High voltage pulsed performance of advanced dielectric materials

Insulating fluids and laminations consisting of fluid-impregnated films were tested for their dielectric constant (k) and dielectric loss at high frequencies, and for their pulsed high-voltage breakdown strength. The objective of these investigations is to develop a high-voltage, repetition-rated pulse line for applications where high energy density, low loss and high reliability are primary design considerations. The dielectric constant and loss of plastic films were studied by propagating pulses in a parallel plate transmission line consisting of two copper strips separated by the dielectric film under test. Results indicate that almost all the high-k plastic films containing polyvinylidene fluoride (PVDF) have losses which significantly degrade the pulse risetime. Risetimes which start out in the range of 2 to 4 ns (10 to 90%) can be changed to 20 to 25 ns in a distance less than 3 m. Various high-k development fluids were also evaluated for their high-frequency pulse propagation characteristics at low voltage. Water, propylene carbonate, and some of the Pennwatt fluids were found capable of propagating fast-risetime pulses with only limited risetime degradation