At present, ac motor has been used

At present, ac motor has been used in various fields of social production, especially squirrel-cage asynchronous motor, which has the advantages of simple structure, convenient manufacture, low price, durability, small moment of inertia, reliable operation, unrestricted use environment and structural development, etc., and has become the main power equipment for industrial production. In this paper, the influence of the electromagnetic parameters of the three-phase squirrel-cage asynchronous motor connected to the power grid and the transient process of power supply recovery after power failure are analyzed and studied.With the development of power electronics technology, in order to make ac motors more efficient in energy conversion, and to control and adjust the motor speed according to the process requirements of production machinery, factories generally use advanced ac speed control system to control the motor and provide electrical energy. However, in real production and life, when the power supply system of the grid is temporarily decomposed, or the instantaneous voltage of the grid drops by more than 50%, the power supply voltage of the motor will be reduced to the normal operating value in an instant, which will cause the line protection device, that is, instantaneous travel, so the car loses power and stops running. In this process, when the motor runs in a stable state, it is still in the current state of high speed operating power loss, the rotor will not immediately stop running, because its flux linkage cannot suddenly change, the original current continues to exist, and the stator windings between the voltage induction terminal, resulting in a reverse electromotive force. The induction voltage decreases slowly with the decrease of the rotor speed of the motor and can be maintained for a certain time. This voltage is the residual voltage.The remaining voltage feeds back the electrical energy to the speed regulation system that supplies the motor and charges the filter capacitor at the output end of the system. The amount of charge depends on the size of the capacitor. When the residual voltage is greater than the rated voltage of the filter capacitor, the capacitor will break down and affect the stability of the whole speed regulation system.In addition, in the whole process, the stator current, rotor current, rotor speed and electromagnetic torque of the motor will also produce unpredictable oscillations, which also become a hidden danger for the safe and reliable operation of the motor. Therefore, it is of great significance to study and analyze the influence of instantaneous power outage on three-phase asynchronous motors for the safe and stable operation of the motors in practical industrial production.Motor is the most widely used, widely used in all walks of life, driving a variety of production machinery, is the main load of the power system, therefore, this chapter mainly introduces the working principle of asynchronous motor.Induction motors, also known as induction motors, are mainly divided into two types: winding type and squirrel-cage type. No matter what kind of asynchronous motor it is, it is made up of two parts: the fixed part is called the stator, the rotating part is called the rotor, and the small space between the stator and the rotor is called the air gap.(1) asynchronous motor statorThe stator of asynchronous motor includes stator core, stator winding and stator frame.The stator core, as a part of the magnetic circuit of the motor, is used to place the stator windings. The stator winding is the circuit part of the asynchronous motor. Its main function is to use the rotor winding to generate the electromotive force and realize the electromechanical energy conversion of the motor through the current. The main function of the frame is to fix and support the stator core, which is responsible for the internal loss of the motor as it runs through the core, and the heat from the base to the surrounding air.(2) asynchronous motor rotorThe rotor of asynchronous motor includes rotor core, rotor winding, rotor shaft and so on.The rotor core and the stator core function in the same way. They are also used as part of the magnetic circuit of the motor to place the rotor windings. The rotor windings, like the stator windings, form part of the circuit of the asynchronous motor, generating electromotive force with the stator windings and generating electromagnetic torque through the current. There are two types of construction: winding and squirrel-cage. The squirrel cage rotor windings do not need external power supply, so they can be closed by themselves to form a short-circuit winding. Winding and rotor winding of the stator winding and rotor core embedded in the slot insulated wire, connect to the three-phase symmetric winding star connection method, and then respectively three output terminals connected to the slip ring rotor shaft, then th