The influence of inappropriate temperature and voltage on film capacitors

Does inappropriate temperature and voltage affect film capacitors?

Often contact capacitors are clear when breaking the capacitor bank, if the circuit breaker breaks down heavily, a loop will appear in the circuit, and multiple operating overvoltages will appear on the capacitor terminals. Under the action of such a high operating overvoltage, strong partial discharge and dielectric damage will occur inside the film capacitor, and even lead to capacitor breakdown. Therefore, the quality of the circuit breaker used to switch the capacitor is closely related to the actual service life of the capacitor. In order to prevent excessive inrush current and overvoltage, when the capacitor is withdrawn from the network, the capacitor (group) should be discharged in time. Before the capacitor is put into grid operation again, the remaining voltage on the capacitor should not exceed 10% of its rated voltage.

The service life of the film capacitor is related to the ambient temperature:

The temperature category of each capacitor is marked on the label, for example: "-40/A", which means that the capacitor can be put into power grid operation at a low ambient temperature of -40°C. The high ambient temperature at which this capacitor can operate continuously is: the Ih average high temperature is 40℃, the 24h average high temperature is 30℃, and the annual average high temperature is 20℃. This is because at low temperatures, the viscosity of the impregnant inside the capacitor increases, the internal voltage decreases, and the capacitor's electrical withstand capability decreases.

Putting it into operation at a temperature lower than its allowable low temperature is likely to cause partial discharge inside the capacitor, thereby accelerating its electrical aging and reducing the actual service life of the capacitor. On the other hand, if the film capacitor is operated at a temperature higher than its high allowable temperature for a long time, it will accelerate the thermal aging of the capacitor. Therefore, on the one hand, it is necessary to select a capacitor whose temperature category is compatible with the actual operating environment temperature. On the other hand, in the installation and use of the capacitor, special attention should be paid to the ventilation, heat dissipation and radiation problems of the capacitor under actual use conditions, so that the capacitor is The heat generated during operation can be dissipated in time, and every effort can be made to reduce the temperature of the medium inside the capacitor under high temperature conditions to achieve the purpose of extending the actual service life of the capacitor.

So pay attention to the voltage and temperature when using the film capacitor, so that the life of the film capacitor can also be guaranteed.