New Publications are available for Electrostatics
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New Publications are available now online for this publication.
Please follow the links to view the publication.Application of wedge functions to 2D magnetostatic problems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0027
In this paper the application of so called wedge functions is presented to solve two-dimensional simple geometries magnetostatic and electrostatic problems, e.g. rectangles of varying aspect ratio and with different values of the magnetic permeability μ. Such wedge solutions contain surface pole distributions of a certain power. The same pole distribution functions have been used in the analysis of conducting and infinite permeability structures. Here we apply such functions in a boundary integral analysis method of finite permeability.Effect of initial accumulated charge on electromagnetic radiation of ESD
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1292
Electromagnetic pulse radiation generated by Electrostatic discharge (ESD) would damage even destroy the normal work of the electronic system. It was usually not considering the impact of the initial accumulated charge in previous studies of ESD electromagnetic radiation. In this paper, on the basis of taking into account the cumulative effect of the initial charge, the electromagnetic radiation of ESD has been analyzed on different distance and the threshold of "near-field" and "far-field" has been calculated on different discharge voltage. The results show that under a certain discharge voltage, the electric field generated by current and current differential item is negligible compared to the accumulation of the initial charge on the electrode, which has a great influence on the "near-field". The initial accumulated charge on the role of the electric field decline rapidly with the increase in distance between the electric field point and the discharge point. The threshold of "near-field" and far-field" increased along with the discharge voltage.Unconditionally stable PSTD method based on weighted Laguerre polynomial expansion
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.1336
A novel unconditionally stable (US) pseudo-spectral time-domain (PSTD) method is implemented by virtue of weighted Laguerre polynomial expansion. This novel algorithm preserves both unconditional stability and less spatial resolution and hence is proved to be an efficient and accurate method. Numerical examples are included to verify the validity of the proposed algorithm.Analysis of the doping fluctuation on robustness of ESD protection devices
http://dl-live.theiet.org/content/conferences/10.1049/ic_20080207
Electrostatic discharge (ESD) is a major threat to the reliability of integrated circuits, where approximately 20% of total integrated circuit (IC) failures are due to ESD. Discharge of charged objects or human discharge into IC chip pins with very high currents (up to 10 A) in a short time period (1 ns to 200 ns) causes serious damage to the very sensitive devices of the circuitry. This may happened during manufacturing, assembly, shipment, and in the field. Since the phenomenon is unavoidable, there is a strong need of developing proper strategies to protect the functional devices, circuits and systems. In this paper we present the analysis of the ESD protection structure supported by the advanced 2-D mixed mode electro-thermal device and circuit simulation.An electrostatic charging model for aircraft fuel tanks
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080232
Electrostatic charging caused by non-conducting liquids flowing through metallic pipes can result in an electrostatic discharge hazard (ESD) in the aviation industry when aircraft are being refuelled. Due to the large quantities of fuel concerned and the high flow rates involved, large potentials can be developed inside aircraft fuel tanks leading to a possible electrostatic discharge hazard. It becomes important therefore to predict the voltage developed during fuelling to evaluate this threat. Also, the ever increasing use of composite materials in aircraft manufacture including fuel tanks and pipes, may change the nature of the hazard and the models must be developed to reflect this change.Small-signal input admittance characteristics of a brushless DC motor drive
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080576
To carry out stability studies on more electric systems in which there is a preponderance of motor drive equipment, input admittance expressions are required for the individual pieces of equipment. In this paper the techniques of averaging and small-signal linearisation will be used to derive a simple input admittance model for a low voltage, trapezoidal back EMF, brushless, DC motor drive system.A new dynamic model for lead-acid batteries
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080488
A new equivalent circuit model for lead-acid batteries is presented, taking into account internal losses due to self- discharge and polarisation effect within a battery. This model is compact in describing both the ohmic voltage drop and overvoltage effects in a combined form of polarisation effect, using a single equivalent resistance for each operating mode. The battery electromotive force is represented by a dependent voltage source whose value changes with the state of charge. The circuit parameters expressed in non-linear function forms are used to describe the charging and discharge characteristics. The model has been derived from the manufacturer's data and validated by experiment.Power quality and sensitive microprocessor loads
