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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Progress in Superconductivity and Cryogenics
Journal Basic Information
Journal DOI :
The Korea Institute of Applied Superconductivity and Cryogenics
Editor in Chief :
Volume & Issues
Volume 5, Issue 3 - Nov 2003
Volume 5, Issue 2 - Sep 2003
Volume 5, Issue 1 - May 2003
Selecting the target year
NMR/MRI Superconducting Magnet Technologies: Recent Activities at MIT Francis Bitter Magnet Laboratory
Yukikazu Iwasa ; Lee, Haigun ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 1~12
In this paper we present a brief description and summary results of each of our recent activities in three areas, all devoted to NMR and MRI superconducting magnet technologies: 1) development of a high-field LTS / HTS NMR magnet; 2) development of a novel digital flux injector for slightly resistive NMR magnets; and 3) a proposal fer a low-cost MRI magnet system based on
composite and an innovative cryogenic design / operation concept.
Application of Taguchi Method and Orthogonal Arrays for Optimization of Adhesion of
Coatings on Ag/Bi(2223) Tapes
Lee, Se-Jong ; Lee, Deuk-Yong ; Song, Yo-Seung ; Kim, Bae-Yeon ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 13~16
resistive oxide barrier on Ag sheathed Bi(2223) tapes prepared by the sol-gel and dip-coating method was evaluated with an aid of Taguchi method and Lie(
) orthogonal arrays to determine the optimal process combination of levels of factors that best satisfy the bigger is better quality characteristic (QC=B). For analyses of results statistical calculations such as average and analysis of variance (ANOVA) were employed to analyze the results for improving the performance qualities of the dip-coated
film. Experimentally, the performance of the films was evaluated in terms of bond strength by varying Sr/Zr moi ratio (A), amount of organic vehicle additives (B), drying temperature (C) and time (D), heat treatment temperature (E) and time (F), respectively. The optimal combination of levels of factors was determined to be
having a 90% confidence level.
Experimental Investigations on Barrier Oxidation in
Kim, Kyu-Tae ; Hong, Hyun-Kwon ; Lee, Sang-Hwa ; Nam, Du-Woo ; Lee, Kyu-Won ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 17~20
Josephson junctions were fabricated for several oxidation conditions and several junction sizes. Considering self-field effect suppressing the observed critical current (Ic) at large junctions, the observed Ic values were in good agreement with theoretical prediction. The predicted junction critical current for small junction limit was also confirmed by experiment. The dependence of the estimated Jc as a function of oxidation exposure showed that our junctions have lower Jc than other authors' at the same oxidation exposure. This is thought to be one of equipment-specific phenomena. Details of experimentals will be reported with brief discussion.
A semispherical SQUID magnetometer system using high sensitivity double relaxation oscillation SQUIDs for magnetoencephalographic measurements
Lee, Yong-Ho ; Hyukchan Kwon ; Kim, Jin-Mok ; Kim, Kwoong ; Park, Yong-Ki ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 21~26
We designed and constructed a multichannel superconducting quantum interference device (SQUID) magnetometer system to measure magnetic fields from the human brain. We used a new type of SQUID, the double relaxation oscillation SQUID (DROS). With high flux-to-voltage transfers of the DROS, about 10 times larger than the dc SQUIDs, simple flux-locked loop circuits could be used for SQUID operation. Also the large modulation voltage of the DROS, typically being 100
, enabled stable flux-locked loop operation against the thermal offset voltage drift of the preamplifier. The magnetometers were fabricated using the Nb/AlOx/Nb junction technology. The SQUID system consists of 37 signal magnetometers, distributed on a semispherical surface, and 11 reference channels were installed to pickup background noises. External feedback was used to eliminate the magnetic coupling with the adjacent channels. The liquid helium dewar has a capacity of 29 L and boil-off rate of about 4 L/d with the total 48 channel insert. The magnetometer system has an average noise level of 3 fT/√Hz at 100 Hz, inside a shielded loon, and was applied to measure auditory-evoked fields.
