USOO7034648B2

(12) United States Patent (10) Patent No.: US 7,034,648 B2

Shirahata et al. (45) Date of Patent: Apr. 25, 2006
(54) AMORPHOUS METAL CORE 3,464.043 A 8, 1969 Benko et al. ................. 336/60
TRANSFORMER 3,617,966 A 11/1971 Trench
3,659,239 A 4, 1972 Marton
(75) Inventors: Toshiki Shirahata, Shibata (JP): 3,750,073. A 7, 1973 Okano
Masayuki Horiuchi, Y Niigata-ken
- 88
(JP); 4,327,311 A
4,368,407 A
4,1/1983
1982 Wroblewski
Wroblewski
Katsutoshi Inagaki, Niigata (JP); 4,523,169 A * 6/1985 Hay ............................ 336/60
Shinya Urata, Niigata-ken (JP) 4,609,900 A 9, 1986 Bachhofer et al.
5,225,630 A 7/1993 Hopkinson et al.
(73) Assignee: Hitachi, Ltd., Tokyo (JP) 5,889,373 A 3/1999 Fisher et al.
6,005,468 A 12/1999 Shirahata et al.
(*) Notice: Subject to any disclaimer, the term of this
patent is extended or adjusted under 35 FOREIGN PATENT DOCUMENTS
U.S.C. 154(b) by 600 days. JP 60-178609 9, 1985
JP 60-178609 * 12/1986
(21) Appl. No.: 09/825,339 JP O4-155907 * 5/1992
JP O6163283 6, 1994
(22) Filed: Apr. 4, 2001 JP O8O31667 2, 1996
JP 9-254494 9, 1997
(65) Prior Publication Data JP 10-340815 12/1998
WO WO83O2.194 6, 1983
US 2001/OO33216 A1 Oct. 25, 2001
* cited by examiner
Related U.S. Application Data Primary Examiner Tuyen T Nguyen
(63) Continuation of application No. 09/363,836, filed on (74) Attorney, Agent, or Firm—Mattingly.Stanger. Malur &
Jul. 30, 1999, now Pat. No. 6,750,749. Brundidge, P.C.
(30) Foreign Application Priority Data (57) ABSTRACT
Jul. 31, 1998 (JP) ................................. 10-216755
(51) Int. Cl. An amorphous metal core transformer is provided with a
HOIF 27/28 (2006.01) plurality of wound magnetic cores composed of amorphous
(52) U.S. Cl. ...................................................... 336/22O metal strips, and a plurality of coils, each of the coils
(58) Field of Classification Search ........ 336/210-213, including a primary coil and a secondary coil, each of the
336/216, 223, 234, 57, 58, 61, 60, 69,233, coils further including a bobbin. The primary coil employs
336/220, 221 different material from that of the secondary coil, e.g., a
See application file for complete search history. copper conductor is employed in a primary coil, while an
aluminum conductor is employed in a secondary coil. The
(56) References Cited bobbin has higher strength than that of the amorphous metal
strips.
U.S. PATENT DOCUMENTS
3,200,357 A 8, 1965 Olson et al. 2 Claims, 11 Drawing Sheets

22
26
262
U.S. Patent Apr. 25, 2006 Sheet 1 of 11 US 7,034,648 B2

FG.2
201 112 202 113 2 22 114 21 26 115
111

2/
11 b 11 b 262 b 261 1a
U.S. Patent Apr. 25, 2006 Sheet 3 of 11 US 7,034,648 B2

FG4A

23
U.S. Patent Apr. 25, 2006 Sheet 4 of 11 US 7,034,648 B2

FG.5A

N N
HHN NHE
NH
t TT NH
NH
N
H N NH
NH
T? NH
NH
HN NHE
Nii
H
HEN Ri
H RN
H N N
HEN
tT - - - - - -- - - - - - -
N
N

FG.5B FG5C
21 22
21 a 21b y 22a 22a 22a

&
U.S. Patent Apr. 25, 2006 Sheet S of 11 US 7,034,648 B2

FG.6
261
26
26

FG.7

16
Ø

©)
U.S. Patent Apr. 25, 2006 Sheet 6 of 11 US 7,034,648 B2

FG.8

26
)
s 2
13

) (

() 6

)
U.S. Patent Apr. 25, 2006 Sheet 7 of 11 US 7,034,648 B2

FG.9

FG.1 O
U.S. Patent Apr. 25, 2006 Sheet 8 of 11 US 7,034,648 B2

(C)
U.S. Patent Apr. 25, 2006 Sheet 9 of 11 US 7,034,648 B2

F.G. 12

6 s
C S
U.S. Patent Apr. 25, 2006 Sheet 10 of 11 US 7,034,648 B2
U.S. Patent Apr. 25, 2006 Sheet 11 of 11 US 7,034,648 B2

