Profile URL: https://hdl.handle.net/20.500.12573/2694
Job Title:Dr. Öğr. Üyesi
Email Address:didem.tekgun@agu.edu.tr
Main Affiliation:02.05. Elektrik & Elektronik Mühendisliği
Status: Current Staff
ORCID:
0000-0003-4143-0720
0000-0003-4143-0720Scopus ID:
57194420295
57194420295YÖK Akademik: 6AC6308DEC9F5107
Google Scholar:
UbU30AAAAJ&hl
UbU30AAAAJ&hlWeb of Science ID:
JDD-4552-2023
JDD-4552-2023Name Variants:
Didem Tekgün Tekgun, Didem
20 results
Scholarly Output Search Results
Now showing 1 - 10 of 20
Article Citation - WoS: 1Citation - Scopus: 1Investigating the Tradeoff Between the MMF Distortion and End Turn Length of a 2-Pole Line Start SynRM Performance(Springer int Publ Ag, 2023-07-19) Tekgun, Didem; Cosdu, Muhammed M.; Tekgun, Burak; Alan, IrfanConventional 2-pole AC machine windings have long end windings and generate harmonics, which increase losses and reduce torque density. This study investigates the performance tradeoff between the level of distortion (THD) in winding magneto-motive force (MMF) and end turn length on a 2-pole line start Synchronous Reluctance Machine (LS-SynRM) machine. A two-stage approach is used, winding and geometry optimization. Various multilayer winding configurations having unevenly distributed number of turns are investigated. First, the percentage of the turns in a coil group is optimized for minimum harmonics and end turn length for all structures. Second, geometric optimization is performed on selected winding configurations. Sixteen different configurations are optimized, and Pareto optimal solutions are obtained. Later, these solutions are graded with a new score-based assessment method to quantify the quality of the results. It is concluded that the designs having lower THD in winding MMF perform better than the designs with shorter end turns in terms of efficiency and torque density.Article Citation - Scopus: 1Noninvasive Condition Monitoring for Eccentricity Fault Detection in Large Hydro Generators(TÜBİTAK Scientific & Technological Research Council Turkey, 2026) Lemeski, Atena Tazikeh; Tekgun, Didem; Keysan, Ozan; Leblebicioglu, Kemal; Gol, Murat; Leblebicioglu, Mehmet KemalEccentricity faults in electric machines remain a critical concern, as they generate uneven magnetic forces that increase vibration and noise, ultimately raising the risk of premature motor failure. This study proposes a method for the early detection of dynamic eccentricity (DE) faults in hydropower plants through an advanced optimization-based parameter identification technique integrated with finite element analysis (FEA). Finite element modeling (FEM) is first used to analyze an existing salient-pole synchronous generator (SPSG) from a hydroelectric power plant in T & uuml;rkiye. The effects of DE faults on the SPSG's magnetic equivalent circuit parameters are then examined under various fault severities. A comprehensive hydropower plant model-including the synchronous generator, governor, and excitation system-is developed in MATLAB/Simulink, with all input parameters obtained from real plant data and equivalent circuit variations extracted from FEA. After completing the modeling stage, including fault scenarios, MATLAB and Simulink are employed together to estimate key magnetic equivalent circuit parameters using a modified particle swarm optimization (MPSO) algorithm, achieving highly accurate parameter estimation. Since the hydropower system allows measurement of the three-phase output currents, parameter estimation is performed based on current variations under different fault conditions. The simulation results verify the method's ability to detect faults with high accuracy; thus, this integrated and noninvasive approach provides a robust framework for ensuring the operational reliability and longevity of large hydro generators.Article Citation - WoS: 1Citation - Scopus: 3Investigating the Role of Stator Slot Indents in Minimizing Flooded Motor Fluid Damping Loss(MDPI, 2023-12-14) Tekgun, Didem; Tekgun, BurakThis research examines how fluid damping loss affects the operation of a two-pole, 5.5 HP (4 kW) induction machine (IM) within the context of different slot opening configurations developed for downhole water pump applications. Since these motors operate with their cavities filled with fluid, the variations in fluid viscosity and density, compared to air, result in the occurrence of damping losses. Furthermore, this loss can be attributed to the motor's stator and rotor surface geometry, as the liquid within