Showing papers on "Insulator (electricity) published in 1993"

Flashover of insulators in vacuum: review of the phenomena and techniques to improved holdoff voltage

Abstract: Reviews surface flashover of insulator, primarily in vacuum, although some comments are made about the effect of ambient gases on surface flashover. It presents theoretical mechanisms of surface flashover and pertinent experimental results. The holdoff voltage of insulators depends upon many insulator parameters, such as material, geometry, surface finish, and attachments to electrodes, but also on the applied voltage waveform (duration, single pulse or repetitive), the process history of the insulator operating environment, and previous applications of voltage. Several suggestions are made regarding choice of the material, geometry, and processing when selecting an insulator for a particular application. Some specific techniques for improving the holdoff voltage of insulators are recommended. >

Dynamic arc modeling of pollution flashover of insulators under DC voltage

Abstract: A dynamic model that computes the flashover voltages of polluted insulators energized with DC voltage is presented. The salient feature of this model is that it takes into account the configuration of the insulator profile at every instant, which plays an important role in the flashover process of the DC polluted insulators. A number of practical insulator geometries have been studied, and the validity of the model is verified by comparing the computed results with the experimental results of previous researchers. >

Thermal conductivity sheet

Abstract: A thermal conductivity sheet is provided which is superior all in heat radiating characteristics (thermal conductivity) in the direction of sheet thickness, close-contact with respect to parts to be cooled, and electrical insulation. In a thermal conductivity sheet 1 in which a plurality of highly thermally conductive insulators 3 are dispersed in a matrix insulator 2, the highly thermally conductive insulators 3 are oriented obliquely or erectly in the direction of thickness of the thermal conductivity sheet 1 such that at least one end faces of the highly thermally conductive insulators 3 are exposed to a surface of the matrix insulator 2. Preferably, a ratio of the total sectional area of the highly thermally conductive insulators 3 to the total surface area of the thermal conductivity sheet 1 is set to be equal to or larger than 1%.

Thermotropic liquid crystal polymer composition and insulator

Abstract: The improved thermotropic LCP composition comprises 10-13 wt. % of a thermotropic liquid crystal polymer resin and 90-87 wt. % of zircon and is useful as an electrical insulator. The composition is a good electrical insulator, permits good heat conduction and experiences small thermal expansion, thus insuring high reliability. The composition may be injection molded to form an electrically insulated housing of a stator for electric machines or appliances that includes a coil and terminals thereof.

A calculation method and some features of transient field under polarity reversal voltage in HVDC insulation

Abstract: Mathematical equations are derived for the transient electric field in insulation media with permittivity and resistivity during boundary excitation due to changing from one steady state to another, such as a polarity reversal voltage imposed on the insulation of HVDC apparatus. The equations are solved by the finite element method, and a program for calculating the transient field is developed. Calculated results of some illustrative examples, including a typical bushing barrier system of power converter transformers, verify the method. Some distinguishing features of the transient field are discussed. >

Capacitive moisture sensor.

Abstract: A capacitive moisture sensor includes insulator means (22); capacitance means including a sensing capacitor having as plurality of spaced capacitive sensor conductors (14) mounted with the insulator means for exposure to the atmosphere; and first (26, 28) and second electrodes (44, 46) mounted with the insulator means remote from the spaced capacitive sensor conductors; means for applying a periodic input current across the first and second electrodes; and means for detecting a change in capacitance between the first and second electrodes indicative of moisture bridging at least two of the capacitive sensor conductors.

Power frequency and impulse field calculation around a HV insulator with uniform or nonuniform surface pollution

Abstract: HV outdoor insulators are always subjected to pollution of different nature and severity and the performance of a HV insulator under polluted conditions is quite different from that under pollution-free conditions. The present paper is concerned with the field distribution around a post-type insulator for different severities of surface pollution. The capacitive-resistive field distribution around the polluted insulator is calculated by a charge simulation method. The field calculations are carried out for power frequency voltage and also for lightning and switching impulse voltages. The effects of uniform or partial surface pollution and the presence of dry bands on the field distribution around a polluted post insulator are presented and discussed in detail. >

Aging and related phenomena in modern electric power systems

Abstract: Recent progress in the research and development of electrical insulation for modern electric power systems is reviewed. Cross-linked polyethylene cables, gas-insulated switchgear, composite insulators and oil-immersed transformers are covered. A number of aging processes are presented and analyzed. Typical aging processes are considered to be due to tree formation, partial discharge, electrochemical processes and thermochemical processes. Almost all causes of aging have been itemized and have been phenomenologically verified. Several other theoretical aspects that need to be clarified are identified. >

