Showing papers on "Liquid dielectric published in 1982"

Conference on Electrical Insulation and Dielectric Phenomena

Abstract: Whilst the discovery and development of manmade polymer materials dates from the pioneering works of Goodyear (vulcanized rubber) and Hyatt (celluloid plastics) in the mid-nienteenth century, and to Baekeland (Phenol-formaldehyde resins) at the beginning of this century, the remarkable growth of the synthetic fiber, rubber and plastics industries followed the preparative achievements of the I.C.I. group in Cheshire (polyethylene), Carothers at Du Pont, Wilmington (linear polyesters and nylons) and the German chemists (polyvinyl halides) in the 1930's, and the U.S. Government Synthetic Rubber Program during World War II. The ability to vary chemical structure and composition (e.g. for copolymers) and physical structure (by fillers, plasticizers, thermal and mechanical treatments, processing methods) made it possible to create materials which could be tailor-made for a particular application. Thus the industries grew to the dominant positions they hold today.

Chaotic Behavior of Instability Due to Unipolar Ion Injection in a Dielectric Liquid

Abstract: The chaotic regime encountered in electrohydrodynamic instability of an insulating liquid subjected to space-charge-limited unipolar injection has been investigated experimentally. Two types of behavior of the power spectra of the intensity fluctuations have been characterized: an exponential decay obtained when viscous terms are dominant and a power-law decay obtained when inertial terms are dominant. Emphasis is put on the quasiuniversality of these behaviors and this is discussed in relation to the phenomenon of smallscale intermittency.

Apparatus for continually upgrading transformer dielectric liquid

Abstract: Electrical inductive apparatus having a tank, an insulating and cooling liquid in the tank and an electrical winding structure immersed in the liquid, the liquid having a low vapor pressure and containing contaminants derived from various sources within the tank. Filter means associated with the liquid including a liquid recirculating device for degassing, demoisturizing, and filtering insoluble particles out of the liquid, whereby the liquid is decontaminated and upgraded in a continual process.

Liquid filled variable capacitor

Abstract: A liquid filled variable capacitor or PFL which provides variable frequen impedance, and pulse length without changing the capacitor or PFL hardware. The capacitor is constructed from two or more conducting surfaces. A dielectric fluid mixture separates the conductors. A fluid supply system furnishes the dielectric fluid mixture to the conductors and provides for varying of the dielectric constant of the fluid and thus the capacitor operating characteristics, by varying the mixture composition. The fluid supply system has a mixing tank connected to both a supply of high dielectric constant fluid and a supply of low dielectric constant fluid. The high dielectric constant fluid and low dielectric constant fluid are mixed proportionally to obtain a dielectric fluid having the desired dielectric constant. A pump conveys the dielectric fluid between the mixing tank and the conductors while a heat exchanger controls the temperature of the dielectric fluid.

Prebreakdown Phenomena in High-Viscosity Dielectric Liquids

Abstract: The shadowgraphic image reflects only those regions of disturbance occurring in a dielectric liquid, which differ in refractive index from their surroundings. The time required for the onset of a prebreakdown disturbance after the application of a step voltage, and the rate of growth of the disturbance depend strongly on the viscosity (or the temperature) of the liquid. The refractive index is lower inside the disturbance region than outside. The variation of the external current is consistent with the temporal change of the disturbance. It is proposed that the formation of a disturbance region is due to the coulombic repulsion of local homocharges which in turn causes a decrease in local density and hence a decrease in refractive index. At highfields the anode injects holes to form positive ions and the cathode injects electrons, and theelectric conduction is filamentary. The electric breakdown in condensed materials (liquids and solids) involves double injection and the creation of low density regions to enable the charge-carrier multiplication processes to take place. Thus the breakdown strength is governed by the parameters which control the conditions for such prebreakdown phenomena to arise.

Investigation on the Use of Water As a Dielectric Liquid in E.D.M.

Abstract: This paper summarizes the experimental investigations conducted on the Electric Discharge Machining (E.D.M.) where water has been used as dielectric liquid instead of usual hydrocarbon oils. Distilled water, tap water and water with salt and glycerine additives have been used in the presented research. The best machining performances have been obtained when distilled water is used. The experimental results for distilled water are compared with the results obtained for commercial kerosene, which is the most common dielectric liquid for E.D.M. applications.

Supersaturated vapor dielectrics

Abstract: Disclosed is an apparatus which is resistant to electrical breakdown consisting of a chamber containing electrodes separated by dielectric gas supersaturated with the vapor from a dielectric liquid.

