Items used for the experiment:
1 electric motor (4 kw 3 ph ). The rotor must rev very easy by hand.
2 capacitors (10 uF 400 V each).
Wiring diagram: The motor must be wired in Rotoverter mode, i.e. in STAR configuration (not DELTA).
Pole nr.1 and 2 must be connected to the capacitors. The 2 capacitors are in parallel.
Pole nr. 1 and 3 must be connected to the grid (220V in my country).
When connected to the grid the rev rise until 2840 - 2850 rot/min and the current drops from 4.5 to 0.7 Amps.
If I disconnect the capacitors the current drop to 0.2 Amps. When I connect a load the current rise to 1.2 Amps, but when I reconnect the capacitors the current drops to 0.0 Amps. If I increase the load beyond the sweet point, the curent start to rise until 4.5 Amps when the motor halts. You may see the demonstration on youtube: