Author Topic: axial flux stator plate (Read 10773 times)

fanman · « **on:** November 16, 2008, 12:47:15 PM »

mornin all fanman here again

well i new i would get alot of heat about a metal framed stator frame so i decided to spin er up for a answer to all concerned, when i first built this stator i worked with many types of metal and finialy found that 316L stainless steel had almost no conductivity to a magnet, i mean very very little, almost nothing if you ask me, alot of the stainless amterial has much conductivity, so i started to build it and did spin check it along the way, and the only thing that happened was nothing, i could not find any eddie problems, so i just carried on with the build,

so i hooked it up to my truck and spun it up for a while, to be exact i spun it for 16 minutes at 144 rpms, to my understanding if you have eddies you will basicaly create a heater out of it by the recirculating currents from the spinning mags and the metal.

like i said i spun it for 16 minutes 144 rpms and all it did was nothing, i could not find any hot spots whatsoever, i figured if any hotspots it would be were the bars from the fram cross the mag path, but i couldnt find any, if you notice those bars are aucualy 3 .25 inch bars welded together at the far ends, when i first built this i had flat stock for these and there was huge eddie problems , so i switched to round bar and they disappeared,

sorry about the blurry picture,i am very happy with this stator right now and i really believe that it will run 110% cooler than the other, and wont warp and i will be able to run it much harder than most, i really believe to get the most out of it rather than running it slow and stalled.

Janne · « **Reply #1 on:** November 16, 2008, 06:29:03 AM »

Fanman,

Superb work. Having no eddy current heating problems with the setup, I think you're on a way to a well cooled stator. I think in earlier post you mentioned about dipping the coils in insulating varnish, so fatigue shouldn't be a problem.

Also I like the use of tractor PTO on the test rig. You won't be stalling you power source anytime soon

Flux · « **Reply #2 on:** November 16, 2008, 06:33:08 AM »

I am pleased that the eddies are low enough not to worry you, fortunately the resistivity of the stainless seems to be high enough for you to get away with it, it has nothing to do with whether a magnet attracts it or not, that would only introduce a cog issue.

You should now only be limited by the temperature the coils can survive and more likely by the varnish or whatever you hold them together and in position with.

" i really believe to get the most out of it rather than running it slow and stalled."

Sorry I can't follow that bit at all, unless you forgo the low wind performance or use some sophisticated method of loading it will stall like anything else and you will still have to dissipate the heat in the coils and keep its efficiency down to about 40% to keep the prop up on its power curve.

The heat you put into it will be the same as a potted version. You may be able to work it a lot harder for the same temperature rise but the stall issues stay the same.

Probably with it well stalled, if you can cope with the heat problem you may get a lot of kW in a gale but you will have to sort the matching issue to get the full potential in sensible winds.

This brute force stall it and get rid of the heat somehow loading is not ideal even if you solve the heat problem.

Flux

Sly · « **Reply #3 on:** November 16, 2008, 06:54:28 AM »

Fanman,

Did you use the same loading as your previous test?

P.S. The "U" joint seems awful close to the wheel studs or maybe it is just an optical illusion but before careful!!! if ever it caught....

sly

Flux · « **Reply #4 on:** November 16, 2008, 09:34:27 AM »

I have had a quick look at your figures and it seems that at 6kW you are up near 60% which is not at all bad.

With a 20ft prop it looks as though your cut in is plenty on the low side and you will be below tsr6 at cut in.

At 6kW it looks as though you will be down to tsr 2.8 or thereabouts and most likely hard stalled.

As you are committed to the coils it looks as though it will benefit from an increase in air gap compared with the potted winding ( may be needed anyway with the cages).

If you set the gap to best suit your low winds you can add some resistance to keep it from stalling in the higher winds. If the cooling works well enough you may be able to get it up to the 6kW at least for wind rating. It will be interesting to see what rating you can get out of it on the tractor with the wire ( or varnish ) kept within its thermal limits.

Star jerry connect it and you might make 10kW.

Flux

tecker · « **Reply #5 on:** November 16, 2008, 09:45:08 AM »

Very nice build . I like this idea a lot especially for maintainability . You must have a cover planned for this unit .I would suggest some Teflon under the clamps to the coils and bonding from the stator to the frame like is done with a transformer . An isolated frame will develop a static bubble in bad weather although the flux inside a cover will keep the charge down .

GeeMac · « **Reply #6 on:** November 16, 2008, 10:08:51 AM »

I like it. It is experiments such as this that advance the mill craft. Great job.

fanman · « **Reply #7 on:** November 16, 2008, 12:36:08 PM »

hey flux you were talking about tsr and cut in. when i built the blades for this unit i usewd altons wind blade calculaters, and i took it as for a tsr of 6 and 7.8 mph cut in thaqt would put me at 61 rpms, i guess i assumed that the 61 rpms would be a tsr of 6, is this not right? the generater only is going to see the rpms between 60 and 130 or somewhere there for full output, would the tsr vary greatly between these rpms? what should my target tsr be for optimum efficiency?

