CA1169932A - Transformer cores - Google Patents
Transformer coresInfo
- Publication number
- CA1169932A CA1169932A CA000337928A CA337928A CA1169932A CA 1169932 A CA1169932 A CA 1169932A CA 000337928 A CA000337928 A CA 000337928A CA 337928 A CA337928 A CA 337928A CA 1169932 A CA1169932 A CA 1169932A
- Authority
- CA
- Canada
- Prior art keywords
- lamination
- core
- cut
- lengths
- group
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0206—Manufacturing of magnetic cores by mechanical means
- H01F41/0213—Manufacturing of magnetic circuits made from strip(s) or ribbon(s)
-
- 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
- H01F27/25—Magnetic cores made from strips or ribbons
Abstract
ABSTRACT OF THE DISCLOSURE
A method of manufacturing transformer cores of either the continously wound or cut wound type using electrical steel strip having approximately a linear taper.
By selecting a suitable taper, a hexagonal ( or higher order) approximation of a circular cross-section for the legs of the cores is available. Two complementary core strip can be cut from a single rectangular stock strip in a scrapless manner.
A method of manufacturing transformer cores of either the continously wound or cut wound type using electrical steel strip having approximately a linear taper.
By selecting a suitable taper, a hexagonal ( or higher order) approximation of a circular cross-section for the legs of the cores is available. Two complementary core strip can be cut from a single rectangular stock strip in a scrapless manner.
Description
The present invention relates to transformer cores and more particularly to three phase transformers of the wound core type.
There are a multitude of existing designs for trans~
former coreS which can be broadly categorized as rectangular or cruciform. After examination of these existing types, it was considered tha-t the cruciform -types were philosophically supe-rior, but the rectangular types embodied production advantages, -including simplicity.
10The object of the present invention is to improve upon these existing cores.
A preferred object of the invention is to provide a cruciform-like core with legs having a circular cross-section.
Another preferred object of the invention is to provide a core that can be easily manufactured from an electrical ; steel strip without a large number of different widths of electrical steel strip being required.
A further preferred object of the invention is to provide a core of near optimum geometry according to a straight ~ forward procedure, by using a tapered electrical steel strip or produclng a~hexagonal or better approximation to circular cross-section for those portions of the core under the windings.
In its broad aspect, the present invention proposes a method, of manufacturing a transformer core of star or Y
configuration from an electrical steel strip, which core :comprises three ~rames each o~ substan-tlally C-shape in side ~view, the f~rame~being arranged at substantially 120 apart.
This method comprises the steps of:
~; cutting a length of strip into a plurality of laminatlon lengths, each group of three lamination lengths being separated from -the adjacent group at each end by a cut
There are a multitude of existing designs for trans~
former coreS which can be broadly categorized as rectangular or cruciform. After examination of these existing types, it was considered tha-t the cruciform -types were philosophically supe-rior, but the rectangular types embodied production advantages, -including simplicity.
10The object of the present invention is to improve upon these existing cores.
A preferred object of the invention is to provide a cruciform-like core with legs having a circular cross-section.
Another preferred object of the invention is to provide a core that can be easily manufactured from an electrical ; steel strip without a large number of different widths of electrical steel strip being required.
A further preferred object of the invention is to provide a core of near optimum geometry according to a straight ~ forward procedure, by using a tapered electrical steel strip or produclng a~hexagonal or better approximation to circular cross-section for those portions of the core under the windings.
In its broad aspect, the present invention proposes a method, of manufacturing a transformer core of star or Y
configuration from an electrical steel strip, which core :comprises three ~rames each o~ substan-tlally C-shape in side ~view, the f~rame~being arranged at substantially 120 apart.
This method comprises the steps of:
~; cutting a length of strip into a plurality of laminatlon lengths, each group of three lamination lengths being separated from -the adjacent group at each end by a cut
2 -::: : ~ :
3~
at substantially 90 to its longitudinal axis, each said group forming a layer of the core, with the three lamination lengths in the group being separated from each other by cuts at substantially 60 to the longi-tudinal axis;
butt joining the ends of two of the lamination lengths cut at substantially 60 to the sides of a third lamination length adjacent an end of the third lamination length cut substantially 90 to form a lamination layer; and assembling the lamination .layers to form the assem-bled core.
