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    Analysis of electromagnetic and loss effects of sub-harmonics on transformers by Finite Element Method
    (Springer India, 2020) Ozupak, Yildirim; Mamis, Mehmet Salih
    Power transformers are generally designed to be used in conditions where voltage and current are sinusoidal. However, nonlinear loads are increasing in modern power systems with the developing technology. Therefore, line voltages and currents often have harmonically distorted or non-sinusoidal waveforms. In this article, a model has been developed. The mathematically developed model has been proven experimentally and numerically. In this paper, different sub-harmonic content parametric analysis of the loss of transformer under no-load conditions with voltage excitation was performed. For this purpose, the Finite Element Method (FEM) based modeling of the core and windings of the transformer has been developed. An efficient method based on harmonic field model of transformer windings and FEM based modeling of transformer core is used. ANSYS@MAXWELL program, which realizes a solution based on FEM, is used for this. From the results of the analysis, it was seen that the effect of harmonic voltages on the loss of the transformer core is negligible. However, these tensions have been shown to increase winding losses in the unloaded state. This case reveals the importance of harmonics to be taken into account in calculating the losses of power transformers.
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    Realization of electromagnetic flux and thermal analyses of transformers by finite element method
    (Wiley, 2019) Ozupak, Yildirim; Mamis, Mehmet Salih
    When designing transformers, the system to which transformers are to be used, the electrical power to be transferred, and the continuity and safety of the system must be taken into consideration. Paired physical and mathematical models help to develop a system that is both accurate and easy to implement. In this study, a model was developed to determine the electromagnetic flux distribution, losses, and electromagnetic forces of the transformer. A thermal model was also developed to measure the heat generated and to determine the temperature distribution of the transformer. The performances of the proposed models were compared with the performance of the transformer, which was determined analytically, and the performance of the transformer was also determined experimentally and the results were confirmed. When the results were compared, it was seen that the proposed models gave more optimum results. In this way, electromagnetic flux, electromagnetic force, and thermal distribution at each point of the transformer can be easily determined. On the other hand, in this study, the windings and the core were optimized, the electromagnetic forces formed in the windings were calculated, the heat distribution in the winding and core was determined, the electrostatic field distributions were examined, and the problematic areas were determined. The thermal effects of the total losses of the transformer were investigated and optimum design parameters were determined. It was concluded that the methods proposed in this study were more practical than the methods reported in the literature. (c) 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
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    A Smart Campus Integrated With Smart Grid
    (Ieee, 2017) Ozupak, Yildirim; Cetintas, Gulten; Kaygusuz, Asim
    Recently, smart campus projects that will improve quality of the services they received and the daily activities of students and employees in the campus environment, have been put into practise. The smart campus includes issues such as increasing energy efficiency, facilitating transportation, parking area control, provision of access to multiple services with card systems, information systems, monitoring and control of systems, authorization of users, use of social areas, water saving and security. The smart campus also means that all these components are managed centrally. In this study, it is aimed to make intelligent campus compatible with smart grid and supported by renewable energy. For that reason, improvements and solution proposal that can be made on the current situation have been presented.