Voltage/Power question

[cris74nd]

My question is regarding a variable speed, permanent magnet wind generator.  Please correct me if I'm wrong... If you design the generator to produce usable power (high-enough voltage) at low wind speeds such as 5-7 MPH, then at the higher wind speeds (20 mph +)the machine runs very inefficiently.  To operate at the higher speeds, then you could either split the windings up to run some poles in parallel, or you could add some sort of resistence to keep the amperage low enough for the generator to keep running.  Is it possible as another option to lower the source voltage (coil voltage) by widening the magnet gap (weakening the flux) on-the-fly?  I envision this being one of those mechanical engineering marvels, but wouldn't the machine run at maximum efficiency throughout a wide range of wind and rotor speeds if you could vary the coil voltage with the changing wind/rotor speeds?  Maybe this has been done before, but can anyone tell me if this is a good thought, or where it's been tried before with a permanent magnet generator?  Your help, as always, is greatly appreciated!!

CRIS

[commanda]

You'll probably gain a lot of insight if you read this thread.

http://www.fieldlines.com/story/2006/3/17/185646/194

Amanda

[SparWeb]

Cris,

You're basically correct.  There has been a lot of discussion on these topics on this board and some searching will produce a lot of answers to your question.  Using Google's advanced search and limiting the "site" field to this URL works best for me.

The term "Efficiency", however, isn't very important when your source of energy is FREE.  This is an important point to take away from Flux's text in "Matching the Load".  More important is safety, either protection from overspeeding blades, overcurrents in wires, overcharging batteries, or overheating the stator.  These requirements box you in, and the only way out is $$.  Mechanical complexity, like the variable gap you mentioned, or variable pitch, on the other hand, can help, but there is always a cost.