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Power required to reverse an electropermanent magnet

  1. Oct 24, 2012 #1
    I need to know how to calculate the power level and pulse width required to revers the polarity of a rod or bar shaped alnico magnet, depending on the width. I also don't know whether to use AC or DC power.

    I'm prototyping an invention and it needs to be as power efficient as possible.
  2. jcsd
  3. Oct 25, 2012 #2


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    If you don't understand if you need to use AC or DC power, then I have to question if you know enough to be making prototypes and inventing things involving magnets and electromagnets. Do you know how an electromagnet works? What would happen if you pump DC through an electromagnet? How about AC?
    Unless you are asking something else related to the AC or DC part. I assume you are asking about pumping it through the coils.
  4. Oct 25, 2012 #3
  5. Oct 26, 2012 #4
    power enough to heat the metal to 900 degree C plus the power to produce a magnetic field strong enough to magnetise the metal while it cools. Does not sound efficient. why not just turn it around ?
  6. Oct 27, 2012 #5
    Hi Folks,
    Just to avoid confusion, I need to send pulses something like 1ms duration (or shorter), maybe 2 or 3 times a second down a wire coil around an alnico magnet to reverse its polarity. This process doesn't require heating the magnet at all. Just a strong burst of electricity.

    The theoretical materials I've found out there are a bit short on the details as to the power and pulse width required for the given physical size. This design is used in switchable magnets from a lot of manufacturers.

    If Drakkith knows the answer but doesn't want to give it, then he doesn't have to. ... :-)
  7. Oct 27, 2012 #6

    Hi Undacuva,
    Are you asking about the –H demagnetising force? In that case the above websites provide a wealth of information on alnico magnets. Mind you I’ve not gone through all of them but mostly they are dealing with a constant reverse magnetic force field and not a pulsating one. Maybe there are some which will tell you the minimum required time needed.
  8. Oct 27, 2012 #7
  9. Oct 27, 2012 #8


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    Can't say I do. I just usually play intercept to a lot of the "new guys" here that ask questions that sometimes make no sense or that makes them appear like they don't know what they are doing. It seems like you know a bit more than that however. My apologies.
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