The most basic of all types of electric motors is the squirrel box induction motor which is used with three-phase power. The armature of this type of motor is in three fixed coils and is similar to the one of the synchronous motor. The rotating element focuses on a core, which includes a series of large capacity drivers placed in a circle around the tree and parallel to it. https://www.mrosupply.com/automation/ac-variable-frequency-drive/2527065_17465800_leeson/ When they do not have the core, the rotor drivers look in their shape to the cylindrical cages that were used to hunt squirrels.
The flow of the three-phase current inside the coils of the fixed armature causes a rotational magnetic field, and this induces a current in the drivers of the cage. The magnetic reaction between the rotating field and the rotor drivers that carry the chain causes it to turn. If the rotor rotates at exactly the same speed as the magnetic field, there will be no induced currents in it, and therefore, the rotor must not rotate at a synchronous speed. In operation, the rotational speed of the rotor and that of the field differ from one another by 2 to 5%. We call that difference in speed.