Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
llVI-04044
~;33~ :
This invention relates to an electric circuit interrupter .
of the vacuum type and, more particularly, to a circuit
interrupter of this type which comprises two sets of
relatively movable contacts electrically connected in parallel
for carrying continuous current through the interrupter.
In most vacuum interrupters, the force required to
hold a pair of separable contacts in engagement during the
passage of high current therethxough varies directly with
the square of the current. It has been recognized that
this force can be reduced by providing a plurality of
se~s of contacts electrically connected in parallel for
sharing the total current through the interrupter~ One
way of constructing such an interrupter is to mount the~
movable contact of each pair on the usual long slander~ .
movable contact rod and to arrange these movable contacts
rods in close side-by-side relationship. A problem involved
in such an arrangement is that the high magnetic forces
developed between the movable contalct rods when high currents ..
flow therethrough tend to ~orce the rods together, making
it difficult to properly guide and operate the contact ;
ro~s. ~-
One solution to this pro~lem is disclosed and claimed
in Canadian Patent No. 1,046,115 - Kurtz and Sofianek .
issued January 9, 1979, and assigned to.the assignee of
the present invention~ In that application/ the two
electrically-parallel pairs of contacts are located at .. :
opposite ends of the envelope of the interrupter, and
current is carried physically.past each contact pair via an
.- .
electricall~-parallel conductive path extending through the ; .
, ......... .
? 30 other pair. Each of these parallel conduGtive paths is .. ~-
. constituted, in part, by a single one of the rod electrodes
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~6~3~ llVI-04044
of a rod-array type of electrode arrangement of the general
type disclosed and claimed in U.S. Patent No. 3,679,474
dated July 25, 1972 - Rich, assigned to the assignee of
the present invention. On the distal end of this single
rod electrode, means i5 provided for mounting the stationary
contact of the pair of relatively movable contacts in the
parallel path.
A problem involved in such a design is that high
magnetic forces of attraction can be developed between the
movable contact rod and the parallel single rod electrode
in the region where these parts are in proximity. In the
aforesaid Kurtz and Sofianek Patent, this problem is
solved by providing around each movable contact rod a
conductive tube that is electrically connected in series with
the aforesaid single rod electrode. This tube distributes
, the current flowing through the single rod electrode circum- -
.. .
ferentially above the movable contact rod surrounded by the
` tube, thereby providing a coaxial conductor arrangement
wherein relatively low forces are present between the con-
ductors.
An object of our invention is to provide an interrupter ,
design of generally the type disclosed in the aforesaid
Kurtz and Sofianek Paten~ wherein a conductive tube i~
not required around the movable contact rod in order to
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limit the transversely-directed forces acting on the movable
contact rod during high momentary currents.
~i ' .
As pointed out hereinabovet in the Kurtz and Sofianek
, Patent the stationary contact of each contact pair is
;lf mounted on the distal end of a single rod electrode of a
l 30 rod array type of electrode arrangement~ It may be necessary
-, to locate the stationary contact in a location radially off-
~' set from the longitudinal axis of the single rod electrode
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~ ~663~ llVI-04044
by a relatively great distance. Such radially-offset mounting
on the distal end of a single rod electrode is not an ideal
arrangement from a mechanical strength viewpoint. More
specifically, closing forces on such contacts heavily load the
single supporting rod electrode in cantilever bending and also
subject the mounting element between the contacts and the
supporting rod electrode to relatively serve cantilever bending
stresses.
Accordingly, another o~ject is to provide, for a rod-
array type of vacuum interrupter having parallel connected sets
of contacts near opposite ends of the interrupter, means for mount-
~ .
ing the contacts on the rods in such a way that the rods and the
~ contact mounting can easily withstand high closing forces on the
`~ contacts.
~ Another object is to mount the stationary contact structure -
`1 of each set of relatively-movable contacts in such a manner that
the closing forces on each set are distributed between a
! plurality of the rod electrodes.
