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Arc erosion characteristics of Cu‐W contact at load current range in SF 6 gas
Author(s) -
Hori Koichi,
Ohtsuka Masao,
Hara Masanori
Publication year - 1997
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/(sici)1520-6416(19970115)118:1<41::aid-eej4>3.0.co;2-n
Subject(s) - materials science , electric arc , anode , erosion , cathode , magnetic field , arc (geometry) , current (fluid) , grain size , analytical chemistry (journal) , evaporation , metallurgy , composite material , electrical engineering , electrode , chemistry , thermodynamics , geology , paleontology , physics , geometry , mathematics , engineering , quantum mechanics , chromatography
Development of SF 6 gas‐insulated switches that have a long service life and are highly reliable at medium voltage ratings require arc erosion of contacts in SF 6 gas to be decreased. The effects of SF 6 gas pressure and magnetic field for arc blow‐out on erosion were studied experimentally in detail using sintered Cu‐W contacts. The test current, SF 6 pressure and magnetic field were 100 to 400 A, 0.1 to 0.6 MPa and 0 to 50 mT, respectively. The results show that the arc erosion rate increased linearly with the SF 6 pressure. The magnetic field effectively reduced anode erosion (i.e., the application of a mere 50 mT lowered the erosion rate to 1/3 to 1/4). These phenomena may be attributed, respectively, to the increase in evaporation rate according to the shrinkage of arcing spot areas caused SF 6 pressure and a decrease of the evaporation rate correlating to high‐speed movement of the arcing spot on the anode by the magnetic field. However, the cathode erosion was insensitive to the magnetic field. The influence of both W grain size and composition ratio, Cu:W, on the erosion rate was also studied. The smaller W grain at Cu content of 50 to 70 wt.% was found to be best for suppression of erosion under the present conditions. Further, the increase of N 2 mixture ratio to SF 6 under constant total gas pressure greatly decreased contact erosion. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (1): 41–51, 1997