Applications Of High Temperature Superconductors Research Articles

DEVELOPMENT AND TESTING PROTOTYPE OF HTS MODULE FOR THE SYSTEM OF MAGNETIC LEVITATION OF VEHICLE

In recent years increasingly discusses the prospects of application of high-temperature superconductors (HTS) as the winding current-carrying elements of magnetic systems for various purposes. It seems particularly attractive possibility of such systems at liquid nitrogen temperature. The article describes the prototype of module of the magnetic system which is made on the basis of high-temperature superconducting tapes, designed for the installation and testing on a working model of a static levitation. In the working model levitation of the platform carried by the interaction of the magnetic field of the assembly of permanent magnets mounted on the platform with a field similar to assemblies located in the track structure. Compact HTS module replaces the two assemblies of permanent magnets mounted on the platform. Each block of the module represents HTS racetrack coil with current inputs, power structure, positioning system and bracing which is placed in a cryostat, providing at minimum wall thickness of the required mechanical strength and thermal insulation at liquid nitrogen temperature. The prototype of unified superconducting module successfully passed preliminary tests.

Combined magnetic screen made of Bi-2223 bulk cylinder and YBCO tape rings—Modeling and experiments

Recent advances in the measurements with sensitive magnetic field sensors made the issue of magnetic shielding important. The application of high temperature superconductors allows to obtain full shielding in zero field cooling conditions for DC and low frequency magnetic fields by the means of the Meissner effect. However, currently used conventional bulk magnetic shields maintain full shielding only in low magnetic fields—up to approximately 10 mT. In this paper, it is proposed to apply an additional screen made of a coated superconducting tape in order to increase the magnetic field interval of full shielding region. Computer model of such set of screens was created in Matlab and validated experimentally. Improvement of shielding quality was observed experimentally and calculated with the model.

Effect of variations in terminal contact resistances on the current distribution in high-temperature superconducting cables

Future application of high-temperature superconductors in large volume, high field magnets and in magnet current distribution systems requires cabling of RE-Ba2Cu3O7 − δ coated conductor tapes. The substantial aspect ratio of RE-Ba2Cu3O7 − δ coated conductors and the highly resistive buffer layers in these tapes make the development of compact and homogeneous cable terminals complex. The contact resistance between individual tapes and the cable terminations of two types of high-temperature superconducting cables was determined at 77 K at relatively low current ramp rates using a non-destructive method. The current distribution between tapes in the cables caused by a variation in contact resistance was calculated with a simple model, which was validated using different experimental methods. The results show that the current distribution at low current ramp rates in cables made from RE-Ba2Cu3O7 − δ coated conductors is mainly dictated by the variations in contact resistances between tapes in the cable and the cable terminals. Development of practical cable terminals that minimize the variations in contact resistances is therefore instrumental for the successful application of high-temperature superconducting cables in magnets.

Large Scale Applications of HTS in New Zealand

New Zealand has one of the longest-running and most consistently funded (relative to GDP) programmes in high temperature superconductor (HTS) development and application worldwide. As a consequence, it has a sustained breadth of involvement in HTS technology development stretching from the materials discovery right through to burgeoning commercial exploitation. This review paper outlines the present large scale projects of the research team at the newly-established Robinson Research Institute of Victoria University of Wellington. These include the construction and grid-based testing of a three-phase 1 MVA 2G HTS distribution transformer utilizing Roebel cable for its high-current secondary windings and the development of a cryogen-free conduction-cooled 1.5 T YBCO-based human extremity magnetic resonance imaging system. Ongoing activities supporting applications development such as low-temperature full-current characterization of commercial superconducting wires and the implementation of inductive flux-pump technologies for efficient brushless coil excitation in superconducting magnets and rotating machines are also described.

Heat transfer from Ni–W tapes in liquid nitrogen at different orientations in the field of gravity

Ni–W tapes of the micrometric thickness are considered as the basis for the cost-effective manufacturing of coated conductors – the 2nd generation of high-temperature superconductor (HTS). Many HTS applications involve widely-available and inexpensive liquid nitrogen. The transition from superconducting to normal state may however occurs due to unexpected temperature fluctuations. In this case Ni–W tape is significantly heated by electrical current propagating through it. The amount of heat transferred from the tape to coolant is defined by heat transfer from the surface of tape to liquid nitrogen. The heat transfer, in turn, is strongly dependent on the tape orientation in the field of gravity. The present paper reports the experimental results on the heat transfer from Ni–W tape to a pool of liquid nitrogen. The heat transfer coefficients are quantified for three subsequent heat transfer regimes: natural convection of liquid nitrogen, nucleate boiling regime and film boiling. The dependence of heat transfer coefficient on inclination angle of the tape from vertical are experimentally clarified for each regime. The expression for the heat transfer coefficient at different inclination angles is derived for the case of nucleate boiling.

