Hugh Piggott's blog

I got an email question today and it seems important enough to answer with a new post.  Here is the question “How many amp of 14,15,17,18 and 20 awg wire for wind turbine. Can you give me any chart? Please!!!!! ”

If you are winding a stator according to my style – about 13mm thick coils with some glass cloth on the faces and plenty of wind blowing past it – then my rule of thumb is about 6A RMS current per sqmm of wire cross section. If the stator is star/wye connected, with a single wire in hand and all coils in series then the DC output will be about 22% higher than the RMS AC current.

The relationship between AC current in each phase and the DC output of the rectifier depends on the waveform. But the simplest way to think of it is to say that each wire carries the full DC current for 2/3 of the time, and is resting for 1/3 of the time. The result is that the rms AC current in each wire is root(2/3) = 0.82 times the DC current. In reality the wires share current some of the time, so the % is very slightly lower in relation to the DC.  But this 0.82 is the worst case, and it is very close to the reality usually.
So maximum DC current should be about 1.22 x maximum allowed AC current as in the table.

So here is my answer:

It’s OK if the current surges way above this value in a gust, but this is the maximum sustained current I would design for, as a safe target. Your furling tail should prevent the machine from kicking out more than this on a continuous basis. If output is higher then make the tail lighter to reduce amps.

I used to teach blade design.  I went to Wales to learn (more) about windpower on a course (in about 1989), but the guys there made me teach the session on blade design.  They just announced that I would do that class and sat down. That was scary.

I kept on going back down there and helping with the courses for years, and so ten years or so later my blade design lecture got to be recorded in a PDF (which was a pretty novel thing at the time).  You can find this PDF on my old website here.

Today I found out that the notes have been translated into Russian.  That’s cool 🙂  I love the Russian language although I have not tried to understand it since I was at school.  I am glad nobody is asking me to teach blade design in Russian(!), but if they did I would at least have the notes to make a powerpoint for the class.

(ERNI e.V., www.erni-kollektiv.org) together with the VHS Braunschweig conduct a 5-day-workshop for a 2F HP Turbine from 14th to 15th May in Braunschweig, Germany.

Application is available here: https://www.vhs-braunschweig.de/die-vhs-braunschweig/kurssuche/kurs/Workshop-zum-Bau-einer-Kleinstwindkraftanlage/nr/BMUB01/bereich/details/

Costs: 70€ for all 5 days

Information flier here

hello again from Wyoming.. The larger wind generator at 45 mph + winds is doing a whooping 150 to 200 amps.  24 volts battery bank.

Maybe would do more, but tail cuts out of wind after 45 or 50 mph winds. 

The machine probably does 44 volts at a higher output. Battery bank voltage is 28.2. i guess the loss in the wire is the resistance.  

I used the same magnet as you used on your 8ft turbine, 1/2″ x 1 ” x 2″ . And used 40 copper coils, 20 inner coils and 20 outer coils. 17 gauge wire, 150 turns. Resin thickness 3/4″.  Inner coils are off set from outer coils, but magnets are in line so to make it smoother turning, and it was. Inner coils are together with 1 neutral ring. And outer coils are isolated from the inner coils with there own Neutral . It seems that the inner coils start to make power a little sooner than the outer coils. Same amount of magnates passing the coils on both inner and outer of the stater, but the inner coils are a little closer together than the outer  coils because of diameter. But the volt is not much different, maybe 2 volts. I guess the phase lag is different than the other. But is seems to work good. SO 20 coils are hooked to a neutral and the other 20 coils are hooked to a neutral . 40 WIRES are a lot to hook up to the 20,  10 amp rectifier that are on a aulimum heat sink. I wish i would have used bigger rectifiers but i thought i it was only going to make MAX 120 amps. i was wrong. it makes much more.But thank God that they hold up Ok. With a RPM meter, a little hand held one that i have with a lazer and a sticker you put on it. At 90 rpms it produced 24 volts. Blades seem to work well with the gen. At around 5 mph it is making around 4 or 5 amps. Sometimes it takes 6 mph wind to start the turbine, but sometimes much less like 3mph.

With that much power, i was concerned about heat produced, so designed it so air flow can get through coils for better cooling. 

In the middle of coils i used tapped wood block that was waxed, and screw to hold it in place. Then before i poured it, i put tape on top, so resin would not get in there, and leave a hold for more cooling on high out put. The small wood blocks must be tapped and waxed so they can be removed after screw is removed.