what's up with this stator??

[birdhouse]

saw this on youtube, seems a tight airgap would be tricky with all the overlapping wires!

http://www.youtube.com/watch?v=fF9zBkq5mAM&feature=related

adam

[ghurd]

Plus it will have a higher resistance.
G-

[ChrisOlson]

saw this on youtube, seems a tight airgap would be tricky with all the overlapping wires!

That's Sam Chamas up in Canada.  I helped him build a couple generators better than two years ago and he's big into the serpentine windings, which require an elaborate winding jig but work quite well.  Ed Lenz has used serpentine windings on his machined stator plates for years, with 1:3 pole/coil ratio and overlapped phase windings.

The serpentine winding eliminates the extra resistance associated with coils because you eliminate one winding head.  So you can fit more copper in and get more volts out of a given diameter.

I got a half dozen serpentine wound stators laying around here.  But I always had problems with harmonics in my high output generators and could never keep the stator tight.  Now that I've gone to a different method of mounting my stators, I could use them.  But they're still noisy running because they'll hit the first harmonic at a certain current frequency and the whole unit howls like a wolf on the hunt.

With Sam's slow speed generators he doesn't have that problem.
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Chris

[birdhouse]

thanks for the explanation chris!

i'm continually amazed at how many different ways there are to build an alternator. 

adam

[Wolvenar]

I remember Tom and I think zubbly discussing this style of winding years back.
I am not sure but I think I remember that I used this for a gen I made with microwave mags.
Not so sure anymore  I made a couple different stators for this and bench tested , before putting it up live and finding it has a major flaw in design. Eventually it became destin for the recycling heap.

[ChrisOlson]

For anybody that wants to learn how to build a serpentine wound three phase generator I can highly recommend Ed Lenz's little kit:
http://www.windstuffnow.com/main/3phase_turbine_kit.htm

It comes with the three coils already pre-wound, has one of his machined stator plates with it, has excellent instructions with it, and for only 42 bucks will show you how to build a serpentine wound 6 pole/18 coil generator the right way.

It's a little VAWT turbine that makes more power than them converted Delco 10SI "PMA's" that get pedaled on eBay all the time.
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Chris

[Dale S]

I had to turn off the porno soundtrack, other than that it's pretty cool, bout five minutes too long though.

[ghurd]

with 1:3 pole/coil ratio and overlapped phase windings.

The serpentine winding eliminates the extra resistance associated with coils because you eliminate one winding head.  So you can fit more copper in and get more volts out of a given diameter.

That video is 1:4.
1:4 is overly complex 1:2.
1:3 is better than 1:2.

I will stand by my statement that it has more resistance.
Draw a 12 pole with 40 turns per phase, then do the math.

"get more volts out of a given diameter"?

[oztules]

Birdhouse,
I can find no reason to go with that technique. It is difficult, and offers no positive attributes not already available with the standard 3:4 simple version.
I cant agree with Chris on "The serpentine winding eliminates the extra resistance associated with coils because you eliminate one winding head.  So you can fit more copper in and get more volts out of a given diameter."

So we must be looking at the same thing and seeing different things. (if you shift the bottom winding head under the next coil, you end up with the same thing without the overlapping problems, which as you said will increase gap.... so more resistance ... or less copper in the same winding window.

I agree with Ghurds summation, and it is unlikely to do as well as the standard fare.

I wouldn't be keen to waste my wire on it for the main show, but for an experiment........ maybe.



...............oztules

[Watt]

Birdhouse,
I can find no reason to go with that technique. It is difficult, and offers no positive attributes not already available with the standard 3:4 simple version.
I cant agree with Chris on "The serpentine winding eliminates the extra resistance associated with coils because you eliminate one winding head.  So you can fit more copper in and get more volts out of a given diameter."

So we must be looking at the same thing and seeing different things. (if you shift the bottom winding head under the next coil, you end up with the same thing without the overlapping problems, which as you said will increase gap.... so more resistance ... or less copper in the same winding window.

I agree with Ghurds summation, and it is unlikely to do as well as the standard fare.

I wouldn't be keen to waste my wire on it for the main show, but for an experiment........ maybe.



...............oztules

Oz, with the serpentine coils, would the total wire and therefore stator resistance, also be effected by coils spacing?  I can see the point you have made by coil winding being tacked up under the next coil in a serpentine arrangement.  Reminds me somewhat of a sine wave.  If, from the zero voltage point of the first wave to the zero point after a full cycle, the two points were cut and folded around, there would be a completed path. 

Thanks for that realization. 

[oztules]

"Reminds me somewhat of a sine wave."...... the area under the sine wave is of interest as we fiddle the coils too.

Coil spacing will be dictated by the pole count and diameter... in either winding scheme. If we make the magnets lonely (big intermagnet spacing) then the coils will be too. If we keep both the magnet size and number and the coils size and number the SAME, the area under the sine wave should be the same regardless of the diameter we place them on.

Bigger diameter, bigger the emf spike, but skinnier wave form... etc. Same for either system.

It is the vector addition of each wire added to all the other wires in the same phase that gives us the emf. Each wire will have emf dictated by flux change in proportion to the "angle of attack"  at all points along the wire/coil. Reminds me somewhat of a sine wave.

We don't even need a N and S pole. The full sine wave shape will come up with just N poles passing the coil..... eg positive sign as say N magnet pole approaches, and back to zero at top dead center, and changes to negative sign after the magnet passes TDC and the coil sees a basically receding field....... presto full sine wave from a single pole. In this instance the emf max is when the magnet is over either leg

If we do that on a single wire, not a coil, TDC is when the pole is directly over the top of the wire  ( zero emf) and sine will change to negative from there.

