Originally posted by joe shmo
"By flipping just two of the three wires". That was the original method described by sonhouse. Using this method you can always get the propper rotation on the second try. I think because I ommited that condition in my response to your statement you thought I was mistaken.
That is in fact the case, flip any two wires of a three phase power supply to a 3 phase motor and the spin reverses. Not sure what happens to flipped wires in higher phase numbers though. There are 4,5,6 phase equipment also. My guess is if you flip one phase of a quad, it will either stop running or have seriously reduced torque. I don't think flipping 2 phases out of 4 will reverse spin though. 3 phase is power to each phase at 120 electrical degrees apart. 4 phase is each phase is 90 degress apart, 5 phase, 72 degrees apart, 6 phase, 60 degrees apart.
Higher phase numbers gives smoother rotation like internal combustion engines, 1 cylinder is pretty shaky, 2 better, 3 better, 4 better (on balancing and left over jerkiness of the engine rotation)