GB378062A - Improvements in and relating to the transmission of electric power - Google Patents

Abstract

378,062. Converting. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Bedford, B. D. ; 329, Germania Avenue, Schenectady, New York, U.S.A.) April 25, 1931, No. 12299. Convention date, April 25, 1930. [Class 38 (ii).] In an arrangement for supplying an A.C. load circuit 11 with current derived from a D.C. source 10 through an inductive winding 12 and a pair of metal vapour discharge devices 13, 14 associated with means such as a condenser 21 for eflecting commutation of current therein, provision is made for subjecting the grid of each of the valves 13, 14 to a transient of negative potential immediately upon interruption of current in the corresponding valve in order to effect rapid deionization thereof. In the arrangement shown, the grid circuits comprise a transformer 25 and a condenser 28 across which is impressed an alternating potential derived from a transformer 29, of sufficient magnitude to render the valves conducting in turn and thus determine frequency of the inverter. The primary of the transformer 25 is connected across a resistance 22 connected in series with a condenser 23 across the terminals of the winding 12. The arrangement is such that discharge of the condenser 23 consequent on starting of current in either of the valves causes such a potential to be developed in the secondary of transformer 25 as to apply a negative voltage impulse to the grid of the other valve in which current has been interrupted by the action of the commutating condenser 21. Modifications are described with reference to arrangements in which the grid circuits are in self-exciting connection, the auxiliary source feeding transformer 29 and condenser 28 being dispensed with. In one such modification, Fig. 4 (not shown), the condenser 23 also is dispensed with, the transient of negative potential whereby the valves are deionized being produced by reversal of current in the primary of the grid transformer on discharge of the commutating condenser 21.