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Патент USA US2410756

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Nov. 5, 1946.
Filed Nov. 15, 1939"
2 Sheets-Sheet 1
Nov. 5, 1946. ‘
Filed Nov. 15, '1959
2 Sheets-Sheet 2
552711040 sPEM/GEE
Patented Nov. 5:, ‘1946
2,416,756 ’
2,410,756 " ‘
Berthold Springer, Berlin W. 30, Germany; ‘vested
in the Alien Property Custodian
Application November 13, 1939, Serial No.‘ 304,193
In Germany November 19, 1938;
5 Claims. (Cl. 117>—.65)
' 1
‘Thepresent invention relates to a process and >
a device for impregnating electrical condensers
with impregnating agents which are solid at or
' Figs. 1, v2 and3 are ‘diagrams showing'volum‘e
and temperature change in the‘mateiial' being
treated and showing respectively, three'separate
dinary temperature, as for example para?‘ine,
ozocerite, Vaseline and similar substances.
Ways in which the cyclic process in‘ accordance
with my invention may be carried out.
As'is known, ?xed condensers and the like are
usually impregnated in such a manner that the
condenser rolls, which for instance consist of
cordance with my invention, _' _
ing sheets after being dried in vacuum at an ele
vated temperature are ?ooded with the molten
of apparatus for carrying out the process in ac
metal foils with interposed impregnable' insulat
impregnating means.
‘ Fig. 4 is a, diagrammatic view showing one. form
j “
Fig. 5 is a sectional view showing an electrical
condenser, in the making of which the improved
method and apparatus of I my invention may be
employed, and
The present impregnating processes show the
Figs. 5a and 5b are detail views‘ of a portioniof
disadvantage that the electric properties of- the
g the structureshown in Fig. 5.
' ?nished condensers deteriorate Very, much owing
, Curve 101 shows the’ isobar of a certain amount
of an impregnating agent in solid and liquid
to the volume contraction ‘which takes place to
gether with the solidi?cation‘ of the impregnating
agents, especially after long storage. This is be
state under atmospheric pressure. The volume
of this amount at room temperature is called 11!.
The curves p2 and Y103 show the isobars of the
sides other reasons mainly caused by the fact
that owing to the volume contraction during so 20 same amount at considerably increased pressures
lidi?cation near the ends of the ?nished roll the =
p2 and 273, respectively.
solid impregnating agent shows series of small
The changes‘ in volume V
which take place at the melting temperatures'Ti,
cracks. The water coming from the air which
T2 and .T3 are called w1, H72, H23.‘ They decrease,
as can be seenv in the drawings, with increasing
slowly penetrates into these cracks. causes de
terioration of the electric properties of the con 25 pressures. The process for impregnating of ‘con
denser. With certain kinds of rolling, as for in
densers can be realised according to the inven
stance the rolling of noninductive condensers,‘ the
tion in vmany different kinds of cyclic processes '
in?uence of the cracks can be especially trouble
which suit the constants of the‘ used impregnat
~ some.
Till now it has been tried to improve the
disadvantage of decreasing the dielectric strength .30 In curve I of Fig. _1 merely one way of con
ing agents.
by making the insulating coils considerably larg
er thanthe metal foils. '
ducting the cyclic process is shown. Theim
pregnating agent isuheated at atmospheric pres
The present invention intends to abolish the
appearance of disturbing cracks by suppressing
.the volume contraction of the impregnating agent.
This contraction takes place during solidi?ca
sure to a temperature which is higher than ‘the
melting point and higher than thetemperature
T3. At constant temperature 1 the pressure is
raised from 211 to 123, the impregnating. ‘agent re
maining liquid and assuming a ‘volume which is
equal to its volume at room temperature. After
‘ that it is cooled to ordinary temperature 'at'con
tion. When impregnating condensers-Jwith- im
pregnating‘agents which are solid at room ‘tem
perature, according to the present invention, the
impregnating'agent is at ?rst, starting at room 40
temperature, lique?ed in-a cyclic processandin '
stant volume.
By reducing the impregnating agent to the de
sired volume (for) ma ‘liquid state; as‘ described
above, the solidification occurring at the follow
presence, of the condenser submitted‘to such high
temperatures and such high pressures that'the
volume of the impregnating agent, whether'to- ‘ ing cooling as well as the‘further reducingv down
tally liquid orpartly liquid and partly solid, is 45 to ordinary temperaturejtakesfplace without any
reduced to the volume which the impregnating
change in volume, whichjjcould, be disturbing b
agent takes‘at room temperature and at atmos
the formation of troublesomejc'racks.
