U.S. patent application number 10/186824 was filed with the patent office on 2004-01-01 for high-voltage winding including double-sided insulating tape and associated methods.
This patent application is currently assigned to Siemens Westinghouse Power Corporation. Invention is credited to Emery, Franklin T..
Application Number | 20040000982 10/186824 |
Document ID | / |
Family ID | 29779945 |
Filed Date | 2004-01-01 |
United States Patent
Application |
20040000982 |
Kind Code |
A1 |
Emery, Franklin T. |
January 1, 2004 |
HIGH-VOLTAGE WINDING INCLUDING DOUBLE-SIDED INSULATING TAPE AND
ASSOCIATED METHODS
Abstract
A high-voltage winding is described for use in a dynamoelectric
machine. The high-voltage winding includes an electrical conductor
(12), an insulator (14) surrounding the electrical conductor, and
an electrically conductive layer (16) surrounding the insulator.
The insulator (14) may include a tape (18) arranged to define a
wrapped layer. A double-sided tape may be provided that includes a
flexible tape substrate (20) with an inner major surface (22)
adjacent the conductor (12) and an outer major surface (24)
opposite the inner major surface. An inner silicate layer (26) may
be secured to the inner major surface and an outer silicate layer
(28) to the outer major surface. A single-sided tape may also be
provided between the conductors and double-sided tape.
Inventors: |
Emery, Franklin T.; (Fort
Payne, AL) |
Correspondence
Address: |
Siemens Corporation
Intellectual Property Department
186 Wood Avenue South
Iselin
NJ
08830
US
|
Assignee: |
Siemens Westinghouse Power
Corporation
|
Family ID: |
29779945 |
Appl. No.: |
10/186824 |
Filed: |
July 1, 2002 |
Current U.S.
Class: |
336/209 |
Current CPC
Class: |
H02K 3/40 20130101; Y10T
29/4902 20150115; Y02E 10/725 20130101; Y02E 10/72 20130101 |
Class at
Publication: |
336/209 |
International
Class: |
H01F 027/30 |
Claims
What is claimed is:
1. A high-voltage winding for a dynamoelectric machine comprising:
at least one electrical conductor; an insulator comprising at least
one tape arranged to define at least one wrapped layer surrounding
said at least one electrical conductor, said at least one tape
comprising a double-sided tape including a flexible tape substrate
having an inner major surface adjacent said at least one electrical
conductor and an outer major surface opposite the inner major
surface, an inner silicate layer secured to the inner major surface
of said flexible tape substrate, and an outer silicate layer
secured to the outer major surface of said flexible tape substrate;
and an electrically conductive layer surrounding said
insulator.
2. A high-voltage winding according to claim 1 wherein said
double-sided tape defines at least an outermost wrapped layer of
said insulator.
3. A high-voltage winding according to claim 1 wherein said
double-sided tape is arranged to define at least one half-lapped
wrapped layer.
4. A high-voltage winding according to claim 1 wherein said
double-sided tape is arranged to define at least one butt-lapped
wrapped layer.
5. A high-voltage winding according to claim 1 wherein said at
least one tape further comprises a single-sided tape arranged in a
plurality of wrapped layers between said at least one electrical
conductor and said double-sided tape.
6. A high-voltage winding according to claim 5 wherein said
single-sided tape comprises: a flexible tape substrate having an
exposed inner major surface adjacent said at least one electrical
conductor and an outer major surface opposite the exposed inner
major surface; and an outer silicate layer secured to the outer
major surface of said flexible tape substrate.
7. A high-voltage winding according to claim 1 wherein said at
least one electrical conductor comprises copper.
8. A high-voltage winding according to claim 1 wherein said at
least one electrical conductor comprises a plurality of electrical
conductors arranged in substantially parallel relation defining a
generally rectangular cross-sectional shape.
9. A high-voltage winding according to claim 1 wherein said outer
electrically conductive layer comprises a tape impregnated with
carbon and resin.
10. A high-voltage winding for a dynamoelectric machine comprising:
a plurality of electrical conductors; a insulator comprising a
single-sided tape arranged to define at least one wrapped layer
surrounding said plurality of electrical conductors and a
double-sided tape arranged to define at least one wrapped layer
surrounding the at least one wrapped layer of said single-sided
tape, said single-sided tape comprising only an outer silicate
layer and said double-sided tape comprising inner and outer
silicate layers; and an electrically conductive layer surrounding
said insulator.
