U.S. patent application number 11/286060 was filed with the patent office on 2009-07-16 for composite coatings for groundwall insulation, method of manufacture thereof and articles derived therefrom.
Invention is credited to Yang Cao, Patricia Chapman Irwin, Qi Tan, Abdelkrim Younsi.
Application Number | 20090182088 11/286060 |
Document ID | / |
Family ID | 37758870 |
Filed Date | 2009-07-16 |
United States Patent
Application |
20090182088 |
Kind Code |
A9 |
Irwin; Patricia Chapman ; et
al. |
July 16, 2009 |
Composite coatings for groundwall insulation, method of manufacture
thereof and articles derived therefrom
Abstract
Disclosed herein is an article comprising an electrical
component; and an electrically insulating layer disposed upon the
electrical component, wherein the electrically insulating layer
comprises a thermosetting polymer and a nanosized filler; wherein
the nanosized filler comprises metal oxide and diamond
nanoparticles that have an average largest dimension of less than
or equal to about 200 nanometers.
Inventors: |
Irwin; Patricia Chapman;
(Altamont, NY) ; Tan; Qi; (Rexford, NY) ;
Younsi; Abdelkrim; (Ballston Lake, NY) ; Cao;
Yang; (Niskayuna, NY) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
PATENT DOCKET RM. BLDG. K1-4A59
NISKAYUNA
NY
12309
US
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20070117911 A1 |
May 24, 2007 |
|
|
Family ID: |
37758870 |
Appl. No.: |
11/286060 |
Filed: |
November 23, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10747725 |
Dec 29, 2003 |
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11286060 |
Nov 23, 2005 |
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Current U.S.
Class: |
524/495 ;
428/323; 428/328; 428/329; 428/339; 428/447; 524/430 |
Current CPC
Class: |
C08K 3/22 20130101; H01L
21/3122 20130101; H01B 3/006 20130101; Y10T 428/252 20150115; Y10T
428/256 20150115; Y10T 428/259 20150115; B29C 48/03 20190201; H01L
21/02282 20130101; C08K 3/04 20130101; B29K 2995/0007 20130101;
H01L 21/02126 20130101; Y10T 428/251 20150115; H01L 21/3146
20130101; B29C 48/154 20190201; C08K 2201/011 20130101; H01L 21/31
20130101; H01L 21/02216 20130101; Y10T 428/31663 20150401; Y10T
428/25 20150115; B82Y 30/00 20130101; Y10T 428/257 20150115; Y10T
428/26 20150115; Y10T 428/269 20150115; C08K 3/04 20130101; C08L
83/04 20130101 |
Class at
Publication: |
524/495 ;
428/323; 428/328; 428/447; 428/329; 428/339; 524/430 |
International
Class: |
B32B 5/16 20060101
B32B005/16; B32B 27/18 20060101 B32B027/18; C08K 3/22 20060101
C08K003/22; C08K 3/04 20060101 C08K003/04 |
Claims
1. An article comprising: an electrical component; and an
electrically insulating layer disposed upon the electrical
component, wherein the electrically insulating layer comprises a
thermosetting polymer and a nanosized filler; wherein the nanosized
filler comprises diamond nanoparticles, or a combination of metal
oxide and diamond nanoparticles that have an average largest
dimension of less than or equal to about 200 nanometers.
2. The article of claim 1, wherein the electrical component
comprises copper.
3. The article of claim 1, wherein the insulating layer has an
elongation of greater than or equal to about 200%, as measured in a
tensile test at room temperature.
4. The article of claim 1, wherein the thermosetting polymer
comprises polyurethanes, epoxies, phenolics, silicones,
polyacrylics, polycarbonates polystyrenes, polyesters, polyamides,
polyamideimides, polyarylates, polyarylsulfones, polyethersulfones,
polyphenylene sulfides, polysulfones, polyimides, polyetherimides,
polytetrafluoroethylenes, polyetherketones, polyether etherketones,
polyether ketone ketones, polybenzoxazoles, polyoxadiazoles,
polybenzothiazinophenothiazines, polybenzothiazoles,
polypyrazinoquinoxalines, polypyromellitimides, polyquinoxalines,
polybenzimidazoles, polyoxindoles, polyoxoisoindolines,
polydioxoisoindolines, polytriazines, polypyridazines,
polypiperazines, polypyridines, polypiperidines, polytriazoles,
polypyrazoles, polycarboranes, polyoxabicyclononanes,
polydibenzofurans, polyphthalides, polyacetals, polyanhydrides,
polyvinyl ethers, polyvinyl thioethers, polyvinyl alcohols,
polyvinyl ketones, polyvinyl halides, polyvinyl nitriles, polyvinyl
esters, polysulfonates, polysulfides, polythioesters, polysulfones,
polysulfonamides, polyureas, polyphosphazenes, polysilazanes, or a
combination comprising at least one of the foregoing thermosetting
polymers.
5. The article of claim 1, wherein the thermosetting polymer has
the structure (I) ##STR2## wherein R.sub.1, R.sub.2, R.sub.3,
R.sub.4, R.sub.5 and R.sub.6 are the same or different and wherein
at least one of R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and
R.sub.6 is a reactive functionality prior to cross linking; m and n
can be any integer including 0, with the exception that both m and
n cannot both be 0 at the same time.
6. The article of claim 5, wherein the sum of m and n is about 1 to
about 50,000.
7. The article of claim 5, wherein R.sub.1, R.sub.2, R.sub.3,
R.sub.4, R.sub.5 and/or R.sub.6 are reactive functional groups and
comprise alkyl, aryl, aralkyl, fluoroalkyl, vinylalkyl, aminoalkyl,
vinyl, epoxy, hydride, silanol, amine, carbinol, methacrylate,
acrylate, mercapto, haloalkyl, halogen, carboxylate, acetoxy,
alkoxy, or a combination comprising at least one of the foregoing
functional groups.
8. The article of claim 5, wherein the thermosetting polymer has a
number average molecular weight of about 75 to about 500,000 g/mole
prior to crosslinking.
9. The article of claim 1, wherein the insulating layer comprises a
thermosetting polymer in an amount of about 50 to about 98 wt %,
based on the total weight of the insulating layer.
10. The article of claim 5, wherein the thermosetting polymer is
further mixed with a silane.
11. The article of claim 10, wherein the silane is a chlorosilane,
vinylsilane, vinylalkoxysilane, aklylacetoxysilane or a combination
comprising at least one of the foregoing silanes.
12. The article of claim 1, wherein the insulating layer displays a
creep of less than 10% of its original length when subjected to a
tensile or compressive force of greater than or equal to about 100
kilograms/square centimeter for a time period of up to about 24
hours at room temperature.
