Single-Phase AC Induction Motors:

If two stator windings of unequal impedance are spaced 90 electrical degrees apart and linked in parallel to a single-phase source, the field generates will appear to rotate.  This is known as phase splitting.

In a split-phase motor, a beginning winding is utilized.  That winding has a higher resistance and lower reactance than the major winding that was show in the above figure.  When the similar voltage V_T is applied to the starting and main windings, the current in the main winding (I_M) lags behind the current of the starting winding I_S. The angle among the two windings is sufficient phase difference to give a rotating magnetic field to generate a starting torque.  While the motor reaches 70 to 80% of synchronous speed and a centrifugal switch on the motor shaft opens and disconnects the beginning winding.

Single-phase motors are used for extremely small commercial applications like as buffers and household appliances.

Figure: Wound Rotor