Author Topic: 2 Rings of Mags on an Axial Flux Alternator (Read 5851 times)

wind4Reg · « **on:** February 28, 2007, 07:53:16 PM »

I have been tossing around ideas for my VAWT alternator. Because of the mounting structure I am going to have a 3' steel disk that the arms mount on so I figured why not make this into the alternator as well. What I came up with was an axial flux alternator with two rings (24 mags inner ring, 48 mags outer ring) of magnets (2"x1"x0.5")so that there would be 6" of space between the rings. I drew up a pic of what this could look like. Anyone see any reason why this might not work? Maybe the rings of magnets are too close? Suggestions welcome.

asheets · « **Reply #1 on:** February 28, 2007, 01:29:16 PM »

There'll be some radial losses, I expect. Will you be using 2 sets of coils as well?

vawtman · « **Reply #2 on:** February 28, 2007, 03:02:49 PM »

Holly quantity discount on mags Reg.

I would think it will work and your turbine could handle it i think.I would also think the flux would stay in the area of the mags has long has the stator isnt too thick.

Now to conjure up a stator support.Maybe dual rings one supported from the inside and one from the outside.

Too many thinks though.

wdyasq · « **Reply #3 on:** February 28, 2007, 05:07:01 PM »

That has been debated here, several times, to absurdity.

Ron

vawtman · « **Reply #4 on:** February 28, 2007, 05:59:50 PM »

Ron do you have a link to past stories about this.Been around a couple years and not seen one?

No big deal if your Too busy.Thanks

Just a curiosity for me.

wdyasq · « **Reply #5 on:** February 28, 2007, 09:12:57 PM »

No, I don't keep up with stupid stuff.

Ron

RP · « **Reply #6 on:** February 28, 2007, 09:36:19 PM »

If you use a different number of magnets on the different rings then you'll essentially have two seperate alternators on the same axle with different phases. Since you'll have so much more potential power to extract from the outer rim, I can't see an advantage to doing a smaller "inner" unit.

I think if I was going to build a 3foot rotor-stator I'd line up 2x1 inch magnets end to end radially out at the perimeter and do an overlapped winding 3 phase stator. You should have plenty of space to manage the coil overlap on the inner diameter.

Also, plan on some kind of spacer system to keep the two discs from becoming cup shaped on that large diameter. At that size you might be better off to have one rotor (maybe with spokes cut out) and the other being simply a ring of steel attached through spacer blocks to the main rotor disc.

Beings this is for a VAWT, if the rotors will be near the ground I'd put a serious guard around it to prevent damage or injury! :-)

richhagen · « **Reply #7 on:** February 28, 2007, 11:49:13 PM »

I also recall this being debated before. Basically, if cost, material and time are factors, you would get more efficient use of your materials with the outer magnets. The linear speed relative to the coils would be greater, making for better use of the magnetic material if you simply use a larger volume of magnetic material on the outer ring and redesign the coils accordingly. Hence, fewer turns of thicker wire, and less resistance in the stator. Rich

wind4Reg · « **Reply #8 on:** March 01, 2007, 04:36:39 AM »

Yes if I was to go with this configuration I would use 2 rings of coils as well.

wind4Reg · « **Reply #9 on:** March 01, 2007, 04:52:41 AM »

The reason I went for the second inner ring was because it just looked like such a waste of space and I figured that if it would work then it would produce just that much more power. I like the end to end idea, I'll have to take a look at that option. I am not worried about cupping for the magnet rotor because there will be a significant amount of support on the other side of it for the cross arm mounting. I will have to make sure that the stator disk is well supported at this diameter.

This is going 80' up so it won't be near the ground, I think I will close it in some to protect it from the elements, this should be easy enough just by putting "skirting" around the outer magnet disk.

wdyasq · « **Reply #10 on:** March 01, 2007, 06:04:22 AM »

That was s good, basic summary of the discuion.

Ron

wind4Reg · « **Reply #11 on:** March 01, 2007, 06:15:59 AM »

So from what most are saying, putting the magnets end to end and making a larger outer magnet ring would be the better approach?

DanB · « **Reply #12 on:** March 01, 2007, 06:36:55 AM »

Yes, you'd be much better off to put them end to end - or just buy longer magnets in this situation. You're first idea would work, but you'd get very little power from the inner ring compared to the outer one and I doubt it'd be worth the trouble.

