GB465051A - Improvements in or relating to electric circuit interrupters - Google Patents

Abstract

465,051. Gas - blast switches. WESTINGHOUSE ELECTRIC & MANUFACTURING CO. Oct. 29, 1935, No. 29824. Convention date, Nov. 3, 1934. [Class 38 (v)] Cases.-A circuit interrupter comprises a member formed with an arc passage, the said passage having a material capable of evolving an arc-extinguishing gas when placed in proximity to an arc, an element movable only on the occurrence of an arc the current value of which is below a substantially predetermined value, within said passage during the operation of the interrupter to decrease the volume of said passage. A structure such as is shown in Fig. 2 is mounted at the foot of each of a pair of lead-in conductors 16 passing through insulators in a tank having an insulating bottom plate and provided in the walls near its base with vents to atmosphere for the arc gases. A pull-rod operated bridge 17 carries at each end a movable contact rod 19 to form a double break per pole, Fig. 1 (not shown). Each rod 19 is movable in an arc passage 27 formed by central holes in a stack of circular plates 25 of hard fibre or other insulating material capable of evolving arc-extinguishing gas when acted on by an arc, the uppermost plate having a sector-shaped, pressurerelieving, cut-out part 33. The stack is secured by insulating bolts 29 to a metal cylinder 23 to which are pivoted a pair of spring-controlled fixed contacts 35, the inward travel of which is limited by recesses in member 31. A rod 59 of hard fibre or other gasevolving insulating material is secured to a spring-controlled guide 61 freely movable in 23 and having an extension 63 co-operating with a cylindrical chamber 57 in the head 45 to form a dashpot. The head also contains an adjustable spring ball-valve 47. In opening heavy currents, when 19 disengages 35, the rod 59 does not immediately follow owing to the dashpot effect of 63, 57 and the volume of gas liberated, acting on the guide 61, is sufficient to prevent movement of 59. With small-current arcs, however, the gas-pressure is incapable of arresting the movement of 61, which therefore moves downwards, subject to the delay action of the dashpot, so decreasing the cross-section of the passage 27 and forcing the arc into intimate contact with its walls. The delay of the dashpot is preferably from three to ten cycles, during which time large-current arcs are normally extinguished, the extinguishing action being enhanced by the longitudinal movement of the gas through passage 27 due to the presence of opening 33. The piston-like action of 61 may be prevented by making its dimensions sufficiently small. In Fig. 6, the spring- controlled piston 181 engaging the walls of casing 123, carries a metal rod 175 to which is secured the rod 159 of hard fibre &c. A latch 177 on 175 co-operates with a latch 181 urged by a spring 187 into the latching position, but capable of being withdrawn by a plunger 185 when solenoid 189 is energized. So long as the arc current is large, a further electromagnet maintains 189 de-energized, but with moderate overloads, energization of 189 is effected and causes withdrawal of 181 and functioning of 159. Even if 181 were withdrawn when a largecurrent arc was formed, the gas-pressure acting on piston 161 would prevent movement of the rod 159. In a further modification, Fig. 8 (not shown), the plunger is retracted by its solenoid under the action of a dashpot so as to delay the movement of the rod until a predetermined time after establishing the arc. Specification 430,482, [Group XXXVI], is referred to.