Research Progress of High Temperature Superconducting Filters in China

Recent developments in China for the design and application of high temperature superconducting (HTS) filters are reviewed. Progress in fabrication of HTS thin films with various physical and chemical methods are introduced first, since high quality double-sided thin films provide the groundwork for filters. In the past decade, hundreds of HTS filters have been designed in China with excellent performance, e.g., 0.05 dB minimum insertion loss, -23 dB return loss, -110 dB out-of-band rejection and 220 dB/MHz band-edge slope, etc. Novel design methods, i.e., coupling matrix extracting method, bandpass filters with wide stop band, linear phase filters, multiplexers, multi-band and multi-mode filters as well as tunable filters will be discussed in detail. Applications to mobile communication base stations, meteorological radar, deep space detection and satellite technology will be also reviewed.

A Novel Calorimetric Method for Measurement of AC Losses of HTS Tapes by Optical Fiber Bragg Grating

This paper presents an innovative calorimetric method for measurements of ac losses of high-temperature superconducting (HTS) tapes by using the effect of optical fiber Bragg grating (FBG) wavelength shift resulting from temperature change caused by ac losses, where it is adopted as a temperature sensor. The HTS specimen on which the FBG is attached on are adiabatically processed before measuring. Compared with conventional electric and calorimetric methods, FBG temperature sensor has the advantage of rapid response and anti-electromagnetic interference due to its thin geometrical sizes and optical characteristics; it is thus very suitable to ac loss measurement of HTS applications in much more complicated electromagnetic circumstance. By measuring the effect of temperature on wavelength shift in low temperature range, it is indicated that FBG has good-enough repeatability of dependence of wavelength shift on temperature measurement around liquid nitrogen temperature of 77 K. After calibration, ac loss of BSCCO HTS tape in self-field is measured by the FBG sensor, and the measured loss is also measured by conventional electric method using a lock-in amplifier. It is shown that the measured ac loss is in agreement with the results measured by electric method and those based on Norris theory so that the presented calorimetric method is available for measuring the ac loss of superconductors and expected to be generalized to ac loss or thermal measurements of other bulk superconductors.

Review of AC Loss Measuring Methods for HTS Tape and Unit

AC loss measuring methods of high-temperature superconducting (HTS) tapes and units, generally consisting of electronic, magnetic, and calorimetric techniques, have matured and made great contributions to ac characteristics of HTS materials, research, and development of HTS applications. This paper briefly introduces and summarizes the principles of ac loss measurement techniques, focusing particularly on electric and calorimetric method for measuring ac losses of HTS tapes. A novel developed calorimetric method for measuring ac loss based on optical fiber Bragg grating (FBG) was introduced a little bit in detail. After comparing the sensitivities of various measuring methods, ac loss measuring methods available for HTS tapes and units are suggested.

Estimation of the Engineering Critical Current Criteria for HTS Wire Carrying an Alternating Current

This paper deals with a method to estimate the engineering critical current criteria for high temperature superconducting (HTS) wire in alternating current (ac) operation. There are plenty of high temperature superconducting devices used in ac operation, such as superconducting fault current limiters and superconducting cables. However, the operating currents of those ac superconducting devices are mostly designated by the critical current measured in direct current operation based on International Electrotechnical Commision (IEC) 61788-3, so the engineering critical current criteria of the HTS wire for ac operation is needed. In this paper, the engineering critical current criteria of HTS wires for ac operation are estimated considering the odd harmonic electric fields, the calculated ac loss, and the temperature. The authors expect that the method and approaches used in this study will help to estimate the engineering critical current and to decide the operating currents of HTS applications.

Experiment and Numerical Simulation on Quench Detection in Cryocooler-Cooled YBCO Coil for SMES Application

In the real application of high-temperature superconducting (HTS) coils to a superconducting magnetic energy storage (SMES) system, coated conductors are cyclically subjected to tensile strain due to electrical charging and discharging. A quench is not only caused by failure in the power supply and cooling system but also could be induced by local deterioration of the superconducting characteristics because of the cyclic strain during operation. In such a local deterioration case, the conventional detection method using voltage signal for low-temperature superconducting (LTS) coils is not applicable for the HTS coils because of the significantly slow velocity of normal-zone propagation. Furthermore, the voltage detection method is considered to be extremely difficult because the noise of the converters and other equipment is much larger than the local normal-zone voltage of the HTS coils. Therefore, a new quench-detection method for HTS coils is required. In our previous studies, a current detection method was developed for a cryocooler-cooled SMES coil wound with a kA-class laminated bundle conductor composed of four electrically insulated coated conductors. In the present study, experiments and numerical simulations were carried out on a double pancake model coil that assumes real SMES operation to verify the validity of the current detection method.

