Design of Processing System for State Diagnosis of Electrolytic Capacitors

International audience; In this paper, a system for predictive maintenance of electrolytic capacitors in static converters is presented. The failure of these capacitors leads to an increase of their equivalent series resistance ESR and therefore the voltage ripple across the components rises. This waveform must be filtered to extract its fundamental component to get a good image of ESR. For power supply with variable switching frequency, electronic filter with controlled center frequency is realised. This center frequency is adjusted by the V.C.O. of converter's control circuit. The voltage ripple also depends on the converter parameters such as input voltage, output current and ambient temperature. A reference system taking into account all these parameters is determined for sound capacitors. A good interpretation of the increase of the ripple voltage allows then, the determination of ESR value. The remaining time to the failure of the capacitors is then deduced.