Showing papers on "Liquid dielectric published in 2004"

Integrated circuit devices having dielectric regions protected with multi-layer insulation structures and methods of fabricating same

Abstract: A dielectric region, such as a ferroelectric dielectric region of an integrated circuit capacitor, is protected by a multi-layer insulation structure including a first relatively thin insulation layer, e.g.,. an aluminum oxide or other metal oxide layer, and a second, thicker insulating layer, e.g., a second aluminum oxide or other metal oxide layer. Before formation of the second insulation layer, the first insulation layer and the dielectric preferably annealed, which can increase a remnant polarization of the dielectric region. The first insulation layer can serve as a hydrogen diffusion barrier during formation of the second insulation layer and other overlying structures. In this manner, degradation of the dielectric can be reduced. Devices and fabrication methods are discussed.

Understanding of electrohydrodynamic conduction pumping phenomenon

Abstract: Electrohydrodynamic (EHD) phenomena can be applied to enhance and control mass and heat transfer in both terrestrial and microgravity environments. The emerging EHD conduction pumping technique shows its potential as an active control method of the flow distribution. The EHD conduction pumping is associated with the heterocharge layers of finite thickness in the vicinity of the electrodes, which are based on the process of dissociation of the neutral electrolytic species and recombination of the generated ions. This paper theoretically and experimentally studies the EHD conduction phenomenon in a dielectric liquid. The analytical solutions provide the non-dimensional distributions of electric field and charge density in the vicinity of the electrodes. The characteristic heterocharge layer thickness is also theoretically predicted. Measured pressure heads and current levels are compared with the theoretical results. The EHD conduction pump presented here is capable of electrically driving and controlling the dielectric liquid flow motion in a single-phase loop.

Numerical modeling of electrohydrodynamic (ehd) effect on natural convection in an enclosure

Abstract: Mathematical and numerical modeling of electrohydrodynamic (EHD) enhancement of natural convection in enclosures is carried out. An electric current in dielectric liquid is modeled as a directed motion of electrically charged particles injected into a neutral fluid; the electric body force and Joule heat are added to the momentum and energy equations, respectively. Based on this, numerical studies are carried out for EHD effects on natural convection in enclosures. It is found that, at the same electric field intensity, the EHD enhancement of heat transfer is different for different electric density injections; applying a nonuniform electric field offers better EHD enhancement of heat transfer than applying a uniform electric field.

Vegetable oil based dielectric fluid and methods of using same

Abstract: In one aspect, the present invention provides a dielectric fluid for use in electrical equipment comprising a vegetable oil or vegetable oil blend. In another aspect the invention provides devices for generating and distributing electrical energy that incorporate a dielectric fluid comprising a vegetable oil or vegetable oil blend. Methods of retrofilling electrical equipment with vegetable oil based dielectric fluids also are provided.

Hollow metallic microspheres produced by spark erosion

Abstract: Hollow spherical particles of Ni, CoFe, the ferromagnetic shape memory alloy Ni49Mn30Ga21, and the giant magnetostrictive alloy Fe83Ga17, with diameters up to several tens of microns were produced by spark erosion, using liquid nitrogen as the dielectric liquid. In contrast, the particles were primarily solid when the dielectric liquid was argon. The wall thicknesses of the hollow particles depended on the elemental composition. Different models are considered to account for the formation of the spark-eroded hollow spheres, and some of the potential benefits to be derived from their use are described.

Electrohydrodynamic instability of a rotating layer of a viscoelastic fluid heated from below

Abstract: The stability of a rotating layer of viscoelastic dielectric liquid (Walters’ liquid B’) heated from below is considered. Linear stability theory is used to derive an eigenvalue system of ten orders and exact eigenvalue equation for a neutral instability is obtained. Under somewhat artificial boundary conditions, this equation can be solved exactly to yield the required eigenvalue relationship from which various critical values are determined in detail. Critical Rayleigh heat numbers and wavenumber for the onset of instability are presented graphically as function of the Taylor number for various values of electric Rayleigh number and the elastic parameters.

Dielectric response analysis of real insulation systems

Abstract: Real insulation systems are often heterogeneous and sometimes non-linear. In this paper we discuss the application of dielectric frequency response methods to a number of such practically important systems. Important examples of composite insulation systems are the oil/cellulose insulation of power transformers and the glass-mica-epoxy system of machine insulation. A few examples of non-linear effects and their implication for dielectric response analysis are discussed. These include narrow liquid ducts in transformer insulation, exhibiting a voltage dependent conductivity, polymer cables with water trees exhibiting non-linear behaviour that is the basis for diagnosis. The relation between partial discharges and dielectric response is elucidated and finally the special problems of measuring non-linear field grading material is discussed.

