O.T. Stepper motors for Wind Turbine

[gerryv]

During a Google search, I came across several references to using stepper motors to make home scale wind turbines. Apparently, they are much better suited and more efficient than "trying" to use automobile alternators. It struck me that some folks here may have an extra stepper or two sitting around and the 'bot is just the machine to carve out the prop. Maybe someone here already has a prop cutting file to share. Unfortunately, I've no expertise in this area but just thought it might be of interest to some of the tinkerers (best people in the world;)) who may be wanting to cut their power bill a bit, especially in these trying times.

[dana_swift]

Gerald- I am specifically interested in your results. I would think a stepper with a permanent magnet rotor might work well indeed. I downloaded some airfoil models with the intention of building a pair of wind turbines, but have not gotten around to that yet. Cutting airfoils was the primary reason for buying the indexer for my bot. That day will get here... D

[myxpykalix]

Gerald,
I'm not an expert on this stuff however i have gotten more into solar alternatives lately having built my own solar hot air heater which works great.

As far as using a stepper motor on a wind turbine, i would disagree with dana for this reason. I believe that the stepper motors are geared for lower speeds and higher torque and I think you want something that will spin faster like an alternator which will operate slow or fast and not be geared.
But he may have some more technical insight on the mechanics of the steppers then me.:eek::confused:

[gerryv]

Based on what I read (not what I know) that is typically the case except for Steppers Jack. Apparently, spinning fast can actually cause over voltage. This would necessitate at least a simple voltage regulator I imagine. The discussions I read explain it better than I can unfortunately but I think a bit of searching beginning with google and Yahoo would enlighten far more than I could hope to. Unfortunately, where I live, our wind conditions are very poor otherwise I'd be doing it.

[gerryv]

Jack, here is one of the brief articles that make reference to the low RPM benefit. I'm afraid I don't speak electric though :-)
http://www.reuk.co.uk/Electricity-with-Stepper-Motors.htm

[srwtlc]

I don't know much about the subject, but I've seen a number of articles or "How-to's" where they use treadmill motors.

[CNYDWW]

I've done some research on the subject before. For the tinkerers, i always liked the vertical turbines. Less mechanical mess trying to get the damn thing pointed in the right direction. Some have used pvc or other pipe split in half setup on a frame.

http://www.youtube.com/watch?v=Vojd9VQtvLA

[dana_swift]

Gerald: Ignore the following if you dont want the electrical engineering perspective.

The voltage rating of a stepper motor is almost meaningless when it comes to using it as a generator. That rating is for when the motor is receiving electrical power and outputting torque. It is based on the ability of the windings to dissipate heat at its rated load.

When a motor is used "backwards", receiving torque and outputting electrical power, the "unloaded" voltage should be much higher than the rated voltage. What will be constant is its tolerance for handling power. If the motor can dissipate 10 watts as a motor, it can dissipate 10 watts as a generator.

The open-terminal voltage of any permanent magnet generator varies with RPM, just as does its short circuit current. Somewhere in the middle of those two limits is its maximum power point. Ideally you set up the load to regulate itself to keep the source at its maximum power point. Not easy to do tho.

You can get wind based battery chargers that allow you to set the voltage for the maximum power point, so they get as much energy as possible at any given time. That is probably the easiest way to go if you cant design a custom regulator yourself for some other kind of load.

The day will come when I will build one or two myself.

Keep us posted-

D

[gerryv]

Thanks much Dana and I appreciate your putting it in plain english - a lot easier to grasp for guys like me :-) Just on my way out the door so I have some bedtime reading. - Gerry

[myxpykalix]

"As far as using a stepper motor on a wind turbine, i would disagree with dana for this reason"

I didn't say I was right....:)

"But he may have some more technical insight on the mechanics of the steppers then me"

He obviously does....:eek: being an electrical engineer

This is what i like about this group. You're not just getting woodworkers. You get engineers, woodworkers, electricians and all varied backgrounds that bring something to the table. You learn something new here everyday!:D
Am i going nuts with the emoticons?:confused: