Structure and Degradation of Aluminum Electrolytic Capacitors

Aluminum Electrolytic Capacitors (AECs) are used at the dc-link of power electronic converters (PECs) as an energy buffer. During their lifecycle operation, various voltage and current stresses are imposed on these capacitors. These stresses lead to the degradation and hence, the failure of the AEC. This paper is based on studying the internal structure of AEC so as to understand its degradation. The construction and the stacked structure of the capacitor is investigated by opening it. The top and cross-sectional view of the aluminum foil of the AEC is observed under Field Emission Scanning Electron Microscope (FESEM) and the images are analysed. It helped in understanding the topography of the aluminum foil due to etching and oxidation. Then, the effect of temperature and electrical stresses on the degradation of the AEC is discussed.