Precautions for using film capacitors

Precautions for using film capacitors

Film capacitors are electronic components that store electrical charge and energy in the form of an electric field between two metal plates separated by a dielectric film. They are commonly used in a variety of electronic circuits, including power supplies, filters, and signal processing circuits. To ensure the proper operation and longevity of film capacitors, it is important to take certain precautions when using them.

 Working voltage

The choice of film capacitor depends on the highest voltage applied and is affected by such factors as the applied voltage waveform, current waveform, frequency, ambient temperature (capacitor surface temperature), and capacitance. Before use, please check whether the voltage waveform, current waveform, and frequency at both ends of the capacitor (in high-frequency occasions, the allowable voltage varies with the type of capacitor, please refer to the manual for details) are within the rated value.

Working current

The pulse (or AC) current through the capacitor is equal to the product of the capacitance C and the rate of voltage rise, that is, I = C × dV / dt. Due to the loss of the capacitor, when you use it under high frequency or high pulse, the pulse (or AC) current through the capacitor will cause the capacitor to heat itself, which will cause thermal breakdown (smoke, fire). Therefore, the safe use conditions of capacitors are not only limited by the rated voltage, but also by the rated current.

Rated current is considered to be composed of pulse current (peak current, which is limited by dV / dt index) and continuous current (expressed in peak-to-peak value or effective value), which is determined by breakdown mode.

For capacitors used under high frequency or high pulse conditions, we recommend polypropylene film capacitors or CL23B laminated capacitors. CBB81 / A / B series polypropylene film high-voltage capacitors give a rated peak-to-peak current at a duty ratio (DUTY) of 15%. CBB21 / A / B series S correction capacitors are rated for peak-to-peak current. Under normal circumstances, it is not allowed to exceed the rated peak-to-peak current.

When the actual operating current waveform is different from the given waveform, in general, polyester film capacitors are used when their own temperature rise is 10°C or less, and polypropylene membranes have their own temperature rise of 5°C or less. The surface temperature of the capacitor must not exceed the rated upper limit temperature.


The effective value conversion relationship of various waveforms