Energy storage capacitors: aging, and diagnostic approaches for life validation

Lifetime tests on a high ohms/square metalized high crystalline polypropylene film capacitor with application to a Marx modulator

“…However, because of the non-smooth capacitance degradation in experiments D and E and because it was demonstrated that thermal effects are partially contributing to determining the end of life, these data are censored from the linear regression summarized in Table IV. The coefficient k 2 represents the voltage scaling exponent, exp, for this film. For similar polypropylene, self-healing film capacitors, voltage scaling exponents in the range of 13.5-16.4 [7] or 18.7-20.3 [11] are reported. The target application for the capacitors utilized in the P2 Marx calls for a lifetime of 10 5 hours.…”

“…The data were transformed into the model given by (7). Results from the analysis are summarized in Table III.…”

“…In the case of selfhealing capacitors, the electric field stress across the film impacts the characteristics of the "clearing" process of discharges through the film. Details on this process are outside the scope of this paper [7]. In general, high temperatures and high electric field stresses will reduce capacitor lifetime.…”

Lifetime testing of metallized thin film capacitors for inverter applications

“…1) [8]. The eventual build-up of metallized vapor can cause catastrophic failure either through the pressure increasing enough to burst the capacitor casing [14] or the vaporized metal concentration increasing enough to become conductive and cause a flashover event [15]. Clearing events result in a steady decrease in capacitance until soft failure (A, ΔC=2% in this case).…”

A prognostic method for scheduling maintenance on the P2-Marx modulator

“…As these capacitors age, an overall gradual reduction in capacitance is observed [10], and the total energy stored by the capacitor for a given voltage is reduced. A reduction in capacitance of 5% will indicate that the capacitor is approaching its end of life.…”