| T O P I C R E V I E W |
| windnovice |
Posted - 17/04/2008 : 08:09:53
Hello,
I was thinking that my next project that i was going to pick up for the summer would be to build my own alternator because i hear that if done correctly you can achieve higher volts at lower rpm than most bought generators. I saw an article where this guy reached 12 volts at a little over 100 rpm and 30 volts around 500-600 rpm and thought that this would be amazing if i could achieve just a fraction of that.
I know the basics of how one works, the materials involved and how to build it, However i havent been lucky and finding any detailed plans on how to build it and get it producing electric. any help here would be appreciated.
If anyone has any other pros/Cons about building an alternator and if its worth the hassle any tips tricks and hints would be great!
Thanks |
| 15 L A T E S T R E P L I E S (Newest First) |
| windnovice |
Posted - 20/04/2008 : 17:05:43
Well i decided that if i was serious about building this alternator i would just go and buy hugh's book, so i looked on ebay and found them selling for $18 which i thought was a good deal, so i should have the book within 5 days and then i can really start going to town on the alternator. Thanks for all the help, and i will keep you updated on my progress. |
| windnovice |
Posted - 20/04/2008 : 01:48:24
Once I have the coils wired up i am left with the 3 wires. from here i am not sure what to do, i know i have to connect to a rectifier but is there any other steps that i have to take before connecting it to my system. |
| ghurd |
Posted - 19/04/2008 : 21:15:33
Good call, mostly.
Tesla changes with distance. H vs. B.
Tesla units include area. 1 Weber per square meter.
If area was the most important factor, everyone would use N52 0.050" thick magnets.
http://www.magneticsolutions.com.au/fluxgraphs-entry.html
(I didn't study it, and I'm not qualified, but it looks OK for these concepts)
Tangential velocity in this context is smoke-and-mirrors. It is included in the RPM and pole factor of any common formula for a well designed PMA. Tangential velocity, in basic form, comes down to an RPM X poles factor.
If tangential velocity was the most important factor, everyone would use only 2 magnets, and only short thin fast blades.
Usually,
Stronger magnets are better. (just a little)
Thicher magnets are better. (much)
More magnets are better. (much)
More magnets per disk are better. (much)
It is a balancing act.
G-
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| MattM |
Posted - 19/04/2008 : 13:24:13
From what I've gathered its the combination of surface area and tesla force per square inch that matters. So thicker is only better if you are also more surface area. However, the size of your stator limits the amount of surface area available to you. Mounting magnets on dual (opposing) rotors seems to be where Hugh is pointing people in order to maximize your potential.
The sum of the magnetic flux, to focus as much as possible at the point of each stator coil, is the key. From experimenting with the math I gathered it was critical to have the best possible magnets that you can afford to buy; putting a relative increase of money into the stator is less significant. More wraps in your stator coil are significant but they increase the volume of the coil so quickly they become a limiting factor in no time. The next factor after the magnets and number of wraps per coil is the velocity of the magnets past the stator coil, which is why larger diameter stators help. The wider your stator and rotors the faster the tangential velocity at the point of the magnets as the rotors turn.
Go Huskers! |
| ghurd |
Posted - 19/04/2008 : 03:34:52
Thicker magnets 'shoot' the flux out more, allowing more room for coils.
Rule of thumb: If the magnet is 1/2" thick, then the distance from the magnet to the laminations can be almost 1/2" thick. The distance should be less than the thickness of the magnets.
1/8" thick means there is no space left for clearance and coils.
The 1/2" magnets offer good bang for the buck, and plenty of space for coils.
Don't bother with non-neo magnets.
G- |
| gholt |
Posted - 18/04/2008 : 20:01:09
WN,
http://www.windstuffnow.com/main/alt_from_scratch.htm (good description of why to choose star or delta depending on your wind and your machine)
http://www.reuk.co.uk/Star-Delta-Wiring-for-Alternators.htm
http://www.reuk.co.uk/Star-Delta-Wiring-Calculator.htm
G.
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| windnovice |
Posted - 18/04/2008 : 17:34:26
As i have been researching about these axial alternators and i have come across alot of good information and i think i have a good basis to start building mine, however when it comes to wiring it all together thats where my knowledge ends. I havent come across anything that tells you how to wire it and i have seen many different configurations and am not sure where to start. anybody know of a simple way or of a source that would explain this step.
Thanks. |
| windnovice |
Posted - 18/04/2008 : 17:22:44
Are thicker magnets better when you are trying to make an alternator, b/c it seems like everyone keeps pointing out the 1/2" magnets. Just curious if it matters or if your just want to look at the strength of the magnets.
