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Патент USA US2405853

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Aug. 13, 1946.
‘ s, J, ROSCH
2,405,853
OIL-FILLED ELECTRICAL APPARATUS
Filed May 29, 1942
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ENVENTOR
SAMUEL J. RoscH
'
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ATTORNEYS
Patented Aug. 13, 1946
2,405,853 '
UNITED STATES PATENT OFFICE
2,405,853
OIL-FILLED ELECTRICAL APPARATUS
Samuel J. Bosch, Yonkers, N. Y., assignor to
Anaconda Wire and Cable Company, a corpora
tion of Delaware
Application May 29, 1942, Serial No. 445,007
8 Claims.
(Cl. 210-203)
2
This invention relates to electric apparatus
latter end, anti-oxidants, or sludge inhibitors,
such as transformers in which transformer wind
ings or other electrical equipment is immersed
in oil within a tank or case, and has for its prin
cipal object the provision of means for minimiz
ing deterioration of oils in such electric appa
are sometimes added to the oil. Such addition
agents are relatively expensive and many of them
have the disadvantage that they increase the
attack upon the metals of the transformer, or
they break down at the high operating tempera
ratus.
'
tures such as commonly result from imposing
Electric transformers, except very small elec
heavy loads on the transformer.
tric transformers, generally have the transformer
It has been proposed to minimize deteriora
windings mounted in a liquid tight case (or 10 tion of transformer oils by circulating the oil in
tank). The case is ?lled with an insulating oil
contact with loose carbon black in a suitable
which is caused to circulate (either by thermally
container. This expedient has not proven com
induced currents or by mechanical circulating
mercially satisfactory because it is impossible
means such as a pump) to effect cooling of the
practically to prevent a proportion of the ?ne
windings, and the oil also provides an insulating 15 particles of carbon black from entering suspen
medium between these windings. The most sat
sion in and circulating with the oil. When this
isfactory cooling and insulating oils are petro
.occurs the deleterious components which the
leum oils which have been highly refined to re
carbon black is supposed to remove still circulate
move constituents which would otherwise lower
with the oil, come in contact with the iron of the
the dielectric strength of the oil. Such constit
case and core and the copper of the conductors,
uents include moisture, acidic compounds, sludge
and tend to accumulate in voids, cracks, and
particles and entrapped air. The resulting ?n
other locations in much the same manner as if
ished insulating oil possesses initially high dielec
the carbon black were not employed. As a result
tric strength, but the conditions to which it is
deterioration of the oil is not prevented, even
subjected in use promote deterioration of the oil 25 though it may be somewhat retarded. Moreover,
which results in lowering its dielectric strength.
carbon black is an electrical conductor, and the
For example, it is not usually practical to make
tendency of loose particles of carbon black and
a. transformer case completely airtight, as the
sludge or other contaminants to accumulate in
need for expansion room required due to ?uctu
small voids of the winding insulation enhances
ating temperatures of the insulating oil generally
the hazard of electrical vbreak-down within the
requires the provision of breather openings in
transformer.
the case. The oil thus is allowed to‘ come in
In the course of extensive investigation of
contact with air, which effects oxidation of the
means for minimizing deterioration of trans
oil with formation of acidic constituents and
former insulating oils, I have discovered that
deterioration products known as sludge. The 35 carbon black incorporated in and held in place
relatively high temperatures to which the oil
by a ?brous material has the desirable charac
becomes heated in normal operation of trans
teristic of inhibiting oxidation of such oil and
formers and the like accelerate this oxidation
of removing (probably by preferential absorp
of the oil. Furthermore, oxidation is catalyzed
tion) deterioration products such as sludge, so
by the metallic iron and copper in contact with do that deterioration of the oil is substantially pre
the oil within the transformer, and reaction
vented over prolonged periods. Based upon this
which takes place between acidic constituents
discovery, the present invention provides the
and the metallic iron and copper yields reaction
combination, with an electric transformer com
products which further catalyze oxidation and
prising a case having therein transformer wind
deterioration of the oil.
