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Help with low wind Alternator
By CmeBREW, Section Wind Posted on Mon May 7th, 2007 at 03:53:46 AM MST
Help with low wind Alternator

Good summer to you friends!
I would appreciate some help with the number of turns (16ga.)for my coils with this smaller low wind alternator i am currently working on. This one is alittle different--so any info. or suggestions are most welcome. It is a 20mag / 15 coil dual rotor 3-phase set-up.(5 coils per phase) I will show my layout board. Hope I done it right. I am still more of a beginner and this hopefully will be my first real, usable power alternator. I had stupidly purchased 75 of these smaller 1" diam. by 1/4" thick N42 magnets and needed to do something with them. I WISH I had spent alittle more money on the decent size magnets (2"x1"x1/2"thick) now. (live and learn!!) On this alternator I also made (welded) a fan in the center of the rotors that pulls some fresh air in thru 15 small (3/8") holes on each rotor. The holes are on both rotors (30 total/lined up) since I am trying to make a variable pitch hub.(Basically- 3 little cams and one big adjustable center spring / The angles of all 3 blades will always be the same). I don't have the hub made yet--but will fairly soon. It is very challenging. Nevertheless, the 5 fan fins work quite good. The magnets are epoxied down and make some moving air by themselves-- but the fan makes it at least twice as good--especially over 400rpm. I plan on leaving the holes in the center of the stator coils open for better heat dissipation. I'm going to do the good old fiberglass resin method.

The 1" diam. mags do not have holes in them--- I simply used 1" washers to do my layout board. Everything is centered and balanced.

The thing already must weigh 40lbs. However, all 40 of the magnets only weighed 2.5 lbs. I doubt I'm going to get much power out of this one in low winds. I was hoping for 20-40 watts in a 10-12 mph low summer breeze/wind. I was thinking of an 8' rotor and controlling furling ONLY with the variable pitch blades via the adjustable spring in the center. (Now that its summer time,,i was hoping to get as much power as possible out of the lower winds (7-15mph), even if it means sacrificing high wind power.
I am quite mechanical, but I'm not to swift on the #of turns for my coils since this project is alittle unusual. There also is some "stainless" in the steel rotors. I hope it doesn't take too much flux away. There may be some silicon in them also. I got the 1/4" thick steel (for the rotors) from a friend who works at a big factory that makes giant motors and generators. These are from the scrap there. They do not rust. But my magnets stick VERY well to them though. These rotors are 11.25" diameter. I used a small trailer hub with these rotors.

The 'fan fins' are 3/4" wide by 2.25" long. They are only welded on the bottom rotor. The cooling air it makes, seems to be about the same with the rotors turning in either direction. As you can see, I'm no heating and air expert. I'm just trying anything to help with cooling the coils! You can feel good wind coming out the sides. Of course, thats without the stator inside though. But it will have 3/8" air flow on each side of the stator. So it should be pretty cool.
Ok. Back to the coils. If I leave anything out, please ask me. I'm sure I will.
I plan on a 3/8" thick stator and close to a 1/2" magnet to magnet air gap. I did a test coil with the 1/2" magnet air gap and using my 16 GA. wire. I did 64 turns, but it was too big for the spacing. (55 turns should fit) Anyway it only showed about .3 volts @ 60rpm and 1 volt @ about 150 rpm. (guessing) I held the coil in there with my hand. That is way under what I hoped for. I guess the flux is somewhat weak for those little mags and that air gap. I guess I can always use small ga. wire to get the volts up. Its for a 12volt system. I was thinking of a star hook up. I want the stator to be 3/8" thick for minimum stability and less possible warpage.
But only 1 volt is only 5 volts per phase @150rpm. --Which is not going to swing it. Did I even do the 20/15 layout right?? I thought with 40 mags I would've got more than this. Anyway, any help would be greatly appreciated!
--Thanks.

