Person: TERZİ, ÜMİT KEMALETTİN
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TERZİ
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ÜMİT KEMALETTİN
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Publication Metadata only The effect of heat on the metallurgical structure and B-H characteristic of (stator) armature with iron-silicon alloy in electric machines(TUBITAK SCIENTIFIC & TECHNICAL RESEARCH COUNCIL TURKEY, 2010) TERZİ, ÜMİT KEMALETTİN; Kentli, Fevzi; Terzi, Uemit KemalettinCoils in electric machines are varnished for insulation after winding. These varnished coils are formed in stiff construction in slots. Under heavy-duty operating conditions, all or part of some coils may be burnt or broken. Thermal method is one of several ways to remove the defective coils. In this method, current is passed through the defective coils by an autotransformer (variac) until all the varnish of the coils is burned. If all the coils are out of order, the varnish is burned by replacing the stator or armature in a burning room. Consequently, defective coils in the stator (armature) slots can be easily removed. In this study, the latter way has been preferred and varnish of the damaged coils has been burned in a flame burning room to investigate the effect of heat on both the metallurgical structure and the magnetic characteristics of stator (armature) iron core material after removal of the defective coils. The relation between the magnetic characteristics and the metallurgical structure of the material and their solutions have been examined under laboratory conditions.Publication Open Access Comparative Analysis of Lighting Elements’ Effects on Electric System(2021-12-01) TERZİ, ÜMİT KEMALETTİN; DURSUN S., TERZİ Ü. K., AKAR O., SÖNMEZOCAK T.Due to the increase of demand for energy requirement, and the decrease of energy sources day by day, it is being understood that it is required to efficiently use the energy sources in order to ensure the balance of demand for electric energy. The lighting elements use about 1/5 of the electric energy produced in our country. Especially while selecting the lamps with high energy efficiency, it is important to consider the circumstances which may create negativities such as harmonics, power factor, crest factor, inrush current, and flicker effect in terms of quality of power. Moreover, impurity which may occur in the network affects the other devices negatively. In this study, the quality of power of lighting elements of more than one type was examined in detail. In the experiments, technical analyses were performed by the use of 13 different lighting elements extensively used in our country at site, factory, and domestic environments, and they were evaluated in terms of their positive and negative effects on the network.Publication Metadata only A different algorithm for correcting secondary current of current transformer(2010) TERZİ, ÜMİT KEMALETTİN; Ozgonenel O., Terzi U.K., Guney I.This work is about the negative effects of protection devices during current transformer (CT) saturation because the performance of the protection devices such as differential and impedance relays is mainly based on the operating condition of the CTs. Distorted secondary currents due to CT saturation depending on the magnitude of the fault current and a remnant flux in the iron core can cause misoperation or operating time delay of protective relays. Therefore, protective relay engineers have to take account of the CT saturation problem when they design a protective relay, especially such as current differential relay. The objective of this paper is to propose a simple and effective algorithm based on fast Fourier transform (FFT) for correcting secondary current of CT under saturation.Publication Open Access A Study on Electrical Properties of Nanofiber Composites: Effects of PCL/AgNO3/ZnO Concentration Percentages(2022-06-01) POLAT, ZÜHAL; ATİŞ, SELÇUK; TERZİ, ÜMİT KEMALETTİN; Kurt U., Atis S., Polat Z., Tektas M., Terzi Ü. K.Nanofibers with multifunctional properties hold great promise as they allow components for a wide range of medical applications. In this study, zinc oxide, silver nitrate and Polycaprolactone were used in the production of nanofiber composite material by coaxial electrospinning process. PCL concentrations of 5, 10, and 15% by weight were utilized in all of the samples, and different amounts of silver nitrate and zinc oxide were used. Functional groups of silver nitrate, zinc oxide, and Polycaprolactone materials were determined by Fourier transform infrared spectroscopy. Morphological analyzes were carried out with scanning electron microscopy. For all solutions, before coaxial electrospinning, physical properties such as density, liquid state ac conductivity, and viscosity were measured. For the 20 Hz-3 MHz frequency range, after coaxial electrospinning, D-factors and capacitance of nanofiber composite materials were measured and dielectric loss, permittivity, and the solid-state alternating current conductivity were calculated for all solutions. The effects of silver nitrate, zinc oxide, and Polycaprolactone concentration percentages on the solid-state ac conductivity and the dielectric constant were analyzed and comparisons were made with the results obtained.Publication Open Access Analyzing High Efficiency Asynchronous Motors Using Scalar Control Technique(2018-04-01) AKÜNER, MUSTAFA CANER; H. UZUN;O. AKAR;A DEMİRCİ;M.C. AKUNER;U K TERZİIn industry, more than half of the total electrical energy produced in developed countries is converted into mechanical energy by electric motors. The usage rate of asynchronous motors is estimated to be 90% of all electric motors. For these motors, an improvement in efficiency may result in huge savings. These electric motors which have minimized losses can be