Characteristics of HTS Tube Depending on Chemical Compositions
Jung, Seung-Ho ; Jang, Guneik ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 27~30
The Bi2212 based HTS tubes with 4 different compositions, Bi:Sr:Ca:Cu = 2.0:2.0:1.0:2.0, 2.1:2.0:1.0:2.0,2.2:1.8:1.0:2.0 and 2.2:18.104.22.168.2:2 with 10% of SrSO
were studied. For tube fabrication the optimum range of melt temperatures and preheating temperature and time for mold were 105
for 30min respectively. The mold rotating speed was 1000rpm. Typical tube dimension was 30/24mm in outside/inside diameter and 60mm in length. A tube was annealed at 84
for 40 hours in oxygen atmosphere. The plate like grains more than 20
were well developed along the rotating direction of mold regardless of initial chemical compositions. The specimen with Bi2212 composition exhibited
of 83K while the specimen with other compositions are lower than 60K. The measured
at 77K(B = 0T) in Bi2212 composition were about 80A and 266A/
Effect of pre-annealing conditions on critical current density of Bi-2223 tapes
Ha, Dong-Woo ; Yang, Joo-Saeng ; Ha, Hong-Soo ; Oh, Sang-Soo ; Lee, Dong-Hoon ; Hwang, Sun-Yuk ; Park, Jung-Gyu ; Kwon, Young-Kil ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 31~34
Bi-2223 superconducting wires with 55 filaments were fabricated by stacking, drawing process with different heat-treatment histories. Two kinds of powders were prepared. One was pre-annealed at 760-820
and low oxygen partial pressure, and the other was only calcined state. Before rolling process, round wires were pre-annealed at 760 -820
and in a low oxygen partial pressure. We confirmed that pre-annealing step was to transform Bi-2212 orthorhombic structure from Bi-2212 tetragonal structure and to reduce the formation of second phases at superconducting wire. However Bi-2223 phases were formed at higher pre-annealing temperature. Bi-2223 conductor was needed frequently annealing at low temperature because pre-annealing at precursor powder brought about decrease in workability. We could achieve highest Je of 6500 A/
at the tape using Bi-2212 orthorhombic phase by introduced slightly overheating at the 1st sintering process.
Pitch Calculation of 4-layer HTS Power Transmission Cable far Balanced Sharing Current
Joo, Jin-Hong ; Kim, Seog-Whan ; Jeonwook Cho ; Bae, Joon-Han ; Kim, Hae-Jong ; Seong, Ki-Chul ; Hong, Jung-Pyo ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 35~39
A typical HTS power transmission cable has multi-layer conductor structure to increase the current capacity. The tapes of the innermost layer are wound on a round former, and adjacent tapes of another layer are separated by a thin insulating film. However, usually the current is not evenly distributed among the layers because of inductance difference of each layer, and the inductance is provided by the winding pitch of each layer's tape. Consequently n method to make the current distribution more uniform is a adjusting the tape winding pitch, hence reduce the AC loss. This paper describes a current distribution by adjusting a tape winding pitch of each layer. Also, this paper shows recommendations for future cable conductor prototypes.
Controlling the secondary phase of BSCCO 2223 tapes by thermal slide heat treatment(TSHT)
Park, Sung-Chang ; Yoo, Jai-Moo ; Ko, Jae-Woong ; Kim, Young-Kuk ; Kim, Cheol-Jin ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 40~43
The phase transformation, variation of secondary phase, and critical current density
tapes have been studied through the thermal slide heat treatment (TSHT) process. This process consists of a multiple variations of oxygen partial pressures and temperatures at the initial heat treatment During the initial heat treatment some secondary phase such as
(2201, amorphous phase) farm in Bi-2223 tapes, especially at the 2223 grain boundaries. These secondary phases are detrimental to the phase transformation and final properties. In order to control the secondary phase in Bi-2223 tapes the amount and size of secondary phases among the TSHT process were observed. The results indicate that the amount and particle size of AEC particles were smaller when the TSHT process was used than when the normal process at the initial heat treatment was used which results in the improved
properties after the final process.
