Jensen Genny

[tajim]

In my last post I was trying to decide on a coil design. I decided to proceed with the full coil retainer that captured the coils fully, instead of the bobbin design. In the last week I made two of these out of phenolic material, one for each side of the stator plate. I'm using 18 guage wire with a 200 C rating. Using the formula developed by Edwindstuffnow, and calculating based on a star configuration 50 turns required per coil. Of course there are two coils, one on each side so it's actually 25 per coil per side. I developed a fixture in the lathe so that I could turn both coils at the same time. There is a spacer plate in between simulating the stator plate on the fixture.

After making the coils and mounting it to the plate it was time to assemble the rotors. That was a very scary experience, not knowing what to expect with a plate full of neo's!

Luckly, I had four 1/2-20 jack screws that made the instillation a breeze.

I wanted to find out if the 50 turns per coil was enough for my targeted rpm range. I had to use the available rpm's of the lathe to do my testing.

Here are the results so far.

110. rpm - 0.6 volts x 18 = 10.8 volts
     
155. rpm - 0.9 volts x 18 = 16.2 volts
     
260. rpm - 1.6 volts x 18 = 28.8 volts
     
520. rpm - 3.5 volts x 18 = 63.0 volts
     
     

Based on 18 coils it looks like I will hit my 12 volt charging range at approximately 130 rpm.I hpe this is the way to calculate this? I actually was shooting for 150 rpm so not bad for a first try.

Here is a close up of the coils.

I still need to add some type of epoxy to the sides of the coils to reduce mechanical vibrations. I believe that this coil should dissipate heat efficiently.

The only other thought is that elusive star or delta. After I finish the assembly, I will wire it in both to see which one will best suite my needs.

I will finish the coil retainers this week and the the fun begins. Coils!

[hiker]

why the diffrent type of coils....

with those mags -and 2 in hand #14 wire 55 or 75 turns would make some great power.

  oh well...looks like you could compress those coils in a vice to make them a bit flatter..just toss them between a couple pieces of hard wood and compress the heck outa them[one at a time].... looks like a interesting alt.

[Flux]

Are you going to persist with this or stop now and do something better?

Considering the enormous waste of air gap and the fact that you insist on only using half the magnets you are doing very well, but the clever design and better cooling is never going to let you get anywhere near the normal output that the conventional winding achieves from those magnets.

Your method of arriving at cut in speed is wrong, but surprisingly you are not far away.

Taking your 110 rpm figure, I take it you have .6v ac from the coil so if you have a total of 18 coils you have 6 per phase.

That is 3.6v ac per phase. 1.7 x 3.6v line and the dc will be 1.4 x ac line volts

or 8.56v dc.

Cut in at 12v will be 12/8.56 x 110  = 154 rpm.

This roughly works out to a gap flux density of about 200mT. Normally the figure is around 600mT.

At the start others encouraged you to try something new and adventurous although it was obvious that your coil arrangement was far from good.

I would convert it back to 9 coils, you can keep the winding method with half of the coil on the front and half on the back and if you use a thin support disc it could be a good idea if done well.

If you insist on using 18 coils then it has to be an overlapped winding to make full use of the magnet.

Flux

[willib]

tajim

what is your rotor dia

and the size and number of mags per rotor?

[RogerAS]

Hey,

I think you may be on to something very special here despite what others may think and say.

I really don't feel every single watt of output power is all that matters when you build a turbine. Forcing those watts out comes at the price of heat. I've seen several stators here fail because of this attitude of making every watt possible. Sure furling is SUPPOSED to protect the stator form burnout, but sometimes it doesn't. I personally don't think the "learning experience" of such an event is all that valuable, and is very costly in material and time. Copper is getting more expensive every day. Burned out magnets and destroyed machines do not invite the timid to even begin a DIY turbine.

Jerry from Oregon sells little plastic blades that bend back in really high winds (intentional stalling), and he makes all sorts of power with them. Heck he runs most of his stereo shop that way. You'll notice he doesn't post much (if at all) here anymore. His machines don't have furling. His machines really crank the power too! There are other ways of doing things and I feel yours is a very interesting approach. Set a formula in stone and it drags down creativity. It's your idea, run with it!

The criteria for success in constructing a turbine is a machine that will supply the builder with usable power and remain reliable. It doesn't have to be the latest and greatest with perfectly matching components and methods. If some feel you are wasting your time in the process oh well it's your time, not theirs.

Keep us updated and stick to your plans. I'm one idiot that thinks you've got a good idea there. I'd love to have a lathe like that too! You lucky dog.

RogerAS

[tajim]

Rotor Dia. is 9 inches. There are 12- 1"x1.5"x.5 N40 magnets on a 7 3/8" center.

The distance between magnets is    .935".

The target was 12 volts at 150 RPM's.

It looked like it was doing what it was suppose to do, but I guess I was wrong.

[Flux]

Roger

I agree that he has some good ideas, his mechanical work is excellent and there is nothing wrong with trying to produce a stator by other methods than casting in resin.

I accept that there are an infinite number of methods of winding a stator and spinning a magnet near virtually any combinations of coils will produce something, but when you get it far from optimum you need so many turns of thin wire to produce the volts that it has so much resistance that you increase the risk of burn out or you accept a tiny amount of power.

With any design, if you burn it out it is because you are greedy, have no idea of how hard you are pushing things or just don't understand furling schemes.

I have no idea what power he is expecting, but with a cut in as low as 150 rpm I assume he is thinking of a 10 ft prop, if not it will have to be very low tsr or it will stall.

Making some sort of guess at his resistance, ( which may not be desperately accurate from the details I have), with a cut in of 150 rpm, it will probably produce about 18A at 600 rpm. At which point the losses will be about 3 times the generated power. If it is well cooled, it may not burn out , but it is a miserable power for a frantic and noisy 10 ft prop running away.

If winds never get over 12 mph then in that region the high resistance will not matter a lot.

To use the magnet effectively the total flux must link the coil, When the outside of the coil fits within the area of the magnet you can't even start to approximate to reasonable use.

The surest way to prevent burn out is to make the alternator as efficient as possible, then for a given output the losses( heat) is a minimum.

I am not trying to discourage experiment or new ideas, that is why I let him get this far, I thought that now that we have figures,was the time to point out the problems and let him decide which way to proceed.

Flux

[DanG]

http://www.homepower.com/files/battvoltandsoc.pdf

Its too easy for us to generalize cut-in as 12 volts when it's really not. You will have diode and line losses THEN the need to forfill a nominal 14+ volts to get the battery above 80% charged where its useful life is greatly extended.

To see effective rpm vs. charging cut-in I think we'd do best calculating cut-in at least around 15 volts stator output before committing to a blade design : TSR...

I guess its human nature to assume wind surpluses - weeks of actual cut-in will NOT be intermittant, swinging in and out with meek winds, so committing to a baseline 12V rpm is only academic - but isn't raising the cut-in point voltages while still in design stage a good thing?

~