Kalman filter used for on line monitoring and predictive maintenance system of aluminium electrolytic capacitors in UPS

The electrolytic capacitor usually has the shortest span of life in the power converter. This paper presents a new low cost implementation of a real time condition monitoring and a predictive maintenance system of an electrolytic capacitor used in Uninterruptible Power Supplies (UPS). It consists of detecting the changes in real time in equivalent series resistance (ESR) and the capacitance C values of the electrolytic capacitors. The proposed method can be used in UPS where waveforms are continuously varying in amplitude, frequency and versus ambient temperature. This method has the merits of using known algorithms and only the existent resources in UPS.