13. The article of claim 1, wherein the nanosized filler is in the
form of spheres, flakes, fibers, whiskers, or a combination
comprising at least one of the foregoing forms.
14. The article of claim 1, wherein the metal oxide nanoparticle
has the formula (II) (MeO).sub.x.(Fe.sub.2O.sub.3).sub.100-x (II)
where MeO is any divalent ferrite forming metal oxide or a
combination comprising two or more divalent metal oxides, and "x"
is less than 50 mole percent.
15. The article of claim 14, wherein Me represents a metal, and
wherein the metals are iron, manganese, nickel, copper, zinc,
cobalt, magnesium, calcium, or a combination comprising at least
one of the foregoing metals.
16. The article of claim 1, wherein the metal oxide nanoparticle
has the formula Ni.sub.0.5Zn.sub.0.5Fe.sub.2O.sub.4.
17. The article of claim 1, wherein the nanosized filler further
comprises mineral fillers, and wherein the mineral fillers are
asbestos, ground glass, kaolin, silica, calcium silicate, calcium
carbonate, magnesium oxide, zinc oxide, aluminum silicate, calcium
sulfate, magnesium carbonate, sodium silicate, barium carbonate,
barium sulfate, mica, talc, alumina trihydrate, quartz,
wollastonite or a combination comprising at least one of the
foregoing mineral fillers.
18. The article of claim 17, wherein the mica comprises anandite,
annite, biotite, bityte, boromuscovite, celadonite, chemikhite,
clintonite, ephesite, ferri-annite, glauconite, hendricksite,
kinoshitalite, lepidolite, masutomilite, muscovite, nanpingite,
paragonite, phlogopite, polylithionite, preiswerkite, roscoelite,
siderophillite, sodiumphlogopite, taeniolite, vermiculite,
wonesite, zinnwaldite or a combination comprising at least one of
the foregoing micas.
19. The article of claim 1, wherein the diamond nanoparticles have
an average particle size of less than or equal to about 50
nanometers.
20. The article of claim 1, wherein the metal oxide particles
comprise calcium oxide, cerium oxide, magnesium oxide, titanium
oxide, zinc oxide, silicon oxide, copper oxide, aluminum oxide, or
a combination comprising at least one of the foregoing metal oxides
and wherein the nanosized metal carbides comprise silicon carbide,
titanium carbide, tungsten carbide, iron carbide, or a combination
comprising at least one of the foregoing metal carbides.
21. The article of claim 1, wherein the electrically insulating
layer has a thickness of about 25 to about 300 micrometers and an
electrical breakdown strength of greater than or equal to about
0.75 kilovolt.
22. The article of claim 21, wherein the insulating layer has an
electrical breakdown strength of greater than or equal to about 1
kilovolt and is corona resistant to an applied voltage of 5000
Volts at a frequency of 3 kilohertz for a time period of over 100
minutes.
23. The article of claim 21, wherein the insulating layer displays
a creep of less than or equal to about 10% of its original length
when subjected to a deforming force of about 700
kilogram-force/square centimeter for 1000 hours at 155.degree.
C.
24. A method of manufacturing an article comprising: disposing an
electrically insulating layer upon an electrical component, wherein
the electrically insulating layer comprises a thermosetting polymer
and a nanosized filler; wherein the nanosized filler comprises
diamond nanoparticles, or a combination of metal oxide and diamond
nanoparticles that have an average largest dimension of less than
or equal to about 200 nanometers; and curing the thermosetting
polymer.
25. The method of claim 24, wherein the insulating layer is
disposed upon the electrical component by dip coating, spray
painting, electrostatic painting, brush painting, spin coating or a
combination comprising at least one of the foregoing methods.
26. The method of claim 23, wherein the curing of the thermosetting
polymer is conducted at a temperature of about 100 to about
250.degree. C.
27. An article manufactured by the method of claim 24.
28. A composition comprising: a thermosetting polymer and a
nanosized filler; wherein the nanosized filler comprises diamond
nanoparticles, or a combination of metal oxide and diamond
nanoparticles that have an average largest dimension of less than
or equal to about 200 nanometers.
29. The composition of claim 28, wherein the nanosized filler is in
the form of spheres, flakes, fibers, whiskers, or a combination
comprising at least one of the foregoing forms.
30. The composition of claim 28, wherein the metal oxide
nanoparticle has the formula (II)
(MeO).sub.x.(Fe.sub.2O.sub.3).sub.100-x (II) where MeO is any
divalent ferrite forming metal oxide or a combination comprising
two or more divalent metal oxides, and "x" is less than 50 mole
percent.
31. The composition of claim 30, wherein Me represents a metal, and
wherein the metals are iron, manganese, nickel, copper, zinc,
cobalt, cerium, magnesium, calcium, or a combination comprising at
least one of the foregoing metals.
32. The composition of claim 30, wherein the metal oxide
nanoparticle has the formula
Ni.sub.0.5Zn.sub.0.5Fe.sub.2O.sub.4.
33. The article of claim 30, wherein the nanosized filler further
comprises mineral fillers, and wherein the mineral fillers are
asbestos, ground glass, kaolin, silica, calcium silicate, calcium
carbonate, magnesium oxide, zinc oxide, aluminum silicate, calcium
sulfate, magnesium carbonate, sodium silicate, barium carbonate,
barium sulfate, mica, talc, alumina trihydrate, quartz,
wollastonite or a combination comprising at least one of the
foregoing mineral fillers.
34. The article of claim 33, wherein the mica comprises anandite,
annite, biotite, bityte, boromuscovite, celadonite, chemikhite,
clintonite, ephesite, ferri-annite, glauconite, hendricksite,
kinoshitalite, lepidolite, masutomilite, muscovite, nanpingite,
paragonite, phlogopite, polylithionite, preiswerkite, roscoelite,
siderophillite, sodiumphlogopite, taeniolite, vermiculite,
wonesite, zinnwaldite or a combination comprising at least one of
the foregoing micas.
35. The article of claim 30, wherein the diamond nanoparticles have
an average particle size of less than or equal to about 50
nanometers.
36. The article of claim 30 wherein the metal oxide particles
comprise calcium oxide, cerium oxide, magnesium oxide, titanium
oxide, zinc oxide, silicon oxide, copper oxide, aluminum oxide, or
a combination comprising at least one of the foregoing metal
oxides.
37. An article manufactured from the composition of claim 30.
38. A method comprising: feeding a stator bar into a central bore
of a die, wherein the central bore being is of a configuration
sufficient to allow relative movement of the die over the stator
bar; extruding an insulating layer into the die so that it is
deposited simultaneously onto each side of the stator bar; wherein
the insulating layer comprises a thermosetting polymer and a
nanosized filler; wherein the nanosized filler comprises diamond
nanoparticles, or a combination of metal oxide and diamond
nanoparticles that have an average largest dimension of less than
or equal to about 200 nanometers; and traversing the die along an
entire length of the stator bar.
