# Windmill

Discussion in 'The Projects Forum' started by zor, Apr 21, 2011.

1. ### zor Thread Starter New Member

Apr 21, 2011
1
0
Hi I am constructing a PMG VAWT(Vertical Axis Wind Turbine) and I need help with the circuitry to control it. It is a 3 phase PMG. I am testing the VAWT this summer to determine RPM's/Minute/MPH wind. After that I will design the coils. But I need help with the following.

1.How do I calculate the RPM's in a "loaded" PMG based on the RPM's in an "unloaded" PMG. Put in another way. The coil design will be based on the RPM, and Gauss force field from the magnets, But I am guessing the RPM for a given windspeed will be lower once the PMG is connected........and thus the coil calculation is no longer valid.

2.Can anybody guide me to a diagram that takes the following in to account.

-Cut in speed
-Overspeed protection
-Stopping the VAWT....electronic brake
-Cut out speed
-Rectifying

The whole thing will charge 12V batteries, so I need an output of about 13.4VDC.

I know this is a tall order, so thank you in advance.

2. ### wayneh Expert

Sep 9, 2010
12,391
3,246
Modeling windmills and alternators is very difficult, and when you put the two together, it's even tougher. So optimizing a design from end to end "on paper" is almost impossible without a lot of data on closely related devices. It's great that you're planning to collect such data.

One thing that might help you to know is that the "drag" induced by extracting power will be done efficiently. I mean that the PMG will add very little drag on its own - only when power is being withdrawn will there be energy pulled out of the turbine.

But for your VAWT, you're going to need to know its power curve (power-generating capacity versus operating rpm) at every windspeed. The rotation speed when unloaded is interesting, but not all that you need. This will allow you to optimize output under any conditions.

On the upside, once you get 3-phase AC from your generator, the rest is easy. Or easier, anyway. You'll still have the basic problem of all wind turbines, that voltage varies over such a wide range.

3. ### russpatterson Member

Feb 1, 2010
351
16
I don't have any experience with wind turbines although it's very interesting. I did see an article a while back in Nuts and Volts that has some information that'd probably be interesting to you. http://nutsvolts.texterity.com/nutsvolts/201001?pg=46&search_term=3 phase wind#pg46

Would adding a DC/DC buck converter between the output of your turbine and the battery be an effective way to get the power into your battery efficiently? Given the wide voltage swing? I'm building one for a solar system to do the maximum power point tracking trick. That might apply here too. Let me know if you want more info on that.

4. ### THE_RB AAC Fanatic!

Feb 11, 2008
5,435
1,305
I second that. Use a buck converter and control the PWM duty with a MPPT brain, so it gives the best power output into your batteries at all wind speeds.

That will also let you use the F&P 3-phase motor(generator) with the existing windings so you don't need to re-wind it to produce a lower voltage output.