Note: Descriptions are shown in the official language in which they were submitted.
The invention relates to an alternating
current electrical transformer and more particularly to
a toroidal electrical transformer having a core wound
from one or more continuous strips of core material and
high and low voltage windings, each wound in substantial
part from a continuous conductor.
Ideally, an electrical toroidal transfonmer
having a continuously-wound, annular or toroidal core
and continuous toroidal low voltage and high voltage
~indings, with each winding or se~ment thereof being
wedge-shaped, would provide a transformer of nearly
optimum operating efficiency. The continuously wound
annular or toroidal transformer core of such a transfor-
mer would rl n;~; ze the effective magnetic path length
and the parasitic core losses. Furthermore, the
continuous toroidal electrical windings of such a
transformer with each winding being wedge-shaped, would
optimize the use of an annular or toroidal transformer
core by providing the smallest effective electrical
coil path length. Previously known transformer designs
have not, however, accomplished all of these objectives.
Various proposals have been made to provide a
transformex having a wound, annular core and toroidal
windings surrounding the core. For example, the patent
to Bastis, et al, U~S. Patent No. 3,430,48~, issued
September 5, 1967, discloses an air-cooled toroidal
transfonmer in which the core is severed into two
segments so that khe windings can be positioned onto
the core segments before they are joined. A similar
technique is shown in the patent to Conner, et al,
IJ.S. Patent No. 3,996,543, issued December 7, 1976. A
segmented core is used in Conner, et ~l, b cause of the~
3~ 2~
problems associated with winding the primary and
secondary windings on a continuous toroidal core using
conventional winding machines.
Efforts have been made to wind a more-or-less
continuous annular or toroidal core into preformed,
generally-rectangular primary and secondary windings.
Examples of such efforts are shown in the patents to
Humphreys, U.S. Patent No. 2,191,393, issued February
2, 1940; Vance, U.S. Patent No. 2,249,~06, issued July
25, 1941; Gxanfield, U.S. Patent No. 2,160,588, issued
May 30, 1939; Boyajian, U.S. Patent No. 2,245,180,
issued June 10, 1941; Brand, U.S. P tent No. 2,246,239,
issued June 17, 1941; Brand, U.S. Patent No. 2,246,240,
issued June 17, 1941; Camilli, UOS. Patent No. 2,248,606,
issued July 8, 1947; Driftmeyer, U.SO Patent No.
2,282,854, issued May 12, 1942; Steinmayer, U.S. Patent
No. 2,344,006, issued March 14, 1944; and Steinmayer,
U.S. Patent No. 2,401,984, issued June 11, 1946. The
aforementioned patents, however, illustrate that it was
not deemed feasible to wind such a continuous core into
continuous, preformed toroidal windings.
Finally, a process for heat treating a toroid
wound from an amorphous metal material is disclosed in
a patent issued to Becker et al, U.S. Patent No.
4,116,728, issued September 26, 1978; and a process for
dipping a pre-formed electrical coil in a liquid
insulation bath and curing the insulative coating in an
oven is disclosed in a patent issued to Schou, U.S~
Patent No. 2,061,388, issued November 17, 1936.
According to the present invention, a toroidal
electrical txansformer of near optimum efficiency
includes a wound magnetic core that is continuous at
least in substantial part and generally toroidal or
annular i~ configuration. The magnetic core is surroun-
ded by high an~ low voltage coils or windings that are
also continuous in subs~antial part and gen~rally
toroidal in configuration. Such high and low voltage
coils or windings form an arcuate elongated passage
extending therethrough in which the magnetic core is
disposed. Although the arcuate elongated passage
encompasses at least one-half of the circumferential
length of the ma~netic core, the advantages of the
present invention are best obtained if such arcuate
elongated passage encompasses 75 to 95 percent of said
circumferential length of the magnetic core.
The above structure and configuration is
preferably accomplished by preforming the high and low
voltage windings into two coreless and semi-toroidal or
arcuate transformer portions or sections, each constitu-
ting substantially one-half of the transformer. The
magnetic core material is then fed through a small
circumferentially-extending gap between adjacent ends
of such semi~toroidal portions or sections and continu-
ously wound in place into the generally toroidal orarcuate elongated passage formed in said portions or
sections. Such circumferentially-extending gap is
preferably sufficient in circumferential length, but
not longer than necessary, to allow the magnetic core
material to be fed therethrou~h and wound in place
within the arcuate elongated passage to form the
annular magnetic core.
In the preferred embodiment of the toroidal
transformer, the high voltage coil or winding is wound
into a number of wedge-shaped bundles or segments with
connecting loops of wire or conductor. Preferably in
order to achieve the advantages of the invention, such
wedge-shaped segments and connecting loops are wound
and formed from a pre-insula-ted wire or conductor that
is continuous over 30 to 50 percent of the total length
of the high voltage coil. At a minimum, according to
the invention, each wedge-shaped segment is wound and
formed from a continuous wire or conductor.
The low voltage coil or winding in the
preferred ~mbodiment is wound and fcrmed from conductor
stock in a singular or a multifilar arrangement wherein
each turn is wedge-shaped and may also be composed of
two parallel coils interleaved in a spiral or double
helix configuration as is explained in detail below.
Preferably in order to achieve the advantages of the
invention, such conductor is continuous over 30 to 50
percent of the total length of the low voltage coil for
at least each voltage winding thereof in a multi-voltage
arrangement. At a minimum, according to the invention,
such low voltage conductor is continuous over three or
more turns of the coil in each of the above~mentioned
transformer portions or sections for each voltage
winding thereof.
The preferred magnetic core is fed through a
gap between the ends of the high voltage and low
voltage windings and is wound in place into a generally
toroidal or annular opening which extends through the
high and low voltage coils to form an arcuate elongated
passaye therethrough. The core is preferably formed
and wound from a single continuous ribbon-like strip of
core material. Alternatively, however, the magnetic
core may be wound from a number of continuous strips of
core material in a parallel bifilar or parallel multifi-
lar arrangement. Also, in the construction of very
large toroidal transformers, a separate single strip or
a multifilar group of strips may be used to wind an
inner portion of the core diameter, with one or more
subseguent single strips or multifilar group of strips
serially connected thereto for forming increasing
diametric regions or portions of the wound core. In
this configuration, the subsequent, or serially-co~nected,
single strips or groups of strips may include different
types of core material, having different loss &haracter-
istics, at different diametric regions of the wound
core as is described in U.S. Patent No. 4,025,288,
~2~
issued to Lin et al, on May 27, 1980. In such serially
wound configurations, the magnetic core is considered
to be substantially continuous or continuous in substan
tial part.
The toroidal or arcuate configuration of the
high and low voltage coils in the preferred embodiment
is that of a torus generated by the revolution of a
generally trapezoidal shape about an external axis,
while the toroidal or annular configuration of the
preferred magnetic core is that generated by the
revolution of a generally rectangular shape about an
external axis with such core configuration being
substantially defined by the above mentioned arcuate
elongated passage through the high and low voltage
coils. As is explained below, however, such toroidal
configurations may alternatively be -those generated by
the toroidal revolution of any of a number of geometric
shapes, including, for example, circles, ovals, squares,
or even irr~gular shapes.
Since the core s-tructure in the present
invention is continuous, as described above, magnetic
flux losses due to gaps or breaks in the core material
are 1 nl ml zed. Since th~ structure of the primary and
secondary windings is continuous in substantial part,
as described above, electrical losses due to connections
in those windings are likewise ml ni 1 7.ed. Because the
high voltage and low voltage windings are toroidal in
configuration, with each winding segment being wedge-
shaped, optimum use is made of the wound-in toroidal or
annular transformer core. The ~i nl m; Y.ing of such
magnetic flux losses and electrical losses is especially
timely since energy conservation is presently a national
goal.
