Publish Time: 2023-09-25 Origin: Site
This article will lead you to know and understand the structure and principle of asynchronous electric motors and a detailed explanation of some basic structures.
Here is the list
Basic structure of asynchronous electric motor
Detailed explanation of the structure of the electric motor
Squirrel cage rotor winding
The asynchronous electric motor is mainly composed of two parts, the stator and the rotor, and there is an air gap between the stator and the rotor. In addition, there are end caps, bearings, bases and other components. The stator is the fixed part of the asynchronous electric motor and consists of a frame, a stator core and a stator winding. The frame, the frame is the outer casing of the electric motor, which plays the role of supporting the electric motor. It is usually cast in cast iron, but can also be cast in aluminum alloys. Large electric motor bases are mostly welded with steel plates. The stator core is a part of the magnetic circuit, which is laminated into a hollow cylindrical shape with 0.5mm thick silicon steel sheets, and then loaded into the machine base. In order to reduce eddy current losses, insulation treatment is required between the laminations. Generally, the surface of the silicon steel sheet of the small-capacity electric motor is insulated with an oxide film, and the silicon steel sheet of the large-capacity electric motor is coated with insulating paint. The stator winding, which is the circuit part of the electric motor. The stator winding of the small electric motor adopts high-strength enameled round copper wire or aluminum wire. . The winding and slot walls are separated by insulating material.
The air gap of an asynchronous electric motor is much smaller than that of a DC electric motor of the same capacity, generally 0.2 to 2.0 mm. This is because the excitation current of the asynchronous electric motor is provided by the grid. When the air gap is large, the excitation current is large, which will reduce the power factor of the electric motor. In order to improve the power factor, the air gap should be made as small as possible. However, if the air gap is too small, the assembly will be difficult, the operation will be unreliable, and the higher harmonic magnetic field will increase, thereby increasing the additional losses. The rotor consists of a rotating shaft, a rotor core and a rotor winding. The main shaft and the rotating shaft are generally made of medium carbon steel, which supports and fixes the rotor core and transmits power. The rotor iron core is also a part of the magnetic circuit of the electric motor. A 0.5mm thick silicon steel sheet is laminated on the rotating shaft to form a cylindrical sleeve, and the rotor winding is embedded in the iron core in the outer groove of the rotor. Rotor winding, asynchronous electric motor has two types: squirrel cage type and wound type. The difference lies in the structure of the rotor windings. The structure of the wound electric motor is relatively complex, and it is generally used in occasions with high requirements on starting and speed regulation performance.
The squirrel cage rotor winding has no iron core, and the entire winding looks like a squirrel cage. The rotor core also has slots, and each slot has a copper or aluminum bar as the rotor conductor. Both ends of the bar are short-circuited with short-circuit rings to form a closed loop. The guide rods for medium and large electric motors are made of copper. When making, insert the bare copper bar into the rotor core slot, then cover the heads of the copper bars at both ends with copper rings and weld them together; the guide rails of most small electric motors are made of aluminum. Yes, the stacked rotor cores are put into a cast aluminum mold at the time of manufacture, the squirrel cage and inner fan are poured at the end in one go.
Wound rotor windings are similar to the three-phase symmetrical windings of the stator, embedded in the rotor slots. The tail end of the three-phase winding is inscribed in a star shape, and the head end is led from the center of the rotor shaft to the slip ring. The slip ring is connected in series with the external resistor through the brush, which can improve the starting and speed regulation performance of the electric motor. Some wound electric motors are also equipped with brush lifts. After the external series resistor is started, lift the brush and directly short-circuit the three-phase slip ring to reduce the loss during operation.
Hangzhou New Hengli Electric Machine MFG. Co., Ltd. (Originally Hangzhou Hengli Electric Machine MFG. Co., Ltd.) was founded in 1954. Over 68 years of manufacturing experience in kinds of DC & AC Motors built up the customer-centered product development methodology and do under the special requirements of customers.