Paper Capacitors under Direct Voltages

This article discusses and illustrates the influence of voltage, temperature, and materials on the life of paper capacitors under direct voltages. The life decreases as the applied voltage and ambient temperature increase. Operating voltages which are safe at room temperatures may produce rapid dielectric failure at high temperatures unless the most suitable materials and best manufacturing practices are employed. It is essential that temperature as well as voltage be taken into account in the design, manufacture, and use of paper capacitors if trouble-free service is to be insured. Paper capacitors should be rated for a maximum direct operating voltage at a maximum ambient temperature. An accelerated life test on representative samples is the best criterion of the life performance that may be expected of a manufactured lot of capacitors in service. This article also describes some types of asphalt-sealed and hermetically sealed paper capacitors designed for direct-current operation in different types of service.