A Study on the No Insulation Winding Method of the HTS Coil

Choi, Sukjin; Jo, Hyun Chul; Hwang, Young Jin; Hahn, Seungyong; Ko, Tae Kuk

doi:10.1109/tasc.2011.2175892

Cited by 86 publications

(33 citation statements)

References 5 publications

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“…First, all the NI GdBCO test magnets to date have proven self-protecting [11][12][13][14][15][16][17][18] at 4.2 K and 77 K; the largest has a center field of 4 T with a 140-mm winding diameter. 11 Nevertheless, the self-protecting feature of a "large" NI magnet, such as our 100 T, needs further verification.…”

Section: The 100 T Is Wound With Gdbco Tape Manufactured Bymentioning

confidence: 99%

First-cut design of an all-superconducting 100-T direct current magnet

Iwasa

Hahn

2013

Applied Physics Letters

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A 100-T magnetic field has heretofore been available only in pulse mode. This first-cut design demonstrates that a 100-T DC magnet (100 T) is possible. We base our design on: Gadoliniumbased coated superconductor; a nested-coil formation, each a stack of double-pancake coils with the no-insulation technique; a band of high-strength steel over each coil; and a 12-T radial-field limit. The 100 T, a 20 mm cold bore, 6-m diameter, 17-m height, with a total of 12 500-km long superconductor, stores an energy of 122 GJ at its 4.2-K operating current of 2400 A. It requires a 4.2-K cooling power of 300 W. A 100-T DC field, one million times the earth field, is more than double 45 T, 1 the highest DC field created to date. Upon completion, a 32-T magnet at the National High Magnetic Field Laboratory (NHMFL) will achieve the highest DC field by an all-superconducting magnet.2,3 Fields greater than 45 T have been beyond DC magnet technology. Simply stated, this is because no electrical conductor meets two requirements for generation of a >45-T continuous field: high mechanical strength and good electrical conductivity. Copper is unable to withstand the high magnetic stresses. Steel can cope with the large stresses, as has been demonstrated by pulse magnets, 4,5 but its large electrical resistivity leads to huge Joule heating that rapidly overheats the steel, reducing its strength and thereby forcing >45-T steel magnets to operate only in pulse mode. 6,7 Although the range of experiments that can be done with pulsed fields continues to expand, 7 the words of Francis Bitter remain valid, "there are many experiments that are extremely difficult or impossible to perform in a hundredth of a second" 8 as a reason to drive the maximum DC field limit much higher. Our 100-T DC magnet (100 T) uses a superconductor of sufficient strength, with the winding reinforced by overbands of high-strength stainless steel. With electrical resistivity anchored to zero, one inherent weakness of the pulse magnet is eliminated.The two crucial design issues in high-field superconducting magnets are: (1) mechanical integrity; and (2) protection. In this first-cut design, based on the no-insulation (NI) technique, 9-18 we assumed 100 T self-protecting; thus, we focused chiefly on mechanical stress. Our key design approach is fourfold. The 100 T is wound with GdBCO tape manufactured bySuperPower, specifically 12-mm wide and 95-lm thick, comprising 50-l thick Hastelloy substrate (room-temperature yield stress and strain, respectively, of 970 MPa and 0.95% 19 ), two 20-lm thick electroplated copper layers, and 5-lm thick remainder (1-lm thick GdBCO layer and other materials). 2. The 100 T consists of 39 nested coils, each a stack of double-pancake coils (DPs) wound with the NI technique.3. To keep the peak tensile stress on GdBCO tape to 700 MPa at 4.2 K, each DP is reinforced over its outer diameter with a high-strength stainless steel band (overband) of 300-K ultimate strength of 1400 MPa and Young's modulus of 200 GPa. 4. To limit the maximum radial fi...

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Section: The 100 T Is Wound With Gdbco Tape Manufactured Bymentioning

confidence: 99%

First-cut design of an all-superconducting 100-T direct current magnet

Iwasa

Hahn

2013

Applied Physics Letters

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“…Additionally, another advantage is that since the HTS field coil is not moved together by the rotation of the rotor core, the mechanical support structure can be simplified, and it can be free from epoxy impregnation of the HTS field coil. This makes it possible to apply the no-insulation winding method, which can dramatically improve the stability of the HTS field coil [17][18][19][20][21][22]. NI winding is one of the most actively researched methods as a protection technology for HTS coils.…”

Section: Introductionmentioning

confidence: 99%

Design and Characteristic Analysis of a Homopolar Synchronous Machine Using a NI HTS Field Coil

