Bi-2223 High Temperature Superconducting Tape Research Articles

Fabrication of Bi-2223 High Temperature Superconducting Tapes With Groove Rolling Process

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.

Critical current performance of Bi-2223 HTS tape in temperature range above liquid nitrogen vaporization temperature

<p indent=0mm>(Bi, Pb)₂Sr₂Ca₂Cu₃O₁₀ (Bi-2223) high temperature superconducting (HTS) tape is one of the high temperature superconducting wires for commercial applications recently. Its superconducting critical transition temperature is <sc>105–110 K,</sc> which is higher than that of another commercially coated HTS REBa₂Cu₃O₇ conductor tape <sc>(90–93 K).</sc> The Bi-2223 tape has a wide range of superconducting temperatures above the vaporization temperature of liquid nitrogen <sc>(77 K).</sc> The critical currents of two Bi-2223 tape specimens were systematically calculated, and the findings evaluated to understand the superconductive current-carrying characteristics of Bi-2223 tape in the temperature range above <sc>77 K.</sc> To research their effects on the critical current of the specimens in this temperature range, we applied magnetic fields of different intensities and angles to the specimens. The results of the measurement are recorded in this paper in the temperature range of <sc>77–92 K,</sc> the magnetic field strength range of <sc>0–0.2 T</sc> and the magnetic field angle range of 0°–90°. The results show that the Bi-2223 tape can still bear the practical significance of the superconducting current at <sc>92 K.</sc> If there is no external magnetic field, or the external magnetic field is almost parallel to the HTS tape surface and weaker than <sc>0.1 T,</sc> the critical current in the self-field can still sustain 40%–50% of its critical current at <sc>77 K.</sc> For example, the results of this study have a significant reference price for its use in this temperature range, providing basic information for the creation of cable applications that are superconductive.

고온초전도 선재와 정합회로를 이용한 RF coil 제작에 대한 기초연구

The substantial improvement of the signal-to-noise ratio (SNR) can be achieved with small-size samples or low-field MRI system by high-temperature superconducting(HTS) RF coil. The typical HTS RF coil made of HTS thin film is expensive and is limited the coil geometry to planar surface coil. In this study, commercial Bi-2223 HTS tapes was used as RF coil for a 0.35T permanent MRI system. It has advantages of both much lower cost and easier fabrication over HTS thin film coil. SNR gain of the image obtained from the HTS RF coil over a conventional Cu RF coil at room temperature was about 2.4-fold and 1.9-fold using the spin echo pulse sequence and gradient echo pulse sequence respectively.

The Design and Winding Method of a Conduction-Cooled 1.5 T Bi-2223 High Temperature Superconducting Magnet

A conduction-cooled 1.5 T high temperature superconducting (HTS) magnet was designed. The magnet will be used to provide a steady and confining magnetic field, which requires the uniformity within ±5% of the central field, over a ? 25 mm × 120 mm cylindrical region. Totally 0.8 km Bi-2223 HTS tapes will be used to wind 22 double-pancakes. The inner and outer diameters are 60 mm and 88 mm respectively; the notched shape was employed to improve the field uniformity. An improved method other than the traditional was employed to determine the size of the magnet. The magnet is expected to be cooled down to 30 K by a GM cryocooler through the conduction cooling method. The operating current is 100 A, with which the magnet generates 1.5 T at the center of the bore. In order to facilitate the winding process and enhance the heat conduction, a new method was specially developed to wind the double-pancake, which was named as the cassette-pancake.

A SFCL modeling and application with real HTS material connecting to real time simulator

We propose a real time simulation method for the SFCL (superconducting fault current limiter) modeling and application with the real HTS (high temperature superconducting) material by using RTDS (real time digital simulator), and the transient phenomenon of SFCL system was analyzed in the simulated utility power network. SFCL components were modeled with the test sample of Bi-2223 and YBCO HTS tape with stabilizer of copper and brass material due the electrical characteristics of SFCL are dominantly dependent on the start of HTS tapes. The results from the simulation analysis proposed by this paper can be a good guideline for the selection of the SFCL material.

Investigation of Bi-2223 high temperature superconducting tape as the material for gradient coil in MRI

The use of Bi-2223 high temperature superconducting (HTS) tape as a material for gradient coils in MRI is evaluated in this paper. Bi-2223 tapes have a very high critical current and a very low power loss. A HTS tape gradient coil is expected to provide much higher gradient strength and generate much lower heating than a copper coil. Measurements of the AC power loss of Bi-2223 tapes at typical operating frequencies for gradient coils are presented. The degradation of the critical current and its effect on the increase of AC power loss is analyzed. Practical technical issues such as resistance, gradient strength and mechanical performance are also discussed. A prototype Bi-2223 HTS tape gradient coil is evaluated to verify the concept.