11. A high-voltage winding according to claim 10 wherein said
double-sided tape defines at least an outermost wrapped layer of
said insulator.
12. A high-voltage winding according to claim 10 wherein said
double-sided tape is arranged to define at least one half-lapped
wrapped layer.
13. A high-voltage winding according to claim 10 wherein said
double-sided tape is arranged to define at least one butt-lapped
wrapped layer.
14. A high-voltage winding according to claim 10 wherein each of
said plurality of electrical conductors comprises copper.
15. A high-voltage winding according to claim 10 wherein said
electrical conductors are arranged in substantially parallel
relation defining a generally rectangular cross-sectional
shape.
16. A method for making a high-voltage winding for a dynamoelectric
machine comprising: forming an insulator surrounding at least one
electrical conductor by wrapping at least one tape surrounding the
at least one electrical conductor to define at least one wrapped
layer, the at least one tape comprising a double-sided tape
comprising inner and outer silicate layers; and forming an
electrically conductive layer surrounding the insulator.
17. A method according to claim 16 wherein the double-sided tape
comprises: a flexible tape substrate having an inner major surface
adjacent the at least one electrical conductor and an outer major
surface opposite the inner major surface; an inner silicate layer
secured to the inner major surface of the flexible tape substrate;
and an outer silicate layer secured to the outer major surface of
the flexible tape substrate.
18. A method according to claim 16 wherein wrapping comprises
wrapping the double-sided tape to define at least an outermost
wrapped layer of the insulator.
19. A method according to claim 16 wherein wrapping comprises
wrapping the double-sided tape to define at least one half-lapped
wrapped layer.
20. A method according to claim 16 wherein wrapping comprises
wrapping the double-sided tape to define at least one butt-lapped
wrapped layer.
21. A method according to claim 16 wherein wrapping the at least
one tape further comprises wrapping a single-sided tape arranged in
a plurality of wrapped layers between the at least one electrical
conductor and the double-sided tape.
22. A method according to claim 21 wherein the single-sided tape
comprises: a flexible tape substrate having an exposed inner major
surface adjacent the at least one electrical conductor and an outer
major surface opposite the exposed inner major surface; and an
outer silicate layer secured to the outer major surface of the
flexible tape substrate.
23. A method according to claim 16 wherein the at least one
electrical conductor comprises copper.
24. A method according to claim 16 wherein the at least one
electrical conductor comprises a plurality of electrical conductors
arranged in substantially parallel relation defining a generally
rectangular cross-sectional shape.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to high-voltage
windings, and more particularly to insulated high-voltage
windings.
BACKGROUND OF THE INVENTION
[0002] High-voltage windings are used in various dynamoelectric
machines, such as motors or generators. For example, high-voltage
windings commonly referred to as stator windings are used in
high-voltage electrical generators. A high-voltage winding, such as
a stator winding, can be formed from at least one winding bar that,
in turn, comprises one or more electrical conductors. The
electrical conductors individually are formed of a highly
conductive material, such as copper. The electrical conductors are
ordinarily individually-insulated and bundled together to form the
winding bar. The bundle, in turn, is surrounded by insulation,
often referred to as a winding insulator or groundwall insulator.
The groundwall insulator can be a single-sided epoxy resin/mica
paper tape wrapping, usually comprising multiple layers of a
glass-backed mica paper tape.
[0003] Overlaying the groundwall is an outer conductive ground
electrode that surrounds the groundwall insulator. The outer
conductive ground electrode can be a coating of conductive paint or
a wrapped conductive tape over the groundwall insulator. The outer
conductive ground electrode is connected to ground so that the
voltage of the outer surface of the high-voltage winding is at
ground potential.
[0004] Over time, especially at high temperatures, partial
discharge (PD) activity can occur within the high-voltage winding
causing damage to the outer conductive electrode of the winding.
Used in an air-cooled generator, a high-voltage winding is
especially prone to PD activity because partial discharges may
occur at a relatively low voltage in air.
