Comparitive insulation tests with DC and AC at 50 Hz and 50 kHz

Modern DC/DC-voltage-converters for the generation of high DC voltages make use of the resonance principle applying frequencies in the range of some ten kilohertz. The assessment of the ageing performance of insulating materials supposed to be suitable for this application requires tests with high voltages ranging from DC to AC at low and high frequencies as well as their superposition. Ageing tests of different insulating materials described in this paper have been carried out with the following kinds of test voltages. Low frequency: DC high voltage; AC high voltage at 50 Hz. High frequency: AC high voltage at 50 kHz; AC high voltage at 50 kHz superposed by DC high voltage. The results are summarized in the paper. They reveal remarkable differences based on different frequency relevant ageing mechanisms.