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Патент USA US3028476

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April 3, 1962
v. E. PHILLIPS
3,028,466
ELECTRIC CIRCUIT INTERRUPTER OF THE LIQUID-BREAK TYPE
Filed May 28, 1959
2 Sheets-Sheet 1
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Inventor:
Virgel E. Phi||ips,|
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His Attorneg.
April 3, 1962
3,028,466
V. E. PHILLIPS
ELECTRIC CIRCUIT INTERRUPTER OF’ THE LIQUID-BREAK TYPE
Filed May 28, 1959
2 Sheets-Sheet 2
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United States Patent 0 "ice
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3,028,466
Patented Apr. 3, 1962
1
2
3,028,466
pump is assisted in its pressure-maintenance function
by a bu?er device submerged within the arc-extinguishing
liquid. This buffer device contains a volume of gas which
ELECTRIC CIRCUIT INTERRUPTER OF
THE LIQUID-BREAK TYPE
Virgel E. Phillips, Spring?eld, Pa., assignor to General
Electric Company, a corporation of New York
is compressed by pressures developed within the housing
during initial operation of the pump, and this compressed
Filed May 28, 1959, Ser. No. 816,630
9 Claims. (Cl. 200-450)
pressure peak by expanding and thus increasing the in
gas responds to a transient drop in pressure following a
stantaneous pressure within the housing to a level sub
stantially exceeding the pressure that would be developed
This invention relates to a circuit interrupter of the
liquid-break type and, more particularly, to a circuit in-‘ 10 without the buffer device. The buffer device has a
limited area ori?ce that reduces the ?ow of pressurized
terrupter of this type which has an exceptional ability to
successfully interrupt capacitance currents, particularly in
?uid into compressing relationship relative to the gas
the higher current range.
It has been found that pressurizing the ?uid within an
volume to such an extent that the pump can initially
build up pressure at a rate and to a level sufficiently high
interrupter materially aids in the successful interruption
to substantially maintain the ability of the interrupter to
of capacitance currents. In order to obtain the desired
prevent restrikes during initial pressure build-up as com
pared to a corresponding interrupter without the buffer
pressure level within the interrupter during capacitance
current interruptions, interrupters have been provided
device. The interrupter is further constructed in such
a manner that just prior to an interrupting operation, the
combination with a pump communicating with the inter 20 free internal space within the housing outside of the
with one or more pressure-responsive exhaust valves in
buffer device is substantially entirely ?lled with the arc
rupter. When circuit interruption is initiated, the pump
extinguishing liquid.
applies a force to the ?uid within the interrupter, and the
exhaust valves substantially block the liquid from ?owing
through the exhaust ports of the interrupter, thereby
For a better understanding of my invention, reference
may be had to the following description taken in conjunc
25 tion with the accompanying drawings, wherein:
resulting in a pressure build-up within the interrupter.
FIG. 1 is a side elevational view partly in section show
I have found that it is most important that the pres
ing a circuit interrupter embodying one form of my in
sure within the interrupter be built up to a relatively high
vention.
level within a very short time after the contacts part.
FIG. 2 is a one~line circuit diagram illustrating the
Any appreciable delay in such presstu‘e build-up results in
lower dielectric strength in the interrupter during a possi 30 use of a circuit interrupter for interrupting capacitance
currents.
bly-critical interval, with the result being that a harmful
FIG. 3 is a graphical representation of certain voltage
restrike across the contacts might occur which could
and current relationships occurring during capacitance
result in an excessive voltage build-up. In view of the
current interruptions.
desirability of a high rate of pressure build-up. I have
constructed my interrupter in such a manner that possible 35
FIG. 4 is in enlarged detailed view, partly in section,
of a portion of FIG. 1.
gas traps within the interrupter have been largely
FIG. 5 is a graphical representation of certain pres
eliminated so that the free space within the interrupter
is substantially entirely ?lled with liquid. This has
sure, current and voltage relationships occurring during a
capacitance current interruption.
resulted in a more rapid rate of pressure build-up because
any gas trapped within the interrupter had tended to act
FIG. 6 illustrates a modi?ed form of the invention.
