In the metallurgical industry, the high energy loading electric heaters (such as fthe erroalloy electric furnace, the calcium carbide furnace, etc.) have the characteristics of low voltage and high current, and their power factors are generally small; however, the power factor is one of the important indexes of the overall electrical performance of an electric furnace, and it is the main factor that affects the daily output and power consumption. If the electric furnace is equipped with the active power capacitor compensation cabinet is performed for , its power factor can be increased the and the purpose of energy saving and increasing efficiency can be realized.
I.scope of application of the system
The reactive power capacitor compensation cabinet system of the electric furnace is suitable for the electric furnace furnaces in the ferroalloy industry and the calcium carbide furnaces in chemical industry. It can be used as an auxiliary equipment of the electric furnace and plays the role of increasing the power factor and releasing the production capacity.
II. Composition and appearance of the active power capacitor compensation cabinet system
The active power low voltage capacitor compensation cabinet system includes:
The active power capacitor compensation cabinet: The built-in low voltage compensation capacitors and the special switching switches.
The large current short network: The reactive power compensation large current short network system which is connected to the capacitors.
The automatic control cabinet: The automatic measurement device, the automatic switching device, the automatic control device in the active power capacitor compensation cabinet system.
The active power capacitor compensation cabinet and the automatic controller in operation
II.An introduction to the function and effect in the case where the active power capacitor compensation cabinet is provided
1. The power factor is Increased, the active power increased, the output is increased and the furnace condition is improved.
2. Most of the furnaces are overloaded for a long time. After the active power capacitor compensation cabinet is provided, the furnace can increase the output by 8 - 10% when the furnace is not in the overloaded state. The operational variations and noise of the furnace transformer and the short network are reduced, and the service life of the main equipment is improved.
3. The losses in the high voltage line are reduced, the primary voltage and the electrode voltage are increased. The electric furnace can still run normally even in the low system voltage condition.
4. The harmonic effect is reduced, the electrical parameters of the system are improved, and the power quality is improved.
5. The penalties charged by the electricity supply authorities, which have been caused by low power factor have been avoided.
6. The microcomputer controlled active power capacitor compensation cabinet device can automatically print the daily report, automatically count the blackout time, automatically calculate and print the active energy and the reactive energy, improving the management and operation level of the electric furnace.
The practice has proved that the electric furnace with the low voltage active power capacitor compensation cabinet has the effects such as providing a strong power, ease in control and operation as well as in inserting of the convenient electrode, which can not only increase the power factor and release production capacity, but also play the role of optimizing and improving the furnace condition to a great extent.
IV. Technical characteristics
1. The switch of the switching capacitor adopts the large-scale intelligent compound switch, which is more reliable than the contactor and the vacuum circuit breaker as well as more energy efficient than the silicon controlled rectifier, to realize impact-free over zero voltage switching.
2. The large current and short network connected to the capacitance cabinet is made of high quality T2 series copper pipe, and the seamless interface is realized by using the high reliability argon arc welding technology. The distribution of the hangers and the clamps should meet the requirements of thermal stability and dynamic stability in case of occurrence of a short circuit; the connection with the original short network should be made by special module; and the waterway system should be connected by a special nozzle to ensure the reliability of each connecting component.
3. The compensation capacitor is the high quality self-healing shunt capacitor.
4. The technical performance of the automatic control device:
1) The automatic control device can realize the automatic switching according to the operating condition as well as the power factor of the electric furnace. The principle of switching includes the cyclic switching, the coded switching and the fuzzy control switching.
2) The automatic switching function of the compensation capacitor: After the system has been put into operation, the automatic device can automatically switch on/off all the active power capacitor compensation cabinets according to the scheduled procedures, without any manual intervention.
3) The core processor of the automatic device adopts the latest embedded processor of MOTOROLA, which has high reliability. The utility model has a liquid crystal display screen with indications in Chinese character and a list of setting values is available for the power supply personnel to adjust and change the operational state according to the furnace conditions.
4) It has such functions as the over-current, overvoltage and undervoltage protections, which can be activated quickly and remove the fault in the event that any active power capacitor compensation cabinet has failed.
5) When the transformer has been de-energized, all of the active power capacitor compensation cabinets will automatically withdraw; when the high voltage supply has been restored, the active power capacitor compensation cabinets are put into operation step by step according to the procedures.
6) It has such functions as automatically printing of the daily report. With this function, it is possible to automatically record and print the primary voltage, current, active power, reactive power, power factor, electrode voltage, capacitance current and so on.
7) In case of any resonance occurring in the low voltage, all of the active power capacitor compensation cabinets are automatically switched off and the resonance is eliminated through changing the parameters.
8) The blackout time can be counted and printed automatically;
9) The active energy and the reactive energy are automatically calculated and the are printed.
10) The following data can be online and in real time monitored during the normal operation: the electrode voltage, the capacitor current, the three-phase power factor, the high voltage, the high voltage current, the active power and the reactive power.
11) It has the fault report information recording function, which will not lose in case that the clock has been de-energized.
12) It has the real-time clock function, which will not lose in case that the clock has been de-energized.
13) It has the function of RS485 and CANBUS field bus interface, and the remote data transmission with the power plant according to IEC870-5-101 protocol or CDT protocol can be realized.