Life Testing of Aluminum Electrolytics and the End of Life Dilemma

摘要

Historically, calculations of aluminum electrolytic performance both energized and on shelf testing have been poor predictors of actual performance in the field. Particularly alarming has been the use of Arrhenius based acceleration calculations to demonstrate that a particular design will meet the life requirements for the application. This paper looks in detail at the shelf life and general chemical reactions occurring in the capacitor. The data reveals that there is wide variation in the reaction rates of different electrolyte - paper - aluminum systems. Depending on the relative aggressiveness of the electrolyte, an activation energy can be empirically determined that ranges from agreement with the historical model, to an energy well below the value required to sustain a reaction. This low extreme leads to shelf performance where end of life is limited to simple loss of electrolyte through elastomer seals. Shelf oxide performance can be contrasted to performance under electrical field, and leads to electrolyte selection criteria that can shift widely based on the capacitor duty requirements.