Referring now to FIG. 1, the interrupter 1 shown
as a compressible cushion delaying the desired pressure
build-up.
therein is of the general type described and claimed in
Although the above approach has been highly effective
Patent No. 2,749,412 McBride et al., assigned to the
in minimizing restrikes when interrupting relatively light
assignee of the present invention. This interrupter 1 is
or medium range capacitance currents, e.g., less than 45 mounted, along with another similar interrupter (not
about 100‘ amperes, I have found that it is not as effective
shown) inside a relatively large oil-?lled enclosing tank.
as desired when the capacitance currents are of a higher ‘ The two interrupters are electrically connected by a re
ciprocable blade contact 2 of conventional form, such as
value, e.g., 200 or more amperes. Restrikes have occurred
with undue frequency in spite of the high rate of pressure
shown for examplein US. Patent 1,548,799 Hilliard,
build-up.
.
An object of the present invention is to materially
50 assigned to the assignee of the present invention.
The interrupter 1 is supported within the oil-?lled tank
from an insulating bushing structure 3 having a conductor
stud to which an adapter 4 is suitably secured in a known
manner. Adapter 4 is arranged to cooperate with suit—
lessen the frequency of such restrike occurrences when
interrupting relatively high capacitance currents with a
pressurized interrupter of the type that is normally liquid
?lled.
Another object is to substantially increase the dielec
55
able tie bolts (not shown) which structurally intercon
nect the interrupter unit 1 and the adapter 4.
The interrupter 1 comprises a tubular insulating cas
ing 5 enclosing a plurality of pairs 8, 9 of separable in
transient low pressure interval that I have found to occur
terrupting contacts which are electrically connected in
after the initial pressure peak has been reached, yet with-'
out harmfully delaying or interfering with the action of 60 series. The upper pair 8 of separable contacts comprises
the pump during initial pressure build-up.
‘ a relatively ?xed contact assembly 10 and a relatively
movable rod-type contact 11. The ?xed contact assem
In carrying out my invention in one form, I provide
a housing containing arc-extinguishing liquid in which
bly 10 is preferably of the conventional cluster-type com
tric strength of the ?uid within the interrupter during the
circuit-interrupting arcs are adapted to be established.
The housing is provided with an exhaust passage for vent
prising a plurality of ?ngers urged radially inwardly by
tially closed-off by means including a normally-closed
pressure-responsive exhaust valve in the exhaust passage.
A pump operable upon the establishment of a capaci
tance current are builds up and maintains a pressure
contact '13. The pairs of interrupting contacts 8 and 9
are electrically connected in series by means of suitable
current transfer contacts 14 and the transversely-extend
ing contact support casting 15. For supporting the mov
within the housing to aid in extinguishing the arc. The
able contacts 11 and 13 and for interrelating them for
suitably resilient means (not shown). In a correspond
ing arcing products to its exterior. During the usual 65 ing manner, the lower pair 9 of contacts comprises a sim
ilar ?xed contact assembly 12 and a relatively movable
capacitance current interruption, the housing is substan
3
3,628,466
simultaneous movement so as to draw a pair of simulta
neously-occurring arcs, there is provided a common cross
head 16 of conducting material to which the lower rod
contact 13 is directly secured and to which the upper rod
contact 11 is ‘suitably ?xed by means of an interconnect—
ing insulating rod 17.
4
For controlling the flow of ?uid through the hollow
valve body, there is disposed therewithin a pivotally
mounted valve member in the form of a metallic vane or
?apper 110. This vane 110 is ?xed to a pivotally-mount
ed shaft 112 which extends horizontally across the bore
of the valve body at an off center location, which, in FIG.
In order to complete the electrical circuit through the
1, is shown as being closer to the bottom inner surface
interrupter and to provide an isolating contact arrange
of the valve body than to the top inner surface. Prefer
ment for the interrupter, there is provided on the head
ably, the ‘shaft 112 is of a rectangular cross section, and
16 ‘an external contact button '18 which cooperates with 10 the shaft-receiving opening in the valve member 110‘ is of
an isolating contact 19 secured ‘to the movable switch
blade 2 to form a pair of isolating contacts. From the
~ above description, it will be apparent that the electrical
a similar shape so as to preclude relative rotation be
tween these parts. This shaft 112 is suitably journaled“
at its opposite'ends within the walls of‘the valve body 102
‘circuit through the interrupter extends ‘from the adapter
so as to allow for pivotal motion of the shaft 112 on the
4 ‘through the conductor 20, through the upper inerrupt 15 valve body.
