Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
This invention relates to puffer type circuit
interrupters, and more specifically relates to a novel arrange- -
ment whereby the movable contact of a puffer type interrupter
is flexibly connected to a gas directing nozzle so that the
arc between the separating interrupter contacts is initially
drawn downstream of the nozzle, with the movable contact later
returning to its preferred upstream position within the nozzle ;
after the initial arcing operation.
Single pressure SF6 type puffer interrupters are
well known in the art and commonly comprise a pair of separable
contacts which are contained within a sealed container filled
with sulfur hexzfLuoride gasor the like. One of the contacts
is normally fixed to a nozzle-shaped member which encloses
; the area of engagement between the two cooperating contacts.
The movable contact is connected to a piston and cylinder
arrangement such that, when the movable contact moves to -
a disengaged position, the piston and cylinder force gas
flow through the nozzle and through the region at which
the contacts se~arate. This then provides a temporarily
high-pressure region which moves gas through the arcing
region to assist in the extinction of the arc drawn between
the separating contacts and to sweep the space between the
separating contacts clear of ionized products.
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In order to obtain interruption in this type breaker,
two conditions must be satisfied:
(1) The opening stroke of the movable contact must
be sufficient to establish an open gap large enough to with-
- stand the crest of the system recovery voltage; and
(2) The opening stroke must develop a sufficient
pressure differential across the nozzle to provide effective
sweeping and deionization of the arc spa~e.
During the opening stroke of the movable contact,
it is also desirable to keep the energy released in the
arc space to a minimum and to release this energy in such --
a manner as to minimize its effect on the interior components
and to minimize the forces necessary to operate the interrupter.
In puffer interrupters of this type, it is common
practice to fix a movable contact to the nozzle so that
both move relative to a stationary contact, and further
to fix the end of the movable contact at some fixed and
preferred location which is upstream of the interrupter
nozzle throat. The arc which is drawn between the separating
contacts in such a device is then initiated upstream of
the nozzle and will be drawn through the nozzle throat during
the first part of the opening stroke.
During the opening stroke and as pointed out above,
the arc produces various types of arcing products and ionized
gas in the region which is upstream of the nozzle so that
these products and ionized gases must be swept free if inter-
ruption is to be obtained. Moreover, the arc and heated gases
produced by the arc are immediately adjacent to the no~zle and
the nozzle throat, thereby causing thermal deterioration of the
nozzle which can reduce the interrupting lifetime of the device.
A further disadvantage of the fixed positioning of
the movable contact upstream of the nozzle throat is that the
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initial arc which is drawn will cause a high-pressure zone in the nozzle :~-
throat which results in a back pressure which must be overcome by higher
operating forces from the operating mechanism. Note further that the back
pressure in the nozzle can result momentarily in a back flow of gas so
that arc products could be brought into the puffer piston area.
In accordance with the invention, the movable contact and the
movable nozzle are movably connected to one another and the movable contact
is normally biased to a preferred location slightly upstream of the nozzle -
throat. However, upon operation of the interrupter, the movable contact
and nozzle move relative to one another so that the end of the movable
contact is downstream of the nozzle throat at the time an arc is initiated -
between the separating contacts. Following the initial arcing interval, ;~ -
the movable contact returns to its preferred upstream location relative
to the nozzle, when a sufficiently large open gap is formed to withstand
the crest of the system recovery voltage and enough pressure has developed ;
to produce effective arc sweeping action.
Therefore, according to this invention, a puffer type circuit
; interrupter comprises a stationary elongated contact and a movable contact
movable between an engaged and disengaged position with said stationary
contact. An insulation nozzle surrounds said movable and stationary
- contacts and an operating rod is connected to said movable contact, means
being provided for flexibly mounting said nozzle on said operating rod
with said nozzle being axially movable with respect to said movable con-
tact. Piston meanS are connected to said operating rod for producing a
flow of gas through said nozzle and through the arc space produced by the
separation of said movable and stationary contacts. A housing surrounds
said contacts, said nozzle and said piston means and is filled with a
relatively high dielectric gas. Said nozzle has an internal nozzle
throat restriction, and biasing means are provided for biasing said nozzle
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and said movable contact to a position wherein the end of said movable
contact is downstream of said nozzle throat restriction. Said operating
rod moves said end of said movable contact upstream of said nozzle throat
restriction at~a time following the initial movement of said movable
contact to its disengaged position, whereby the initial arcing between
said movable and stationary contacts occurs in an arcing space downstream
of said nozzle throat restriction, and whereby said arcing space is
thereafter located downstream of said nozzle throat restriction and is
swept free of arcing products by gas flow from said piston means and
through said nozzle throat restriction. Said movable contac~, said
stationary contact and said nozzle are coaxially disposed and are each
generally axially elongated. Preferably, the dielectric gas is sulfur
hexafluoride.