A toroidal electrical transformer according
to the invention is preferably constructed by preforming
the high voltage and low voltage coils or windings,
which are then assembled onto toroidal or annular
insulation ~tructure~ to form a coreles~ toroidal
winding and lnsulation s~ructure having a generally
annular or t~roidal-shaped central void or core forming
5 tunnel which forms an arcuate elongated passage there-
through. Thereafter, the core material is fed into the
preformed toroidal winding and insulation structure
through a relatively small, circumferentially-extending
gap between adjacent ends of the portions or sections
of such structure and wound in place t3 form the
finished transformer. Yarious novel techniques are
disclo~ed herein to accomplish these steps.
Of particular importance is the fact that the
core material of a toroidal transformer according to
the invention may be extremely ~hin. Recent advances
in core material technology have provided amorph~us
metals, an example of which is known by thetrade mark
METGLAS. Because such amorphous metals are fabricated
by solidifying the molten metal in a very short period
of time, such amorphous metals must be of an extremely
thin gauge as compared with core materials composed of
conventional grain oriented metals. Such thin-gauge
core materials are difficult, if not impractical, to
use with conventional core manufacturing t~chnigues.
The transformer manufacturing method of the present
invention, however, can efficiently accommodate such
thin-gauge amorphous metal core material~, ~hereby
further improving the efflciency and reducing the
parasitic losses of the transformer.
Other features and advantages of the invention
will become apparent in the description of the preferred
embodiments ~et forth below.
Exemplary embodiments o~ ~he present invention
are illustrated in the accompanying drawings, wherein:
Fi~ure 1 i~ a partially cut-away, partially
exploded, perspective view of a preferred toroidal
,,, ~
, .
~ q
electrical transformer according to the preset invention;
Figure 2 is a partially cut-away top view of
the toroidal electrical transformer of Figure l;
Figure 3 is a partial cross-sectional view of
the toroidal electrical transformer taken along line
3-3 of Figure 2;
Figure 4 is an exploded perspect.ive view of
one section of the preferred core insulation tube of
the present invention;
Figure 4A is a perspective view of an assembled
section of the core insulation tube of the present
invention and a spreading ~ool therefor;
Figure 5 is an exploded perspective view of
one section of the preferred high/low insulation
barrier of the present invention;
Figure 6 is a fragmented perspective view of
one of the insulation members of the preferred toroidal
electrical transformer, illustxating a preferred
cooling fluid ch~nnel structure;
Figure 7 is a schematic view illustrating the
preferred assembly of the major transformer components
prior to installation of the magnetic core;
Figure 8 is a block diagram, generally
illustxating the preferred method of manufacturing a
toroidal electrical transformer according to the
present invention;
Figure 9 is an overall view of a preferred
low voltage coil forming and winding apparatus used in
connection with the present inventioni
Figure 10 is a dPtail view of the low voltage
coil forming portion of the apparatus of Figure 9;
Figures 11 and 12 are detail views of the low
voltage coil forming roller assembly of the apparatus
of Figure 9, wherein:
Figure 11 illustrates the roller position
for forming the inner leg of the low voltage
coil; and
{~D,,~a
Figure 12 illustrates the roller position
for forming the outer leg of the low voltage
coil;
Figure 13 is an end view of the low voltage
coil forming portion of the apparatus of Figure 9,
illustrating various roller and mandrel positions
during the coil forming operation;
Figure 14 is a detail view illustrating a few
interleaved turns of two finished low voltage coil
lengths;
Figures 15 and 16 are two variations of the
method for applying insulation to the low voltage coil
assemblies, wherein:
Figure 15 illustrates an apparatus for
dipping the low voltage coil into a liquid
insulation material; and
Figure 16 illustrates an apparatus for
electrostatically applying a powdered insula-
tion material to the low voltage coil;
Figure 17 is an overall perspective view of
an apparatus for winding the high voltage coil and
forming a plurality of wedge-shaped segments from a
continuous wire;
Figure 18 is a partially cut-away detail view
of the winding and forming portion of the apparatus of
Figure 17, with the winding and forming dies in their
open position;
Figure 19 is a partially cut-away view of the
winding and forming portion of the apparatus of Figure
17, with the winding and forming dies in their closed
position;
Figure 20 is a top view of the winding and
formin~ portion of the apparatus of Figure 17, illustra-
ting the wire guide assembly therefor;
Figure 21 through 23 are top views of thewinding and forming portion of the apparatus of Figure
~ ~1 ~qD~3~
17, illustrating the coil segment pressiny operation,
wherein:
Figure 21 shows one of such segments
after winding and during pressing;
Figure 22 i~ similar to Figure 21, but
is partially cut-away to show the interlocking
structure for one of the split die portions;
and
Figure 23 shows one of such segments in
its compressed state during bonding of the
wire turns;
Figure 24 illustrates the insulation piercing
structure of the apparatus of Figure 17;
Figure 25 is a perspective view of an apparatus
for pre-winding the core material of the present
invention;
Figure 26 is a schematic representation of
the Anne~ling operation of the pre-wound core material
of Figure 25;
Figure 27 is a partially cut-away perspective
view of a core sleeve being installed in the core
insulation tube of the present invention;
Figure 28 is a fragmented view showing the
ends of the core sleeve of Figure 27 being joined;
Figure 28A illustrates an arrangement whereby
the use of the core sleeve of Figure 28 may be eliminated
for a core fabricated from sufficiently thick core
material;
Figure 29 is an overall perspective view of a
preferred cor~ wind-in apparatus of the present inven-
tion;
Figure 30 is a schematic view of the major
portions of the apparatus of Figure 29;
Figure 31 is fragmented detail view of the
winding belt position at the completion of ~he core
wind-in operation;
,a
Figure 32 is a side view of an alternate
apparatus for winding the low voltage coil of the
present invention;
Figure 33 is a top view of an al-ternate
apparatus for forming the wedge-shaped turns of the low
voltage coil;
Figure 34 is a side view of the apparatus of
Figure 33;
Figure 35 is a side view of an alternate
interleaving apparatus for two lengths of low voltage
coil;
Figure 36 is a partially fragmented view of a
few representative turns of an alternate low voltage
coil structure wound in a generally bifilar arrangement
wherein the low voltage coil is wound from a pre-
insulated conductor to form approximately wedge-shaped
turns of said coil;
Figure 37 illustrates a few turns of the low
voltage coil of Figure 36 as installed on a core
insulation tube of the invention;
Figure 38 illustrates an alternate core
sleeve of the present invention;
Figure 39 illustrates an alternate method for
winding in the core material, using the alternate core
sleeve of Figure 38;
Figure 40 is a top view of still another
alternate core wind-in apparatus according to the
present invention, and
Figure 41 is a side view of the apparatus of
Figure 40.
Figures 1 through 41 o~ the drawings depict
various preferred and alternate embodiments of the
present in~ention for purposes of illustration only.
One skilled in the art will readily recognize from the
following discussion that still other alternate embodiments
of the structures and methods illustra~ed herein may be
employed without departing from the principles of the
invention described herein. ~'
Figures 1 through 3 illustrate a preferred
toroidal electrical transformer 10 including a continu-
ously wound, toroidal or annular core 20 disposed
within a core insulation tube 30. A low voltage coil
or winding 40 surrounds the core insulation tube 30 and
is encased by a high/low insulation barrier 50, which
is in turn surrounded by a high voltage coil or winding
60.
