DC Current through Magnet


by ebaqui
Tags: current, magnet
ebaqui
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#1
Apr26-13, 04:00 PM
P: 3
Hi

I want to pass DC current through a magnet, essentially using it as connector. The magnet I am using specifically is Neodymium (NdFeB) grade N42. The DC current I would like to pass through it is 100mA ~ 150mA (3V DC ~ 7V DC)

I would like to know if there is any downside to the magnetic effect of this permanent magnet?

Is there a way to determine how high i can go with the DC current in this situation without a noticeable detrimental effect on the magnetic effect of the magnet, like 1A ~ 2A?

Thank you
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Jim_A
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#2
Apr26-13, 07:10 PM
P: 3
Nothing special should happen. But if you heat the magnet above its curie temp it will lose all its magnetic field.
The curie temp is especially low for neodymium magnets, for some types it's only about 80 degrees C.
So 150mA would most likely be OK. At 2A it will depend on the size,shape and mounting of the magnet how much it is heated.
berkeman
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#3
Apr26-13, 07:26 PM
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Quote Quote by ebaqui View Post
Hi

I want to pass DC current through a magnet, essentially using it as connector. The magnet I am using specifically is Neodymium (NdFeB) grade N42. The DC current I would like to pass through it is 100mA ~ 150mA (3V DC ~ 7V DC)

I would like to know if there is any downside to the magnetic effect of this permanent magnet?

Is there a way to determine how high i can go with the DC current in this situation without a noticeable detrimental effect on the magnetic effect of the magnet, like 1A ~ 2A?

Thank you
Welcome to the PF.

In addition to Jim's comments, keep in mind that what you are suggesting will not be a very good or reliable connector. To be reliable, the connection interface needs to have enough contact force to provide a gas-tight interface between the two conductors. If the interface is not air-tight, corrosion will happen in the interface (at different rates, depending on the contact material). Also, a good connector should have multiple points of contact. The surface of the magnet will be flat, with no dimples to give multiple contact points with gas-tight seals.

What is the application?

ebaqui
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#4
Apr27-13, 12:40 PM
P: 3

DC Current through Magnet


Quote Quote by Jim_A View Post
Nothing special should happen. But if you heat the magnet above its curie temp it will lose all its magnetic field.
The curie temp is especially low for neodymium magnets, for some types it's only about 80 degrees C.
So 150mA would most likely be OK. At 2A it will depend on the size,shape and mounting of the magnet how much it is heated.
I am currently using spherical magnets 0.25" diameter. I cut a wire and connected magnets on each end, so when the magnets come in contact the circuit of leds will turn on. The 2A is for potentially running a number of leds.

Thanks for your help on this Jim
ebaqui
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#5
Apr27-13, 12:48 PM
P: 3
Quote Quote by Jim_A View Post
Nothing special should happen. But if you heat the magnet above its curie temp it will lose all its magnetic field.
The curie temp is especially low for neodymium magnets, for some types it's only about 80 degrees C.
So 150mA would most likely be OK. At 2A it will depend on the size,shape and mounting of the magnet how much it is heated.
Quote Quote by berkeman View Post
Welcome to the PF.

In addition to Jim's comments, keep in mind that what you are suggesting will not be a very good or reliable connector. To be reliable, the connection interface needs to have enough contact force to provide a gas-tight interface between the two conductors. If the interface is not air-tight, corrosion will happen in the interface (at different rates, depending on the contact material). Also, a good connector should have multiple points of contact. The surface of the magnet will be flat, with no dimples to give multiple contact points with gas-tight seals.

What is the application?
That is an interesting point , I did not consider. The magnets are 0.25" spheres, Ni plated. I could use a magnet each for the positive and negative terminal contacts, right?

I am using this for an led circuit to light my workbench.

Thanks for your help Berkeman
sophiecentaur
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#6
Apr27-13, 04:47 PM
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The new Apple Macbooks have a magnetic power connector. You could take a look at one of them to see how they do it.
It strikes me that you could put a thin layer of good conductor on the surface of the two magnets, connecting your wires to them and by-passing the magnet material yet still have enough force to keep the contacts together. I'm not sure you would need to worry too much about the shape / completeness of the contacts. It's a factor in all switches and a slight radius on each pole is usually sufficient for a contact.


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