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 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 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 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.Publication Metadata only Production of the go-doped pla-based nanofibers and investigation of their electrical properties(2018-07-18) TERZİ, ÜMİT KEMALETTİN; KORKMAZ, HAYRİYE; EKREN, NAZMİ; GÜNDÜZ, OĞUZHAN; CESUR, SÜMEYYE; Özen S., Aydoğdu M. O., Ege Z. R., Cesur S., Terzi Ü. K., Korkmaz H., Ekren N., Gündüz O.Publication Metadata only High performance adaptive active harmonic filter design for non-linear led loads(2022-01-01) TERZİ, ÜMİT KEMALETTİN; Sonmezocak T., Akar O., TERZİ Ü. K.Today, illumination systems use approximately 1/3 of the electrical energy produced. For this reason, new technologies constantly increase energy efficacy in illumination technology. Consequently, the use of LED type light sources gets more widespread with low power electronics-based versions. The most important advantage of this type of systems has high luminous efficacy. However, since electronic systems have non-linear static loads, they cause unwanted harmonics in electrical distribution systems. Harmonics affect the operational safety as they cause unnecessary heating of the conductors in the electrical network. It also adversely affects the measuring and control systems of the buyers and so decreases the energy performance. In this study, an adaptive Butterworth low pass active harmonic filter model that can cut all current/voltage harmonics outside the operating frequency of different types of LED driver light sources is designed. In addition, harmonic analysis of different LED driver systems is performed experimentally by considering the total harmonic distortions (THD,%). In this way, harmonic components and (THD) values of different LED systems are obtained. These harmonic components obtained is filtered with the designed filter structure and the effects of the filter structure at each filtering degree on the harmonic components and THD were investigated. In this way, the designed filter is proved to be an adaptive model that can be adjusted automatically for different types of LED systems.Publication Metadata only Calculation of fundamental power frequency for digital relaying algorithms(2010) TERZİ, ÜMİT KEMALETTİN; Kocaman C., Ozgonenel O., Ozdemir M., Terzi U.K.This paper describes two different measuring methodology for calculating fundamental power system frequency (50 - 60 Hz) with high accuracy for numeric protection algorithms. Especially in distance protection, to measure the fundamental power frequency is a vital fact to locate the fault correctly. The problem is complex because the power frequency changes from 49.0 Hz to 51.0 Hz over a wide range for 50 Hz systems. Assuming the frequency of only 50 Hz or 60 Hz may cause under or over reach problem in distance relaying algorithms. Therefore the aim of this paper is to present a high accuracy, with a wide range frequency estimation algorithm for either sinusoid or non-sinusoid signals. The experimental results reported prove that the first method is more accurate than the second one. In this paper, two different calculation procedures are introduced. The first one is curve fitting approach and needs only six samples of the current or voltage signal. The second one is based on auto correlation function of sampled data. The proposed methods are robust for a wide range of sampling frequency, Fs and give more accurate results than the traditional ones.Publication Metadata only Grid-connected induction generator interturn fault analysis using a PCA-ANN-based algorithm(TUBITAK SCIENTIFIC & TECHNICAL RESEARCH COUNCIL TURKEY, 2016) TERZİ, ÜMİT KEMALETTİN; Bayar, Haydar; Terzi, Umit KemalettinIt is difficult for short circuits among the internal windings of one phase in electrical machines to be determined in a reliable and speedy manner. The failure currents that occur, especially in short circuits with a few windings, are at such low levels that they cannot be determined by relay systems. This results in growing faults and damage. In this study, we designed a model that can define winding failures successfully at very small levels by using the PCA and ANN algorithms. We tested the real-time faults and measured the system performance with the installed test rig. The developed protection model determined fault determination in very small (2.5%) winding failures with acceptable accuracy. The suggested model is a counter-speed, selective, flexible, and economical protection model that may be used for internal failures of electrical machines. It has a structure that may be used in different systems or kinds of failure with data receiving and software changes.