Abstract
Content
- Introduction
- 1. Self-assembly of asynchronous and synchronous electric motors
- 2. Self-starting of electric motors of own needs
- Conclusions
- References
Content
Self-launch is called restoration of the normal operation of an electric treadmill after a short period of power supply or a deep voltage drop without personnel interference.
1. Self-assembly of asynchronous and synchronous electric motors
The self-launch of asynchronous and synchronous electric motors began to be used at thermal power plants and is currently used for all the main mechanisms of own needs of different types of power plants. In recent years, it has become widespread in many industries, especially with complex continuous technological processes.
Self-starter can be considered to be secured if under reduced voltage the excess engine moment is sufficient to bring the mechanism to a nominal angular velocity and if during the time of acceleration the heating temperature of the windings does not exceed the permissible value. From this point of view, the period of power breaks should be as small as possible.
Self-launch with temporary unloading of the mechanism is used only in the extreme case, and only in the scheme with the introduction of bit resistance. Those engines that should not be included with self-launch, have a magnetic starter in the circuit. The latter is disabled when the voltage is extinguished, since its coil is de-energized and again not activated before the automatic or manual (key) command.
At pump and compressor stations, automatic reactivation of the engine is applied after it is disconnected by devices of protection of a minimum voltage. In practice, this means that the group self-launch is replaced by the automatic start-up of each engine or small groups of them in a given order, according to the command of the APV device.
2. Self-starting of electric motors of own needs
Significant increase in the reliability of the station can be achieved if, in the case of short-term reductions or even the complete disappearance of voltage on their own needs due to short circuits, do not disconnect the electric motors of the responsible mechanisms from the network. Then, after restoration of normal voltage, their self-launch begins, which can be considered as a group start from the intermediate frequency of rotation, which had time to slow down the engines in emergency mode.
Due to large starting currents in transformers there is a significant voltage drop, the group self-oscillation occurs at reduced voltages on the clamps of electric motors and can be successful or unsuccessful..
An effective means to increase the reliability of the equipment of their own needs in the mode of self-launching of electric motors is to reduce the power interruption, which is ensured by rational settings of relay protection and system automatics.
Conclusions
Self-launching of electric motors allows the most complete use of means of automation of power supply systems. If the damage caused by a power cessation or a deep decrease in voltage is quickly eliminated by the action of relay protection and automation devices, then with the provided self-start, this is not an accident or marriage in the power supply system. The damage practically does not arise.
If the self-starter is not provided, the engines stop, and although the automation devices have worked, the damage can be significant, especially in the event of a complex technological cycle (for example, in the chemical industry).
References
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- Основные отличия самозапуска https://studopedia.info....
- Князевский Б.А., Липкин Б.Ю. Электроснабжение промышленных предприятий. М.: Высшая школа, 1979.–431 с.
- Ермилов А.А. Основы электроснабжения промышленных предприятий. М.: Энергоатомиздат, 1983.