FG.15

a NYNNVNSYNYS

2 NSNYNNNNNNNNYYY
SS SNNNNNNNYS
a ZZZZZ14 Z.
Ñ?<Sx ==SNY
2 UN ZZZZZZZZZ
s2ZZZZZZZZZZZZZZZZZZZZZZ
||||
R

&Z
NCOITÑEK,N
NN
22
NNNNT
N. NYa YaYaNYaNYal
N.
4. SNoYR.<
22ZZat
NN

261
21
22
 US 7,034,648 B2
1. 2
AMORPHOUS METAL CORE different conductor materials are used for the two coils, the
TRANSFORMER current densities calibrated by electrical resistances of the
coils are also nearly equal. Further, as connection Systems
This application is a continuation application of U.S. Ser. for three phase transformers, Y (star) connection and A
No. 09/363,836, filed Jul. 30, 1999 now U.S. Pat. No. 5 (delta) connection are known. When the capacity of the
6,750,749. transformer is small. A connection is disadvantageous
because a greater number of turns are required than that
BACKGROUND OF THE INVENTION required in Y connection. On the other hand, when the
capacity of the transformer is in the medium range or above,
This invention relates to an amorphous metal core trans 10 Y connection is disadvantageous because a wider cross
former, and particularly relates to an amorphous metal core sectional area of the conductor is required than that required
transformer capable of reducing core losses and watt losses. in A connection. Therefore, in the Small capacity range of
An amorphous metal core transformer, which transforms 500 kVA or less, Y-A connection is used, and in the medium
A.C. power of a high voltage and a small amperage into that capacity of 750 kVA or more, A-A connection is mainly
of a low voltage and a large amperage, or vise Versa, using 15 used. And in the latter, some transformers use Y-A connec
amorphous metal sheets as for a material of its magnetic tion. Where Y connection is used, it is possible to reduce the
core, is so popular nowadays. As for the magnetic core of the turns of the coil windings 1/V3 times to that in A connection.
amorphous metal core transformer, a wound core or a However, the amperage of the current flowing through the
laminated core is employed. The wound core is chiefly coil is the same value as that in A connection, which requires
employed and it is formed by winding amorphous metal the same cross-sectional area of the coil conductor as that in
strips. For example, as disclosed in Japanese Patent Appli A connection. On the other hand, though A connection
cations Nos. Hei 9-149331 (Japanese Patent Laid-open No. requires the turns of the coil windings v3 times to that in Y
JP-A-10-340815) and JP-A-9-254494, an amorphous metal connection, amperage of the current flowing through the coil
core transformer for three phase 1000 kVA use with five is reduced to 1/V3 times to that in Y connection, which
legged core, employs wound cores and coils in a transformer 25 enables to reduce the cross-sectional area of the coil con
casing. In actual designing of the transformer in these related ductor.
arts, amorphous magnetic strips are wound to form a unit An magnetic core-coil assembly, as shown in FIGS. 7 and
core of approximately 170 mm in width and approximately 8 of the JP-A-10-340815, is composed of eight unit mag
16200 mm in cross-sectional area. Two unit cores are netic cores and three coils. The unit magnetic core has a joint
juxtaposed edgewise to compose a set of unit cores to portion in one of its yokes, and when this joint portion is
increase (in this case, to double) the cross-sectional area. opened, the core is formed into U-shape so as to be able to
Four sets of unit cores are arranged side by side so as to insert its legs into the coils. After insertion, the joint portion
compose a five-legged core. Three coils are combined with is closed and the magnetic core and the coil are assembled.
the five-legged core so as to compose the three phase A transformer casing has a similar configuration to one
transformer. The five-legged core has first leg, second leg. 35 shown in FIG. 3, which accommodates the magnetic core
third leg, fourth leg and fifth leg arranged in this order. The coil assembly and insulating oil inside, and has external
coils consist of three coils, which are first coil, second coil terminals, cooling fins outside. The external terminals are
and third coil and are inserted in the second leg, the third leg electrically connected to the coils through line wires. The
and the fourth leg respectively. Actual weight of the inner cooling fins radiate the heat generated in the coils or
unit cores and outer unit cores are about 158 kg and about 40 magnetic cores and the heat transmitted to the insulating oil
142 kg respectively. into the atmosphere to keep the temperature increase within
Coils in an amorphous transformer according to the an allowable range. The height of the cooling fins is
related art, as shown in FIG. 4B, are composed of a primary designed to be approximately 100 to 200 mm. The total
coil 121 and a secondary coil 122 for three phases. The surface area of the cooling fins is supposed to be about 10
primary coil 121 uses a rectangular insulated copper wire 45 times as large as the surface area of the casing, and is
measuring 3.5 mmx7.0 mm, having a conductor cross designed to be approximately 50 m.
sectional area of 24.5 mm, which is wound 418 turns. The In case of a conventional amorphous metal core trans
secondary coil 122 uses two parallel copper conductor strip former for three phase 1000 kVA use, total losses will
having a conductor cross-sectional area of 603.5 mm. amount to approximately 11730 W including core losses of
which is wound 13 turns. The primary coil 121 is arranged 50 approximately 330 W and watt losses of approximately
outside the secondary coil 122 in the radial direction of the 11400 W, which requires a large cooling area to keep the
coil. In order to let out the heat generated inside the coils, temperature increase within the allowable range. In addition,
duct space layers 24 are formed within the coils 2 for if loss reduction is attempted by reducing the watt losses so
circulating insulation oil therein. In each of the duct space as to increase the conductor cross-sectional areas of the