http://dl-live.theiet.org/content/conferences/10.1049/ic.2007.1702
Presents a collection of slides covering the following topics:power quality; sensitive microprocessor loads; fault analysis; earth noise; BALUN; differential-mode noise currents; current carrying conductors; common mode noise currents;balanced to unbalanced transformer and electromotive forces.A novel and powerful TCAD methodology to evaluate performance of ESD protection devices
http://dl-live.theiet.org/content/conferences/10.1049/cp_20070677
On-chip electrostatic discharge (ESD) protection requires not only extensive technical experience but also scientific technology computer aided design (TCAD) methodology for evaluation. A novel and powerful TCAD methodology aimed to evaluate performance of ESD protection devices objectively is developed and presented. Mix-mode transient circuit simulation, which depicts ESD events better, is acquired in this simulation method. This TCAD methodology pays more attentions to the transient behaviors and characteristics of ESD protection devices which are more valuable to predict performance of ESD protection devices. This TCAD methodology with good ability of convergence can evaluate the performance of ESD protection devices scientificly and has strong direction ability to the design of ESD protection devices.Influence of conducting body on the biconical electrode field
http://dl-live.theiet.org/content/conferences/10.1049/ic.2007.1186
One above signed author has suggested an optimal system composed of two thin hollow conical electrodes and can be used for uniform electric field generation. The influence of an external object to obtain field's homogeneity is examined. The external object is designed as spherical, oblate and prolate elliptical conducting body placed axially symmetrical in the system. Equivalent electrode method, image theorem in spherical body and software package FEM are used for potential and electric field distribution calculation. (6 pages)A model for flexural vibration of laminated beams embedded with piezoelectric layers including shear deformation
http://dl-live.theiet.org/content/conferences/10.1049/cp_20061147
A beam embedded piezoelectric layers is widely used as actuator to excite or control the vibrations of machines and structures. It is also applied as sensor to measure vibrations. By using the hypothesis of Timoshenko beam theory and assuming the distribution of the electric potential in the z-direction, this paper derives the governing equations for sandwich beams coupled with piezoelectric layers. The eigen solution and frequency equation of the free vibration are then obtained for the beam with two simply supported ends and numerical results are also presented to demonstrate the availability of the presented method.Finite element modelling of ion convection by electrostatic forces
http://dl-live.theiet.org/content/conferences/10.1049/cp_20040438
Different formulations of the problem of a cloud of ions convected by electrostatic forces are presented and compared with each other, from the point of view of the numerical error done on charge conservation.Teaching electrostatics: developing understanding and a powerful modelling capability
http://dl-live.theiet.org/content/conferences/10.1049/cp_20040434
This paper describes a new approach to teaching students electrostatics. The basic physical concepts are described and the students are shown how an electric field can be directly modelled using a spreadsheet. No vector calculus is required. The modelling method is has a rigorous logical basis and is also a powerful tool they could use when they become practicing engineers. An assignment requires the students to build a two-dimensional model of the electric field between two metal bars and obtain the values of capacitance. This includes the fringing capacitance and the classic parallel plate capacitance between the bars. The values are measured in a laboratory session and compared with the calculated values. This approach illustrates that expertise in calculus is not a pre-requisite and this allows students to concentrate on the concepts instead of the calculus. Also the subject could be introduced earlier in the course and used to help students who have difficulty with calculus.Electrostatic discharge clearance for Eurofighter typhoon air to air refuelling
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020194
