A little bit I found about about 3-phase power, because I really didn't know much about it either.
Three-phase is much more costly to install, but is much more efficient for high horsepower motor loads.
Have you ever done any singing in rounds? ''Row, row, row your boat, merrily, merrily....'' When the first group reaches merrily, the second starts ''Row''. Eventually you have 3 different groups singing the same thing at different times. So 3 phase. In addition to the familiar sine wave of single phase, 3 phase has a second phase starting 120 degrees after the first, and a third phase at 240 degrees.
The big advantage to 3 phase is that motors can be smaller for the same horse power. Just as a single phase AC motor is smaller than a similar DC motor, so a 3 phase motor is smaller than a single phase. Airplanes use electric motors with even more phases where weight is even more important then size. In factories, it is common to have many high loads, and most of them use 3 phase motors and 240 or 480 volts.
Also, motors dont need a capacitor to start on 3 phase
Single phase 120/240 volt service at 100 amps can provide 24000 watts of power.
The largest single phase motor available is approximately 10 HP.
Typical 3 phase 120/208 volt service at 100 amps can provide 35984 watts of power.
3 Phase motors are available up to 3000 HP.
*The above were copied/pasted from various sources*
And of course :
Three-phase electric power - Wikipedia, the free encyclopedia
Dave