Prototype Stator

[Lumberjack]

This stator is a prototype and was not meant for actual use. I wound it to help resolve a number of issues with my design. My design is intended for low speed vawt use with a high copper density and a minimal amount of non - generating copper. The first problem I ran into was that 10d nails were too large to place one at 1 degree intervals for a 12 " stator so I set this one up at 10 degrees per leg. The rotor that would go with it would have a magnet every 30 degrees. This would leave a magnet over every leg of the coil at once.

Put in other terms I wound the stator with 3 coils of twelve legs each or the rough equal of 18 coils and 12 magnets. Each coil ended up with 16 turns of  12 gauge wire and the stator ended up about 1 inch thick using about 100 feet of wire per phase coil.  The stator turned out with a much lower density and twice as thick as I wanted. I tried to wind it 3 in hand but controlling 12 wires without a jig created more foul language then any real results.  

For my first real attempt I am scaling down to a 6 inch stator /rotor combination. I am keeping the 10 degree leg spacing and the 30 degree magnet spacing as well. Instead of winding each turn separately I will be making each coil separate and then placing it on the form. I am using much smaller nails this time but have not decided how to protect the wire from being scratched by the nails. To hold the stator together and prevent wire chaffing I plan to epoxy it all together. For the test rotor I simply hot glued 1 by .75 ceramic magnets to a 6 inch flue cap. Now all I have to do is annoy the theory types until my wire arrives. :}

[Lumberjack]

[Flux]

You say the stator turned out twice as thick as you intended, that is fairly normal if you calculated the thing from wire dimensions. Obtaining 50% stacking factor is reasonably normal.

You have only used about half the winding area for the bits that you have wound so you will probably have more resistance than the conventional way. It takes a lot of skill and effort to beat the other method on a radial.

You seem to have used an 18 coil winding, this bit about 3 coils with 12 legs is beyond me. Also the bit about active and inactive copper is a bit of a red herring.

Anyway what you have should work ok and if you can really refine your winding technique you will get it better. The final crunch is what happens on test, your method is fine but to me it seems hard work with little to be gained in performance over the simple 9 coil scheme.

You don't mention the magnets, if they are the wedge shape ones you will have the best results, if rectangular you would probably do better with 9 coil single layer.

Flux

[tecker]

The winding rack is a good idea .I've been saveing some Cat5 to strip out for a test like this .Good luck and shoot us some data.

[tecker]

As far as scuffing the wire . I use nylon screws but there probably not rigid enough to handle this job . Ed had a coil winder with some sleeves over the studs but the diameter might be too large . Maybe some  6/32 screws with teflon tape.

[Lumberjack]

So far pre - coiling the wire before placing it on the form seems to the easiest method but I have not found a reliable way to determine the correct length yet.

Scrap cat 5 is a bit large unless you plan to strip the outer jacket. I found a 100 foot spool of three strand bell wire the hardware store had in the bargin bin. Scrounging is almost as fun as the construction at times....

[Lumberjack]

The target design is to be wound every 1 degree or so with a magnet every 3 degrees. Magnet wise I was thinking 1/2 by 4 inches possibly using multiple magnets. For this prototype I scaled things back to 10 and 30 degrees to make things easier and get a better idea of where the problems would be. (The prototype will never have a matching rotor made). The second test stator is scaled down to 6 inches so I also kept the 10 and 30 degree spacing due to space issues.

Had I achieved the density I wanted the stator should have been about 1/4 inch thick but winding 3 or 4 in hand per phase proved extremely difficult.

There are actually only 3 coils in this stator. The winding crosses the form 12 times each crossing forming a coil leg. I was trying to avoid confusion but I guess I was not very clear.

[Flux]

Thanks, it is an 18 coil wave winding. I have never got used to coils having legs, every nation has different ways of describing things.

Did you wind the turns round individually or did you wind a big skein and put all the turns in together, comes out to the same thing.

Flux

[Lumberjack]

"Wave winding", I like that, good term for it. The prototype was individually wound but making a skein seems to be a much better way to get the density I want. I just have not figured out how to accurately determine the skein size.

I am a very big fan of legs myself but it may just be a personal preference :}

[tecker]

Strip out the cat and wind 4 pairs at a time.

[Lumberjack]

Well the box of shiny copper showed up today. After spending an hour fondling and drooling over it I started the 6 inch form... wish me luck!

(anyone know if drool is ok on the finish?) :}

[Lumberjack]

a short note to self, 10 strands of 17 guage wire is hard to bend for this type of project. next time use 2 in hand 20 guage.