In the above described performance of the proc
‘The process according to the vinvention is-eX
v ess according to the inventionz‘generally compar
atively high ‘ pressures andlrcorresponding high J
plained in the following: with the isobarsfor the
liquid and solid-state of a pure impregnating.‘
agent in a diagrammatic drawing.I It is to be
temperatures have to,_be, used. ,Thereforegin a
preferred method of performiiigrth'e cyclic procé '
ess according to the invention, vthe'in'ipreg'nating
.understoodthat according to theiinvention im
pregnating agents consisting ofcmirturest canbe
, agent which‘ has to. be t're ted is'exhibited at a
of Hg) to such a pressure that it solidi?es and
ing the pressures and temperatures used in the
then it is cooled at the same or at a higher pres
sure'isobarically to its volume at ordinary tem
process according to the invention. This sub
stance may have the following constants:
The melting temperature at 760 mm. of Hg is
Such a cyclic process is shown in Fig. 2, curve 5 Ti=50° C.; the change in melting temperature
.with pressure._is4-10-3 degree/atm. .. 1_, gram of
. .
11, of the accompanying drawings.
:the substance shall talge’ at ordinary: temperature
The impregnatingiagent is hfea'te'd’at the pres
a volume of 1 cc. The relation between volume,
sure in, which may di?er from the atmospheric
temperature and pressure is the same for the
pressure, to the melting temperature T; corre
sponding to the isobar 122, then exhibited to the 10 solid and the liquid state and the thermal ex
pansion coefficient is 510-4 and the compressi
pressure m which makes it solidify, and is cooled
bility 2-10—5.
The contraction of volume dur
to such a degree, for instance isobarically,luntil
.ing solidi?cation ,at atmospheric pressure is
it assumes the desired volume (or) .
w1=5~10—2 cc./gr. and the decrease in the con
The above described method has the '\-effect
that owing to the pressurepz being far above 15 traction of volume with pressure is 4- 10—6 cc_/atm,
The ?gures given above correspond roughly to
atmospheric pressure, thecontractionpf volume
(wz) connected with solidi?cation is-considerably
the‘?gures of known substances, as for instance
cetylic-alcohol as can be seen from the tables of
smaller than the contraction of volume 1(w1) at
the melting point (at ‘760 mm‘. of Hg). The con
Landolt-Bérnstein, the International Critical Ta
traction connected .with'ithe‘ isobaric cooling of 20 bles etc, and .fromthe publications on which
these‘?smes,arebased- iTheimpresnatinaasents
the solid material at. 'th'epresSure $92,113,816 be
used..practicallv?o not differ ‘principally in their
‘kept _,su?iciently .jsmall ,.Joy “choosing sufficiently
behaviour ‘from‘hcmogeneous substances.
high ‘pressure ,Qinl order. -to v‘ prevent troublesome
Assuming aypure substance with theabove men
cracks. Furthermore,etheiormation .of. undesired
cracksatltheen'ds .of thepondenser roll accord 25 tionedconstants, the following. picture is obtained
for the. cyclic?process shown inj‘Fig. jl1by I, which
ing .to .thelcontractionjof ..volume during ‘.solidi
requires especially high pressures ,and' tempera
?cation cannot occur .in _.the .CGOll-lllg. of the ., im
pregnating agent in ‘the'solid state.‘ ’
tureshas compared .v with the cyclic processes in
_ l j
Figs.12 and 3.
' ‘ , It .is . also advantageous .tofsubmitlthe. impreg- V
.Lgra'mof'the impregnating agent is'heated at
"hating. material.j-which'i'sctos betiieatedwat attem ‘g0 apressure
of'760~mm. of Hg ‘from ordinary tem
perature abovefthe melting ‘point lat .1160 him.