Located externally of the valve body 102 are crank
ing contacts 10, 11, through the current transfer contacts
14 and the casting 15, then through the lower interrupt
arms 115 which are suitably fastened to the shaft 112
at opposite ends thereof. Each of the vanes 110 is urged
ing contacts 12, 13, the crosshead ‘16, the contact button
"18, the isolating contact 19, and ?nally through the switch
into its closed position of FIG. 1 by means of a tension
blade 2 and to the cooperating interrupter (not shown), 20 spring 116 which interconnectes the outer ends of the
which is disposed at the opposite end of the switch
blade 2.
crank arms 115. This tension spring 116 extends about
the top exterior of the valve body 102 and is suitably
A circuit-opening operation is produced by driving the
anchored to the valve body 102 adjacent to top surface
of the valve body. The means for anchoring the spring
switch blade 2 rapidly downward. This allows suitable
compression springs ‘6 to force the crosshead 16 together 25 116* to the valve body preferably comprises a lug 118
which is fastened to the valve body 1102, as by suitable
with the contacts 11 and 13 rapidly downward so as to
screws. The lug comprises a curved ?ange extending
draw a pair of circuit-interrupting arcs in the regions
about a portion of the spring periphery, as shown in FIG.
‘where these contacts part from their mating stationary
1, and thereby preventing movement of the top portion
contacts. After a predetermined downward movement,
the crosshead 16 is blocked by suitable stop means (not 30 of the spring 116 axially along the valve body 102.
When the pressure within the interrupter exceeds a
shown) from following the switch blade 2. The switch
predetermined value, it forces the valve member 110
blade 2 however, continues moving downwardly and, as
a result, establishes an isolating break between the con
counterclockwise about the axis of pivot shaft 112 thereby
»‘tacts 18 and ‘19 in a conventional manner.
opening the central exhaust passageway through the valve
The compression springs 6, it will be noted, bear at 35 body 102 and allowing fluid to ?ow therethrough. As is
their upper end against a stationary plate 7. This plate
pointed out in greater detail in the aforementioned
7 ‘and the adapter 4 act to enclose the interior of the in
Schneider application, the resilient means 115, 116 exerts
terrupter 1 at its respective lower and upper ends.
a generally decreasing force on the valve member 110
‘Adjacent to the serially-related interrupting contacts
as it travels away from its closed position toward its fully
8 and 9 are a pair of arc-extinguishing units in the form 40 open position. This follows from the fact that the effec
vof ba?le stacks 21 and 22. Ba?ie stack 21 is formed of
tive moment arm through which tension spring 116 acts
a plurality of superposed apertured ba?ie plates 23 of in
on the vane 110 becomes progressively smaller as the
sulating material which ‘together provide a central inter~
vane 110 moves from its closed position toward its fully
ruptin'g passageway 24 and a plurality of vertically
open position.
spaced, ‘angularly-aligned exhaust passages 25 radiating 45 In its fully-open position the vane 110* bears against a
therefrom. The exhaust passages are preferably formed
suitable stop 121, which is so located that it blocks open
by slotting certain of the baf?e plates 23 in a well-known
ing movement of the vane prior to the crank arms 115
manner. When a high current arc, say, of short circuit
reaching a dead center position relative to the spring 116.
proportions, is drawn within the passageway 24- 'in re
As a result, the spring 116 still exerts a closing bias on
spouse to separation of contacts 10 and 11, the arc reacts 50 the vane 110 when the vane is fully open and is, accord
with the surrounding oil to produce pressure within the
oila?lled casing 5, and such pressure is elfective to force
ingly, capable of restoring the vane to closed position
passages 25, 26, there is provided a pressure-responsive
vided for pressurizing the ?uid within the interrupter
when the pressure within the interrupter falls below a pre
a blast of dielectric ?uid and are products through the
determined level.
slots or exhaust passages 25 and out the registering ex
A basic function of the exhaust valves 100, is to re
haust port 26 formed in the adjacent wall of casing 5. 55 strict the exhaust ports during those low current inter
The pressure and flow conditions present during this in
ruption which generate relatively small quantities of gases.
