1, stator core

Function: a part of the magnetic circuit of the motor and stator winding is placed on it.

Structure: The stator core is generally made of silicon steel sheet with a thickness of 0.35~0.5 mm, with insulating layer on the surface, and evenly distributed slots are punched in the inner circle of the core for embedding the stator winding.

Stator core groove types are as follows:

Semi-closed slot: the efficiency and power factor of the motor are high, but the winding is difficult to embed and insulate. Generally used for small low-voltage motors.

Semi-open slot: special-shaped winding can be embedded, which is generally used for large and medium-sized low-voltage motors. The so-called shaped winding means that the winding can be insulated in advance and then put into the slot.

Open slot: it is used to embed the forming winding, and the insulation mode is convenient. Mainly used for high-voltage motors.

2. Stator winding

Function: it is the circuit part of the motor, which is connected with three-phase alternating current to generate rotating magnetic field.

Structure: It consists of three windings with the same structure, with an interval of 120 electrical angle, arranged in a straight line. Each coil of these windings is embedded in each slot of the stator according to certain rules.

The main insulation items of the stator winding are as follows: (Ensure reliable insulation between the conductive part of the winding and the iron core and between the winding itself).

(1) Insulation to ground: insulation between the whole stator winding and stator core.

(2) Interphase insulation: insulation between stator windings of each phase.

(3) Turn-to-turn insulation: Turn-to-turn insulation of each phase stator winding.

Wiring in the motor junction box:

There is a terminal board in the motor junction box. Six terminals of three-phase winding are arranged in two rows. The number of three terminals in the upper row from left to right is 1(U 1), 2(V 1) and 3(W 1), and the number of three terminals in the lower row from left to right is 6(W2). All manufacturing and maintenance should be arranged according to this serial number.

3. Basic framework

Function: Fix the stator core and front and rear end covers, support the rotor, and play the role of protection and heat dissipation.

Structure: the frame is generally cast iron, the frame of large asynchronous motor is generally welded with steel plate, and the frame of micro motor is cast aluminum. There are cooling ribs outside the frame of the enclosed motor to increase the cooling area, and the end covers at both ends of the frame to protect the motor have ventilation holes, so that the air inside and outside the motor can directly convection, which is beneficial to heat dissipation.

(2) Rotor (rotating part)

1 rotor core, three-phase asynchronous motor;

Function: As a part of the motor magnetic circuit, the rotor winding is placed in the iron core slot.

Structure: The material used is the same as the stator, and it is made of 0.5 mm thick silicon steel sheets, and the excircle of the silicon steel sheets is stamped with evenly distributed holes for installing rotor windings. Usually, the back inner circle of silicon steel sheet is used to punch the stator core to punch the rotor core. Generally, the rotor core of small asynchronous motor is directly press-fitted on the rotating shaft, and the rotor core of large and medium asynchronous motor (rotor diameter is above 300~400 mm) is press-fitted on the rotating shaft with the help of rotor bracket.

2. Rotor winding of three-phase asynchronous motor

Function: the rotating magnetic field of the cutting stator produces induced electromotive force and current, forming electromagnetic torque to make the motor rotate.

Structure: divided into squirrel cage rotor and wound rotor.

(1) squirrel-cage rotor: The rotor winding consists of a plurality of guide rods inserted into the rotor slot and two circular end rings. If the rotor core is removed, the whole winding looks like a squirrel cage, so it is called cage winding. Small-sized cage motor adopts cast aluminum rotor winding, and motors above 100KW are welded with copper bars and copper end rings.

(2) Wound rotor: The wound rotor winding is similar to the stator winding, and it is also a symmetrical three-phase winding, which is generally connected in a star shape. The three outlet heads are connected to the three slip rings of the rotating shaft, and then connected to the external circuit through brushes.

Features: The structure is complex, so the wound motor is not as widely used as the squirrel-cage motor. However, in order to improve the starting, braking and speed regulation performance of asynchronous motor, additional resistors and other elements are connected in series in the rotor winding circuit through slip rings and brushes, so it is used in equipment that requires smooth speed regulation within a certain range, such as cranes, elevators, air compressors and so on.

(3) Other accessories of three-phase asynchronous motor.

1, end cover: support function.

2. Bearing: connecting the rotating part and the fixed part.

3. Bearing end cover: protect the bearing.

4. Fan: cooling motor.