US3918153A - Method of constructing a magnetic core - Google Patents

Method of constructing a magnetic core Download PDF

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Publication number
US3918153A
US3918153A US126632A US12663271A US3918153A US 3918153 A US3918153 A US 3918153A US 126632 A US126632 A US 126632A US 12663271 A US12663271 A US 12663271A US 3918153 A US3918153 A US 3918153A
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United States
Prior art keywords
assembly
laminations
leg
yoke
group
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Expired - Lifetime
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US126632A
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English (en)
Inventor
Charles E Burkhardt
Belvin B Ellis
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ABB Inc USA
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Westinghouse Electric Corp
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Priority to US126632A priority Critical patent/US3918153A/en
Priority to FR7209814A priority patent/FR2130493B1/fr
Priority to JP1972033203U priority patent/JPS5211126Y2/ja
Application granted granted Critical
Publication of US3918153A publication Critical patent/US3918153A/en
Assigned to ABB POWER T&D COMPANY, INC., A DE CORP. reassignment ABB POWER T&D COMPANY, INC., A DE CORP. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: WESTINGHOUSE ELECTRIC CORPORATION, A CORP. OF PA.
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/24—Magnetic cores
    • H01F27/245—Magnetic cores made from sheets, e.g. grain-oriented
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/4902—Electromagnet, transformer or inductor
    • Y10T29/49075—Electromagnet, transformer or inductor including permanent magnet or core
    • Y10T29/49078—Laminated