Dave B · « **Reply #8 on:** November 16, 2008, 02:22:38 PM »

Fanman,

Fantastic work, I'm glad to see you going your own way and sharing this information as you go besides.

There are many people out there who mean well with their suggestions to you but there is no substitute for paving the way. The comments from the arm chair quarterbacks about what should happen, could happen, would work better if .. and should have done that are unfortunately not usually presented by "doers" such as yourself who have done what you are doing.

Certain things weren't supposed to work very well with my direct hot water system either, I've earned the right to chuckle a bit during a steaming shower after a breezy night. Great work and thanks for sharing your project as you go, keep us posted. Dave B.

TheCasualTraveler · « **Reply #9 on:** November 16, 2008, 02:35:24 PM »

Just a note to also say, nice work. That has got to be one of the most interesting improvements in axial flux design as well as something many of us have pondered but not had a solution to. Somewhere out there I'm sure someone has seen it and is hurrying to come up with a carbon fiber mold and a patent to boot. Luckily your work is all documented here. Thank you for sharing it so openly.

Flux · « **Reply #10 on:** November 16, 2008, 03:23:32 PM »

Yes the tsr6 comes out right for cut in.

"the generater only is going to see the rpms between 60 and 130 or somewhere there for full output,"

That is where the trouble starts. If you cut in at 60 rpm then at 28 mph the ideal rpm would be 240 . You should reach 130 at just over 14 mph.

If you hold the speed down then the tsr must fall. The usual compromise is to cut in with tsr as high as the blades will reasonably tolerate ( perhaps tsr . This gives you a chance to start beyond the prop power curve peak and you will find that the tsr falls very rapidly as the wind picks up. you will be down to tsr 6 near 10 mph, where you will get a lot of useful wind. Perhaps even up to 20 mph you may still keep the tsr above hard stall and still get reasonable power from the prop.

Somewhere below tsr 4 the stall comes on badly and the prop falls of the decent part of the power curve and things start to tail off to something near constant current.

Increasing gap will help you get above design tsr at cut in and will hold you from stall higher up the wind speed range. If that is not enough then you will need some resistance if you want to keep the stall off to something over 25 mph.

Because of the cube nature of the power curve you need load to increase slowly at first then come on more sharply in higher winds. The common alternator curve is far too steep in the early part for ideal loading. The higher your efficiency the steeper it is and the worse the load matching.

The situation is so bad that you actually gain power by making the electrical circuit inefficient and improve the prop matching.

Using a 2 speed approach to the alternator helps a lot ( hence the star/Jerry) but it is still much of a compromise The transition point is messy. If we had high wind days and low wind days it would be far better. The wind will spend too much time at the wrong speed for the connection you are in during the change over period.

You also need to remember that the stalled operation is very easy on the machine even if it leads to poor performance. Once you get the matching right it will be far more responsive, faster and subjected to worse gyroscopic forces and you may have issues with blade leading edge erosion. These issues may not prove too difficult but just be prepared for them as DaveB will testify.

Flux

ibeweagle · « **Reply #11 on:** November 16, 2008, 05:59:20 PM »

remove the resin from magnet plates and have a plasma cutter cut you out a magnet holder out of #14 awg metal and epoxie on magnets not supper glue as it does not stick good I now have a 12 footer flying and getting top amps so far of over 42 amps at 29 volts so does work rotor plat size is 12.5 and 16 magnets 1,2,.5 n45 will email you some drawing if you email me ibeweagle@hotmail.com will work up drwing for rotors at 29.5 and see if can get it done cheers Mike

electrondady1 · « **Reply #12 on:** November 17, 2008, 07:29:16 AM »

what kind of rod do you use for this 316L stainless?

fanman · « **Reply #13 on:** November 17, 2008, 12:22:31 PM »

i used 316L welding wire for my mig welder, i suppose you could use 316L rod for a stick welder also, i got a 2# roll for $27 or so.

Ungrounded Lightning Rod · « **Reply #14 on:** November 17, 2008, 03:56:58 PM »

I like the design, if I understand it correctly:

I take it you have:

- An outer ring of metal,

- welded-on mounting lugs,

- a strip of metal (or set of rods) between each pair of coils, edge-on to the magnets and welded on to the outer ring, providing support and separation for the coils.

- An inner ring of metal with the other end of the strips or rods welded to it.

- Coil hold-down clamps composed of rings of metal outside the pole path, screwed to additional mounting lugs.

Yes, such a setup would have relatively low eddy current issues. The stuff outside the magnet pole path isn't subject to much field and the stuff within the pole path is thin and edge-on to the field path.

The main current loops would be through:

- the outer ring,

- the radial strips/wires,

- the inner ring, and

- back through the radial strips/wires.

