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Comparison of different experimental methods for determining the magnetically nonlinear iron core characteristics of transformers

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This paper is divided into two sections. In the first section, different experimental methods for determining magnetically nonlinear iron core characteristics of transformer are described and evaluated. In the second section the obtained characteristic were used in nonlinear dynamic model of a single-phase transformer. The comparison of the measured and by the dynamic model calculated results is given for the case of transformer steady state operation at rated load and for the case of switch-on of unloaded transformer. Streszczenie. Artykł jest podzielony na dwie części: w pierwszej doświadczalne metody są opisane i ewaluowane, w dtugiej otrzymane doświadczalnie charakterystyki są uzyte w modelu jednofazowego transformatora. Porównanie pomierzonych i obliczonych z modelu wartości zostało przeprowadzone dla warunków pracy ustalonej i dla przypadku właczenia transformatora do sieci. (Porównanie różnych metod doświadczalnych dla okresślenia charakterystyki magnetycznie nieliniowego rdzenia transformatora) Keywords: dynamic model, magnetic nonlinearities, parameters, power transformer Słowa kluczowe: model dynamiczny, magnetyczne nieliniowości, parametry, transformator mocy Introduction This paper deals with determining parameters of a magnetically nonlinear dynamic model of power transformer. The paper focuses on determination of magnetically nonlinear iron core characteristic (i). It is determined by the classical methods based on no load test and by the alternative methods based on numerical integration of measured currents and voltages [1-3]. A power grid and linear amplifier were used as a voltage source. The linear amplifier was used to generate sinusoidal and stepwise changing voltage waveforms. A comparison of magnetically nonlinear characteristics determined by the different methods is presented. The magnetically nonlinear dynamic model of power transformer is evaluated through a comparison of measured and calculated c[...]

Comparison of experimentally and by the finite element method determined magnetically nonlinear iron core characteristics applied in the dynamic model of a single phase transformer

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This paper deals with comparison of experimentally and by the finite element method determined magnetically nonlinear iron core characteristics. The obtained characteristic were used in the dynamic model of a single phase transformer. The comparison of the measured and by the dynamic model calculated results is given for the case of transformer steady state operation at rated load and for the case of switch-on of unloaded transformer. Streszczenie. W artykule przedstawiono porównanie podejścia eksperymentalnego i metody elementów skończonych w wyznaczaniu nieliniowej charakterystyki magnetycznej rdzenia żelaznego. Analizy dokonano poprzez wykorzystanie wyznaczonych charakterystyk w modelu dynamicznym transformatora jednofazowego i ich porównaniu dla pracy w stanie ustalonym z obciążeniem oraz przy załączaniu nieobciążonego transformatora. (Porównanie podejścia eksperymentalnego i metody elementów skończonych w wyznaczaniu nieliniowej charakterystyki magnetycznej rdzenia żelaznego w transformatorze jednofazowym z wykorzystaniem modelu dynamicznego urządzenia). Keywords: dynamic model, magnetic nonlinearities, experimental methods, FEM, power transformer. Słowa kluczowe: model dynamiczny, nieliniowości magnetyczne, metody eksperymentalne, FEM, transformator energetyczny. Introduction This work deals with magnetically nonlinear dynamic model of a single phase transformer. In order to achieve the best possible agreement between the measured and calculated responses the dynamic model is completed by the magnetically nonlinear characteristic of the tested transformer. It is given as current-dependent flux linkage characteristic, which is determine experimentally and by applying the finite element computations. Nowadays, there exist many electromagnetic devices with magnetically nonlinear iron core. For analysis of these devices and for their control design dynamic models are required. When the magnetically nonlinear properties of the devi[...]

Parameter determination of a solar cell model using differential evolution algorithm DOI:10.15199/48.2019.01.42

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Research and development of photovoltaic (PV) cells has led to higher efficiencies, significant cost reductions and long operating lifetimes with minimal degradation [1]. The double diode model of the photovoltaic cell/module is fast becoming a viable alternative to the highly popular single diode model for PV simulations [2]. In general, there are two ways to extract the solar cell parameters: (1) analytical and (2) numerical method The analytical technique requires information on several key points of the I-V characteristic curve, i.e. the current and voltage of at the maximum power point (MPP), short-circuit current, open-circuit voltage and slopes of the I-V characteristic at the axis intersections. It has been noted that the I-V is highly non-linear and any wrong selected points may result in significant errors in the computed parameters [3]. While the numerical extraction technique relies on mathematical algorithm to fit all the points in the I-V characteristic curve. The results obtained by numerical extraction technique are more accurate, compared to the analytical technique, due to utilization of all points on the I-V curve. The following authors present different approaches to extract solar cell parameters. AlRashidi [4] presents a new technique based on pattern search (PS) optimization for estimating different solar cell parameters. The proposed approach is tested and validated using double diode model, in which the estimated parameters are generated photocurrent, saturation current, series resistance, shunt resistance, and ideality factor. Chin [2] presents the implementation of a hybrid solution, i.e. by incorporating the analytical method with the differential evolution (DE) optimization technique. Three parameters, i.e. generated photocurrent, saturation current of the first diode and shunt resistance are computed analytically, while the remaining ideality factors, saturation current of the second diode and s[...]

