Surface discharge characteristics of silicone gel and DBC under positive repetitive square voltage

Abstract

• The surface discharge characteristics of silicone gel and DBC under positive square wave are different from AC and DC. • Surface discharge on the interface of silicone gel and DBC is a discharge phenomenon coexisting with single pulse and multiple pulses. • The discharge current pulse and displacement current can be separated. • The waveform parameters affect the initial voltage of surface discharge. Silicone gel and direct bonded copper (DBC) as the key components of high voltage power devices are widely used in the insulation packaging of high voltage power devices, respectively. With the increase of the voltage level, the insulation problem between silicone gel and DBC interface limits the development of high voltage power devices under positive square wave voltage. In this paper, an experimental platform under this voltage is established. The surface discharge characteristics of silicone gel and DBC interface are investigated. In order to remove the displacement current interference on the discharge current generated at the rising and falling stage of positive repetitive square voltage, high frequency discharge current and high-frequency magnetic field measured by antennas are simultaneously measured, and the discharge current pulse are extracted based on the one-to-one relationship between high frequency discharge current and high-frequency magnetic field. Furthermore, the specific characteristics of the forward and backward discharge current pulses of interface between silicone gel and DBC, such as amplitude, discharge number and partial discharge repetition rate, under different voltage amplitudes, frequencies and duty cycles are extracted and analyzed. Besides, the influences of frequency and duty cycle of the positive repetitive squarevoltage on the discharge initiation voltages are investigated. Finally, the mechanism of surface discharge between silicone gel and DBC under positive repetitive square wave voltage has been explained.