Ultimate properties of the polypropylene film for energy storage capacitors

Classic products have been improved, especially those based on the metallized all-polypropylene film. The properties of this film show a uniform range in terms of breakdown, with few thickness-dependent variations. For extended lifetime and high current values, the dielectric stress is far from the breakdown level of the polypropylene film. The evolution of the metallization-segmentation is described through the results obtained on three types of design. Conversely, for short capacitor lifetime and moderate currents, the stress can be situated in the breakdown area of the polypropylene film. Therefore, the working conditions must be precisely defined, especially in terms of charging time and hold time. In both cases, the inrush energy in the defect must be limited and controlled in order to avoid any secondary effect. The resistivities of the metallization play a significant role in controlling the high energy density products. The behavior of the galvanic contacts between the reinforced edges of the metallization and the metal spray is strong enough to allow the use of resistivities of several tens of ohms per square unit.