GB728613A - Improvements relating to radio frequency generating equipment - Google Patents

Abstract

728,613. Rectifying; automatic voltage control systems. RADIO HEATERS, Ltd. Dec. 1, 1953 [Dec. 4, 1952], No. 30820/52. Classes 38 (2) and 38 (4). [Also in Group XL (c)] The H.T. D.C. power supply unit for the valve oscillator of a radio-frequency heater (see Group XL (c)) produces an output voltage which rises as the current rises in accordance with the characteristic 5V - 31 = 42 (where V is in kilovolts and I is in amps.). The unit comprises a three-phase full-wave rectifier 20, 22 feeding the load 25 and associated with a saturable reactor 30 comprising a coil 27 producing a field representing the term- 31, a coil 31 producing a field representing the term 5V and a coil 33 carrying a current derived from a stabilized source 35, 40 and producing a field representing the term - 42 so that the A.C. output from coil 41 follows derived from a source 34 the required characteristic. This output is rectified at 42 and applied to a " peaking " transformer 43 and to five similar transformers (not shown), one for each rectifier valve 22. These transformers have a further winding 46 in series with the output current path and a winding 51 fed with A.C. The transformers produce output voltage pulses when the A.C. field crosses the zero axis. If, for example, the current drawn from the rectifiers increaess the field due to coil 44 changes such that the pulses occur earlier and as the pulses are applied to the grids of the corresponding rectifiers the H.T. output also rises. Winding 33 is fed from a stabilized source and the power supply is accordingly compensated for mains voltage fluctuations.