Showing papers on "Liquid dielectric published in 1972"

Dielectric liquid-immersed corona generator

Abstract: A plurality of air-tight corona generating cells of a corona generator are supported in a liquid-tight housing where they are immersed in a dielectric liquid such as transformer oil for preventing arcing between the edges of the two electrodes of each corona generating cell. The dielectric liquid is in heat exchange relationship with the external surface of each electrode and is circulated between a cooler and the housing for cooling the electrodes. A center support disc located between the electrodes of a cell unexpectedly increases the ozone yield.

An electrohydrodynamic heat pipe.

Abstract: Dielectric liquid for transfer of heat provides liquid flow from the condenser section to the evaporator section in conventional heat pipes. Working fluid is guided or pumped by an array of wire electrodes connected to a high-voltage source.

Electric Field Distortions Produced by Solid Dielectric Spacers Separating Uniform Field Electrodes in Nitrobenzene

Abstract: Whenever a liquid dielectric is used as an insulant in an electrical apparatus, it is necessary to provide an insulating mechanical support to hold the conducting members at the required spacing. The space between the conductors is therefore bridged at some point by a solid dielectric. It is found in practice that the solid surface bridging the conductors is a weak point electrically. It is commonly assumed that the electric field at a point on the interface is in some manner made greater than the breakdown field of the liquid and then the surface flashover is initiated by a discharge in the high field region. In order to understand the reasons for the lowered dielectric strength it is desirable to know how the solid spacer changes the field distribution between the electrodes, and the dependence of this change on the dielectric properties of the solid and upon time. Probes have been used to map the field within a dielectric liquid1 but distortion of the field by the probe is possible and time variations are difficult to observe, therefore an alternative means of field measurement was sought. The Kerr effect2 has been used to measure electric fields in situations where there is little or no distortion3 and has proved to be a reliable, precise, instrumental technique. The work reported here is a study of field distortions produced by solid dielectric spacers in pure nitrobenzene where the field is measured by the Kerr electrooptic effect.

Temperature sensitive fiber-optic devices

Abstract: An optical fiber with a quartz cladding and a liquid core is used to create an aperture coupler and a low loss small radius bend light guide by controlling the temperature of the fiber. Also, a directional coupler is formed by placing two light carrying quartz rods in a dielectric liquid and controlling the temperature of the liquid and rods.

Interfacial parametric electrohydrodynamics of insulating dielectric liquids.

Abstract: When a high‐intensity electric field with a strong gradient, periodic in time, is imposed tangentially at the interface of an insulating dielectric fluid, parametric surface instability may result. Under typical conditions this instability grows to a certain amplitude, where nonlinear effects become dominant, resulting in a steady‐state standing‐wave pattern. In the linear small‐amplitude limit, the surface dynamics are described by the Mathieu equation. The wavelength observed in the nonlinear amplitude‐limited state is successfully correlated with the linear theory by determining the ``most unstable wavelength'', that is, the wavelength with the maximum growth rate for given conditions of applied electric field strength and frequency.

Solid insulation for electrical apparatus

Abstract: An improved thermally stable polymeric insulation for use in electrical apparatus and particularly in transformers operated in the presence of transformer oil is a substitute for the conventional cellulosic pressboard, which improved insulation consists of an isotactic polymeric hydrocarbon resin in at least partially crystalline form and cross-linked, 1,2-butadienes and copolymers having a low dielectric constant substantially matching that of the liquid dielectric and having relatively low swelling characteristics when immersed in hot liquid petroleum oil dielectric over an extended period of time.

Machining of workpieces by electro-erosion

Abstract: The energizing circuit of an electro-erosion system, connected across an electrode and a workpiece to be machined, comprises a source of alternating current with an operating frequency of up to 5,000 Hz from which an unbroken succession of voltage pulses is obtained by means of a full-wave raw-rectification circuit. A reactance common to both branches of that circuit, such as an inductance effectively in series therewith, maintains a residual potential difference across the erosion gap as the driving voltage of the source goes to zero, resulting in continuing ionization of a substantially stationary dielectric liquid in the gap to increase the service life of the electrode by limiting the amplitude of the current pulses.

