60 Hz (Speed) x (#poles) = 120 x (freq)
The alternator has six diodes inside to recify the ac that is generated. One side of the diodes is the ac side, so maybe you can solder on three live wires and use the case as the neutral, then you have 3-phase four wire, about 300 watts.
Fast speed requires more current than slow speed on the same motor unless the slower speed is caused by additional load. Two motors, one turns 1725 RPM and the other equal hp motor turns 3450 RPM, each draw same current because AC motors run at speeds close to the synchronus speed of the rotor poles. 2pole, 3600; 4pole, 1800.
Phases in AC refer to the number of sine waves of alternating current used to generate the average voltage. In 2 phase, two opposing sine waves are overlapped to give the average voltage delivered, eg 240V in household supplies. In 3 phase, three sine waves are overlapped to produce a more consistent average voltage.