(2) Rotor (rotating part)
1. Rotor core of three-phase asynchronous motor:
Function: As part of the magnetic circuit of the motor and placing the rotor windings in the core slot.
Construction: The material used is the same as that of the stator. It is made of 0.5 mm thick silicon steel sheet and laminated. The outer surface of the silicon steel sheet is punched with evenly distributed holes for the rotor winding. The inner core of the silicon steel sheet that is behind the stator core is usually used to punch the rotor core. Generally, the rotor core of a small asynchronous motor is directly press-fitted on a rotating shaft, and the rotor core of a large and medium-sized asynchronous motor (with a rotor diameter of 300 to 400 mm or more) is pressed against the rotating shaft by means of a rotor bracket.
2. Rotor winding of three-phase asynchronous motor
Function: Cutting the rotating magnetic field of the stator to generate induced electromotive force and current, and forming electromagnetic torque to rotate the motor.
Construction: divided into squirrel cage rotor and wound rotor.
(1) Squirrel-cage rotor: The rotor winding consists of a plurality of bars inserted into the rotor slots and two end rings of the ring. If the rotor core is removed, the entire winding looks like a squirrel cage, so it is called a cage winding. The small cage motor adopts a cast aluminum rotor winding, and is welded by a copper strip and a copper end ring for a motor of 100 KW or more.
(2) Wire-wound rotor: The wound rotor winding is similar to the stator winding, and is also a symmetrical three-phase winding, which is generally connected into a star shape, and three outgoing heads are connected to three collecting rings of the rotating shaft, and then passed through a brush. Connected to an external circuit.
Features: The structure is more complicated, so the application of the wound motor is not as extensive as the squirrel cage motor. However, through the collector ring and the brush, additional components such as resistors are inserted in the rotor winding circuit to improve the starting and braking performance and speed regulation performance of the asynchronous motor. Therefore, equipment that requires smooth speed regulation within a certain range, such as Cranes, elevators, air compressors, etc. are used above.
