| 论文简介 |
Abstract—The objective of this paper is to experimentally
determine a relationship between an anode spot formation
threshold current Ith and a dynamic solid angle in drawn vacuum
arcs subjected to axial magnetic fields (AMFs). Experiments
are performed in a demountable vacuum chamber, in which a
Helmholtz coil is installed coaxially with a pair of butt type
contacts. Dynamic solid angle is related to arcing process,
which is subtended by the anode from the cathode center or by
a ratio of the anode diameter D to the contact separation length
l as arc extinguishes (D/l) in a drawn vacuum arc. Although a
traditional definition of solid angle (D/g) is related to a fixed full
contact gap g, no arcing process is considered. In the experiments,
butt type contacts are used with contact material CuCr25 (25%
Cr), and the contact diameters D are 12, 25, 40, 60, and 80 mm.
The contact separation length l as arc extinguished is controlled
in a range of 12–24 mm determined by an opening velocity with
an arcing time fixed at 10 ms. A dc AMF is applied to the
pair of contact with the flux density BAMF adjusted from 0 to
122 mT. Arc current in the tests is at a range of 0–30 kA rms
at 50 Hz. The results show that anode spot formation threshold
current Ith is linearly dependent on the dynamic solid angle D/l
adjusted either by D or l, respectively. And the threshold current
Ith is also linearly dependent on the AMF flux density BAMF
applied. Contact diameter D shows more significant influence on
the threshold current Ith than the contact separation length l
as arc extinguished. In a given contact diameter D and contact
separation length l as arc extinguished, there is a critical peak
arc voltage value, at which an anode spot first formed, regardless
of arc current Iarc and AMF flux density BAMF applied. |
(创新港)
