Influence of Temperature on Surface Discharge Characteristics of PEEK under Positive Repetitive Square Voltage

PEEK (Polyetheretherketone) and N2 are used as the frame material and insulation gas in the packaging of high voltage power electronic devices, respectively. Considering the IGBT device in normal operation, the chip will produce a large amount of Joule heat, which will increase the temperature of the insulation material in sub-modules. However, there has been no investigations on the influence of temperature on the surface discharge characteristics and mechanisms under positive repetitive square voltage (PRSV). In this paper, surface discharge current pulses and optical photos of surface streamer propagation of PEEK in N2 at different temperatures are collected under PRSV. The effects of different temperatures on discharge current pulse, charge quantities of discharge and time delay of discharge are analyzed in detail. Besides, the surface trap parameters at different polarization temperatures are measured by TSDC. The effects of temperature on the effective ionization rate, surface trap depth and densities are revealed. A reasonable model is used to explain the role of surface traps in the streamer propagation along the surface of PEEK. Besides, the time delay theory is introduced to quantitatively analyze the effect of temperature on the time delay of forward discharge (FD) and backward discharge (BD). The influence mechanism of temperature on specific pulse parameters of discharge current, time delay of discharge and charge quantities of discharge are all analyzed on the basis of the trapping and detrapping of surface electrons and ions at different temperatures.