When the voltage across a capacitor exceeds its rated voltage, several factors come into play that can lead to its failure, which might even include explosions. These key factors contribute to the potential failure of the capacitor.
- Dielectric Breakdown
- Internal Arcing
- Gas Production
How it happens?
The dielectric material inside a capacitor has a specific
breakdown voltage. When the applied voltage exceeds this breakdown voltage, the
dielectric becomes conductive, allowing current to flow between the plates.
This leads to a rapid discharge of energy, resulting in localized heating and
vaporization of the dielectric material. The vaporization process generates
gases within the capacitor, causing them to rapidly accumulate and subsequently
increasing the pressure inside the capacitor. If the pressure becomes too high,
the casing may rupture, leading to an explosion. This series of events is referred
to as thermal runaway.
Explanation of Each Factor
Dielectric Breakdown
The dielectric material inside a capacitor is not perfect
and has a certain breakdown voltage. When the voltage exceeds this level, the
dielectric can lose its insulating properties and become conductive, allowing
current to flow between the plates. This can lead to a rapid discharge of
energy and potentially cause the capacitor to overheat or explode.
Internal Arcing
If the voltage is too high, the electric field between the plates can become strong enough to cause arcing or sparking within the capacitor. This discharge can cause localized heating and vaporization of the dielectric material, which can result in a sudden increase in pressure and potentially rupture the capacitor’s casing.
Gas Production
The breakdown of the dielectric material or the vaporization of the internal components can generate gases within the capacitor. These gases can rapidly accumulate and increase the pressure inside the capacitor. If the pressure becomes too high, the casing may rupture, causing an explosion.
Thermal Runaway
If the voltage exceeds the capacitor’s rating, it can lead to an excessive current flow and localized heating. This heating can further exacerbate the other failure mechanisms mentioned above, leading to a chain reaction known as thermal runaway. This process can result in the rapid release of energy, potentially causing an explosion. The dielectric material inside the capacitor possesses a specific breakdown voltage. If the applied voltage exceeds this threshold, the dielectric becomes conductive, permitting current to flow between the capacitor plates. This results in a rapid discharge of energy, causing localized heating and vaporization of the dielectric material.
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