What Is The Basic Structure Of The Motor?
Basic structure: composed of stator, rotor and other accessories.
(1) Stator (stationary part)
1. Stator core
Function: Part of the magnetic circuit of the motor, and the stator winding is placed on it.
Structure: The stator core is generally punched and laminated with silicon steel sheets with an insulating layer of 0.35 ~ 0.5 mm thick on the surface. There are evenly distributed slots in the inner circle of the core to embed the stator windings.
There are the following types of stator core slots:
Semi-closed slot: The efficiency and power factor of the motor are higher, but the winding embedding and insulation are more difficult. Generally used in small low-voltage motors.
Half-open slot: It can be embedded with shaped windings, and is generally used for large and medium-sized low-voltage motors. The so-called shaped winding means that the winding can be put into the slot after being insulated beforehand.
Open slot: It is used for insert molding winding, the insulation method is convenient, mainly used in high voltage motor.
2. Stator winding
Function: It is the circuit part of the motor, which is fed with three-phase alternating current to generate a rotating magnetic field.
Structure: It is made up of three identical windings which are symmetrically arranged at an electrical angle of 120 ° in space, and each coil of these windings is embedded in each slot of the stator according to a certain rule.
The main insulation items of the stator winding are as follows: (to ensure reliable insulation between the conductive parts of the winding and the core and reliable insulation between the winding itself).
(1) Insulation to ground: the insulation between the entire stator winding and the stator core.
⑵ Insulation between phases: insulation between stator windings of each phase.
(3) Insulation between turns: insulation between turns of each phase stator winding.
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 wiring piles in the upper row are numbered 1 (U1), 2 (V1), 3 (W1), the three terminals in the lower row are numbered from left to right as 6 (W2), 4 (U2), and 5 (V2). Connect the three-phase windings into star connection or triangle connection. All manufacturing and maintenance should be arranged according to this serial number.
Function: Fix the stator core and front and rear end covers to support the rotor, and play a role in protection and heat dissipation.
Structure: The base is usually cast iron, the base of the large asynchronous motor is generally welded with steel plate, and the base of the micro motor is made of cast aluminum. There are heat dissipation ribs on the outside of the frame of the enclosed motor to increase the heat dissipation area. The two ends of the frame of the protective motor are provided with ventilation holes, so that the air inside and outside the motor can be directly convected to facilitate heat dissipation.
(2) Rotor (rotating part)
1. The rotor core of the three-phase asynchronous motor:
Function: As a part of the magnetic circuit of the motor and to place the rotor winding in the core slot.
Structure: The material used is the same as that of the stator. It is made of 0.5 mm thick silicon steel sheet punched and laminated. The outer circumference of the silicon steel sheet is punched with uniformly distributed holes for the placement of rotor windings. The rotor core is usually punched with the inner circle of the silicon steel sheet punched by the stator core. The rotor core of the general small asynchronous motor is directly pressed on the rotating shaft, and the rotor core of the large and medium asynchronous motor (rotor diameter is more than 300 ~ 400 mm) is pressed on the rotating shaft by means of the rotor bracket.
2. Rotor winding of three-phase asynchronous motor
Function: Cutting the stator rotating magnetic field generates induced electromotive force and current, and forms electromagnetic torque to rotate the motor.
Structure: divided into squirrel-cage rotor and winding rotor.
(1) Squirrel-cage rotor: The rotor winding is composed of a plurality of guide bars inserted in the rotor slot and two end rings that are circular. If the rotor core is removed, the shape of the entire winding looks like a squirrel cage, so it is called a cage winding. The small cage motor uses cast aluminum rotor windings, and the motors above 100KW are welded with copper bars and copper end rings.
⑵Wound rotor: The wound rotor winding is similar to the stator winding, and is also a symmetrical three-phase winding, generally connected in a star shape, three outlets are connected to the three current collecting rings of the rotating shaft, and then through the brush Circuit connection.
Features: The structure is more complicated, so the application of the winding motor is not as wide as the squirrel cage motor. However, additional resistors and other components are connected in series in the rotor winding circuit through the current collecting ring and the brush to improve the starting and braking performance and speed regulation performance of the asynchronous motor. Therefore, the equipment for smooth speed regulation within a certain range, such as Used on cranes, elevators, air compressors, etc.
(3) Other accessories
1. End cover: support.
2. Bearing: connecting the rotating part and the stationary part.
3. Bearing end cover: protect the bearing.
4. Fan: cooling motor.