GB677145A - Improvements in or relating to control systems for x-ray tubes - Google Patents

Abstract

677,145. Supply system for X-ray tubes. PHILIPS ELECTRICAL, Ltd. Sept. 27, 1949 [Sept. 30, 1948], No. 24751/49. Class 38 (iv). In a high-tension supply system for an X-ray tube employing a variable ratio transformer by which the voltage applied to the tube may be controlled, the ratio of the circuit resistance on the mains side of this transformer to the circuit resistance on the tube side of the transformer is made such that the total voltage loss in the circuit is proportional to the input power to the tube and is constant for a constant power input at varying voltage, whereby the voltage loss may be compensated throughout the voltage range by an auxiliary boosting voltage proportional to the load. A formula for determining the required resistance ratio is included in the Specification. Fig. 8 shows a system for supplying either of tubes 17, 18 through a high-tension transformer 12, filament transformer 19 and multipole change-over switch 14-16. The filament transformer is supplied from the mains 8 through a constant voltage device 6 and regulators 3, 4, the last two of which are coupled, respectively, with the voltage selector switch of a tapped autotransformer 7 through which the high-tension transformer is supplied, and the timer 25. By this means the tube current is limited by the settings of the high-tension and time controls and overloading of the tube prevented. A resistor 5 may also be switched into the filament circuit if the two tubes have different characteristics. A resistor 9 in the mains circuit permits adjustment to the required ratio the resistances of the circuits on the two sides of the autotransformer 7. The auxiliary boost voltage for compensating for the supply circuit voltage drop comprises a pre-set component derived from a secondary winding 20 on transformer 7 and a component dependent upon the timer setting. This component is obtained from a tapped reactor 22 energized from transformer 7 and having a wiper 21 ganged with the timer, the voltage appearing between the tapping of the reactor and the wiper being injected into the primary circuit of the hightension transformer by a further transformer 23.