DIY Alternator low output

[bigfoot]

I have a small stream, low head, year round flow - that I want to use for a 12 VDC battery charging application. We use two 200AH batteries to power a 150W load with an inverter at our camp for a few hours every night.

I have a home brewed Pelton setup in a 5 gallon pail, its fed with a 1" well pipe, 15GPM at about 40PSI. I can spin the shaft 950 RPM all day. I believe I have the mechanical part figured out, the drive train,  if you will - seems to be pretty stable.  I have tried a couple motors, none of them produced enough charging power, so I wound an alternator. I have 6 coils, 20AWG @ 100 turns, wired in a 'Y' to make 3 phase AC. The coils are arranged in a circular pattern with a 4" diameter, each coil has about a 1" center diameter.

 I have 8 cylindrical magnets 3/4 diameter and 1/4 thick rated N48. I have the stator mounted on an adjustable base, and I can adjust the gap fairly easily. Even with the magnets very close to the stator, I get less than a volt across any pair of phases when spun by hand at relatively low RPM - my guess is it should be higher . I only have a single rotor, and would prefer to use only one to make the assembly somewhat easier. My question is: Did I buy magnets that are too small? I want to keep the stator, and I don't mind changing the magnets, although they are somewhat expensive (but not compared to gas for the generator). Any help would be appreciated.

My project is documented here: http://web.me.com/lroloson/Micro_Hydro/Welcome.html

[artv]

Hi Bigfoot,...I read your link where you mentioned "tip-up wire"?.......It is enameled (coated wire) right?

Also you have plastic behind your coils?? If so thats not going to create a path for the flux lines.

Theres lots of info in the search board here just look for stator design, dual rotor , or laminated cores
If you use the advanced search option that seems to work the best......good-luck.........artv

[bigfoot]

Artv - thanks for the reply. Yes, I have the stator sitting on a plastic backing plate. That plate has the adjusters so I can control the gap.

The tip-up line was used to calculate the amount of wire that I needed to wind the coils, the coils are wound with 20AWG copper transformer wire that is coated. I will try testing with the plastic mounting plate removed from under the stator.

thanks again!

[ghurd]

Like you guessed, the magnets are not thick/long enough.
The single rotor has no clear flux path.  The only coil turns that are doing much good will be the ones closer than about 3/16" to the magnet face.

Removing the plastic will not help because the plastic has no effect.

First thing that comes to my mind is getting another set of neos, and glueing them on top of the existing neos, which will help.  The flux path is still not complete.

Second thing is what Art said.  Try a laminated core.
I use metal from microwave transformers.
Here are a couple oters,
http://www.windstuffnow.com/main/alt_from_scratch.htm
http://www.otherpower.com/woodax.html

Even with a laminated core, still need to add more neos on top of the existing neos (or replace them with thicker neos).

Something else... placing 1/4" thick neos in an 1/8" deep iron hole is costing you a lot of the flux.  A very high percentage of the flux is just shorted out.
The magnet disk with the holes should have been aluminum.

G-

[bigfoot]

Ghurd - thanks for taking the time to read all the stuff I have posted, and also for providing some much needed feedback. I appreciate the pointers, this is my first one and I expected to have a few things be wrong.

First, I am thinking about larger neos 1" diameter by 1/2" thick @ N52. I will recut the plate with the holes from aluminum, or I maybe I will eliminate it and just use a single plate with the neos glued in place. The laminate idea looks interesting as well, currently my setup has the stator sitting about 1/2 above the metal lid on my 5 gallon bucket, but I could redesign the stator mount to sit on a laminate base with steel in it. 

If you get a minute could you let me know if you think the 1" N52's are a good choice?

thanks again !!!

[ghurd]

N52 is 'fancy'... but not much better than N42 or N45.  Doubt it is worth the cost difference.

Be advised:  The neos vs laminated core will pull like a son of a gun.  I doubt you will believe how much, until you try it!

If re-doing basically the whole thing, may consider different neo and coil spacing.  There is a lot of wasted space in the one you have now.

If you intend to keep the diameter of the whole contraption, might consider going with 12/9 instead of 8/6.

Don't leave un-laminated metal behind the stator.  It makes an eddy current brake.
G-