U.S. patent number 3,617,966 [Application Number 04/814,733] was granted by the patent office on 1971-11-02 for core and coil assembly.
Invention is credited to Vaughan I. C. Marks, Anthony B. Trench.
United States Patent |
3,617,966 |
Trench , et al. |
November 2, 1971 |
CORE AND COIL ASSEMBLY
Abstract
A shell core transformer having a core and coil assembly located
in a casing with each coil being a separate element having a
plurality of windings of conductor encapsulated in a potting
compound. The coils are assembled in side-by-side relation and
embraced by a magnetizable material preferably in the form of
ribbon bands spirally wound around two or all four legs of the
rectangularly shaped coils. Posts are formed integral with the
encapsulant which serve as terminals and mounting members
supporting the core and coil assembly within the casing. Each coil
has a semiconductive film on the surface of the encapsulant. To
facilitate dissipating heat, heat sinks are provided consisting of
flat plates or fins having a portion disposed between adjacent
faces of the coils and a further portion projecting radially
outward therefrom and in contact with the casing. The casing also
is provided, in some instances, with fins. There is also a method
of forming a coil which includes winding a plurality of turns onto
a disc having a groove in one face thereof for receiving the
conductor and subsequently assembling further members to enclose
the wound coil in a chamber for receiving an encapsulant.
Inventors: |
Trench; Anthony B. (Thornhill,
CA), Marks; Vaughan I. C. (Scarborough,
CA) |
Family
ID: |
4084176 |
Appl.
No.: |
04/814,733 |
Filed: |
April 9, 1969 |
Foreign Application Priority Data
Current U.S.
Class: |
336/61; 336/92;
336/107; 336/84R; 336/96; 336/205 |
Current CPC
Class: |
H01F
27/40 (20130101); H01F 27/306 (20130101); H01F
41/122 (20130101); H01F 27/327 (20130101); H01F
41/127 (20130101); H01F 27/22 (20130101); H01F
30/10 (20130101) |
Current International
Class: |
H01F
30/06 (20060101); H01F 27/30 (20060101); H01F
27/00 (20060101); H01F 27/40 (20060101); H01F
30/10 (20060101); H01F 27/32 (20060101); H01F
41/12 (20060101); H01F 27/22 (20060101); H01F
27/08 (20060101); H01f 027/06 () |
Field of
Search: |
;336/61,92,84,96,205,105,107 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kozma; Thomas J.
Claims
We claim:
1. Inductive device including
a core and coil assembly comprising at least two closed loop coil
elements disposed with exterior closed-loop surfaces in
side-by-side contiguous relationship, each of such coil elements
comprising a plurality of electrically insulated turns in an
integral encapsulation and at least one body of magnetizable
material embracing in common a selected portion of the side-by-side
coils and,
casing means enclosing the core and coil assembly,
the coil encapsulation including integral projection means
extending from the coil elements to the casing means so as to
support the coil elements within the casing means.
2. The structure of claim 1 further including a semiconductive film
covering the external surface of at least one of the integral
encapsulations.
3. The structure of claim 1 including at least one heat conductive
member having a portion interposed between the contiguous
coils.
4. The structure of claim 3 wherein the heat conductive member is
extended to engage the casing.
5. The inductive device of claim 1 in which the plurality of
electrical turns of an electrical coil terminate in a bushing which
is unitary with the encapsulation.
6. A coil assembly for use in an encased inductive device
comprising a casing and a plurality of electrical turns in an
integral encapsulant including post means integrally formed of such
encapsulant and supporting the integral encapsulant in the
casing.
7. The structure of claim 6 in which the post means include
bushings secured thereto and which project outwardly from the
casing.
Description
The present invention relates to an insulated coil encapsulated in
a potting compound, to an encapsulated coil having a metallized
coating on the surface thereof, to a transformer consisting of a
plurality of individual coils disposed side-by-side and each of
which consists of a plurality of turns of conductor encapsulated in
a potting compound, and to a transformer wherein at least one of
the coils is covered by a metallized coating on the surface
thereof.
It is an object of the present invention to provide a coil which
may be used along with one or more similar coils to form an
induction device.
A further object of the present invention is to provide a
transformer of individual discrete coil elements which may be
readily removed and replaced.