39. The method of claim 38, wherein the stator bar is a generator
stator bar.
Description
BACKGROUND
[0001] This disclosure relates to composite coatings for groundwall
insulation in electromagnetic devices such as motors, generators,
and the like, methods of manufacture thereof, and articles derived
therefrom.
[0002] Groundwall insulation for electrical components that are
utilized in electrical devices has generally been manufactured from
multilayered materials. Multiple layers facilitate a higher
resistance to corona discharge. It is also desirable for the
insulating layer to have a high value of breakdown voltage so that
it can withstand the high voltage environment of electrical devices
such as motors and generators. The multiple layers are generally
comprised of a fibrous backing manufactured from glass as well as
additional layers manufactured from mica. The use of multiple
layers is both time-consuming as well as expensive. In addition,
the use of multiple layers generally results in a thicker layer of
insulation and consequently larger parts.
[0003] It is therefore generally desirable to use insulating layers
that can be applied in a single step process and that can withstand
higher voltages while have reduced thickness when compared with
insulation that is made from multilayered materials.
SUMMARY
[0004] Disclosed herein is an article comprising an electrical
component; and an electrically insulating layer disposed upon the
electrical component, wherein the electrically insulating layer
comprises a thermosetting polymer and a nanosized filler; wherein
the nanosized filler comprises diamond nanoparticles, or a
combination of metal oxide and diamond nanoparticles that have an
average largest dimension of less than or equal to about 200
nanometers.
[0005] Disclosed herein too is a method of manufacturing an article
comprising disposing an electrically insulating layer upon an
electrical component, wherein the electrically insulating layer
comprises a thermosetting polymer and a nanosized filler; wherein
the nanosized filler comprises diamond nanoparticles, or a
combination of metal oxide and diamond nanoparticles that have an
average largest dimension of less than or equal to about 200
nanometers; and curing the thermosetting polymer.
[0006] Disclosed herein too is a composition comprising a
thermosetting polymer and a nanosized filler; wherein the nanosized
filler comprises diamond nanoparticles, or a combination of metal
oxide and diamond nanoparticles that have an average largest
dimension of less than or equal to about 200 nanometers.
[0007] Disclosed herein too is a method comprising feeding a stator
bar into a central bore of a die, wherein the central bore is of a
configuration sufficient to allow relative movement of the die over
the stator bar; extruding an insulating layer into the die so that
it is deposited simultaneously onto each side of the stator bar;
wherein the insulating layer comprises a thermosetting polymer and
a nanosized filler; wherein the nanosized filler comprises diamond
nanoparticles, or a combination of metal oxide and diamond
nanoparticles that have an average largest dimension of less than
or equal to about 200 nanometers; and traversing the die along an
entire length of the stator bar.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0008] It is to be noted that the terms "first," "second," and the
like as used herein do not denote any order, quantity, or
importance, but rather are used to distinguish one element from
another. The terms "a" and "an" do not denote a limitation of
quantity, but rather denote the presence of at least one of the
referenced item. The modifier "about" used in connection with a
quantity is inclusive of the stated value and has the meaning
dictated by the context (e.g., includes the degree of error
associated with measurement of the particular quantity). It is to
be noted that all ranges disclosed within this specification are
inclusive and are independently combinable.
[0009] Disclosed herein is an insulating layer that may be used to
protect and insulate electrical components of electrical devices
such as motors, generators, and the like. Disclosed herein too, is
a method for applying the insulating layer onto electrical
components that may be utilized in electrical devices. Suitable
examples of such electrical components are electrical conduction
windings, stator bars, or on the inside of a stator piece, or the
like. The insulating layer generally comprises a thermosetting
polymer and a nanosized filler. In one embodiment, the nanosized
fillers comprise a combination of metal oxides and diamonds. In
another embodiment, the nanosized fillers comprise diamonds. The
nanosized fillers can also optionally include nanosized mineral
fillers and/or nanoclays.
[0010] The insulating layer is advantageous in that it can be
applied to the electrical components in thicknesses of about 30 to
about 300 micrometers, which is generally less than or equal to the
thickness of other commercially available insulating layers. The
insulating layer advantageously has a compressive strength and
hardness effective to withstand a compressive force of about 250 to
about 1000 mega-Pascals (MPa). Application of the insulating layer
also provides an opportunity for excluding the tape wound, micaeous
and polymeric groundwall insulation or slot liner material that is
generally used in electrical devices. The insulating layer can be
easily applied in a single step process such as dip coating, spray
painting, extrusion, coextrusion, or the like. It also provides the
potential for thinner insulation layers and provides a more robust
insulation material because of its ability to withstand higher
voltages. It also displays a significant corona resistance compared
with other comparative insulating materials that do not contain
nanosized fillers and improved thermal conductivity.
[0011] In one advantageous embodiment, the insulating layer
comprises an elastomer having a modulus of elasticity of less than
or equal to about 10.sup.5 gigapascals (GPa) at room temperature.
The elastomer generally comprises a thermosetting polysiloxane
resin and a nanosized filler. The elastomeric insulating layer
advantageously displays an elongation of greater than or equal to
about 200% in a tensile test at room temperature while at the same
time displaying no substantial creep when subjected to a
compressive or tensile force at prevailing temperatures in an
electrical generator.
[0012] The thermosetting polymer generally comprises a polymer that
may be a homopolymer, a copolymer such as a star block copolymer, a
graft copolymer, an alternating block copolymer or a random
copolymer, ionomer, dendrimer, or a combination comprising at least
one of the foregoing polymers that may be covalently crosslinked.
Suitable examples of thermosetting polymers are polyurethanes,
epoxies, phenolics, silicones, polyacrylics, polycarbonates
polystyrenes, polyesters, polyamides, polyamideimides,
polyarylates, polyarylsulfones, polyethersulfones, polyphenylene
sulfides, polysulfones, polyimides, polyetherimides,
polytetrafluoroethylenes, polyetherketones, polyether etherketones,
polyether ketone ketones, polybenzoxazoles, polyoxadiazoles,
polybenzothiazinophenothiazines, polybenzothiazoles,
polypyrazinoquinoxalines, polypyromellitimides, polyquinoxalines,
polybenzimidazoles, polyoxindoles, polyoxoisoindolines,
polydioxoisoindolines, polytriazines, polypyridazines,
polypiperazines, polypyridines, polypiperidines, polytriazoles,
polypyrazoles, polycarboranes, polyoxabicyclononanes,
polydibenzofurans, polyphthalides, polyacetals, polyanhydrides,
polyvinyl ethers, polyvinyl thioethers, polyvinyl alcohols,
polyvinyl ketones, polyvinyl halides, polyvinyl nitriles, polyvinyl
esters, polysulfonates, polysulfides, polythioesters, polysulfones,
polysulfonamides, polyureas, polyphosphazenes, polysilazanes,
polybutadienes, polyisoprenes, or the like, or a combination
comprising at least one of the foregoing thermosetting polymers.
