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Détails du magazine
Format
Magazine
eISSN
2255-8896
Première publication
18 Mar 2008
Période de publication
6 fois par an
Langues
Anglais

Chercher

Volume 56 (2019): Edition 3 (June 2019)

Détails du magazine
Format
Magazine
eISSN
2255-8896
Première publication
18 Mar 2008
Période de publication
6 fois par an
Langues
Anglais

Chercher

6 Articles
Accès libre

Design of a Three-Phase Bidirectional PWM Rectifier with Simple Control Algorithm

Publié en ligne: 12 Jul 2019
Pages: 3 - 12

Résumé

Abstract

The paper covers the main aspects of designing a low voltage three-phase PWM rectifier for bidirectional AC/DC power flow with unity power factor. A model in Matlab/Simulink environment has been built for a 10kW active rectifier with an LCL filter connected to grid side of the rectifier. The primary goal of the model is to achieve low grid current harmonic content for frequency ranges described in worldwide applicable standards and above. LCL filter parameter design procedure is described in the paper and implemented in the rectifier model to achieve a better power quality with limitations in passive element size. A simple “p-q” theory-based voltage oriented control algorithm is used in the model and described in the present paper. Model performance is characterised by dynamic response, stability and grid parameters during simulation. The simulation results demonstrate that the modelled rectifier system is stable and the grid current harmonic content is low both in the low-and high-frequency ranges.

Mots clés

  • bi-directional AC/DC rectifier
  • LCL filter
Accès libre

Magnetostrictive Vibration Model for Evaluation of Mechanical Integrity of Power Transformer Magnetic Core

Publié en ligne: 12 Jul 2019
Pages: 13 - 25

Résumé

Abstract

Magnetostriction process creates vibrations within magnetic core of a power transformer. This effect can cause delamination of magnetic core layers and increase the vibration amplitudes on the surface of transformer tank. In this paper, a magnetostrictive vibration model is proposed for improved evaluation of the mechanical integrity of magnetic core and the finding of possible mechanical defects. This model is based on the simulation of magnetostrictive vibrations by replacing the magnetic core with mass and spring system, and application of a dynamic genetic algorithm in order to find the necessary system configuration. A case study is provided structurally modelling magnetic core in Matlab and Matlab Simulink with the analysis of simulated vibrations that indicate a possible mechanical defect.

Mots clés

  • magnetostriction
  • numerical simulation
  • transformer cores
Accès libre

Utilisation of the Safety Index (Elmeri Index) as the OSH Indicator at Coal Mines

Publié en ligne: 12 Jul 2019
Pages: 26 - 36

Résumé

Abstract

The article describes the main performances of the global coal industry, as well as key occupational safety and health indicators (OSH indicators) of the coal mining industry of the Russian Federation. The main goal of the article is to present the results of research of potential utilisation of the Elmeri observation method in order to evaluate safety levels at underground coal mines. The investigation performed taking into consideration two root causes of the occupational traumatism (methane and/or dust explosions, as well as rock falls) has demonstrated good correlation between the calculated values of the safety index and results of the risk assessments at the same underground coal mine under consideration. In addition, the article includes a brief discussion of advantages and restrictions in respect of utilisation of the safety index as the OSH monitoring tool at coal mines.

Mots clés

  • coal production
  • dangers
  • methane explosions
  • observation
  • occupational fatalities
  • rock fall
  • safety indicator
Accès libre

Impact Modelling of Explosion of Mixture Explosive Charges on the Environment

Publié en ligne: 12 Jul 2019
Pages: 37 - 49

Résumé

Abstract

The present paper provides the modelling of the explosion of the charges of the traditional (trotyl) and new blended explosive substances: polymix GR1/8 (74 %) + KRUK2 (26 %), compolite GS6, polymix GR4-T10. As a result of the research, it has been established that when using TNT a specific impulse is formed, which is by 40 % more than an explosion of new mixed explosives, and the safe distance from the source of the explosion of such explosives is increased by 25 %–50 %. On the basis of the established dependences of excess pressure, the specific impulse on the type and mass of charge, as well as the distance from the epicenter of the explosion, an engineering method has been developed for calculating dangerous parameters of the explosion impact on the environment.

