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9" Axial Flux Dual Rotor Stator Design ,,, will this work?
By arc, Section Newbies Posted on Tue Jun 02, 2009 at 10:36:49 PM MST
Approx. 9

This is one though I had on a mini 3 phase, Dual Rotor, Axial Flux Stator.
I have 28 Neos this size but will probably go with 24 so I can go the 3 phase route.
I lose about 15% of the potential by dropping the number but have the possibility of gaining more by making it 3 phase.
I want the stator as ultra thin as possible so I opted to wire two coils in series to get the number of windings spread between two coils. I think this should be one of the more efficient uses of my salvaged neos.
I'l love to hear your thoughts, don't have any idea of the number of wraps or wire size yet.
I just noticed that I may have a problem with cancellation ...
One coil is using N+N on each leg and the next coil in series is using S+S.
I'm confused now ... looked good on paper.
any suggestions ... can I just reverse the second of the series or do I need to stretch the coils to bridge the neos more or less.
Thanks,
arc

9" Axial Flux Dual Rotor Stator Design ,,, will this work? | 15 comments (15 topical)

Back to the drawing board. (3.00 / 0) (#1)
by arc on Tue Jun 02, 2009 at 06:44:09 PM MST

I think I had better epoxy myself to Ed's website for a while to get this straight or I'm going to end up with a mess of burnt wire and no Watts to show for it.

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

Perhaps you can at least see what it is that I'm trying to do here.
I'm trying to reduce the thickness of the stator by running two coils in series.
I'll, no doubt need a relatively high number of wraps to keep the voltage up at relatively low wind speeds.

I seem to have in my mind that I need to have a blade diameter of around five feet.
I suppose there's another way to look at this. I could decrease the diameter of the blades and depending on the TSR get get some higher RPMs to ultimately decrease the number of windings I'll need per coil. This would allow for a thinner stator or larger wire size and I'm not sure which is more important in this case.

Eventually I will put magnets on the other rotor and stator thickness won't be quite such an issue ... but for now I need to get all I can from these neos.
I plan on winding the coils to accommodate another row of magnets also so I have room to improve this alternator as money permits.

I'll go study up at Ed Windstuffnow's site, he has a way of making it look easy (or at least much easier).

I'll still take all the suggestions you feel like throwing my way.

Thanx,

arc

Re: Back to the drawing board. (3.00 / 0) (#2)
by electrondady1 on Tue Jun 02, 2009 at 08:37:33 PM MST

ed is an alternator wizard .
your diagram illustrates an over lapping coil three phase layout.
it might be prudent to try a simpler method for your first try.

you can do a three phase stator with all the coils on one level.
it's the standard method.
you would need 21 coils and each phase would have seven coils.
each one of these coils is wired in series.
once your mag rotor is in place, you can turn a test coil.
the center of the coil is about the same size as your mag and the outside of the coil must fit within a segment that is 1/21 of the total area.
those are the peramiters you use to build the coil jig.

[ Parent ]

Re: Back to the drawing board - again (3.00 / 0) (#3)
by arc on Tue Jun 02, 2009 at 10:16:35 PM MST

Hi ElectronDady1,

I appreciate the info, you are probably right on doing something a bit easier for my first axial flux.

My initial inclination was that if I go to all the hard work of getting the dual rotor setup laid out and done correctly, I may as well use a stator configuration that makes the most out of what I've got. However, stators aren't so tough to make that I couldn't make an easier one for now then later add some nice magnets and make a new stator to take advantage of them later.

I think I'll make the dual rotors so that I can easily adjust the gap to accommodate additional magnets (on the second rotor) and a slightly wider stator later if needed.
If I can find some decent brake disks to use I'll have a good starting point and go from there.

My plan now is to make this stator very thin and make the rotors such that the tolerances are pretty tight to allow for a narrow gap. Some good bearings and careful work on the stator should help there.

Thanks for your input ElectronDady1, it really helps to bounce ideas and concepts around a bit before letting them solidify. I always seem to think more clearly when writing things down and for me nothing beats the sketchpad but CAD really helps in working out clearances and conveying ideas to others as I go.
I'd be lost without some guidance from those who have been here done this. I like a challenge but don't necessarily need to pioneer the trail when others have already paved the road.

Thanks again,

arc

[ Parent ]

Re: Back to the drawing board - again (3.00 / 0) (#4)
by stop4stuff on Tue Jun 02, 2009 at 11:37:58 PM MST

take a look at Windstuffnow's 'slotty former' for 3 phase;
http://www.windstuffnow.com/main/3phase_turbine_kit.htm
much easier than making overlapping coils;
http://www.fieldlines.com/story/2004/5/26/15451/3307

[ Parent ]

Re: Back t (3.00 / 0) (#5)
by Flux on Wed Jun 03, 2009 at 12:59:56 AM MST

If you are prepared to do a multilayer winding you can use 3 phase with any even number of poles. 28 poles is perfectly possible.

