Elektrik Elektronik Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/411
Browse
Recent Submissions
Article Citation - Scopus: 6Design of Frameless Gimbal Motor for Uav Applications(International Organization on 'Technical and Physical Problems of Engineering', 2022) Arslan, S.; İskender, İres; Iskender, I.; Arslan, Serdar; Elektrik-Elektronik Mühendisliği; Bilgisayar MühendisliğiRecently, application areas of the Unmanned Aerial Vehicle (UAV) systems have started to expand very rapidly due to the fact that offering more effective, economical, reliable and safe solutions compared to manned air platforms, satellites and/or various ground platforms. However, desire to develop higher performance, resourceful, lighter, small and low powered payload make the gimbal platforms mandatory part of the UAVs in a short time and their role is getting increased day by day. In parallel with the increasing demand for precise stabilization, robustness, lightness and agility in gimbal systems, it has become an important trend to use more-electric (ME) customed systems instead of traditional market products. The electric motors that control the speed and position of the gimbal system are simply referred to as gimbal motors. Related design study focuses on designing direct-drive in-runner frameless gimbal motor with the following features; 8.5 VAC line voltages, 24-slot/28-pole combination, 60 rpm, 80 mN.m. Permanent magnet synchronous motor topology is determined to offer higher torque density, higher precision and fast response required for gimbal platforms. The selecting criteria of dimensions, performance parameters, materials, machine type with rotor structures and motor duty cycle are also explained. The gimbal motor is performed analytically in Ansys RMxprt with parametric assignments, statistically and sensitively tuned in Maxwell 2D and optimized in Maxwell 3D by finite element method (FEM) optimetric convergence approach with magnetostatic and transient solutions to get the final machine shape. This study is currently part of the gimbal system to be produced for medium sized surveillance UAV. Since the gimbal motor has been prototyped, all dimensions given are valid. © 2022, International Organization on 'Technical and Physical Problems of Engineering'. All rights reserved.Article Citation - Scopus: 1High Voltage Dc Systems and the Related Commisioning(International Organization on 'Technical and Physical Problems of Engineering', 2020) Haliloglu, A.B.; İskender, İres; Iskender, I.; Elektrik-Elektronik MühendisliğiThe number of High Voltage Direct Current (HVDC) projects worldwide has increased considerably due to the growing interest in this mature technology. Rapid development in semiconductor technology have led to the development of converter technology and thus new application areas have emerged. In this study, historical development of HVDC systems, differences among them considering installation types and application areas are explained. Circuit models of HVDC systems, working principle and general usage purposes are also explained. The differences between conventional Current Source Converters (CSC) and Voltage Source Converters (VSC), which are expressed as relatively new technology, are discussed. Also, within the scope of a project, a HVDC prototype system developed by local engineers from mechanical design to control and protection software has been described. In addition, the tests to be performed before commissioning of HVDC and similar systems are explained. Descriptions of the tests, methods to perform the tests and some issues that should be considered while performing the tests are given. © 2020, International Organization on 'Technical and Physical Problems of Engineering'. All rights reserved.Article Citation - Scopus: 5Three-Phase Buck Type Pfc Rectifier for Electrical Vehicle Battery Charger(International Organization on 'Technical and Physical Problems of Engineering', 2019) Demirkutlu, E.; İskender, İres; Iskender, I.; Elektrik-Elektronik MühendisliğiThree-phase AC/DC buck-type power factor correction (PFC) rectifier is presented in this paper. State of the art three-phase AC/DC rectifiers and improvements of the rectifier topologies are researched in this study. The SWISS Rectifier is implemented for Electrical Vehicle (EV) battery charger with 220 VLN-rmsS / 50 Hz three-phase input. The SWISS Rectifier for EV charger application is implemented by means of simulations. Depending upon the battery pack needs, 48 VDC output voltage is examined under both steady-state and dynamic load change conditions. © 2019, International Organization on 'Technical and Physical Problems of Engineering'. All