Title of Invention	A METHOD OF FORMING A TRANSFORMER COIL ASSEMBLY
Abstract	A method of forming a transformer coil assembly (100) is disclosed. The method involves providing a first fabric layer (600, 210) having a plurality of fibers (220) interconnected and a plurality of protruding spacers (230) affixed to a surface of the fabric (210): applying, to the first fabric layer (210), a conductor layer (145) in contact with at least one of the plurality of protruding spacers (230);-applying resin (110) to cover at least the first fabric layer (210) and the conductor layer (145); applying, to the conductor layer (145), a second fabric layer (210)having a plurality of fibers (220) interconnected and a plurality of protruding spacers (230) affixed to a surface of the fabric (210); and applying sufficient resin (110) to cover the first fabric layer (210), the conductor layer (145), and the second fabric layer (210).

Title of Invention

A METHOD OF FORMING A TRANSFORMER COIL ASSEMBLY

Abstract

A method of forming a transformer coil assembly (100) is disclosed. The method involves providing a first fabric layer (600, 210) having a plurality of fibers (220) interconnected and a plurality of protruding spacers (230) affixed to a surface of the fabric (210): applying, to the first fabric layer (210), a conductor layer (145) in contact with at least one of the plurality of protruding spacers (230);-applying resin (110) to cover at least the first fabric layer (210) and the conductor layer (145); applying, to the conductor layer (145), a second fabric layer (210)having a plurality of fibers (220) interconnected and a plurality of protruding spacers (230) affixed to a surface of the fabric (210); and applying sufficient resin (110) to cover the first fabric layer (210), the conductor layer (145), and the second fabric layer (210).

