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A conduction-cooled high temperature superconducting (HTS) magnet for the SPMS was fabricated and tested. To achieve an adequate uniformity of background magnetic field, a split-pair winding configuration is used. Room temperature bore of this magnet was 38 mm (length) × 134 mm (width) × 360 mm (depth) in dimension. The magnetic field uniformity of HTS magnet was achieved lower than 1% within the virtual sample region 15 mm (width) × 100 mm (depth). Also, this HTS magnet could be operated to generate 3 T for 7 h.

The authors designed and manufactured a toroidal-type superconducting magnetic energy storage (SMES) system. The toroidal-type SMES was designed using a 3D CAD program. The toroidal-type magnet consists of 30 double pancake coils (DPCs). The single pancake coils (SPCs), which constitute the double pancake coils, are arranged at an angle of 6° from each other, based on the central axis of the toroidal-type magnet. The cooling method used for the toroidal-type SMES is the conduction cooling type. When the cooling method for the toroidal-type SMES was designed, the two-stage Gifford–McMahon (GM) refrigerator was considered. The Bi-2223 HTS wire, which was made by soldering brass on both sides of the superconductor, is used for the magnet winding. Finally, the authors connected the toroidal-type SMES to a real-time digital simulator (RSCAD/RTDS) to simulate voltage sag compensation in a power utility.

This paper analyzes the operational characteristics of conduction cooling Superconducting Magnetic Energy Storage (SMES) through a real hardware based simulation. To analyze the operational characteristics, the authors manufactured a small-scale toroidal-type SMES and implemented a Real Time Digital Simulator (RTDS) based power quality enhancement simulation. The method can consider not only electrical characteristics such as inductance and current but also temperature characteristic by using the real SMES system. In order to prove the effectiveness of the proposed method, a voltage sag compensation simulation has been implemented using the RTDS connected with the High Temperature Superconducting (HTS) model coil and DC/DC converter system, and the simulation results are discussed in detail.

A laboratory-scale conduction cooled high temperature superconducting (HTS) magnet is fabricated and tested. This HTS magnet was designed in order to generate 2 T at center of room bore in operating current 120 A. It consists of eight double-pancake sub-coils, two HTS current leads, a GM cryocooler and a cryostat without a radiation shield vessel. Sub-coils were wound with 1G HTS tapes of Sumitomo Electric Industries Ltd. using wet winding method. Assembled magnet was impregnated with epoxy resin in vacuum. Room bore diameter of this magnet was 70 mm. Each bobbin of double-pancake coils was of GFRP and aluminum alloy. Upper and lower supporting plates of coils is made by aluminum alloy in order to improve thermal conduction. In this paper, fabrication and test results of HTS magnet including magnetic field and temperature variation are reported.

This paper describes design, fabrication, and evaluation of the conduction cooled high temperature superconducting (HTS) magnet for superconducting magnetic energy storage (SMES). The HTS magnet is composed of 22 of double pancake coils made of 4-ply conductors that stacked two Bi-2223 multi-filamentary tapes with the reinforced brass tape. Each double pancake coil consists of two solenoid coils with an inner diameter of 500 mm, an outer diameter of 691 mm, and a height of 10 mm. The aluminum plates of 3 mm thickness were arranged between double pancake coils for the cooling of the heat due to the power dissipation in the coil. The magnet was cooled down to 5.6 K with two stage Gifford McMahon (GM) cryocoolers. The maximum temperature at the HTS magnet in discharging mode rose as the charging current increased. 1 MJ of magnetic energy was successfully stored in the HTS magnet when the charging current reached 360A without quench. In this paper, thermal and electromagnetic behaviors on the conduction cooled HTS magnet for SMES are presented and these results will be utilized in the optimal design and the stability evaluation for conduction cooled HTS magnets.

