The auxiliary phase electric motor is an induction motor consisting of a squirrel cage rotor and a stator formed by iron-silicon insulated sheet crowns, with grooves in the inner part, fixed to a housing. The windings, called the main and auxiliary windings, are housed in the isolated grooves, offset by an electrical 90 ° angle from one another. Single-phase induction motors without starters do not have their own startup because they do not produce a rotating field, hence the need to use the auxiliary phase with different characteristics of the main so that the magnetic fields lagged between each other produce a rotating resultant, which by induction moves the cage-type rotor, placed inside it.

The main winding is accurately evaluated, but the auxiliary is achieved empirically, but always in relation to the main, that is, the auxiliary runs from 34% to 80% of the number of conductors of the main and the section of the conductor varies from 30% to 50% of the driver employed in the main, calculated for 110V. For two voltages, simply extend the main winding calculated initially to 110V by twice the number of conductors, with its section halved, divided into two circuits, so that it can be connected in parallel to 110V and in series to 220V.