A still further object of the present invention is to provide a
method of making a transformer whereby transformers of various
capacities may be manufactured from appropriate selection of
standard coil assemblies.
In accordance with one aspect of the present invention, there is
provided a coil for use in an induction device comprising a
plurality of turns of conductor encapsulated in a potting compound
and a metallized film coating on the external surface of the
encapsulant.
In accordance with a further aspect of the present invention, there
is provided a coil for a transformer comprising at least two coil
elements disposed side-by-side adjacent one another and each coil
element comprising a plurality of turns of conductor encapsulated
in a potting compound and having a metallized film on the external
surface thereof.
In accordance with a further aspect of the present invention, there
is provided a transformer comprising a plurality of individual
discrete coils disposed side-by-side in close adjacent relation and
at least one body of magnetizable material embracing a selected
portion of the assembled coils, said coils each consisting of a
plurality of turns of conductor encapsulated in a potting
compound.
The invention is illustrated, by way of example, in the
accompanying drawings wherein:
FIG. 1 is a partial sectional, top plan view of a transformer
constructed in accordance with the present invention;
FIG. 2 is a cross-sectional view taken substantially along the line
2--2 of FIG. 1;
FIG. 3 is a partial section, oblique view of a portion of a
transformer illustrating a modified casing;
FIG. 4 is a cross-sectional view of the casing illustrated in FIG.
3, taken substantially along line 4-4;
FIG. 5 is an elevational view of a portion of a core and coil
assembly for an induction device;
FIG. 6 is a section taken along section 6--6 of FIG. 5;
FIG. 7 is a sectional view taken along section 7--7 of FIG. 6;
FIG. 8 is a side elevational view of the assembly illustrated in
FIG. 5;
FIG. 9 is a section similar to FIG. 6;
FIG. 10 is a top plan view of a portion of one terminal and bushing
for the coil assembly;
FIG. 11 is a partial cross-sectional view of one terminal and
bushing for the coil assembly;
FIG. 12 is an oblique view, in partial section, of a form for use
in making a coil and encapsulating the same;
FIG. 13 is a diagrammatic illustration of one method of making a
coil; and
FIG. 14 is a diagrammatic illustration of apparatus for
encapsulating a coil.
Referring now in detail to the drawings, there is illustrated in
FIGS. 1 and 2 a transformer 10 consisting of a casing 20 enclosing
a core and coil assembly 50 and a plurality of heat sinks 70 which
engage the core and coil assembly and the casing.
The casing 20 consists of respective front and rear panels 21 and
22 each appropriately formed to provide a side wall and a portion
of an end wall. Each panel includes, at opposed marginal edges, an
outwardly directed flange 23 substantially parallel to and offset
from the main portion of the panel. A pair of flanges 23 on panel
21 are attached to the correspondingly oriented flanges 23 on the
panel 22 by means of bolts, welding or the like and thereby provide
a space between the side faces to receive the core and coil
assembly. A cover member 24 overlies the panel members 21 and 22
except for the outwardly directed flanges 23 and, if desired, a
downwardly turned lip may overlap a selected upper portion of the
side walls. The core and coil assembly 50 may be suspended from the
cover 24. Alternatively, the core and coil assembly may be
supported upon a bottom wall 25 secured to the casing panel members
21 and 22 as, for example, by welding, riveting, or the like. The
cover member 24 and the bottom wall 25 have respective high-voltage
bushings 26 and low-voltage bushings 27 projecting therethrough and
arranged in a manner to be described in more detail
hereinafter.
In FIGS. 3 and 4, there is illustrated a transformer 10A consisting
of a modified casing 30 and a core and coil assembly 50. The casing
30 includes a generally oblong-shaped tank portion which is closed
at opposed ends by respective walls 32 and 33. The end wall 33 is
preferably detachably secured to the sidewalls (provided by the
tank and identified by reference numeral 34) and projects laterally
beyond such walls for the purpose which will become apparent
hereinafter. A plurality of cooling fins project outwardly from the
casing sidewall 34 and consist of a plurality of channel members
each having a plurality of fins 36 projecting outwardly from a web
member 37. The members, each consisting of a web 37 and fins 36,
may be extruded or rolled and are from a highly heat-conductive
material. The webs 37 are disposed in spaced relation with respect
to the casing sidewall 34 (see FIG. 4) and adjacent elements are
also disposed in spaced relation. The elements are secured to the
casing as, for example, by welding the upper and lower ends to the
side walls of the casing. Since the end wall 33 projects laterally
beyond the side wall 34 of the casing, the cooling fins may also be
secured thereto. Alternatively, the end wall 33 may terminate flush
with the sidewall of the casing in which event spacer elements may
be utilized to interconnect the webs 37 and the sidewall 34.
