Note: Descriptions are shown in the official language in which they were submitted.
104B'~17
This învention relates to a method of manufacturing an electrical-
ly insulated coil using a vacuum-pressure impregnation process.
Recently, as a result of applylng a high voltage and large
capacitance to an electric appliance, high electrical intensity and
mechanical strength are demanded of an electrically insulatea coil
for use with such an electric appliance.
Conventionally, as the method of manufacturing an electrically
insulated coil capable of satisfying such demand there has been
adoptea a vacuum-pressure impregnation process which comprises winding
a mica sheet or tape around a coil, subjecting said coil as a whole to
vacuum-desiccation to remove the solvent, water content or the like,
subsequently vacuum-impregnating a non-solvent resin such as poly-
; ester, epoxy resin or the like into space portions within the insula-
tion body of the coil, thereafter applying a pressure to the resultant
coil, and solidifying the non-solvent resin. Where the electrically
insulated coil is manufactured utilizing the foregoing process, use is
made o~ ~1) compounds (thermoplastic bituminous material), (2) un-
saturated polyester, ~3) epoxy resins or the like, as the impregnant
while use i9 made of the corresponding materials to those constituting
- 20 said impregnant, as the mica bonding agent. The above enumerated
material (1) has a defect in heat-resistance, and the material (2)
has a defect in heat-resistance and water-resi.stance, respectively.
Accordingly, ~he materials (1) and (2) have recen~ly been little
in u~e, and the last-mentioned epoxy resins (3) having high water-
resistance and excellent electrical characteristics have principally
been adopted. ~owever, the combinations o~ curing agents and curing
accelerators and the types of epoxy resins result in a wide variety
of range. Where, therefore, the epoxy resins are employed as the ~`~
impregnant, combinations made by taking only the properties of such
materials into consideration do not serve as those fully satisfying
the necessary requirements for the manufacturing steps~ -
For this reason, an insulated coil of highly reliable quality
:
3Z17
can not easily be obtained with the result that the chaxacteri~tic
of the coil so produced frequently pres~nt3 a high degree of varia-
tion to become a cause of coil accidentsO :~
This invention has been achieved in view of the aforeaaidcircumstances, and is intended to provide a meth~ of manufacturing
a highly reliable, electrically insulated coll of excellent quality
having the characteristics enabling the coil manufacturing steps
(press~remolding and solidi~ying steps) to be ~tably carried out.
That is, the characterizing feature of th~ inv~ntion resides
in that in the manufacture of an electrical insulation coil by the
vacuum-pressur~ Lmpregnation proce~s employing epoxy resins the
above object has been attained by selectively effectively combining
epoxy resins, curing agent~ and curing accelerator~ used as the
~ Lmpregnant and the mica bonding agentO
- The method o~ manufacturing an electric~ ly insulated coil
according to the invention will now be describedO A mica tape
~: ~oated with a varnish (mica bonding agent) containing 0.3 to 105
weight parts or preferably 003 to loO weight parts of boron tri-
fluoride serie~ latçnt curing agent based on 100 weight Earts of
20 ~poxy resin is wound around a coil, and the result~nt coil is sub-
~ected to preliminary desiccation by vacuum-hea~ingO The amount of
varnish used as said mica bonding agent is preferred to account for
10 to 20~ of the sum amount of mica and rein~orcing materialO A
mica tape coated with such mica bonding agent remains ~table, high-
ly flexible due to little soli~ification, highly operable and dur-
able for long use, and further is not af~ected by the heating (up ~ :
to about 90C)"per~vrmed for preliminarily desiccating said
resultant coilO
Next, an impregnation resin consisting of acid anhydride
3 ~exies curing agen~ and cyc1oaliphatic epoxy resin is impregnated
.
~ 1048Z~7undar vacuum-pressure into the preliminarily de~iccated oilO Sub-
sequently, the coil impregnated i9 fa~tened with a metal pad applied
thereto and i9 subjected to 301i~ification, thereby obtaining a
final coil product~ At this time, though the impregnation resin
itself is low in viscosity and accordingly low in solidification
speed, it reaches the mica tape layar and i9 mixed with the mica
bonding agent to become integral therewith, so that the boron tri-
fluoride serie~ latent curing agent contained in tha mica bonding
agent concurrently acts on the impregnation res in as a curing ~ ?
accelerator. For thi~ reason~ the solidif ication speed i8 effective-
ly ad3us ted during the solidification stap to form an ideal in- :~:
sulation body with the aid of the fastening forceO
A3 the epoxy re~in of the mica bonding agent a bisphenol
epichlorohydrin series epoxy resin (~or example, Epikotes 828 and
1001 manufactured under such trade names by Shell Chemical Company
or DER 331 and DER 661 manu~actured under ~uch trade name3 by ~ow ~.