improved with speed control drives to be more efficient in terms of energy consumption and performance. In speed control drives of asynchronous motors widely used in industry; scalar, vector control and direct torque control are used.In this study, in a Matlab/Simulink environment, high efficiency and standard asynchronous motors with the same characteristics were driven with scalar control technique and the simulations were compared in detail. From the point of view of both speed control performance and energy saving, it observed that high efficiency motors have more advantages.Publication Metadata only Techno-economic and environmental analysis of grid connected hybrid wind/photovoltaic/biomass system for Marmara University Goztepe campus(TAYLOR & FRANCIS INC, 2020) TERZİ, ÜMİT KEMALETTİN; Aykut, Ercan; Terzi, U. KemalettinThis study focuses on techno-economic and environmental feasibility study of a hybrid grid connected wind/PV/biomass energy system for Marmara University Goztepe Campus in Istanbul. HOMER software is used to determine the optimum size of the equipment, based on the geographical and meteorological data of the campus. According to the simulation results, the energy system with the minimum net present cost (NPC) and cost of energy (COE) is chosen as the optimum system. Besides, this study aims to reduce greenhouse gas emissions, polluting the air by using renewable resources. Because of negative impacts of the fossil fuels on human health and environment, all the energy sources for this system are renewable energies which have less pollution. In the simulation, PV, wind, and biomass energy resources are used, but the optimum hybrid energy system is determined as grid connected wind/biomass system consisting of 1000 kW grid, 1000 kW biomass generator, and 1500 kW wind turbine. The NPC of the optimum system is calculated as $5.612.501 while the COE is 0,067$/kW. The system also decreases the emissions of greenhouse gases.Publication Metadata only Novel electrospun polycaprolactone/graphene oxide/Fe3O4 nanocomposites for biomedical applications(ELSEVIER SCIENCE BV, 2018) OKTAR, FAİK NÜZHET; Aydogdu, Mehmet Onur; Ekren, Nazmi; Suleymanoglu, Mediha; Erdem-Kuruca, Serap; Lin, Chi-Chang; Bulbul, Ertugrul; Erdol, Meltem Nur; Oktar, Faik Nuzhet; Terzi, Umit Kemalettin; Kilic, Osman; Gunduz, OguzhanIn this study, one of the most promising methods of tailoring a composite scaffold material in nano sized diameters, electrospinning method were used to produce Polycaprolactone (PCL)/Graphene Oxide (GO)/Iron(II, III) Oxide (Fe3O4) nanocomposite fibers as biocompatible scaffolds for biomedical applications. Products were analyzed by scanning electron microscopy (SEM) for morphological analysis of the electrospun nanocomposites and Fourier Transform Infrared Spectroscopy (FTIR) was used to determine functional groups of the PCL, GO, and Fe3O4 materials in the electrospun nanocomposites. For physical properties, viscosity, density, permittivity, dielectric loss and liquid and solid state alternating current conductivity, measurements were done for each nanocomposite fibers. Effects of concentration percentage of GO on permittivity, dielectric loss and AC conductivity have been analyzed by using measured and calculated data. Trend lines have been drawn for permittivity, dielectric loss and conductivity via concentration percentage of GO. The relation between ac conductivity and frequency have been studied for each concentration percentage of GO and interpretations have been done by using the obtained results.Publication Open Access Location of transformers during the extension of an electricity distribution network(2022-10-01) AKAR, ONUR; TERZİ, ÜMİT KEMALETTİN; Akar O., Terzi Ü. K., Ozgonenel O.The electricity network of a country is in continuous development, including the distribution transformers that provide power within a city. Efficient electricity networks depend on the good implementation of the principles of network planning and development. Moreover, technology development and the increasing standard of living are creating greater electricity demand. Besides, housing developments alter the need for electricity in an urban area and will require changes to control load density, adjustment of the voltage on distribution lines, installation of new lines and substations, and restructuring of existing ones. This study develops new mathematical and geometric methods that can be applied to all Low Voltage distribution networks to investigate load distribution, the effects of change and, provide a tool for distribution network planning. The analysis included the electrical power values to the new transformer, the shortest distribution routes between the transformers, and the costs, and provided optimum locations for new transformers. In this way, distribution network planning has been approached with a new method.Publication Metadata only A hybrid approach for power quality monitoring(TUBITAK SCIENTIFIC & TECHNICAL RESEARCH COUNCIL TURKEY, 2012) TERZİ, ÜMİT KEMALETTİN; Ozgonenel, Okan; Terzi, Umit Kemalettin; Khan, AbdeshThis paper presents a novel hybrid approach for detection of power quality (PQ) disturbances. The proposed hybrid algorithm is based on applications of principle component analysis, discrete wavelet transform, and fast Fourier transform on voltage and current waveforms. The proposed PQ monitoring (PQM) software uses 3-phase voltage and current signals in order to detect possible power disturbances such as voltage say, flicker, harmonics, transients, DC component, and electromagnetic interference. The test results demonstrate the potential of the proposed hybrid technique for PQM and PQ assessment.Publication Metadata only Yapı Tabanlı Mikro Dağıtılmış Enerji Üretim Sistemleri(2013-01-01) TERZİ, ÜMİT KEMALETTİN; Akar O., Terzi Ü. K.