A novel real time monitoring unit for PWM converter electrolytic capacitors

In this paper a novel monitoring unit for PWM converter electrolytic capacitors is introduced. In state-of-the-art PWM converters in general electrolytic capacitors are used in the DC voltage link. The weak point of these components is the uncertainty in life time especially if the converter is operated within a wide temperature range. To avoid failures in operation the electrolytic capacitors have to be monitored to pre-detect the end-of-life status of the components. To estimate the status of the capacitor, the ohmic resistance of the component has to be determined. The proposed monitoring unit is located directly at the capacitor terminals for measuring itpsilas ohmic resistance. To predict itpsilas end-of-life it is furthermore necessary to consider the componentpsilas operation temperature. In comparison to known monitoring circuits the proposed concept leads to a low-cost unit whose manufacturing costs are almost neglibile as compared to the electrolytic power capacitor.