: Ch#mical Company~ i~ preferably u~ed in a single or mixed form.
Further) as the boron trifluoride series latent curing agent complex
æalts ~uch as BF3-monoethylamine, BF3-piperidineJ ~F3-benzylamine
or the like are suitable. Further, as the acid anhydride ~eries
curing agent acid anhydrides such as hexahydronaphthalic anhydride,
methy?hexahydrophthali~ anhydride, methyltetrahydxophthalic anhy-
dri~c, methylnadic anhydride or the like preferably are respectively
used in a ~ingle or mixed ~orm~ Further, as the cycloaliphatic
epoxy resinJ Chis30nox 221 (manufactured under such trade ~ame by
Chi~o Company) and a glycidyl epoxy type epoxy resin (for example,
XB-2610 manufactured under such trade name by Ciba Geigy Company) :
can be employed~ In addition, $ox ~he purpose of decreaæing the
LmprsgnatiOn viscosity of the ~pregnant, an epoxy series rsacti~e
JO diluent (for example, butylglycidy~ether or arylglycidylether) can
~ _ 3 _
:
" , ., ~ , . . . . .
~48~
be added to the impregnant ~9 required~
As above describedJ bacau~e of a good adaptability between
the mica bonding agent and impregnation re~in a3 selectively efect-
ively mutually combined the electrically insulated coil manufactured
by the above-mentioned method has an axcellent electrical, mechani-
cal and thermal characteri~tic~ and i~ mainta~ned highly reliable
in qualityO
- 3a -
' -: . , . .: ,
L7
This invention will be more fully understood by re~erence to
the concrete example which ~ollows.
Example
Five types of varnishes (a 50% solution of methylethylketon)
were first prepared each of which has such a resin composition as is ~ ?
shown in the respective columns of examples 1 to 3 and controls 1
-~ and 2 of Table 1. The varnish so prepared was coated on a mica sh~et
consisting of a bonded mica paper or flake mica and glass reinorcing
material as a lining material to obtain a mica tape. The mica tape
was wound around a coil whose elemental wire is previously insulated,
and the resultant coil was introduced into an impregnation tank and
was subjected to preliminary vacuum desiccation under a tamperature
of 70C to 80C and under a pres~ure of 0.3 mm Hg. Subsequently,
said coil was cooled to normal temperature and was vacuum impregnated
: with an impregnation resin consisting of acid anhydride and cyclo-
aliphatic epoxy resin, and thereafter was ~ubjected to a pressure of
7 kg/cm2 for 15 hours.
Thereafter, said coil was taken out of the impregnation tank,
.~ and a metal pad was applied to the taken-out coil. The resultant .: .
~ 20 coil was wound with a thermal shrinkable tape such as shrinkable
polyester tape and was gradually heated for solidi~ication, and
thereafter was finally heated ~or 20 hours at a temperature of 150C
to obtain a final product, iOe~ ~ an electrically insulated co~ lo
: The coil thus obtained has such electrical characteristics as
presented in Table 2. The respective coils obtained from the examples :
1, 2 and 3 had a prescribed dimension and a good insulation layer `~
~ having a uniform thicknessO On the other hand, the surface of the
insulation layer of the coi7 according to the control 1 was coloured ::
whitish, which indicates that the impregnation resin flows out from
the surface of the insulation ~ayer and accordingly is not held
:` thereinO The coil according to the control 2 presented a good
appearance but the insulation layer thereof failed to be sufficiently
compressed to have a somewhat lar~er thickness. When this coil was
: ' '
; - 4 -
16~4~2~7'
cut off, an impre~nation resin layer proved to be formed thick
between the insulation layers and to have innumerabl~ small cracks.
Since, in the insulated coil of the invention, the boron tri
fluoride series latent curing agent affects the suitability of the
coil itself~ the addition amount thereof is of greak importance.
