Showing papers by "Guangtong Ma published in 2018"

Superconducting magnetic bearings simulation using an H-formulation finite element model

Abstract: The modeling of superconducting magnetic bearings (SMBs) is of great significance for predicting and optimizing their levitation performance before construction. Although much effort has been made in this area, there 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 SMBs is summarized. Then its effectiveness for simulating SMBs in 2D, 2D axisymmetric and 3D 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 2D model for a stack-type SMB modeling the tapes' real thickness, implementation of a 2D axisymmetric SMB model, implementation of a 3D SMB model, and 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 having proven, it now has 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.

Experiment and simulation of superconducting magnetic levitation with REBCO coated conductor stacks

Abstract: 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.

Potentials of an Integrated Levitation, Guidance, and Propulsion System by a Superconducting Transverse Flux Linear Motor

Abstract: We devised a transverse flux linear motor (TFLM) that uses the superconductor-aluminum hybrid as the secondary to explore the potentials of integrating the propulsion with the levitation and guidance, which are generally separated in existing magnetic levitation (MAGLEV) systems. In this proposal, the hybrid secondary is made of aluminum plate and close-ended coated superconductor coils, with the latter placed over the former to achieve the stable levitation and self-propulsion. To validate the proposal, analytical formulations for describing the electromagnetic responses of such hybrid secondary were established, and the resultant magnetic forces were calculated and compared with a 3-D finite-element model, in which the actual geometry of the proposed TFLM and the nonlinear behavior of superconductor were represented. Afterward, the proposed TFLM was demonstrated and its 3-D forces were measured by a test rig developed for this paper. It was proven that the derived analytical formulations and built finite-element model are both able to reproduce the main feature of the measured results. Characteristic studies clearly display that, although the levitation capability is limited in the proof-of-concept demonstrator, the self-stability and self-propulsion could be integrated by the proposed TFLM, which provides a novel alternative to the scientific community of MAGLEV transit.

Superconducting Magnetic Bearings Simulation using an H-formulation Finite Element Model

Abstract: 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.

Electromagnetic Investigation of a High-Temperature Superconducting Linear Synchronous Motor for High-Speed Railway

Abstract: High-temperature superconducting (HTS) linear synchronous motor (LSM) with low power loss, high thrust density, and large mechanical gap, makes it a promising candidate for driving the future high-speed rail transit and even ultrahigh-speed magnetic levitation (Maglev) vehicle. However, superconducting magnet can produce strong enough magnetic field, which will inevitably lead to the saturation of stator iron and generate significantly attractive force between the stator and the on-board HTS magnet. Therefore, a coreless-typed HTS LSM has attracted much attention in recent years. This paper, served as a fundamental study on a linearly driven system for rail transit or Maglev, is aimed to investigate the electromagnetic properties of an HTS LSM, by means of numerical modeling, experiment, and analytic model. First, a two-dimensional (2-D) finite element model was established. Then, a force-measuring system, being able to measure the 3-D forces of motor, was fabricated. Finally, a set of analytic expressions to describe the magnetic field distribution of coreless-typed LSM, were derived, which was verified by comparing with a finite element model and ultimately tailored to study the electromagnetic properties of the coreless-typed HTS LSM.

Experimental Studies on the Dynamic Responses of Coated Superconductor Stack Levitated Above a Permanent Magnet Guideway

Abstract: In this work, we experimentally investigated the dynamic responses of stacked coated conductor tapes that were levitated over an Nd-Fe-B magnet guideway. The experiments were carried out on a recently designed test rig that can simultaneously measure the acceleration and levitation force during a vibration process. We applied three typical excitations, viz., unloading, free fall, and pulsed excitation. The attenuation coefficient and damping ratio of such stack-based maglev system were analyzed by means of free vibration attenuation method. Last, the dynamic response of mechanical components of the stack-based maglev on pulsed excitation was visualized clearly. Results obtained by this study tell us that the damping ratio is relative to the intensity of external disturbance, which means a weak excitation will cause a small damping ratio and a longer convergence time; however, a larger damping ratio and a faster convergence of vibration will be presented when a stronger stimulation is imposed on. This phenomenon could be contributed by the metal components of the stack, and is promising in practical application, particularly, in construction of HTS maglev where a large damping ratio is required.

A linear induction motor with a coated conductor superconducting secondary

Abstract: A linear induction motor system composed of a high– T c superconducting secondary with close-ended coils made of REBCO coated conductor wire was designed and tested experimentally. The measured thrust, normal force and power loss are presented and explained by combining the flux dynamics inside superconductors with existing linear drive theory. It is found that an inherent capacitive component associated to the flux motion of vortices in the Type-II superconductor reduces the impedance of the coils; from such, the associated Lorentz forces are drastically increased. The resulting breakout thrust of the designed linear motor system was found to be extremely high (up to 4.7 kN/m 2 ) while the associated normal forces only a fraction of the thrust. Compared to its conventional counterparts, high- T c superconducting secondaries appear to be more feasible for use in maglev propulsion and electromagnetic launchers.

Novel Homopolar Linear Synchronous Motor with E-Shape Primary Core

Abstract: One novel homopolar linear synchronous motor (H-LSM) with E-shape primary core is proposed for maglev rail transport system. Firstly, the specific topology and operation theory of the proposed H-LSM are introduced in detail. Then, a magnetic circuit model is built to analyze the machine performance qualitatively, and the analytic equations of electromagnetic performance, such as the no load back electromotive force (back EMF), the cogging force and the levitation force, are derived based on the equal magnetic circuit method. Finally, the three-dimension finite element algorithm (3-D FEA) model is built to compare the propulsion and levitation performances of the proposed H-LSM with those of the conventional one under the same design constraints. It is indicated the higher levitation force and lower force ripple can be obtained by the proposed novel structure.