A Changing Capacitor Technology - Failure Mechanisms and Design Innovations

During the past few years the ac capacitor industry has seen almost a complete change in dielectrics, electrodes, and impregnants. The dielectric has changed from paper to all poly-propylene film, the electrode from plain foil to either metallized film, metallized paper, or embossed foil, and the fluids have changed from polychlorinated biphenyls (PCB) to those based on hydrocarbon or phthalate ester chemistries. This paper discusses the rational behind this changing technology, the improved performance aspects of these new designs, and some of the degradation mechanisms that have accompanied these changes.