The high voltage winding 60 is preferably
made up of two sections 61 and 62, each including a
plurality of winding bundle~ ox segments continuGusly
wound from a common wire and connected by loops of said
common wire, e.g., twenty 2 ~yO voltage segments in each
of said sections. At least the segments of the high
voltage winding 60 near the ends of the sections 61 and
62 are pre~erably separated by inserts 70, around which
said loops extend, for purposes of i n; ; zing impulse
stresses resul~ing from any non-linear voltage distribu
tion to which the high voltage winding may be subjected,
~uch as those encountered during high voltage impulses
caused, for example, by lightning. Such inserts 70 may
in some cases be required between all high voltage
winding segments as shown in ~he drawings, or more than
one insert may be required between each se~ment. The
inserts 70 are preferably composed of a synthetic
material, such as l'MYLAR"*or "KAPTON"*for example, and
are retained in place by thermo-formed cuffs 71 which
extend circumferentially under the high voltage winding
segments as ~hown in Figure 2. Similarl~, the preferred
low voltage wi n~; ng 40 is also made up of two ~ections
41 and 42, corresponding to the high voltage winding
sections 61 and 62. Such preferred low voltage coil
sections 41 and 42 may each include either a singular
winding conduc~or, bifilar or multifilar parallel
* Trade Mark
12
conductors in an interleaved configuration, one oE such
parallel conductors for each voltage winding, as is
explained in detail below. In the preferred embodiment,
as shown in the drawings, the high voltage winding
sections 61 and 62 and the low voltage winding sections
41 and 42 each extend circumferentially through an arc
of approximately 165 degrees on each side of the
transformer 10. Correspondingl~, the co.re insulation
tube 30 and the high~low insulation barrier 50 are each
formed in two-section pairs 31, 32 and 51, 52, respec-
tively, with each of the sections extending circumferen-
tially through an arc of approximately 165 degrees on
each of the two sides of the preferred transfsrmer 10.
Thus, the low voltage coil 40 is preferably disposed
within the high voltage coil 60, and the two coils
preferably encompass approximately 165 degrees of the
circumferential length of the toroidal or annular core
20.
The term "continuous" as used herein in connec-
tion with the high vo~tage winding or coil 60, and the
sections 61 and 62 thereof, includes a preferred
configuration wherein the wedge-shaped segments and the
connecting loops are wound and formed from a single
wire or conductor that is continuous over the length of
each of the high voltage coil sections 61 or 62, or in
other words, over substantially one-half of the toroidal
transformer 10. Such term "continuous" also refers to
various alternate configurations of the high voltage
coil 60, wherein at least each wedge-shaped segment is
wound from such a continuous wire or conductor.
With respect to the low voltage winding or
coil 40, and the sections 41 and 42 thereof, the term
"continuousl' includes the above-mentioned preferred
æingular, bifilar or multifilar arrangements, wherein
the conductor is continuous over the length of each of
the low voltage coil sections 41 or 42, or over the
length of each of the interleaved windings for each
13
section, as is described in detail below in connection
with Figuxe 14. Thus in sllch prPferred embodiment, the
low voltage coil is continuous over substantially
one half of the toroidal transformer 10. The term
"continuous" also includes any of several alternate low
voltage coil structures wherein at a minimum the low
voltage conductor, whether singular, multifilar, or
otherwise, and whether interleaved or not, is continuous
over at least three turns thereof.
The term "continuous", as used with reference
to the magnetic core 20, includes such core structures
wound from a single or multifilar group of ribbon-like
strips of continuous core material as well as a succes-
sive, serially-connected group of core material strips,
wound-in successively to form increasingly large
diametric regions of the core 20.
The terms "toroidal" or "annular" as used
herein in connection with the high and low voltage
coils 60 and 40, respectively, and in connection with
the magnetic core 20, refer to the configuration of a
torus generated by the revolutions of any of a nu~ber
of regular or irregular shapes about an external axis.
The various preferred and alternative structures and
configurations of the high and low voltage windings or
coils 60 and 40, respectively, and of the magnetic core
20 are described in detail below.
Figures 4 and 4A represent detail views of
the section 31 of a preferred core insulation tube 30.
Although the section 31 is shown in Figures 4 and 4A
for purposes of illustration, one skilled in the art
will appreciate that the section 32 is identical to the
section 31.
The core insulation tube section 31 includes
a pair of upper and lower half-se~tions 33 which are
preferably molded from a synthetic material and are
identical in configuration but inverted with respect to
each other. Thus the four identical half-sections
14
reguired to form the core insulation tube 30 may all be
molded from a single mold. The half sections 33 are
preferably molded from a high-strength, glass-filled
synthetic material, such as polyester, nylon, or epoxy,
for example.
The half-sections 33 o the core insulation
tl~e 30 each include inner and outer walls 34 and 35,
respectively, e~tending in an axial direction from a
base portion 36. One or more interlocking protrusions
preferably in the form of teeth or tabs 37 protrude
axially from the inner wall 34, with a corresponding
number of circumferential spaces 38 between adjacent
teeth 37. The teeth or protrusions 37 and the spaces
38 are oriented such that when the id~ntical upper and
lower half-sections 33 are joined together to form the
section 31, as shown in Figure 4A, the teeth 37 intermesh
to prevent relative circumferential displacement of the
inner walls 34 of the upper and lower half-sections 33.
The teeth 37 have vertical edges oriented along radius
lines passing through the center of the transformer 10,
thereby providing for a flush, interference-free
engagement of the upper and lower teeth 37.
The axial length or height of each inner wall
34 and the teeth 37 is preferably greater than tha-t of
the outer leg 35, thereby forming an axial gap 39
around the periphery of the core insulation tube 30 as
is illustrated in Figure 4A. The purpose of the axial
gap 39 will be described in detail below in connection
with the core wind-in process illustrated in ~igures 29
through 31. The teeth 37 are preferably of an axial
length or height such that the sections 31 and 32 may
be axially collapsed to a hPight allowing easy insertion
into the toroidal opening or arcuate elongated passaye
formed by the low volt~ge coil sections 41 and 4~, as
will be described below. After such insertion, the
half-sections 33 may be spread by means o a suitable
spreading device such as ~he wedge-shaped spreader tool
92 shown in Figure 4A, for example. The spreading of
the half-sections 33 after insertion into the low
voltage coil section 41 allows the core insulation
section 31 to substantially conform to the inside of
the low voltage coil section 41 thus providing sufficient
space in the arcuate elongated passage for winding in
the core 20, as will be described later in this discus-
sion. Such spread position may be maintained by
providing detents formed on the teeth 37, or by other
means known to those skilled in the art.
Figure 5 shows the preferred section 51 of
the high/low insulation barrier~50, for purposes of
illustration. One skilled in the art will readily
understand that section 52 is identical to section 51.
The section 51 of the high/low insulation barrier 50
includes a pair of upper and lower half-sections 53 and
54, respectively, which like the half-sections 33 of
the core insulation tube section 31, may be molded from
a suitable reinforced synthetic material. A set of
inner and outer walls, 55 and 56, respectively, extend
axially from each of the base portions 57 and in the
preferred embodiment include opposite-oriented, radially
recessed end portions 58 and 59, respectively.
When the upper and lower half-sections 53 and
54 are axially joined together over the low voltage
coil 41, the respective preferred r~cessed end portions
58 and 59 of the inner and outer walls 55 and the
overlap in a general flush, mating relationship,
thereby providing insulation protection to withstand
electrical stresses occurring during high impulse
voltages associated with the high voltage coil 60. The
half-sections 53 and 54 must then be compressed axially,
thereby allowing ~or assembly of the high voltage coil
segments over the low voltage windings and the core
insulation barrier subassembly.
The particular cross-sectional shapes of the
generally toroidal or annular shaped core insulation
16
tube 30 and high/low insulation barrier 50 correspond to
the the desired cross-sectional shapes of the toroidal
or annular magnetic core 20 and high and low voltage
coils 60 and 40, respectively.
Figure 6 illustrates a broken away portion of
the high/low insulation barrier 50 including a preferred
but not necessary internal wall structure of the
present invention. The wall structure shown in Figure
6 and the related discussion herein are egually applic-
able to the core insulation tube 30.
Transformers of the type disclosed herein
frequently employ oil or other fluids, either liquid or
yaseous, for cooling their components during operation.