Measurement and Simulation Study of RSFQ OR gate
Nam, Doo-Woo ; Jung, Ku-Rak ; Hong, Hee-Song ; Joonhee Kang ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 44~47
There are several simulation programs in studying superconductor RSFQ (Rapid Single flux Quantum) electronic devices, which include WRspice, WinS, PSCAN, and JSIM. Even though different research groups use different simulation programs, it is not well known about which program gives the simulation results closer to the measurement values. In this work, we used both WRspice and WinS to simulate RSFQ OR gate and to compare the results from the different simulations. This comparison would help in deciding which program is better in the RSFQ circuit design. In the confluence buffer, which is the one of the main components of the DR gate, the measured bias margins were
, while the margins from the simulations were
from WRspice and it 53.1% from WinS. However, with the actual fabricated circuit parameters WRspice gave
. In WinS the circuit did not operate. We concluded that WRspice is more reliable.
Design of a 1 MVA HTS Transformer with Double Pancake Windings
Kim, Woo-Seok ; Park, Kyeong-Dal ; Joo, Hyeong-Gil ; Han, Jin-Ho ; Hong, Gye-Won ; Park, Jungho ; Heesuck Song ; Kim, Sung-Hoon ; Hahn, Song-yop ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 48~51
A 1 MVA transformer with BSCCO-2223 high Tc superconducting (HTS) tapes was designed. The rated voltages of each sides of the transformer are 22.0 kV and 6.6 kV respectively. Double pancake HTS windings, which have advantages of insulations and distribution of high voltage, were adopted. Four HTS tapes were wound in parallel fer the windings of low voltage side. Each winding was composed of several double pancake windings made of four parallel conductors were transposed in order to distribute the currents equally in each conductor. A core of the transformer was designed as a shell type core made of laminated silicon steel plate and the core is separated with the windings by a cryostat with a room temperature bore. The operating temperature of HTS windings will be 65K with liquid nitrogen, and a cooling system using a cryocooler was proposed and designed conceptually. This HTS transformer is going to be manufactured in near future based on the design parameters presented in this paper.
Breakdown Properties of Coolant for HTS Apparatus Operating at Cryogenic Temperature
S.M. Baek ; J.M. Joung ; Kim, S.H ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 52~55
For the dielectric insulation design of any high temperature superconducting (HTS) apparatus in the electrical power systems, the breakdown properties of cryogenic coolants such as
are an important factor of the insulating engineering. Therefore, this paper presented an experimental investigation of breakdown phenomena in
under AC voltage. And we studied the breakdown properties of LN2 with decreasing temperature. Also, the Weibull plots of the breakdown voltage of subcooled
at 65 K for the needle-plane electrode with electrode distance d= 10 mm are studied. The dependence of breakdown voltage for needle-plane and pancake coil-pancake coil electrode on temperature is illustrated. The experimental data suggested that the breakdown voltage of L
depend strongly on the temperature of
. The breakdown characteristics of
under quasi-uniform and non-uniform electrical field for temperature ranging from 77 K to 65 K were clarified.
EMTDC Modeling Method of DC Reactor type Superconducting Fault Current Limiter
Lee, Jaedeuk ; Park, Minwon ; Yu, In-Keun ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 56~59
As electric power systems grow to supply the increasing electric power demand short-circuit current tends to increase and impose a severe burden on circuit breakers and power system apparatuses. Thus, all electric equipment in a power system has to he designed to withstand the mechanical and thermal stresses of potential short-circuit currents. Among current limiting devices, Fault Current Limiter (FCL) is expected to reduce the short-circuit current. Especially, Superconducting Fault Current Limiters (SFCL) offer ideal performance: in normal operation the SFCL is in its superconducting state and has negligible impedance, in the event of a fault, the transition into the normal conducting state passively limits the current. The SFCL using high-temperature superconductors offers a positive resolution to controlling fault-current levels on utility distribution and transmission networks. This study contributes to the EMTDC based modeling and simulation method of DC Reactor type SFCL. Single and three phase faults in the utility system with DC reactor type SFCLs have been simulated using EMTDC in order to coordinate with other equipments, and the results are discussed in detail.
