Film capacitor selection considerations (1)

1. Capacitor rated voltage:

Refers to the peak value of the highest DC voltage or pulse voltage that can be continuously applied to the capacitor within the rated temperature range. Considering the requirements for reliability derating, it is usually required that the actual operating voltage should be less than 80% of the rated voltage.

2. Capacitor operating voltage selection:

Through the pulse voltage and withstand voltage of the capacitor, due to the loss of the film capacitor, when used under high frequency and high pulse conditions, if the current through the capacitor is large, the film capacitor will self-heat, and in severe cases, there will be thermal breakdown. The danger of smoking (smoke, breakdown) is therefore limited by the rated current of the capacitor during use.

It must be ensured that both voltages are within the allowable range. If the actual working voltage (current) waveform cannot be determined, it can be determined by the temperature rise of the capacitor operation. Usually, the polyester capacitor is allowed to be used at a temperature less than 10C. For polypropylene capacitors, it is allowed to use at a temperature rise of less than 5 °C. (The actual measurement should be tested on the surface of the capacitor end lead solder joint).