Bi-2223 HTS Tape Research Articles

Influences of filament numbers on the sintering process of Bi-2223 HTS tapes

Influences of filament numbers on the sintering process of Bi-2223 HTS tapes

Characteristics of Bi-2223 HTS tapes under short-circuit current impacts in hybrid energy transmission pipeline

Characteristics of Bi-2223 HTS tapes under short-circuit current impacts in hybrid energy transmission pipeline

Observation of self-magnetic field relaxations in Bi2223 and Y123 HTS tapes after over-current pulse and DC current operation

The development of power transmission lines based on long-length HTS tapes requires the production of high quality tapes. Due to fault conditions, technical mistakes and human errors during the operation of a DC power transmission line, an over-current pulse, several times larger than the rated current, could occur. To study the effect of such over-current pulses on the transport current density distribution in the HTS tapes, we simulated two start-up scenarios for one BSCCO and two YBCO tapes. The first start-up scenario is an initial over-current pulse during which the transport current was turned on rapidly, rising to 900A during the first milliseconds, then reduced to a 100A DC current. The second start-up scenario is normal operation, and involved increasing the transport current slowly from 0A to 100A at a rate of 1A/s. For both scenarios, we then measured the vertical component of the self-magnetic field by means of a Hall probe above the tape, and afterward, by solving a linear equation of the inverse problem we obtain the current density profiles. We observe a change of the self-magnetic field above the edge of the BSCCO and YBCO tapes during 30min after the 5ms of over-current pulse and during the normal operation. The current density profiles are peaked in the centre for over-current pulse, and more peaked around the edge of the HTS tape for normal operation, which means that the limited time over-current pulse changes the current density profiles of the HTS tapes. We observe also a loop of current for YBCO tapes and we show the role of the HTS tape stabilizer.

Preliminary investigation of Ic homogeneity along the longitudinal direction of YBCO coated conductor tape under tensile loading

In this study, the homogeneity of critical current, , along the lengthwise direction in the coated conductor (CC) tape under uniaxial tension was investigated using a multiple voltage tap configuration. Initially, a gradual and homogeneous degradation occurred in all subsections of the tape up to a certain strain value. This was followed by an abrupt degradation in some subsections, which caused scattering in values along the length with increasing tension strain. The degradation behaviour was also explained through n-value as well as microstructure analyses. Subsections showed scattering corresponding to damaged areas of the CC tape revealed that transverse cracks were distributed throughout the gauge length. This homogeneous degradation behaviour under tension is similar with the case under torsion strain but different with the case under hard bending which were previously reported. This behaviour is also different with the case using Bi-2223 HTS tapes under tension strain.

1-G HTS Split Coil Magnet for Research Purposes

A practical split coil magnet using Bi-2223 HTS tapes has been developed and tested. The design parameter is the maximal magnetic field at the aperture of a coil. 1-G Bi-2223 tape was used for magnet's winding produced by Sumitomo Electric Industry Co. The maximum magnetic field in the magnet is determined by the dependence of 1-G tape's critical current on magnetic field normal to the HTS surface of a tape. Reduction of the normal component of the magnetic field to the HTS tape was achieved by using the iron plates. The finite element modeling has been used to design the magnet configurations. The simulation results are in good agreement with the measurement data. The maximum magnetic field at the aperture of the magnet reached 0.75 T at 77.4 K with ~1 T of maximum field on winding. The split coil is used to test anisotropy of critical currents of HTS tapes in our standard HTS wires characterization test program. The details of split coil design and magnet test results are presented.

Critical Current and Its Magnetic Field Effect Measurement of HTS Tapes Forming DC Superconducting Cable

We constructed a test stand of 20 m-class DC superconducting power transmission cable in Chubu University, in 2006. The cable consisted of thirty-nine Bi-2223 HTS tapes in two layers; nineteen tapes were used in the first layer and twenty tapes were used in the second layer. One of the features of the cable is that each HTS tape in the first layer is electrically isolated. Therefore, we can apply the current to the individual HTS tapes in the first layer. We measured critical current of the one HTS tape in the first layer when current was applied to the other HTS tapes, and compared the result with the magnetic field calculation due to the applied current. The critical current increased by 2 ~ 4% when the current was applied to all other eighteen HTS tapes in the same layer. From the magnetic field calculation, we concluded that the self magnetic field of the measured HTS tape was eliminated at the tape edge by the applied magnetic field from the neighbor HTS tapes, and then the critical current increased.

HTS Transformer: Construction Details, Test Results, and Noted Failure Mechanisms

An experimental high temperature superconducting transformer has been designed and built using Bi2223 HTS tape. The transformer is unique in that the magnetic circuit is comprised of air and a silicon steel partial core. Electrical tests were performed on the transformer and it was found to be 98.6% efficient at full load. The transformer failed during a full load endurance run and an investigation was carried out to determine the cause of the failure. The cause was believed to be from operating the HTS windings close to critical conditions. Presentation of the failure details will be of use to other researchers who are building HTS transformers.

