High voltage breakdown (HV
bd) tests were performed to investigate electrical properties of high temperature MgO–ZrO
2 insulation coatings on long-length stainless steel (SS) tapes under various ...pressures at room temperature (298
K) and liquid nitrogen temperature (77
K) for applications of HTS/LTS coils and magnets. After solutions were prepared from Mg and Zr based precursors, solvent and chelating agent, the coating were fabricated on SS substrates using reel-to-reel sol–gel technique. Coating thicknesses for 4, 8, and 9 dippings were about 7, 12, and 13
μm, respectively, and thickness of epoxy-impregnated samples (stycast 2850 FT/24 LV) were measured to be 32
μm. The pressure from 0
GPa to 0.54
GPa was applied on to test couples, the stycast thicknesses between the layers were varied 32–20
μm. Thickness of the coatings and epoxy-impregnated using stycast were determined by using environmental scanning electron microscopy (ESEM). The resistance, capacitance, and HV
bd of the samples were measured by using standard machines HP 439 a high resistance meter, 161 analog digital capacitance meter and model 200–02R high voltage power supply, respectively. Electric strength and dielectric constant were calculated at 298 and 77
K under various pressures. The high HV
bd, and electric strength values of the samples were 2.84
kV and 45.91
kV/mm, respectively. ESEM observation revealed that arcing spots in the insulation coatings become larger and deeper for higher HV
bd’s.
In this paper, the effect of insulator geometry and shield electrode design for a practical 270-degree bent, high power (60kV, 60kW) indirectly heated cathode-based electron gun has been ...investigated. This will ensure improved electron gun performance by reducing high voltage breakdown of electron gun insulators in vacuum. For this purpose, different insulator geometries: 1) Cylindrical 2) Positive Angled 3) Negative Angled and different metal shield electrode designs: 1) Cylindrical Ring 2) Conical Frustum and their combination have been modelled and simulated. This has been done for both the gun insulators: one connected between the ground plate and filament holder assembly (60kV insulator) and other connected between filament beam former and grid cup (1.5kV insulator). To achieve this, 3-D electrostatic gun simulations have been performed by using CST Studio v. 2020. Percentage reduction in the electric field strength at the triple junctions has been evaluated. It was found out that negative angled insulator geometry offered better high voltage performance as compared to positive angled geometry. Comparing all, conical frustum shield electrode design was found out to be the most optimum design.
The electrical breakdown failure of insulated gate bipolar transistor(IGBT) is one of the common failure mechanisms. Because of the existence of stray inductance distributed inside the circuit and ...device, excessive voltage spike occurs during the turnoff transient, which leads to overvoltage breakdown. Based on the adiabatic process analysis of IGBT electric breakdown, the failure mechanism of IGBT electric breakdown is obtained. Because the IGBT module is composed of IGBT chip and anti-parallel diode, it is difficult to judge the fault location only by the failure waveform. Therefore, this paper analyzes the failure mode of IGBT chip and anti-parallel diode by opening the package observation and real-time observation by infrared thermal imager, which shows that the chip has stronger ability to withstand electric breakdown than diode and the failure location is smaller.
Developments in deep-sea technologies has led to pressure tolerant electrical and electronic systems. These systems do not use pressure resistant enclosures, but instead rely on the encapsulating ...material to transfer the forces to the embedded components and to provide electrical insulation and protection against water and corrosion. When designing high voltage, high power electronic systems on printed circuit boards (PCBs), the choice of encapsulating material and the integrity of the interfacial boundaries are critical to ensure adequate insulation. In this study, the effect of water ingress on the high voltage breakdown behaviour between two tracks on an encapsulated PCB is investigated. A group of PCBs, with different gaps between their conductive tracks, are encapsulated in an RTV-silicone gel and then immersed in de-ionized-and sea-water respectively to study its breakdown voltage and discharge characteristics over time. Prolonged immersion in deionised water shows a reduction in the breakdown strength between the tracks as well as anomalous breakdown on the rear surface of the PCBs whereas the breakdown behaviour did not change significantly over the evaluation period for the sample immersed in seawater. These results may have been caused by weak bonding between surfaces and the deposition of salts in the outer layer of the test specimens.
The sol-gel MgO-ZrO 2 electrical insulations were coated on Stainless-Steel-304 (SS) tapes by reel-to-reel process for investigation of electrical properties under various pressure at room ...temperature (298 K) and liquid nitrogen temperature (77 K) for HTS/LTS high field insert coil. Solutions consist of Mg and Zr based precursors, solvent and chelating agent. The electrical insulation was made on long-length SS substrate. Insulation thickness for 4, 8, and 9 dippings were determined 7, 12, and 13 mum, respectively. Three different types of stycast, 2850 FT/24 LV Black and Blue, and White Buecher Epoxide Resin were studied. Stycast thicknesses were varied from 33-20 mum, when the pressure was applied from 0 to 0.54 GPa. The thicknesses of high temperature insulation coatings and epoxsies were measured by using Environmental Scanning Electron Microscope (ESEM). Resistance, capacitance and High Voltage Breakdown (HV bd ) of the samples were measured by using standard machines Model 6517A Electrometer/High Resistance Meter, 161 analog digital capacitance meter and Model 200-02R High Voltage Power Supply, respectively. The results were presented graphically.
Cellulosic fibre composites from agriculture waste product bast fibre such Empty Fruit Bunch (EFB) oil palm has lower cost than normal softwood fibre and they are great alternative to be considered ...in insulation papermaking. For this purpose, EFB fibre, kenaf fibre and their blend were used to fabricate electrical presspaper samples through a laboratory papermaking process. The study of physical, mechanical and electrical properties such as cellulosic structure, tensile strength, AC voltage breakdown and lightning impulse breakdown strength were conducted according to the standard testing method of insulation IEC60243-1:2013. From this research, the physical structure, mechanical and electrical behaviour of mixed EFB and kenaf fibre insulation paper are comparable to Kraft paper and qualified the basic criterion to be an electrical insulation paper as required by IEC60641-2 standard. The purposes of this insulation paper produced is to be use in electrical transformers, therefore the same test should be repeated to the insulation paper that have undergone aging process at normal and accelerated operating temperatures.
With the development of VSC-HVDC technology, the performance and application technology of bypass thyristors are constantly updated and improved. This paper studies a power electronic device that can ...effectively protect the VSC-HVDC system-sacrificial bypass thyristor, analyzes application methods and test results of gate current injection sacrificial thyristor and voltage breakdown sacrificial thyristor in the VSC-HVDC system. Through research, it is pointed out that the gate current injection sacrificial thyristor needs to add energy storage power source and requires a certain time for heat accumulation, which is currently less practical. The voltage breakdown sacrificial thyristor not only has the functions of forward conduction and reverse blocking, but also has the characteristics of reverse precise breakdown and great rupture resilience. The voltage breakdown sacrificial thyristor can realize comprehensive protection of MMC submodules, which has already been implemented in Rudong Project, and the prospect of subsequent application promotion is broad.
A high voltage (up to 80 kV for 20 ms and 110 kV for 10 ms) resonant RF probe operating at 52 MHz is used to study the influence of surface effects and plasma on the operation of high voltage ion ...cyclotron RF antennas for nuclear fusion devices with magnetic confinement.
From the measured DC charging characteristic of the blocking capacitor, the field emission currents are derived. The measurements are performed both with and without plasma at He pressure p⩽0.1 Pa, lower than the threshold pressure for ignition of a high voltage RF glow discharge in the system. Effects of conditioning and presence of plasma on the field emission properties (effective emission area ARF and amplification factor βRF) are studied.
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