GB602693A - Improvements in or relating to electric current conversion systems - Google Patents

Abstract

602,693. Converting. SHEPHERD, G. R. (Westinghouse Electric International Co.). Nov. 9, 1945, No. 29962. [Class 38 (ii)] In a conversion system comprising one or more pairs of valves of the immersion-ignition type, a capacitor, continuously charged, is connected across the make-alive electrodes, and a controlled electric valve is inserted in the return circuit from the cathodes of the valves to the capacitor. A condenser 22 is charged from A.C. supply 10 through transformer 21 and is connected through unidirectional conductors 27, 28 to the ignition electrodes 17 of the two valves 13, 14 connecting A.C. circuit 10 with D.C. circuit 11. A valve 35 is connected between the connected cathodes 16 and the junction of two unidirectional conductors 27, 28 across the capacitor. The grid 36 of this valve, which is biassed from potentiometer 38, is controlled so that condenser 22 is discharged at a desired moment in the cycle through ignition electrodes 17 of valves 13, 14 alternately, by way of unidirectional conductors 27, 30 and 28, 29 respectively. Inductance 23 controls the rate of charging of condenser 22 and the follow current of the impulses which have a steep wave front. In Fig. 10 in which six valves convert the supply between threephase system 10 and D.C. system 11, control circuits to grids 36 of the three control valves 35 are shown supplied through transformer 61 from system 10. Automatic control is obtained by the variation of a resistance 60 in the supply by variations of D.C. voltage or other operating condition. In other modifications, valve 35 is of the immersion-ignition type, Fig. 2 (not shown) ; condenser 22 is replaced by two condensers with their junction point connected through a resistance to the centre point of the secondary, of transformer 21, Fig. 3 (not shown), and the return path may be connected to the centre of a high impedance inductor which is connected across condenser 22 in place of rectifiers 29, 30, Fig. 5 (not shown). Also the supply to the ignition circuit may be taken direct from transformer 12 which supplies the main valves, Fig. 7 (not shown). In Fig. 8, the impulsing circuit is connected to the ignition electrodes which are not connected together, through a transformer 48, with rectifiers 27, 28 as shown or between transformer 21 and the condensers 122, 123, Fig. 9 (not shown). Transformer 21 may be replaced by an autotransformer, Fig. 6 (not shown).