the motor cavity moves unrestrictedly within the motor housing. This study involves the examination of the damping loss in a 24-slot IM under different stator slot indentations. The investigation utilizes computational fluid dynamics (CFD) finite element analysis (FEA) and is subsequently validated through experiments. The aim of this work is to emphasize the significance of fluid damping loss in submerged machines. Results reveal that the damping loss exceeds 8% of the motor output power when the stator surface has indentations, and it diminishes to 3.2% of the output power when a custom wedge structure is employed to eliminate these surface indentations.Article Farklı Rotor Geometrilerine Sahip Senkron Relüktans Makinelerde Eksantriklik Hata Göstergeleri(2026) Tekgun, DidemSenkron relüktans motorları (SynRM’ler), mıknatıssız rotor yapıları, yüksek verimleri ve farklı çalışma koşulları altında gösterdikleri sağlam performans nedeniyle modern tahrik uygulamalarında önemli ölçüde dikkat çekmektedir. Bununla birlikte, SynRM’ler güvenilirliklerini azaltabilecek elektriksel ve mekanik arızalara karşı hassastır. Bu arızalar arasında, rotor ve stator arasındaki küçük hizasızlıkların dahi dengesiz manyetik kuvvetlere, artan titreşime ve elektromanyetik gerilime yol açabilmesi nedeniyle, eksantriklik arızaları kritik öneme sahiptir. Bu çalışma, üç ve dört akı bariyerli rotor geometrilerine sahip SynRM’lerdeki statik (SE), dinamik (DE) ve karışık (ME) eksantriklik arızalarını iki boyutlu sonlu eleman analizi yöntemiyle incelemektedir. Sonuçlar, ME arızasının en ciddi elektromanyetik bozulmaya neden olduğunu, üç akı bariyerli rotorun ise azalmış çıkık kutupluluk nedeniyle daha yüksek moment dalgalanması ve daha düşük moment ürettiğini göstermektedir. Moment dalgalanması, ME koşullarında %33’e kadar artış göstererek en hassas arıza göstergesi olarak belirlenmiştir. Bu bulgular, rotor geometrisi, arıza şiddeti ve makina performansı arasındaki ilişkiye dair değerli içgörüler sunarak gelecekteki SynRM tasarım ve izleme stratejilerine rehberlik etmektedir.Conference Object Citation - WoS: 2Citation - Scopus: 3Influence of Eccentricity Faults on IPM Motor Equivalent Circuit Characteristics(IEEE, 2025-06-11) Tekgun, DidemInterior Permanent Magnet (IPM) machines are preferred in various modern applications due to their high efficiency, compact design, and reliability. They are especially favored in electric vehicle (EV) powertrains but also play a key role in hybrid vehicles, electric motorcycles, industrial automation systems, robotics, and home appliances such as air conditioners and washing machines. Eccentricity is a critical and challenging issue since it causes an unbalanced airgap magnetic flux and forces, eventually resulting in vibration, noise, and a higher likelihood of motor malfunction over time. This study investigates the effects of eccentricity faults on the motor's magnetic flux density and corresponding equivalent circuit parameters through Finite Element Analysis (FEA). The results show that the two types of eccentricity, static and dynamic, produce noticeable variations in the airgap magnetic flux as well as in key equivalent circuit parameters. Specific equivalent circuit parameters are particularly sensitive to different eccentricity faults, making them key indicators for early fault detection.Conference Object Citation - Scopus: 2Effect of the Stator Slot Indents on Fluid Damping Loss in Submersible Pump Applications(IEEE, 2022-06-14) Tekgun, Didem; Cosdu, Muhammed Muhsin; Tekgun, Burak; Alan, IrfanIn this study, the effect of fluid damping on the performance of a 2-pole, 4-kW line start synchronous reluctance machine (LS-SynRM) with different slot opening structures for submersible water pump applications is investigated. Since the submersible pump motors run inside a fluid-filled environment and the fluid viscosity and density differ from the air, it causes an increased damping effect comparing air-filled machines. Hence, a non-negligible damping loss occurs. In this study, the damping effects of the fluids in a 24 slot LS-SynRM for various stator slot indentations are investigated with computational fluid dynamics (CFD) finite element analysis (FEA) to highlight the importance of the fluid damping loss in flooded machines. Results show that the damping loss can go as high as 10% of the motor output power when the stator surface has indentations, and this loss can be cut down to 3.5 % when the surface indentations are eliminated with