Full Text	BACKGROUND Transformer coils used in high-voltage and other applications are formed by winding a conductor and casting and curing a thermosetting resin composition around the conductor windings to form a resin body covering the coil. The resin body provides dielectric properties to the transformer coil assembly, as well as holding the conductor windings in place. The resin also provides protection and more uniform thermal properties to the coil assembly. Without some form of support structure for the coil assembly, the resin may develop cracks during casting or during use when the assembly is subjected to external conditions, such as high temperature, high humidity, moisture penetration and the like, or due to internal factors, such as heat generation or stress due to high current flow, electrical fault conditions, and the like. The resin body is subjected to thermal forces from coil temperatures well above ambient during operation due to l2R losses in the conductors, from eddy currents, from hysteresis losses in the core, and from stray flux impinging the axial ends of the windings. Further, the resin body may be subject to vibratory forces during operation. The resin body should satisfactorily restrain, resist, and withstand all of these forces over long term operation. SUMMARY A transformer coil assembly is disclosed that includes a first layer having a plurality of fibers interconnected to form a fabric and a plurality of spacers. Each spacer is affixed on a first side of the spacer to the fabric and protruding from a first surface of the fabric. A second layer has a conductor in contact with at least one of the plurality of spacers on a second side of each spacer that opposes the first side. The first and second layers are covered by resin. A method of forming a transformer coil assembly is disclosed that includes providing a first fabric layer having a plurality of fibers interconnected and a plurality of protruding spacers affixed to a surface of the fabric A conductor layer is applied to the first fabric layer in contact with at least one of the plurality of protruding spacers. A resin is applied to cover at least the first fabric layer and the conductor layer. A transformer coil assembly is disclosed that includes a means for establishing a support structure for the transformer assembly, the support structure having a first thickness along a first dimension. Spacer means are affixed to the support structure and have a second thickness along the first dimension, the second thickness being greater than the first thickness. The spacer means are formed of a material having a lower compressibility than material used to form the support structure. Conductor means are in contact with the spacer means. Dielectric means cover the support structure means, the spacer means, and the conductor means. A fibrous material for reinforcing a resin cast transformer coil assembly is disclosed that includes a plurality of fibers interconnected to form a fabric. A plurality of spacers is affixed to the fabric and protrudes from a surface of the fabric. The spacers are arranged in a plurality of rows, where each row is segmented such that superimposing rows onto each other provides an unsegmented row of spacers. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Objects and advantages will become apparent to those skilled in the art upon reading this description in conjunction with the accompanying drawings, in which like reference numerals have been used to designate like elements, and in which: FIG. 1 is a perspective view of a transformer coil assembly. FIG. 2 shows a support structure and spacers. FIG. 3 shows an area of detail of the transformer coil assembly of FIG. 1. FIG. 4A shows a support structure, spacers, and a conductor. FIG. 4B illustrates a feature of a spacer pattern of FIG. 4A. FIGs. 5A-5D show other possible arrangements of the spacers. FIG. 6 is a flow chart illustrating a method of forming a transformer coil assembly. DETAILED DESCRIPTION FIG. 1 is a perspective view of a transformer coil assembly 100 according to an exemplary embodiment. The transformer coil assembly 100 includes a first layer 130 and a second layer 140. Referring also to FIG. 3, which details an area of the transformer coil assembly 100 of FIG. 1, a first layer 130 of the transformer coil assembly 100 includes means for establishing a support structure 310. The means for establishing a support structure 310 can include multiple fibers interconnected to form a fabric. The fabric can include glass fibers and can include electrical grade glass. The fabric can include any of a variety of fibers that are known in this art to be suitable for transformer cast applications, such as polyphenylene sulfide (PPS), polyamides (nylon), polyvinyl chloride (PVC), flouropolymers (PTFE), and the like. The first layer 130 of the transformer coil assembly 100 also includes spacer means 330, affixed to the support structure means 310. The spacer means 330 can include multiple spacers and is preferably formed of a less compressive material than fabric, such as resin or epoxy. The spacer means 330 are affixed to a surface of the support structure means 310. Here, the term "affixed" means that the spacers can be secured adjacent to a surface of the support structure means 310, by adhesives or other known means, or can be partially embedded in the support structure means 310. The spacer means 330 protrude from the support structure means 310 by a distance, i.e., height, 335. It should be appreciated that although the spacer means 330 are shown affixed to only one surface of the support structure means 310, the spacer means 330 can also be attached to both opposing surfaces of the support structure means 310. The second layer 140 includes a conductor means 145 in contact with at least one of the spacers of the spacer means 330 on a second side 332 of each spacer that opposes the first side 331. The conductor means 145 can be a single conductor that is wound continuously to form a single transformer coil winding, or can be multiple conductors, depending on the type of transformer coil assembly 100. The conductor means 145 can include tabs 160 for accessing the conductor means 145 by other electrical components outside the transformer coil assembly 100. The transformer coil assembly 100 includes a dielectric means for covering the support structure means 310, the spacer means 330, and the conductor means 145. The dielectric means can be a resin body 110 covering the layers of the transformer coil assembly 100. Although the dielectric means will be described hereinafter as a resin body 110, or simply resin 110, one of skill in this art will recognize that a number of dielectric materials may be used that are suitable for use in a transformer cast. The thickness of the resin body should be uniform to provide dielectric properties that are uniform throughout the transformer coil assembly. Here, the term uniform means substantially the same throughout with some tolerance. A dielectric with favorable properties will resist breakdown under high voltages, does not itself draw appreciable power from the circuit, is physically stable, and has characteristics that do not vary much over a fairly wide temperature range. The transformer coil assembly 100 can optionally include a third layer 150 having support structure means 315 and spacer means 335. The third layer 150 can be made of the same materials as the first layer, although this is not a requirement. When the optional third layer 150 is employed, the dielectric means, such as a resin body 110, can cover the first, second, and third layers 130, 140, 150, providing an overall thickness 160. The means for establishing support structure 310 provides reinforcing support to the resin body 110 to prevent the development of cracks during casting or during use when the assembly is subjected to external conditions, such as high temperature, high humidity, moisture penetration and the like, or due to internal factors, such as high coil temperatures or vibratory forces during operation. The spacer means 330 protrude from the support structure means 310 by a distance 335. The protrusion of the spacer means 330 creates a space 320 between conductor means 145 and the support structure means 310, where the resin 110 can more easily flow during the casting process. That is, without the spacers, the resin would have to "wick" into the support structure, which takes additional time and may produce uneven dispersion of the resin 110. Uneven dispersion produces a resin body 110 that does not have uniform dielectric