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ABSTRACT: AC loss characteristics of high temperature superconducting tape in external AC magnetic field carrying AC transport current were theoretically and experimentally studied. We measured the AC transport current and magnetization losses in a conventional Bi2223/Ag multifilamentary tape in the external AC magnetic field carrying the AC transport current. The measured AC magnetization loss, AC transport current loss and total AC loss were compared with the numerical results. The measured AC loss characteristics of the tape can not be explained by the critical state model. Numerical calculations on the AC losses in the tape were performed by using our analytical model introducing the electric field and current density relation locally determined in the filamentary region of the tape. The numerical losses by our model reasonably agree with the measured data.
IEEE Transactions on Appiled Superconductivity 07/2003; · 1.04 Impact Factor
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ABSTRACT: The Committee on Applied Superconducting Apparatuses and
Characteristics of Superconductors, the Institute of Electrical
Engineers of Japan (IEEJ) has made a database on low temperature
superconducting magnets which have been built over the last ten years in
Japan. Based on the data, trends of magnet technology are investigated.
In this paper, an outline of the database is explained and, based on it,
recent trends of magnet technology are investigated, focusing on sizes
and configurations of magnets, current density of magnet windings and
conductor configurations
IEEE Transactions on Appiled Superconductivity 07/1999; · 1.04 Impact Factor
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ABSTRACT: The committee on applied superconducting apparatuses and
characteristics of superconductors, the Institute of Electrical
Engineers of Japan (IEEJ) has made a database on superconducting magnets
which were built over last ten years in Japan. The outline of the
database is explained part I. In part II, stability and hot-spot
temperature of a magnet are investigated. Minimum quench energies,
minimum propagating zones, and Stekly's stability factors are calculated
using the database. Dependence of those stability parameters on the
magnet scale is studied and the design trends of the stability are
discussed. Hot-spot temperatures of the pool-cooled magnets at quench
and energy dump process are also calculated based on the database, and
the trends of design rules for the quench protection are studied
IEEE Transactions on Appiled Superconductivity 07/1999; · 1.04 Impact Factor
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ABSTRACT: We are developing a 4 pole 50 Hz 30 kVA class fully
superconducting generator to investigate the characteristics of
superconducting armature windings subject to a rotating magnetic field.
Compared with other fully superconducting generators that have been
developed and tested, our machine is designed to obtain a higher
armature current. It is generally observed in coils wound from AC
superconducting cable that the AC quench current of the coil is much
lower than its DC quench current. Countermeasures against these AC
current degradation phenomena were developed and applied to the AC cable
and armature winding of our generator. Results of the electrical tests
of the generator are presented and the validity of the countermeasures
is discussed
IEEE Transactions on Magnetics 08/1994; · 1.36 Impact Factor
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ABSTRACT: The development of large-current-capacity AC superconducting
cables is an important step in the realization of AC superconducting
power apparatus. The authors have developed and tested a kA-class
superconducting cable, bundled and twisted with 343 strands. The
measured AC quench current was much smaller than the sum of the critical
current of each strand. The authors theoretically and experimentally
investigate the causes of this current degradation. Many factors were
considered as the causes of this AC current degradation, and the focus
is on the nonuniform current distribution among the strands of a cable
was measured. The measured current distributions are compared with
theoretical current distributions, and the component of AC quench
current degradation is discussed
IEEE Transactions on Appiled Superconductivity 04/1993; · 1.04 Impact Factor
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ABSTRACT: When AC transport current is supplied to an imperfectly transposed
AC superconducting cables, the current distribution among strands
becomes nonuniform because of the inductance imbalance. The influence of
the nonuniform current distribution on the AC quench characteristics of
seven-strand cables was experimentally investigated. It was observed
that the center strand carries the inverse current as compared to the
total transport current. The influence of the current distribution on
the quench current is discussed. The AC quench currents of the following
three cases are compared: a seven-strand cable with small series
impedance, a seven-strand cable with large series impedance, and a
six-strand cable. The quench current of the second case was the largest,
and that of the first case was the smallest. It can be qualitatively
explained by the current distribution among strands, but the difference
between their quench currents was smaller than expected. In a
seven-strand cable with small series impedance, the magnitude of the
inverse current in the center strand was smaller than the theoretical
value. Its peak was eliminated when the total transport current became
large
IEEE Transactions on Appiled Superconductivity 04/1993; · 1.04 Impact Factor
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ABSTRACT: The committee on applied superconducting apparatuses and characteristics of superconductors, the Institute of Electrical Engineers of Japan (IEEJ) has made a data base on low temperature superconducting magnets which have been built over the last ten years in Japan. Based on the data base trends of magnet technology are investigated. In this paper (Part I), out-line of the data base is explained and based on the data base the recent trends of the magnet technology are investigated focusing on sizes and configurations of magnets, current density of magnet windings and conductor configurations. The stability and quench protection of magnets are also investigated in other paper (Part II).
