Here is part two. You were asking about the wiring in particular, and I guess I strayed a bit off topic with constructional techniques. The wiring starts with deciding how much voltage you want to generate and at what maximum speed. Like motors, generators generate a voltage in proportion to thier speed. The current they draw (for a motor) or supply (for a generator) depends on the external torque. For example a generator spinning at 1000 rpm might generate 20V but no current will flow through the coils until an electrical load is applied to the generator output. The voltage varies with speed, while the current varies with external torque. Winding resistance smudges this ideal a little bit but this can be practically ignored.
Other snippets of information are;
The voltage generated across the output is also proportional to the number of turns in the coils.
The current that is generated by an external torque is also proportional to the number of turns in the coils.
The power you can generate from your generator depends on how much copper you have managed to pack into your coils. You can have lots of turns of a thin wire or fewer turns of a thick wire. if the volume of copper is the same in both circumstances then the power output will be the same. The difference is how the power output is best transferred to the outside world. Thin wire = high voltage, low current; thick wire = low voltage, high current. Once you have decided where on the scale you want to be you can design a coil set.
For a prototype around the 200W range I would think about using 0.4-0.6mm diameter wire for windings with a flat disc generator diameter of around 200-300mm. for a 3-phase generator you want 1.5 times the number of coils than magnets, in multiples of 3 coils; i.e. 6 coils and 4 magnets, or 15 coils and 10 magnets etc. The magnets are positioned in alternating polarity N-S, S-N, N-S etc all the way round. The way to check this when offerring up a magnet to its position in the ring is that it should be repelled by its neighbour when held above it. It will be attracted by its neighbour once it is positioned on the plate though so be careful. A good starting point for a gap between the magnets is around 1-2x the magnet thickness. Make the magnet thickness no more than 20% of its width, or efficiency will suffer. You may be able to buy arc segment magnets off the shelf which are approximately right for your generator. For a prototype round discs are OK or rectangular blocks could be used. If this is the case then make the gap between the magnets virtually zero round the inner diameter of the magnet ring and keep the magnets approximately square in shape. You can buy very powerful NdFeB rare earth magnets these days, so cheaper grades are readily available. Buy them nickel coated so that they don't corrode.
Your coils should be wound all in the same direction on your production line to avoid confusion. Make them no taller than about 20% of the magnet width, again for efficiency purposes. For the coil width make them roughly square in section. The more copper the more power, but you start to compromise efficiency if you try and pack in too much. Your coil shape should be trapezoidal with the length of the radial sides just about as long as the magnet. You can buy auto-bonding transformer wire that has a heat activated glue coating the outside of the wire. make a former for winding the coil and when wound, put a heat gun on it for a coule of minutes and it will bond itself together. Watch the temperature though, and let it cool a little before removing. This way you dont mess around with messy glue, and it is quicker to make the coils.
Try and make the air gap between the magnets and the coils small. If it is too small they will rub, and the magnets will smudge the copper from offending wires across neighbouring wires causing shorting and a right old mess. Too big a gap though and you lift the coils out of the magnetic field of the magnets and reduce efficiency. Wiring up the coils is not too difficult. If you have 6 coils, then make 3 pairs, so 1 and 4 are wired together, 2 and 5 are wired together and so on. (you can wire them in series or paralell - this is one place you can tune the generator to match the ouput you want) If you have more coils just connect them in 3 sets. Next connect the inside ends of any two sets to the outside end of the third set, and the three remaining ends (2 outside ends and 1 inside end) are the generator phase outputs. Look up a 3-phase rectifier circuit such as
http://www.opamp-electronics.com/tutorials/images/semiconductor/03267.png to work out how to connect them to the outside world.
a 3-phase generator sounds complicated but it is very easy to make an efficient one and there are no contacts, brushes etc to wear. Good luck!