The increasing use of high-temperature superconducting (HTS) materials for advanced power applications has generated much interest in the acquisition of the voltage–current ( V – I ) characteristic curve to measure the critical current ( I c ) of HTS tape. Cryogen free I c measurement system for HTS wires or coils was designed and fabricated by using a GM-cryocooler and two HTS current leads. The sample cools conductively by 2nd stage of SRDK-408D cryocooler manufactured by Sumitomo Heavy Industries Ltd. (SHI). Each high temperature end of HTS current leads is thermally connected to 1st stage of the cryocooler and electrically disconnected. HTS tape samples cooled down by about 10 K. I c measurements were conducted on a BSCCO-2212 tape, a BSCCO-2223 tape with joints and a BSCCO-2223 small coil under self-field. A description of cryogen free I c measurement system design and results from a series of measurements will be presented.

A 600 kJ HTS SMES is under development in Korea. Before the specific design of the HTS SMES, its model coil is fabricated and tested to verify the thermal and electrical characteristics. The model coil consists of two single pancakes and one double pancake coil with copper conduction plates between the coils. Each pancake is fabricated with a soldered 4-ply HTS conductor to increase the coil current. The model coil is cooled by two GM-cryocoolers and cooled down to below 20 K. Copper conducting plates between the coils are used as the thermal path to the cryocooler. With the model coil, experiments are performed to investigate the thermal stability related with the transport current and the charge/discharge rate. The results are used to develop the 600 kJ HTS SMES by clarify the several source of the heat generation.

A conduction-cooled high-temperature superconducting (HTS) coil consisting of two double pancake coils was fabricated. The current–voltage ( I – V ) characteristics of HTS coil were obtained at different temperatures by using GM cryocooler. Using OPERA 2D, magnetic field ( B r ) perpendicular to the surface of the tape at each layer of HTS coil was obtained. In order to compare with the measured values, I – V curve of the HTS coil was simulated, in the basis of the magnetic field dependence of the critical current ( I c ) in Bi-2223 tapes and index of n -value. Results showed pretty good agreement between the simulated and the measured critical currents at 77.3 K and 40 K, with a bit difference under simple assumption of index of n value.

This paper deals with cryogen, which is used as solid nitrogen (SN 2 ) to keep the operating temperature of high temperature superconducting (HTS) synchronous rotating machine. To solidify liquid nitrogen, liquid helium (LHe) passed into the heat exchanger and cools its own temperature. Two types of heat exchangers were designed and fabricated for making the SN 2 , and the temperature characteristics of both case was compared. The rotor of HTS synchronous rotating machine was cooled by latent heat of SN 2 and it was kept under 40 K for 2 h and 30 min without the additional supplement of LHe.

We report the successful fabrication of single-filament composite MgB 2 /stainless-steel ribbons, as an ultrarobust conductor type. The transport critical current of the non-sintered MgB 2 /stainless-steel ribbons is remarkably high, as an unexpected result. Transport critical currents I c ∼316 A at T =4.2 K and I c ∼82 A at T =20 K were observed at self-field for the non-sintered composite MgB 2 /stainless-steel ribbons. The I c value of 316 A is the higher than any other value reported so far. In addition, the persistent current density, that was estimated by Bean formula, of the sintered composite MgB 2 /stainless-steel ribbons was more than J p ∼6×10 5 A/cm 2 at T =5 K with H =0 G, and J p ∼1.1×10 5 A/cm 2 at T =30 K with H =0 G.

Superconducting racetrack coils have different shapes from those of ordinary solenoid coils which have the same curvature along the windings. So they have different or worse performance from the viewpoint of quench characteristics due to the different structures. Racetrack coils also have round curvatures along their end portions; however, the main difference of their structures from solenoid coils exists in the straight portions. It is considered that the worse performance is due to the straight portions. In the round portions, there exists strong continuous constraint along the windings against the movement toward the perpendicular direction during coil excitation. On the contrary, in the straight portions, there is almost no constraining. As a result, especially in the case of dry magnet, they show even worse characteristics than solenoid counterparts. For the compensation of this worse performance, we proposed one idea to improve quench characteristics of racetrack coils. We manufactured one racetrack coil with an ordinary shape and the other with the proposed idea. By experiments we made sure that the proposed one had a higher quench current. Moreover, after we had made an application of the proposed idea to the four field coils of an actual 30 kVA superconducting generator, we could get very good output voltage and current waveforms.