Whenever an aircraft flies through the air an electrostatic charge is built up on that aircraft. The size of this charge is dependant upon several factors including aircraft size and speed. In an air to air refuelling operation two aircraft, each with a different amount of static charge, are connected together via an electrically conductive refuelling pipe. When this connection is first made an electrical pulse flows along this refuelling pipe, as the amount of charge on the two aircraft is redistributed. This electrostatic discharge pulse causes currents to be induced on the wiring of the two aircraft. This induced current could cause damage or malfunction of flight safety critical systems on the aircraft, if the systems and airframe are not designed to protect against this threat. It is a requirement that before air to air refuelling operations can take place a clearance against the electrostatic discharge threat is obtained for the Eurofighter aircraft. This paper will describe how a transmission line matrix (TLM) code with an incorporated multi-core wire solver has been used, as part of an advanced computational electromagnetic modelling facility, to provide the electrostatic discharge clearance for Eurofighter development aircraft. (2 pages)A strategy for finite-element mesh adaptation in optimisation problems of inverse electrostatics
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020167
The finite element method (FEM) is quite commonly employed in electromagnetic device optimisations, where computation of the field or energy is required for objective function evaluation. It is well known, that the FEM brings about a remarkable computational burden, so that objective function evaluations often take most of the optimisation time. In this paper, an approach is proposed, based on the principle of evolutionary search: the required precision is directly related to the search resolution, determined by the optimiser at the current iteration. (2 pages)The equivalence between cell method, TDTD and FEM
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020135
Some equivalences between the cell method (CM) and other methods, like the finite difference in time domain method (FDTD) and the finite elements method (FEM), are proved. In particular the equivalence of the equations arises between CM and electrostatic 3D FEM, between CM and magnetostatic 3D FEM and between CM and FDTD in 3D electrodynamics. (2 pages)Novel hybrid method for computing electric field of SF<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">6</sub> circuit breaker
http://dl-live.theiet.org/content/conferences/10.1049/ic_20020164
The electric field of a SF<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">6</sub> circuit breaker is computed based on the hybrid method of finite element method (FEM) and charge simulation method (CSM), taking the axisymmetric configuration into consideration. It is verified that the hybrid FEM-CSM is capable in calculating the complex open boundary problems, and the calculation results are of higher precision than those of the traditional FEM or CSM, respectively. (2 pages)Electrostatic analysis of multi-megavolt flash X-ray machines at AWE, Aldermaston
http://dl-live.theiet.org/content/conferences/10.1049/ic_20000277
Historically, X-ray machines at AWE have been designed using a combination of back of the envelope calculations and field plotting using electrolytic tanks. The continuing increase in computer power now makes it practical to increase the sophistication of the calculations and to analyse much more detailed models than previously possible using physical methods. All of the current in-service flash X-ray machines have been electrostatically modelled and some of the results of that investigation are presented. (4 pages)A new optimised design of integrated three phase gas insulated bus duct
http://dl-live.theiet.org/content/conferences/10.1049/cp_19990970
The paper highlights the techniques adopted for design optimisation of a three phase single enclosure, 145 kV class gas insulated bus duct. The design is based on extensive electrostatic field studies in three dimensions using special software. A unique feature of this design is the introduction of individual rib insulators for supporting each phase conductor, in place of the conventional single conical shaped insulator. A model bus duct has been fabricated and successfully tested for its specified dielectric duties. (4 pages)New approach to high voltage electrodynamic drum separator. Part I. Theoretical model
http://dl-live.theiet.org/content/conferences/10.1049/cp_19990973
Electric fields have a number of applications in technology. One of them is electrodynamic separation: the electric field influences selectively granular solids of different electric moments or charges. A mathematical model of the separation process in a high voltage drum separator is presented in the paper. Particles are charged both with induction and corona phenomena: next, they are separated with field forces. The computational results are presented and analysed. (4 pages)The accumulation of surface charge due to a conducting particle on a spacer
http://dl-live.theiet.org/content/conferences/10.1049/cp_19990792
