Showing papers on "Insulator (electricity) published in 1972"

Effect of Conducting Particles on AC Corona and Breakdown in Compressed SF6

Abstract: This paper describes studies of the effects of conducting particles on breakdown phenomena in compressed SF6 under alternating voltage conditions. Results with free particles of different shapes and materials are compared with those obtained with fixed particles for both parallel-plane and coaxial electrode geometrics. Calculations of the particle motion and of the energy in microdischarges between particle and electrodes are used to suggest mechanisms by which breakdown is initiated. It is shown that the breakdown voltage, which can be as low as 10% of the uncontaminated value, is markedly dependent on particle shape, size and material, and that the nature of the motion in alternating fields is important in establishing conditions for free- particle-triggered breakdown.

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.

Line protector having arrester and fail-safe circuit bypassing the arrester

Abstract: A line protector has an arrester through which overvoltages on the line of short duration are grounded. The arrester may be of the type having an arc gap sealed within a gas tube. For an overvoltage of longer duration, a pellet is melted causing a spring to close a circuit bypassing the gas tube and provide a direct metallic path from the line to ground. A secondary arc gap between opposed conductors separated by an insulating sleeve has an arc-over voltage that is greater than the normal arc-over voltage of the first-mentioned arc gap and provides a path to ground for short duration overvoltage conditions in the event of failure of the arrester. Excessive current across the secondary arc gap may melt the insulator sleeve and engage the opposed conductors for grounding purposes.

Multilevel conductor structure and method

Abstract: The present invention relates to a multilevel conductor structure and to a method of insulating an upper level of conductors from a lower level of conductors on a silicon substrate of an integrated circuit. An undoped silicon oxide insulator layer and a doped silicon oxide insulator layer are successively placed on the lower level of conductors and the structure is heated to a temperature which is sufficient to cause the doped oxide insulator layer to soften and to flow above the lower conductors to produce tapered steps over the edges of the lower level of conductors. An upper level of conductor is then formed on the tapered doped silicon oxide insulator layer. The undoped silicon oxide insulator layer formed between the doped silicon oxide insulator layer and the lower level of conductors prevents doping atoms of the doped silicon oxide insulator layer from penetrating into source or drain regions of the silicon substrate which are usually in the vicinity of the lower level of conductors to change their conductivity.

Method of connecting a contact pin to laminated bus bars

Abstract: A bus bar of laminar construction useful for power distribution systems and the like is disclosed which features an improved contact pin arrangement for providing input, output, and ground connections to the bus bar, together with an improved method of fabricating the bus bar and installing the contact pins or posts. The bus bar comprises a plurality of metallic conductors in sheet form separated by insulator films in a laminated structure, alternate conductor sheets serving as ground planes with the power signal conductors interleaved between the ground conductors. The conductor sheet - insulator film sandwich is clamped between cover members of phenolic or glass epoxy and the whole is encapsulated in a semi-rigid epoxy which extends between and under the conductor sheets at one end thereof. Finally, a series of holes is drilled through the laminated structure thus formed and particularly through the conductor sheets and semirigid epoxy and metallic pins or posts are inserted under force into these holes to effect a mechanical and electrical connection of high quality with the separate signal conductors and ground conductors for external access to the elements of the bus bar. The post or pin is larger in cross-sectional area than the hole and at least one cross-sectional dimension of the pin through the center of the cross-section is larger than the diameter of the hole. A bead of an epoxy adhesive is placed over the hole prior to pin insertion. Insertion of the pin then carries only so much epoxy therewith as will go into the hole to provide additional adhesion of pin to bus bar as well as hermetic seal.

Electron currents through barriers between two metals

Abstract: The current flow between two (normal) metal electrodes, separated by a vacuum gap or an insulating layer, is considered from a general point of view as a process of electron transits through and over a potential energy barrier. The main results of a unified theory of field and thermionic emission, which takes into account the band structure of the insulator, are discussed. Experiments confirming the theory both for the cases of electron emission in vacuum and in some insulators are also considered. Certain directions of future work on experimental tests of the independent-electron model for the emission process are suggested.