perature to its meltingpoint of v50°C; ‘expanding
‘of Hg) to_.,a. pressure-cat, which the impregnating
.015 cc._ ,The changejof volumeduring~ melting
age'ntis still liquid, whereupon it )issolidi?ed by
cooling at constant .voliimecjand.reduced..lto the ‘_ _ amounts‘to 115cc.‘ *The'molten substance istur,volume which ._ it _ assumes. at ordinary tempera- ‘ 35
ture. llnrFig. 3,.curve IILLisshown, for instance,
one'lway of conductingthis'kind of cyclic process‘
The impregnating.agentlislheated _at;the pres
fdecrease'to ‘its volumeat ordinary-temperature
atmospheric _ pressure vto 1a vItemperature 'higher r‘ ‘O
than.‘theptemperature T2. _jlt§is‘then submitted
» glnthis method of carrying Voutithejfprocess jac
fjoordin'g.,tojheinvention gin-importantpartiofjthe
volume. reduction. takes _1plac§e',_in", the liquid state
before ‘the ‘solidi?cation jof .the impregnating
‘ 'jFOI‘V quite ‘ different purposes; namely i for ren
0 ibeen used ‘ on -the ‘liquid impregnating ‘agent. »It
‘ can be seen‘thatthepressures jused in the process
according to theinventicha-re of av‘di?erent' order
- ‘of; magnitude.‘
._ agent starts,‘ and therefore "thelformatio‘n of
cracks > during 'isclidi?catiqn _ is gnra?cticallpyelinw
‘ Vnatedf"
In realisingithe‘processaccording;to
;th, .
ve'ntionjjthe ‘cyclic processes, Tillustratcdghin fthe
diagrammatic vdrawing may generally not be
obeyed strictly, ljhe di?erent tracksinthe'?cé'i‘l
liilainé may‘: not. Lie-completely"isotherms .or'liso
loaric'; for 'ins'téincefthe ‘compressionlin'rthe; cyclic
"12. :ma'ypnqt take
' “place
, exactl‘ in
of which ‘changesstronger withfpressure- than it
>deringyharmlessthe traces of gas-which remain
in vthe [ badly evacuated ~_condenser 'rolls, -a~- small
overpressure of ‘several atmospheres has already
in the solid?statléto; the ‘volume (or) .at‘Tz‘ and
then'cooled'to ordinary‘ temperature at __const_ant
‘415 'correspondingto- Figs. 2_ andj3.
> , . either cooledgisobaricallyp @or,‘ ,at - ‘?rst compressed
' jlffsubstances are used "the volume contraction
'is‘f the case with’ thejabove mentioned; substance,
considerable smaller pressures, "as 'for-instanceup
to 10.00, atm., are suii'icientin the-cyclic processes
tova ‘pressure higherhthanlthe‘melting pressure
I702 corresponding to‘ T2," remaining liquid. , 'It is
cooled isochoricallyto the ,temperature‘Tz, where
this ‘temperature itjis ‘exposed toapressure of
about*2500 to"30GO;a*trn., which-makes‘the volume
‘and TSO‘mm'oi‘I-Ig.
surefjpi whichfmay be‘. equal .‘orjdiiier?nt ,from [I ‘
' _>byjllthe?impreg‘nating jagent' solidi?es. I'I‘heirit is
temperature "T2...
{In "Fig. ‘ fl -~are¥{sh0wn -di_agrammatically - the
essential parts» of a¥device~ adaptedefor perform
‘ ing the process‘ according to - the --invention.
impregnating- vessel 1 consists; of a~number of
pressure chambers 2, suitable iortakinglthelcon
denser rolls-which-caneb'e tightly-closedat >3.
~The- chambers 2}, are ‘connected évia'bore ‘holes 4
thepigxg-line 5. > This line is connected-with
the evacuating- deviee, 9"via- valve »-8. By-valveill)
“it is separated vfront-the container-H~which~is
‘ ?lled’ with‘ the'impregnating- agenh?and by» valve .
inor" may the icoolinsffollow strictly‘ paralleljito gr fl Zjfrom the high» pressure part i 3 and the medium
'ithe T-axis. Generally‘ ‘thermctical‘perform
ance a .cvcli¢._.prio ess‘lls hosen. whichiavoidsithe
'_ formation. of 1 craclgs rand 7 also; wciiksiiwith jtem
lperatures .andpressurles which.canieasilyhetob
Qtained in', the iprach llyavailable dericesfflsuch
.- (a; cycliqprocess can. eénerallytbenicturcd as an
entirely enclosed pclirve'lin the -.(v+‘T)..planeg ‘i l
iiiregn'atins agent'sa notv kiri’olrntin‘ t
*therpheated ;_to about 61°C. expanding -.O06 cc; At
T"pressure part 1 5~'of;the compressor.