terval aid in extinguishing the arc. The lower baf?e stack
Without the valves, the liquid displaced by these gases
22 generally corresponds to the ba?ie stack 21 except
would be dissipated so quickly through the large exhaust
that ba?le stack 22 is provided ‘with an opening 27
ports that no appreciable pressure build up would occur
through which reciprocates the insulating portion of the 60 within the interrupter, which is a condition that would
upper ‘rod contact 11.
tend to interfere with interrpption, especially of capaci
For controlling the ?ow of ?uid through the exhaust
tance currents. A pump 30, soon to be described, is pro
exhaust valve 100 for each of the arc extinguishing units
during low current interruptions, but its effectiveness in
21 and 22. These exhaust valves are preferably con 65 this regard would be substantially impaired by the absence
structed as described and claimed in the application S.N.
of. any material downstream restriction in. the exhaust
717,892, Schneider, now Patent No. 2,927,181, assigned
ports, which would be the case if the valves 100 were
to the assignee of the present invention. Each of these
not present. With the exhaust valves 100‘ present, how:
exhaust valves 100 comprises a tubular valve body 102
ever, ‘the pump 30 produces a pressure build-up which
which is suitably clamped to the casing 5, as by means 70 greatly aids in “interrupting the low‘current arc. There is
of a nut 104 on the exterior of the tubular body 102.
some minor leakage out of the interrupter during pump
When the nut 104 is tightened, it acts to force a shoulder
operation but not enough to materially interfere with
106 formed on the tubular housing 102 into clamping en
the desired "pressure build-up. For this reason, I refer
gagement with a recessed portion formed in the interior
to my interrupter as being substantially closed-oft during
of casing 5.
75 the time the valves 100 are closed.
3,028,468
When a higher current are, say, of 500 or more am
peres, is established within the interrupter 1, the arc
generates su?icient pressure to force each of the valve
members 110 out of its closed position into its fully-open
position. Such higher current arcs are capable of gen
erating su?icient pressure and ?ow to effect are extinc
tion without reliance upon any downstream restriction, as
is present when the valves are closed. The valves, in
opening widely during such’ interruptions help to prevent
excessive pressure rises within the interrupter.
As soon as the interrupting operation for relatively
high currents has been completed, the pump 3% operates
6
the breaker. Hence there is then essentially no voltage
across the breaker contacts. Thereafter, the source volt
age E1 begins reversing, but the capacitor voltage E2
remains at approximately the crest value due to the energy
storage properties of the capacitor C. This results in a
voltage Eb being established across the breaker contacts.
Interruption at the ?rst current zero B is effected by
the interrupter with comparative ease at a relatively short
contact-separation. This is the case because there is no
appreciable voltage Eb across the breaker contacts for
several hundred microseconds after the instant B.
This
interruption, however, might be only temporary because
as the source voltage E1 continues reversing toward its
opposite crest value, the voltage Eb across the breaker
for possible reclosure ‘followed by another interruption. 15 contacts approaches double this crest value. It is under
such conditions and during this interval that an arc is
To this end, the pump 30 forces a flow of fresh insulating
likely to restrike across the partially-separated contacts.
liquid through the arc extinguishing unit via thepassage
Such restrikes, being of an oscillatory nature, can produce
ways 31 and 25, 26 and the exhaust valves 100, all in a
seriously high voltages of a possibly harmful value. In
manner soon to be described in greater detail. .
The pump 30, which is structurally similar to a cor 20 referring to “restrikes” in this application, I am referring
to those current resumptions which occur more than one
responding pump described in the aforementioned Mc
quarter cycle after a current zero such as shown at B.
Bride patent, comprises a cylinder 32 suitably secured
A reignition occurring before this time usually does not
to the interrupter casing 5 and connected with the pas
result in excessive voltages being built-up.
sageways 31 by means of ducts 43. The pump 30 also
to scavenge the interrupter 1 of any ionized gases remain
ing after the interruption so as to prepare the interrupter
comprises an impulse piston 35 which is spring biased 25 By employing the pressure-responsive exhaust valves
100 in combination with the pump 30, it has been possible
downwardly by a compression spring 36. The compres
sion spring 36 is mounted between a stationary part 37
and a stop 39 ?xed to the piston rod 40, which in turn
is ?xed to the piston 35. The compression spring 36 is
to greatly decrease the frequency with which such re
strikes have occurred (in comparison to the same inter
rupter without the valves). The pressures developed by
held charged during the time the interrupter is closed
the coaction of the pump 30 and the valves 100 have
by means of a plunger 39a ?xed to the switch blade 2
raised the dielectric strength between the parting contacts
and abutting against the stop 39. However, when the
to a relatively high level capable in most cases of with
standing the voltage Eb impressed across the contacts
switch blade 2 is driven downwardly to open the inter
rupter, the restraint of the plunger is removed and the
spring 36 is free to begin driving the piston 35 downwardly
after a current zero.
