GB599855A - Improvements in or relating to excitation systems for vapour electric devices - Google Patents

Abstract

599,855. Metal - vapour converters. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. June 19, 1945, No. 15600. Convention date, July 7, 1944. [Class 39 (i)] In a control circuit for the continuous excitation of a vapour-electric valve 13 having a make-alive electrode 18 and a keep-alive electrode 19, both energized from a condenser 23 connected across the output terminals of a rectifier 22, an impedance of such size is connected in the alternating current input circuit to the rectifier that the input voltage to the rectifier drops rapidly with increase in current, whereby the current flowing to the keep-alive electrode reduces the voltage below that required for operation of the make-alive electrode. As shown, Fig. 1, the impedance in the input circuit of the rectifier comprises a transformer 21 having a shunt flux path 28 between its primary and secondary windings. The potential across the condenser 23 is applied to the make-alive electrode 18 through a reactor 26 which when saturated permits a flow of current for initiating the cathode spot. An arc is then established to the keep-alive electrode causing a flow of current through the secondary winding of the transformer with consequent reduction of potential. This reduction of potential is such that the reactor 26 is no longer saturated and current flows substantially only to the keep-alive electrode. In an alternative arrangement, Fig. 2 (not shown), a condenser is connected in series with the primary winding of the transformer and the linear reactor 27, Fig. 1, in series with the keep-alive electrode, is replaced by winding the connection to the keep-alive electrode on an unbroken middle leg of the transformer. In a further embodiment, Fig. 3 (not shown), the input circuit to the rectifier includes a variable reactor having a saturation winding connected in series with the make-alive electrode. This saturation winding corresponds to the saturable reactor of Fig. 1. The Specification as open to inspection under Sect. 91 comprises also an arrangement, Fig. 3 (Cancelled, not shown), in which the keep-alive electrode is controlled by a D.C. potential which may be derived from an A.C. source and a full-wave rectifier, and the make-alive electrode is connected to the secondary of a transformer whose primary winding is in series with a condenser. In a modification, Fig. 6 (Cancelled) in which an alternating current keep-alive arc is used, two keep-alive electrodes A are provided and supplied with current by a transformer 133 the winding in the return circuit 25 serving the dual purpose of controlling the potential of transformer 35 and as a stabilizing reactor in series with the keep-alive arc. A further modification, Fig. 7 (Cancelled, not shown) utilizes two half-wave rectifiers between the secondary terminals of transformer 133 and a single keep-alive electrode. This subject-matter does not appear in the Specification as accepted.