The electrical properties of the widely used gas insulated systems for switchgear depend strongly on the properties of the used gas. Electrical field-strength and the field distribution determine the behaviour. If the field gets disturbed the insulation properties decrease significantly. Conducting particles lead to local field enhancement. When these particles get stuck on a spacer surface, the field-strength in the vicinity of the particle is increased. This increase in field-strength yields more ionization and can result in a dielectric failure. To investigate the behaviour of particles on spacers a simplified spacer model with an adhering particle was tested under homogenous field conditions in SF<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">6</sub>. The gas pressure and the particle length were used as parameters. Investigations on the electrical strength and charge distribution were performed under clean and particle contaminated conditions. The surface charge accumulated during AC and LI stress and its distribution was measured during the experiment. A specially designed setup was used to acquire the surface charge data; stressing the sample and subsequent measurements of the charge distribution could be performed without distortion of the latter. This enabled the application of voltage stress to a known charge distribution. Thus the effects of surface conditioning and decreasing or increasing insulation strength could be studied. Special attention was paid to the charge distributions concerning on-site test procedures. (4 pages)High-voltage field computation using bi-cubic surface splines
http://dl-live.theiet.org/content/conferences/10.1049/cp_19990600
Integral equation methods are used to compute the electric field stress on high-voltage arrangements. This paper combines the geometric description of surfaces, using bi-cubic spline functions on individual patches, with the boundary element method for calculating three-dimensional electrostatic fields. After the calculation of spline function coefficients from a given geometric design, the electric boundary conditions of electrode and dielectric parts are applied. Numerical integration by means of Gaussian quadrature leads to a linear system of equations, determining the charge density on the surface elements. This solution is used to calculate the potential and field strength on the electrode or insulator contour. The accuracy of the method is illustrated by an example. (4 pages)Separation of fine dust with AC-energized electrostatic precipitators
http://dl-live.theiet.org/content/conferences/10.1049/cp_19990967
In addition to studies with DC-energized electrostatic precipitators (ESPs) this paper presents the results of experimental investigations with a plate-type laboratory-scale AC ESP. These precipitators are relatively insensitive to the dust resistivity. The paper's theoretical part deals with the basic physical mechanisms of the separation of particles with AC energization. This is followed by an overview of general methods for AC-precipitation. Finally, this paper describes experiments with a modified laboratory-scale AC ESP, excelling by the absence of back corona. Fractional efficiency measurements were conducted for various geometric and electric parameters and constant gas conditions. (4 pages)Electrostatic discharge
http://dl-live.theiet.org/content/conferences/10.1049/ic_19990004
Electrostatic discharge (ESD) is a common phenomenon that can have serious consequences for electronic systems. This paper introduces the physical processes that lead to electrostatic discharges occurring and describes the potential effects of such discharges. An overview is given of typical test methods and control measures for developing “ESD proof” products. ESD in vehicles is used as a case study to demonstrate the points raised. (8 pages)A study of memory effect of partial discharges
http://dl-live.theiet.org/content/conferences/10.1049/cp_19990946
From the computed conditional pulse amplitude and phase distributions it is shown that, as the gap spacing is reduced, the charging of a dielectric surface affects the corona pulse-time distribution which becomes significant at lower gap spacings. Most probable values are found to be the best statistical indicators for interpreting the results. (4 pages)Delay characteristics of surface charging on a cylindrical insulator in vacuum
http://dl-live.theiet.org/content/conferences/10.1049/cp_19990769
The charging of an insulator is considered as a critical phenomenon leading a bridged gap to flashover in vacuum. Based on the theory which Harmisch and Boersch (1963) proposed as secondary emission electron avalanche (SEEA) mechanism, Anderson (1980) explained the V-t characteristic of a bridged vacuum gap exposed to a short voltage pulse in connection with space charge effects due to ionization of desorbed gases in vacuum. In this theory, however, it is assumed that the charging takes place immediately after the voltage application, thereby neglecting the time necessary for the surface. charging. We have developed a probe method which enables us to do a real-time observation of the surface charging in vacuum. The probe measures the electric field change associated with the surface charging on the cathode very close to the triple junction, where the insulator, cathode and vacuum meet, without disturbing the electric field in the gap nor the charge distribution on the insulator. This paper reports the results of probe measurement which characterize temporal behavior of charging on a cylindrical insulator when it is exposed to a trapezoidal or a stepped DC voltage. (4 pages)New modelling of the boundary between wet and dry zones on the surface of polluted high-voltage insulators
http://dl-live.theiet.org/content/conferences/10.1049/cp_19990589
