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Stacking structure is the widely-accepted method to improve the current carrying capacity of second-generation high temperature superconducting (2G HTS) tapes. Meanwhile, due to the influence of high aspect ratio, narrowing concept becomes an effective way to improve the electromagnetic characteristics of HTS tapes. Solder-Stacked-Square (3S) HTS wire is novel HTS conductor with 1 mm width, which is derived from the normal HTS tapes and combined the meaning of both stacking and narrowing. As is known, the external magnetic field affects the critical current of HTS tapes. In order to get the reliable critical current of 3S HTS wire for the real application, it is important to evaluate the magnetic field dependence of 3S HTS wire in detail. However, the stacking process makes the 3S wire structure flexible and changeable. To be clear about the stacking effect of 3S wire on the critical current, we prepared 3S wire samples, which are respectively stacked by three different structures. In this paper, we measured the magnetic field dependence of critical current for these 3S wire samples. The experimental results are the necessary support for the design of 3S wire applications.

A new HTS maglev vehicle called “KENYON” that can carry 8 passengers was successfully developed in December 2019. The vehicle adopted the bogie structure of independent running gear, which brings the improvement of curve passing performance. In order to further optimize vehicle curve passing performance in view of the small radius curve of the ring test line, corresponding experimental research was carried out in this paper. The experimental results show that the small wheelbase and centripetal arrangement were beneficial to improve the vehicle's curve passing ability.

China Fusion Engineering Experimental Reactor (CFETR) is a major scientific project independently designed and developed by China and jointly with international cooperation. Engineering design and project infrastructure construction are currently underway. The design goal of CFETR is 1.5–2.0 GW fusion power, and the central magnetic field is up to 15 Tesla, which is much larger than the design parameters of ITER under construction in Europe. In order to achieve the desired high magnetic field, the pre-research of Bi-2212 high temperature superconducting CICC magnet was carried out. The performance test of Bi-2212 cable is the most direct criterion for the successful development of the cable. New cable performance judgment method is proposed because of the long test time and high test cost of sub-size cables. Two cables are manufactured, and one cable is disassembled into single wires for performance evaluation. If the performance of single wires is not significantly attenuated in comparison with the performance of single wires that have not been twisted, we will conduct the second cable critical current test. The test results show that the method of dismantling the cable test is feasible. It is also feasible for cables of different structures. This method can be used to judge the performance of the cable in advance. This method is only suitable for detecting damage in the cable manufacturing process.

The Tri-axial high temperature superconducting (HTS) cable usually subjects to the impact of the fault currents in the power system. During the fault, a large amount of the Joule heat is generated, which may be damage cable. In this paper, an analysis model of electromagnetic thermal transient characteristics of the 10 kV/1 kA cable is built. The transient characteristics of the HTS cable are analyzed under a fault current of 15 kA rms lasting 0.14 s, and the current, resistance and temperature of the HTS cable are obtained. The maximum temperature of the HTS cable is 153.1 K under fault current. Meanwhile, the safe operating range of the HTS cable under the fault current of 15 kA to 25 kA is obtained. the analysis results will provide the theoretical basis for the quench protection and relay protection strategy of the tri-axial HTS cable in the Grid.

Combining several high temperature superconducting (HTS) tapes into an assembled HTS conductor can enhance the current-carrying capacity, mechanical strength and improve the large width-to-thickness ratio of HTS tapes. And in practical applications, joints can extend the assembled HTS conductors to required lengths. Therefore, encapsulated joints for Soldered-stacked (SS) wire has been proposed as a preliminary study to achieve long length Soldered-Stacked-Square (3S) wire. And in this paper, we numerically study the performances of different types of encapsulated joints. Firstly, encapsulated joints are divided into two categories according to their positions, and a nonlinear circuit model is presented to demonstrate the numerical study process and experiments are conducted to determine the parameters in this model. Then, resistance performances of the encapsulated joints are discussed such as the “multilinear resistance” phenomenon where the encapsulated joints show different resistance under different current. And HTS tape arrangements in the encapsulated joint are also discussed to achieve minimum resistances.