The 2 layer winding is far from ideal for axial machines but with your small magnets it will probably work fine on a machine with little difference between the inside and outside dimensions of the coils. It tends to be a problem with space near the centre when the inner stator dimension is small.

Winding 2 layer windings without slots to hold the coils id a major issue and it takes someone such as Ed to go to the lengths needed to do it satisfactorily.

If you can manage to get the end windings in without ending up with large lengths of wire and a higher resistance than a single layer winding then you will gain.

You need a single coil thickness in the air gap but you will have two thickness's at the crossing point. These have to be outside the magnet swept circle so you can't really pot magnets for protection. I did a few with ceramic magnets, they were a real pain to do but the ceramics didn't need potting so I could fit the end windings very close to the magnets.

In your case where it is a labour of love you could end up with a better machine. Normally I would spend a bit more on magnets and have an easy life and get the same result with a fraction of the effort.

Probably if you have all the facilities to do a 2 layer winding really effectively you will have enough facilities to do the thing as a radial.

I haven't checked your connection drawing, I can't face anything that confusing so early in the morning. multilayer windings can be of two types, one requires reversed coils and one doesn't. You will have to get to understand about full cols and consequent poles.

Flux

[ Parent ]

Sharpen the pencil and find a fresh sheet of paper (3.00 / 0) (#7)
by arc on Wed Jun 03, 2009 at 09:48:46 AM MST

Thanks for your thoughts Flux,

Like you said, "it's too early in the morning", same problem here searching and/ or grasping the "End Windings" and "full cols and consequent poles" but it will give me some good subjects to look up and ponder when I wake up more and have some time.

Since I'm still at a stage where I'm juggling ideas around and have no immediate need to get to building something I'll use the time and freedom to wander outside the box a bit to see what I come up with.

If I can arrive at a suitable design, I'd love to make a small radial, however, there are good reasons that most people build the axial. Axials are, of course, better suited for a durable, easy to build machine using the great assortment of neodymium magnets, water jet cut rotors and easy mounting bearing assemblies available today.

I always thought that, apart from the inherent difficulties in construction, it made a lot of sense to utilize the higher speed at the perimeter of a revolving disk or drum to get the most out of each revolution. Now the F&P and Seeley revolve the magnets around a stationary stator core ... but I rather like the concept of making a stationary outer ring of windings with a revolving magnetic core (armature). A conversion is a nice shortcut to go this route but I've been thinking along the lines of a more compact design using, for example, a small diameter brake rotor (armature) with incorporated hub (blade mount). These two units would turn freely on the axle as an assembly. 28 slots could be cut around the perimeter of the steel rotor to capture the neos. Mounted outside of this would be a ring of coils (stator) that is held stationary, in position using stand-offs from a backing plate.

A plastic ring with slotted holes around the inner diameter would be easy to make but I see the major flaw here. There is no path to return the lines of flux (no continuity).
A stack of laminated rings with slotted holes around the inside diameter would be the answer but how to make these with a suitable material is probably beyond my capabilities. If they could be cut from sheet metal, I could probably stack, clamp and cut them out using a jig saw then drill the slotted holes.
LOTS OF WORK and little way of knowing what the results might be. This would not be something I would try unless I knew a lot more about materials and how they conduct flux (galvanized sheet metal is probably not the best material to use for this.)

Well, back to the drawing board, thinking outside the box is fine but doesn't ALWAYS lend itself to coming up with a better mousetrap. I'll hit the search button some more and see what else I can find to narrow things down.

As always, thanks for your generous input.
It's appreciated!

arc

[ Parent ]

Re: Sharpen the pencil and find a fresh sheet (3.00 / 0) (#8)
by ghurd on Wed Jun 03, 2009 at 10:48:45 AM MST

Kind of sounds like you are re-inventing Hugh's old brake drum and motor core PMA, but inside out. Might be something to look at for ideas, especially about the laminates.
http://www.scoraigwind.com/brakeupdate/index.htm
G-
Ghurd.info
[ Parent ]

Re: Sharpen the pencil and find a fresh sheet (3.00 / 0) (#9)
by arc on Wed Jun 03, 2009 at 11:49:47 AM MST

Hey, Gary ...

Great resource.
Lots of good stuff there, I'll be checking it out in more detail.
Thank You for the link!

I just love tossing these ideas around. For me it's more fun than buying a kit or following a guide verbatim. I tend to get pretty creative when I'm broke ... sometimes it even leads me to clean up the shop so I can find stuff I already have instead of just going out and buying another one. In my case I think the end product of this project will depend a lot on just what parts/ materials I find to work with.
I've found that in such cases it really helps to NOT be in any kind of great hurry.

It's that time of year for garage sales and lots of them around here (rural) have motors, car parts and lots more industrial type stuff than those in some places I've lived. I just hope I don't do what I always do and find a bunch of really cool stuff I can't live without ... that I bring home and rarely if ever use.

Thanks to guys like Hugh and Ed, the Dans and so many others of you for the pioneering, the creative minds and especially for documenting the work. Makes it much easier for folks like me to learn from those who have done the testing, worked out the numbers and already separated fact from fiction.