The arrangement of the present invention permits release of
energy during the initial arcing period in a region which is downstream
of the nozzle, so that pressure release can be effected through the
relatively open gap between the nozzle wall and the fixed contact as well `
as through the hollow fixed contact if such an arrangement is used. Thus,
the undesirable effects on the nozzle of upstream reverse flow and early
contamination of the nozzle throat are largely overcome.
` There is also a reduction of total energy release by elimin-
:~ :, ..ating or reducing gas blast in the early part of the opening stroke
(when interruption cannot be effected) so that arc voltage and thus arc ,~
energy can be kept lower. There is also a reduction of the swept volume
necessary in the puffer piston due to the elimination of the need to
clear away initial upstream arc products which reach the piston region
and a reduction of useless gas flow when the contact gap is too small to
effect an eruption. That is to say, the actual time at which contact
separation occurs may be slightly delayed while the nozzle moves relative
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to the contact and toward a position in which the contact is downstream
of the nozzle throat. This same time delay also allows time for a gas -
pressure differential to build to a sufficiently high value to enable
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interruption of the arc when the contacts open. A further advantage `~
obtained by the invention is an improvement in capacitor switching per-
formance by minimizing the possibility of interruption of the arc while
the contacts are still very close together so that restrike is more
probable.
The invention will now be described further by way of example ;
only and with reference to the accompanying drawings wherein:
FIGURE 1 is a cross-sectional view of a portion of an inter-
rupter which falls within the concept of the invention, with the contacts
in their closed position and wherein the nozzle is fixed to the operating
rod while the movable contact is flexibly connected to the operating rod.
FIGURE 2 shows the interrupter of Figure 1 immediately after -
the contacts have separated, with the separating contacts being down-
stream of the nozzle throat.
FIGURE 3 shows the interrupter of Figures 1 and 2, with the
contacts in their fully open position.
FIGURE 4 shows in cross-sectional view an embodiment of the
invention as particularly claimed, wherein the stationary contact is
fixed to the operating rod, while the nozzle is flexibly connected to -
the operating rod.
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Figure 5 shows the in-terrupter of Figure 4 just
after the contacts have separated, with the initial arc being
formed at a location downstream of the nozzle throat.
Figure 6 shows the embodiment of Figures 3 and 4
after the contacts are fully opened and the nozzle is retracted
to effect a greater open gap distance.
DETAILED DESCRIPTION OF THE DRAWINGS
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Referring first to Figures 1, 2 and 3, there is shown
- a portion of a puffer breaker which includes a stationary
conductive piston 10 which can be connected to a first terminal
11 of the breaker. The member 10 may be contained within a
suitable housing shown schematically by the dotted block 12, '
which is filled with sulfur hexafluoride at some positive
- pressure. Other gases and gas mixtures could also be used if
desired.
A conductive operating rod 13 then terminates in an
enlarged head 14 which may be segmented if desired, and is in
sliding engagement with movable contact cylinder 15. The
movable contact cylinder 15 may be segmented into fingers at its
right-hand end, where the fingers engage the stationary tubular
contact 16. Operating rod 13 is then electrically connected to
the stationary conductive member 10 by suitable sliding contact
members 17.
- The conductive member 15 may then terminate in an
annular disk-shaped end region 18 and may have arcing contact
finger type elements 19 at its right-hand end which engage
the arcing contact end of stationary contact 16. Movable
contact 15 is then supported within an insulation cup 20
which extends from disk 21 which is fixed to the interior
- 30 of the baffle cylinder or nozzle 22. The baffle cylinder 22 then
consists of a cylindrical body 23 having a restricted
nozzle throat 24 where baffle cylinder 23 is slidable on
the stationary member 10 which serves as a stationary
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piston for the puffer interrupter.
The disk 21 then has a plurality of openings
including openings 25 and 26 therein which permit the fl~w
of gas from the volume between disk 21 and member 10 to
flow to the right and through the nozzle throat 24 when
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; the circuit breaker is opened as will be later described~ ~
A sliding seal 30 may be provided between :
; stationary member 10 and cylindrical portion 23 of the nozzle ~ ~
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22 if desired. A biasing spring 35 is then captured within
10 insulation cup 20 and biases contact cylinder 15 to the '~
left and into its seat in the plate 21. Note that the
movable components of the breaker are all connected to one
another and consist of the operating rod 13, plate 21 and
baffle 22. These components move as a single unit when
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operating forces are applied to the operating rod 13.
In order to move contact 15 to the right and i~
I toward its engaged position, the left-hand end of contact,~ ,
15 is picked up by the plate 21 and is driven to the right
with the operating rod 13. In order to move the contact
to its open position, the operating rod 13 moves to the
left. '
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The operation of the interrupter shown in Figure
1 is as follows:
- The contacts are shown in their normally closed ~ -
position in Figure 1. In order to open the breaker, the ~'
operating rod 13 is moved to the left. The initial movement
of operating rod 13 and of disk 21 and nozzle 22 to the left
is independent of the movement of contact 15 which is held
in position since the frictional engagement forces between
30 inwardly turned contact end 19 and the stationary contact 16 ;~
are greater than the initial force from spring 35.
