Dingfeng Capacitor--- What consequences are expected when the voltage exceeding the rated voltag
Update Time:2018-06-13
Q: What consequences are expected when the voltage exceeding the rated voltage is applied on an aluminum electrolytic capacitor?
 A:  On the anode foil of aluminum electrolytic capacitor, an oxide film capable of withstanding the rated voltage even if it is continuously applied at the maximum operating temperature.
In case when the voltage higher than the withstand voltage of this oxide film (overvoltage) is applied, the anode foil of aluminum electrolytic capacitor will form the oxide film equivalent to the applied voltage. Owing to the reaction, gases will be generated, thus leading to the pressure buildup in the capacitor. As the characteristics of capacitor, decrease in electrostatic capacity and increase in tangent of loss angle will be caused. The higher the applied voltage is and the higher the ambient temperature is, the more the gases are generated and the higher the internal pressure. This may sometimes lead to the phenomena such as swelling of sealing material (rubber packing) and further to activation of safety device (slipping out of rubber packing in the products with no safety device). Therefore, avoid the use of capacitor in the circuit where the voltage exceeding the rated voltage may be applied to it.

The structural breakdown modes in case when overvoltage is applied are as follows:
(1) Open
The safety device is activated (or rubber packing slips out), and liquid electrolyte in the capacitor is flown out, thus leading to dryup and finally to open condition.
(2) Short-circuiting
If the voltage higher than the withstand voltage of anode foil, that of liquid electrolyte and that of separator paper is applied and it is no longer possible to keep insulation, dielectric breakdown will be caused, thus leading to short-circuiting.