Mots clés

  • air shock wave
  • compolite explosives
  • destructive action
  • environment
  • explosion
  • modelling
Accès libre

Low-Cost L-Band Receiving System Front-End for Irbene RT-32 Cassegrain Radio Telescope

Publié en ligne: 12 Jul 2019
Pages: 50 - 61

Résumé

Abstract

Irbene RT-32 radio telescope is one of the main instruments operated by Ventspils International Radio Astronomy Center (VIRAC), which is used for participation in VLBI and single-dish mode observations, including European VLBI Network (EVN) and other astronomy projects such as recently started research on small bodies of solar system, which involves weak spectral line detection at L-band. Since start of the operation as a radio telescope, single C-X band receiver has been available at RT-32, but regular demand for L-band frequencies has been received due to its importance in spectral line science. In case of RT-32 geometry, optimum dimensions of L-band feed antenna system are inconveniently large and its installation without significant feed cone rebuilding is complicated. While work is currently ongoing to redesign the feed cone for multiple receiver support and to develop high performance L-band feed system, temporal, compact and low-cost receiver has been built and installed laterally to secondary focus, which in sense of performance and functionality has been proven to be appropriate for most of the current needs. Receiver is based on small parabolic reflector allowing one to use a compact dual circular polarized horn antenna, which together with a Cassegrain antenna forms a three-mirror system. Front-end is uncooled that allows reducing operational and maintenance costs, while still providing acceptable noise performance. Practical tests show average overall sensitivity of 750 Jy at 1650 MHz in terms of system effective flux density (SEFD). The paper describes the development of the receiver and presents the main results of performance characterization obtained at Irbene RT-32.

Mots clés

  • feed antenna
  • radio telescope
  • receiver
Accès libre

Evaluation Principles of the Dust Influence of Mining Enterprises on the Environment

Publié en ligne: 12 Jul 2019
Pages: 62 - 69

Résumé

Abstract

It has been noted that the areas disturbed by open-pit mining together with the production processes in the extraction of mineral resources (drilling, blasting, transportation, etc.) have a negative influence on the environment in general and the atmosphere in particular. It has been indicated that, in percentage terms, dusting of refuse dumps and tailing dumps plays a prevailing role in the total amount of dust generated. It has been stated that the processes of formation and subsequent transfer of dust in the atmosphere depend on the combination of meteorological and mining factors that have a probabilistic nature in time and space. It has been shown that the maximum value of environmental risk characterises the level of dust influence, at which reduction environmental protection measures should be directed. The present paper proposes a procedure for evaluation of the dusty influence of mining enterprises on the environment. Under the conditions of Olenegorsk GOK, a GIS has been compiled – a project of the study area and, based on geo-information modelling, the results of calculating dust concentrations in the air have been imposed on a digital map of the area.

Mots clés

  • dust influence
  • GIS modelling
  • open cast mining
  • population intoxication risk
  • refuse dumps
  • tailing dumps
6 Articles
Accès libre

Design of a Three-Phase Bidirectional PWM Rectifier with Simple Control Algorithm

Publié en ligne: 12 Jul 2019
Pages: 3 - 12

Résumé

Abstract

The paper covers the main aspects of designing a low voltage three-phase PWM rectifier for bidirectional AC/DC power flow with unity power factor. A model in Matlab/Simulink environment has been built for a 10kW active rectifier with an LCL filter connected to grid side of the rectifier. The primary goal of the model is to achieve low grid current harmonic content for frequency ranges described in worldwide applicable standards and above. LCL filter parameter design procedure is described in the paper and implemented in the rectifier model to achieve a better power quality with limitations in passive element size. A simple “p-q” theory-based voltage oriented control algorithm is used in the model and described in the present paper. Model performance is characterised by dynamic response, stability and grid parameters during simulation. The simulation results demonstrate that the modelled rectifier system is stable and the grid current harmonic content is low both in the low-and high-frequency ranges.

Mots clés

  • bi-directional AC/DC rectifier
  • LCL filter
Accès libre

Magnetostrictive Vibration Model for Evaluation of Mechanical Integrity of Power Transformer Magnetic Core

Publié en ligne: 12 Jul 2019
Pages: 13 - 25

Résumé

Abstract

Magnetostriction process creates vibrations within magnetic core of a power transformer. This effect can cause delamination of magnetic core layers and increase the vibration amplitudes on the surface of transformer tank. In this paper, a magnetostrictive vibration model is proposed for improved evaluation of the mechanical integrity of magnetic core and the finding of possible mechanical defects. This model is based on the simulation of magnetostrictive vibrations by replacing the magnetic core with mass and spring system, and application of a dynamic genetic algorithm in order to find the necessary system configuration. A case study is provided structurally modelling magnetic core in Matlab and Matlab Simulink with the analysis of simulated vibrations that indicate a possible mechanical defect.