45 ings immersed in oil, of a cartridge comprising
The acidic constituents formed in transformer
?brous material (advantageously ?brous sheet
insulating oils, in addition to promoting further
material) having carbon black incorporated
therein, the cartridge being disposed within the
deterioration of the oil, are of low dielectric
strength and may attack the insulatingrmaterial
transformer case in contact with the oil. Prefer
about the transformer windings. These factors, 50 ably the cartridge is readily replaceable so that
together with the accumulation of sludge in the
it may be removed from time to time, as may be
oil, are likely to lead to electrical break-down
required, to maintain the oil in the best possible
within the transformer unless the oil is replaced
condition.
at proper intervals or unless some provision is
made to retard deterioration of the oil. To the
55
The ?brous material may with advantage be
paper, and the carbon :black is advantageously
2,405,853
3
the paper so that it is thoroughly impregnated
and ?rmly held in place therein.
In the usual oil-?lled transformer the oil serves
material impregnated with carbon black which
as a cooling medium, and is caused to circulate
may be mounted conveniently within the trans
former is shown in Fig. 3. This container com
prises a perforated body portion 56 having a per
(by thermal currents or mechanical pumping
means) upwardly in close proximity to the wind
ings and downwardly in close proximity to the
walls of the case (or other heat-radiating sur
face).
It is advantageous to dispose the car
4
vantageously are located, as shown in the draw
ing, in the path of upwardly circulating oil rising
between the transformer windings l2.
A form of container and cartridge of fibrous
incorporated in the pulp during manufacture of
forated cover ll. The perforations are sufficiently
10 large and closely spaced so that oil may circulate
tridge of ?brous material impregnated with car
bon black in the path of oil circulation so that
the oil flows in contact with the Carbon black and
through the container freely. A mounting bracket
18 is affixed to the container body so that it may
be attached to any convenient support within
the transformer". Disposed within the container
the entire body of oil is thus kept free of delete
rious contaminants. The cartridge may be dis 15 i5 is the cartridge E9 of ?brous material impreg
nated with carbon black. A convenient form of
posed either in the path of upward circulation or
cartridge l9 (shown best in Fig, 4:) comprises a
in the path of downward circulation whichever is
sheet
of ?brous material such as paper which has
the more convenient. If desired, a plurality of
been tho-roughly impregnated with carbon black
cartridges disposed in the path of upward or
and wound into the form of an open spiral, having
downward circulation, or both, may be employed.
an outer diameter such that it may easily be
What has been said above with respect to the
slipped into or removed from the container 16.
deterioration of transformer oils and the im
A spider ‘26 may be arranged at each end of the
provements according to the invention for pre
spirally wound sheet of ?brous material to main
venting such deterioration, is true also of oils in
tain it permanently in its loose spiral form. The
other oil-?lled electrical apparatus such as oil- I
spirally wound cartridge presents a large surface
?lled switches or circuit-breakers, oil-?lled rheo
to contact with the oil, and since the spiral is
stats, and other electrical apparatus comprising a
wound loosely, oil circulates freely between the
case having therein electrical equipment im
successive convolutions. If desired, the fibrous
mersed in oil. The invention therefore contem
material may itself be perforated so that the oil
plates the provision in all such apparatus of a
may circulate laterally through the cartridge as
replaceable cartridge comprising ?brous mate
well as vertically between the successive convolu
rial having carbon black incorporated therein, the
tions.
cartridge being disposed within the case in con
A modi?ed type of cartridge 2| is also shown
tact with the oil, whereby the oil is preserved from
mounted
in the transformer of Figs. 1 and 2. This
deterioration and its initially high dielectric
form of cartridge is roughly in the form of a short
strength is substantially maintained.
cylinder of su?icient internal diameter so that it
The invention is described in greater detail be
may
be passed over the transformer windings l2.
low with particular reference to the embodiments
It may, of course, be other than truly cylindrical
shown in the accompanying drawing, in which
and is shown in Fig. 2 as being somewhat squared.
Fig. l is a longitudinal section through a core
type transformer showing replaceable cartridges
according to the invention mounted therein;
Fig. 2 is a cross section taken substantially
along the line 2-2 of Fig. 1;
This form of cartridge may be hung on hooks 2la
secured to the wall of the transformer case. The
construction of the cartridge 2| is shown more in
detail in Fig. 5. It comprises a pair of ring-form
Fig. 3 is a longitudinal section through a con 45 supporting elements 22 held in spaced relation
by generally U-shaped brackets 23 located at in
tainer for one form of cartridge according to the
invention;
tervals about the ring. The supporting rings 22
are formed with grooves 24 which face each other,
Fig. 4 is a plan of the container shown in Fig, 3,
and held in the grooves are the edges of succes
with cover removed to show the cartridge in place;
Fig. 5 is a fragmentary perspective of a modi 50 sive convolutions 25 (arranged either spirally or
concentrically, as desired) of ?brous sheet ma~
fied form of cartridge; and
Fig, 6 is a cross section through a modi?ed
shell-type transformer showing a convenient lo
cation of replacable cartridges according to the
invention.
