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Permanent magnets.

  1. Dec 17, 2006 #1


    Hello!

    I have a deeply magnetizing question. I have an attractive magnetic assembly and I am interested in finding some forces, acting on its parts.

    Set-up details ( if to be specific ):

    I have two cylinder-shaped neo magnets with identical dimensions and properties, such as residual induction, dimensions, mass, etc.

    I fix both of 'em as shown in the attachment A1.gif below. M1 is fixed on the ground, M2 can only move thru Y-axis. M2 is attracted by gravity, but hangs in the air because of the repulsive force between those two.

    Target:
    I have to find the net force in Newton units, acting on M2, thus it's being fixed in its levitated state and doesn't move. The sticky point is that I want to design a magnet, which will hold another one at certain air gap, but for this purpose a horse, pardon, a force value needed.

    What I do know:
    I know nothin' about it, as the school project has just begun; this is my first week with permanent magnets. So my questions to you:

    • Could you provide me with any ( specific ) guidelines for further reading? Google did not help me a lot in this case.
    • or, could you give me some kind of hint for the strategy of calculation, which I should follow?
    • How the Magnetic Flux Density ( induction ) of a given magnet does relate to the resulting force?
    • I have gotten a link to so-called "magnetic moment" or torque as a force expression, but it just doesn't make sense, I am not sure it's what I need. Is it?

    I’m totally lost in this forest. Any help would be appreciated.. ..even if there are no threes.



    Lyric notes:
    When I’m talking about induction, I visualize the following calculation in my mind: see att. A2.gif
    The purpose of this project is to develop ( OK, to try to develop ) a magnetic ( frictionless ) bearing for the windmill. It is interesting to check – will it work or will it not do so.
     

    Attached Files:

    • A1.GIF
      A1.GIF
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    • A2.GIF
      A2.GIF
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  2. jcsd
  3. Dec 17, 2006 #2

    OlderDan

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  4. Dec 17, 2006 #3
    All right, thank you for the help, I'll take a look at it. :redface:

    - - - - - - - - - - - - - - - -
    Now I understand..

    I've found most of the needed literature, and will make sure not to repeat this kind of mistakes in the future.
    Thank you for the right kick!


    Best regards,
    I.L.
     
    Last edited: Dec 17, 2006
  5. Dec 17, 2006 #4

    AlephZero

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  6. Dec 18, 2006 #5
    Thank you, A. Zero.
    It is a very good information to start with. My current point of view is, that AMB's need an energy source, and therefore they are likely not to become useful in a windmill, because it is a bit risky and can cost a lot, if it fails.

    I'm trying to find out, what a PMB*[1] might be able to do. There is a tricky problem of fixed magnetic configuration, and some calculations have to be performed on this basis. So I am searching for the basic "rules" for the game, so to speak, because I am startin' from the beginning.

    What our group wants to do - is to allow a windmill to start at lower wind speeds due to reduced energy loss by using a frictionless PMB assembly, and if we can't build it, we will model it. Inspiration came from energybulletin.net, or more precise, from this link - the difference is, that we want to build and test our own.

    Best regards,
    I.L.

    *[1] Passive Magnetic Bearing.
     
    Last edited: Dec 18, 2006
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