When we use N and S alternately, we want the S pole over one leg, and the N pole over the other leg at the same time ( of the same coil).... we double the changing flux and double the emf at that rpm.

Thats  why we do what we do (in standard axials), and so coil placement can have  a great effect on as to what happens, and when it happens.


Did that help or hinder



.................oztules

[ChrisOlson]

I guess I'd have to refer back to my notes on the half dozen or so of those that I built.  But I do believe that the resistance of them was 2-3% lower than the "standard" 4:3 ratio "flat" three phase in all the homebrew books.  And I believe Ed Lenz will tell you the same thing - he got 2-3% better rpm/volt performance with the serpentine wound 1:3 ratio units he builds on his machined stator plates in the same diameter or space.

The thing is, you don't need many turns of wire with the 1:3 ratio.  I know one of the 12 volt ones I built only has 7 turns of wire in each coil.  A similar 4:3 "flat" three phase would've needed 33 turns for a 12 pole, and by the time you add all the coil interconnects in, the resistance is higher.

GM alternators are an example of radial serpentine wound 1:3 ratio stator cores, and those typically will have anywhere from 3-7 turns per coil in a 14 pole, depending on the voltage.
--
Chris

[Watt]

"Reminds me somewhat of a sine wave."...... the area under the sine wave is of interest as we fiddle the coils too.

Coil spacing will be dictated by the pole count and diameter... in either winding scheme. If we make the magnets lonely (big intermagnet spacing) then the coils will be too. If we keep both the magnet size and number and the coils size and number the SAME, the area under the sine wave should be the same regardless of the diameter we place them on.

Bigger diameter, bigger the emf spike, but skinnier wave form... etc. Same for either system.

It is the vector addition of each wire added to all the other wires in the same phase that gives us the emf. Each wire will have emf dictated by flux change in proportion to the "angle of attack"  at all points along the wire/coil. Reminds me somewhat of a sine wave.

We don't even need a N and S pole. The full sine wave shape will come up with just N poles passing the coil..... eg positive sign as say N magnet pole approaches, and back to zero at top dead center, and changes to negative sign after the magnet passes TDC and the coil sees a basically receding field....... presto full sine wave from a single pole. In this instance the emf max is when the magnet is over either leg

If we do that on a single wire, not a coil, TDC is when the pole is directly over the top of the wire  ( zero emf) and sine will change to negative from there.

When we use N and S alternately, we want the S pole over one leg, and the N pole over the other leg at the same time ( of the same coil).... we double the changing flux and double the emf at that rpm.

Thats  why we do what we do (in standard axials), and so coil placement can have  a great effect on as to what happens, and when it happens.


Did that help or hinder



.................oztules

Sorry Oz, I was using the sine wave as picture reference not as a product of either serpentine or traditionally wound round coils.  Also, I was thinking that with the serpentine type wiring arrangement that the further the magnets were apart, the more wire would be required.  Sorry for not explaining very well and I still may be to vague. 

Oz, I do like your explanation.  Very well put and I did learn something.  Hats off to ya.

[Watt]

I guess I'd have to refer back to my notes on the half dozen or so of those that I built.  But I do believe that the resistance of them was 2-3% lower than the "standard" 4:3 ratio "flat" three phase in all the homebrew books.  And I believe Ed Lenz will tell you the same thing - he got 2-3% better rpm/volt performance with the serpentine wound 1:3 ratio units he builds on his machined stator plates in the same diameter or space.

The thing is, you don't need many turns of wire with the 1:3 ratio.  I know one of the 12 volt ones I built only has 7 turns of wire in each coil.  A similar 4:3 "flat" three phase would've needed 33 turns for a 12 pole, and by the time you add all the coil interconnects in, the resistance is higher.

GM alternators are an example of radial serpentine wound 1:3 ratio stator cores, and those typically will have anywhere from 3-7 turns per coil in a 14 pole, depending on the voltage.
--
Chris

Chris, I do apologize for not making my question very clear to Oz regarding the wiring of the two type of stators.  However, I think you helped answer my question as well.  Thanks

[ChrisOlson]

I was trying to absorb everything oz said as well, and it makes sense.

The way I've always viewed the serpentine winding is that when you look at it, it looks sort of like a sine wave in a circle.  The peak and valleys of the winding each make a "coil" but it's not really a coil, as the whole winding is one big single phase coil with the same number of peaks and valleys as you have poles.  You just put bends in the wires do they can cut lines of flux from many magnets at once.

It works the same as a bunch of individual coils wired series for a single phase, but basically one winding head on each "coil" is missing with the serpentine winding.  The winding heads don't do anything except connect the legs together and add resistance to the winding with regular coils.  The serpentine winding gets rid of one winding head on each "coil".

I suspect that's why the serpentine winding has been used for ages in automotive alternators with great success.  They aren't that common in axials because of the difficulty of construction.  But stacking three phases can still yield a stator under 1/2" thickness if you build a decent jig or use a machined stator plate like Ed Lenz does.

The problem I had with every one I built was vibration.  The windings vibrated against each other something horrible and the generators made weird howling noises at certain rpm and current freq.  I never did figure out what caused that.  I flew one for awhile but the noise was so terrible my wife made me take it down.  She said she wasn't listening to it anymore, and I either get it off the tower or she was going to take it off herself with a 12 gauge shotgun   
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Chris