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Ready to wind coils. It's too late for me, im hooked.
By Parameter, Section Homebrewed Electricity Posted on Thu Apr 29, 2004 at 01:43:16 PM MST
The eternal question, how much turns....

I got my wire and am ready to wind. Is there a simple receipe to get the number of coils right? Got a 10 inches single disk, 18 small magnets/18 coils, wire is #14 and I would like it to run on a 3 blade 6 foot diameter blade. Expected power is about 300 watts at 20mph on a 12v system. I guess I just should try some coils, but then I will then have to decide on star/delta OR maybe a 2 phase machine and get the maths right... right ;)
Cut in should be the lowest realisticaly possible with no real care for high end winds (above 25). I know that with the single disk there will be some drag and I will most probably have a good gap because of this.
I know there are a lot of posts about coils but I just need some startup info on this rather small one I build. Any comments are welcome. Thanks
Para

Ready to wind coils. It's too late for me, im hooked. | 9 comments (9 topical)

Re: Ready to wind coils. It's too late for me, im (none / 0) (#1)
by DanB on Thu Apr 29, 2004 at 02:24:30 PM MST

What size are the magnets Para? Thats a fairly important part of it.

18 magnets and 18 coils is a single phase configuration. So Star/Delta does not apply...
(parallel series could...)
You might try 16 magnets and 12 coils for 3 phase.

Is it a single rotor, or a dual rotor machine?

If your trying something different (which it seems you are) the best bet in my opinion....

Assemble your magnet rotor(s)
wind a coil up of the right size and test it under exactly the same conditions itll see in the alternator. (if its a dual rotor, poke it between the rotors)
so you need to setup 1 coil to be tested, spin the machine at a known rpm - see what sort of AC voltage you get from the coil.
Then youll have a good starting point.

Re: Ready to wind coils. (none / 0) (#2)
by Parameter on Thu Apr 29, 2004 at 03:08:04 PM MST

Well, i just did that a minute ago, here are some results...

This is the test jig, nothing elaborated.

Here are the 2 coils, the one to the right is too big and produce .3 volts at around 200 rpm.

This is the small coil. .6 v AC is nice for one coil at around 200 rpm.

This is the big one that hugh had me changed a while back. There is a hughe difference between the 2 even if winding is pretty much the same. ;)

Well, I tough I could make 3 phases of 6 coils for 18 coils totals but I see I will not have space to offset them on the magnets. With 16 mags and 12 coils, would I need to make the coils bigger than usual to have a wider reach?

Thanks

Para

Ready to wind coils (none / 0) (#3)
by Parameter on Thu Apr 29, 2004 at 04:46:43 PM MST

oh, and its the small magnets ( 1 x 1 x 1/4 square neos). The coils are #20 gauge about 40 to 50 turns each. I will use the #14 wire after testing. seems I need like 100 turns or so and 12 coils with 16 mags.

More to come.

Para

Re: Ready to wind coils (none / 0) (#4)
by DanB on Fri Apr 30, 2004 at 08:20:46 AM MST

Its important to keep the inside dia. of the coils no larger than necessary - perhaps exactly the size of the magnets or a touch smaller. If you use 9 coils:12 magnets, then the outer diameter of the coils can be such that they fit tightly together.

In your test - testing with only 1 rotor, you could assume that your output will be approx 1/2 of what youd see with 2 rotors.

Remember that your measuring AC voltage - probably RMS or some approximation, so after you rectify it youll have about 40% higher voltage - approx 1.4 volt drop across the rectifiers.

[ Parent ]

Re: Ready to wind coils. It's too late for me, im (none / 0) (#5)
by wooferhound on Fri Apr 30, 2004 at 11:01:06 AM MST

You should try running the output through a bridge rectifier with a capaciter across it, and measure the D C Voltage...

}=- W o o f -={

Ready to wind coils. (none / 0) (#6)
by Parameter on Fri Apr 30, 2004 at 04:38:02 PM MST

thanks. the first coils are the hardest ones to make.

So if I understand well, i got to keep my coils the same size as to reach across 2 magnets but no more. Make sure the top and bottom are not directly under the magnet and space em evenly even tough there is a gap between them? Makes sense as there it create the offset to make the 3 phases.

I'll rectify this with a small diode bridge and capacitors before I send more results. These were just my first tests with the setup. Thanks guys.

Para

Re: Ready to wind coils. It's too late for me, im (none / 0) (#7)
by hvirtane on Sat May 01, 2004 at 03:10:40 PM MST

The important thing is to make
the coil width the same as the
distance between magnets.

Then the currents induced
by different magnets are not
canceling each others.

Here are some drawings I made for
a friend to illustrate the principles.

3 phase with 24 magnets.

5 phase with 24 magnets 30 coils.

The same as the above with wiring the phases.

The same as the above with different wiring
for slower speeds.

- Hannu

Re: Ready to wind coils. It's too late for me, im (none / 0) (#8)
by Parameter on Mon May 03, 2004 at 05:55:04 PM MST

Thanks for the comments hannu, my worry is that since the coils are high, i will not be able to stack them or the like. so I'll have say 12 coils and 16 mags. Coils should be made so that magnets are correctly positionned over the legs (correct spacing). And must both legs be same or different polarity when I do this?

[ Parent ]

Re: Ready to wind coils. It's too late for me, im (none / 0) (#9)
by hvirtane on Tue May 04, 2004 at 04:34:24 PM MST

Hello, please see here for
the correct shape of the coils
and magnets:
http://www.fieldlines.com/story/2004/4/28/195225/620

To illustrate the geometry, please see this:

Many people are thinking
that you need
big spaces between magnets,
about as big
as the size of the magnets.
That depends on
the air gap size, too.

To know how many turns
you'll need it is best
to make test coils.

You can later also make
a difference between getting low RPM
charging voltage, if
you'll hook the rectified currents
in series or in parallel
as illustrated in my drawings
of 5-phase machines above.

- Hannu

[ Parent ]

Ready to wind coils. It's too late for me, im hooked. | 9 comments (9 topical)

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