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Re: [axialflux] Re: Coils

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  • daniel.bromley@cox.net
    Steve, Being non-magnetic, I didn t think aluminum would create any drag or cogging. mmmm. I ll take your word for it Steve. Thanks for the input! Loved Dan
    Message 1 of 75 , May 31, 2011
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      Steve, Being non-magnetic, I didn't think aluminum would create any drag
      or cogging. mmmm. I'll take your word for it Steve. Thanks for the input!

      Loved Dan Lenox's turbine build write up!  Great piece of work and should
      be required reading by all !! "59 turns #14 2-in hand"  Oh yeah!! Great stuff!!


      On Tue, May 31, 2011 at 6:50 PM, Steve Spence wrote:

      > And create large amounts of drag.
      >
      > On Tue, 31 May 2011 14:03:58 -0400, <daniel.bromley@...> wrote:
      >
      > >
      > > Dan, consider this for a moment if you will....
      > >
      > >   * Make the stator plate with the likes of 1/4" 6061 aluminum plate....
      > >      then, dipping the outer circumference in insulating resin... THEN
      > >      winding the coils on it.  ....Seems to me the plate would absorb
      > > unwanted
      > >      heat rather well while offering great structural rigidity.
      > > Thoughts/input ?
      > >
      > >                                           Dan Bromley
      > >
      > > On Tue, May 31, 2011 at 7:26 AM, Dan Fink wrote:
      > >
      > >     We plan on a stator cast from vinyl ester resin with ATH filler to
      > > be
      > > able to dissipate about 3 watts per square inch of surface area over
      > > the coils, *in the wind.* (less when dyno testing).
      > >
      > > If your stator is getting so hot that complicated cooling systems or
      > > expensive epoxies are needed, you are wasting tremendous amounts of
      > > energy as heat, and should consider re-designing the alternator for a
      > > better match to the blades (more copper, lower resistance, more
      > > magnetic material)....or simply making the turbine furl earlier, as a
      > > quick stop-gap measure.
      > >
      >
      >
      > --
      >
      > Steve Spence
      > Renewable energy and self sufficiency
      > http://www.green-trust.org
      > http://arduinotronics.blogspot.com
      >
      >
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    • Dan Fink
      My answers are *starred* below. Dan Fink, co-author, Homebrew Wind Power Executive Director Buckville Energy Consulting Buckville Publications LLC NABCEP /
      Message 75 of 75 , Jun 2, 2011
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        My answers are *starred* below.

        Dan Fink,
        co-author, "Homebrew Wind Power"
        Executive Director
        Buckville Energy Consulting
        Buckville Publications LLC
        NABCEP / IREC accredited Continuing Education Providers
        970.672.4342 (voicemail)
        970.373.1311 (FAX)



        Posted by: "James Morris" james-morris@...
        james-morris@...
        Wed Jun 1, 2011 4:30 pm (PDT)


        Aluminum will have zero effect on the magnetic lines

        *That is correct

        and if well insulated, will have zero effect on the electrical properties.

        * Incorrect. The problem we are discussing is eddy current drag, and
        there is no way to block a magnetic field.

        I think Steve must have meant that a large aluminum plate would create
        wind drag. That would have little effect on a vertical axis wind
        turbine, but would be significant on a horizontal axis wind turbine.

        * Not really -- the outer 1/3 of the blades towards the tips provides
        most of the power in a wind turbine rotor. The inner part towards the
        root where the alternator lives is insignificant for power production,
        due to small swept area, slow speed, and mismatched angle of attack.

        As Steve speaks of furling, he is probably thinking of a horizontal
        axis. But axial flux generators are not really suitable for horizontal
        axis wind turbines for that very reason. They have an unusually large
        diameter. Standard generator configurations are more suitable for
        horizontal axis wind turbines, but they are more difficult to build in
        a home shop.

        * See above. Alternator diameter is not an issue unless it is extreme,
        and the use of strong magnets keeps the diameter relatively small. An
        example of a commercial machine with a large alternator diameter would
        be the Proven.

        --
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