Help with low wind Alternator | 13 comments (13 topical, 0 editorial)

Re: Help with low wind Alternator (3.00 / 0) (#1)
by willib (willibur at comcast dot net) on Mon May 7th, 2007 at 01:12:19 AM MST
(User Info) http://www.njwind.com/webcam.html#

I dont recomend to someone else, something i havnt done myself
if you make your coil hole 0.54" dia , the distance between your mags, you can fit 101 turns , if you desire.
i suspect you coil dimensions were not near what they could have been.
ie. 2" od x 0.54 ID x 3/8 thick.
you made them round i hope?
i ran your coil through my program and got this output..

Wire dia. = 0.0520 inches ohms per foot 0.0040160
coil od = 2.000 coil width = 0.375 coilid= 0.540

Final Diameter = 1.996
coil radius = 0.730
Num turns per coil radius = 14.038
Number of turns per coil width = 7.212
total number of turns 101.239
wire length(feet)= 33.866
Single wound ohms per coil 0.136007 ohms
Total ohms for one phase (5 coils) 0.68 ohms

i used 0.052" dia for the #16 ga even though it is 0.0508"dia to account for the build
the ohms per phase are a little high , but if you want the charging voltage you need , this is the way to go IMO
also you can leave off the last 7 turns and save 43" of wire and 15 milliohms per coil
Carpe Ventum (seize the wind)

Re: Help with low wind Alternator (3.00 / 0) (#2)
by Flux on Mon May 7th, 2007 at 01:50:56 AM MST
(User Info)

You are close. Your voltage readings don't tie up between the 2 speeds, cheap meters are not very accurate on ac below about 2v so that may explain it or you may not have been accurate enough. I don't know your grade of magnet and there is the question of the material for the discs but I predicted a higher output than you measured so it would be a good idea to go back and repeat the test accurately and preferably at a higher speed.

Using your 1v ( ac I assume) at 150 rpm, that gives you 5v ac rms per phase.

Star connection gives you 5 x 1.73 = 8.65v rms. DC volts will be 8.65 x 1.4 = 12.1vdc.

So allowing for diode drop your 12v cut in speed will be a bit over 150rpm, fine for an 8ft prop.

I suspect you can get what you want with less turns of thicker wire but if you have that wire then use it. You can squeeze the coils oval ( wind on an oval former) to get more turns in. I would keep the hole 1" in the radial direction but it won't matter if you reduce it in the circumferential direction to gain a bit of space.

Try your test more accurately. Don't aim for a cut in below 150 and that is lower than you will probably end up with ( you can raise it a bit by opening the magnet gap but don't go too low to start with).

You will need to set your pitch control to keep things down to about 200W maximum output with that thin wire but it should work well in low winds. You should get about 60W at 10 mph.

Flux

[ Parent ]

Re: Help with low wind Alternator (3.00 / 0) (#4)
by CmeBREW (smke833f@hotmail.com) on Mon May 7th, 2007 at 08:30:31 PM MST
(User Info)

Thanks Flux and others,
You are all correct. I can't get anything by you guys! That test coil i did was in a hurry and it had alot of air in it. (crossing wires) That is why it was too wide for the space. I think my meter is fairly accurate. It has a 2v scale. I think its one of the finer "cheap" chinese meters. The coil was about impossible to hold in there by hand to get a good reading as Luv2weld said. It was weird. I kept trying to hold it steady but the magnets kept hitting it. It almost vibrated or something. It was strange I couldnt seem to hold it steady. I even put electrical tape all around it, but it still would start hitting magnets. It was amazing to also short the coil though---because it made the rotor difficult to turn just with the one coil! 15 coils will surely hold it back for an electrical shut-down. The coil was oval shaped. Also they are N42 mags. Most likely tomorrow I will fasten the test coil in there with plywood and get a more accurate reading. Or I may make another test coil more carefully this time. I probably need to make a better coil winder set-up. Winding coils surely takes calm and patience!
I am very glad my set-up is correct and that It will work. I would be very happy with 50 watts+ at 10mph. My 4' treadmill generator gets "El Zippo Nothingness" in these lower breezes of summertime. So 180-200rpm cut-in is OK for an 8 footer. Thanks for clearing that up. I remembered the 1.7volt "star" thing later that night, but I never could understand the 1.4v AC to DC thing. Well that is great news. I am in the right 'ball park' after all! For certain, the polarity of all the magnets is one million percent correct. I did check that 10 times over. Can't wait to see what it will do! I'll get back to you when I redo the test coil. I also had one little question about the variable pitch blades that would help me alot. -Thanks!!