properties. The spacer means 330 provides a more even resin body 110 having more uniform dielectric properties than using, for example, a support structure 310 only. Moreover, the height 335 of the spacer means 330 can be selected to provide a desired overall thickness 120 of the first layer 130 using less support structure means 310, such as fabric. That is, to achieve the same thickness 120 of the first layer 130, and therefore the same dielectric properties, without the spacer means 330, many layers of fabric would typically be required. The layers of fabric would not only cause uneven dispersing of the resin 110, as described above, but would be subject to compression by the conductor means 145 as the conductor means 145 is applied, e.g., wound, over the fabric layers. Compression is typically uneven and results in a non-uniform thickness of the first layer, causing non- uniform dielectric properties. The spacer means 330 therefore preferably is less compressive, i.e., is less subject to changes in volume when a force is applied, than the support structure means 310. For example, epoxy spacers are less compressive than layers of electrical grade glass. FIG. 2 shows a support structure 210 with spacers 230. The support structure 210 includes a plurality of fibers 220 interconnected to form a fabric. Although a grid- like pattern is illustrated, any pattern can be used. Multiple spacers 230 are affixed to the fabric 210 and protruding from a surface of the fabric 210. The spacers 230 can be arranged in a plurality of rows 240A, 240B. The rows 240A, 240B can be segmented as shown. FIG. 2 shows the spacers 230 arranged in one of many patterns that can be used. FIGs. 5A-5D show other possible patterns of the spacers that can be used. FIG. 4A shows a support structure, spacers, and a conductor. The spacers 230 are shown arranged in a plurality of rows 240A, 240B. A conductor 430 has a first end 410 and a second end 430 and is continuous such that segment ends 420A and 420B are connected, i.e., represent the same point, and so on. The spacers 230 are shown arranged in a pattern so that the conductor 430 contacts only the spacers 230, and contacts a spacer 230 at least every two rows. This pattern provides support for the conductor 430 every two rows. FIG. 4B illustrates this feature of the spacer pattern of FIG. 4A. The superimposition of row 240A onto 240B provides an unsegmented row of spacers. Here, the term "unsegmented" is meant to include both a contiguous row of adjacent spacers and a row of overlapping spacers. This feature helps define the pattern of FIG. 4A. Likewise, as can be appreciated, in the pattern of FIG. 5A, the superimposition of three rows onto each other provides an unsegmented row of spacers. In FIG. 5B, the superimposition of four rows onto each other provides an unsegmented row of spacers. In FIGs. 5A and 5B, the respective pattern provides support for the conductor 430 every three rows and every four rows. This can be expanded to any number of rows. As can be appreciated from FIG. 5C, the rows need not be segmented, although it is preferable as discussed below. Moreover, as can be appreciated from FIG. 5D, the spacers can be of varying sizes and patterns, and need not be in rows. The spacer pattern can be purely random if desired. It is, however, preferable to use segmented rows of spacers. The segmenting allows better flow of the resin around the spacers. In addition, longer spacers are more likely to conduct electricity from one area of the conductor to another, or create a voltage potential between spacers. FIG. 6 is a flow chart illustrating a method of forming a transformer coil assembly. A method of forming a transformer coil assembly includes providing a first fabric layer having a plurality of fibers interconnected and a plurality of protruding spacers affixed to a surface of the fabric (600). A conductor layer is applied to the first fabric layer in contact with at least one of the plurality of protruding spacers (610). A resin is applied to cover at least the first fabric layer and the conductor layer (620). It will be appreciated by those of ordinary skill in the art that the invention can be embodied in various specific forms without departing from its essential characteristics. The disclosed embodiments are considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims, rather than the foregoing description, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced thereby. It should be emphasized that the terms "comprises", "comprising", "includes" and "including" when used in this description and claims, are taken to specify the presence of stated features, steps, or components, but the use of these terms does not preclude the presence or addition of one or more other features, steps, components, or groups thereof. WE CLAIM: 1. A method of forming a transformer coil assembly (100), comprising: providing a first fabric layer (600, 210) having a plurality of fibers (220) interconnected and a plurality of protruding spacers (230) affixed to a surface of the fabric (210): applying, to the first fabric layer (210), a conductor layer (145) in contact with at least one of the plurality of protruding spacers (230); applying resin (110) to cover at least the first fabric layer (210) and the conductor layer (145); applying, to the conductor layer (145), a second fabric layer (210)having a plurality of fibers (220) interconnected and a plurality of protruding spacers (230) affixed to a surface of the fabric (210); and applying sufficient resin (110) to cover the first fabric layer (210), the conductor layer (145), and the second fabric layer (210). 2. The method as claimed in claim 1, wherein applying the conductor layer (145) comprises applying the conductor (145) to contact, of the first fabric layer (210), only the protruding spacers (230). 3. The method as claimed in claim 1, wherein applying a second fabric layer (210) comprises applying the second fabric layer (210) so that only the protruding spacers (230) contact the conductor (145). 4. The method as claimed in claim 1, wherein the spacers (230) are arranged in a plurality of rows (240A, 240B) on the fabric (210), and wherein in each row (240A, 240B), the spacers (230) are separated by spaces. 5. The method as claimed in claim 4 wherein the spacers (230) comprise a plurality of first rows (240A) and a plurality of second rows (240B), wherein the spacers (230) in the first rows (240A) are offset from the spacers (230) in the second rows (240B), and wherein the first rows (240A) and the second rows (240B) are arranged in an alternating manner. 6. The method as claimed in claim 5, wherein the first and second rows (240A, 240B) are arranged to extend in the axial direction of the transformer coil assembly (100). 7. The method as claimed in claim 1, wherein the spacers (230) are partially embedded in the fabric (210). 8. The method as claimed in claim 1, wherein the fibers (220) comprise glass fibers. 9. The method as claimed in claim 7, wherein the spacers (230) are comprised of an epoxy resin (110). 10. The method as claimed in claim 1, wherein the application of the resin (110) fills spaces between the conductor layer (145) and the fabric (210) with the resin (110), thereby forming an insulating layer having a uniform thickness. 11. The method as claimed in claim 10, comprising selecting a height for the spacers (230) based on a desired thickness for the insulating layer. 12. The method as claimed in claim 1, wherein the step of providing the first fabric layer (600, 210) comprises securing spacers (230) to the fabric (210) using an adhesive. 13. The method as claimed in claim 1, wherein the first fabric layer (210) has a grid pattern. ABSTRACT A METHOD OF FORMING A TRANSFORMER COIL ASSEMBLY A method of forming a transformer coil assembly (100) is disclosed. The method involves providing a first fabric layer (600, 210) having a plurality of fibers (220) interconnected and a plurality of protruding spacers (230) affixed to a surface of the fabric (210): applying, to the first fabric layer (210), a conductor layer (145) in contact with at least one of the plurality of protruding spacers (230);-applying resin (110) to cover at least the first fabric layer (210) and the conductor layer (145); applying, to the conductor layer (145), a second fabric layer (210)having a plurality of fibers (220) interconnected and a plurality of protruding spacers (230) affixed to a surface of the fabric (210); and applying sufficient resin (110) to cover the first fabric layer (210), the conductor layer (145), and the second fabric layer (210).

