GB1082453A - Arc extinguishing chambers for alternating current - Google Patents

Abstract

1,082,453. Arc extinguishing in switches. E. MAGGI. Jan. 8, 1965 [Jan. 29, 1964; April 9, 1964], No. 970/65. Heading H2B. An arc-chute is assembled from a plurality of insulated permanent magnets arranged in two sections each section being designed to take the arc of a different half-cycle of the A.C. and to extinguish it before the current zero. In its simplest form the chute comprises four permanent magnets 5, 6, 7, 8 arranged symmetrically to provide a central channel 10, in which the contacts 1, (2) are separated, and spaced apart to provide narrow slots 11, 12 into which the arc is driven and extinguished. Each magnet is formed with a plurality of tapered ridges increasing in height away from the contacts so that the arc is made to follow a zig-zag path of increasing length as it moves away from the contacts; the surfaces of the magnets are insulated by refractory ceramic plates 13 and the magnets may be insulating. The magnetic circuits of the magnets 5, 6 and 7, 8 are completed by insulating magnetic members (66, 67) (Fig. 12, not shown). The chute may be extended by similar sections but with the magnetic poles reversed (Figs. 4-7, not shown) so that the arc is displaced upwards in one pair of sections and downwards in the other to further increase its length. The magnets (70, 71) (Fig. 14, not shown) may be separated from the insulation by steel polepieces (72, 73) to reduce their loss of magnetism by heating and demagnetization by the field of the arc itself. In another embodiment (Figs. 8-11, 13, not shown) the chute is composed of a plurality of plate magnets (57, 58) with magnetic circuits (63) and ceramic plates (59) arranged so that the arc must follow a tortuous path as before. In addition, a plurality of sets of magnets (53-56) are arranged adjacent to the initial arc path in the contact channel (50). Arc runners (51, 52) are connected with the fixed contact 41 and a further set of magnets (45-48) drives the arc root on to the appropriate runner; the magnets (45-48) have external magnetic circuits (39, 49). The magnets may again be separated from the ceramic insulation by steel polepieces (72<SP>11</SP>, 73<SP>11</SP>) (Figs. 16-18, not shown) or the plates within the chamber may be formed entirely as steel polepieces with the permanent magnets (75, 75<SP>1</SP>) (Figs. 19-21, not shown) mounted externally. The polepieces may be of insulating magnetic material. The chute may be mounted in free air or in a chamber filled with air, gas (e.g. SeF 6 , SF 6 ), water, oil or evacuated.