When the movable contacts reach the position of
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1038g28
- Figure 2, the spring 35 has been compressed to a point
where it is able to overcome the engagement forces bet-
ween contact 15 and stationary contact 16, and the region of
contact disengagement is now downstream of the nozzle
throat 24. Consequently, as the contacts separate in
Figure 2, the initial arcing is downstream of the nozzle
throat 24 resulting in low-arc energy and minimum pres-
sure effect upstream of the nozzle. It should be further
noted that the pressure created by the initial downstream
arc will bear against surface 40 of throat 24, thereby
to provide a pressure assist in the movement of the
movable components to the left during the opening of
the breaker. The spring 35 accelerates contact 15 to the
left, thereby increasing the effective speed with which a
contact gap is achieved. Furthermore, the contact 15
blocks nozzle 40 to eliminate gas flow and pressure loss
before the contacts reach a point where effective inter-
- ruption can be obtained. -
As the moving components continue to move to the
left, the movable contact ultimately reaches the preferred
position which is upstream of the nozzle throat 24, which
is most favorable for arc interruption and prevention of ,-
restrike. It will be noted that, during this operation,
relatively little ionized gas and contaminated arc pro-
ducts will flow back toward the piston area or the region
between disk 21 and tpe end of stationary member 10.
Figures 4, 5 and 6 show a preferred embodiment of
the invention which differs from the embodiments of Figures
1, 2 and 3 in that the relatively movable components in
Figures 4 to 6 is the nozzle portion of the movable system
rathér than the contact portion of the movable system as `
in Figures 1, 2 and 3.
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103842B ~ ~
Referring now to Figures 4, 5 and 6, the puffer
interrupter consists of a fixed puffer piston 50 which
may be of conductive material and which slidably receive~
a puffer cylinder 51 which is fixed to the movable contact
operating rod 52 by the plate 53. Note that plate 53
is similar to plate 21 of Figures 1, 2 and 3 and contains
suitable openings, such as openings 54 and 55 which per-
mit the flow of gas into the interrupting area upon the
movement of the puffer cylinder 51 to the left. The
; 10 moving contact rod 52 may then be electrically connected
to the conductive piston 50 by transfer contacts 56 and
one terminal of the breaker may be connected to the
- puffer piston 50 and is shown as the terminal 57. The
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right-hand end of the contact operating rod 52 then
carries a segmented movable contact member 60 which coop-
erates with a stationary contact tube 61 which defines
the second terminal 62 of the breaker.
The contacts 60 and 61 are then surrounded by
nozzle 63 which is flexibly carried on the puffer cylinder
by the compression spring 70 which is disposed between the
inwardly turned flange 71 of cylinder 51 and the outwardly
turned flange 72 of nozzle 63. Note that nozzle 63,
like nozzle 22 of Figures 1, 2 and 3, is of any desired
insulation material.
The operation of the system of Figures 4 to 6
is as follows: ~
In order to open the breaker, the operating rod
52 is initially moved to the left from the position of
Figure 4 toward the position of Figure 5. At this time
the movable operating rod 52, plate 53, cylinder 51 and
nozzle 63 move as a unit to the left and the throat of the
nozzle 63 moves with contact fingers 60. During this time,
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10384~8
the major portion of the nozzle throat is generally down-
stream of the contact region at which initial arcing
will take place when the position of Figure Z is reached.
The contact 60 is substantially blocking gas flow
through the nozzle 63, thus promoting early build-up
of pressure upstream of the contacts.
Once the position of Figure 2 is reached, a
pressure within nozzle 63 and against interior surface
63a has been reached to move the nozzle 63 to the
dotted-line position which is the interrupting position
for the nozzle and for the system. However, this position
is not assumed until sufficient internal pressure has
been produced to ensure effective arc interruption and
clearing of arc products from the interruption space.
At the same time, the nozzle is moved to its interrupt-
ing position only after a suitable interrupting gap
has been reached between the contacts 60 and 61. Thusr
the initial arcing will be downstream of the nozzle to
result in minimum pressure effects upstream of the nozzle
while the initial interrupting position is reached with
all components in their preferred position to obtain
effective permanent interruption.
Note further that, if there is extensive down-
stream pressure which is arc-generated on surface 63b
of nozzle 63, this excess pressure will prevent the -
nozzle 63 from moving to its position in Figure 5 until
; a sufficient pressure differential is developed across
the nozzle throat to permit effective interruption.
After the interruption operation, the nozzle 63 is spring-
retracted to the position shown in Figure 6 with the contacts
in their fully open position.
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~ lthougll tJIis invcntion h~s bcen dcscri~cd
witll respect t~ its preferred cmbodiments, it should be
understood that many variations and modifications will
now be obvious to those skilled in the art, and it is
preferred, thcrefore, that the scope of the invention
be limited not by the specific disclosure herein, but
only by the appended claims.
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