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Publication
Modeling cathode spots in vacuum arcs burning on multi-component contacts
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Advisor(s)
Abstract(s)
A self-consistent space-resolved numerical
model of cathode spots in vacuum arcs is developed on
the basis of the COMSOL Multiphysics software. The
model is applied to cathode spots on copper-chromium
(CuCr) contacts of vacuum interrupters. In the limiting
case of large grains, the main effect of change in cathode
material from Cu to Cr is the reduction of thermal
conductivity of the cathode material, which causes a
reduction of spot radius and spot current. Hence, the
model indicates that spots with currents of the order of
tens of amperes on Cu coexist with spots on Cr with
currents between one and two amperes. The parameters
of spots on small Cr grains of the order of 10 µm size are
rather close to those of spots on pure Cu, whereas the
parameters for spots on medium-size Cr grains of
around 20 µm are quite different from those of spots on
both pure Cu and pure Cr. The power flux is directed
from the cathode into the plasma, i.e., it is the cathode
that heats the plasma – and not the other way round.
What maintains the spot is a substantial Joule heating
inside the cathode bulk. About 70 percent of the heat is
generated in the grain and 30 percent in the surrounding
copper. One may hypothesize that such grains are highly
unstable, leading to explosive-like behavior with a
consequent additional loss of cathode material, and a
severe limitation in spot lifetime.
Description
Keywords
Cathode spots Modeling cathode spots Vacuum arcs . Faculdade de Ciências Exatas e da Engenharia
Citation
Benilov, M. S., Benilova, L. G., Cunha, M. D., Hartmann, W., Lawall, A., & Wenzel, N. (2012, September). Modeling cathode spots in vacuum arcs burning on multi-component contacts. In 2012 25th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV) (pp. 317-320). IEEE.
Publisher
IEEE