Publikační činnost Katedry elektrotechniky / Publications of Department of Electrical Engineering (420)

Permanent URI for this collectionhttp://hdl.handle.net/10084/70102

Kolekce obsahuje bibliografické záznamy publikační činnosti (článků) akademických pracovníků Katedry obecné elektrotechniky (420) v časopisech registrovaných ve Web of Science od roku 2003 do roku 2022.
Do kolekce jsou zařazeny:
a) publikace, u nichž je v originálních dokumentech jako působiště autora (adresa) uvedena Vysoká škola báňská-Technická univerzita Ostrava (VŠB-TUO),
b) publikace, u nichž v originálních dokumentech není v adrese VŠB-TUO uvedena, ale autoři prokazatelně v době jejich zpracování a uveřejnění působili na VŠB-TUO.

Bibliografické záznamy byly původně vytvořeny v kolekci Publikační činnost akademických pracovníků VŠB-TUO, která sleduje publikování akademických pracovníků od roku 1990.

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Now showing 1 - 20 out of 48 results

Dynamic stray current measuring methods in urban areas
(RTU Press, 2022) Vranešić, Katarina; Serdar, Marijana; Lakušić, Stjepan; Kolář, Václav; Mariscotti, Andrea
In areas where urban tracks are used as public transportation, dynamic stray currents cause high maintenance costs for the tracks and metal s tructures n ear t he t racks. S tray c urrents c aused b y r ail v ehicles depend on many factors (traffic density, vehicle speed, acceleration and deceleration, soil and track moisture), so it is very difficult to get a clear picture of the harmfulness of the stray current based on the results of a single field measurement. However, there are several measurement methods that can be used to determine the presence of stray currents and predict appropriate track maintenance actions. Some of these methods are described in this article, namely the use of stray current mapper, measurement of rail potential and rail current, measurement at the stray current collection system, and the use of nondestructive sensors. In track construction, measuring the electrical potential between rail and ground is one of the most common methods of detecting the damaging influence of stray current.
Innovative bidirectional isolated high-power density on-board charge for vehicle-to-grid
(MDPI, 2022) Hrbáč, Roman; Hrdina, Libor; Kolář, Václav; Slanina, Zdeněk; Blažek, Vojtěch; Vantuch, Tomáš; Mišák, Stanislav; Bartłomiejczyk, Mikołaj
This paper deals with developing and implementing a bidirectional galvanically isolated on-board charger of a high-power density. The power density of the new charger was 4 kW/kg and 2.46 kW/dm(3), and the maximum efficiency was 96.4% at 3.4 kW. Due to the requirement to achieve a high-power density, a single-stage inverter topology was used. Regarding switching losses, due to the topology of the circuit with so-called hard switching, the switching frequency was set to 150 kHz. A laboratory prototype was built to verify the properties and operating principles of the described charger topology. The on-board charger has been tested in a microgrid test platform. Due to the parasitic properties of the transformer and other electronic components, overvoltage with subsequent oscillations occurred on the primary side of the transformer and damped resonance on its secondary side. These parasitic properties caused interference and especially voltage stress on the semiconductor elements. These undesirable phenomena have been eliminated by adding an active element to the charger topology and a new transistor control strategy. This new switching control strategy of transistors has been patented.