EDM using two separate dielectric fluids and a system for maintaining segregation of the fluids

Abstract: In an electric discharge machining method, a workpiece is subjected to an electric discharge machining at a high working speed using water as the dielectric fluid, and after this, the workpiece is finish-machined using oil as the dielectric fluid. An apparatus for carrying out the method has a feeding system for selectively feeding water or oil as the quenched surface of a workpiece is removed by using water as a dielectric fluid in electric discharge machining (EDM) the dielectric fluid to a machining gap between the workpiece and a tool electrode and a returning device for selectively returning the dielectric fluid used in the machining gap to an oil tank or a water tank.

A physical explanation of the effects of electrode area on the breakdown of liquid dielectrics

Abstract: It is well established that the breakdown strength of a dielectric liquid falls as the electrode area or the volume of liquid under stress increases. The usual explanation of this effect is statistical. In this paper, an explanation is offered in terms of the change in the local stored energy. The results of experiments in which the stored energy is changed while the electrode area and test volume are kept constant are presented. The experimental results support the proposed mechanism.

Machining Characteristics of E.D.M. Using Water As a Dielectric Fluid

Abstract: Although it is the general practice to use mineral oil like kerosene as a dielectric fluid medium in EDM, many problems such as inflamability, arcing by decomposed carbon, harmfullness of the vapor, gaseous products and fluid itself to the operator, and etc. are still to be solved. The use of water in lieu of oil seems to be an effective measure to avoid most of the above difficulties. In this paper, some experimental results are described concerning the removal rate, electrode wear and the surface roughness in EDM using water as dielectric fluid. The characteristics of metal removal mechanism in water are also discussed. Machining rate and electrode wear ratio are measured for various pulse duration and pulse peak current. Right from surface roughness to machining rate characteristics in case of water, shows several features comparable to the conventional EDM using oil for the same condition. A lower efficiency of the removal of the molten metal in each discharge is concluded from the above results; and the tendency of producing tall burr at the machined edge gives an explanation for this. The adequacy of substitution of water in place of oil in some cases is concluded.

Flow rate detection device

Abstract: A flow rate detection device is constructed so that electrodes for forming an electric field whose intensity spatially changes along a stream of a dielectric fluid are coaxially arranged, and a current detecting means measures a dielectric polarization current flowing when the dielectric fluid flows between the electrodes which form the electric field. The device can detect even a flow rate having a large change therein, for example, of an intermittently flowing stream, and is suitable as a device for measuring a flow rate of a fuel.

Water decomposition method and device using ionization by collision

Abstract: This invention relates to the decomposition of water into oxygen and hydrogen by the effect of ionization by collision among the water molecules. Water of liquid dielectric characteristics is contained within a solid dielectric container having higher dielectric constant relative to that of the water, the solid dielectric also having thermostability. A high voltage is then applied to the solid dielectric, creating a strong enough electric field, exceeding the covalent bond of the liquid dielectric, to decompose the water, while the solid dielectric container maintains its stability.

Dispersion type electroluminescent element with liquid dielectric and jelling agent

Abstract: A dispersion type electroluminescent element comprising dielectric, which is liquid at -20° to +60° C. and has a dielectric constant of 30-80, a gelling agent, and an electroluminescent phosphor, when used as an electroluminescent layer, has a practical brightness, which is never lowered for a long time, and has less disturbance to the electroluminescent surface.

Process and device for heating a dielectric or nearly dielectric liquid, and use of this device for heating, in particular of a calorific fluid

Abstract: 1. Process for heating a dielectric liquid consisting in immersing at least one bare resistor, to the terminals of which a potential difference is applied, directly in the said liquid contained in an enclosure, characterized in that for heating a liquid with a resistivity higher than 10**8 OMEGA /cm the liquid is conducted along plate-shaped resistors so that the velocity vectors of the general motion of the liquid under natural or forced flow, in the vicinity of the resistor or resistors are tangent or parallel to the faces of the said plates.

Electrical circuit interrupting devices

Abstract: An electrical circuit interrupting device such as a circuit breaker or switch has openable contacts immersed in a first relatively dense liquid, such as a perfluorocarbon, constituting an arc interruption medium and has a second less dense non-flammable dielectric liquid e.g. a halogenated liquid such as perchloroethylene or trichlorobenzene or carbontetrachloride constituting a coolant forming a second phase above the first liquid.

Dielectrophoretic, thermal instability in a spherical shell of fluid

Abstract: This paper is concerned with the dielectrophoretic instability of a spherical shell of fluid. A dielectric fluid, contained in a spherical shell, with rigid boundaries is subjected to a simultaneous radial temperature gradient and radial a.c. electric field. Through the dependence of the dielectric constant on temperature, the fluid experiences a body force somewhat analogous to that of gravity acting on a fluid with density variations. Linear perturbation theory and the assumption of exchange of stabilities lead to an eighth order differential equation in radial dependence of the perturbation temperature. The solution to this equation, satisfying appropriate boundary conditions, yields a critical value of the electrical Rayleigh number and corresponding critical wave number at which convective motion begins. The dependence of each critical number is presented as a function of the gap size and temperature gradient. In the limit of zero shell thickness both the critical Rayleigh number and critica...

