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fatigue on critical current and n-value are reported. Fatigue
studies include strains up to 0.1 %. Scanning electron
micrographs of the fatigued conductors are used to identify
the sources of failure in conductors.
WEA02PO10
Quench Behavior of YBa2Cu3O7 Coated Conductors
with an AC Transport Current
J. Schwartz, U. Trociewitz, NHMFL; D. Knonll, D. Nguyen,
P. Sastry, X. Wang, G. Zhang, Center for Advanced Power
Systems, Florida State University; C. Thieme, American
Superconductor Corp.
Normal zone creation and quench propagation
measurements were performed on YBa2Cu3O7 coated
conductors with AC transport current. The minimum
quench energy and the quench propagation velocity were
measured as a function of temperature, AC transport
current and frequency. Self-field AC losses of the tapes
were also measured at the same temperatures and
currents to calculate the internal thermal loads. The
samples were conductively cooled in vacuum using a
cryocooler. A resistive heater was used to create a local
normal zone whose propagation was followed through
temperature and voltage measurements along the sample
length. An analysis of the results is presented.
WEA02PO11
Temperature Dependence of Critical Currents and AC
Losses of Bi2Sr2Ca2Cu3Ox and YBa2Cu3Ox Tapes
J. Schwartz, U. Trociewitz, NHMFL; D. Knonll, D. Nguyen,
P. Sastry, X. Wang, G. Zhang, Center for Advanced Power
Systems, Florida State University; C. Thieme, American
Superconductor Corp.
Critical currents and AC transport losses of YBa2Cu3Ox
and Bi2Sr2Ca2Cu3Ox tapes were measured between 40 K
and 80 K. The AC losses were measured electrically at
power frequency using the lock-in method. The samples
were conduction cooled by a cryocooler and a temperature
controller was used to maintain a constant temperature. AC
losses were measured for transport current frequencies
between 50 Hz and 500 Hz. Results of the analysis of the
temperature and frequency dependence of critical current
and AC losses are presented.
WEA02PO12
Optimization and Design of the Permanent
Magnet Guideway with the High Temperature
Superconductor
H. Song, J. Zheng, X. Wang, S. Wang, J. Wang, Southwest
Jiaotong University.
To optimize the high temperature superconductor (HTS)
and permanent magnet guideway (PMG) levitation system,
the levitation and guidance forces were calculated for
different kinds of the PMG. Given a cross section area of
the permanent magnet and the superconductor arrays, the
ratio between the thickness and width of the PMG has
adverse influence on levitation and guidance force. It
seems that, the more the thickness, the more the levitation
force, the less the guidance force. Moreover the materials
and geometries of the PMG were verified, it was found that
the iron has great influence on the flux distribution and
even the levitation or guidance force. Additionally, the
cross section of the PMG was changed from rectangle to
trapezium in size and its optimum design was present for
the given HTS arrays in the end.
WEA02PO13
Alternating current characterization of the HTS
Bi2223/Ag High Strength Tape under magnetic field
produced by direct current
E. Ruppert Filho, R. Cassiolato de Freitas, State University
of Campinas; C. Alberto Baldan, C. Yujiro Shigue,
Chemical Engineering Faculty of Lorena.
HTS tapes are commercially available for applications in
power system devices. However to do that it is necessary
to have the superconductor material characteristic curve
which relates the values of the critical AC electrical current
circulating in the material with the magnetic flux density at
the material surface at 77K. This paper presents a
methodology to construct the characteristic curve of the
HTS Bi2223/Ag High Strength Tape, manufactured by the
American Superconductor, under DC magnetic field using
a short material sample. The DC magnetic field is produced
by an electromechanical device constituted by a magnetic
core with a small air-gap and an insulated copper wire coil
wound on one of its columns carrying DC electrical current.
The material sample is inserted in the air-gap firstly in
perpendicular position, and after in parallel position, related
to the air-gap magnetic field . Many different curves relating
rms AC voltage between the sample terminals with the AC
rms current in the sample are constructed for different
values of the magnetic flux density. The critical current
value for each magnetic flux density value is the one where
the voltage on the sample reaches a defined value. Care
must be taken with the measurements and positioning of
the sample in the test assembly. The methodology, data
test assembly, a lot of results for perpendicular and parallel
position of the tape and the conclusions are completely
reported in the paper.
WEA02PO14
Analysis of residual Bi-2212 in extracted Bi-2223/Ag
filaments using X-ray diffraction
O. van der Meer, B. Metz, S. Harkema, B. ten Haken, H.
ten Kate, University of Twente, Low Temperature Division;
V. Vonk, H.Graafsma, ESRF.
Bi-2223/Ag superconducting tapes are made by a powderin-tube
process in which the Bi-2212 phase is converted
into the desired Bi-2223 phase during several heat
treatments. The critical current density Jc of state-of-the-art
Bi-2223/Ag tapes in self field is about 400 A/mm2, which is
about 15-20% of the maximum local values found by
magneto-optical imaging. Magnetization experiments
indicate that the residual 2212 concentration is closely
correlated to the Jc of the superconductor. However such
experiments provide no spatial information about the
location of 2212 still present in the tape. Quantitative
information on the local amount of Bi-2212 and its exact
location is obtained from X-ray diffraction measurements. A
very small but powerful X-ray beam of 1.5x13 µm2 is used
provided by the ESRF. We studied the variation in residual
Bi-2212 concentrations in three different filaments
extracted from one tape and also at different location within
the single filament. Regions of 5-20 µm size with lower and
higher Bi-2212 concentrations are observed. In the paper
the experimental set-up is presented, characteristic results
are presented and the results are interpreted in relation to
the transport properties of the Bi-2223 filaments.
WEA02PO15
Critical current degradation of Bi-2223 composite
tapes induced by cyclical deformation and fatiguerelated
effects
C.Y. Shigue, U. Oliveira, F. Carvalho-Junior, C. Baldan,
DEMAR/FAENQUIL; E. Ruppert-Filho, State University of
Campinas.
Superconductors based on the HTS Bi2Sr2Ca2Cu3Ox (Bi-
2223) compound embedded in an Ag matrix have been
93 MT-19 2005, Genova