I have found that in order to pre
vent a restrike, it is most important that this pressure he
built up to a relatively high level before the restrike
against the opposition of the oil disposed therebeneath.
During high current interruptions the spring 36 is in
producing voltage can be developed. Depending upon
effective to produce substantial downward movement of
the point in the current wave at which the contacts are
parted, such voltages can be developed even in one-fourth
tinguished. This is the case because these high current 40 cycle after the contacts part. In view of the desirability
of a high rate of pressure build-up, the interrupterof the
arcs generate su?icient pressure to overcome the action
present invention is constructed in such a manner that
of the spring 36. It is only when these pressures subside
that the pump becomes effective to impel liquid through , possible gas traps within the interrupter have been sub
stantially eliminated so that the free space within the
the arc extinguishing unit.
the piston 35 until after the high current arcs are ex
For protecting the pump 30 from high arc-generated 45 interrupter is substantially entirely ?lled with liquid.
Thus, with one exception soon to be described, no sub
pressures, the ducts 43 are preferably provided with check
stantial amount of residual gas is present within the inter
valves 44 disposed in each of the ducts 43. These check
rupter to act as a cushion to delay pressure build-up.
valves are adapted to cooperate with valve seats 45 lo
This, in combination with the fact that the exhaust ports
cated within each of the ducts. The valves are free to
slide on their centrally disposed spindles 46 which are 50 are substantially closed off by the valves 100, has resulted
in a very rapid rate of pressure build-up in my interrupter.
supported from the valve seats by suitable spiders. These
The above approach has been highly effective in
valves freely permit ?uid ?ow therethrough from the
minimizing restrikes when interrupting relatively light or
pump 30 except when the pressure produced by the arcs
medium range capacitance currents, e.g., less than about
drawn by the contacts 11 and 13 predominates. Under
such conditions, the valves close automatically to protect 55 100 amperes. I have found, however, that it is not as
effective as desired when the capacitance currents are
the pump from objectionable arc-generated back pres
sures.
A type of low current interruption that provides an ex
tremely severe test for an interrupter is that encountered
of a higher value, e.g., 200 or more amperes but not of
sufficient value or duration to open the valves 100. For
such currents, restrikes have occurred with undue fre
when opening predominantly capacitive circuits. This 60 quency despite the high rate of pressure build-up.
I have overcome this problem by equipping my pres
type of interruption is depicted in FIG. 2 where a cir
surized interrupter with a special gas-?lled buffer device,
cuit breaker 10 is shown disposed between a capacitive
load C and a source S. Assume ?rst that the breaker is
which is shown at 50 in FIGS. 1 and 4.
in closed position and that alternating power is ?owing
vice St} comprises a cup-like metallic member 52 provided
This buffer de
with a centrally disposed recess 54 ?lled with a suitable
The
gas such as air. The gas is maintained within the recess
current I ?owing through the circuit breaker contacts will
by means of a resilient diaphragm 53 secured between the
lead the terminal voltage E1 of the source by 90 degrees
cup 52 and an ori?ced cover 55 provided for the cup.
inasmuch as the load is substantially entirely capacitive.
The cover 55 is clamped against the rim of the cup 52
This phase relationship is depicted in FIG. 3. If the
breaker is tripped toward open position and its contacts 70 by suitable bolts 57 peripherally spaced about the cover.
Several of these bolts extend entirely through the cup and
part at an instant A in FIG. 3, arcing will take place until
a ?rst current zero is reached at an instant B (when the
are threaded into the casting 15 to hold the buffer device
in position within the interrupter.
voltage E1 is at its crest value). At this instant B, the
voltage level E2 at the capacitor C side of the breaker
The cover 55 is provided with a limited area ori?ce 56
10 is equal to the voltage level E1 at the source side of 75 through which oil from the interrupter is forced ?rst in
between the source S and the capacitive load C.