EMTDC Modeling Method of Resistive type Superconducting Fault Current Limiter
Taejeon Huh ; Lee, Jaedeuk ; Park, Minwon ; Yu, In-Keun ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 60~65
An effective modeling and simulation scheme of a resistive type Superconducting fault Current Limiter (SFCL) using PSCAD/EMTDC is proposed in this paper. In case of High Temperature Superconducting (HTS) resistive type fault current limiter current limiting is implemented by the ultra-fast transition characteristics from the superconducting (non-resistive) state to the normal (resistive) state by overstepping the critical current density. The states can generally be divided into three sub-states: the superconducting state the quench state and the recovery state respectively. In order to provide alternative application schemes of a resistive type SFCL, an effective modeling and simulation method of the SFCL is necessary. For that purpose, in this study, an actual experiment based component model is developed and applied for the simulation of the real resistive type SFCL using PSCAD/EMTDC. The proposed simulation scheme can be implemented to the grid system readily under various system conditions including sort of faults and the system capacity as well. The simulation results demonstrate the effectiveness of the proposed model and simulation scheme.
Magnetic Field Analysis of 1 MVA HTS Transformer Windings
Park, Chan-Bae ; Kim, Woo-Seok ; Lee, Sang-Jin ; Han, Jin-Ho ; Park, Kyeong-Dal ; Joo, Hyeong-Gil ; Hong, Gye-Won ; Hahn, Song-Yop ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 66~70
In a HTS transformer, the perpendicular component of magnetic flux density (
) applied to HTS tapes of pancake windings becomes larger than that of solenoid winding, thereby decreasing the critical current in the HTS tapes. This paper introduces several methods to reduce
applied to the HTS tapes in the transformer with double pancake windings by changing winding arrangements and the relative permeability of flux diverters. We have conducted a winding design for a single-phase 1MVA 22.9kV/6.6kV HTS transformer. We observed a change of
due to a variation of gap-length between the high voltage windings and the low voltage windings, reciprocal arrangement and an increase of the number of the high voltage pancake. We also observed a change of Br on the HTS tapes due to variation of the relative permeability of flux diverters placed between the high voltage winding and the low voltage winding. Finally, we have designed a 1MVA 22.9kV/6.6kV HTS transformer winding using suggested methods and calculated transformer parameters by the 3D finite element method.
Variation of Residual Welding Stresses in Incoloy 908 Conduit during the Jacketing of Superconducting Cables
Lee, Ho-Jin ; Kim, Ki-Baik ; Nam, Hyun-Il ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 71~75
The conduit fer superconducting cable is welded and plastically deformed during the jacketing process to make the CICC (Cable-in-Conduit-Conductors) fer a fusion magnet. The jacketing process of KSTAR (Korea Superconducting Tokamak Advanced Research) conductors is composed of several sequential steps such as rounding, welding, sizing, and square-rolling. Since the welded zone in Incoloy 908 conduit is brittle and easy to have flaws, there may be a possibility of stress corrosion cracking during the heat treatment of coil when both the induced tensile residual stress and the concentration of oxygen in the furnace are sufficiently high. The steps of the jacketing process were simulated using the finite element method of the commercial ABAQUS code, and the stress distribution in the conduit in each step was calculated, respectively. Furthermore, the variations of residual welding stresses through the steps of the jacketing process were calculated and analyzed to anticipate the possibility of the stress corrosion cracking in the conduit. The concentrated high tensile residual welding stresses along the welding bead decrease by the plastic deformation of the following sizing step. The distribution in residual stresses in the conductor for magnet coil is mainly governed by the last step of square-rolling.
