Aging Characteristics on.Epoxy Resin Surface Under Repetitive Microsecond Pulses in Air at Atmospheric Pressure

Research on aging characteristics of epoxy resin （EP） under repetitive microsecond pulses is important for the design of insulating materials in high power apparatus. It is because that very fast transient overvoltage always occurs in a power system, which causes flashover and is one of the main factors causing aging effects of EP materials. Therefore, it is essential to obtain a better understanding of the aging effect on an EP surface resulting from flashover. In this work, aging effects on an EP surface were investigated by surface flashover discharge under repetitive microsecond pulses in atmospheric pressure. The investigations of parameters such as the surface micro-morphology and chemical composition of the insulation material under different degrees of aging were conducted with the aid of measurement methods such as atomic force microscopy （AFM）, scanning electron microscopy （SEM）, and X-ray photoelectron spectroscopy （XPS）. Results showed that with the accumulation of aging energy on the material surface, the particles formed on the material surface increased both in number and size, leading to the growth of surface roughness and a reduction in the water contact angle; the surface also became more absorbent. Furthermore, in the aging process, the molecular chains of EP on the surface were broken, resulting in oxidation and carbonisation.

Abnormal Polarity Effects of Streamer Discharge in Propylene Carbonate under Microsecond Pulses

Propylene carbonate （PC） has a great potential to be used as an energy storage medium in the compact pulsed power sources due to its high dielectric constant and large resistivity. We investigate both the positive and negative breakdown characteristics of PC. The streamer patterns are obtained by ultra-high-speed cameras. The experimental results show that the positive breakdown voltage of PC is about 135% higher than the negative one, which is abnormal compared with the common liquid. The shape of the positive streamer is filamentary and branchy, while the negative streamer is tree-like and less branched. According to these experimental results, a charge layer structure model at the interface between the metal electrode and liquid is presented. It is suggested that the abnormal polarity effect basically arises from the electric field strength difference in the interface between both electrodes and PC. What is more, the recombination radiation and photoionization also play an important role in the whole discharge process.

Electrical and aerodynamic characteristics of sliding discharge based on a microsecond pulsed plasma supply

Plasma flow control technology has broad prospects for application.Compared with conventional dielectric barrier discharge plasma actuators(DBD-PA),the sliding discharge plasma actuator(SD-PA)has the advantages of a large discharge area and a deflectable induced jet.To achieve the basic performance requirements of light weight,low cost,and high reliability required for UAV(Unmanned Aerial Vehicle)plasma flight experiments,this work designed a microsecond pulse plasma supply that can be used for sliding discharge plasma actuators.In this study,the topology of the primary circuit of the microsecond pulse supply is determined,the waveform of the output terminal of the microsecond pulse plasma supply is detected using the Simulink simulation platform,and the design of the actuation voltage,the pulse frequency modulation function and the construction of the hardware circuit are achieved.Using electrical diagnosis and flow field analysis,the actuation characteristics and flow characteristics of sliding discharge plasma under microsecond pulse actuation are studied,the optimal electrical actuation parameters and flow field characteristics are described.