Changes to my first wind machine.

[TheCasualTraveler]

     Well I finished my first alternator and was happy that it went smoothly and worked right away. It didn't however put out much power. I hoped to use it for low winds and it does just that, working almost everyday for most of the day but only putting out 3 to 5 watts. A trickle charger. A couple of times in a gust it put out 30 watts but they were few and far between.

     Then while reading posts I saw something Flux wrote, that it is actually easier to build a 24 volt machine than 12 volt due to the size of the wire and losses. Well I was downstairs in no time rewireing the bank for 24 volts and within a few minutes I saw it putting out 2 amps at 25 volts. Still small but 50 watts beats 5 to 10. I already knew that the higher wind speeds were more efficiant but for some reason it just didn't sink in that my 120 turns of #22 wire was more in line with 24 volts and a small machine doing high rpm's. On the other hand now I have to build furling since it spins so much faster. At 12 volts it took a 30 mph wind to make the blades make any noise at all.

     This all opens up a whole lot of possibilities just when I was starting to see the limits of what was possible for my wind area at 12 volts.

     Questions I have if I could get some opinions...

Would it be worthwhile to change my 8" rotor with 12 poles to an 8 pole but double up the magnets so they are 1/2 inch thick instead of 1/4 inch? The magnets are the 1/4 " thick wedge magnets from windstuff Ed. The stator is 9 coils, 3 phase , 120 turns #22 wire and the coils are 1/4 inch thick with a gap between the stator and rotor of approx. 1/8 to 3/16 inch. (I know most of you immediatly think dual rotor but I'm not there yet design wise but would still be glad to hear what I could expect with dual rotor.)

Would I be better off using delta instead of star for 24 volts?

You can see my setup
HERE

Made the link clickable. TW

[wooferhound]

You are pushing 22ga wire to the limit if you are getting 4 amps and it should be getting hot at 4 amps. Trying to get more from that wire will heat it up even more.

[ghurd]

Might try it Jerry Rigged for 12V.

G-

[TheCasualTraveler]

Thanks Ghurd, I looked up jerry rigged till I understood it. I had misconceptions about it from reading differant posts but it's clear now, except for 1 thing. I need 3 bridge rectifiers and wonder how important the type is. My first impulse is to go to Radio Shack and buy the least expensive ones that can handle several amps each. Would that work ok for my small mill? Also, do I still need some sort of blocking diode between the batteries and the already rectified output of the mill or would that be redundant?

[TomW]

Traveler;

If you have a bridge on the output no blocking diodes are needed. The bridge does that.

Cheers.

TomW

[ghurd]

The RatShak ones should be OK.

I'd use the 25~30A 400V (or PIV), if they still have them.

Might get a tube of heat sink grease too.  

RatShak won't have heat sinks nearly big enough.

The larger bridges have metal on the back to get the heat to the heat sink.

Avoid anything they have that is totally plastic.  Bad luck with those.

Of course, if it was me, I wouldn't get it there except in an emergency.

I think you will be very surprised with the 12V output in Jerry Rig if it was more like a 24V machine in Star.

Give us an update when the numbers are in.  Everybody makes a new stator because their wires are burried.  

I'd love to see how it compares!

G-

[TheCasualTraveler]

    Well, tonight I took my mill down and did some experimenting. For reference, single 8" rotor 12 pole 9 coil 3 phase, 120 turns #22. I had already changed the blades from 55" flat plywood blades to 64" PVC blades. Since I have 16 magnets the first thing I wanted to try was pulling the 12 poles and redoing it with 8 poles with the magnets doubled up. I slid the rotor back in and gave it a spin, 1 and a half volts! I didn't understand so I looked at the rotor and coils and saw the phases not lining up with the magnets. For some reason I thought 8 poles went with 9 coils but I see now they don't.

     So, next experiment I tried 6 poles but instead of doubling up the magnets I put a second set on the back of the rotor. So it was magnet/ disc/ magnet. Didn't work so well and I was surprised that either pole of the second magnet would stick to the back of the rotor even though the magnets were in line with the ones on the front. Over all my best guess on why this didn't work is that it might have pulled the flux away from the coils instead of increasing it. Oh well, next test,

     I put the magnets back on for 12 poles and rewired it Jerry rigged. That worked but I could see that although it might put out more current on windy days I was going to lose power from the steady light winds that we have most of the time as cut-in was going to be higher. I haven't been able to measure it but I estimate cut-in in star is about 150 +/- (and that seems to depend on the size of the battery. Probably something to do with the resistance cause with a small AH battery cut in seemed lower)

     So, in the end I figured the only way to get more out of this windmill would be dual rotor. I don't think this one is worth a second set of magnets so I think I will just add a second blank rotor. In light winds it was bouncing pretty steady between 5 and 20 watts so maybe I can boost that to 10 to 30.

     I know you seasoned folks like us newcomers to DO something instead of just asking questions so there it is, my ongoing research. I've started my next mill and I think it will be an improvement. I'd be glad to hear any input on the above, especially what cut in should be for this mill as well as what the maximum output could be expected. My guess is that if #22 AWG wire is rated for a little under 1 amp then for three phases times 14 volts , something like 40 watts? I'd be curious also as to what diameter blases might work best.

[ghurd]

No idea.

But I do know that aiming to get power out of wind below about 6.5MPH will not be so great.

Using a 24V machine to charge 12V batteries means it will stall, just about when it should be making a lot of power.  Just about the same idea as running it shorted, but not quite that bad.

TSR and RPM is confusing.  Blades will run faster if not loaded.  A bench test at X RPMs isn't the same as the machine in the wind.  Wired for 24V and charging 12V will keep the blades from working right.

The 1A 3-ph 40W is way off.  In star, the same 1A is running through all 3 at the same time, though unbalanced.  I guess it would be 1.73A in star is the same as 1A in the wire.  1.73A x 14V = 24W.  That might be off.

Jerry rig will lower the resistance, and raise the RPM.  The blades hopefully get out of stall, and when there is enough wind, the amps will really climb fast.

And instead of X amount of amps before it melts, the current can be 3X. So 1A per phase x 3 phases x 14V = your 40W.  

It will be easier to get amps with lower resistance. Want 24W or 40W?  See what I mean?

Was it fun?  That's what counts.

G-

[TheCasualTraveler]

     ""Was it fun?  That's what counts.""

This much work for this little power? It would be crazy if I wasn't having fun.

[ghurd]

Never take that tone with me, young Andy!

I spent $hundreds on hard-drives.  For the "cheap magnets".  LOL.

This is what I got, but it works quite well (No BS, after it was wired in Jerry Rig)...

http://www.otherpower.com/images/scimages/2050/3phHD.jpg

I spent $hundreds on steppers too.  If that works out, I will post it.

I am simply saying, it never hurts to try.

Fun is fun.

G-