Author Topic: Coils, 9 or 36 (Read 2333 times)

Capt Slog · « **on:** February 05, 2007, 02:10:34 PM »

I understand how the three phase bit works and I can see that either 9 coils or 36 coils in a overlap is possible.

Apart from the work involved, what are the pros and cons of each system? Basically, will I gain by using 36 and in what way?

And would 18 coils work if they were arranged as 2 sets of 9 overlapping and wired as 3 phase twice?

Flux · « **Reply #1 on:** February 05, 2007, 07:29:17 AM »

The basic 12 pole 3 phase winding would be 3 single phase windings displaced 120 electrical degrees and would have 36 coils.

If you based it on a virtual pole single phase version you would achieve the same thing with 18 coils with twice as many turns of half csa wire.

Either arrangement can only intelligently be done with overlapped coils. Unless you can get the coil sides for all 3 phases into the air gap of a single phase you loose all the advantage of 3 phase except for vibration issues.

With a radial winding the overlapped coil design is almost universal.

I assume you are talking about an axial design and you will find an overlapped coil set up extremely difficult to do. There is just not enough room for the overlaps at the centre. You will need such long coil ends to do it that you will end up with more winding resistance than if you left half of the 18 coils out so that they ended up on a single layer.

If you accept the fact that it is virtually impossible and change the magnet spacing to make best advantage of the 9 coil arrangement you will have a better result.

If you try to directly compare a 9 coil with a 18 coil overlapped with the optimum magnet layout for the 18 coil, the 18 coil will win if you waste enough time and effort into squeezing the thing in as tightly as possible.

Even with the wrong magnet spacing for the 9 coil, 9 will win out unless you are an extremely skilled winder.

Flux

stop4stuff · « **Reply #2 on:** February 05, 2007, 09:13:13 AM »

Making ovelapping coils is not easy...

WindstuffEd has a simple method that gives the equivalent of 36 coils and is relativly easy to impliment.

see;

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

& http://www.fieldlines.com/story/2004/5/26/15451/3307

finnsawyer · « **Reply #3 on:** February 05, 2007, 09:19:42 AM »

In what way are you trying to gain? If you don't mind a single phase output and want more power you might consider the alternator design that I proposed in my diary. This would use 18 coils arranged in three phases of six coils each with the same twelve magnets. By winding the coils as two in hand using the same wire you can get 1.73 times the output voltage at 3/4 the resistance than with the 9:12 design. It would, however, require twice the copper wire and a rotor about 2.5 times the diameter.

TomW · « **Reply #4 on:** February 05, 2007, 12:26:30 PM »

FinS;

I keep waiting for you to build this and share the results. I suspect most folks don't have time or resources to test your idea in hardware.

I gotta give you points for persistence on suggesting it to people. Maybe someone else will try it and share the results. Be interested to see the data.

I am not much of a builder or I might give it a try myself.

Cheers.

TomW

vawtman · « **Reply #5 on:** February 05, 2007, 02:56:58 PM »

http://www.fieldlines.com/story/2006/10/3/1859/32879

Hello Capt above is a posting i did awhile back and learned alot.I figure i'll get 20 turns no.17 per coil.Hoping for high voltage no bats.

The mags are always up to something.

Capt Slog · « **Reply #6 on:** February 06, 2007, 02:08:56 AM »

It was the stator that Ed Lenz made that gave me the idea of using the 36 coils. There are two pictures of it in the thread that you quoted, but I don't know how to get them here, (I'm not very PC savvy). Although this stator looked a lot of work, it didn't seem beyond what I could achieve given enough time. I'd also been thinking along the 'wedge' idea that Stop4Stuff made here..

http://www.fieldlines.com/story/2004/5/26/15451/3307

but made from plastic.

However, it seems from Flux's comments that it isn't worth the effort, and that I'd be better of with the standard 9 coils.

Capt Slog · « **Reply #7 on:** February 06, 2007, 03:02:11 AM »

Thank you Flux. Looks like a 9 coil then, at least as a first build

finnsawyer · « **Reply #8 on:** February 06, 2007, 08:52:05 AM »

As I mentioned before, it will probably take many incarnations of this to chase down its best use. Since introducing the concept I've tried to refine my thinking to make as valid a comparison as possible with the 3:4 alternator. What I posted here is the result. In the example I gave one could also wind the wire three in hand to reduce the resistance to 1/3 that of the 9:12 alternator. This would reduce the voltage to 1.15 that of the 9:12 alternator. While the 1.15 voltage gain may or may not occur in practice, the point is that a relatively small increase in voltage coupled with a drop in resistance gives a greater power output and hence can be coupled to a larger wind turbine. The large rotor size needed would limit its use to small wind turbines, which, of course is what this site is about. The output would be single phase, but would be three times the frequency of the 9:12 alternator. This could be a benefit if you want to run the output through a transformer, as sometimes happens.

For those who might be interested, the analysis is based upon circular magnets and coils with the coil diameter twice that of the magnet. The crux of the analysis is that in my 18:12 design the coils of two phases produce a voltage when added that would be identical to that of a single phase coil of the 9:12 design as they move across the magnets at the same speed. That is, phase one starts centered over a magnet as phase two begins to move over an opposite polarity magnet. In the 9:12 alternator a single coil performs both actions by itself. Electrically the two open circuit voltages should be identical.

vawtman · « **Reply #9 on:** February 06, 2007, 05:55:00 PM »

If you dont have a drill press,vice and level table it would be hard if not impossible to line things up.

I just found a piece of plastic(hdpe)and had fun drilling holes in it.Has flux mentioned its not easy and if your building a hawt to charge batteries not worth the effort.

And yes Ed did a great job has always with his.

From a fellow tinkerer.

finnsawyer · « **Reply #10 on:** February 07, 2007, 08:32:00 AM »

I suppose I should have mentioned that when someone says overlapping coils it sets off alarm bells in my head. Why would you want to increase the stator thickness by a factor of three and reduce the flux by a factor of three? So, I figure if they're going off the beaten path, so to speak, they should be made aware of other possibilities. Maybe at some point I'll catch a college student looking for a project. You never know. Also, introducing an extra paragraph doesn't require much bandwidth. If someone is set on doing a 3:4 alternator I keep my peace. Oftentimes, it's hard to tell just what they are thinking.

vawtman · « **Reply #11 on:** February 07, 2007, 03:36:38 PM »

Finsawyer, Isn't this lovely weather?

One doesn't increase the stator thickness at all.Two coil legs share a 1/2in slot(36slots) so the stator thickness could be around 5/8-3/4in.Sure not has many turns but 4 times more coils.

So you can turn the alarm off now.

finnsawyer · « **Reply #12 on:** February 08, 2007, 08:30:43 AM »

I believe the original posting wanted a comparison involving the usual 9 coil 12 magnet construction. No slots. That's why I gave the response I gave. With two coils sharing the same slot, it seems either the thickness of each coil is cut in half or the flux linking each coil is reduced. Can you show that that would give better results than the standard 9:12 arrangement? As far as the weather, yeah, real nice. Actually it's the 20 to 30 mile an hour winds that are bad around here. We really don't have that much snow.

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