U.S. patent application number 10/186835 was filed with the patent office on 2004-01-01 for insulation insert for preventing strand-to-strand contact in high-voltage coils.
This patent application is currently assigned to Siemens Westinghouse Power Corporation. Invention is credited to Emery, Franklin T..
Application Number | 20040000423 10/186835 |
Document ID | / |
Family ID | 29711408 |
Filed Date | 2004-01-01 |
United States Patent
Application |
20040000423 |
Kind Code |
A1 |
Emery, Franklin T. |
January 1, 2004 |
INSULATION INSERT FOR PREVENTING STRAND-TO-STRAND CONTACT IN
HIGH-VOLTAGE COILS
Abstract
An insulation insert (40) is provided for preventing electrical
shorts and/or arcing between adjacent strands in a stator coil. The
insulation insert includes a thin base (42) of substantially
uniform cross section and a lead-in nose (43) formed in the thin
base (42) for guiding the insulation insert (40) into a position
between adjacent strands. The insulation insert (40) includes two
substantially vertical cuts (45) in the thin base (42) above the
lead-in nose (43), which delineate a center section (44) flanked by
two ear portions (46). A head (54) and two wings (52) are formed in
the insulation insert by folding the ear portions (46) along
substantially horizontal creases (47).
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: |
29711408 |
Appl. No.: |
10/186835 |
Filed: |
July 1, 2002 |
Current U.S.
Class: |
174/138E |
Current CPC
Class: |
H02K 3/14 20130101; H02K
3/40 20130101 |
Class at
Publication: |
174/138.00E |
International
Class: |
H01B 017/00 |
Claims
What is claimed is:
1. An insulation insert for preventing electrical contact or arcing
between adjacent strands in a stator coil, comprising: a thin base
of substantially uniform cross section; a lead-in nose formed in
said thin base for guiding said insulation insert into a position
between said adjacent strands; two substantially vertical cuts in
said thin base above said lead-in nose delineating a center section
flanked by two ear portions; and a substantially horizontal crease
in each of said ear portions to form opposing wings in said
insulation insert.
2. The insulation insert of claim 1, wherein said thin base
comprises a material selected from the group consisting of
Nomex.TM. 410 insulation, Kevlar.TM. insulation, and mica
insulation.
3. The insulation insert of claim 1, wherein said center section is
folded along a substantially horizontal line at a point midway
along said vertical cuts to form a head for facilitating insertion
of said insulation insert between said adjacent strands.
4. The insulation of claim 1, wherein said ear portions include
substantially horizontal cuts to facilitate folding of said ear
portions to form opposing wings.
5. The insulation insert of claim 1, wherein said ear portions
include substantially horizontal perforations to facilitate folding
of said ear portions to form opposing wings.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to insulation for preventing
strand-to-strand contact in high-voltage coils, and more
particularly to an insulation insert for preventing electrical
shorts and/or arcing in high-voltage stator coils.
BACKGROUND
[0002] Stator coils used in modern generators, such as the ones
illustrated in FIG. 1, are typically manufactured using a technique
referred to as Roebelling to improve the electrical performance of
the individual copper strands that make up a stator coil.
Roebelling involves transpositioning of the individual copper
stands in a stator coil, as illustrated in FIG. 2, to vary the
radial position of each copper strand over the axial length of the
stator coil. Without such transpositioning, copper strands closer
the center of a generator would be subjected to higher magnetic
flux densities, and thus higher temperatures and loses, than those
located further from the center of the generator. By
transpositioning the copper strands, Roebelling helps insure that
each copper strand in a stator coil is exposed to comparable
magnetic flux and temperature conditions.
[0003] In order to transpose the copper strands in a stator coil,
one or more crimps or bends must be placed in each of the
individual copper strands. A number of techniques exist for forming
such crimps. One such technique, known as 3D-crimping, utilizes a
three-dimensional crimp configuration like the one illustrated in
FIGS. 3A and 3B.
[0004] FIGS. 3A and 3B illustrate two copper strands 32 that have
been crimped using the 3D-crimping technique. The crimped-copper
strands 32 include a number of individual crimps 34. These crimps
34 may be formed, for example, using a crimping fixture having a
crimping die and an actuator. Once crimped, the copper strands 32
are assembled to form a transposed stator coil as illustrated in
FIG. 3B.
[0005] In their assembled state, the copper strands 32 are packed
closely together. Therefore, adjacent copper strands may contact
each other or come into close proximity of each other. To prevent
electrical shorts and/or arcing between adjacent copper strands,
manufactures generally purchase and utilize copper strands that
have been pre-coated with one or more thin layers of insulation
coatings.
[0006] One problem with this appoach is that the insulation
coatings are frequently damaged during the crimping process. If an
insulation coating on a copper stand is damaged, the bare copper of
the copper strands may be exposed, which may lead to electrical
shorts and/or arcing between adjacent copper strands. The problem
is made worse in 3D-crimp configurations because, as illustrated in
FIGS. 3A and 3B, the crimps in one copper strand tend to line up
with the crimps in an adjacent copper strand. Thus, electrical
contact and/or arcing between adjacent strands is even more
likely.
