Repetitive-pulse lifetime, statistical results of design/process factor matrix study of liquid-impregnated, discrete film/foil capacitors

Two design/process factor matrix studies have been performed utilizing the Sandia-designed and developed liquid-impregnated, discrete multilayer film and foil capacitor technology. Repetitive 1 kHz charge/discharge cycle lifetimes were utilized to evaluate the process-factor variable changes in the capacitor fabrication processes. Of the five process variables investigated (perfluorcarbon liquid type, fill pressure, film crystalline to amorphous ratio or film condition, number of film layers at constant total thickness, and winding tension or space factor), only the fill pressure and film condition were shown to statistically affect the cycle lifetimes. However, definite performance improvement trends, particularly for capacitors fabricated with the 8-{mu}m thick film, were found for the higher winding tension levels. The eighty-seven capacitors fabricated for these matrix studies functioned at 20 J/kg energy density, and seven survived 100 million cycles. All were tested in a 7{degree}C oil bath. (Sandia National Laboratories has routinely fabricated capacitors of similar design with an energy density of 100 J/kg that have demonstrated reliabilities exceeding 0.999). For these two matrix studies, lifetimes ranged from 120 thousand cycles to the 100 million cycle upper test limit with capacitors charged to 5 kV and with the total film, dielectric-pad thickness held constant at 24 {mu}m. 11 refs.,more » 4 tabs.« less