With an additional similar path through the clamping structures. Yes, this is not all that great a loss, especially with reasonably thin and resistive material.

But you could do still better:

If the inner portions of the radial structure are insulated from each other you break the loops.

Alternatively you could take advantage of the fact that the induced voltage along every third radial strip is the same. So for two out of three radial strips break them in the middle, or somewhere between the inner and outer clamps (unless the set of clamps on the "break" end are held on only to every third strip, or held with non-conductive screws or insulated by shoulder washers on the ohters.) Bingo: No currents around the loops. (You can fasten the cut ends together with a non-conductive epoxy to avoid abrasion if the break is where the coils would rub on it.)

Another approach would be to have THREE inner rings, insulated from each other, with each ring connected to 1/3 of the radial structures. And another approach to the inner clamp rings would be to similarly have three of 'em, each screwed to 1/3 of the radial structures.

With this arrangement eddy current losses are comparable to that in a copper wiring turn of comparable thickness, i.e. nearly non-existent.

Ungrounded Lightning Rod · « **Reply #15 on:** November 17, 2008, 04:10:01 PM »

Reading closer I see the radial "strips" are triples of rods.

Is this a single-rotor? Strips of thickness comparable to the rods' diameter should have a SOMEWHAT higher eddy current loss. (Maybe as much as a factor of 3.) But a MUCH higher eddy current loss would indicate the field has a large component along the rotation direction.

fanman · « **Reply #16 on:** November 17, 2008, 05:34:11 PM »

hey ulr

yes the machine is dual rotor and the strips connecting the outer and inner ring are 3 peices x.25inch stainless, they are not insulated from one another, which i should have done that, and they are welded together at the ends were the rings meet, that connects them all together,

jmk · « **Reply #17 on:** November 17, 2008, 06:13:15 PM »

Nice work, and very interesting! I was waiting for your postings on this machine. Keep up the good work.

chubbytrucker01 · « **Reply #18 on:** November 17, 2008, 07:50:32 PM »

I know someone is gonna correct my numbers but didn't Edison figure out 120 ways not to make a lightbulb before he made one that did? I love the fact everyone says the stator won't work but everyone is still watching. Kinda like Edison and Tesla. Edison said Tesla was a fool for wanting to use ac electricity. He said it was dangerous. He even killed an elephant by electrocution to prove his point. But here we are using ac for everything from toasters to tv's. Everything I have read about electricity some of it from well known people, even they still learn new ways to funnel electrons.

Flux · « **Reply #19 on:** November 18, 2008, 01:53:41 AM »

Dan's results with an engine driven alternator using strip copper also lends credibility to the fact that there is significant flux that doesn't go straight across. This surprised me at the time and this confirms it.

Flux

electrondady1 · « **Reply #20 on:** November 18, 2008, 07:37:02 AM »

" the only thing that happened was nothing,"

hey, thanks for the info on the welding rods and wire

i was afraid the 316L stuff was going to be some really exotic material.

i think what you have come up with here, might prove to be a significant step in

the evolution of these alternators.

don't be surprised if some commercial builder starts using your method .

congratulations!!

Ungrounded Lightning Rod · « **Reply #21 on:** November 18, 2008, 01:21:11 PM »

Perhaps the eddy currents "drag" the field enough to bend it in the middle as it leaves, like a rubberband being pulled from molasses, so the strip sees a significant into-the-strip component with a large associated circulating current - in a "theta" shape as viewed along the direction of rotation.

Replacing the strip with a series of rods (or square bars) would break up most of the circulating currents in the same way as laminating a magnetic core does.

Ungrounded Lightning Rod · « **Reply #22 on:** November 18, 2008, 01:30:17 PM »

I wouldn't sweat insulating them from each other, unless they're forced against each other by some sort of clamping. (Or I'd give them a little spray of varnish just in case - especially since stainless won't form much of an insulating oxide coat.)

The induced voltages driving eddy currents are pretty low. (I think that's why you're getting away with having the rods welded on both ends. B-) )

The resistance of a small spot or a ridge of contact between two rods is enormously higher than if they were "welded together and filled in" to form a rectangular strap of continuous metal.

Ungrounded Lightning Rod · « **Reply #23 on:** November 18, 2008, 01:34:51 PM »

Also: I was thinking of doing coils of strip copper. But now I think I'll stick with the tried-and-true round wire.

(I was inspired by the copper-strip coils in automobile starter motors. But now that I think about it they only use those for the field coils, where the magnetic field is essentially constant, and use heavy round copper rods/wires for the rotor, where the field is being dragged/pushed through the conductor.)

hamitduk · « **Reply #24 on:** January 18, 2009, 01:32:55 AM »

Well what is it doing, is it fling? what is the real output?, love to see it fly!

Hami

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Author Topic: axial flux stator plate (Read 10773 times)