3,028,466
7
£5
one'direction and then in an opposite direction during a
Oil ?ow into the buffer
tween 0.1 and 1.0 square inch and the compressible vol
ume of the butter device between 1 and 18 cubic inches.
device 50 through the ori?ce 56 deforms the diaphragm
53, as shown by the dotted lines in FIG. 4, and com
given interrupter during capacitance current interruption,
circuit interrupting operation.
In general, the larger the volume of gases generated by a
the larger should be the ori?ce area and the larger should
presses the gas within the recess 54. Expansion of the gas
after such compression forces oil out of the buffer device
be the volume (within the above-described area and vol
through the ori?ce 56 and tends to return the diaphragm
ume ranges). The ratio of the volume in cubic inches to
to its original position. The diaphragm isolates the oil
the area in square inches should be between 3 and 20.
of the interrupter from the air within the recess 54 and
In an ori?ce area of a size appreciably exceeding 1.0
thereby prevents absorption of the air by the oil.
10 square inch is utilized, then the butter device will detri
I have found that, without the butter device 50 present,
mentally delay the pressure build-up, whereas an area
the pressure developed within the interrupter during the
appreciably smaller than 0.1 will not allow su?icient oil
interruption of relatively high capacitance currents quick
to flow into the buffer device to render it eifective when
ly reaches a peak value exceeding the pressure developed
the pressure is subsiding from its peak. Similarly, a
at a corresponding instant with no load or light capaci
volume of excess or insui?cient size will render the butter ,
tance currents. I have found, however, that as the cur
device ineffective during the time the pressure is sub
siding from its peak.
rent decreases to zero and is interrupted, the gas gen
erated by arcing begins to cool and in so cooling causes
the interrupter pressure transiently to fall to a value con
siderably lower than the no load pressure at a correspond
It is preferable to provide a butter device such as 50
for each break of the interrupter and to locate such bu?er
20 devices as close as possible to the arcing regions, but if
ing instant. This low value of pressure can prevail at the
time when high dielectric strength is most needed to pre
vent. restrikes, i.e., between one-fourth and one-half cycle
after current zero. With insu?icient dielectric strength
for some reason this is not practical, then a single butter
device communicating with the fluid at all of the arcing
regions may be employed. The dimensions speci?ed here
inabove are for a single buffer device for the entire inter
to withstand the voltage prevailing during this critical 25 rupter. If a plurality of buffer devices are utilized, then
interval, a harmful restrike occurs. The above described
the recommended dimensions should be divided by the
pressure relationships are illustrated by FIG. 5 where
number of buffer devices used. If a buffer device is to
pressure inside the interrupter (and certain other quanti
be utilized for each break, the butler device 50 could serve
ties) are plotted against time as an abscissa. The dotted
as the buffer device for break 9 and a similar buffer device
line curve NL represents the no load pressures, and the 30 at 50a could serve as the buffer device for break 8. Lo
dot-dash ‘curve G represents the pressures developed while
switching approximately 200 amperes of capacitance cur
cating the buffer devices near the arcing regions is desir
able in that this proximity lessens the amount and mass
rent without the buffer device 50. In the depicted inter
ruptions, almost a full half cycle of current I ?owed un
of oil which the gas pockets, in expanding during the low
pressure interval, must displace toward the arcing region
til the instant B was reached. Thereafter, the voltage Eb 35 in order to perform their desired pressure-maintenance
across the contacts began building up. One-fourth of a
function.
cycle after the instant B, the pressure within the inter
rupter is at a low value, with the result being a restrike
occurring at X as broadly described earlier in this
It is to be noted that the buffer device 5th is positioned
with the recess 54 disposed above the diaphragm rather
than below it. This positioning helps to prevent any loss
40 of air in the event that the diaphragm should develop a
paragraph.
The butter device 50 of the present application acts to
leak and, thus helps to assure continued availability of the
raise the instantaneous pressure prevailing during the
gas volume in the buffer device 50.