This paper describes a new technique for calculating the potential, leakage current and field distributions of polluted high voltage (HV) insulators. This technique is based on a new modelling of the boundary between wet and dry zones on the surface of polluted insulators. Surface charge simulation method (SCSM) and discrete charge simulation techniques are used to get the basic solution of the linear system of equations. An example of a two-dimensional case with a rotationally-symmetrical configuration shows the usefulness of the developed technique. (4 pages)Calculation of the electrostatic force acting on axisymmetric objects in non-uniform electric fields
http://dl-live.theiet.org/content/conferences/10.1049/cp_19990598
This paper presents the evaluation of the resultant force acting on an axisymmetric body in an electrostatic field. The objects can be either dielectrics or conductors, charged or uncharged. Basically, the computation is carried out by linking the Maxwell stress tensor to a 2D field calculation program. The main purpose of the work is to create a numerical tool for calculating forces on dielectric and metallic particles in the presence of nonuniform electric fields. As a demonstration, two examples are presented in the paper. One of them, the force on a charged dielectric sphere due to a point charge external to the sphere, has an analytical solution and is therefore used to check the validity of the model. The analytical result verified the approach. The other example is an uncharged ellipsoid placed in a rod-plane gap. The force on the ellipsoid is investigated for different positions in the gap and for different choices of dielectric constant. (4 pages)Surface charge measurement using an electrostatic probe
http://dl-live.theiet.org/content/conferences/10.1049/ic_19980220
The existence of a charge at a dielectric surface gives rise to the electrification by electrostatic induction of the probe. In turn this phenomenon leads to the probe signal. The procedure by which such signals are analysed to yield the unknown surface charge distribution forms the subject matter of the present contribution. In particular, we will discuss the elegant field approach proposed by Pedersen. This we have now fully developed, and controlled against the experimental data of Yashima et al. (4 pages)EMC techniques for microprocessor software
http://dl-live.theiet.org/content/conferences/10.1049/ic_19980836
As many design engineers have found, embedding microcontrollers into products provides extra features and functionality, but also introduces a new set of EMC problems, including susceptibility. Microcontroller based equipment is particularly vulnerable to electrical transients such as electrostatic discharge (ESD), electrical fast transient bursts (EFT), high energy surges and supply dips, interruptions and variations. Hardware countermeasures should always be the first line of defence, to achieve any chance of immunity to transient phenomena. However, there are also defensive measures that may be applied in software. Through experience gained on a variety of microcontroller based products, the author has compiled a simple strategy for hardening microcontroller based systems. It is assumed that general EMC principles and immunising strategies are known and implemented as far as is practically appropriate, and these measures are not restated. (5 pages)Transient protection for high speed datacomnunication applications
http://dl-live.theiet.org/content/conferences/10.1049/ic_19980006
This paper is concerned with the protection of high speed data lines from damage caused by ESD and EOS (electrical overstress) transients. When a data communications network is implemented with an electrical physical layer there is a possibility of transient damage to the electronic systems. This can happen when the network is configured, through mechanisms such as ESD and cable charging, and during operation by induced transients and power supply disturbances. The problem of protecting such systems is becoming increasingly difficult as greater levels of circuit integration make the cable interface electronics more susceptible to transients and higher frequencies of operation make the system more sensitive to the electrical loading introduced by protection networks. In this paper, examples are given based on the author's practical experience with computer disk file subsystem development, although the basic principles are relevant to many other data communication standards and applications. The growth of this sector in such areas as computer networking and data storage has focused attentions on how such systems can be protected from electrical transients. (9 pages)EMC-hardening microprocessor-based systems
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970599
As many design engineers have found, embedding microprocessors into products provides extra features and functionality, but also introduces a new set of EMC problems, including susceptibility. Microprocessor-based equipment is particularly vulnerable to electrical transients such as electrostatic discharge (ESD), electrical fast transient bursts (EFT), high energy surges and supply dips, interruptions and variations. Hardware countermeasures should always be the first line of defence, to achieve any chance of immunity to transient phenomena. However, there are also defensive measures that may be applied in software. Through experience gained on a variety of microprocessor-based products, the author has developed a strategy specifically for hardening microprocessor-based systems. (6 pages)In-situ radiated EMI measurements of EDM machines and EMI reduction techniques
