Reducing Parasitic Oscillations of Capacitive Dividers Using Coaxial Symmetry in the Low-Voltage Arm

In this article, a new design rule to mitigate parasitic oscillations superimposing to the measurement of high-voltage pulses is proposed. We establish a transfer function of capacitive dividers that includes not only the self-inductances of the high- and low-voltage arms of the divider but also the mutual inductance that exists between both arms of the dividers. The mathematical analysis and experimental validation demonstrate that the parasitic oscillations can be significantly reduced by using a coaxial configuration of the low-voltage arm printed circuit board (PCB). The proposed design rule can be implemented on any capacitive divider, enabling a compact low-voltage side design, whose voltage division factor can be conveniently modified. In this work, the design rule is validated on a custom-built capacitive divider, designed to measure high-voltage pulses generated by spiral generators. The designed capacitive divider successfully measured pulses up to 289 kV with a voltage division factor exceeding 100000 with minimal parasitic oscillations.