Synergistic impact of molecular vibration and charge behavior on enhanced insulation failure in silicone gel under ultra-fast pulsed electric field

Due to the extreme operating conditions of high voltage rising rate, silicone gel materials used in the encapsulation insulation of power electronic devices are prone to insulation failure. In this paper, we proposed a mechanism of insulation degradation under the ultra-fast pulsed electric field by considering the synergistic effect of molecular vibrations and charge behaviors. With the quantum dynamic simulation, it is found that the motion of space charge will induce a strong local vibration of the surrounding molecules to produce phonons in addition to the normal thermal vibration. The steeper the edge time, the higher the amplitude of vibration. With assistance of phonons, a portion of charge is excited to a high-energy state, resulting in an increased probability of induced charge trapping and detrapping. This image well microcosmically confirms the phenomenon of molecular vibration and intensified electric tree formation under ultra-fast pulsed electric fields.