formula for capacitor on 3 phase motor

[GEOFFREY]

I have read from 40µF/kW, thats near to your amount, in a thumbrule there are 3Amps/kW. But maybe you need a separate start capacitor, which is switched off after a second or so. But, you can't run such a big motor with only one fase.
The Motor need some 24Amps to run and triple of it to start. With a small motor maybe half as strong, you can make this.

I agree. I haverun several 3ph motors in Delta using caps with a timer switched extra "starter" cap. the system works well for motors up to about 3HP, above that and you will notice the lights dim on start up, and that will be the same with any neighbours connected to the same phase. G.

[m.marino]

At 4KW I would suggest the VFD is the best route. There is more than one reason; which a few of them have already been stated.