Determination of Electric Field Distributions Along Fluid-Solid Dielectric Interfaces Using a Schlieren Technique

Abstract: On the basis of the principle that an applied electric field will cause a change in spatial distribution of the dielectric constant produced by a small applied temperature difference due to the interaction of the gradient of the dielectric constant with the field, the electric field distributions along the interface between a dielectric fluid and a dielectric solid can be measured using a Schlieren technique. Some experimental results for the interfaces between n-hexane and a glass plate surface, and between n-hexane and a semiconducting layer surface obtained with this technique show that the space charge is the dominant factor controlling the field distributions. The other factors, such as the dielectric constants and resistivities of the two materials forming the interface, would play an important role in determining the field distributions if and only if the space charge effect is negligibly small or can be ignored. This technique can be used to study electric field and space charge distributions along fluid-solid dielectric interfaces for practical insulation systems under both steady-state and transient conditions.

Condenser feed-through for high-voltage electrical apparatuses

Abstract: The invention relates to a capacitor feed-through, filled with dielectric fluid (8), in an open air configuration for high-voltage electrical apparatuses, especially for transformers and inductor coils. By means of the invention, a capacitor feed-through is produced, which is filled with dielectric fluid and requires little servicing, whose freedom from icing is ensured even in severe weather conditions, for example at a high wind speed and temperatures below 0 DEG Celsius, especially also close to power station cooling towers. This is achieved in that the dielectric-fluid filled internal space of the feed-through, is connected via inlet and outlet openings (13; 14) in the flange fitting (3) to a circulation system consisting of tubes (24), heating elements (9; 11), a bypass line (22) with a switch-off device (23), and a circulation pump (12).

Calorimetric Measurements of Water Dissolved in Dielectric Fluids

Abstract: In order to investigate how the water dissolved in dielectric fluids at room temprature behaves when subjected to cooling/heating, such dielectric fluids as alkyldiphenylethane and dimethyl silicone liquid in which various amounts of water were dissolved were investigated calorimetrically, using very precise Differential Scanning Calorimetry (DSC). Moreover, the degree of turbidity of the specimens which were cooled or heated at a constant rate in a low temperature bath, was observed visually to detect the appearance and disappearance of coagulation of dissolved water. As a result, it has been found that, whereas the water dissolved in alkyldiphenylethane appears to form an icy state, a coagulated state and a dissolved state at low temperatures, depending on its water contents, that on the other hand the water in dimethyl silicone liquid appears to form a coagulated state and a dissolvedstate, without any indication of formation ofice crystals. The author has succeeded in determining quantitatively the ice crystals produced from the water dissolved in a dielectric fluid at low temperatures using DSC. Thus, it has beenconcluded that this method has proved very useful for investigating the crystallization behavior of dissolved water existing in dielectric fluids at low temperatures.

A system for computer-aided theoretical and experimental analysis of impurity particle motion in dielectric liquids

Abstract: A model of impurity particle motion in a dielectric fluid under the action of an electric field, previously developed by some of the authors, is presented with the improvements suggested by both a larger amount of experimental data and the need of application to practical field configurations. A system for both computer-aided analysis of data obtained from high speed movie and electrical measurements about impurity particle motion and theoretical simulation of the phenomenon is presented, and some obtained results are displayed and discussed.

Method of mixing and atomizing liquid

Abstract: PURPOSE:To obtain the spray of two kinds of liquids uniformly mixed at a desired mixing ratio, by electrostatically bonding the two kinds of liquids having different permittivities by use of the action of corona discharge or electrolysis under the condition that the two kinds of liquids are uniformly dispersed and atomized. CONSTITUTION:A dielectric liquid fed into a central passage 3 in the main body 1 of a spray nozzle is ejected under an ionized condition by applying high voltage to a discharge electrode 6 located inside the passage 3, while another dielectric liquid fed into a passage 4 concentrically formed around the passage 3 is ejected through a porous member 8. The fine particles of the liquid ejected through the passage 4 are charged with electricity by applying high voltage, having the opposite polarity to that of the electrode 6, to an annular discharge electrode 9 surrounding the spray opening of the passage 4 at the top end of the main body 1. Said fine liquid particles are merged into fine liquid particles ejected from the passage 3 by an air current let flow through a passage 11 between the electrode 9 and the main body 1, so that the two kinds of fine particles are electrostatically bonded and electrically neutralized.