The optimal tracking strategies for two-axis PV system

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This paper deals with two-axis tracking system of photovoltaic (PV) systems. The new method for determining the optimal trajectories of the tracking system is proposed. The optimization goal is the maximum of electric energy production in the PV system, considering the consumption of the tracking system. The determination of the tracking system trajectories is described as a non-linear and bounded optimization problem. The stochastic search algorithm called differential evolution is used as an optimization tool. Streszczenie. Artykuł przedstawia system dwu-osiowego sterownia systemem fotowoltaicznym. Zaproponowana została nowa metoda określania optymalnej trajektorii systemu. Celem optymalizacji jest uzyskanie maksymalnej energii wyprodukowanej w systemie fotowoltaicznym z uwzględnieniem wydatku energii na system sterowania. Określenie trajektorii systemu stanowiło rozwiązanie nieliniowego problemu z ograniczeniami. Jako narzędzie zastosowano algorytm stochastyczny ewolucyjny.(Optymalne strategie sterowania dwuosiowym systemem fotowoltaicznym) Keywords: two axis tracking system, electromechanical system, solar radiation, differential evolution. Słowa kluczowe: dwuosiowy system naprowadzania, system elektromechaniczny, promieniowanie słoneczne, ewolucja różniczkowa Introduction European union‘s directive upon increasing the production of electricity from the renewable energy till 2020 has contributed to the growth of photovoltaic (PV) systems connected to the electric grid. The main elements of the PV systems are solar modules which convert the solar radiation directly into the electricity. The efficiency of this conversion depends on the solar radiation that reaches the surface of the solar cells, the temperature of the solar cells, the impedance matching between the solar modules and dc/dc converters, and the quality of the inverters. This paper focuses on the increase of energy conversion efficiency which can be achieved by t[...]

Energy efficiency and use of renewable solutions of small and medium enterprises DOI:10.15199/48.2016.09.50

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Increasing energy efficiency and the development of renewable energy resources has a positive impact on economic growth. Energy efficiency offers a powerful and cost-effective tool for achieving a sustainable energy future and it can actually be pursued by a virtuous combination of a wide range of initiatives involving a growing number of public organisations together with service and industrial companies. This article summarizes a part of the work within the CO-EFFICIENT project and highlights the main methodologies and approaches for evaluating energy efficiency, its improvement and use of renewable resources. The project will also assist small and medium enterprises with limited R&D capacities and develop customized energy efficiency solutions. Streszczenie. Wzrastająca sprawność energetyczna i rozwój odnawialnych źródeł energii mają pozytywny wpływ na wzrost gospodarczy. Jakość energii oferuje efektywne narzędzie w osiąganiu zrównoważonej energetycznie przyszłości a to może być wykonane przez wirtualna kombinacje wielu inicjatyw, wlączających wzrastającą liczbę organizacji publicznych razem z usługowymi I producyjnymi podmiotami gospodarczymi. Artykuł podsumowuje część prac wykonanych w ramach projektu COEFFICIENT i podkreśla główne metodologie i podejścia dla oceny sprawności energii, jej polepszania oraz użycia źródeł odnawialnych. Wspomniany projekt asystuje również małym I średnim przedsiębiorstwom z ograniczoną bazą naukowo-badawczą oraz rozwija rozwiązania sprawności energetycznej.(Sprawność energetyczna i użycie źródeł odnawialnych w małych I średnich przedsiębiorstwach) Keywords: energy efficiency, energy audit, renewable solutions, small and medium enterprises. Słowa kluczowe: sprawność energetyczna, audit energetyczny, źródła odnawialne, małe i średnie przedsiębiorstwa Introduction The purpose of CO-EFFICIENT project is to set-up a permanent collaborative framework for energy efficiency innovation in operations and productio[...]

Numerical Analysis of the Electromagnetic Brake DOI:10.15199/48.2019.01.01

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Introduction Electromagnetic brakes (EMBs) are most commonly used in elevators, trains, lifting cranes, automotive industry, mining and wind power plants for braking or stopping the rotors of electrical machines. Generally speaking electromagnetic brakes are electrically activated but transmit torque mechanically [1]. The advantages of EMBs compared to conventional mechanical brakes are:  large braking torques,  stable braking at high temperatures,  fast response times (accurate engaging and clean releasing),  low noise and cheaper production. Because of these advantages the number of manufacturers and providers of EMBs on the market is increasing. According to the principle of operation we know mechanical, hydraulic, air, vacuum and EMBs. The EMBs can be further classified according to the principle of operation or according to the type of a power source (AC or DC). According to the principle of operation we know:  steel spring EMBs,  single or multiple disc EMBs,  hysteresis EMBs,  f particle EMBs and  eddy current EMBs. The principle of operation is similar for these types of EMBs, they differ only in the way of creating the braking torque [2]. This paper consequently presents a numerical analysis of a DC EMB with steel springs. It consists of a [3]:  magnetically nonlinear iron yoke, =[...]

