Metallized polypropylene energy storage capacitors for low pulse duty are those that are required to use their stored energy intermittently or only just one time. This means that the required capacitor life expectancy is relatively short compared with most capacitor applications. Applications for low pulse duty capacitors include cardiac defibrillators, lasers, military systems and high-energy research. These applications make use of the described capacitor technology because it affords higher stored energy per unit volume and mass than longer life designs.
There are many different types of capacitors that are available today. Most capacitors produced are designed for mounting on circuit boards or other electronic equipment and are referred to as tantalum, or electrolytic, or DC film capacitors. Larger capacitors are used in applications like AC drives, and power conditioning equipment. The larger, higher voltage capacitors for 60 Hz circuits have traditionally been manufactured with paper or Polypropylene or some combination thereof with or without a liquid impregnant. Progress has been made in all these fields over the past decade. This paper is focused on defining the state-of-theart for large (over 5kg) capacitors for pulsed power applications.
Over the past few years, CDE has been replacing foil electrode construction with metallized electrode construction in a variety of high energy density pulsed power capacitors. These capacitors are used in defibrillators, copy machines, nuclear fusion experiments, electric armament, and similar applications. The use of metallized electrode capacitors in these applications affects many capacitor characteristics including life expectancy, energy density, fault current withstands, reversal capability, and dissipation factor. This paper discusses the design experience using metallized electrode construction on high energy density pulse power capacitors.
This is the first time that energy discharge capacitor technology capable of graceful ageing has been demonstrated at these energy levels. When a capacitor is selected to perform properly in an electronic circuit, its characteristics are optimized to provide the designer with a well-defined level of reliability for the component throughout the design lifetime of the circuit [l-5]. Fig. 1 shows a number of the more important technical factors that influence the capacitor designer's choice of geometry, connections, and materials [3, 5, 6]. The selection of a capacitor design requires matching available capacitor characteristics and parameters to the application needs. In addition to the basic capacitance value and voltage rating, specifying all the characteristics allows the supplier to provide the most cost-effective capacitor for the given application.
A new dielectric film has been developed that greatly increases the energy density capability of plastic film capacitors. This film has been developed over the past four years by a consortium consisting of Lithium Power Technologies, CDE Corp., Dupont Teijin Films (DTF), Case Western Reserve University, and Ohio Aerospace Institute in an Advanced Technology Program funded by the Department of Commerce. We are now entering the commercialization stage of this project.