custom no-slotting wedge structures.Master Thesis Inter-Turn Short Cırcuıt Fault Detectıon of a Permanent Magnet Assisted Vernıer Machıne Through Stray Magnetıc Field(2026) Atar, Nazif Kerem; Tekgün, DidemPMVM are increasingly preferred in direct-drive applications such as wind turbines, in-wheel electric vehicles and robotic systems owing to their high torque density and magnetic gearing effect. However, inter-turn short-circuit (ITSC) faults in the stator windings remain a critical reliability issue; if undetected, they rapidly propagate, causing torque ripple, overheating and possible demagnetization. Traditional motor current signature analysis (MCSA) suffers from low sensitivity and poor localization capability in PMVMs because of the machine's high armature reaction. This was validated through 2D transient finite element analysis (FEA), specifically a 24-slot/10-pole-pair stator and 28-pole rotor PMVM at 550 rpm. Faults with severities ranging from 3% to 16% were induced in the Phase-A coil L5. Twenty-four virtual sensor positions were considered in the radial and tangential directions outside the machine, and the ratios of the normalized RMS values of the components of the stray flux were plotted in polar coordinates. The results clearly indicate the localized asymmetries; for example, the radial flux almost doubles at the sensor near the faulted coil, and the tangential flux decreases significantly at this sensor location. The technique thus allows for initial-fault identification and accurate fault localization independent of loading, which compares favorably with MCSA in sensitivity and robustness. Hence, the technique provides an easy-to-implement and low-cost condition monitoring approach for PMVMs, which would make renewable energy systems and electric transport systems more reliable and sustainable.Research Project Dalgıç Pompa Uygulamaları İçin Doğrudan Yol Vermeli Senkron Relüktans Motorunun Tasarım Optimizasyonu Ve Gerçeklemesi(ELEKTRİK, ELEKTRONİK VE ENFORMATİK ARAŞTIRMA DESTEK GRUBU GRUBU: EEEAG, 2023) Tekgun, Burak; Alan, Irfan; Tekgun, DidemGünümüzde doğal kaynakların korunması ve enerji maliyetlerinin düşürülmesi için enerji kayıplarının azaltılması ortak bir amaç olarak görülmektedir. Elektrik tahrik sistemlerinin küresel enerji tüketiminin yaklaşık %40?ını oluşturduğu düşünüldüğünde elektrik makinalarının verimlerinin artırılması ile sağlanacak avantajların hem ülke bazında hem de evrensel olarak büyük bir öneme sahip olduğu görülmektedir. Uygulama odaklı olarak bakıldığında yer altından su, petrol vb. çıkarmakta kullanılan pompa motorlarının endüstride kullanılmakta olan motorlar arasında oldukça büyük bir paya sahip olduğu görülmektedir. Özellikle dalgıç pompa uygulamalarında kullanılmakta olan pompa motorları gerek motor tasarım hatalarından, gerekse de yanlış motor-pompa konfigürasyonları seçiminden kaynaklanan hatalar nedeniyle çok düşük verimlerle çalışmaktadır. Sağlamlık, ucuzluk ve doğrudan yol verme gibi özelliklerinden dolayı pompa uygulamalarında genellikle indüksiyon motorları (İM) tercih edilmektedir. Fakat İM?lerin en büyük sorunu özellikle küçük ve orta güçte düşük enerji verimi ile çalışmalarıdır. Doğrudan yol vermeli sürekli mıknatıslı motorlar (DY-SMSM) yüksek güç yoğunluğuna sahip olmaları sebebiyle verimi yükseltmek adına İM?lere uygun bir alternatiftir. Fakat bu makinalarda doğrudan yol verme esnasında mıknatısların demagnetizasyonu ve en önemlisi doğada nadir bulunan mıknatısların kullanımından kaynaklı yüksek maliyet ve dışa bağımlılık sorunları araştırmacıları bu makinalara yeni bir alternatif arayışı içine itmektedir. Bu doğrultuda hem doğrudan yol verme özelliği hem de mıknatıs içermeyen yapısı ile doğrudan yol vermeli senkron relüktans motorlar (DY-SenRM) İM?lere uygun bir alternatif olarak karşımıza çıkmaktadır. En basit tanımla bu tip motorlar çalışma prensibi bakımından relüktans motor ve İM?nin bir kombinasyonudur. DY-SenRM?de makinanın rotoruna uygun şekilde gömülen rotor barları ile doğrudan yol verme özelliği kazandırılırken, İM?lerin aksine rotor bakır kayıpları sürekli rejimde sıfıra indirilmektedir. Dahası SenRM?ler İM?lere kıyasla daha yüksek güç ve moment yoğunluğuna sahiptir. SenRM?lerin dezavantajlarına bakıldığında düşük güç faktörü ile çalışma ve rotordaki açıklıklardan kaynaklı yapısal entegrasyon problemleri göze çarpmaktadır. Bu problemler tasarım aşamasında iyi incelenip gerekli önlemler alınmalıdır. Gerekli olduğu durumlarda nadir element bulundurmayan mıknatısların