Contractible Beat Pipe for Conduction Cooled Superconducting Magnets
Kim, Seokho ; Sangkwon Jeong ; Jin, Hong-Beom ; Kideok Sim ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 76~80
A contractible heat pipe is designed and tested to improve cooling performance of conduction cooled superconducting magnet. When the heat pipe temperature drops below the triple point temperature, heat pipe working fluid freezes to create low pressure. From this moment the heat pipe does net work any more (OFF state) and it just works as a heat leak path when the temperature of the first stage is higher than that of the second stage. Considering small cooling capacity of the second stage around 4.2 K, the conduction loss is not negligible. Therefore, the contractible heat pipe, made of a metal bellows and copper tubes, was considered to eliminate the conduction loss. Nitrogen and argon are as working fluid of heat pipe. The copper block is cooled down with these heat pipe and the cooling performance for each heat pipe is compared. At off state, the bellows is contracted due to the low pressure of heat pipe and the evaporator section of the heat pipe is detached about 3 mm from the second stage cold head of the cryocooler. In this way, we tan eliminate the conduction loss through the heat pipe wall.
1-Dimensional simulation of nonlinear magnetic diffusion in high-Tc superconductor
Heo, K.S. ; Seol, S.Y. ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 81~86
This paper presents a numerical analysis of transient magnetic diffusion in a melt-cast-processed BSCCO-2212 tube subjected to sinusoidal applied fields. The nonlinear f-
relation obtained by experiments in liquefied
is used to find the magnetic diffusion coefficient. The magnetic flux density, shield current density and p-J
loss are considered. According to the result of this study, the shielding current density is varied with external applied field and coordinate in the superconductor tube. The result of analysis can be used to explain the response of a Supercon -ductor-Shield-Core-Reactor subjected to sinusoidal applied fields.
Effects of the External Magnetic field on the Critical Current and AC Loss of HTS Stacked Tapes
Lee, Seungwook ; Hyoungwoo Lim ; Park, Myeongseob ; Lee, Heejoon ; Gueesoo Cha ; Lee, Jikwang ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 87~91
According to the improvement of the HTS wires performance, several types of HTS superconducting machines are being developed. Stacked HTS tapes are used to conduct the current of the HTS power machines. To develop the HTS power machines, the critical current characteristics of a stacked HTS tapes in external field need be examined. In this paper, we present effect of the external magnetic field on the critical current of HTS stacked tapes. The critical current of various Hinds of multi-stacked HTS tapes in external magnetic filed are compare with that of a single HTS tape. Test results show that critical current of single HTS tape is smaller than that of multi-stacked HTS tape in the external field.
Fabrication and Test of Persistent Current Switch for HTS Magnet System
Hyoungku Kang ; Kim, Jung-Ho ; Jinho Joo ; Yoon, Yong-Soo ; Ko, Tae-Kuk ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 92~96
This paper deals with the characteristics of persistent current switch (rCS) system fer applied HTS magnet system. To apply the high-Tc superconductor in superconducting machine such as motror, generator, MAGLEV, MRI, and NMR, the study on high-Tc superconducting persistent current mode must be performed. In this experiment, the PCS system consists otd superconducting magnet, PCS and magnet power supply. The superconducting magnet was fabricated by connecting four double pancake coils (DPCs) in series. The PCS was inductive double pancake coil type and heated up by the SUS 303L tape heater. The optimal length of PCS was calculated and thermal quench state of PCS was simulated by using finite element method(FEM) and compared with experimental results. The optimal energy to normalize the PCS was calculated and introduced. Finally, the persistent current was observed with respect to various ramping up rate and magnitude of charging current.
