Why does a capacitor explode?
Published time: 2019-11-27
If a capacitor explodes, its power cannot be underestimated. The following is the capacitor explosion test found by Xiaorong Yirong on the Internet. I believe that after watching it, you will not underestimate this small capacitor.
So what exactly caused the capacitor to explode? Let's take a look.
The quality of the capacitor is not enough
If the quality of the capacitor is not sufficient (poor manufacturing process, etc.), it may cause breakdown of the internal components of the capacitor, damage to the insulation of the case, etc., and may cause the capacitor to explode. Search results page).
Internal free and bulging
When corona, breakdown discharge and severe dissociation occur within the capacitor, the capacitor will reduce the initial dissociation voltage of the element below the working electric field strength under the action of overvoltage, which will cause a series of physical, chemical and electrical effects and accelerate insulation aging. , Decomposition generates gas, forming a vicious cycle, so that the pressure of the box shell increases, causing the outer wall of the box to bulge and then cause an explosion.
Poor sealing and oil leakage
The poor sealing of the mounting sleeve will cause moisture to enter the interior, which will cause the insulation resistance to decrease; or the oil level will be lowered due to oil leakage, which will lead to electrical discharge to the shell or component breakdown.
Capacitor explosion caused by high temperature
If the temperature of the capacitor is too high, the electrolyte inside the capacitor will evaporate and expand rapidly, breaking out of the enclosure and bursting. The general causes are as follows: ① The voltage is too high, causing the capacitor to break down, and the current passing through the capacitor rapidly increases; ② The ambient temperature is too high, exceeding the allowable operating temperature of the capacitor, causing the electrolyte to boil; ③ The polarity of the capacitor is reversed.
For polarized capacitors, the positive and negative electrodes are reversed, such as tantalum capacitors. If the positive and negative electrodes are reversed, the capacitors will be burnt in light, and the capacitors will explode in heavy.
Charged closing causes capacitor explosion
It is forbidden to close the capacitor bank of any voltage when it is under voltage. Each time the capacitor bank is reclosed, the capacitor must be discharged for 3 minutes before the switch is turned off, otherwise the voltage polarity at the moment of closing may be opposite to the polarity of the residual charge on the capacitor and cause an explosion. For this reason, it is generally stipulated that capacitor banks with a capacity of more than 160kvar should be equipped with an automatic trip device when no voltage is provided, and it is stipulated that the switches of the capacitor bank are not allowed to be installed with automatic reclosing.
Damage to enclosure insulation
The high-voltage side lead of the capacitor is made of thin steel sheet. If the manufacturing process is not good. The edges are uneven and have burrs or severe bends, and the tip is prone to corona. Corona will decompose the oil, expand the casing, and lower the oil level, which will cause shock wear. In addition, when the lid is sealed, if the welding time is too long at the corner, the internal insulation will be burned and oil and gas will be generated, which will greatly reduce the voltage and damage it.
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