Such cooling fluid is typically an electrical grade
insulation oil. The high/low insulation barrier 50 in
Figure 6 includes a number of ridges 95 molded into the
internal side of the outer wal~ 56. The ridges 95 may
be inclined, spiral, involute, or the like, and form a
plurality of cooling fluid branch channels 96 therebe-
tween. The ridges 95 are interrupted short of the base
portions 57 and thereby form common header c~nnels 97
at the upper and lower peripheries of the outer wall
56. The branch channels 96 and the header channels 97
act as conduits for the convective flow of the cooling
liquid. The configuration of the xidges 95, being
inclined or spiral, etc., imparts a convectively
induced circulating motion to the cooling fluid flow
throughout the inside of the high/low insulation
barrier 50, as illustrated by the flow arrows in Figure
6. Such circulating motion promotes both cooling of
the components and uniform temperature distribution
throughout the transformer.
As i~ shown schematically in Figure 7, the
corresponding sections of the above-described components
are assembled into two preferred transformer half-por-
tions or sections 11 and 12, each extending circumferen
tially through an arc of approximately 165 degrees as
17
described above. The pr~ferred transformer portions ll
and 12, when combined, thus form a substantial portion
of a torus made up of two symmetrical halves with a
circumferential space of approximately 15 degrees
therebetween on each side. One of the primary purposes
for the above-described constructicn is to form an
arcuate elongated passage for allowing the core 20 to
be continuously wound in place in a toroidal or annular
configuration as is illustrated in Figures 1 through 3
and described in detail below. Once the core wind-in
operation is completed, the transformer assembly is
retained in its proper configuration by means of
supporting blocks 80 (see Figure 13, which maintain an
equal spacing between the half-portions 11 and 12 on
both sides of the transformer 10. The transformer
assembly is then installed in a suitable cont~' -nt
structure such as the tank or housing 85 shown in
Figure 1. Various additional features will become
readily apparent from the following description of the
methods employed in the manufacture of a toroidal
electrical transformer and the components thereof
according to the present invention.
Figure 8 illustrates, in block diagram form,
an ov~rview of the major operations involved in the
preferred method of manufacturing the toroidal electrical
transformer 10. Although for purposes of illustration,
the reference numerals in Figure 8 and in the following
discussion relate to the transformer half-portion 11,
the structure and production methods of the transformer
half-portion 12 are preferably identical to those of
the transformer half-portion 11.
The low voltaye coil section 41 is prefera~ly
wound from continuous conductor stock with each turn
being formed into a wedge shape to provide the toroidal
or annular configuration. Preferably, each turn is
formed with a generally constant cross-sectional area
throughout. The formed coil is then coated with
18
insulation, and the in6ulation is cured to finish the
coil section 41. The above low voltage coil producing
steps are de~cribed in detail below in connection with
Figures 9 through 16 of the drawings.
The low voltage coil 41 is then positioned
onto the exterior of the pre-assembled core insulation
barrier 31 and encased within the upper and lower
halves of the high/low insulation barrier section 51 as
is shown schematically in Figure 7. The sub-assembly
is then ready for addition of the high voltage coil
section 61.
The high voltage coil section 61 is preferably
wound from a continuous wire and formed into a number
of wedge-shaped bundle~ or segments. The segments are
then compressed, and the individual turns of wire in
each segment are bonded together to form a tightly
wound continuous coil with a greater number of turns of
the wire per unit cross-sectional area of the coil than
existed before the segments were compressed. Such
increase in the numbei of turns per unit cross~sectional
area of the coil ~x; rl ~es the use of the volume of the
toroidal or annular space and thereby increases the
efficiency of the transformer. These operations are
~5 described in detail below in connection with Figures 17
through 24.
As is illustrated sch~matically in Figure 7,
the inserts 70 are located at each end of the high
voltage coil section 61 and be-tween adjacent se~ents
with the cuffs 71 extending into the toroidal openings
in the segm~nts. The high voltage coil section 61 and
the inserts 70 are then positioned onto the ~xterior of
the high/low insulation barrier section 51 to complete
the operation of forming the half-portion 11 prior to
the winding in of the core 20.
The core material, which is of a relatively
thin, ribbon~like configuration, is preferably pre-wound
into a tight coil and automatically severed at a
19
prescribed leng-th determined by the size of the transfor-
mer being produced. The coil is then restrained and
annealed to relieve its in~ernal stresses, as is
illustrated in Figures 25 and 26. The resultant
structure is a pre-wound, coil-shaped core 20 which is
ready for winding into the above-described transformer
half-portions 11 and 12.
The rPm~i ni ng steps in the production process
include forming and installing a core sleeve from a
blank of core material, if deemed to be necessary for
the particular core material being used (Figures 27 and
28); the winding of the pre-formed, pre-annealed core
20 into the arcuate elongated passage through the
interdisposed high and low ~oltage coils 50 and 40,
respectively, (Figuxes 29 through 31~; and the finished
assembly steps of installing the supporting blocks,
electrically connecting the respective sections of the
low voltage coil 40 and the high voltage coil 60, and
mounting the asse~bly in a suitable housing structure
(see Figure 13.
Figures 9 through 13 illustrate a preferred
winding and forming apparatus 120 for fabricating the
low voltage coil sections 41 and 42, which may be
composed of suitable conductor material such as all]mlnl7m
or copper. The preferred aluminum coil may be fabricated
from preshaped EC grade conductor stock of the redraw
type or from other suitable conductor stock known to
those skilled in the art. The coil feedstock 121,
which may be round, square, or other desirable cross-
section, is fed from a reel 122 onto a forming mandrel 123
having a cross-sectional shape corresponding to the
desired cross-sectional shape of the toroidal low
voltage coil 40. The forming mandrel 123, which is
secured to a rotating shaft 124, includes a forming die
plate 125 and an axially-projecting shoulder portion
126 for receiving the feedstock 121. The feed~tock 121
is engaged and pressed into the desired cross-sectional
~a ~q3
shape by means of a conical pressure roller 127 and a
vertically reciprocating cylindrical pressure roller
128, which cooperate with the forming mandrel 123 to
forcibly deform the feedstock 121 into the desired
shape as the shaft 124 rotates. A conical backing
roller 129 provides a counteracting force against the
opposite side of the forming mandrel 123 to balance the
force exerted by the conical pressure roller 127,
thereby providing the lateral stability required for
the forming operation. A guide 131 directs the formed
coil onto a storage mandrel 132 that rotates in unison
with the forming mandrel 123, thereby producing a
continuously wound coil configuration which is wound
around the storage mandrel 132 as the process continues.
The cylindrical roller 128 is free-floating
between the conical pressure roller 127 and the ccnical
backing roller 129 in th~ preferred embodiment and is
supported vertically by a pair of cylindrical back-up
rollers 137. The cylindrical back-up rollers 137 are
rotatably attached to the yoke member 138. A pressure
piston, which may be a pneumatic or hydraulic device,
urges the cylindrical back-up rollers 137 against the
cylindrical roller 128, which in turn forcibly enyages
the conductor feedstock 121 during the forming operation.
By supporting the cylindrical roller 128 between the
conical rollers 127 and 129, its contact point is
maintained directly between the lines of contact of the
conical rollers 127 and 129. The use of the two
spaced-apart cylindrical back-up rollers 137 provides
clearance for the conical rollers 127 and 129 as the
cylindrical rollex 128 oscillates in engagement with
the forming mandrel 123 and the conductor feedstock
121. Preferably, the sides of the cylindrical roller
128 are slightly concave, ~hereby limi~ing the contact
with the conical rollers to only the rim portion of the
cylindrical roller 128 in order to rlnir-i7.e scuffing
and wear resulting from differences in the surface
21
speed o the rollers. Alternatively, a single cylindri-
cal roller (not shown) may be rotatably supported by a
yoke member and may be sized large enough to avoid
interference between its axis and the conical rollers
127 and 129. Such a single cylindrical roller would
also have concave sides to rl ni ; ze scuffing and
friction therebetween. In such an arrangement, however,
the cylindrical roller would have to be reciprocable
laterally so as to maintain its pressure point between
the lines of contact of the conical rollers.