[0005] Various insulation materials and techniques have been
proposed for reducing or eliminating PD activity in high-voltage
windings. U.S. Pat. No. 6,190,775 to Smith et al., for example,
discloses a flexible insulating tape comprising a silicate matrix
(i.e., mica or mica-like matrix) with intercalated metal ions and
having a flexible backing. The tape is applied to a high-voltage
winding in thin cross-sections to provide insulation. U.S. Pat. No.
6,075,303 to Schuler discloses insulation formed of layers of mica
paper arranged on a base, the base being composed of polyimide or
polyethylene naphthalate and containing a metal oxide, such as
aluminum oxide or boron nitride, as a filler.
[0006] FIGS. 1A and 1B illustrate a conventional groundwall
insulation 9. The groundwall insulation 9 is formed of layers of
woven glass fibers 11 surrounded by resin 15 and backed by a mica
paper layer 17. Voids 13 can form in the resin 15 surrounding the
woven glass fibers 11. When these voids 13 extend, as illustrated,
to the surface of the groundwall insulation 9, the surface of the
groundwall insulation tends to be pitted or rough. This leaves
voids between the outer surface of the groundwall insulation 9 and
the outer conductive electrode (not shown). If even small voids
exist between the outer surface of the groundwall insulator 9 and
the conductive ground electrode, then PD can occur between the
outer surface of the groundwall insulation and the outer conductive
ground electrode. Partial discharge can damage the outer conductive
ground electrode, causing the inside surface of the ground
electrode to erode. Once damage occurs to the outer conductive
ground electrode it can lead to subsequent damage to the groundwall
insulation owing to the development of greater PD activity.
[0007] Exposing the high-voltage winding to high temperatures
accelerates the deterioration by causing relative expansion and
separation between the groundwall insulator and the outer
conductive ground electrode. Once damage occurs to the conductive
electrode, corona activity can occur between the ground electrode
and surfaces of the conductors. The corona damage may also
accelerate the deterioration of the ground electrode, which, in
turn, can erode the groundwall insulator. The problem is
particularly acute in the context of electrical generators where
failure of the ground plane on the outer surface of the stator
winding can lead to coil slot discharges that erode the groundwall
insulator and, over time, can lead to a complete breakdown of the
groundwall insulator and subsequent stator winding failure.
SUMMARY OF THE INVENTION
[0008] In view of the foregoing background, it is an object of the
present invention to provide a high-voltage winding that is less
susceptible to insulation breakdown that can result in winding
failure.
[0009] This and other objects, features, and advantages in
accordance with the present invention are provided by a
high-voltage winding that includes at least one electrical
conductor, an insulator around the at least one electrical
conductor, and an electrically conductive layer surrounding the
insulator. The insulator may include at least one tape that is
arranged to define at least one wrapped layer surrounding the at
least one electrical conductor. The tape, more particularly, may be
a double-sided tape. In other words, the tape may include a
flexible substrate having an inner major surface adjacent the at
least one electrical conductor, and an outer major surface opposite
the inner major surface. An inner silicate layer may be secured to
the inner major surface of the flexible tape substrate. An outer
silicate layer may be secured to the outer major surface of the
flexible tape substrate.
[0010] The double-sided tape, moreover, may define at least an
outermost wrapped layer of the insulator. In addition, the
double-sided tape may be arranged to define at least one
half-lapped wrapped layer, or, alternately, the double-sided tape
may be arranged to define at least one butt-lapped wrapped
layer.
[0011] The insulator may further include a single-sided tape
arranged in a plurality of wrapped layers between the at least one
electrical conductor and the double-sided tape. The single-sided
tape may also have a flexible tape substrate. The substrate of the
single-sided tape, moreover, may have an exposed inner major
surface adjacent the at least one electrical conductor and an outer
major surface opposite the exposed inner major surface. An outer
silicate layer may be secured to the outer major surface of the
flexible tape substrate of the single-sided tape. The single-sided
tape may comprise only one silicate layer, the outer silicate layer
secured to the major surface of the tape substrate.
[0012] The at least one electrical conductor of the high-voltage
winding, more specifically, typically will comprise a material
having high electrical conductivity, such as copper. In addition,
the at least one electrical conductor may be a plurality of
electrical conductors. The plurality of electrical conductors,
moreover, may be arranged in substantially parallel relation to
define a generally rectangular cross-sectional shape.
