Dissipation Factor as a Degradation Indicator for Electrolytic Capacitors

Abstract

Capacitors are one of the most critical components in power electronic converters, yet they are notoriously susceptible to failure. Avoiding unforeseen outages caused by capacitor failures is one of the most effective approaches to increase system availability. Therefore, a variety of methods have been proposed to monitor a capacitor health condition based on different degradation indicators. This article proposes a new approach based on the accurate measurement of an electrolytic capacitor dissipation factor (DF) to detect its end-of-life. Since the DF is affected by both the capacitor resistance and capacitance simultaneously, it can provide more information about the health condition of the capacitor. To employ the DF as an aging indicator, beyond its accurate measurement, it must be possible to establish an end-of-life criterion and investigate the effect of other environmental factors. Therefore, increasing the frequency of the DF measurement has been suggested as a solution to minimize the effect of the angle measurement error, for which an optimal frequency range has been calculated. In the following, several electrolytic capacitors are subjected to a laboratory study to investigate the effects of capacitor aging, temperature, and measurement frequency on the DF. According to the obtained results, changes in the capacitor resistance dominate the DF, thereby enabling the same end-of-life criterion to be applied for monitoring a capacitor condition.