Definitions

  • 126632 cal inductive apparatus such as transformers and reactors, having stepped-lap joints between adjoining leg [52] US. Cl. 29/609; 336/217; 336/234 and yoke portions thereof.
  • the method provides a [51] Int. Cl. HOlF 41/02 contin ous s epped-lap joint which extends aro nd [58] Field of Search 29/602, 609; 336/216, 217, each corner of the magnetic core, while incrementally 336/234 clipping only one end of each leg and yoke lamination, and the laminations are assembled without any portion [56] References Cited thereof protruding past the major outline of the mag- UNITED STATES PATENTS, netic core configuration.
  • the invention relates in general to magnetic cores for electrical inductive apparatus, and more specifically to methods of constructing magnetic cores of the stacked type for such apparatus.
  • the stepped-lap type of joint in a magnetic core structure i.e., where the joints between the leg and yoke portions of the core, ineach layer of the laminations, are incrementally offset from similarly located joints in adjacent layers, in a predetermined stepped or progressive pattern, substantially improves the performance of a core, compared withthe butt-lap type joint.
  • Examples of the stepped-lap construction are shown in U.S. Pat. Nos. 3,153,215; 3,477,053 and 3,540,120, and the butt-lap construction is shown in U.S. Pat. No. 2,300,964, all of which are assigned to the same assignee as the present application.
  • the performance of the stepped-lap magnetic core structure can be optimized by increasing the number of steps in the stepped-lap pattern before the pattern repeats, and by increasing the amount of overlap between adjacent joints.
  • the larger overlap is also desirable in larger magnetic cores, as it increases the mechanical strength of the core and makes stacking of long laminations less critical from a tolerance viewpoint.
  • Increasing the number of joints per basic pattern, and the amount of overlap between adjacent joints increases the void volume generated at the corners of the core opening or window, which is undesirable" due to the natural "tendency of the magnetic flux to hug thesein'ner corners of the magnetic core.
  • U.S. Pat. No. 3,477,053 discloses a structure which reduces the void volume at the window corners by transferring a portion of the void volume to the 'outer comers of the magnetic core, where it has less adverse affect on the losses of the magnetic core, but the disclosed construction requires that both' ends of certain laminations be clipped, in order to prevent the ends of certain of the laminations from protruding past the major outline configuration of the magnetic core. In certain applications protruding ends may cause. no problem, but in other applications they may interfere with the end frames, or with form-fit tanks, and in those applications they must be clipped to conform to the major core outline.
  • U.S. Pat. No. 3,540,120 discloses stepped-lapjoint constructions which generate no void volume. How ever, die cutting is required, which'is a disadvantage 2 where it is desirable to utilize existing shear equipment. Thus, it would be desirable to cut all of the laminations of the stepped-lap core with a shear, which cuts completely across the width dimension of the sheet to form the required leg and yoke laminations.
  • the present invention is a new and improved method of constructing magnetic cores with steppedlap joints between the adjoining leg and yoke portions, which method substantially doubles the number of joints in the stepped pattern without any protrusions beyond the major core outline configuration, while clipping only one end of the laminations, and without generating any more void volume at the corners of the window or opening in the magnetic core than prior art patterns having approximately half the number of steps.
  • the resulting basic stepped pattern is located on both sides .of each corner of the magnetic core, with this construction being accomplished even though the ends of groups of laminations are incrementally clipped and aligned against a plane surface.
  • leg and different length yoke laminations are stacked in different groups with the incrementally clipped ends against" a plane surface, to step or space the diagonally cut edges of the laminations of the stack in a predetermined progressive arrangement.
  • Two groups of leg laminations and two groups of yoke laminations are assembled, which groups are all similarly oriented with the longest lamination on. one side of the group and the shortest lamina-' tion. on the other side of the group, to provide a first assembly.
  • two groups of leg laminations and two groups of yoke laminations are assembled to form a second assembly, and the second assembly is superposed on the first assembly, with the second assembly being similar to the first except in rotational symmetry therewith about an axis of the first assembly which is parallel to the major planes of the laminations therein.
  • the longest laminations of the second assembly are disposed against the longest laminations of the first assembly.
  • the unclipped end of the longest lamination of each group is placed to start at an outer geometrical corner of the magnetic core configuration.
  • the laminations do not protrude past the major core outline configuration.
  • the void volume at the inner corners of the core iseffectively reduced because it is shifted back and forth from assembly to assembly, between the leg and yoke portions of the core.
  • the number of joints in the stepped pattern is substantially doubled, without increasing the effective void volume, compared with a magnetic core having one half the number of steps in the basic stepped-lap pattern, and the laminations may all be formed with a 'shear,-as each lamination is cut with a single straight cut, completely across the width dimension of the strip from which it is formed.
