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Forum Index : Windmills : Linear output of F&P Generator

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Randysworkshop
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Joined: 25/10/2006
Location: United States
Posts: 10

Posted: 02:38pm 29 Mar 2012

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As most windmill buffs are aware the power of the wind goes up as a cube of the wind speed, yet most generator outputs are linear. So you are trying to match a line with a curve. You try to design your blade so that the size and pitch gives you speed and power. The output of the F&P motor as a generator is very linear at about 0.9 watts per RPM. So as the speed goes up we need a larger blade for the increased power, however a larger blade spins slower. We normally re-wire the coils to reduce the voltage thus increasing the amperage. The newer model has 36 coils. If we keep it three phase, (recommended) we have twelve coils to work with. Changing the grouping we use with a single 3 phase bridge rectifier just changes the voltage angle of that straight line output. My thought is to split the coils into two sets of two, one set of three and one set of five which would require the use three bridge rectifiers. Attached is a picture of the wiring. I have not tried this yet, but it should change the output from a line to a curve. The next challenge would be to match a blade to it.

randy burmeister

Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5110

Posted: 10:46pm 29 Mar 2012

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Hi Randy

Great minds think alike

I played around with this idea a few years ago, and built a dual stator machine with 4 stages. I called them staggered stators. You can read about it here http://www.thebackshed.com/windmill/articles/StaggeredStator s.asp, that page also includes a couple of forum links. It was based on the 42 pole stators.

It was the last F&P windmill I built before selling my pace, and I still have it, so will put it up at my new place in a few months.

I feel it works very well, and is worth investing more time into, especially with the 36 pole stators that are becoming more popular.

Glernn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

Rastus

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Joined: 29/10/2010
Location: Australia
Posts: 301

Posted: 12:11pm 01 Apr 2012

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Hi Guy's,
Matching the mill to the available wind with staggered stators seems the ultimate for a 42 pole or a 36.Is the real improvement of a 36 pole the neutral cogging?Cheers Rastus

see Rastus graduate advise generously

yahoo2

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Joined: 05/04/2011
Location: Australia
Posts: 1166

Posted: 10:40pm 02 Apr 2012

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Randy,
I am wondering what is the relationship between input power and output power with the F & P. I have always assumed it is not linear and increases with RPM.

I guess there has been some input torque testing done that has been posted on the net. I might have a look later.

yahoo

I'm confused, no wait... maybe I'm not...

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