Low-Voltage Circuit-Breaker Behavior under Overload Conditions

This article deals with temperature-rise of current path of modern low-voltage circuit-breaker with rotary contact system at overloads and subsequent experimental verification of selected model. The first part describes optimal setting of input conditions of simulation and mainly transient phenomena at contacts causing dynamic change of contact resistances due to change of total contact force, a new challenge to be solved in this contribution. The second part devotes laboratory measurement on prepared sample of the breaker for verification of transient simulation. These simulations are not only important for understanding of rotary system behavior under overloads, but forms an essential part of R & D process due to the speed-up of optimal current path design. In the end, both the financial costs and time effort could be decreased

Cattle Overwintering Areas in Middle-European Conditions - Important “Point” Sources Of Nitrous Oxide Emissions

Nitrous oxide (N2O) emissions in grazed grasslands are strongly influenced by animal excreta (Fowler et al., 1997). In addition, soil compaction caused by animal traffic significantly influences soil physical conditions and thus directly or indirectly impacts on the microbial processes producing N2O. In the Czech Republic pastures are mostly located in hilly and mountain areas. During the growing season, cattle are typically grazing, while during the winter the animals are concentrated near the animal house on a relatively small plot called an overwintering area . The objective of this study was to estimate the fluxes of N2O from a typical overwintering area, where the combined effects of soil compaction and deposition of urine and dung occur

Rotating Gliding Arc: Innovative Source for VOC Remediation

The large-scale plasma treatment of waste gas in industrial or municipal conditions requires high efficiency of plasma conversion process at high processing speed, i.e., large volumetric flow. The integration of the plasma unit into existing systems puts demands on the pipe-system compatibility and minimal pressure drop due to adoption of plasma processing step. These conditions are met at the innovative rotating electrode gliding arc plasma unit described in this article. The system consists of propeller-shaped high voltage electrode inside grounded metallic tube. The design of HV electrode eliminates the pressure drop inside the air system, contrary the plasma unit itself is capable of driving the waste gas at volumetric flow up to 300 m3/hr for 20 cm pipe diameter. In the article the first results on pilot study of waste air treatment will be given for selected volatile organic compounds together with basic characteristic of the plasma unit used

Thermal Plasma of Electric Arc Discharge Between Composite Cu-Cr Electrsodes: Optical Emission and Electrode Surface Interaction

This work deals with investigations of thermal plasma of electric arc discharge between sintered composite Cu-Cr electrodes, which can be used in electrical contacts of vacuum circuit breakers. Breaking arcs between composite Cu-Cr as well as single-component copper electrodes were used to study the electrical properties, plasma optical emission and electrodes surface modification behavior. In particular, the temporal evolution of plasma emission spectra of electric breaking arcs in air atmosphere was investigated by Optical Emission Spectroscopy (OES). Scanning Electron Microscopy (SEM) with Energy-dispersive X-ray Spectroscopy (EDXS) were applied to analyze the cross-section of working layer of electrodes surface modified by the heat flux from the discharge

Composite Cu-Cr materials under thermal action of electric arc discharge plasma

The results of optical emission spectroscopy (OES) investigation of plasma of electric arc discharges in steadystate mode between Cu-Cr composite electrodes, manufactured at different sintered temperatures: 750, 850, 950 or 1050 °C, is presented. In particular, the impact of sintering temperature on erosion resistanceof such composite materials, which was determined in indirect manner by estimation of metal vapours content in the midsection of discharge gaps, is studied by the analysis of plasma parameters. These contents were calculated in assumption of local thermodynamic equilibrium (LTE) on the base of experimentally obtained radial distributions of plasma temperature and electron density.Представлено результати дослідження плазми дугових розрядів у стаціонарному режимі методами оптичної емісійної спектроскопії (ОЕС) між електродами з Cu-Cr-композитних матеріалів, виготовлених при різних температурах спікання: 750, 850, 950 та 1050 °С. Зокрема, на основі аналізу параметрів плазми досліджено вплив температури спікання на ерозійну стійкість таких композиційних матеріалів, яка визначалась у непрямий спосіб – шляхом оцінки вмісту парів металів у середньому перерізі розрядних проміжків між електродами. Розподіли вмісту парів металів були розраховані в припущенні локальної термодинамічної рівноваги на основі експериментально одержаних радіальних розподілів температури плазми і електронної концентрації.Представлены результаты исследования плазмы дуговых разрядов в установившемся режиме методами оптической эмиссионной спектроскопии (ОЭС) между электродами из Cu-Cr-композитных материалов, изготовленных при различных температурах спекания: 750, 850, 950 и 1050 °С. В частности, на основе анализа параметров плазмы исследовано влияние температуры спекания на эрозионную стойкость таких композиционных материалов, которая определялась косвенным способом ‒ путем оценки содержания паров металлов в среднем сечении разрядных промежутков между электродами. Распределения содержания паров металлов были рассчитаны в предположении локального термодинамического равновесия на основе экспериментально полученных радиальных распределений температуры плазмы и электронной концентрации

Plasma-surface interaction of electric arc discharge between composite Cu-Cr electrodes

