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Author Topic: Finding the right generator  (Read 26386 times)

Offline irethedo

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Finding the right generator
« on: November 17, 2008, 11:48:33 PM »
I am helping my son with a science project and attempting to build a very efficient small wind generator.

We have a very efficient rotor design which can spin (without load) in 1.5 MPH wind but now we need  to
find a very inexpensive generator which can be spun easily and with as powerful of an output as possible.

I have read aboout people using tape drive motors but from what I have read, these are typically yield lower output
levels less than 10 W.

I have heard of people that use car alternators but these require too high of an RPM for substantial
power. Someone also mentioned to me that the older police cars and emergency vehicles had higher output
alternators which had a full output at idle but I have not been able to find much on these.

We would like to rectify the output and pass it through an inverter for ~ 120V AC @ 60Hz and perhaps we are dreaming but
we would also like to get 100 W if possible...

I was playing around with a flywheel off a briggs and the coil but didn't get very far...Not sure if there are any overunity configurations
out there that might be retorfitted for this task or not but thought I might ask on this board to see if anyone had any suggestions...

Can anyone recomend a relatively inexpensive generator that we might use for this project?

thanks in advance for any helpful ideas

Free Energy | searching for free energy and discussing free energy

Finding the right generator
« on: November 17, 2008, 11:48:33 PM »

Offline capthook

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Re: Finding the right generator
« Reply #1 on: November 18, 2008, 12:58:28 AM »
irethedo -

The power you can generate is directly related to the wind resource.  There are a number of formulas you can look up to give the potential energy related to wind speed.

As such - trying to extract 100W from 1.5 MPH is impossible.  You could generate a tiny amount of power given such low wind speeds - but it's not practical.  A min. wind speed of 7mph, while still quite low, is kind of a min. rule of thumb for practical (tiny) generation.

As far as generator designs - you have a number of options.  The current DIY that offers the best output with the least amount of losses while being relatively easy to construct is the axial flux dual rotor design by Hugh Piggott.
It uses air coils surrounded by two rotors of magnets allowing for a large flux to the coils without the large losses associated with iron core/stator designs.

Hear are some links to get you started.  The 1st site has a .pdf you can download with details of an early model: http://www.scoraigwind.com/pmgbooklet/index.htm

http://www.scoraigwind.com/
http://www.fieldlines.com/
http://www.windstuffnow.com/main/

Offline irethedo

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Re: Finding the right generator
« Reply #2 on: November 18, 2008, 11:33:54 AM »
thanks Capthook-

I will check these out...

Free Energy | searching for free energy and discussing free energy

Re: Finding the right generator
« Reply #2 on: November 18, 2008, 11:33:54 AM »
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Offline khabe

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Re: Finding the right generator
« Reply #3 on: November 18, 2008, 01:36:57 PM »
It is difficult to advice any generator when given info about rotor is just only:  <i>very efficient rotor design which can spin (without load) in 1.5 MPH wind</i>
Iron core or ironless ... there I have seen also many misunderstandings about.
Efficency could be higher than 90% for both - iron core or iron-less brushless motor/generator.
Ironless design has no cogging but well designed iron-core generator could have near zero cogging as well.
Iron-less generator need to have at least twice bigger magnets as iron-core brother. Art least! In reality all the mass of Stator need to be added for rotor magnets ...
Most of ironless generators made by "masters" are made totally unprofessionally - they are speaking about "coils" as well as design based on the "coils" - forgotten about
basic physics laws about left/right hand rules (moving_magnetic_field_wire_current) wheres "coil" need to meet two magnet poles at the same time - N-left and S-right side of "coil" and conversely.
And only part of "coil" is useful when we are speaking about ironless machine - only wires what crossways to moving direction of magnet poles.
Iron core generator is bit easier to build for first-timer, especially when low rpm and low power. There is several ways for reduce cogging torque near to zero:
Choice number of stator slots versus number of rotor poles - Pole-Slot Combinations
Skewing rotor poles or stator slots.
Unequal tooth width - influence of pole number
Unequal distance between rotor magnets ...
etc ...
And combination of mentioned above
There are a lot of perfect styles and designs worldwide - it will take full year to expand upon even part of more precise ...
The best choice is some older brushless servo motor from ebay - older because cheaper. Usually you can find out unique Pole-Slot Combinations like 39 slots / 12 poles ... + skewd rotor poles or skewed stator slots ... Nominal power and KV (rpm/volt) gives enough info about is it useful or not for your project.
When you like to choice axial flux ironless desigh anyway - then do not use too weak (thin) magnets and too large airgap between. Airgap (between magnets or between magnet and return iron) must to not exceed 1/2 of thickness of magnet when one-side magnets or 1 thickness of magnet when two-side magnet design.  Less airgap = less "turns of coils" for the same Voltage ... well wound you can use larger total cross area of wire ...
You have to think about Eddy losses - do not use thicker wire than 0,5mm. When higher current then stranded wire. Litz wire is the best choice when airgap machine (ironless generator).
Hereby one good PDF file how its look correctly made windings for slotless generator. Please look at only like "coils" must to be placed. Please note - 6 pole machine, but actual magnets are too weak ... and just 6 poles - requests higher rpm ...
http://www.windstuffnow.com/3phasekit.pdf
But you can see how windings need to look like - and that there are no "coils" literally - just wires between magnetic flux!
Regards,
khabe

