Electric arc - definition

An Electric Arc is a physical phenomenon involving the passage of an electric current through ionised air or other gas, accompanied by very high temperatures and intense light radiation. It is usually formed between two electrodes, which are initially short-circuited and then separated when an applied voltage is maintained. The sustained conductive channel, formed by the ionisation of the gas molecules, allows the current to continue to flow despite the considerable distance between the contacts.

This phenomenon is non-linear and highly dynamic. The high temperature of the arc - up to several thousand degrees Celsius - causes intense thermal and luminous emissions and can lead to melting and erosion of the electrode materials. The arc channel is maintained by a self-sustained ionisation process that allows continuous conduction of current, even under conditions of low external resistance.

In technology, the electric arc finds both useful applications and is an undesirable phenomenon. Under controlled conditions, it is used in arc welding, plasma cutting, arc furnaces and ignition equipment. In switchgear such as circuit breakers and contactors, on the other hand, the arc poses a threat to contact life and installation safety, so arc extinguishing systems are designed to quickly interrupt the discharge.

Arc parameters such as ignition voltage, length, stability or current-voltage characteristics depend on the type of gas, pressure, current and geometry of the system. Understanding the mechanism of arc formation and development is fundamental to the design of safe and efficient power systems, as well as to engineered plasma technologies.

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