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Lossy conductors are not perfectly electric conductors and their finite conductivity needs to be carefully accounted for in the accurate solution of electromagnetic problems. Traditionally, surface integral equations (SIEs) are used to approximately describe the problems, but we use volume integral equations (VIEs) to exactly formulate the problems by treating the lossy conductors as dielectric-like...
This study presents experimental results on the variation of dielectric constant, electrical conductivity, attenuation and loss tangent of five different soil samples at three different MHz frequencies. The most important parameters needed for Ground Penetration Radar study are dielectric constant and electrical conductivity of various soil samples. Such type of studies may find very useful for designing...
Site dependent parameters such as soil resistivity, maximum grid current, fault duration, shock duration, surface layer material resistivity, and grid geometry have substantial impact on the design and performance of an earth grid. The grid geometry, i.e. the area occupied by the grid system, conductor spacing and the depth of burial of earth grid specifically have much impact on the mesh, step, touch...
An investigation is reported into the structure of Ball Grid Array/Permanent Stencil/Printed Circuit Board interconnects produced when semi-elastomeric bituminous stencils are formed or placed within standard interconnects. Such interconnects have the potential to extend the service life of Printed Circuit Boards especially for use in aviation, shipping and military applications.
Bruggeman dielectric mixture expression is one of the widely used methods to characterize properties of heterogeneous materials. In this contribution, dielectric response of mixture systems generated with the Bruggeman effective mixture expression is studied to investigate the broadening of dielectric relaxation at various filler contents. The mixture is composed of two dielectric media. The studies...
Materials with nonlinear conductivity is sometimes used as field grading materials in high voltage applications. With respect to this, the electrical conductive properties of composites containing polyaniline (PAni) and carbon black (CB) as electroactive fillers have been studied with respect to the filler/matrix ratio, type of matrix material and how the composites were processed. Flat pads were...
Not all dielectrics are perfect. The experimentalist would know how materials would react to an external excitation, and would record bulk conductivity values depending on their test setups and measurement system. To measure the correct bulk conductivity isothermal time domain measurement at room temperature could take long times and requires good current measurement and sometimes high voltage setups...
The conductivity of XLPE insulation plates has been measured with different levels of water concentration. Tapes have been used to humidify the insulation plates in a heat treatment step. Three different levels of water concentration was provided by the tapes. The apparent conductivity was measured for 24 h at 70°C and 30 kV/mm. It is found that the conductivity is increasing with increasing water...
The method of the split cylinder resonator cavity (SCR) is used to characterize accurately and simultaneously in one temperature cycle, dimensional and electrical characteristics of the cavity and the electromagnetic properties of a dielectric material. To do this several modes are used, some to control the cavity and others to control the sample.
A battery separator isolates anode and cathode electrically and contributes to the ionic conductivity on the one side. On the other side, it is a highly sensitive functional component concerning mechanical loads. During production as well as the operation of a battery this thin, polymer based film is stressed by compressive and tensile forces. This contribution presents an enhanced characterization...
In earlier work it was recommended that accelerated tests, using elevated currents, be used to evaluate the performance of contact designs using materials that may be susceptible to electro-migration. This is necessary since it was found in earlier work that the type of self-diffusion in some cases had a major impact on time to failure. Since the type of diffusion is generally not known in advance,...
Through past testing it has been observed that the endurance life of contacts tested using DC automotive type loads is better if the polarity of the test is set to use the terminal contact as the anode as opposed to using the thin contact spring as the anode. A DOE approach was used to look at the effect on contact erosion and transfer for changing the thermal characteristics of the terminal with...
A one-dimensional electrochemical DC pulse simplified model for an 8Ah lithium ion phosphate battery monomer is built with the help of COMSOL software on the base of the porous electrode theory. Based on the experimental data and analysis, the model can be optimized by putting the values of effective conductivity and the concentration of the lithium at different temperature as well as the equilibrium...
A model is developed to determine the peak current required to weld large area closed contacts with ‘n’ points of contact when passing short duration, high fault currents. The model also predicts the threshold welding current for parallel contact structures used to carry large currents in high current switching devices. The model considers: (1) the total contact resistance of the closed contacts by...
This paper presents a comparison of the thermal properties between infiltrated and non-infiltrated copper windings. The focus is on thermal conductivity in the radial direction on the winding. The samples have a fill factor above 65 % due to the manufacturing method of the samples. Samples are produced and measured with the transient plane source technique and then compared to FEM simulations and...
The Copper-Chromium (CuCr) contact material is the most widely used material for the contacts of the vacuum interrupters (VI). Performance of the VI is greatly influenced by the properties of contact materials. During switching operations, such as short-circuit current interruption, a vacuum arc is generated which in turn produces melted and resolidified layers at the contact surface. Melting followed...
The resistance of vacuum interrupters can be calculated from the geometry and resistivity of current carrying parts and the additional resistance of the contact points between movable and fixed contacts. Since vacuum interrupter contacts are designed as flat contacts facing each other, the resistance is mainly determined by contact force, hardness and resistivity of the contact material. It is known...
Terahertz time-domain spectroscopy was used as a nondestructive and a noncontact optical probe to investigate the material properties and high frequency carrier dynamics of undoped and Al-doped ZnO nanowires (NWs). The frequency dependent refractive index was first determined through effective medium theory and numerical iteration process applied to the detected terahertz signals transmitted through...
Electrode material seriously influences the characteristics of vacuum arc and further affects the performance of switches. In this paper, thermal processes of six kinds of metal anodes (including pure metal and alloy anodes) are simulated and researched. Two kinds of temperature calculation methods are used. Simulation results show that W and Mo anodes have the higher temperature than Cu, Cr, CuCr25...
A THz TDS study of permittivity and conductivity properties of new variant of Yttria-stabilized-Zirconia (YSZ) produced using tape-cast method is reported. This study extends the frequency coverage of some of the previously published work. We find a general agreement with published results but the frequency gap in the mm-wave range needs to be measured more carefully before final conclusions on the...
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