Direct measurement of electric field at line conductors during a.c. corona

Abstract: An electrostatic-fluxmeter probe has been used to obtain a direct measurement of the electric field at a cylindrical conductor during a.c. corona. For conductor diameters of 1.59, 2 and 2.75 cm, the resultant electric field falls below the onset level for both positive and negative corona. For the positive discharge, the field becomes independent of the applied voltage, a maximum fall of 9%, being observed. In contrast, the average field in the negative corona discharge decreases with increasing applied voltage, the effective field being reduced by up to 15% of the onset value. The assumption in many theoretical analyses of the discharge that the surface field remains at the onset value is thus invalid. It is suggested that increased secondary ionisation processes account for the maintenance of corona at reduced field strength. The measurements also fail to support the hypothesis that field enhancement occurs during positive corona owing to a negative-ion sheath. Field enhancement is observed to occur in a.c. corona prior to onset, because of remnant space charge from the preceding half cycle, but the effect is small. The field immediately following negative corona extinction is reduced, but, after positive corona, is enhanced because of electron attachment near the anode surface. The method, suitably modified, would appear to offer a useful means of study of bundle-conductor corona and precipitator assemblies of parallel line conductors.

Flashover across polyethylene and tetrafluoroethylene surfaces in vacuum under direct, alternating and surge voltages of various waveshapes

Abstract: Investigations were made of various factors which affect the flashover values across polyethylene and tetrafluoroethylene surfaces in vacuum. The factors studied included sample conditioning under sustained direct and power frequency voltages, and the effect of surge voltage waveshape. The breakdown values for a given voltage waveshape increased with the time of conditioning up to a maximum value which then remained constant within about 10%. Alternating voltages were found to be more effective in the conditioning process. The average breakdown voltage for each insulator decreased with increasing the surge front duration from 1 μs to about 150 μs and thereafter remained constant.

Corona charging device

Abstract: A negatively biased corona discharge system includes a conductive electrode having a thin inorganic dielectric outer layer bonded thereto which is employed as a corona discharge electrode. The discharge system is utilized for uniformly placing a negative charge on an insulator substrate such as an electrophotographic imaging surface. The coating on the electrode acts to suppress the widely spaced emission nodes common to all negatively biased metal corona discharge electrodes. The coated electrode may, therefore, be placed in close proximity to the substrate which it is charging and operated at low emission densities without sacrificing charge uniformity thereby reducing the power requirement of the corona discharge system.

Radiation hardened field effect transistor

Abstract: In a field effect transistor, including a semiconductor element, a source and drain, a gate and an insulator between the gate and the semiconductor element, the insulator thereof comprises an amorphous insulating semiconductor material instead of a dielectric material for radiation hardening purposes. The amorphous insulating semiconductor material has a high glass transition temperature, a large band gap and substantially no current carrier centers having activation energies substantially less than the band gap, and substantially satisfied chemical bonds. Accordingly, the insulator has high stability and resistivity, substantially no tendency to react or alloy with the semiconductor element and gate, and substantially no deep traps so that charges caused by external radiation are not trapped therein and internal fields due to such charges are substantially immediately neutralized in said insulator.

On the discharge of static electricity from an insulator surface

Abstract: A partly new and sensitive technique is described for measuring the net charge on a small object. The electrostatic energy of a charged circular insulator plate is calculated. The technique is then used for energy measurements on discharges from insulator surfaces. Simultaneously with these measurements the discharges are photographed. A powder technique is also used for studying the surface discharges.

Barrier Energies in MIM Structures from Photoresponse: Effect of Scattering in the Insulating Film

Abstract: Scattering of electrons photoexcited into the insulator conduction band prevents photoresponse from following the Fowler relation in MIM structures. However, barrier energies can be obtained without specific knowledge of the scattering process either by measuring the threshold for photo response directly, or by applying sufficiently large voltages across the insulator.

Signal storage device

Abstract: A solid-state device consisting of an interface between a semiconductor material and an insulator material, such as in a metal-oxide-semiconductor (MOS) sandwich, serves to store electric charge when an electron beam penetrates the insulator material. The stored charge effects the size of a depletion region in the semiconductor material adjacent the interface and, subsequently, when an electron beam penetrates the depletion region and creates electrons in the semiconductor conduction band and corresponding holes in the semiconductor valence band, the built-in field in the depletion region sweeps the electrons and holes in opposite directions causing a substantial transient electron-hole current, which can be registered by an external current detector. Thus, the same area of the insulatorsemiconductor interface (or the MOS sandwich) serves to store an electric charge when conditioned in one manner by an electron beam and produces an output current pulse indicative of the stored charge when conditioned in another manner by an electron beam and the area of the interface which is involved need be no greater than approximately the cross-section area of the electron beam.