The tube structure is an important guarantee for the dynamic stability of the high temperature superconducting maglev-evacuated tube transport (HTS Maglev-ETT) system, it is necessary to conduct relevant research on it. Based on simulation calculations with the FLUENT software, this paper studied the influences of different tube section forms on the aerodynamic drag of maglev train in tube, as well as the pressure distribution in the tube system. In addition, the effects of the setting of cross aisle on the aerodynamic drag of maglev train and pressure fluctuation of flow field in tube were also studied. It was found that the difference in the section forms of tube has little effect on the aerodynamic drag of maglev train and pressure distribution of the tube system under low pressure; the setting of cross aisle can be helpful to reduce the aerodynamic drag of maglev train and the pressure fluctuation around the train to a certain extent. Therefore, the design of cross aisle is recommended for the HTS Maglev-ETT system.

In the field of high-temperature superconductors, atom probe tomography is a relatively new instrument, with the ability to provide a new perspective on the 3D nanoscale microstructure. However, field evaporation of nonmetallic materials is fraught with unique challenges that matter little in the world of metallic evaporation. In this study, we review the laser absorption, correlated evaporation, molecular dissociation, and the crystallographic effects on the field evaporation of 800-m ${\rm RB}{\rm a}_ 2{\rm C}{\rm u}_ 3{\rm O}_{ 7-{\rm \delta }}$ (R = Gd, Sm) coated conductor tapes deposited by Reactive Co-Evaporation Cyclic Deposition and Reaction (RCE-CDR). Ultraviolet 355 nm laser pulsing was found to have a substantial beneficial effect on minimizing the fracture probability compared with 532 nm illumination, especially when evaporating insulating oxide precipitates. This, in turn, allows for the 3D compositional analysis of defects such as flux pinning centers introduced by precipitation and doping. As a result, evidence for the precipitation of nanoscale ${\rm G}{\rm d}_ 2{\rm C}{\rm u}_ 2{\rm O}_ 5$ is discussed. The effect of crystallographic orientation is studied, where [001] aligned evaporation is found to develop compositional aberrations.

Superconducting devices composed of the second-generation high-temperature superconducting (2 G HTS) RE-Ba-Cu-O (REBCO, RE is rare earth) tapes have extensive applications in high magnetic flux den...

Experiments on quench propagation in high-current, high field High Temperature Superconducting (HTS) Cable-In-Conduit Conductors (CICCs) for fusion applications are forthcoming. Among the conductor designs to be tested, there is the ENEA slotted core proposal. In order to support the design of the samples and plan the diagnostics to be employed, a 1D multi-region thermal-hydraulic and electric model of the samples has been developed using the H4C code. After an experimental electric characterization, the model is applied to the simulation of quench propagation in the samples. The simulations show how current redistributes among the tapes and the slots. Additionally, they show that the quench protection strategy is suitable to prevent too high hot-spot temperatures.

The performance degradation of High Temperature Superconducting (HTS) tape, which may be influenced by various heat exchange conditions due to different cooling methods, is of significant for HTS devices under repeated overcurrent. In this article, considering different heat exchange conditions, a series of repeated overcurrent experiments were carried on YBCO tapes under 50Hz sinusoidal alternating current. The degradation of critical current of YBCO tapes after repeated overcurrent was recorded. the resistance characteristics of YBCO tapes under different cooling conditions were analyzed. Through finite element simulation, the temperature and current distribution of YBCO tape under different heat exchange conditions were simulated. The experimental results show that the overcurrent capability of the conductor under conduction cooling is far inferior to the liquid nitrogen immersion method.

