High-voltage switches with arc preventing or extinguishing devic – Arc preventing or extinguishing devices – Vacuum
Reexamination Certificate
2000-06-02
2002-11-12
Donovan, Lincoln (Department: 2832)
High-voltage switches with arc preventing or extinguishing devic
Arc preventing or extinguishing devices
Vacuum
C218S123000, C218S127000
Reexamination Certificate
active
06479778
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a vacuum switch including windmill-shaped electrodes therein.
FIG. 12
is a sectional view showing the overall structure of a vacuum switch which has a pair of contacts hermetically sealed within a highly evacuated vacuum vessel. An insulating cylinder
21
has attached to its opposite ends end plates
22
a
and
22
b
to constitute a vacuum vessel
23
of which an inner portion is highly evacuated. Opposingly disposed within the vacuum vessel
23
are a stationary electrode
1
a
secured to a tip of a stationary electrode rod
24
a
extending through one of the end plates
22
a
and a movable electrode
1
b
secured to a tip of a movable electrode rod
24
b
extending through the other of the end plates
22
b.
A bellows
25
is disposed across the movable electrode rode
24
b
and the end plate
22
b.
The bellows
25
allows the movable electrode rod
24
b
connected to an operating device (not shown) to be driven to move the movable electrode rod
24
b
in the axial direction. This movement of the movable electrode rod
24
b
causes the electrode
1
a
of the stationary side and the electrode
1
b
on the movable side to be brought into and out of electrical contact. In order to prevent metal vapor diffused from the arc generated across the electrodes
1
a
and
1
b
from depositing on the inner wall surface of the vacuum vessel
23
, a shield
26
is mounted to the inner wall surface of the insulating cylinder
21
by a shield support
27
.
The electrodes
1
a
and
1
b
of such vacuum switch have the same configuration, which are windmill type with grooves in the electrode. By the provision of these grooves, the electrical path in the electrode is limited to define an electrical path of a reciprocating loop-shape extending in the circumferential direction, whereby the arc is driven by a magnetic field to move along the circumference of the electrode, so that the arc is prevented from staying at one position to avoid a local melting of the electrode, thus improving the interrupting performance. Also, in order to obtain a strong magnetic drive force immediately after the arc generation, the structure has the arc-running surface and contact surface in accordance with each other.
FIGS. 13
to
16
illustrate a structure of a windmill-shaped electrode of a conventional vacuum switch tube disclosed for example in Japanese Patent Laid-Open No. 4-368734,
FIGS. 13 and 15
being plan views and
FIGS. 14 and 16
being side views.
In the figures, the electrode rod
24
(the stationary electrode rod
24
a
or the movable electrode rod
24
b
) have thereon a windmill-shaped electrode
1
(the stationary side electrode
1
a
or the movable side electrode
1
b
). The windmill-shaped electrode
1
is integrally comprised of an auxiliary electrode
31
and a ring-shaped electrode
32
. The auxiliary electrode
31
comprises a central portion
33
mounted to an end portion of the electrode rod
24
, a plurality of arms
34
disposed to the central portion
33
in a windmill-shape manner or Buddhist cross-shape and extending in an arc from the central portion
33
toward the outer circumferential portion, and connecting portion
35
disposed at each of the tips of the plurality of the arms
34
. The ring-shaped electrode
32
has an annular shape with its width substantially equal to the width of the arms
34
of the auxiliary electrode
31
and the ring-shaped electrode
32
is connected to the connecting portions
35
.
In such an arrangement, when the windmill-shaped electrodes
1
(the stationary side electrode
1
a
and the movable side electrode
1
b
) are separated, an electric arc generates at the contacting surface of the ring-shaped electrode
32
. When the arc generates at the point A of
FIGS. 15 and 16
, for example, an electric current
11
flowing through the arms
34
of the auxiliary electrode
31
generates a magnetic drive force F in the circumferential direction of the ring-shaped electrode
32
, whereby the arc is driven to rotate around the outer circumference of the ring-shaped electrode
32
.
Also, when the arc generates at the position which is not the connecting portions
35
, such as the point E of
FIGS. 15 and 16
, for example, a magnetic drive force in the circumferential direction of the ring-shaped electrode
32
is also generated by an electric current
12
flowing into the ring-shaped electrode
32
from the arms
34
of the auxiliary electrode
31
. Therefore, the arc is rotated along the ring-shaped electrode
32
.
As has been described, in the conventional windmill-shaped electrode
1
, the arc generates at the ring-shaped electrode
32
and the arc is magnetically driven immediately after the arc generation. As a result of this, the local temperature rises at the windmill-shaped electrodes
1
due to the arc before it is magnetically driven after the arc generation, thus improving the interrupting performance.
In the windmill-shaped electrode
1
of the above-described conventional vacuum switch tube, when an electric arc is generated at a point E
1
of
FIG. 17
, for example, between the neighboring connecting portions
35
and
35
, in addition to the current I
2
flowing into the arc through the arms
34
a
, an electric current I
3
from the arm
34
b
flows. This current I
3
generates a force F
3
in the direction of preventing the rotation of the arc, so that the time from the arc generation until the magnetic driving of the arc cannot be made short, not improving the interrupting performance.
Accordingly, an object of the present invention is to provide a vacuum switch free from the above-discussed problems of the conventional vacuum switch.
Another object of the present invention is to provide a vacuum switch in which an electric arc can be strongly magnetically driven immediately after the arc generation irrespective of the position on the contacting surface between the stationary side electrode and the movable side electrode at which the arc is generated, thereby improving the interrupting performance.
SUMMARY OF THE INVENTION
With the above objects in view, the present invention resides in a vacuum switch comprising: a pair of windmill-shaped electrodes disposed within a vacuum tube and each having formed therein a plurality of spiral grooves extending from a central portion to a circumferential portion thereof, and including a windmill-shaped portion separated from each other by said grooves and a plurality of contact portions separated by said grooves and having a thickness larger than that of said windmill portion; said windmill-shaped electrodes being arranged such that said contact portions are brought into contact with each other when said pair of windmill-shaped electrodes are closed, an electric arc is generated on said contact portions when said pair of windmill-shaped electrodes are separated from each other, a magnetic flux is generated by an electric current flowing into the electric arc from said windmill portion, and that a component parallel to a contact surface of said magnetic flux and serving as an arc driving force with respect to a range of 0.5 mm from the contacting surface contacting with said contacting portion of the leg portion of said arc has a magnetic flux density equal to or larger than 0.01 tesla with respect to an electric current of 1 kA.
A ratio of an inner diameter Di of said contact portion to an outer diameter D of said windmill-shaped electrodes may be equal to or greater than 0.4.
The difference in thickness between the windmill portions and the contact portions may be equal to or less than 5 mm.
Each of said windmill-shaped electrodes may be connected to each of the pair of electrode rods, a ratio of a diameter d of said connection portion of said electrode rod to an inner diameter Di of said contacting portion may be equal to or less than 0.6.
The windmill-shaped electrodes may be made of a Cu—Cr material including 20—60 weight % of Cr.
REFERENCES:
patent: 3522399 (1970-07-01), Crouch
patent: 4629839 (1986-12-01), Falkingham
patent: 5293506 (1994
Kimura Toshinori
Koga Hiromi
Koyama Ken-ichi
Sawada Atsushi
Donovan Lincoln
Leydig & Voit & Mayer
Mitsubishi Denki & Kabushiki Kaisha
LandOfFree
Vacuum switch including windmill-shaped electrodes does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vacuum switch including windmill-shaped electrodes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vacuum switch including windmill-shaped electrodes will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2974533