In accordance with a preferred embodiment of the in-ventlon the portion of the strip can be cut with an approxi-mately linear taper to obtain C-shaped frames hexagonal or substantially circular in cross-section.
In accordance with another preferred embodiment of the invention, each layer is rotated one third of a turn from the previous layer prior to assembling it.
III another aspect, the present invention proposes a transformer core constructed according to the abo~e method.
The invention, in its preferred simplest form, namely ~the hexagonal form approximation, can be achieved in either of~two~ways, both using a single wldth size of conventionally slit steel strip~, which is then specially slit. For scrapless production of corès, two identioal cores can be slit from the normal parallel sided strip in such a manner that the tapered pieces are complementary to each other. Two identical tapered strips can readlly be cut from a suitable rectangular piece by cutting it at an appropriate angle.
.
~ The invention will be better understood with reference .
to the following general description of a method of manufacture of a number of different transformer cores, and of a preferred 30 ~ embodiment of the invention applied to a three-phase, Y-shaped transfGrmer core.
3~
In the accompanying drawings:
Fig. 1 is afront view oE a single phase core of substantially hexagonal cross~section Fig. lA is a cross--sectional view taken on line lA-lA
of Fig. 1, Fig. lB shows the cutting plan of the strip for the core of Fig. 1 L
Fig. ~ is a cross-sectional view of a modified form of the core of Fig. l;
10- Fig. 2A shows the cutting plan of the strip for the core of Fig. 2 L
Fig. 3 is a frontview of a single phase shell type corei Fig. 3A is a cross-sectional view taken on line 3A-3A
of Fig. 3;
Fig. 4 is a front view of a three pahse delta~> core Fig. 4A is a cross- sectional view taken on line 4A-4A
of Fiy. 4;
;~ ~ Fig.~ 5A is a view of an assembled layer of a three-phase star core according to the invention;
Fig. 5B is a plan view of the strips for the assembled layer of Fig. SA; and Fig. SC is a perspective ~view of the ~oint of the three-phase~ star core~made from assembled layers as shown in Fig. 5A.
The production of the tapered electrical steel strip used for manufacturing transformer cores of the wound core type ncluding those according to the lnvention is implemented by a suitable slitting machine. Because ~ ~ r : , ::
.... __ ~_ ____ _ . ..... ___ .. __ .,, ~ 4 -' 3~
-the angle Or tclper is so smcll:L e.g. less tl-an 1 , the ax,is of the sli-tting roller~s is set perperlcliclllar to the 5 trip of e.l,ectrical s-teel, and -the nece~sl:ry -tal)er is achieved by f`orcing the ro:Llers ac.ross the shee-tO The need fo:r precise con-t:rol of` the l~osi-tionir~ of` the slittin.g rollers means thnt the slit-ti.n~.r mach:irle is best built with a single pair of rollers :for thc slitti,ng operation. This means tllat it only has I;o accomodate the wiclth of steel needed for the largest core to be cut by the method~ The details of~ the mettlod are mos-t e~sily illus-trated by a description of the relevant parts Or the machine. After dereeling, the strip is passed through a pair of plain rollers, comprising a clriven roller to control the speed of the strip~ and its idler. The strip then passes through two guides with tungsten carbide wear parts which control its latercal position, and then -through a second pair of rollers similar to the firstO The second idler is identical to the first, but the other roller is mQchined to have a circumference which matches the nurnber of pulses ~r revolution of -the pulse generator (sha~t encode:r) that it driYesO This unit thus measures the length along the strip as it lS fed through, ancl the slitting roller assembly : : ~ is immediately adjacent to it. The s,l,itting rollers are mo~mted on a very rigid frame, a~d can be set so that they are pre~
Loaded to minimize deflection:and with the desired a~lount of over-lap. fhe roller :frame is wlder than the strip~ since it mt~ t ~ ' ~ 5~
' :
be able to move back and forth across the strip. The frame is mounted on a machine bed and driven by a worm drive from a direct current motor geared down by a large amount because of the slow travel required. Included in this assembly is a second shaft encoder with its own small roller which enables the position of -the slitting rollers to be known and controlled.
The control system for the slitting roller assembly is straight-forward in that the motion of the slitting rollers sideways across the strip is directly proportional to the length of strip passing through. This can be implemented by ordinary logic and servosystem components, but is better and simpler done by a microprocessor based computer which may control the rest of the machine. Thus the tapered strip required for the core designs can readily be produced.
