{'fraction_non_alphanumeric': 0.02077562326869806, 'fraction_numerical': 0.00554016620498615, 'mean_word_length': 5.628440366972477, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Breakdown characteristics of epoxy dielectric film under high frequency square wave voltage

Dielectric breakdown of insulating material by high frequency square wave stress with high dV/dt is new challenging issue in design and application of high power electronic equipment. This paper illustrates and discusses the new breakdown phenomena of epoxy resin film through the frequency dependence of breakdown strength experiments. We constructed a high frequency dielectric breakdown platform, including the high frequency power supply, breakdown signal detection and temperature control and voltage boosting units. It is useful to measure breakdown voltage and current waveforms. Breakdown measurements under various temperatures (20°C-140°C) and frequencies (50 Hz-3 kHz) were carried out. The results indicate that the dielectric breakdown strength (Eb) of epoxy resin film decreases with the increase in frequency of bipolar square voltages. As the temperature increases, the Eb shows an initial increase slightly, and then an obvious reduction. We found that the breakdown occurs at the interface between the electrode and sample with a high probability. Apart from the internal partial discharges (PDs) and high dielectric heating, the space charges, trapping and polarization at the interfaces play important roles under high-frequency stresses. Further researches should focus on the interface effects underlying the breakdown mechanism.