WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
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Article Noninvasive Condition Monitoring for Eccentricity Fault Detection in Large Hydro Generators(TÜBİTAK Scientific & Technological Research Council Turkey, 2026-01-16) 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.Conference Object Structural Integrity Analysis of a Two-Pole Synchronous Reluctance Machine With Non-Circular Shaft(IEEE, 2023-06-14) Tekgun, Didem; Tekgun, Burak; Alan, IrfanThis paper investigates the structural strength of a 6-inch diameter, two-pole, 4 kW line start synchronous reluctance machine (LS-SynRM) designed with a new non-circular shaft structure that serves as a pump motor. Flux paths on the rotor are widened while narrowing down the shaft of the motor on the q- axis to improve the motor efficiency. By using this method, a wider path is created for the flux in the d-axis. As a result, the inductance in the d-axis, the ratio of inductance between the d-axis and q-axis (referred to as saliency ratio), and the difference in inductance between the d-axis and q-axis are all amplified. To evaluate the structural strength of the machine, a series of analyses are conducted, including modal, harmonic, and static examination on the rotor using ANSYS Structural. The findings indicate that to prevent redundant deformations and undesirable vibrations because of resonance, the maximum safe limit for shaft size reduction is determined as 8 mm.Conference Object Power Factor Improvement of a Permanent-Magnet Vernier Machine with Harmonic Injected Excitation Currents(IEEE, 2025-06-11) Karatepe, Hasan Can; Tekgun, DidemPermanent-magnet vernier machines (PMVM) are recognized for their high torque density but low power factor (PF) due to high inductive reactance. This paper presents a method for improving the PF of a PMVM by injecting additional harmonics into the excitation currents. This injection is done through the motor drive, unlike many proposed methods for enhancing PF, thus eliminating any modifications needed on the machine's geometric design. In this paper, different sets of harmonic injected currents are fed to a 14-rotor pole 12-slot PMVM with short-pitched coils on Finite Element Analysis (FEA) to demonstrate the effects of individual and combined harmonic currents. Corresponding performance characteristics of each simulation case, such as PF and torque density, are investigated. Simulation results indicate that PF can be improved by the proposed method of harmonic current injection. A comparison with a similarly sized permanent-magnet synchronous machine (PMSM) is made to demonstrate that the proposed method can be an alternative to widely used PMSMs.Article Citation - WoS: 1Citation - Scopus: 1Modified Induction Machine Equivalent Circuit Including Solid Shaft Eddy Currents(MDPI, 2023-12-15) Tekgun, DidemThe shaft eddy currents cause a significant saturation in two-pole induction machines (IMs) as they generate an opposing field and repulse the main flux, thus tightening the flux path. This results in inaccurate performance estimations with the magnetizing inductance measured in no-load conditions when the machine is loaded. This article presents a modified IM equivalent circuit considering the rotor back iron saturation effects caused by the solid shaft eddy currents using experimental measurements and recursive parameter estimation techniques. The classical equivalent circuit (CEC) parameters are determined with the standard test techniques followed by the parameter estimation of the newly introduced modified equivalent circuit (MEC) parameters. The proposed modified equivalent circuit is benchmarked with CEC and finite element analysis (FEA) simulations with and without considering eddy effects. The proposed MEC model and the FEA that consider eddy effects performed better than the other models and yielded a negligibly small error over a wide range of loading conditions. Compared to the FEA, the proposed MEC estimates the IM performance much faster, which makes it more appealing for IM performance estimations.Conference Object Citation - WoS: 5Citation - Scopus: 5Investigation of the Effects of Multi-Layer Winding Structures in Two Pole Synchronous Reluctance Machines(IEEE, 2021-10-05) Tekgun, Didem; Cosdu, Muhammed Muhsin; Tekgun, Burak; Alan, Irfan; Muhsin Cosdu, MuhammedIn this paper, a comparative study is performed between single, various double, and triple-layer winding structures to investigate the effects of the winding MMF harmonics and end winding length on the two-pole synchronous reluctance machines (SynRM). A two-step design approach is used including winding and geometry optimization using multi-objective differential evolution (MODE) algorithm. In the first stage, a Pareto front is obtained which determines the number of turns for each coil group for all winding configurations. Later in the second stage, three results are selected from the first stage to perform a geometric optimization to distinguish the effects of the THD and end winding length on the synchronous performance of a 4 kW two-pole SynRM. For the same average torque output, efficiency, mass, and the torque ripple of the selected designs are investigated and compared. Based on the analysis, it is concluded that rather than focusing on shortening the end winding length, reducing the MMF harmonics have a more positive effect on the machine performance as reduced harmonics resulted in efficiency improvement up to 2 points and torque ripple is reduced up to 8 points while having similar motor mass.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 - 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.Conference Object Citation - WoS: 2Citation - Scopus: 2Influence 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.Article Citation - WoS: 10Citation - Scopus: 10FEA 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.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.