GB822117A - Improvements in or relating to electric contact converters - Google Patents

Abstract

822,117. Converting. SIEMENS-SCHUCKERTWERKE A.G. Sept. 25, 1957 [Sopt. 29, 1956], No. 30117/57. Class 38 (2). Premagnetization current for a switching choke SD in a contact converter circuit is provided by an arrangement of transistors which is so controlled by voltage developed by the switching choke that it passes only during the duration of the current step. The premagnetization current passes through winding V which is actually on the switching choke core, when amplifier transistor T2 is made conductive by current passing through its base-emitter circuit. This latter current flows through transistor T1 as a result of voltage developed by flux changes in winding H on the switching choke, and its value, and therefore that of the current in winding V, is determined solely by the value of resistor W in series with battery U1 in the emitter-base circuit of transistor T1 and not by the voltage developed in winding H. Rectifier G protects the transistors against excessive inverse loading. In a modification transistor T1 lies in the output circuit of transistor T2 (Fig. 2, not shown). The arrangements obviate the need for a basic load to maintain the switching chokes appropriately saturated on no load.