layers, a spacer members having a plurality of rod-shaped 55 primary and secondary coils, it is necessary to use thicker,
members 23 shown in FIG. 4C, is inserted so as to form a accordingly more rigid copper wires. This makes the wind
loop within the coil. Since the amorphous metal core trans ing work more difficult due to rigidity of the wires, and in
former in the related art has large losses, a sufficient cooling addition, connection between the secondary coil and the line
capacity is required for the duct space layers 24. Accord wire becomes more difficult, which deteriorates productivity
ingly, six duct space layers 24 are disposed both between the 60 requiring more man-hours.
second leg and the third leg and between the third leg and the
fourth leg. Since the duct layers 24 are formed in coaxial SUMMARY OF THE INVENTION
loops, both coil ends of the coil 2 is disposed facing the cores
by narrow gaps, which impedes circulation of insulation oil. It is therefore an object of the present invention to solve
In general, a transformer is designed in such a manner that 65 the problems of the related art explained above. In view of
the current density in the primary coil and that in the the objective of solving the problems explained above, the
secondary coil are nearly equal as possible and, when construction of the amorphous metal core transformer
 US 7,034,648 B2
3 4
includes a plurality of wound magnetic cores composed of FIG. 3 shows a perspective view of the external appear
amorphous metal strips, and a plurality of coils, each of the ance of the amorphous metal core transformer of the
coils including a primary coil and a secondary coil, each of embodiment.
the coils further including a bobbin, wherein the primary coil FIGS. 4A, 4B and 4C show diagrams illustrating layouts
employs different material from that of the secondary coil, of duct space layers in coils of the amorphous metal core
and the bobbin has higher strength than that of the amor transformer. FIG. 4A shows a layout of the duct space layers
phous metal strips. in the embodiment. FIG. 4B shows a layout of the duct space
In another embodiment of the amorphous metal core layers in the related art. FIG. 4C shows a spacer member in
transformer, the primary coil is composed of copper con the embodiment.
ductor coil, the secondary coil is composed of aluminum 10 FIG. 5A shows a cross-section of the coil assembled with
conductor coil, and the secondary coil is disposed outside the magnetic core.
the primary coil in radius direction of the coil. FIG. 5B shows a cross-section of the conductors in the
In the third embodiment of the amorphous metal core primary coil.
transformer, current density calibrated by electrical resis FIG. 5C shows a cross-section of the conductors in the
tance of the primary coil is higher than that of the secondary 15 secondary coil.
coil. FIG. 6 shows a perspective view of a bobbin in the
In the fourth embodiment of the amorphous metal core embodiment.
transformer, the secondary coil has a greater length than the FIG. 7 shows a perspective view of the unit core in the
primary coil in the axial direction thereof. embodiment.
In the fifth embodiment of the amorphous metal core FIG. 8 shows diagrams illustrating one example of assem
transformer, the primary coil employs a rectangular copper bling process for the amorphous metal core transformer in
wire, and the secondary coil employs an aluminum Strip. the embodiment. In FIG. 8, (a) through (g) show first step
In fifth embodiment, the amorphous metal core trans through seventh step of the assembling process, respectively.
former further includes a casing for containing the magnetic FIG. 9 shows a perspective view of metal core-coil
cores and the coils, the casing being filled with an insulative 25 assembly in the embodiment.
cooling medium, the casing having cooling fins formed so as FIG. 10 shows a perspective view of unit core in the
to project from a Surface of the casing, wherein, the cooling embodiment.
fins project from the surface of the casing from 17 mm to FIG. 11 shows diagrams illustrating a modified example
280 mm in height, and the total Surface area of the cooling of assembling process for the amorphous metal core trans
fins and the casing is 130 m or less. 30 former. In FIG. 11, (a) through (g) show first step through
In sixth embodiment of the amorphous metal core trans seventh step of the assembling process, respectively.
former, four pieces of the wound magnetic cores and three FIG. 12 shows a perspective view of magnetic core-coil
pieces of the coils are assembled so as to compose a three assembly manufactured in the modified assembling process
phase transformer having five-legged magnetic cores. of the embodiment.
In seventh embodiment of the amorphous metal core
35 FIG. 13 shows a perspective view of protection member
transformer, the three phase transformer has a capacity of in the embodiment. In FIGS. 13, (a) shows a perspective
750 kVA or more and the three coils are connected in A A view of the protection number when attached to the coils,
connection system. and (b) shows a details of a corner portion of a coil window.
The present invention provides an amorphous metal core FIG. 14 shows a perspective view of the modified pro
transformer capable of reducing a total losses resulting in a
40 tection member in the embodiment. In FIGS. 14, (a) shows
reduction of temperature increase and size of cooling fins. a perspective view of the protection member when attached
The present invention also provides an amorphous metal to the coils, and (b) shows a details of a corner portion of a
coil window.
core transformer capable of improving productivity. FIG. 15 shows a diagram illustrating one example of
BRIEF DESCRIPTION OF THE DRAWINGS
45 single phase amorphous metal core transformer in the
present invention.
The foregoing and a better understanding of the present DESCRIPTION OF THE EMBODIMENTS
invention will become apparent from the following detailed
description of exemplary embodiments and the claims when 50 Before beginning a detailed description of the subject