Hwang

2021

Energies

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This paper deals with a homopolar synchronous machine (HSM) applying high-temperature superconducting (HTS) field coils. Superconductors, especially high-temperature superconductors, have high potential as advanced materials for next-generation electrical machines due to their high critical current density and excellent mechanical strength. However, coils made with high-temperature superconductors have a high risk of being damaged in the event of a quench due to the intrinsic low normal zone propagation velocity (NZPV). Therefore, the coil protection issue has been regarded as one of the most important research fields in HTS coil applications. Currently, the most actively studied method for quench protection of the HTS coils is the no-insulation (NI) winding technique. The NI winding technique is a method of winding an HTS coil without inserting an insulating material between turns. This method can automatically bypass the current to the adjacent turn when a local quench occurs inside the HTS coil, greatly improving the operating stability of the HTS coils. Accordingly, many institutions are conducting research to develop advanced electrical machines using NI HTS coils. However, the NI HTS coil has its intrinsic charge/discharge delay problem, which makes it difficult to successfully develop electrical machines using the NI HTS coil. In this study, we investigated how this charging/discharging problem appeared when the NI HTS coil was used in an HTS homopolar synchronous machine (HSM) which is one of the electrical machines with a high possibility of applying the HTS coil in the future because it has a stationary field coil structure. For this, the characteristic resistances of HTS coils were experimentally obtained and applied to the simulation model.

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“…Therefore, in order to apply superconducting coils wound with HTS wiring to electrical machines, it is very important to protect the HTS coils from the quenching phenomenon. The approach known as the no-insulation (NI) winding technique is a viable quench-protection method for HTS coils [16][17][18][19][20][21][22][23][24][25]. The NI winding technique involves the fabrication of coils without insulation materials between the turns.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the current flows through the stabilizer layer constituting the superconducting wire, and it is thus bypassed. As a result, NI coils can be protected from quenching without complicated quench detection schemes and/or protection devices, simplifying these HTS coil systems [16][17][18][19][20][21][22][23][24][25]. However, the NI HTS coil is associated with an intrinsic charging/discharging delay phenomenon.…”

Section: Introductionmentioning

confidence: 99%

A Flux-Controllable NI HTS Flux-Switching Machine for Electric Vehicle Applications

2020

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This paper deals with a flux-controllable NI HTS flux-switching machine (FSM) for electric vehicle (EV) applications. In a variable-speed rotating machine for EVs, such as electric buses, electric aircraft and electric ships, an electric motor capable of regulating the flux offers the advantage of constant output operation. In general, conventional HTS rotating machines have excellent flux-regulation performance, because they excite an HTS field coil. However, it is difficult to ensure any flux-regulation capabilities in HTS rotating machines using HTS field coils that apply the no-insulation (NI) winding technique, due to the inherent charge and discharge delays in these machines. Nevertheless, the NI winding technique is being actively researched as a key technology for the successful development of HTS rotating machines, because it can dramatically improve the operational stability of HTS field coils. Therefore, research to implement an HTS rotating machine with flux-regulation capabilities, while improving the operating stability of the HTS field coil using the NI winding technique, is required for EV applications. In this paper, we propose an HTS rotating machine with a flux switching structure, a type of topology of a rotating machine that is being actively studied for application to the electric motors used in EVs. The proposed HTS flux-switching machine (FSM) uses NI field coils, but additional field windings are applied for flux regulation, which enables flux control. In this study, an NI HTS field coil was also fabricated and tested because the characteristic resistance value should be used for the design and characteristic analyses of machines which utilize an NI coil. The simulation model used to analyze the flux-regulation performance capabilities of the NI HTS FSM were devised based on the characteristic resistance values obtained from a charging test of the fabricated NI HTS field coil. This study can provide a good reference for further research, including work on the manufacturing of a prototype NI HTS FSM for EV applications, and it can be used as a reference for the development of other HTS rotating machines, such as those used in large-scale wind power generation, where flux-regulation capabilities are required.

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A Study on the No Insulation Winding Method of the HTS Coil

Cited by 86 publications

References 5 publications

First-cut design of an all-superconducting 100-T direct current magnet

First-cut design of an all-superconducting 100-T direct current magnet

Design and Characteristic Analysis of a Homopolar Synchronous Machine Using a NI HTS Field Coil

A Flux-Controllable NI HTS Flux-Switching Machine for Electric Vehicle Applications

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