Nuclear magnetic resonance (NMR) probes using thin-film high temperature superconducting (HTS) resonators offer high sensitivity and are particularly suitable for small-sample applications. We are developing an improved 1.5 mm HTS NMR probe designed for operation at 14.1 T and optimized for (13)C detection. The total sample volume is about 35 μL and the active sample volume is 20 μL. The probe employs HTS resonators for (13)C and (1)H transmission and detection and the (2)H lock. We examine the interactions of multiple superconducting resonators and normal metal tuning loops on coil resonance frequency and probe sensitivity. We test a recently introduced (13)C resonator design, engineered to significantly increase (13)C detection sensitivity over previous all-HTS probes. At zero field, we observe a (13)C quality factor of 6000 which is several times higher than previous resonators. In this work the coil design considerations and probe build-out procedure are discussed.

This paper presents a 14-pole dual-band high selective high temperature superconducting (HTS) filter including two narrow notches. A flexible half-wavelength resonator, two cross-coupling structures and a novel feeding structure are proposed and analyzed successively. The HTS filter is fabricated on a 2-inch-diameter double-side DyBa2Cu3O7 HTS thin film with a 0.5-mm-thick MgO substrate and measured with a low-temperature test system at 65 K. The measured results show that the filter has 1 dB passbands of 1363–1440 MHz and 1490–1566 MHz, respectively. The filter has two narrow notches with maximum notch depths of more than 30 dB. Due to the cross-coupling structures, five transmission zeroes are located at both sides of the two passbands, which further improve the selectivity of the filter. The measured results are in good agreement with the simulated ones.

The alternating current (AC) loss is a key consideration of the operation economy and stability of the high temperature superconducting (HTS) cables. In this paper, the sources of the AC loss in the HTS cable are analyzed firstly. The three-phase HTS cable, adopted in the 35 kV km-level HTS cable demonstrating project in Shanghai, China, is modeled by the finite element method (FEM) to calculate the AC loss by the COMSOL Multiphysics. The AC loss of the designed 35 kV HTS cable is 1.31 W/m. The theoretical calculation method is also implemented to verify the modeling results. Furthermore, considering the on-site conditions of the demonstrating project in Shanghai, China, the calorimetric method is conducted by measuring the temperature difference between the inlet and outlet of liquid nitrogen. The obtained results provide useful indications for the future design and research of HTS AC systems.

With the gradual complexity of the high temperature superconducting (HTS) applications, the calculation model of large-scale devices is time-consuming. A semi-homogeneous modeling method based on the T-A formulation is proposed to study the electromagnetic characteristic of HTS magnet. Compared to the homogeneous model, the proposed model can improve the calculation accuracy without compromising speed. The model in this paper is beneficial to the design, rapid optimization and evaluation of the HTS magnet.

The 35-kV km-level domestic high-temperature superconducting (HTS) power cable project in Shanghai, China, is expected to be deployed in 2021. Facing the complex operating environment in the metropolitan area, such as the vibration excitation from the subway, pile driving, and seismic activities, the vacuum degree, sealability, and insulation performance of the HTS cables may be affected by the unavoidable mechanical perturbations. The response to the potential vibration excitation is a key factor for the safety and stability of the HTS cables in operation. Therefore, this paper conducts a set of vibration testings for the HTS cable under four kinds of vibration conditions, which include the subway vibration, pile-driving vibration, typical earthquake vibration, and Shanghai artificial wave vibration. Results show that the leakage and outgassing rate of the HTS cable is 1.3×10−6 Pa m3/s at a static state, and increases to 1.4×10−6 Pa m3/s after the vibration testing. The HTS cable exhibits insignificant changes after the vibration testings in the dielectric spectrum examination. The HTS cable can keep its function after the vibration testing that possibly occurred in the metropolitan area.

The design considerations of AC machines with windings made of high-temperature superconductors (HTS) are presented in the following paper. The considerations were narrowed to permanent-magnet excited machines, although the results can be extrapolated to many other machine types as general guidelines. The influence of basic machine parameters and coefficients during the design of such machines are considered in order to estimate operating conditions of HTS windings. The number of poles, number of slots or slot dimensions, coil placement, and arrangement, are taken into account with the intent to fully utilize features of superconducting materials such as the capability of conducting high current density without significant losses. The attention is placed on low power machines, below 1 kW, operating at liquid nitrogen temperature (77 K). For analysis purposes, the finite element method (FEM) is used to calculate the distribution of the magnetic field and its effect on the critical current of the HTS coil. The numerical analysis is carried out in ANSYS software.