Figs. 1 and 2 show in section, more or less dia
grammatically, an oil-filled core-type transformer.
The transformer comprises a case or tank iii to
which a cover l i may be bolted. Within the tank
or case are the transformer windings l2 about the
usual iron core is’. The tank is ?lled with a good
duality of insulating oil to a level L so that the
transformer elements are completely immersed.
Fibrous material impregnated with carbon black
and put up in the form of replaceable cartridges
is disposed within the transformer case below the
level L of the oil. One type of cartridge is held
in a perforated container iii. As shown in the
drawing, two such containers it are supported at
the top of the core is by a bracket it. The con
tainers H5 are perforated on all sides so as to per
terial impregnated with carbon black. The sup
portiing rings are liberally perforated, preferably
between the grooves 24, so that oil may circulate
between the successive convolutions of the sheet
fibrous material held in place by the rings. One
or both of the rings 22 advantageously is provided
with a bracket 28 for mounting it in the trans
former.
The two forms of cartridge described above
are merely examples of suitable cartridges for
use in accordance with the invention. Many
other mechanical forms of cartridges may be de
signed by one skilled in the art. For example,
the cartridge may comprise a single sheet or
strip of fibrous material impregnated with carbon
black positioned, for example, about the trans
former windings (or other electrical equipment),
the sheet or strip being spaced advantageously
70 from both the windings and the case. In all
such cartridges, however, it is desirable that a
mit free passage of circulating oil therethrough
substantial area of the ?brous material impreg
and into- contact with the cartridge of ?brous ma
terial impregnated with carbon black which is dis
posed within the container. The containers ad
nated with carbon black be exposed to the oil,
and the form of the cartridge or its container
2,405,863
‘Should be such that the oil is able to circulate
6
may be of ordinary kraft paper of ‘the weight
freely in contact therewith.
The location of the cartridge within the trans
and quality usually employed as electrical in
sulation. For a cartridge of the type shown in
former case is not particularly critical so long
Fig. 5, on the other hand, the carbon black paper
‘as it is in good contact with the oil, but for 5 should be of rather heavy weight so as to have
most effective results it is desirable that the
adequate inherent stiffness to retain its form
cartridge be placed in the path of circulation
and resist sagging or buckling when wetted by
of the oil so that the oil is continuously flowing
the oil in which it is to be immersed.
in contact with the ?brous material. In the
In referring herein to “carbon black,” I mean
case of transformers where the oil circulation
particularly finely divided carbon produced as a
is thermally induced, the oil flows upwardly in
result of imperfect combustion of natural gas or
close proximity to the transformer windings and
similar hydrocarbon gases. This carbon black
core and downwardly in close proximity to the
(by which name it is known to the trade) is to
walls of the case 10 or other heat radiating
be distinguished from lamp black, for example
surface. As shown in Figs. 1 and 2, the con
(produced by the imperfect combustion of car
tainers 14. for the carbon black impregnated
bonaceous oils or oily liquids), and other forms
?brous cartridges are mounted so that it is in
of carbonaceous blacks or carbons produced in
the path of oil ‘circulating upwardly in close
other ways from other materials. Such forms
proximity to the windings l2 and the core. The
of carbon as lamp black or graphite, for example,
cartridge 23 is so positioned as to be in the path 20 are quite incapable of maintaining transformer
of oil circulating downwardly in close proximity
or other electrical oil at its initially high dielec
to the walls of the case [0.
tric strength, and may even detract therefrom.
