I do understand that in a Three phase Motor, a rotating magnetic field is produced in stator and the induced magnetic field in rotor tries to aligns itself with the stator field which makes the rotor rotate.
But in case of a single phase supply, there is only a pulsating stator field. So to start the motor, an auxiliary winding is used which has a field that lags the main field by 90 degrees.
After the motor starts, the auxiliary winding is disconnected and now we only have the pulsating field in stator which can not generate any torque. Then how does the motor continues to produce torque and rotates?