Diferent voltages from 3 phases combo.

[amiklic1]

I build another 4' Piggot's design wind generator, somewhat modified, and after I put it on the stand to test it, I take some measurements of a three phases (three combinations of a phase 1, 2 and 3 - 1-2, 1-3 and 2-3). I get a different readings. From two combinations I get 10 V, and with the third, I get only around 7V. Stator is wired in star.

I thought that I made some coils different, and I build another one genny. I get pretty the same results with this one, too.

The only reasonable way I can explain is that I get tired while turning the rotor by hands, so the third combination comes out somewhat different than the first ones.

Any other explanation?

[Nothing40]

Maybe extra resistance in one of the wires?

If you're using alligator-type jumper leads for testing,try a different jumper lead,etc.Maybe there's a bad conection somewhere.

Or maybe you're just getting tired by then. :-)

[hiker]

strange readings at that...

might try hooking one wire to the starpoint then -the other to any one lead out wire.

just make a small hole in your stator to get to the starpoint

 just curioes how many use the starpoint as a extra power out??

[Flux]

If you can get at the star point, check each phase as Hiker suggests.

If you are getting tired then try the low phase first next time, it should always be the last one you check that is low.

You would be better off checking at a moderate speed that you can keep up. Try something like 120 rpm and count the turns at 2 per second to be sure you have the same speed.

It almost seems that you have reversed the connections to one coil, but a little odd that you would do it twice.

If there is any sign of unusual resistance to turning then you may have a shorted coil, may show as vibration or lumpiness when turning.

Flux

[spinner]

or better yet (from sad experience) don't use clip jumpers like the radio shack ones at all...they can drive ya c-r-a-z-y when they start opening up (and they will)

spinner

[dinges]

Hmmm. Seems I'm not the only one who learnt that lesson the hard way...

I've soldered mine, instead of relying on the lousy factory crimp. They are great tools, handy to have around, but they have their limitations. In my case, they have a resistance (when soldered!) of about .5 ohm per cable.

[finnsawyer]

You may not have a true three phase alternator.  If you can get at the star point, break it and connect all three phases in series and measure the voltage.  With a true three phase alternator the resulting voltage will be zero.  If it is not, you will have a hybrid alternator, which may be somewhere between a true three phase and the alternator design that I give in my diary.  Of course, you may study my design and check it against what you actually have.  I've noticed lately that some built or proposed alternators are not true three phase.  Connecting the three supposed phases in series is a simple way to check whether the alternator is behaving as three phase.  Everyone should incorporate it as part of their alternator evaluation procedure.  That is, make the star connection available (bring out both leads from each phase).

If one takes my design and connects the three "phases" in star, one would expect just the kind of result that you got.