I have a three phase induction motor (a fan motor) that get power from a two phase power line. To start the motor I have a start capacitor.
I need to change the speed of the motor to reach the 70% of the nominal one, a colleague of mine said that I can use the scheme of CASE 2, so I have to add an additional capacitor. I was not aware of this configuration, so I seached on the internet. I find some example: Speed control on a ceiling fan induction motor
I understand that the additional capacitor produce a phase shift to reach the desired speed.
My question is related to the sizing of the two capacitors to reach the target speed. If I know the motor data how can I size the additional capacitor C2 to reach the desired speed value? Do I need to use some equivalent motor circuit?