[0013] An additional aspect of the invention pertains to a method
for making a high-voltage winding for a dynamoelectric machine. The
method may include forming an insulator around at least one
electrical conductor, the insulator being formed by wrapping at
least one tape around the at least one electrical conductor thereby
defining at least one wrapped layer. The method, moreover, may
further include forming an electrically conductive layer around the
insulator.
[0014] With respect to wrapping at least one tape around the at
least one electrical conductor to define a wrapped layer, the at
least one tape may comprise a double-sided tape having both inner
and outer silicate layers. The double-sided tape may include a
flexible tape substrate having an inner major surface adjacent the
at least one electrical conductor and an outer major surface
opposite the inner major surface, inner silicate layer secured to
the inner major surface and the outer silicate layer secured to the
outer major surface.
[0015] The method may further include wrapping the double-sided
tape to define at least an outermost wrapped layer of the
insulator. Wrapping, according to the method, may include wrapping
the double-sided tape to define at least one half-lapped wrapped
layer. Alternately, the wrapping may include wrapping the
double-sided tape to define at least one butt-lapped wrapped
layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1A is a top plan view of winding insulation according
to the prior art.
[0017] FIG. 1B is a cross-sectional view taken along line 1B-1B of
FIG. 1A.
[0018] FIG. 2 is a perspective fragmentary view of a high-voltage
winding consistent with the illustrated embodiment of the present
invention.
[0019] FIG. 3 is a cross-sectional view taken along lines 3-3 of
FIG. 2.
[0020] FIG. 4 is a greatly enlarged, schematic cross-sectional view
of the dual-sided tape as used in the high-voltage winding of FIG.
2.
[0021] FIGS. 5 and 6 are schematic longitudinal cross-sectional
views of the double-sided tape as shown in FIG. 2 in a half-lapped
and butt-lapped configuration, respectively.
[0022] FIG. 7 is a greatly enlarged, schematic cross-sectional view
of a single-sided tape as used in the high-voltage winding FIG.
2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
preferred embodiments of the invention are shown. This invention
may, however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. Like numbers refer to like
elements throughout. The prime notation indicates similar elements
in alternate embodiments.
[0024] Referring initially to FIGS. 2 and 3, a high-voltage winding
10 according to the invention is first described. More
specifically, the high-voltage winding 10 may be for use in a
dynamoelectric machine and, as shown, may include electrical
conductors 12, an insulator 14 surrounding the conductors, and an
electrically conductive layer 16 surrounding the insulator.
[0025] Illustratively, the conductors are arranged in substantially
parallel relation to define a generally rectangular cross-sectional
shape. As will be readily appreciated by one skilled in the art,
each of the plurality of electrical conductors may be formed of a
material having a high electrical conductivity, such as copper, and
an insulating layer surrounding the copper. In other embodiments,
only a single conductor may be used.
[0026] The insulator 14 may include at least one tape arranged to
define at least one wrapped layer surrounding the conductors 12.
More particularly, the insulator includes a single-sided tape 30,
and a double-sided tape 18 surrounding the single-sided tape. A
conductive layer 16 surrounds the double-sided tape 18. The
conductive layer 16 serves as a ground electrode and may comprise a
paint or other coating.
[0027] Turning now additionally to FIGS. 4-6, the double-sided tape
18 illustratively includes a flexible tape substrate 20 having an
inner major surface 22 adjacent the electrical conductors 12 and an
outer major surface 24 opposite the inner major surface. An inner
silicate layer 26 is secured to the inner major surface 22 of the
flexible tape substrate 20. In addition, an outer silicate layer 28
is secured to the outer major surface 24 of the flexible tape
substrate 20. As will be readily appreciated by those skilled in
the art, each of the silicate layers 26, 28 may include silica, a
crystalline compound, SiO.sub.2, found in quartz, sand, or flint.
As will also be readily understood by those skilled in the art, the
silicate layers 26, 28 may comprise mica, one of a group of
silicates, such as KAl2AlSi.sub.3O.sub.10(OH).sub.2 or
KMg.sub.3AlSi.sub.3O.sub.10(OH).sub.2 known to have particularly
high dielectric strength, low dielectric loss, high resistivity,
thermal stability, and corona resistance.
