The difference between 220 1ph and 208 3ph is probably marginal, as the 3ph supply to the motor is reconstituted from a DC source, the 3ph peak DC would be around 294vdc and the 1 ph 220 would be around 310vdc, BUT the DC derived from three phase has far less ripple than the rectified 1ph, where the ripple is =100% before filtering.
The DC derived from 3ph is far more efficient for the same voltage due to the very small comparative ripple than that of 1ph.
While we are talking VFD's the standard induction motor can never reach synchronism as mentioned, increase the frequency and the motor will increase rpm, but always at around 4~7 cycles below applied frequency.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.