A flux pumping method applied to the magnetization of YBCO superconducting coils: frequency, amplitude and waveform characteristics

Fu, Lin; Matsuda, Koichi; Lécrevisse, Thibault; Iwasa, Y.; Coombs, Tim

doi:10.1088/0953-2048/29/4/04lt01

Cited by 39 publications

(13 citation statements)

References 16 publications

(25 reference statements)

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“…Figure 2(a) shows the structure of the designed miniaturized linear flux pump device. It is more compact than previous flux pumps [35,39], with an overall size of 4.6 cm × 4.6 cm × 3.4 cm. The flux pump consists of a magnetic circuit composed of silicon steel and eight copper coils.…”

Section: Operational Principlesmentioning

confidence: 99%

“…Recently, HTS flux pumps have received a lot of attention, such as transformer-rectifier flux pumps [13][14][15][16][17] and traveling wave flux pumps [18]. At present, there are several types of travelling wave flux pumps, mainly including thermally actuated flux pumps [19][20][21], HTS dynamo flux pumps [22][23][24][25][26][27], linear-motor type flux pumps [28][29][30][31], pulsetype flux pumps [32,33] and linear flux pumps [34,35]. Increasing the charging current is a major task in flux pump research.…”

Section: Introductionmentioning

confidence: 99%

“…Compared to HTS dynamo flux pumps, linear flux pumps operating by sequentially switching the copper solenoids to generate a moving flux profile, have no rotor parts, which means less vibration and noise. In terms of research progress, in 2016, Fu et al proposed a linear flux pump in which four 12 mm wide superconducting tapes were connected in parallel to achieve a 90 A charging current; the size of the flux pump was 14 cm × 12.8 cm × 4 cm [35]. In 2021, Fu et al achieved a maximum charging current of 71 A in the linear flux pump using a 46 mm wide superconducting tape [40].…”

Section: Introductionmentioning

confidence: 99%

“…Studies have been conducted on the common parameters of linear flux pumps. Fu et al [35] studied the effects of the waveform, frequency, and amplitude of the applied current on a linear flux pump, and proved that the triangular wave is the most effective for pumping superconducting current among unipolar sinusoidal, trapezoidal, and triangular waves [35]. Fu et al investigated further characteristics of flux pumping efficiency, including duty ratios and wavelength of applied trapezoidal waves, effect on the number of poles, and control of the saturated superconducting current [41].…”

Section: Introductionmentioning

confidence: 99%

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Miniaturized HTS linear flux pump with a charging capability of 120 A

Chen

et al. 2023

Supercond. Sci. Technol.

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Owing to the presence of joint resistance and flux creep, high-temperature superconducting (HTS) coils without a power supply inevitably suffer from current decay. A flux pump is a voltage supply that requires connections with smaller footprints and a lower heat load than traditional current leads. In this study, we explain the principle of the upper limit for the output current of the traveling wave flux pumps. Based on this principle, a miniaturized linear flux pump device was developed. With narrow and misaligned iron teeth, elaborate 3D geometry of the iron pieces, and optimized driving current waveform, the miniaturized flux pump can support more than 120 A output current with only a 10 mm wide HTS tape and a compact size of 4.6 × 4.6 × 3.4 cm. Our experimental results show that the critical current of the HTS tape has a significant effect on the flux pump output. An HTS tape with a larger critical current supports a higher maximum transport current, whereas an HTS tape with a smaller critical current requires less applied current for positive output. Finally, excitation tests on HTS coils were performed. Charge/active discharge and field supplement experiments were done on a maglev HTS racetrack coil of 0.4 H, where charging/field supplement capbility of the miniaturized flux pump were demonstrated up to 46.8 A (close to the critical current of the coil). It has also been proved that the flux pump can work together with an external power supply with persistent current switch. The miniaturized flux pump can also independently charge an HTS coil of 60 μH to 91.6 A, which is the critical current of the coil at a low voltage criterion.

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Section: Operational Principlesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Miniaturized HTS linear flux pump with a charging capability of 120 A

Chen

et al. 2023

Supercond. Sci. Technol.

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“…REBCO coated conductors (CCs) deliver DC currents under an AC magnetic field in many high temperature superconducting applications, such as the field-triggered persistent current switches (PCSs) [15][16][17]169] , flux pumps [12,13,19,170,171] , and field windings of synchronous rotating machines [6,[172][173][174][175][176] . As introduced in the previous section 2.5.3, dynamic resistance occurs in the CCs when the applied magnetic field exceeds the threshold magnetic field because the flux transvers through the DC current region.…”

Section: Dynamic Resistance and Total Loss In Rebco Coated Conductorsmentioning

confidence: 99%

AC Loss Research of REBCO High-Tc Superconductors Carrying a DC Current in an AC Magnetic Field

