Arc Quencher

Arc Quencher

 

a subassembly in a high-voltage switch that is designed to extinguish the electric arc that occurs on the switch contacts when a circuit is broken. The arc is extinguished by rapid cooling and deionization or by fragmenting into several short arcs.

In electrical apparatus for voltages up to 1,000 volts (V) the arc quencher consists of a chamber made of an arc-resistant material (ceramics, asbestos cement, asbodin, or special plastics) inside which are partitions. The arc is drawn into the chamber by a magnetic field created by the disconnect current or by permanent magnets. As a result of cooling the arc by the chamber’s walls and of its deionization, its resistance is sharply increased, and the current is thereby decreased to zero.

In arc quenchers of gas switches for voltages above 1,000 V, the electric arc is cooled either by the stream of gas formed as a result of the decomposition of transformer oil or by a stream of air or elegaz (sulfur hexafluoride) fed under pressure to the arc combustion zone. In arc quenchers of magnetic switches the arc is cooled in a ceramic chamber, into which it is drawn by a powerful magnetic field created by the disconnect current. In arc quenchers of vacuum switches the contacts are broken in a medium with a pressure of 10-4 newtons per sq m (10-6 mm of mercury). The arc formed at the contacts is extinguished when the alternating current passes through zero because of the resorption of the charged particles in the vacuum and the high electrical strength of the rarefied medium.

A variety of arc quencher is a deionization grid that consists of several flat ferromagnetic (copper-plated) or copper plates that are insulated from one another and positioned in such a way as to facilitate entry of the arc into the grid. As the magnetic field of the arc is closed through the plates, the arc is drawn into the grid, where it is broken up into several short arcs. After the alternating current passes through zero, a high electrical strength, on the order of 100–200 V, is developed at each pair of plates in the gap. A deionization grid is also used in automatic devices for extinguishing the field of AC generators.

REFERENCES

Bron, O. B. Elektricheskaia duga v apparatakh upravleniia. Moscow-Leningrad, 1954.
Taev, I. S. Elektricheskaia duga v apparatakh nizkogo napriazheniia. Moscow, 1965.
Chunikhin, A. A. Elecktricheskie apparaty. Moscow, 1967.

V. T. NEZHDANOV

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