GB582061A - Improvements relating to apparatus for frequency multiplication of alternating electric currents - Google Patents

Abstract

582,061. Frequency changing. WESTINGHOUSE BRAKE & SIGNAL CO., Ltd., and WALKER, A. H. B. July 11, 1944, No. 13249. [Class 38 (ii)] In a circuit for producing single phase A.C. from a polyphase input in which rectified half waves of successive waves at the input frequency are alternately applied to the ends of a suitable choke or transformer winding having a centre point connected to all the phases, and which supplies the higher frequency output, saturable inductances are connected in the input lines to introduce a third harmonic component into the input current. In a circuit suitable for operation from a two-phase supply, the phases are connected respectively to input terminals 1, 2 and 3, 4 of rectifier bridges R1, R2 and saturable chokes are connected in the input. Output terminals 14, 15 are connected together and through a resistance or load 18 to the mid-point 17 of a choke coil 13. The other output terminals 9, 10 of the rectifier bridges R1, R2 are connected to end terminals 11, 12 of choke 13. The voltage across 11, 12 has twice the frequency of the input, Fig. 2 (not shown). Fig. 3 shows the improved wave form FVV of the output current which results from the third harmonic introduced into the inputs R1I, R2I by the saturable chokes. A modification is described in which a tripled frequency results from a three-phase input, Fig. 4 (not shown). A transformer has a # connected primary with saturable chokes in the supply and two star-connected, threephase groups of secondary windings which are connected to the ends of the choke coil through half-wave rectifiers, and have their star points connected together and to the centre point of the choke through the resistance. Specification 577,270 is referred to.