GB344988A - Improvements relating to arc extinguishing devices for electric circuit interrupters - Google Patents

Abstract

344,988. Arc-rupturing in switches. ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Bush House, Aldwych, London.-(Assignees of Slepian, J. ; 1115, Lancaster Street, Pittsburg, U.S.A.) Jan. 7, 1930, No. 647. Convention date, Jan. 18, 1929. [Class 38 (v).] An arc-extinguishing device comprises an open-ended enclosure which is bounded in respect of one direction by the surfaces of two arc horns and is sub-divided by a series of parallel insulating partitions in planes transverse to the general direction of the arc. The partitions are pitched sufficiently closely so that the arc traversing their end edges between the horns, and acted upon by a transverse magnetic field, is forced against the said edges and restricted in cross-section without being able to expand into the spaces between the partitions, and is cooled by an air blast set up by the field acting on the ionized gas forming the arc. The arc horns 4, 5 laminate in contacts 6, 7, the latter being pivoted at 25 and urged by a spring 26 against the movable member 8. An arc chamber 14 enclosed by insulating fireproof walls contains spaced insulating plates 16 and shorter plates 17, 18, above which are metal deionizing plates 27, of which preferably alternate ones are extensions of the plates 16, 17, 18. The blow-out poles 19, 20 are located adjacent the outer walls of the chamber 14 and energized by windings 22 on a laminated yoke 21. In operation, the arc moves along the horns 4, 5 and upwardly against the edges of the plates 16, 17, 18 (Fig. 3) and finally is driven a short distance into the spaces between the plates. Here the blow-out is stated to cause a draught of air through the arc which thereby contracts, increasing the voltage/inch length required to maintain the arc. With an A.C. arc, the contraction follows the current wave so that the arc is extinguished at the zero of the wave. While the arc is formed, its terminals move up the straight part of the horns 4, 5, until the voltage between the lower end of the straight part and the part of the arc immediately opposite causes a restriking thereacross, the new arc then travelling up the horn; this process goes on as long as the arc persists and minimizes the risk of burning the horns. The number of plates 16 depends on the voltage, one only being necessary for voltages up to 600 (Fig. 6, not shown). The Specification as open to inspection under Sect. 91 (3) (a) refers also to the use of a shielding structure for voltages in excess of 2500. This subject-matter does not appear in the Specification as accepted.