Asynchronous motor is mainly composed of stator and rotor two parts, stator and rotor in the middle of the air gap. In addition, there are end caps, bearings, frames and other components.
1. Stator
The stator is the fixed part of the asynchronous motor, which is composed of the frame, the stator core and the stator winding.
(1) Engine base
The frame is the shell of the motor, which plays the role of supporting the motor, usually cast with cast iron, but also cast with aluminum alloy. Large motor frame is mostly made of steel plate welding.
(2) Stator core
The stator iron core is a part of the magnetic circuit, and is laminated into a whole hollow cylinder with 0.5mm thick silicon steel sheet and then loaded into the frame. The outer wall is matched with the frame, the inner wall is slotted, and the stator winding is embedded in the groove. In order to reduce eddy current loss, the laminates need to be insulated. Generally, the surface of the silicon steel sheet of the small-capacity motor is insulated by oxide film, and the silicon steel sheet of the large-capacity motor is coated with insulating paint.
(3) Stator winding
It is the circuit part of the motor, and the stator winding of the small motor is wound with high-strength enamelled round copper wire or aluminum wire. Large motor wire cross-section is large, the rectangular section of copper or aluminum wire made of coil embedded in the stator slot. The winding is separated from the groove wall by insulating material.
2. The air gap
The air gap of the induction motor is much smaller than that of the same capacity DC motor, generally 0.2~2.0mm. This is because the induction motor excitation current is supplied by the power grid, when the air gap is large, the excitation current is large, which will reduce the power factor of the motor. In order to improve the power factor, the air gap should be made smaller. However, if the air gap is too small, the assembly will be difficult, the operation will be unreliable, and the high-order harmonic magnetic field will be enhanced, thus increasing the additional loss.
3. Rotor
The rotor is composed of a rotating shaft, a rotor core and a rotor winding.
(1) Rotating shaft
The shaft is generally made of medium carbon steel, which plays the role of supporting and fixing the rotor core and transmitting power.
(2) Rotor core
The rotor core is also a part of the magnetic circuit of the motor, and the 0.5mm thick silicon steel sheet is laminated into a whole cylindrical shape set on the rotating shaft, and the rotor winding is embedded in the circular groove of the rotor core.
(3) Rotor winding
Asynchronous motors have squirrel cage and winding two types, the difference is that the rotor winding structure is different, winding motor structure is more complex, generally used for starting and speed regulation performance requirements of higher occasions.