BTW, when I get to where I need to hook things up to the batts, I'll be needing one of your circuit boards, some resistors and a few other dodads from your stash.

arc

[ Parent ]

Re: Sharpen the pencil and find a fresh sheet (3.00 / 0) (#10)
by ghurd on Wed Jun 03, 2009 at 12:04:52 PM MST

I know what you mean about
First building stuff... for free, from junk, that often (usually?) has a slim chance of working.
Second... buying more junk because you can't find the junk you bought last time.
(I currently can NOT find several ECMs. The key word being SEVERAL!)

Might check out all of Hugh's "older" section too.
http://www.scoraigwind.com/#older

G-
(There are a few Gary's on the board, but that G- is Glen)
Ghurd.info
[ Parent ]

Re: Sharpen the pencil and find a fresh sheet (3.00 / 0) (#11)
by arc on Wed Jun 03, 2009 at 01:55:37 PM MST

"Glen" it is ...
... sorry about that.

... time to clean the shop again?
... na, then you'd never find anything, right?
I always "kind of" know what general vicinity that most everything is, "most of the time".
Good luck finding those ECM's ... they're probably just under something else that you can't find.

"Might check out all of Hugh's "older" section too."

Probably some real gems in there as well, I'll feel like a wealthy man when I get through reading all of that.

Thanks Glen!

Dave
(aka arc)

[ Parent ]

Re: Back to the drawing board - again (3.00 / 0) (#6)
by arc on Wed Jun 03, 2009 at 06:42:00 AM MST

Hi Stop4stuff,

The slotty is a good example of continuous loop winding, I'll look over the winding directions for that to get a better picture in my mind. That's a darn good price for that little kit ... I'd love to get one sometime for a small HAWT rather than the VAWT.
Great example, thanks!

I see you've been doing some extensive testing with that mini stator, nice work.
Keep it up, looks like you are enjoying all aspects.

arc

[ Parent ]

Re: 9" Axial Flux Dual (3.00 / 0) (#12)
by willib on Wed Jun 03, 2009 at 04:03:35 PM MST

http://www.otherpower.com/images/scimages/2965/IM001955.JPG
above is a single phase scope output from my mini gen(the first one)
one volt per division
it uses 1/2" x 1/2 inch round (cylinder neo mags)
it has nine coils and 12 mags and uses 20 gauge wire (114 turns iirc)
the coils are 1" dia i dont remember the rotor dia but you can lay out nine coils of one inch dia if ya want, this may give you an idea of what to expect
the story can be found here
http://www.fieldlines.com/story/2006/4/17/52649/8594
if i was to do it again i would use more coils and mags to increase the diameter
iirc doubling the dia almost doubles the output which is what electrondaddy and flux alluded to, plus more coils will further increase output.
also i would use a little thinner wire to get more turns to boost the voltage a little more, at the expense of current capacity( because the amount of current that it can produce(on such a small machine) is sort of irrevalent if the voltage isnt there.)
also i would make the holes in the coils smaller to allow the coils to be thinner
i used a home made coil winder and had some polyester resin handy and paint on the coils as i wound them,i used polyester because thats what i had on hand and the chances of them overheating was really small ..
my 2 cents

Bill

Carpe Ventum (seize the wind) One needs faith in the future

Re: 9" Axial Flux Dual (3.00 / 0) (#13)
by arc on Wed Jun 03, 2009 at 11:27:13 PM MST

Very helpful Bill!

The information from your link will give me some good comparisons and help me know where to start guessing on wire size and possible number of windings per coil.
Some nice construction techniques you've used, it's not clear to me what your blade setup is but I'll read more and take a look at your photo collection to get some more ideas. I see Glen was doing something along the same lines so perhaps there are pics and information from that build as well.

I will definitely use a larger diameter and all 28 of my neos.
I'll need to check again, but do you say there how you wired this up.
3 phase Star is what I'm shooting for now.

I may have some questions after I reread the thread a number of times.
Pictures always help a great deal, thanks for the link, it will help.

arc

[ Parent ]

Re: 9" Axial Flux Dual (3.00 / 0) (#15)
by willib on Thu Jun 04, 2009 at 06:47:04 AM MST

yes its three phase star.
The blades in the beginning looked like that , but later they looked much better as i perfected the method. I may do a diary on the process of my construction technique but i cant do it right now.
bill

Carpe Ventum (seize the wind) One needs faith in the future
[ Parent ]

Re: 9" Axial Flux Dual (3.00 / 0) (#14)
by arc on Wed Jun 03, 2009 at 11:34:29 PM MST

Oh BTW, I forgot to mention what a nice clean wave that puts out, I'm impressed.
I don't have access to a scope so I'll just log my data, make some charts and from the output to my Watts-Up meter to see what's up.

Very interesting blades, can you tell me anything about them or is that classified information? ;)

Thanks again,

arc

[ Parent ]

9" Axial Flux Dual Rotor Stator Design ,,, will this work? | 15 comments (15 topical)

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