The particular location of the cartridges with
A carbon black of the grade known to the trade
in the transformer case also depends to some
as “Micronex” is highly satisfactory. Such car
extent on the design and construction of the
bon black advantageously constitutes about 10%
particular transformer. It is customary in core
by weight of the paper or other ?brous material
type transformers to have terminal posts for
from which the cartridge is formed.
the windings arranged on an insulating support
Although the invention has been described
mounted at the top of the core l3. In such a
above with particular reference to oil-?lled trans
transformer the containers 14 may have to be 30 formers, it is of course understood that the re
displaced somewhat from the position shown in
placeable cartridge of the invention may be em
Figs. 1 and 2 in order to make room for the
ployed with advantage in other oil-?lled electri
terminal posts and the supporting structure
cal apparatus in which the oil is subject to de
therefor. Other types of transformers may re
terio'ration after use for any considerable period
quire mounting of the containers in other loca 35 of time. For example, suitable cartridges ‘com
tions. For example, Fig, 6 shows in cross sec
prising ?brous material impregnated with carbon
tion a modi?ed shell-type transformer compris
black are readily designed for use in such oil
ing a case 39 ?lled with oil in which the trans
?lled electrical apparatus as oil-?lled switches,
former unit is immersed. This unit comprises
oil-?lled circuit breakers, oil-?lled rheostats, and
a core 31 which is X-shaped in plan. The core 40 the like.
3| has a central leg about which coils 32 are
I claim:
disposed and peripheral legs outside the coils
for completing the magnetic path. In a trans
former of this sort, cartridge containers 33 ac
1. A cartridge for immersion in the insulating
oil used in transformers to absorb deterioration
products from the oil which comprises a support
cording to the invention may be mounted at the 45 ing structure, a plurality of spaced sheets of
extremities of the peripheral legs of the core,
?brous material having carbon black incorporated
either on the core itself or on any convenient
therein, said sheets being so spaced that substan
tially the entire surface of each of the sheets is
exposed to contact with the oil, means for secur
' It is desirable that the cartridge (or the 50 ing the sheets in said spaced positions in the sup
cartridge container) be fairly accessible so that
porting structure whereby the oil may flow be
if required from time to time an old cartridge
tween the sheets without passing therethrough,
may be removed easily and a new cartridge sub
the space between said sheets being substantially
.stituted therefor in order to maintain the di
free of encumbrance to the flow of oil there
electric strength of the oil at a high value for 55 through and passage means in the supporting
prolonged periods of time.
structure through which the oil may ?ow and
Any ?brous material into which carbon black
pass into the space between the spaced sheets in
may be impregnated may be employed in making
the course of normal circulation of the oil in the
up the cartridge. However, it is advantageous
transformer.
to have the ?bre-us material in sheet form so
2. A cartridge for immersion in the insulating
as to present a relatively large surface per unit
oil used in transformers to absorb deterioration
of volume to the oil. The most inexpensive and
products from the oil which comprises a support
generally satisfactory ?brous material for this
ing structure, a plurality of spaced sheets of
purpose is paper. The carbon black is readily
?brous material having carbon black incorporated
supporting structure within the transformer case
below the level of the oil therein.
and completely incorporated in paper by beating 65 therein, said spaced sheets being in the form of
it with the pulp from which the paper is made.
a spiral and being so spaced that substantially
The resulting. carbon black paper is highly effec
the entire surface of each turn of the spiral sheet
tive for the purposes of the invention, and ?rmly
is exposed to contact with the 011, means in the
retains the carbon black in place, so that no
supporting structure for securing the sheets in
free particles of carbon black are allowed to enter
70 said spaced positions substantially free of encum
and circulate with the oil.
brance to the ?ow of oil therethrough, and pas
Any suitable weight of paper may be employed,
sage means for permitting the ?ow of oil through
depending upon the mechanical structure of the
the cartridge and in the spaces between the sheets
cartridge itself. A cartridge designed to be held
without passing through the sheets in the course
in a container, such as is shown in Figs. 3 and 4, 75 of normal circulation of the oil in the transformer. _
2,405,853
6. A transformer comprising a transformer core
and windings mounted in a tank, oil ?lling the
residual space in said tank and circulating there
in, a replaceable cartridge serving to remove de
terioration products from the oil removably
mounted within the tank, said cartridge compris
ing a supporting structure, a plurality of contact
elements in the form of spaced sheets of ?brous
being so spaced that substantially the entire sur
material having carbon black incorporated there
face of each of the sheets is exposed to contact
in, said sheets being so spaced that substantially
with the oil, means for securing the sheets in said
the entire area of each of the sheets is exposed
spaced. positions in the supporting structure
to contact with the oil ?owing therebetween,
whereby the oil may ?ow between the sheets
means for securing the sheets in such spaced
without passing therethrough, the space between
positions in the supporting structure that the oil
said sheets being substantially free of encum
brance to the flow of oil therethrough, and pas 15 may flow between the sheets without passing
through the sheets, the space between said sheets
sage means in the supporting structure through
being substantially free of encumbrance to the
which the oil may ?ow and pass into the space
?ow of oil therethrough, and passage means in
between the spaced sheets in the course of normal
the supporting structure through which the oil
circulation of the oil in the apparatus.
