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How to recharge neodymium magnets?

  1. Mar 10, 2010 #1
    This is my first post and I am not sure if I am posting it in the right place.
    But I believe some electrical engineer could answer it better than any other engineer.
    Please anyone correct me if I am in the wrong place.

    I am using Neodymium magnets on a machine I am developing. They are positioned in a few sets of two magnets, with same pole faces oposing each other, to cause a floating effect.

    I have noticed that this magnets are loosing the magnetic field force, therefore the floating effect is weaker. Instead of replacing them for new ones, I was wondering If I could project any built in system to periodically remagnetize the magnets. I searched for some usefull information on google, but couldnt find details about the process of polarization.

    Does anyone here nows how the polarization is done?? I know it uses a very strong magnetic field do allign the magnetic dipoles, but how is it done??

    Thank you for the help
     
  2. jcsd
  3. Mar 10, 2010 #2
    As a preventative measure, try not to induce any mechanical shock to the magnets when they are in close proximity with similar poles facing one another. This will tend to demagnetize them.

    Regeneration requires that they be bathed in an H field stronger than they possess. This could be as simple as mating them with other magnets, opposite poles and inducing some mechanical shock or thermal variations and the means to re-separate them. How well this would work depends upon the properties of neodymium magnets of which I am unfamiliar.
     
  4. Mar 10, 2010 #3
    interesting..
    I heard something about a capacitive discharge to remagnetize them.. Do u happen to know anything about it?
     
  5. Mar 10, 2010 #4
    Not directly. Some capacitors can deliver a large impulse current to an inductor. The inductor can develop, for a short time a large H field. Apparently, this is a method to regenerate magnets.

    Your issue with this method might be that you have two magnets in opposite orientation, where both require regeneration. The impulse field, H would regenerate one and degrade the other. You would need to separate them first.
     
  6. Mar 10, 2010 #5
    quite simple then... thank you very much for the fast and practical answer
     
  7. Mar 10, 2010 #6
    let me see if I got this right..

    I was thinking of the constructive issues of this "recharging system" and thought of a simple way of making it.

    If I take a cupper wire connected to the capacitors, roll around one of the magnets and produce a big enough current, I would recharge it?? as simple as that??

    Thank you
     
  8. Mar 10, 2010 #7
    Herllo Zipit-

    To recharge neo magnets, you should aim for at least 3 megamps (MA) per meter magnetization. See

    https://www.physicsforums.com/attachment.php?attachmentid=23832&d=1266698681

    Second, you can use a pulse system as shown in

    https://www.physicsforums.com/attachment.php?attachmentid=21794&d=1258147485

    This pulse network gives a 16,000 amp pulse through a 13 uH coil. Be careful to design the coil with the correct inductance, or rerun the simulation. Eddy currents may be a problem in the neo magnets, so calculate them to make sure the pulse is long enough. Finally, the series diode has to carry 16,000 amps peak.

    Bob S
     
  9. Mar 10, 2010 #8
    Thank you bob.

    That is a very usefull post :D

    I will gather some information on coil design to start with.

    Regarding the eddy currents, will they be generated in the coil or in the magnet? coz I know a way to calculate them in wires or thin plates, but I have no idea how to calculate them on a neo magnet.

    And in respect of time, how long would it be long enough?
     
  10. Mar 10, 2010 #9
    The magnetic field needs to penetrate to the center of the neo magnet. The radial skin depth of the magnet is

    δ = [2/ωσμ0]1/2

    There is probably a correction for short (finite length) magnets, but I don't know it. Smythe "Static and Dynamic Electricity" Third Edition, problem 24 on page 411 may help (it has the answer).

    Bob S
     
  11. May 16, 2012 #10
    I have 1500 pcs 2" x 2" x .750" I am looking to sell and want to charge them, any easy solutions ?

    N-50 Neodymium Rare Earth Magnet, Ni-Cu-Ni, composition. Looking for cheap easy solution
     
  12. May 16, 2012 #11
    Commercial magnetizers tend to be a bit too big to be integrated elsewhere... You pretty much can buy them off the shelf, but to pay the bill you will have to sell more than 1500 Nd magnets.

    http://www.metis.be/en/products/magnetizers.php
     
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