Theoretical analysis shows that a r

Theoretical analysis shows that a rotating magnetic field, if the stator winding is a symmetrical three-phase symmetrical three-phase voltage is applied, there is a symmetrical three-phase current, and a rotating magnetic field in the air gap, the magnetic field rotational speed n1 of the motor is formed is called the synchronous speed, the magnetic poles motor and its relationship to the grid frequency f1 is: n1 = 60 f1 / p phase sequences and three-phase windings and three-phase current steering arrangement of FIG relevant U, V, W-phase are arranged in the clockwise direction, when the three-phase current Walter stator windings U, V, W phase sequence when a stator, a rotating magnetic field rotates clockwise. Since the rotor is stationary, the rotating magnetic field between the rotor and the relative motion, since the rotor conductor cuts the magnetic field generating induction power of the stator, the rotor windings due to its closed, current will flow in the rotor winding. Active rotor current and rotor phase induced electromotive force, which direction may be "right generator" normal. Current active stator member carries a rotating magnetic field of the rotor winding, the electromagnetic force F., To determine the direction from "left motive gives" a. An electromagnetic force forming a magnetic torque shaft, which is consistent with the action of the rotating field direction of the direction of rotation direction of the rotating magnetic field of the rotor, the power input into rotational mechanical energy. If the motor shaft has a mechanical load, a mechanical load with the rotation of the motor, the mechanical motor load is completed. The foregoing analysis shows that the basic principle of rotation of the three-phase asynchronous motors are: (1) three-phase symmetrical three phase winding currents Walter circular rotating magnetic field. (2) cutting the conductor rotor and the rotating magnetic field EMF currents; (3) a carrier as a conductor rotor by electromagnetic forces in a magnetic field, thereby forming a rotation electromagnetic torque, the motor drives the rotor. For the same time there are some electrical classification, it can be divided by function for turning and breaking electrical circuit, electrical circuitry for controlling, for electrical cutoff circuit for detecting electrical circuit coefficient for protecting the circuit appliances. There are low-voltage electrical appliances, low-voltage distribution can be summarized as electrical and low-voltage electrical control two categories. Since these two types of Status and Role in the low-voltage electrical circuit which is also different from a greater difference of their performance requirements.