Figures 11, 12, and 13 illustrate schematically
the relationship of the forming components during
various stages of rotation of the forming mandrel 123,
and Figure 14 shows a number of wedge-shaped interleaved
turns of the formed low voltage coil 40 as discussed in
detail below. In Figure 11, an inner leg 44 of the low
voltage coil 40 is being formed. As may be best seen
in Figure 14, the inner leg 44 is wide in the radial
direction and thin in the circumferential direction,
said directions being relative to the toroidal or
electrical transformer 10. Thus, in Figure 11 the
cylindrical roller 128 is in following engagement with
the edge 130 of the forming die plate 125 of the
forming mandrel 123. Also as is shown in Figure 11,
the axial thickness of the forming die plate 125 is
large compared to the overall thickness of the forming
mandrel 123 thereby forming a thin cavity in which the
conductor feedstock 121 is forced. Thus, the feedstock
121 is forcibly compressed and deformed into a generally
quadrilateral space having a high height-to-width
aspect ratio, thereby forming the inner leg 44 of the
low voltage coil 40.
In Figure 12, the forming mandrel 123 has
rotated 180 degrees from the posîtion shown in Figure
11 in order to form an outer leg 43 of the low voltage
coil 40. As may be best seen in Figure 14, the preferred
outer leg 43 is generally quadrilateral in cross-section,
~
22
with a low height-to-width aspect ratio. Accordingly,
in Figure 12, the thickness of the forming die plate
125 is thin compared to the overall thickness of the
forming mandrel 123, thereby forming a thicker cavity
into which the conductor feedstock 121 is forced.
As the forming mandrel 123 rotates from its
Figure 12 position to its Figure 11 position, as is
shown in part in the schematic representation in Figure
13, the cylindrical roller 128 raises and lowers in
followiny engagement with the corners of the forming
mandrel 124. Also, the radial excursion of the die
forming plate 125 increases to form the wedge-shaped
upper portion 45 and, subseguent to forming the inner
portion 44, decrease~ to form the wedge-shaped lower
portion 46.
The winding and forming process described
above continues until a predetermined number of low
voltage turns have collected on the storage mandrel
132, at which time the conical pressure roller 127l the
cylindrical pressure roller 128, and the conical
backing roller 129 are indexed away from the forming
mandrel 123 thereby allowing the fabrication of a
cross-sectionally unformed terminal portion on the ends
of the formed coil. Finally, the feedstock 121 is
automatically severed, the formed coil is removed, and
the process is repeated to form another length of low
voltage coil.
In forming the preferred low voltage coil 40,
two lengths of coil formed as described above are
intertwined or interleaved into a generally double-spixal,
or double-helix, configuration as is illustrated in
Figure 14 to form one of the coil sections 41 or 42.
Each of such coil lengths in the low voltage coil
section 41 is connected in series to a corresponding
coil length in the low voltage coil section 42 upon
final assembly of the toroidal transformer 10. Each of
such lengths is designed for one~fourth of the total
23
low voltage. Thus, each of the resultant sections 41
and 42 of low voltage coil 40, when connected as
described ab~ve, comprises two parallel toroidal coil
lengths, interleaved in a double-helix configuration,
each of sa.id sections 41 and 42 being designed to carry
one-half of the total low voltage value of the transfor-
mer. One end of each of such parallel coil lengths is
connected to one of two low voltage transormer terml nal S,
and the opposi-te end of each coil length is connected
together to the common neutral terminal of the transfor-
mer. This connection facilitates a low voltage electri-
cal output (or input), with one half of such voltage
being above neutral and one~half below neutral for ease
of single phase multivol~age wiring. One reason for
intertwining or interleaving the parallel lenyths low
voltage coil sections 41 and 42, as de~cribed above, is
that if only a 120 volt load, for example, is applied
across one of the low voltage terminals and the neutral
terminal, a balanced ampere-turn relationship will
exist between the loaded low voltage 120 volt coil
section and the fully series-connected winding segments
of the entire length voltage coil 60.
If the low voltage coil 40 were to be fabri~
cated in a non-interleaved configuration, with only a
single half-voltage coil length in each coil section 41
or 42, and with all of the high voltage coil segments
of the entire high voltage coil 60 being connected in
series, an application of a half-voltage load ~e.g.,
120 volts~ to one of such low voltage coil sections 41
or 42 would result in an excessively high circuit
impedance. This is because one-half of the series-
connected high voltage coil 60 would be ~- ~n~ionally far
removed from the low voltage coil section being used.
If such a non-interleaved low voltage coil configuration
is desired, however, a balanced ampere-turn relationship
may be obtained by winding the high voltage coil 60
into two full voltage (e.g., 7~00 volts per each coil
24
section 61 or 62~ and then simply connecting th~ coil
sections 61 and 62 in parallel, thus obtaining good
inductive coupling between each high voltage coil
section 61 or 62 and its associated non-interleaved low
voltage coil section 41 or 42. In such a case, one of
the transformer sections ll or 12 would provide trans-
formation of one-half the output voltage (e.g. 120
volts) one side of neutral, with the other transformer
section providing equal transformation on the opposite
side of neutral.
Although it would be d~sirable to wind and
form the low voltage coil 40, as described above, from
pre-lnsulated conductor feedstock (e.g., anodized or
film-insulated), it may not be possible in some cases
to do so by the above-described method without damaging
the insulation coating. Therefore, if bare conductor
feedstock is used, the formed coil sections should be
insulated after forming and winding. Figures 36 and
37, and the corresponding discussion below, illustrates
an alternate low volt~ge coil structure and method of
winding that is perhaps better suited for use with
pre-insulated conductors.
Figures 15 and 16 illustrate alternative or
optional methods of applying insulation to the formed
low voltage coil windings either before or after
interleaving. In Figure 15, a tank 140 contains a
liquid insulation coating material 142, into which the
coils are dipped and passed by means of a conveyer wire
144 with a series of hanger-type clamps 146 for retain-
ing the formed coils. After the formed coils are
dipped in the coating material 142, they are conveyed
through a drying and curing apparatus 148 for solidify-
ing the insulation. An insulation material recovery
system, indicated generally by reference numeral 150
may be employed, if desired, to recycle insulation
material vapors from the curing apparatus 148 to the
tank 140.
In Figure 16, an alternate powdered insulation
material is electrostatically applied to the formed
coils in an electrostatic spray bath 152. After
application of the powdered insulation, the formed
coils are cured in a curing oven 154.
Figures 17 throuyh 24 illustrate a preferred
apparatus and method for winding the high voltage coil
60 with a number of wedge-shaped segments preferably
being formed and wound from a continuous wire. Figure
17 shows an overall view of a preferred winding apparatus
170, which includes a winding and pressing assembly
172, a rotatable storage mandrel 174, and a wire guide
assembly 176 adapted for feeding and guiding a continuous
wire 178 into the winding apparatus 170. The preferred
wire 178 is coated with an insulation material composed
of a combination of a fully cured dielectric coating
overcoated with a so-called "B" stage semi-cured
thermosetting adhesive coating that is dry to the
touch. The adhesive coating ~erves to bond the turns
together and to enhance the insulating qualities of the
insulation combination. Such insulation material as
well as other similar materials are known to those
skilled in the art.
As shown in Figures 18 and 19, the winding
and pressing assembly 172 includes an integral winding
form 180 and upper and lower portions 182 and 184,
respectively of a split winding form 186. The integral
and split winding forms 180 and 186, respectively, are
operatively connected to a w;n~-ng mandrel 188, which
rotates in unison with the rotatable storage mandrel
174.
