Repeatability analysis in HV capacitor charging applications

Pulse-to-pulse repeatability, R, is an important parameter in capacitor charging applications. It influences stability of various physical processes ranging from lasing to pulsed X-rays to plasma chemistry applications. This paper delves into the subject mostly from theoretical standpoint of view; experimental evidence is given in an accompanying paper. It is stated that R depends on the quality of the HV measurement and the ratio of the energy stored in the HV transformer magnetic system, its parasitic capacitance, etc., to that stored in the output capacitor. The influence of the second factor is studied on an example of an energy-dosing converter topology. The governing equations are derived, and solutions in a closed form are obtained for the worst case assuming that the converter is shut down at an arbitrary time point. It came clear that empiric formulae usually used in literature are too simplistic to account for the complex electromagnetic processes; they may give hugely overstated values. The theoretical findings are compared with both PSpice simulations for the worst case and experimental results obtained with a 20-kJ/s, 10-kV, 1-kHz repetition-rate charger.