Coils/windings/# of turns..hybrid AX

[steak2k1]

I am working on a 12V battery charging genny:

Here's what I have done: (the effort was to sorta duplicate the Wood AX but not use plywood, go three phase, use a 5' diam prop - 3 blade)and use an aluminum base..once generator is working to where I like, then I shall work on the yaw bearing and furling set up.

I have built 2 stators: (mainly because I needed/wanted to get good at casting them and secondly to test total output- after the bridges)

Both Stators are wired star. The actual gap between surface of stator and magnet ring is less than 1/16" with the total air gap being 1/16" + 1/2" for the stator..if I understand "air gap" at all..??

1st one was simply 9 coils of AWG 18 @ 40 winds. @ ~150 rpm I managed to get 2.25 V dc spinning by hand.

2nd Stator was also 9 coils/ same wire 90 winds. @ ~150 rpm managed to get to almost 5 Vdc. I had to make adjustments to my coil winder in order to make the coils fit the same mold - make the centre smaller. (To hold the coils into place, I drilled very small holes in my mold and used small tie wraps to keep the coils placed in their best position..once crazy glued together, I cut the tie wraps at the back of the mold and filled the little holes with silicone sealant. That seems to work well.)

So at this rate and if I simply increase the # of windings to actually get 12V+ at 150 - 200 rpm (or am I dreaming of that low a cut-in..?), I am thinking that I would need around 135-160 turns of same size wire. On this size of mag rotor diam, those coils will be fun to make and place.  

I would love to hear some Lay term info on this. And what I should try as far as # of turns.  At this time I only have 18AWG as that was what was used for the Wood AX. So, should I consider going to a smaller AWG size  20/22..?? but larger amount of turns...or continue to try with larger # of turns and same wire size.??

As well, will pulling the mag ring back from the stator have any positive effect..?? easy enuff to try...just curious.

Secondly:  I have read many times here persons referencing 12V 24 V 48 V Charging systems...what determines whether one gets 12 / 24 or 48Vdc.??  This is about as clear as fog to me..!!

I appreciate any commentary and suggestions on first part and explanation on second.

....and (Soopraz Soopraz ala Gover Pyle), I am actually starting to understand some of this stuff...!

Lot of Q's..

Rgds,

stk

[Flux]

I am not sure what you are doing. I seem to remember that the woodAX had one magnet rotor and a laminated iron core at the back.  Have you kept the laminated iron core or substituted an aluminium plate which is what it looks like from the picture. Or have gone to a dual rotor with magnet rotors front and back.

If you have a single magnet rotor and an aluminium plate you will have lots of eddy currents to make it hard to turn and you will not make good use of your magnets.

What magnets do you have and how are they spaced, the woodAX was single phase and the round magnets were spaced too close for good results with a 9 coil 3 phase winding.

150rpm is very slow for a 5 ft prop, 250 to 300 would be nearer but it depends on your prop. It is difficult to judge from your picture but I think you could cut in at 250rpm.

You can use more turns of thinner wire to get the volts up but if you only have a single rotor with no laminations it may come up to volts with the present winding if you add a laminated backing. With a cast stator you could use a single magnet rotor but add a second spinning rotor at the back with no magnets to close the flux gap.

If you want to use a fixed laminated core you would do better to stick the coils directly on it and not have a second air gap.

The system voltage is decided by the number of batteries, then you choose the winding to cut in at the desired speed with that battery voltage, high voltage systems have thinner wire with more turns.

I hope this has helped but I have asked more questions than answered.

Flux

[BigBreaker]

As flux said - it looks like you have an aluminium plate opposite the magnets and stator.  You need to complete the magnetic "circuit" so that it passes through your windings.  Without opposite pole magnets or fermomagnetic lamenates on the other side of that stator you will get VERY little power.

[DanB]

yes...  you need some return path for the flux here I think, unless your using very large magnets and being a bit wasteful with the resources.

Also very important... you cannot have stationary aluminum behind the moving magnets like that, I think the eddy currents will kill you.  It's hard to tell so far though exactly what you've got going on.  I think to say much more, it'd be fun if we knew...

how big the magnet rotor is

what size magnets you've got and how many.

do you plan to have a 2nd magnet rotor, or some steel laminates?

(if you've not figure that out yet - you could also just have a blank rotating steel disk behind the stator, that would provide some return path for the flux here)

Looks like fun!  the blades look very nice...

[steak2k1]

Guys I apologize for not giving all the info in first post.

I have 12 neo 1 X .375" on a 7" OD on a .250" MS Pl.  Mag spacing is about .50" between each mag...and now that I think about it, maybe should go with a larger mag rotor plate..??

The aluminum plate there is simply my stator bracket. Being in the welding bus, mtl is sometimes easier to come by than wood and usually free.

I used steel banding for the lamination as it was free and relatively easy to use.  I did not anneal it. I tried that (threw it in a nice fire in the backyard pit), however it became a major pain in the (_/_).. to work with. So although the laminate material may well become magnetized as I have read..I decided to use it anyway for the sake of expediency.

So:  If I understand you guys, I could if I wanted to go to say 20 AWG - add another 50-60 windings (to the 90 I have), for a total of say ~ 150  and yet still charge 12V but at a lower cut-in..?? or just add 20-30 windings with the 18AWG I currently have to increase voltage & or lower cut-in rpm..?  Or given the blade diam, will cut-in be somewhat set due to swept area and avail wind speed.  Still tryin to wrap my neurons around that.

