Zeitschriften und Ausgaben

Volumen 18 (2022): Heft 1 (June 2022)

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Volumen 15 (2019): Heft 2 (December 2019)

Volumen 15 (2019): Heft 1 (September 2019)

Volumen 14 (2018): Heft 2 (December 2018)

Volumen 14 (2018): Heft 1 (July 2018)

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Zeitschriftendaten
Format
Zeitschrift
eISSN
2255-9159
Erstveröffentlichung
31 Jan 2013
Erscheinungsweise
2 Hefte pro Jahr
Sprachen
Englisch

Suche

Volumen 15 (2019): Heft 1 (September 2019)

Zeitschriftendaten
Format
Zeitschrift
eISSN
2255-9159
Erstveröffentlichung
31 Jan 2013
Erscheinungsweise
2 Hefte pro Jahr
Sprachen
Englisch

Suche

7 Artikel
Uneingeschränkter Zugang

Improving Legibility of Motor Current Spectrum for Broken Rotor Bars Fault Diagnostics

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 1 - 8

Zusammenfassung

Abstract

In this paper, the harmonic contribution of the broken rotor bar of an induction machine is investigated using an effective combination of the fast Fourier transform (FFT) and a band stop filter. The winding, spatial, grid fed and fault-based harmonics are investigated. Since the fundamental component is the most powerful component as compared to the other frequencies, it decreases the legibility of spectrum, making logarithmic scale inevitable. It also remains a potential threat of burying the fault representative side band frequencies because of its spectral leakage. In this paper, a band stop Chebyshev filter is used to attenuate the fundamental component, which makes the spectrum clearer and easier to understand even on the linear scale. Its good transition band and low passband ripples make it suitable for attenuating the main supply frequency with low impact on the neighbouring side band frequencies. To study the impact of fault on magnetic flux distribution, simulation is done using finite element method with good number of mesh elements and very small step size. The line current is calculated and frequency spectrum is investigated to segregate the spatial and fault frequencies using the proposed technique. The results are further validated by implementing the algorithm on the data measured in the laboratory environment including the grid fed harmonics.

Schlüsselwörter

  • Digital filters
  • Fault diagnosis
  • Fourier transform
  • Induction motors
Uneingeschränkter Zugang

Analysis of the Local and Global Forces Acting on the Coil Structure of a Modular Slotless Permanent Magnet Generator

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 9 - 14

Zusammenfassung

Abstract

This paper investigates the local and global forces acting on the coil structure of a low-speed modular permanent magnet generator for wind energy application. Two different configurations of the coil structure are studied. The first one consists of separately replaceable single-coil modules, whereas the second consists of three-phase coil-module assemblies. The purpose of the analysis is to investigate the advantages and disadvantages of each configuration in terms of vibrations and mechanical robustness. The investigations also provide the load for the mechanical analysis needed in the design of the retaining structure of the generator. The results show that there are strong fluctuations in the radial forces acting on the single-coil structure. The three-phase coil-module assembly reduces the fluctuations of the radial forces, but it results in an increase of the cogging torque, which is not suitable for the slotless design. Namely, the advantage of the slotless design is to reduce the cogging torque. The computed forces are then used in a structural mechanical simulation, the results of which are validated through strain measurements. The validation procedure is carried out on a specially built mock-up as accessing the generator on site is not possible.

Schlüsselwörter

  • Cogging torque
  • Coil forces
  • Modular system
  • Permanent magnet generator
  • Slotless design
Uneingeschränkter Zugang

Determination of Heat Transfer Coefficient for the Air Forced Cooling Over a Flat Side of Coil

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 15 - 20

Zusammenfassung

Abstract

The paper deals with the analytical and experimental determination of the forced convection heat transfer coefficients over the flat coil module. In the analytical part, the forced convection coefficients at different wind speeds are calculated based on various known equations of the forced convection heat transfer coefficient with unheated starting length. The experimental part presents the description of the test: loading the coil with DC current and measurements of the coil temperatures with thermal sensors while it was inside a wind tunnel. Based on the measurement, the convection coefficients were determined. In the final part, the experimental and analytical results are compared. It is found that the accuracy of the analytical results is more precise in highly turbulent flows.

