GB549554A - Improvements in or relating to automatic electric circuit breakers - Google Patents

Abstract

549,554. Electrically-released switches. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. May 23, 1941, No. 6629. Convention date, June 8, 1940. [Class 38 (v)] In an automatic circuit-breaker adapted to trip electromagnetically without time-delay on severe overloads and having inverse-time characteristics for moderate overloads, the electromagnetic armature is restrained by a loadcurrent carrying bimetal strip adapted to deflect in the tripping direction so as to give decreasing restraint with rising current. On severe overloads, the armature is attracted and, aided by a spring, overpowers the bimetal. The latch lever 63 is pivoted at 75 to the upper limb of a U-shaped magnet core 69 and has a projection 79 on an extension 77 which co-operates with the free end of a bimetal strip 67 in series with the magnet winding 73. A spring 83 anchored to the lever 63 provides a constant force in the tripping direction, which force is adjustable by a screw 87 having its threads engaging the coils of the spring. The latching surfaces 79, 81 are so arranged and directed that the force of opening springs 33 does not bias lever 63 in either direction, but in Fig. 5 (not shown) they are arranged to provide an extra bias in the trip direction. The surface 81 is formed on a lever 35 which is pivoted to a frame 27 at 45 and retains the movable contact lever 15 by means of the overset toggle 37, 39.. The pivot 45 also serves as one anchorage for the spring 33 and to support the operating handle lever 41 having a connection 59 with a lever 43 pivoted to the toggle-knee. Provided 35 is latched, manual operation can be effected by breaking and resetting the toggle. If 35 is unlatched the whole mechanism rotates in a generally-anticlockwise direction without movement of the handle and collapse of the toggle, resetting being effected by moving the handle to open position to break the toggle and then back to cloced position to overset it. Resetting can be effected with very little delay after disconnecting a heavy overload owing to the strip 67, freed from the force of the electromagnet, springing back slightly.