Evolution of the DC capacitors

This paper describes the evolution of the medium and high voltage DC capacitors, used for filtering and energy storage applications. This evolution was accelerated in the 1990s because of the new requirements for the DC capacitors for rolling stock. The basic design was radically changed thanks to the combination of existing but seemingly incompatible raw materials. Over the last 10 years, all the improvements have been based on a better knowledge of the influence of the metallization, including the resistivities and the segmentation modes. The successful experiences obtained on more than 50000 large filter capacitors have led to transfer this technology to the energy storage field. For this application in which the voltages and the energy are often high, the self-healing process is secured by some other resistivity levels and some different modes of segmentation in order to reduce the inrush energy in the local breakdown and to meet the discharge current requirements.