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Forum Index : Windmills : 8’ Lenz II ??
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| darlak Newbie  Joined: 13/08/2010 Location: United StatesPosts: 9 |
Hello, My name is dave darlak, I live near niagara falls, NY. I think a windmill is calling me, so... I want to build a Lenz II twice the size. I went to windgenkits.com and swiped there stator-rotor drawing and mocked it up to a 18 coil 24 magnet generator. question? will this work? I don't know enough to know what i'm doing, but i know enough to know i want to make this....  |
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MacGyver Guru  Joined: 12/05/2009 Location: United StatesPosts: 1329 |
darlak Welcome to the 4m. You seem eager. My advise would be to research this until you're blue in the face, then: Go for it! There are a few basic "rules" and they are as follows: Coil-to-magnet ratio should be 3:4. Space between magnets should be about half of one magnet's width. Once you've decided on (alternator) size, build your magnet wheels and wind ONE "test coil". From it, you will be able to determine how many turns per volt your combination of magnets and spacing will produce. Once you have the turns-per-volt number, figure out how many individual small-gauge wires will fill the winding space and combine as many individual wires as you can to fill the space. This is called winding "in hand". OR you can use a single wire of the appropriate gauge, but you will waste valuable space this way as smaller wires fill the spaces better than large ones do; your call. From your drawing, it appears you are choosing to wire this in "STAR". That's fine, but I'd research both star and delta to see which you would prefer. Star is the most prevalent from what I've seen, but it would be good to know the difference and make the choice based on your research. For best results, wind your coils in the approximate shape of your magnets. If using round magnets, make sure the "hole" through the center is no smaller than the outside diameter of one magnet or you will experience what is termed a "canceling effect" and actually lose voltage each pass. That should start you off in the right direction and give you enough to do for a while. Be sure to post your results for all of us to keep track of your progress and use a digital camera to post pictures by clicking on the little picture of a tree with a blue arrow up in the tool bar of the "Post Reply" box. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| darlak Newbie Joined: 13/08/2010 Location: United StatesPosts: 9 |
thanks for the reply. looks like dumb luck got me the first two points pretty good. Once you have the turns-per-volt number, figure out how many individual small-gauge wires will fill the winding space and combine as many individual wires as you can to fill the space. This is called winding "in hand". OR you can use a single wire of the appropriate gauge, but you will waste valuable space this way as smaller wires fill the spaces better than large ones do; your call. this i will have to sink my teeth into and try and comprehend. i'm slightly a jack of all, master of none, i'll have to give it some thought and slow down. I'm busy at work right now, this is supposed to be my winter project, but i think it's taking over at the moment... thanks mac, i'll be updating and asking more questions! |
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| darlak Newbie Joined: 13/08/2010 Location: United StatesPosts: 9 |
now you've opened up a can of worms..... i want to make it switchable... Ideally an alternator starts off wired in star, and then at a certain RPM switches to Delta. This maximises the amount of power sent to the batteries and the overall efficiency of the system. Most large commercial wind turbine generators do exactly this switching from star to delta when optimal to do so. The technology is very simple since it is essentially the same as that used to soft-start motors - starting in star and then switching to delta when everything has got going. |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Star delta switching is common but you would be far better off to build the thing right and not messing with this unless you have to. (its a bandaid for a poor design) If you get the coils right you will not need to have switching as the whole avantage with a AXFX generator is to wind the coils to suit the design, with regards to rpm, cutin, blade size, to suit the voltage required and the average wind speed. Pete. Sometimes it just works |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Is it just me or did the page actually grow sideways a bunch? . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Its the strong wind and steriods that has made the page grow 
This happens when people dont downsize their photos to a suitable size. Hint..Hint.. Pete. Sometimes it just works |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