Applied forces in the handling unit fixation mechanism
(Sveučilište Josipa Jurja Strossmayera u Osijeku. Strojarski fakultet; Elektrotehnički fakultet; Građevinski fakultet., 2022) Hrabovský, Leopold; Mlčák, Tomáš; Žáček, Václav
The paper presents a construction design of a testing device, which was built for the purpose of checking the functional properties of the movement fixation mechanism of handling units, which is used for locking pallets with cars in place in some parking houses, developed by the enterprise KOMA Industry s.r.o. The testing device uses two positioning tables, whose moving parts are attached perpendicular to each other in the frame of the testing device. A pallet lock is attached to the sliding part of the vertical positioning table, which consists of three basic parts: body, pulley holder and compression coil spring. A plate is attached to the sliding part of the horizontal positioning device which is adapted to receive the stop of the fixation mechanism. This paper presents values of the measured vertical forces acting on the force transducer, which were generated by the reshaped coil spring with a wire of circular cross-section during the rolling of the pallet lock roller over the sloped surface of the stop. It presented an experimental procedure and the results of the measured vertical forces exerted by a reshaped coil spring with a wire of circular cross-section on the force sensor during the insertion of the pulley roller into the gap between the two end faces of the stop assembly. The experimental procedure and the results of the measured vertical forces exerted by the reshaped coil spring with a wire of circular cross-section on the force sensor during sliding of the lock pulley roller out of the gap in the stop are given in one of the chapters. The conducted experimental measurements of the functional properties of the fixation lock of the pallet and the acquired values of acting vertical forces will serve to optimize the attaching of pallet fixation locks to the steel girders of the structure of the cell rack parking space of the automatic parking house, over which the chain conveyer transports pallets with vehicles into specified parking positions.
Error analysis of narrowband power-line communication in the off-grid electrical system
(MDPI, 2022) Blažek, Vojtěch; Slanina, Zdeněk; Petružela, Michal; Hrbáč, Roman; Vysocký, Jan; Prokop, Lukáš; Mišák, Stanislav; Walendziuk, Wojciech
Narrowband power-line communication seems to be a suitable communication technology designed for off-grid renewable energy solutions. Existing electrical installations can be designed both for the transmission of electricity and for the communication of electrical equipment operating inside such an installation. This study presents an implementation of the above-mentioned off-grid communication system and examines the basic problems related to its exploitation. The authors of this article focused their attention primarily on examining the disturbance of the communication channel caused by the use of typical electrical devices, such as: a light bulb, a kettle, etc. used in a household. The aim of the research was also to find the impact of switching on individual devices and their combinations on the disturbances during data transmission. Measurements of incorrectly transmitted data packets were carried out and then the test results were referred to the error measures. Moreover, the influence of the carrier frequencies on the signal attenuation and the method of eliminating the existing interferences were also discussed.
Application of traction supply system for charging electric cars
(MDPI, 2022) Bartłomiejczyk, Mikołaj; Jarzebowicz, Leszek; Hrbáč, Roman
The development of electromobility involves the development of electric cars charging infrastructure. The increase of the number of chargers poses new demands for the AC power grid, especially in regard to its capacity of delivering high peak power. As an alternative for the public AC power grid, urban electrified transportation systems (trams, trolleybuses, and metro) can be used for supplying electric cars chargers. The article discusses four options of integrating electric cars chargers with a traction power supply system. The option of connecting the charger to the traction overhead supply line has been selected due to the spatial availability of the power source and possibility to use regenerative braking energy for charging. A set of criteria has been developed for analysing the capability of the traction supply system to feed electric cars chargers. An exemplary feasibility analysis was carried out for trolleybus traction supply system in Gdynia, Poland. The impact of installing the charging station on specific traction supply parameters has been predicted using present-state recordings of electrical parameters and assumed charging station power. The study shows that every supply section of the considered trolleybus traction system has the capability of installing a fast-charging station, which provides opportunities of expanding the charging stations network in Gdynia.
Study on the selection of the number of magnetic poles and the slot-pole combinations in fractional slot PMSM motor with a high power density
(MDPI, 2022) Wolnik, Tomasz; Stýskala, Vítězslav; Mlčák, Tomáš
Fractional slot, PMSM motors with a properly designed electromagnetic circuit allow for obtaining high power density factors (more than 4 kW per 1 kg of total motor weight). The selection of the number of magnetic poles to the specific dimensions and operating conditions of the motor, as well as the number of slots for the selected number of magnetic poles is the subject of the analysis in this article. This issue is extremely important because it affects the mass of the motor, the value of shaft torque, shaft power and the value of rotor losses. The aim of the work is to select solutions with the highest values of power density factor and, at the same time, the lowest values of rotor losses. The object of the study is a fractional slot PMSM motor with an external solid rotor core with surface permanent magnets (SPM). Motor weight is approximately 10 kg, outer diameter is 200 mm and a maximum power is 50 kW at 4800 r/min. The article analyzes the selection of magnetic poles in the range from 2p = 12 to 2p = 24 and various slot-pole combinations for individual magnetic poles. The target function of the objective was achieved and the calculations results were verified on the physical model. The best solutions were 20-pole, 30-slots (highest efficiency and lowest rotor loss) and 24-pole, 27 slots (highest power density).