In carrying out the invention in one form, we provide a
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vacuum interrupter comprising a highly evacuated envelope that
has metal end caps at its opposite ends. A first plurality of
`! rod electrodes within the envelope are mounted on the first end
cap and are electrically connected thereto. A second plurality
. . .
of rod electrodes within the envelope are mounted on the second
end cap and are electrically connected to the second end cap.
The first and second~pluralities of electrodes are positioned so
~, as to form a ring of electrodes within the envelope. The
~li electrodes of the first plurality interleave with those of the
-'~ second plurality. The electrodes of the first plurality have a
~i 30 polarity opposite to the polarit~ of the electrodes of the second
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~66334 llVI-^04044
plurality, whereby inter-electrods gaps are defined between
juxtaposed interleaving electrodes of said ring. Extending
transversely of the rod electrodes and attached to the
distal ends of predetermined rod electrodes of said second
plurality, we provide ~irst conductive support structure
on which a first generally stationary contact is supported
in a position intermediate the locations at which said first
support structure is attached to said predetermined rod
electrodes of said second plurality. Extending transversely
of the rod electrodes and attached to the distal ends of
predetermined rod electrodes of said first plurality, we :
provide second conductive support s~ructure on which a
second generally stationary contact is supported in a position `
intermediate the locations at which said second support
structuer is attached to said predetermined rod electrodes
of the first plurality The first and second stationary :
contacts are disposed in positions spaced longitudinally
o~ the longitudinal aXis of the ring. First and second
movable contacts are provided within the envelope ~or re- -
1 20 spectively engaging the irst and second yenerally stationary
contacts A first movable contact rod on which said first
contact rod on which said ~irst contact rod is mounted ex- .:
tends in sealed relationship through the first end cap. :
A second movable contact rod on which said second contact
is mounted extends in sealed relationship through said
second metal end cap. The t~o pairs of engageable contacts
are electrically connected in parallel with each other . -
. . .
while the interrupter is closed. ; :
For a better understanding of the invention7 re~erenc~ ~ ;
may be had to the accompanying drawings, wherein~
FIG 1 is a side-elevational view, mostly in section~
showing a vacuum interrupter embodying one form of the in-
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1~633 ~ llVI-04044
vention.
Fig. 2 is a sectional view along the line 2-2 of Fig. 1 .
Fig, 3 is a sectional view of a portion of an interrupter
embodying a modified form of the invention.
Referring now to Fig. 1, the illustrated vacuum inter-
rupter comprises a highly evacuated envelope 10 that comprises
a tubular housing 11 of insulating material and a pair of
metal end caps 12 and 13 disposed at opposite ends of the
housing and sealed thereto by conventional scals 14~
'.:
m e interrupter comprises two pairs 20 and 22 of
separable contacts electrically connected in ~ with
each other in a manner that will soon become apparent. Con-
. tact pair 20 is located near the upper end cap 12, and con-
o tact pair 22 is located near the lower end cap 13. Each :
contact pair comprises a generally stationary con~act 25
suppoxted in a manner soon to be described, and a movable
contact 26 vertically movable into and out of engagement
with stationary contact 25~ The movable contact 26 of each
pair is brazed to the inner end of a vertically-movable
2 0 conductive contact rod 28 that extends through the adjacent
end cap.
` Por providing a ~eal b~tween each contact rod 28 andthe envelope, an elongated metal bellows 30 is provided for
-l each contact rod~ Each of thase bellows has one end joined
' to the contact rod by a suitable vacuum-tight joint and its
`1 opposite end joined to the adjacent end cap by anothçr suit- :
~ able vacuum-tight joint. The bellows allows the contact
`-~, rod to be move~ vertically without impairing the vacuumI in~ide the envelope. :
To assist in guiding each contact rod 28 for substan-
tially straight-line motion along its longitudinal axis, a
~I tubular guide 32, preferably o~ non-magnetic material, is
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llVI-04044
~6~3~
provided around each contact rod. This quide 32 has a
radially extending flange that is fixed to the adjacent
; end cap. At the inner end of guide 32, there is a sleeYe
bearing 34~ preferably of polytetrafluorethyleneg fixed to
the guide and slidably receiving contact rod 28.
