Squirrel cage motors are suitable for light-load general-purpose machinery and equipment, and are used in many occasions, almost used in daily life, factory equipment, such as fans, pumps, compressors, mining machinery and other fields, which is what we usually call fans. Motor, water pump, motor, compressor, motor, mining motor, this kind of motor has the advantages of simple structure, no winding on the rotor, relatively small starting torque, low maintenance cost, and long service life.



At present, the main products corresponding to the series are:

Y high voltage motor YKK high voltage motor YKS high voltage water-cooled motor

　The rotor winding of a three-phase asynchronous motor is not wound by insulated wires, but a three-phase asynchronous motor made of aluminum or copper strips welded with a short-circuit ring is called a squirrel cage motor.

Structure

　The structure of the motor rotor:

The rotor is the rotating part of a three-phase asynchronous motor, which is composed of a rotor core, a rotor winding, a shaft, and a fan. The iron core of the rotor is also a part of the magnetic circuit of the motor. It is made of laminated silicon steel sheets punched with uniform grooves on the outer circumference and fixed on the rotating shaft. The rotor winding is placed in the slot of the rotor core. According to different rotor winding structures, three-phase asynchronous motors can be divided into two types: squirrel cage and winding.　The rotor winding of the squirrel-cage asynchronous motor is named after its shape resembles a squirrel cage. Its structure is embedded in a wire slot with a copper strip as a conductor, and the two ends of the copper strip are welded with short-circuit rings. Small and medium-sized squirrel-cage asynchronous motors use cheaper aluminum instead of copper, and cast the rotor conductor, short-circuit ring and fan into a whole to become a cast aluminum squirrel-cage rotor.



The core of the wound rotor is the same as that of the squirrel cage rotor. The rotor winding is similar to the stator winding. It is wound by insulated wires and is embedded in the rotor slot according to a certain rule to form a three-phase symmetrical winding. Usually the ends of the three windings are connected together, and the head ends are respectively connected with three mutually insulated copper slip rings fixed on the rotating shaft (externally connected with three-phase symmetrical alternating current), and connected into a star shape. The rotor winding is connected with an additional three-phase varistor through the slip ring and the brush on it, for motor starting and speed regulation in a small range. The working principle of squirrel cage and wound three-phase asynchronous motors is the same, and the difference lies in the structure of the rotor winding.

working principle 

　　The stator of the motor is a three-phase scattered embedded distributed winding, and the rotor is a cage bar (because the shape of the bar is similar to a squirrel cage, it is also called a squirrel cage asynchronous motor). After adding three-phase alternating current to the stator windings of the motor, a rotating magnetic field will be formed. The closed conductive bars on the rotor will induce electric potential and current due to the cutting of the magnetic field lines of the stator magnetic field, and the charged (current) conductor will generate in the magnetic field. Move, so that the motor rotor rotates.

Starting method 

　　 Squirrel-cage asynchronous motor starting methods include direct starting and reduced voltage starting. The reduced voltage starting includes self-coupling compensation starting, star-angle switching starting, and Yanbian delta starting.　　 General small and medium squirrel cage asynchronous motors can be started directly, and the direct starting of the equipment is simple and the method is simple and convenient. But the starting current is large and the starting torque is small. Large-capacity squirrel-cage asynchronous motors generally start by reducing the voltage at the stator winding end. When starting at reduced voltage, the starting current can be reduced, but the starting torque is inevitably reduced.　　The comparison of various reduced voltage starting methods is as follows:　　

Step-down start method

Auto-compensation start

Star angle conversion start

Yanbian triangle start

Starting voltage

Multiply the voltage drop factor by the rated voltage

0.577* rated voltage

Depends on the stator winding tap voltage 0.78*rated voltage

Starting current

Voltage drop coefficient multiplied by starting current (direct)

1/3 *Starting current (direct)

Depends on the stator winding tap voltage 0.6*starting current (direct)

Starting torque

The square of the voltage drop coefficient* multiplied by the starting torque (straight)

1/3 *Starting torque (straight)

Depends on the stator winding tap voltage 0.6*starting current (direct)

Characteristics of starting method

The stator winding of the motor is started by the step-down of the autotransformer, and the autotransformer is cut off after the start

The stator windings of the motor are connected in a star shape when starting, and switched into a delta after starting

When the motor stator winding is started, it is connected to the Yanbian triangle and then it is switched to the triangle.

Pros and cons

1 The starting current is small 　　 2 The starting control equipment cannot be started 　　 3 The equipment is more expensive, but the starting torque is larger than the torque of the star-angle conversion method, so it is used more

1 Low starting current 　　 2 Small starting torque 　　 3 Can be started frequently 　　 4 Low price, suitable for motors with delta-connected stator windings, generally used for light-load starting of small-capacity motors

1 The starting current is small 　　 2 The starting torque is large 　　 3 It can be started frequently 　　 4 Only applicable to the motor with a center-tapped stator winding

Secondly, soft starters and frequency converters have been widely used. For small-capacity equipment, they can be promoted and used to facilitate control. For large-capacity and high-voltage motors, they must be used with caution. Although the technology in this area is mature, it is because of the non-linear components in the line. There will be a lot of harmonic components that pollute the power supply. Although there are harmonic control equipment, there are still very irregular waveforms in the low-voltage line, which affects the normal use of office electronic equipment, and also has certain hazards to the breakdown of capacitors. 
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