Figs. 1, lA and lB show a core 10 which can be continuously wound from strips produced as disclosed hereina-boce. This core 10 has a substantially hexagonal cross-section as shown in Fig. lA, comprising a section 10A of increasing width, a central section lOB of maximum width, and a section lac of decreasing width.
Referring to Fig. lB, section lOA is wound from strip llA which is cut from a rectangular stock strip 12, the ; strip;llA having a linear taper from a su~stantially zero width upto the~width of the stock-strip 12.
Section 10B is wound from a strip llB cut from a length of the stock strip 12 and has parallel sides.
: ~ :
' -.,. ,~ .
3~
Section lOC is wound from a strip llC cut from stock strip 12 and has a linear taper from the width of the stock strip 12 down to substantially zero width. As the strip llA, llC are of the same width, they can be cut from lengths of stock strip 12.
A core 20 having the modified form illustrated in Figs. 2 and 2A can be obtained by using substantially the same method of manufacture. The core 20 has a section 20A
of increasing width and a section 20B of decreasing width.
The sections both have a maximum width equal to the maximum width of the core and a minimum width equal to one-half of the core, the sections 20A, 20B being wound from strips 21A, 21B
respectively from rectangular stock strip 22 which has a width equal to 1.5 times the maximum width of the core 20. As the strips 21A, 21B are complementary, two transformer cores 20 can be cut from a single length of stock strip 22 without scrap.
The single phase shell~type core 30 of figs. 3 and : .
~ 3A has a pair of core frames 3IA each with a cross-section . :~ .
which is substantially identical with an isosceles trapezium.
When the two rames are placed back-to-back, the central leg is substantially hexagonal in cross-section ~as shown in Flg. 3A). ;Each~frame can be wound from a single strlp of ~ ~:
increasing~width, such as strips 21A, 21B shown in fig. 2A.
As these strips are complementary, the core 30 can be produced from a single piece oE rectangular stock strip i.e. strip 22.
; The three-phase delta core 40 shown in figs. 4 and :
: ;' , /
~_ _. ______. __ . __ _.. __ ~ ~ - 7 -:: ::
-, .~ ,:
at substantially 90 to its longitudinal axis, each said group forming a layer of the core, with the three lamination lengths in the group being separated from each other by cuts at substantially 60 to the longi-tudinal axis;
butt joining the ends of two of the lamination lengths cut at substantially 60 to the sides of a third lamination length adjacent an end of the third lamination length cut substantially 90 to form a lamination layer; and assembling the lamination .layers to form the assem-bled core.
In accordance with a preferred embodiment of the in-ventlon the portion of the strip can be cut with an approxi-mately linear taper to obtain C-shaped frames hexagonal or substantially circular in cross-section.
In accordance with another preferred embodiment of the invention, each layer is rotated one third of a turn from the previous layer prior to assembling it.
III another aspect, the present invention proposes a transformer core constructed according to the abo~e method.
The invention, in its preferred simplest form, namely ~the hexagonal form approximation, can be achieved in either of~two~ways, both using a single wldth size of conventionally slit steel strip~, which is then specially slit. For scrapless production of corès, two identioal cores can be slit from the normal parallel sided strip in such a manner that the tapered pieces are complementary to each other. Two identical tapered strips can readlly be cut from a suitable rectangular piece by cutting it at an appropriate angle.
.
~ The invention will be better understood with reference .
to the following general description of a method of manufacture of a number of different transformer cores, and of a preferred 30 ~ embodiment of the invention applied to a three-phase, Y-shaped transfGrmer core.
3~
In the accompanying drawings:
Fig. 1 is afront view oE a single phase core of substantially hexagonal cross~section Fig. lA is a cross--sectional view taken on line lA-lA
of Fig. 1, Fig. lB shows the cutting plan of the strip for the core of Fig. 1 L
Fig. ~ is a cross-sectional view of a modified form of the core of Fig. l;
10- Fig. 2A shows the cutting plan of the strip for the core of Fig. 2 L
Fig. 3 is a frontview of a single phase shell type corei Fig. 3A is a cross-sectional view taken on line 3A-3A
of Fig. 3;
Fig. 4 is a front view of a three pahse delta~> core Fig. 4A is a cross- sectional view taken on line 4A-4A
of Fiy. 4;
;~ ~ Fig.~ 5A is a view of an assembled layer of a three-phase star core according to the invention;
Fig. 5B is a plan view of the strips for the assembled layer of Fig. SA; and Fig. SC is a perspective ~view of the ~oint of the three-phase~ star core~made from assembled layers as shown in Fig. 5A.
