Basic knowledge of AC asynchronous motor
What is an AC induction motor? AC asynchronous motor is leading the motor AC voltage operation, widely used in all kinds of household appliances such as electric fans, refrigerators, washing machines, hair dryer, vacuum cleaners and other, and all kinds of electric tools and small electrical and mechanical equipment in.
AC asynchronous motor is divided into induction motor and AC commutator motor of the two, and induction motor is divided for single-phase asynchronous motor, AC / DC dual-purpose motor and repulsion motor. The rotational speed of the motor (rotor speed) is less than that of the rotating magnetic field. Called asynchronous motor. It is basically the same as the induction motor. S= (ns-n) /ns, s slip, NS N magnetic speed, rotor speed.
Basic principle:
1, when the three-phase asynchronous motor is connected with a three-phase AC power supply, three-phase stator winding through the symmetry of the three-phase current of three-phase magnetic motive force (the stator rotating magnetic motive force (MMF) and produce a rotating magnetic field.
2. The rotating magnetic field and the rotor conductor have relative cutting motion. According to the principle of electromagnetic induction, the rotor conductor has the induction electromotive force and the induced current.
3, according to the law of electromagnetic force, carrying the rotor conductor in the magnetic field by the electromagnetic force, the electromagnetic torque, drive the rotor rotation, when the motor shaft with mechanical load, then the output of mechanical energy.
Induction motor is a kind of AC motor, the speed of load is not constant and the ratio of the frequency of the power grid is not constant. And also with the corresponding changes in the size of the load. The greater the load torque, the lower the speed of the rotor. Asynchronous motor induction motor is the most widely used, in not cause misunderstanding or confusion, generally known as the induction motor for asynchronous motor, but asynchronous motor also includes doubly fed asynchronous motor and AC motor commutator.
The stator winding of the common asynchronous motor is connected with the AC power grid, and the rotor winding is not connected with other power supply. Therefore, it has simple structure, manufacture and use and convenient maintenance, reliable operation and small mass, low cost, asynchronous motor has higher efficiency and better working characteristics, from no load to full load range close to the constant speed operation to meet the requirements of most of the industry and agriculture machinery transmission. Asynchronous motors are also easy to send to generate a variety of protective form, in order to adapt to the requirements of different environmental conditions. When the induction motor is running, it must absorb reactive power from the grid, so that the power factor of the electric network becomes worse. Therefore, the high power, low speed of the mechanical equipment, we usually use the synchronous motor. Because the rotating speed of the induction motor and the rotating speed of the rotating magnetic field have a certain difference, the speed regulation performance is poor. On the requirements of a wide range of speed and smooth speed of the transport, and so on, we often use DC motor, more economical and convenient. But with the development of high power electronic devices and AC speed regulation system, the speed control performance and economic performance of asynchronous motor which is suitable for wide speed regulation can be compared with DC motor.