Schlüsselwörter

  • Flat surface
  • Forced convection
  • Heat transfer coefficient
  • Laminar and turbulent flow
Uneingeschränkter Zugang

Machine Learning Platform for Profiling and Forecasting at Microgrid Level

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 21 - 29

Zusammenfassung

Abstract

The shift towards distributed generation and microgrids has renewed the interest in forecasting algorithms and methods, which need to take into account the advances in information, metering and control technologies in order to address the challenges of forecasting problems. Technologies such as machine learning have been proven useful for short-term electricity load forecasting, especially for microgrids, as they can also take into account several types of historical data and can adapt to changes often encountered in small-scale systems and on a short time scale. In this paper, we present a flexible and easily customized modular toolbox, called Divinus, for electricity use profiling and forecasting in microgrids. Divinus may support a variety of machine learning algorithms for forecasting and profiling that can be used independently or combined. For demonstration purposes, we have implemented Self-Organizing Maps for profiling and k-Neighbors for forecasting. The testing of the platform was based on electricity consumption data of the Euripus campus of the National and Kapodistrian University of Athens in Evia, Greece, from January 2010 till March 2018. The tests that have been carried out so far show that the platform can be easily customized and the algorithms examined yield high accuracy and acceptable mean errors for the case of a university campus energy profile.

Schlüsselwörter

  • Clustering algorithms
  • Forecasting
  • Machine learning algorithms
Uneingeschränkter Zugang

Study of Load Characteristics of Various Types of Silicon PV Panels for Sustainable Energy Efficient Road Pavement

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 30 - 38

Zusammenfassung

Abstract

This paper presents a new approach to the creation of innovative roads having sustainable energy efficient road pavement as their basis. It is a new type of intelligent roads that is able to service itself and provide power, i.e. it is also a renewable source of electricity. It is planned to use the studies on the PV panels in sustainable energy efficient road pavement to determine their load parameters. The work used the methods of mathematical analysis and theoretical electrophysics to carry out the studies on load characteristics of various types of silicon PV panels in order to define the most effective panels from the point of view of generated electrical energy load resistance values. The analysis of the obtained results of the experimental research has shown that in order to make the operation of PV panels of series FS-100M and FS-110P most efficient, their load must be maintained within 3–3.5 Ω range. If load resistance exceeds the specified limits, the work of PV panels of this series will be ineffective. The road having a sustainable energy efficient road pavement is able to track road conditions, traffic, weather conditions and react quickly to their changes. It is shown how road markings can change dependance on road conditions.

Schlüsselwörter

  • Energy efficiency
  • Photovoltaic systems
  • Renewable energy sources
  • Solar energy
  • Solar panels
Uneingeschränkter Zugang

Raman Spectroscopy Principles for in vivo Diagnostic by Ellipsoidal Reflectors

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 39 - 46

Zusammenfassung

Abstract

The paper presents the analysis of the functional abilities of measurement tools with ellipsoidal reflectors for Raman spectroscopy. The investigated structural scheme of the setup is intended for use in Raman spectroscopy in vivo by ellipsoidal reflectors. The setup can be used as a prototype for development of a device for non-invasive control of sugar level. Additionally, the investigation demonstrates the efficiency of ellipsoidal photometry method for registration of Raman scattering signal on test-solutions. The testing was performed for different sugar concentrations with the laser radiation wavelength 980 nm. In addition, the selecting principles of laser radiation source parameters (including beam diameter and power) were investigated. During the research, the data about spatial distribution of the backscattered light in human shoulder and finger tissues during photometry by ellipsoidal reflectors were received. The procedure involves application of Monte Carlo simulation. The dependency of the external and middle ring illuminance of photometric images on the diameter and power of the laser beam is represented based on the zone analysis.

Schlüsselwörter

  • Biomedical electronics
  • Biomedical optical imaging
  • Biophotonics
  • In vivo
  • Mirrors
Uneingeschränkter Zugang

Ontology-Based Design of the Learner’s Knowledge Domain in Electrical Engineering

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 47 - 53

Zusammenfassung

Abstract

This research addresses some personalization aspects of education in electrical engineering. Its goal is to help students and educators evaluate the complexity of the disciplines they have chosen for studying and optimize the order of the learned courses and topics. A new instrument, namely, an educational thesaurus, is presented and its assembling procedure is shown. The offered educational thesauri implemented in the labs and integrated in the exercises have become smart platforms suitable for design and management of the students’ individual knowledge domains. The ontology-based Web manuals in Electronics and Power Electronics for the Bachelor study cycle have been introduced. An example of ontology graph to be applied within the Master study cycle has been developed and explained in the paper. According to the authors’ investigation, the decrease of stress caused by the new educational environment and achievement of success in learning were observed thanks to the individual knowledge domain organization proposed in this study.

