Simulation of Capacitive Current Compensation in Prebreakdown Current Measurements in Vacuum Under AC Voltages

This paper presents computer simulation results of prebreakdown (PBD) current growth in a high vacuum environment traditionally used for carrying out basic experimental studies with plain parallel electrodes. In this work, an attempt is made to analyze the PBD measuring circuit only since the elimination of displacement current is an essential prerequisite to measure emission current. The scope of the simulation results presented in this work is limited to the measuring circuit. Using conventional circuit theory, a circuit model is realized, and simulation is carried out using MATLAB SIMULINK. Since the experimental method of measurement under AC excitations involves the gap capacitance current and its compensation using a cancellation technique, an effort is made to run the simulation study for three different percentages of compensation and validate the simulation. The experimental test gap is modeled as a parallel plate capacitor. The effectiveness of the compensation provided by the variable capacitor is checked for two extreme percentages and one mid percentage value.