Originally Posted by Beezer
something in the generator system has to move in order to generate... there a permanent magnet on the crank, rotating in the middle of the field coil yes?
I stole this diagram and photo from Practical Machinist. Part 7 is the field coil which is bolted to the engine case. Part 6 is the set of generating coils which is bolted to the engine case. Part 3 is the rotor. It is steel, but it is not permanently magnetic; it is magnetized only when the field coil is energized. It does NOT have wires going to it; this diagram must be cut from a more comprehensive one.
The left photo is the rotor alone. The field coil is magnetized so that left is North and right is South and that the wave pattern in the rotor causes the magnetic field to switch from N to S to N to S . . . . But the rotor is not permanently magnetized, but only pulls the magnetic field from the field coil.
The right photo has the rotor beside the nested field coil and generating coils. The rotor spins in the space between the field coil and the generating coils.
So many motorcycles use permanent magnet alternators and generate the maximum amount of electricity all the time then dump some with the regulator. In 1969 Honda tried generating only what was needed by changing the strength of the field coil to generate only the electricity that was needed.
EDIT: To correct polarities.