GB914847A - Improvements in or relating to x-ray apparatus - Google Patents

Abstract

914,847. Control systems for X-ray apparatus. PHILIPS ELECTRICAL INDUSTRIES Ltd. Feb. 9, 1961 [Feb. 12, I960], No. 4861/61. Class 38 (4). Each switching arm of an electromagnetic switch connecting an X-ray apparatus to a 3-hose supply may be separately actuated so as to interrupt the supply to the apparatus at a current zero by means of variable phase auxili. ary voltage pulses, the peak level of which may be changed from that at which they are ineffective, to a second level, so that the next following pulse moves one of the switching arms. Separate switching arms 8-10 of an electromagnetic switch may each be actuated by energizing coils 17-19 and thus interrupt the supply of 3-phase current from lines 5-7 to a high-voltage generator 4 of an X-ray apparatus 1, by opening contacts 11-13. The discharge of condensers 27 charged from a power supply 23 through energizing coils 17-19 is separately controlled by gas discharge valve 22-20 whose ignition effects the opening of the contacts. Negative going pulses of adjustable phase are fed to the control electrodes 26 of the discharge valves 20-22 from rectifying circuits 34 supplied from transformers 30 through phase-shift arms 32, 33. The common positive rectifier output is connected through a resistor 37 to the cathodes 25 of the valves. Thus, when the X-ray tube 1 is non-operative, the gas discharge valves are prevented from igniting. When X-ray tube 1 is energized by closing the switch contacts 11-13, an X-ray sensitive cell 40 is actuated, thus enabling a capacitor 43 to charge, which after a given time delay renders conducting a previously non-conducting electronic vacuum valve 46, thus causing current to flow through a resistor 37. The volt-drop across the resistor 37 increases the potential of the voltage pulses appearing at the control electrodes 26 of the discharge valves 20-22 so that the valves will be ignited by the next following pulse peak, this instant being arranged to be the same as that for which the phase current is zero. The variable resistors 32 are individually adjustable so that the instant of ignition of each valve may be individually determined.