[0028] Illustratively, the double-sided tape 18 defines at least an
outermost wrapped layer of the insulator 14. The double-sided tape
18, may be arranged to define at least one half-lapped wrapped
layer 18' (FIG. 5), or alternately, the double-sided tape may be
arranged to define at least one butt-lapped wrapped layer 18" (FIG.
6).
[0029] Turning now additionally to FIG. 7, the single-sided tape 30
is further described. The single-sided tape 30 may be arranged in a
plurality of wrapped layers between the electrical conductors 12
and the double-sided tape 18. The single-sided tape 30 preferably
includes a flexible tape substrate 32. The flexible tape substrate
32 of the single-sided tape 30 has an exposed inner major surface
34 adjacent the electrical conductors 12 and an outer major surface
36 opposite the exposed inner major surface. An outer silicate
layer 38 is illustratively secured to the outer major surface 36 of
the flexible tape substrate 32 of the single-sided tape 30. The
outer silicate layer 38 may comprise of any of the silicate
materials described above.
[0030] The high-voltage winding 10 has distinct advantages over a
conventional one. A conventional high-voltage winding, for example,
relies on an insulator formed of layered wrappings, usually formed
of a tape having a glass backing or base formed of a similar
material. Owing to such a base or backing, the insulator of a
conventional high-voltage winding provides only an irregular
insulating surface when applied around the electrical conductors.
The irregular surface typically leaves voids. With even small
voids, partial discharge can occur beneath the electrically
conductive ground layer that normally surrounds the insulator and
one or more underlying conductors. Partial discharges can damage
the conductive layer, which, in turn can result in damaging corona
activity and eventually in a complete breakdown of the insulator
that, in turn, may ultimately result in winding failure.
[0031] By contrast, the insulator 14 of the present invention
includes a double-sided tape 18 having dual silicate layers 26, 28
that can provide a surface substantially free of voids.
Accordingly, the resulting void-free surface reduces the risks of
partial discharge. The reduced risk of partial discharge, in turn,
results in less risk of corona activity and ultimate failure of the
winding. Accordingly, the insulator 14 according to the present
invention results in a high-voltage winding 10 less susceptible to
damage and failure.
[0032] An additional aspect of the present invention relates to a
method for making a high-voltage winding for a dynamoelectric
machine. The method includes forming an insulator 14 around at
least one electrical conductor 12 and forming an electrically
conductive layer 16 surrounding the insulator. More specifically,
the insulator 14 may be formed by wrapping at least one tape 18
around the at least one electrical conductor 12 to define at least
one wrapped layer, the tape being a double-sided tape including a
flexible substrate 20 that has an inner major surface 22 adjacent
the at least one electrical conductor 12 and an outer major surface
24 opposite the inner major surface. Moreover, as described above,
an inner silicate layer 26 may be secured to the inner major
surface 22 of the flexible tape substrate 20, and an outer silicate
layer 28 may be secured to the outer major surface 24 of the
flexible tape substrate.
[0033] The method includes wrapping the double-sided tape 18 to
define at least an outermost wrapped layer of the insulator 14. As
will be readily understood by those skilled in the art, the
double-sided tape 18 may be wrapped to define at least one
half-lapped wrapped layer, or alternatively, to define at least one
butt-lapped wrapped layer.
[0034] The method also includes wrapping a single-sided tape 30
arranged in a plurality of wrapped layers between the at least one
electrical conductor 12 and the double-sided tape 18. As also
described above, the single-sided tape 30 may include a flexible
tape substrate 32 having an exposed inner major surface 34 adjacent
the at least one electrical conductor 12 and an outer major surface
36 opposite the exposed inner major surface. An outer silicate
layer 38 may be secured to the outer major surface 36 of the
flexible tape substrate 30.
[0035] Many modifications and other embodiments of the invention
will come to the mind of one skilled in the art having the benefit
of the teachings presented in the foregoing descriptions and the
associated drawings. Therefore, it is to be understood that the
invention is not to be limited to the specific embodiments
disclosed, and that modifications and other embodiments are
intended to be included within the scope of the appended
claims.
* * * * *