rights reserved.Article Citation - Scopus: 4Comparing Control Performances of Mrac and Pid Applied on a Brushless Dc Motor(International Organization on 'Technical and Physical Problems of Engineering', 2020) Ciba, S.; İskender, İres; Iskender, I.; Ariani, H.A.; Elektrik-Elektronik MühendisliğiBrushless DC motors are powered by a DC electric source and are used widely used in appliance, automotive, aerospace, medical and industrial equipment due to their compact size and light weight. Parallel to improvements in semiconductor industries the operating frequency of semiconductor switches and microcontrollers are getting improve and this provides conditions to use different algorithms in motor control. In this study the reference model adaptive control of a DC brushless motor will be studied. Brushless DC motors have some advantages such as long working life, high efficiency, and low maintenance requirements; however their control is a bit complicated. For this reason, there have been published many studies in relative with speed control of brushless DC motors. Classical or modern control methods can be used for this purpose. In this study, BLDC motor is controlled with firstly classical PID controller and secondly model reference adaptive control (MRAC) based on MIT law method and the results are compared. © 2020, International Organization on 'Technical and Physical Problems of Engineering'. All rights reserved.Conference Object Citation - WoS: 5Citation - Scopus: 31A New Narrow Band Dual-Mode Microstrip Slotted Patch Bandpass Filter Design Based on Fractal Geometry(Ieee, 2012) Eyyuboğlu, Halil Tanyer; Mezaal, Yaqeen S.; Eyyuboglu, Halil Tanyer; Elektronik ve Haberleşme MühendisliğiA narrowband, compact, and easily fabricated microstrip bandpass filter design is introduced in this paper as a candidate for use in modern wireless systems. The proposed filter design is based on the use of dual-mode (two pole) square slotted microstrip resonator. This microstrip bandpass filter has the advantages of possessing much narrower and sharper performance responses than those of the single mode resonator and conventional square patch filter. The proposed microstrip filter structure is fractally generated using Sierpinski fractal curve geometry applied to the conventional square microstrip patch. Filter structures resulting from the successive iterations in the fractal generation process show a considerably low insertion loss, and sharper response of about 1% fractional bandwidth as compared with the conventional microstrip square patch filter of 3% fractional bandwidth designed at the same frequency using the same substrate material. The performance of filter structures, based on dual-mode resonators up to the third iterations, has been evaluated using a full-wave based electromagnetic simulator Sonnet software package. Performance simulation results show that these filter structures offer narrower fractional bandwidth percentages as compared with other types of non- fractalized filter structures.Conference Object Citation - WoS: 2Flat-Topped Field Correlations in Extremely Strong Turbulence(Electromagnetics Acad, 2011) Baykal, Yahya Kemal; Baykal, Yahya; Elektrik-Elektronik MühendisliğiIn extremely strong turbulent horizontal atmospheric optical links, field correlations of flat-topped Gaussian incidence are evaluated. Field correlations are represented versus the diagonal distance at the receiver plane, for variations in the number of beams forming the flat-topped structure, receiver points, source sizes, link lengths, structure constants and the wave-lengths. Our results in extremely strong turbulence are compared to their free space counterparts which only reflect the diffraction patterns at the receiver plane. The effects of the inner scale of turbulence on the field correlations in extremely strong turbulence are examined in detail and it is observed that the size of the inner scale in extremely strong turbulence can considerably influence the field correlations of flat-topped beams.Conference Object Citation - Scopus: 2Associativity Tick Averaged Associativity Based Routing (Ataabr) for Real Time Mobile Networks(2009) Převeze, B.; Preveze, Barbaros; Şafak, A.; Elektrik-Elektronik MühendisliğiThis study proposes a long lived routing method which is also based on Associativity such as ABR (Associativity Based Routing) for real time applications. The main purpose of our work is improving the ABR algorithm in order to reduce the outage of the nodes and decreasing the number of reconstructions required to keep the nodes in communication. The performance of ABR is compared with other long-lived relay selection