GB258588A - Improvements in or relating to electric slowly acting relays for use with automatic circuit breakers for protecting electric circuits - Google Patents

Abstract

258,588. Siemens - Schuckertwerke Ges. Sept. 15, 1925, [Convention date]. Protective arrangements; induction motor relays; differential switches.- An inverse time-lag, differentiallyactuated relay for the selective isolation of an overloaded section comprises two induction-motor-meter elements of known construction which close the relay when they rotate at different speeds, the time elapsing before the closure is effected being dependent upon the difference of speed. In the arrangement shown, one induction meter is driven by electromagnets 33, 34 energized from a current transformer 14 in the line section to be protected and its disc 12 drives through bevel gearing one crown wheel 16 of a differential gear. The other crown wheel 15 of the gear is driven by a constant speed induction disc 11 energized from a constant source 13 (which may be a constant voltage derived from a part of the line). Instead of the induction disc a clockwork motor driven disc may be used. The floating intermediate pinions 18 are connected with the switch actuating lever 21 and when, on overload, the speed of the disc 12 exceeds that of the other disc the lever 21 is carried round at a speed dependent on the overload until it brings together the contacts 23 in the tripping circuit of the main circuit-breaker 25. The switch actuating arm 21 may be journaled eccentrically on its shaft 19 under the control of a spring so that in approaching the contacts it first engages a stop from which, by further movement, it is released with a quick action due to the spring. When the overload falls off so that the disc 11 rotates faster than the disc 12, the relay 23 is not immediately opened as some idle movement of the shaft 19 is necessary before the spring is strained to cause the actuating lever to follow. In this way a time-lag is imposed also on the resulting movement.