Laboratory device detecting the magnitude of the static friction coefficient of brake lining
(Lublin University of Technology, 2021) Hrabovský, Leopold; Hrbáč, Roman
The paper describes the design of laboratory equipment, which was created for verification and determination of the value of the static coefficient of friction in the contact surfaces of the brake lining and the brake drum of the drum brake with external shoes by experimental procedure. Suppliers of brake linings state the values of the friction coefficients which correspond to different operating temperatures, but do not state the values of the friction coefficient of the respective brake lining with regard to the state of contamination of the contact surfaces. In practice, the brake contact surfaces are exposed to moisture, dust, lubricants and oils; these weather and operational influences significantly affect the value of the coefficient of friction. The results of the laboratory tests performed with two types of brake linings (commonly used in practice) (fabric, hardened rubber) show that the coefficient of friction of a given brake lining is strongly influenced by the state of contamination of the contact surfaces.
A development of a capacitive voltage divider for high voltage measurement as part of a combined current and voltage sensor
(Kauno technologijos universitetas, 2020) Hrbáč, Roman; Kolář, Václav; Bartłomiejczyk, Mikołaj; Mlčák, Tomáš; Orság, Petr; Vanc, Jakub
This article deals with the development of capacitive voltage divider for high voltage measurements and presents a method of analysis and optimization of its parameters. This divider is a part of a combined voltage and current sensor for measurements in high voltage power networks. The sensor allows continuous monitoring of the network distribution status and performs a quick diagnosis and location of possible network failures. Deployment of these devices will support semi-autonomous control of power networks and it can be considered as a step from traditional power grids toward smart grids. This is a worldwide trend connected with increasing number of renewable energy sources and plug-in electric vehicles as described in. In this way, it contributes to the reliability of the distribution network. Together with automated control techniques and fault location methods, it enables its self-healing capability. The following characteristics required for the sensor include: current measurement error up to 2 %, voltage measurement error up to 0.5 %, and power measurement error up to 5 %. At the same time, it is necessary that the sensor is cost-effective - relatively cheap. There were selected capacitors made in series production for the capacitive divider designing. The capacitive voltage divider was tested in terms of time and temperature stability; the results are described in the paper. Then, the method of mathematical correction of a temperature dependence of the capacitive voltage divider was suggested and tested.
Vertical forces acting on the lock-off element of the pallet brake system
(Lublin University of Technology, 2020) Hrabovský, Leopold; Mlčák, Tomáš
The paper presents an experimental device that was created in order to obtain the real values of the forces acting in the vertical direction on the lock-off element, the so-called brake body, the 2nd design option. The lock of this design is used in the automated parking garage, designed by KOMA-Industry. s.r.o, to lock the parked vehicles on pallets in the units of the rack parking system. The forces acting in the vertical direction on the body of the fixation lock when pushing the brake pulley into the circular recess in the brake ramp are theoretically calculated for two design variants of the brake ramp used in practice, i.e. "without" and "with" a rounded (filleted) circular recess segment in the brake ramp. The experimentally determined forces acting in the vertical direction on the brake body were determined for two types of compression coil springs with a rectangular cross section of the spring wire.
