Analytical Computation and Experimental Validation of Self-Inductance for High-Voltage Pulse Capacitors

Abstract

There have been continuous efforts to reduce self-inductance or equivalent series inductance (ESL) of energy storage capacitors for various high voltage (HV) pulsed power applications. Reduction in self-inductance increases peak discharge current, life, and reduces the voltage reversal and rise of current. This further actually increases the effective use of the stored energy of the pulse capacitor (PC). These pulsed power applications include electromagnetic forming and welding, rail gun, coil gun, plasma device-based neutron and x-ray, high power microwave, exploding wire-based shockwave for oil well and rock fracturing, etc. In this research, similar rating energy storage capacitors for pulsed power applications are designed, developed, and electrically tested for reduction in self-inductance. Four types of stack configuration capacitors with insulating bushings are developed for $8~\mu $ F, 4 kV, 8.5 nH in series-connected two capacitor elements; $3.1~\mu $ F, 110 kV, 40 nH in horizontal assembly of capacitor elements, and $25~\mu $ F, 15 kV, 25 nH in vertical assembly of capacitor elements with six- and eight-packs configurations to demonstrate the reduction in inductance. Position of current path and magnetic flux loop area have also been studied and inferred a major role in the reduction of the self-inductance while incorporating the coaxial insulating bushing and circular conducting terminals. An attempt is put forth to numerically estimate the ESL values, and they are validated with experimental results with good agreement. This article will contain a detailed mathematical estimation methodology of self-inductance for different capacitor configurations and bushings, and will be a good value addition in this HV pulsed power technology. Further, this analytical estimation methodology of ESL is an effective, less time and energy consumption, and economical solution in the development of HV PCs for various pulsed power applications.