Schlüsselwörter

  • Distance learning
  • Education courses
  • Engineering education
  • Engineering students
  • Learning management systems
  • Ontology
  • Thesauri
7 Artikel
Uneingeschränkter Zugang

Improving Legibility of Motor Current Spectrum for Broken Rotor Bars Fault Diagnostics

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 1 - 8

Zusammenfassung

Abstract

In this paper, the harmonic contribution of the broken rotor bar of an induction machine is investigated using an effective combination of the fast Fourier transform (FFT) and a band stop filter. The winding, spatial, grid fed and fault-based harmonics are investigated. Since the fundamental component is the most powerful component as compared to the other frequencies, it decreases the legibility of spectrum, making logarithmic scale inevitable. It also remains a potential threat of burying the fault representative side band frequencies because of its spectral leakage. In this paper, a band stop Chebyshev filter is used to attenuate the fundamental component, which makes the spectrum clearer and easier to understand even on the linear scale. Its good transition band and low passband ripples make it suitable for attenuating the main supply frequency with low impact on the neighbouring side band frequencies. To study the impact of fault on magnetic flux distribution, simulation is done using finite element method with good number of mesh elements and very small step size. The line current is calculated and frequency spectrum is investigated to segregate the spatial and fault frequencies using the proposed technique. The results are further validated by implementing the algorithm on the data measured in the laboratory environment including the grid fed harmonics.

Schlüsselwörter

  • Digital filters
  • Fault diagnosis
  • Fourier transform
  • Induction motors
Uneingeschränkter Zugang

Analysis of the Local and Global Forces Acting on the Coil Structure of a Modular Slotless Permanent Magnet Generator

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 9 - 14

Zusammenfassung

Abstract

This paper investigates the local and global forces acting on the coil structure of a low-speed modular permanent magnet generator for wind energy application. Two different configurations of the coil structure are studied. The first one consists of separately replaceable single-coil modules, whereas the second consists of three-phase coil-module assemblies. The purpose of the analysis is to investigate the advantages and disadvantages of each configuration in terms of vibrations and mechanical robustness. The investigations also provide the load for the mechanical analysis needed in the design of the retaining structure of the generator. The results show that there are strong fluctuations in the radial forces acting on the single-coil structure. The three-phase coil-module assembly reduces the fluctuations of the radial forces, but it results in an increase of the cogging torque, which is not suitable for the slotless design. Namely, the advantage of the slotless design is to reduce the cogging torque. The computed forces are then used in a structural mechanical simulation, the results of which are validated through strain measurements. The validation procedure is carried out on a specially built mock-up as accessing the generator on site is not possible.

Schlüsselwörter

  • Cogging torque
  • Coil forces
  • Modular system
  • Permanent magnet generator
  • Slotless design
Uneingeschränkter Zugang

Determination of Heat Transfer Coefficient for the Air Forced Cooling Over a Flat Side of Coil

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 15 - 20

Zusammenfassung

Abstract

The paper deals with the analytical and experimental determination of the forced convection heat transfer coefficients over the flat coil module. In the analytical part, the forced convection coefficients at different wind speeds are calculated based on various known equations of the forced convection heat transfer coefficient with unheated starting length. The experimental part presents the description of the test: loading the coil with DC current and measurements of the coil temperatures with thermal sensors while it was inside a wind tunnel. Based on the measurement, the convection coefficients were determined. In the final part, the experimental and analytical results are compared. It is found that the accuracy of the analytical results is more precise in highly turbulent flows.

Schlüsselwörter

  • Flat surface
  • Forced convection
  • Heat transfer coefficient
  • Laminar and turbulent flow
Uneingeschränkter Zugang

Machine Learning Platform for Profiling and Forecasting at Microgrid Level

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 21 - 29

Zusammenfassung

Abstract

The shift towards distributed generation and microgrids has renewed the interest in forecasting algorithms and methods, which need to take into account the advances in information, metering and control technologies in order to address the challenges of forecasting problems. Technologies such as machine learning have been proven useful for short-term electricity load forecasting, especially for microgrids, as they can also take into account several types of historical data and can adapt to changes often encountered in small-scale systems and on a short time scale. In this paper, we present a flexible and easily customized modular toolbox, called Divinus, for electricity use profiling and forecasting in microgrids. Divinus may support a variety of machine learning algorithms for forecasting and profiling that can be used independently or combined. For demonstration purposes, we have implemented Self-Organizing Maps for profiling and k-Neighbors for forecasting. The testing of the platform was based on electricity consumption data of the Euripus campus of the National and Kapodistrian University of Athens in Evia, Greece, from January 2010 till March 2018. The tests that have been carried out so far show that the platform can be easily customized and the algorithms examined yield high accuracy and acceptable mean errors for the case of a university campus energy profile.