The effect of insulator charging on breakdown and conditioning

Abstract: As part of a study on HV design concepts for microwave tubes, a number of different insulator designs have been studied. Analysis of the measured DC current, partial discharge activity and breakdown voltage shows that surface charging of insulators is a key mechanism in the breakdown process and in the conditioning process. Insulator parameters are not only the breakdown voltage, but also the conditioning speed and the sensitivity to gas exposure or charge leakage. In all these respects insulators with a field enhancement at the anode are superior. Field enhancements at the cathode are less harmful if stepped insulator shapes are chosen. Effective conditioning requires at least a limited number of breakdowns. With sufficient conditioning breakdowns, all insulator geometries tested reached a breakdown field exceeding 12 kV/mm. >

Integration of CMOS-electronics and particle detector diodes in high-resistivity silicon-on-insulator wafers

Abstract: A new approach to monolithic pixel detectors, based on silicon on insulator (SOI) wafers with high resistivity substrate, is being pursued by the CERN RD19 collaboration. The fabrication methods and the results of the electrical evaluation of the SOI-MOSFET devices and of the detector structures fabricated in the bulk are reported. The leakage current of the high-resistivity PIN-diodes is kept of the order of 5 to 10 nA/cm/sup 2/. The SOI preparation processes employed-SIMOX (separation by implantation of oxygen) and ZMR (zone melting recrystallization)-produce working electronic circuits, and appear to be compatible with the fabrication of detectors of suitable quality. >

Method of making thin film transistors

Abstract: A method of making thin film transistors such that the first conductive layer of a thin film transistor is formed with an aluminum system metal having a low electric resistance, and another metal capable of anodic oxidation is deposited to prevent the aluminum system metal from producing hillocks. The metal capable of anodic oxidation and part of the aluminum system metal are changed into an insulator by an anodic oxidation treatment. In all, the gate insulator of the thin film transistor comprises three layers of aluminum oxide, an oxide of the metal capable of anodic oxidation, and silicon nitride. The method makes it possible to form the lower-layer wiring and gate electrode having a low electric resistance and a flawless gate insulator having excellent insulative quality.

Current, luminosity, and X-ray emission in the early phase of dielectric surface flashover in vacuum

Abstract: With high-speed electrical and optical diagnostics, an attempt is made to elucidate the physical mechanisms leading to surface flashover. The experimental device uses a cable discharge to study self-breakdown along the surface of an insulator in vacuum. Preflashover current, breakdown voltage, luminosity, and soft X-ray emission are measured in temporal correlation with a resolution of 1 ns. The results show a linearly increasing current in the subampere range, and a corresponding linearly increasing luminosity, before an exponential increase of both signals takes over. The linear phase is accompanied by X-ray emission which ceases at the onset of the exponential phase. The strong influence of externally applied magnetic fields on the linear phase points to the existence of free electrons above the surface during the early phase of flashover. A linear current rise without magnetic field and the formation of a current plateau with an insulating magnetic field indicate a saturation of the current amplification mechanism in the early phase. >

The CRRES IDM spacecraft experiment for insulator discharge pulses

Abstract: The internal discharge monitor (IDM), designed to observe electrical pulses from common electrical insulators in space service, is described. The IDM was flown on the Combined Release and Radiation Effects Satellites (CRRES). The 16 insulator samples included G10 circuit boards, FR4 and PTFE fiberglass circuit boards, FEP Teflon, alumina, and wires with common insulations. The samples were fully enclosed and mutually isolated, and space radiation generated 0.02 cm. >

Emission in the Early Phase of Dielectric Surface Flashover in Vacuum

Abstract: Abstruct-With high-speed electrical and optical diagnostics, an attempt is made to elucidate the physical mechanisms leading to surface flashover. The experimental device uses a cable discharge to study self-breakdown along the surface of an insulator in vacuum. Preflashover current, breakdown voltage, luminosity, and soft X-ray emission are measured in temporal correlation with a resolution of one nanosecond. The results show a linearly increasing current in the sub-ampere range, and a corresponding linearly increasing luminosity, before an exponential increase of both signals takes over. The linear phase is accompanied by Xray emission which ceases at the onset of the exponential phase. The strong influence of externally applied magnetic fields, on the linear phase, points to the existence of free electrons above the surface during the early phase of flashover. A linear current rise without magnetic field, and plateau formation of the current with an insulating magnetic field, indicates a saturation of the current amplification mechanism in the early phase.

Printed antenna with strip and slot radiators

Abstract: A printed antenna comprises a window formed in a grounded conductor provided on one surface of an insulator substrate, a first strip conductor formed in the window, and a second strip conductor provided on the other surface of the insulator substrate.

Novel high voltage vacuum surface flashover insulator technology

Abstract: Electrically stressed insulators in vacuum often fail due to dielectric breakdown in the form of surface flashover which usually occurs at a lower field than bulk breakdown. Surface flashover also appears to be a time independent phenomenon in the range from dc to microsecond (psec) pulse widths. From microsecond *to ;;~os~;;;~c~nsec) pulse widths, the mechan;;: damage change (Ref. 1). microsecond pulse width regime appears to straddle both regimes.

