Due to the fact that they only present one feeding phase, this category of machine does not present a rotating field, as it happens in three-phase motors. However, they have a pulsating magnetic field, which can prevent them from obtaining starting torque, since in the rotor magnetic fields are properly induced in line with the stator field. To solve the problem, we use auxiliary windings, sized and positioned in a way capable of creating a second phase, allowing the formation of the rotating field necessary for starting.
Single-phase electric motors are called this way due to their field windings, which are connected directly to a source known as single-phase. Single-phase induction motors are seen as a natural option compared to three-phase induction motors in places where three-phase power is not available, such as in rural areas, workshops, offices and homes, for example. Its use is only indicated 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. https://www.mrosupply.com/motors/ac-motors/general-purpose-motors/26523_vm3546_baldor/