The production of the tapered electrical steel strip used for manufacturing transformer cores of the wound core type ncluding those according to the lnvention is implemented by a suitable slitting machine. Because ~ ~ r : , ::
.... __ ~_ ____ _ . ..... ___ .. __ .,, ~ 4 -' 3~
-the angle Or tclper is so smcll:L e.g. less tl-an 1 , the ax,is of the sli-tting roller~s is set perperlcliclllar to the 5 trip of e.l,ectrical s-teel, and -the nece~sl:ry -tal)er is achieved by f`orcing the ro:Llers ac.ross the shee-tO The need fo:r precise con-t:rol of` the l~osi-tionir~ of` the slittin.g rollers means thnt the slit-ti.n~.r mach:irle is best built with a single pair of rollers :for thc slitti,ng operation. This means tllat it only has I;o accomodate the wiclth of steel needed for the largest core to be cut by the method~ The details of~ the mettlod are mos-t e~sily illus-trated by a description of the relevant parts Or the machine. After dereeling, the strip is passed through a pair of plain rollers, comprising a clriven roller to control the speed of the strip~ and its idler. The strip then passes through two guides with tungsten carbide wear parts which control its latercal position, and then -through a second pair of rollers similar to the firstO The second idler is identical to the first, but the other roller is mQchined to have a circumference which matches the nurnber of pulses ~r revolution of -the pulse generator (sha~t encode:r) that it driYesO This unit thus measures the length along the strip as it lS fed through, ancl the slitting roller assembly : : ~ is immediately adjacent to it. The s,l,itting rollers are mo~mted on a very rigid frame, a~d can be set so that they are pre~
Loaded to minimize deflection:and with the desired a~lount of over-lap. fhe roller :frame is wlder than the strip~ since it mt~ t ~ ' ~ 5~
' :
be able to move back and forth across the strip. The frame is mounted on a machine bed and driven by a worm drive from a direct current motor geared down by a large amount because of the slow travel required. Included in this assembly is a second shaft encoder with its own small roller which enables the position of -the slitting rollers to be known and controlled.
The control system for the slitting roller assembly is straight-forward in that the motion of the slitting rollers sideways across the strip is directly proportional to the length of strip passing through. This can be implemented by ordinary logic and servosystem components, but is better and simpler done by a microprocessor based computer which may control the rest of the machine. Thus the tapered strip required for the core designs can readily be produced.
Figs. 1, lA and lB show a core 10 which can be continuously wound from strips produced as disclosed hereina-boce. This core 10 has a substantially hexagonal cross-section as shown in Fig. lA, comprising a section 10A of increasing width, a central section lOB of maximum width, and a section lac of decreasing width.
Referring to Fig. lB, section lOA is wound from strip llA which is cut from a rectangular stock strip 12, the ; strip;llA having a linear taper from a su~stantially zero width upto the~width of the stock-strip 12.
Section 10B is wound from a strip llB cut from a length of the stock strip 12 and has parallel sides.
: ~ :
' -.,. ,~ .
3~
Section lOC is wound from a strip llC cut from stock strip 12 and has a linear taper from the width of the stock strip 12 down to substantially zero width. As the strip llA, llC are of the same width, they can be cut from lengths of stock strip 12.
A core 20 having the modified form illustrated in Figs. 2 and 2A can be obtained by using substantially the same method of manufacture. The core 20 has a section 20A
of increasing width and a section 20B of decreasing width.
The sections both have a maximum width equal to the maximum width of the core and a minimum width equal to one-half of the core, the sections 20A, 20B being wound from strips 21A, 21B
respectively from rectangular stock strip 22 which has a width equal to 1.5 times the maximum width of the core 20. As the strips 21A, 21B are complementary, two transformer cores 20 can be cut from a single length of stock strip 22 without scrap.
The single phase shell~type core 30 of figs. 3 and : .
~ 3A has a pair of core frames 3IA each with a cross-section . :~ .
which is substantially identical with an isosceles trapezium.
When the two rames are placed back-to-back, the central leg is substantially hexagonal in cross-section ~as shown in Flg. 3A). ;Each~frame can be wound from a single strlp of ~ ~:
increasing~width, such as strips 21A, 21B shown in fig. 2A.
