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MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 04:15am 17 May 2011
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Crew
I'm putting this here, because I don't where else to ask a silly question, being a senior member and all, but here it is anyway:
All of us here, myself included, have made alternators where we spin the magnets about a stationary stator. Has anyone tried it the other way?
The reason I'm asking is because I build all small stuff and making something small, but still robust enough to hold together when it revs up is somewhat of a challenge. I figured it would be less mass spinning about if I were to spin the stator. The only thing extra would be 4 slip rings (3 if you want ground to be the star connection). If you didn't want another three on the tower, you could rectify the current atop the genny and send it down the tower with one wire and a ground.
Also, for a small-ish build, it would be easier to create a huge magnetic field using ginormous magnets, then spin a hefty stator between them. That way, there'd be less chance of a magnet(s) shifting position while in use and turning the thing into a blender!
A mill turning a stator would need less inertial torque to get going too. It would still have to have the revs and torque at "cut-in" but in my opinion, it would seem to put less stress on things, assuming the coils were properly potted in the stator of course.
Sounds feasible to me; any takers?
. . . . . MacNothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495
Posted: 06:55am 17 May 2011
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Ummmm... but isn't that just how an old car generator or brush-type DC motor works?
The difference is - you're doing away with the commutator - which I think would make your design less (rather than more) efficient, as you couldn't have multiple coils on the shaft unless you rectified on the rotor itself.
My gut feeling is that you'd end up with as much (or more) mass in copper windings and iron than you'd have had with magnets.
VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539
Posted: 09:24am 17 May 2011
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Hi mack
The beauty of the axfx design is no iron in the stator to have eddy currents and decrease efficiency also the versatility of having a few combination of coils for different voltages.
To make a stator into a rotor as this design is made it would requite a lot of balancing of the then rotor which with our manufacture methods would be difficult and would require a lot of extra reinforcement in the structure to allow for the centrifugal forces.
The addition of the extra set of slip rings means extra losses and something else to go wrong.
It certainly could be made to work but as Ross said would it be a step backwards? I think that a design based on an outrunner model motor would be a good experiment, but would require a lamination press to make the stator.
All the best
BobFoolin Around
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 01:59pm 17 May 2011
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Mac, I even went one step further, spun each in opposite directions to get a very low cut in . This requires counter rotating blades BTW.
It was was done with a F&P and a Lenz 2 VAWT. Balancing was no big problem with the F&P stator, I even mounted all the rectifiers on the stator disk so only 2 slip rings were required.
Did it work? Well, you might want to find out for yourself if the tinkering bug really gets hold of you .
Suffice to say this arrangement is no longer up on my windgen mast Klaus
MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329
Posted: 09:46pm 17 May 2011
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Crew
Thanks for the input, guys. I kinda thought that's the way this would go and it's why I initially called it a 'silly question'. I have a very tiny (read that 4") ax-fx dual magnetic plate set-up that has been nothing but a pain in the arse. I have all but decided to turn it into an air core and let it light an LED just to have something spinning above my place; something to yack and cackle about. I may still do just that using a skein-wound, single-phase stator just for ease of assembly. Yeah, I know . . . it'll vibrate like hell.
Because all my stuff is so small (read that too small to be practical) I'm seriously thinking about going back to building windmills that compress air. That would at least give me a several-minute burst of energy if I were to run a tank of stored compressed air through an air engine coupled to an alternator.
I'm just finishing up my solar water heater rebuild and when it's done, I'll get back to building things that spin in the wind.
Thanks again.
. . . . . MacEdited by MacGyver 2011-05-20Nothing difficult is ever easy!
Perhaps better stated in the words of Morgan Freeman,
"Where there is no struggle, there is no progress!"
Copeville, Texas
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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. This requires counter rotating blades BTW.
.