Blends of thermosetting polymers may also be utilized. An exemplary
thermosetting polymer is a silicone polymer. The term polymer as
used herein is used to mean either a small molecule (e.g., monomer,
dimer, trimer, and the like), a homopolymer or a copolymer.
[0013] As noted above, the thermosetting polymer can be an
elastomer. Examples of thermosetting polymers are polybutadienes,
polyisoprenes, polysiloxanes, polyurethanes, or the like, or a
combination comprising at least one of the foregoing elastomers. An
exemplary thermosetting polymer is a polysiloxane polymer
(hereinafter silicone polymer).
[0014] The silicone polymers that may be used in the preparation of
the insulating layer generally has the formula (I) prior to
reacting to form the thermoset ##STR1## wherein R.sub.1, R.sub.2,
R.sub.3, R.sub.4, R.sub.5 and R.sub.6 may be the same or different
and wherein at least one of R.sub.1, R.sub.2, R.sub.3, R.sub.4,
R.sub.5 and R.sub.6 is a reactive functionality prior to cross
linking; m and n can be any integer including 0, with the exception
that both m and n cannot be 0 at the same time. In general, while
it is preferred for at least one of R.sub.1, R.sub.2, R.sub.3,
R.sub.4, R.sub.5 and R.sub.6 to be reactive, it is generally
desirable for two or preferably three of R.sub.1, R.sub.2, R.sub.3,
R.sub.4, R.sub.5 or R.sub.6 to be chemically reactive. It is
generally desirable for the sum of m and n to be about 1 to about
50,000. Suitable examples of groups that may be present as R.sub.1,
R.sub.2, R.sub.3, R.sub.4, R.sub.5 or R.sub.6 in the equation (I)
are alkyl, aryl, aralkyl, fluoroalkyl, vinylalkyl, aminoalkyl,
vinyl, epoxy, hydride, silanol, amine, carbinol (hydroalkyl),
methacrylate, acrylate, mercapto, haloalkyl, halogen, carboxylate,
acetoxy, alkoxy, or the like. Exemplary reactive functional groups
are vinyl or epoxy. Exemplary non-reactive functional groups are
alkyl, fluoroalkyl or phenyl. An exemplary silicone polymer is a
condensation cure silicone having methyl, phenyl and hydroxyl
functional groups. One of the commercially available silicone
polymer is MC 550 BKH.RTM. commercially available from General
Electric Silicones in Waterford, N.Y. MC 550 BKH.RTM. contains 78
wt % of a reinforcing agent. The reinforcing agent is not nanosized
and comprises fused silica and fiberglass in a weight ratio of
80:20. Nanosized fillers of interest are then added to this
material.
[0015] It is generally desirable for the thermosetting polymer to
have a number average molecular weight of about 75 to about 500,000
grams/mole (g/mole) prior to reacting to form the thermosetting
polymer. In one embodiment, it is generally desirable for the
thermosetting polymer to have a number average molecular weight of
about 150 to about 100,000 g/mole prior to reacting to form the
thermosetting polymer. In another embodiment, it is generally
desirable for the thermosetting polymer to have a number average
molecular weight of about 300 to about 75,000 g/mole prior to
reacting to form the thermosetting polymer. In yet another
embodiment, it is generally desirable for the thermosetting polymer
to have a number average molecular weight of about 450 to about
50,000 g/mole prior to reacting to form the thermosetting polymer.
An exemplary number average molecular weight of the thermosetting
polymer is about 75 to about 5,000 g/mole prior to reacting to form
the thermosetting polymer.
[0016] It is generally desirable to use the thermosetting polymer
in an amount of about 50 to 98 wt %, based on the total weight of
the insulating layer. In one embodiment, it is desirable to use the
thermosetting polymer in an amount of about 55 to about 90 wt %,
based on the total weight of the insulating layer. In another
embodiment, it is desirable to use the thermosetting polymer in an
amount of about 60 to about 85 wt %, based on the total weight of
the insulating layer. In yet another embodiment, it is desirable to
use the thermosetting polymer in an amount of about 65 to about 80
wt %, based on the total weight of the insulating layer.
[0017] The thermosetting polymer may optionally be mixed with
reactive precursors such as silanes in order to increase the
crosslink density. Suitable silanes are chlorosilanes,
vinylsilanes, vinylalkoxysilanes, aklylacetoxysilanes, and the
like. Suitable examples of chlorosilanes are methyltrichlorosilane
and dimethyldichlorosilane. It is generally desirable for the
dimethyldichlorosilane to have about 1 to about 35 mole percent of
hydroxyl groups. In one embodiment, it is desirable for the
dimethyldichlorosilane to have about 2 to about 15 mole percent of
hydroxyl groups. In one embodiment, it is desirable for the
dimethyldichlorosilane to have about 4 to about 8 mole percent of
hydroxyl groups.
[0018] It is generally desirable to use the reactive precursor in
an amount of about 0.1 to 50 wt %, based on the total weight of the
thermosetting polymer. In one embodiment, it is desirable to use
the reactive precursor in an amount of about 0.5 to about 40 wt %,
based on the total weight of the thermosetting polymer. In another
embodiment, it is desirable to use the reactive precursor in an
amount of about 1 to about 30 wt %, based on the total weight of
the thermosetting polymer. In yet another embodiment, it is
desirable to use the reactive precursor in an amount of about 1.2
to about 25 wt %, based on the total weight of the thermosetting
polymer.