  • FIG. 1 illustrates a strip of magnetic, metallic material, with the pattern shown thereon for cutting leg and yoke laminations according to the new andimproved method of constructing a magnetic core;
  • FIGS. 2A-2E illustrate trapezoidal shaped yoke laminations cut from the strip of magnetic, metallic material shown in FIG. 1, with the incremental clipping pattern indicated thereon;
  • FIGS. 3A-3E illustrate trapezoidalshaped leg laminations cut from the strip of magnetic, metallic material shown in FIG. 1, with the incremental clipping pattern indicated thereon;
  • FIG. 4 illustrates the stacking and the start of the assembly of two groups of leg laminations with two groups of yoke laminations, to provide a first basic assembly of groups
  • FIG. 5 is a plan view of the first basic assembly after the assemblyof the groups of leg and yoke laminations has been completed;
  • FIG. 6 is a plan view of the second basic assembly, which is similar to the first basic assembly, except in 180 rotational symmetry therewith about an axis parallel with the planes of the major surfaces of the laminations; 7
  • FIG. 7 is a plan view illustrating the second basic assembly superposed on the first basic assembly, to form a composite assembly
  • FIG. 8 is a cross sectional view of the basic steppedlap pattern of the composite assembly shown'in FIG. 7, taken in the direction of arrows VIII-VII'I.
  • FIG. 7 the figures illustrate the steps of a new and improved method of forming a magnetic core 9, shown in a plan view in FIG. 7, having first and second leg portions 22 and 24, respectively, disposed in spaced parallel relation, the adjacent ends of which are joined by first and second yoke portions 26 and 28, respectively.
  • the assembled leg and yoke portions define a substantially rectangular window or opening 29, with the opening having corners'92, 94, 96 and 98.
  • the magnetic core 9 also has a substantially rectangular outer configuration, having four outer corners referenced 100, 102, 104 and 106. While portions 22 and 24 are referenced leg portions, and portions 26 and 28 are referenced yoke portions, it will be understood that their functions may be interchanged, de-
  • the magnetic core 9 may function as one-half of a magnetic core of the shell-formed type, wherein a similar structure would be placed adjacent thereto, with the windings of the electrical apparatus proceeding through the openings in both of the magnetic core structures.
  • the first step of the new and improved method of constructing magnetic core 9 is to provide a strip 10 of metallic, magnetic material, as shown in FIG. 1.
  • Strip 10 which is preferably formed of grain oriented material, such as silicon steel having apreferred direction of magnetic orientation which is parallel with the sides 17 and 19 of the strip, has a predetermined width dimento show where spaced, straight cuts 11, 13 and 15 may be made to provide a plurality of trapezoidal shaped yoke laminations for the magneticcore 9, such as yoke laminations 14 and 16, and a plurality of trapezoidal shaped leg laminations for the magentic core 9, such as leg laminations 18 and 20.
  • the cuts 11, 13 and 15 extend'across the complete width dimension of strip 12, at an angle of substantially 45 relative to the sides or edges 17 and 19 of the strip 10.
  • the leg and yoke laminations may be assembled with their diagonally cut ends butting together, to provide a joint which presents the least reluctance to magnetic flux, for strip which has a preferred direction of magnetic orientation parallel with the edges 17 and 19 of the strip 10. Since the cut lines 11, 13 and 15 are straight, and extend completely across the width dimension 12 of the strip 10, the cuts may be conveniently made with ashear.
  • Magnetic core 9 shown in FIG. 7 has stepped-lap joints between the various leg and yoke portions, in
  • the stepped pattern is achieved by forming all of the yoke laminations to like predetermined dimensions, and all of the leg laminations to like predetermined dimensions, and then incrementally cutting one end of the leg and yoke laminations to form a plurality of different dimensioned leg and yoke laminations.
  • the number of different yoke and leg laminations, and the increments used to cut the different maximum'lengths of these laminations will depend upon the number of steps desired in the basic pattern, and the amount of overlap desired between adjacent joints.
  • the maximum tolerable void volume generated at the inner corners of the core i.e., at the window corners, limited the overlap dimension and the number of steps in the basic pattern.
  • the present invention enables the number of steps in the basic pattern to be substantially doubled, without doubling the effective void volume at the inner corners of the core.
  • the effective void volume may be reduced, or given a predetermined maximumv effective void volume
  • the overlap and number of steps in the basic pattern may be both increased by following the teachings of the present invention, compared with the teachings of the prior art, without requiring die cutting of the laminations, and without clipping both ends of certain of the laminations to prevent them from extending beyond the sides of the magnetic core.
  • the pattern is to have nine steps in succession before repeating, four on each side of the comer of the magnetic core, and one at the corner.
  • the overlap will depend upon the size of the magnetic core, with /8 inch overlap being common for small magnetic cores, and onefourth or even three-eighths inch common for the larger magnetic cores.
  • the nine step pattern requires five different length dimensions for both the yoke and leg laminations, when constructing the core according to the teachings of the invention, with FIGS. 2A, 2B, 2C, 2D and 2E indicating yoke laminations 30, 32, 34, 36 and 38, respectively, which were similarly dimensioned prior to the step of incrementally cutting one of their ends.