algorithms for real-time applications.Article Design of a Novel Converter Between Li-Ion Battery and Supercapacitor To Feed Synthetic Aperture Radar Loads for Satellite Applications(int Journal Renewable Energy Research, 2020) Tulay, Gencer; İskender, İres; Iskender, Ires; Elektrik-Elektronik MühendisliğiFor satellite applications the active duty life of a satellite depends mainly on the battery lifespan. The charging or discharging current has an important role in useful life of batteries. For this purpose, the converters used in power supplies including batteries should be accurately designed such that the large current of batteries can be prevented. The power converter proposed in this paper is used to transfer energy from battery to supercapacitor when SAR (Synthetic Aperture Radar) load is active. Accordingly, the lifespan of battery and hence the lifespan of satellite will be extended. Parallel to preventing the large discharging current of batteries the proposed converter has another important property such that it is able to vary the input voltage without having any stability problems. The operating performance of the converter that is composed of Weinberg and Buck converters is analyzed using PSpice software and the results of simulations are verified through experiments. The results show that how well the converter operates satisfying the conditions required for satellite applications.Conference Object Effects of Type of Incidence on the Second and Fourth Order Moment Parameters Evaluated in Turbulent Atmosphere(2010) Baykal, Y.; Baykal, Yahya Kemal; Elektrik-Elektronik MühendisliğiUsing a general type incidence, the second and fourth order moments are formulated in atmospheric turbulence. Received field and intensity correlations are evaluated and the behaviour of these correlations are compared for different beam types. © 2010 OSA/FiO/LS.Conference Object Citation - Scopus: 2Scintillation Index of Partially Coherent Asymmetrical Multi Gaussian Beams in Extremely Strong Turbulence(2010) Baykal, Yahya Kemal; Öztan, M.A.; Baykal, Y.; Elektrik-Elektronik MühendisliğiIt is investigated whether partial coherent asymmetrical annular and flat-topped Gaussian beams provide advantage to decrease the scintillation noise effect when free space optics systems are used in long distance (longer than 5km) transmission links. Scintillation index of partially coherent asymmetrical multi Gaussian beam propagating in extremely strong turbulence is formulated and the scintillation indexes of asymmetrical annular and flat-topped Gaussian beams are calculated. Scintillation index variations are plotted against the source size and asymmetry ratio. It is determined that asymmetric beams have advantage over the symmetric beams in terms of the scintillation. It is found that the scintillation index decreases as the asymmetry ratio increases. It is also detected that by decreasing the coherence degree scintillation index of the propagating beam quickly goes to zero.Article A Novel Method To Solve 2nd Order Neumann Type Boundary Value Problems in Electrostatics(Applied Computational Electromagnetics Soc, 2017) Sener, Goker; Şener, Göker; Elektrik-Elektronik MühendisliğiIn this paper, the numerical method of nonpolynomial spline approximation is used to solve 2nd order Neumann type boundary value problems (bvp's) in electrostatics. This new approach provides more accurate results than the polynomial approximations and the spectral methods. The literature contains very little on the solution of Neumann type bvp's because of the fact that a unique solution does not exist for all problems. In electrostatics, Neumann type bvp's are encountered for finding the electrostatic potential inside closed surfaces where the normal derivative of the electric potential is specified everywhere on the surface. Two examples are presented to prove the accuracy of the proposed method. In these examples, the governing differential equation is solved to find the electrostatic potential inside a region bounded by conductors that are maintained at constant voltages. The results are compared with the analytic solutions.Article Citation - WoS: 3Citation - Scopus: 6Grid Connected Three-Phase Boost-Inverter for Solar Pv Systems(int Journal Renewable Energy Research, 2021) Demirkutlu, Eyyup; İskender, İres; Iskender, Ires; Elektrik-Elektronik MühendisliğiThis paper presents a transformerless grid-connected three-phase boost-type inverter derived from the Swiss Rectifier (SR) and can be used in solar systems. The proposed boost-inverter retains the great advantages of the Swiss rectifier. Since the number of switches that are instantly switched with