What is the purpose of capacitor in a motor

Why do we use capacitor in a motor

Capacitors are necessary for single-phase motors which are not self-starting machines. A 3-phase induction motor has no need for capacitors because these are self-starting machines. in single-phase induction, motor capacitors give starting torque to run a motor.

The purpose of the capacitor in the single-phase induction motor is to displace the current in the starting winding by 90⁰ from that in the running winding. This enables the formation of a rotating magnetic field on the surface of the stator. The rotating magnetic field then induces an EMF in the rotor windings which produces a torque that turns the rotor.