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Öğe Clarification of magnetic levitation force and stability property of multi-seeded YBCO in point of supercurrent coupling effect(Elsevier Ltd, 2016) Ozturk K.; Kabaer M.; Abdioglu M.; Patel A.; Cansiz A.In our study as different from the literature, which are mostly related to superconductor fabrication, application and optimization, especially physical origins of bulk supercurrent generation, magnetic levitation and stability properties of the multi-seeded YBCO superconductor are investigated in point of supercurrent coupling effect. Besides the experimental measurements, a simplified simulation of the supercurrent coupling in the multi-seeded bulk YBCO is carried out based on the experimental Jc(B) data taken from literature and using the critical state method and H-formulation together in COMSOL Multiphysics package, to further elucidate the mechanism of supercurrent generation and guidance force. The bigger guidance force and lateral magnetic stiffness values of PMG-B arrangement with three Bzpeaks than the other arrangements with one Bzpeak in small cooling height of 5 mm are attributed to the more robust individual intragrain supercurrents, rather than intergrain supercurrent, due to the position coincidence in the z-direction between grains and permanent magnet poles. Additionally, it can be said that PMG-C arrangement with one Bzpeak getting to the maximum guidance force value when the cooling height increase from 5 mm to 15 mm, points out for large cooling height the intergrain supercurrents dominate, whereas for the small cooling height the intragrain supercurrents have most effect on the guidance force. Also, performed the supercurrent simulations, using different current flow constraint ratio f (or supercurrent coupling parameter), clearly reproduced the qualitative change in the trapped field profile when the allowed intergrain current compared to no intergrain current (f = 0). It is thought that the presented results, related to the supercurrent generation, coupling mechanism and their effect on levitation and lateral force properties, have utilization potential for researches not only they study on new multiseed superconductor fabrication method, but also they study on superconductor applications. © 2016 Elsevier B.V.Öğe Comparative study of the magnetic stiffness, levitation and guidance force properties of single and multi seeded YBCOs for different HTS-PMG arrangements(Elsevier Ltd, 2015) Ozturk K.; Sahin E.; Abdioglu M.; Kabaer M.; Celik S.; Yanmaz E.; Kucukomeroglu T.Abstract It is crucial to improve the magnetic levitation, guidance and stiffness performances of the HTS Maglev systems for real-scale applications. In this study, the magnetic levitation force, guidance force and magnetic stiffness values were determined for single and multi-seeded YBCOs on different PMGs in ZFC regime and different cooling heights (CHs) after the magnetic flux distributions simulation of the using PMGs. Implemented study showed that the additional downward PMs make an enhancing contribution on the magnetic levitation force, guidance force and magnetic stiffness of both single and multi-seeded YBCOs. It was also determined that both the force and stiffness ratios of multi-seeded YBCO to single-seeded YBCO increase with increasing CH, indicating that the multi-seeded YBCO has much more interaction domain than single-seeded at higher gaps. It is considered that the results obtained in this study are very useful in technological applications of Maglev and bearing systems, because there is no detailed study on the magnetic stiffness, levitation and guidance force comparison to clarify electromagnetic behavior of single and multi-seeded YBCOs for different HTS-PMG arrangements. © 2015 Elsevier B.V.Öğe Comparison of Levitation Forces of Bulk MgB2 Superconductors Produced by Nano Boron and Carbon-Doped Nano Boron(Springer New York LLC, 2014) Duz I.; Guner S.B.; Erdem O.; Demir I.; Kapucu V.; Çelik Ş.; Ozturk K.; Hossain S.; Gencer A.; Yanmaz E.MgB2 bulk superconductors were prepared by hot press plus furnace heating method. Two types of boron powders were used, one is amorphous nano boron and the other is C-doped boron. Characteristics of superconductors were determined by XRD and resistance measurements. Systematic levitation force measurements were performed by using a modular system at low temperatures. These bulk superconductors showed around 9 N repulsive and 4 N attractive forces in the z-axis at 20 K at closest point to the cryostat lid which contains the MgB2 superconductor. These values slightly decreased by increasing temperature to 24 and 28 K for both samples. Comparing two samples, nano boron MgB2 showed slightly higher levitation force than C-doped MgB2 although C-doped MgB2 has higher attractive force value at the closest point. This situation points out that C-doped MgB2 is much proper for attractive force applications (as guidance force) while the nanoboron MgB2 sample is much appropriate for repulsive force (as levitation). © 2014, Springer Science+Business Media New York.