Medium frequency furnace capacitor knowledge
Power capacitors are oil-filled devices that may catch fire or explode if installed, operated, or improperly operated. The residual charge of the capacitor may also pose a direct threat to personal safety. Therefore, the safe operation of capacitors is of great significance.
A, capacitor operating parameters
The current in the capacitor operation should not exceed 1.3 times the rated current of the capacitor for a long time. The voltage should not exceed 1,1 times the rated voltage of the capacitor for a long time. The ambient temperature of the capacitor should not exceed the limits provided in Table 13-3. The capacitor case temperature must not exceed the manufacturer's specifications (typically 60 ° C or 65 ° C).
The contacts of the capacitors should be kept in good condition, and there should be no signs of looseness or overheating; the casing should be clean and there should be no discharge marks; the casing should not be obviously deformed and there should be no oil leakage marks. Capacitor switching devices, protective devices and discharge devices should remain intact.
B, capacitor input or exit
When one of the following fault conditions occurs, the capacitor bank should exit the operation urgently:
1. The connection point is severely overheated or even melted;
2. The porcelain casing is severely flashed and discharged;
3. The capacitor casing is seriously expanded and deformed;
4. The capacitor or its discharge device emits a severe abnormal sound;
5. Capacitor blasting;
6, the capacitor caught fire and smoke.
C, medium frequency furnace capacitor operation
The intermediate frequency furnace should pay attention to the following four points for capacitor operation:
1. Under normal circumstances, when the whole station is powered off, the switch of the capacitor is first opened, and then the switch of each line is opened. Under normal circumstances, when the whole station resumes power transmission, the switch of each line is first closed, and then the capacitor is closed. Line switch.
2. After the power failure of the whole station, the switch of the capacitor should be opened.
3. After the capacitor breaker is tripped, it must not be powered strongly; after the fuse is blown, the fuse cannot be replaced before the cause is found.
4. Whether it is a high voltage capacitor or a low voltage capacitor, it is not allowed to close with its residual charge. Otherwise, a large current surge may occur. Discharge at least 3 minutes before the capacitor is reclosed.
5. For the purpose of inspection and repair, after the capacitor is disconnected from the power supply, the worker must use a special discharge load that can be manually discharged before the worker approaches, regardless of whether the capacitor is equipped with a discharge device.
D. Fault diagnosis and treatment of medium frequency furnace capacitors
1. Leakage oil Leakage oil is mainly caused by poor product quality or poor operation and maintenance. When the outer casing is slightly oily, the oil seepage shall be derusted, repaired and painted, and repaired; it shall be replaced when the oil leaks seriously.
2. The expansion of the casing is mainly caused by the internal decomposition of the capacitor / breakdown of the gas or internal components. The capacitor should be replaced if the casing is significantly expanded.
3. Excessive temperature is mainly caused by overcurrent (high voltage or harmonics of the power supply) or poor heat dissipation conditions, and may also be caused by increased dielectric loss. It should be closely monitored to find out the cause and deal with it in a targeted manner. If the temperature cannot be effectively controlled, the operation should be exited; if it is a problem with the capacitor itself, it should be replaced.
4. Casing flashover discharges are mainly caused by casing contamination or casing defects. If the casing is not damaged, the discharge is only caused by dirt. The power should be cleaned and the casing cleaned; if the casing is damaged, the capacitor should be replaced. Processing should be carried out with power outages.
5. Abnormal sounds Abnormal sounds are caused by internal faults. When the abnormal sound is serious, the operation should be immediately exited and the capacitor should be replaced after power failure.
6. Capacitor blasting is caused by a serious internal fault. The power should be turned off immediately and the capacitor replaced after the site is processed.
7. Fuse blown If the capacitor fuse is blown, whether it is a high voltage capacitor or a low voltage capacitor, the cause should be ascertained and put into operation after proper treatment. Otherwise, a large inrush current may be generated.
