An acidified film is formed on the anode foil of aluminum electrolytic capacitor, but it can only withstand the continuous application of specified voltage at the highest service temperature. When a voltage higher than the endurance of the acidification film is applied, the anode foil of the aluminum electrolytic capacitor will form an acidification film equivalent to the applied voltage. The reaction at this time makes the capacitor produce gas and the internal pressure rises.

As the characteristics of capacitance, there will be a decrease in electrostatic capacity and an increase in the positive connection of loss angle. The amount of gas generated will increase with the applied voltage and the temperature around the capacitor. Subsequently, the internal pressure of the capacitor rises, the sealing material (rubber band) expands, and the safety device starts to act (the rubber band will fly out for products without safety device).

Extended data

Electrolytic capacitors usually use metal foil (aluminum/tantalum) as the positive electrode, and the insulating oxide layer of metal foil (aluminum oxide/tantalum pentoxide) as the dielectric. Electrolytic capacitors can be divided into aluminum electrolytic capacitors and tantalum capacitors according to their anode. The negative electrode of aluminum electrolytic capacitor consists of tissue paper/film or electrolyte polymer soaked in electrolyte (liquid electrolyte); Manganese dioxide is usually used as the negative electrode of tantalum electrolytic capacitor. Electrolyte is the negative electrode (note that it is different from dielectric), so it is named electrolytic capacitor.

Polar electrolytic capacitors usually play the roles of power supply filtering, decoupling, signal coupling, time constant setting and DC isolation in power supply circuits or medium and low frequency circuits. Generally, it cannot be used in AC power supply circuits. When used as a filter capacitor in DC power supply circuit, its anode (positive pole) should be connected to the positive terminal of power supply voltage, and its cathode (negative pole) should be connected to the negative terminal of power supply voltage, and it is not allowed to be connected reversely, otherwise the capacitor will be damaged.

Therefore, the loss factor (DF) of electrolytic capacitors is also called loss tangent in many technical documents. The voltage indexes of aluminum electrolytic capacitors mainly include rated DC voltage, rated surge voltage, instantaneous overvoltage and reverse voltage. Rated DC voltage VR is the continuous working voltage allowed by the capacitor within the rated temperature range, which includes the sum of DC voltage between two electrodes of the capacitor and pulsating voltage or continuous pulse voltage.

References:

Baidu encyclopedia-electrolytic capacitor