Öğe The effect of magnetic field distribution and pole array on the vertical levitation force properties of HTS Maglev systems(Institute of Electrical and Electronics Engineers Inc., 2015) Ozturk K.; Abdioglu M.; Sahin E.; Celik S.; Gedikli H.; Savaskan B.In this paper, the levitation force measurements have been carried out by the magnetic force measurement system under both field-cooling and zero-field-cooling regimes, whereas the magnetic field distribution over the permanent-magnet guideway (PMG) was calculated by numerical analysis based on the finite-element method. It was shown in this study that the vertical levitation capability and stability of Maglev systems can be improved depending on the cooling regime, pole number, and suitable arrangement of the PMG. In this paper, it was shown that when the pole number increases, the levitation force density increases. It also appeared that the reasonable position of the supplementary permanent magnet and appropriate cooling heights are key parameters for both levitation performance and stabilization of the high-temperature superconductor (HTS) Maglev. It is believed that the numerical and experimental data in this paper are useful for relative design and practical application of HTS Maglev systems. © 2015 IEEE.Öğe Effect of magnetic flux distribution and magnetic powder addition on the magnetic levitation force of Sm123 superconductors(2012) Abdioglu M.; Ozturk K.; Kutuk S.; Bolat S.; Yanmaz E.Sm123 and Sm211 were prepared by melt-powder-melt-growth and solid-state-reaction techniques, respectively, to have the nominal composition of (Sm123) 0.75 (Sm211) 0.25. After the preparation of this composition, the Fe-B magnetic powder (MP) was added to the composition for 0.000, 0.010, 0.015, 0.025, 0.050 wt.% to investigate the effect of MP addition on the levitation force density (LFD). Additionally, different permanent magnets (PM) were used as magnetic-field source to investigate the effect of magnetic-field gradient on the LFD of MP added superconductors. Our findings indicate that the MP addition acts as a flux pinning centre in the sample and enhances the LFD up to 0.025 wt.% adding amount, and the optimum flux gradient which produces a screening current in the sample occurs when the B/d (magnetic-field intensity/ diameter of PM) ratio is equal to 0.060. These results imply that the experimental data can be useful for fabricating process of superconducting samples with larger MLF values, and designing of superconducting magnets, flywheel energy storage and maglev systems. © 2012 Springer Science+Business Media, LLC.Öğe Effect of onboard PM position on the magnetic force and stiffness performance of multi-seeded YBCO(Elsevier Ltd, 2015) Ozturk K.; Kabaer M.; Abdioglu M.Abstract In implemented studies before, although some advancements have been achieved in improving on the levitation or guidance force efficiency of YBCOs separately, both of these forces could not been enhanced simultaneously. In our study, we investigated levitation, guidance force and magnetic stiffness properties of multi-seeded YBCO bulk depending on different position of onboard PM in different CHs above a Halbach PMG to obtain larger vertical load capability, stability and relating stiffness values at the same time. The levitation, guidance force and relating stiffness measurements were carried out between multi-seeded YBCO and Halbach PMG depending on the onboard PM positions and cooling heights after the magnetic flux distributions modelling of Halbach PMG with onboard PMs. In this paper, it has clearly seen that the levitation force and the vertical magnetic stiffness values increase in optimal onboard PM position, with negligible lose in guidance force and lateral magnetic stiffness values. It is inferred from this study that reasonable position of the onboard PM according to PMG, the cooling conditions and compatibility of YBCO-PMG arrangement in point of magnetic flux distribution are key parameters for efficiency of the load, guidance force and relating magnetic stiffness of Maglev systems. The results obtained in this study have a potential on improvement of HTS Maglev system electromagnetic force capability. © 2015 Elsevier B.V.Öğe Effects of initial cooling conditions and measurement heights on the levitation performance of bulk MgB2 superconductor at different measurement temperatures(Springer New York LLC, 2014) Erdem O.; Ozturk K.; Guner S.B.; Celik S.; Yanmaz E.The levitation properties of MgB2 prepared by hot press at 200 ° C and then pellet/closed tube method has been investigated. The vertical and lateral levitation forces (Fz and Fx) on a cylindrical NdFeB permanent magnet (PM) below a disk-shaped bulk MgB2 were measured during the vertical and lateral traverses of the PM in different cooling heights (CHs) and measurement heights (MHs) at temperatures of 20, 25 and 30 K to investigate the effect of the initial CH and MH on the levitation performance of MgB2. For temperatures below 30 K, it was observed that Fz increases with increasing CH. However, a minute variation in Fz and a big hysteresis loop are observed at 30 K. From the lateral traverses, it was obtained that the Fz with attractive character increases with decreasing MH and the hysteresis effect increases for small MHs due to the increment of the magnetic field intensity which the sample feels with decreasing MH. In addition, it was seen that the character of Fx varies depending on both MH and measurement temperature. The higher hysteresis obtained in Fx than in Fz during lateral traverses implies that the motion of the flux lines in MgB2 is especially in lateral rather than vertical direction. Finally in this study, it was shown that the levitation performance of MgB2 depends not only on the measurement temperature but also on the CH and MH conditions. These results can be useful for optimizing the levitation performance of MgB2 superconductors for potential applications. © 2014 Springer Science+Business Media New York.