[0007] In an effort to overcome the problem described above,
manufacturers often add an additional durable-varnish-insulation
coating to the copper strands before assembly and crimping. This
durable-varnish-insulation coating tends to withstand the crimping
process. However, it also adds significant cost to the end
product.
SUMMARY OF THE INVENTION
[0008] With the above in mind, an insulation insert consistent with
the present invention is described that effectively prevents
electrical shorts and/or arcing between adjacent copper stands, but
significantly reduces the costs associated with conventional
techniques.
[0009] An insulation insert consistent with the present invention
is provided for preventing electrical shorts and/or arcing between
adjacent strands in a stator coil. The insulation insert includes a
thin base of substantially uniform cross section and a lead-in nose
formed in the thin base for guiding the insulation insert into a
position between adjacent strands. The insulation insert includes
two substantially vertical cuts in the base above the lead-in nose,
which delineate a center section flanked by two ear portions. The
center section may be formed into a head by horizontally folding
the center section at a point midway along the vertical cuts. The
insulation insert may also include a substantially horizontal cut
in each of said ear portions to facilitate bending of said ear
portions in opposite directions to form opposing wings in said
insulation insert.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 illustrates stator coils in a conventional generator
stator.
[0011] FIG. 2 illustrates a conventional Roebelled stator coil.
[0012] FIGS. 3A and 3B illustrate copper strands formed into a
3D-crimp configuration.
[0013] FIGS. 4A and 4B illustrate an insulation insert consistent
with an exemplary embodiment of the present invention.
[0014] FIG. 5 illustrates a perspective view of the insert of FIGS.
4A and 4B.
[0015] FIG. 6 illustrates the insulation insert of FIG. 5 after
being inserted between copper strands in a 3D-crimp
configuration.
DETAILED DESCRIPTION
The Insulation Insert
[0016] FIGS. 4A and 4B illustrate an exemplary embodiment of an
insulation insert 40 consistent with the present invention. The
insulation insert has a thin base 42 of substantially uniform cross
section. The base 42 may be formed, for example, from a thin sheet
of insulation material that is sufficiently flexible to be bent and
folded without fracturing. The material from which the base 42 is
formed should be capable of withstanding temperatures up to about
155.degree. C. The material should have good insulation
characteristics that enable it to withstand voltages up to about
1000 VAC (volts alternating current). The material should also be
sufficiently durable to withstand compression and tearing forces
that arise during the assembly and use of the stator coil.
[0017] In the exemplary embodiment, the base 42 is formed from a
sheet of Nomex.TM. 410 insulation, which is available from DuPont
Corporation, Advanced Fibers Systems, 5401 Jefferson Davis Highway,
Richmond, Va. 23234. However, one skilled in the art will
appreciate that the base 42 could be formed from any material with
the characteristics discussed above. Additional examples of
suitable materials include Kevlar.TM. insulation, which is also
available from DuPont Corporation, Advanced Fibers Systems, 5401
Jefferson Davis Highway, Richmond, Va. 23234, and mica
insulation.
[0018] As illustrated in FIG. 4A, the lower end of the insulation
insert 40 includes a lead-in nose 43, which acts as a guide to help
position the insulation insert 40 into position between adjacent
copper stands during assembly of a stator coil. Above the lead-in
nose 43 is a center section 44, which is formed from a portion of
the base 42 that is located between two substantially vertical cuts
45 in the base 42. Above the lead-in nose 43, on both sides of the
center section 44, are ear portions 46. Each ear portion 46 may
include a substantially horizontal cut 47 to facilitate
horizontally bending the ear portions 46 at a consistent
location.
[0019] The shape described above may be formed in the base 42 of
the insulation insert 40, for example, by manually cutting the base
42 or, more preferably, by cutting the base 42 with a cutting die
in an automated cutting fixture. Once the shape has been formed in
the base 42, the insulation is folded to form the folded insulation
insert illustrated in FIG. 5. The folded insulation insert 50
includes two opposing wings 52 that are formed in the two ear
portions 46 by folding the ear portions 46 in opposite directions
along a horizontal line corresponding to cuts, perforations, or
creases 47. When the ear portions 46 are folded, a head 54 is also
formed in the center section 44. Because of its position relative
to the lead-in nose 43, the head 54 serves as an excellent handle
or grip for use by a person inserting the insulation insert 40 into
a stator coil. The resulting folded insulation insert is ready for
assembly into a stator coil.
Assembly of the Insulation Insert
[0020] Referring now to FIG. 6, a method of assembling the
insulation insert into a stator coil will now be described. After
being folded as shown in FIG. 5, the folded insulation insert is to
be inserted between adjacent copper strands in a stator coil. This
insertion is generally accomplished by a person, such a shop
assembly worker.
[0021] The assembly worker begins installation of the folded
insulation insert by grasping the folded insulation insert between
his or her fingers at the head of the folded insulation insert. The
assembly worker then inserts the lead-in nose of the folded
insulation insert into the gap 62 in the stator coil and guides the
wings of the folded insulation insert into position between
adjacent copper strands, as illustrated in FIG. 6.
[0022] The exemplary embodiment described above is only one of many
possible embodiments consistent with the present invention. Thus,
the scope of the present invention should be determined with
reference to the appended claims and their legal equivalents,
rather than the specific example given.
* * * * *