Need Advice for Electrical and Alternator Theory

[bhatman]

Hi Folks... Although I am quite new to this website, but  I am overtly excited to complete my 10 ft machine. It has taken me a month to complete the blades and the mechanical part i.e. yaw bearing assembly and tower components etc. I have also completed casting of magnet rotor. But I m still at loss in understanding the alternator aspect. I have also "reverse enginneered" coil winding with 18 AWG coils for 150 turns (2 in a hand) with the help of details available on http://www.otherpower.com/otherpower_wind.html. I am planning to make a 24 V machine. Please help me in undertanding the concept of cut-in speed, voltage & current variation with blade speed etc.. etc.

Thanx

[finnsawyer]

Review some of Flux's recent comments.  I believe he had something to say about wire size and ten foot machines.  In any case he's the man to ask.  I know that what you are asking is covered on this site if you go back far enough.

[Flux]

If you are happy to copy the blades and mechanical features I really don't see why you can't just copy the winding details as well.

Cut in speed is the speed at which the rectified output of the alternator exceeds the battery voltage. Below that speed nothing will happen, above it you will charge the battery.

For most wind areas cut in is chosen to occur with winds about 7mph, there is little power in lighter winds.

Voltage is largely irrelevant, on open circuit, voltage is directly proportional to speed, but beyond cut in, voltage is dictated by the battery.

Current is dependent on the difference between the open circuit voltage and the battery voltage and the circuit resistance.

You can calculate the power you can expect from the alternator at a given speed if you know the open circuit voltage at a given speed and its resistance but it is not easy to relate that to wind speed as it then involves the propeller characteristics and you know very little about that.

You don't say what magnets you have used so it is not possible to say if your chosen winding is suitable.

Just pick the winding that Dan suggests you use for the size of magnets you have chosen and you will not go far wrong.

I know that Dan has changed the design of the 10ft machine to use bigger magnets over the years so you want to use the winding intended for your magnets.

If you can't find what you want on the Otherpower site then give details of your magnets and I will check your proposed figures.

Flux

[Flux]

I have just had a quick look at this and whatever magnets you used, your 150 turns is a long way out.

As yet I haven't gone back to look at what Dan has used, but even for the smaller 2 x 1 x 1/2 " magnets, 150 turns would be nearer 48v and probably slow for that.

Come back with your magnet details.

Flux

[Flux]

As far as I can find quickly, Dan used 2 in hand #14 with 33 turns for 12v.

For 24 V you could use 60 turns of #14 or two in hand  #17.

I am sure there is a lot more detail somewhere but I am no good at finding these things.

Your 150 turns is a long way out, but I seem to remember some machines using larger magnets and these would probably need even less turns.

I think that Dan said that the stock magnets are now N40 instead of N35 so a few turns less wouldn't hurt if you know what grade you have.

Flux

[Jerry]

Hi bhatman.

As Flux said, you've got more turns than the original design caslls for. This would make your machine work at much higher voltage and less amperage.

But don't through that stator away. If you have access to each coils leads you could try "Jerry Rigged" or what I now call Jerry phased.

I think the results would be great.

Just a thought. OK hit me guys.

                          JK TAS Jerry

[bhatman]

Hi Flux, firstly thanx a ton for such a detailed and prompt response. I am using N35 grade 2" x 1" and 1/2" magnets Qty-12 each on 12" dia rotors. I have made an alternator cast comprising 10 coils of size 18 AWG, each having 150 turns. I want my alternator to produce 5-phase AC by connecting coils in Star configuration. I have connected the starting point of all coils together and I plan to take the AC output from the finished tails and also using a rectifier for converting the AC to DC. I have uploaded a picture of mechanical portion of my wind turbine for you all to see. I shall also be uploading some more pictures of my project very soon.

[Flux]

I assumed that you were using 3 phase.

Those turns will be ok with parallel 5 phase. Sorry for the confusion.

Keep up the good work.

Flux

[bhatman]

Hi Folks, I have finally casted the stator with 10 coils and both the magnet rotors are also ready for assembly. What would be the correct gaps between the stator and rotors.

Thanx