Light‐ and Electric‐Field‐Dependent Oscillation of Space‐Charge‐Limited Current in Bi12 GeO20

Abstract: Low‐frequency oscillations which are light and electric‐field dependent have been observed in a positive resistance I‐V characteristic in Bi12GeO20. The photocurrent‐voltage characteristic has been interpreted in terms of space‐charge‐limited injection current theory and indicates that oscillation begins in the shallow‐trapping regime and ceases in the trap‐free insulator regime. Values for some of the material parameters involved have been calculated for the specific photoinjection conditions used.

Electric Potential and Field of Conical Insulators for SF6 Metalclad Switchgear

Abstract: Potential gradient at the surface of the electrode is the most important factor in the breakdown of SF6 gas gaps as has been reported in the previous papers. 1, 2

Heating element support

Abstract: An electric heating element assembly for a moving air system in which the element is composed of a thin strip of apertured, foillike material. According to the invention, the strip is formed with a series of continuous corrugations which establish a wavy pattern. The corrugated foil is immobilized and supported by a plurality of insulators which are connected to a support rod. The entire length of the resistance material between adjacent insulators is formed as a single, continuous, smoothly curved corrugation and the insulators maintain separation of those corrugations to prevent shorting or arcing. Various connecting arrangements are provided between the support rod and each insulator to prevent axial and rotational movement of each insulator relative to the support rod. The entire length of the resistance material between adjacent insulators is formed as a single, continuous, smoothly curved corrugation and the insulators maintain separation of those corrugations to prevent shorting or arcing. Various connecting arrangements are provided between the support rod and each insulator to prevent axial and rotational movement of each insulator relative to the support rod.

Continuous Recording of Outdoor Insulator Surface Conductance

Abstract: Surface conductance of outdoor insulators exposed to pollution and moisture from rain or fog is related to two aspects of insulator application: 1) possibility of insulator flashover and 2) duration and severity of surface arc discharges. This paper will discuss some of the experience with monitoring the surface conductance of porcelain and synthetic insulation under voltage stress and exposed to outdoor weathering in various locations in the U. S. Simple flat surfaces mounted at a 30° angle from the horizontal and some shed-type insulators have been followed in this study. Recordings have been made over periods of several years, comparing results with low and high voltage stress. Results of these outdoor tests are also compared with results of tests of similar surfaces in a synthetic salt-fog chamber.

Arc Driver Operation for Either Efficient Energy Transfer or High-Current Generation

Abstract: An investigation is made to establish predictable electric arcs along triggered paths for research purposes, the intended application being the heating of the driver gas of a 1 MJ electrically driven shock tube. Trigger conductors consisting of wires, open tubes, and tubes pressurized with different gases were investigated either on the axis of the arc chamber or spiraled along the chamber walls. Design criteria are presented for successful arc initiation with reproducible voltage-current characteristics. Results are compared with other facilities and several application areas are discussed.

Device for passing a conductor through the cover of an electrical precipitation apparatus

Abstract: Improved lead-in device passing a conductor through the cover of an electrical precipitation apparatus down to its spray system. The improved device is characterized in that a porous insulator is used as the insulator and a gas-tight insulating cylinder concentrically surrounds the porous insulator. The device is further fitted with a tubular gas inlet opening into the porous insulating cylinder. The upper and lower ends of the insulator and the insulating cylinder, respectively, are connected together by annular metal plates so as to form a space therebetween, and the space is occupied by a sealing gas maintained at a relatively higher pressure than that prevailing inside the electrical precipitation apparatus.

Electrical bus system

Abstract: An Electrical Bus System utilizing insulated conductors which may be readily assembled as desired from standard components to achieve an efficient, low cost installation. The conductors, generally hollow members, are joined by couplings so that any section of conductor may be removed as desired. Straight sections as well as elbows and the like are provided to result in a conductor assembly with a substantially unrestricted passage therethrough so that cool air may be circulated through the conductor. The conductors are assembled into a protective housing and retained therein by molded insulator blocks which are molded with screw sockets therein so as to be retainable in the assembly by self-threading screws. The conductors are provided with an insulating jacket thereon which may be readily locally cut away and then a hole drilled and tapped in the conductor to provide an attachment for a power tap.

