The single-phase induction electric motor does not have the rotating magnetic field characteristic of the three-phase motor, so it will not have starting torque. The inversion of the field in the stator induces a voltage in the rotor, which aligns with the stator field, but without starting torque. 15hp motors In this way, an auxiliary starting device is required so that the magnetic force generated between the stator and rotor fields starts rotating and maintains its constant speed. The split-phase motor is based on a simple principle, which can be explained as follows: when applying a single-phase alternating-current power supply in two parallel but 90 ° lagged windings, called the main and the starting windings.

The magnetic field that is established produces a sufficient starting torque to cause the rotor to move. This type of motor is used on machines with low torque, such as washing machines. When in the split-phase motor we put a capacitor in series with the starting winding, the phase difference between the supply voltage and the starting winding current is modified and can reach close to 90 °, resulting in a torque increase.