Browsing by Author "Iskender, I."

Now showing 1 - 15 of 15

Citation - WoS: 2
Citation - Scopus: 3
Analysis and Design of a Special Type Power Transformer Used in Solar Power Plants
(Gazi Universitesi, 2022) Yükselen, E.; Iskender, I.; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Due to growing of greenhouse gas emissions and lack of the fossil sources, governments encouraged all scientists and utilities for looking to the alternative energy sources such as solar renewable energy which can help to reduce carbon dioxide emissions. In this respect, Photovoltaic (PV) power plants have become more important in recent years and renewable energy sources integrated into the power system are increasing day by day. Transformers are the main components of electrical grids and are widely used in renewable power plants to transfer the energy they produce to the grid. Accordingly, transformers are one of the most critical equipment of PV plants, and their safe operation and stability in the electrical network are important. This type of transformer is supplied from solar panels through inverters and needs to be customized to work with each system. In this type of transformer, the losses are higher than those for transformers used in electrical power systems supplied by sinusoidal voltage considering existence of different voltage and current harmonics content produced by the inverter. In this study, a special type of PV transformer was designed in accordance with the target performance criteria, taking into account the effects of harmonics, and keeping the transformer losses and temperature rise at a safe level. In this paper also the simulation results are compared with those of experiments test to verify the design procedures. © 2022. International Journal of Renewable Energy Research.All Rights Reserved
Citation - Scopus: 4
Analysis of Short Circuit Electromagnetic Force in a Three Winding Transformer Used in Solar System
(Institute of Electrical and Electronics Engineers Inc., 2021) Iskender, I.; Jahi, A.; 133746; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Due 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 renewable solar energy. Power transmission from solar systems to grid is achieved using step up transformers. This type of transformer is energized from two inverter with or without variable frequency. Power transformers are deals with a variety of mechanical, electrical and thermal stresses during normal life time operation. Transient electromagnetic forces cause mechanical stress on transformer parameters where calculation of these forces with traditional methods is extremely complex due to the geometry of the transformer. Accordingly in this study, the electromagnetic forces takes place in the windings of a Photovoltaic (PV) transformer are investigated and for calculation of these forces, the 3D and 2D model of transformer is adapted in the ANSYS Workbench. The analysis of electromagnetic forces during the three line fault on high voltage side of the transformer are performed by the Finite Element Method (FEM) and compared with the analytical results. The numerical modeling technique discussed in this study would be useful in the design stage of PV transformer with regard to evaluate ability of transformer to withstand the short circuit current. © 2021 Chamber of Turkish Electrical Engineers.
Citation - Scopus: 4
Comparing 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.; 133746; Elektrik-Elektronik Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Brushless 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.
Citation - Scopus: 4
Cost Optimization of Oil Type Distribution Transformer Using Multi-Objective Genetic Algorithm
(Erol Kurt, 2024) Iskender, I.; Yükselen, E.; Telli, S.; 133746; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
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)
Citation - Scopus: 9
Design 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.; 133746; Elektrik-Elektronik Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Due 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.
Citation - Scopus: 6
Design 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; 133746; Elektrik-Elektronik Mühendisliği; Bilgisayar Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Recently, 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.
Firçasiz Doǧru Akim Motorlarinin Model Referans Adaptif Kontrol Yöntemi - Mıt Kurali ile Kontrol Edilmesi
(Institute of Electrical and Electronics Engineers Inc., 2019) Iskender, I.; Ciba, S.; 133746; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In this study, the control of Brushless DC Motors (BLDC), which gained popularity in recent years, is discussed. As a result of insufficient classical control methods, modern control methods have been needed and BLDC is controlled with model reference adaptive control (MRAC) - with MIT law method. For this purpose pulse function, sine wave and step function were applied as a reference speed and the output speed of the system was observed. Simulation results show that the speed of the system follows the speed of the reference model. Then it was thought that in the course of time the resistance value will change because of heated motor and according to this situation the resistance value increased and the output of the system is observed again. © 2018 IEEE.
Citation - Scopus: 1
High Voltage Dc Systems and the Related Commisioning
(International Organization on 'Technical and Physical Problems of Engineering', 2020) Haliloglu, A.B.; İskender, İres; Iskender, I.; 133746; Elektrik-Elektronik Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The 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.