high frequency is only two, the switching losses are very low, therefore the proposed boost-inverter is very advantageous in terms of efficiency. Without having large transformer and electrolytic bus capacitors, the boost-inverter has an advantage in terms of size and weight. The switching states of the topology are given in detail. The operation principle of the boost-inverter is described with the help of equivalent circuits. A cascaded control method including current and voltage loops is designed. Simulation results are presented to validate the operation of the boost-inverter and show quality performance of the designed control approach.Article Citation - Scopus: 9Sensorless Speed Control of a Bldc Motor Using Improved Sliding Mode Observer Technique(International Organization on 'Technical and Physical Problems of Engineering', 2019) Topal, M.; İskender, İres; Iskender, I.; Genc, N.; Elektrik-Elektronik MühendisliğiThis paper proposes controlling the velocity of BLDC motor using sliding mode observer technique based on the estimation of back electromotive force (back EMF). There are many different sensorless control methods for BLDC motor, but in this paper one of them is examined in detail, comparing with the zero crossing points detection of back EMF and hall sensor control. The proposed method estimates the velocity and rotor position by measuring terminal voltages and currents. According to the rotor position, two inverter switches are energized to commutate the phases of BLDC motor. As comparing desired and real line currents, the commutation signals are acquired with hysteresis band. The simulation model of the suggested method is performed by using MATLAB Simulink environment and results have been simulated to interrogate the performance of the BLDC motor under a load change condition also with reference speed. © 2019, International Organization on 'Technical and Physical Problems of Engineering'. All rights reserved.Article Citation - Scopus: 2Pi Control of a Novel Power Converter by Using Heuristic Optimization(International Organization on 'Technical and Physical Problems of Engineering', 2021) Tulay, G.; İskender, İres; Karakaya, M.; Iskender, I.; Elektrik-Elektronik MühendisliğiIn this study, obtaining the PI control coefficients of a power converter using the heuristic optimization method was investigated. A new converter has been designed to increase the lifetime of the energy storage unit of a satellite power subsystem. It is also possible to increase the active duty life of the satellite by using the aforementioned converter according to the increased battery life. © 2021, International Organization on 'Technical and Physical Problems of Engineering'. All rights reserved.Article Citation - Scopus: 11Performance Analysis of a Distribution Transformer Using Ansys Maxwell(International Organization on 'Technical and Physical Problems of Engineering', 2020) Ariani, H.A.; İskender, İres; Iskender, I.; Karakaya, M.; Elektrik-Elektronik MühendisliğiThe purpose of this study is to verify the theoretical calculations of a three-phase transformer by analyzing its magnetic field behaviors and losses under no-load and full-load working conditions using an advanced simulation program that runs based on finite elements method (FEM). This paper presents detailed explanations on defining the parameters and obtaining the results, and also the calculation method for determining the magnitude of the magnetic field and the core and ohmic losses of the transformer. The reliability of the analysis is confirmed by theoretical calculation results. © 2020, International Organization on 'Technical and Physical Problems of Engineering'. All rights reserved.Article Citation - Scopus: 9Design and Performance Analysis of a Three Winding Transformer Used in Solar System(International Organization on 'Technical and Physical Problems of Engineering', 2021) Jahi, A.; İskender, İres; Iskender, I.; Elektrik-Elektronik MühendisliğiDue to the increasing of the fossil fuels prices in the past years and lack of these sources, all scientists encouraged to looking for the alternative energy sources. One of these energy sources is the renewable solar resources. Power transfer from solar systems to grid is achieved using step up transformers. This type of transformer is energized from a converter/inverter with or without variable frequency. The losses of such transformer are higher than those used in sinusoidal voltage power systems. This is due to harmonics content in the transformer input voltage and current. In this study the design and production of a PV transformer have been done according to the IEEE C57.159 guide