The upper and lower portions 182 an~ 184,
respectively, of the ~plit winding form 186 are movable
into and out of interlocking engagement with a pair of
cavities 190, formed by the winding mandrel 188 and the
storage mandrel 174, by means of upper and lower
carriers 192 and 194, respectively. The upper and
8~
26
lower carriers 192 and 194 are operated by a pair of
hydraulic or pneumatic cylinders 196, or alternatively
by any other suitable mechanical or electrical motion
imparting operator known in the art. Each of the
carriers 192 and 194 includes at least a pair of
retaining devices 198 for selectively retaining or
releasing the upper and lower portions 182 and 184 of
the split winding form 186. The preferred retaining
devices 198 each include a slidable armature 200 which
extends to engage, or retracts to release, one of the
retaining apertures 202 on each of the upper and lower
form portions 182 and 184. The armatures 200 may be
actuated by any suitable means such as an electric
solenoid device, or by a hydraulic or pneumatic cylinder,
for example. The preferred upper and lower fo.rm
portions 182 and 184 also include a pair of locking
apertures 204 adapted to receive a pair of locking pins
206 which are extendible from the storage mandrel 174
to retain the upper and lower forms portions 182 and
184 in position in the cavities 190.
As may be best seen in Figures 18, 19 and 22,
the above-described upper and lower carriers 192 and
194 thus operate to move the upper and lower form
portions 182 and 184 into position in the cavities 190
under the force of the cylinders 196, where they are
retained by ~he locking pins 206 and released by the
armatures 200, at which point the upper and lower
carriers 192 and 194 are retrarted as shown in Figure
19. When the upper and lower form portion~ 182 and 184
are to be moved out of the cavities 190, the upper and
lower caIriers 192 and 194 move into engagement therewith,
the armatures 200 slide into the retaining apertures
202, the locking pins 206 are retracted from the
locking apertures 204, and the upper and lower form
portions 182 and 184 are moved away from the winding
mandrel 188 by the upper and lower carri~rs 192 and
194. The purpose and timing of such movement of the
27
upper and lower form portions 182 and 184 relative to
the winding operation are discussed in detail below.
The wire guide assembly 176, which may be
best seen in Figures 18 through 21, includes vertical
feed rollers 212, horizontal feed xollers 214, and a
set of guide rollers 216 rotatably mounted on a guide
arm 218 which is pivotally secured to a shaft 220. As
the wire 178 is wound into the winding apparatus 170
between the wedge-shaped winding forms 180 and 186, the
guide rollers 216 automatically oscillate in a lateral
direction ko direct the wire 178 onto the winding
mandrel 188 in a generally uniform pattern, as shown in
Figure 20, thereby i ni ri 2ing the gaps between wire
turns and efficiently using the allotted space for each
coil segment. As the winding of a particular coil
segment 222 is nearly completed, an insulation piercer
226 (located near the feed rollers 212) makes a small
cut in the lnsulation, thereby exposing the bare
conductor. The winding then continues until the
exposed portion of the wire is indexed in a position
where it can be contacted by an electrode 227 after the
wire segment 222 is compressed as is described below.
The electrode 227 is located on the winding mandrel 188
(see Figures 18 and 23), and its purpose is explained
below. The guid~ arm 218 and the guide rollers 216
pivot to the position shown in Figure 21 to form the
continuous loop portion 221 ~see Figure 18), with the
above-described exposed portion therein, between each
of the coil segments 22~ and to allow for the compressing
and bonding of the wire in the segments 222.
Figures 21 through 23 illustrate the preferred
apparatus and method for the pressing and bonding of
the wire turns of each coil segment 222. Once the
winding of each coil segment 222 is completed, and the
guide rollers 216 have pivoted into their position as
shown in Figure 21, a pair of rams 230 extend to
forcibly decrease the spacing between the integral
28
winding form 180 and the split winding form 186 from a
distance dl, to a distance d2, as indicated in Figure
21, thereby forcibly compressing the turns of the coil
segment 222. Such compression of the coil segment 222
further 1 ni ~i zes the space or gaps between the indivi-
dual turns of wire and thereby ~x' 'zes the use of the
space around the toroidal transformer 10.
The integral winding form 180 and the split
winding form 186 are preferably hinged, as indicated by
reference numeral 187, so as to overcompress the wider
ou~board leg of the coil se~nent 222. Such hinged
arrangement on the windin~ forms 180 and 186 thereby
form sides on the coil winding segment ~22 that are
parallel both to each other and to a radial center-line
through said segment. Alternatively, the facing
surfaces of the winding forms 180 and 186 may be
biplanar with the portions adjacent the outer leg of
the coil seyment 222 being parallel, thus eliminating
the need for the hinges 187 while accomplishing nearly
the same result.
While the coil segment 222 is held in its
compressed state, as illustrated in Figures 21 through
23, the exposed portion of the wire 178 is engaged by
the electrode 227 located on the winding mandrel 188,
as is shown in Figure 23. Another electrode 229 makes
contact with the previously pierced and exposed portion
of the wire 178 in the loop portion 221 on the other
side of the coil segment 222. The winding apparatus
170 then briefly applies a high frequency voltage
through the coil segment 222 which guickly heats the
periphery of the wire 178 to a temperature of approxi-
mately 175C and causes the thermo-setting adhesive
insulation to bond to itself. Because the high frequency
voltage causes only the periphery of the wire 178 to
heat up substantially, while leaving the center or core
relatively cool, the interior of the wire acts as a
heat sink after the voltage is removed. Thu~ ~he coil
29
se~nent 222 cools quickly and as a result is wound,
compressed and bonded into its final wedge-shaped
configuration.
Alternatively, a high cuxren-t ~D.C. or low
frequency A.C.) may be imposed across the coil segment
222, causing an essentially uniform temperature elevation
of conductor which in turn causes the surface adhesive
coating to flow and bond. Although such alternate
method results in a somewhat longer cool-down period
than the above-described preferred method, this result
is mitigated somewhat by the heat sink effect of -the
winding forms 180 and 186 drawing heat from the coil
segment.
The upper and lower carriers 192 and 194 then
engage the upper and lower form portions 182 and 184,
the locking pins 206 retract, and the armatures 200
extend, as shown in Figure 22, thereby allowing the
form portions 182 and 184 to be moved away from the
winding mandrel 188. Finally, the rams 230 extend even
further to push the winding form 180 and the coil
segment 222 onto the stoxage mandrel 174. The winding
form 180 is retracted and the winding of the coil
segments from the continuous wire 178 continues as
described above until the required number of sesments
have been formed to make up a complete high voltage
coil section 51 or 62, at which time the continuous
wire 178 is automatically severed. The previously
pierced portions of the loop portions 221 are covered
with pieces of insulation, if necessary, upon final
assembly.
Figures 25 and 26 illustrate the fabrication
and anneali~g of the core 20, which may be performed
independently of the above-described operations. In
Figure 25, the ribbon-shaped stock core material 260 is
fed into a core forming apparatus 262, including
tension rollers 263 which tightly wind the core material
260 onto a spindle 266, thereby forming a core coil
~22~
264, prefexably in the siæe and shape of the finally
wound-in core 20 in Figure l. ~hen the build of the
core reaches the dimension for the transformer being
manufactured, a stack gauge or sensing mechanism 268
causes the winding mechanism to stop and a cutting
blade (not shown) to automatically sever the core
material 260. The core coil 264 is then secured by a
steel bonding strap or by spot welding the finished end
to the remainder of the coil to maintain its shape and
annealed in an annealing oven 270, as shown schematically
in Figure 26, to relieve the internal stresses resulting
from the winding operation.
If the thin-gauge amorphous steel is used for
core material, the core winding step may not be necessary.
In such a case, the amorphous steel may be wound in
place directly into the core insulation tube 30 and
annealed in place while a magnetic fiPld is simultaneous-
ly being applied by the energized windings, thereby
obtaining the optimum magnetic performance due to the
core being annealed t~ its operating position. Even
though the annealing temperature of amorphous steel is
relatively low (approximately 350~C), the insulation on
the electrical coils would have to be selected so that
it would be capable of withstanding such temperatures
for a short time.
