Delta Issues

[ejl7007]

Can anyone help me please?  I have made an alternator that weighs about 120 lbs.  I used 18 neo magnets, grade N42 4"x1"x1" and glued them on an 18" diameter wooden disk.  The rotor is made up of nine coils facing-up, 11 awg, high temp wire with 200 turns per coil.  The coils are mounted on a steel disk 1/2" thick and 18" in diameter.  The gap between the rotor and the stator is less than a 1/4". The rotor is connected via a pulley to a motor and I run it to check my speed and measurements.  It cogs a bit but once it gets going I get a reading of 15 or so VAC @ 120 rpm approx. per phase.  So here is the question.  When I connect the wires in star the voltage increases but I designed the machine to be wired in Delta.  But when I hook up the third and last phase to complete the delta connection, I feel that I'm kinda shorting out the alternator as it slows down a lot, almost to the point of stopping.  It becomes tremendously difficult to spin it by hand.  IN star, no problem.  What could be wrong?  

Sincerely

Ejl7

[deloiter]

Let's get past one issue first.  Did you really mean to say that you have the magnets glued to a wooden disk and the coils mounted to a steel disk?  

[Flux]

No I think he means a steel disc and he has built an eddy current heater.

If he has done what he said it will be no use in star, the eddy losses will be serious. In delta the circulating harmonics will induce 3 times frequency eddies into the disc and the drag will be dreadful.

Flux

[clflyguy]

Hey EJL,

  (Is this a joke?) If not, then buy 6 more magnets and another steel disc.

Carefully remove existing magnets from wood and and existing coils from steel.

  Start over- 12 magnets go on each steel disc, 9 coils go in coil shaped holes in the plywood. Suggest you re-read and carefully look at the photos in the Dan's

article on this site about building their 10' turbine. -Gus

[ejl7007]

Yes that is correct.  Should I have gone the other way around? Glued the magnets instead on the steel disk and the coils on the wood instead?  No wonder the attraction on the steel disk and the magnets is so strong, which I suppose cause the so called "Eddie Currents"

Thank you deloiter, for your help  

[ejl7007]

Ooops!!! I have it all backwards it seems.

Thank you Flux for your help.

Very much appreciated!!!

[ejl7007]

I've got it all wrong.  I will start over and re-read all the instructions.  

Thank you, Gus for your helpful insight.  

[Todd a]

Yup and those magnets need to go on pretty thick steel... possible 1/2" would do.  and it is best if the stator ring is between 2 sets of magnet rings.  That is why the stator is incased in a resin instead of mounted on a board.  This also cuts down on failure from heat and vibration.  The ratio of magnets to coils is usually 4:3 so 12 magnets on each plate for 9 coils, but if you have the room for more coils you can actually use different ratios.  The big problem you have is those coils ae all hitting magnets at the same time.  This is bad.  This makes it hard to hook the coils together without basically having one phase.  With a 12:9 then you only have 3 magnets hitting at any one time with them staggered out.  This way each 3 coils can be attached together in a star pattern.

[ejl7007]

Thank you for your advice Gus!  Most likely I will use the 1/2" steel plate and 16 magnets and recast my stator with 12 coils of possibly 13 awg wire.  That is ratio of 4/3.  The neo magnets were fairly expensive ($20.00) a piece, so I don't think i can afford to buy more of them for now.

Thanks