Citation - WoS: 4
Citation - Scopus: 3
Nonlinear Adaptive Magneto-Thermal Analysis at Bushing Regions of a Transformers Cover Using Finite Difference Method
(Asme, 2019) Iskender, I.; Zahedi, Mohammad Zia; 133746; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In this study, losses analysis at bushing regions of a transformer covers is done using finite difference method (FDM), considering that FDM being more flexible to deal with the nonlinear constitutive law and easier to be implemented than finite element (FE) and analytical methods. The analysis is performed based on a 2-level adaptive mesh solution of Maxwell equations and Ohm law at the cross section area in the axial symmetry page of a steel disk, taking account the nonlinear magnetic permeability of the steel. The losses density obtained, as a heat source, is imported into an alternating direction implicit (ADI) approach of heat conduction equation. Therefore, a finite difference (FD) solution algorithm for magneto-thermal analysis on cover plate is obtained by combination of adaptive mesh refinement and ADI-FDM, which improves the accuracy and decreases the computational time without losing accuracy. The reliability of the proposed technique is confirmed by experimental and FE method (FEM) results, considering the temperature distribution of the cover. The comparison of the results with those obtained from FEM and experiments shows the efficiency and capability of the method.
Citation - Scopus: 2
Optimal Design of an In-Runner Direct-Drive Synchronous Permanent Magnet Starter/Generator for Uavs
(Institute of Electrical and Electronics Engineers Inc., 2022) Iskender, I.; Navruz, T.S.; Arslan, S.; 133746; 06.03. Elektrik-Elektronik Mühendisliği; 06.01. Bilgisayar Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The aim of improving efficiency, safety, and reliability as part of more-electric-aircraft initiatives is mediating the rapid development of aerospace systems. In addition, the increasing need for leadership in the sociomilitary-economic area brings the focus of studies on unmanned aerial vehicles in aviation. However, developments in power electronics and control algorithms, permanent magnets, high-speed transmission elements, and iron core material technologies reveal the need for using Starter/Generator structures in hybrid propulsion systems. This paper explores the optimum design of an In-runner Synchronous Permanent Magnet Starter/Generator with specifications of 1 kW-4500 rpm for motor mode and 1.25 kW-5500 rpm for generator mode, especially for small UAVs equipped with a piston engine. Thus, charging the battery packs and the required thrust can be provided with higher efficiency. The preliminary dimensions are obtained analytically. The design issues of materials and topologies are discussed. The novel model is optimised in Ansys Maxwell 2D based on finite element analyses. Dynamic and static simulations are performed with the optimetric sensitivity method, and the efficiency study is carried out in Maxwell 3D. The data obtained as a result of analytical and numerical calculations are verified. © 2022 IEEE.
Citation - Scopus: 3
Performance Analyses of a Three Winding Double Stack Pv Transformer
(International Organization on 'Technical and Physical Problems of Engineering', 2021) Jahi, A.; Iskender, I.; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Transformers are the main components of electrical systems and are widely used in renewable energy systems that transfer the energy they produce to the grid. Recently, due to the lack of fossil fuels, governments have encouraged utilities to seek alternative energy sources. In this respect, PV (Photovoltaic) power plants have become more important in recent years. Accordingly, transformers are one of the most critical equipment of PV plants, and their safe operation and stability in the electrical network are important. This type of transformer is energized from the inverter and needs to be customized to work with each system. The main purpose of this study is to analyze and model the magnetic field behavior of a special type PV transformer. This transformer has two similar separate windings on the low voltage side and one winding on the high voltage side. The simulation results are compared with those obtained from the experiments. The effects of the unbalanced operation of the inverters on the transformer performance were also investigated in this study. © 2021, International Organization on 'Technical and Physical Problems of Engineering'. All rights reserved.
Citation - Scopus: 10
Performance 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.; 133746; Elektrik-Elektronik Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
The 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.
Citation - Scopus: 2
Pi 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.; 133746; Elektrik-Elektronik Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In 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.
Citation - Scopus: 9
Sensorless 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.; 133746; Elektrik-Elektronik Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
This 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.
Citation - Scopus: 5
Three-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.; 133746; Elektrik-Elektronik Mühendisliği; 06.03. Elektrik-Elektronik Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Three-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.