Study of Induced Current in Closed HTS Magnets Under AC Fields: Simulation and Experiment

Zhong, Zhuoyan; Wu, Wei; Wang, Longbiao; Li, Xiaofen; Li, Zhuyong; Hong, Zhiyong; Jin, Zhijian

doi:10.1007/s10948-021-06016-4

Cited by 4 publications

(4 citation statements)

References 37 publications

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“…Notice that the instantaneous ĪT of the coil (see the solid lines) includes not only the original persistent DC current but also the induced AC current generated by the external axial field. It is already known that the closed loop formed by the PCM coil allows the circulation of an induced current generated by an external axial field [107]. The period-averaged ĪT (see the dashed lines) is used to filter the AC component of the instantaneous ĪT .…”

Section: Demagnetization By Axial Ac Fieldmentioning

confidence: 99%

“…The period-averaged ĪT (see the dashed lines) is used to filter the AC component of the instantaneous ĪT . The mechanism of the current decay can be attributed to that of the superposition of an induced AC current that increases the overall current density in the superconductor (especially when the induced AC current is in the same direction as the original persistent DC current), causing larger resistance in the superconductor [107]. The low-R ct coil decays faster than the high-R ct coil, though both coils exhibit similar waveforms of the induced AC current in the first cycle of being exposed to the AC field.…”

Section: Demagnetization By Axial Ac Fieldmentioning

confidence: 99%

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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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Section: Demagnetization By Axial Ac Fieldmentioning

confidence: 99%

Section: Demagnetization By Axial Ac Fieldmentioning

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.

Self Cite

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“…To tackle this issue regarding the current decay simulation, several improved approaches have been proposed. For instance, induction magnetization techniques are employed to establish the current in the HTS coil, achieving the free variation of the current [41][42][43]. Other approaches involve calculating the dynamic resistance under specific conditions first and then using an interpolation method to obtain the current decay curve [41,42].…”

Section: Introductionmentioning

confidence: 99%

“…For instance, induction magnetization techniques are employed to establish the current in the HTS coil, achieving the free variation of the current [41][42][43]. Other approaches involve calculating the dynamic resistance under specific conditions first and then using an interpolation method to obtain the current decay curve [41,42]. In addition to the FEM method, the circuit approach is also utilized, using the pre-measured dynamic resistance values [31,34].…”

Section: Introductionmentioning

confidence: 99%

Effect of local and global screening current on the current decay in closed-loop HTS coils

Zhou,

Zhang,

Wang

et al. 2024

Supercond. Sci. Technol.

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High-temperature superconducting (HTS) coils are typically operated in a closed-loop persistent current mode to maintain their stability and minimize heat generation. However, factors such as joint resistance, flux creep, and losses due to external fields can lead to accelerated decay of the coil's current, making it challenging to achieve an effective persistent current mode. To gain insight into the current decay characteristics of HTS coils, we built a finite-element-method (FEM) based model coupled with a lumped parameter electric circuit model. The model is initially verified against the experiment of an inductive magnetized HTS coil subject to a magnetic field perpendicular to the tape surface. The results indicate that the proposed model is highly effective in predicting the current decay behavior of this magnetized HTS coil and is able to provide high accuracy. With the help of this model, we have experimentally and numerically studied the behavior of a current-carrying closed-loop HTS coil subject to external alternating fields. The HTS coil is charged by a DC power supply and then shorted using a thermally-controlled persistent current switch. The current decay behavior of the HTS coil is examined under various scenarios. The simulation results show excellent agreement with experimental data, further validating the effectiveness and versatility of the modeling strategy. The influence of both global and local screening currents on the current decay performance of the closed-loop HTS coils has been investigated. Additionally, the resulting resistance has been thoroughly characterized. These insights contribute to the knowledge of the behavior and performance of closed-loop HTS coils, facilitating their practical application

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Experiment and Numerical Modeling of Current Distributions Inside REBCO Tapes of No-Insulation Superconducting Magnet Coils Under Time-Varying Fields

Zhong

Hong

et al. 2022

J Supercond Nov Magn

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Study of Induced Current in Closed HTS Magnets Under AC Fields: Simulation and Experiment

Cited by 4 publications

References 37 publications

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

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

Effect of local and global screening current on the current decay in closed-loop HTS coils

Experiment and Numerical Modeling of Current Distributions Inside REBCO Tapes of No-Insulation Superconducting Magnet Coils Under Time-Varying Fields

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