Screening current induced magnetic field and stress in ultra-high-field magnets using REBCO coated conductors

Yan, Yufan; Li, Yi; Qu, Timing

doi:10.1088/1361-6668/ac392b

Cited by 45 publications

(18 citation statements)

References 107 publications

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“…t=−10 s). This phenomenon is caused by the 'screening current effect' [59], rather than the transport current redistribution induced by dynamic resistance. Therefore, this phenomenon is explained in detail in the appendix.…”

Section: Simulation Analysismentioning

confidence: 99%

“…The lower of figure A1 shows the current density distribution with the radial AC field, B AC, r , applied, corresponding to the red line in the upper plot. After charging the coil (see t = −2 s), the screening current distribution lessens the central field as much as possible [59]. As the B AC, r is applied for the first time shown by t∈[0 s, 2 s], the screening current distribution is reshaped by the magnetization current densities induced by the AC field.…”

Section: Lossmentioning

confidence: 99%

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Time-variant magnetic field, voltage, and loss of no-insulation (NI) HTS magnet induced by dynamic resistance generation from external AC fields

Zhong

et al. 2023

Supercond. Sci. Technol.

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High-temperature superconducting (HTS) coils serving as DC magnets can be operated under non-negligible AC fields, like in synchronous machines of maglev trains and wind turbines. In these conditions, dynamic resistance generates in HTS tapes, causing redistribution/bypassing of the transport current inside the no-insulation (NI) coil and its unique operational features. This issue was studied by experiments on an NI coil with DC current supply put into external AC fields. Due to the current redistribution induced by dynamic resistance, the central magnetic field and voltage of the NI magnet initially undergo various transient processes, and eventually exhibit a stable central magnetic field reduction and a DC voltage. These time evolutions have implications for a time-varying torque and loss of an HTS machine. These time evolutions are strongly affected by the contact resistivity distribution, and whether it is the first time of the NI magnet being exposed to the AC field, showing several qualitatively different waveforms (e.g., some are even non-monotonic with time). The magnitudes of the stable central field reductions, and their observed linear correlation with the DC voltages are found to be decided by the local contact resistivity of the innermost and outermost several turns. It is also noted that the non-insulated turn-to-turn contact help lessening the loss induced by the dynamic resistance. A numerical model is established to analyse/explain those experimental results by observing the microscopic current distribution. Two risks of quench are noticed: (i) azimuthal current of the middle part turns increases as the AC field is applied; (ii) a concentration of radial current is observed near the terminals of the NI coil.

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Section: Simulation Analysismentioning

confidence: 99%

Section: Lossmentioning

confidence: 99%

Time-variant magnetic field, voltage, and loss of no-insulation (NI) HTS magnet induced by dynamic resistance generation from external AC fields

Zhong

et al. 2023

Supercond. Sci. Technol.

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“…Ueda evaluates the electromagnetic force and stress due to the screening current by using the developed numerical simulation code [30]. Yan studies screening-current-induced mechanical strains in HTS insert coils [31,32]. The effect of the changing rotation angle of the conductor on the electromagnetic and stress state is investigated [33].…”

Section: Introductionmentioning

confidence: 99%

An electromagnetic-thermal-mechanical analysis model for high temperature superconducting magnets

Yang¹,

Ren²,

Xu³

et al. 2023

Phys. Scr.

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High temperature superconducting magnet is the core component of superconducting power device, and its stability is the key factor that restricts the safe operation of superconducting power devices. In order to accurately and effectively evaluate the stability of superconducting magnets during operation, an electromagnetic-thermal-mechanical numerical simulation method for high temperature superconducting magnets is studied in this paper. Based on the model, the 150kJ SMES magnet as case is studied, the magnetic field and current density distribution are solved during the operation of the 150 kJ magnet, and its temperature rise, AC loss and stress analysis of the magnet are achieved. In addition, this work further analyses the critical current declination degree of superconducting tapes in the 150kJ HTS magnet under multi-field coupling, the dangerous region in operation is obtained and suggestions are put forward to avoid quench. The electromagnetic-thermal-mechanical model may provide an appropriate stability assessment with rapid and real-time calculations for HTS magnets.

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“…The use of an over-banding build at the outermost turn, wound with materials with a high modulus of elasticity, shares similar effects [2]. In dry-wound REBCO coils, it is shown that stresses in the superconducting winding can be reduced by adjusting the size and winding tension of the over-banding build [18][19][20][21][22]. In practice, thin stainless-steel (SS) tapes are often chosen considering its commercial availability and high modulus of elasticity.…”

Section: Introductionmentioning

confidence: 99%

Measurement and analysis of winding stresses in dry-wound pancake coils considering nonlinear compressive behaviors

Yan,

Kim,

Bong

et al. 2023

Supercond. Sci. Technol.

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Considering coil stress management, conductor thermal stability, and susceptibility to delamination, the dry-winding approach has been gradually applied and tested in high-temperature-superconducting coils wound with REBa2Cu3O 7 − x (REBCO) coated conductors (CCs). In dry-wound coils, the winding tension can be a useful tool for managing the mechanical stresses and maintaining the structural stability. It is also related to the contact resistivity characteristics of no-insulation and metal-as-insulation coils. In this paper, we present a study on the winding stresses in dry-wound pancake coils considering nonlinear compressive behaviors in the radial direction. Coils wound with stainless-steel (SS) tapes and REBCO CCs were prepared, respectively, with various sizes (90–140 turns) and winding tensions (26–61 MPa). The radial pressure was obtained by applying the pressure measurement films, which cover a pressure range up to 50 MPa. A relatively moderate radial pressure buildup was observed in coils wound with SS tapes, indicating that the effective radial modulus of the coil as an entity is considerably lower compared to the tensile modulus in the azimuthal direction. This is consistent with the nonlinear stress–strain relationship of stacked thin sheets under transverse compression, which can be further explained by the contact behaviors between two rough surfaces. The average radial pressure in CC coils shared similar characteristics as that in SS coils, whereas the radial stress along the conductor edges were significantly higher compared to the middle. Cross-sectional microscopy of the CCs suggests that this can be primarily attributed to the thickness variations across the conductor width. These results suggest that the microscopic rough-surface contact and thickness variation of the wound tape play a critical role in the coil stiffness as well as the winding stress distributions.

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Screening current induced magnetic field and stress in ultra-high-field magnets using REBCO coated conductors

Cited by 45 publications

References 107 publications

Time-variant magnetic field, voltage, and loss of no-insulation (NI) HTS magnet induced by dynamic resistance generation from external AC fields

Time-variant magnetic field, voltage, and loss of no-insulation (NI) HTS magnet induced by dynamic resistance generation from external AC fields

An electromagnetic-thermal-mechanical analysis model for high temperature superconducting magnets

Measurement and analysis of winding stresses in dry-wound pancake coils considering nonlinear compressive behaviors

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