GB951588A - Improvements in electrical contactors and circuit breakers - Google Patents

Abstract

951,588. Air-break switches. H. T. BALDWIN. June 14, 1960 [March 14, 1959], No. 8907/59. Heading H2B. In a circuit-breaker or contactor having the or each set of contacts in a separate substantially closed arcing-chamber, the walls of the chamber consist, at least partly, of magnetic material insulated from the contacts and closely surround the path of the arc. The term " closely surround " is used to set out that a compromise is achieved between the desired limitation of the volume of air enclosed and the proximity of the walls to the arc path. In Figs. 1 and 3, a three-phase circuit-breaker has moving contact bridges 4 with ends carrying contacts 3 in D-section arcing chambers into which fixed contacts 1 project. Each chamber is formed by a magnetic U-shaped member 15 having its outside exposed to the atmosphere, retained between top and bottom plates 18, 17 which are parts of insulating casings 25 or 26 which are bolted together and retain between them slidable members 5 carrying the movable contact bridges 4 and having walls 16 which. substantially close the arcing chambers. The fixed contact 1 is surrounded by magnetic ring 19 to assist the blow-out effect. The arcing chambers of one phase may be interconnected through the space in the member 5 enclosing the contact biasing spring 7. For higher current ratings an alternative arcing-chamber shown in Figs. 5 and 6 has an additional magnetic member 37 which is inside the chamber but is shorter than the member 15 so that it is spaced from the contact 1 and does not form a current path on arcing thereto. In Fig. 7, a chamber, for still higher current ratings, has its fixed walls formed by alternate plates 42, 43 of insulating and material respectively, the latter plates projecting closer to the arc path so as to form air pockets 45.