Schlüsselwörter

  • Clustering algorithms
  • Forecasting
  • Machine learning algorithms
Uneingeschränkter Zugang

Study of Load Characteristics of Various Types of Silicon PV Panels for Sustainable Energy Efficient Road Pavement

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 30 - 38

Zusammenfassung

Abstract

This paper presents a new approach to the creation of innovative roads having sustainable energy efficient road pavement as their basis. It is a new type of intelligent roads that is able to service itself and provide power, i.e. it is also a renewable source of electricity. It is planned to use the studies on the PV panels in sustainable energy efficient road pavement to determine their load parameters. The work used the methods of mathematical analysis and theoretical electrophysics to carry out the studies on load characteristics of various types of silicon PV panels in order to define the most effective panels from the point of view of generated electrical energy load resistance values. The analysis of the obtained results of the experimental research has shown that in order to make the operation of PV panels of series FS-100M and FS-110P most efficient, their load must be maintained within 3–3.5 Ω range. If load resistance exceeds the specified limits, the work of PV panels of this series will be ineffective. The road having a sustainable energy efficient road pavement is able to track road conditions, traffic, weather conditions and react quickly to their changes. It is shown how road markings can change dependance on road conditions.

Schlüsselwörter

  • Energy efficiency
  • Photovoltaic systems
  • Renewable energy sources
  • Solar energy
  • Solar panels
Uneingeschränkter Zugang

Raman Spectroscopy Principles for in vivo Diagnostic by Ellipsoidal Reflectors

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 39 - 46

Zusammenfassung

Abstract

The paper presents the analysis of the functional abilities of measurement tools with ellipsoidal reflectors for Raman spectroscopy. The investigated structural scheme of the setup is intended for use in Raman spectroscopy in vivo by ellipsoidal reflectors. The setup can be used as a prototype for development of a device for non-invasive control of sugar level. Additionally, the investigation demonstrates the efficiency of ellipsoidal photometry method for registration of Raman scattering signal on test-solutions. The testing was performed for different sugar concentrations with the laser radiation wavelength 980 nm. In addition, the selecting principles of laser radiation source parameters (including beam diameter and power) were investigated. During the research, the data about spatial distribution of the backscattered light in human shoulder and finger tissues during photometry by ellipsoidal reflectors were received. The procedure involves application of Monte Carlo simulation. The dependency of the external and middle ring illuminance of photometric images on the diameter and power of the laser beam is represented based on the zone analysis.

Schlüsselwörter

  • Biomedical electronics
  • Biomedical optical imaging
  • Biophotonics
  • In vivo
  • Mirrors
Uneingeschränkter Zugang

Ontology-Based Design of the Learner’s Knowledge Domain in Electrical Engineering

Online veröffentlicht: 18 Sep 2019
Seitenbereich: 47 - 53

Zusammenfassung

Abstract

This research addresses some personalization aspects of education in electrical engineering. Its goal is to help students and educators evaluate the complexity of the disciplines they have chosen for studying and optimize the order of the learned courses and topics. A new instrument, namely, an educational thesaurus, is presented and its assembling procedure is shown. The offered educational thesauri implemented in the labs and integrated in the exercises have become smart platforms suitable for design and management of the students’ individual knowledge domains. The ontology-based Web manuals in Electronics and Power Electronics for the Bachelor study cycle have been introduced. An example of ontology graph to be applied within the Master study cycle has been developed and explained in the paper. According to the authors’ investigation, the decrease of stress caused by the new educational environment and achievement of success in learning were observed thanks to the individual knowledge domain organization proposed in this study.

Schlüsselwörter

  • Distance learning
  • Education courses
  • Engineering education
  • Engineering students
  • Learning management systems
  • Ontology
  • Thesauri

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