  • the incremental cuts start a predetermined dimension-from one end and the cut is made perpendicularto the side of the lamination and it intersects the diagonally cut end of the lamination.
  • fla mination30 shown in FIG. 2A is out along line 40 a predetermined dimension from end 42, and, the small piece 44 is removed from the lamination.
  • Lamination 32 shown in FIG. 2B, is cut along line 46, which is further from point 42 than cut 40 on lamination 30, by the selected increment.
  • lamination 34, 36 and 38 shown in FIGS. 2C, 2D and 2E, respectively. are incrementally cut along lines 48, 50 and 52, respectively.
  • the maximum length dimensions of laminations 30, 32,34, 36 and 38 are decreased in predetermined increments.
  • the lengths of the increments are purposely exaggerated in the drawings, relative to the overall sizes of the lamination, in order to make the incremental clipping of the laminations more readily apparent.
  • FIGS. 3A, 3B, 3C, 3D and 3E illustrate leg laminations 54, 56, 58, 60 and 62, respectively, which are incrementally cut along lines 64, 66, 68, 70 and 72, respectively.
  • the maximum length dimensions of laminations 54, 56, 58, 60 and 62 are thus decreased in predetermined increments, reducing their maximum overall length, without affecting the shorter dimension of each lamination between the two diagonal cuts.
  • the maximum length of lamination 54 shown in FIG. 3A is reduced to dimension 65, while dimension 67 remains unchanged by the incremental cutting.
  • each leg and yoke lamination may be conveniently performed while shearing the lamination from the strip 10.
  • the leading edge of strip may be clipped atthe same time as the associated lamination is being sheared from the strip 10.
  • the next step, shown in FIG. 4, is the stacking of the laminations into groups.
  • the yoke laminations are stacked into groups, each of which includes at least one of the different incrementally cut yoke laminations.
  • the leg laminations are stacked into groups, with each group including at least one of the different incrementally cut leg laminations.
  • the different laminations in each group are sequenced such that the lamination with the longest length dimension is on one side of the group, and the lamination with the shortest length dimension is on the opposite side of the group, with the length dimensions of the remaining laminations decreasing in steps between the longest and shortest laminations.
  • FIG. 4 illustrates first and second groups or'stacks 74 and 76, respectively, of leg laminations, and first and second groups 78 and 80, respectively, of yoke laminations. All of the groups shown in FIG. 4 are similarly stacked, with the longest lamination on top of the stack and the shortest on the bottom, as viewed in FIG. 4, with the clipped ends of the laminations in each group being on the same end of the group. The clipped ends of each group are all placed against a plane surface while superposing the edges of the laminations, to incrementally step or space the diagonally cut edges of the laminations at both ends thereof.
  • Group 74 is thus stacked such that lamination 62 is on the bottom, followed in sequence by laminations 60, 58, 56, and 54.
  • Group 76 is similarly stacked, with the reference nu- 6 merals of the laminations of this group including a prime mark'to distinguish them from the reference numerals of the laminations of group 74.
  • Group 78 is stacked with yoke lamination 38 on the bottom of the stack, followed in sequence by laminations 36, 34, 32 and 30. Group is similarly stacked. with the reference numerals of the laminations of group 80 including a prime mark to distinguish them from like laminations of group 78.
  • the next step is assembling the first and second groups 74 and 76, respectively, of leg laminations with the first and second groups 78 and 80, respectively, of yoke laminations.
  • these groups of leg and yoke laminations are oriented with the longest lamination on top of each group.
  • FIG. 4 illustrates the groups or stacks 74 and 76 of leg laminations disposed in the required spaced par allel relation, with groups 78 and 80 of yoke laminations shown just prior to their assembly with groups 74 and 76.
  • Assembly of the groups requiresthat groups 78 and 80 be moved toward one another, as indicated by arrows 82 and 84, respectively, until the diagonally cut edges of the laminations of the groups 78 and 80 butt against the diagonally cut edges of groups 74 and 76, to provide a first basic assembly 90, shown in FIG. 5, having a plurality of layers of laminations, with stepped-lap joints formed at the junctions of the yoke and leg groups.
  • the first basic assembly defines a substantially rectangular opening or window 29, dimensioned similar to the opening 29 in the magnetic core 9 shown in FIG. 7, with the opening 29 having corners 92', 94', 96 and 98'.
  • the outer configuration of the first basic assembly 90 has corners 100, 102, 104 and 106.
  • the adjoining groups of leg and yoke laminations are placed relative to one another, such that the laminations in the top layer, as viewed in FIGS. 4 and 5, fit together with substantially no void volume at the inner corners. Further, the generated void volume at the corners of the opening 29 alternate between the leg and yoke portions from corner to corner of the window 29'.
  • the groups of laminations are assembled such that the start of the diagonal cuts on the laminations of the top layer are substantially in contact with each other, eliminating any void volume in this layer of laminations.
  • the void volume generated at corner 92 is in the leg portion of the core, the void volume generated at corner 94 is in the yoke portion, the void volume generated at corner- 98 is in the leg portion, and the void volume generated at corner 96 is in the yoke portion.
  • the next step of the method is providing a second basic assembly 110 of groups of leg and yoke laminations, as shown in FIG. 6.