Thermal power station is made up of a steam turbine and a steam condenser which need a lot of water. The water of steam condenser should be replaced, since scales consisting of iron oxide mainly are accumulated on the surface of condenser pipes as it goes. Superconducting high gradient magnetic separation (HGMS) system has merits to remove paramagnetic substance like iron oxides because it can generate higher magnetic field strength than electromagnet or permanent magnet. In this paper, cryo-cooled Nb–Ti superconducting magnet that can generate up to 6 T was used for HGMS systems. Magnetic filters were designed by the analysis of magnetic field distribution at superconducting magnets. The result of X-ray analysis showed contaminants were mostly α-Fe 2 O 3 (hematite) and γ-Fe 2 O 3 (maghemite). The higher magnetic field was applied up to 6 T, the more iron oxides were removed. As the wire diameter of magnetic filter decreased, the turbidity removal of the sample was enhanced.

Tl-1223/Ag tapes with a nominal composition of Tl 0.8 Pb 0.2 Bi 0.2 Sr 1.6 Ba 0.4 Ca 2 Cu 3 O z were prepared using the powder-in-tube method combined with an in-situ reaction method, and their characteristics were mainly compared to those of Tl 0.93 Bi 0.22 Sr 1.6 Ba 0.4 Ca 2 Cu 3 O z tapes. As a result, the morphology in the present tapes seemed to be almost similar to those in Tl 0.93 Bi 0.22 Sr 1.6 Ba 0.4 Ca 2 Cu 3 O z tapes, except that it became denser. However, the temperature range for the stabilization of Tl-1223 phase widened a little, and J c 's at 77 K and 0 T increased. The enhanced J c 's in the tapes were attributed to enhanced effective area for current flow due to enhanced densification, probably resulting from doping of both Pb and Bi. In the present study, a high transport J c of 18,100 A/cm 2 at 77 K and 0 T was obtained.

High- T c Tl-1223/Ag tapes with a nominal composition of (Tl 0.93 Bi 0.22 )(Sr 1.6 Ba 0.4 )Ca 2 Cu 3 O x were prepared using the powder-in-tube method combined with the two step reaction method. Their microstructures were examined using scanning and transmission electron microscopy. Tape A ( J c = 5 500 A/cm 2 at 77 K under 0 T) prepared using rolling only has a lower J c than tape B ( J c = 14 000 A/cm 2 ) prepared using pressing. In both tapes Tl-1223 forms plate-like grains. Although the size of the plates in tape A is larger than those in tape B, their mutual connection is poorer. Many subgrains are formed in each grain with small angle boundaries, which are composed of tilt-type as well as twist-type components in most cases. The boundaries might be considered as effective pinning sites for magnetic flux as far as the tilt component predominates. Additionally, small holes were found at the subgrain boundaries.

A TlBa 2 Ca 2 Cu 3 O 9 (Tl-1223) superconductor (T c =116 K) has been synthesized by using solid state reaction method and AC susceptibility was measured. Since the flux line lattice dynamics has been especially interesting topics in the critical current density, we measured the frequency dependence of the susceptibility in the range 1 kHz ≤ ω /2 π ≤ 2 MHz and compared it with various models. The experimental results of the vortex dynamics could be well fitted by the diffuse model. The behavior of the flux line means a flux diffusive motion and an ohmic motion at the low magnetic field.

Ag-sheathed BiPbSrCaCuO tapes were prepared using three different heat treatments, and studied in terms of T c , J c , χ dc and microstructure. The results suggested that a complicate process using quenching partial melt, cold working, partial melt growth and sintering will be effective for the preparation of highly densified and well grain-aligned Bi-2223 tapes within a short period of time.