What Is a Squirrel-Cage Rotor?

The squirrel-cage motor is a kind of three-phase asynchronous motor. The squirrel-cage rotor is the rotating part of the squirrel-cage motor. Generally, a rotor coil made of copper or aluminum is cast in a cage-shaped slot of the rotor core. The coil is a closed closed circuit that is not connected to other parts, and its main function is to suppress the stator current. Simple structure and wide application.

The rotating part of the squirrel-cage motor, namely the squirrel-cage rotor, includes

Because the squirrel-cage rotor structure cannot form an open circuit state, resistance cannot be connected in the rotor circuit, and measures can only be taken from the stator circuit to improve the starting performance of the motor.

(1) Stator circuit resistance or reactor start

The resistance or reactor is connected in series in the motor stator circuit to share part of the voltage and reduce the voltage across the stator winding of the motor, thereby reducing the starting current of the motor.

(2) Star-corner start

It is suitable for the stator winding triangle-connected motor. When starting, the stator winding is star-connected and changed to angular connection after starting. This method reduces the voltage across the stator winding of the motor to the

, Thereby reducing the starting current of the motor.

(3) Step-down start of autotransformer

The autotransformer is actually a step-down transformer. The primary winding of the autotransformer is connected to the power supply, and the secondary winding is connected to the two ends of the motor stator winding.

(4) Motor output torque in squirrel-cage motor starting mode

The above-mentioned traditional squirrel-cage rotor three-phase asynchronous motor starting methods all belong to the category of reduced voltage starting, that is, the purpose of reducing the starting current is achieved by reducing the voltage across the stator windings of the motor. Because the electromagnetic torque of the three-phase asynchronous motor is proportional to the square of the voltage across the stator windings of the motor, the above method reduces the starting current of the motor while losing most of the output torque. Therefore, this method has limitations and is only suitable for no-load start or light-load start. ^[3]