Full Text

BACKGROUND
Transformer coils used in high-voltage and other applications are formed by
winding a conductor and casting and curing a thermosetting resin composition
around the conductor windings to form a resin body covering the coil. The resin
body provides dielectric properties to the transformer coil assembly, as well as
holding the conductor windings in place. The resin also provides protection and
more uniform thermal properties to the coil assembly. Without some form of
support structure for the coil assembly, the resin may develop cracks during
casting or during use when the assembly is subjected to external conditions, such
as high temperature, high humidity, moisture penetration and the like, or due to
internal factors, such as heat generation or stress due to high current flow,
electrical fault conditions, and the like.
The resin body is subjected to thermal forces from coil temperatures well above
ambient during operation due to l2R losses in the conductors, from eddy currents,
from hysteresis losses in the core, and from stray flux impinging the axial ends of
the windings. Further, the resin body may be subject to vibratory forces during
operation. The resin body should satisfactorily restrain, resist, and withstand all of
these forces over long term operation.
SUMMARY
A transformer coil assembly is disclosed that includes a first layer having a
plurality of fibers interconnected to form a fabric and a plurality of spacers. Each
spacer is affixed on a first side of the spacer to the fabric and protruding from a first
surface of the fabric. A second layer has a conductor in contact with at least one of
the plurality of spacers on a second side of each spacer that opposes the first side.
The first and second layers are covered by resin.