TomW · « **Reply #13 on:** March 01, 2007, 07:45:45 AM »

vman;

Not to speak for Ron but I "think" he means VAWTs not the twin magnet rings. I also am still waiting to see a long term functional power producing VAWT. Toys do not count in my search for one that works. Lots of talk but no long term power production that I am aware of. Funny thing is, I was a vertical enthusiast for quite some time before I decided it was just not a DIY attainable project for the average guy. Or think tanks with large budgets to waste, either.

Just thought I might clarify what he might maybe almost kinda mean. I am fairly certain of his stance on the verticals

This is where Ron pops in to tell me I am cracked.

Cheers.

TomW

vawtman · « **Reply #14 on:** March 01, 2007, 03:38:55 PM »

Tom

Ron is an inspiration for me.Gotta love him

Im finding it very tough to match the load of mine.Last fall i put my 5hp 4pl conversion on the 8x8 geared 3:1 and the slight cogging it had reverberated through the blades and made starting hard.However,once past that it played with it like it wasnt there.Got the elements pretty hot also.Around a 15mph wind and motor running at around 300rpm.

Im hoping this 12/36 axial motor im working on will help starting and can adjust gearing.Direct drive would get pricey.Still have the flywheels in the back of my thick skull though.

Some day i"ll build you one for the farm.

gizmo · « **Reply #15 on:** March 01, 2007, 07:20:30 PM »

You guys keep making these silly statements about no such thing as a functional power producing VAWT, and I'll keep posting these links to a functional power producing VAWT, the ropatec.

http://www.ropatec.com/

http://www.soe-townsville.org/strandwindproject/

Why is this NOT a power producing, reliable, functional and commercial VAWT?

Glenn

wind4Reg · « **Reply #16 on:** March 02, 2007, 05:30:55 AM »

"I also am still waiting to see a long term functional power producing VAWT."

What is long term in your book? The Carl Brothers successfully operated a 35 kW DAF-Indal VAWT (Darrieus style) for over 15 years on Prince Edward Island, Canada.

If you really are a VAWT basher, then I am sure you will come up with some other criteria to discount this one too. If you are objectively minded however, then you will see that VAWTs do have a future in wind power, and no one is claiming anything outrageous about them, they are just the preference for some of us and we like to build them. It will be a couple of years before mine is ready to fly and when it does I will definitely post the story here, whether the result is good or bad.

wdyasq · « **Reply #17 on:** March 02, 2007, 05:33:25 AM »

Glen,

I still have yet to see a practical 'homebuilt' VAWT. I do think the 'twin rotor' as shown will help with the torque surges high speed designs of VWATs are know for. I suspect 'Tripplet' or the Gorlov Turbine might solve that problem.

The main think I hate to see is a person with few resources pouring money into a project without understanding the design has some well documented and built in problems. On this particular post I was referring to ONLY the inner/outer rows of magnets. But, my caution of research what one is building still holds.

I also wish all of you VWAT fans 'luck'. Although I suspect research would serve most better.

Ron

alancorey · « **Reply #18 on:** March 06, 2007, 03:18:45 PM »

Haven't there been cases where people have written that you almost want two generators on the same shaft if you're going cover a wide range of wind speeds with good efficiency? One with a low cut-in, probably wound with many turns of fairly small wire. That will limit by its own wire resistance above a certain RPM (too much attempted current). That's when you have the second one wound with less turns of heavier wire cut-in. You'd probably want to hook them up something like Jerry does with the start and run windings on the Garbogen, paralleling the outputs of bridge rectifiers so they both contribute to the current flow.

Other than that, it might be a good place for cooling fins to suck or blow air past the coils in the outer ring.

Or (heh, heh) you could use the smaller ring with permanent magnets as an exciter to provide current to electromagnets for the outer ring. You'd need slip rings, but you'd have the possibility of doing voltage regulation by regulating the field current to the outer coils like an auto alternator uses. Could overspeed though.

3 foot disks? Man, I wish I had 1 foot disks...

Alan

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Author Topic: 2 Rings of Mags on an Axial Flux Alternator (Read 5851 times)