Electric breakdown
What is Electric Breakdown?
Electric breakdown, also known as dielectric breakdown, is a phenomenon that happens when insulating material is exposed to a high enough voltage and abruptly becomes an electrical conductor, allowing electric current to flow through it. When the electric field created by a supply voltage surpasses the material's dielectric strength, an insulating material will fail. The voltage at which an insulating item becomes conductive is known as its breakdown voltage, and its size, form and material determine it. Electrical breakdown may occur inside solids, liquids, gases, or vacuum under sufficient electrical potential. However, the particular breakdown processes vary depending on the dielectric medium.
The Mechanism of Electric Breakdown
A dielectric may lose its insulator qualities in electromagnetic fields if the field surpasses a threshold value. Breakdown voltage Ubreak is the minimum voltage value that leads to the breakdown of a dielectric. Ohm's law does not apply in the dielectric state before the breakdown when the current steadily increases. Such a situation is referred to as a pre-breakdown state.
The dielectric breadth, electric field, and electrode arrangement influence the breakdown voltage. It is distinguished by the dielectric's capacity to endure an electric field. When the breakdown begins, the electric endurance of a dielectric is a minimum field: Ebreak=Ubreakh
If a dielectric gas breaks down and the power is switched off, the gas might regain its insulating qualities. Because their insulation is damaged, solid dielectrics cannot recover insulating abilities after a breakdown. Dielectric breakdown may occur in an insulator in an electric field due to electric, thermal, or electrochemical reactions. Strike and photoionization cause the breakdown of air as well as other gases.
Dry air, for example, is electrically insulating in typical ambient circumstances. When a high voltage is put over a tiny gap (i.e., a high electric field), the ionization of air molecules causes a spark, enabling electric current to flow across the gap. This abrupt electron movement inside an electrical insulator is a material feature, and a higher breakdown threshold indicates more insulation capacity.
Ceramic materials like alumina (Aluminium Oxide) are commonly used as dielectrics in electrical components. The dielectric breakdown threshold values of most dielectric ceramics, including alumina, are in the 10–25 kV mm− 1 range.