The casings 20 and 30 each preferably consist of an aluminum or an
aluminum alloy or any other material of highly heat-conductive
characteristics. Cooling fins may be provided on either of the
casings 20 or 30 and they may consist of separate elements, as
previously described, or alternatively be formed integral with the
side walls. A pair of bushing members 26 are secured to the top
wall and a pair of bushings 27 are secured to the bottom wall in
each of the transformers illustrated and provide connections to the
coils located within the casing.
The core and coil assembly 50 consists of a coil portion 51 and a
core portion 52. The core portion 52 consists of a ribbon of highly
magnetizable material spirally wound flatwise around each of the
legs of the generally rectangular-shaped coil 51. The magnetizable
material is preferably a silicon steel with grain orientation
parallel to the length of the ribbon well known and commonly used
in transformers. The coil portion 51 of the core and coil assembly
50 consists of a primary winding 53 sandwiched between a pair of
secondary windings 54. Each of the primary and secondary coils
consists of a plurality of turns of conductor 55 encapsulated in a
potting compound 56 of preferably a high-temperature resistant
epoxy resin or some other potting compound, for example, phenolic
resins.
The potting compound may be a resin such as an epoxy, polyester or
silicone type either filled or unfilled, or any other well-known
types selected to provide suitable characteristics such as
temperature of operation and thereby class the transformer as to
operation. A high-temperature potting compound minimizes heat
sinking and an epoxy found suitable in No. 2258 Epoxy of Union
Carbide with CIBA's No. 972 hardener. Anhydride epoxy systems are
deemed suitable. Numerous proposals have been made concerning
various suitable encapsulants and in this regard, attention is
directed to Canadian Pat. Nos. 761,601 and 734,998 issued,
respectively, June 20, 1967 and May 24, 1966.
The encapsulant 56 has a smooth external surface 57 covered with a
thin semiconductive coating 58 of, for example, metal. The coating
58, for example, may be a resin filled with carbon black and/or
metal powder, or it may be a metal surface. The resin-filled
material may be applied by painting, spraying or the like, or the
metal may be applied as, for example, by metal flame spray. It is
most important that the surface 57 be extremely smooth and the
conductivity low enough so as not to provide a short circuit turn
for the coils.
The primary and secondary coils may be rectangular in cross
section, as illustrated in FIG. 6, or alternatively, only the
primary winding 53 may be rectangular in cross section, as
illustrated in FIG. 9, having a pair of opposed flat faces 59 and
60 disposed adjacent a flat face 61 of respective ones of the pair
of secondary coils 54. The remaining external surfaces of the coils
53 and 54 are such that the assembled coils define a substantially
circular outline. The coil portion 51 may consist of two or more
coils assembled in side-by-side relation although only three coils
have been illustrated in the drawings.
Each coil element, that is, the primary 53 and secondaries 54 are
physically in the form of closed loops as illustrated in FIG. 5.
Each coil element further includes a pair of posts 62 projecting
outwardly therefrom and in selected spaced relationship with
respect to one another. The posts 62 are formed from the
encapsulant and include a ferrule 63 (see FIG. 11) embedded
therein. The ferrule 63 serves to connect a terminal 64 to the
terminal end of the conductor 55. The ferrule 63 has a bore 65
extending inwardly from one end thereof receiving an end portion of
the conductor 55 and may be crimped or otherwise deformed to
clampingly engage the conductor. Alternatively or additionally, a
set screw may be used which is threaded into the ferrule and
projects into the bore 65 for engagement with the conductor. The
opposite end of the ferrule has a threaded bore 66 threadingly to
receive a terminal post 64. The ferrule 63 and conductor 55 may be
the same material or alternatively, dissimilar materials. For
example, conductor 55 may be aluminum and the ferrule 63 may be
aluminum or copper or brass. The ferrule and conductor are embedded
in the encapsulant 56 and, accordingly, interaction of dissimilar
metals is minimized because of being unexposed to the
atmosphere.