http://dl-live.theiet.org/content/conferences/10.1049/cp_19971117
The radiated EMI from various EDM (electrostatic discharge machining) machines was measured in-situ. The spark is found to be the origin of the excessive emissions. Classic techniques to reduce the radiated EMI of these machines were checked and new techniques such as reduction of the driving-cables have been investigated.The development of FIBCs for use in flammable atmospheres - a review
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970003
Flexible intermediate bulk containers (FIBCs) are used to transport powder materials at relatively inexpensive packaging costs. A great deal of experimental work was undertaken to develop a container which would satisfy a requirement of a resistance to earth of <10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">8</sup> Ω. Some of this work is outlined. The development of a container by LINQ using a new fabric with a base weave of polypropylene and a coating of glycerol monostearate on the internal surface is discussed. The testing of the LINQ container for electrostatic ignition hazards is described. (5 pages)Electrostatic ignition hazards associated with FIBC filling or emptying and presently available FIBC safety design types
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970002
Flexible intermediate bulk containers (FIBCs) or Bulk Bags are frequently used in industry for the packaging and transport of powder materials. The electrostatic hazard associated with this type of packaging has been reported by several authors. In the case of ignition due to the build-up of static electricity, different ignition mechanisms have been identified depending on the construction of the FIBC and the explosive atmosphere present. Thus, there are various measures to prevent ignition. These depend on the type of FIBC and sensitivity of the explosive atmosphere. The types of discharges which may occur when filling or emptying FIBC are discharges associated with the FIBC fabric, and discharges associated with the product and the surroundings. These are briefly discussed as are available bag designs to reduce electrostatic hazards. (3 pages)Electrostatic hazards in the use of flexible intermediate bulk containers (FIBCs)
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970001
FIBCs are essentially big bags used for the transport and storage of intermediate quantities of powder product. Made traditionally of woven polypropylene, they hold from around 300 kg to 1000 kg of material in a shape which is approximately cubic, are fitted with filling chute, emptying cone and chute and are usually stacked on pallets or lifted by 4 loop straps at each bag corner. For many companies, FIBCs provide a very convenient way of handling medium quantities of powder which otherwise would require many drums or small bags. Their use is now widespread and they are to be found in many industry sectors including chemicals, fine chemicals, agrochemicals, food stuffs and others besides. Unfortunately the extensive use of FIBCs has lead to a significant number of fires and explosions which are directly attributable to electrostatic activity in the normal use of these bags. A lot of work has subsequently been performed both to understand the hazard and to produce bags which are safer to use than the first all-polypropylene bags. This paper reviews the electrostatic hazards associated with the use of FIBCs. (3 pages)Problems not solved by antistatic fabrics
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970004
The volume of a flexible intermediate bulk container (FIBC) is 1.5-2.5 m<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sup> and during filling the ullage can contain a dust cloud particularly if the FIBC is inflated prior to filling. Some 70% of industrial powders can form flammable dust clouds and a dust explosion can result from ignition. Full assessment of the dust explosion hazard requires consideration not only of electrostatic discharges-spark, propagating brush, brush and cone-but also of burning powder from upstream units. Spark discharges emanating from insulated metal components can be eliminated by earthing. Propagating brush discharges associated with the accumulation of high charge densities on nonconducting layers can be controlled by the anti-static fabrics but a decision has to be made as to whether or not a nonanti-static fabric will be safe. The breakdown voltage of the fabric can be used to assess its capacity to be the source of propagating brush discharges. Antistatic fabrics do not necessarily eliminate the possibility of brush and/or cone discharges from the bulk powder within the FIBC. (3 pages)Electrostatic analysis of triggered spark gaps
http://dl-live.theiet.org/content/conferences/10.1049/ic_19960394
