Hysteresis Loss of REBCO Conductor Up to 35 T

Bai

et al. 2020

High Voltage

Second generation (2G) high-temperature superconductor (HTS) (RE)Ba 2 Cu 3 O x (REBCO) shows a great potential in building high field magnets beyond 23.5 T. The electromagnetic modelling is vital for the design of HTS magnet, however, this always suffers the challenge of huge computation for high field magnets with large number of turns. This study presents a novel electromagnetic modelling based on T-A formulation for REBCO magnets with thousands of turns. An equivalent turn method is proposed to reduce the number of turns in calculation, so that the computation cost can be reduced significantly, and meanwhile the key electromagnetic behaviour of HTS magnet can be simulated with enough accuracy. The ramping operation of a fully HTS magnet with 12,000 turns are analysed using both the original T-A model with actual turns and improved T-A model with equivalent turns. The two models show a good agreement on the key electromagnetic behaviours of the magnet: distribution of current density, magnetic fields, screen current induced field and magnetisation loss, so that this improved T-A model using equivalent turns is validated. The T-A modelling of REBCO magnet is a powerful tool for the electromagnetic analysis of industry-scale high field magnets.

({, \begin{matrix} W_{m} = d \int_{l} bold-italicE \cdot bold-italicJ normald l \\ Q_{m} = \int_{} W_{m} (t) normald t \end{matrix})

where W m and Q m are the magnetisation loss power and energy, respectively.…”

Section: Resultsmentioning

confidence: 99%

Electromagnetic modelling using T‐A formulation for high‐temperature superconductor (RE)Ba ₂ Cu ₃ O _x high field magnets

Bai

et al. 2020

High Voltage

“…As shown in the Eq. (25), the real ramping rate of azimuthal current in this period is mainly determined by the coil's time constant τ, and has nothing to do with the ramping rate k of power supply. Therefore, the peak magnetization loss power converges to a maximum value with the increase of ramping rate k, which agrees well with the results in Fig.…”

Section: B Discussion On Magnetization Lossmentioning

confidence: 99%

“…The total loss generated in the ramping process is an important issue for superconducting coils and magnets, which needs to be precisely studied to predict and reduce the refrigeration requirements of applications [22][23][24][25][26][27] . For the conventionally insulated HTS coils, a magnetization loss are generated because of flux creep and flux jump in superconductors during the ramping operation, which is the main part of the traditional AC loss 24,[28][29][30][31] .…”

Section: Introductionmentioning

confidence: 99%

Ramping turn-to-turn loss and magnetization loss of a No-Insulation (RE)Ba2Cu3Ox high temperature superconductor pancake coil

Journal of Applied Physics

Song

Yuan

et al. 2017

This paper is to study ramping turn-to-turn loss and magnetization loss of a no-insulation (NI) high temperature superconductor (HTS) pancake coil wound with (RE)Ba2Cu3Ox (REBCO) conductors. For insulated (INS) HTS coils, a magnetization loss occurs on superconducting layers during a ramping operation. For the NI HTS coil, additional loss is generated by the 'bypassing' current on the turn-to-turn metallic contacts, which is called "turn-toturn loss" in this study. Therefore, the NI coil's ramping loss is much different from that of the INS coil, but few studies have been reported on this aspect. To analyze the ramping losses of NI coils, a numerical method is developed by coupling an equivalent circuit network model and a H-formulation finite element method (FEM) model. The former model is to calculate NI coil's current distribution and turn-to-turn loss, the latter model is to calculate the magnetization loss. A test NI pancake coil is wound with REBCO tapes and the reliability of this model is validated by experiments. Then the characteristics of the NI coil's ramping losses are studied using this coupling model. Results show that the turn-to-turn loss is much higher than the magnetization loss. The NI coil's total ramping loss is much higher than that of its insulated counterpart, which has to be considered carefully in the design and operation of NI applications. This paper also discusses the possibility to reduce NI coil's ramping loss by decreasing the ramping rate of power supply or increasing the coil's turn-to-turn resistivity.

“…The Joule loss generated inside coils is a critical issue in charging of HTS magnets, which is called 'ramping losses' in this study. The temperature rise beyond threshold induced by the ramping losses is often the main cause of a ramp failure [14][15][16] . With such a considerable heat load, the total ramping losses has to be accurately estimated in the system cryogenic design.…”

Section: Introductionmentioning

confidence: 99%

Non-uniform ramping losses and thermal optimization with turn-to-turn resistivity grading in a (RE)Ba2Cu3Ox magnet consisting of multiple no-insulation pancake coils

Journal of Applied Physics

Zhang

Yuan

et al. 2017

This paper presents a study on the ramping losses of a high temperature superconductor (HTS) magnet consisting of multiple no-insulation (NI) (RE)Ba2Cu3Ox coils. The (RE)Ba2Cu3Ox (REBCO) conductor is the second generation HTS thin tape where RE stands for rare-earth. During a ramping operation of the NI HTS magnet, Losses are generated both across turn-to-turn resistances and inside superconducting layers. The former comes with radial current, which is called 'turn-to-turn loss'; the latter one is induced by flux creep and jump, called 'magnetization loss'. The modeling and experimental studies on the ramping losses have been reported on a single NI pancake coils in the previous part. In a HTS magnet consisting of multiple NI coils, the electromagnetic coupling between coils have a considerable influence on the distribution of ramping losses. Here the experimentally validated model is used to investigate a HTS magnet consisting of 14 single pancake (SP) REBCO coils. Results show that both the turn-to-turn loss and magnetization loss present a significant non-uniform distribution among coils. The highest turn-to-turn loss occurs to the middle coils of the magnet, while the highest magnetization loss happens on the end coils. The non-uniform distribution of ramping losses can result in a considerable temperature difference among coils in the NI HTS magnet. It leads to an additional quench risk on the magnet and requires more attentions in design. The distribution of the turn-to-to-turn loss can be optimized by adjusting the turn-to-turn resistivity. A much more uniform turn-to-turn loss distribution among coils is achieved by applying a graded turn-to-turn resistivity on the multiple coils.