Its a bit of a kludge to use a single value capacitor, as during start, or heavy load, the motor will present a lower impedance, and the phase shift is too high, (as it gets nearer the 90 degees you get with a capacitor and a small R in series ) but if you get it right for a decent start up, then it is too much ( and the phase shift too little) once up to speed (so it never gets up to speed).
Posh units switch caps in and out to get more or less equal voltages accross the two "flying" phase voltages.
on 50 Hz and 250V mains you need circa 50-100uF per horse power, and be prepared to switch some C in and out if you have trouble starting, and do realise it will never be as good as a real 3 phase PSU.
Its a bit of a kludge to use a single value capacitor, as during start, or heavy load, the motor will present a lower impedance, and the phase shift is too high, (as it gets nearer the 90 degees you get with a capacitor and a small R in series ) but if you get it right for a decent start up, then it is too much ( and the phase shift too little) once up to speed (so it never gets up to speed).
Posh units switch caps in and out to get more or less equal voltages accross the two "flying" phase voltages.
on 50 Hz and 250V mains you need circa 50-100uF per horse power, and be prepared to switch some C in and out if you have trouble starting, and do realise it will never be as good as a real 3 phase PSU.
