Insulator (electricity)

About: Insulator (electricity) is a research topic. Over the lifetime, 15941 publications have been published within this topic receiving 108950 citations. The topic is also known as: electrical insulator.

High breakdown voltage AlGaN/GaN MIS–HEMT with SiN and TiO2 gate insulator

Abstract: We report the fabrication of AlGaN/GaN high electron mobility transistor (HEMT) with high breakdown voltage by employing the metal-insulator-semiconductor (MIS) gate structure. SiO2, SiN, and TiO2 were used for the insulators. The gate leak current was significantly reduced by employing the MIS structure, and the breakdown voltage characteristics were improved. The breakdown voltage of the MIS–HEMTs increased non-linearly with the increase of gate-drain length Lgd. The TiO2 insulator exhibited highest breakdown voltage of 2 kV with the on-resistance of 15.6 mΩ cm2 for Lgd = 28 μm. On the other hand, the breakdown voltage and on-resistance for SiN MIS–HEMT were found to be 1.7 kV and 6.9 mΩ cm2, respectively. We demonstrated that AlGaN/GaN MIS–HEMTs are promising not only for high speed applications but also for high power switching applications.

Pulsed metallic-plasma generators

Abstract: A pulsed metallic-plasma generator is described which utilizes a vacuum arc as the plasma source. The arc is initiated on the surface of a consumable cathode which can be any electrically conductive material. Ignition is accomplished by using a current pulse to vaporize a portion of a conductive film on the surface of an insulator separating the cathode from the ignition electrode. The film is regenerated during the ensuing arc. Over 108ignition cycles have been accomplished by using four 0.125-in (0.318-cm) diameter zinc cathodes operating in parallel and high-density aluminum-oxide insulators. A plasma consisting of cathode material is emitted at the rate of about 10-7kg for each coulomb of charge emitted. The plasma is ejected in the form of a high-velocity highly directional conical plume through a ring-shaped anode. One or more magnetic field coils may be used to control the impedance and the direction of the plume. The normal pulsed operating parameters for the generator are a few hundred volts and a few hundred amperes with pulsewidths ranging from 50 to 500 µs and repetition frequencies up to 300 pulses per second (pps). Among the applications being investigated for the generator are metal deposition, vacuum pumping, electric propulsion, and high-power dc arc interruption.

Design optimization of high breakdown voltage AlGaN-GaN power HEMT on an insulating substrate for R/sub ON/A-V/sub B/ tradeoff characteristics

Abstract: High breakdown voltage AlGaN-GaN power high-electron mobility transistors (HEMTs) on an insulating substrate were designed for the power electronics application. The field plate structure was employed for high breakdown voltage. The field plate length, the insulator thickness and AlGaN layer doping concentration were design parameters for the breakdown voltage. The optimization of the contact length and contact resistivity reduction were effective to reduce the specific on-resistance. The tradeoff characteristics between the on-resistance and the breakdown voltage can be improved by the optimization of the above design parameters, and the on-resistance can be estimated to be about 0.6 m/spl Omega//spl middot/cm/sup 2/ for the breakdown voltage of 600 V. This on-resistance is almost the same as that for the device on a conductive substrate.

Mapping Relation of Leakage Currents of Polluted Insulators and Discharge Arc Area

Abstract: A fundamental parameter of polluted insulator online monitoring is the leakage current, which has already been shown to be well related with the pollution discharge of insulators. In this paper, in an effort to quantitatively reflect the discharge intensity as well as the discharge status by the leakage current, we carried out an experimental study on artificial pollution discharge of insulators. A high-speed photographic apparatus was utilized to capture the entire process of local arcs on porcelain insulator surface, including the arc generation, the arc development and the flashover, for which the associated leakage current of insulators was synchronously digitized. A comparative analysis of the relation between the two-dimensional discharge image and the leakage current waveform in the process of arc generation and development shows that, if the arc area on insulator surface is relatively small and the leakage current passes through zero, the arc might completely extinct, whereas this phenomena will not occur if the arc area is larger. In addition, the amplitude of discharge arc area is found to be roughly proportional to the square of leakage current over the range of leakage current amplitude from 0 to 150 mA. Our results can provide an important guidance for judgment of the discharge status and the discharge intensity on insulator surfaces using the leakage current of insulators.

Insulator surface charge accumulation under impulse voltage

Abstract: The surface charge distribution under impulse voltage is measured using a static capacitance probe. A probe with very small charge leakage is designed. The condition of surface charge accumulation under impulse voltage is analyzed, and it is concluded that micro discharges in the gas near the insulator surface such as the corona caused by free and fixed metal particles is usually a prerequisite condition. The dynamic equation describing the relationship between surface charge density and the applied voltage is established, and the process of surface charge accumulation under impulse voltage is analyzed. Theoretical analysis and experimental results show that the decrease of wave front time of the impulse voltage can result in an increase of surface charge accumulation. A GIS spacer is used to investigate the influence of charge accumulation on the flashover characteristics. It is shown that the 50% impulse flashover voltage can be reduced by 23.4%, and the lower limit of the V-t characteristics can be lowered drastically if the polarity of the surface charge is opposite to that of the applied voltage.