~ Each movable contact rod 28 is electrically connected
; to the end cap th~ough which is extends ~y suitable flexible
conductive braid. Such braid is schematically shown at 36
and at 37. The purpose of this braid will soon appear
10 more clearly.
me interrupter also includes an interleaving rod elec~
~; trode arrangement of the general type disclosed and claimed
- in the aforesaid Rich U.S. patent ~o. 3,6799474 dated
July 251 1972. This arrangement compxises a ~irst plurality
of rod electrodes 40 mounted on and electrically connected
to lower end cap 13 and a second plurality of rod electrodes
42 mounted on and electrically conmected to upeer end cap
12. The rod electrodes 40 and 42 are positioned so as to
form a generally circular ring of electrodes concentrically
~urrounding the ce~tral longitudinal axis 45 of the in-
. . .
terrupter. The upwardly_projecting electrodes 40 inter-
leave with and longitudinally overlap the downwardly-project-
ing electrodes 42 and are spaced circumferentially o the
ring from the immediately-adjacent electrodes 42. Since
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alternate electrodes are connected to opposite end caps,
the juxtaposed electrodes are considered to alternate in
' ~ ~c}~ai~y polarity when the interrupter is open.
For supporting the stationaxy contact 25 o~ the lower
pair 22 of contacts, a spider 56 of highly conductive metal
i~ provided at the lower9 or distal9 ends of the downwardly
projecting rod electxodes 42. As shown in Fig, 2, this
spider compri~es a central portion 57 and ~our arms 58
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llVI-04044
radiating outwaxdly therefrom. Contact 25 is suitably
brazed to the central portion 57 of the spider, and the
outer ends of arms 58 are suitably brazed to the lower
ends of the downwardly projecting rod electrodes 42 The
stationary contact 25 is an annular meimber having a hole
through its center, and the central portion 57 of the
spider has a hole therein aligned with the hole in the
~` annular contact~ the two holes forming a centrally-disposed
passage 60, the purpose of which will soon appear more
clearly. -
The stationary contact 25 of the upper pair 20 of --
contacts is supported on the upper ends of the upwardly-
projecting rod electrodes 40 in substantially the same
way as the lower stationary contact is supported on the
downwardly_projecting rod electrodlss 42. The spider 66 of
this upper support is o~ the same configuration as the
lower spider 56. A passage 70, corresponding to passage
60 in the lower spider, axtends through the upper spider
and stationary contact 25 supported thereon.
It should be noted that the upwardly-projecting rod
electrodes 40 extend pask the lower spider 56 through large
indentations 59 in the periphery of the spider and are su~fi-
ciently spaced ~rom the spider, as shown in Fig. 2, to
provide ample electrical clearance between these parts~ which
are at opposite polarities when the interrupter is open.
Similarly, the downwardly-projecting rod electrodes 42 ;~
extends past the upper spider 66 with sufficient electxical
' clearance to withstand the voltage present between these
; parts.
The outer ends 28a o~ the two movable contact rods 38
may be thought of as the terminals of the interrupter. When
the interrupter is closed, current entering through lower
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633~ llVI 04044
terminal 28a flows upwardly through th~ interrupter via
either o~ two electrically parallel paths One path is
through the series combination of: lower contact rod 28,
lower contact pair 22, spider 56, the four rod electrodes
42 in parallel, and partæ 12, and 37. The obher path is
through the series combination of: parts 36 and 13, the ~-
four rod electrodes 40 in parallel, spider 66, upper
contact pair 20, and the upper contact rod 28. ~hose two
parallel paths are constituted by substantially identical
parts, as a result of whlch their impedances are substantially
equal, thus forcing the total current to divide substantially
equally between them. Since only about half the total
current pas~es through each pair of contacts as compared
to an interrupter where there is only a single pair of
contacts, the force required to hold each of our sets of
contacts clo ed against the magnetic forces developed by
;i a given total current through the interrupter is only about
.
