Characteristics of Chlorinated Impregnants in Direct-Current Paper Capacitors

Direct-current capacitors of the impregnated-paper type play an important role in electronic equipment required by the Armed Services. In some of these applications good performance is required over very wide temperature ranges. A new chlorinated-hydrocarbon composition which maintains reasonable capacitance constancy over a wide temperature range is described. The properties of this liquid are compared with conventional chlorinated impregnants. Since some alternating voltages usually accompany the direct voltages applied to capacitors, the alternating-current behavior over wide temperature and frequency ranges is described for capacitors impregnated with three different liquids. The effect of voltage and temperature on the resistance of capacitors is discussed. Considerable attention is devoted to the life behavior of capacitors impregnated with chlorinated liquids under direct-current stresses at high temperatures. A life-testing procedure is described which has yielded very satisfactory results on capacitors of varying sizes and ratings. A means for prolonging the life of capacitors impregnated with chlorinated impregnants involving the addition of stabilizers is discussed. Data showing effect of a number of stabilizers are presented. Finally, some data are presented showing the effect of voltage on the life of direct-current capacitors.