Metal-clad three-conductor high-voltage transmission line

Abstract: The three conductors of the high voltage transmission line are arranged in triangular array within the metal-clad casing and are supported at longitudinally spaced apart points. At each support point, three insulator bodies are provided so that each conductor is supported by a single insulator body. Each insulator body surrounds one conductor, at least partially, and is attached at two points of the metal casing which are separated from each other by at least an angle of 90* relative to the periphery of the casing.

The Flashover Voltage of Polymethylmethacrylate in Vacuum under Direct, Alternating, and Surge Voltages of Various Front Durations

Abstract: This paper presents results on flashover voltages across insulation surfaces and on the rate of surface deterioration in a vacuum of 10-5 torr under direct, alternating, and surge voltages of front duration in the range from 1-600 ?s. The insulation material used was polymethylmethacrylate (PMMA) of cylindrical shape fitted between uniform field electrodes. The measurements were carried out on insulator specimens 25 mm in diameter and 5, 10, and 20 mm in length.

Electrical insulator having additional protective insulating portion

Abstract: An electrical insulator having an insulating portion, to which an electrode is applied, whose resistance to leakage currents is greater than the leakage current resistance of the remaining portion of the insulator to prevent the formation of an electrical discharge between the electrode and the remaining portion of the insulator.

Performance of Simple Insulator Shapes under Heavily Contaminated Conditions

Abstract: Flashover voltage, scintillation current, resistance of a number of simple insulator geometries (rods, disks, and cones) have been measured under contaminated conditions. Results have been compared with porcelain suspension insulators. Tests were made in a high-density conducting mist and correlated with the resistivity of the contaminant solution. With such tests it seems possible to optimize insulator geometries. Flashover voltage of about twice that for conventional 6-in-long porcelain suspension insulators has been demonstrated for small-diameter cones on rods. While maintaining the same clearance distance1 for an insulator design, the effectiveness (per unit length of additional creepage distance) decreases with an increase in creepage distance. This is especially true in the vertical orientation. An increase in insulator diameter decreases effectiveness. Small-diameter rods perform well. Current measurements and photographs of scintillation and partial flashovers provide insight into insulator performance. Scintillation and arcing currents may lead to tracking and erosion of plastic insulators. Optimized design can reduce such currents by as much as 20 times.

Effect of band structure on the voltage-current characteristics of metal-insulator-metal tunnel junctions

Abstract: This paper discusses explicitly the effect of non-parabolic E - k relation on the voltage-current characteristics of metal-insulator-metal tunnel junctions. For this purpose, a tractable current-voltage relationship is obtained which is valid for arbitrary band structure and arbitrary barrier shape in the insulator region. It is seen in general that a non-parabolic band structure affects the tunnel current roughly by 2–3 orders of magnitude, and almost invariably (except for the temperature dependence of the tunnel current) provides a better correlation between theory and experiment. Comparison of the band-structure effect with those due to uncertainties in other barrier parameters is also made.

Bonding an insulator to an inorganic member

Abstract: A method for joining an insulator to another member of poor electrical conductivity. The latter member is formed with a metal surface for contact with the insulator in a Mallory type bonding process wherein a potential is applied across the contact surfaces while heating below a molten state. In particular embodiments, the poor electrical conductor is a ferrite sputtered with metal to form the bonding surface and the method is used to manufacture a ferrite magnetic head having pole tips separated by a gap filled with a glass insulator. In other embodiments, a very thin layer of insulator is made more suitable for Mallory type bonding by RF sputtering onto a substrate from a target which is cooled by disposing a heat conductor between the target and the RF electrode. Mallory bonding of the thin insulator layer is enhanced by a reversal of polarity of the applied potential following a decrease in electric current flow.

Electrical insulator having sheds arranged at an angle to its axis

Abstract: The invention describes a shedded insulator for supporting electric conductors particularly the conductors of overhead transmission lines. Instead of making the sheds normal to the axis of the insulator the sheds are arranged at an angle to a plane normal to the axis of the insulator. The sheds may be of the same or different diameters.