The search for superconductors with high values of the critical temperature has started shortly after the first observation of the phenomenon in 1911. At present, there are several paths towards reaching this goal. Here we focus on the direction based on observing high temperature superconducting state in some metallic nanoclusters. The macroscopic high Tc superconducting current can be provided by the Josephson tunneling between such clusters.

In this article, the operating current and torque of surface-mounted permanent magnet (SPM) wind power generators with high-temperature superconducting (HTS) armature windings are analyzed. The influence of coil location and current angle on the electromagnetic performance is investigated systematically. The results show that the location of the HTS coils significantly affects the operating current and torque. Furthermore, the maximum torque current angle of SPM wind power generators with HTS armature windings can be different from 180° due to the interaction between the armature and magnet fields. A design optimization method for wind power generators with HTS armature windings is developed in this article. The optimal design is then identified with consideration of the coupling influence of coil location and current angle.

Optimization of the helically-winding structure required for the helical fusion reactor utilizing the high temperaturesuperconductor (HTS) tape is studied by numerical calculation. When the HTS tapes are wound to bethe helical structure without the torsion, a significant edgewise strain appears. This might lead to the degradationof the performance of the HTS tape. Therefore, the edgewise strain must be minimized. It is found that the edgewise strain can be suppressed by the proper determination of the torsion by the optimization utilizing the Fourier decomposition of the distribution of the edgewise strain. The HTS tapes with edgewise strain are intrinsically deformed due to the torsion to reduce the edgewise strain so to be an “edgewise-strain-free” helical shape.

Given the unique electrical and magnetic properties of superconductors, high temperature superconducting (HTS) transformers will play a central role in the electricity industry in the future. Therefore, identification and analysis of this type of transformers seems necessary and indispensable. To date, many types of development plans for HTS transformers have been carried out by major power companies and important research institutes, and it is expected that this type of transformers will become one of the superconducting power equipments installed at the first stage of commercialization in the power system. However, a review of reports and papers published in this field shows that there is still much work to be done to improve the design and performance of these transformers. This article presented a review classified by subject of previous research to help orient future research into the design, analysis, and manufacturing of this type of transformers.

Precursor powders of Bi2Sr2Ca2Cu3O10+δ (Bi-2223) high temperature superconducting tapes were prepared with spray pyrolysis technique. By tuning the oxygen partial pressure in calcination atmosphere as 1.0%, 7.5%, and 10.0%, respectively, the influences of calcination atmosphere on the phase evolution dynamics during the precursor powders calcination process have been discussed. Then the optimal calcination temperatures have been obtained correspondingly. Moreover, Bi-2223 multi-filament tapes have been fabricated with the precursor powders calcinated under different atmosphere. The effects of precursor powder calcination parameters on the phase composition, microstructures as well as the current capacity of final tapes have been systematically studied. Due to the proper secondary phase content and enhanced Bi-2223 texture structures, the maximum critical current of 109 A at 77 K, self-field, corresponding to the critical current density of 23.3 kA cm−2 has been obtained with the oxygen partial pressure of 7.5% in calcination atmosphere and the calcination temperature of 790 °C.

Utilization of superconducting equipment increases every day due to availability of the HTS tapes with reasonable prices, commercially. Since 1997, many high-temperature superconducting (HTS) transformers have been designed and fabricated. In this paper, all the different developments of HTS transformer windings since 1997 will be reviewed. Additionally, the advantages and disadvantages of the application of the two main winding types (the pancake and the layer) in the HTS transformer will be studied.

The performance degradation of superconducting equipment under repeat fault is a key issue for the operation of superconducting equipment in grid operation. The mechanism of the High Temperature Superconducting (HTS) tape performance degradation behavior is an important issue that need to be figured out. Therefore, it's necessary to carry out the performance degradation study of HTS tape under repeat overcurrent. In this paper, considering overcurrent duration, a series of repeated overcurrent experiments were carried on YBCO tapes under 50 Hz sinusoidal alternating current. The degradation of critical current of YBCO tapes after repeat overcurrent was recorded. The critical current density of the YBCO tape was scanned to track sample's structural change during experiment. The mechanism of the degradation development of YBCO tapes after their first degradation was described. The research could provide a reference for the design of fault protection and life assessment of HTS devices.

