GB515055A - Improvements in and relating to circuit arrangements for supplying x-ray apparatus - Google Patents

Abstract

515,055. Control systems for X-ray tubes. GENERAL ELECTRIC CO., Ltd., and CALDWELL, J. T. May 20, 1938, No. 15096. [Class 38 (iv)] Relates to the control of the H.T. of an X-ray tube to keep it constant, notwithstanding necessary variations of current in the cathode, by interconnected resistance regulating controls. In order to avoid the use of a regulating switch capable of carrying the full current of the primary of the transformer supplying the tube, a smaller switch is employed in the secondary circuit of a transformer through which the tube is supplied. In Fig. 1, the primaries of transformers 8 and 5 which supply a hot cathode X- ray tube 7 with low tension and high tension respectively are fed from alternating current mains 2 through an auto-transformer 1. A variable resistance 9 in series in the primary circuit of transformer 8 serves to vary the filament current, while the high tension voltage on the tube may be adjusted by means of a selector switch 3. Adjustment of a variable resistance 12 is effected conjointly with the adjustment of variable resistance 9 and the resulting variation in the impedance of a compensating transformer 4, connected in the primary circuit of transformer 5, maintains the voltage applied to the tube constant with varying filament current at any one setting of selector switch 3. The variable tapping from the switch 3 is taken through one winding of a transformer 4 to supply the primary of the tube transformer 5. The secondary of transformer 4 is connected across the regulating resistance 12 controlled conjointly with the resistance 9. The transformer coupling enables a regulating switch of relatively low rating to be used.