may freely flow and pass between and in contact
4. A cartridge capable, upon immersion in the
with substantially the full area of both surfaces of
insulating oil in oil-?lled electrical apparatus, of
the sheets during the course of its normal circu
absorbing deterioration products from the oil by
lation within the transformer, said cartridge be
contact between the oil and the cartridge as the
ing so positioned within the tank that the pas
oil flows between contact elements in the car
sages through the supporting structure and be
tridge in the course of normal circulation of the
tween the sheets thereof is in line with the path
oil within the apparatus, the cartridge compris
taken by the oil in the course of its normal cir~
ing a supporting structure, a plurality of contact
culation within the tank.
elements in the form of spaced sheets of ?brous
7. A cartridge for immersion in the insulating
material having carbon black incorporated there
in, said sheets being so spaced that substantially 30 oil used in electric apparatus in which electrical
equipment is immersed in oil, the cartridge being
the entire area of each of the sheets is exposed
adapted to absorb deterioration products from
to contact with the oil ?owing therebetween,
the oil and comprising perforated end members
means for securing the sheets in such spaced posi
having disposed therebetween a plurality of
tions in the supporting structure that the oil may
spaced sheets of ?brous material having carbon
flow between the sheets without passing through
black incorporated therein, said sheets being so
the sheets, the space between said sheets being
spaced that substantially the entire surface of
substantially free of encumbrance to the flow of
each of the sheets is exposed to contact with the
oil therethrough, and passage means in the sup
oil, the space between said sheets being substan
porting structure through which the oil may flow
and pass into the space between the sheets in the 40 tially free of encumbrance to the ?ow of oil there
through and the perforations in said end mem
course of normal circulation of the oil'in the oil
bers being so positioned with respect to the spaced
?lled apparatus.
sheets as to permit the oil to pass into the space
5. In an electric transformer having a case
between the sheets and to flow between the sheets
within which are arranged transformer windings
without passing therethrough in the course of
immersed in oil, the improvement which corn
normal circulation of the oil in the apparatus.
prises a replaceable cartridge capable of absorb
8. A cartridge for immersion in the insulating
ing deterioration products from the oil by con
oil used in electric apparatus in which electrical
tact between the oil and the cartridge as the oil
equipment is immersed in oil, the cartridge being
flows between contact elements in the cartridge
adapted to absorb deterioration products from
in the course of normal circulation of the oil
the oil and comprising a plurality of spaced sheets
within the transformer, the cartridge comprising
of ?brous material having carbon black incor
a supporting structure, a plurality of contact ele
porated therein, and perforated end members
ments in the form of spaced sheets of ?brous ma
supporting the sheets in spaced position, said
erial having carbon black incorporated therein,
said sheets being so spaced that substantially the , sheets being so spaced that substantially the en
tire surface of each of the sheets is exposed to
entire surface of each of the sheets is exposed
contact with the oil, the space between the sheets
to contact with the oil ?owing therebetween,
being substantially free of encumbrance to the
means for securing the sheets in such spaced
?ow of oil therethrough and the perforations in
positions in the supporting structure that the
said end members being so positioned with respect
oil may ?ow between the sheets without passing
to the spaced sheets as to permit the oil to pass
through the sheets, the space between said sheets
directly into the space between the sheets and
being substantially free of encumbrance to the
to flow between the sheets without passing there
flow of oil therethrough, and passage means in
through in the course of normal circulation of
the supporting structure through which the oil
may flow and pass into the space between the 65 the oil in the apparatus.
sheets in the course of normal circulation of the
SAMUEL J. BOSCH.
oil in the transformer.
3. A cartridge for immersion in the insulating
oil used in electric apparatus in which electrical
equipment is immersed in oil, the cartridge being
adapted to absorb deterioration products from the
oil and comprising a supporting structure, a plu
rality of spaced sheets of ?brous material having
carbon black incorporated therein, said sheets
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