High-voltage switches with arc preventing or extinguishing devic – Arc preventing or extinguishing devices – Vacuum
Reexamination Certificate
2002-02-27
2004-07-20
Donovan, Lincoln (Department: 2832)
High-voltage switches with arc preventing or extinguishing devic
Arc preventing or extinguishing devices
Vacuum
C218S118000, C218S128000
Reexamination Certificate
active
06765168
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrode of a vacuum circuit breaker, and a method of producing the electrode of the vacuum circuit breaker. Especially, the present invention is applicable to an electrode which is shaped substantially into a cup and has a longitudinal magnetic field.
2. Description of the Related Art
An electric arc occurs between electrodes during circuit break. For improving breaking capability of a vacuum circuit breaker, an entire surface of each of the electrodes is subjected to a damage caused by the electric arc. In other words, concentration of the electric arc in one spot on the surface should be prevented. For receiving the damage (caused by the electric arc) on the entire surface, a constitution having a longitudinal magnetic-field electrode (axial magnetic-field electrode) is adopted, as is seen in FIG.
7
and FIG.
8
.
As is seen in
FIG. 7
, there is provided a constitution of the longitudinal magnetic-field electrode having an electrode
01
(immovable side) and an electrode
02
(movable side). The electrode
01
is constituted of a contact
01
a
, and a coil electrode
01
b
which is disposed on a side opposite to a contact face of the contact
01
a
. The movable electrode
02
is constituted of a contact
02
a
, and a coil electrode
02
b
which is disposed on a side opposite to a contact face of the contact
02
a
. Each of the coil electrode
01
b
and the coil electrode
02
b
has an arm extending radially from an axial center thereof. The arm has a peak end which is fitted with a coil extending circumferentially. With electric current flowing in the coil circumferentially, a magnetic field is caused in parallel with the electric arc (longitudinal magnetic field). The longitudinal magnetic field applied to the electric arc prevents radial diffusion of charged particles, to thereby stabilize the electric arc. The thus stabilized electric arc reduces loss, to thereby control increase in temperature of the electrode. With this, the breaking capability of the vacuum circuit breaker is improved.
The longitudinal magnetic-field electrode is, however, complicated in overall constitution. Moreover, each component part used for the longitudinal magnetic-field electrode is also complicated in constitution (unit constitution). Therefore, producing the longitudinal magnetic-field electrode is costly. For reducing the production cost, the longitudinal magnetic-field electrode should be simple in constitution and reduced in number of component parts.
As is seen in
FIG. 8
, there is provided a constitution of the longitudinal magnetic-field electrode having an electrode
011
and an electrode
012
opposed to the electrode
011
. On a periphery of a cup member of the electrode
011
, a slit
011
a
(inclined) is formed to provide a coil section
011
b
. On a periphery of a cup member of the electrode
012
, a slit
012
a
(inclined) is formed to provide a coil section
012
b
. Moreover, the cup member of the electrode
011
has an opening which is sealed with a contact
011
c
, while the cup member of the electrode
012
has an opening which is sealed with a contact
012
c.
As is seen in
FIG. 9
(cross section of the longitudinal magnetic-field electrode in FIG.
8
), the electrode
011
has a reinforcing pipe
011
d
in addition to the cup member (coil section
011
b
) and the contact
011
c
, while the electrode
012
has a reinforcing pipe
012
d
in addition to the cup member (coil section
012
b
) and the contact
012
c
. Each of the reinforcing pipe
011
d
and the reinforcing pipe
012
d
is mated in a hollow section of the cup member, so as to reinforce stability (of the longitudinal magnetic-field electrode) against mechanical impact caused by a contacting of the contact
011
c
on the contact
012
c
when the vacuum circuit breaker is inputted.
The longitudinal magnetic-field electrode (having the cup member) in FIG.
8
and
FIG. 9
is smaller in number of component parts than the longitudinal magnetic-field electrode in FIG.
7
. However, it is necessary for the cup member in FIG.
8
and
FIG. 9
to be formed with the slit
011
a
and the slit
012
a
, so as to provide, respectively, the coil section
011
b
and the coil section
012
b.
Therefore, as is seen in
FIG. 10
, there is provided a turn blade
013
shaped substantially into a disk. For machining the cup member (copper) so as to form the slit
011
a
and the slit
012
a
, the turn blade
013
is turned with a predetermined inclination angle relative to the cup member. Conventionally, this is a general machining (slitting) method.
As shown in
FIG. 10
, machining with the turn blade
013
has advantages such as easiness and low cost. The machining with the turn blade
013
has, however, difficulty in securing a long circumferential dimension of the slit
011
a
and the slit
012
a
. Smaller inclination angle of the turn blade
013
(relative to the cup member) makes the machining more difficult.
The longitudinal magnetic field between the electrode
011
and the electrode
012
is proportional to a product of electric current (flowing in each of the coil section
011
b
and the coil section
012
b
) and a turning angle. The product is defined as “ampere·turn=i·n”. In other words, the circumferential length of each of the slit
011
a
and the slit
012
a
is an important determinant of the turning angle (number of turns n) of the electric current. The longer the circumferential length is, the higher the longitudinal magnetic field is.
The above summarizes that the electrode
011
(having the cup member) and the electrode
012
(having the cup member) constituting the longitudinal magnetic field according to the related art have a difficulty in obtaining strong magnetic field, and therefore are not sufficient for the vacuum circuit breaker that requires capability of breaking a high voltage and a large electric current.
Moreover, the vacuum circuit breaker with the electrode
011
and the electrode
012
according to the above related art is disadvantageous in terms of strength for the following causes: The smaller the inclination angle of slitting the slit
011
a
and the slit
012
a
is, the more acute the junction A (see
FIG. 8
) is. The acuteness of the junction A (coil section
011
b
with the contact
011
c
, and the coil section
012
b
with the contact
012
c
) causes stress concentration. Thereby, the junction A is likely to peel after repeated operations (opening and closing) of the electrode
011
and the electrode
012
of the vacuum circuit breaker.
Hereinafter described are more details of the vacuum circuit breaker having the electrode
011
and the electrode
012
.
As is seen in
FIG. 11
, there is provided a conceptual view of the vacuum circuit breaker having the electrode
011
and the electrode
012
. The vacuum circuit breaker is constituted of a vacuum envelope
017
, the electrode
011
and the electrode
012
as main component parts. The vacuum envelope
017
has an insulator tube
014
made of material such as ceramic, glass and the like. The insulator tube
014
has a first end (upper) sealed with an end plate
015
made of metal, and a second end (lower) sealed with an end plate
016
made of metal. With the thus sealed internal section, the vacuum envelope
017
is highly exhausted (vacuum). In the vacuum envelope
017
, the electrode
011
is fixed to an end (lower in
FIG. 11
) of an immovable rod
018
while the electrode
012
is fixed to an end (upper in
FIG. 11
) of a movable rod
019
. The electrode
011
and the electrode
012
are opposed to each other, and make a relative movement toward (contacting) and away (parting) from each other. With an inclination, an electric current I flows in the coil section
011
b
(of the electrode
011
) and the coil section
012
b
(of the electrode
012
), to thereby generate a longitudinal magnetic field B. With the thus generated longitudinal magnetic field B, the vacuum circuit breaker has a good breaking capability. In
FIG. 11
, also shown
Fukatsu Yoshihiro
Matsui Yoshihiko
Nishijima Akira
Takebuchi Hidemitsu
Donovan Lincoln
Foley & Lardner LLP
Kabushiki Kaisha Meidensha
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