Present state of power electronics circuitry and perspectives of its development

This paper is devoted mainly to the circuitry, because element base is a big independent issue. Let us say a few words about terminology. A modern converter can be rarely represented as a simple device like “rectifier”, “inverter” etc. It usually consists of the combination of several units, performing elementary functions. For such multistage units it makes sense to use a definition of converter “technology”, keeping in mind some actions with electric current for a certain purpose. It is similar to the step activities in chemistry: to take a substance, to heat it etc. After the formulation of a goal and a number of necessary actions it is possible to present a corresponding structure circuit. According to described above we tried to mention basic technologies used in modern power electronics. The perspectives of the electronics in the nearest future are connected with the further improvement of basic technologies, because their combination allows for developing new technologies. In our opinion, there are four such technologies.Стаття присвячена проблемам схемотехніки у сучасній енергетиці. Розглянуто декілька напрямків розробок електроприводів, відмічено їхні переваги та недоліки. Описано сучасні схемотехнічні можливості та перспективні напрямки їхнього подальшого розвитку в Україні

The use of radiolocation control methods to protect the perimeters of large objects

To detect an intruder for the perimeter security of a large object it is proposed to use radiolocation sensors. The sensors are chosen with taking into account the use conditions, which are inhomogeneous along the object perimeter. The way to simplify a synthesis of the security system is to use a space imaging data

The structural and parametrical organization of elements of a power supply system in the conditions of network centrism

Purpose. Development of indicators of the structural and parametrical organization of effective active and adaptive system of service of power supply systems in the conditions of ideology of Smart Grid. Methodology. In the conditions of application of ideology of Smart Grid for increase of intellectualization of electrical power system there is a need of introduction of the principle of a network centrism in the structural and parametrical organization of elements of power supply systems that involves performance of conditions on implementation of provisions of the principle of Situational Awareness. The essence of this principle consists in that, information on a condition of system has to be presented in the form convenient for the analysis, recognition, transfer, distribution and storage, to be coordinated for flexible and optimum development at the subsystem and object-by-object levels. Results. Structural and parametrical optimization of elements of power supply systems in the conditions of a network centrism and the concept of SG involves use of provisions of the theory of systems and concepts of multicriteria optimizing synthesis. It is offered to use the modified adaptive indicator of the generalizing effect of synthesis of structure of active and adaptive system of service of power supply systems in the form of a difference of the generalizing effects: the introduced option of structure of system and basic. Originality. Introduction of an adaptive indicator of synthesis of system of service of power supply systems considers the concept of «service of system on the basis of a response» in the presence of false and true refusals. Practical value. Use of the specified indicator will allow to specify procedure of selection of competitive options for the purpose of definition of a set of admissible structures which meet the requirements of criterion function.В статье рассмотрены тенденции развития и принципы организации интеллектуальных энергосистем при введении понятия сетецентризма в условиях идеологии Smart Grid. В качестве решения задач указанной проблематики предлагается создание активно-адаптивной системы, реализующей концепцию «обслуживания системы на основе отклика»

NMR relaxation in half-integer antiferromagnetic spin chains

Nuclear relaxation in half-integer spin chains at low temperatures (T << J, the antiferromagnetic exchange constant) is dominated by dissipation from a gas of thermally-excited, overdamped, spinons. The universal low temperature dependence of the relaxation rates $1/T_1$ and $1/T_{2G}$ is computed.Comment: 7 pages, 1 uuencoded postscript figure appende

Numerical computation of electric fields in presence of curvilinear interface between conductive and non-conductive media

Purpose. To elaborate a method of electric field numerical calculation in systems with curved boundaries between conductive and non-conductive media at final volume method usage and application of the rectangular grids. Methodology. At electric field calculation in quasi-stationary approximation, potential of the whole conductive object (rod) is constant. At final difference scheme writing, presence of the curved part of the boundary between conducting and non-conducting media has been taking into account as follows. It was supposed that curved section complements the closed loop on which integration of the solvable equation is done instead of a straight section which extends within a conducting medium. Usage of this approach allows taking into account square of the curved sections of the boundary and distance between surface of non conductive medium and nearest nodes of the computational grid. Results. Dependence of the maximum electric field intensity on the height and radius of curvature peaks rods has been got with the help of calculations. As a result, a polynomial approximation for the analytical expression of the external electric field intensity, upon which application to the conductive object of a certain height and radius of curvature of its top, corona discharges will develop.Описаны принципы учета криволинейных границ раздела при использовании метода конечных объемов для расчета усиления электрического поля на вершинах проводящих стержней. С помощью проведенных расчетов получена зависимость максимальной напряженности электрического поля от высоты и радиуса скругления вершин стержней. В результате аппроксимации данной зависимости полиномом записано аналитическое выражение для напряженности внешнего электрического поля, при приложении которого к проводящему объекту определенной высоты и радиуса скругления вершины на нем развивается коронный разряд

