GB514341A - Improvements in or relating to the control of frequency changers employing gas or vapour electric discharge devices - Google Patents

Abstract

514,341. Frequency changing. SIEMENSSCHUCKERTWERKE. AKT.-GES. May 3, 1938. Nos. 13205, 13206, and 13207. Convention dates, May 3, 1937, June 24, 1937, and Jan. 26, 1938. [Class 38 (ii)] A frequency multiplier comprises gridcontrolled gas- or vapour-filled electric discharge devices arranged to form two or more parallel-type inverters each controlled by ignition impulses of the higher frequency which are rendered alternately effective and ineffective at the lower frequency so that the inverters, each of which when operative operates at the higher frequency, become operative and inoperative in turn at the lower frequency. Fig. 1 shows a simple phase arrangement in which a high frequency circuit 3 is supplied from a low frequency circuit 1 through two parallel-type inverters 4, 5 associated with an input transformer 2 and an output transformer 3a. Grid potentials at the higher frequency are supplied through a transformer 8 but are rendered alternately effective and ineffective by injection into the grid circuits across resistances 9, 10, of voltages of rectangular wave form produced by an auxiliary inverter 12 operating at the lower frequency. The resultant grid voltages for the inverters 4, 5 are indicated by full and dotted lines respectively in Fig. 2a. The phase of the voltage of rectangular wave form may be adjusted manually or automatically in dependence on the load by a phase shifter 13 to control the amplitude of the output voltage. A similar control arrangement for three parallel-type inverters operating on a three-phase supply is described with reference to Fig. 3 (not shown). Fig. 4 shows a modified arrangement in which a polyphase circuit 21 feeds a single phase circuit 23 of higher frequency through three parallel-type inverters 24, 25, 26 each of which is supplied with grid potentials of the higher frequency developed across resistances 34, 35 The latter are in the anode circuits of auxiliary devices 30, 31, 32 which are fed with A.C. of the required frequency by a transformer 33 but are rendered alternately operative and inoperative by grid potentials of the lower frequency supplied through a phase shifter 38 which affords the same regulating provision as in the previously described arrangement. Thus the grids of the inverters 24, 25, 26 are fed with impulses of the higher frequency which are suppressed in turn in the three inverters at the frequency of the input circuit. In a further modification, Fig. 7. a group of full-wave auxiliary rectifiers 72, 73 the anodes of which are supplied at the higher frequency through a transformer 75 are rendered operative and inoperative in turn by grid transformers 74 energized at the lower frequency. Thus rectangular voltage waves of the lower frequency are produced across resistances 71 in the anode circuits, which voltage waves are superposed on higher frequency impulses supplied by a transformer 70 to the grid circuits of the main inverters 65, 66, 67 whereby the latter are rendered operative in the required sequence. Further modifications are described in which each pair of grid-controlled auxiliary discharge devices of the arrangements described with reference to Figs. 4 and 7 are replaced by a single grid-controlled device and one or more uncontrolled rectifiers.