In this work the plasma of electric arc discharges between Cu-Cr composite electrodes, which material were pressured and sintered at different temperatures 750 or 1050°C, are investigated by Optical Emission Spectroscopy (OES). The Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDXS) are used to study the working surface of electrodes, modified by thermal effect of breaking electrical arc in the air atmosphere. The erosion intensity of electrodes’ material due to plasma-surface interaction is estimated in indirect way by determination of metal vapours content in the discharge gap in an assumption of local thermodynamic equilibrium (LTE). The plasma composition is calculated in this case on the base of experimentally determined plasma parameters: temperature and electron density.Методами оптичної емісійної спектроскопії досліджується плазма електродугових розрядів між композитними Cu-Cr-електродами, матеріал яких y процесі виготовлення піддавався пресуванню та спіканню при різних температурах: 750 або 1050°C. Для дослідження робочої поверхні електродів, які зазнали впливу термічної дії розривної електричної дуги в атмосфері повітря, використовується скануюча електронна мікроскопія (СЕМ), доповнена енергодисперсійною рентгенівською спектроскопією (ЕДРС). Інтенсивність ерозії матеріалу електродів внаслідок взаємодії плазма-поверхня оцінювалась у непрямий спосіб шляхом визначення вмісту парів металів у розрядному проміжку в припущенні локальної термодинамічної рівноваги (ЛТР). Склад плазми в даному випадку розрахований з експериментально отриманих параметрів плазми: температури та електронної концентрації.Методами оптической эмиссионной спектроскопии (ОЭС) исследуется плазма электродуговых разрядов между композитными Cu-Cr- электродами, материал которых в процессе изготовления подвергался прессованию и спеканию при разных температурах: 750 или 1050°C. Для изучения рабочей поверхности электродов, подвергающейся термическому воздействию разрывной электрической дуги в атмосфере воздуха, использована сканирующая электронная микроскопия (СЭМ), дополненная энергодисперсионной рентгеновской спектроскопией (ЭДРС). Интенсивность эрозии материала электродов вследствие взаимодействия плазма-поверхность оценивалась косвенным методом путем определения содержания паров металлов в разрядном промежутке в предположении локального термодинамического равновесия (ЛТР). Состав плазмы в этом случае рассчитан из экспериментально полученных параметров: температуры и электронной концентрации

The Passive Yet Successful Way of Planktonic Life: Genomic and Experimental Analysis of the Ecology of a Free-Living Polynucleobacter Population

Background: The bacterial taxon Polynucleobacter necessarius subspecies asymbioticus represents a group of planktonic freshwater bacteria with cosmopolitan and ubiquitous distribution in standing freshwater habitats. These bacteria comprise,1 % to 70 % (on average about 20%) of total bacterioplankton cells in various freshwater habitats. The ubiquity of this taxon was recently explained by intra-taxon ecological diversification, i.e. specialization of lineages to specific environmental conditions; however, details on specific adaptations are not known. Here we investigated by means of genomic and experimental analyses the ecological adaptation of a persistent population dwelling in a small acidic pond. Findings: The investigated population (F10 lineage) contributed on average 11 % to total bacterioplankton in the pond during the vegetation periods (ice-free period, usually May to November). Only a low degree of genetic diversification of the population could be revealed. These bacteria are characterized by a small genome size (2.1 Mb), a relatively small number of genes involved in transduction of environmental signals, and the lack of motility and quorum sensing. Experiments indicated that these bacteria live as chemoorganotrophs by mainly utilizing low-molecular-weight substrates derived from photooxidation of humic substances. Conclusions: Evolutionary genome streamlining resulted in a highly passive lifestyle so far only known among free-living bacteria from pelagic marine taxa dwelling in environmentally stable nutrient-poor off-shore systems. Surprisingly, such a lifestyle is also successful in a highly dynamic and nutrient-richer environment such as the water column of the investigate

Enrichment of Omnivorous Cercozoan Nanoflagellates from Coastal Baltic Sea Waters

Free-living nano-sized flagellates are important bacterivores in aquatic habitats. However, some slightly larger forms can also be omnivorous, i.e., forage upon both bacterial and eukaryotic resources. This hitherto largely ignored feeding mode may have pronounced implications for the interpretation of experiments about protistan bacterivory. We followed the response of an uncultured group of omnivorous cercozoan nanoflagellates from the Novel Clade 2 (Cerc_BAL02) to experimental food web manipulation in samples from the Gulf of Gdańsk (Southern Baltic Sea). Seawater was either prefiltered through 5 µm filters to exclude larger predators of nanoflagellates (F-treatment), or prefiltered and subsequently 1∶10 diluted with sterile seawater (F+D-treatment) to stimulate the growth of both, flagellates and bacteria. Initially, Cerc_BAL02 were rapidly enriched under both conditions. They foraged on both, eukaryotic prey and bacteria, and were highly competitive at low concentrations of food. However, these omnivores were later only successful in the F+D treatment, where they eventually represented almost one fifth of all aplastidic nanoflagellates. By contrast, their numbers stagnated in the F-treatment, possibly due to top-down control by a concomitant bloom of other, unidentified flagellates. In analogy with observations about the enrichment of opportunistically growing bacteria in comparable experimental setups we suggest that the low numbers of omnivorous Cerc_Bal02 flagellates in waters of the Gulf of Gdańsk might also be related to their vulnerability to grazing pressure