Design and Testing of a Compact 40 KV Capacitor Based on Nanodielectric Composites

Compact pulsed power systems are often limited by the size and shape of the capacitors required for high voltage energy storage. Marx banks, pulse forming networks, and other devices requiring multiple capacitors are larger than necessary due to the size and shape of the capacitors as well as the geometry of the connection terminals. The size and weight of the capacitor are determined by the energy density of the capacitor dielectric and the dielectric strength of the surrounding insulation. While doorknob-style capacitors are commonly implemented in these devices, the cylindrical shape does not permit efficient packing of multiple capacitors to fill the available volume. Alternative capacitors, such as those based on mica films, have an improved form factor but have end terminations that add inductance in many assemblies. A new effort is addressing these design issues by building the capacitor with nanodielectric composites. The nanodielectric composites combine high dielectric constant ceramic particles with low dielectric constant, high dielectric strength polymers to produce materials with both high dielectric constant and high dielectric strength [1]. The combination of these two properties enables higher energy densities than possible with conventional ceramics. The composite materials can also be formed or machined into complex shapes, including rectangular, cylindrical, or coaxial form factors, to improve capacitor packing density while maintaining low inductance connections. The present effort is focused on development of 40 kV, 2.5 nF capacitors for compact capacitor banks in a counter-materiel program. In this contribution, the tradeoffs are discussed in the design and simulation of the new capacitors. The first prototypes are described with preliminary test results.