As these strips are complementary, the core 30 can be produced from a single piece oE rectangular stock strip i.e. strip 22.
; The three-phase delta core 40 shown in figs. 4 and :
: ;' , /
~_ _. ______. __ . __ _.. __ ~ ~ - 7 -:: ::
-, .~ ,:
4~ comprises three frames 41 each conjoined at their sidesto the other two frames, the legs of the core having a substantially hexagonal cxoss-section. Each frame 41 is continuously wound from a section 42 of fixed width (equal to 0.5 times the diameter of the leg) cut from a length of rectangular stock strip of that width, and then a section 43 of decreasing width. As the sections 43 of two of the frames can be complementary, they can be cut from rectan~ular stock strip having a width equal to 0.5 times the diameter of the core legs. The core 40 is assembled by placing the frames ~1 in the configuration shown in figs. 4 and 4A and securing the frames together.
All the cores shown in figs. 1 to 4A have been disclosed by way of interest only, in order to better explain how core legs having a substantially hexagonal or circular cross-section can readily be obt~ained from steel strips of increasing and/or decreasing taper and/or constant width.
The invention however is restricted to the manufacture of transformer core of star or Y configuration.
~ Figs.5~, 5B an~-5C illustrate the manufacture of such a three-phase astar or aY core 50 with legs of substantially hexagonal cross-section. The core 50 comprises three frames 51A, 51B, 51C each of substantially C-shape in side view.
Each frame 51A, 51B, 51C is formed from a series of lamination lengths A, B, C respectively cut from atapered strip 53.
The strip 53 is of increasing taper to form section 52A of each frame,and of decreasing taper to Eorm section 52B, and may be cut as shown in Fig. 2A.
Lamination lengths A.B.C are cut to selected length of square-ended strip 53 with two cuts at 60 to the longitu-dinal axis of the strip 53. This cutting step for most size , . .
93~
cores can i~nore the taper on the layers which come from the tapered strip because of the small angle of taper.
Each layer is formed as shown in FIG. 5A where the angled cut ends of each lamination length are butted to the side of adjacent strip adjacent its free ends.
The method of assembling such a star core is to lay together all the laminations so that one joint (e.g. the bottom joint) is assembled and the core has the appearance Or three radial arms. The joint is clamped and the lamination arms A, s, C are bent upward until they are perpendicular to the plane of the joint. The arms are secured hy claimping and then the joint is unclamped enabling the clamped arms to be separated from the joint. The top portion of each clamped laminated arm is then folded to form a substantially C-shaped laminated assembly of lamination lengths. The electromagnetic properties of the joint are best when each layer is rotated one third of a turn from the previous layer, that is when piece A
of FIG. 5A is placed one each core leg in turn. This core joint~is the only straight cut, scrapless butt inter-leaved ~star or Y core joint, and applicable not only to cores with tapered strip, but to any core of this type, also known as Y
~(wye) cores.~ The section labelled E can be seen to protrude from the joint, but there is no advantage to be gained by removing it.~
All of the new desings, being of the wound core type, require annèaling after -they have been cut and formed to shape.
By using the tapered strip to form the cores, which can be continuously wound ~except for the star core 50 of ~FIGS. 5A and 5B~, the transformer designer can achieve great .
..... _ ~ .. ~ . , 9 _ ' - ' ~
~6~
flexibility in design~ By careflll selection of the taper of the electrical strip, he cc~ achieve almost any core cross-section W~iC~I he may recluire and can almost achieve the theoretica.lly optirnum circular cross-sectiorlO ~or simplicity, the hexagonal cross-sectiorl as an approximation of the circular cross-section is readily achicvable~
The invention~ in addition to its application as a means of producing the hexagorlal foIm approximation, can in an analogous .iashion to the cruciform case, be used to produce octagonal or hig~er order even regular sided approximations to a circular cross-section. However, for each pair of sides in excess of six an additional size of parallel strip is required to allow scrapless production of the core.
Various changes and modifications may be made to the methods described without departing from the scope of the present invcntion~
, ~ .
.
~ 20 , .
: ~ : :: :
~ ~ ' : :: : :: :
, ~: :
3~
SUPPLEMENTARY DISCLOSURE
The present supplementary disclosure is intended to better emphasize some advantageous and unique features of the core according to the invention and its method of manufac-ture~.
