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Browsing by Author "Zahedi, Mohammad Zia"

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    Citation Count: Zahedi, Mohammad Zia; Iskender, Ires, "Non-Linear Eddy Current Loss and Thermal Analysis on Transformer Cover", Gazi University Journal of Sience, Vol. 32, No. 2, pp. 558-570, (2019).
    Non-Linear Eddy Current Loss and Thermal Analysis on Transformer Cover
    (Gazi Univ, 2019) Zahedi, Mohammad Zia; İskender, İres; 133746
    High current conductors of transformers cause to produce losses and thermal problems in their tank cover. Finite Difference (FD) Method (FDM) magnetic analysis is used to find out an exact estimation of the magnetic field and the losses near the bushings in the transient solution, considering the non-linear magnetic permeability of the cover plate, because FDM is more flexible to deal with the nonlinear constitutive law and easy-to-be implemented especially in the case of simple geometry. Finite Element Method (FEM) thermal analysis is used to determine the plate temperature based on magnetic FD analysis, taking account non-linear heat flux boundary condition. A calibration procedure is used between the analyses to ensure the precision of assumptions. The reliability of the technique, confirmed by experimental and FEM results.
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    Article
    Citation Count: Zahedi, Mohammad Zia; Iskender, I., "Nonlinear Adaptive Magneto-Thermal Analysis at Bushing Regions of a Transformers Cover Using Finite Difference Method", Journal of Thermal Science and Engineering Applications, Vol. 11, No. 1, (2019).
    Nonlinear Adaptive Magneto-Thermal Analysis at Bushing Regions of a Transformers Cover Using Finite Difference Method
    (ASME, 2019) Zahedi, Mohammad Zia; İskender, İres; 133746
    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.