Offline irethedo

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Re: Finding the right generator
« Reply #4 on: November 27, 2008, 08:09:50 AM »
Are there any other motors out there used in other applications which are low RPM
and require little force to turn them that can be used for a reasonable output generator?

Perhaps a washing machine or dryer motor or a treadmill or electric scooter type motor???

Not sure if these would work or not or if they are difficult to turn or not...

Any ideas?

thanks

Free Energy | searching for free energy and discussing free energy

Re: Finding the right generator
« Reply #4 on: November 27, 2008, 08:09:50 AM »
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Offline khabe

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Re: Finding the right generator
« Reply #5 on: November 28, 2008, 12:53:19 PM »
Are there any other motors out there used in other applications which are low RPM
and require little force to turn them that can be used for a reasonable output generator?

Perhaps a washing machine or dryer motor or a treadmill or electric scooter type motor???

Not sure if these would work or not or if they are difficult to turn or not...

Any ideas?

thanks

No ideas until you have not gave more info about turbine(blades) you planned to use. Is it 3m diameter ... or half meter ... or you have no ideas at all >:(
cheers,
khabe

Offline gyulasun

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Re: Finding the right generator
« Reply #6 on: November 28, 2008, 02:18:51 PM »
Are there any other motors out there used in other applications which are low RPM
and require little force to turn them that can be used for a reasonable output generator?

Perhaps a washing machine or dryer motor or a treadmill or electric scooter type motor???

Not sure if these would work or not or if they are difficult to turn or not...

Any ideas?

thanks

Hi,

Just come across this link on a generator,  maybe useful for you: http://www.fieldlines.com/story/2008/11/27/211427/37

The video link is here:  http://www.youtube.com/watch?v=Axo8v37beM0   And he tests the output current when rotates the rotor by his hand: http://uk.youtube.com/watch?v=CzsD6iaLE0c

And see the same generator working as a pulse motor, pulsed by hand from an AA 1.5V dry battery:
http://uk.youtube.com/watch?v=IcR9V3umdJI



Free Energy | searching for free energy and discussing free energy

Re: Finding the right generator
« Reply #6 on: November 28, 2008, 02:18:51 PM »
Sponsored links:




Offline khabe

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Re: Finding the right generator
« Reply #7 on: November 28, 2008, 09:55:23 PM »
Yes - this is by principle correct made generator. You can see you dont need any "coils" - just WIREs between  magnetic field.
Right hand and left hand rules ... motor and generator effect ...
http://www.youtube.com/watch?v=9Zy0VHBXxLU
http://waowen.screaming.net/Maghandrules.htm
Faraday law - iron core motor
Lorentz Law - air core motor (ironless ...).
cheers,
khabe

PS:
Newman´s motor uses also  Lorentz Law, right hand rule  - but ... he does not use closed magnetic cheme, flux of rotor magnet stays "on the air" - there is no outer side magnets or flux returning ring (rotating steel or laminated stationary ...)