Numerical evaluation of a novel high-temperature superconductor-based quasi-diamagnetic motor

An investigation is being pursued at the Budapest University of Technology and Economics, Department of Electric Power Engineering for the application of high-temperature superconductors (HTS) in electrical power systems. In this paper we are going to propose a novel electrical machine construction based on the quasi-diamagnetic behaviour of the HTS materials. The basic operation principle of this machine will be introduced with detailed numerical simulations. Also a possible geometric outline will be presented.

Development of a large cooling capacity single stage GM cryocooler

Sumitomo Heavy Industries, Ltd. (SHI) has developed 4K Gifford–McMahon (GM) cryocoolers for various cryogenic fields including Magnetic resonance imaging (MRI) systems. However, for the purpose of cooling high temperature superconductor (HTS) devices, the needs for cryocoolers with a large cooling capacity in the range of 20–30K has been rapidly increasing.Recently, SHI developed a large cooling capacity single-stage GM cryocooler, for HTS applications. A typical cooling capacity is 46/52W at 20K or 85/96W at 30K with 6.9/7.9kW input power at 50/60Hz. The cooling capacity degradation caused by inclination is within 24%.And also, a low mechanical vibration and a low acoustic noise have been achieved because the displacer is driven by a motor instead of a pneumatic force. In addition, the cryocooler does not contain lead as a regenerator material, so it complies with restriction of hazardous substances (RoHS) directive.

Race-track coils for a 3 MW HTS ship motor

Since the discovery of high-temperature superconductivity (HTS), Sumitomo Electric has been developing silver-sheathed Bi2223 superconducting wire and products. Ship propulsion motors are one of the most promising applications of HTS. Sumitomo Electric Industries, Ltd. (SEI) has recently manufactured 24 large racetrack coils, using 70km long DI-BSCCO wires, for use in a 3MW HTS motor developed by Kawasaki Heavy Industries, Ltd. (KHI). The 3MW HTS motor, using our newly developed racetrack coils, has successfully passed the loading test. It is particularly important that the HTS field coils used in ship propulsion motors can withstand the expansive forces repeatedly applied to them. As racetrack type coils have straight sections, the support mechanism they require to withstand expansive forces is very different from that of circular coils.Therefore, we ran tests and obtained the basic data to evaluate the 20-year durability of racetrack coils against the repeatedly applied expansive forces expected in domestic ship propulsion motors.

Flux-Pinning-Induced Stress Behaviors in a Long Rectangular Superconducting Slab With a Central Rectangular Hole

In this paper, the rectangular hole problem is investigated for a long high-temperature superconducting slab under electromagnetic forces. The effects of rectangular hole on the magnetic flux density distribution in the slab are considered in either the Bean model or the Kim critical state model in the case of the descending field both for the zero-field cooling (ZFC) and the field cooling (FC) magnetization processes. Based on the finite element method, both the corresponding stress concentration factors near the corners and the distributions of nonzero principle stress along the hole edge are numerically calculated and discussed. Numerical results obtained show that the ZFC activation process has more significant influence on the stress concentration factors than the FC activation process. For every activation process, the peak values of stress concentration factors in the Bean model are larger than the corresponding ones in the Kim model. In addition, in the Kim model, the peak values of stress concentration factors generally decrease with the increasing of the introduced dimensionless parameter p. Additionally, the stress concentration factors usually increase with the increasing of the ratio of length and width of the hole. The present study should be helpful to the design and application of high-temperature superconductors.

HTS応用機器の冷却システムと冷凍機

The cooling system of high-temperature superconductivity (HTS) applications has become the most important issue in this field nowadays. Some HTS applications are mostly developed as systems that have an established place in our society. However, cooling systems are not developed for the HTS applications and are still in the experimental stage. Cooling systems should be developed as systems which can be used in the commercial world. In this paper, cooling systems, refrigerators and pumps were described and the available and the required cooling systems were shown.