In a high voltage dc (HVDC) high temperature superconducting (HTS) cable composed of polypropylene laminated paper (PPLP), butt-gaps are unavoidable during fabrication, which may lead to formation of voids. When dc voltage higher than partial discharge inception voltage (PDIV) is applied, partial discharge occurs in the void. If void discharge sustains, the electrical ageing of PPLP accelerates, and eventually dielectric breakdown may occur due to the lowering of dielectric strength. Thus, for timely maintenance and repair of HVDC HTS cable, identification technology for void defects is required. However, there is no previous research and technologies for defect identification and insulation diagnosis on HVDC HTS cables. Therefore, in this paper, in order to suggest the insulation diagnosis method for void defects of the HVDC HTS cable based on the pulse sequence analysis (PSA) method, void discharges were measured according to the size of void and magnitude of applied voltage. Also, patterns of the void discharge were obtained using PSA methods and PYTHON program. Experimental results indicate that, although the magnitude, time difference and repetition rate of partial discharge are different depending on the configuration of the void and the applied voltage, but the patterns of void discharge are consistent. Therefore, it is considered that identification and insulation diagnosis for void defects in HVDC HTS cable is possible through the obtained DC void partial discharge patterns.

With the development of the high temperature superconducting (HTS) materials technology, the manufacturing process of the HTS tape has been further improved and hundreds of meters of HTS tapes have been applied in industry. In beneficiation field, the magnetic separation facility of using HTS technology can not only improve the work efficiency of the material purification and separation, but solve the problem that some weak magnetic materials are difficult to separate due to the high magnetic intensity and gradient. Today, a 3.5 T HTS magnetic separation facility cooled by a cryocooler was manufactured in China. This paper focuses on the manufacturing process and performance test of the HTS magnet. Some new structure was adopted in the design and manufacture of the magnet and verified in the magnet performance test. Test results indicated that the magnet could be cooled below 20 K by the direct heat conduction, the center magnetic field could reach 3.57 T and the center axis uniformity of the magnetic field was better than 95% in the range of ±100 mm from the mid-plane. In short, the magnet design is reasonable and it is likely to be applied on other similar magnet in future.

This paper introduces a insulation design for a 10 kV three-phase concentric high temperature superconducting (HTS) cables with cold dielectric mode. Insulation properties of PPLP (Polypropylene laminated paper) and its dielectric strength under AC voltage endurance test and the lightning impulse test in liquid nitrogen have been performed. According to test results and the standard for 10 kV paper insulation cable, the main insulation and the stress cone for the 10 kV three-phase concentric HTS cables have been designed. The voltage endurance test under power frequency and the lightning impulse test have been carried out, indicating that the cable is complied with the insulation requirements.

Bi 1.76 Pb 0.34 Sr 1.93 Ca 2.02 Cu 3.06 O 10+δ (Bi-2223) high temperature superconducting tapes were fabricated with Powder in tube (PIT) process. The traditional drawing process was partially replaced by groove rolling. The influence of cold working method on the filament density, the phase evolution mechanism as well as superconducting properties has been systematically studied. The groove rolling process could obviously enhance the filament density of Bi-2223 green wires, which thus led to the change of Bi-2223 formation rate. Meanwhile, although the heat treatment process has not been thoroughly optimized, the residual secondary phase content was still high, the critical current has been improved for more than 20% with groove rolling process, which should be attributed to the improved intergrain connections. On the other hand, the groove rolling process was also effective on the fabrication of Bi-2223 tapes with larger filament number, such as 85 or 121 to maintain the uniformity of filament deformation.