Mots clés

  • magnetostriction
  • numerical simulation
  • transformer cores
Accès libre

Utilisation of the Safety Index (Elmeri Index) as the OSH Indicator at Coal Mines

Publié en ligne: 12 Jul 2019
Pages: 26 - 36

Résumé

Abstract

The article describes the main performances of the global coal industry, as well as key occupational safety and health indicators (OSH indicators) of the coal mining industry of the Russian Federation. The main goal of the article is to present the results of research of potential utilisation of the Elmeri observation method in order to evaluate safety levels at underground coal mines. The investigation performed taking into consideration two root causes of the occupational traumatism (methane and/or dust explosions, as well as rock falls) has demonstrated good correlation between the calculated values of the safety index and results of the risk assessments at the same underground coal mine under consideration. In addition, the article includes a brief discussion of advantages and restrictions in respect of utilisation of the safety index as the OSH monitoring tool at coal mines.

Mots clés

  • coal production
  • dangers
  • methane explosions
  • observation
  • occupational fatalities
  • rock fall
  • safety indicator
Accès libre

Impact Modelling of Explosion of Mixture Explosive Charges on the Environment

Publié en ligne: 12 Jul 2019
Pages: 37 - 49

Résumé

Abstract

The present paper provides the modelling of the explosion of the charges of the traditional (trotyl) and new blended explosive substances: polymix GR1/8 (74 %) + KRUK2 (26 %), compolite GS6, polymix GR4-T10. As a result of the research, it has been established that when using TNT a specific impulse is formed, which is by 40 % more than an explosion of new mixed explosives, and the safe distance from the source of the explosion of such explosives is increased by 25 %–50 %. On the basis of the established dependences of excess pressure, the specific impulse on the type and mass of charge, as well as the distance from the epicenter of the explosion, an engineering method has been developed for calculating dangerous parameters of the explosion impact on the environment.

Mots clés

  • air shock wave
  • compolite explosives
  • destructive action
  • environment
  • explosion
  • modelling
Accès libre

Low-Cost L-Band Receiving System Front-End for Irbene RT-32 Cassegrain Radio Telescope

Publié en ligne: 12 Jul 2019
Pages: 50 - 61

Résumé

Abstract

Irbene RT-32 radio telescope is one of the main instruments operated by Ventspils International Radio Astronomy Center (VIRAC), which is used for participation in VLBI and single-dish mode observations, including European VLBI Network (EVN) and other astronomy projects such as recently started research on small bodies of solar system, which involves weak spectral line detection at L-band. Since start of the operation as a radio telescope, single C-X band receiver has been available at RT-32, but regular demand for L-band frequencies has been received due to its importance in spectral line science. In case of RT-32 geometry, optimum dimensions of L-band feed antenna system are inconveniently large and its installation without significant feed cone rebuilding is complicated. While work is currently ongoing to redesign the feed cone for multiple receiver support and to develop high performance L-band feed system, temporal, compact and low-cost receiver has been built and installed laterally to secondary focus, which in sense of performance and functionality has been proven to be appropriate for most of the current needs. Receiver is based on small parabolic reflector allowing one to use a compact dual circular polarized horn antenna, which together with a Cassegrain antenna forms a three-mirror system. Front-end is uncooled that allows reducing operational and maintenance costs, while still providing acceptable noise performance. Practical tests show average overall sensitivity of 750 Jy at 1650 MHz in terms of system effective flux density (SEFD). The paper describes the development of the receiver and presents the main results of performance characterization obtained at Irbene RT-32.

Mots clés

  • feed antenna
  • radio telescope
  • receiver
Accès libre

Evaluation Principles of the Dust Influence of Mining Enterprises on the Environment

Publié en ligne: 12 Jul 2019
Pages: 62 - 69

Résumé

Abstract

It has been noted that the areas disturbed by open-pit mining together with the production processes in the extraction of mineral resources (drilling, blasting, transportation, etc.) have a negative influence on the environment in general and the atmosphere in particular. It has been indicated that, in percentage terms, dusting of refuse dumps and tailing dumps plays a prevailing role in the total amount of dust generated. It has been stated that the processes of formation and subsequent transfer of dust in the atmosphere depend on the combination of meteorological and mining factors that have a probabilistic nature in time and space. It has been shown that the maximum value of environmental risk characterises the level of dust influence, at which reduction environmental protection measures should be directed. The present paper proposes a procedure for evaluation of the dusty influence of mining enterprises on the environment. Under the conditions of Olenegorsk GOK, a GIS has been compiled – a project of the study area and, based on geo-information modelling, the results of calculating dust concentrations in the air have been imposed on a digital map of the area.

Mots clés

  • dust influence
  • GIS modelling
  • open cast mining
  • population intoxication risk
  • refuse dumps
  • tailing dumps

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