Forces generated in the parking brake of the pallet locking system
(Lublin University of Technology, 2019) Hrabovský, Leopold; Mlčák, Tomáš; Kotajný, Gustav
Automatic parking systems are parking structures with a computer-controlled automated vehicle loading and unloading process using sophisticated technological equipment. The paper describes a construction design for a pallet locking system, which is used to lock parking pallets with or without a vehicle, at a particular location and floor, that is, in a rack cell. This is one of the basic design concept variants of "Multi-Tower" automatic parking systems. This concept makes it possible to store cars stacked in rack cells. Cars on pallets are guided to the vertical cells of the parking system, stacked above each other on pallets, by an electric freight traction elevator. Pallets are stacked into the horizontal cells, on either or both sides, on a given floor of the parking system by means of a chain transfer device. After the pallet has been guided to a particular position, the pallet must be fixed in this position by the pallet locking system so that when the vehicle needs to be retrieved, the chain transfer device can again latch onto it and move it to the traction lift cage without any problems. The locking system also functions as a brake for the pallet carrying the parked vehicle. The paper also presents the theoretical calculations of the pallet brake, which is a crucial element of the pallet locking system of the conceptual variant of the "MULTI TOWER" automatic parking system.
Low-cost extra-low voltage LED dimmer for tuneable white lighting
(Kauno technologijos universitetas, 2019) Hrbáč, Roman; Mlčák, Tomáš; Kolář, Václav; Vantuch, Tomáš
The colour appearance of light sources has a major impact on how people perceive space. With LED illumination lighting, the colour output can be tuned to virtually any perceivable colour, including any hue of white light. It has been established that the right shade of white light during the 24-hour day cycle has a positive effect on the human body's biological system. For this reason, it is very important to focus on the development and application of new lighting systems that have dynamically variable light outputs in order to imitate the sunlight. Circadian regulation is most responsive to short-wavelength light (460 nm = blue colour). This paper describes the development of a low-cost extra-low voltage LED dimmer for tunable white lighting systems aiming to achieve maximum electrical performance and light-output. This dimming module has two independent LED control channels and allows for a variable colour temperature control from warm white to cold white light. Experimental results of the dimming module efficiency measurements, correlated colour temperature (CCT), colour rendering index (CRI), illuminance and power consumption of the luminaire depending on the duty cycle for different control frequencies (200 Hz, 1.5 kHz, 5 kHz, 10 kHz and 20 kHz) are presented. The paper further describes the principle of creating control curves for an independent regulation of correlated colour temperature and illuminance. In the form of a table, the control curve outputs may be uploaded into a microcontroller. The paper details the construction, function and the advantages of this LED dimmer prototype.
Simulation of selected induction motor operating conditions using comsol software
(Vysoká škola báňská - Technická univerzita Ostrava, 2018) Kocman, Stanislav; Orság, Petr; Pečínka, Pavel
In this paper, some results from a simulation of three-phase squirrel-cage induction motor using COMSOL Multiphysics software are shown for the selected motor operating conditions. The simulation has been carried out under the nominal operating condition at the nominal rotational speed, for the operation under no-load and for the operation under locked rotor. The waveforms of the stator current, the currents in two neighbouring rotor bars, the current in the rotor ring and the motor inner torque are presented for each tested condition. The simulated values of some motor parameters are compared to their values from the motor catalogue, the manufacturer's measurement, or the measurement in our laboratory, respectively. The simulated values of the rotor bar current and the rotor ring current are compared to their values from the scientific literature. The parameters of the motor equivalent circuit are calculated by COMSOL and compared to the values calculated from the motor data plate and from the measured values.
Limiting the influence of regulated electrical drainage on track circuits
(Kauno technologijos universitetas, 2018) Hrbáč, Roman; Kolář, Václav; Mlčák, Tomáš
For the past two years, the authors of this paper have been working on the development of a new regulated electrical drainage system for tram tracks, which may also be used on railways in the future. When this drainage is used on train tracks equipped with track circuits, it is necessary to make sure that the drainage does not generate current harmonics which may be dangerous for the correct functioning of the circuits. In the Czech Republic, requirements regarding the operation of track circuits are stated by Standard CSN 342613. When the drainage was tested on tram tracks, where there are no track circuits, it was found out that in certain operation modes, the drainage generates frequencies which collide with the frequencies of track circuits. Therefore, a passive filter was designed to solve this problem. With the use of computer simulation and measurements on a laboratory model, it was verified that this filter is able to suppress unwanted current harmonics, so that they are in agreement with the above mentioned Standard. These measurements and simulations are described in this paper.
