The modeling of superconducting magnetic bearing (SMB) is of great significance for predicting and optimizing its levitation performance before construction. Although lots of efforts have been made in this area, it still remains some space for improvements. Thus the goal of this work is to report a flexible, fast and trustworthy H-formulation finite element model. First the methodology for modeling and calibrating both bulk-type and stack-type SMB is summarized. Then its effectiveness for simulating SMBs in 2-D, 2-D axisymmetric and 3-D is evaluated by comparison with measurements. In particular, original solutions to overcome several obstacles are given: clarification of the calibration procedure for stack-type and bulk-type SMBs, details on the experimental protocol to obtain reproducible measurements, validation of the 2-D model for a stack-type SMB modeling the tapes real thickness, implementation of a 2-D axisymmetric SMB model, implementation of a 3-D SMB model, extensive validation of the models by comparison with experimental results for field cooling and zero field cooling, for both vertical and lateral movements. The accuracy of the model being proved, it has now a strong potential for speeding up the development of numerous applications including maglev vehicles, magnetic launchers, flywheel energy storage systems, motor bearings and cosmic microwave background polarimeters.
Three superconducting stacks made of 120 REBCO coated conductor tapes were each fabricated and assembled to obtain several REBCO modules. Their levitation responses over two different permanent magnet (PM) guideways were investigated by experiment and finite element simulation. For the experiment, a test rig was developed that can measure the force in the three directions for any given relative movement between the REBCO stacks and the PM guideway. For the finite element simulation, a 2D H-formulation was adopted. To treat the high aspect ratio of REBCO tapes, an anisotropic homogenization technique was used. The agreement between the measurements and the simulations is good, thus validating the modeling methodology. It was observed from the experiment and simulation results that the perpendicular field contributes to the levitation force whereas the parallel field is responsible for the guidance force, as a result of the existence of anisotropy on the local magnetic stimulation. Based on that, promising REBCO modules including both longitudinal and transverse arrangements of REBCO stacks were proposed and tested, in terms of providing a significant levitation force with the lateral stability preserved. Moreover, a pre-load process able to suppress the relaxation of the levitation force was put forward. To conclude, this study outlines explicit principles to obtain an appropriate layout of coated conductor stacks that could be effective for practical magnetic levitation operation.
In order to improve the cost performance of the present
high-Tc
superconducting (HTS) Maglev vehicle system for practical application, the multi-pole
permanent magnet guideway (PMG) concept was introduced. A well-known double-pole
Halbach PMG was chosen as a representative of multi-pole PMGs to compare with
traditional monopole PMGs from the point of view of levitation efficiency and cost.
Experimental results show that YBCO bulks above the double-pole Halbach PMG can
exhibit better load capability and guidance performance as well as dynamics stability at
the applied working height between the bulk HTSC and the PMG due to a more reasonable
magnetic field distribution at the working range of bulk HTSC. Furthermore, the
double-pole PMG configuration can play a more important role in improving guidance
performance due to the potential-well field configuration. By comparing with former
‘century’ PMGs, the double-pole Halbach PMG shows another remarkable advantage in
reducing the cost of levitation. As another necessary issue, magnetic field homogeneity
and the corresponding magnetic drag force of a double-pole Halbach PMG has
been considered by experiment in spite of the above highlights. Synthetically,
the multi-pole Halbach PMG design is concluded to be one important choice for
future HTS Maglev vehicle applications because of its high efficiency and low cost.
In this paper, the 3-D model proposed in Part I of this study is verified in detail on the basis of a levitation/suspension system composed of a rectangular single-domain Y-Ba-Cu-O and a cylindrical Nd-Fe-B magnet or a permanent magnet guideway (PMG) assembled by the Nd-Fe-B magnets. The magnetic forces along the vertical direction perpendicular or the transverse direction parallel to the surface of the PMG (or magnet) were calculated and compared well with the measured data under vertical and transverse displacements. The computed results of the induced current distribution within the Y-Ba-Cu-O domain, as well as the magnetic field profiles in the Y-Ba-Cu-O and its vicinal region, were also presented and discussed.
Experimental data reveal that the classical description of transport ac losses in high-temperature superconducting (HTS)-coated conductors (CCs), based on investigations at low frequencies, is incomplete in some aspects when transport currents in the kilohertz range are considered. More specifically, above a certain "transition frequency," the ac losses per cycle no longer increase with the frequency as the theory predicts. Using a finite element model to allow for loss separation, we find that this phenomenon is caused by a combination of several factors that appear only above the transition frequency: the hysteresis and ferromagnetic losses per cycle are no longer independent of the frequency, while the eddy current losses per cycle no longer increase proportionally to the frequency. Based on a circuit model, we propose that the physical reason for this is that when the frequency increases, part of the supercurrent starts migrating into the metallic path. We argue that the current in the metallic path is not an eddy current but a transport current inductively coupled to the superconducting current. Finally, we discuss the relationship between the magnetic material magnetization, the critical current, and the transport current frequency. This study provides explicit insights into the frequency-dependent transport ac losses of HTS CCs in a broad frequency band, which is valuable for the design and optimization of HTS CC-based power devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.