and the loss analyses of transformer have been done using ANSYS MAXWELL considering the procedures proposed in standards of IEC 61378-1, IEEE C57.110 and the method proposed by Dowell. Finally, the thermal modeling and behavior of the transformer was investigated using the thermal model given in [25] to determine the hot spot and life time of the transformer using MATLAB program. © 2021, International Organization on 'Technical and Physical Problems of Engineering'. All rights reserved.Book Part How To Use Novel Methods for Improving the Performance of Wireless Cognitive Networks(CRC Press, 2016) Preveze, B.; Preveze, Barbaros; Elektrik-Elektronik MühendisliğiArticle Citation - WoS: 9Citation - Scopus: 6Multimode Beam Propagation Through Atmospheric Turbulence(Pergamon-elsevier Science Ltd, 2024) Baykal, Yahya; Ata, Yalcin; Gercekcioglu, Hamza; Gokce, Muhsin CanerThe investigation focuses on studying the propagation characteristics of multimode lasers in the turbulent amosphere. By employing the Huygens-Fresnel integral, we develop analytical formulations for various propagation parameters. These include the average intensity distribution, kurtosis parameter, beam spread, and the average transmittance of multimode beams in turbulent atmosphere. Our findings reveal that as the propagation distance or the structure constant of the atmosphere increases, i.e., turbulence becomes stronger, the kurtosis parameter and the beam spread increase. The multimode beam exhibits a Gaussian like intensity profile when the propagation distance is significantly increased or when the structure constant becomes sufficiently large. For the case of the Gaussian beam, the kurtosis parameter is found to be 3. The multimode beam's kurtosis parameter rises as the turbulence becomes stronger and eventually approaches 3. Raising the mode content leads to a rise in the average transmittance; however, it leads to a decline in the Kurtosis parameter and the beam spread.Article Citation - WoS: 3Citation - Scopus: 4Depth Dependence of Oceanic Turbulence Optical Power Spectrum Under Any Temperature and Salinity Concentration(Iop Publishing Ltd, 2024) Gercekcioglu, Hamza; Baykal, YahyaThe Oceanic Turbulence Optical Power Spectrum (OTOPS) with depth variations is acquired under any temperature and salinity concentration. It is supposed that specific medium is the Atlantic Ocean at high latitude and the Pacific Ocean at high, mid and low latitudes. For the OTOPS model, a depth-varying functions that include low-latitude, high- and mid-latitude-summer and mid-latitude-winter salinity and temperature changes are found. With the help of the equations for the temperature and salinity changes, figures are obtained for the eddy diffusivity ratio depth of seawater and OTOPS model against the depth and kappa at these media. In the ocean, downlink (uplink) is defined as the optical wireless communication link where the receiver (transmitter) is located at a deeper point than the transmitter (receiver), i.e., in the downlink, optical signal proceeds from a point close to ocean surface to deeper ocean and in the uplink, optical signal proceeds from deeper ocean to a point close to ocean surface. In this paper, the OTOPS model is investigated on how its properties change in the underwater environment in downlink and uplink. Different behavior of the OTOPS model is exhibited.Article Citation - Scopus: 4Cost Optimization of Oil Type Distribution Transformer Using Multi-Objective Genetic Algorithm(Erol Kurt, 2024) Iskender, I.; Yükselen, E.; Telli, S.The demand for electrical energy is increasing day by day with the development of technology in the world. Distributing electric energy to all regions that need energy is a principal issue, and this necessitates the use of transformers to convert the voltage to the desired level. Accordingly, the use of transformers, one of the electrical devices converting AC voltage level at a defined frequency has grown significantly. In this study, design parameters of a 25 kVA, 33/0.4 kV, Yzn11, oil-type distribution transformer are optimized using the Multi-Objective Genetic Algorithm (MOGA) technique by decreasing the weight of the significant materials and manufacturing cost. Electromagnetic analysis of the transformer is performed with ANSYS Maxwell based on the design results obtained from the optimization study for validation of the method. The experimental design parameters are also compared with the optimization results. It is observed that optimum results are achieved by using the proposed approach. © 2024 Published by peer-reviewed open access scientific journal, JES at DergiPark (https://dergipark.org.tr/jes)