A method of forming a transformer coil assembly is disclosed that includes
providing a first fabric layer having a plurality of fibers interconnected and a
plurality of protruding spacers affixed to a surface of the fabric A conductor layer
is applied to the first fabric layer in contact with at least one of the plurality of
protruding spacers. A resin is applied to cover at least the first fabric layer and the
conductor layer.
A transformer coil assembly is disclosed that includes a means for establishing a
support structure for the transformer assembly, the support structure having a first
thickness along a first dimension. Spacer means are affixed to the support
structure and have a second thickness along the first dimension, the second
thickness being greater than the first thickness. The spacer means are formed of a
material having a lower compressibility than material used to form the support
structure. Conductor means are in contact with the spacer means. Dielectric
means cover the support structure means, the spacer means, and the conductor
means.
A fibrous material for reinforcing a resin cast transformer coil assembly is disclosed
that includes a plurality of fibers interconnected to form a fabric. A plurality of
spacers is affixed to the fabric and protrudes from a surface of the fabric. The
spacers are arranged in a plurality of rows, where each row is segmented such that
superimposing rows onto each other provides an unsegmented row of spacers.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Objects and advantages will become apparent to those skilled in the art upon
reading this description in conjunction with the accompanying drawings, in which
like reference numerals have been used to designate like elements, and in which:

FIG. 1 is a perspective view of a transformer coil assembly.
FIG. 2 shows a support structure and spacers.
FIG. 3 shows an area of detail of the transformer coil assembly of FIG. 1.
FIG. 4A shows a support structure, spacers, and a conductor.
FIG. 4B illustrates a feature of a spacer pattern of FIG. 4A.
FIGs. 5A-5D show other possible arrangements of the spacers.
FIG. 6 is a flow chart illustrating a method of forming a transformer coil assembly.
DETAILED DESCRIPTION
FIG. 1 is a perspective view of a transformer coil assembly 100 according to an
exemplary embodiment. The transformer coil assembly 100 includes a first layer
130 and a second layer 140. Referring also to FIG. 3, which details an area of the
transformer coil assembly 100 of FIG. 1, a first layer 130 of the transformer coil
assembly 100 includes means for establishing a support structure 310.
The means for establishing a support structure 310 can include multiple fibers
interconnected to form a fabric. The fabric can include glass fibers and can include
electrical grade glass. The fabric can include any of a variety of fibers that are
known in this art to be suitable for transformer cast applications, such as
polyphenylene sulfide (PPS), polyamides (nylon), polyvinyl chloride (PVC),
flouropolymers (PTFE), and the like.

The first layer 130 of the transformer coil assembly 100 also includes spacer
means 330, affixed to the support structure means 310. The spacer means 330
can include multiple spacers and is preferably formed of a less compressive
material than fabric, such as resin or epoxy. The spacer means 330 are affixed to
a surface of the support structure means 310. Here, the term "affixed" means that
the spacers can be secured adjacent to a surface of the support structure means
310, by adhesives or other known means, or can be partially embedded in the
support structure means 310. The spacer means 330 protrude from the support
structure means 310 by a distance, i.e., height, 335. It should be appreciated that
although the spacer means 330 are shown affixed to only one surface of the
support structure means 310, the spacer means 330 can also be attached to both
opposing surfaces of the support structure means 310.
The second layer 140 includes a conductor means 145 in contact with at least one
of the spacers of the spacer means 330 on a second side 332 of each spacer that
opposes the first side 331. The conductor means 145 can be a single conductor
that is wound continuously to form a single transformer coil winding, or can be
multiple conductors, depending on the type of transformer coil assembly 100. The
conductor means 145 can include tabs 160 for accessing the conductor means 145
by other electrical components outside the transformer coil assembly 100.
The transformer coil assembly 100 includes a dielectric means for covering the
support structure means 310, the spacer means 330, and the conductor means
145. The dielectric means can be a resin body 110 covering the layers of the
transformer coil assembly 100. Although the dielectric means will be described
hereinafter as a resin body 110, or simply resin 110, one of skill in this art will
recognize that a number of dielectric materials may be used that are suitable for
use in a transformer cast. The thickness of the resin body should be uniform to
provide dielectric properties that are uniform throughout the transformer coil
assembly. Here, the term uniform means substantially the same throughout with