The application of High Temperature Superconducting (HTS) technology in the maglev field has met a giant improvement in the recent years. With the success in the laboratorial test lines, the scientists started to focus on the research of practical issues on reality applications. Lately, our team devoted ourselves into the study of Electromagnetic Guideway (EMG) for improve the flexibility and the practicability of guideway in an HTS maglev system. In this paper, a fan-shaped EMG was proposed, its basic unit was analyzed through magnetic equivalent circuit method, in order to decide the rated magnetomotive force. Afterward, a prototype was made to verify the design feasibility, the comparison among three arrangements of HTS bulks were carried out with the experiments under different measuring conditions. The levitation and guidance performances of each arrangement were comprehensively discussed as the summary.

This paper introduces the basic situation of the 35-kV domestic high temperature superconducting (HTS) power cable project in Shanghai. The target of this project is to construct and put into operation the first 35-kV km level three-phase turn-key HTS power cable project in the world. The cable transmission capacity, cable routing selection, cable structure design, cooling system configuration, etc. of the project are introduced. The project is implemented by the State Grid Corporation Shanghai Electric Power Company. A 35-kV, 1.2-km-long 220-kV inter-substation connecting HTS cable line will be constructed in the core urban area of Shanghai. So far, the type test of the HTS power cable system has been completed, and the construction of the project has begun. The project is expected to be completed and put into operation in the second half of 2020.

Bi-2212 wires, which have high critical current density and critical magnetic field without anisotropy, offer significant potential applications for ultrahigh-field superconducting magnets. The Bi-2212 wire is very sensitive to strain. The strands are inevitably subjected to cyclic thermal or electromagnetic stress during application. There is a lack of understanding regarding the fatigue properties. In this paper, the degradation behavior of critical current for Bi-2212 wires under axial tensile fatigue loading was investigated. It was found that the fatigue life decreases with the increase in maximum fatigue stress.

A cold dielectric high temperature superconducting (HTS) cable system, which consists of 100 m three-phase cables, terminals, cryogenic system, and monitoring system, was developed by Futong Group in Tianjin. The rated voltage and rated current of the HTS cable system was designed to be 35 kV and 1 kA, respectively, and the YBCO tapes provided by SWCC were used as the conductors and shielding layers. The HTS cable system was installed at Futong Science Park and put into operation on February 15, 2017. Since then, the HTS cable system has been running stably for more than 20 months with an operating current of ∼200 A at a coolant temperature from 72 to 77 K.

Designs of three-phase high-temperature superconducting (HTSC) cables with shielded phases have been studied. Phase sectioning, use of HTSC tapes with changed configuration, and changing the phase diameter have been proposed as methods to optimize these cables. These methods make it possible to decrease the total electromagnetic losses from 0.3 to 0.01 W/m.

High-temperature superconducting (HTS) maglev has the potential in high-speed transportation owning to its capability of passive stabilization. As an important research field of vehicle dynamics in HTS maglev area, the curve negotiation performance is in connection with the vehicles’ operational safety and comfort. This article reports the curve negotiation performance of the HTS maglev through three steps. First, the guidance force is measured to determine the safe motion range, and the range will be used as the indicator of the safety. Second, the dynamic model of HTS maglev vehicle “Super-Maglev” is established and compared with the experimental results to verify the correctness. The magnetic guideway irregularity is measured, and the measured value is used as the input of dynamic simulation. Finally, the dynamic curve negotiation characteristics of maglev vehicle are simulated. Results show the HTS maglev freight vehicle can safely pass through the curves at a certain speed without external rail superelevation. However, as a passenger vehicle, it can pass through the curve safely and smoothly when the suspension system and the superelevation are added. The curve radius of HTS maglev line, the superelevation outer rail, and the suspension parameters of maglev vehicle are also suggested in this article.

We present electronic structure calculations of rare earth doped Ca1−xRxFeAs2, 112 Fe-based high temperature superconducting materials with special emphasis on Sb doping at the chain As-site. The e...