read in connection with the accompanying drawings, all invention, mention of the following is in order. When
forming a part of the disclosure hereof this invention. While appropriate, like reference numerals and characters are used
the foregoing and following written and illustrated disclo to designate identical, corresponding or similar components
Sure focuses on disclosing exemplary embodiments of the in differing figure drawings.
invention, it should be clearly understood that the same is by 55 One embodiment of the amorphous metal core trans
way of illustration and example only and is not to be taken former of the present invention will be described with
by way of limitation, the spirit and the scope of the present reference to FIGS. 1 to 15.
invention being limited only by the terms of the appended An amorphous metal core transformer of the present
claims. embodiment is a transformer with five-legged magnetic
The following represents brief descriptions of the draw 60 cores for three phase 1000 kVA, 50 Hz use, having wound
ings, wherein: magnetic cores 1, coils 2, and a transformer casing 4. In the
FIG. 1 shows a perspective view of an magnetic core-coil present embodiment, an magnetic core-coil assembly 3 is
assembly with clamps for an amorphous metal core trans composed by assembling four wound magnetic cores 1 and
former in one embodiment of the present invention. three coils 2. As shown in FIG. 1, each magnetic core 1 is
FIG. 2 shows a horizontal cross-sectional view in the 65 composed of two unit cores 11. Two unit cores 11 are
plane II—II of the magnetic core-coil assembly in the juxtaposed edgewise to compose a magnetic core 1 to
embodiment. increase (in this case, to double) the cross-sectional area.
 US 7,034,648 B2
5 6
Four magnetic cores 1 are arranged side by side So as to industrially manufactured at present are available in three
compose a five-legged core. In this embodiment, eight unit different widths, i.e., 142 mm, 170 mm and 213 mm. Among
cores 11 are totally employed to compose the five-legged the three widths, 170 mm wide strips are currently distrib
core. Three coils 2 are combined with the five-legged core uted in greatest volume and more readily available for
So as to compose a magnetic core-coil assembly 3. The industrial use. Therefore, two unit cores 11, using 170 mm
five-legged core has first leg 111, second leg 112, third leg wide magnetic strip, are juxtaposed edgewise So as to obtain
113, fourth leg 114 and fifth leg 115 arranged in this order the cross-sectional area of approximately 16800 mm in the
(In FIGS. 1 and 2, from left to right). Three sets of coils 2, present embodiment. In addition, the amorphous magnetic
which are first coil 201, second coil 202 and third coil 203 strip has a high hardness level of 900 to 1000 HV, and is a
(In FIGS. 1 and 2, from left to right), are inserted in the 10 very brittle material as well. For this reason, in manufac
second leg 112, the third leg 113 and the fourth leg 114 turing large capacity transformers for power distribution use
respectively. Thus, by combining eight unit cores 11 in total industrially, it is an essential point to compose a large
with three sets of coils 2, the magnetic core-coil assembly 3 cross-sectional area core by combining Small cross-sectional
is composed. The magnetic core-coil assembly 3 is installed area cores, which reduces the masses of unit cores 11, and
in the transformer casing 4. The core-coil assembly 3 is set 15 improves workability. Then, assembly into the coil configu
between an upper clamp 31 and a lower clamp 32, and the ration, which is described later, makes the mass of the outer
upper clamp 31 and the lower clamp 32 are fastened by studs unit core outside 11a about 173 kg and the mass of the inside
34. Each of the coils 2 is placed between the upper clamp 31 unit core 11b about 197 kg. As the magnetic core 1 of the
and the lower clamp 32. Coil supports 33 support the coil 2 present embodiment generates little heat thanks to low core
between the upper clamp 31 and the lower clamp 32 at the losses, and also has a large area of contact with the cooling
upper end and the lower end of the coil 2. Each of the first medium, i.e. insulating oil in this embodiment, by virtue of
leg and the fifth leg is enclosed in a set of U-shaped clamp the five-legged iron core, magnetic cores and a transformer
35 and an E-shaped clamp 36. These sets of the U-shaped with little temperature rise can be obtained.
clamp 35 and the E-shaped clamp 36 are combined to the Each of the coils 2 includes a primary coil 21, a secondary
upper clamp 31 and the lower clamp 32 so as to keep the 25 coil 22 and a bobbin 26. The primary coil 21 employs
positional relationships between individual magnetic cores 1 different material from that of the secondary coil 22, i.e. the
and individual coils 2. For wire connection, a A-A con primary coil 21 employs a rectangular copper wire, and the
nection system is adopted among the three coils 2. Then, an secondary coil 22 employs an aluminum Strip. The primary
insulative cooling medium (in this embodiment, insulating coil 21 uses two types of rectangular copper wires, 2.6
oil) is filled into the transformer casing 4, and the three phase 30 mmx6.5 mm and 2.0 mmx6.5 mm, arranged in parallel as
amorphous metal core transformer is composed. Inciden disclosed in FIG. 5B and having a conductor cross-sectional
tally, the insulative cooling medium may be such insulating area of about 29.9 mm, and is wound 418 turns around the
gas as SF (Sulfur hexafluoride) or N (nitrogen). bobbin 26. The secondary coil 22 uses three aluminum strips
The unit core 11 is composed by cutting amorphous of 1.70 mmx475 mm arranged in parallel as disclosed in
magnetic strip of approximately 170 mm in width to a 35 FIG. 5C, having a conductor cross-sectional area of about
prescribed length beforehand, stacking a prescribed number 2420 mm, and is wound 13 turns. One example of the
of pieces of the pre-cut amorphous strip into a core of bobbin 26 is depicted in FIG. 6. The bobbin 26 is made of
approximately 16800 mm in cross-sectional area and plac a material having a greater strength than that of the amor
