What Is The Squirrel Cage Structure Of The Motor?

Squirrel-cage rotor structure of three-phase asynchronous motor

Structural composition

Squirrel cage rotor is an important part of asynchronous motor. It is mainly composed of a rotor core and a rotor winding. The rotor core is usually made of laminated silicon steel sheets, which are cylindrical in shape and have evenly distributed grooves on the outer circumference of the core.

The rotor winding is a self-closing short-circuit winding, shaped like a "squirrel cage". It is formed by embedding copper or aluminum strips in the slots of the rotor core, and then connecting these strips with short-circuit rings at both ends. If it is a small motor, it can also be directly cast aluminum, the aluminum liquid is injected into the groove of the rotor core, and the guide bar and short circuit ring are formed.

Working principle

When the stator winding is connected to three-phase AC, a rotating magnetic field is generated inside the motor. This rotating field cuts the guide bar of the squirrel-cage rotor, which, according to the laws of electromagnetic induction, generates an induced electromotive force. Because the rotor winding is closed, an induced current is generated in the guide bar under the action of induced electromotive force.

This induced current, in turn, is acted upon by a rotating magnetic field, producing an electromagnetic force. The electromagnetic force acting on the rotor will cause the rotor to rotate in the direction of the rotating magnetic field. Because the speed of the rotor is always slightly lower than the speed of the rotating magnetic field (which is the origin of the name of the asynchronous motor), it can continue to produce relative motion, so as to maintain the induced electromotive force and induced current, to ensure the continuous operation of the motor.

Characteristics and application

Advantages: simple structure, strong, convenient manufacturing, low cost. It has high reliability and can withstand large load torque and high speed. For example, in some industrial occasions, such as fans, pumps and other equipment, the reliability of the motor is high, and the load characteristics of these devices are relatively stable, and the squirrel cage asynchronous motor can meet the requirements well.

Disadvantages: Its speed regulation performance is relatively poor. In situations where precise speed regulation is required, such as some high-precision machine tools, etc., a simple squirrel cage asynchronous motor may not be suitable. However, through some frequency conversion speed regulation technology, its speed regulation performance can be improved to a certain extent.