Referring back to Figures 7 and 8, and the
related description, the major components are each
fabricated as described above and then assembled into
two transformer sections 11 and 12 ~see Figure 1),
which are joined by means o~ a core sleeve 280 as is
illustrated in Figures 27 and 2~, The use of a core
sleeve 280 will generally be required for magnetic
cores fabricated from the typically thin amorphous
metals, but may not be required for the thicker conven-
tional silicon steel core material (typically g mils to
12 mils in thickness) as described below. The core
sleeve 280 is formed from a strip of core material with
~ 31
one or more protrusions ox tabs 282 cut or lanced and
bent outwardly from one end thereof. The core sleeve
280 may be slightly thicker than that used for winding
the core 20 in order to provide added stability during
the wind-in process. The core sleeve 280 is inserted
into the arcuate elongated passage or tunnel in the
core insulation tube 30, as shown in Figure 27. The
ends 284 and 286 are then fixed to each other, with the
tabs 282 left in their outwardly-protruding positions,
preferably by resistance spot welding as shown in
Figure 28. The end 286 preferably overlaps the end
284, as shown in Figure 28, so as to form a backward-
facing step 292 relative to the direction of rotation
of the core sleeve 280 during core wind-in, as indicated
by direction arrow 288. The provision of the backward-
facing step 292 helps to ;niml7e the friction and
hang-up between the core sleeve 280 and the core
insulation tube sections 31 and 32.
When finally installed, the core sleeve 280
acts as a bushing or bearing which is freely rotatable
about the inner walls of the core insulation tube
sections 31 and 32. The use of a core sleeve 280 is
preferred, at least for amorphous metal core materials,
in order to allow the core material to be seated
against the tabs 282, and to ;nlmize the possibility
of the core material snagging or becoming hung-up on
the core insulation tube 30, during the core wind-in
operation described below. Furthermore, the core
sleeve 280 helps to keep the transformer sections
axially aligned prior to and during the wind-in opera-
tion. However, to avoid breaking the welds or otherwise
damaging the core sleeve a suitable carrier ~not shown)
may also by used when transporting the core-less
sub-assembly to be sure that the sections 11 and 12 are
maintained in their proper relative positions. A pair
of transformer section handling clamp type structures,
~uch as those indicated by reference numeral 290 in
32
Figure 27, may also be used for ease in handling the
sub-assembly both before, during and after installation
of the core sleeve 280.
As is mentioned above, a core sleeve 280 may
not be necessary for cores fabricated from the thicker
conventional silicon steel. In such a case, as shown
in Figure 28A, a tang 281 is ~ormed on the initial end
of the core material. The tang 281 is adapted to be
received in a slot ~83 formed in the core material at a
distance from the initial end substantially equal to
the circumference of the inner wall of the core insula-
tion tube 30. As the core material 280 is initially
wound in, the tang 281 is secured in the slot 283 to
form an integral core "sleeve", and the wind-in process
continues essentially as described below.
Figures 29 through 31 illustrate the preferred
apparatus and method for winding the previously annealed
core material 264 into the window or tunnel of the core
insulation tube 30. A preferred wind-in apparatus 310
generally includes a core material support assembly 312
having a rotating table 314 for rotating the core
material 264 during wind-in, a support roller or pulley
315 for supporting the core material 264, a coil
support fixture 316 for aligning and supporting the
transformer sections 11 and 12, a driven endless drive
belt 318 (with a discsnnectable joint 320) for support
ing and winding in the core material 264, and a belt-
tensioning mechanism 322 for automatically maintaining
proper tension on the endless drive belt 318 during the
wind-in operation. The belt-tensioning mechanism 3~2
may comprise a pneumatic or hydraulic cylinder, for
example, with an idler roller or sheave on the outer
end of its piston rod fox engaging the endless drive
belt 318 as shown in Figure 2g~ Th~ pre-assembled
coreless transformer section~ 11 and 1~, with the core
sleeve 280 in place, are positioned on the preferred
wind-in apparatus 310 with their axis oriented hori-
,3 ~ ~ ,
33
zontally. Such horizontal axis orientation is preferredso th~t the endless drive belt 318 may support the
weight of the core 20 as it is being wound, thereby
aiding in the maintaining of tension on the endless
drive belt 318 and in the centering of the core 20 with
the transformer sections 11 and 12. In con-trast,
however, the weight of the transEormer sections 11 and
12 is preferably supported by the coil support fixture
316. Various automatic controls known to those skilled
in the art are also provided for the various functions
described herein.
As was discussed above, the transformer
sections 11 and 12 each extend circumferentially
through an ~rc preferably of approximately 165 degrees,
thereby forming a circumferential gap of approximately
15 degrees on each side of the completed toroidal
transformer 10. Thus, when the transformer sections 11
and 12, with the core sleeve 280 in place, are positioned
on the coil support fixture 315, they may be rotated
slightly such that the upper gap 324 forms an angle of
approximately 25 degrees and the lower gap 326 forms an
angle of approximately 5 degrees, thereby allowing
sufficient clearance to feed the core material 264
through the upper gap 32~ and wind it in place within
the core insulation tube 30, thereby forming the
annular magnetic core 20.
Once the transformer sections 11 and 12 are
properly positioned on the wind~in apparatus 310, the
end of the core material 264 is inserted through the
upper gap 324 and restrained by the tabs 282 of the
core sleeve 280 ~see ~igures 27 and 28). As was
described in detail above, the core material 264 is
pre-wound and pre-annealed into a configuration substan-
tially identical ko thak of -the finished core 20.
Accordingly, the core material 264 is fed into and
wound in place within the core insulation tube 30 from
the inside, or inner diameter, of the pre-wound,
34
pre-annealed core coil. As a result the finished
preferred core 20 is a continuous, tightly wound,
substantially stress-free structure, with virtually no
air gaps, thereby ~x' mi zing the magnetic flux flow of
the core 20 and the efficiency of the toroidal electrical
transformer 10.
In order to wind-in the core material 264,
the endless belt 318 is fed through the ;upper gap 324
such that it paxtially surrounds and engages both the
core sleeve 280 and the end portion of the core material
264 as is shown in Figure 30. The endless drive belt
318 may then be reconnected at the joint 320, and the
belt-tensioning mechanism 322 may be activated, thereby
lS tensioning the endless drive belt 318 and preparing the
apparatus for the wind-in operation. When the wind-in
apparatus 310 is started, the rotating table 314 beings
to rotate at a speed that is automatically synchronized
with the movement of the endless drive belt 318, which
drivingly feeds and winds the core material 264 through
the upper gap 324 and around the core sleeve 280.
A pair of spring loaded conical rollers 330
(only one of which is shown) are preferably provided on
opposite sides of the upper gap 3~4 and apply a light
force on the edges of the core material 264 to keep the
layers properly aligned during winding. The conical
rollers 330 may be driven, if desired, in order to
assist the endless drive belt 318 in winding the core
material 264. A conical shape for such rollers is
preferred for purposes of matching their surface speed
along the line of contact with the core material 264
with the increasing speed of the core material 264 as
the core is rotated during winding.
As the core material 264 is wound into the
core insulation tube 30, the diameter of the core 20
increases as the core builds, layer-by~layer. Accord-
ingly, the belt~tensioning mechanism 322 automatically
adjusts to allow for the increased core diameter and to
maintain the proper level of belt tension. The process
continues until the core 20 is complete, at which time
the endless belt 318 leaves the core insulation tube 30
through the gap 39 between the outer wall portions
thereof, as shown in Figure 31. The provision of the
gap 3~ thus allows the core insulation tube 30 to be
completely filled with the core material 264 without
leaving an unusable annular space for the endless drive
belt 318 around the periphery of the core 20. Once the
endless drive bPlt 318 is removed upon completion of
the core 20, the gap 39 may be filled with an insulative
transformer cooling fluid, thus achieving dielectric
insulation suficient to withstand voltage stresses
between the core and the low voltage windings.
