It is necessary to know that each of the poles found inside a machine counts on a part that represents approximately 25% to 35% of the same, that is hidden by a projected turn in copper in short circuit. The current induced therein allows the flow through it to have a delay compared to the flow of the part not received by it. The result https://www.mrosupply.com/motors/dc-motors/washdown-motors/2525303_10822600_leeson/ will be similar to a rotating field that moves in the direction of the uncaged part to the pole, causing the torque to reach the nominal rotation, which will cause the motor to rotate the direction of rotation, varying according to the side in which lies the embraced part of the pole.
It can be said that motors with distorted field have a single direction of rotation, however, that direction can be reversed by changing the position of the rotor axis tip in relation to the stator. There are other ways to achieve rotation inversion. Shaded pole electric motors are also called distorted field motors because of their starter process, which is the simplest and cheapest single-phase induction type motors.