Each phase has the same voltage in a sinewave, but 120 degrees out of phase. The question then becomes which phase leads the other. This is what determines the direction of the motor. 

How to change rotation direction of 3-phase electrical machines?
Is it possible to find all entries in a crontab that run between time X and time Y without having to parse the cron time entries myself? I'm mainly concerned with time hour and  minute, not so much the other 3 time fields.