For final assembly of the preferred toroidal
electrical transformers 10, the transformer sections or
half-portions 11 and 12 are rotated back to their
original positions with e~ual circumferential gaps of
approximately 15 degrees on each side. The corresponding
ends of both the low voltage coil sections 41 and 42
and the high voltage sections 61 and 62 are connected
together or fitted with external connector devices as
required for the desired application of the transformer.
The upper and lower portions of the supporting blocks
80, shown in Figure 1, are inserted into the 15 degree
circumference gaps and are secured together by suitable
fastening means known to those skilled in the art. The
assembly is then ready for mounting in a housing or
cont~ nt structure, such as that indicated by
reference numeral 85 in Figure 1, and for evacuating
and charging with transformer cooling fluid, which is
typically an electrical grade insulation oil.
The present invention, as disclosed above,
provides for an electrical transformer, which is
suitable for either step-down or step-up applications,
and which employs continuously wound high and low
voltage coils as well as a continuous magnetic core, all
36
of which are arranged in a toroidal or annular configu-
ration. By such a structure and configuration, the
toroldal electrical transformer according to the
present invention provides for maximum efficiency and
optim~lm use of space, thereby representing a great
stxide in the advancement of transformer technology
Furthermore, it is believed that the disclosed method
and structure for the continuously wound~in core of the
present invention allows the greatest use of the
~fficiency gains to be derived from the use of the
thin-gauge amorphous metal core materials rather than
the traditional grain-oriented material.
Although the discussion herein, in connection
with the Figures 1 through 31, discloses the structure
and method of production for the toroidal electrical
transfo~mer 10, alternate structures and methods of
producing the various components of such a transformer
may ~e employed without departing from the spirit and
scope of the invention. The following discussion, in
conjunction with Figures 32 through 41, illustrate a
few examples of other alternate embodiments of the
present invention.
Figures 32 through 35 illustrate an alternate
method and apparatus for forming the low voltage coil
sections 41 and 42. In Figure 32, the conductor
feedskock 121 is fed from the reel 122 by means of a
pair of tension rollers 410 onto a rotating mandrel
412, driven by a motor 414. After winding the requisite
amount of feedstock to form one of the lengths of the
coil section 41 or 42, a cut-off mechanism 416 automati-
cally severs the feedstock 121. The length of coiled
feedstock is then conveyed to the forming press 420
shown in Fiyures 33 and 34.
At the forming press 420, the coil length is
slipped onto a support mandrel 422 and retained by a
bearing plate 423. The support mandrel 422 is then
moved into a position such that each of the turns 424
37
of the coil leng~h is between a pair of tapered pres~
forms 424. ~n upper press plate 426 is then forcibly
urged downward, as viewed in Fi~ure 34, to compress the
turns 424 of the coil length into the same wedge-shaped
confi~ration as is discussed above in connection with
the preferred low voltage coil forming apparatus.
Two of the coil lengths are then inserted
into a winding apparatus 430 for interleaving as is
shown schematically in Figure 35. The winding apparatus
430 includes a rotatable head 432 which is movable
upwardly and downwardly on a support post 434. Th~
upper coil length 436 is attached to the rotatable head
432 and is turned as it is moved downwardly to interleave
the upper coil length 436 with the lower coil length
438 which is fixed to a stationary base plate 440.
Figures 36 and 37 illustrate still another
alternate low voltage coil structure and a method of
forming such a coil. The structures and method shown
in Figures 36 and 37 are especially well-suited for
winding the low voltage coil from pre-insulated conductor
because of the limited forming required by such me~lod.
As is perhaps best seen in Figure 36, a pair of parallel
bifilar conductors 450 and 452 are wound together.
Each of the conductors 450 and 452 has a generally
rectangular, or possibly square, cross-section and are
preferably copper thereby reducing electrical losses
and more efficiently using the available space because
of the smaller ~ross-section. It should be noted,
however, that it may be desirable for each of the
conductors 450 and 452 to be of a different cross-sec-
tion, one of a sguare and one of a non-square rectangular
cross-section, or each of different rectangular dimen-
sions, for example.
The bifilar conductors 450 and 452 are wound
in a ~nner so as to lie one inboard of the other in a
radial direction, relative to the toroidal transformer,
on the inner legs of the low voltage coil. As they are
38
wound, however, the conductors 450 and 452 are turned
or rotated 90 degrees in the upper radial portion so as
to lie side-by-side in the circumferential direction,
relative to the toroidal transformer, on the outer
legs. On the lower radial portion, the conductors 450
and 452 are then turned or rotated 90 degrees in the
opposite direction, thus returniny to their original
orientation (one inboard of the other) on the inner
legs of the coil. It should be noted that the same two
faces of the conductors 450 and 452 remain in contact
with each other throughout each winding turn. Further~
more, as is shown in Figures 36 and 37, the turned
portions on the upper and lower radial portions of
adjacent turns are circumferentially nested together in
order to conserve space.
Such a construction, as shown in Figures 36
and 37, thereby approximates the wedge-shaped configura-
tion of each turn of the above-discussed preferred low
voltage coil 40, without the necessity of the substantial
forming operations which would tend to damage the
pre-insulated conductor. Even though the construction
of a coil formed as shown in Figures 36 and 37 only
approximates a wedge-shape for its turns, and thus does
not make the mosk efficient use of space in the toroidal
electrical transformer, such a construction may be
desirable in applications where such efficient space
utilization is not critical. ~owever, through modest
forming in conjunction with the turning described
above, efficient use of space may be improved.
Figures 38 and 39 illustrate an alternative
core wind-in method, employing an alternate core sleeve
460 which includes a plurality of gear teeth 462,
preferably stamped or forged therein such that the
overall thickness of the core slee~e 460 is not substan-
tially increased over that of its parent material.
Like the core sleeve 280, discussed above in connection
with the preferred embodiment, ~he thickness of core
39
sleeve 460 is preferably greater than ~hat of the core
material 264 in order to provide st~bility during the
core wind-in process. Also like the preferred core
sleeve 280, the alternate core sleeve 460 preferably
r~ ~i n~ in place in the core insulation tube 30 after
completion of the core 20.
To facilitate the wind-in of the core 20, an
end of the core material 264 is attached to the core
sleeve 460. Such attachment may be made in any of a
number of ways, such as by spot welding the end of the
core material 20 to the outer surface of the core
sleeve 460 or by way of lanced tabs thereon similar to
the protrusions or tabs 282 shown in Figures 27 and 28.
A pinion gear 464 is positioned in the circumferential
space or gap 324 between the transformer sections 11
and 12 and drivingly rotated so as to rotate the core
sleeve 460 and wind-in the core material 264 in lieu of
the endless drive belt 318 of the preferred apparatus
shown in Figures 29 and 31 and discussed above.
Finally, Figures 40 and 41 illustrate still
another alternate method and apparatus for winding in`
the core 20, which is perhaps less desirable for use
with the thin-gauge amorphous metal core materials than
it is for use with the heavier and thicker, grain-ori-
ented metal materials. In such alternate apparatus,
the inner end of the previously wound and annealed core
material 264 is fed through a pair of tensioning
rollers 480 and pulled by a drive roller 482 and a
spriny-loaded bark-up roller 483 until a complete loop
is formed around the inner walls of the core insulation
tube sections 31 and 32. A tack weld is made to secure
such inner loop to the r~ ~;nder of the incoming core
material 264, and the wind-in process continues until
the entire core 20 is formed. Alternatively, the inner
end of the core material 264 may be secured to a core
sleeve 280 as is described above in connection with the
preferred wind-in method. The core material 264 is
supported and rotated on a rotating table 314, similar
to that described above, and a pair of conical support
rollers 490 are disposed in the gaps between the
transformer sections 11 and 12 for vertically supporting
the core material 264 during the wind-in process.
The foregoing discussion discloses and
describes merely exemplary methods and embodiments of
the present invention. One skilled in the art will
readily recognize from such discussion that various
changes, modifications and variations may be made
therein without departing from the spirit and scope of
the invention as defined in the following claims.