Thanks |
| Capt Slog |
Posted - 18/04/2008 : 14:21:22
quote:
Originally posted by windnovice
Yes i am confused but i think i get some of it. I think im going to stay away from parallel currents when i make mine seems like it would be easier anyways, and seeing as the winds here are normally around 8-10 mph it would be best for it to reach 12v at a lower rpm.
what type of neodymium magnets should i look for, i found some N50 circle ones 1" diameter by 1/8" thick on ebay. would those be good to use for this type of application?
If you're looking at that sort of size then try here
https://www.magnet4sale.com/xcart4/home.php?cat=358&sort=productcode&sort_direction=0&page=3
1/2" thick for $2.19, and this price comes down when you get to buying 24 |
| MattM |
Posted - 18/04/2008 : 13:51:09
gholt is not kidding. Two of those magnets together is something like 100 pounds of pull force together. Sharp corners on them coupled with the instant acceleration when they attract can mean serious permanent damage to you. Just playing with a small group from hard drives made my little brother appreciate these warnings. They are substantially smaller but a few interacting in an unexpected way pinched him real good.
Go Huskers! |
| gholt |
Posted - 18/04/2008 : 04:24:42
Hello WN,
The magnets recommended by Hugh Piggott are 2"x1"x1/2" [46mm x 30mm x 10mm] from his manual. There are many available magnets in this size range one can use, and Ed Lenz has some tapered magnets which are fantastic - if he has any left. Check his site, send him an email to discuss what's currently available.
You might also consider the donut magnets found in old microwave ovens - they're free if you can find an appliance repair shop in the neighborhood who is willing to have you take away the dead microwave ovens they accumulate.
WARNING: any of these magnets are VERY dangerous. We're not talking blood blisters here, but rather crushed fingers or hands. Please be very careful when using these magnets.
G. |
| windnovice |
Posted - 17/04/2008 : 19:20:01
Yes i am confused but i think i get some of it. I think im going to stay away from parallel currents when i make mine seems like it would be easier anyways, and seeing as the winds here are normally around 8-10 mph it would be best for it to reach 12v at a lower rpm.
what type of neodymium magnets should i look for, i found some N50 circle ones 1" diameter by 1/8" thick on ebay. would those be good to use for this type of application? |
| ghurd |
Posted - 17/04/2008 : 16:14:13
1) The laminations complete the magnetic circuit. Think about it like keeping the magnetism focused. They must be steel/iron.
A single sheet of steel will make eddy currents (electric moving in circles). That's why the laminates are laminated. It keeps eddy currents from flowing.
Eddy currents are bad. They hold the blades from turning very well. Take a magnets and coin about the same size. Put them on an aluminum cookie sheet and shake it around. Tip the sheet up on a steep angle, and let the coin and magnet slide down at the same time. That resistance to motion is due to eddy currents in the aluminum.
2) It doesn't matter... sort of? It is all part of the balancing act. Too many variables.
2 sets in parallel need twice the RPM to reach 12V.
However if the 12V RPM is too low for the blade design, it will stall the windmill (making very little power), then they can be paralleled to get the blades going faster before 12V.
Or maybe the wire you have is too small, then twice as many turns makes the right voltage at the right RPM, and it would be easier to parellel the coils.
"Best" is what matches everything else.
Confused yet?
G-
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| windnovice |
Posted - 17/04/2008 : 15:35:28
I hear alot of good things about Hugh Piggott as i keep researching the subject and i was hoping to stay away from buying something but seeing as he is so recommended i might just give in.
Couple of questions...
1) the metal laminates that are placed in the stator, im just curious what this does, does it just create that magnetism with the magnets and metal which creates the electricity in the coils, and if so couldnt i just use a sheet of steel and it would do the same thing?
2) What is the best coil setup, i was reading that if you run two sets parallel you get a little less volts but more amps and if you run them all separate you get more volts and less amps. any suggestions? |
| gotwind |
Posted - 17/04/2008 : 09:22:54
I agree with gholt,
Hugh Piggott's axial flux alternator design is hard to beat, and his manual is required reading.
A lot of people have built this style of alternator, that has zero cogging and can be configured for many cut in speeds/ voltages.
The only concern I see, is the use of large neodymium magnets, that require a huge amount of respect.
http://www.scoraigwind.com/axialplans/index.htm
Also 'windpower workshop' by Hugh is a an excellent read also - it maybe available at a library - it is here in the U.K
Ben.
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