Electrical insulation is an essential component of high temperature superconducting (HTS) dc cable systems and polypropylene laminated paper (PPLP) and has been widely used as insulation material for cold dielectric (CD) HTS cables due to its excellent dielectric mechanical properties. In this paper, mini-model cables were fabricated to simulate CD-type HTS cables and the insulation tests were carried out. DC and the lightning impulse breakdown strength of the 1% Weibull distribution of PPLP at 0.3 MPa helium gas (GHe) were investigated. Based on these results, the insulation design of a 10-kV bipolar coaxial HTS dc cable was performed. Furthermore, a model cable was manufactured according to the insulation design and tested for dc and impulse withstand voltage, which verified that the insulation design was qualified.

An air-core high-temperature superconducting quadruple magnet (AHQM) is composed of high-temperature superconductor (HTS) coils without an iron yoke. An AHQM exhibits magnetic field characteristics that vary linearly with respect to changes in the operating current. Further, the AHQM is more suitable for use in high heat load regions. A conventional iron-core quadruple magnet (IQM) contains an iron yoke to achieve the specific shape and magnitude of the magnetic field. In the case of IQMs, the iron yoke generates most of the magnetic field. In the case of AHQMs, the magnetic fields are generated solely by HTS coils. Thus, an AHQM requires a larger number of coils to generate a magnetic field, because the iron yoke has been removed. Consequently, the influence of manufacturing errors in the AHQM is high; these errors deteriorate the designed magnetic field. Therefore, magnetic field correction is required to reduce the deterioration in the magnetic field of an AHQM. This paper, proposes a novel active shim method to compensate for the deteriorated magnetic field of an AHQM. This method improves the uniformity, but does not affect the gradient and effective length of the quadruple magnet. The effectiveness of this method is verified by simulation.

Utilizing high temperature superconducting (HTS) magnets coupled with iron core on the rapid cycling synchrotrons is considered as an effective way to reduce their construction and running costs. However, the heat generation by ac loss in HTS wires is a critical obstacle for the application, and prediction and reduction of ac loss in HTS magnets coupled with iron core are essential. In this work, we built one HTS double pancake coil (DPC), a stack of two DPCs, and an iron core comprising laminated steel to couple with the coil windings. The HTS-coated conductors are 200 A-class 4-mm–wide Shanghai Conductors. We report the ac loss measurement results on the coil windings with/without the iron core at three different frequencies. The ac loss in the HTS windings was significantly increased due to the existence of the iron core. Increasing the number of stack of the DPCs may help reduce the difference in ac loss values in the coil windings with/without iron cores.

We have proposed a new system using pick-up coil pairs to detect normal transitions in the high temperature superconducting (HTS) coils which are applied to several applications, high field magnets, SMES, transformer, and so on. In the previous study, we have demonstrated that our system can detect local normal transitions in the winding of the test transformer wound by Bi-2223 multifilamentary tapes even if the operation of the transformer is ongoing. However, it is not sufficient to detect normal transitions for operations of practical devices because sudden breaks are not allowable for practical operation. It is important that soundness of the coil, such as critical currents, are monitored and diagnosed for actual operation of practical superconducting devices. In this paper, the external magnetic fields and temperature dependences of signals measured by our system are investigated, in order to make possible to diagnose soundness of the windings from the signals. And then it is shown that critical current of the windings, as an indicator of soundness, can be estimated under ac operation. The diameter of the sample coil is 70 mm. The results indicate that the critical currents of the winding can be estimated from our measured signals.

In South Korea, Korea Electrotechnology Research Institute (KERI) has developed a 154 kV smart High Temperature Superconducting (HTS) cable system with fault current limiting function since May 2017. This project is funded by the Ministry of Trade, Industry, and Energy of Republic of Korea. It is very important to design the protective relay system for a successful application of the smart HTS cable system to a practical power grid. In general, the smart HTS cable can have a negative impact on the protective coordination in power transmission system because of the variable impedance of the cable. This paper reviews some protection problems which can be caused by the application of the 154 kV smart HTS cable to power transmission systems in Korea and proposes a protection scheme for a test power system. And then we conduct a basic study to find solutions for the problems using an electromagnetic transient program, PSCAD/EMTDC.

