GB258234A - Improvements in or relating to arc-rupturing devices for electric circuit interrupters - Google Patents

Abstract

258,234. Metropolitan-Vickers Electrical Co., Ltd., (Assignees of Slepian, J.). Sept. 8, 1925, [Convention date]. Sparking, preventing. - Relates to means for extinguishing the arc in A.C. circuit-breakers, involving the provision of devices which so increase the de-ionization of the arc path that the arc cannot be supported. In the typical example shown, lifting the handle 28 opens circuit by toggle action, circuit being first broken at 1 and 2 then, with a wiping action, at 33, 34 and finally between the moving contact 19 and the spring- pressed stationary contact 20, which is connected to one bottom wall 41 of the arc shoot 40, while the contact 19, when fully open, abuts against the other wall 42. Any arc drawn between these contacts is blown by the coils 24 up into the shoot, which is divided by partitions 45, 46 into three sections. Perforated metal grids 51 extend from side to side of each section but leave room for the arc to play Fig. 2. The theoretical considerations involved are discussed at length, but. shortly, the effect is to cause each grid to become the centre of an non-ionized space. As shown in Fig. 4, the effect is heightened by putting a shunting resistance 85 across the first section, and a higher resistance 86 across the second, so as to increase the quenching effect of the arc which, by the partitioning of the shoot is in three consecutive parts. Numerous modifications in detail are described having for object, for instance (1) the prevention of the hanging of the arc in the shoot month, (2) ensuring slow travel along the grids, (3) restriction of the arc path to the grids. The pole shoes 55, 56, Fig. 2, diminish in thickness, as shown, or the upper parts are perforated to reduce the magnetic effect. Again, individual grids may be shunted by a high resistance, or successive grids joined in pairs by resistors. The space between the grids may be filled with hydrogen or, again, may be evacuated. In other modifications the moving contact passes through a space in the body of the grids themselves and in a further modification the arc is moved into the shoot by an air blast. It is expected that these means will obviate the necessity for immersing the breaker in oil, but such immersion is not precluded. Mercury switches.-In one form, the grids or barriers are shown applied to a reversible mercury switch.