GB538894A - Improvements in or relating to electric circuit interrupters having arc-extinguishing devices - Google Patents

Abstract

538,894. Arc-rupturing in switches. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. March 15, 1940, No. 4865. Convention date, March 22, 1939. [Class 38 (v)] An arc-quenching structure comprises a series of refractory insulating plates 75 slotted at 79, the slots in adjacent plates being staggered. The spacing members 77 between them consist of hard fibres or other gas-evolving material and are so shaped as to provide a constricted part, Fig. 3, at an intermediate point in the length of the slots. At each end of the stack of plates 75 is a shield plate 71 of refractory insulating material having a slot 73, Fig. 3, which is considerably less deep than the slots 79, the plates 71 being spaced from arcing plates 55, 63, which in turn are spaced from insulating end plates 31, 33 and are slotted at 89 to allow of gas-escape in advance of the arc and provided with a plate 87 of arc-resistant metal such as a tungsten-silver alloy. Below the limbs of the plates 75 extend refractory members 85 having inclined surfaces extending on either side of the fixed and movable arcing contacts 21, 23 to form a continuation of slots 79. In operation, the arc is transferred from contacts 21, 23 on to the plates 55, 63 and driven by a magnetic blowout into the slots. While the middle part of the arc continues its upward movement to the ends of slots 79, the end portions are impeded, due to the shorter slots 73, but the arc-tips continue moving up the plates 55, 63 until the arc restrikes at points closer to the ends of slots 73. This process occurs rapidly and minimizes the vaporization of plates 55, 63. The blast of unionized gas produced by the magnetic field is supplemented by the gas produced by members 77, flow of generated gas being assisted by the increasing cross section of the spaces between the plates 75. The side-walls 35 of the structure are recessed to enable the structure to fit within, and rest upon, the laminated blow-out poles 39, which are screwed to a non-magnetic bracket 41 on an insulator 43 and interconnected by a core 45 carrying the blow-out coil 47. One coilend 49 is connected to a main fixed-contact carrier 13, whereas the other is connected to a fixed blade contact 51 from which a pair of blades 59 on the plate 55 can be disengaged to allow the quenching-structure to be bodily slid off the poles.