Insulator structure and method of construction

Abstract: A composite link and insulator (10), and method of construction, includes a fiberglass body. The body (20) is formed by coating glass fibers (24, 26) with a liquid resin and winding the fibers around a plurality of tubular fittings or bushings (50, 60, 70) in two layers, a first (24) extending longitudinally of the body and the second (26) transversely and around the first. A polymer shield layer (30) and weathersheds (40) are injection molded over the fiberglass body (20) to create an insulator. The insulator may also be provided with stiffening plastic inserts (80) at either end for increasing strength without adding significantly to the insulator's overall weight.

Influence of insulator contamination by copper evaporation on neutron yield in a low-energy plasma focus

Abstract: Deterioration of neutron yield in a low-energy plasma focus operated by a single 32 mu F, 15 V, (3.6 kJ) capacitor is observed. When the cumulative discharge energy over successive shots across an insulator sleeve approaches 1.6 MJ, the neutron yield from the device starts deteriorating. The insulator sleeve, when examined, is found to have a approximately 3 mu m thick layer of copper deposit. The contaminated sleeve surface appears rough with a grain-type structure. It is therefore concluded that the degradation of neutron yield in the low-energy device occurs due to Cu deposit on the insulator sleeve surface. The situation may improve if low-sputtering-rate conductors are employed for the electrodes of the device.

Voltage programmable links programmed with low current transistors

Abstract: An electrical path can be formed through a transformable insulator between first and second conductors by applying a voltage between such conductors across at least one selected region of the insulator. Much of the current required to complete the link is provided from parasitic capacitance of the writing circuit or from capacitance which is removable from the circuit during normal operations. As a result, small transistors of less than 100 microamps may be used in the writing circuit which applies the programming voltage.

Nonlinear optical device

Abstract: This invention is intended to provide a nonlinear optical device with sufficiently high nonlinearity for efficient wavelength conversion or optical modulation The nonlinear optical device according to this invention comprises a substrate and material layers disposed thereupon, at least a portion of said material layers being alternate insulator layers and semiconductor layers comprising a multi-quantum-well structure, the potential for electrons in said semiconductor layers being asymmetric in the z-direction normal to said substrate A quantum well structure that uses an insulator layer as the barrier layer and a semiconductor layer as the well layer satisfies the requirements of a well depth of 3 eV or more, and of a difference between the minimum energy level (e₁) of the electrons in the conduction band and the maximum energy level (h₁) of the electrons in the valence band of 3 eV or more, whereby the device is transparent for visible light, including second harmonic generated blue light

Superconducting power cable

Abstract: PURPOSE:To provide a superconducting power cable having excellent electric characteristic and thermal mechanical characteristics (flexibility and thermal behavior characteristic) of superconductor. CONSTITUTION:The outside valley part of a central part corrugated cooling medium pipe 1 in which a superconductive medium passes is filled with a conductive valley filter such as a carbon cloth tape 10. A superconductor 12 and an insulator 2 are fitted to the outside thereof.

Radiation-induced voltage on spacecraft internal surfaces

Abstract: The charging of the surfaces of insulators beneath the thermal control blankets on spacecraft has been numerically simulated. Such insulators are found on wiring harnesses, bulkhead feed-throughs, component mounting hardware, tiewraps, thermal sensors, etc. These insulators are shielded from the low-energy space plasma by the grounded solar blankets. It is determined that the surfaces of these insulators rise to many tens of kV in the Earth's electron belts unless sufficient conduction to the spacecraft frame is established. Secondary electron emission is not sufficient to hold the potential to low values. The dependence of charging on insulator thickness, electron energy spectra, and material properties is investigated. This phenomenon is posited as an explanation for the anomalies seen on many spacecraft, and on the CRRES (Combined Release and Radiation Effects Satellite) in particular. >

Moisture measurement gauge for particulates including a transmission line forming part of a resonant circuit

Abstract: A particulate moisture measurement gauge of the type using a resonant electric circuit connected to a diode detector and to an AC signal generator having a frequency near the resonant frequency of the resonant circuit and in which the resonant circuit is electrically coupled to the particulate by a capacitor having the particulate as its dielectric. A probe is formed as a transmission line having a length which is approximately an integral number of one quarter wave lengths long. One end of the transmission line is connected to the circuitry and its opposite, moisture sensing end is immersed in the particulate. Preferably the probe is a rigid, conductive tube with a central rod having a ceramic insulator sealing its moisture sensing end and the circuitry housed in its opposite end.

