Three-phase induction motor rotor speed is lower than the speed of the rotating magnetic field, the rotor winding there is relative motion between the magnetic field induced emf and current and the magnetic field generated by the interaction of electromagnetic torque, and energy conversion. Compared with the single-phase induction motor, three-phase asynchronous motor is running good, and save a variety of materials. Different rotor structure, the three-phase asynchronous motors can be divided into the cage and the two wound. Cage rotor induction motor, simple structure, reliable operation, light weight, cheap, and has been widely used, its main drawback is speed control difficult. Wound three-phase induction motor rotor and stator as well as set up the three-phase windings connected through slip rings, brushes and external rheostat. Can improve the starting performance of the motor and adjust the motor speed regulating rheostat resistance.

    Generated when the symmetrical three-phase alternating current to the three-phase stator windings by the rotation of the rotating magnetic field at synchronous speed n1 in the clockwise direction along the inner circle of the stator and the rotor space. Due to the rotating magnetic field rotational speed n1, the rotor conductor is stationary, the rotor conductors will cut the stator rotating field and generate an induced electromotive force (the direction of the induced electromotive force is determined using the right-hand rule). The shorting ring guide sub-conductor is short-circuited at both ends, the induced electromotive force under the action of the rotor conductors will be substantially consistent with the direction of the induced electromotive force induced current. The current carrying conductor of the rotor by the electromagnetic force in the stator magnetic field (the direction of the force with the left hand determination). The electromagnetic force of the electromagnetic torque on the rotor shaft, drive the rotation of the rotor along the rotational direction of the magnetic field.

    Through the above analysis can be summed motor working principle: When the three-phase stator windings of the motor (each, a difference of 120 electrical degrees), which leads to the three-phase alternating current will produce a rotating magnetic field, the rotating magnetic field cutting rotor windings, the rotor induction current is generated in the winding (rotor winding passage is closed), the current-carrying conductor of the rotor in the stator rotating magnetic field will produce an electromagnetic force, thereby forming the electromagnetic torque on the motor shaft to drive rotation of the motor, and the motor rotation direction and the rotating magnetic field same direction.