What is special about high voltage power supplies used to drive X-ray tubes?
Some special considerations are employed (or should be) in a power supply used to drive an X-ray tube. X-ray tubes will arc internally from time to time. Sometimes called a “flashover” or “tube arc”, these events suddenly dissipate the stored energy of the power supply and any high voltage cables into the X-ray tube. Unless this current is limited somehow, piezoelectric stresses on the tube envelope can fracture and break it, rendering it useless. Surge limiting resistances are generally used in series with the output terminals of a high voltage power supply employed to drive an X-ray tube. In this fashion, the current is limited (to one ampere, generally) when the tube arcs. When operating an X-ray tube near its full voltage rating, the high voltage potential should be applied slowly over time. This “ramp up”, or warmup time is sometimes specified by the tube manufacturer, and typical values are as follows: Turn on at 50% of full voltage, and then increase the voltage to 100% over 30
