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The use of SF6 in electrical insulation and fast-switching applications cannot be overemphasized. This is due to its excellent dielectric properties and high breakdown voltage, which are especially important for practical applications such as gas-insulated switchgears and pulsed power switches where pressurized SF6 is used. Breakdown in the gas occurs via streamer–leader transition; however, this transition is difficult to quantify numerically at atmospheric pressure because of the electronegativity of the gas. In the present work, streamer discharges in SF6 gas at pressures of 10 and 100 kPa were studied using a plasma fluid model implementation. Analysis of the electric field in the streamer body, streamer velocity, diameter, and the effect of the high electronegativity of the gas on streamer parameters are presented for positive polarity in a point-to-plane geometry. The streamers in SF6 for non-uniform background fields are compared to those in air, which have already been studied extensively in the literature. [ABSTRACT FROM AUTHOR]

The dielectric performance of gases in insulation systems used in high voltage power and pulsed power applications is a subject of intensive theoretical and experimental investigations. Transient breakdown processes in gases stressed with short, high-field impulses, have been studied for many decades. However, there are still significant gaps in the understanding of the main breakdown processes and mechanisms associated with fast transient breakdown processes in gases. This knowledge is important for the optimization of gaseous insulating systems and for the coordination of gaseous insulation in power and pulsed power apparatuses. This information is also required for the development of gas-filled components such as circuit breakers and plasma closing switches. This article is aimed at the analysis of the field-time breakdown characteristics of air, N2, CO2, and SF6, using kinetic and drift-diffusion approaches. The kinetic approach is based upon the avalanche-to-streamer transition criterion, while the fluid drift-diffusion model requires self-consistent numerical solution of the continuity equations for charged species, and the Poisson equation for the electric field. The time to breakdown as a function of the applied field was obtained for all investigated gases. The obtained analytical results agree well with the experimental data reported in the literature, which suggests that both approaches can be used for insulation coordination, and for the development of gas-insulated power and pulsed power systems and components. [ABSTRACT FROM AUTHOR]

The proposed study is about the design and experimental results of a power supply for gate drivers that can sustain 40 kV of insulation voltage with a parasitic capacitance of 4 pF. The first section focuses on insulation materials suitable for medium voltage capabilities and therefore to justify the use of polyesterimide and Teflon polytetrafluoroethylene materials. In a second step, experimental results are provided to guaranty that with a thickness of 1 mm of the insulation material, an insulation voltage of 40 kV is provided. Then, a DC-DC converter based on a series-series topology is designed and lead to a physical prototype of 5 W. The measured parasitic capacitance is 4 pF between the primary and the secondary sides. [ABSTRACT FROM AUTHOR]

For the operation of the semiconductor components in medium voltage converter or multilevel converter applications (where the DC bus voltage up to several ten kilovolts), their gate driver systems require very high galvanic insulation voltage capabilities. Hence, this study details a design methodology to optimise a power supply function for insulated gate bipolar transistor gate drivers with high insulated voltage capabilities. To achieve this, a dc-to-dc full-bridge series-series resonant converter with a high air gap pot core planar transformer is selected. This air gap length and the dielectric material define the high insulation voltage capability. The objective of the study is to optimise the geometric elements of the transformer and its associated electrical components in the proposed converter. Magnetic and electrostatic modellings are provided. Maximise the converter efficiency (ηcon) is the main objective of the proposed optimisation design. Thus, the optimisation results are proposed: the converter efficiency (ηcon) as function of converter output power (Pout). Finally, to validate the authors' proposed methodology, the experimental results are compared with the simulation ones. Then, the results of an improved optimisation design are provided. [ABSTRACT FROM AUTHOR]

Teflon Fluorinated Ethylene Propylene (FEP), used as thermal blankets on satellites, has a specific electrical behavior under space ionizing environment. Charging behaviors of this dielectric material, under electron beam irradiation, is of special interest for future spacecraft needs. Hence, ground experimental parameters have been adjusted in order to distinguish between the different physical mechanisms that steers FEP charging potential. The effect of incident electron spectrum, electric field, and dose rate has been investigated through surface potential measurements during and after the irradiation process. The experimental results especially reveal that charging potential evolution as a function of time is not strongly dependent upon the electron spectrum and the electric field but varies noticeably with dose rate. These results have been analyzed in the light of a physical model that takes into account ionization, trapping/detrapping, and recombination mechanisms for negative and positive charges. [ABSTRACT FROM PUBLISHER]

The high radiation dose received by space used polymers may greatly alter their electric properties. This effect could, for instance, reduce significantly radiation-induced conductivity (RIC) leading to high charging risks that were not predicted from pristine sample. For an optimized qualification and prediction, it is therefore highly important to characterize the charging properties of polymers and their evolution as a function of the received dose. This paper aimed at studying aging of electric properties of four different polymers (Teflon FEP, Kapton, polyepoxy DP 490 adhesive, and silicon QS1123 adhesive) at high dose level (10^5 and 10^6~Gy). We have been able to demonstrate that aging could lead to the reduction of RIC on some polymers (for polyepoxy and silicone adhesives, and FEP) or inversely to the increase of RIC on others (e.g., Kapton). Ionization effect must, however, be considered in the analysis of the results. Relaxation processes could drastically affect the charging profile and macroscopic electric properties. [ABSTRACT FROM PUBLISHER]

Surface and internal charging of dielectric materials is a potential cause of surface discharges and satellite anomalies, due to the fluctuating irradiation levels induced by space environment. Understanding conduction mechanisms and reducing charging levels are therefore important industrial issues for satellite designers and manufacturers. Surface potential measurements under irradiation and after charging (potential decay) are the most significant laboratory tests to qualify and understand the charging and discharging behavior of insulating materials. We present here experimental results obtained using the SIRENE facility at ONERA. Kapton and Teflon FEP films respond differently when subjected to a 20 keV charging electron beam combined with a 400keV ionizing electron beam. The physics underlying these experimental results is discussed. A simple numerical model has been developed. It is shown that different combinations of mobility, trapping and recombination may explain the results on both materials. The complex behavior observed on Teflon FEP may be attributed to the progressive deep trapping of the negative charge, enhancing holes recombination. [ABSTRACT FROM PUBLISHER]