ing it on a mandrel, forming it into a U shaped open-ended phous magnetic strip Such as steel, steel alloy or a resin. In
core as shown in FIG. 7 and annealing after closing its ends. 40 the present embodiment, since the bobbin 26 is made of
After annealing, the core 11 is covered with a fragment silicon Steel plate having an electrical conductivity, a slit is
prevention member 12, 14 as shown in FIG. 7, then, the ends formed where an insulating member 261 is inserted on the
are opened and its legs are inserted into the coil 2. After the bobbin 26 so as to prevent formation of one-turn coil. The
legs are inserted into coils 2, the opened ends are closed so secondary coil 22, as shown in FIG. 5A, is arranged outside
as to form a butted joint. Greater core cross-sectional area 45 the primary coil 21. This configuration provides safe trans
than that of a conventional core is gained for the unit core former, since high Voltage is applied to the primary coil 21.
11 in this embodiment. By juxtaposing two unit cores 11 The current density of the primary coil 21 using copper
edgewise, a cross-sectional area of about 33600 mm for conductor is approximately 0.72 A/mm when calibrated
each magnetic core 1, approximately 3.7% greater than in a into the current density in an aluminum conductor, and the
conventional core, is gained, which enables to reduce the 50 current density of the secondary coil 22 is approximately
magnetic resistance, and to obtain an magnetic core with 0.655 A/mm; thus the current density in the primary coil 22
reduced core losses. The first coil 201 is inserted into the is about 1.1 times as high as that in the secondary coil 22,
core window between the first leg 111 and the second leg when calibrated into the current density in an aluminum
112, and the third coil 203 is inserted into the core window conductor. The coils 2 are connected to the line wire and led
between the fourth leg 114 and the fifth leg 115. The first coil 55 to the outside. In order to let out the heat generated inside the
201 and the second coil 202 are inserted into the core coils, duct space layers 24 are formed within the coils 2, as
window between the second leg 112 and the third leg 113, shown in FIG. 4A, for circulating insulation oil therein. In
and the second coil 202 and the third coil 203 are inserted each of the duct space layers 24, a spacer members 120
into the core window between the third leg 113 and the having a plurality of rod-shaped members 23 shown in FIG.
fourth leg 114. 60 4C, is inserted coaxially so as to form a C-shaped duct space.
Among amorphous magnetic strips industrially manufac The amorphous metal core transformer of the present
tured at present, those usable for transformers are approxi embodiment has a greater cross-sectional area of the coil
mately 0.025 mm in thickness and at most approximately conductors than the related art has (approximately 120% in
213 mm in width. If this kind of strip is applied to a large the primary side, approximately 400% in the secondary side
capacity transformer of three phase 1000 kVA class for 65 compared with the related art), electrical resistance of the
power distribution use, desirable magnetic core width is conductors is lower, and the calorific value is Smaller thanks
estimated to be about 400 mm. Amorphous magnetic strips to Small losses. As the cross-sectional area of the secondary
 US 7,034,648 B2
7 8
side, where the amperage is large, is approximately 400% of perature increase in the primary coil can be prevented. In
that of the related art, a decrease in calorific value accom addition, in the amorphous metal core transformer of the
panied by a Substantial reduction in resistance can be present embodiment, the connection between the secondary
achieved. In the magnetic core-coil assembly 3, unit cores coil 22 and the wire, as it is between aluminum and
are arranged on the upper and lower sides of the coils 2 at 5 aluminum, is easy to accomplish.
parts 25. Duct spaces 24 can be eliminated within the parts As shown in FIG.5A, the length (L) in the axial direction
25, since Substantially no circulation of insulating oil is of the secondary coil 22 is made greater than the length (L)
induced between the cores and the coils impeded by the in the axial direction of the primary coil 21. This enables to
narrow gaps therebetween. For this reason, coils inserted reduce deformation caused by electromagnetic force due to
into U-phase leg (second leg) 112 and W-phase leg (fourth 10
short-circuit current, even when the two coils 21 and 22 are
leg) 114, no duct space is disposed within the parts 25 of the disposed in Such a manner that the centers of the electro
coils 21 and 22. Similarly, no duct space is disposed within magnetic forces coincide. Incidentally, watt losses in the
the parts 25 of the coil inserted into V-phase leg (third leg) transformer can be reduced by increasing the cross-sectional
113. On the other parts than the parts 25 on coil ends of the area of the wires used for the coils 2. Rectangular wire, strip,
coils 2, a plurality of C-shaped duct spaces 24 are provided. 15
round wire can be employed as a wire in the coils 2. Use of
Since heat generated in the coils 2 is reduced, overall a plurality of Strands in parallel contributes to improvement
configuration of the duct space is reduced, whereby the in processability and easy winding. In FIG. 5B, one example
radial dimension of the coils 2 can be reduced. Therefore, of the primary coil 21 composed of two rectangular wires
the width of the magnetic core window, where the coil 2 is 21a and 21b of respectively t and t in thickness and w in
inserted, can be narrowed, and the dimensions of the unit width is depicted. In FIG. 5C, one example of the secondary
core 11 can also be reduced, which enables to lighten the coil 22 composed of three strips 22a of t in thickness and
weight of unit core 11 as well. w in width is depicted. In addition to the reduction of watt
In the amorphous metal core transformer of the present losses, disposing the duct spaces 24, where insulation oil
