Today let's learn more about the differences and functions of different types of motors:
I. AC asynchronous motor
Ac asynchronous motor is a leading ac voltage operation motor, widely used in electric fans, refrigerators, washing machines, air conditioners, hair dryers, vacuum cleaners, range hoods, dishwashers, electric sewing machines, food processing machines and other household appliances and various electric tools, small mechanical and electrical equipment.
Ac asynchronous motors are divided into induction motors and AC commutator motors. Induction motors are divided into single - phase asynchronous motors, AC - DC motors and repulsion motors.
The speed of the motor (rotor speed) is less than the speed of the rotating magnetic field, so called asynchronous motor. It's basically the same as an induction motor. S = (ns - n)/ns. S is the slip rate,
Ns is the magnetic field speed, n is the rotor speed.
Basic Principles:
1. When the three-phase asynchronous motor is connected to the three-phase AC power supply, the three-phase stator windings flow through the three-phase symmetrical current to generate the three-phase magneto motive force (stator rotating magneto motive force) and generate a rotating magnetic field.
2. The rotating magnetic field has relative cutting motion with the rotor conductor. According to the principle of electromagnetic induction, the rotor conductor produces induced electromotive force and induced current.
3. According to the law of electromagnetic force, the current carrying rotor conductor is affected by the electromagnetic force in the magnetic field, forming electromagnetic torque, driving the rotor rotation, when the motor shaft with mechanical load, it will output mechanical energy.
Asynchronous motor is a kind of ac motor, its load speed and the frequency ratio of the grid is not a constant relationship. It also varies with the size of the load. The greater the load torque, the lower the rotor speed. Induction motor includes induction motor, doubly-fed induction motor and AC commutator motor. Induction motor is the most widely used, in the case of not causing misunderstanding or confusion, generally can be called induction motor induction motor.
The stator windings of ordinary asynchronous motors are connected with AC power grid, and the rotor windings do not need to be connected with other power sources. Therefore, it has the advantages of simple structure, convenient manufacture, use and maintenance, reliable operation, small quality and low cost. Asynchronous motor has higher operation efficiency and better working characteristics, from no load to full load range close to constant speed operation, can meet most of the industrial and agricultural production machinery transmission requirements. Induction motor is also easy to be derived into various types of protection to meet the needs of different environmental conditions.
When the asynchronous motor is running, reactive excitation power must be absorbed from the grid, so that the power factor of the grid becomes bad. Therefore, synchronous motors are often used to drive ball mills, compressors and other high-power, low-speed mechanical equipment. Because the speed of induction motor and its rotating magnetic field speed has a certain difference, its speed regulation performance is poor (except ac commutator motor). Dc motor is more economical and convenient for transportation machinery, rolling mill, large machine tool, printing and dyeing and papermaking machinery, etc. But with the development of high-power electronic devices and AC speed regulation system, the speed regulation performance and economy of asynchronous motor suitable for wide speed regulation can be comparable with that of DC motor.
Two, single-phase asynchronous motor single-phase asynchronous motor
Single-phase asynchronous motor consists of stator, rotor, bearing, housing, end cover and so on.
The stator consists of a frame and an iron core with windings. The core is made of silicon steel sheet by punching groove and pressing, and the groove is embedded with two sets of main winding (also known as running winding) and secondary winding (also known as starting winding composed of secondary winding), which are separated by 90° electric Angle. The main winding is connected to the AC power supply, and the secondary winding is connected to the centrifugal switch S or the starting capacitor and the running capacitor, and then the power supply is connected.
The rotor is a cage type cast aluminum rotor, which is the core of the iron after the folding of aluminum cast into the core of the groove, and together cast the end ring, the rotor guide bar short circuit into a squirrel cage type.
Single-phase asynchronous motors are divided into single-phase resistance start asynchronous motors, single-phase capacitor start asynchronous motors, single-phase capacitor operation asynchronous motors and single-phase double-value capacitor asynchronous motors.
Three and three phase asynchronous motors
The structure of three-phase asynchronous motor is similar to that of single-phase asynchronous motor, and its stator core groove is embedded with three-phase windings (there are three types of single-layer chain type, single-layer concentric type and single-layer cross type). After the stator winding is connected to the three-phase AC power supply, the rotating magnetic field generated by the winding current generates induced current in the conductor of the rotor. Under the interaction of the induced current and the rotating magnetic field of the rotor, the electromagnetic cabinet (that is, asynchronous cabinet) is generated to make the motor rotate.
Four, cover pole motor
Ac synchronous motor
Shaded pole motor is the simplest type of unidirectional AC motor, usually using a cage chute cast aluminum rotor. According to the different stator shape structure, it is divided into convex pole type cover pole motor hidden pole type cover pole motor.
Salient pole type cover pole motor stator core shape is square, rectangular or circular magnetic field frame, magnetic pole protruding, each magnetic pole has one or more short circuit copper ring auxiliary role, namely cover pole winding. The central winding on the salient pole is the main winding.
Non-salient pole type cover pole motor stator core is the same as the common core of single-phase motor, the stator winding adopts the distributed winding, the main distribution in stator slot winding, shaded pole winding don't short circuit copper ring, but with the coarser the enameled wire wound as distributed winding (series after short circuit) embedded in the stator slot (about two-thirds of the total number of slots), a support group. The main winding is at a certain Angle from the cover winding in space.
When the main winding of the covered pole motor is energized, the covered pole winding will also generate induction current, so that the flux of the covered part of the stator magnetic pole winding and the uncovered part of the covered part of the direction of rotation.
V. Single phase series motor
The stator of single-phase series motor is composed of salient pole core and excitation winding, and the rotor is composed of hidden pole core, armature winding, commutator and rotating shaft, etc. A series circuit is formed between the field winding and the armature winding through a brush and commutator.
Single-phase series motor belongs to ac and DC dual motors, it can use BOTH AC power supply and DC power supply.