High Temperature Superconducting Flux Pumps for Contactless Energization

Flux pumps provide a promising solution for contactless charging of high-temperature superconducting (HTS) coils, eliminating the need for bulk current leadsand reducing the heat burden for the cryogenic system. Characterizing the nonlineareffects of an HTS coil charged by a flux pump and understanding the dynamics ofthe charging process is essential for promoting the practical application of flux pumps.Numerical models provide a fast and cost-effective way of achieving this. In this study,we propose a methodology for coupling HTS coil and flux pump models using anelectrical circuit, resulting in reduced computation costs. We validate the effectivenessof our approach against the experimental results of an HTS coil charged by a dynamo-type flux pump. Specifically, we obtain the voltage produced by the HTS dynamo usinga 3D model based on the minimum electromagnetic entropy production (MEMEP)method and apply this voltage to the load HTS coil using a T-A formulation finite-element method (FEM) model coupled via an electrical circuit. The simulated chargingcurrent shows good agreement with experimental observations, validating our modelingstrategy. The results demonstrate that the flux flow state in the HTS coil is theprimary factor limiting the charging performance of the HTS dynamo as the chargingcurrent approaches the coil’s critical current. Furthermore, based on the simulation,we demonstrate that, when using flux pumps, it is advisable to leave a margin betweenthe operating current and the critical current of the coil. Overall, our approach hasthe potential to be applied to HTS coils charged by any device.

Section: Introductionmentioning

confidence: 99%

Characterization of flux pump-charging of high-temperature superconducting coils using coupled numerical models

Zhou,

Ghabeli,

Ainslie

et al. 2023

“…A flux pump usually refers to a device that eliminates bulky current leads and indirectly injects current into the superconducting coil, which is a promising power source for HTS coils [9][10][11][12]. 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].…”

Section: Introductionmentioning

confidence: 99%

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

Chen

et al. 2023

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.

“…This 'self-rectification' method was originally described for hightemperature superconductors by Vysotsky et al [8], and can be compared with FPs that employ various active switching mechanisms to vary the I c of the bridge [1,[9][10][11][12]. Selfrectifying FPs are capable of delivering large currents at modest voltages [3] without a requirement for direct electrical and thermal connection between the superconducting load and an ambient temperature power supply, which can lower the overall heat load on the cryogenic system when compared with a conventional power supply [1,13,14]. Furthermore, selfrectifying FPs do not contain moving parts, unlike dynamobased FPs, and do not require additional electromagnets as 'switching' components [13,14].…”

Section: Introductionmentioning

confidence: 99%

“…Selfrectifying FPs are capable of delivering large currents at modest voltages [3] without a requirement for direct electrical and thermal connection between the superconducting load and an ambient temperature power supply, which can lower the overall heat load on the cryogenic system when compared with a conventional power supply [1,13,14]. Furthermore, selfrectifying FPs do not contain moving parts, unlike dynamobased FPs, and do not require additional electromagnets as 'switching' components [13,14]. This makes self-rectifying FPs an attractive option for applications with demanding size, weight and power requirements, such as those found on spacecraft [15,16] or as portable high-field electromagnets [17].…”

Section: Introductionmentioning

confidence: 99%

Effective circuit modelling and experimental realization of an ultra-compact self-rectifier flux pump

Mallett

Venuturumilli

Geng

et al. 2023

This paper presents experimental and modelling results of an ultra-compact self-rectifier flux pump energizing a superconducting coil. The device fits inside a volume of 65x65x50 mm and generates up to 320 A dc through the coil and a peak output voltage up to 60 mV. We also develop and present a full electromagnetic effective circuit model of the flux pump and compare its predictions to the experimental results. We show that our model can reproduce accurately the charging of the load coil and that it reproduces the systematic dependence of the maximum load coil current on the input current waveform. The experiments and modelling together show also the importance of dc-flux offsets in the transformer core on the final achievable current through the coil. The miniaturization possible for this class of flux pump and their minimal heat-leak into the cryogenic environment from thermal conduction make them attractive for applications with demanding size, weight and power limitations. Our effective circuit model is a useful tool in the understanding, design and optimization of such flux pumps which will accelerate their progression from research devices to their application.