[0019] The insulating layer may optionally contain a reinforcing
agent that is not nanosized. The reinforcing agent is a filler
having particle dimensions of greater than or equal to about 500
nanometers (nm). Suitable reinforcing agents are silica powder,
such as fused silica, crystalline silica, natural silica sand, and
various silane-coated silicas; talc, including fibrous, modular,
needle shaped, and lamellar talcs; glass spheres, both hollow and
solid, and surface-treated glass spheres; kaolin, including hard,
soft, and calcined kaolin; mica, including metallized mica and mica
surface treated with aminosilanes, acryloylsilanes,
hexamethylenedisilazane, or coatings having a chemical composition
similar to the thermosetting polymer so as to impart good physicals
to compounded blends; feldspar and nepheline syenite; silicate
spheres; cenospheres; fillite; aluminosilicate (armospheres),
including silanized and metallized aluminosilicate; quartz;
quartzite; perlite; tripoli; diatomaceous earth; silicon carbide;
molybdenum sulfide; zinc sulfide; aluminum silicate (mullite);
synthetic calcium silicate; zirconium silicate; barium titanate;
barium ferrite; barium sulfate and heavy spar; flaked fillers and
reinforcements such as glass flakes, flaked silicon carbide,
aluminum diboride; processed mineral fibers such as those derived
from blends comprising at least one of aluminum silicates, aluminum
oxides, magnesium oxides, and calcium sulfate hemihydrate;
synthetic reinforcing fibers, including polyester fibers such as
polyethylene terephthalate fibers, polyvinylalcohol fibers,
aromatic polyamide fibers, polybenzimidazole fibers, polyimide
fibers, polyphenylene sulfide fibers, polyether ether ketone
fibers, boron fibers, ceramic fibers such as silicon carbide,
fibers from mixed oxides of aluminum, boron and silicon; single
crystal fibers or "whiskers" including silicon carbide fibers,
alumina fibers, boron carbide fibers, glass fibers, including
textile glass fibers such as E, A, C, ECR, R, S, D, and NE glasses,
fiber glass and quartz; or the like, or a combination comprising at
least one of the foregoing reinforcing agents.
[0020] Exemplary reinforcing agents are fused silica and fiber
glass. It is generally desirable for the weight ratio of fused
silica to fiber glass to be about 1:5 to about 10:1. In one
embodiment, the weight ratio of fused silica to fiber glass is
about 1:3 to about 8:1. In another embodiment, the weight ratio of
fused silica to fiber glass is about 1:1 to about 6:1. An exemplary
weight ratio of fused silica to fiber glass is about 4:1.
[0021] When present, the reinforcing agent is used in amounts of
about 20 to about 90 wt %, based on the total weight of the
insulating layer. In one embodiment, it is desirable for the
reinforcing agent to be used in amounts of about 30 to about 85 wt
%, based on the total weight of the insulating layer. In another
embodiment, it is desirable for the reinforcing agent to be used in
amounts of about 50 to about 80 wt %, based on the total weight of
the insulating layer. An exemplary amount of reinforcing agent is
about 78 wt %, based on the total weight of the insulating
layer.
[0022] As stated above, the insulating layer comprises nanosized
fillers. The nanosized fillers are those having an average largest
dimension of at least one characteristic length of the particle
being less than or equal to about 200 nm. A characteristic length
may be a diameter, edge of a face, length, or the like. The
nanosized fillers may have shapes whose dimensionalities are
defined by integers, e.g., the particles are either 1, 2 or
3-dimensional in shape. They may also have shapes whose
dimensionalities are not defined by integers (e.g., they may exist
in the form of fractals). The nanosized fillers may exist in the
form of spheres, flakes, fibers, whiskers, or the like, or a
combination comprising at least one of the foregoing forms. These
fillers may have cross-sectional geometries that may be circular,
ellipsoidal, triangular, rectangular, polygonal, or a combination
comprising at least one of the foregoing geometries. The fillers,
as commercially available, may exist in the form of aggregates or
agglomerates prior to incorporation into the insulating layer or
even after incorporation into the insulating layer. An aggregate
comprises more than one filler particle in physical contact with
one another, while an agglomerate comprises more than one aggregate
in physical contact with one another.
[0023] In one embodiment, the nanosized fillers comprise diamond
nanoparticles having an average particle size of less than or equal
to about 200 nanometers. In another embodiment, the diamond
nanoparticles have an average particle size of less than or equal
to about 75 nanometers. In yet another embodiment, the diamond
nanoparticles have an average particle size of less than or equal
to about 50 nanometers. In yet another embodiment, the diamond
nanoparticles have an average particle size of less than or equal
to about 25 nanometers. Exemplary nanosized fillers are diamond
nanoparticles having an average particle size of about 50
nanometers.
[0024] The diamond nanoparticles can be added in an amount of about
1 to about 50 wt %, based upon the total weight of the insulating
layer. In another embodiment, the diamond nanoparticles can be
added in an amount of about 3 to about 40 wt %, based upon the
total weight of the insulating layer. In yet another embodiment,
the diamond nanoparticles can be added in an amount of about 5 to
about 30 wt %, based upon the total weight of the insulating layer.
An exemplary amount of diamond nanoparticles is about 15 wt %,
based upon the total weight of the insulating layer.
[0025] As noted above, the nanosized fillers comprise either
diamond nanoparticles or a combination of metal oxides
nanoparticles (nanosized metal oxides) and diamond nanoparticles.
In one embodiment, the nanosized metal oxides can be in the form of
ceramics (i.e., chemically or mechano-chemically synthesized metal
oxide powder). Nanosized metal oxides that may be used in the
insulating layer are metal oxides of alkali earth metals, alkaline
earth metals, transition metals and other commercially used metals.
Suitable examples of metal oxides are calcium oxide, cerium oxide,
magnesium oxide, titanium oxide, zinc oxide, silicon oxide, copper
oxide, aluminum oxide (e.g., alumina and/or fumed alumina), silicon
dioxide (e.g., silica and/or fumed silica), or the like, or a
combination comprising at least one of the foregoing metal oxides.
Nanosized metal carbides such as silicon carbide, titanium carbide,
tungsten carbide, iron carbide, or the like, or a combination
comprising at least one of the foregoing metal carbides may also be
used in the insulating layer. Exemplary metal oxides are fumed
alumina, alumina, fumed silica, silica and combinations comprising
at least one of the foregoing metal oxides.
[0026] The metal oxides and carbides are generally particles having
surface areas in an amount of about 1 to about 1000 square
meter/gram (m.sup.2/g). Within this range it is generally desirable
for the metal oxides and carbides to have surface areas greater
than or equal to about 5 m.sup.2/g, specifically greater than or
equal to about 10 m.sup.2/g, and more specifically greater than or
equal to about 15 m.sup.2/g. Also desirable within this range is a
surface area less than or equal to about 950 m.sup.2/g,
specifically less than or equal to about 900 m.sup.2/g, and more
specifically less than or equal to about 875 m.sup.2/g.
[0027] It is generally desirable for the nanosized metal oxide and
carbide particles to have bulk densities in an amount of about 0.2
to about 2.5 grams per cubic centimeter; true densities in an
amount of about 3 to about 7 grams per cubic centimeter and an
average pore diameter of about 10 to about 250 angstroms.
[0028] Commercially available examples of nanosized metal oxides
are NANOACTIVE.TM. calcium oxide, NANOACTIVE.TM. calcium oxide
plus, NANOACTIVE.TM. cerium oxide, NANOACTIVE.TM. magnesium oxide,
NANOACTIVE.TM. magnesium oxide plus, NANOACTIVE.TM. titanium oxide,
NANOACTIVE.TM. zinc oxide, NANOACTIVE.TM. silicon oxide,
NANOACTIVE.TM. copper oxide, NANOACTIVE.TM. aluminum oxide,
NANOACTIVE.TM. aluminum oxide plus, all commercially available from
NanoScale Materials Incorporated. Commercially available examples
of nanosized metal carbides are titanium carbonitride, silicon
carbide, silicon carbide-silicon nitride, and tungsten carbide all
commercially available from Pred Materials International
Incorporated.
