wind switch to control heat in slater

[pepa]

After watching 60+ mph wind gust trying to destroy my windmills, I started thinking about some way to protect them during the few times that wind this high hits in my area. I searched the board and found a lot of good ideas but none that would work the way I wanted mine to work. One of the first posts I remember reading here was by DanB about shorting out the windmill in high winds without damaging the generator. Several other posts talked about wind switches and wind flaps to activate different applications. I build a spring loaded flap that could be adjusted by turning a screw tapped into the spring lever so it could be adjusted to any wind speed that I chose to use. This unit depressed a contact switch that activated a solenoid switch to short out the generator until the wind slowed enough to release the flap. Standing in the back of my truck with the wife driving, I adjusted the tension on the spring until I had the unit switching on at two or three mph over my furling speed of 35mph. I used an ohms meter to show contact. I mounted the switch to a small pivoting tail on a 4x4 post 16' long and put the post up under my main windmill. I have only seen it work once while I was there to watch it, but it worked great the windmill would furl and then slow down enough to count the blades and then it would start up again. It worked like this for about twenty minutes and then went back to normal operation. I made two more for my other windmills. pepa

[harrie]

Hi pepa, Im wondering, how long your stator will hold up if your device shorts the coils out each time you want it to slow down, I think most of the guys try not to short the turbine out when it is at High RPMs, they wait until there is a lull between gusts because of torqe on the stator. but maybe you have a different kind of turbine that it wouldnt matter???. It would be great if we could do something like that tho.

[Flux]

I have to agree with Harrie that this may not be a benefit.

If you have a stiff enough machine to stop it with a short you may be ok, but you say it slowed to the point where you could count the blades, that may be a significant speed and you may be making more heat in the stator than if you left it alone. Unless you can stop it to a slow crawl under all wind conditions it may not be safe.

If your furling works there should be no problem but for peace of mind in the occasional high winds it may make sense to actually stop it if the alternator can do it. You would be better to latch your relay so that it stays stopped until you reset it.

Harrie also has a point about throwing the stop switch when there is an instant of low wind.

I once shorted a big alternator at part load on my test rig, the forces are frightening and the loading on the blades and stator mounts must be such that I can't see it being wise to do this repeatedly from high speed.

Air X does this, but it is a tiny machine with little inertia. I wouldn't be happy without lots of tests to make sure it is a long term solution.

Flux

[pepa]

thanks for the comments and suggestions,i am still learning and i love to tinker and work out problems with as much information as i can find. i have the switch adjusted to contact at the point of furl and when the blades are at their slowest rpm. by having the switch at a place where i can adjust it by watching the blades i an able to get it pretty close. here on the coast we dont get a lot of extremely high wind and this device will not be used often. i am also counting on the relay to fail, if the winds stay high for to long at one time, by having such a large short across it. this was intended to be used as a safety device for those times i am not around to watch it. would it be better to use the switch to dump instead of shorting? any help would be welcome, thanks pepa