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gotwind
Forum Admin
United Kingdom
932 Posts |
 Posted - 07/06/2006 : 18:35:48
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Due to a lot of spam entries in the previous guestbook, I have started a more secure forum.
It is reasonably straight forward to use.
You will have to register only once to post on this forum.
Be sure to bookmark this forum, to find out the latest news
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mattew
Starting Member
United Kingdom
1 Posts |
Posted - 10/06/2006 : 21:54:34
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I've been reading your page about trying to use a stepper motor as an alternator, I've got a 24v one that I am trying to do similar things with.
You asked for commments on it: One thing I did read, was if you use schottky diodes the voltage drop across them is less than a 1n400x, - see http://www.powerdesigners.com/InfoWeb/design_center/articles/Diodes/diodes.shtm
You could use a DC-DC charge pump IC to generate a higher voltage, then regulate that to 14v. ICL7660 can double voltages, but probably not at any sort of current. Obviously these would introduce losses.
What would happen if you used the out of phase coils to generate a negative voltage, giving you AC. Would that allow you double the output voltage?
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gotwind
Forum Admin
United Kingdom
932 Posts |
Posted - 11/06/2006 : 20:14:28
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Thanks Mattew for your thoughts, I'm by no means an electronics expert so can't really comment.
I have found stepper motors to be poor as generators, plenty of volts but very little amps, shame because there are plenty about.
I am focusing on the (no longer made) Ametek range of DC permenant magnet motors - still found on eBay U.S for about $20.
They are capable of about 300 watts, but only available in the U.S.
Shipping costs approx $50 (airmail) to the U.K.  |
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al_
Starting Member
United Kingdom
2 Posts |
Posted - 13/08/2006 : 18:50:17
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Hello, just wondering if anyone knows of an inexpensive motor/alternator/whatever that generates a good amount of voltage and current and is still commercially available?
I have an idea that I need to test out, and it could be a commercially viable one, but it's pointless unless I know that the components exist!
cracking site by the way
al
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gotwind
Forum Admin
United Kingdom
932 Posts |
Posted - 13/08/2006 : 20:38:07
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Hi Al.
I have been looking for long enough for a suitable 'still in production' motor alternative.
The best is the Ametek range of D.C motors, but are no longer made and generally only available in the U.S if you can find one on eBay.
This 1.2Kw PM alternator is great if you have £150 - not a bad price all things considered.
http://www.gotwind.org/FuterEnergy_Gen.htm
Ben.
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al_
Starting Member
United Kingdom
2 Posts |
Posted - 14/08/2006 : 09:55:12
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| OK thanks Ben, I'll look in to these and let you know how the invention is coming along! |
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skids
Starting Member
USA
1 Posts |
Posted - 04/10/2006 : 07:19:32
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RE: stepper motors, indeed you can take the two pairs and rectify/smooth each to DC and wire them in series. Or even voltage double first -- just as long as they are the bipolar variety without the common central pin, or you cut the leads to the common, separating the two coil pairs.
Though the steppers you find as old servo motors don't produce much power, if you have a rotary CAD machine take one of them apart for instruction and you should be able to build a larger diameter one that has a lot more punch -- while at it making it 3-phase (6 pole) can kill most of the cogging torque. The ones in bubblejets probably will max out at about 5W.
These "hybrid steppers" use a single ring magnet which, for a large unit, you can get off the back of large bass speakers (though getting it out of the housing is a challenge and usually involves drilling through the permalloy backplate and self-threading a bolt or three through slowly to crack the glue.) A very ingenious design with very little to worry about in the way of keeping magnets in place. Perhaps its greatest inefficiency is in larger than normal magnetic hysterisis and eddy loss (which could be corrected by molding ferroceramic/ferroplastic core rather than using steel plates) and the greatest fabrication hurdle in getting a small airgap. Oh and the central axle should be an alloy with low permeability.
As far as your attempt to amplify a motor with NdFeB magnets, other than getting the pole pitch right there's another reason this won't work: as designed a motor will already have large enough magnets to fully saturate the steel stator peices. Unless they are replaced with a higher permeability/saturation material, intensifying the PM poles doesn't really do much -- unless of course the motor is air core.
For voltage regulation lately I've been wondering if just dumping the rectifier into some of those new nanotech lithium phosphate batteries with the very high (in the 100W/cell range) charge/discharge rates sized to fit your max anticipated power (with a power diode shunt for overload deflection) would be a good first stage, and then a single-IC voltage regulator can be used with a narrower input range. Those batteries seem to be able to handle quite a large amount of abuse as long as they are kept mostly charged. They are made by Valence Tech and by A123 Systems.
You should really try a dareius. They are a lot easier to get working than they might appear and have decent rotation speeds compared to savonius (which are cool too, but need a super-low rpm genset.)
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