If you want to know why the electrolytic capacitor explodes, first you have to know what the electrolytic capacitor is. An electrolytic capacitor is a kind of capacitance, the metal foil is the positive electrode (aluminum or tantalum), and the oxide film (aluminum oxide or tantalum oxide), which is closely attached to the metal, is the dielectric. The cathode consists of conductive material, electrolyte (which can be liquid or solid) and other materials. Because electrolyte is the main part of the cathode, the electrolytic capacitor is hence named. At the same time, the capacitance of the electrolytic capacitor cannot be connected wrongly.
Tantalum electrolytic capacitor mainly consists of sintering solid, foil winding solid, sintering liquid, and so on. The sintered solids account for more than 95% of the current production, which are mainly composed of non-metallic sealed resin.
The aluminum electrolytic capacitor can be divided into four types: the lead type aluminum electrolytic capacitor; the horn type aluminum electrolytic capacitor; the bolted aluminum electrolytic capacitor; solid aluminum electrolytic capacitor.
The possible reasons for the capacitor explosion are as follows:
- The breakdown of the internal components of the capacitor is mainly due to the poor manufacturing process.
- The damage to the shell insulation by the capacitor. The high voltage side of the capacitor is made of thin steel sheet, and the edge will be uneven with the burr or bent seriously if the manufacturing process is poor, then the tip of which is prone to generate corona that cause the breakdown of oil, the expansion of the case and the drop of oil. In addition, when the cover is closed, the internal insulation will burn and produce oil and gas that make the voltage drop greatly and damage if the welding time is too long.
- Poor sealing and oil leakage. The insulation resistance is reduced due to the poor sealing of the assembly casing. Or the oil surface dropped because of the oil spill that resulting in the extreme shell direction discharge or component breakdown.
- The belly and the inside dissociation. Due to the internal corona, breakdown discharge and serious dissociation, the starting free voltage of the element is reduced to the working electric field intensity under the action of overvoltage, which causes the physical, chemical and electrical effects to accelerate the aging and decomposition of the insulation that will produce gas and form a vicious circle, and later the pressure of the case is increased and the drum exploded.
- A capacitor explodes with an electric charge. All capacitors with rated voltages are forbidden to be charged. Each time the capacitor bank recloses, the capacitor must be discharged for 3min after the switch is disconnected. Otherwise, the voltage polarity of the closing moment may be caused by the opposite polarity of the residual charge on the capacitor.