Sun¹

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AbstractREBCO (REBa2Cu3O7-d, RE stands for rare earth) high temperature superconducting (HTS) coated conductors (CCs) have become the preferred wire choice for HTS applications due to their high current carrying capacity and advanced mechanical properties. In many HTS applications such as HTS synchronous motors, HTS flux pumps and HTS persistent current switches, REBCO CCs, stacks and coils carry DC currents in an AC magnetic field environment, generating AC loss comprising of dynamic loss component arising from dynamic resistance and the magnetization loss component due to the shielding currents. AC loss behaviours of commercial-available REBCO CCs in such operating conditions haven’t been fully explored with the most prominent research question of how the AC loss and each loss component evolve and behave in the single REBCO CC, REBCO stacks and REBCO coils at different temperatures with various operating conditions. Other interesting open questions are also put forward to underpin relevant engineering applications: how the shielding effect of REBCO CCs influences the eddy current loss in adjacent copper layers at various field orientation; what kind of inherent correlation exists between the asymmetric field-orientation-dependent critical current characteristics and the magnetization loss behaviors; and how the loss behaviours in REBCO stacks and coils differentiate from the REBCO CC; what’s the difference between the REBCO racetrack coil and the REBCO double pancake coil regarding characteristics of the critical current, magnetization loss, dynamic resistance and AC loss under the condition of the combined DC current with the AC magnetic field. This thesis aims to underpin the REBCO HTS applications and reveal the underlying AC loss mechanism through systematically experimental and numerical research on AC loss and dynamic resistance in REBCO CCs, REBCO stacks and REBCO coils that operate at various electromagnetic conditions and temperatures (65 K ~ 77 K). This research has revealed many new phenomena in the loss evolution process and reached illuminating conclusions. We uncover the shielding effect of REBCO CCs under various field orientations is dominated by the perpendicular magnetic field component, and so does the reduced eddy current loss in the adjacent copper layers of the copper-superconductor stacks. When exploring the role of asymmetric field-orientation-dependent critical current on the magnetization loss of REBCO CCs, we reveal that the asymmetry of critical current about the ab-peak within the 360 full-field-angle range causes differences in magnetization loss values at the field angles which are in mirror symmetry relative to the ab-plane. Furthermore, it is surprising and contradicting to find that magnetization loss at any given field orientation is unequal between the positive and the negative half-field cycle due to the asymmetry of critical current upon the field reversal. The asymmetric field-orientation dependence of both critical current and magnetization loss becomes more obvious with the increasing magnetic field amplitudes and the decreasing temperatures. The complicated AC loss evolution process in REBCO CCs under AC magnetic fields and DC currents is probed by demonstrating the striking behaviours: the dynamic loss region and magnetization loss region vary across the conductor width at high magnetic fields or high DC current levels; the (positive) DC current is superposed with the anti-parallel (negative) shielding current at high DC current levels that approaching to the self-critical current, which drives the local current density of one conductor edge to the subcritical stage and leads to one-sided loss generation in each half-cycle. At the liquid nitrogen temperature range, experimental and simulation results exemplify that the AC loss is mostly dominated by magnetization loss when DC current is less than 20% critical current, while dynamic loss makes a comparable, even greater contribution to AC loss when DC current is larger than 50% critical current. The dynamic resistance shows an obvious frequency dependence due to the heating accumulation at high field amplitudes, high DC current levels and high operating temperatures, which provides a useful reference for the application designs of HTS flux pumps and HTS persistent current switches. Compared with the single REBCO CC, the onset of dynamic resistance/loss in REBCO stacks and REBCO coils is much slower, and the contribution of the dynamic loss component to the AC loss is also much smaller. Dynamic loss in the stack becomes greater than the magnetization loss when the DC current is larger than 70% critical current, while always less than the magnetization loss in the coils when the AC magnetic field is less than 0.1 T. We also conclude that the critical current, magnetization loss and dynamic resistance/loss per unite length in the REBCO racetrack coil is slightly larger than those of the REBCO pancake coil. The main contribution of this work is to reveal the complex AC loss mechanism in REBOC CCs, stacks and coils carrying DC currents in the AC magnetic field and characterize the loss behaviours via solid experimental measurements and numerical simulations. Meanwhile, the magnetization loss as the dominant loss component is further explored concerning its shielding effect and the asymmetric critical current characteristics. This work exemplifies the underlying nature of AC loss behaviours, providing a valuable reference to understand the loss mechanism and to underpin relevant HTS applications.

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High-temperature superconducting (HTS) transformer-rectifier flux pump for powering no-insulation superconducting magnet with low characteristic resistance

Geng

Gawith

et al. 2019

Physica C: Superconductivity and its Applications

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A flux pumping method applied to the magnetization of YBCO superconducting coils: frequency, amplitude and waveform characteristics

Cited by 39 publications

References 16 publications

Miniaturized HTS linear flux pump with a charging capability of 120 A

Miniaturized HTS linear flux pump with a charging capability of 120 A

AC Loss Research of REBCO High-Tc Superconductors Carrying a DC Current in an AC Magnetic Field

High-temperature superconducting (HTS) transformer-rectifier flux pump for powering no-insulation superconducting magnet with low characteristic resistance

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