some tolerance. A dielectric with favorable properties will resist breakdown under
high voltages, does not itself draw appreciable power from the circuit, is physically
stable, and has characteristics that do not vary much over a fairly wide temperature
range.
The transformer coil assembly 100 can optionally include a third layer 150 having
support structure means 315 and spacer means 335. The third layer 150 can be
made of the same materials as the first layer, although this is not a requirement.
When the optional third layer 150 is employed, the dielectric means, such as a
resin body 110, can cover the first, second, and third layers 130, 140, 150,
providing an overall thickness 160.
The means for establishing support structure 310 provides reinforcing support to
the resin body 110 to prevent the development of cracks during casting or during
use when the assembly is subjected to external conditions, such as high
temperature, high humidity, moisture penetration and the like, or due to internal
factors, such as high coil temperatures or vibratory forces during operation.
The spacer means 330 protrude from the support structure means 310 by a
distance 335. The protrusion of the spacer means 330 creates a space 320
between conductor means 145 and the support structure means 310, where the
resin 110 can more easily flow during the casting process. That is, without the
spacers, the resin would have to "wick" into the support structure, which takes
additional time and may produce uneven dispersion of the resin 110. Uneven
dispersion produces a resin body 110 that does not have uniform dielectric
properties. The spacer means 330 provides a more even resin body 110 having
more uniform dielectric properties than using, for example, a support structure 310
only.

Moreover, the height 335 of the spacer means 330 can be selected to provide a
desired overall thickness 120 of the first layer 130 using less support structure
means 310, such as fabric. That is, to achieve the same thickness 120 of the first
layer 130, and therefore the same dielectric properties, without the spacer means
330, many layers of fabric would typically be required. The layers of fabric would
not only cause uneven dispersing of the resin 110, as described above, but would
be subject to compression by the conductor means 145 as the conductor means
145 is applied, e.g., wound, over the fabric layers. Compression is typically
uneven and results in a non-uniform thickness of the first layer, causing non-
uniform dielectric properties. The spacer means 330 therefore preferably is less
compressive, i.e., is less subject to changes in volume when a force is applied,
than the support structure means 310. For example, epoxy spacers are less
compressive than layers of electrical grade glass.
FIG. 2 shows a support structure 210 with spacers 230. The support structure 210
includes a plurality of fibers 220 interconnected to form a fabric. Although a grid-
like pattern is illustrated, any pattern can be used. Multiple spacers 230 are affixed
to the fabric 210 and protruding from a surface of the fabric 210.
The spacers 230 can be arranged in a plurality of rows 240A, 240B. The rows
240A, 240B can be segmented as shown. FIG. 2 shows the spacers 230 arranged
in one of many patterns that can be used. FIGs. 5A-5D show other possible
patterns of the spacers that can be used.
FIG. 4A shows a support structure, spacers, and a conductor. The spacers 230
are shown arranged in a plurality of rows 240A, 240B. A conductor 430 has a first
end 410 and a second end 430 and is continuous such that segment ends 420A
and 420B are connected, i.e., represent the same point, and so on. The spacers
230 are shown arranged in a pattern so that the conductor 430 contacts only the

spacers 230, and contacts a spacer 230 at least every two rows. This pattern
provides support for the conductor 430 every two rows.
FIG. 4B illustrates this feature of the spacer pattern of FIG. 4A. The
superimposition of row 240A onto 240B provides an unsegmented row of spacers.
Here, the term "unsegmented" is meant to include both a contiguous row of
adjacent spacers and a row of overlapping spacers. This feature helps define the
pattern of FIG. 4A. Likewise, as can be appreciated, in the pattern of FIG. 5A, the
superimposition of three rows onto each other provides an unsegmented row of
spacers. In FIG. 5B, the superimposition of four rows onto each other provides an
unsegmented row of spacers. In FIGs. 5A and 5B, the respective pattern provides
support for the conductor 430 every three rows and every four rows. This can be
expanded to any number of rows.
As can be appreciated from FIG. 5C, the rows need not be segmented, although it
is preferable as discussed below. Moreover, as can be appreciated from FIG. 5D,
the spacers can be of varying sizes and patterns, and need not be in rows. The
spacer pattern can be purely random if desired.
It is, however, preferable to use segmented rows of spacers. The segmenting
allows better flow of the resin around the spacers. In addition, longer spacers are
more likely to conduct electricity from one area of the conductor to another, or
create a voltage potential between spacers.
FIG. 6 is a flow chart illustrating a method of forming a transformer coil assembly.
A method of forming a transformer coil assembly includes providing a first fabric
layer having a plurality of fibers interconnected and a plurality of protruding spacers
affixed to a surface of the fabric (600). A conductor layer is applied to the first
fabric layer in contact with at least one of the plurality of protruding spacers (610).