Design and Test of a Thermal Triggered Persistent Current System using High Temperature Superconducting Tapes

A superconducting magnet which is operated in persistent current mode in SMES, NMR, MRI and MAGLEV has many advantages such as high uniformity of magnetic field and reduced thermal loss. A high temperature superconducting (HTS) persistent current switch (PCS) system was designed and tested in this research. The HTS PCS was optimally designed using two different HTS tapes, second generation coated conductor (CC) HTS tape and Bi-2223 HTS tape by the finite element method (FEM) in thermal quench characteristic view. The CC tape is more prospective applicable wire in these days for its high n value and critical current independency from external magnetic field than Bi-2223 tape. Also a prototype PCS system using Bi-2223 tape was manufactured and tested. The PCS system consists of a PCS part, a heater which induces the PCS to quench, and a superconducting magnet. The test was performed in various conditions of transport current. An initial current decay appeared when the superconducting magnet was energized in a PCS system was analyzed. This paper would be foundation of HTS PCS researches.

Long-term test of the 22.9kV HTS power cable system in LS Cable Ltd

Since 2001, LS cable Ltd. has been developing the design, manufacturing and evaluation technologies for high temperature superconducting (HTS) power cable system as a member of DAPAS (Dream for Advanced Power system by Applied Superconductivity technology) program in Korea. The 30 m HTS cable system that is rated at 22.9 kV and 1.2 kA giving a rated capacity of 50 MVA had been developed and tested. The cable was designed as a cold dielectric type employing Bi-2223 HTS tapes and polypropylene (PP) laminated paper as the conductor and electrical insulation, respectively. The cable is cooled with sub-cooled liquid nitrogen at temperature from 75 to 77 K. The manufacturing and the installation of the cable system were completed in 2004. Long-term performance test of the cable system has been conducted for six months to verify its electric and mechanical properties in 2005.

Electrical breakdown properties of liquid nitrogen for electrical insulation design of pancake coil type hts transformer

In the electrical insulation design of a pancake coil type high temperature superconducting (HTS) transformer, knowledge of the dielectric behavior of both liquid nitrogen (LN/sub 2/) and gaseous nitrogen (GN/sub 2/) is very important. Also, the breakdown strength under a quench conditions is an important factor of the insulation engineering. Since spacers are used in the pancake coil type HTS transformer, the liquid nitrogen and the spacer must be considered together in the design of the insulation and cooling of this type transformer. This paper describes the results of an experimental study on the electrical breakdown phenomena and properties of liquid nitrogen with the electrode of the pancake coil made with Ag sheathed Bi-2223 HTS tape. When bubbles occur, the breakdown characteristics of LN/sub 2/ in a simulated cooling channel are examined to understand the optimal dimensions of the cooling channel. Open and closed cooling channels were made to compare the breakdown voltage to each other. The breakdown voltage in the open cooling channel appeared higher than the breakdown voltage in the closed cooling channel. The open cooling channel type is recommended for higher stability of equipment. This research will be useful in the electrical design of pancake coil type HTS transformers that are cooled by LN/sub 2/.

Design and electrical characteristics analysis of 100 HP HTS synchronous motor in 21st century frontier project, Korea

A 100 hp class superconducting motor in the 21st Century Frontier R&D Program of Korea has been designed. A theoretical model of high temperature superconducting (HTS) motor was presented by two-dimensional electromagnetic field analysis. The motor is composed of HTS field winding, cold damper shield, air-gap armature winding and laminated machine shield. The HTS field winding consists of racetrack type double pancake coils wound with Bi-2223 HTS tapes operated at about 30 K. The operating current of the HTS tape conductor could be determined by the magnetic field distribution calculated in the HTS field winding and the I/sub c/ - B characteristics of a practical HTS conductor, taking account of its anisotropy.

Set-up for calorimetric measurements of the AC losses in HTS tapes due to longitudinal magnetic fields and transport currents

For the design of power applications based on high-temperature superconducting (HTS) tapes, knowledge of the AC losses is needed. In most such applications the HTS tape is exposed to a magnetic field oriented perpendicular to the current path. However, in certain applications, the HTS tape is exposed to a field oriented in parallel with the current path; a longitudinal magnetic field. To study the AC losses due to combinations of longitudinal magnetic fields and transport currents, we have developed a calorimetric measurement system. Current in a solenoid generates the magnetic field along the straight sample, which simultaneously can be fed with a DC or an AC transport current. The system operates at liquid nitrogen temperature. The AC losses are determined by the temperature rise of the sample. For calibration the sample is fed by a DC current exceeding the critical current. Measurement results are presented for a Bi-2223 HTS tape.