Calculation of electric field and dielectrophoretic force on spherical particles in chain

Abstract: This article presents an analytical method for calculating electric field and dielectrophoretic force in three-dimensional arrangements of spherical particles. The analytical method is based on the method of images that utilizes the multipole re-expansion and the fundamental solutions for several arrangements of a multipole. It is capable of calculating electric field for various conditions of particles and energization. The method needs much less memory than the already proposed one. The calculation results show that force on a dielectric particle chain in a dielectric fluid depends on the number of particles and the chain direction. However, the maximal attractive and repulsive forces reach their saturation values at about 32 and 12 particles, respectively. When the lower particle of a two-particle chain is in contact with a plate electrode, the dielectrophoretic force on the chain becomes higher on the whole, and it always attracts the chain to the electrode. As a result, the particle chain is stabilized for a wider range of the angle between the chain and the applied field. Neglecting the interaction between the electrodes and particles usually gives adequate accuracy in the force calculation, unless the electrodes are not very close to particles.

Fluid circulation in an enclosure generated by electrohydrodynamic conduction phenomenon

Abstract: Fluid circulation/mixing inside an enclosure, nonmechanically, is of significant importance in various applications. This study investigates, theoretically, the circulation of an isothermal dielectric liquid inside an enclosure based on the electrohydrodynamic (EHD) conduction phenomenon. The theoretical model and the numerical solutions are presented in dimensionless forms to illustrate the effects of the controlling parameters on the induced flow. The EHD induced flow, based on the conduction phenomenon, is associated with the process of dissociation of the neutral electrolytic species and recombination of the generated ions. The charges generated by dissociation are redistributed in the region by the applied electric field resulting in heterocharge layers in the immediate vicinity of the electrodes. The Coulombic attraction between a given electrode and the charges within the corresponding heterocharge layer induces a fluid motion near that electrode. With a proper electrode design, a significant flow circulation/mixing can be achieved within an enclosure based on the conduction phenomenon.

Additive for dielectric fluid

Abstract: A dielectric fluid comprising hydrocarbon liquid admixed with an ester-based compound, wherein the ester-based compound is present in an effective amount to impart breakdown inhibiting properties to a paper insulation material when the dielectric fluid is in contact with the paper material.

Gate dielectric breakdown: A focus on ESD protection

Abstract: The challenge of electrostatic discharge (ESD) design is that as scaling continues and operating voltages are lowered, the interface to the outside world and therefore the ESD specifications remain the same. Moreover, as has been highlighted by Duvvury et al. (1996), the first breakdown voltage for snapback of a transistor and the median breakdown voltage of the gate dielectric are converging, making it difficult to ensure the robustness of gate dielectrics in an ESD event. This is particularly true for 1V I/O's in high-speed, high-performance applications, where transistor gates may be directly connected to an external pin or NFETs may be used as compact decoupling capacitors between VDD and VSS, exposing the thin gate dielectric to ESD stress. The ESD protection and interconnects can both contribute voltage drops during an ESD pulse, and their sum must not be higher than the voltage which a dielectric can withstand. Especially alarming is the fact that in the sub-2nm regime, significant statistical variation exists as well as a dependence on area for dielectric breakdown. A vast knowledge base exists for oxide breakdown in the long time-scale, and a few publications have addressed short time-scales. For the most part, studies which described breakdowns at short times have used methodology developed for thicker oxides. In the case of thinner oxides or oxynitrides, the voltage acceleration is no longer 1/E, the dielectric breakdown voltage depends sensitively on the dielectric area, and small differences in thickness have a significant effect on the dielectric breakdown voltage. Therefore, the purpose of this paper is to study the relevance of long time-scale TDDB data in predicting the response to short time-scale ESD events, especially for sub-2nm dielectrics in both NFETS and PFETS.

Drying of transformer insulation using zeolite

Abstract: Power and distribution transformers are some of the most important components in the power network. The presence of moisture in a transformer deteriorates the transformer insulation by decreasing both the electrical and mechanical strength of the solid insulation. It is of great importance to pay attention to the moisture content of composite insulation systems in order to maintain low dielectric loss, high dielectric breakdown strength and low rates of degradation of the insulating system in HV equipment. In this paper, an approach to the said problem is presented. With the application of a synthetic hygroscopic mineral (molecular sieve zeolites) - a revolutionary, environment friendly, multipurpose mineral - a continuous drying process of the transformer oil during operation without the need for service interruption is achieved. A study of the effects of zeolite on the electrical and dielectric behaviour of the insulating liquid of the transformer is included in this paper.

