The single-phase electric motor offers some characteristics because of its shape, because instead of a concentrated coil, the winding is arranged in grooves to produce a quasi-sinusoidal motor magnet force. This caused magneto motive force causes the engine does not present a starting torque due to the mutual cancellation of it. It is said that the single-phase motor offers no rotating field, but a pulsating magnetic field.
The motor will need auxiliary means such as auxiliary windings and the use of a capacitor to give rise to a second false phase, allowing the origin of a rotating and conjugate field sufficient to make it leave the home. The current in the auxiliary winding when coupled with the main winding current enables a rotating magnetic field in the stator. Produced at engine start, a switch shuts off the auxiliary winding and in these cases the starting torque is still softened. As a solution, to create a sufficient torque for certain applications of the electric motor, the use of a capacitor in series with the auxiliary winding is given. https://www.mrosupply.com/motors/ac-motors/200-575-volt-motors/699711_vem3709t-5_baldor/