A resin is applied to cover at least the first fabric layer and the conductor layer
(620).
It will be appreciated by those of ordinary skill in the art that the invention can be
embodied in various specific forms without departing from its essential
characteristics. The disclosed embodiments are considered in all respects to be
illustrative and not restrictive. The scope of the invention is indicated by the
appended claims, rather than the foregoing description, and all changes that come
within the meaning and range of equivalents thereof are intended to be embraced
thereby.
It should be emphasized that the terms "comprises", "comprising", "includes" and
"including" when used in this description and claims, are taken to specify the
presence of stated features, steps, or components, but the use of these terms does
not preclude the presence or addition of one or more other features, steps,
components, or groups thereof.

WE CLAIM:
1. A method of forming a transformer coil assembly (100), comprising:
providing a first fabric layer (600, 210) having a plurality of fibers (220)
interconnected and a plurality of protruding spacers (230) affixed to a surface of the fabric
(210):
applying, to the first fabric layer (210), a conductor layer (145) in contact with at least
one of the plurality of protruding spacers (230);
applying resin (110) to cover at least the first fabric layer (210) and the conductor layer
(145);
applying, to the conductor layer (145), a second fabric layer (210)having a plurality of
fibers (220) interconnected and a plurality of protruding spacers (230) affixed to a surface of
the fabric (210); and
applying sufficient resin (110) to cover the first fabric layer (210), the conductor layer
(145), and the second fabric layer (210).
2. The method as claimed in claim 1, wherein applying the conductor layer (145)
comprises applying the conductor (145) to contact, of the first fabric layer (210), only the
protruding spacers (230).
3. The method as claimed in claim 1, wherein applying a second fabric layer (210)
comprises applying the second fabric layer (210) so that only the protruding spacers (230)
contact the conductor (145).
4. The method as claimed in claim 1, wherein the spacers (230) are arranged in a plurality
of rows (240A, 240B) on the fabric (210), and wherein in each row (240A, 240B), the
spacers (230) are separated by spaces.
5. The method as claimed in claim 4 wherein the spacers (230) comprise a plurality of
first rows (240A) and a plurality of second rows (240B), wherein the spacers (230) in the
first rows (240A) are offset from the spacers (230) in the second rows (240B), and wherein
the first rows (240A) and the second rows (240B) are arranged in an alternating manner.

6. The method as claimed in claim 5, wherein the first and second rows (240A, 240B) are
arranged to extend in the axial direction of the transformer coil assembly (100).
7. The method as claimed in claim 1, wherein the spacers (230) are partially embedded in
the fabric (210).
8. The method as claimed in claim 1, wherein the fibers (220) comprise glass fibers.
9. The method as claimed in claim 7, wherein the spacers (230) are comprised of an
epoxy resin (110).
10. The method as claimed in claim 1, wherein the application of the resin (110) fills
spaces between the conductor layer (145) and the fabric (210) with the resin (110), thereby
forming an insulating layer having a uniform thickness.
11. The method as claimed in claim 10, comprising selecting a height for the spacers (230)
based on a desired thickness for the insulating layer.
12. The method as claimed in claim 1, wherein the step of providing the first fabric layer
(600, 210) comprises securing spacers (230) to the fabric (210) using an adhesive.
13. The method as claimed in claim 1, wherein the first fabric layer (210) has a grid
pattern.

ABSTRACT

A METHOD OF FORMING A TRANSFORMER COIL ASSEMBLY
A method of forming a transformer coil assembly (100) is disclosed. The method
involves providing a first fabric layer (600, 210) having a plurality of fibers (220)
interconnected and a plurality of protruding spacers (230) affixed to a surface of the fabric
(210): applying, to the first fabric layer (210), a conductor layer (145) in contact with at least
one of the plurality of protruding spacers (230);-applying resin (110) to cover at least the first
fabric layer (210) and the conductor layer (145); applying, to the conductor layer (145), a
second fabric layer (210)having a plurality of fibers (220) interconnected and a plurality of
protruding spacers (230) affixed to a surface of the fabric (210); and applying sufficient resin
(110) to cover the first fabric layer (210), the conductor layer (145), and the second fabric
layer (210).

A METHOD OF FORMING A TRANSFORMER COIL ASSEMBLY

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