Person: TERZİ, ÜMİT KEMALETTİN
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TERZİ
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ÜMİT KEMALETTİN
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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 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 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 Open Access A New Speed Control Technique for a Separately Excited Direct Current Motor by PID(2018-04-01) TERZİ, ÜMİT KEMALETTİN; O. AKAR;U K TERZİ;O OZGOENELAbstract—In this study, by deriving electro-mechanic mathematical model of separately excited direct current motor (SEDCM) via equivalent circuit, a new control block diagram has been formed. By using this block diagram, state space model of SEDCM has been created and block diagram of motor has been formed in Matlab Simulink environment. Steady state and transient values of armature current, emf, produced torque, speed and position angle have been obtained using this new model. By adding PID controller to block diagram, SEDCM has been remodeled. Finally, results of steady state and transient analysis of SEDCM have examined through speed control of the proposed model.It is reported that the suggested modeling technique is able to analyze the speed control of the SEDCM.Publication Open Access A study on torque ripple improvement compared to a modified rotor and stator poles SRMs with classical SRMs using dynamic and FFT analysis(2023-01-01) TERZİ, ÜMİT KEMALETTİN; Çalik H., ÖZOĞLU Y., Undil S. H., TERZİ Ü. K.SRMs have high torque ripples. Modifying the stator and rotor shape of SRMs is one of their methods to remove torque ripples. In this study, new rotor and stator geometries have been proposed for SRM. Performance characteristics are obtained and dynamic analyses are carried out for both novel and classical 6/4 SRMs. FFT analyses of the torque characteristics are also performed for the both SRMs. The changes in performance and the FFT results of torque characteristics are determined for both the current-controlled and uncontrolled operations in both SRMs. 23.60% and 15.20% improvements in torque ripples are achieved for the uncontrolled and current-controlled operations in SRMs respectively. When the FFT analyses are applied to the torque characteristics, the THD values are obtained as 21.19% and 8.31% in the uncontrolled and controlled motor current operations respectively. A 122 W three-phase 6/4 SRM simulation based on the MATLAB–SIMULINK environment is performed to validate the improvement of the torque ripple of the proposed model.Publication Open Access Determination of the Optimum Hybrid Renewable Power System: A case study of Istanbul Gedik University Gedik Vocational School(2019-10-30) TERZİ, ÜMİT KEMALETTİN; O. AKAR;U K TERZİ;T. SONMEZOCAK;B. K. TUNCALPIn this study, Hybrid Renewable Power System (HRPS) has been designed to meet the energy requirement of Istanbul Gedik University Vocational School (IGUVS) in an optimum way. The energy requirement will be achieved mainly with wind and solar power generation system. The hybrid regenerative power system will be requested from the network when it can’t meet its energy needs. The optimum configuration of grid-connected solar/wind hybrid power generation system will be determined by considering the wind speed data and solar radiation data of the location of IGUVS. Moreover, sensitivity analysis will be carried out taking into consideration the wind speed and solar radiation values. If the optimum hybrid power generation system specified is used, the carbon emission values obtained will be examined.Publication Open Access DEVELOPMENT OF A COST-EFFECTIVE HEAVY-DUTY LEAD-ACID BATTERY_x000D_ CAPACITY TESTER(2020-12-18) TERZİ, ÜMİT KEMALETTİN; Mustafa ERGUN;Habib KAYMAZ;Ümit Kemalettin TERZİ;K. R. İrfan GÜNEYBatteries are the energy source that provides energy to the vehicle for the first_x000D_ movement. Batteries used in motor vehicles nowadays are usually lead-acid_x000D_ batteries. This paper introduces the basic components of lead-acid batteries_x000D_ and describes the concept of a battery capacity test. The general definition of_x000D_ the standard for testing, EN50342, and the required conditions are presented._x000D_ Furthermore, a cost-effective capacity tester for heavy-duty lead-acid_x000D_ batteries in compliance with the standard was developed and introduced.Publication Open Access Experimental investigation of the effect of inrush current created by LED drivers on switching elements(2024-08-01) AKAR, ONUR; TERZİ, ÜMİT KEMALETTİN; Balci S., AKAR O., TERZİ Ü. K.The demand for lighting technology is increasing rapidly with the increasing population and the advancement of industrialization. Significant developments are taking place in the field of lighting to meet this demand. LED lighting technology, which is the most current of these developments, is preferred to a high degree as it is more efficient, long-lasting, and advantages compared to conventional lighting technologies. However, this technology is still in its development stage and problems may be encountered that need to be solved. In this study, the problems that caused by inrush current and damage to the switch contacts of LED armatures using different protection classes as a result of multiple switching were observed with switching elements complying with IEC 60669-1 standards. The damage on these two switching elements was tested by connecting them with 69 LED armaturesof 12A-36W and starting-stopping 10000 times, 40 times per minute. As a result of the test, corrosion/damage that could cause major fires was observed in the LED switching elements and pictures were taken with the help of Scanning Electron Microscope (SEM).The study shows the importance of creating a special international material standard for LED switchingsystems and ensuring that manufacturers comply with this standard.Keywords:Lighting, LED, Inrush Current, SEM