[ Parent ]

Re: Help with low wind Alternator (3.00 / 0) (#5)
by rpcancun (hobbyshopmx@hotmail.com) on Tue May 8th, 2007 at 12:27:54 AM MST
(User Info)

Do you have any pics or diagrams on your blade pitch control?

Thx

[ Parent ]

Re: Help with low wind Alternator (3.00 / 0) (#6)
by CmeBREW (smke833f@hotmail.com) on Tue May 8th, 2007 at 05:08:11 PM MST
(User Info)

Ok, I did further testing. I secured the same test coil on one of my stator bracket bolts with alittle piece of plywood and taped it down. Now I am getting .7 volt(AC) @ 60 rpm //and 1.4 volt @120rpm. So it looks very close to 1.6 volts (AC) at 150rpm. This is with 64 turns of 16ga. I should be able then to get 70 turns in the space (2"OD for each coil) easily. This allows some room for 'not so tightly perfect' wrapped coils. So,,, 1.6 x5 =8volts. / Star connection is 8 x 1.73 =13.8V ///13.8 x 1.4 (ac to dc) =19.3 volts. That sounds more like it! However, If the final open voltage is something like 24 volts @150 rpm, could I have a problem with early SLALL?? The alternator will be about 100 feet away from batts. It also would be nice to open the mag air gap another 1/16" for more 'safety room' incase the rollerbearings loosen a bit. I think this will work. If it did stall early, I could open the gap alittle which is what i would like anyway. -Thanks amillion!

I also had a little question about the Variable pitch hub and blades I am going to try to make.(for Flux or anybody)
I would appreciate brief opinions. Below in Rpcancun's question I posted the basic design I am thinking about trying first. My question is: CAn I make my 3 blades with a 12 degree angle all the way down the blade clear to the tip, in order to, as the wind mph (and thus pressure on the blades) increases, the wind will slowly turn the pitch angle all the way up to 0 degrees and then go past zero degrees alittle bit to air brake? This method seems the best way to go, since it seemingly would also increase efficiency when the blades go to a steeper angle as the wind speed increases, causing less drag and thus increased speed. I do not quite understand "feathering" the blades in the other direction since it would cause more drag. It is difficult to even explain this without drawings. Sorry about that.

[ Parent ]

Re: Help with low wind Alternator (3.00 / 0) (#7)
by CmeBREW (smke833f@hotmail.com) on Tue May 8th, 2007 at 05:27:54 PM MST
(User Info)

It put my last comments in the wrong place. I will put the drawing here.
I have only seen one drawing of a variable pitch hub---and it was incomplete. So I am going with the first most obvious design in my brain. It would be nice if I could see some other designs instead of remaking the wheel again. But I can't seem to find much info. on variable pitch hubs. I drew the basic idea of what I am going to try to make first. I may add 'linking rods(arms)' to the blades later if the angles of the blades do not stay close enough together with the center control bushing. After I make it I will post the pictures, and then you can see in 3-D. I know its difficult to see. Sorry I don't have a CAD.

