Operating Thermal Characteristics of REBCO Magnet for Maglev Train Using Detachable Cooling System

Mun, Jeongmin; Lee, Changyoung; Kim, Kihwan; Sim, Kideok; Kim, Seokho

doi:10.1109/tasc.2019.2906410

Cited by 20 publications

(7 citation statements)

References 19 publications

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“…To characterize the MFD of the SCM required for the calculation of b, general numerical methods, such as FEM and boundary element method (BEM), experimentally measured data, or a distributed multilevel current (DMC) model that utilizes equivalent magnetizing point currents to describe the MFD of electromagnetic components [27], can be used. For example, Figure 6 shows the MFD pattern of the SCM with a magnetomotive force (MMF) of 300 kAt that consists of a pair of N and S poles computed by the DMC model for the fast computation of the MFD, and b can be easily obtained by applying the MFD to Equations ( 22) and (23). If the characteristics of b for the SCM, which consists of N and S pole pairs, are further analyzed, for the z-axis, B x is symmetric and B y and B z are anti-symmetric.…”

Section: Induced Emf Model For the Levitation Coilmentioning

confidence: 99%

“…Recently, the Korea Railroad Research Institute has been researching a capsule train with SCMs and a null-flux EDS device for the Hyperloop. HTS (high-temperature superconducting) magnets with a detachable cryocooling system [22][23][24][25] have been widely investigated to develop lightweight capsule trains. However, the null-flux EDS device is also being developed, as it is suitable for HTS magnets, and it can be relatively small in size, but its performance is lower than that of the SCMs with onboard cryocooler system.…”

Section: Introductionmentioning

confidence: 99%

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Design Model of Null-Flux Coil Electrodynamic Suspension for the Hyperloop

Lim

Lee

et al. 2020

Energies

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The Hyperloop has been developed using various technologies to reach a maximum speed of 1200 km/h. Such technologies include magnetic levitation technologies that are suitable for subsonic driving. In the Hyperloop, the null-flux electrodynamic suspension (EDS) system and superconducting magnets (SCMs) can perform stable levitation without control during high-speed driving. Although an EDS device can be accurately analyzed using numerical analysis methods, such as the 3D finite element method (FEM) or dynamic circuitry theory, its 3D configurations make it difficult to use in various design analyses. This paper presents a new design model that fast analyzes and compares many designs of null-flux EDS devices for the Hyperloop system. For a fast and effective evaluation of various levitation coil shapes and arrangements, the computational process of the induced electromotive force and the coupling effect were simplified using a 2D rectangular coil loop, and the induced current and force equations were written as closed-form solutions using the Fourier analysis. Also, levitation coils were designed, and their characteristics were analyzed and compared with each other. To validate the proposed model, the analyzed force responses for various driving conditions and the changed performance trend by design variables were compared with analyzed FEM results.

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Section: Induced Emf Model For the Levitation Coilmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Design Model of Null-Flux Coil Electrodynamic Suspension for the Hyperloop

Lim

Lee

et al. 2020

Energies

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“…Recently, our group adopted NI PCM REBCO coils to develop the first HTS electrodynamic suspension train system in China [14,40,41]. The Korea Railroad Research Institute is trying metalinsulation (MI) PCM REBCO coils as the on-board magnets for a vacuum tube maglev train project [3,4]. Under these conditions, the non-negligible AC fields from the stator windings demagnetize the PCM coils [42][43][44][45].…”

Section: Introductionmentioning

confidence: 99%

“…The principle of PCM operation is illustrated by the circuit diagram in figure 1. The PCM operation provides the HTS magnet with advantages of: (a) less refrigerant consumption and higher thermal stability due to elimination of the heat leakage through current leads [1][2][3][4]; (b) robustness against unexpected power-off conditions [2,4]; (c) higher flexibility due to elimination of the cumbersome power source while running [4,5]; (d) possibility to generate a more stable DC magnetic field than the driven mode [2,6]. Therefore, PCM coils are desired in some energy storage systems [7,8], a few NMR/MRI projects [2,6,9,10] and most practically, the on-board magnets of maglev train systems [4,[11][12][13][14][15], which require high flexibility, safe off-power operation and efficient refrigeration.…”

Section: Introductionmentioning

confidence: 99%

Study of the demagnetization behavior of no-insulation persistent-current mode HTS coils under external AC fields by 3D FEM simulation

Zhong,

Wu,

et al. 2024

Supercond. Sci. Technol.