embodiment, the secondary coil 22 is made of aluminum flows through, within the coils 2 reduces the temperature rise
strips, which helps to improve the workability of coil 25
caused by the heat generated inside. Thus, coils 2 with low
winding. Incidentally, aluminum has a lower density and a temperature rise is provided. Further, in the present embodi
higher electrical resistance than copper, which boosts Vol ment, by combining or assembling the coils and the amor
ume when used for a coil. For this reason, it is preferable to phous five-legged core, the magnetic core-coil assembly
reduce the amount of aluminum conductor used, and it is with low temperature rise is provided.
recommended to use it only for the secondary coil 22 30
The amorphous metal core transformer of the present
outside. The conductor cross-sectional area of the primary
coil 21 is about 1.2 times larger than that of the related art. embodiment is for three phase 1000 kVA, 50 Hz use in
The conductor cross-sectional area of the secondary coil 22 which core losses are approximately 305 W and watt losses
is about 4.0 times larger than that of the related art. These are approximately 7730 W, resulting in total losses of
larger conductor cross-sectional areas reduce the resistances 35 approximately 8035 W. The amorphous metal core trans
of the coils 21 and 22, which reduces watt losses in the former of the present embodiment can reduce core losses,
amorphous metal core transformer consequently. Moreover, watt losses and total losses more than an amorphous metal
A—A connection system of coils 2 in the present embodi core transformer in the related art. It also suppresses the
ment reduces the cross-sectional area of coil conductor temperature increase of the transformer, which realizes an
approximately to 1/V3 compared with Y-A connection sys 40 amorphous metal core transformer with Smaller cooling
aca.
tems. This enables to use a wire with smaller diameter, and
since radius of bending can be reduced, winding the coil Not only in the amorphous metal core transformer of three
conductor on the bobbin becomes easier, resulting in a phase 1000 kVA, 50 Hz use described in the embodiment,
compact coil and improvement of the workability in winding but also in a transformer of different capacities, more
coils. And, as the coils 2 are wound around the bobbin 26 45 reduction in core losses, watt losses and total losses can be
having a greater strength than the amorphous magnetic strip, achieved by present invention. For example, in a transformer
the work of winding the primary coil 21 composed of of 750 kVA use, core losses will be approximately 255 W.
rectangular copper conductor wires and the secondary coil watt losses, approximately 5790 W and total losses, approxi
22 composed of aluminum strips is facilitated. Furthermore, mately 60455 W, in a transformer of 500 kVA use, core
magnetic characteristic of the unit cores 11 composed of 50 losses will be approximately 240 W, watt losses approxi
amorphous magnetic strip are Subject to degradation by the mately 2860 W and total losses approximately 3100 W. and
compressive force resulting from deformation caused by the in a transformer of 300 kVA use, core losses will be
elasticity of the material of the coils 2, or deformation approximately 185 W, watt losses, approximately 1580 W
caused by electromagnetic force. However, since the unit and total losses, approximately 1765 W. The losses are
magnetic cores 11 are inserted into a bobbin spacer 262 55 reduced in every case.
inside the bobbin 26, the degradation of magnetic charac As for the current density calibrated due to difference of
teristics caused by the compression force is circumvented, the electrical resistance of conductor materials in the coil
and watt losses in the amorphous metal core transformer is (hereinafter equivalent current density), the ratio of the
reduced. In the amorphous metal core transformer of the equivalent current density in the primary coil to that in the
present embodiment, the primary coil has higher current 60 secondary coil is 1.1 (i.e. the equivalent current density in
density than that in the secondary coil when calibrated into the primary coil is 1.1 times higher than that in the secondary
the current density in an aluminum conductor. Therefore, coil) in the 1000kVA use transformer in the present embodi
though the calorific value generated in the primary coil is ment. As for the transformers of different capacities, the ratio
greater than that in the secondary coil, as the magnetic cores is 1.2 in the transformer of 750 kVA use, and is 1.53 in the
are present inside the primary coil with the bobbin in 65 transformer of 500 kVA. Anyway, it is desirable to set the
between, and the magnetic cores serve as the coolant to equivalent current density in the primary coil higher than
absorb the heat generated from the primary coil, the tem that in the secondary coil. The preferable value of the ratio
 US 7,034,648 B2
10
of the equivalent current density in the primary coil to that five legs are formed in the protective member 13 made of
in the secondary coil is 1.05 or higher. rectangular-shaped insulating material. In FIG. 13, (b) is a
One example of the assembling method for the magnetic magnified view of the notch C1.
core-coil assembly 3 of the present embodiment will be In FIGS. 13, (a) and (b), a piece of the triangular
described referring to FIGS. 7 to 9. The magnetic core-coil insulating material emerging in the notch C1 is folded
assembly 3 obtained by this assembling method has a downward to forman angular part 131. This angular part 131
configuration in which the unit wound cores 11 are inserted is stuck to the innermost circumference of the coil or the
into the coils 2 disposed in a row. bobbin 23 with an adhesive tape 18a, such as a kraft paper
FIG. 7 is a schematic diagram of the unit iron core 11 after tape, so as to form no gap between the angular part 131 and
annealing. The core 11 is formed in an inverted U shape with 10
the innermost circumference of the coil or the bobbin. 23.
