Generator

Winding the coils and making the stator

Generator

Postby bramar on Thu Mar 20, 2008 11:54 am

Hello to all,

I want to construct a wind power generator. I looked all over the Internet and saw that there is a lot of stuff, but, only on this site I found something about home made generators. This is the Stator that I want to build
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http://windpower.org.za/stator03/index.html
I saw that there are pictures, but I need measurements. Or, can you give me some informations about making a home made generator, how much coils, how much magnets, polarity of magnets, wiring and so on. I already make blades and tried with a car alternator, but had success only with lots of wind (charged battery successfully). I need a generator that will charge a battery (12V 75Ah) on low RPM-s. Can someone help me???

Thanks...

bramar
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Re: Generator

Postby windgat on Thu Mar 20, 2008 3:54 pm

Hello Bramar. You are on the right track - RPM is a problem when using alternators. I suggest you use 9 coils and 12 magnets per rotor. Size the coils to fit the magnet size. Draw the magnet spacing on tracing paper, and sketch the coils, then rotate the tracing paper to see where the best place for the coils are. The aim is to make all the Norths pass over the down legs of the coils at the same time, while the Souths are passing over the up legs.
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Re: Generator

Postby Bahati on Sat Mar 22, 2008 3:54 pm

is it possible to wind also 9coils on the two sides of the stator and get power on each side?because there are 12magnets on each rotor.At witch speed m/s or km/h of the wind your windpower start to generate power?What is the limit speed?If there is overspeed of the wind ,how your system can stop to prevent damage of generator?
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Re: Generator

Postby windgat on Sun Mar 23, 2008 9:01 am

Hi Bahati. I don't quite understand the 'two sides of the stator' thing. The coils are embedded in the stator, with the rotors on either side. The cut in speed depends on the number of windings in each coil, the number of coils per phase, the strength of the magnets, and the voltage of the battery bank. Oh, and also the TSR of the blades and blade radius (this is Tip Speed Ratio - the speed of the tip of the blades relative to the wind speed). Cut in happens when the generated voltage exceeds the battery voltage - see the 'bench testing' page of the website for more details.

Limit speed depends also on the TSR - the blades will stall at some point, limiting the speed. I also use a small offset (the generator is mounted slightly to one side of the pole), so that in very strong winds the generator will yaw out of the wind (this is allowed by the free swinging vane). I also use a dump load control circuit (see the 'electrics' page), which limits the voltage coming out of the generator, which has the effect of limiting the speed - I will make this circuit available to others soon.
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Re: Generator

Postby bramar on Mon Mar 24, 2008 10:43 am

windgat wrote:Hello Bramar. You are on the right track - RPM is a problem when using alternators. I suggest you use 9 coils and 12 magnets per rotor. Size the coils to fit the magnet size. Draw the magnet spacing on tracing paper, and sketch the coils, then rotate the tracing paper to see where the best place for the coils are. The aim is to make all the Norths pass over the down legs of the coils at the same time, while the Souths are passing over the up legs.


Hello Windgat,

Thank you for your reply. I have to buy a magnets. Tell me, is it OK to buy NdFeB Permanent Magnets or can buy weaker magnets??? Is 3 x 1,5cm Rectangle OK for magnet size??? If it is OK, then I will make coils to fit that magnet size. Just give me a little clue about measurements, and I will see with a magnet supplier does it have that measurements. :D That's 3 phase generator. I need DC from it. I think that this is OK for connecting coils together:

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http://www.windstuffnow.com/main/3_phase_basics.htm


Hope to hear you soon... :) Best regards...

bramar
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Re: Generator

Postby Bahati on Mon Mar 24, 2008 11:57 am

think you for your reply, THE TWO SIDES OF THE STATOR it means THE TWO FACES Aand B of the rotor
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Re: Generator

Postby windgat on Tue Mar 25, 2008 8:05 am

Hello Bramar. Weaker magnets will produce less power - unless you use more of them and more copper wire in the coils. Try and get the 'lifting force' of the magnets you are considering, and then you will be able to see the relative strength. Some people have used magnets from microwave ovens which are quite strong, but apparently they are disappointing compared to the rare earth magnets. 3 x 1.5 cm is about right for a small generator - what thickness? I use 2 x 5cm x 8mm, or 2.5 x 5 x 1.2 cm.

For DC from 3 phase get two bridge rectifiers, and use one and a half of them - that page you gave describes it well, although I recommend star not delta.
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Re: Generator

Postby windgat on Tue Mar 25, 2008 8:12 am

Hello Bahati. I am still confused! In my design the stator is in between the rotors. There is one set of coils, inside the stator, which is acted on at the same time by the magnets on each rotor, which face towards the stator... :?
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Re: Generator

Postby bramar on Tue Mar 25, 2008 11:13 am

Hello windgat,

I just received prices for magnets and have to tell you that they are not cheap. :) I have to pay 7.89 EUR for 40 x 20 x 5mm magnet. That will be 189.36 EUR for 24 peaces. A little too expensive for people here in Serbia. OK. I need windmill only for charging Car Accumulator. Will 30 x 10 x 5 mm magnets do the job. If that is OK, I will by them. Maybe thin wire with more turns per coil will do the job (I forgot that. It was long ago when I study that in school :D ). I will have to calculate that somehow. :D
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Re: Generator

Postby Bahati on Tue Mar 25, 2008 12:07 pm

ok i understand like coils are one set,other preoccupations are :-can i work whith 5 or 8mm thick wooden stator?and 2mm thick steel plates as rotors. What can be the result.To me is difficult to get mild steel and magnets, in witch way you can help some one to obten materials from South-Africa to Democratic Republic of Congo/East.Please i need your help,think you my teacher.
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Re: Generator

Postby windgat on Tue Mar 25, 2008 12:09 pm

The magnets are certainly the most expensive part of the whole thing! :cry:

Try here for maybe better prices: Applied magnets

30x10x5mm seems small. All depends how many watts you need... Thinner wire helps, but remember that then the current is limited - before it melts the thin wires!
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Re: Generator

Postby bramar on Tue Mar 25, 2008 1:05 pm

Thanks for the link. They really are much, much cheaper... Just to see if they will send magnets to Serbia (I see that there are Serbia in the list of countries, but, that doesn't mean anything :D). The size is 5 cm x 1.2 cm x 6 mm. The size is almost like the one that you are using. 24 magnets, are 30.48$ (that's about 20 EUR, and that is very cheap). And, what kind of plate do I need for rotor and stator. I think that will be the easiest thing to get (if it is steel, I have a steel factory in my city). :)
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Re: Generator

Postby windgat on Tue Mar 25, 2008 1:36 pm

Good you found something cheaper!

For the rotor steel is good - mild steel. It needs to be flat, so if that is a problem you may need to go for tool steel, but that can be expensive.
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Re: Generator

Postby windgat on Tue Mar 25, 2008 1:46 pm

Oh, Bahati, maybe you could look at the new 3d (VRML) model on the website at http://windpower.org.za/drawings/drawings.html
or here are some exploded views: http://windpower.org.za/windpower/kit/kit.html

That should make it clear what I mean...
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Re: Generator

Postby Bahati on Fri May 16, 2008 12:33 pm

Hi, Peter. I need the mesuarings of your steel winding machine ,that will help me to build one and so make coils ,see i attached photos of that machine on forum@ windpower.org.za and info@windpower.org.za , i wait for your answer, thanks for sharing the project.
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Re: Generator

Postby windgat on Sun Jun 01, 2008 2:03 pm

Hi Bahati. Did you get the measurements I emailed you? How are the coils looking?
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