alt.energy.homepower

On Fri, 21 Sep 2007 15:55:27 +1000, Jordan wrote:

>Neon John wrote:
> > I STILL
>> don't know how large the mill is to be or how much power it will harvest.
>
>>
>The artist wants four flat radial squarish vanes, each approx 3ft x 3ft.
>There's an electronics guy who's in on the project, and he can make a
>speed sensor. This could trigger a circuit that crowbars a PM
>motor/generator, to cause it to (almost) stop when it reaches a fixed
>maximum speed. This is Plan B, if A doesn't work - the eddy current brake.

As I mentioned before, no speed sensor is necessary. The PM motor's output is
directly proportional to speed. Simply trigger the crowbar on voltage.

An eddy current brake will work if you have a good source of rare earth magnets. An
eddy current brake is fairly linear so it'll take some work to get the slope of the
absorption curve just right to let the thing spin but not over-speed.

John
--
John De Armond
See my website for my current email address

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