Direct Voltage Performance Test for Capacitor Paper

Performance of capacitors on accelerated life test may vary over a wide range depending upon the capacitor paper used. Indeed, at present a life test appears to be the only practical means for evaluating capacitor paper, since, within the limits observed in commercial material, the chemical and physical tests usually made do not correlate with life. Lack of correlation is ascribed to obscure physical factors which have not yet been identified. Generally, several weeks are required to evaluate a paper by life tests of the usual severity. Unfortunately, the duration of these tests is too long for quality control of paper. The desire for a life test which requires no more than a day or two for evaluation led to the development of a rapid dc test. The philosophy of rapid life testing is based upon the experimental evidence that the process of deterioration under selected temperature and voltage conditions is principally of a chemical nature, and also upon the well-known fact that rates of chemical reaction increase exponentially with temperature. Life tests on two-layer capacitors conducted at 130°C provide an acceleration in deterioration many fold more than that obtained in the lower-temperature life tests, and correlate well with these tests.