Rated voltage of capacitor

All capacitor have a maximum rated voltage, and when choosing a capacitor, consider the amount of voltage applied across the capacitor. The data sheet usually gives the maximum amount of voltage applied to the capacitor without damaging the capacitor's dielectric material: WV (working voltage) or WV DC (direct current working voltage).

If the voltage applied to the capacitor is too large, the dielectric will break down (called electrical breakdown) and an arc will be generated between the capacitor plates, resulting in a short circuit. The operating voltage depends on the type of dielectric material used and its thickness.

This is the DC working voltage of a capacitor. For a capacitor with a rated DC voltage of 100 volts, the maximum DC voltage cannot safely withstand an AC voltage of 100 volts. Then, a capacitor that is required to operate at a 100 volt AC voltage should have an operating voltage of at least 200 volts. In fact, a capacitor should be selected so that its operating voltage DC or AC is at least 50% greater than the highest effective voltage to be applied.

Another factor that affects the operation of capacitor is dielectric leakage.

Generally, it is assumed that the resistance of the dielectric is extremely high, and a good insulator will prevent DC current from flowing through the capacitor from one plate to the other (as in an ideal capacitor). However, if the dielectric material is damaged due to excessive voltage or overheating, the leakage current flowing through the dielectric will become extremely high, resulting in rapid loss of charge on the board and overheating of the capacitor, eventually leading to premature failure of the capacitor. Then, never use the capacitor in a circuit with a voltage higher than the capacitor's rating, otherwise it may become hot and explode.