Capacitor with non-halogenated impregnant

Abstract: Electrical capacitors are impregnated with liquid dielectric compositions comprising mixtures of diaryl sulfones and halogenfree aromatic organic compounds.

A statistical analysis of the light pulses emitted before electrical breakdown of a liquid dielectric

Abstract: The light pulses emitted before the electrical breakdown of a liquid dielectric have been detected with a photomultiplier and their characteristic shapes recorded. The times to the first recorded light pulses have been statistically analysed to relate the hitherto theoretically derived statistical and formative breakdown times to actual measurements of prebreakdown phenomena.

Experimental consequences of the EHD stability criterion for dielectric liquids

Abstract: The electrohydrodynamic stability theory of Atten and Moreau yields precise criteria for the onset of cellular motion in a dielectric liquid subjected to uniform unipolar charge injection; but these are not in terms of convenient experimental variables. An on-line computer program to give instantaneous evaluation of experimental conditions is described. It has been used to produce curves which enable the consequences of the theory to be discussed with respect to a typical nonpolar liquid. The results show that measurements made in the linear regime, with the techniques of uniform injection available at present, are free from errors of an electrohydrodynamic origin.

Corona discharge device for removing dielectric liquid

Abstract: A device for removing dielectric liquid from a holder member for a photosensitive medium or the like used in an electrophotographic copying machine includes a corona discharging electrode, a shield member substantially surrounding the corona discharging electrode in electrically isolated relationship therewith and having at least a discharge opening, corona discharge converging means provided adjacent to the discharge opening of the shield member, and a power source from which a voltage is applied to the corona discharge electrode.

A system for imparting movement to an ionizable dielectric fluid medium

Abstract: 1,274,875. Loudspeakers. GUIDANCE TECHNOLOGY Inc. 21 May, 1969- No. 25793/69. Heading H4J. [Also in Divisions H1 and H2] A system for importing movement to an ionizable dielectric fluid medium comprises a pair of spaced electrodes with a D.C. source connected across them and a control electrode located between them, the electrodes being immersed in the fluid and constructed so that the fluid can flow through them. In the embodiment shown in Fig. 1, the rate of flow of an ionizable, dielectric fluid produced by the application of a high D.C. voltage to electrodes 11, 13 is controlled by varying the electrostatic potential of the control electrode 12. The electrode 11 is in the form of a wire grid and electrode 13 comprises a set of parallel plates the combined surface area of which is greater than that of electrode 11. The control electrode 12 also comprises a wire grid having a surface area between those of electrodes 11, 13. The emissivity of the electrodes 11, 13 may be improved by coating them e.g. with caesium, barium chloride, thorium oxide or radioactive materials. Alternatively the electrodes may be heated. For example, electrode 11 may be heated through a step-down transformer 19 and the plates 13a of electrode 11 may incorporate heating elements connected to a suitable power supply. The D.C. potential applied to the control electrode may be modulated by an A.C. signal so that pressure waves are produced in the dielectric fluid. The signal may be applied through a transformer (23), Fig. 4 (not, shown), in series with electrode 12 or through a, single stage pre-amplifier (25), Fig. 5 (not shown). In these cases the devices may function as electro-acoustic transducers. Fig. 6 shows a loudspeaker utilizing a pair of devices according to the invention in push-pull. A common anode electrode 11 is located between a pair of cathode electrodes 13 and has a pair of control electrodes 12 disposed on opposite sides thereof to which the modulating signal is applied either through a transformer 33 or through a pre-amplifier stage comprising a pair of triodes in push-pull, Fig. 6 (not shown).

Techniques used to photograph the breakdown of a dielectric liquid with picosecond time resolution

Abstract: This paper describes the techniques that have been developed in attempts to photograph in detail the events occurring during the electrical breakdown of an insulating liquid. As the breakdown occurs at random times, it has been necessary to develop a means of synchronizing the recording system with this breakdown. The techniques discussed make it possible to photograph the discharge in the streak mode with a time resolution of only a few picoseconds.