[0029] An exemplary type of nanosized fillers are the ferritic
nanosized particles represented by the formula (II):
(MeO).sub.x.(Fe.sub.2O.sub.3).sub.100-x (II) where "MeO" is any
divalent ferrite forming metal oxide or a combination comprising
two or more divalent metal oxides, and "x" is less than 50 mole
percent. Suitable examples of ferrite forming divalent metal oxides
are iron oxide (FeO), manganese oxide (MnO), nickel oxide (NiO),
copper oxide (CuO), zinc oxide (ZnO), cobalt oxide (CoO), magnesium
oxide (MgO), calcium oxide (CaO), ceria (Ce.sub.2O.sub.3), or the
like. Single metal oxides, multi-metal oxides, doped oxides are
also envisioned for use in the insulating layer.
[0030] Suitable examples of commercially available ferrite forming
metal oxides are zinc oxide having average largest dimensions of 30
nm and 80 nm. All of the foregoing commercially available ferrite
forming metal oxides may be obtained from Advanced Powder
Technology based in St. Welshpool in Australia.
[0031] Other examples of commercially available metal oxides are
ceria having a particle size of less than or equal to about 20 mm;
gadolinium doped ceria having particle sizes of less than or equal
to about 20 nm; samarium doped ceria having particle sizes of less
than or equal to about 20 nm; or the like, or a combination
comprising at least one of the foregoing commercially available
metal oxides. All of the foregoing commercially available ferrite
forming metal oxides comprising ceria may be obtained from
Microcoating Technologies based in Atlanta, Ga.
[0032] A suitable example of commercially available ferritic
nanosized fillers is Ni.sub.0.5Zn.sub.0.5Fe.sub.2O.sub.4
manufactured and sold by NanoProducts, Inc. The crystallite size
for the Ni.sub.0.5Zn.sub.0.5Fe.sub.2O.sub.4 is 12 nm, specific
surface area is 45 square meter/gram (m.sup.2/g) and the equivalent
spherical diameter is 47 nm.
[0033] When ferritic nanosized fillers are used, they may be used
in amounts of about 2 to about 15 wt %, based on the total weight
of the insulating layer. In one embodiment, the ferritic nanosized
fillers are used in amounts of about 3 to about 12 wt %, based on
the total weight of the insulating layer. In another embodiment,
the ferritic nanosized fillers are used in amounts of about 4 to
about 12 wt %, based on the total weight of the insulating layer.
In an exemplary embodiment, the ferritic nanosized fillers are used
in amounts of about 5 wt %, based on the total weight of the
insulating layer.
[0034] Suitable examples of other nanosized fillers are nanosized
mineral fillers such as asbestos, ground glass, kaolin and other
clay minerals, silica, calcium silicate, calcium carbonate
(whiting), magnesium oxide, zinc oxide, aluminum silicate, calcium
sulfate, magnesium carbonate, sodium silicate, barium carbonate,
barium sulfate (barytes), mica, talc, alumina trihydrate, quartz,
and wollastonite (calcium silicate). Mica is an exemplary nanosized
mineral filler.
[0035] Examples of mica that may be used are anandite, annite,
biotite, bityte, boromuscovite, celadonite, chernikhite,
clintonite, ephesite, ferri-annite, glauconite, hendricksite,
kinoshitalite, lepidolite, masutomilite, muscovite, nanpingite,
paragonite, phlogopite, polylithionite, preiswerkite, roscoelite,
siderophillite, sodiumphlogopite, taeniolite, vermiculite,
wonesite, and zinnwaldite.
[0036] Exemplary forms of mica are phlogopite
(KMg.sub.3AlSi.sub.3O.sub.10(OH).sub.2) or muscovite
(K.sub.2Al.sub.4[Si.sub.6Al.sub.2O.sub.20](OH,F).sub.4). The
phlogopite or muscovite or both are subjected to a process in which
they are heated to an elevated temperature of about 500 to about
850.degree. C. This heat causes the mica crystals to partially
dehydrate and release a portion of the water, which is bonded
naturally in the crystal. When this occurs, the mica partially
exfoliates, resulting in smaller particles. The mica is then ground
to produce small nanosized filler particles. A suitable from of
commercially available mica is mica dust from VonRoll Isola.
[0037] Nanosized fillers such as nanoclays (nanosized clays) may
also be used in the insulating layer. Nanoclays are generally
plate-like materials, the clay mineral being generally selected
from smectite, vermiculite and halloysite clays. The smectite clay
in turn can be selected from montmorillonite, saponite, beidellite,
nontrite, hectorite or the like, or a combination comprising at
least one of the foregoing clays. An exemplary clay mineral is the
montmorillonite clay, a multilayered alumino-silicate. The nanoclay
platelets generally have a thickness of about 3 to about 3000
angstroms and a size in the planar direction ranging of about 0.01
to about 100 micrometers. The aspect ratio of the nanoclays is
generally of the order of about 10 to about 10,000. The respective
clay platelets are separated by a gallery, i.e., a space between
parallel layers of clay platelets containing various ions holding
the platelets together. One such material is CLOISITE.RTM.10A
commercially available from Southern Clay Products, its platelets
having a thickness of about 0.001 micrometers (10 angstroms) and a
size in the planar direction of about 0.15 to about 0.20
micrometers.
[0038] In one embodiment, a combination of nanosized fillers,
nanosized mineral fillers and/or nanoclays may be used in the
insulating layer. When such a combination is used, it may be added
to the insulating layer in an amount of about 1 to about 80 wt %,
based on the total weight of the insulating layer. In one
embodiment, the combination of nanosized fillers, nanosized mineral
fillers and/or nanoclays may be used in an amount of about 2 to
about 75 wt %, based on the total weight of the insulating layer.
In another embodiment, the combination of nanosized fillers,
nanosized mineral fillers and/or nanoclays may be used in an amount
of about 3 to about 70 wt %, based on the total weight of the
insulating layer. An exemplary insulating layer is one having metal
oxide nanosized fillers in an amount of about 5 wt %, based upon
the total weight of the insulating layer. Another exemplary
insulating layer is one having mica dust in an amount of about 20
wt %, based upon the total weight of the insulating layer.
[0039] In one embodiment, it may be desirable to add nanosized
fillers of a particular chemical composition to the insulating
layer along with micrometer sized fillers of the same chemical
composition. In general, the micrometer sized fillers have average
largest dimensions of greater than or equal to about 500 nm. For
example mica dust having nanosized particle of an average largest
dimension of less than or equal to about 200 nm may be added to the
insulating layer in conjunction with micrometer sized mica dust
having an average particle sizes of about 50 micrometers.