[ Parent ]

Re: Help with low wind Alternator (3.00 / 0) (#9)
by Disaster Transport (kjehgahagan@yahoo.com) on Wed May 9th, 2007 at 07:04:40 PM MST
(User Info)

It looks like fun to make. All the welds concern me especially with getting everything square and flat where you need it to be.Heat causes metals to do funny things so weld little as possible (tack) the entire thing. Allow to air cool and then,stich where needed, you will have greater success and stronger metal as a result. over laping steel and clamping it before welding is also a must.do not bend hot welds it causes stress fractures in steel that will show up later possibly in a imploding manner that will have you searching for your parts in your gutter.....HA. Grind off unsatisfactory welds and start over.If all these precautions are followed you have one fine weldment, exactly like every thing you have desidned thus far...
Wind power is the key to time travel....
[ Parent ]

Re: Help with low wind Alternator (3.00 / 0) (#10)
by CmeBREW (smke833f@hotmail.com) on Thu May 10th, 2007 at 07:43:53 PM MST
(User Info)

Thanks Disaster,
Yes, it is and will be very interesting and fun. I can't wait to see what it does.(even IF it fails) As you may have quessed, I don't have a lathe. Of course a lathe would be way better. But I've had decent success with tack welding parts. Alignment of everything is always tricky. I always 'criss-cross' (alternate to opposite side) my tacks to even out the heat some. For this first prototype, I will also tap a grease zirk fitting into each big bushing. And tack weld a couple more washers to 'lock' each blade mount pivot into it's respective bushing.(on each side) And semi-harden the steel like dear Old grandpa use to. -We'll see!

[ Parent ]

Re: Help with low wind Alternator (3.00 / 0) (#11)
by Disaster Transport (kjehgahagan@yahoo.com) on Fri May 11th, 2007 at 02:20:08 PM MST
(User Info)

I will make this Monday with a hub Im picking up toniteDo you see any thing wrong with the design.Do you like the sspotface for accurate layous and securing the mags better. I havent purchased the 2 inchers yet...But check this out if you dont see a diagram just go check out my files here at the site.Later

Wind power is the key to time travel....
[ Parent ]

Re: Help with low wind Alternator (3.00 / 0) (#12)
by Disaster Transport (kjehgahagan@yahoo.com) on Fri May 11th, 2007 at 02:45:49 PM MST
(User Info)

Sorry new format..

Wind power is the key to time travel....
[ Parent ]

Re: Help with low wind Alternator (3.00 / 0) (#3)
by luv2weld (luv2weld at hughes dot net) on Mon May 7th, 2007 at 07:58:34 AM MST
(User Info)

Really nice work. If the rest of the build is as good as the pictures you posted,
you should have a very nice generator.
How about selling those small magnets and moving up to larger
ones??
The one thing that caught my attention was " I held the coil in there with my hand".
I really don't think you're going to get accurate measurements that way.
You want to know how the thing is going to work after you get it on top of the
tower. And since you won't be up there holding the coils,-----get the picture??
Even on your best day, you're probably moving a little, in and out from the
magnets, so your results might be close but not as good as you'd get with a
solid mount.
One more thing, where is this factory that you got the rotors from?????
Man, I would love to go through the scrap pile there if they are throwing
things out like that!!!!!!!

Ralph
"The best way to kill time is to work it to death!!"

Re: Help with low wind Alternator (3.00 / 0) (#8)
by CmeBREW (smke833f@hotmail.com) on Wed May 9th, 2007 at 07:26:29 AM MST
(User Info)

Thanks Luv2weld,
Sadly, that factory is being shut-down after 60 years due to down sizing,etc. I appreciated the free steel, but the problem is you never know whats in the steel. I got one small piece from there once that kept catching on fire everytime i welded on it! Must of had magnesium in it or something. Anyway I have a couple of other sources to get steel cheap.(or free)

[ Parent ]

Re: Help with low wind Alternator (3.00 / 0) (#13)
by CmeBREW (smke833f@hotmail.com) on Fri May 11th, 2007 at 03:55:10 PM MST
(User Info)

Wow! what happened to my pictures all of a sudden?? There gigantic. They are well under 100k. They are normal in my photo files. I wonder how that happened? Can it be fixed?? Man thats weird.

Help with low wind Alternator | 13 comments (13 topical, 0 editorial)

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