One of the major considerations associated with the overall performance of a high pressure trigatron is that of lifetime and this becomes particularly important for high repetition rate pulsed power applications. The problems associated with short trigatron lifetimes are usually related to the erosion of the trigger pin due to successive arcing. Although the erosion per pulse will be dependent upon the specific operating conditions it will eventually lead to an insufficient level of field distortion in the main electrode gas region when triggered, resulting in poor switch performance. In order to maximise the lifetime of a trigatron switch whilst still maintaining good switching performance, an experimental programme was undertaken in which the preliminary design of the trigatron was determined through electrostatic field modelling. The above procedure has led to the production and testing of a 500 kV triggered switch which has been operated successfully with a sub nanosecond jitter and relatively long lifetime. The final trigatron design also contains a small corona discharge cell which generates a negative ion population in the gas, which is SF<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">6</sub>. This ensures initiatory electron production through ion detachment resulting in sub-nanosecond jitter. In order to spatially optimise the overall switch design, electrostatic field analysis has been applied to all regions of gaseous and solid insulation in the switch. (4 pages)On spatial inhomogeneity of electric field in thin layer of dielectric liquid
http://dl-live.theiet.org/content/conferences/10.1049/cp_19961015
The model proposed is based on the measurement of resistivity to calculate the distribution of electric field in thin layer of dielectric liquids. This model was applied to investigate the spatial inhomogeneity of the electric field in benzene, toluene and carbone tetrachloride of high purity. The feature of behaviour of thin layer in the electric field must be taken into account in modelling the conduction process in dielectric liquids.An electroquasistatic finite element model of electric fields and currents generated by coronating electrodes in an electrostatic precipitator
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960170
A three-dimensional finite element model is being developed to predict the effects of high-voltage corona discharge electrode geometry on charge injection, space charge distribution and electric field within an electrostatic precipitator. The motivation is to have a tool for improving the designing of discharge electrodes and enabling them to be custom-designed for specific applications. The problem which will be solved by the model is Poisson's equation coupled with current continuity (i.e. the ion drift problem in air) with geometry dependent charge injection at the discharge electrode surface and an arbitrary static background space charge density (which is assumed not to contribute to the current) due to a charged airborne particulate.Ultimate numerical accuracy of the surface charge method for electrostatics
http://dl-live.theiet.org/content/conferences/10.1049/cp_19960158
The surface charge method (also known as the boundary charge, charge density, boundary element and integral equation method) has been used to solve problems in electrostatics since at least 1878, when Maxwell used it to find the capacitance of a thin square plate. The inherent simplicity of the method can confer high accuracy on the results obtained with it. We consider the highest accuracy that can be obtained in practice for various problems, giving examples in each case. We start with a brief description of the method, and then deal with (1) capacitance calculations, (2) the calculation of potentials and fields, (3) trajectory integrations, and finally (4) cathode and space-charge problems.Static electrification - chemical methods to suppress the charging behaviour in transformer oils
http://dl-live.theiet.org/content/conferences/10.1049/cp_19961062
The phenomenon of electrostatic charge generation due to friction between the flowing insulating liquid and the fixed solid insulation is well known. The increase in power and voltage ratings of transformers has made the static charge phenomenon an important parameter to be controlled to prevent transformer failures due to charge accumulations. To mitigate this problem of charge accumulations and to suppress the developed charge density in transformer oils, different methods, like, mixing low charging oils with high charging oils, use of additives like benzotriazole (BTA) have been suggested in the literature. In this paper, the authors studied the origin and manifestation of static electrification phenomenon of Indian Paraffinic oils by measuring the charge density of transformer oil base stock (TOBS) and oil samples drawn before clay treatment and oils as received in drums. The authors studied different chemical methods to suppress the charge density of oils by using different additives, like, triazoles, tetrazoles, imidazoles and high molecular weight alcohols. The authors also studied the charge suppression by blending oils with linear alkyl benzene (LAB) and processing with different adsorbents like molecular sieves, alumina, and fullers earth.The modelling of pulse charge injection within a powder flow system
http://dl-live.theiet.org/content/conferences/10.1049/ic_19950077
