(1) When a flameproof three-phase asynchronous motor is connected to a three-phase AC power source (with a phase difference of 120 degrees in electrical angle), the three-phase stator winding flows through the three-phase symmetrical current to generate a three-phase magnetic electromotive force (stator rotating magnetic electromotive force) and generates a rotating magnetic field, which rotates clockwise along the inner circular space of the stator and rotor at a synchronous speed n0.
(2) The rotating magnetic field has relative cutting motion with the rotor conductor. According to the principle of electromagnetic induction, the rotor conductor (the rotor winding is a closed path) generates induced electromotive force and induced current (the direction of the induced electromotive force is determined by the right-hand rule).
(3) According to the law of electromagnetic force, under the action of induced electromotive force, an induced current will be generated in the rotor conductor that is basically in the same direction as the induced electromotive force. The current carrying rotor conductor is subjected to electromagnetic force in the magnetic field generated by the stator (the direction of the force is determined by the left-hand rule). The electromagnetic force forms electromagnetic torque on the motor rotor shaft, driving the motor rotor to rotate in the direction of the rotating magnetic field. When there is a mechanical load on the motor shaft, mechanical energy is output to the outside. Due to the fact that the magnetic flux without a short-circuit ring is ahead of the magnetic flux with a short-circuit ring, the direction of motor rotation is the same as the direction of the rotating magnetic field.
