1. According to the rotor structure of three-phase asynchronous motor
Can be divided into squirrel cage motor and wound motor.
2, according to the protection type of three-phase asynchronous motor
Can be divided into open (IP11) three-phase asynchronous motor, protective three-phase asynchronous motor (IP22 and IP23), closed three-phase asynchronous motor (IP44), explosion-proof three-phase asynchronous motor.
Open type (IP11): It is cheap and has the best heat dissipation conditions. Because the rotor and winding are exposed to the air, it can only be used in environments with dry, low dust and no corrosive and explosive gases.
Protective type (IP22 and IP23): The ventilation and heat dissipation conditions are also good, which can prevent foreign matter such as water droplets and iron filings from falling into the motor. It is only suitable for environments with less dry and less dust and no corrosive and explosive gases.
Closed (IP44): Suitable for damp, dusty, weather-resistant, corrosive gas and other harsh working environments, the most common application.
3. According to the ventilation cooling mode of three-phase asynchronous motor
It can be divided into self-cooling three-phase asynchronous motor, self-fan cooling three-phase asynchronous motor, his fan-cooled three-phase asynchronous motor, and pipeline-ventilated three-phase asynchronous motor.
4. According to the installation structure of three-phase asynchronous motor
It can be divided into horizontal three-phase asynchronous motor, vertical three-phase asynchronous motor, three-phase asynchronous motor with foot, and three-phase asynchronous motor with flange.
5, according to the work quota
Can be divided into continuous three-phase asynchronous motor, intermittent three-phase asynchronous motor, intermittent three-phase asynchronous motor.
6, according to the insulation level of three-phase asynchronous motor
Can be divided into E-class, B-class, F-class, H-class three-phase asynchronous motor.
Second, the structure of three-phase asynchronous motor
(1) Stator (still part)
1, the stator core
Function: A part of the magnetic circuit of the motor and the stator windings placed on it.
Structure: The stator core is generally formed by laminating and laminating a silicon steel sheet having an insulating layer on the surface of 0.35 to 0.5 mm thick, and a uniformly distributed groove is punched in the inner circle of the core for embedding the stator winding.
There are several types of stator core slots:
Semi-closed groove: The efficiency and power factor of the motor are higher, but the winding and insulation are more difficult. Generally used in small low voltage motors.
Semi-opening groove: It can be embedded with molded windings, and is generally used for large and medium-sized low-voltage motors. The so-called forming winding, that is, the winding, can be placed in the groove before being insulated.
Open type slot: used to embed the formed winding, the insulation method is convenient, mainly used in high voltage motors.
2, stator winding
Function: It is the circuit part of the motor, which is connected to three-phase alternating current to generate a rotating magnetic field.
Structure: It is made up of three identical windings in which the space is separated by 120° electrical angle and the team is arranged. The coils of these windings are respectively embedded in the slots of the stator according to certain rules.
The main insulation items of the stator windings are as follows: (to ensure reliable insulation between the conductive parts of the windings and the core and reliable insulation between the windings themselves).
(1) Insulation to ground: insulation between the stator winding and the stator core.
(2) Turn-to-turn insulation: insulation between turns of each phase stator winding.
(3) Interphase insulation: insulation between stator windings of each phase.
Wiring in the motor junction box:
There is a terminal block in the motor junction box. The six wire ends of the three-phase winding are arranged in two rows, and the three terminal blocks in the upper row are numbered 1 to 1 (U1), 2 (V1), and 3 from left to right. (W1), the three wiring posts in the lower row are numbered 6 (W2), 4 (U2), and 5 (V2) from left to right, and the three-phase windings are connected in a star connection or a delta connection. All manufacturing and maintenance should be arranged according to this serial number.
3, the base
Function: Fix the stator core and the front and rear end caps to support the rotor, and play the role of protection and heat dissipation.
Construction: The base is usually cast iron, the large asynchronous motor base is usually welded with steel plate, and the base of the micro motor is made of cast aluminum. There is a heat dissipation rib on the outer surface of the closed motor to increase the heat dissipation area. The end caps of the protective motor have ventilation holes at both ends, so that the air inside and outside the motor can be directly convected to facilitate heat dissipation.
(2) Rotor (rotating part)
1. Rotor core of three-phase asynchronous motor:
Function: As part of the magnetic circuit of the motor and placing the rotor windings in the core slot.
Construction: The material used is the same as that of the stator. It is made of 0.5 mm thick silicon steel sheet and laminated. The outer surface of the silicon steel sheet is punched with evenly distributed holes for the rotor winding. The inner core of the silicon steel sheet that is behind the stator core is usually used to punch the rotor core. Generally, the rotor core of a small asynchronous motor is directly press-fitted on a rotating shaft, and the rotor core of a large and medium-sized asynchronous motor (with a rotor diameter of 300 to 400 mm or more) is pressed against the rotating shaft by means of a rotor bracket.
2. Rotor winding of three-phase asynchronous motor
Function: Cutting the rotating magnetic field of the stator to generate induced electromotive force and current, and forming electromagnetic torque to rotate the motor.
Construction: divided into squirrel cage rotor and wound rotor.
(1) Squirrel-cage rotor: The rotor winding consists of a plurality of bars inserted into the rotor slots and two end rings of the ring. If the rotor core is removed, the entire winding looks like a squirrel cage, so it is called a cage winding. The small cage motor adopts a cast aluminum rotor winding, and is welded by a copper strip and a copper end ring for a motor of 100 KW or more.
(2) Wire-wound rotor: The wound rotor winding is similar to the stator winding, and is also a symmetrical three-phase winding, which is generally connected into a star shape, and three outgoing heads are connected to three collecting rings of the rotating shaft, and then passed through a brush. Connected to an external circuit.
Features: The structure is more complicated, so the application of the wound motor is not as extensive as the squirrel cage motor. However, through the collector ring and the brush, additional components such as resistors are inserted in the rotor winding circuit to improve the starting and braking performance and speed regulation performance of the asynchronous motor. Therefore, equipment that requires smooth speed regulation within a certain range, such as Cranes, elevators, air compressors, etc. are used above.
(3) Other accessories for three-phase asynchronous AC motors
1. End cap: support function.
2. Bearing: Connect the rotating part and the moving part.
3. Bearing end cover: protect the bearing.
4. Fan: Cool the motor.
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