’ r I
' v*Afterfeed-ing the chambers 2 with condenser
rolls, container l is heated by an electric heater 1
"?xedin an insulating envelope 6. At lthe same
f’time the aireXpands-outof thechambers through
=the1opening ofvalve 8. Afterclosing-thevalve
ialitheiimpreg’nating agent~~molten in ‘the4con
‘_" tainer ‘H :is, vallowed'to; enter-‘by opening the valve
7H! intdt-helin‘esiand lfwhich are all'heatable
- "fa‘liomogeneous substance is used for'demonstrat-“75._and heat-insulated. According to the process
which has to be carried out, and according to the
impregnating agent used, at ?rst a medium over
pressure may be produced with the compressor I5
the invention a multiple increase in strength of
breakdown is obtainable. Even with small bor
ders safety against sparks around the border is
obtained. Therefore, non-inductive condensers
in the chambers 2 which at the same time have
to be heated to a suitable temperature. After
of a certain capacity can be manufactured with
closing the valve [0 the high pressure device I3
considerable smaller length with the present
can be fed under medium pressure with impreg
process than with the known processes.
nating agent from the compressor I5, valve I 4
What I claim as new and desire to secure by
being open, and after opening valve 12 the cham
Letters Patent is:
bers 2 can be put under the desired high pressure.
1. The process for impregnating electrical ap
All the auxiliary devices, as thermometers, elec
paratus with insulation material solid at normal
trical and mechanical manometers etc. are omit
temperature and pressure, which comprises es
ted in the drawings.
sentially, impregnating the apparatus with the
As mentioned at the beginning the process
insulation material and bringing the material by
according to the invention can be applied with 15 application of heat and pressure to substantially
special advantage for impregnating non-induc
that volume which is the normal volume for the
tive condensers of known construction. Such a
condenser is shown diagrammatically in section
in Figs. 5, 5a and 5?).
One of the electrodes of the condenser is
material at normal atmospheric pressure and
temperature, and then cooling the impregnating
material isochorically.
2. The process for impregnating electrical con
formed by the metal foils l1 interconnected at 19,
the other electrode being formed by the foils l8
connected at 20.
Adjoining metallic turns are
separated by impregnable insulating layers Hi.
The higher the wanted dielectric strength of the
condenser has to be, the less the layers l1 and
i8 can overlap. The free border given by the
distance between 2! and 22 has to be sufficiently
large, which increases the length of the condenser
if the capacity is kept at a constant value. Even
with large borders sparking-over, cannot be
avoided with certainty. For explanation of this
fact it is referred to Figs. 5a and 5b which repro
duce the inner edge 22 of the border in large
scale. Fig. 5a. shows a condenser impregnated 35
according to the known process and Fig. 5b
according to the present invention, the impreg
densers with insulating material solid at normal
temperature, which comprises liquefying the
impregnating material by heat, applying the
lique?ed material to the condenser, compressing
the lique?ed material to that volume which is its
normal volume at normal atmospheric tempera
ture and pressure and cooling the material while
maintaining it at substantially constant volume.
3. The process for impregnating condensers
with impregnating agents solid at normal atmos
pheric temperature and pressure, which com
prises liquefying the impregnating material, com
pressing the material under a pressure of 1,000
to 3,000 atmospheres and cooling the same, as
vand for the purposes described.
4. The process as described in claim 3, wherein
the pressure used is between 2,000 and 3,000
nating agent being marked 23. In the known
process of impregnation small cracks and bigger
traction of the impregnating agent during solid
5. The process for impregnating electrical con
densers with insulating material solid at normal
temperature, which comprises heating the im
i?cation (compare Fig. 5a).
pregnating material to ?uent condition, impreg
cavities are formed by the strong volume con
This does not assure in the region of the border
safety against sparking especially after the pene
tration of moisture into the cracks.
By the process of impregnation according to
the invention, however, a considerable uniform
?lling 23 free from cracks is achieved in the
border region (compare Fig. 517). As experi
ments have shown, by the process according to 60
nating the condenser with the ?uent material
and. applying pressure su?icient to compress the
impregnating material substantially to that vol
'ume which is the normal volume for the material
at normal atmospheric pressure and tempera
ture and then cooling the material at substan
tially constant volume.
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