  • the second basic group 110 is similar to the first basic group 90 shown in FIG. 5, except the second basic group is in rotational symmetry with the first basic assembly 90 about an axis of basic assembly 90 which is parallel with the major planes of the laminations of basic assembly 90.
  • the second basic assembly 110 includes first and second groups 74' and 76' of leg laminations, and first and second groups 78 and 80 of yoke laminations.
  • the groups located in the same relative positions as those of the first basic assembly 90 are given the same reference numeral as those of the first assembly, with the prime marks added to distinguish them.
  • the second basic assembly 110 defines an opening or window 29", which has corners 92", 94", 96", and 98", and the outer configuration of the second basic assembly 110 has corners 100", 102", 104", and 106".
  • the void volumes generated at window corners 92", 94", 98" and 96" are in the yoke, leg, yoke and leg portions, respectively, opposite to the locations of the void volume in like corners of the first basic assembly.
  • the next step is superposing the second basic assembly 110 on the first basic assembly 90, with their openings29" and 29 aligned.
  • This provides a composite assembly of first and second basic assemblies, and forms the basic core structure 9 shown in FIG. 7.
  • the magnetic core 9 shownin FIG. 7, however, may have as many superposed composite assemblies as required to obtain the des'iredbuild dimensionof the magnetic core.
  • the step of disposing the second assembly 110 on the first assembly 90 places the layers of the twogroups together which have the longest laminations therein.
  • the shortest laminations are in the bottom and top layers of the composite group, and the longest laminations are at the midpoint of the group.
  • This placement and orientationof the first and second basic assemblies 90 and 110, respectively provides a continuous, stepped-lap joint at each comer of the magnetic core, which has almost twice the number of steps per basic pattern as'the number of laminations in each basic assembly of groups. Further, the step pattern progre sses around each corner of the magnetic core.
  • FIG. 8 is a cross sectional view of the stepped-lap joint located between the inner corner 96 and the outer corner 104 of the magnetic core 9 shown in FIG. 7, with the cross sectional view being taken in the direction of arrows VIIIVIII.
  • the joint 119 located in the bottom layer of the composite assembly starts on the left-hand side of the corner, with the corner being represented by the line 120, and then the stepped joint moves incrementally towards the c'orher, from layer to layer, until reaching the last lamination of the first assembly, with this joint being aligned with the corner.
  • the stack height of the first assembly is indicated by the dimension 124.
  • the second basic assembly represented by the stack dimension 122, has the joint of its bottom layer aligned with the corner 120, and thus it is also aligned with the joint in the top layer of the first basic assembly.
  • the joints then continue on the right-hand side of corner 120, incrementally stepping through the layers of laminations until reaching the top layer of the second basic assembly. Therefore, a single substantially continuous steppedlap pattern having nine steps therein has been created with [0 layers of laminations.
  • the effective length of the flux path has been reduced, as the void I 8 volume appears to be located in both the leg and yoke por'tionsfbut with each being about one-half the void volume of eitherbasic group appearing alone.
  • the effective void volume'at the outer corners of the magnetic core 9 is also reduced, as the clipped ends of the longest laminations extend completely to the geometrical corners of the magnetic core, with'the alternating locations of the first and second basic groups at the outer corners of the core alternately filling different areas of the corner with magnetic material, resulting in a smaller effectivevoid volume due to'this averaging effect.
  • a new and improved method of constructing a magnetic core with stepped-lap joints which method may utilize a shear to cut the laminations from a single strip of magnetic, metallic material, as all of the cuts are straight cuts made completely across the width dimension of the strip of magnetic material.
  • the method provides substantially twice the number of steps in the basic group pattern, without doubling the number of different lamination dimensions, and the basic pattern includes joints on both sides of the corners of the magnetic core while retaining the advantage of being able to incrementallyspace the laminations with incremental clips.
  • the incremental clipping of the laminations is required on only one end of each lamination, enabling the clipping step to be performed while the lamination is being sheared, and the magnetic core resulting from the new and improved method has no protrusions extending beyond the sides of the magnetic core, facilitating the use of the magnetic core with a form-fit type of tank.
  • a method of constructing a magnetic core of the stacked type comprising the steps of:
  • step of superposing the second assembly on the first assembly includes orienting the assembly such that void volume appearing at each comer of the substantially rectangular opening of the composite assembly, is in the yoke portion in one assembly and in the leg portion of the other assembly, to reduce the effective void volume at these corners of the composite assembly.
  • step of assembling the groups of leg and yoke laminations assembles the layer having the longest laminations with substantially no void volume at the inner corners of the assembly.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Manufacturing Cores, Coils, And Magnets (AREA)
US126632A 1971-03-22 1971-03-22 Method of constructing a magnetic core Expired - Lifetime US3918153A (en)

