1. The rotor core of a 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 rotating magnetic field of the stator 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.
(3) Other accessories of phase asynchronous motor
1. End cover: supporting function.
2. Bearing: connect the rotating part and the immovable part.
3. Bearing end cover: protect the bearing.
4. Fan: to cool the motor.
2. The DC motor adopts an octagonal full lamination structure, which not only has a high space utilization rate, but also can withstand pulsating current and rapid load current changes when a static rectifier is used for power supply. DC motors generally do not have series windings, and are suitable for automatic control technologies that require forward and reverse rotation. According to user needs, it can also be made into a series winding. Motors with a center height of 100-280mm have no compensation windings, but motors with a center height of 250mm and 280mm can be made with compensation windings according to specific conditions and needs, and motors with a center height of 315-450mm have compensation windings. The overall installation dimensions and technical requirements of the motor with a center height of 500～710mm meet the IEC international standard, and the mechanical dimension tolerance of the motor meets the ISO international standard.
The working principle of DC motor:
The coil is connected to the commutator segments, the commutator segments are fixed on the shaft and rotate with the motor shaft. The commutator segments and between the commutator segments and the rotating shaft are insulated from each other. The whole formed by them is called the commutator. The brushes A and B are fixed in space.
Applying DC voltage to the two brush ends of the motor, the electric energy is introduced into the armature coil due to the action of the brush and the commutator, and it is ensured that the current in the coil side of the same pole is always in the same direction, thus ensuring the The direction of the electromagnetic force on the coil side under the pole does not change, which ensures that the motor can continuously rotate to realize the conversion of electrical energy into mechanical energy to drive the production machinery. This is the working principle of a DC motor. Note: The direction of current in each coil side is alternating.
2. Working principle of DC generator:
As shown in the figure, when the armature is driven by the prime mover to rotate counterclockwise, the coil edge will cut the magnetic field lines to induce an electric potential, and the direction of the electric potential can be determined according to the right-hand rule. Due to the continuous rotation of the armature, the coil sides ab and cd will alternately cut the magnetic lines of force under the N pole and S pole. The direction of the induced electromotive force in each coil side and the entire coil is alternating, and the induced electromotive force in the coil is alternating. Electromotive force, but due to the action of brushes and commutators, the current flowing through the load is a unidirectional direct current, and this direct current is generally pulsating.