`~ one-fourth that required in the case of the interrupter
with a single pair o contacts. m is means the total force
required on our t~o sets of contacts is only about one-half
~ that required in an interrupter with a single set o~ contacts.
; This substantial reduction in for~e requiremen$s is a dis-
tance advantage in that it permits a substantial reduction
~!, in the size o~ ths required closing mechani~ma
For effecting opening of the interrupter, the two
movable contact rods 28 are drivan substantially simultaneously
outwardly of the interrupter rom their illustrated closed
positions to ef~ect ~ubstantially simultaneous contact-
; separation at the two sets o contact~ 20 and 22 Closing
30 is effected after such an opening operation by simultaneouslyreturning the movable contact rods 28 to their illustrated
positions to produce substantially simultaneou~ contact-
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llVI-04044
" ~16633~
engagement at the two contact pairs 20 and 22. The linkage
for effecting such contact-rod motion is not shown since
it can be of any suitable conventional design, e.g., that
illustrated in Fig. 2 of Canadian Application Serial No.
228,770 dated June 5, 1975 - Crouch et al, and assigned
to the assignee of the present invention.
During a circuit-interrupting operation, the substantially
simultaneous contact-separation occurring at the two contact pairs
20 and 22 normally results in an arc being established between
- 10 the contacts 25, 26 of each pair. Ionized arciny products from
these arcs are quickly propogated into the gaps between the
adjacent rod electrodes 40 and 42, causing these inter-electrode
` gaps to break down electrically, thus forming diffuse arcs
between juxtaposed pairs of rod electrodes. These di~fuse
arcs extend circumferentially o~ the envelope and are capable of --
carrying relatively high currents ~ithout the formation of
anode spots, as is explained in the aforesaid Rich U.S. Patent
No. 3,679,474 dated July 25, 1972. Although current may
sometimes continue to flow through the inter-contact gaps
af~er arcs are established between the rod electrodes, this
inter-contact current is only a small percentage of the total
current and does not prevent interruption at an early current
, . - .
- zero.
-j To assure prompt breakdown of the inter-electrode gaps
following arc-initiation at the contact pairs 20 and 22, it
, is important that there be good communication between the
.;., . ~,
inter-contact gaps and the inter-electrode gaps so that
ionized arcing products from the inter-contact arcs can be -
~uickly propogated into the inter-electrode gaps. The
passageways 60 and 69 extending through the stationary con-
tact structures into the central region o~ the interrupter
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contribute to such good communication. In this respect,
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~ ~ llVI-04044
arcing products from arc~ between the contacts 25, 26 can
flow inwardly through these passage and diffuse radially
outwardly into the inter-electrode gaps, It should also be
apparent from Fig. 2 that the large indentations in the
peripheries of spiders 56 and 66 provide relatîvely un-
restricted passages through which arcing products can flow
between the intar-contact gap and the inter-electrode gaps
to promote the desired prompt breakdwon of the inter-
electrode gaps.
For protecting the insulating housing 11 from being
coa~ed by arc-generated metallic particles, a plurality of
tubular metal shields 70, 71, and 72 are provided. Central
shield 70 is electrically isolated from the end caps 12 and
13, and shields 71 and 72 are end shields electrically con-
nected to the end caps. m ese shields act in a known
manner to intercept and condense arc-generated metallic vapors
be~ore they can reach the insulating housing 11.
Each o~ the rod 40 and 42 is preferably a composite
member comprising a tubular shell of vacuum-melted ~teel and
a copper core filling the ~hell. me stoel shell is relied
upon or high mechanical strength and high dielectric
strength and the copper core, which ha~ high electrical and
tharmal conductivity, is relied upon primarily for carry-
.. . . .
