Gage and Wrapping Question

[TuvaScott]

I too would like to start by congratulating Dave Brugge and Rex Ewing for getting the article about wind energy in Countryside. I look forward to getting countryside and it was a really pleasant surprise to see this article.

As my username indicates, my name is Scott and I work in Tuva. Actually I'm in the US right now, but I'm hoping to return to the Tuva Republic of Siberia in a month. In Tuva I do transformational development, aka sustainable development with an emphasis on community organization. The Tuva Republic as a whole has an energy crisis and during my stay in the States this past year, I've been experimenting with alternative energy which could be implemented sustainably in Tuva. Tuva's geography is much like that of Montana or the South Dakota Badlands and wind is a ready resource.

Having said all that, I have two follow up questions for Dave or Rex or whoever may know the answers to them. First: because of the multiple applications for wind energy, are there any graphs or diagrams that explain exactly what wire gage and how many wraps it takes in a coil to create X watts of power? I'm well acquainted with the construction of axial flux wind alternators having built one myself, but I'm not an electrician and my knowledge is limited in the specifics of coil construction and output. Second: has any progress been made on the "controller that will start out in a high-resistance mode and automatically switch to a low resistance mode." The star to delta configuration that Dave mentions in the article?

Almost all construction in Siberia utilizes heat convection from hot water run through radiators. This simple and sustainable yet real problem solving technology could be utilized in Siberia for great benefit. If anyone could help me out I'd be very grateful.

[wdyasq]

Scott,

I'll attempt give you an idea on the turn question.

The voltage is a factor of the flux density, the speed the magnetic field changes and the number of turns.

The flux density depends on the quality of magnets, the backing material and the distance between the magnets (which may be partially determined by the number of turns and wire size). So, there are three unknown variables there.

The speed of flux change depends on the actual speed of the rotor, which is dependent on wind speed and airfoil parameters (another bucket of worms), the number of magnets, the diameter of the rotor and the number and shape of the coils. That looks to me to be at least five more variables.

Which brings us to the last item - which depends on the first ~125 or more variables.

Fortunately, there are many mills now constructed that can be used as a starting point and many are documented here:

http://www.otherpower.com

Good luck,

Ron

[wooferhound]

When Building a new wind generator it is best to go ahead and build your magnet rotors and assemble the machine without the stator. Then spin up your magnets to the speed you want to operate at. Place "Test Coils" in between your magnet rotors and get your electrical readings. As soon as you make a coil that produces the voltage you are interested in for your design, then just duplicate the test coil that works to finish the machine. When completed you can be fairly confident of the total output of your new machine.

Generally

More turns equals more voltage and more resistance

Bigger wire equals more amps and less resistance

[Ungrounded Lightning Rod]

And within a coil a given cross-section of copper makes a particular amount of power and a particular percentage of resistive loss, regardless of whether it's a few turns of thick wire or many turns of thinner stuff.  Changing the number of turns while keeping the cross section constant just changes the tradeoff between voltage and current.

(Or at least to a VERY close approximation.  Really thick wire has slightly higher eddy current losses than thinner stuff.  So using thin pipe instead of wire so you can water-cool the stator isn't really all that practical.  B-)  )