The paper is concerned with the measurement and control of powder flows, particularly in the electrostatic powder coating industry. Electrostatic coating with dry powder is used in many industrial painting applications as a substitute for wet paint, mainly for reasons of economy and quality. At present, the flow rate of powder out of the electrostatic spray gun is not measured, and the flow is controlled indirectly by altering the air pressure to the gun. As a result the thickness of the coating will vary from one production run to the next. This lack of quality control is unacceptable to many commercial applications where a uniformity of coating thickness is critical. Current research is concerned with the use of pulse corona charge injection as a technique to measure the powder mass flow rate. A corona needle is located along the axis of the pipe, from which a pulse of charge is injected into the powder flow. Sensors located downstream of the injection may be used to derive the density and velocity of the flow. The paper describes the charge injection system used to measure the mass flow rate and presents a model for the electrical field distribution and the charge induced on the sensors. Further consideration is given to secondary effects of the system, including charge deposition and re-entrainment. (6 pages)The physical and geometrical basis of electrostatics
http://dl-live.theiet.org/content/conferences/10.1049/ic_19950071
The purpose of the article is to provide a very general survey of the most important electrostatic magnitudes, which occur in all computation schemes. It shows that there is a close association between the physical properties and the geometry of electrostatic systems. The geometry has two aspects. The first is the obvious one of the shape and disposition of the electrodes and insulators. There is also the less obvious inherent geometry of electrostatic fields and this inherent geometry leads to remarkably simple and efficient algorithms. (2 pages)ESD testing
http://dl-live.theiet.org/content/conferences/10.1049/ic_19950412
With the increased use of plastics and synthetic materials in the modern environment and the wide spread use of metal-oxide technologies the effects on electronic systems due to ESD have become more significant. The main problem today is not one of permanent damage but rather of soft failure and malfunction of equipment in the field. According a test specification IEC8O1-2 for the testing of immunity to ESD failure was introduced in the 1980s. This is a generic standard and forms the basis for all of the modern national and European `harmonised' specifications. (16 pages)Electrostatic discharge: a review
http://dl-live.theiet.org/content/conferences/10.1049/ic_19950410
The advent of practical problems associated with electrostatic discharge (ESD) has reawakened a wider interest in static electricity and again brought it to the fore. One of the main practical problems has been as a consequence of electronic circuits getting smaller, since it takes less energy to destroy them. While this paper mainly addresses ESD with respect to electronics, it must not be forgotten that ESD can affect most modern production facilities in one way or another. It can attract dust to surfaces that must be kept clean. It can also be a source of discomfort to personnel and more importantly it can create a fire hazard in combustible environments. (8 pages)ESD - still a problem 10 years on
http://dl-live.theiet.org/content/conferences/10.1049/ic_19950411
Identifies a major training problem for the electronics industry and develops an innovative solution. Electrostatic discharge remains a major problem for the industry today despite the excellent training materials available. What is required is a systematic method and training materials which are designed with the learner in mind. Such a method is described. (5 pages)Methods of measurement to assess the suitability of materials for the control of static electricity
http://dl-live.theiet.org/content/conferences/10.1049/ic_19950415
Static electricity presents risks of damage to semiconductor devices in manufacture, circuit board building, handling and servicing. It presents risks to the microelectronic systems through data corruption and operational upset from static discharges. The various ways that the characteristics of materials are relevant to these risks are noted and methods used to assess these characteristics are outlined. (6 pages)Simulation and measurement of EM fields caused by electrostatic discharges
http://dl-live.theiet.org/content/conferences/10.1049/ic_19950414
This paper describes experimental and numerical results of Electromagnetic (EM) pulses caused by Electrostatic Discharge (ESD) in the IEC802.2 standard set-up. Results obtained by combined Spice-TLM model of the ESD event were compared with E and H field measured by a small optically linked field sensor. They enable the distribution of the EM field above the conductive table to be determined. This provides an opportunity to estimate of the induced currents and voltages in sensitive elements during ESD testing. (6 pages)Finite elements for electrostatics
http://dl-live.theiet.org/content/conferences/10.1049/ic_19950074
A general formulation for electrostatics is discussed. A convenient technique for modelling devices which move, such as electrostatic micromachines, is described. Electrostatics problems may sometimes be formulated in terms of the electric scalar potential. (1 page)