Instructables

Step 13: A Brief Explanation

Okay, so I haven't really gone over much in the way of what has been wired up here. What you have now is a Y circuit for a 3-phase alternating current generator. Instead of how we usually think of AC, like one big sine wave, this contraption has three waves working at three different phases at the same time.

The benefit of doing it this way is that we can jam in some more coils than we would if we just did a simpler version that produced a simple AC wave. Also, this method allows us to get about 1.7 times more voltage out of the generator than the coil groups would produce on their own. That's the magic of this "Y" configuration: it gets us more voltage for low RPM generators, which is definitely what we have here.

There is another configuration worth mentioning (and it's the reason my "B" looked out of order in the photos). The "Delta" configuration gives us the same voltage as the individual coil groups but about 1.7 times the current. So, if you really needed more current, and you could get the turbine spinning fast enough to take care of your voltage needs, that might be the way to go. It wasn't for me, but feel free to research it for your own stuff and let me know how it works for you.
Cool project and great explanations! A question and a suggested improvement: Is your three phase "Y" (wye) rectifier circuit connected half wave? I think so. If it is, rewiring to a full wave circuit could supply even greater voltage or current. Pages 23 and 24 of http://www.autoshop101.com/forms/alt_bwoh.pdf show full wave, three phase rectifier circuits, wye-connected and delta-connected, respectively.
I can confirm that the circuit is a full bridge rectifier. In you link, I believe the reference to 8 diodes includes the field coil diodes on some alternators. In car alternators for example, you have no permanent magnets, instead they use a much more powerful electromagnet. To start power generation, the battery must power the field coil but when the alternator is up to speed, it feeds it's own field coil on top of recharging the battery.
If it were connected half wave he would have used three diodes.
It doesn't explain the 8 diodes, what would you do with the 2 extra ones?  It is already a full wave.