the joint portion opened. A reinforcement member 15 is
provided on the inner circumference of the core 11 and a Further, it is preferable to stick an adhesive tape 19 to the
reinforcement member 16 made of a silicon steel plate is inside corners of the coil window for reinforcement. Fur
provided on the outermost circumference of the core 11. thermore, instead of using the adhesive tape 19, attaching
Moreover, the insulating members 14 and 12 are adhered so 15 may be accomplished with glue.
as to cover surfaces of the core 11 except the joint portion One modified example of the method for assembling the
for protecting its edges of the yoke portion and leg portion. magnetic core-coil assembly 3 will be described with ref
Assembling process of the unit cores 11 into the coils 2, erence to FIGS. 10 to 12. Referring to FIG. 10, in this
i.e., steps (a) to (g), will be explained with reference to FIG. modified example, protection members of an insulating
8. material are provided on the upper and lower end Surfaces of
At step (a), on the end surface of the coils 2 (i.e. lower end the coils 2.
portions of the coils 2 in FIG. 8(a)), the protective member
13 is adhered to the insulating member on the innermost In FIG. 10, an unit core 11 formed in the inverted U shape
circumference of the coils or the bobbin 23. No gap is by opening the joint portion after annealing is disclosed. A
formed between the protective member 13 and the insulating 25 reinforcing member 15 for providing strength to the unit
member on the innermost circumference of the coils or the core 11 is provided on the innermost circumference, and a
bobbin 23. On the protective member 13, notches C1 for reinforcing member 16 of a silicon steel plate is provided on
inserting the unit core 11 are provided as disclosed in FIG. the outermost circumference.
13. Referring to FIG. 11, steps to insert the unit magnetic
At step (b), the unit magnetic cores 11 formed in the 30 cores 11 of FIG. 10 into the coils 2 are disclosed.
inverted U shape are inserted into the protective member 13 At step (a), as shown in FIG. 11, on both end surfaces of
through the coil windows 26 as shown in (b) of FIG.8. The the coils 2, two protective members 13 are adhered to the
protective member 13 is made of insulating material and insulating members on the innermost circumference of the
may be either a single continuous member or a continuous coils or the bobbins 23. No gap is formed between the
member formed by Sticking together a plurality of split parts 35 protective members 13a, 13b and the insulating members on
with adhesive tape. the innermost circumference of the coils or the bobbins 23.
At step (c), the insertion of the unit magnetic cores 11 is Each of the protective members 13a and 13b has the same
completed as shown in FIG.8. configuration as the protective member 13 shown in FIG. 13.
At step (d), the magnetic cores 11, the coils 2 and the On the protective member 13a, 13b notches C1 for inserting
protective member 13 are turned so that the surface of said 40
the unit core 11 are also provided as disclosed in FIG. 13.
protective member 13 be vertically oriented as shown in At step (b), the unit magnetic cores 11 formed in the
FIG.8. Then the joint portions 11j of the inverted U-shaped inverted U shape are inserted into the protective members
cores 11 are closed so as to form butted joints in the yoke 13a, 13b and the coil windows 26 as shown in FIG. 11. The
portion. protective members 13a, 13b are made of insulating material
At step (e), as disclosed in FIG. 8, the yoke portions 45
and may be either a single continuous member or a con
including the joint portions 11j of the magnetic cores 11 are tinuous member formed by Sticking together a plurality of
covered by the protective member 13. The protective mem split parts with adhesive tape.
ber 13 is folded so as to cover the yoke portions of the At step (c), the insertion of the unit magnetic cores 11 is
magnetic cores 11. No gap is formed between the protective completed as shown in FIG. 11.
member 13 and the insulating member on the innermost 50
circumference of the coils or the bobbin 23 to prevent At step (d), the magnetic cores 11, the coils 2 and the
amorphous fragments from entering inside the coils 2. protective members 13a, 13b are turned so that the surface
At step (f), as shown in FIG. 8, the yoke portions of of said protective members 13a, 13b be vertically oriented
magnetic cores 11 are wrapped with the protective member as shown in FIG. 11. Then the joint portions 11j of the
13, and amorphous fragments are prevented from falling off. 55 inverted U-shaped cores 11 are closed so as to form butted
At step (g), as shown in FIG. 8, the unit magnetic cores joints in the yoke portion.
11 configured as described above are erected and thereby At step (e), as shown in FIG. 11, the yoke portions
completed. including the joint portions 11j of the magnetic cores 11 are
By the steps (a) through (g) described above, the magnetic covered by the protective member 13b. The yoke portions
core-coil assembly disclosed in FIG. 9 is obtained. 60 without the joint portions 11j of the magnetic cores 11 are
A second modified example of the method for assembling covered by the protective member 13a. The protective
the magnetic core-coil assembly will be described with members 13a, 13b are folded so as to cover the yoke
reference to FIG. 13. portions of the magnetic cores 11. No gap is formed between
FIG. 13 discloses an example of a method for sticking the the protective members 13a, 13b and the insulating mem
protective member 13 to the insulating member on the 65 bers on the innermost circumference of the coils or the
innermost circumference of the coil or the bobbin. 23. As bobbins 23 to prevent amorphous fragments from entering
disclosed in (a) of FIG. 13, five notches C1 corresponding to inside the coils 2.
 US 7,034,648 B2
11 12
At step (f), as shown in FIG. 11, the yoke portions of outside. Insulating oil, not to contain any gas, should be
magnetic cores 11 are wrapped with the protective members deaerated beforehand or saturated with nitrogen gas after
