X=ray tube test equipment power control - has rectifier bias circuit on high voltage transformer primary to control tube output by characteristic modification

摘要

X-ray equipment with an mAs relay is used to control the X-ray tube current and ensure that the output and film exposure, i.e. dose, is independent of the characteristic curve of the primary voltage across the high voltage transformer. The mAs relay is related to the phase angle and designed so that, according to the setting selected, a definite average and peak current is obtained, exposure is constant and all are independent of circuit component characteristics. Phase angle (alpha) modification is achieved by using a rectifier bridge circuit (18) controlled by a mAs product biassing circuit (19) in the primary (6) of the high voltage transformer (4,5,6). Biassing the primary for phase angle modification is also coupled to the operation of the main exposure thyristor switching circuit (17) in the primary circuit and which is controlled by the exposure timing circuit (16,t). The tube (1) heater circuit is supplied independently from a heater transformer (8) with its own feedback regulation circuit (13,12,9,10).