Test results of HTS magnet for SMES application

The magnet for a superconducting magnetic energy storage system (SMES) conducting cooled by SRDK-408 cryocooler is described in this paper. The superconducting magnet consists of 7 double-pancake coils made of Bi-2223 HTS tape with the inner and outer diameters 210 mm, 315 mm respectively and height of 191 mm. The inductance of the magnet is approximately 1 H. In this paper we report the design improvements and the measurement results taken at the cooling of the magnet.

Performance of SMES System With HTS Magnet

The SMES system with superconducting magnet cooled by SRDK-408 crycooler has been described in this paper. The superconducting magnet consist of 7 double-pancake coils made of Bi-2223 HTS tape with the inner and outer diameters 210 mm, 315 mm respectively and height of 191 mm. The inductance of the magnet is about 1 H. The superconducting magnet is fabricated and tested. In the paper the design and the performance results of the SMES magnet were reported.

Recent Main Events in Applied Superconductivity in China

With strong support from Chinese government bodies such as the National High Technology Research and Development Program of China, National Natural Science Foundation of China and the National Basic Research Program of China, the field of applied superconductivity in China has been developed in different areas. Especially in the fusion application area, the first fully-superconducting tokamak, EAST (Experimental Advanced Superconducting Tokamak), has been successfully constructed and commissioned in the last two years. Based on the requirement from the ITER project, high performance Bi-2223 HTS tape, and Nb3Sn and NbTi strands have been developed as well. In the area of HTS applications for electric power systems, R&D has been focused on superconducting power cable, superconducting magnetic energy storage, superconducting transformer, superconducting fault current limiters. In this paper, the recent progress in applied superconductivity in China is reported.

Design and Performance Results of First Polish SMES

The magnet for superconducting magnetic energy storage system (SMES) cooled by SRDK-408 cryocooler has been described in this paper. The superconducting magnet consists of 7 double-pancake coils made of Bi-2223 HTS tape with the inner and outer diameters 210 mm, 315 mm respectively and height of 191 mm. The inductance of the magnet is about 1 H. In the paper we report the design and the first measurements results of the magnet.

Bending Strain Characteristics of Critical Current in Double-Layered Bi-2223 Superconducting Tapes

The evaluation of reliability of HTS tapes is necessary for practical applications such as magnet, power cables, motors, SMES and HTS coils. The bending strain effect on the critical current, Ic, in multifilamentary Bi-2223 HTS tapes have been investigated. Single and double layered tapes (for high current capacity) were subjected to thermal and pressurization cycles at pressurized liquid nitrogen (LN2) up to 1 MPa. After the pressurization test, the subsequent occurrence of damage like ballooning due to the diffusion and expansion of LN2 into the tapes were investigated and compared. The Bi-2223 tapes showed different Ic degradation behavior depending upon the geometry and ratio of reinforcement to superconductor adopted.

Research activities of DC superconducting power transmission line in Chubu University

A experiment of a DC Superconducting power transmission line using HTS conductor was started in Chubu University, Japan in autumn 2006. The first cooling down began in October 2006. The coolant is liquid nitrogen, and the cooling system used a cryogenic cooler and cold pump. The operation temperature is the range of 72 K - 80 K. The power cable has a total length of 20 m, and composed of thirty-nine Bi-2223 HTS tape conductors with critical current approximately100 A. The power cable achieved a 2.2 kA. The insulation voltage of the cable is 20 kV. In order to reduce the heat leakage and to avoid the current imbalance in the HTS tapes, we installed the Pelteir Current Lead (PCL) for each of the nineteen HTS tapes of the cable, with remaining twenty HTS tapes connected individually by the usual copper leads (CCL). Depending on the visual observation, and the measurement of temperatures of the current leads, the heat leakage of the PCL is lower than that of CCL. We installed a current transformer for each individual HTS tape conductor circuit, and measured the current of each HTS tape conductor. We measured the critical current of each HTS tape after the cable was installed into the cryostat, and degradation was not observed. Since the variation of the current in each tape is less than 10%, we eliminated the problem of current imbalance. Computational Fluid Dynamics is used to estimate the pressure drop, showing that the straight-tube cryostat has the advantage against the bellows- and corrugated-tube cryostats to reduce the pressure drop of the circulation of coolant. We proposed further to use the siphon for circulating the coolant in order to reduce the circulation losses and costs. We proposed that the voltage of the system be kept below 30 kV in order to use low cost power inverters. This choice can increase the storage energy of the power transmission line itself if we do not use a co-axial cable system because of it allows use of large current. And the magnetic energy of power grid is estimated to 4.5MJ/km for ±30 kA.

Development of quench protection system for HTS coils by active power method

Recently, HTS coils have been developed for electric power apparatuses. In superconducting coils, local and excessive joule heating may give damage to the superconducting windings when a quench occurs and therefore it is essential that the quench is detected quickly and precisely so that the coils can be safely discharged. Resistive voltage measurement method is universally used for the quench detection, however, it is vulnerable to an electromagnetic noise which causes insufficient quench detection and at least needs a central voltage tap in windings. In a large superconducting coil, a lead-wire from the central voltage tap may cause a short-circuit when high voltage will be applied. In this paper, we present a quench protection system based on the active power method which detects a quench by measuring the instantaneous active power generated in a superconducting coil. The protection system based on this method is very strong against to the noise and no more needs a central voltage tap. The performance of system developed by us is confirmed by using test coil wound with Bi-2223 HTS tapes.