; ing continuous currents through the rod and for heat dis-
~ sipation purposes, A suitable steel is one of those dis-
-~ closed and claimed in U,S. Patent Nv, 3,769,538 dated
.~ .' .
October 30, 1973 - Harris, assignsd to the assignee of the
present invention. In anothsr form of the invention, each
rod electrode comprises a copper shell and a core of stesl.
The material o~ the shell, in either ~orm, should be re-
latively gas-ree so as to substantially prevent the
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evolution of gases therefrom when exposed to arcingO
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llvI-04044
3~
As pointed out hereinabove, an interrupter having side~
by-side parallel connected movable contact rods is subject
to the problem that under high current conditions~ high
magnetic forces are developed between the adjacent movable
contact rods, ~ending to force the xods together and deform
them making it difficult to guide and properly operate the
movable contact rods. In the aforesaid Kurtz and Sofianek
application~ this problem is overcome by locating the two
i~ contact pairs at opposite ends of the interrupter and by
carrying current to one contact pair past the other contact
pair via a conductive tube surrounding the movable csntact
rod, We are able to dispense with such a tube because we
carry the current past each contact pair via a plurality of
rod electrodes distributed generally symmetrically about
the periphery of the movable contact rod. ~or example, the
current flowing past the lower contact pair 22 flows through
the rod electrodes 40 in the region of the movable contact
rod 28, Since these rod electrodes 40 are generally
symmetrically located about the periphery of the contact rod
~, .
~, 20 28, as will be e~pecially apparent from Fig, 2~ and since
the contact rods ~arry subst~ntially equal currents, there
will normally be little net transversely-acting force on the
movable contact rod. The magnetic attraction between the
~ movable conta~t rod 28 and each rod electrode 40 is balanced
.. i :. . ..
'~! by a substantially equal and opposite magnetic attraction
i' between the contact rod and a rod electrode 40 in a location
', diametrically oppo~ed to that of the first rod electrode.
~he net transversely-acting magnetic force present on the
upper movable contact rod 28 is correspondingly limited to
a low value since rod electrodes 42 carrying substantially
equal currents symmetrically surrounded this upper movable
contact rod.
~3~ llVI~04044
In the reyion where the rod electrodes 40 and 42 over-
lap, the current paths through adjacent rod electrodes are
in close proximity~ but the magnetic attraction force
between adjacent rods is not very great because each of
these current paths is carrying only one-eight o the total
current. There isj~ however, an azimuthal magnetic field
encircling the whole rod assembly which interacts with t~e
current flow in the rods to produce a radially inward force
on the rods. This radially inward force, which can be
termed a magnetic wrap-around force, can be substantial at
high currents. The rod electrodes 42 and 40 are able to
e~fectively resist these magnetic forces because each of the - ~ --
spiders 56 and 66 across their distal ends acts as a brace
opposing displacement of the rod ell_ctrodes by these attrac-
tive forces and also because each of the rods, as mentioned
hereinabove, includes a shallj~ or a core, of high strength ~-
steel that is highly resistant to d~s~ormation.
When the interrupter is in its closed position shown,
relatively high hold-closed forces must be exerted on the
two movable contacts 26 in oxder to hold the contacts closed
against high currents, e.g., momentary currents, These hold- -
closed forces are, o~ course, transmitted to the stationary
. . . .
contacts and their supporting structure. The presence of
the spiders 56 and 66 imparts a desirably high amount of
rigidity to this supporting structure. These spiders tie ` :~
the rod electrodes together$ eliminating the cantilever-
i ~ . ..
beam type construction of the a~oresaid Kurtz and Sofianek
application and providing, in effect~ a box-like framework.
Since each spLder is supported on the rods at its four,
diametrically-opposed ends, it too is rigidified as compared
to the cantilever~beam type contact suppoxts o~ the afore-
said Kurtz and Sofianek application.
