Let a three-phase voltage be connected to the stator of a synchronous electric motor, in a second in which the currents in each coil, with the current in the coil a-a ‘in position 1.
Due to the poles created by the field (2-pole motor), one conductor is located on the N pole and another on the S pole. From the relationship between the current in the conductors and the fields, as the conductor is effective, the upper polar face is exposed to A torque to the right, while the lower pole face is subjected to a torque to the left.
Therefore, the rotor is subject to a torque that would tend to reallocate it clockwise. For the current in position 2 is the alternating current and the rotor is exposed to a torque that would tend to move it in the counterclockwise direction.
Due to the inertia of the rotor, the torque formed in one second is zero because the rotor was precisely drawn alternately in the clockwise and counterclockwise directions 60 times at that time for the frequency of 60 Hz. If the rotor is driven at the speed Synchronous, in the second in which the direction of the current is reversed, the field is changed, which will allow a liquid torque.