The single phase current flowing through a single phase motor can not produce a rotating magnetic field. It needs to be used to divide the phase. The purpose is to make the current in the two windings produce the phase difference near 90, in order to produce a rotating magnetic field.
The capacitive induction motor has two windings, the starting winding and the running winding. The two windings have a difference of 90 degrees in space. A large capacity capacitor is connected in the starting winding. When the running winding and the starting winding pass through the single-phase alternating current, the current in the starting winding is 90 degrees ahead of the current of the running winding in time due to the action of the capacitor, and the maximum value is reached first. Two identical pulsed magnetic fields are formed in time and space, which causes a rotating magnetic field in the air gap between the stator and the rotor. Under the action of rotating magnetic field, the induction current is generated in the rotor of the motor. The current and the rotating magnetic field interact to produce electromagnetic torque to make the motor spin.