Basic 3 - Phase Stator question

[TomW]

ghurd;

I was kind of thinking along the same lines a "band" around the half way point up the wings like barrel bands.

Cheers.

TomW

[electrondady1]

fin, i believe it's a dual rotor alt.

[CmeBREW]

I wish I had good news. That tiny vawt rotor is smaller surface area than a 3 foot hawt. I'm sure most everyone here already knew what was going to happen.  STALL,STALL, and terrible STALL!

I just thought it would stall alittle later though. I was wrong.

It does alot of 'trickle charge' (.5 - 5 watts) upto 100rpm, but in the big winds it's like hitting a brick wall around 100-120rpm.  It usually stalls at only 6 watts(.5amp) even in a 20mph wind.

 I could disconnect one of the phase wires and it would go up to about 12 watts before stall. But then you miss the 'trickle charges' keeping that way.

Or, I could disconnect all and let it free spin faster and then hook up ammeter quick and it would briefly show 30 watts or so. (Which is cheating by the way)

There were even upto 30mph gusts today.  

I hate to say this, but I am beginning to believe there is not much power in these basic drag pvc vawt rotors like I just made. I was just experimenting. At least I tell the TRUTH. I will keep messing around with it though. It is discouraging though. I will try to contain my hopeful 'speculations' more, from now on.

Since they are now outlawing small windmills in many,many counties everywhere,(more than ever now)  I was just hoping to make something less noticable, even if it does only do a fraction of the power a HAWT does.(I wanted to put up several)

  But designing and making something new and matching a generator to it is extremely difficult and (will be) alot of work to actually make one that usefully works.  

Finsawyer:  I think stators like you're talking about (or similar) have been done before, (overlapping coils, electronic switching between sets of 3-phase coils,etc.) but,,, it is simply over my abilities to make at this time. I had a heck of a time with the basic one i just made . (and I am very glad that it works!)  I had alot of cross-overs and alot of air in the coils. Plus, the exact spacing of my coils is FAR from perfect.  I will keep it in mind If I ever get the skill to believe I could make something like that. Besides, for me, cut-in is not the problem anymore. I can get 30rpm cut-in now.  Yes, its the WHOLE thing is the problem now!  -Thanks.

 

[TomW]

Brew;

If they are working on outlawing you best get one or six up so you get "grandfathered" in.

Seriously. I doubt they can make you remove it once its up because they write a new law.

Cheers.

TomW

[ghurd]

Maybe open the air gap a little.

My stuff stalls when the PMA is too efficient or powerful for the blades.

G-

[electrondady1]

i'm not sure i follow your last post

 and what the source of your disappointment is .

you designed the alt. for your big mill but found it didn't turn fast enough to reach a charging voltage.

but by using the smaller mill it could reach charging voltage (thats good)

you also found that even in higher winds the mill has a peak of 120rpm .

you also found out that even with strong winds your mill design does not fall apart.

i hate to go all optimistic on you but you seem to have designed and built a

devise that will charge a battery in modest winds,  survive a storm

and looks really good. !!!

[CmeBREW]

I quess I was overly dissappointed last night. Sorry about that. Yes, I went to the OTHER extreme by putting that tiny vawt rotor on that strong alternater--which is obviously big time STALL.

It stalls QUICK too. I can turn the alternator by hand (no rotor on), and I had no idea it requires such extreme Torque (from my arm) just to make 25 watts at about 150rpm. It would probably make a nice 100watt Pedgen. This alternator sure wants to raise the AMPS FAST after about 100 rpm. It may do 100watts at only 200rpm!! But the TORQUE required would be INSAIN. Now I fully understand the need for speed. To keep cutting the torque requirements in half. I wonder if everyone else has such a hard time getting 25 watts turning their alternator by hand?

Ghurd is right. I will go buy some more 1/2" washers and open the gap some. He and others are also right about the big rotor being 'flimsy' especially in bigger winds.

I will work on stabilizing them with a band or another disc in the middle hopefully this weekend.

Maybe I can get something out of it yet.

Also, I was thinking last night, that that nice rotor design from Ed (Len2) might just work great for this alternator.  