[Quote=darlak]this i will have to sink my teeth into and try and comprehend. This took me a while to understand also, so don't feel like the Lone Ranger. Here's the deal: Depending on the strength and placement of your magnets, plus the size of the "air gap" between the magnet wheels, the arrangement will produce a certain amount of energy. That reminds me, I forgot to tell you the air gap rule. It is, simply stated, twice the thickness of your magnets times 75%. The resulting number is the size of the space between the wheels. Remember that you have to leave a little room for things to glide past each other and not drag against coils/magnets and that's the size of the space you have to work with. Now, what you do is wind a coil that fits. Personally, I like to use 30-gauge enameled copper wire. The reason is simple for me; I have a ton of the stuff kicking around my shop. A better reason would be to get as many turns on the coil as you can jam into it without things striking each other as this turns. Remember, the stator, which holds the coils, is stationary; it does not move. The magnet wheels whir by on each side with a N-S, then a S-N, then another N-S and so forth in an alternating fashion. Anyway, once you have the coil constructed, hold it in place and spin up the magnet rotor(s) [they're hooked together on the same shaft], then take a voltage reading. Set your meter to alternating current. Let's say you have 400 turns and the thing produces 40 volts at a "cut-in" speed (I'll explain this term later on) of 300 rpm, but all you really need is 10 volts. That means you can get rid of one forth of the windings and still have all you need, but now you have way more room. What that means is you can go to a thicker wire, which will mean less resistance in the winding and you'll get better amperage. If on the other hand you have a situation where you've used a thicker wire for your test coil and that size wire produces not enough voltage, but you're out of room, you can step down to a smaller size wire, but pull from two or three or however many spools you need to as you wind the coil to make the number of turns better match your requirement. Remember, voltage = number of turns on the coil. But here's the trick: what you'll do is join the ends of each individual wire together, so "electrically" it's just one wire made of several "strands" joined at the ends (soldered). This arrangement will have less resistance and produce more amperage and is called winding "in-hand". You'll see that all over the place and that's what it means; winding using several strands together to form one wire joined at the ends. Make sense? Mull it over a bit and remember that voltage = number of turns and amperage is dependent on resistance. That's just how it works. Think about it until it "clicks"! Another "trick" I do on test coils is to bare the ends using a propane cigarette lighter to ignite the enamel on the ends of the wire, then I scrape it off with sanding cloth and finally, I pass it through a tiny galvanized washer and twist the end. This arrangement allows me a positive surface on which to clamp my meter leads. There's nothing more frustrating than to be holding the coil in just the right spot between the wheels as the lathe spins things and you get no reading because the silly alligator clip has slipped off the end of the copper wire! When you understand this much, ask and I'll try to explain "cut-in" speed. It's not hard. None of this is actually hard, but there's a learning curve and too much too fast is not good. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| darlak Newbie Joined: 13/08/2010 Location: United StatesPosts: 9 |
picture adjusted, thanks for that post mac, i'll read it later tonite at a slower speed when i'm not supposed to be working so it has a better chance of grabbing some brain cells and making them get it. dave |
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| itsandbits1 Regular Member  Joined: 13/08/2010 Location: CanadaPosts: 81 |
the thing you have to keep in mind when you make a larger diameter is that the speed of revolution slows down and as the alt volts depends on rpm it could cost a lot of power to go bigger rather than the opposite |
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| darlak Newbie Joined: 13/08/2010 Location: United StatesPosts: 9 |
excellent point. i was thinking bigger was better, but i can see i have more homework to do. |
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niall1 Senior Member  Joined: 20/11/2008 Location: IrelandPosts: 331 |
mmm...but erm maybe as the pole count is now double ...the frequency would be the same Itsandbits1 ?...not sure about about my reasoning there it would though be a real beast of an alt at that scale up...those mags seem pretty strong and build wise it would be an enormous challenge....i think some of the big 17 foot hawt axial machines might even use something similar rotor size wise.... i like really vawts but am guilty of never trying to build one ....i wonder how much extra power you could expect from doubling the the size to 8 feet and leaving the diameter the same ? ...an axial alt capable off 1k wouldnt have to be near as big or complex...i think ps...very nice work on the mock up diagram Darlak..it shows the phase relationship very nice...i like looking at pictures ,cant understand anything else...  niall |
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| itsandbits1 Regular Member Joined: 13/08/2010 Location: CanadaPosts: 81 |
I don't think he was going to make the alt that big, just the vawt in my understanding. the speed of rotation would slow way down in the same wind but in where the coils are the frequency would be reduced a lot too unless you increased the amount of coils and magnets to match the speed reduction of the vawt, because it is all related to the speed you pass through the coil with the magnets. I haven't tried to figure it out but I think that is the way it would go. when you have to do that you would probably be better off gearing the system up to the gen |
