High temperature superconducting (HTS)-coated conductors show various advantages in practical applications because of its zero resistance and large current capacity. Owing to the superior properties of HTS material in high magnetic fields, the HTS linear synchronous motor (LSM) is able to output high performance at relatively large air gap. Many experiments and prototypes have been implemented, which requires great consumption of HTS-coated conductors. In this paper, an analytical model of coreless HTS LSM was established and the magnetic flux density dependence of the critical current density of HTS-coated conductors was taken into account. An HTS-generalized racetrack coil was introduced to the analytical model for easy parameterization. A small scale prototype of the LSM which has a coreless stator and a HTS secondary was manufactured to validate the analytical model. It is indicated that the calculations have a good agreement with the experiments. As an application of the analytical model, an optimization task of the HTS LSM was carried out to improve its performances.
A numerical model has been developed to investigate the dynamic characteristics of the Superconducting electrodynamic suspension (EDS) system. Modeling of the guideway with the surface irregularity and the Maglev vehicle are described. Numerical simulations were performed in Simulink to solve the coupled problem. A 3-D model of the electromagnetic system of the superconducting EDS train is established, and the computed real electromagnetic forces are coupled with the maglev train. The EDS train was simulated by using the SIMPACK multi-body dynamic program. The simulation was carried out by using two body models of rigid and flexible bodies. In order to use the modal information to construct the flexible car body, the finite element method and the ABAQUS software were used to construct it together with equivalent elements. The final framework is constructed in MATLAB/Simulink to simulate dynamics and electromagnetic forces together with the constructed simulation framework. In order to consider the interference caused by irregularities, randomness and power spectral density (PSD) are used to analyze vibration interactions. We compared random signal inputs with PSD, greatly enhancing accuracy, and analyzed the vibrational interaction between car body and ride quality.
Abstract No-electrical-insulation (NEI) magnets are gradually exhibiting significant appeal due to their robust thermal stability and elevated mechanical strength. However, when exposed to AC conditions, these magnets will suffer more significant AC losses in dynamic electromagnetic devices, such as motors and maglev systems. Presently, the numerical methods for predicting the electromagnetic and loss behavior of large-scale NEI magnets entail high computation costs due to the substantial degrees of freedom or complicated modeling strategies. Thus, we propose a fully finite element method, referred to as the field-circuit coupling method, to efficiently assess the overall behavior of NEI magnets while preserving adequate accuracy. This method couples the T-A formula and the single-turn equivalent circuit through a global voltage, to avoid the costly and complicated inductance calculations, and to simultaneously consider the induced current. By further integrating the homogenization method, the calculation speed can be increased up to ten times. Additionally, we study the critical current, and the electromagnetic and loss behavior of the NEI magnets based on the proposed model. We identify some measurement methods that offer more precise estimations of the critical current and the turn-to-turn contact resistance of NEI magnets. Meanwhile, the results indicate the severe impact of high AC fields on the losses, and emphasize the importance of a reliable shielding structure for operational safety. Finally, the influence of turn-to-turn contact resistivity on the loss behavior is also investigated, which can provide valuable insights for the design of NEI magnets in dynamic electromagnetic devices.
A series of high temperature superconducting (HTS) flux pumps have been developed to achieve the persistent current mode (PCM) operation for HTS magnets. However, most of the HTS flux pumps work with a small operating air gap, or with an iron core, the extra heat load brought by the conventional components deployed in the cryogenic environment is inevitable. To address this problem, in this study, in conjunction with the wireless power transfer (WPT) approach and transformer-rectifier type HTS flux pump, we have proposed a contactless self-regulating HTS flux pump. A circuit model and a 2D H-formulation finite-element model have been built for better understanding this system. Furthermore, a basic prototype was proposed to experimentally validate this concept. The measured results indicate that this method has the potential to charge the HTS magnet with all the conventional constituents outside the cryostat, and the operating frequency could be very low to evade inducing large eddy current as well as losses on the cryostat wall.