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US126632A US3918153A (en) 1971-03-22 1971-03-22 Method of constructing a magnetic core
FR7209814A FR2130493B1 (enrdf_load_stackoverflow) 1971-03-22 1972-03-21
JP1972033203U JPS5211126Y2 (enrdf_load_stackoverflow) 1971-03-22 1972-03-22

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US126632A US3918153A (en) 1971-03-22 1971-03-22 Method of constructing a magnetic core

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JP (1) JPS5211126Y2 (enrdf_load_stackoverflow)
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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4200854A (en) * 1979-01-04 1980-04-29 Westinghouse Electric Corp. Core with step-lap joints
US4201966A (en) * 1979-01-04 1980-05-06 Westinghouse Electric Corp. Magnetic core structure
US4283842A (en) * 1979-01-04 1981-08-18 Westinghouse Electric Corp. Method of making an electrical inductive apparatus
US4482880A (en) * 1981-09-10 1984-11-13 Mitsubishi Denki Kabushiki Kaisha Iron core for three-phase electromagnetic induction machine
US20080290982A1 (en) * 2007-05-24 2008-11-27 Berkin B.V. Transformer core
US20210391111A1 (en) * 2018-11-01 2021-12-16 Toshiba Industrial Products and Systems Corp. Stacked core for stationary induction apparatus
US11488759B2 (en) * 2016-12-20 2022-11-01 Hyosung Heavy Industries Corporation Transformer iron core

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS53112933U (enrdf_load_stackoverflow) * 1977-02-16 1978-09-08

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2628273A (en) * 1948-12-17 1953-02-10 Gen Electric Magnetic core
US2898565A (en) * 1954-07-02 1959-08-04 Mc Graw Edison Co Magnetic core
US3540120A (en) * 1968-11-12 1970-11-17 Westinghouse Electric Corp Method of constructing magnetic core structures

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2628273A (en) * 1948-12-17 1953-02-10 Gen Electric Magnetic core
US2898565A (en) * 1954-07-02 1959-08-04 Mc Graw Edison Co Magnetic core
US3540120A (en) * 1968-11-12 1970-11-17 Westinghouse Electric Corp Method of constructing magnetic core structures

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4200854A (en) * 1979-01-04 1980-04-29 Westinghouse Electric Corp. Core with step-lap joints
US4201966A (en) * 1979-01-04 1980-05-06 Westinghouse Electric Corp. Magnetic core structure
US4283842A (en) * 1979-01-04 1981-08-18 Westinghouse Electric Corp. Method of making an electrical inductive apparatus
US4482880A (en) * 1981-09-10 1984-11-13 Mitsubishi Denki Kabushiki Kaisha Iron core for three-phase electromagnetic induction machine
US20080290982A1 (en) * 2007-05-24 2008-11-27 Berkin B.V. Transformer core
US7843306B2 (en) * 2007-05-24 2010-11-30 Berkin B.V. Transformer core
US11488759B2 (en) * 2016-12-20 2022-11-01 Hyosung Heavy Industries Corporation Transformer iron core
US20210391111A1 (en) * 2018-11-01 2021-12-16 Toshiba Industrial Products and Systems Corp. Stacked core for stationary induction apparatus
US12033782B2 (en) * 2018-11-01 2024-07-09 Toshiba Industrial Products and Systems Corp. Stacked core for stationary induction apparatus

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JPS5211126Y2 (enrdf_load_stackoverflow) 1977-03-10
JPS485221U (enrdf_load_stackoverflow) 1973-01-22
FR2130493B1 (enrdf_load_stackoverflow) 1975-04-25
FR2130493A1 (enrdf_load_stackoverflow) 1972-11-03

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