Abstract: The structural stability of the model of a nonelectroneutral current sheath is investigated. The stationary model of a current sheath represents the system of four connected nonlinear differential first-order equations and thus they should manifest structural instability property, i.e. sensitivity to the infinitesimal changes of parameters and starting conditions. Domains of existence of the solutions of current sheath type are found. Those solutions of the current sheath type are realized only in some regions of sevendimensional space of parameters of the problem. The phase volume of those regions is small in comparison with the whole phase volume of the definition range of those parameters. It is shown that the offered model of a nonelectroneutral current sheath is applicable for theoretical interpretation of the bifurcational current sheaths observed in the magnetosphere.
Abstract: High voltage generators are being subject to higher
voltage rating and are being designed to operate in harsh conditions.
Stator windings are the main component of generators in which
Electrical, magnetically and thermal stresses remain major failures
for insulation degradation accelerated aging. A large number of
generators failed due to stator winding problems, mainly insulation
deterioration. Insulation degradation assessment plays vital role in the
asset life management. Mostly the stator failure is catastrophic
causing significant damage to the plant. Other than generation loss,
stator failure involves heavy repair or replacement cost. Electro
thermal analysis is the main characteristic for improvement design of
stator slot-s insulation. Dielectric parameters such as insulation
thickness, spacing, material types, geometry of winding and slot are
major design consideration. A very powerful method available to
analyze electro thermal performance is Finite Element Method
(FEM) which is used in this paper. The analysis of various stator coil
and slot configurations are used to design the better dielectric system
to reduce electrical and thermal stresses in order to increase the
power of generator in the same volume of core. This paper describes
the process used to perform classical design and improvement
analysis of stator slot-s insulation.
Abstract: In the present work, an attempt is made to understand
electromagnetic field confinement in a subwavelength waveguide
structure using concepts of quantum mechanics. Evanescent field in
the waveguide is looked as inability of the photon to get confined in
the waveguide core and uncertainty of position is assigned to it. The
momentum uncertainty is calculated from position uncertainty.
Schrödinger wave equation for the photon is written by incorporating
position-momentum uncertainty. The equation is solved and field
distribution in the waveguide is obtained. The field distribution and
power confinement is compared with conventional waveguide theory.
They were found in good agreement with each other.
Abstract: In nature, electromagnetic fields always appear like
atmosphere static electric field, the earth's static magnetic field and
the wide-rang frequency electromagnetic field caused by lightening.
However, besides natural electromagnetic fields (EMF), today human
beings are mostly exposed to artificial electromagnetic fields due to
technology progress and outspread use of electrical devices. To
evaluate nuisance of EMF, it is necessary to know field intensity for
every frequency which appears and compare it with allowed values.
Low frequency EMF-s around transmission and distribution lines are
time-varying quasi-static electromagnetic fields which have
conservative component of low frequency electrical field caused by
charges and eddy component of low frequency magnetic field caused
by currents. Displacement current or field delay are negligible, so
energy flow in quasi-static EMF involves diffusion, analog like heat
transfer. Electrical and magnetic field can be analyzed separately.
This paper analysis the numerical calculations in ELF-400 software
of EMF in distribution substation in shopping center. Analyzing the
results it is possible to specify locations exposed to the fields and
give useful suggestion to eliminate electromagnetic effect or reduce it
on acceptable level within the non-ionizing radiation norms and
norms of protection from EMF.
Abstract: A power cable is widely used for power supply in
power distributing networks and power transmission lines. Due to
limitations in the production, delivery and setting up power cables,
they are produced and delivered in several separate lengths. Cable
itself, consists of two cable terminations and arbitrary number of
cable joints, depending on the cable route length. Electrical stress
control is needed to prevent a dielectric breakdown at the end of the
insulation shield in both the air and cable insulation. Reliability of
cable joint depends on its materials, design, installation and operating
environment. The paper describes design and performance results for
new modeled cable joints. Design concepts, based on numerical
calculations, must be correct. An Equivalent Electrodes
Method/Boundary Elements Method-hybrid approach that allows
electromagnetic field calculations in multilayer dielectric media,
including inhomogeneous regions, is presented.
Abstract: The role of the pollen grain, with to the reproductive
process of higher plants, is to deliver the spermatic cells to the
embryo sac for egg fertilization. The aim of this project was study
the effect of electromagnetic fields on structure and pollen grains
development in Chenopodium album. Anthers of Chenopodium
album L. were collected at different stages of development from
control (without electromagnetic field) and plants grown at 10m from
the field sources. Structure and development of pollen grains were
studied and compared. The studying pollen structure by Light and
Scanning electron microscopy showed that electromagnetic fields
reduction of pollen grains number and male sterility, thus , in some
anthers, pollen grains were attached together and deformed compared
to control ones. The data presented suggest that prolonged exposures
of plants to magnetic field may cause different biological effects at
the cellular tissue and organ levels.
Abstract: A complete spectral representation for the
electromagnetic field of planar multilayered waveguides
inhomogeneously filled with omega media is presented. The problem
of guided electromagnetic propagation is reduced to an eigenvalue
equation related to a 2 ´ 2 matrix differential operator. Using the
concept of adjoint waveguide, general bi-orthogonality relations for
the hybrid modes (either from the discrete or from the continuous
spectrum) are derived. For the special case of homogeneous layers
the linear operator formalism is reduced to a simple 2 ´ 2 coupling
matrix eigenvalue problem. Finally, as an example of application, the
surface and the radiation modes of a grounded omega slab waveguide
are analyzed.