Flux pumps are a type of wireless superconducting power supply which can provide advantages over traditional superconducting systems. This work reports on time-domain circuit simulations in LTspice of a transformer-rectifier flux pump. The simulations are compared with an experimental system employing ac-field switches and show good agreement. Further simulations show that a key component for the advance of transformer-rectifier flux pumps is the development of improved superconducting switches. Work to date by the authors towards developing high temperature superconducting (HTS) switches with high off-state resistance, fast recovery time and high critical current is reported on. Future work is detailed, and it is concluded that if improved HTS switches are developed, flux pumps will be a competitive technology and may start to replace conventional superconducting power supplies.

High temperature superconducting (HTS)-coated conductors show various advantages in practical applications because of its zero resistance and large current capacity. Owing to the superior properties of HTS material in high magnetic fields, the HTS linear synchronous motor (LSM) is able to output high performance at relatively large air gap. Many experiments and prototypes have been implemented, which requires great consumption of HTS-coated conductors. In this paper, an analytical model of coreless HTS LSM was established and the magnetic flux density dependence of the critical current density of HTS-coated conductors was taken into account. An HTS-generalized racetrack coil was introduced to the analytical model for easy parameterization. A small scale prototype of the LSM which has a coreless stator and a HTS secondary was manufactured to validate the analytical model. It is indicated that the calculations have a good agreement with the experiments. As an application of the analytical model, an optimization task of the HTS LSM was carried out to improve its performances.

In order to improve the high torque density of coaxial magnetic gear, a novel high temperature superconducting (HTS) bulks coaxial magnetic gear (CMG) with an eccentric pole of inner rotor and Halbach arrays of outer rotor is proposed in this paper. According to the Meissner effect, the HTS bulks replace the traditional epoxy resin to improve the flux-modulation effect. Moreover, the HTS bulks CMG has an eccentric structure of permanent magnets (PMs) on inner rotor and has Halbach PMs arrays on the outer rotor. The proposed HTS bulks CMG topology with 4 inner and 23 outer pole pairs is established. The topology performance is assessed and verified by finite element analysis.

In this paper, the I c degradation of bent YBCO tapes has been experimentally studied. The I c characteristics in length direction was measured through a non-contact, continuous I c measurement equipment (Mcorder), which is suitable for all kinds of high temperature superconducting (HTS) tapes. The detailed J c mapping of bent tapes was investigated by a Hall microscopy equipment (Mcorder 2-D), which scans the fields distribution on the surface of the films or bulks. A 4.1-m-long YBCO tape was wound on a 4.5-mm-diameter core with YBCO face outside or inside. The critical current of the YBCO tape before and after winding was measured lengthwise. And the 2-D J c map of the samples of degraded sections was measured. The result shows that the smallest safe bending diameter is larger than 14 mm and smaller than 4.5 mm, for YBCO face outside and inside, respectively, which indicates that the YBCO face is recommended to be inside in bending cases. The relation between critical current of YBCO face outside bent tapes and diameters was fitted to a sigmoid-like function, to help further development where YBCO face outside bending is unavoidable.

We have been developing a liquid-helium-free magnet using High-Temperature Superconducting (HTS) wire for MRI. The aim of this research and development is to commercialize a 3-T HTS magnet for whole body MRI which has the characteristics of being liquid-helium-free, small, and light-weight. HTS coil requires tolerance of a high magnetic field, 7 T, and it must have high current density, 200 A/mm 2 , for developing a small and light weight magnet used for 3-T MRI. A half-size 5-T HTS magnet will be manufactured in order to demonstrate the tolerance of high magnetic field and high current density of the coil, which are equivalent to a whole-body 3-T MRI magnet in a half-size HTS magnet. In this paper, we have investigated the arrangement of coils of a half-size 5-T coil. The designed coil consists of 124 double-pancake coils, whose inner diameter is 560 mm, outer diameter is 1200 mm, and axial length is 1100 mm. The uniformity of designed magnetic field is under 2.0 ppm (250 mmDSV).