The posts 62 each have a tapered conical recess 67 in the end
thereof for receiving a correspondingly shaped portion of a bushing
26 (see FIG. 2 where there are illustrated bushings 26 and 27).
Each of the bushings 26 and 27 have a tapered end portion 68 which
projects into the conical recess 67 and has an enlarged outer end
portion 69 which overlies the remaining portion of the post 62. The
bushings 26 and 27 may be ceramic, epoxy resins, phenolic resins or
the like and have a central bore for receiving the terminal post
64. The bushing 26 is held in assembled relation by a lock nut N1
threaded onto the terminal 64 and a further nut N2 may be provided
for connecting conductors to the terminal. When assembled, the
bushings 26 and 27 have the sloped tapered ends 68 thereof in
pressural engagement with the sloped sidewalls of the recess 67
preventing entry of foreign matter into the connection of the
terminal post to the ferrule. The connectors accordingly are
projected from the elements and, if desired, suitable sealing
materials may be utilized between the bushing 26 and the terminal
post to completely separate the connection of terminal 64 to the
ferrule 63 from air and thus avoid deterioration which might
otherwise be caused.
In the transformer illustrated in FIG. 2, the enlarged portion 69
of the bushing 26 engages the outer face of the casing top wall 24
and the opposite side of the wall 24 engages the pair of posts 62.
Similarly, the downwardly directed posts 62 of the coil assembly
engage the casing bottom wall 25 supporting the core and coil
assembly in the casing and the bushings 27 engage the lower face of
the bottom wall. The bushings 26 and 27 accordingly retain the core
and coil assembly in assembled relation with respect to the casing
which surrounds the core and coil assembly. In the arrangement
illustrated in FIG. 2, bushings 26 with the terminals thereon
project upwardly above the casing and it will be noted that the
casing sidewalls project downwardly below the bottom bushings 27
and the terminals associated therewith. The lower terminals,
accordingly, are protected from atmosphere and a further cover
plate may be secured to the casing providing an enclosed area for
the lower terminals.
The coil portion of the transformer is illustrated in FIGS. 6 to 9
inclusive and, as previously mentioned, there is a primary coil
located intermediate a pair of secondary coils. Each of the primary
and secondary coils are discrete separate elements consisting of
conductors encapsulated in a potting compound having a smooth outer
surface which preferably is covered with a semiconductive coating.
The secondaries need not be coated but it is preferable that at
least the primary or high voltage winding be coated. The coils 53
and 54 are disposed in side-by-side relation as illustrated in
close abutting relation, and the core for the transformer consists
of a ribbon of magnetizable material wound flatwise around each of
the four legs of the rectangularly shaped coils. The ribbon may be
wound tightly to hold the primary and secondary coils in an
assembled relation. Alternatively, the spirally wound ribbon
material may be replaced by flat sheet stock consisting of arranged
pairs of oppositely directed U-shaped elements suitably joined as
is commonly known in the transformer art (see, for example,
Canadian Pat. No. 521,487 issued Feb. 7, 1956). In a transformer of
this type arranged with discrete coil elements, one coil may be
readily replaced when burned out merely by removing the core
material and substituting an operative coil for the unserviceable
one.
In order to facilitate dissipating heat from the transformer
illustrated in FIGS. 1 and 2, heat sinks 70 are provided and
consist of highly heat-conductive metal fins directly engageable
with the transformer casing 20. The fins 70 may be welded to the
casing or clampingly engaged between the casing flanges 23, as
illustrated in FIG. 1. There is a pair of heat sinks 70 located at
each of the four corners of the rectangular core and coil assembly
in the transformer illustrated in FIG. 2. Each heat sink 70
includes a flat portion 71 disposed intermediate adjacent coils 53
and 54 with a portion 72 projecting inwardly of a core 52 wound on
one leg and a further portion 73 projecting inwardly of the core 52
located on a leg adjacent thereto. The portions 72 and 73 of the
heat sinks are effectively, arms extending at right angles to one
another and are clampingly engaged between the adjacently disposed
coils. Each heat sink 70 includes an angular portion 74 merging
into an outer end portion 75 located between the casing flanges 23.
