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wind friend

Newbie

Joined: 01/05/2007
Location: Australia
Posts: 39

Posted: 02:57am 03 Jul 2009

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Melbourne in Australia a windy place at the moment. Running a 300mm axial flux alternator with 2400 mm blades. Best Ive seen from it was 280w at 12 v nominal. Curiously put the same machine over 24 v, apart from the cutin speed doubling to 120 rpm ish, it made 410 w! there is a 1 ohm resistor in series with the batteries.

The limiting factor would seem to be the current. A function of the wire size? Perhaps this indicates that the machine is almost always in a stall condition. Would it be better to add more resistance or open up the air gap. What should the cutin speed be for 12v please.

Thanks

Hans

GWatPE

Senior Member

Joined: 01/09/2006
Location: Australia
Posts: 2127

Posted: 08:00am 04 Jul 2009

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Hi Hans,

My 2m AxFx has made up to 500W into 24V battery bank. Sustained current will test the wiring. Sounds like stall limiting is in action.

Gordon.

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Janne
Senior Member

Joined: 20/06/2008
Location: Finland
Posts: 121

Posted: 08:34am 04 Jul 2009

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I tend to agree with Gordon. I think it would still benefit from a faster cut-in speed, 120rpm is in the low side for a 2.4m rotor.

Of course it also depends on the blades you have, so you'll be the only one that knows the best.

If at first you don't succeed, try again.

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windlight
Guru

Joined: 03/03/2007
Location: Australia
Posts: 331

Posted: 12:12am 07 Jul 2009

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Hans you don't say if it's a duel magnetic rotor or single, but from my experience the cut in speed is way too low, so opening the air gap is the best option. It will increase the cut in speed and shift the maximum power output to higher speed (wind) bands.

Blades are complex things, if you watch a turbine in complying winds you will see it start then as it accelerates the rate of acceleration rises rapidly, like a hyperbolic curve, for my money trying to get much out of a turbine until your blades are at that rapid acceleration point is stalling.

My duel rotor 3m blades cuts in @ 200 rpm into a 24V system, voltage is only relevant to how the coils were wound. If you can readily lower the turbine then open the air gap.

allan

"I like this place and willingly could waste my time in it" - (Act II, Scene IV).

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