vertically staked stators and rotors, PMA

Discussion in 'The Projects Forum' started by Burnit0017, Feb 27, 2011.

  1. Burnit0017

    Thread Starter Member

    Feb 15, 2010
    Greetings, I have been working on a permanent magnet alternator, axial flux configuration.
    It has been configured with vertically staked stators and rotors. The vertical configuration that I am use requires ½ the magnets then the traditional fabrication method.
    Example: 3 phase, 8 coils per phase
    Traditional fabrication requires 64 magnets
    Stacked Vertical fabrication 32 magnets
    . What I am really trying to find out is does the pull force or flux density accumulate when the magnets are stacked in a vertical configuration even with the added air gaps?
  2. wayneh


    Sep 9, 2010
    I'm not sure I understand your question but there are some issues I would think about.

    Magnetic field lines need a return path - a circuit - just as electricity does. I suppose in your design that the rotors and center axis accomplish this. The magnetic permeability of those metals will have an impact, and you've claimed the rotors are non-magnetic (stainless steel?). Also, including the small magnet to hold the larger ones unnecessarily narrows the field; you'd be better off to use two larger, or even a single large magnet. They'll want to jump out, so you'll need adhesive.

    Your rotors may not be magnetic, but don't forget that passing ANY conductor through a magnetic field will produce eddy current braking. Just try sliding one of your magnets over an aluminum slab sometime - you'll feel the "viscosity" due to eddy currents. So any time there is current in your coils and they can "see" the moving conductor, you'll have drag. It looks like the magnets protrude, and that the rotors are farther away from the coils. That'll help, but I'm still predicting substantial drag at high currents and rpm.

    Air gap is something to minimize as much as your manufacturing tolerances will allow.

    You should add magnet pole orientation to your diagram - it matters. They should alternate poles. That's because one side of a coil's windings need to see a pole moving past that is opposite what the other side of the coil sees, when the magnets are not in the center of the coil. Otherwise the two sides of the coil will be fighting each other.

    You could get quite a lot more juice by having more magnets per disk, as far from the center as possible. Power production is related to the rate of change of the magnetic field, so the faster they spin and the faster they change polarity, the more juice you get.

    PS: Please fix the spelling in the title of your first post. It'll really help folks.