Single-phase machines are thus referred to by their field windings, which are driven directly to a single-phase source. It can be emphasized that single-phase induction motors are generally considered as a natural option when compared to three-phase induction motors in places where three-phase power is not available, such as in rural areas, workshops , offices and residences. Its use is recommended only for reduced power, on average of one to two kw. Amongst the various types of single-phase electric motors, the cage-type rotor can be highlighted, considering its simplicity, ease of projection, reduced maintenance and robust body.
Therefore, this type of motor single phase motors has only one phase of power, this machine does not present a rotating field, as usually happens in three-phase motors, however, they have a pulsating magnetic field, which can prevent them from obtaining starting torque, magnetic fields aligned with the stator field are induced in the rotor. Thus, auxiliary windings are used, which are dimensioned and positioned so as to create a second phase, allowing the formation of the rotating field required for starting.