magnetic switch[mag¦ned·ik ′swich]
an electric switch that is used to break high-voltage load circuits under normal or emergency operating conditions. A magnetic switch differs fundamentally from other types of switches in that the electric arc that occurs between the switch contacts that open when a circuit breaks is extinguished directly in the air by a magnetic blowout in an arc quencher.
In a magnetic switch, the arc is drawn into an arc blowout chamber by a strong magnetic field generated by electromagnets in whose coils the current to be interrupted flows. The polarity of the electromagnet coils is such that the generated magnetic field draws the arc into the arc blowout chamber or chambers, where the arc is lengthened and cooled, the resistance of the arc is sharply increased, and the arc is extinguished. The arc blowout chambers are made of heat-resistant materials that have a high dielectric strength, a high thermal conductivity, and a high heat capacity. To improve the reliability of operation of AC magnetic switches, such switches usually include an air blast that accelerates the movement of the arc into the arc blowout chamber.
Magnetic switches are usually employed in electric supply and distribution systems that carry 6–10 kilovolts.
REFERENCESBabikov, M. A. Elektricheskie apparaty, part 3. Moscow-Leningrad, 1963.
Bronshtein; A. M.; V. P. Kuritsyn, and I. N. Ulissova. “Elektromagnitnye vykliuchateli i opyt ikh ekspluatatsii.” Elektrichestvo, 1971, no. 4.
Bykov, E. I., and A. M. Koluzaev. Elektromagnitnye vykliuchateli VEM-6 i VEM-10. Moscow, 1973.
R. R. MAMOSHIN