Polymer concrete electrical insulator and method and apparatus for making

Abstract: An improved electrical insulator for high voltage transmission lines is formed from certain polymer-based concrete compositions An apparatus provides for the molding of the polymer-based mixture to form a highly degassed product The method and apparatus include the ability to combine the constituents of the mixture in a mixer A vacuum is applied to the mixture to degas the mixture A mold is filled with the degassed mixture without introducing air thereinto in the absence of a vacuum The resulting insulator has highly reduced air entrainment

Analytical studies of HV insulators in Saudi Arabia-theoretical aspects

Abstract: Digital computer studies of long, contaminated insulator strings are performed using linear, lumped circuit models. The voltage distribution, currents, phase angle and wattage for each unit on the string are evaluated for practical combinations of uniform and nonuniform distribution of contamination. The variations in performance as a function of stray capacitance and shielding fields are discussed, taking into account a wide range of the pollution index, tower designs varying at different areas, and the environmental conditions of Saudi Arabia, the physics of the evaluation of the voltage distribution and phase angle variations along the insulator string as the surface is changed from clean, to dirty, to contaminated, to polluted are evaluated. The iteration technique is used to explore the effect of nonlinearities in resistance as a function of temperature variations and current limits. Changes in surface resistance due to liberated energy are considered. Studies are performed on a per-unit basis to simplify the adoption of the results to insulator strings used under various conditions. >

Film forming device and film formation

Abstract: PURPOSE:To form a film of good quality with high forming speed, generating no powder by isolating discharging space from the atmosphere by a purge gas and by impressing the second electric field except electromagnetic energy required to keep the discharge between the discharging space and a substrate. CONSTITUTION:Purge gas is blown out from a blow-off port 6 of a purge gas nozzle 3 to the circumference of a substrate 71 to isolate discharging space from the atmosphere. When the AC electric field is impressed from a high frequency power source 51 to a central conductor 1, electric discharge is generated between the central conductor 1 and a cylindrical insulator 2 to form free radicals. The formed free radicals is conveyed by the gas flow in the direction of the substrate 71. Further, solenoids 61 and a permanent magnet 62 are arranged in the outer circumference of the device and on the back side of a substrate holder 70 respectively to pull out the free radicals along the magnetic fluxes in the direction of the substrate 71. A film of good quality with high film forming velocity is formed, generating no powder.

Semiconductor device with conductor clad insulator wiring

Abstract: A semiconductor device which comprises a first insulator, a first conductor disposed on one side near a semiconductor substrate, a second conductor disposed on the opposite side to the substrate forming a tubular member together with the first conductor, and a second insulator surrounding the member. The first insulator is incorporated into the member, and the member and the first insulator constitute an electrical wiring. Since the wiring is composed of the first insulator and the first and second conductors surrounding the first insulator, an electric current flows through the tubular member of the conductors. Therefore, when the device is operated by a high-frequency (for example 80 GHz or more) electric current, apparent increase of the wiring resistance due to the "skin effect" hardly occurs and as a result, reduction of the operating speed can be prevented.

Soldering iron with quick change heater assembly with static dissipative and strain relieving receiver for detachable power cord-heater connections

Abstract: A soldering iron including an insulator, a dissipator, and a hollow, cylindrical handle through which the electrical cable travels, and in which the wires, extending from the electrical cable and connected to the heater unit by individual plug and socket connectors, are able to move freely for making it easier to exchange the heating element but prevent the wires from being accidentally disconnected by pulling on the electrical cord during use. More specifically, a single electrical insulator body, which fits inside the dissipator, receives all of the electrical connectors. Furthermore, the insulator provides unidirectional strain relief by trapping the wires against an inside tapered portion of the dissipator when mounted within the dissipator and releases the wires in the opposite direction simply by the act of being removed from the dissipator. Furthermore, the electrical insulator together with a minimal contact area joining of the dissipator to the handle serves to achieve a cool handpiece while making it possible to limit the use of expensive, high temperature resistant, static dissipative materials to only the dissipator, it being suitable to use high temperature resistant plastics that are not static dissipative for the electrical insulator and low temperature resistant, static dissipative plastic for the handle.

On the formation of negative coronas

Abstract: Negative coronas in nitrogen and in air have been studied. The transition from low-current discharge to strong-current discharge or to the spontaneous and initiated corona pulse regimes has been investigated. Corona pulses were initiated by an excimer laser pulse or by an X-ray pulse. The influence of point electrode surface conditions on the corona pulse formation has also been under observation. In the interpretation of the results the similarity of this transition to the electron emission and consequent breakdown processes in vacuum and other gases is emphasized. This approach permits an explanation of the existence of low-current discharge by Fowler-Nordheim type field emission and the transition to strong-current discharge or corona pulse by a large burst of electrons due to the breakdown of the insulator layer on the electrode surface.