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The no-insulation (NI) winding technique is promising to be applied in the persistent-current mode (PCM) operation of high-temperature superconducting (HTS) coils to provide those advantages. To apply the NI PCM coil, its demagnetization behaviour (i.e., decay of persistent DC current) by external AC field, which occurs in maglev trains, electric machines, and other dynamic magnet systems, is essential to be understood. For this purpose, a 3D FEM model, capturing the full electromagnetic properties of NI HTS coils, is established. This work has studied three kinds of AC fields, observing the impact of turn-to-turn contact resistivity on demagnetization rates, which is attributed to current distribution modulations. Under transverse AC field, the lower contact resistivity attracts more transport current to flow in the radial pathway to bypass the ‘dynamic resistance’ generated in the superconductor, leading to slower demagnetization. Under axial AC field, the demagnetization rate exhibits a non-monotonic relation with the contact resistivity: (1) the initial decrease of contact resistivity leads to concentration of induced AC current on the outer turns, which accelerates the demagnetization; (2) the further decrease of contact resistivity makes the current smartly redistribute to avoid to flow through the loss-concentrated outer turns, thus slowing down the demagnetization. Under the rotating DC field, a hybrid of the transverse and axial fields, the impact of contact resistivity on the demagnetization rate exhibits combined characteristics of the transverse and axial components. Besides, quantitative prediction on the demagnetization rate of NI PCM coil under external AC field is instructive for practical designs and operations, which is tried by this 3D FEM model, and a comparison with experimental result is conducted.

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“…Since their introduction by Hahn et al [1], HTS non-insulation (NI) coils have been widely used in many applications, such as in nuclear magnetic resonance (NMR) [2,3] and electrodynamic suspension (EDS) systems [4][5][6], owing to the high current-carrying density in steady-state operation. In addition, NI coils present a good self-protection capability, as the operational current can flow in the azimuthal and radial directions through the loop and turn-to-turn contact approaches, respectively, thus bypassing the hot-quenching point [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Study on current discrepancy and redistribution of HTS non-insulation closed-loop coils during charging/discharging and subsequent transient process toward steady-state operation

Gao

et al. 2022

Supercond. Sci. Technol.

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It has been previously demonstrated that currents in HTS non-insulation (NI) coils exhibit a discrepant distribution during charging and discharging. However, for NI closed-loop coils, novel phenomenons that arose from the current discrepancy have not been fully studied, especially during transient processes after charging and discharging, or more strictly speaking, after the persistent current switch returns to the superconducting state. For example in our project of a prototype maglev system, a rapid decrease in the magnetic field was observed immediately after charging, which could be easily misinterpreted as a sign of local damage. However, the subsequent stability of the magnetic field with the expected decay rate of < 1\%/day illustrated that there was no such damage. To address this issue, in this study, a NI closed-loop coil was fabricated and simulated by an equivalent circuit model (per 46 turns as a L-R circuit element and 20 elements in total for 920 turns) coupled with a 3D finite-element-method model. Simulated results were in reasonable agreement with experimental measurements, demonstrating a significant discrepancy in azimuthal currents during charging and discharging; this is essentially due to variations in inductances across each turn of NI coils. Besides, azimuthal currents may initially flow in the direction opposite to the coil voltage in turns with lower resistivity relative to other turns. In correspondence with the observed novel phenomenons, after charging or discharging, azimuthal currents undergo redistribution until converging to a stable value, which exhibits a transient process and leads to a rapid decrease or increase of magnetic field in specific positions. The following issues were also discussed: 1) The judgement of operational current could be disturbed by the discrepant current distribution, due to its impact on the spatial magnetic field, not only for NI closed-loop coils but also for open-loop ones; 2) The non-uniformity of currents in NI closed-loop coils is lower, compared to that in open-loop ones with the same joint resistance and turn-to-turn resistivity distribution; 3) A new strategy with multiple charging processes is necessary for precisely charging NI closed-loop coils to the target current.

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Operating Thermal Characteristics of REBCO Magnet for Maglev Train Using Detachable Cooling System

Cited by 20 publications

References 19 publications

Design Model of Null-Flux Coil Electrodynamic Suspension for the Hyperloop

Design Model of Null-Flux Coil Electrodynamic Suspension for the Hyperloop

Study of the demagnetization behavior of no-insulation persistent-current mode HTS coils under external AC fields by 3D FEM simulation

Study on current discrepancy and redistribution of HTS non-insulation closed-loop coils during charging/discharging and subsequent transient process toward steady-state operation

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