First of all, the voltage in the circuit is too high, which leads to the breakdown of film capacitors.

The most important parameter of a film capacitor is the rated working voltage. If the voltage on the circuit is far exceeding the rated working voltage of the film capacitor, under the action of such high voltage, strong partial discharge and dielectric damage will occur inside the film capacitor, even leading to the breakdown of the capacitor.

Secondly, the temperature is too high.

Film capacitors all have their rated operating temperatures.

Most of the film capacitors manufactured by CRE have a maximum temperature resistance of 105℃. If the film capacitor is operated at a temperature higher than the maximum allowed for a long time, it will accelerate the thermal aging of the capacitor and the life will be significantly shorter. On the other hand, in the installation and use of capacitors, special attention should be paid to the ventilation, heat dissipation, and radiation under the actual working conditions, so that the heat generated in the operation of capacitors can be dissipated in time, which can prolong the service life of film capacitors.

Finally, buying poor-quality film capacitors.

Now the industry is too confusing, due to the market playing a serious price war. Some manufacturers, to make their capacitors more price competitive, will choose to use low withstand voltage capacitors to pretend to be high ones, which will lead to the problem that the actual withstand voltage of the capacitor is not enough, and also easy to have the film capacitor being broken down due to high voltage.