Magnet placement on steel plate

Discussion in 'General Electronics Chat' started by Sirropo01, Oct 13, 2013.

  1. Sirropo01

    Thread Starter New Member

    Oct 13, 2013
    Bear with me, not a magnet expert, this is in reference to Wind Power Generation, home brew, if you are familiar with this, magnet placement is akin to the digits on an analog clock, lets say 12 magnets on a round plate 15 inches in diameter.

    There are those whom stress placement of magnets on plyboard (non-magnetic) and those whom stress placement on steel plate (hub).

    Those whom stress placement on steel plate point out that the somewhat close proximity of the magnets to each other, allows them to efficiently (thru the steel plate) share flux fields which enforces/strengthens their individual flux fields, which I can see but here is my thought and question:

    Wouldn't the steel plate also absorb a certain amount of the flux fields REDUCING the over all "external" flux fields of the individual magnets ?

    The "external" flux fields being what is needed to cut across the stator windings.
  2. PackratKing

    Well-Known Member

    Jul 13, 2008
    Are you possibly building a sort of generator ?? this will work, but the actual output is rather disappointing...

    I have found, that it is necessary to keep the individual magnets' polarities aligned, which means gluing one set on one side, if two-sided, and then opposing the tendency to repel on the other side, when attaching the second set.

    I would consider two perforated non-ferrous plates, [ akin to the diffusion plate inside a microwave door -aluminum 'perfboard '] as opposed to wood or steel. JB Weld is your best bet for glue...

    Hope that made sense...:D
    Last edited: Oct 13, 2013
  3. wayneh


    Sep 9, 2010
    You don't want any arrangement that moves a magnetic field past a big conductor, or vice versa (it's all relative), as this will act like a brake and heat the conductor. See here.

    It is true that magnetic flux can be greatly increased by completing a magnetic "circuit", minimizing any air gaps. But it's a challenge to accomplish that without that same metal "seeing" current in the coils or a moving magnet and causing braking.
  4. WBahn


    Mar 31, 2012
    But isn't braking an inevitable consequence of generating power? You are extracting power from the rotation, and thus the generator is going to impact that rotation by trying to slow it down.
  5. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    A closed circuit is required to allow current flow, and the subsequent counter field. Placing magnets on a ferrous plate will distribute the flux, reducing build up with neighbouring fields.
    Brownout likes this.
  6. praondevou

    AAC Fanatic!

    Jul 9, 2011
    For those experiments I can really recommend It will simulate and show you the field strength at the point of interest. It works very well, I tested it with a setup I used to determine hysteresis curves of steel rings.

    If you close a magnetic circuit with a material that has higher permeability than air , the field strength in the remaining gap will increase.
    shortbus likes this.
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Nicely said!
  8. wayneh


    Sep 9, 2010
    Yes, but there is avoidable and unavoidable braking. Spinning a brake drum past an electromagnet coil (commonly seen in DIY wind generators) is an avoidable source of eddy current drag.