GB846462A - Improvements in and relating to delayed tripping mechanisms for electric switchgear - Google Patents

Abstract

846,462. Automatic circuit-breakers. ENGLISH ELECTRIC CO. Ltd. Jan. 11, 1957 [Jan. 11, 1956], No.937/56. Class 38 (5). A circuit-breaker has an overload coil 13 wound about a core 11 so as to attract a pivoted armature 10, to trip the circuit-breaker, against the action of both a spring 12 and a time delay device which is rendered ineffective after a predetermined movement of the armature 10. The device comprises a link 15 pivoted to the armature 10 and to a lever 16 which is also pivoted to a bell-crank 19 movable about a fixed pivot A and connected to an oil dashpot 20, 21 having a non-return valve in the piston member 20 (Fig. 3, not shown). The lever 16 also carries a roller 17 which engages a cam 18 freely mounted on the pivot A and urged against an adjustable stop 26 by a spring 27. When the armature 10 is attracted to the core 11, the roller 17 first moves along the arcuate face of the cam 18 so that the lever 16 moves the crank 19 against the delaying action of the dashpot 20, 21. When the roller 17 passes the corner of the cam 18 the lever 16 can move without the crank 19 so that the dashpot has no further effect on the movement of the armature 10. The roller 17 moves the cam 18 against the action of the spring 27 during the latter part of the armature travel. Fig. 4 (not shown) illustrates means of current setting by adjustment of the spring 12, and means for setting the time lag by adjustment of the stop 26. An additional armature may be provided (Fig. 5, not shown) so as to be attracted by the core 11 at high overload currents, and move the stop 26 so that the time lag is reduced.