[0040] In general when nanosized fillers are used in conjunction
with micrometer sized fillers having the same chemical composition,
it is generally desirable for the nanosized filler to constitute up
to about 50 wt %, more specifically up to about 60 wt %, and even
more specifically up to about 70 wt %, based on the total weight of
combination of nanosized and micrometer sized fillers.
[0041] As stated above, there is no particular limitation to the
shape of the nanosized fillers, which may be for example,
spherical, irregular, plate-like or whisker like. The nanosized
fillers may generally have average largest dimensions of at least
one characteristic length being less than or equal to about 200 nm.
In one embodiment, the nanosized fillers may have average largest
dimensions of less than or equal to about 150 nm. In another
embodiment, the nanosized fillers may have average largest
dimensions of less than or equal to about 100 nm. In yet another
embodiment, the nanosized fillers may have average largest
dimensions of less than or equal to about 75 nm. In yet another
embodiment, the nanosized fillers may have average largest
dimensions of less than or equal to about 50 nm.
[0042] As stated above, the nanosized fillers may generally have
average largest dimensions of less than or equal to about 200 nm.
In one embodiment, more than 90% of the nanosized fillers have
average largest dimensions less than or equal to about 200 nm. In
another embodiment, more than 95% of the nanosized fillers have
average largest dimensions less than or equal to about 200 nm. In
yet another embodiment, more than 99% of the nanosized fillers have
average largest dimensions less than or equal to about 200 nm.
Bimodal or higher particle size distributions may also be used.
[0043] The nanosized fillers may be used in amounts of about 1 to
about 80 wt %, based on the total weight of the insulating layer.
In one embodiment, the nanosized fillers may be used in amounts of
about 3 to about 75 wt %, based on the total weight of the
insulating layer. In another embodiment, the nanosized filler
particles may be used in amounts of about 5 to about 70 wt %, based
on the total weight of the insulating layer. In yet another
embodiment, the nanosized filler particles may be used in amounts
of about 6 to about 60 wt %, based on the total weight of the
insulating layer. In an exemplary embodiment, the nanosized filler
particles may be used in an amount of about 20 wt % based on the
total weight of the insulating layer.
[0044] In one embodiment, the nanosized fillers may be coated with
a silane-coupling agent to facilitate bonding with the
thermosetting polymer. It is generally desirable for the fillers
utilized in the curable polymeric resin coating to be treated with
a silane-coupling agent such as tetramethylchlorosilane,
hexadimethylenedisilazane, gamma-aminopropoxysilane, or the like,
or a combination comprising at least one of the foregoing silane
coupling agents. The silane-coupling agents generally enhance
compatibility of the nanosized filler with the thermosetting
polymer and improve the mechanical properties of the insulating
layer.
[0045] Solvents may optionally be used in the insulating layer. The
solvent may be used as a viscosity modifier, or to facilitate the
dispersion and/or suspension of nanosized filler. Liquid aprotic
polar solvents such as propylene carbonate, ethylene carbonate,
butyrolactone, acetonitrile, benzonitrile, nitromethane,
nitrobenzene, sulfolane, dimethylformamide, N-methylpyrrolidone, or
the like, or a combination comprising at least one of the foregoing
solvents are generally desirable. Polar protic solvents such as,
but not limited to, water, methanol, acetonitrile, nitromethane,
ethanol, propanol, isopropanol, butanol, or the like, or a
combination comprising at least one of the foregoing polar protic
solvents may be used. Other non-polar solvents such a benzene,
toluene, methylene chloride, carbon tetrachloride, hexane, diethyl
ether, tetrahydrofuran, or the like, or a combination comprising at
least one of the foregoing solvents may also be used. Co-solvents
comprising at least one aprotic polar solvent and at least one
non-polar solvent may also be utilized. An exemplary solvent is
xylene or N-methylpyrrolidone.
[0046] If a solvent is used, it may be utilized in an amount of
about 1 to about 50 wt %, of the total weight of the insulating
layer. In one embodiment, if a solvent is used, it may be utilized
in an amount of about 3 to about 30 wt %, of the total weight of
the insulating layer. In yet another embodiment, if a solvent is
used, it may be utilized in an amount of about 5 to about 20 wt %,
of the total weight of the insulating layer. It is generally
desirable to evaporate the solvent before, during and/or after the
curing of the thermosetting polymer.
[0047] In one method of manufacturing the insulating layer, the
thermosetting polymer is blended with the nanosized filler under
high levels of shear in order to facilitate mixing. The level of
shear imparted to the mixture of the thermosetting polymer and the
nanosized filler is effective to facilitate dispersion of the
filler in the thermosetting polymer. The energy imparted during the
shearing process is about 0.001 kilowatt-hour/kilogram (kWhr/kg) to
about 10 kWhr/kg. In one embodiment, the energy imparted during the
shearing process is about 0.01 to about 8 kWhr/kg. In another
embodiment, the energy imparted during the shearing process is
about 0.1 to about 6 kWhr/kg. In yet another embodiment, the energy
imparted during the shearing process is about 0.5 to about 4
kWhr/kg.
[0048] The shear may be imparted in a melt blending process or it
may be imparted via other means such as the application of
ultrasonic energy to the mixture. Suitable examples of melt
blending equipment are extruders such as single screw extruders,
twin screw extruders, or the like; buss kneaders, roll mills, paint
mills, helicones, Waring blenders, Henschel mixers, Banbury's, or
the like, or a combination comprising at least one of the foregoing
melt blenders. Ultrasonic blending may also be carried out to
facilitate the suspension and/or dispersion of the nanosized filler
in the thermosetting polymer. In order to facilitate the suspension
of the nanosized filler, it is desirable that both aggregates and
agglomerates are broken into smaller particles.
[0049] As stated above, the insulating layer is disposed upon
electrical components such as electrical conduction windings or
stator bars or on the inside of a stator piece, and subjected to
curing. In one embodiment, the electrical component comprises
copper. An initiator and/or crosslinking catalyst may be added to
the mixture of the thermosetting polymer and the nanosized filler
prior to or during the disposition of the insulating layer upon the
winding. The insulating layer may be applied to the winding via dip
coating, spray painting, electrostatic painting, brush painting,
spin coating, injection molding, coextrusion or the like, or a
combination comprising at least one of the foregoing processes.
[0050] In one embodiment, the insulating layer may be disposed upon
a electrical components such as electrical conduction windings or
stator bars or on the inside of a stator piece in several steps.