Dielectric fluids and processes for making same

Abstract: Dielectric fluids comprising oil fractions derived from highly paraffinic wax are provided. Further provided are processes for making these dielectric fluids comprising oil fractions derived from highly paraffinic wax. The dielectric fluids are useful as insulating and cooling mediums in new and existing power and distribution electrical apparatus, such as transformers, regulators, circuit breakers, switchgear, underground electrical cables, and attendant equipment.

High-voltage loadbreak switch with enhanced arc suppression

Abstract: A high-voltage loadbreak switch operates submersed in a dielectric fluid and may be configured to switch one or more phases of power using one or more phase switches. Each phase switch may include first and second stationary contacts. The first stationary contact may be connected to a phase of a high-voltage power source. Each phase switch also may include a non-stationary contact. The non-stationary contact may be placed in a first position to electrically couple the first stationary contact to the second stationary contact, and in a second position to decouple the first stationary contact and the second stationary contact. The region of motion of the first non-stationary contact between the first position and the second position includes an arcing region. The high-voltage loadbreak switch uses a fluid circulation mechanism to improve circulation of the dielectric fluid through the arcing region. To suppress arcing between different phases, a non-conductive baffle may separate different phase switches when more than one phase switch is used. A non-conductive baffle also may separate a phase from ground to prevent phase-to-ground arcing.

Parallel cooling of heat source mounted on a heat sink by means of liquid coolant

Abstract: A module includes a cold plate. Solid-state heat sources are thermally mounted on the cold plate in a chamber defined by the cold plate and a lid. Cooling of the heat sources is enhanced by a dielectric liquid within the chamber. The liquid has a boiling point slightly below the temperatures of “hot” spots, to form small bubbles during operation, which enhance convection flow. The liquid may be a mixture of fluorocarbons of different boiling points. The liquid may contain diamond particles.

Simple theoretical estimation of the dielectric strength of gases

Abstract: Understanding how a gas is able to strongly insulate electric devices is certainly of great importance to the electrical engineering community. More precisely, modeling how a dielectric gas stops an electric current requires to understand what makes a gas a good dielectric, or in other words, what makes a gas presenting a high dielectric strength (DS). We show how to easily estimate the DS of a gas by calculating its ability to absorb light.

Heat transfer enhancement in a vertical annulus by electrophoretic forces acting on a dielectric liquid

Abstract: In the presence of a sharp HV electrode, free charge can build up in a single-phase liquid by ion injection at the metal/liquid interface. Electrophoretic forces acting on ions can generate strong convective motion, thus augmenting the heat transfer rate. In a vertical annular duct, uniformly heated on the outer wall, a dielectric liquid is weakly forced to flow upward. Sharp points are added perpendicularly to the inner cylinder and d.c. voltages as high as 22 kV are applied to it, while the outer wall is grounded. Prior to the application of the electric field, a regime of turbulent aided mixed convection is obtained. Being in a region of thermally developing flow, laminarization effects are observed, with local heat transfer coefficients depending non-trivially on longitudinal position, heat flux, and flow rate. With the electric field on, heat transfer turns out to be only weakly influenced by the heat flux and the flow rate. The heat exchange reveals to be highly enhanced by this technique and can be modulated by varying the applied voltage. In all cases, the heat transfer improvement is accompanied by a slight increase in pressure drop through the test section and a negligible Joule heating.

Design, modeling, and verification of a high-pressure liquid dielectric switch for directed energy applications

Abstract: A high-power liquid dielectric switch is being developed to satisfy the requirements for future directed energy applications. A flowing, high-pressure liquid dielectric was chosen for the design of a megavolt class switch operating at 100 pps. This paper reports on the design philosophy, modeling, and experimental results of a full size, single-shot prototype 250-300 kV concept validation test (CVT) switch which can transfer kilojoules per pulse. Analysis of design criteria and scaling for a compact, 100-pps, kilojoule, high-voltage switch are presented. Optimization studies indicate that a pressure range of 6.9-13.8 MPa (1000-2000 psi) appears to be ideally suited to a flowing dielectric rep-rate switch.

Dielectric spectroscopy in time and frequency domain on insulation system of high voltage rotating machines

Abstract: In this work the relations between the time and frequency domain parameters of the dielectric spectroscopy will be discussed. Then the results of dielectric response measurements in time and frequency domain on the insulation systems which are used for high voltage rotating machines will be reported. As test object, actual stator bars were used based on the epoxy VPI technology. The linearity of the insulation system will be checked and the possibility to transfer the measuring data from one domain to another investigated. The paper compares the calculated and measured data and shows the influence of difference parameter.

