The failure of metallized-paper capacitors used with large series resistances

Although normally self-healing, metallized-paper capacitors sometimes become faulty when used in series with a high resistance. Accelerated life tests have shown that such faults may occur, for example, when 0.5¿F capacitors are connected to an 80 V supply through a resistance of 1 M¿ or more. To calculate similar limiting conditions for other capacitances and supply voltages, the paper assumes that a rapid deterioration begins when a certain critical dissipation is reached at a defective spot, and that the fault will be cleared if the energy then stored in the capacitor is enough to evaporate the electrodes locally. In capacitors of various other kinds, not having metallized electrodes, no faults of this kind have occurred during life tests, or are thought likely.