For example, an insulating layer of a certain thickness may be
disposed upon the electrical components in a first step, while a
second insulating layer of another thickness is disposed upon the
first layer in a second step. In one embodiment, the first
insulating layer may have a different composition from the second
insulating layer. The insulating layers may then be subjected to a
heat treatment or to electromagnetic radiation such as UV curing
and/or microwave curing to facilitate a more effective
crosslinking.
[0051] In one exemplary embodiment, an insulating layer comprising
the thermosetting resin can be extruded onto a complex shape such
as that of a stator bar. As noted above, the insulating layer
comprises a thermosetting polymer and a nanosized filler; wherein
the nanosized filler comprises metal oxide and diamond
nanoparticles that have an average largest dimension of less than
or equal to about 200 nanometers. The method comprises feeding the
complex shape with a length and more than one side into a central
bore of a die wherein the central bore is of a configuration
sufficient to allow the die to be moved along the complex shape or
for the complex shape to be moved along through the die. At least
one thermosetting material comprising the aforementioned
nanoparticles is extruded through the die so that the thermosetting
material is deposited simultaneously onto each side of the complex
shape. In one embodiment, the die is traversed along the entire
length of the complex shape. In another embodiment, the entire
length of the complex shape is permitted to travel through the die
so that it is coated with the insulating layer.
[0052] An exemplary apparatus for applying the insulating layer is
described in U.S. Pat. No. 5,650,031 to Bolon et al., the entire
contents of which is hereby incorporated by reference except in
those cases where a term in the present application contradicts a
term from the incorporated reference, in which event the term from
the present application takes precedence over the conflicting term
from the incorporated reference. The apparatus comprises a die
having a central bore, wherein the central bore is of a
configuration sufficient to allow the die to be moved along a
complex shape with a plurality of sides and a length, and through
which the complex shape is fed. The apparatus also comprises a
means of traversing the extrusion die along the length of the
complex shape, and at least one extruder connected to the die by
flexible coupling means.
[0053] In one embodiment, the thermosetting polymer in the
insulating layer may be subjected to curing at a temperature of
about 100.degree. C. to about 250.degree. C. In another embodiment,
the insulating layer may be cured at a temperature of about
120.degree. C. to about 220.degree. C. In yet another embodiment,
the insulating layer may be cured at a temperature of about
140.degree. C. to about 200.degree. C. In an exemplary embodiment,
the insulating layer may be cured at a temperature of about
180.degree. C.
[0054] It is generally desirable to have an insulating layer having
a thickness of about 25 to about 300 micrometers (.mu.m). In one
embodiment, it is desirable for the insulating layer to have a
thickness of about 30 to about 275 .mu.m. In another embodiment, it
is desirable for the insulating layer to have a thickness of about
40 to about 250 .mu.m. In yet another embodiment, it is desirable
for the insulating layer to have a thickness of about 50 to about
225 .mu.m.
[0055] The insulating layer is advantageous in that it has a
breakdown voltage of greater than or equal to about 0.75 kilovolt
(kV) at a thickness of about 25 to about 300 .mu.m. In one
embodiment, the breakdown voltage for the insulating layer is
greater than or equal to about 2 kV. In yet another embodiment, the
breakdown voltage for the insulating layer is greater than or equal
to about 3 kV. In yet another embodiment, the breakdown voltage for
the insulating layer is greater than or equal to about 4 kV.
[0056] In one embodiment, the insulating layer has an electrical
breakdown strength of greater than or equal to about 1 kilovolt and
is corona resistant to an applied voltage of 5000 Volts at a
frequency of 3 kilohertz for a time period of over 100 minutes. In
another embodiment, the insulating layer has an electrical
breakdown strength of greater than or equal to about 1 kilovolt and
is corona resistant to an applied voltage of 5000 Volts at a
frequency of 3 kilohertz for a time period of over 200 minutes.
[0057] The insulating layer is advantageous in that it can be
applied to the electrical components in thicknesses of about 30 to
about 300 micrometers, which is generally less than or equal to
other commercially available insulating layers. The insulating
layer advantageously has a compressive strength and hardness
effective to withstand a compressive force of about 250 to about
1000 mega-Pascals (MPa). Application of the insulating layer also
provides an opportunity for excluding the tape wound micaeous
combined with polymeric groundwall insulation or slot liner
material that is generally used in electrical devices.
[0058] As noted above, in one advantageous embodiment, the
insulating layer can comprise a thermosetting polymer that displays
elastomeric behavior at room temperature. When the thermosetting
polymer displays elastomeric behavior at room temperature is used
in the insulation, it is desirable for the insulating layer to have
an elastic modulus of less than or equal to about 10.sup.5 GPa when
measured in a tensile test at room temperature. The insulating
layer has an elongation to break of greater than or equal to about
200%. In one embodiment, the insulating layer has an elongation to
break of greater than or equal to about 300%. In another
embodiment, the insulating layer has an elongation to break of
greater than or equal to about 500%. In yet another embodiment, the
insulating layer has an elongation to break of greater than or
equal to about 700%.
[0059] It is desirable for the insulating layer to display
substantially no creep when subjected to tensile or compressive
stresses at temperatures that are greater than or equal to about
room temperature (23.degree. C.) up to about 2000 hours. In one
embodiment, the insulating layer displays a creep of less than 10%
of its original length when subjected to a tensile or compressive
force of greater than or equal to about 100 kilograms/square
centimeter for a time period of up to about 2000 hours at room
temperature. In another embodiment, the insulating layer displays a
creep of less than 15% of its original length when subjected to a
tensile or compressive force of greater than or equal to about 100
kilograms/square centimeter for a time period of up to about 2000
hours at room temperature.
[0060] In another embodiment, the insulating layer displays a creep
of less than or equal to about 10% of its original length when
subjected to a deforming force of 10 kilo-pounds per square inch
(10 kpsi) (about 700 kilogram-force/square centimeter) for 1000
hours at 155.degree. C. In yet another embodiment, the insulating
layer displays a creep of less than or equal to about 6% when
subjected to a deforming force of 10 kilo-pounds per square inch
(10 kpsi) (about 700 kilogram-force/square centimeter) for 1000
hours at 155.degree. C. In yet another embodiment, the insulating
layer displays a creep of less than or equal to about 3% when
subjected to a deforming force of 10 kilo-pounds per square inch
(10 kpsi) (about 700 kilogram-force/square centimeter) for 1000
hours at 155.degree. C.
[0061] The insulating layer comprising the elastomer displays
substantially no creep when subjected to prevailing tensile or
compressive stresses at prevailing temperatures in an electrical
generator that has been operating for a period of over 24 hours.
This ability of the insulating layer to avoid creep at elevated
temperatures makes it useful on stator bars and other pieces of
equipment used in electrical generators.
[0062] While the invention has been described with reference to
exemplary embodiments, it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *