Wireless Power Supply for HTS Magnets: Circuit Topology Design and Cryogenic Testing

Using wireless charging method to charge high-temperature superconducting (HTS) magnet is a way to solve the existing problem of high leakage heat introduced by charging through current leads. However, the available studies on charging HTS magnets using wireless charging methods rarely involves the role of Dewar on the charging process. Nowadays, most HTS magnet use metal Dewar because of the high requirements of Dewar for gas tightness and mechanical strength. How to charge the HTS magnets wirelessly through metal walls of the Dewar is an issue that needs to be addressed. In response to the above concerns, taking into account the role of the metal Dewar, a low-frequency wireless charging system with an isolation transformer as the core is proposed in this paper. Theoretical model of the proposed wireless charging system is developed, and the prototype is fabricated based on the theoretical model. Both theoretical and experimental methods were used to study the operational characteristics of the prototype, and the results obtained proved the validity of the theoretical model in this paper. Experimental results show that the proposed wireless charging system can charge an 8.5 mH HTS magnet with a current of 48.58 A over a 6 cm transmission distance, where the 6 cm gap includes a 1.6mm thick metal wall. Results obtained in this paper can provide a new idea for the research work on charging HTS magnets wirelessly through metal Dewar.

Section: Resultssupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

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Study of a low-frequency wireless charging system crossing the metal Dewar wall of a high-temperature superconducting magnet

Liu

Gao²,

Tian³

et al. 2022

“…During recent years, there has been significant progress in research into HTS flux pumps and related areas, including revealing the rectifying effect [12][13][14][15][16][17][18], understanding the dynamic resistance [19][20][21][22], developing various types of flux pump devicess [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40], superconducting switches [41,42], cryogenic rectifiers [43,44], multi-pulse magnetizations [45,46], and flux transformation [47].…”

Section: Introductionmentioning

confidence: 99%

Maximising the current output from a self-switching kA-class rectifier flux pump

Geng

Bumby

Badcock

2020

High current operation of HTS magnets is desirable for many applications, but operating currents are typically limited by resistive heating of the normal-conducting current leads, which connect the cryogenic magnet coil to a room-temperature electronic power supply. Rectifying flux pumps are a feasible alternative solution as they enable current to be directly injected into the HTS magnet coil via a closed superconducting circuit. In this work, we have developed and demonstrated two prototype HTS self-rectifying flux pump devices capable of delivering very high output currents. One of these devices can deliver a maximum direct current of >2 kA. This is a new record for the flux pump excitation of an HTS coil. Unlike other rectifying flux pumps, the self-rectifying flux pumps reported here do not employ an active switching component. Instead passive 'self-switching' rectification is achieved by applying an assymmetric current waveform to the primary winding. This significantly reduces the complexity of the system compared to other flux pump architectures, and removes the need for dissipative electronic components within the cryogenic environment. We demonstrate that these devices also function when the iron core linking the superconducting secondary and the normal conducting primary is broken by a pair of air gaps. In these conditions DC currents of >600 A can be maintained with a total air gap length of 10 mm. This indicates that this approach represents a feasible practical solution for through-wall excitation of high current HTS magnets.

“…Up to now, there are plenty of works about the contactless charging of the HTS magnets, which demonstrate the potentials of contactless power transfer for engineering applications [11][12][13]. Flux pumping is one effective way among the contactless power transfer technologies, which does not need a complicated power source, and can generate a high current with a small energy supply [5,14].…”

Section: Introductionmentioning

confidence: 99%

Influence of ferromagnetic slice on the charging performance of a through-wall HTS flux pump employing a magnetic coupler

Li¹,

Sun²,

Zhou³

et al. 2022

Self Cite

High-temperature superconducting (HTS) magnets have been investigated widely for their higher upper critical magnetic field, larger engineering critical current density and simpler cryogenic system compared with low-temperature superconducting (LTS) magnets. However, in order to keep the permanent-current mode of the HTS magnets, the external power supply is usually employed to charge the magnet via copper current leads, which is a considerable heat source to the cooling system. Thus, in order to avoid the heat disturbance brought by the current leads, a new “through-wall” dynamo-type HTS flux pump using a pair of magnetic couplers is proposed, realizing the truly wireless power transfer, and exploring its possible application for the conduction cooled system. Based on the proposed structure, the heat conduction, which was calculated to be about 7.75 W, and heat convection could be minimized. In addition, to further improve the charging performance of the dynamo-type flux pump, a ferromagnetic (FM) slice was added into different positions of the system. The effect of the FM slice on charging performance was studied numerically and experimentally. According to the results of simulations and experiments, adding a FM slice under the HTS stator improves the saturated current and the charging speed of the dynamo-type flux pump by 20%~30%.