See if this formula gets you fairly close; although, if someone actually knows what was used would be better. I usually leave this up to the engineers that designed the motor.
(I * 1000000) / (6.2832 x Hz x V) = �F (mfd)
The 6.2832 is Pi x 2
I = current draw of motor from Id plate
Hz = your local line frequency, I suspect yours is 50 Hz where mine is 60 Hz
V = Line voltage applied to motor.
Capacitor voltage needs to be at least a plus 25% of applied voltage for safety and capacitor life. example 220 vac would around 275 vac or higher. Also make sure you use a non-polarized capacitor
From the above formula using 8 amps @ 50 Hz , 220 Vac I get 115.75 �F so I round up to next available size.
