Those certainly are the main causes of stall in windmills. I don't mean to complicate this any more, but it seems to me that some , at times, also refer to the aeronautical aspect of the blades themselves "stalling" in low rpm rotation because the airfoil shape (curved backside)of the blades cannot get to the point of acheiving 'Lift', because of being 'held back' from picking up enough rpm from the reasons just described from everyone's answers.
This might be really saying the same thing. I am still learning myself on this, but is it possible, in a rare occurance, that stall could also be caused by the blades themselves, apart from the stator or line resistance?? Perhaps someone who knows could comment?
-Woof: You might consider putting this thread in the FAQ section for windmills in general because it is good??.
I had never thought anyone would consider it to be anything else. There is nothing in an alternator, line resistance or anything else that causes the phenomena.
The only reason why alternators and line resistance come into this is that they determine the blade input power and that decides the tip speed ratio of the blade. When the tip speed ratio falls well below the ideal the angle of attack becomes too great and the blade stalls.
All you are doing is trading electrical efficiency to keep the blade efficiency high enough to avoid serious stall. Unless you devise a loading that keeps the blade rotational speed in step with wind speed you are changing the tsr.
Flux[ Parent ]
"The tsr falls very rapidly with load and you will soon come on to the peak of the power curve. As you load more you fall below optimum and if you get things right you should just be approaching stall at the time you need to furl to protect the alternator."
I guess it is over my head and you probly dont begin to understand it completely until you get in to buiding motors. Thanks alot. [ Parent ]
Another way to reduce or eliminate the stall issue is to increase the air gap in the alternator. In that case the slope remains the same and the entire alternator curve moves to the right. In that case you could potentially eliminate stall, but you would probably like the alternator curve to just touch the turbine curve at the point of furling. To my eye (I happen to have this case graphed) cut-in would then be at 15 mph and furling at 24 mph. Maximum power looks to be about 500 watts. You do, of course, lose all power generation for wind speeds below 15 mph. So, you pay another kind of price.GeoM[ Parent ]