Optical and electrical investigation of dielectric gel behavior under high electrical field

Abstract: Today, high voltage power semiconductors such as IGBTs, are being developed. As the voltage is increased, local electric fields applied to dielectric materials also increase. Local deterioration of dielectric materials due to partial discharges (PD) may appear and affect the reliability of the whole component. The usual way to detect PD's under ac voltage via electrical measurements is no longer applicable with the pulsed voltage wave shape encountered in power semiconductor applications. This paper presents investigations carried out with optical measurements of PD's in silicone gels, in a typical IGBT module structure. In addition, a very faint light emission is detected below the PD inception voltage. This light can presumably be attributed to an electroluminescence phenomena, such as previously reported in solids or aromatic liquids, and can constitute a non destructive technique that allows to detect the existence of local high fields in the gel.

Antenna for detection of partial discharges in a chamber of an electrical instrument

Abstract: A sensor for picking up partial discharges in an electrical equipment tank filled with a dielectric fluid includes an antenna responsive to the electromagnetic waves generated by such partial discharges. In the sensor, the antenna is formed by two electrodes that are separated from each other by a dielectric resonator. With this arrangement, the sensor has improved sensitivity in the UHF range, while being of dimensions that are considerably smaller than dimensions of a conventional antenna for use in the UHF range.

The moisture effect on dielectric losses of insulating paper

Abstract: The present work concerns the moisture effect on electrical features of insulating paper. Despite the progressive replacement of paper by different materials, several blocks and other insulating screens in transformers contain cellulose which is characterized by a very high hygroscopicity. These cellulosic products appear as a source of moisture. This moisture can lead to a serious damage in the electrical equipments. The aim of this work was also to focus our attention on examination of dielectric losses evolution with the moisture level. For a better understanding of phenomena, we have separately examined the moisture influence on both conductivity and permittivity of the paper.

Characterisation of partial discharge behaviour in liquid nitrogen

Abstract: Interest in superconductors for use in the transmission and distribution of power has grown since the advent of high temperature superconductors (HTS). The benefits of reduced ohmic losses leading to greater operational efficiency appear attractive to power transmission and distribution companies. Potentially this technology will increase power transfer for the same or lower voltage and for the same or smaller physical dimensions. For the successful employment of this technology in the field, power utilities must be convinced of the operational reliability of designs. Many of these designs make use of liquid nitrogen as the system coolant and also as a dielectric fluid. It is therefore vital that liquid nitrogen be well characterised as a dielectric medium. This work describes an experiment to characterise partial discharge behaviour in a nonuniform field geometry. A technique is described which allows synchronised capture and measurement of apparent charge and images of density change streamer activity. A /spl phi/qn analysis of AC results has been completed and characterisation of partial discharge behaviour is presented and discussed.

Three-dimensional electrohydrodynamic temporal instability of a moving dielectric liquid sheet emanated into a gas medium.

Abstract: A linear electrohydrodynamic instability analysis is presented for an inviscid dielectric liquid sheet emanated into an inviscid dielectric gas medium in the presence of a horizontal electric field. The influence of Weber number, gas-to-liquid density ratio, and the applied electric field on the evolution of two-, and three-dimensional disturbances of symmetrical and antisymmetrical types is studied. It is found, for antisymmetrical waves, that two-dimensional disturbances always prevail over three-dimensional disturbances, regardless of Weber number or gas-to-liquid density ratio values, especially for long waves; while for short waves, both two- and three-dimensional disturbances grow at approximately the same rate. It is also found, for symmetrical waves, that two-dimensional disturbances always dominate the instability process at low Weber number, and when the Weber number is large, symmetrical three-dimensional disturbances become more unstable than two-dimensional ones for long waves. The effect of increasing the gas-to-liquid density ratio is to promote the dominance of long three-dimensional symmetrical waves over their two-dimensional counterpart. Finally, the equilibrium Weber number at which the growth rates of two- and three-dimensional modes are equal is discussed for both symmetrical- and antisymmetrical-disturbances cases.

Objective lens driver of optical pickup device using polymer actuator

Abstract: PROBLEM TO BE SOLVED: To realize miniaturization and light weight of an optical pickup device by providing an actuator which is a mechanism using a piezo-electric effect or using a dielectric constant of a dielectric liquid as an objective lens driving mechanism of the optical pickup, and which has a displacement amount equal to a device using an electromagnetic induction phenomenon by a present coil and magnet. SOLUTION: As this objective lens driver of a pickup device, a mechanism using a polymer actuator 1 including an ion-exchange resin 4 and a polarizable organic solvent containing salt or an ionic liquid of a liquid organic compound is adopted between opposing metallic electrodes (2, 2' and 3, 3'). When a predetermined potential difference is applied to the ion-exchange resin 4 through lead wires 5, the polymer actuator is deformed without changing an angle of the optical axis direction. COPYRIGHT: (C)2006,JPO&NCIPI