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Development of kA‐class alternating current superconducting conductors and fabrication of a prototype coreless superconducting autotransformer
Author(s) -
Kajikawa Kazuhiro,
Kaiho Katsuyuki,
Yamamoto Mitsuyoshi,
Fuji Hiroshi,
Sadakata Nobuyuki,
Saito Takashi,
Kohno Osamu
Publication year - 1996
Publication title -
electrical engineering in japan
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.136
H-Index - 28
eISSN - 1520-6416
pISSN - 0424-7760
DOI - 10.1002/eej.4391170504
Subject(s) - electrical conductor , transformer , autotransformer , superconductivity , electrical engineering , materials science , electromagnetic coil , bundle , alternating current , electric power transmission , superconducting magnetic energy storage , voltage , engineering , superconducting magnet , composite material , physics , distribution transformer , condensed matter physics
Recently, multifilamentary superconducting wires with very low ac losses have been produced and practical applications will now be considered. To realize actualsize power machines and apparatuses, it is necessary to develop 1 ‐ 10 kA ac conductors. However, the critical currents of multifilamentary wires at 1 T are several tens of A, and therefore it is necessary to use multistrand conductors consisting of several tens or several hundreds of strands. Such conductors sometimes show ac current degradation because of such factors as (1) nonuniform current distribution, (2) wire motion, (3) temperature increase, (4) longitudinal magnetic field effect, etc. Formerly, a coreless transformer was considered unpractical because of its large exciting current. However, Yamamoto and others proposed that a coreless superconducting transformer could be used as a stepdown autotransformer at the receiving side, utilizing its large exciting current as the reactive power source to cancel the charging current of an underground transmission line or UHV line, and therefore the shunt reactors could be eliminated. In this paper, development of ac‐superconducting conductors aimed at prevention of current degradation are discussed, as well as quench test results of two small coils made with these conductors. In these conductors, low ac low strands with ultrafine NbTi filaments are twisted around a central bundle of stainless steel wires. One of the coils has been designed as a model coreless autotransformer, and its test result is also described.