[disaray1]

Cme, I have come to about the same conclusions as you about vawt (at least simple savonius that is), just after doing a few tests with different pm dc motors. It's clear to me now how inefficient the vawt is compared to the hawt. The single barrel sav has one surface doing all of the work while its mate is resisting the work being accomplished. The hawt, on the otherhand, has all blades working constantly in unison. These same conclusions surely have been recognized by everyone who has ever built one, you and I are just the latest here to figure it out. I think a vawt can work to produce substantial electricity; just not a simple sav. It's got to be a darrieus or derivative to get anything useful out, and still it'll have problems. But building and learning is where the fun lies.

 What I find the most interesting about this whole project, is observing in myself the glitch in human nature that causes generation after generation to try something that's been done thousands of times before with poor results, thinking that everyone before us must have just not done it correctly, or that our results will surely be better than the rest, because we are smarter. Yes?   It's the repeating history thing. As smart as humans are, we just cant help ourselves from making the same mistakes as those before us. Over and over and over. War, politics, religion, government and windmills. Off topic, sorry.

 The best I've gotten so far with the barrel sav was 24 watts...12 volts at 2amps during a storm gust of about 30mph. Lasted for about 3 seconds. I know I can do better...must be time to add the second barrel and make a few more time proven mistakes.

 David

 Ps. I keep thinking about the clean air at 100 feet and up. A DanB machine at eight feet off the ground, I expect, would be a poor performer also (probably because the blades would be in the dirt!)and I suspect that your vawt at 100 feet would be much much happier. Can you put up a tower, or is that out?

 

[finnsawyer]

Well, I don't think it was a cheap shot.  I think the basic question about the diodes was answered.  As far as going off topic, he still was concerned about the relatively high cut-in RPM.  This naturally leads to questions about the construction.  So, the question dealt with the rotor thicknesses.  If they are too thin the iron would be in magnetic saturation.  A possible solution would be to add more thickness to the rotors.  Not a perfect solution, but doable.

It would seem that with about 40 magnets he should get more voltage than he does, even with 1/4 inch thick Neos.  Before he rewinds the stator with thinner wire I think he should do an experiment.  Double the overall air gap and measure the voltages at the same RPM.  The flux should be cut in half as well as the voltage, but if the iron parts are in saturation it may not be.  He may, in fact, be able to wind thicker coils with the same size wire and get a lower cut-in.

As far as the effect of the iron in saturation, think of it this way:  Normally, in a magnetic circuit the reluctance of the iron is low compared to that of the air gap, similar to a 1 ohm resistor in series with a 100 ohm resistor.  So, doubling the 100 ohm resistor cuts the current in half.  Same for doubling the air gap relative to the magnetic flux.  With the iron in saturation it might be equivalent to 50 ohms in series with the 100 ohms.  Doubling the resistance to 200 ohms does not cut the current in half.  A similar effect could exist with the magnetic flux if the iron is in saturation to begin with.  In any case that simple experiment should be worth doing even if the result is negative.

To recap, my original question was not a cheap shot but an attempt to start a dialogue.  If he chooses not to respond that is his decision.

While everybody else around here can voice their opinion, I guess I'm not supposed to.  When I do it, it's a cheap shot.  

[finnsawyer]

Just for the record, the coils in my design do not overlap.  In fact they are spaced by one magnet's width apart.  Since they are not scrunched together accurate placement should be easier (or am I just biased).  Anyway, good luck and enjoy.

[ghurd]

Maybe Ed will chime in, but I don't think that alternator will work with the Lenz2.

Those are lift based and go like heck, so it would stall even quicker than the one you have.

Ed?

G-

[CmeBREW]

Thanks guys.

     Well, I did test some things. I was fearful that I may have put a coil in backwards, and that it may be causing magnetic braking after cut-in. I took the alternator down to test in my shop. I highly doubt thats the case because, once again, all 3 phases tested out at 7 volts AC each at 60 rpm, and 14 volts each at about 120rpm.

I can 'free spin' the alternator pretty fast by hand (UNLOADED) and get between 30-40 volts DC. (after rectifiers) This sounds correct to me. I even tried the 6 diodes like Danb showed incase I hooked the rectifiers wrong---but it did the same exact thing.

I don't think there are any shorts.

I believe this alternator I made is the main problem, NOT the Vawt rotor!

I will try to explain.  Cut-in IS at 70rpm as I had wanted. But It is hard as HECK TO TURN  by hand, especially after only about 90 rpm!!

