Second Rotor (rotating part)

1. Rotor core of three-phase asynchronous motor:

Function: As a part of the magnetic circuit of the motor and placing the rotor winding in the core slot.
Structure: The material used is the same as that of the stator, which is punched and laminated with 0.5 mm thick silicon steel sheets. The outer circumference of the silicon steel sheets is punched with evenly distributed holes to install the rotor windings. Usually, the inner circle of the silicon steel sheet after the stator core is punched is used to punch the rotor core. Generally, the rotor core of a small asynchronous motor is directly press-fitted on the shaft, and the rotor core of a large and medium-sized asynchronous motor (the rotor diameter is more than 300~400 mm) is pressed on the shaft with the aid of the rotor bracket.

2. Rotor winding of three-phase asynchronous motor
Function: Cutting the stator rotating magnetic field generates induced electromotive force and current, and forms electromagnetic torque to make the motor rotate.

Structure: Divided into squirrel cage rotor and wound rotor.

(1) Squirrel cage rotor: The rotor winding is composed of multiple guide bars inserted into the rotor slot and two circular end rings. If the rotor core is removed, the entire winding looks like a squirrel cage, so it is called a cage winding. Small cage motors use cast aluminum rotor windings. For motors above 100KW, copper bars and copper end rings are welded together.

(2) Wound rotor: similar to the stator winding, the wound rotor winding is also a symmetrical three-phase winding, generally connected in a star shape, and the three wire ends are connected to the three current collecting rings of the rotating shaft, and then through the brush Connect with external circuit.

Features: The structure is more complicated, so the application of the wound motor is not as wide as the squirrel cage motor. However, additional resistors and other components are inserted in the rotor winding circuit through the collector ring and brushes to improve the starting and braking performance and speed regulation performance of the asynchronous motor. Therefore, smooth speed regulation equipment within a certain range is required, such as Used on cranes, elevators, air compressors, etc.