Also given I am using a bridge, I am thinking I am losing .7 volts per diode in the rectification.  Would my total then be:  2 X.7 X 3 for a total loss of 4.2V ..??

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I did in fact after posting, use my variable speed drill and definitely got the Volts up to 14.45 but not sure what the rpm was but however I estimate 250-350..??she (why do we always call it a She..??), was definitely spinning..that I must say was kewl..!!

Thank you DanB re the blades..that was definitely a most fun bit of work. As I have been informed: relief cuts and a good rasp will work wonders.

Kudo's to Hugh for his excellent explanations in Windpower Workshop and the Axial plans.

Flux/Big breaker - Thanks for the comments and advice..This is just the best Brd for RE on the planet.

Thanx in advanz,

stk

[Ungrounded Lightning Rod]

I used steel banding for the lamination as it was free and relatively easy to use.  I did not anneal it. I tried that (threw it in a nice fire in the backyard pit), however it became a major pain in the (/).. to work with. So although the laminate material may well become magnetized as I have read..I decided to use it anyway for the sake of expediency.

If you use a steel disk OR your laminates and spin it with the magnet rotor (even though it doesn't have magnets of its own) you'll eliminate your eddy current losses.  You might lose a little flux due to the necessiry to have a gap between the stator and the now-rotating backing, but you might gain more than you lose.

Of course it does require that you put the shaft through the stator.  But it also gets lots of force off the stator/backing mounts and the main bearing.  (If you have an upwind mill and put the rotating magnet assembly on the blade side the wind drag and the magnet attraction add when they load the main bearing.)

You appear to have mounted the plate on the stator, so the stator mounts now have to hold the stator against the attractive force of the magnets as well as the torque from the generation drag.

[steak2k1]

UGLR...I see where you are going with that.  Interesting.

If, as you appear to suggest, remove the laminates (or spin them...which would be a difficult proposition at best), and go with a spinning steel plate....well then my thinking is if I do that, I may as well add 12 more magnets to that plate and end up with a dual rotor genny...? Albeit one that does not have tapered bearings and not really set up to handle the torque/stress.

That is indeed something I have thought of prior to this post...And I have just today found a rather good place to purchase Neo's right here in Canada, which saves me the exchange rate, customs and duties...a not inconsiderable sum. (prices are darn good as well - sorry FF).  

Doing that (2nd rotor plate), will release somewhat the effect of having the laminate, which at this point in time is solidly attached to the stator, add to the torque.

Ok Kool... Now the question, is it worth the $$$ to go ahead and add a 2nd rotor plate or take what I have learned and go forward with a larger dual rotor genny based on a trailer hub...??  using maybe 2 X 1 X .5 Neos

I think I will retro the current unit while scrounging Mtl for Lrg unit:

1. Remove the laminates
   
2. Add a rotating steel plate - I am assuming the same diam./Thickness as the mag rotor.
   
3. If the above results in just a marginal increase then build new stator with 110-120 turns 18AWG or go 20AWG with 150-175 turns and call it done.
   
   

learn something new every day..ya gotta love it..!!

thanx eh.!,

stk

[Flux]

Thanks for the new data and picture, it makes sense now.

Your magnets are small, the disc is small and the air gap is wide for those magnets so you will need a fair number of turns to get a very low cut in speed.

I agree that it would be better to collect material for a dual rotor and use rectangular magnets and a proper hub. I don't know how much wind you have but if that 12v cut in is below 300rpm I would give it a try as it is. With the core material you have the low wind performance will not be very good and you may get better results generally by not going to thinner wire and more turns.

Adding a spinning disc will slightly worsen the cut in speed as you will have to have a small air gap where your core is touching at present. What it will do is remove a lot of drag and make it start easier and free up a few lost watts to allow you to benefit from a slightly slower winding if you so choose. I don't have your prop details but I suspect you would be unwise to go for a cut in below 200rpm.

The power in winds below 8 mph is not great for a 5 ft prop and I think you will loose out all round if you aim too low.

Rectifier drop is 2 diodes in a 3 phase bridge, ie 1.4v. current at any instant flows through one pos and one neg diode.

Flux

[steak2k1]

Rectifier drop is 2 diodes in a 3 phase bridge, ie 1.4v. current at any instant flows through one pos and one neg diode.

Flux...is that per phase.?

Stk

[Ungrounded Lightning Rod]

It's only per phase if you attempt to rectify the phases separately and wire the result in series, as is sometimes suggested in postings here.  That ends up with about 3.6v of drop, and the diodes and heat sinks have to be bigger, too, since they get the full current for more of the time.  (The other problem with that:  You need to add HUMUNGUS capacitors to store the power from each phase for part of a cycle so it can be combined with that of the others.  Much better to wind it for a higher voltage in the first place and rectify it "normally".)

The normal scheme:  Connect the phases in wye or delta, bring out three wires, rectify each with one diode to the + output, one to the -.  That puts the additional diodes "in parallel".  Regardless of which phases are providing the power at a given instant, the current goes through one diode on the plus side and one on the minus, for a two-diode drop of about 1.4v total.

[steak2k1]

Fair enough...what I have done is used 2 bridge rectifiers 600V 40 Amp. cheap enough @ 6.00 CAD ea.

Since I am using two of these units, there are 4 AC taps so to speak..I have used 3 of them and left the fourth open.

I then connected the DC pos on both and then out as well as the 2 neg DC and out...

Both bridges are attached to an aluminum heat sink that I fabricated with fins and using that white heat transfer paste.

Thanx ULR..

Stk