GB425646A - Improvements in high speed automatic electric circuit breakers - Google Patents

Abstract

425,646. Automatic circuit-breakers. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET, Vasteras, Sweden. Feb. 19, 1934, No. 5445. Convention date, March 1, 1933. [Class 38 (v)] In a rapid acting circuit-breaker the " kneeloose " tripping toggle is formed by a roller 3 carried by the contact arm 1 and a link 2 pivoted to an arm 8 movable about a fixed pivot, the lower end of the arm 8 being normally held against the shaped end of a manuallydepressable tripping lever 7. In the " closed " position shown, the link 2 is held against a fixed stop 11 by a laterally-acting spring 10, the link and roller thus forming a slightly underset toggle of which the three pivotal points formed by the pivot of the roller and that of the link and the line of contact between the roller and link lie almost but not quite in a straight line. In this position the moment of the lateral spring force about the link pivot exceeds the opposed moment Pr due to a powerful throw-off spring 4 acting on the contact arm 1. Attached to the contact arm is a bar 6 connected by a pin-and-slot to the armature 5 of an overload magnet and when the latter is sufficiently energized it acts upon the contact arm and increases the moment Pr about the pivot of the link 2 until it becomes greater than the moment of the force 10 about this pivot. The link 2 accordingly commences to move away from the fixed stop 11 and once the tripper motion is initiated it proceeds with extreme rapidity until the parts are in the position shown in Fig. 2. Resetting of the circuit breaker is effected by first depressing the lever 7 so that the link 2 is moved by its spring 10 against the fixed stop 11 and then rotating the lever 8 in a counterclockwise direction. During the resetting a pin 12 at the lower end of the contact arm 1 moves to the left in a fixed guide slot and the contacts engage with a wiping action. The overload setting may be varied by adjustment of spring 13. In an alternative arrangement, Fig. 3, (not shown), the release magnet is provided with series and shunt windings to operate on reversal of current.