After only 100 rpm it is MEGA difficult to turn by hand. I can usually only maintain about 10-12 watts turning it by the threadrod that comes up from the hub. For a second or two I can barely hit 18 watts. (1.5amp) I can't turn it any faster.

Therefore, I believe I have very bad STALL due to the stator I made.

 The amps seem to want to raise way TOO fast.

I believe Finsawyer mentioned it. I will have to re-make the stator and use the same 20 GA. wire and use MORE turns and thus thicker coils and stator. I'm thinking 3/8" thick and a 1/2" mag to mag air gap.  Then I can even lower the cut-in to 50-60 rpm, and because the mag flux is weaker, the amps won't try to raise as fast, thereby causing a severe STALL situation. (and this time I will leave all 6 wires come out)

I still do believe I can get SOME useful power out of my Vawt if I can match the alternator within range.  Making something for the first time is WAY more difficult than simply COPYING someone else's design. So please give me some time.

I haven't even put the REAL Vawt rotor (Vertigo SR.) on the altenator to test it yet! I haven't had time yet. Before I do , I want to stabilize the 'flimsy' long blades by putting in a 3rd round support plywood disc in the middle. I will do it this weekend and test it. I will also try to open the gap 1/16" to maybe bring it out of SOME STALL. But doing this will RAISE the Cut-in point which is not good for my situation. But I will try it anyway.

Finsawyer: Sorry I mis-quoted your idea. I will have to look at it again later. Sorry I don't understand anything about "Saturation" at this time.

I believe LENZ2 is a Drag AND lift rotor.  It goes faster than drag machines, so I was thinking if I opened up the mag gap, that rotor could have the high torque and speed I need for this alternator. His is 3 foot diametor--which is TWICE the torque of my 2 foot diameter--plus his rotor evidently goes much faster than mine.

[ghurd]

I think just opening the air gap will do it.

Two things make me think that way.

One, opening the gap (reduces voltage) and adding more turns (increases voltage) will sort of keep the voltage the same(-ish).  But the output will be limited because of the extra turns resistance, so some of the power drag will be there even if the output numbers don't show it.

Two, opening the gap raises the cut-in, but without the drag at low speed, the mill should go faster in the same low winds, so the low wind trickle charge might not be as different as you'd think.

How far away is the test battery?  Right under the VAWT?

Might find the resistance of the 100' of #14 to the main battery helps the situation too.

Very interesting project!

G-

[CmeBREW]

Thanks Ghurd,,

     These alternators sure are complex! I think you're right. There are SO many things, its difficult to explain. And I am just learning as I go, and I may be confusing some people. I am doing the best I can with my limited knowledge and experience. I only had 3 inches of 'leverage' turning the hub by the threadrod for those tests I just mentioned. I put a bar clamp on to get some more leverage, and now I can get 30 or 40 watts -but its not easy! The clamp gives roughly about 10 inches of leverage from the center point. I have to work most of today, but tonight and tomorrow I will open up the gap a bit, as you say, to hopefully get out of such early stall, and stabilize the flimsy blades and then test it again. By the way, last week I had let that big flimsy rotor 'free-spin' (no load) in a 35 mph BIG wind and it sure appeared to turn quite fast and it actually looked like JELLO as it was turning. It balanced itself good but sorta looked like jello jyrating. Sorta funny looking.

I have never tested the big rotor under the load of the alternator above (what looks to be) a 10-12mph breeze. So I am still excited to do so, even if I did mis-estimate the torque of this simple drag vawt rotor. I still hope to get something out of it, and will improve from there.

My test battery was right under the vawt.(8ft wire)

I was wondering if the fact that my coils are so 'sloppily' wrapped, and two of the coils moved out of place an 1/8" sideways, if that would cause such horrible Eddy currents, that it appears there is a magnetic brake on when you turn it above cut-in??

I had thought that since it is in 'STAR' it wouldnt have that problem. I don't know. But it sure seems like a magnetic brake is on when I turn it by hand, especially after 10 watts. (being inexperienced, I have no idea!)     -Thanks.

[ghurd]

I can't figure how there would be an eddy current problem only above cut-in, but I'm not sure.

The 'magnetic brake' you feel is power being made.

It's OVER twice as hard to make twice as much power, because the losses in the PMA increase as the power flowing in it increases.

