Capacitors for discharge-lighting control circuits

A short Section on manufacture and materials outlines typical features in the construction of a capacitor for discharge lighting and refers briefly to common practice in the choice of impregnating material and vacuum processing conditions. Under the general heading of dielectric life and breakdown the probable effects of conducting paths in tissue are mentioned. The importance of discharge-inception stress is emphasized, reference being made to discharge-inception measurements on capacitors impregnated with petroleum jelly and with pentachlorodiphenyl, and to the interim results of long-term accelerated tests on pentachlorodiphenyl-impregnated capacitors. A suggestion that electrochemical deterioration is not a major factor contributing to failure of paper capacitors under a.c. stress is discussed. A note on chemical decomposition of impregnants during breakdown is followed by discussion of the use of fusing to reduce or eliminate such chemical effects. A final Section discusses power factor as a criterion of capacitor quality.