Comparison of Magnetic Field and AC Losses in Solenoid Coil and Pancake Coil with HTS tape
Park, Myungjin ; Lee, Kwangyoun ; Jungwook Sim ; Gueesoo Cha ; Lee, Jikwang ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 97~101
When HTS tapes are used in power application, they are used by winding form, such as, a pancake and a solenoid. When AC current is applied to the coil, Ac magnetic field is generated in winding. This AC magnetic field acts as an external magnetic field and makes loss. In this paper the radial magnetic field component (
) and the axial magnetic field component (
) in a pancake and a solenoid were calculated by numerical analysis method and compare with measured value. AC losses of a short sample were calculated by Norris equation and n numerical analysis based on Brandt equation. AC losses of the pancake coil and the solenoid coil were also calculated.
Feasibility Study of Superconducting Fault Current Limiter Application to Korean Power System
Kim, Hak Man ; Kim, Jong Yul ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 102~102
Feasibility Study of Superconducting Fault Current Limiter Application to Korean Power System
Kim, Hak-Man ; Kim, Jong-Yul ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 103~106
The short circuit current problem is one of the operational problems that need to be solved by power system engineers in Korea. It is an important issue in the Seoul metropolitan area especially because of highly meshed configuration. Currently, it is regulated by changing 154 kV system configuration from loop connection to radial system, by splitting of the bus where load balance can be achieved, and by upgrading circuit breaker rating. A development project for 154 kV/2 KA SFCL application to 154 kV transmission system after 2010 is proceeding. In this paper, a feasibility study of superconducting fault current limiter (SFCL) is carried out in Seoul metropolitan area to find out the effects of its application and feasibility. This study shows that it can reduce fault current considerably, and as it can minimize the upgrading of circuit breaker rating, the economic potential of SFCL is evaluated positively.
Parametric Study of AC Current Lead for the Termination of HTS Power Cable
Kim, D.L ; Kim, S.H. ; S. Cho ; H.S. Yang ; Kim, D.H. ; H.S. Ryoo ; K.C. Seong ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 107~110
High Temperature Superconductor (HTS) transmission cable can carry more than 2 to 5 times higher electricity and also obtain substantially lower transmission losses than conventional cables. Liquid nitrogen is to be used to cool the HTS power cable and its cost is much cheaper than the liquid helium used for the cooling of metal superconducting wire. In Korea the HTS power cable development project has been ongoing since July, 2001 with the basic specifications of 22.9kV, 50MVA and told dielectric type as the first 3-year stage. The cryogenic system of the HTS cable is composed of HTS cable cryostat termination and refrigeration system. Termination of HTS cable is a connecting part between copper electrical cable at room temperature and HTS cable at liquid nitrogen temperature. In order to design the termination cryostat, it is required that the conduction heat leak and Joule heating on the current lead be reduced, the cryostat be insulated electrically and good vacuum insulation be maintained during long time operation. Heat loads calculations on the copper current lead have been performed by analytical and numerical method and the feasibility study fer the other candidate materials has also been executed.
An experimental study on the cooling performance and the phase shift between piston and displacer in the Stirling cryocooler
Park, S. J. ; Y. J. Hong ; Kim, H. B. ; D. Y. Koh ; B. K. Yu ; Lee, K. B. ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 111~117
In the design of the split type free displacer Stilting cryocooler the motion of the displacer is very important to decide the cooling capacity, which depends upon the working gas pressure, the swept volume in the compression space and the expansion space, operating frequency, the phase shift between piston and displacer, etc. In this study, Stirling cryocooler actuated by the electric farce of the dual linear motor is designed and manufactured. Cool down characteristics of the cold end with laser displacement sensor in the expander of the Stilting cryocooler is evaluated. The charging pressure was 15kg
and operating frequency was 50Hz. Input power and the lowest temperature were about 32W and 67K, respectively. And, displacement of the piston is measured by LVDTs (Linear Variable Differential Transformers), displacement of thedisplacer is measured by laser optic method, and phase shift between piston and displacer is discussed. As the peak-to-peak pressure of the compressor was increased, peak-to-peak displacement of the displacer was increased. The peak-to-peak displacement of the displacer increases in the range of 0 - 64.5Hz(resonant frequency of the displacer), but decreases steeply when the operating frequency is bigger than the resonant frequency. Finally when the phase shift between displacements of the Piston and displacer is 45。, operating frequency is optimum and is decided by resonant frequency of the expander, mass and cross section area of the displacer and constant by friction and flow resistance.e.