Voltage to hydraulic pressure drop transducer - uses electrostatic field to turn fluid flow from laminar to turbulent

Abstract: The transducer converts a d.c. voltage into a variation in hydraulic resistance. A dielectric fluid is pumped through an annular channel between a pipe which acts as an outer electrode and a rod which acts as an inner electrode. The ends of the rod are rounded, and when the applied voltage is zero, the liquid flow is laminar. The rod may be supported by insulating spiders at its ends and has longitudinal wires of dielectric material lying in grooves in its surface. When a voltage is connected across the two electrodes, an electrostatic field is set up which causes the fluid flow to become turbulent, and the pressure drop at a given flow rate is increased. The pressure drop is measured by manometers.

Circuit-breaker having dielectric liquid under pressure

Abstract: A circuit-breaker includes a fluid-tight cutout chamber in which are disposed a fixed contact as well as a sliding movable contact and which encloses a dielectric in the liquid state kept under pressure. The movable contact is brought and kept selectively against the fixed contact by releasable disconnecting means, in opposition to ever-present elastic disconnecting means tending to separate the two contacts and comprising hydraulic elastic means responding only to the volumetric elasticity of the compressed liquid in the circuit-breaker. The dielectric in the liquid state is preferably a compressible liquid having a compressibility at least ten times greater than that of oil and may be a liquified gas dielectric.

Quantitative measurements of corona on high voltage cables for space and high altitude applications

Abstract: High voltages in space and high altitude airborne equipment require highly reliable interconnections which makes the use of high voltage cables necessary. While it is possible to use sealed pressurized cables, the possibility of a leak means that the cable may pass through critical pressure while energized and failure may result. A flexible solid cable has an inherently higher reliability if the ordinary modes of failure can be eliminated. The most important modes of failure of high voltage cables are catastrophic dielectric breakdown and degradation due to corona discharges. The life of the cable is determined by the rate of corona degradation which is a function of the corona intensity in general, and in particular of the energy density of the corona in the largest voids. These modes of failure assume special significance for cables operating at high altitudes or in space vacuum due to the possibilities of exposing the series airgaps in voids or interfaces to low gas pressure. In accordance with Paschen's law, discharges will occur in these gas layers at much lower voltages and, thus, lead to corona at voltages which are lower than operating values.

Ac conduction in polypropylene-liquid insulating system

Abstract: Much research has been devoted to the study of conduction in polymer and liquid dielectrics, however, little effort was given until the last few years to the study of conduction in the more complex case of a polymer impregnated with a liquid. Recently polymers impregnated with dielectric fluids have gained wide acceptance for use in capacitors and are being considered for use in cables and other high voltage equipment because of their low dielectric loss, high corona start voltage, and high dielectric strength. An understanding of conduction in these impregnated polymers is of importance for the design of high voltage equipment using these materials.

Electrical devices containing dielectric fluid

Abstract: IMPROVED ELECTRICAL DEVICES, SUCH AS TRANSFORMERS AND CAPACITORS, CONTAINING MONOCHLOROALKYLSILOXANES AS DIELECTRIC FLUIDS ARE DISCLOSED.

Electrical Breakdown of Liquid Dielectrics (A Review)

Abstract: : The review is a comparison of different test data on liquid dielectric breakdown. It supports the assertion that only in certain particular cases is the liquid breakdown mechanism similar to the mechanism of gas. This mechanism is largely determined by the physical and chemical nature of the substance and by certain external factors, such as the form and material of the electrodes, the form of the applied voltage, and a few others. From this it follows that no unitary mechanism for the breakdown of liquid dielectrics exists, and therefore one can scarcely look for the creation of a breakdown theory which will be generally valid for all liquid dielectrics, regardless of their physical and chemical nature.

Electrophotographic,contact-printing process employing a dielectric liquid layer

Abstract: A METHOD FOR CONTACTING PRINTING AN ELECTROPHOTOGAPHIC RECORDING ELEMENT IS DISCLOSED WHICH COMPRISES INTERPOSING A LAYER OF A DIELECTRIC LIQUID BETWEEN THE CHARGED PHOTOCONDUCTIVE LAYER OF AN ELECTROPHOTOGRAPHIC MATERIAL AND THE PARTIALLY OPAQUE ORIGINAL TO BE DUPLICATED DURING THE IMAGEWISE EXPOSURE OF THE MATERIAL TO A SUITABLE LIGHT SOURCE.