Experimental grounding of the efficiency of the use of elastic operating elements in the devices for pre-sowing seed treatments
(University of El Oued, Faculty of Science and Technology, 2017) Sukhanova, M. V.; Zabrodin, V. P.; Sukhanov, A. V.; Stýskala, Vítězslav; Zegzulka, Jiří; Jezerská, Lucie; Rozbroj, Jiří
The article is devoted to the experimental studies of the effect of elastic operating elements of a mixer-dresser on seeds. Conducted experimental studies have shown the effectiveness of using the elastic operating elements for pre-sowing seed treatments. The proposed device is intended for the intensification of the process of mixing and dressing, excluding the traumatizing of seeds, and the harmful effect of protectant preparations on maintenance workers, while simplifying and reducing the cost of construction without additional power inputs. Experimental studies have confirmed the hypothesis, that the use ofshells, made of elastic materials,in the function of mixing devices, significantly reduces the time of preparation of homogeneous mixtures, due to the ability to accumulate the potential energy and to transfer it to the granular material,in the form of kinetic energy of mixed particles motion. Based on the performed researches, 3D model of the device for pre-sowing seed treatments has been developed. Hybrid elastic mixer-dressers can be used in agricultural enterprises, dealing with the issues of obtaining multicomponent granular mixtures and seed dressing.
Comparative effectiveness of ICA and PCA in extraction of fetal ECG from abdominal signals: Toward non-invasive fetal monitoring
(Frontiers Media S.A., 2018) Martinek, Radek; Kahánková, Radana; Jeżewski, Janusz; Jaroš, René; Mohylová, Jitka; Fajkus, Marcel; Nedoma, Jan; Janků, Petr; Nazeran, Homer
Non-adaptive signal processing methods have been successfully applied to extract fetal electrocardiograms (fECGs) from maternal abdominal electrocardiograms (aECGs); and initial tests to evaluate the efficacy of these methods have been carried out by using synthetic data. Nevertheless, performance evaluation of such methods using real data is a much more challenging task and has neither been fully undertaken nor reported in the literature. Therefore, in this investigation, we aimed to compare the effectiveness of two popular non-adaptive methods (the ICA and PCA) to explore the non-invasive (NI) extraction (separation) of fECGs, also known as NI-fECGs from aECGs. The performance of these well-known methods was enhanced by an adaptive algorithm, compensating amplitude difference and time shift between the estimated components. We used real signals compiled in 12 recordings (real01-real12). Five of the recordings were from the publicly available database (PhysioNet-Abdominal and Direct Fetal Electrocardiogram Database), which included data recorded by multiple abdominal electrodes. Seven more recordings were acquired by measurements performed at the Institute of Medical Technology and Equipment, Zabrze, Poland. Therefore, in total we used 60 min of data (i.e., around 88,000 R waves) for our experiments. This dataset covers different gestational ages, fetal positions, fetal positions, maternal body mass indices (BMI), etc. Such a unique heterogeneous dataset of sufficient length combining continuous Fetal Scalp Electrode (FSE) acquired and abdominal ECG recordings allows for robust testing of the applied ICA and PCA methods. The performance of these signal separation methods was then comprehensively evaluated by comparing the fetal Heart Rate (fHR) values determined from the extracted fECGs with those calculated from the fECG signals recorded directly by means of a reference FSE. Additionally, we tested the possibility of non-invasive ST analysis (NI-STAN) by determining the T/QRS ratio. Our results demonstrated that even though these advanced signal processing methods are suitable for the non-invasive estimation and monitoring of the fHR information from maternal aECG signals, their utility for further morphological analysis of the extracted fECG signals remains questionable and warrants further work.
