Pulsed breakdown characterization of advanced liquid dielectrics for high-power high-pressure rep-rate oil switching

Several advanced oils have been identified by the Air Force Research Laboratory, Materials and Manufacturing Directorate, for characterization by MU as pressurized dielectric switching media. The oils tested were Diala AX transformer oil, a hydrogenated 1-decene polyalphaolefin, two hydrogenated 1-decene/1-dodecene polyalphaolefin mixtures, a silahydrocarbon, an ester, an alkylbenzene, and a silicone oil. Experiments on the pulsed voltage breakdown were performed to characterize the breakdown behavior of these dielectrics. A pulse generator, specifically designed for the characterization of oil breakdown strength, was implemented for this study. The pulse generator produced a voltage rise of 250-kV/¿s across a 1.85-mm electrode gap. Thirty high voltage pulses were applied to each of the eight oils at five oil pressures, totaling 150 breakdown measurements per oil. The oils were pressurized to 3.45, 5.17, 6.89, 8.62, and 10.34-MPa during testing. Before each test cycle, the oil was sparged with dry nitrogen to reduce the water content, and the switch electrodes were polished. Between each of the 150 tests the oil was filtered to remove generated carbon.