 neodyium magnet having a magnetic flux density of 1.3 tesla. The geometry will be width 10mm, height 5mm, depth 5mm.
I have no idea how to add the north pole and south pole of the magnet and add the material.
I am using version 4.3. Any help will be much appreciated.
1 Reply Last Post Nov 27, 2012, 7:55 a.m. EST
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Posted:
1 decade ago
Permanant magnets are ussually mathematically described by surface currents - small layer of currents circulating on surface of magnets (sum of all micro-currents around seperate dipoles), basicaly turning them into solenids.
Therefore generally you have to solve Poisons eq. for vector potential A: lapA = -mi0*j
Surface currents are conected with magnetization and remanent field in following way: rotM = j and M = Br/mi0, where M - magnetization and Br - remanent magnetic field of permanent magnet.
Therefore currnet density you have to define on surface as boundary condition will have form: j = C*Br/(mi0*L), where C - some constant, L - length dimension. I dont know exact formula, sorry... But I would try something like/ C = 1 and L = radius...
I havent done this in COMSOL but I think it should work in similar way.
I hope it helps.
Therefore generally you have to solve Poisons eq. for vector potential A: lapA = -mi0*j
Surface currents are conected with magnetization and remanent field in following way: rotM = j and M = Br/mi0, where M - magnetization and Br - remanent magnetic field of permanent magnet.
Therefore currnet density you have to define on surface as boundary condition will have form: j = C*Br/(mi0*L), where C - some constant, L - length dimension. I dont know exact formula, sorry... But I would try something like/ C = 1 and L = radius...
I havent done this in COMSOL but I think it should work in similar way.
I hope it helps.