Band stop filter with a synthetic inductor with series resistance and a real operational amplifier
(Vysoká škola báňská - Technická univerzita Ostrava, 2018) Mohylová, Jitka; Punčochář, Josef; Zajaczek, Stanislav
This paper deals with application of simple synthetic inductor with series resistance (non-ideal gyrator). Those inductors are seldom used. However, if we use this inductor in the arm of bridge, the circuit is able to achieve high performance. In this way we can get band stop filter with good performance. In the paper we solve influence of real OPA properties. Theoretical considerations are verified by means of simulations (MicroCap) and experiments. Based on theoretical considerations, simulations and experiments are finally determined by criteria that must meet real operational amplifier to make the circuit performed well.
Development of the smart annealing unit and analysis of low-frequency conducted disturbances by connection to low voltage public network
(Kaunas University of Technology, Department of Electronics Engineering, 2017) Hrbáč, Roman; Mlčák, Tomáš; Dudek, Jan; Kolář, Václav
Within the research activities, the realization team did the complete development of the annealing unit with the aid of modern technology and components, such as the programmable logic controller, industrial PC, and microcontrollers, to secure an intelligent way of switching the power semiconductor switches (SSR relays) with regard to minimizing the low frequency conducted disturbances. The annealing unit has the implemented algorithm for two ways of output power control, i.e. phase control and full wave control. The algorithm of the full wave control is designed in a way so as to arrange the balanced power in the load. By using this way of control, the harmonic emission is almost entirely eliminated, but the influence of the flicker effect will surface. The article offers a complex view at the annealing unit from the control method perspective, ensuring the correct annealing cycle and subsequent influence of the annealing unit to supply network. It deals deeply with EMC analysis for both ways of designed annealing unit control. The analysis comes out from the experimental measurements on the functional annealing unit prototype.
Active pre-equalizer for broadband over visible light
(Vysoká škola báňská - Technická univerzita Ostrava, 2017) Stratil, Tomáš; Koudelka, Petr; Martinek, Radek; Novák, Tomáš
This paper introduces a new technology called Broadband over Visible Light (BVL) which combines two technology solutions like Visible Light Communication(VLC) and Broadband over Power Line (BPL). This new technology is suitable for converting modern LED lighting systems into communication systems. However, there are some deficiencies in BVL technology such as the low bandwidth of LED optical transmitters. Pre-equalization may be solution of this problem. This paper proposes higher bandwidth using the pre-equalization circuit. Also, it shows real experimental results demonstrating an improvement of bandwidth and transmission rate.
Coupling of finite and boundary elements for transient eddy current problems
(Vysoká škola báňská - Technická univerzita Ostrava, 2017) Lukáš, Dalibor; Kačor, Petr; Ivánek, Lubomír; Mach, Veleslav; Scheffler, Christian
A symmetric coupling of methods of finite and boundary elements for numerical solution of transient eddy current problems is described. This is an essential step in modelling of electromagnetic forming of metalic sheets. The finite element method is employed in the conducting region of the metalic sheet. The boundary element method relies on the Stratton-Chu representation formula and it models the electromagnetic field in the air including its decay at infinity. We impose external currents by the Biot-Savart law.
The determination of the asynchronous traction motor characteristics of locomotive
(Vysoká škola báňská - Technická univerzita Ostrava, 2017) Kolpakhchyan, Pavel Grigorievich; Shaikhiev, Alexey Rifkatovich; Kochin, Alexander Evgenievich; Perfiliev, Konstantin Stepanovich; Otýpka, Jan; Sukhanov, Andrey Valerievich
The article deals with the problem of the locomotive asynchronous traction motor control with the AC diesel-electric transmission. The limitations of the torque of the traction motor when powered by the inverter are determined. The recommendations to improve the use of asynchronous traction motor of locomotives with the AC diesel-electric transmission are given.

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