Numerical modelling of linear generators DOI:10.15199/48.2019.01.02

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Linear electric machines are devices that directly produce or exploit linear movement. They have become commercially better known between years 1970 and 1980, when there were huge efforts to build a MAGLEV train for carrying passengers, which would be driven by linear synchronous motors. Linear machines are used in many other applications, as they have many good properties, such as high accelerations and decelerations, high thrust forces, high precision and reproducibility of the position [1]. Eric R. Laithwaite wrote that a linear electric machine is easiest to imagine as a rotary machine, of which stator and rotor are cut and unrolled in the plane [2]. Stator and rotor in a rotary electric machine become primary and secondary in a linear machine. Primary is the part of the machine which is supplied with electric current. Secondary is the part of the machine, with permanent magnet excitation system, a squirrel cage or magnetic saliency. All types of linear machines can have different topologies. In general there are two different geometry types; tubular and flat geometry type. Both geometries may have a long or short secondary or primary. Flat linear motors can be one-sided or double-sided [3]. Some most common applications where linear motors are used are sliding doors, swing doors, elevators, pneumatic hammers, electromagnetic pumps, electromagnetic flow meters, automation and robotics [4]. Lineat motor topologies The linear electric machine is represented as a rotary machine, which has been cut and unrolled in a plane. The rotor becomes the secondary; above it the unrolled stator represents the primary. Such a structur[...]

The management and implementation of energy audits of small and medium enterprises DOI:10.15199/48.2016.09.51

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Energy audits have become in recent years a basic tool for determining the current energy situation in the facility and determining the energy balances in the technological processes. It allows us, with the information about the current energy state, to set the objectives for the implementation of energy efficiency measures in a building or technological process. A way to carry out an energy audit is determined by the methodology issued by the Ministry of environment and spatial planning. Management, experiential decision making for appropriate measures largely depends on the experience and technical expertise of individual operators. In the new Energy Act is determined, that larger companies, as those defined in the regulations in the field of commercial companies implement energy audits every four years. Streszczenie. Audyty energetyczne stały sie w ostatnich latach podstawowym narzędziem, pozwalającym określić stan energetyczny urządzenia oraz równowagę energetyczną w procesie technologicznym. Zezwala to, razem z informacją o bieżącym stanie energetycznym, ustanowić wskaźniki do zaimplementowania w pomiarach sprawności energetycznej w budownictwie lub procesach technologicznych. Sposób prowadzenia audytu energetycznego określony jest przez Ministerstwo Środowiska I Planowania Przestrzennego w Słowenii. Zarządzanie oparte na decyzji doświadczeniowej w dużym stopniu zależy od doświadczenia indywidualnych operatorów. W nowym Akcie Energetycznym (Słowenia) wskazano, że większe przedsiębiorstwa, jak te zdefiniowane w przepisach o przedsiębiorstwach komeryjnych, poddane są audytowi energetycznemu c cztery lata. (Zarządzanie I implementacja audytów energetycznych w małych I średnich przedsiębiorstwach). Keywords: energy efficiency, energy management, key performance indicator, small and medium enterprises. Słowa kluczowe: sprawność energetyczna, zarządzanie energią, wskaźnik kluczowego działania, małe I średnie przedsiębiorstwa Introduction In [...]

The efficiency of different orientations of photovoltaic systems DOI:10.15199/48.2017.01.49

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This paper compares the efficiency of different orientations of photovoltaic systems under outdoor conditions over the five-year period in Slovenia. The four different photovoltaic systems were analysed with the same mono-crystalline silicon solar modules. The impact of orientation and inclination on efficiency are evaluated. The analysis of the data obtained shows that the efficiency of the photovoltaic systems depends on the solar irradiation and temperature of solar modules. Based on the analysis and measurements for different photovoltaic systems, the optimal orientation and inclination are presented. Streszczenie. W artykule porównano wydajność systemów fotowoltaicznych o różnej orientacji w warunkach pracy zewnętrznej podczas pięcioletniej ich aktywności na terenie Słowenii. Badano cztery różne systemy fotowoltaiczne z tym samym monokrystalicznym modułem krzemowym. Wpływ orientacji i odchylenia na wydajność tych systemów zostały poddane ewaluacji. Analiza otrzymanych danych pokazuje, że wydajność systemów fotowoltaicznych zależy od promieniowania słonecznego i temperatury modułów. Bazując na analizie i pomiarach czterech systemów fotowoltaicznych wyznaczono optymalną orientację i odchylenie. (Wydajność systemów fotowoltaicznych w różnych ukierunkowaniach ) Keywords: photovoltaic system, orientation, inclination Słowa kluczowe:system fotowoltaiczny, ukierunkowanie, odchylenie Introduction Generally photovoltaic systems are divided into fixed and tracking systems [1]. Fixed systems are often used for small photovoltaic systems installed on the roof of a building, while tracking systems are often usedfor large photovoltaic systems installed to maximize the solar radiation that reaches the surface of the solar modules. When using tracking systems compared to fixed the increase of energy production is expected to be up to 40 % [2 - 4]. There are very few published works that deal with different types and orientations of photovoltaic[...]

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