The single-phase induction electric motor does not exhibit the peculiar rotating magnetic field of the three-phase motor; Thus, it has no starting torque. The inversion of the field in the stator stimulates a voltage in the rotor, which aligns with the stator field, however without starting torque.
Thus, an auxiliary starter is required so that the magnetic force formed between the stator and rotor fields begins to rotate and maintain its continuous speed. The split-phase motor is based on a simple principle, which can be clarified as follows: when inserting a single-phase AC power in two windings in parallel but 90 ° lagged, designated main and starting, the magnetic field that Form produces a suitable starting conjugate to make the rotor move.
This type of motor is used on machines with low torque, such as washing machines. When in the split-phase motor we insert a capacitor in series with the starting winding, the mismatch between the supply voltage and the starting winding current is changed, reaching approximately 90 °, resulting in an increase in torque.