Patent GB-510595-A (GB)
Title: Improvements in and relating to excess current high-speed electric circuit breakers
IPC: H01H71/26
Filed: 1938-01-01
Abstract: 510,595. Electromagnetic switches; electricallyreleased switches; protective cut-out arrangements. BRITISH THOMSON - HOUSTON CO., Ltd. Jan. 1, 1938, No. 42. Convention date, Jan. 2, 1937. [Class 38 (v)] In a modification of the excess-current highspeed circuit-breaker described in Specification 448,255 having a holding magnet excited by the main current, a releasing magnet and an additional electromagnet arranged in the holding magnet, the excitation of the additional electromagnet takes place solely through a current induced from the main current thus dispensing with the D.C. excitation of the holding magnet of that Specification. The contact L in the main circuit is adapted to be opened by the impact on contact-lever D of an armature C, normally retained by a holding magnet B with main-current coil K, and adapted to be torn off by a releasing magnet A with a coil H in the main circuit. A further core F carries a coil G energized by induced current from 'the main current, for example, by magnet A or B, by a blow-out magnet, where provided, or by an inductive shunt to coil H. As shown, however, it is energised by the secondary M of a regulable air-gap curent transformer N, the primary O of which carries the main current. With rising forward or reverse main current, a current is induced in winding M and coil G which, according to its direction as compared with that of main current, strengthens or weakens the normal holding flux, depending on the polarity of G. Thus the armature is pulled away from the holding magnet either later or earlier with a rising forward or reverse current, than if the additional magnet F were not present. An additional release-value can be obtained by opening the circuit of coil G, the excitation of which may be regulated by resistances and the degree of early or late releasing so varied. By connecting rectifiers in series or shunt to coil G, early release in one direction and normal release in the other can be obtained, or alternatively, normal release in one direction and late release in the other can be obtained. The selective property finds application in traction systems fed by rectifiers or converters The Specification as open to inspection under Sect. 91 describes also the following. A busbar supplies several lines over switches provided with early release for current flowing away from the busbars and with late release for current flowing towards the busbars. Thus a faulty line is at once cut out by its switch, whereas the fault current which may flow in the other lines is in the direction of late release, Fig. 3 (Cancelled) (not shown). In Fig. 4 (Cancelled), the sources e. h supply the sections 1..3, having disconnected points s between them, over switches f. g, i, k provided with early release in the direction towards the line. A fault in 1 causes f, i to open, whereas a fault in 2 causes g, i to open, the other switches through which the fault may be fed remaining in each case closed. A line supplying a number of feeders tapped off it has the circuit-breakers in the line time-graded so that only the breaker next the fault operates, Fig. 2 (Cancelled) (not shown). This subjectmatter does not appear in the Specification as accepted.