Öğe Lateral Position Effect of Auxiliary Permanent Magnets on the Magnetic Force Properties of Cylindrical YBCO(Springer New York LLC, 2017) Abdioglu M.; Kabaer M.; Ozturk K.; Erdem O.; Celik S.The magnetic levitation force (MLF) and the guidance force (GF) should be improved for loading capacity and stability of Maglev systems, respectively. Although there are some ways to increase these properties, using of auxiliary onboard permanent magnets (PMs) can be considered as the most efficient one. The auxiliary PMs increase the MLF significantly but, at the same time, decrease the GF. We have searched a solution to overcome this problem in this study. Firstly, we have determined the optimum vertical positions of the auxiliary PMs and then we have investigated the vertical levitation force and lateral guidance force of hybrid Maglev system depending on lateral position of auxiliary PMs in different cooling heights (CHs). A cylindrical YBCO superconductor, fabricated by a top seeding method with the diameter of 45 mm and the height of 15 mm, was used as a high-temperature superconductor (HTS). The maximum increment rate in MLF and the minimum decrement rate in GF were observed as 277 and 54 %, respectively. The increment in MLF was obtained five times more than the decrement in GF, and this reality points out that the results of this study can be useful for improving the loading capacity and thus enhancing the practical applicability of Maglev systems. © 2016, Springer Science+Business Media New York.Öğe Levitation and guidance force efficiencies of bulk YBCO for different permanent magnetic guideways(Elsevier Ltd, 2015) Abdioglu M.; Ozturk K.; Gedikli H.; Ekici M.; Cansiz A.The development of superconductor Maglev systems depends on various disciplinary studies due to the inherent composition of available technologies. Because the fabrication cost is very effective on the Maglev, the requirement of the efficiency improvement focuses the researchers on the design considerations. In this study, the guidance force, the magnetic levitation force (MLF) and magnetic stiffness of different permanent magnetic guideway (PMG) arrangements were investigated in different cooling heights (CH) to enhance the efficiency of Maglev system. The single domain cylindrical bulk YBCO superconductors fabricated by top seeding method with the diameter of 45 mm and the height of 15 mm were used as HTS. Magnetic field distributions of the PMGs were calculated by finite element method to determine optimum HTS-PMG arrangements. We have used auxiliary onboard permanent magnets with YBCOs to improve the MLF of three pole Halbach PMG arrangements. It is seen that the efficiency of Maglev systems can be improved by using suitable HTS-PMG arrangements. In this study cost efficiency of the integrated levitation and guidance force ((Fz)max(Fx)max/(SPMG ? Cost)) was also determined. It is inferred from this study that the cooling height and PMG-HTS arrangement are key parameters for guidance force, levitation force, magnetic stiffness and efficiency of Maglev systems. It is believed that this study will supply useful references for practical application of HTS Maglev systems. © 2015 Elsevier B.V. All rights reserved.Öğe Levitation and guidance force relaxations of the single?seeded and multi?seeded YBCO superconductors(Elsevier B.V., 2018) Abdioglu M.; Ozturk K.; Kabaer M.; Ekici M.The stable levitation and guidance forces at higher force levels are important parameters for technological applicability of high temperature superconductors (HTSs) in Maglev and Flywheel energy storage systems. In this study, we have investigated the levitation and guidance force relaxation of both the single-seeded and multi-seeded YBCOs for different (HTS)?permanent magnetic guideway (PMG) arrangements in different cooling heights (CH). The measured saturated force values of Halbach PMG arrangements are bigger than the maximum force values of other PMGs. It is determined that the normalized magnetic levitation force (MLF) and normalized guidance force (GF) relaxation rate values decrease while the relaxation rates increase with increasing magnetic pole number and the effective external magnetic field area for both the single?seeded and multi?seeded YBCO. Also it can be said that the force stability at the higher force value of Halbach PMG arrangement indicates that the relaxation quality of Halbach PMG is better than that of the others. Additionally, it can be said that both the MLF and GF relaxation qualities of the multi?seeded YBCOs are better than that of the single?seeded ones. This magnetic force and relaxation results of the single?seeded and multi?seeded YBCOs are useful to optimize the loading capacity and lateral reliability of HTS Maglev and similar magnetic bearing systems. © 2017 Elsevier B.V.