Namely, as apparent from the results of the examples 1 to 3 and
controls 1 and 2, it i5 when 0O3 to 1~5 weight parts or preferably
0.3 to loO wei~ht part of said latent curing agent based on 100
weight parts of epoxy resin was added thereto that a good result is
obtained~ Where a solid cyclo-aliphatic epoxy resin (for ex~mple, LT
580 manufactured under such trade name by Ciba Geigy Company) was
used as the mica bonding agent, the reaction of the mica bonding
agent with the impregnation resin, when the ormer was mixed with
the latter~ was promoted due to the high reactivity of boron tri-
fluoride series latent curing agent and cyclo-alipha~ic epoxy resin,
so that a result similar to the control 2 was obtained to present
a low suitabilityO
: Table 1
.
_ Example 1 Example 2 Example 3 Control 1 Control 2
. = ~ : . .............. ~ _
70 weight 60 weight 60 weight 70 weight 60 weight
part of part o part of part o~ part o
Compo- DER 331 828 Ep kote Epikote Ep kote
nents of A
mica 30 weight 40 weight 40 weight 30 weight 40 weight
bo di part of part of part of part of part of
n ng DER 661 DEN 4~8 DEN 438 Epikote DEN 438
agent 1001
_ . .
0O3 weight loO weight 1O5 weight 3 weight
B part of part of part o~ _ part of
BF3-mono- BF3- BF3- BF3-
. _ ethylamine piperidine piperidlne plperidine
A Epoxy resîn
B Boron fluoride series latent curing agent ~:
.
.
~4i~7
Table 2
_ ~ tanS ~ an ~` ~ tan (5' - Voltage
Mica bonding Initial Initial Initial BDV sndurance
a~ent u~ed value~ value ~ ~alue ~ KV/mm characteristics
E/ ~ E 1.5E
__ _ _ _ . .. _ ., . - __
Example 1 0.02 0.05 0.11 2600800<
2 0.01 0.02 0.09 27.01000~
3 0.~2 0.03 0.28 25.07<
Control 1 O33 1.33 1.70 19.0_
o. 18 o . 55 o. 78 17. 5 20r ~ 3~o
In the above ~abl~ 2~ E represent~ the rated voltage, the
initial value i8 the value of the tan ~ at the nonionization time
: when it doe~ not ri~e, in the case where the low voltage as applied
is gradually increased in mea~uring the tan ~ value, BDV is the
insulation braakd~wn voltage~ and the voltage endurance characteris-
tic is the length of time required for the ~oltage having ~ vo}tage
inclination of 9.5 KV/mm to be applied until the insulated condition
.. . .
i5 broken-downO
:~ A~ above de~cribed, a highly reliable electrically insulated
coil of excellent quality ha~ing ths characteristic3 enabling the
coil manufacturing ~teps (pressuremolding and 301idiEying steps) to
; be stably carried out can be ob~ained, in the present method o~
~ manuacturing an electrically insulated coi} by vacuum-pressure
. .
.~ impregnation proces~ employing epoxy resin~, by selectiv~ly effe~tive~
ly combining epoxy resin~, curing agent~ and curing accelerator~
: u~ed a~ the Lmpregnant and the mica bonding agent.
~ hough~ as heretofore mentioned, the coil, to which th~ mica
bonding agant and the impregnant are only applied, pre3ents9 as it
i9, a sufficient per~srmance, the mutual adaptability between the
mica bonding agent and impregnant can further be increased by pre-
~4~
~.iously applying, befor~ the mica bonding agent is coated on themica tape, an uncured epoxy powder containing therein a curing
agent which is ~olid at normal tempsrature as an adhe-~ive between
the mica sheet and the reinforcing material. This i~ because the
respective solidification spe2ds of the impregnation resin ~nd
the mica bonding agent within the insulation layer are kept con-
stant by said previous application of said powder. ~amely~ within
the mica layer there wi}l be attainad the distribution of a small
amount of Lmpregnation re~in and a large amount of mica bonding
agent while between the mica layer~ there will be created a layer
having the distribution of a ~mall amount of adhesive and a large
amount of LmpregnatiOn resin. Accordingly, in any portions of the
mica layer section the solidification is properly advanced due to
the presence of curing agent, i.e~, the boron trifluoride serie~
latent curing agent within the mica layer and the latent curing
agent contained in the powder between the mica layers, so that a
uniform insulation layer having good suitability is formed during
the solidification stepO
In case of the oregoing uncured epoxy powder containing
curing agent therein, fo~ example, a bisphenol series solid epoxide
(Epikote~ 1001, 1004 and 1007 manufactured under such trad~ names
by Shell Chemical Company) i9 de3irable as said epoxide re3in~ and,
for example9 th~ latent cu~ing agent in the said powder such as
anhydride dicyandiamide, diamino-diphenylmethane or imidazole~ is .