13a, 13b, and amorphous fragments are prevented from deaeration. The external terminals 41 are connected by the
falling off. coils 2 and line wires. The cooling fins discharge the heat
At step (g), as shown in FIG. 11, the unit magnetic cores generating from the coils 2 and other internal sources into
11 configured as described above are erected and thereby the atmosphere.
completed. In addition, The present invention is also applied to an
By the steps (a) through (g) described above, the magnetic amorphous metal core transformer with molded resin coils.
core-coil assembly shown in FIG. 12 is obtained. Furthermore, it is also applied to a single phase transformer
Next, One modified example of the protective member is 10 as disclosed in FIG. 15. This single phase amorphous metal
explained referring to FIG. 14. This example shows another core transformer has an magnetic core-coil assembly 3,
method for sticking the protective member 13c to the magnetic cores 1 and coils 2, and the coils 2 have a primary
insulating member on the innermost circumference of the coil 21, a secondary coil 22, a bobbin 26, and a bobbin
coil or the bobbin 3. spacer 262. In the bobbin 26, an insulating member 261 is
As shown in (a) of FIG. 14, in the protective member 13c 15 inserted into a slit in order not to form a one-turn coil.
made of a rectangular insulating material, five notches C2 According to the present invention, as the temperature
shaped as a coil window are formed. In FIG. 14, (b) is a rise within the transformer can be restrained, magnetic cores
magnified view of the notch C2. and coils can be operated at a relatively low temperature, so
As illustrated, the notches C2 are aligned to the edge part that Smaller cooling fins can be used, and accordingly the
of the coil window. The protective members 13c are stuck to amorphous metal core transformer that facilitates wiring
the insulating member on the innermost circumference of work in coil winding can be obtained.
the coil or the bobbin 23 with an adhesive tape 18b at the This concludes the description of the preferred embodi
notches C2. The adhesive tape 18b is a kraft paper tape for ments. Although the present invention has been described
instance. No gap is formed between the notches C2 and the with reference to a number of illustrative embodiments
innermost circumference of the coil or the bobbin 23. In 25 thereof, it should be understood that numerous other modi
addition, the adhesive tape 19 may be stuck to the inside fications and embodiments can be devised by those skilled
corners of the coil window for reinforcement. in the art that will fall within the spirit and scope of the
This invention is not limited to the above-described principles of this invention. More particularly, reasonable
embodiments. It is also applied to an amorphous wound core variations and modifications are possible in the component
transformer having three legs or more, with necessary modi 30 parts and/or arrangements of the Subject combination
fication. This invention is also applied to any transformer arrangement within the Scope of the foregoing disclosure,
having a core configuration in which a plurality of unit the drawings and the appended claims without departing
magnetic cores 11 are arranged in two or more rows in the from the spirit of the invention. In addition to variations and
widthwise direction of the cores. In this case, a plurality of modifications in the component parts and/or arrangements,
unit cores arranged in rows in the widthwise direction of the 35 alternative uses will also be apparent to those skilled in the
cores may be covered with a protecting material row by row, art.
each row being treated collectively, or all the rows may be What is claimed is:
covered with a protecting material collectively. 1. An amorphous metal core transformer comprising:
According to the above-described methods for assem a magnetic core composed of a plurality of amorphous
bling the magnetic core-coil assembly, an amorphous metal 40 metal strips;
core transformer capable of improving insulating perfor a primary coil of a copper conductor material wound on
mance by preventing amorphous fragments from Scattering. said magnetic core; and
Next, the transformer casing 4, if it is provided with a secondary coil of an aluminum conductor material
cooling fins 42 outside, can reduce the temperature rise in wound on said primary coil and disposed outside said
the transformer. In the amorphous metal core transformer of 45 primary coil in a radius direction of said primary coil,
the present embodiment, Smaller watt losses than that in a wherein
conventional amorphous metal core transformer resulting in an amount of heat generated by a current flowing through
less temperature rise enables to reduce the cooling area by said primary coil is greater than an amount of heat
lowering the height of fins or reducing their number. For generated by a current flowing through said secondary
example, since the height of the cooling fins 42 may be 50 coil, so that the heat generated from the primary coil is
within the range of 17 mm to 280 mm, the height can be dissipated in said magnetic core and in said secondary
reduced by approximately 20% compared with the conven coil and;
tional amorphous metal core transformer. The total Surface said secondary coil has a greater length than a length of
area of the cooling fins is set to between 0 m and 100 m. said primary coil in an axial direction of the primary
In addition, as the Surface of the transformer casing also has 55 and secondary coils.
a role in cooling, the total Surface area of the cooling fins and 2. An amorphous metal core transformer according to
the transformer casing is preferably 130 m or less. Inciden claim 1, wherein said primary employs a rectangular copper
tally, the cooling fins can also serve as ribs to enhance the wire, and said secondary coil employs an aluminum Strip
strength of the transformer casing. And the transformer W1e.
casing 4 accommodates the magnetic core-coil assembly 3 60
and insulating oil inside, and has external terminals 41