GB191510130A - Improvements relating to Electrically Controlled Electric Circuit Breakers. - Google Patents

Abstract

10,130. British Westinghouse Electric Manufacturing Co., [Assignees of Smith, B. H.], July 11, 1914. [Convention date]. Automatic circuit-breakers; protective arrangements.-The trip-magnet of an automatic circuitbreaker is constructed with two magnetic circuits, one provided with a winding energized from the main, and the other with a winding which is controlled by an overload or other relay and then acts in conjunction with the permanently energized coil to move a trip-armature. In the form shown in Fig. 1, a coil 16 energized from a series transformer 4 in alternating-current mains 1 surrounds a movable trip-armature 10, other iron parts 11, 12 being disposed in two flux paths with air-gaps 13, 14 so proportioned that, under normal conditions, the attraction on the armature towards the side 12 exceeds the attraction towards the side 11. The preponderant attraction assists a biassing-spring 15 to keep the armature normally in the position shown. A second coil 17 surrounding the limb 12, when short-circuited upon itself by the movement of an overload relay 8, has induced in it a flux counter to that due to the coil 16, thus causing the preponderance of attraction to shift into the limb 11, which moves the armature to trip the circuitbreaker 2. The modification shown in Fig. 2 has two permanently energized coils 22, 24 connected to a series transformer 4 and exerting opposite pulls upon a movable core 21, the downward pull being normally preponderant. A coil 25, mounted on a lower limb of the magnet, when short-circuited on itself by an overload relay 8, is traversed by an induced current which neutralizes the flux due to the coil 24. The core 21 is then pulled up to trip a circuit-breaker 2. In a further modification of the last-described construction, the coil 25, instead of being completely open, is normally shortcircuited through a variable resistance, in order that, under a very excessive current, the coil 22 may act to pull up the core without waiting for the contact 8 to close. Other modifications are described, all having magnetic circuits like that shown in Fig. 2, a coil like 22, Fig. 2, permanently energized from a series transformer, and a second coil which is either opened or closed or shortcircuited by an overload relay in order to allow the first coil to trip the circuit-breaker. In one case, the second coil is in a normally closed circuit with an auxiliary source of current. In the other cases, it is in a normally closed circuit and is energized by current from an inductive winding on one of the upper side limbs of the magnet.