Mini Wind gen question

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Posted by Max Schulte on August 10, 2009, 08:09:05 PM

I have a small Wind turbine that can take 2 to 6 blades. My question is for safety reasons if I switched to 2 blade would that undue strain on the center hub? I understand the principals of wind generating and I have posted here before. I am worried come the winter time that the winds would destroy this turbine. My thoughts are that with 2 blades I will increase its turn on speed but also its self destruct speed. This is a unregulated non-braking turbine. I can side furl the tail but manually. Or should I go 2 blade and 10 degrees of furl? Let me know.

Posted by Ken Hall on August 11, 2009, 10:59:20 AM

Re: Mini Wind gen question (Reply #1)

Max

I wish you had posted the make and model of the turbine.
Is it really designed for 2-6 blades, or is it a 6 bladed machine and you are thinking of removing four ?

Removing the 4 blades will increase the loading on the remaining 2 blades. If not designed for it, a failure at the blade root/hub would be likely.
I am not sure that you would be getting an increase in self destruct speed. You could actually be lowering it.

You will be lowering the output across all wind speeds.

Without any specific info, I would say leave the base design alone and concentrate on adding a furling and/or braking mechanism. Can it tolerate a shorting switch ? Or consider a tilt up tower and lower the turbine when high winds are forecast.

Ken

Posted by Max Schulte on August 13, 2009, 09:56:40 PM

Re: Mini Wind gen question (Reply #2)

Well dare I say I got it off E-bay. I wont say a homemade unit but its not a mass produced unit. The hub is drilled to accept 6 blades but it is shipped with 3. I also had thought that the load on half the hub would probably split it in half. There is no way to put a brake on it and you have to manual furl the tail. If I added 3 more blades would I be asking for problems on the top end.

Posted by Jon C on August 13, 2009, 10:42:48 PM

Re: Mini Wind gen question (Reply #3)

Hi Max S. Automatic furling is not terribly complicated and perhaps you could make your own furling mount. Some of the basics of furling are shown on this link: http://greenterrafirma.com/wind-turbine-furling.html
To prevent overspin and self destruction in high winds, you could use a simple controller that employs back EMF for braking.......the controller simply senses an overvoltage condition and switches the output of the turbine into a resistive dump load. The turbine then works into a high current load that opposes rotation by using the counter electromotive force produced by its own windings. The southwest wind power controllers do this (example...the whisper 200 controller) and provide a "stop" switch that does the same thing manually in the case of a forecast gale force wind condition. Best of luck to you. :-) Jon C.

Posted by David Day on August 27, 2009, 07:45:31 AM

Re: Mini Wind gen question (Reply #4)

Max, would the wind turbine in question come from USA WindGen? I purchased the ~300 watt model and have had good success with it, when the wind blows! We had a pretty good wind storm a month ago and I lost a blade and until I could make another blade, I took off the damaged blade plus a good one, leaving only 4 blades. The claim is that it will run with 2 or 4 but 6 seems to give the best overall performance. I am new to this RE thing also. Good luck.
David

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