The heat sinks 70 are preferably aluminum or an aluminum alloy or
some other highly heat-conductive material and serve to dissipate
heat from the core and coil assembly. The heat sinks further serve
the purpose of retaining the core and coil assembly in a selected
location relative to the casing.
Each of the coils 53 and 54 may be formed in a manner as
illustrated in FIGS. 12 to 14 inclusive. It is important to have
the external surface of the encapsulant of each coil free from
depressions, i.e. a relatively smooth surface and in order to
accomplish this, the coil unit is preferably formed in a mold.
Referring to FIG. 12, there is illustrated a coil 54 in a forming
mold 80. The mold 80 consists of a two-part backing member 81 and a
cover member 82 held in assembled relation by a plurality of
U-shaped clips or clamp members 83. The member 81 may be a unitary
member but in the preferred form, consists of a pair of members 84
and 85 which may be readily assembled and disassembled. The member
84 is generally T-shaped in cross section having a peripheral
concave groove 86 in one face thereof surrounding a generally flat
planar portion 87. The member 81 terminates in an outer peripheral
edge 88 tapered inwardly in a direction outwardly from the mold.
The purpose of this will become apparent hereinafter.
The member 85 is effectively annular in shape, having a
substantially flat bearing surface 89 engageable with an adjacent
flat face of the cover member 82. The member 85 has a peripheral
grooved or recessed portion 90 contiguous with the groove 86 in the
member 84. The grooved portion 90 merges into a further portion 91
which is complementary to the shape of the peripheral surface or
edge 88 of the member 81. The remaining portion of the member 85
may be of any configuration and, for example, may include a
peripheral flange 92 for the purpose of facilitating
interconnecting the members 81 and 82. The members 84 and 85 may be
readily assembled and disassembled merely by fitting the member 84
into the member 85, positioning being facilitated by complementary
shaped abutting surfaces 88 and 91 on the respective members. In
assembled relation, the surface of the groove 86 is contiguous, as
previously mentioned, with the surface of the groove 90 so as to
provide a smooth molding surface for the coil 54 located in the
molding chamber. The clips 83 may be substantially U-shaped, in
cross section, members retained by frictional engagement on the
cover 82 and flange 92 thereby retaining the members 81 and 82 in
assembled relation. Adjustable clips may be utilized or, if
desired, the cover 82 may be fastened by means of studs or the like
to the member 85 and/or 84.
The member 84, as previously mentioned, is readily removable from
the annular outer member 85 and the purpose of such arrangement is
so that the member 84 may be utilized as a winding form or mandril.
In this regard, the coil consists of a plurality of turns of
conductor 55 wound into a closed loop. Referring to FIG. 13, the
conductor 55 may consist of a conductor 700 drawn off a spool 701
pivotally mounted on a shaft 702 by a winding unit 703. The
conductor may be either a bare wire or an insulated wire and in
either event, an adhesive material 705 is applied to at least
selected portions for holding a spacer on the conductor, the
purpose of which will become apparent hereinafter. The adhesive is
preferably a silicone type and may be applied by rollers, brushes
or the like applicators, and either as a continuous film or
alternatively, in strips in which case they would normally extend
longitudinally along the conductor. In FIG. 13, the conductor 700
is illustrated as being drawn through a bath of adhesive material
705 contained within a tank 706. Alternatively, the conductor may
be insulated by a coating which may be suitably treated as, for
example, by the application of heat, solvents or the like to
provide a tacky surface in which case the insulation of the
conductor performs the dual function of being an insulator and
selectively an adhesive surface. The tacky surface or adhesive is
for the purpose of retaining a spacer element on the conductor.