Electrical apparatus containing dielectric solution

Abstract: An electrical apparatus containing a dielectric solution with good wetting properties is disclosed as well as an electrical capacitor assembly containing dielectric material comprised of a polyolefin impregnated with the dielectric solution. The solution is comprised of a dielectric liquid and a block copolymer additive which is surface-active therein. The block copolymer is comprised of at least two polymerized comonomers, one of which is soluble in the dielectric liquid thereby distributing the block copolymer therein, and the second of which is sufficiently surface-active in the solution to produce a solution having a surface tension less than that of the dielectric liquid alone.

Method for testing electronic circuits using variable liquid dielectric constant testing media

Abstract: The combining of chlorothene with a dmethyl silicone fluid to provide a means and the method of testing frequency tuned electronic circuits, to be packaged in a solid resin, under simulated operating conditions.

Heater-cathode insulation leakage test method and apparatus

Abstract: A high voltage, short duration pulse is applied between the heater and cathode of an electron tube to cause an electrical breakdown of dielectric material disposed between the heater and cathode when the dielectric material is defective. After the high voltage pulse, a second voltage having a value less than the peak value of the high voltage pulse is applied between the heater and cathode to provide a sustaining current through the dielectric material when, and only when, a dielectric breakdown has occurred. Current measuring means are disposed between the lower voltage source and either the heater or cathode of the tube to measure the leakage current, if any, that is present during the application of the lower sustaining voltage.

Corona inception voltage in statorettes with various gas-solid dielectric systems

Abstract: Corona inception voltage was calculated and measured for three statorettes in several gases and gas mixtures at pressures from 50.8 to 1270 torr. In helium the corona inception voltage was lowest, and in air it was highest. In argon and mixtures of helium and xenon the corona inception voltage was between that of air and helium. Correlation between experimental and calculated data was good.

Di-n-substituted amide impregnants for electrical capacitors

Abstract: Di-N-substituted amides are advantageously used for dielectric oil applications. The appropriate substitution provides the amides with the required physical and electrical characteristics necessary for use as a dielectric liquid in AC and energy storage capacitors.

The effects of hydrostatic pressure and temperature on the electroluminescence in dielectric liquids

Abstract: There is still no one unified theory which is capable of explaining the following four high-field phenomena beyond doubt: (i) the breakdown strengths of dielectric liquid, gassed or degassed, increase with increasing hydrostatic pressure for pressures between 1 and 20 atmospheres1 and such a pressure dependence diminishes with decreasing duration of the applied field;2 (ii) the conduction currents are independent of hydrostatic pressure up to a guage pressure of 150 lbs/in2 for field strengths up to 90% of the normal breakdown stress but the pressure suppresses the current burst;3 (ii) the electron multiplication due to impact ionization does not take place in n-hexane at field strengths up to 1.2 MV/cm;4 and (iii) the threshold field for the onset of light emission in n-hexane is less than 90% of the normal breakdown stress and the light always commences in the cathode region regardless of the geometry of electrode systems used. 5 In the following we present some new results of prebreakdown electroluminescent phenomena which may have an important bearing on the mechanisms responsible for electric breakdown in liquids.

Advanced Application Report High Voltage XLPE Insulated Power Cable with Semi-Conducting Organic Liquid

Abstract: In our previous paper*1 we reported our fundamental study and, to some extent, application to cables of the semiconductive organic liquid which, when mixed in cross- linked polyethylene insulation for cable, deposits on the surfaces of voids in the insulation or between the insulation and the semiconductive layer with the lapse of time and brings about a remarkable reduction in surface restivity there, thus weakening the electric field within voids and eliminating partial discharges. Furthermore, the voltage- time characteristic curve of the cable with such insulation is more horizontal as compared with that of conventional crosslinked polyethylene insulated cable. We have since continued our study on such semiconductive organic liquid inthe process of its application to cable insulationandfound many phenomena. According to our findings, the breakdown voltage is less affected adversely by defects in the insulation and therefore is stable with very little deviation. The cable insulation containing the semiconductive organic liquid has a higher impules breakdown voltage and is free from breakdown at low voltages.