...or essentially a single phase motor/three phase generator rolled into a single rotating machine (rotary phase converter). You can even use a plain ordinary three phase induction motor as a rotary phase converter; you power it from your single phase supply through two of the leads, do something mechanical to start it spinning (since a single phased 3 phase motor won't _start_), and once it is spinning you can draw the third leg from the motor terminal.
Something that has always bothered me about this- how do you get true three phase which is 120-120-120 degrees out of single phase which is 180-180 degrees unless you use a true motor generator? (Single phase motor coupled to a three phase generator.)
All rotary converters I have ever seen use the single phase hot legs and create a third phase from them. This works if a three phase motor loses a phase- it will generate the third. But the "input" is already two phases at 120-120 degrees.
There was recently a question from someone who was using a rotary converter that supplied 240 volts. He was using a buck transformer arrangement to buck it down to 208. He couldn't figure out why the voltage was not consistant on all three phases. I suggested it was because the phase difference was not 120-120-120 degrees as the transformers expected to see.
-Hal
