GB341513A - Improvements relating to automatic electric circuit-breakers - Google Patents

Abstract

341,513. Automatic circuit-breakers. BRITISH ELECTRICAL & ALLIED INDUSTRIES RESEARCH ASSOCIATION, WEDMORE, E. B., and WHITNEY, W. B., 36, Kingsway, London. Oct. 14, 1929, Nos. 31148/29, 33001/29, and 8538/30. [Class 38 (v).] Circuit-breakers which are tripped on operation of a series-connected fusible or thermal release mechanism are provided with arrangements for short-circuiting the terminals of the fusible or thermal member immediately it has performed its tripping function and before the circuit has been interrupted in order that the release of energy consumption in between these terminals may be realized. As shown in Fig. 1, the fusible member 1 is secured between cup-shaped terminals 2, 3 the upper of which is clamped by a screw 5 in a lateral projection of the incoming circuit-breaker terminal 4 and the lower clamped by a screw 12 in a projection of a lever 10 pivoted at 11. The lever 10 is connected by a flexible connector 13 to the circuit-breaker terminal 7 and has an arm 17 connected to the circuit-breaker tripping mechanism. The lever 10 is under the influence of the spring 15 which, when the fuse 1 is ruptured on overload rotates the arm 10 to cause tripping of the circuit-breaker through the arm 17. During this rotation of the lever 10, however, a contact 19 on its upper end is brought into engagement with a corresponding contacting-surface 19 on the incoming terminal 4 so that the fuse terminals 20 are short-circuited. Thus any arcing at these contacts is immediately suppressed and excessive energy consumption during the current interruption is prevented. The fuse may be substituted as shown in Fig. 2 by a wire 1 which softens with excessive current so that it can be extended by the spring 15 to produce the circuit-breaker tripping without actually rupturing. This element is also short-circuited in the manner previously described during the tripping. In a further modification (Figs. 4 and 5, not shown) a bimetallic strip is employed for producing the tripping, the movement of the strip for tripping being arranged to close shortcircuiting contacts in the manner described. In order to minimize the mechanical force acting on or produced by the thermal or fusible tripping element, instead of acting directly on the circuitbreaker tripping mechanism it may be arranged to produce merely the breaking of a toggle holding up the operation of the spring-controlled trip (Figs. 3 and 6, not shown). The fusible or extensible members 1 may be protected by a fireproof tube 21 with end washers 22 and as an additional precaution against excessive arcing between the terminals of the fusible member the gap between these terminals is made as small as possible.