Watts = amps x amps x ohms.  Say the coil resistance is 1 ohm, so 1A has (1x1x1=) 1W of loss.

But 2A has (2x2x1=)4W of loss. 3A has (3x3x1=)9W of loss.

If you are guessing at wind speed, I expect you are guessing it higher than it actually is.  Many people do.  I guessed it far over what it really was.

G-

[CmeBREW]

YOu are right. There was almost no leverage from the threadrods--what was I thinking!.(3"of leverage!wow)  I rigged up a 12 inche leverage and I can get over 50watts now cranking with my arm-- but I can only go so fast. I am getting a good 'feel' for what it takes to make WATTS at such low rpms now. It is more than I had imagined.

I will test everything together today and tomorrow- and see what I can get out of it.

Of course this is only my second rotor experiment. I think the 6" pvc would have been far better choice for these bigger radius rotors. The small arch seems to be too sharp on the 4" pvc I'm using now-- and I am having doubts that the wind is 'swirling' around correctly in the middle of the cylinder rotor for extra torque. Inotherwords, the 3"wide arch is so small, that it points toward the center point too much. 4" wide blades would be better I think.  (I also have 26ga. sheet metal to try)  

I think you are right about quessing wind speed. I have never seen a wind meter to have any idea. I try to quess low than high.  

I just quess by what the weather people say the wind day is suppose to be. Like today is suppose to be 10-15mph. Tomorrow is suppose to be 10-20mph. Its the best I can do at this time.

[CmeBREW]

Update correction:

"Yes, If I had a 6 volt battery I am certain it would do exactly what I was wanting. But I do not. The only way to make it work well for 12volt I think, is to have bigger and/or thicker magnets and extremely STRONG magnetic flux with a thin stator to raise the AMPS quickly with the slow rpm.  However, the wind rotor STILL manages to turn it slowly even in breezes from the very strong Torque and it should turn fairly fast in bigger winds."

I now believe everything I said above is wrong. Sorry about that,, but I just learnt some new things.  

A 6 volt battery would have STALLED it even WAY earlier-- as would have having thicker magnets and even stronger flux. Using 24ga mag wire (same thickness) would have STALLED it also. The main thing I've learned is--STALL is NOT simple with Vawts!!!

The rotor DID very slowly turn it, but it would have NEVER turned much faster in bigger winds. It was severely STAlled.  I just opened the gap to 1/2" and now the cut-in is close to 80rpm (which is good) and the amps DO raise alittle slower. And I put the round center plywood disc support in the middle of the wind rotor, so its no longer flimsy. I should know soon if it comes out of early stall and generates something.

Believe it or not, I am learning ALOT.  

[electrondady1]

cmebrew.

relax,

 you are simply at the stage of the wind mill disease were it completely changes your mind and body.

(just like vampires and warewolves.) lol

don't be alarmed if you start seeing wind geni possibilities everywhere

fight the impulse to remove bits from your car to make new alternators .

be aware there will be a strong inclination to take time off work so you can mess around with your windmill.

you are not alone , we are here to help you through

once you get your alternator dialed in,

 you might consider moving it to the center position and placing your new center disk to the bottom.

that would be a very stable configuration.

[Ungrounded Lightning Rod]

And with the low frequencies you get from a windmill the caps have to be HUMUNGOUS or you get negligible current.

[Ungrounded Lightning Rod]

It will be cheaper to build a new stator with more turns than to buy capacitors big enough to make the voltage doubler work.

[fcfcfc]

Try this 3 phase voltage tripling circuit...

.....Bill

[ghurd]

"Believe it or not, I am learning A LOT."

I think most people learn a lot more from something that DOESN'T work right the first 10 tries.

Couple thoughts that may give you an idea,

I bet you are greatly overestimating the wind, maybe by a factor of 2 or more.  

Don't even try to get 100ma in 6MPH.  It leads to stall or very poor performance in high winds, or both. If it's unloaded, it turns faster, reaching a higher RPM in the same wind, and it seems to help my stuff a lot.  Couple times it helped me a lot, like instead of 100ma in low wind and 200ma in medium wind, it went to 50ma in low wind and 750ma in medium wind (and did much more total charging).

If it is still stalling, could add a diode or 2 or 4 in series, to jump the cutin up a bit, without hurting the upper range a whole lot. More as an experiment than a permanent fix.

G-