18-Pulse rectifier with electronic phase shifting and pulse width modulation

At present, 12-pulse rectifiers with electronic phase shift are known. Unlike classic rectifiers, they do not use phase-shifting transformers and have a unit power factor. Increasing of the rectifier’s pulse makes it possible to improve the harmonic composition of the input current. This article is devoted to the study of the operation of an 18-pulse rectifier with an electronic phase shift. The use of the principle of electronic phase shift leads to different levels of constant voltage at the output of the rectifiers. The introduction of pulse-width modulation contributes to equalizing the output voltages of the 6-pulse rectifiers which are the parts of the converter. In addition, the use of the pulse-width modulation allows eliminating matching magnetic elements which are used to equalize rectifiers output voltages. This improves the mass and dimension parameters of the converter. The results of modeling are presented

The analysis of technical solutions for medical ozonators

The article deals with the basic principles of control systems construction in the medical ozone generators. The authors present and analyzes the specific diagram of the electrical and pneumatic part of ozonator. According to analysis results the authors give recommendations for the considered systems realization in the medical ozone generators

Identification of potential CepR regulated genes using a cep box motif-based search of the Burkholderia cenocepacia genome

BACKGROUND: The Burkholderia cenocepacia CepIR quorum sensing system has been shown to positively and negatively regulate genes involved in siderophore production, protease expression, motility, biofilm formation and virulence. In this study, two approaches were used to identify genes regulated by the CepIR quorum sensing system. Transposon mutagenesis was used to create lacZ promoter fusions in a cepI mutant that were screened for differential expression in the presence of N-acylhomoserine lactones. A bioinformatics approach was used to screen the B. cenocepacia J2315 genome for CepR binding site motifs. RESULTS: Four positively regulated and two negatively regulated genes were identified by transposon mutagenesis including genes potentially involved in iron transport and virulence. The promoter regions of selected CepR regulated genes and site directed mutagenesis of the cepI promoter were used to predict a consensus cep box sequence for CepR binding. The first-generation consensus sequence for the cep box was used to identify putative cep boxes in the genome sequence. Eight potential CepR regulated genes were chosen and the expression of their promoters analyzed. Six of the eight were shown to be regulated by CepR. A second generation motif was created from the promoters of these six genes in combination with the promoters of cepI, zmpA, and two of the CepR regulated genes identified by transposon mutagenesis. A search of the B. cenocepacia J2315 genome with the new motif identified 55 cep boxes in 65 promoter regions that may be regulated by CepR. CONCLUSION: Using transposon mutagenesis and bioinformatics expression of twelve new genes have been determined to be regulated by the CepIR quorum sensing system. A cep box consensus sequence has been developed based on the predicted cep boxes of ten CepR regulated genes. This consensus cep box has led to the identification of over 50 new genes potentially regulated by the CepIR quorum sensing system

СИЛОВАЯ ЭЛЕКТРОНИКА И КОНЦЕПЦИЯ РАЗВИТИЯ ЭНЕРГЕТИКИ «SMART GRID»

Formulate general requirements for Smart Grid, taking into account the reduction of energy losses in the energy supply system as a result of new semiconductor converters, energy storage and the transition from single-phase to three-phase consumers. On the example of the different power supply systems rated tentative positive effect of the introduction of these measures. References 25, figures 6, tables 2.Сформулированы общие требования к Smart Grid, учитывающие уменьшение потерь энергии в системе электроснабжения в результате применения новых полупроводниковых преобразователей и энергоемких накопителей энергии, а также перехода от однофазной сети потребителей к трехфазной. На примере различных систем электроснабжения оценен ориентировочный положительный эффект от внедрения указанных мероприятий. Библ. 25, рис. 6, табл. 2