Turbine output voltage

[Ethan Brush]

I am planning to purchase a whisper 200 high voltage turbine and am wondering if anyone knows what the typical/actual voltage ouput is for a 220 volt turbine from cut in speed up to fulll speed. Ultimately what I am looking for is what turns ratio is will need for my stepdown transformer. Southwest has a stepdown transformer, but I believe they dont offer it in 12v, just 24,36, and 48. Also they are very expensive- over a $1,000, and I can do it for around $200 (assuming its not a wacky custom ratio). Thanks all in advance.

[Rob Beckers]

Hi Ethan,

This may be somewhat obvious, so you probably already tried: Did you ask Southwest? Doesn't look like this would be a state secret, so they may just tell you.

-Rob-

[Ethan Brush]

Rob,

I Actaully have been trying to ask southwest but their tech support people are hard to get a hold of and dont return my calls, and my work schedule compounds things - just thought someone might know right off the top of their head. Fortunatly I have a good excuse for not buying their transformer and needing the info: they dont make a 12 volt one! I am guessing that the reduction ratio needs to be within a very small range - if the voltage is too low the cut in speed will be too high and if the voltage is too high, thats less current. I find it strange that mppt is not used for wind turbines. Do any of the major wind controllers do any voltage/current conversions for more efficient charging?
Ethan

[Rob Beckers]

I'm still trying to wrap my head around using an alternator as a current source (for a regular, non-MPPT, charger). As you say, too low a voltage out of the transformer would mean too high a cut-in speed. I would think though that too high a voltage will actually mean too much current going into the batteries and a burned-out alternator. So, yes, getting the transformer right would seem to be a very fundamental issue for this type of charge controller.

As to MPPT, there does indeed seem to be a profound shortage of MPPT chargers. See Logan's post about MidnightSolar coming out with one, that will be a very good thing. MPPT is used for small wind turbines, many use MPPT inverters. The Scirocco uses the Power-One (ne Magnetek) Aurora inverter, then there's SMA's Windy Boy. Those are all MPPT.

-Rob-

[Ethan Brush]

Rob,

I finally talked to southwest and they said that a third party makes their transformers and they dont have any specs on them. He also said that the olny meaningful voltage would be under load anyway because the open circuit voltage can be many times higher than the loaded voltage. So since the batteries hold down the voltage to around their nominal voltage, it seems that my step down ration might not be that important after all. But still, I wonder what happens if you have a significantly higher voltage, i.e. say you hooked a 24 v nominal turbine to a 12v battery bank? I assume it would just be very inefficient becasue the turbine cant but out all the current that voltage is trying to push in the batteries? Maybe the blades wouldnt even spin? Solar converters has a mppt controller that they say can be used on wind turbines, but I wonder if they have tested it in action.


Ethan

[Rob Beckers]

Jeez... SouthWest claims they don't know the specs on the transformers that they include in their charge controller? That's a tall one to believe...

Using a transformer that has too small a ratio (so the voltage on the battery side ends up 'high' if it weren't for the batteries pulling it down) would in the extreme act as a turbine brake I think, more likely it will overload the alternator and burn it out. I really don't know how sensitive this is, so maybe there's a wide range of ratios that will do just about as well, maybe not. Send a PM to Matt Tritt, he's the local wind expert here (and let us know what he has to say about it).

Using solar MPPT controllers will IMO not work. My understanding of how they work is that they dynamically do best power-point tracking on the panel's U/I curve. For wind you can't do power-point tracking that way, the MPPT controllers I know for wind all use a lookup table, so they need to be programmed with the turbine's curve. These use either frequency/power or Voltage/current curves. You can read my thread about wind charge controllers, there's quite a bit in there on available controllers.

-Rob-