'
time the pressure is receding from its peak value and thus
Although I prefer to use a ?exible diaphragm for effect~
acts to raise the dielectric strength during this critical
ing isolation between the liquid in the interrupter and the
interval, thereby lessening the chances for a restrike. In 45 gas pocket in the buifer device, it is possible to use, as an
this regard, the initial pressure build-up by the pump
alternative to the diaphragm, a piston disposed between
forces a small amount of oil from the interrupter into the
the liquid and the gas. Such a device is shown in FIG. 6
buffer device through the ori?ce 56 thus compressing the
Where the butter device is shown as comprising a cup~like
air within the buffer device. When the pressure recedes
member 76} having a smooth cylindrical bore 72 in which
from its peak, the compressed air acts to force oil back 50 a piston 74, corresponding to the diaphragm 55, is slid
through the ori?ce 56 thereby materially increasing the
ably mounted. The piston is disposed internally of an
pressure otherwise prevailing. The type of pressure con
ori?ce ‘76 provided in a cover 77 for the buffer device.
ditions prevailing with the butter device present are illus
The ori?ce area and the compressible volume of the modi
trated by the curve H of FIG. 5, where it can be seen that
during the critical interval extending from one~fourth to _
one-half cycle after B, the pressure is substantially above
that prevailing without the buffer device as illustrated by
the curve G.
?ed buffer device are substantially the same as those set
forth in connection with FIGS. 1 and 4. Likewise the
modi?ed bu?’er device would be located in the same loca
tions as the device of FIGS. 1 and 4.
.
While I have shown and described particular embodi
By limiting the area of the ori?ce 56 on my buffer
ments of my invention, it will be obvious to those skilled
device, I am able to effect the desired increase in pressure
in the art that various changes and modi?cations may be
during the critical interval without harmfully interfering 00 made without departing from my invention in its broader
with the rate at which pressure builds up within the inter
aspects, and I, therefore, intend in the appended claims’
rupter. In this regard, the limited area of the ori?ce
to cover all such changes and modi?cations as fall within
limits the amount of oil ?owing into the butter device to
the true spirit and scope of my invention.
a value which does not harmfully interfere with the rate 65
What I claim as new and desire to secure by Letters
of pressure build~up inside the interceptor. Thus, if the
Patent of the United States is:
contacts should be separated at some point in the current
1. In an electric circuit interrupter for interrupting
wave that necessitated an immediate ‘high dielectric
capacitance currents, a housing containing arc~extinguisl1~
strength, say one fourth cycle after contact separation,
ing liquid, means for establishing a circuit—interrupting are
there would still be su?icient pressure available to prevent 70 within said housing, means de?ning an exhaust passage
a restrike despite the presence of butter device 50.
for venting arcing products from the region of said are
In interrupters of the general type shown in the draw
to the exterior of said housing, means for substantially
ing (having from one to four breaks and capacitance cur
closing off said housing during certain capacitance current
rent interrupting ability up to .600 amperes), my tests and
interruptions comprising a normally-closed pressure-re
calculations indicate that the ori?ce area should be be 75 sponsive exhaust valve located in said exhaust passage,
3,028,466
r
9
10
r
a pump operable upon establishment of a capacitance
current are within said housing to bulid up a pressure
within said housing, a buffer device submerged within
said liquid and containing a pocket of gas which is com
current are within said housing to build up a pressure
gas expanding in response to a transient drop in pressure
within said housing, a plurality of butter devices sub
merged Within said liquid and each containing a pocket
of gas which is compressed by the pressure developed
within said housing during initial operation of said pump,
said compressed gas expanding in response to a transient
drop in pressure following a pressure peak to increase the
following a pressure peak to increase the instantaneous ,
instantaneous pressure within said housing to a level
pressed by the pressure developed within said housing
during initial operation of said pump, said compressed
substantially exceeding the ‘pressure that would be de
exceeding the pressure that would be developed without 10 veloped ‘Without said buffer devices, said buffer devices
pressure Within said interrupter to a level substantially
each comprising means de?ning a limited area ori?ce for
said buffer device, said buffer device comprising means
de?ning a limited area ori?ce for reducing the flow of
reducing the flow of pressurized liquid into compressing
pressurized liquid into compressing relationship relative
relationship relative to said gas pocket to such an extent ‘
that the pump can initially build up pressure with-in said
initially biuld up pressure within said housing at a rate 15 interrupter at a rate and to a level sufficiently high to sub
stantially maintain the ability of the interrupter to prevent
and to a level suf?ciently high to substantially maintain
restrikes during initial pressure build-up as compared to
the ability of the interrupter to prevent restrikes during
its corresponding interrupterwithout the buffer device,
initial pressure build-up as compared to a corresponding
to said gas pocket to such an extent that the pump can
said housing having its free internal space outside of said
interrupter without the bu?er device, said housing having
its free internal space outside of said buffer device sub 20 buffer ‘devices substantially entirely ?lled with said arc
stantially entirely ?lled with said arc-extinguishing liquid
extinguishing liquid just prior to an interruption.
just before an interrupting operation.