A Perspective on Medical Applications of High Temperature Superconductors

Superconductivity was first discovered in mercury in 1911 by Dutch physicist Kamerlingh Onnes of Leiden University. Superconductivity has also been discovered in a number of other metallic elements. Collectively these elements are called low temperate superconductors (LTS). In 1986, Bednorz and Muller discovered superconductivity in a brittle ceramic Ba-La-Cu-O compound at 30 K [1]. A number of other compounds like yttrium barium copper oxide (YBCO), bismuth strontium calcium copper oxide (BSCCO) and thallium barium calcium copper oxide (TBCCO) have been found to superconduct at even higher temperatures. The highest superconducting temperature of 138 K was observed in a thallium-doped, mercuric cuprate in 1994. A new family of arsenic based superconducting materials termed oxypnictides has been discovered recently. These compounds are collectively called high temperature superconductors (HTS).

Fracture problems of a superconducting slab with a central kinked crack

In this work, the central kinked crack problem is investigated for a long rectangular superconducting slab under electromagnetic forces. The distributions of both the current density and the magnetic flux density in the slab are obtained analytically in the Kim critical state model for both the zero-field cooling and the field cooling magnetization processes. And based on the finite element method, the stress intensity factors at the crack tips for decreasing magnetic fields are numerically calculated. Numerical results obtained show that the zero-field cooling activation process generally has more significant influence on the stress intensity factors than the field cooling activation process, and that for every activation process, as the applied field decreases, the superconducting slab is most dangerous when the currents in the crack region are just be influenced. In general, both the maximal mode-I stress intensity factors (SIFs) and mode-II SIFs decrease with the increasing of either the introduced dimensionless parameter p in the Kim model or the crack length. However, the effects of kinked angles on the SIFs are complex. The present study should be helpful to the design and application of high-temperature superconductors.

Long-Length Coated Conductor Copper Plating Fabrication

Most application of high-temperature superconducting (HTS) wires require conductor engineering with respect to superior electric and mechanical properties and robustness. A long-length reel-to-reel Cu plating manufacturing technology was developed, tested, and transferred to the Bruker HTS production facility. Details of the design and the structure of the plating unit as well as plating results are reported. The pulse-plating technology provides a high quality of one- or two-sided metallic Cu layers on the surface of the pulsed laser deposition synthesized HTS tape. Acidic copper sulphate CuSO4 has been tested to optimize and enhance the plating process with respect to the Cu deposition rate. Using reel-to-reel mode together with the 6-m-long plating apparatus, up to a 2000 m length conductor has been treated with our unique Cu-plating technique, yielding reproducible Cu stabilizer performance with deposition speeds of up to 50 m/h. The plating technology is considered to have a high flexibility in processing a metallic copper stabilizer of a thickness of 5-50 μm. The resulting Cu-layered conductor has allowed face-to-face standard soldered joints of 10-7 Ωcm2 resistance to become routine. This work describes the overall analysis of the constructed reel-to-reel plating unit and evaluates the final conductor properties.

The Research of Protection Strategy for 110 kV Cold Dielectric High Temperature Superconducting Power Cable

The protective relay is of important significance to ensure the high-temperature superconducting (HTS) cable in safe and reliable operation, which is also the key technology problem that needs to be solved in the process of HTS cable's application. In this paper, the 110 kV cold dielectric (CD) HTS cable is chosen as the research object. First, according to the 110 kV CD HTS cable's technical characteristics and application in power grids, the fault of operation is discussed. Based on the above, the paper presents a protection strategy for the 110 kV CD HTS cable, which combines the advantage of the electric and nonelectric parameters in the detection and could be easily put into use in the projects. Finally, the whole protection strategy is presented. The protection strategy proposed in this paper provides a feasible idea for the protection of HTS cables, which is of positive significance on the promotion of the superconducting cable.

Critical Current Degradation in High-Temperature Superconducting Tapes Caused by Temperature Rise

In the practical application of high-temperature superconductors (HTSs), HTS tapes are frequently exposed to high temperatures during the soldering or epoxy-impregnation process. There is a variety of epoxy resins; high-temperature curing epoxy resin is particularly suitable for superconducting coils because of its high thermal conductivity and low thermal expansion. When applying HTS tapes to magnets, it is necessary to determine the tolerance of the HTS tapes to heat for selecting the epoxy resin. It is also important to gather data on the characteristic changes in the HTS tapes when they are exposed to heat. In this study, we performed experiments to examine the influence of heating on the I- V characteristics of commercially available YBCO and Bi-2223 tapes. We chose temperature and heating duration as experimental parameters. The sample tapes were heated in a thermostatic chamber, and thermocouples were attached to sample tapes to monitor the rise in temperature. We measured the I-V characteristics in liquid nitrogen before and after temperature rise treatment.