Downstream from the adhesive-applying station, the conductor with
the adhesive thereon is indicated generally by the reference
numeral 715. Filament glass 710 in rope form is drawn off a bobbin
711 mounted on a shaft 712 to rotate about a substantially
horizontal axis. The rope form of filament glass is drawn off the
bobbin 711 by a winding arm 713 mounted to rotate about the
longitudinal axis of the conductor. The winding arm consists of a
member directed outwardly from the axis of the conductor and has at
least one arm adjacent the free end thereof extending parallel to
the length of the conductor. The filament glass is drawn off the
bobbin through a combing element 714 to form the strands into a
flat ribbon and such flat ribbon is spirally wound around the
conductor by the winding arm as the wire is moved horizontally to
the right as viewed in FIG. 13. The adhesive-covered conductor 715,
with the filament glass thereon, is wound onto a winding mandril,
preferably under tension so as to place the adjacent windings of
the coil in tight intimate contact. The winding mandril rotates
about the axis of a driven shaft 720 to which is secured a plate
721. The plate 721 includes a plurality of apertures 722 through
which studs may pass and be threaded into the member 84 (FIG. 12)
with the face 87 thereof in abutting relation with the plate 721.
The latter plate may extend laterally beyond the member 84 a
selected amount and together provide effectively a reel for winding
a plurality of turns of the conductor into a closed loop coil.
After the conductor has been wound onto the member 84, which
effectively is a winding mandrel, the latter is removed from the
plate 721 and inserted into the member 85 whereafter the cover 82
is attached by the clips 83. The entire assembly, generally
designated in FIG. 12 by reference numeral 80, is then placed in a
vacuum chamber 1200 and the space confining the coil 54 is
connected by a conduit 1101 to a supply of potting compound 1103.
The potting compound, or encapsulant as it may be referred to, may
be a resin such as an epoxy, silicone, polyesters, e.g. Vibrin or
Permasil or the like, either filled or unfilled, or any type
selected to provide suitable range of temperature operation and
thereby class the transformer as to operation.
A bleeder conduit 1102 is connected to the chamber containing the
coil 54 and a control valve 1104 located in the bleeder line 1102
may be selectively opened and closed to control filling the chamber
containing the coil 54 with the potting compound 1103. The vacuum
chamber 1200 is evacuated to selected negative pressures by a
vacuum pump generally designated 1300. After the chamber containing
the coil has been completely filled with the potting compound, the
the potting compound is then cured and when using a thermal setting
resin as the potting compound, the coil may be energized to provide
the necessary heat to accomplish the curing. The coil assembly 54
in the mold 80 is then removed from the vacuum chamber and the coil
54 removed from the mold. The encapsulated coil is then completely
covered with a metallized surface or semiconductor. The coating,
for example, may consist of a resin filled with carbon black and
may be applied by spraying or, alternatively, it may consist of a
resin filled with a metal powder and likewise applied by spraying.
The coating alternatively may be metal applied by flame spraying so
as to deposit discrete particles of metal in a continuous
layer.
The cross-sectional shape of the encapsulant is determined by the
shape of the chamber in the mold 80. The coils are appropriately
shaped as, for example, that illustrated in FIG. 9 where three coil
assemblies, arranged side-by-side in close abutting relation,
present a substantially circular outline or alternatively,
substantially square as shown in FIG. 7. Coils assembled
side-by-side are then embraced at selected areas by core material
52 which, as previously mentioned, is a ribbon of silicon steel or
the like spirally wound flatwise around the assembled coils to
embrace the same.
With regards to disposing the coil assembly side-by-side, discrete
coil elements, that is, individual primaries and secondaries as
illustrated in FIG. 8, permit stacking a series of coil elements to
vary the size of the transformer. For example, two primary coils
may be located intermediate two secondaries, or alternatively,
primary and secondary coils may be arranged in alternate relation
and the entire assembly embraced by core material. In stacking, it
is preferable to maintain all of the coils physically symmetrical
and when stacked, the coils may be suitably interconnected
electrically, for example, all of the primary coils may be
connected in parallel and likewise all of the secondary coils may
be connected in parallel.
From the foregoing, it is seen that the metallized film which
completely covers each coil segment separates one winding from the
other. The metallized surface provides a transformer which is
substantially free from corona and helps to increase the basic
insulation level of the core and coil assembly. The use of an
encapsulant which is molded to a relatively smooth outer surface
cuts down or eliminates spiking, that is, surfaces which project
inwardly toward the coil and thereby reduces flash inducing edges
or points.
* * * * *