Thoroughly dissect and decompose the detailed structure of three-phase asynchronous motors

A three-phase asynchronous motor consists of two basic parts: a fixed stator and a rotating rotor. The rotor is installed in the stator cavity and supported on two end covers by bearings. In order to ensure that the rotor can rotate freely within the stator, there must be a gap between the stator and the rotor, called an air gap. The air gap of an electric motor is a very important parameter, and its size and symmetry have a significant impact on the performance of the motor.

Motor accessories refer to the original parts of the motor that are assembled by the motor manufacturer. Parts that are damaged or replaced due to improper use or wear are called motor accessories. The classification of motor accessories can be roughly based on the components of the motor, which can be divided into motor stator, motor rotor, stator winding, motor casing, end cover, motor blades, bearings, and other components.

Motor stator

The stator of a motor is an important component of motors such as generators and starters. The stator is an important part of an electric motor. The stator is composed of three parts: stator core, stator winding, and frame. The main function of the stator is to generate a rotating magnetic field, while the main function of the rotor is to be cut by magnetic lines of force in the rotating magnetic field to generate (output) current.

Motor rotor

The motor rotor is also a rotating component in the motor. The motor is composed of a rotor and a stator, which is a device used to convert electrical energy to mechanical energy and mechanical energy to electrical energy. The motor rotor is divided into the motor rotor and the generator rotor.

stator winding

The stator winding can be divided into centralized and distributed types based on the shape of the coil winding and the embedded wiring method. The winding and embedding of centralized windings are relatively simple, but their efficiency is low and their operational performance is also poor. At present, the vast majority of AC motor stators use distributed windings. According to different models, models, and coil embedding process conditions, motors are designed with different winding types and specifications, so the technical parameters of their windings are also different

Motor casing

Motor casing generally refers to the external casing of all electrical motor equipment. The motor casing is a protective device for the motor, made of silicon steel sheets and other materials using stamping and deep drawing processes. Combined with surface rust prevention and spray molding processes, it can effectively protect the internal equipment of the motor. Main functions: dustproof, noise proof, and waterproof.

End cover

The end cover is a rear cover installed behind the casing of a motor, commonly known as the "end cover", mainly composed of a cover body, bearings, and brush blades. Whether the end cover is good or bad directly affects the quality of the motor. A good end cover mainly comes from its heart - the brush blade, which is used to drive the rotation of the rotor, which is a crucial part.

Motor blades

The fan blades of the motor are generally located at the rear of the motor, used for ventilation and cooling of the motor, mainly acting on the rear of the AC motor, or placed in specialized ventilation ducts for DC and high-voltage motors. The blades of explosion-proof motors are generally made of plastic material.

According to material classification: Motor blades can be divided into three types, including plastic blades, cast aluminum blades, and cast iron blades.

Bearing

Bearings are an important component in contemporary mechanical equipment. Its main function is to support the mechanical rotating body, reduce the friction coefficient during its movement, and ensure its rotational accuracy.

Rolling bearings are generally composed of four parts: outer ring, inner ring, rolling element, and retainer. Strictly speaking, they are composed of six parts: outer ring, inner ring, rolling element, retainer, seal, and lubricating oil. Rolling bearings can be defined as rolling bearings mainly having outer rings, inner rings, and rolling elements. According to the shape of rolling elements, rolling bearings are divided into two categories: ball bearings and roller bearings.

The stator is composed of stator core, stator winding, frame, and end cover. The main function of the base is to support various components of the motor, so it should have sufficient mechanical strength and stiffness, usually made of cast iron.

In order to reduce eddy current and hysteresis losses, the stator core is stacked with 0.5 mm thick silicon steel sheets coated with insulation paint. There are many evenly distributed grooves on the circumference of the core, and the stator winding is embedded in the grooves.

The stator winding is distributed in the slot of the stator core, and the stator winding of small motors is usually wound with enameled wire. The three-phase winding is separated by 120 ° from each other in the circumferential space of the stator, with a total of six outgoing terminals, which are respectively led to the terminal posts of the motor junction box.

The three-phase stator winding can be connected in a star or triangle shape. The connection method is determined according to the rated voltage of the motor and three-phase power supply voltage. Generally, the head end of the three windings is represented by U1, V1, W1, and the end is represented by U2, V2, W2.

The rotor is the rotating part of an electric motor, including components such as the rotor core, rotor winding, and shaft.

1. Rotor core

Function: Part of the magnetic circuit of the motor and placement of the rotor winding. Generally, it is made by punching and laminating 0.5mm thick silicon steel sheets, with evenly distributed holes punched on the outer circle of the silicon steel sheets to accommodate the rotor winding.

2. Rotor winding

The function is to cut the rotating magnetic field of the stator to generate induced electromotive force and current, and form electromagnetic torque to cause the motor to rotate. Divided into squirrel cage rotor and wound rotor according to their different structures

Squirrel cage rotor: If the rotor core is removed, the overall appearance of the winding resembles a squirrel cage, hence it is called a cage winding. Small cage motors use cast aluminum rotor windings, and for motors above 100KW, they are welded with copper bars and copper end rings.

Wound rotor: The wound rotor winding is similar to the stator winding and is also a symmetrical three-phase winding, which is generally connected to a star shape. The three outgoing terminals are connected to the three Slip ring (slip rings) of the shaft, and then connected to the external circuit through the brush.

3. Spindle

It is generally made of medium carbon steel or alloy steel to transmit torque and support the weight of the rotor.

（3） Other attachments

End caps, bearings, bearing end caps, fans.