kullanımı güç faktörü sorununu ortadan kaldırdığı gibi verimi de artırmaktadır. Bu projede dalgıç pompaları için 4 kW gücünde DY-SenRM tasarımı üzerine çalışılacaktır. Özellikle sulama amaçlı üretilen yer altı pompa sistemlerinde en çok tercih edilen 6 inç çapındaki dalgıç pompalarına uygun, yüksek verimli 4 kW gücünde bir DY-SenRM?nin tasarım optimizasyonunun yapılması ve gerçeklemesi amaçlanmaktadır. Optimizasyon algoritması olarak çoklu amaç diferansiyel evrim algoritması, benzerlerine göre öne çıkan hızlı yakınsama ve doğru sonuçlara ulaşma özellikleri göz önüne alınarak seçilmiştir. Tasarlanacak DY-SenRM?nin geçici rejim performansı, senkronize olabilme yeteneği, senkron çalışma performansı ve boyutu optimizasyonda göz önüne alınacak metriklerdir. Bu çalışmanın başarıyla sonuçlanması ile DY-SenRM?nin sadece pompa uygulamaları değil, diğer sabit hız uygulamalarında da düşük verimli İM?lerin yerini alması; dolayısıyla düşük maliyetli, yüksek verimli motor teknolojisinin yaygın hale gelmesi ön görülmektedir.Conference Object Citation - WoS: 5Citation - Scopus: 6Design and Control of a Single Phase DC/Rectified AC/AC Inverter for Low THD Applications(Institute of Electrical and Electronics Engineers Inc., 2018-10) Tekgun, Burak; Tekgun, Didem; Alan, İrfan; Badawy, Mohamed O.In this paper, a single phase DC/Rectified AC/AC (DC/RAC/AC) inverter is analyzed and compared to classical single phase PWM inverters. A traditional AC power supply (PS) system consists of a DC/DC converter, a cascaded H-bridge inverter, and a passive filter to generate the sinusoidal output voltage. The presented DC/RAC/AC inverter has a similar structure; however, the control of the cascaded units differ. The presented method generates rectified sine wave at the output of the DC/DC converter unit and the H-bridge inverter alternates the rectified sine wave to generate the full sine wave without having an additional output filter; hence, the switching losses at the H-bridge inverter is limited to the line frequency (50-60 Hz). Moreover, the bulk DC bus capacity at the output of the DC/DC converter is reduced significantly. Therefore, the power consumed by the passive elements are minimized. The circuit modes of operation are analyzed and the system is simulated in Matlab/Simulink environment for both traditional and proposed topologies. Results show that the proposed system is superior to the traditional one in terms of efficiency, generated THD with a simplified control structure, and it offers a reduced system size and cost. © 2019 Elsevier B.V., All rights reserved.Article Citation - WoS: 11Citation - Scopus: 11FEA Based Fast Topology Optimization Method for Switched Reluctance Machines(Springer, 2022-01-04) Tekgun, Didem; Tekgun, Burak; Alan, IrfanIn this paper, a finite element analysis (FEA) based fast optimization method to optimize a lightweight in-wheel switched reluctance machine is presented. This method speeds up the switched reluctance machine optimization procedure by running the FEA simulations with single-phase constant current excitations for half electrical cycle and estimating the machine performance metrics using the gathered FEA data. Hence, the machine`s dynamic performance estimation process takes shorter for each design candidate. The optimization algorithm employs designs of experiments (DOE), response surface (RS) analysis method, and differential evolution algorithm (DE). Here, the DOE method is used to reduce the search space by narrowing down the upper and lower boundaries of each design variable based on the RS analysis. Although this process does not guarantee getting the Pareto front, it places the search space close to the actual one. Hence, the multi-objective DE optimization finds the Pareto optimal solution set without requiring a large number of iterations as well as a large number of candidate designs for each iteration. The method is applied to a 24/16 SRM that is intended to be used in a lightweight race car as a hub motor. Six dimensionless geometric variables are optimized to satisfy three objective functions, namely torque ripple, motor mass, and copper loss. While the conventional DE takes at least 3000 candidate designs, the proposed method considers only 559 designs to reach a similar Pareto front. It is observed that the proposed method takes about 6 h 30 min compared to the conventional method that takes 32 h 50 min using the same computer. Therefore, the computation time is reduced almost five times with the proposed method.