3D finite element analysis of eddy current loss of HTS tapes – External field analysis

The eddy current losses in the matrix of two twisted filaments Bi-2223 HTS tapes in applied external AC magnetic field was calculated using 3D FEM software. The highest eddy current loss in the matrix was experienced when magnetic field is applied perpendicular to the wide side of the rectangular model. Numerically calculated eddy current losses are plotted as the function of frequency, filament twist pitch, matrix conductivity and magnetic field amplitude. Longer filament twist pitch models have higher eddy current losses in transverse magnetic field. In longitudinal magnetic field shorter filament twist pitch have higher eddy current losses. Increases in the applied external field amplitude, frequency and matrix conductivity contributes to higher eddy current losses. Numerical calculation results shows that the contribution of eddy current loss at commercial frequency is not minimal. The numerical results presented are for uncoupled filaments HTS tapes.

AC loss characteristics of Bi-2223 HTS tapes under bending

Superconductor is developed for applications in high-power devices such as power-transmission cables, transformers, motors and generators. In such applications, HTS tapes are subjected to various kinds of stress or strain. AC loss is also important consideration for many large-scale superconducting devices. In the fabrication of the devices, the critical current (Ic) of the high temperature superconductor degrades due to many reasons including the tension applied by bending and thermal contraction. These mechanical loads reduce the Ic of superconducting wire and the Ic degradation affects the AC loss of the wire. The Ic degradation and AC loss of Bi-2223 HTS tape were measured under tension and bending conditions at 77K and self-field. Moreover, the frequency characteristics of AC loss was measured at the 30–480Hz. As a result, self-field penetrates the deeper into the conductor at the lower frequency, which means higher self-field losses per cycle.

Tests results and analysis of inductive superconducting fault current limiter with Bi-2223 tube and HTS tape as secondary winding

The Superconducting Fault Current Limiters are very attractive devices for the electrical power network. The performance comparison of inductive SFCL with three different secondary windings are presented in this paper. As secondary windings we used Bi-2223 tube, HTS tape and HTS tape parallel rings. We proved that the limiting capabilities of the SFCL with different windings are comparable, and the windings made of HTS tape are less expensive and more mechanically stable then HTS tubes. We proposed two method of implementation of shorted secondary winding. The experimental results show that HTS tube can be successfully substitute by cheaper shorted winding made of HTS tape.

Transport AC and magnetic losses in Bi2223 HTS tapes subjected to external field

We present the experimental results of AC losses in Bi2223 tapes at 4.2 K under applied DC magnetic field. The effects of anisotropy of critical current and several factors on the behavior of AC loss were investigated. The AC responses of Bi2223 HTS are investigated by measuring its AC susceptibility with different applied fields and different temperatures, which can provide an insight into the loss mechanism and flux dynamics of HTSCs. The loss volume density is related to χ ″, the imaginary part of the internal AC susceptibility.

Development of Bi-2223 HTS tape and its application to coil and current leads

We are developing Bi-2223/Ag tapes with a high engineering critical current density by optimizing the powder-in-tube process and are studying its application to coil and current leads. We have fabricated 250 m-long tape and investigated optimized processing conditions to enhance engineering critical current density. More bubbling was found when the tape was heat-treated with a higher heating rate. Different kinds of superconducting joints were fabricated with multi-filamentary Bi-2223/Ag tapes, and 58% of retained I c was achieved using the insertion of Bi-2223 core between two exposed tapes. Current decay property of the persistent mode HTS coil was investigated. Rapid current decay was observed when the operating current is in a flux-flow range. We could successfully fabricate a low heat leak type HTS current lead with Bi-2223/Ag–Au tapes by employing a stepped geometry. Using this lead, safe operation of 2 kA current transport was confirmed.

380 kW synchronous machine with HTS rotor windings––development at Siemens and first test results

Applying HTS conductors in the rotor of synchronous machines allows the design of future motors or generators that are lighter, more compact and feature an improved coefficient of performance. To address these goals a project collaboration was installed within Siemens, including Automation & Drives, Large Drives as a leading supplier of electrical machines, Corporate Technology as a competence center for superconducting technology, and other partners. The main task of the project was to demonstrate the feasibility of basic concepts. The rotor was built from racetrack coils of Bi-2223 HTS tape conductor, these were assembled on a core and fixed by a bandage of glass-fibre composite. Rotor coil cooling is performed by thermal conduction, one end of the motor shaft is hollow to give access for the cooling system. Two cooling systems were designed and operated successfully: firstly an open circuit using cold gaseous helium from a storage vessel, but also a closed circuit system based on a cryogenerator. To take advantage of the increased rotor induction levels the stator winding was designed as an air gap winding. This was manufactured and fitted in a standard motor housing. After assembling of the whole system in a test facility with a DC machine load experiments have been started to prove the validity of our design, including operation with both cooling systems and driving the stator from the grid as well as by a power inverter.