: suitable as said curing agent. The amount of said powder bet~eon
mica sheet and reinforcing materials is preferred to account for
3 to 12 weight % of the adhesive powder based on the sum amount of
mica sheet and reinforcing materialO ~he reason i~ that in case
of le88 than 3 weight % the solidification promoting action be-
.
. . . . .
~34~ 7
tween the Lmpreynation r~sin and said powder i~ rsndered ineffec-
tive whereas in ca~e of more than 12 weight % the action of said
powder i9 rendered too effective to render tha re~ultant mica
tape inflexible with the result that its resin impregnability and
operability are decreased to render it unsuitable.
FurtherJ by applying, in addition to ~aid previous application
treatment ~or said powder, a mica layer flow-preventing agent to
the mica tape there can be obtain~d a more highly reliable insulated
coil., That is, where no mica layex flow-preventing agent i~ app-
10 lied to the mica tape, it often happen~ that when the mica tapeof the coil after completion of resin impregnation is pre3se* by
~ingers~ the mica layer is displacedO ~his produces the pos~ibili- ;
ty that in case of the manufacture of an elongate, large coil a mica
layer flow takes place due to the molding pressure during the
solidification ~tep performed after a metal pad i~ applied to an
unfinished coil, which undesirably affects the characteristics o
the coil after ~olidification. Such mica layer flow-preventing
agent application is performed by using a~ small an amount of normal
temperature ~olidifiable epoxy resin composit.ion as Oo l to 1 weight
~ based on the 8um amount o, for example, mica tape and reinforcing
material. A coil wound with a mica tape subjected to previous
application as the mica layer fl~w-preventing agent of 0.5~ of ~`
normal temperature solidifiabLe epoxy resin composition ~onsisting :
of 100 parts of Epikote 828 and 13 parts of triethylenetetramine
based on tha ~um amount of mica tape and r~inforcing material
presented no mica layer flow and had good characteristics after
solidified.
There will now be described a concreta example of the method
of producing a mica tape.
3~ i Tha f ir~t step (Bondin~ step utilizir~g the epoxy powder):
-- 8 --
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1~8Z~L7
An epoxy resin o~ EPX 1346 is applied to a gla~s cloth having
a fiber thickne~3 of 30 m at the rate of 8g per square meter o~ the
glass cloth, and the resultant glass cloth i9 fused to a not-
dehydrated, bonded mica paper having a thickness o~ Ool mm by a
heated roll kept at a temperature range of 125 ~ 5~ at a speed
of 2 m/minO Thi~ extent of thermal hi~tory, however~ does not
cause the ~olidification of the EPX 1346~ which permits th0 EPX
1346 to remain effective as the reaction promoting agent for the
impregnating resin . .
The second step (Mica layer fl~w-preventing ~tep 3:
A varnish consisting of 0.1 kg of Epikote 828, Ool kg of TTA
~txiethylenetetramine), 6075 kg of ~oluene and 2.25 kg of methanol
i9 coated as the mica layer flow-preventing agent on the mica ~heet
obtained in the first step, so as to permit the varni~h thu~ u~ed
to amount to 50 + 5 g/m20 The resultant mica sheet3 after passed
through a drying stove kept at 60C at a speed of 2 m/min., is
allowed to ~tand overnight, thereby to cause the mica layer flow-
preventing agent to be fully solidifiedG
The third s~ep (St~p for coatiny the bonding agent):
A varnish con~iqting o~ 6 kg o~ Epikote 828, 4 kg of DEN 438,
0005 kg o B~3 piperidine, 706 kg o~ methylethylk~ton and 204 kg
o~ toluene i8 coated as the mica bondi~g agent on the mica sheet
obtained in the second step, so a9 to permit the varnish thus used
to amount to 80 ~ g/m20 The resultant mica sheet i9 passed through
a drying 9 tove kept a~ 80 to 90C at a speed of 1 m/minO and is
thereby dried to obtain a desired mica tapeO
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