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Re-magnetized AlNiCo500 but failed

  1. Oct 8, 2015 #1
    I'd like to build an electromagnet coil that's capable of re-magnetizing (Changing the magnetic field direction) AlNiCo500 (LNG44, Hc=50 kA/m). But failed.
    The Magnet is is 3mm in diameter and 12mm in length.
    In the beginning, I used a H-Bridge circuit to do that, shown in the attached thumbnail, the voltage is 20v, but it didn't work.
    I thought maybe my coil is not thick enough, so I made another one.It didn't work too.
    Finally, I directly use my hand to quickly add a 20V voltage on each side of the coil to make a pulse, but it still didn't work.
    The coil was getting very hot. I don't know why. So I ask your help.
     

    Attached Files:

  2. jcsd
  3. Oct 8, 2015 #2

    Hesch

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    Gold Member

    It's not the voltage that magnetizes, but the current, or rather the current multiplied by the number of turns.
    You should look up the magnetizing curve as for the material, reading the H-value that is needed for the magnetization. The material is magnetized within a μs, so you don't have to sit up all night, waiting for the coil to be heated up due to conducting losses.

    Instead you obtain a big capacitor ( say 10mF/64V ) and charge it to 50Vdc, then connect it in parallel with the coil ( keep distance and fasten the material, otherwise it may act as a projectile ).

    That's the principle. Some refinement as of the circuit may be needed, such as a diode preventing the current to be reversed. ( A LC-circuit will oscillate ).
    Also the values mentioned above must be calculated to optimize the process ( capacitor, number of turns, type of wire ).
    F1.jpg
    PS: I have to say, that industrial magnetizing machines are "heavy duty" equipment.

    2011-6-21-2038124884.jpg
     

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    Last edited: Oct 8, 2015
  4. Oct 15, 2015 #3
    Thank you for your answer.
     

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    • F1.jpg
      F1.jpg
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