GB485816A - Improvements in or relating to apparatus for the electrical protection of gaseous discharge-tubes - Google Patents

Abstract

485,816. Protective cut-out arrangements; magnetic switches. BARLOW, H. E. M. June 10, 1937, No. 16063. [Class 38 (v)] [Also in Group XXXV] In a device for protecting electric dischargetubes, the current input to the primary winding of the transformer supplying the tube is interrupted by the action of an electromagnetic relay operated automatically as a result of any change from the normal distribution of the flux of the transformer. The device operates in dependence on overload and short-circuit in the secondary and also on open.-circuit, and is applicable to signs N, valves, and ray appliances. Windings A1, A2 are connected across a coil Q energized in accordance with the flux linking the secondary S, whereas windings B1, B2 are connected across the additively-connected coils M on the leakage-core. Pivoted armatures C1, C2 are normally in the positions shown, to which they are manually restored after operation. On overload in the secondary S, the flux linking the latter diminishes owing to the increased diversion through the leakage-core ; accordingly the currents in windings A1, A2 fall and those in B1, B2 rise. Armature C1 is pulled over against B1 and, by striking projection F, tilts a mercury-switch D about its pivot H, so opening the primary P. On opencircuit in S, the currents in A1, A2 rise and those in B1, B2 fall, so that armature C2 is pulled over to strike projection F. To prevent chattering, the armatures may be oil-immersed or may be separated from the cores by a cushion. The secondary mid-point is preferably earthed, so that an earth-fault produces disconnection of the primary in the same way as an overload. In a modification, the relays may be dispensed with by placing pivoted armatures in the paths of the respective fluxes. The Provisional Specification shows and describes also two forms in which winding Q is located between the two halves of the secondary, and in one of these forms the winding M is a single coil embracing the entire primary flux. The winding Q energizes a single relay similar to A1 and winding M a single relay similar to B 1. The single armature, similar to C1, is normally against the core of the winding energized by Q and is pulled over by the other to operate the mercury switch on overload, due to the fall of flux linking winding Q, with either maintenance of the primary flux or increase of the leakageflux, according to the position of M. The latter winding may be dispensed with, and winding B be placed in series with the primary P.