The linear superconducting magnetic bearing (SMB) discussed in this article consists of a high-temperature superconducting bulk of YBaCuO and a permanent magnet rail to provide the excitation magnetic field. The dynamics of SMB is vital to engineering applications; however, previous experimental and theoretical explorations on dynamic behaviors of linear SMB only provide qualitative analysis, because of limited experimental conditions and approximated analytical models. Furthermore, the pulsed and harmonic excitations have not been taken into account in the published numerical works on the dynamics of linear SMB. In this article, a two-dimensional (2-D) model of the linear SMB was introduced and coupled with the 2-D motion second-order equations with respect to time, to simulate the dynamic behaviors in the vertical and lateral directions. Under the external excitations, the displacements in time and frequency domains, phase trajectories, and motion trajectories are presented in the vertical and lateral directions to discuss the effects of pulsed and harmonic forces on the dynamic characteristics of linear SMB. It turns out that the 2-D model with ease of implementation can provide a utile tool for analyzing the dynamics of linear SMB, and the numerical results, inaccessible through simplified analytical models, provide the quantitative dynamic characteristics and principles for applications of linear SMB.
Self-regulating high temperature superconducting (HTS) flux pump is one of the most effective methods to compensate the current degradation of a closed HTS magnet for its stable operation. In this study, to understand the working principle as well as the influential factors regarding to its operation performance, a basic circuit model has been established. Based on that, we found the saturation load current is strongly related to the added secondary resistance, which could offset the DC bias current induced in the charging loop. Then, we built a prototype experimentally, in which, part of the load coil was used as a HTS bridge and bifilar bridge design has been adopted to minimize the possible flux fluctuation in the load loop. In the experiment, the dependence of the charging performance on the bridge length as well as the added secondary resistance at different frequencies has been clarified. The results show that, the load current is remarkably impacted by the aforementioned parameters. Specifically speaking, with an increasing added secondary resistance, the operating frequency needs to be higher to ensure the secondary current can follow the primary current, which is crucial for maintaining a larger load current.
There is a growing interest in using HTS magnet to improve the performance of the electric devices such as motor/generator, NMR/MRI and EDS train. For the HTS magnet, the critical current is of importance since it determines the current-carrying capacity, i.e., the ability to generate magnetic field. So, it is imperative to estimate the critical current of HTS magnet. However, the numerical modelling of the magnet is not straightforward due to the field-dependent critical current density, a large number of turns and the ultra-high aspect ratio, e.g., of REBCO (REBa2Cu3Ox, where RE = Rare Earth) coated conductor. To make the estimation of the critical current accessible, this paper aims at developing an improved self-consistent model. First, the analytical expressions of the self-field of a generalized racetrack magnet are derived from the Biot-Savart's law. Secondly, the self-consistent model is introduced and validated by comparing the estimated critical current of a racetrack REBCO magnet with the measured one. Thirdly, based on the homogenized technique, the efficiency of self-consistent model is significantly improved with accuracy preserved. Lastly, we estimate the critical current of a generalized racetrack REBCO magnet for EDS train use with the improved self-consistent model.
This year marks the tenth anniversary of the first man-loading high temperature superconducting (HTS) maglev test vehicle “Century” in the world. This report summarizes development advances of major topics related to the HTS maglev vehicle at the Applied Superconductivity Laboratory (ASCLab) at Southwest Jiaotong University (SWJTU). The HTS Maglev measurement systems are described, including the HTS maglev dynamic test system capable of speeds up to 300 km/h. Through these measurement systems, many problems related to the HTS maglev have been studied such as system optimization, stability control, influence from ramp angles, influence from AC field, and investigation of the system's properties at temperatures lower than 77 K. Apart from experimental studies, the 3-D model of the HTS maglev was constructed via two different methods to simulate the Maglev's behavior.
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