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1066~i34 llVI-04044
While we no longer need a conductive tube around the
movable contact rod for force-reduction purposes as in the
aforesaid Kurtz and Sofianek application, it is sometimes
desirable to include such a tube for another purpose. More
specifically, such a tube, if it surrounds the contacts~ can
advantageously be used to intercept th~ relatively large
molten particles generated by arcing at the con-tacts, there-
by pro~ecting the rest of the interrupter from such particles.
Fig. 3 shows an embodiment of the invention that in
cludes such a tube around each set of contacts. The lower
tube is designated 75 and the upper tube 80. The upwardly-
~ projecting rod electrodes 40, instead of being mounted
; directly on the lower end cap~ are moun~ed on the lower
tube 75 through an annular flange 76 at the top o the
tube. The downwardly-projecting rod electrodes 42 are
similarly mounted on the upper tube~ 80 through a ~lange 81.
; To aid in locating the contact: pairs within their res-
pective tubes 75 and 80, the stationary contact 25 of each
pair is mounted on a short conducti.ve rod lO0 that extends
between the stationary contact and the spider 56 and 66
on which it is mounted. This rod 100 projects from the
~pider into its associated tube 75 or 80 and is brazed to
the spidex at one end and to ~he end.
~he inner end of each of the tubes 75 and 80 is open ~-
80 that sufficient communication is present between each
inter-contact gap and the inter-electrQde g~aps to force
; prompt initiation o~ arces acro~s tha inter_electrode gaps
following contact-separation. To facilitate such communi-
cation, passa~eways 60 and 70 are respectively provided in
the stationary rods 100 and 102.
The lower ends of the rod electrodes 42 are inter-
connected by a conductive spider 56 corresponding to the
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.~ llVI-040~4
~1~663;~
spider 56 of Fig. 1. The upper ends of the rod electrodes
40 are interconnec~ed by a conductive spider 66 corresponding
to the spider 66 of Fig. 1. These spiders of Fig. 3 impart
rigidity of their associatQd rod structures in the same
manner as their counterparts function in Fig. 1.
The overall operation of the interrupter of Fig. 3
is generally the same as that of Fig. 1, and further
description of such operation is therefore considered
unnecessary.
One noteworthy point with respect to the interrupter
of Fig. 3 is that since all the rods 43 carry current, the
current in the upper tube 80 distributed more uniformly
;. . . -. -:
about the circumference of the tube with less non-uniformity
at its ends than is the case when only one rod electrode
normally carries current, as in the aforesaid Kurtz and
Sofianek application. This greater uniformity o~ current
distribution further reduces any transversely-acting
magnetic forces on the surrounded movable contact rod 28.
The same conditions as described above with respect to
upper tube 80 are present with reY~pect to the lower tube 75
since all of the rod electrodes 4~ carry current, thus
contributing to more uniform distribution of current in
i, . .
~ the lower tube 75.
. 1
;~l Th~ use of a metal tube around the contacts of an
~'l interleaving rod-electrode vacuum interrupter for in-
tercepting and condensing large molten particles generated
by intercontact arcing before the particles can deposit
: . .
' on the rod electrodes is disclosed and claimed more broadly -
~, in United States Patent No. 4,041,261 to Rich, issued
~ 30 August 9, 1977. The invention of said Rich patent was
f made prior to the present invention.
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It is to be understood that the drawings have been
somewha~ simplified to facilitate an understanding of the
invention. For example, certain details have been omitted
which are needed to facilitate assembly of the disclosed
interrupters. More specifically, each of the end caps 12
and 13, though shown as a single part, will typically be
made from two or more con~entric parts suitably joined
together after the internal parts of interrupter have been
assembled and located.
While we have shown and described a particular embodi- -
ment of our inv~ntion, it will be obvious to those sXilled --
in the art that various changes and modifications may be
made without departing from our invention in its broader
` aspects; and we, therefore, intend in the appended claims
to cover all such changes and modifications as fall within
the true spirit and scope of our invention.
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