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Öğe An analysis on the relation between the seed distance and vertical levitation force for the multi-seeded YBCO using the modified advanced frozen image (MAFI) and experimental methods(Elsevier Science Sa, 2019) Ozturk, K.; Guner, S. B.; Abdioglu, M.; Demirci, M.; Celik, S.; Cansiz, A.The higher magnetic levitation force and related stiffness values are very important for Maglev and magnetic bearing applications. Also, larger superconducting surface area is needed for continuous and larger magnetic mediums with different geometries and dimensions in real scale industrial applications of superconducting systems. In this study, the cylindrical YBCO superconductors were fabricated by top-seeded melt growth (TSMG) method in single and two-seeded forms with different seed distances and then the magnetic force and stiffness measurements were carried out by three axes magnetic force measurement system in different cooling heights (CH) of 20mm and 75 mm. Additionally, a new analytical method, based on the magnetic dipole approximation, is proposed to calculate the levitation force in this study, named as Modified Advanced Frozen Image Method (MAFI), since although the Advanced Frozen Image Method in literature can calculate the levitation force with hysteresis, this method does not include the size effect of the superconductor. In the experimental studies, it is seen that the maximum levitation force values obtained by PMG with three PMs (named PMG-1) are more than two times higher than that of obtained with single PM for all samples with different distance of seeds, because of the higher magnetic flux distribution of related PMG arrangement than the single PM. In addition, the maximum magnetic levitation force value firstly increased and then decreased due to current coupling effect weakness by increasing distance of seeds. The calculated analytical levitation force results are not compatible with the experimental results without current coupling effect, but a well agreement is observed when the current coupling effect is taken into account in calculations. Also the MAFI method was tested with different dimensions of superconductors and the obtained results indicated the success of the proposed method. The maximum levitation force values obtained with MAFI method increased with increasing dimensions of HTS and PMs. Thus, one can say that the MAFI method is useful for the levitation force calculations between multi-seeded superconductors and PMGs with different dimensions and for different CHs. As a result, the analytical levitation force values obtained with the MAFI method are agree with the experimental levitation force sufficiently and this method can give fast calculation results without any divergence problem. This method can be thought as an alternative to the numerical calculation methods, having serious divergence problems for much amount and bigger size superconducting samples, therefore it will be useful to clarify bulk superconducting properties as supporter to the experimental studies. (C) 2019 Elsevier B.V. All rights reserved.Öğe Bulk MgB2 superconductor for levitation applications fabricated with boron processed by different routes(Elsevier Science Sa, 2023) Savaskan, B.; Ozturk, U. K.; Guner, S. B.; Abdioglu, M.; Bahadir, M. V.; Acar, S.; Somer, M.Bulk MgB2 discs were prepared by an in situ route from mixtures of magnesium and boron powders. The boron powders were produced by two methods. The first one consisted of a self-propagating high tem-perature magnesiothermic synthesis (SHS) process followed by acid and fluorine cleaning and a heat treatment in inert atmosphere. This approach produced boron with purities between 86 % and 97 %, where the main impurity was Mg. Depending on the final heat treatment, these boron powders were amorphous or crystalline. In the second route, high purity nano powders (99 %) of boron were obtained by a diborane pyrolysis process. Bulks of MgB2 were characterized by structural, microstructural, and magnetic mea-surements. Critical current density, pinning force aspects and levitation force (including guiding force) details were assessed. Amorphous lower purity boron (86-97 %) obtained by the first processing route was found to promote the largest levitation forces of the MgB2 bulks and, among these samples, the best le-vitation results were recorded when using boron with a purity of 95-97 %. Use of a lower purity boron that decreases the cost of MgB2 promotes large scale production at industrial level of bulk MgB2 super-conducting magnets for levitation applications and enhances the applicability potential of MgB2 super-conductor. The relationship between levitation force and specific features of the samples such as pinning force details are discussed.& COPY; 2023 Elsevier B.V. All rights reserved.Öğe Investigation of magnetic force properties between different PMGs and multi-seeded YBCO superconductors with different seed distances(Elsevier, 2019) Abdioglu, M.; Ozturk, K.; Guner, S. B.; Celik, S.; Kucukomeroglu, T.The magnetic levitation force in vertical direction and guidance force in lateral direction should be increased for enhancing the loading capacity and stability of Maglev systems, respectively. In this study, we have produced multi-seeded YBCO (YBa2Cu3O7) superconductors with two seeds and investigated the effect of seed distance on the vertical levitation force and lateral guidance force properties by using different permanent magnetic guideway (PMG) arrangements. Although there are studies in literature related to different distance, orientation and angle of seeds; there is no detailed study investigating the effect of seed distance on the vertical and lateral magnetic force properties of Maglev systems depending on different types of PMGs. In this study, after the sample fabrication, the optimum PMG arrangement were determined by using numerical simulation to obtain magnetic flux density distribution. It is determined that both maximum levitation and guidance force values firstly increased with increasing the seed distance from 0 to 4 mm and then related forces decreased with increasing the seed distance from 4 to 16 mm but still keep the higher force values than the sample with the seed distances of 0 mm. This situation is clarified as the increasing of the seed distance to an optimum value enhances both the levitation and guidance forces simultaneously and this is very important for levitation force applications because it causes to easy control of the Maglev system in vertical and lateral directions.Öğe Magnetic force and stiffness performances of Maglev system based on multi-surface arrangements with three-seeded bulk YBaCuO superconductors(Elsevier, 2020) Ozturk, K.; Abdioglu, M.; Karaahmet, Z.We have designed a multi-surface HTS (high temperature superconductor with three seeded bulk YBaCuO) Maglev system by increasing the YBaCuO number while decreasing the PM number in HTS-PMG system to enhance the loading capacity and stability of the superconducting Maglev system while reducing the fabrication cost. By this study, a detailed investigation on the magnetic levitation force, guidance force, magnetic stiffness and cost analysis of the multi-surface HTS Maglev system has been carried out for the first time. In this study, it is determined that the multi-surface YBaCuO-PMG arrangements are superior to the single-surface arrangements with respect to the loading capacity and especially the movement stability of Maglev systems together. Additionally, it is seen that the using of the multi-surface YBaCuO-PMG arrangement reduces the fabrication cost of the Maglev systems as 42.0% for 1000 km magnetic rail while increasing of the levitation force efficiency as 43.4% and this emphasizes the advantage of multi-surface arrangements to the classical single-surface ones. The obtained results can contribute to the researchers working on Maglev and have a capability to increase the usage potential of Maglev systems in commercial applications because of both the loading capacity and stability of Maglev systems can be enhanced together with reducing the fabrication cost without any loss in levitation performance.