Experimental results of Stilting type Pulse Tube refrigerator with inertance tube
Hong, Yong-Ju ; Park, Seong-Je ; Kim, Hyo-Bong ; Koh, Deuk-Yong ; Park, Young-Don ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 118~122
Pulse tube refrigerator, which has no moving parts at its cold section, is attractive fer obtaining higher reliability, simpler construction and lower vibration than Stilting refrigerator or Gifford-McMahon refrigerator. Commonly used means to achieve optimum performance of Stilting type pulse tube refrigerator is an inertance tube. The use of inertance tube is a simple way to generate the phase shift needed to make pulse tube refrigerator operate as efficiently as Stilting refrigerator. In this study, the performance of the inertance pulse tube refrigerator (IPTR) was investigated experimentally. An in-line type IPTR consists of a linear compressor with two reciprocating pistons driven by linear motors, which makes pressure waves, a regenerator a pulse tube with the inertance tube, and a reservoir, The dynamic pressures (the compressor, pulse tube, reservior) and the temperature at the cold heat exchanger are measured to explore the dependence of the inertance tube on the performance of the IPTR. The experimental results show the dependency of cool-down characteristics, no-load temperature and amplitude of the pressures on the length and diameter of the inertance tube.
Standardization of Critical Temperature Measurement based on IEC International Standard
Lee, Kyu-Won ; Kim, Kyu-Tae ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 123~127
For disseminating a ney IEC international standard of critical trmperature of NbTi,Nb
Sn and Bi-2223 Composite Suterconductors, we develpted a measuring system and studied standardization of test method. The measuring system consisted of cryogenic reservoir, base plate, thermometer, voltmeter and current source. Various specimens of the Nbti, Nb
Sn and Bi-2223 composite superconductors were tested using this system for measuring their critical temperatures. After measuring the resistance-temperature relation, the data were compensated with thermoelectric voltages for NbTi Nb
Sn specimens. NbTi specimens showed 9.2 K ~ 9.5 K of transition temperature and Nb
Sn specimen showed about 18 K. Bi-2223 specimens showed 104 K ~ 107 K of transition temperature.
The Effect of Butt gaps on Dielectric Strength of Taped Insulation in Superconducting Cable
Andreev, Alexander-M ; Kim, Soo-Yeon ; Lee, In-Ho ; Kim, Do-Woon ; Shin, Doo-Sung ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 128~132
This paper discusses several electrical properties of tape-type insulation impregnated with liquid nitrogen (
) in superconducting cable. Synthetic polypropylene laminated paper has been tested for its short-term breakdown strength and partial discharge(PD) characteristics under AC voltage. furthermore, the effect of winding parameter on breakdown strength, PD incepti on and extinction electrical stress with different test samples are discussed.
Cryogenic Systems for HTS Power Cables
Yeom, Han-Kil ; Koh, Deuk-Yong ; Lee, Bong-Kyu ; Kim, Ig-Seang ;
Progress in Superconductivity and Cryogenics, volume 5, issue 1, 2003, Pages 133~135
Cryogenic systems are requirement for the operation of HTS power cables. In general, HTS power cables require temperature below 77K, a temperature that can be achieved from the liquid nitrogen at latm or sub-cooled LN2 above latm. HTS power cable needs sufficient refrigeration to overcome its low temperature heat loading. This loading typically cones in two forms : (1) heat leaks from the surroundings and (2) internal heat generation. This paper explains the cooling test system of 10m HTS power cable. This system is composed of storage dewar, auto fill system, core cryostat and cold-box. Storage dewar is a LN2 storage tank and auto fill system is a LN2 supply device to the sub-cooler, Core cryostat is a LN2 flow line. Cold box is a control unit of temperature and flow rate. It is composed of control valve, flow meter, sub-cooler and circulation pump, etc..