Finite-Element Modeling of Transients in Capacitor with Distributed Parameters

Abstract

Tantalum capacitors have high capacitance per volume due to the porous anode structure. This feature of their structure leads to the fact that when analyzing at high frequencies or calculating transient processes with a small value of the time constant, the tantalum capacitor can not be considered as an element with lumped parameters. In this case, the ladder equivalent circuit gives more accurate results of calculations in the frequency and time domains. It can be assumed that in the process of charging a capacitor with distributed parameters, the electric field and current density are distributed non-uniformly over the capacitor structure, which can lead to an uneven load on different regions of the capacitor. To test this hypothesis, a finite element analysis of the charging process of the capacitor structure with distributed parameters was conducted, which showed that the regions of the capacitor located near the cathode terminal are exposed to charging currents of a larger amplitude. There are situations in which oscillating transient processes are observed in these regions with the general aperiodic process of charging a capacitor, which leads to the occurrence of overvoltages in these regions. The degree of influence of the distribution of the parameters of the capacitor on the nature of the transient processes decreases with increasing conductivity of the cathode material.