GB428786A - Improvements in or relating to alternating current electric circuit breakers - Google Patents

Abstract

428,786. Arc-rupturing in switches. MARSTON, G. S., and STATTER & CO., Ltd., J. G., 16, Great George Street, London. Nov. 18, 1933, No. 32202. [Class 38 (v)] A circuit-breaker having an auxiliary contact carried on the main movable contact carrying member and an auxiliary contact carried on the fixed main contact support, one auxiliary contact being slidably carried, has electromagnetic means energized from the line for maintaining the auxiliary contacts closed against the action of resilient loading means after the main contacts have opened, until the instantaneous current has failen to such a value that the loading means overcomes the electromagnetic means to open the circuit finally at the auxiliary contacts. Fig. 2 shows diagrammatically a breaker in the act of opening ; one half 12 of a magnetic ring is fixed to an extension of the carrier of the main movable contact 1, whereas the other 13 is controlled by springs 14 and connected by a spring as 10, Fig. 4, so as to move with a contact 8, which is slidably mounted in guides 7 fixed on the main fixed contact 2. The auxiliary movable contact comprises two parts 9 pivoted to a block 6 on the extension and urged apart by a spring 11. When opening on short-circuit or overload, 1, 3 separate and then 4, 5 but owing to the field set up in the ring 12, 13 by the current, 8 slides in the guides 7 and remains in contact with 9. At zero of the cycle the field is insufficient to overcome the force of springs 14, so 8 is separated from 9 and the circuit is finally opened. On normal loads, the field is inadequate, and 8, 9 separate at about the same time as 1, 3 so that the circuit is finally opened at 4, 5, which contacts are also the first to close. In the closed position, the shunt path is short-circuited by 1, 3 so the ring is unable to exert any choking effect, but such effect comes into play when 1, 3 open. The carrier of 1 may be the bridging member of an oil-switch with the parts so shaped as to circulate cooling oil during the opening movement. Instead of the ring being magnetized by a straight extension, a solenoid winding may be formed by looping the extension round the half-ring a desired number of times. In order to prevent sparking at the main contacts due to the choking effect of the ring, a resistance discharge path may be provided, such as shunt contacts adapted to separate before 4, 5 separates. The Provisional Specification refers also to a solenoid and spring-controlled plunger, and to a time-delay action in tripping.