An Experimental Technique for Estimating the ESR and Reactance Intrinsic Values of Aluminum Electrolytic Capacitors

This paper presents an experimental technique that allows the determination of the reactance and ESR intrinsic values of aluminum electrolytic capacitors. The equivalent circuit of an electrolytic capacitor comprises an equivalent series inductance (ESL), an equivalent series resistance (ESR) and a capacitance (C), whose values change with frequency. Therefore, the behavior of an electrolytic capacitor varies from approximately a simple capacitor for low frequencies, to a resistor at its resonance frequency, and finally to an inductor for frequencies higher than its resonance frequency. The knowledge of the resonance frequency of the electrolytic capacitors, as well as their equivalent circuit at the operating frequency becomes of paramount importance for designing purposes. The ESR is one of the most critical problems of static converters that operate near the resonance frequency of the electrolytic capacitors. An increased ESR value leads to a significant increase in the alternate component of the output voltage, requiring a constant action of the control system. To validate the proposed technique and to demonstrate its applicability some experimental and simulated results are presented