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Forum Index : Windmills : De cogging

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kiwitramper

Newbie

Joined: 25/02/2009
Location: New Zealand
Posts: 2

Posted: 04:14am 25 Feb 2009

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I'm just new at this and am making a F & P generator here in New Zealand the home of Fisher and Paykel. I was wondering if having a dual generator setup with the stators offset half a pole would prevent or reduce cogging? Does anyone have any experience?
Thanks

Outdoor Kiwi from new Zealand

RevUpWind

Regular Member

Joined: 03/05/2008
Location: Australia
Posts: 60

Posted: 09:32am 25 Feb 2009

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Hi Kiwitramper
We have two dual F&P's and when putting the second rotor on keep rotating it until we find the spot with least cogging. Once you find this spot you can mark this spot and hopefully get it next time.

This does work and also twisting the coils up to ten degrees to I believe line up N/S relationship. Have not done this and requires to make a special tool. There is quite a bit of info on this forum re doing this.

On another note with 2.4m mill have never had any problem starting in low winds without any decogging at all. Most fine tuning for us has been getting blade shape, rpm and phasing on rotor correct in relation to moderate to high winds where of course most power is made. In light winds 2-3amps with one mill and with two going 4-6amps but in high winds with two mills 40+amps and getting better.

There is heaps of brilliant info here so just keep looking am sure you will find some answers to get you going.
PeterEdited by RevUpWind 2009-02-26

....River Heads - Australia
The wind blows wherever it wishes; you hear the sound it makes, but you do not know where it comes from or where it is going.

Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5119

Posted: 10:10pm 25 Feb 2009

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I had a dual stator windmill with a 6 blade 2.6 meter diameter turbine, with standard non-de-cogged F&P's. As RevUpWind suggests, it would start easily in light winds. So for anything over say 3 blades 2.2 meters I wouldn't worry about decogging, or at least for startup reasons. Decogging is still useful to reduce noise and vibration.

On a earlier dual stator design I did try to offset the stators, but could never find the sweet spot.

Glenn

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

kiwitramper

Newbie

Joined: 25/02/2009
Location: New Zealand
Posts: 2

Posted: 03:17am 26 Feb 2009

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Thanks Guys, that's so encouraging. I'm planning a dual setup with a 3-blade PVC at 2.4 metres so am trusting startup in light winds should be OK. I am however concerned at noise levels as the only place on my city property to attache is on a 6m pole attached to the highest point on my 2-story house. I'm going to fill the poile with sand which should absorb a lot of vibration and therefore noise, and then experiment with padding to see if that helps as well.

Outdoor Kiwi from new Zealand

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