Offline pese

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Re: Finding the right generator
« Reply #8 on: November 28, 2008, 10:50:09 PM »
. Please look at only like "coils" must to be placed. Please note - 6 pole machine, but actual magnets are too weak ... and just 6 poles - requests higher rpm ...
http://www.windstuffnow.com/3phasekit.pdf
But you can see how windings need to look like - and that there are no "coils" literally - just wires between magnetic flux!
Regards,
khabe


Attention (above PDF)
Correct the drawling on page 10.
The star rectifiering is wrong designed.
Gustav Pese

Free Energy | searching for free energy and discussing free energy

Re: Finding the right generator
« Reply #8 on: November 28, 2008, 10:50:09 PM »
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Offline khabe

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Re: Finding the right generator
« Reply #9 on: November 28, 2008, 11:47:38 PM »
Attention (above PDF)
Correct the drawling on page 10.
The star rectifiering is wrong designed.
Gustav Pese
Hm? There is no different in rectifiers in principle when star or delta connected 3ph generator windings.
This guy just trying to show how to use two one phase full bridge rectifiers for three phase ...
Usually people dont use this kind of temporary means - ast least I do never and even do not heed attention ... correct or wrong ...
When now you forced me to look at ... by my opinion it works - it uses three pairs of diodes  +  -I<- ~ -I<- -  of total 4 pairs.
regards,
khabe

Offline TinselKoala

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Re: Finding the right generator
« Reply #10 on: November 29, 2008, 12:31:56 AM »
Never mind.

Getting back to the science fair, I hope you and your kid have a great time.
« Last Edit: November 29, 2008, 01:17:17 AM by TinselKoala »

Free Energy | searching for free energy and discussing free energy

Re: Finding the right generator
« Reply #10 on: November 29, 2008, 12:31:56 AM »
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Offline khabe

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Re: Finding the right generator
« Reply #11 on: November 29, 2008, 01:01:44 AM »
Yeah, but when you need bit bigger generator than spoken above and  buying 6 small diodes does not kill you as well as assembling ::) - then I can recommend well built brushless servo motor from ebay:
http://cgi.ebay.com/BLDC-servo-motor-robot-lathe-mill-cnc-encoder_W0QQitemZ260303719487QQcmdZViewItemQQptZLH_DefaultDomain_0?_trksid=p3286.m20.l1116
$5 + shipping  ::) Encoder from back side you just take apart and throw away. It has hollow shaft OD 1/2" and id 1/4", well made motor, four poles rotor, 24 slot stator - scewed rotor segment magnets - special shape + vintage overlapped winding cheme gives brilliant coggingless run. Rotor OD ca  43.5mm, Total OD ca 102mm x ca 60mm, bearings are rubber sealed 9R8 made in Japan.
Good and cheap found for several projects.
regards,
khabe

Offline pese

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Re: Finding the right generator
« Reply #12 on: November 29, 2008, 01:07:35 AM »
see the last of 3 bridge rectifiers.
the 2.AC  is not connected.
so that cant work
Pese

P.S.
------------  Additional "Post Script"
I controlled again.
It is roght so - as designed.
(sorry, I was to fast .. and not seen my error)
Pese
« Last Edit: November 29, 2008, 01:35:34 AM by pese »

Offline Yucca

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Re: Finding the right generator
« Reply #13 on: November 29, 2008, 01:18:34 AM »
For a small wind genny you could use a brushless outrunner motor similar to what Khabe is recommending.

(http://i8.ebayimg.com/03/i/000/ff/d7/428e_1.JPG)

They are small motors for model cars and planes that have moving neo mags and stationary coils. They are VERY efficient motors and make quite efficient gennys. (Might have to gear your turbine output up a little though?)

They come in all sorts of sizes from tiny to large so you should find one to match your turbine. They are also quite cheap on ebay:

http://shop.ebay.com/?&_nkw=brushless+outrunner

They will generate 3 phase AC when cranked. With bridge rectifiers feeding a cap you get rough DC, can then use efficient regulator for proper DC.

Offline Yucca

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Re: Finding the right generator
« Reply #14 on: November 29, 2008, 01:28:55 AM »
Yeah, but when you need bit bigger generator than spoken above and  buying 6 small diodes does not kill you as well as assembling ::) - then I can recommend well built brushless servo motor from ebay:
http://cgi.ebay.com/BLDC-servo-motor-robot-lathe-mill-cnc-encoder_W0QQitemZ260303719487QQcmdZViewItemQQptZLH_DefaultDomain_0?_trksid=p3286.m20.l1116
$5 + shipping  ::) Encoder from back side you just take apart and throw away. It has hollow shaft OD 1/2" and id 1/4", well made motor, four poles rotor, 24 slot stator - scewed rotor segment magnets - special shape + vintage overlapped winding cheme gives brilliant coggingless run. Rotor OD ca  43.5mm, Total OD ca 102mm x ca 60mm, bearings are rubber sealed 9R8 made in Japan.
Good and cheap found for several projects.
regards,
khabe

Now that´s a good bang for the buck! Shame the international shipping is too high for me or I would go for a couple of those!

 

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