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| niall1 Senior Member Joined: 20/11/2008 Location: IrelandPosts: 331 |
hi Itsandbits so it sounds a bit like building up the vawt x2 in size (including diameter) and kind off gearing the existing alt x2 ....the alt build shown in the utube videos does look a very nice strong build would be an interesting project.... one thing about vawts seems to stick on my mind..theres tons of video on utube of very nice vawt builds , but invariably they seem to be always tested ..kind of...on the ground or just a meter or two off it or a roof top ...maybe just a bit unfair on vawts i think niall |
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| itsandbits1 Regular Member Joined: 13/08/2010 Location: CanadaPosts: 81 |
i don't know what the relationship is balancing the alt against the turbine though there is the lift versus drag concept too to balance out. gearing up creates more drag at the shaft of course because you always have to keep in mind for every action there is a reaction. The only thing is with the drag type you have more start torque available to push the gearing and the wind is always pushing on them whereas the lift type; when the rpm drops in relation to the wind, loose the lift power and most of them don't work very well as drag units . even the commercial units seem to go more tall than wide and I think it is all in the aim of keeping the revs up. The axial flux with the dual rotor though seems to be the best bet what ever is used to drive it; no cogging. |
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| niall1 Senior Member Joined: 20/11/2008 Location: IrelandPosts: 331 |
its interesting now wondering about a vawt machine ...a bit worryingly as well sorry about drifting on your thread Darlak....  niall |
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| itsandbits1 Regular Member Joined: 13/08/2010 Location: CanadaPosts: 81 |
I think we're still on subject; maybe a little in depth in a vague sort of way,but if you are going to build some or all of this should be considered. Good luck when you get to the build. |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Crew There's a commercially-manufactured VAWT called the "Wind Spire" and there are several videos on youtube. If you count the rpms of the one shown "generating at speed" it looks like it's running somewhere in the vicinity of 300 to 400 rpm. One must assume, therefore, that the "cut-in" speed is somewhere at the low end of that range. One nice thing about the axial-flux design is, you can build around the "cut-in" speed. There are many trade-offs, but if your mill only turns 400 rpm maximum, all you'll have to do is figure out a way to get more windings inside the air gap. One way would be to decrease the wire size, but that increases the resistance; not the greatest choice. Another and perhaps better method would be to increase the magnet thickness, thereby increasing the "sweet spot", which is at the middle of the air gap supposedly. The gap size is calculated: 2 x magnet thickness x .75. So, if you were to build a ginormous-diameter and subsequently slower-rotating mill, the ax-fx alternator could be augmented to handle the slower rotation (I think). In conclusion, I think a 'bigger-than-normal' vawt is a possibility. For me it'll never happen simply because I live in a city and the last thing I need is a hot-air-balloon-sized gadget whirling around atop a tower in my back yard! 
. . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| itsandbits1 Regular Member Joined: 13/08/2010 Location: CanadaPosts: 81 |
with vawts it's a lot more difficult because you are working with more variables than the vawt. With the drag, versus lift blades, and the lack of physical torque that the vawts have, you need to be a lot more critical to get a system to work for you. The way the low rpm is tackled is with more coils and magnets but also doubling the rotor; one on each side of the stator which almost doubles the magnetic flux; by all reports. when you have cut in at 100-120 rpm and top speed in the 250-300 rpm area, you want every advantage you can get. This and getting the proper windings in place, makes it challenging and technical so unless you are experienced; and maybe not even then, expect to try things out as you go. |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
[Quote=itsandbits1] . . . doubling the rotor; one on each side of the stator . . . FYI, this (two magnet rotors) is the 'standard' build. If you want to up it even more, you can place a additional set of magnets between the existing two plates, allowing each of their faces to see the opposite face on the wheel magnets. I've done this and I have a picture so you can see what I mean: 
Doing this allows the intermediate magnets to force the magnetic flux lines to travel in a straight line while providing a 'return-circuit' for the flux at the same time. I'm not sure if when doing this trick the air gap is figured in the same way, but it's likely the same. When I did it, I used the same air gap as I would have used for just two wheels. The magnets in the center wheel are press-fit and glued into a HDPE (high density poly ester) wheel I cut out from a flat sheet using the faceplate on my little lathe. Now that I look more closely at the picture, maybe I used foam-filled PVC; I dunno! Hope this helps. . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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