2. In an electric circuit internupted or interrupting ca
4. The interrupter of claim 3 in which the total ori?ce
area of said buffer devices is between 0.1 and 1.0 square
pacitance currents, a housing containing arc extinguish
ing liquid, means for establishing a circuit interrupting
inch, the total compressible volume of the gas pockets
in said bu?er devices is between 1 and 18 cubic inches,
arc within said housing, means de?ning an exhaust pas
and the ratio of said total volume to said total area is
between 3 and 20‘.
sage for venting arcing products from the region of said
are to the exterior of said housing, means for substan
m/
tially closing old said housing during certain capacitance
current interruptions comprising a normally-closed pres
sure responsive exhaust valve located in said exhaust pas
sage, a pump operable upon establishment of a capacitance
current are within said ‘housing to build up a pressure
5. The interrupter of claim 3 in which there is pro
vided means for establishing at least one additional cir
cuit interrupting arc in said housing and in which each
of the arcing regions within said housing has one of
said butter devices located closely thereadjacent.
6. The interrupter of claim 3 in which there is provided
means for establishing at least one additional circuit-in
within said housing, a bu?er device submerged within said
liquid and containing a pocket of gas which is compressed 35 terrupting arc in said housing and in which at least one
of the arcing regions has one of said butler devices lo
‘ by the pressure developed within said housing during ini
cated closely thereadjacent.
tial operation of said pump, said compressed gas expand
7. The interrupter of claim 1 :in which said buffer de
ing in response to a transient drop in pressure following
vice includes a resilient diaphragm isolating said gas
a pressure peak to increase the instantaneous pressure
packet from said arc-extinguishing liquid and disposed be
within said interrupter to a level substantially exceeding
tween said ori?ce and said gas pocket.
the pressure that would be developed without said buifer
8. The interrupter of claim 1 in which said buffer de- ‘
device, said butter device comprising means de?ning a
vice includes a slidable piston isolating said gas pocket
limited area ori?ce for reducing the ?ow of pressurized
liquid into compressing relationship relative to said gas
from said arc-extinguishing liquid and disposed between
housing having its ‘free internal space outside of said buffer
device substantially entirely ?lled with said are extinguish
disposed between said ori?ce and said gas pocket.
volume, said ori?ce having an area of between 0.1 and 45 said ori?ce and said gas pocket.
9. The interrupter of claim 3 in which'at least one of
1.0 square inch, said pocket of gas having a compressible
said buffer devices include-s a resilient diaphragm isolating
volume of between one and 18 cubic inches, the ratio‘
. said gas pocket from said arc-extinguishing liquid and
of said volume to said area being between 3 and 20, said
ing liquid just prior to an interrupting operation.
References Cited in the ?le of this patent
3. In an electric circuit interrupter for interrupting ca
pacitance currents, a housing containing arc-extinguishing
liquid, means for establishing a circuit interrupting are
within said housing, means de?ning an exhaust passage 55
for venting arcing products from the region of said are
to the exterior of said housing, means for substantially
UNITED STATES PATENTS
2,061,945
Koppelmann et al ______ __ Nov. 24, 1936
2,160,673
2,749,412
2,927,181
Prince _______________ .._ May 30, 1939
McBride et a1. _______ _.. June 12, 1956
Schneider ____________ __ Mar. 1, 1960
626,525
518,314
Germany ____________ __ Feb. 28, 1936
Great Britain _________ __ Feb. 23, 1940
closing off said housing during certain capacitance current
interruptions comprising a normally-closed pressure-re
sponsive exhaust valve located in said exhaust passage,
a pump operable upon establishment of a capacitance
FOREIGN PATENTS
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