As indicated on page 8, last paragraph of the original disclosure; the laminations lengths A, B and C used for the ~ -manufacture o a transformer core according to the invention, are to be cut to selected lengt~ of square-ended s~rip 53.
The so-selected lengt~sare, in practice, easily determinable by one skilled in the art, simply by approximation.
However, a computerizable method for calculating the non-lineax increase in length of the lamination lengths, can be used if desired. Such a method is based on making an initial estimate of the required total length and then using the~appropriate taper for the estimated length to calculate the dimensions of each piece. The error in the initial estima-te~will then provide a correcting factor and the process can , ~
; ; be repeated until the exact degree of accuracy required is obtained. As aforesaid, this method can of course be ~ computerized.
For deslgn purposes;, a~method based on such an nitial estimate can be used~with~an accuracy of about 1%. ~ ;
The ~following equations usable for determining the length, volume~and ma~ss of a Star-shaped, tranaformer core with legs of~hexagonal form, are illustrative of such a method.
1) n =~ ~INTEGE~ ~
All the cores shown in figs. 1 to 4A have been disclosed by way of interest only, in order to better explain how core legs having a substantially hexagonal or circular cross-section can readily be obt~ained from steel strips of increasing and/or decreasing taper and/or constant width.
The invention however is restricted to the manufacture of transformer core of star or Y configuration.
~ Figs.5~, 5B an~-5C illustrate the manufacture of such a three-phase astar or aY core 50 with legs of substantially hexagonal cross-section. The core 50 comprises three frames 51A, 51B, 51C each of substantially C-shape in side view.
Each frame 51A, 51B, 51C is formed from a series of lamination lengths A, B, C respectively cut from atapered strip 53.
The strip 53 is of increasing taper to form section 52A of each frame,and of decreasing taper to Eorm section 52B, and may be cut as shown in Fig. 2A.
Lamination lengths A.B.C are cut to selected length of square-ended strip 53 with two cuts at 60 to the longitu-dinal axis of the strip 53. This cutting step for most size , . .
93~
cores can i~nore the taper on the layers which come from the tapered strip because of the small angle of taper.
Each layer is formed as shown in FIG. 5A where the angled cut ends of each lamination length are butted to the side of adjacent strip adjacent its free ends.
The method of assembling such a star core is to lay together all the laminations so that one joint (e.g. the bottom joint) is assembled and the core has the appearance Or three radial arms. The joint is clamped and the lamination arms A, s, C are bent upward until they are perpendicular to the plane of the joint. The arms are secured hy claimping and then the joint is unclamped enabling the clamped arms to be separated from the joint. The top portion of each clamped laminated arm is then folded to form a substantially C-shaped laminated assembly of lamination lengths. The electromagnetic properties of the joint are best when each layer is rotated one third of a turn from the previous layer, that is when piece A
of FIG. 5A is placed one each core leg in turn. This core joint~is the only straight cut, scrapless butt inter-leaved ~star or Y core joint, and applicable not only to cores with tapered strip, but to any core of this type, also known as Y
~(wye) cores.~ The section labelled E can be seen to protrude from the joint, but there is no advantage to be gained by removing it.~
All of the new desings, being of the wound core type, require annèaling after -they have been cut and formed to shape.
By using the tapered strip to form the cores, which can be continuously wound ~except for the star core 50 of ~FIGS. 5A and 5B~, the transformer designer can achieve great .
..... _ ~ .. ~ . , 9 _ ' - ' ~
~6~
flexibility in design~ By careflll selection of the taper of the electrical strip, he cc~ achieve almost any core cross-section W~iC~I he may recluire and can almost achieve the theoretica.lly optirnum circular cross-sectiorlO ~or simplicity, the hexagonal cross-sectiorl as an approximation of the circular cross-section is readily achicvable~
The invention~ in addition to its application as a means of producing the hexagorlal foIm approximation, can in an analogous .iashion to the cruciform case, be used to produce octagonal or hig~er order even regular sided approximations to a circular cross-section. However, for each pair of sides in excess of six an additional size of parallel strip is required to allow scrapless production of the core.
Various changes and modifications may be made to the methods described without departing from the scope of the present invcntion~
, ~ .
.
~ 20 , .
: ~ : :: :
~ ~ ' : :: : :: :
, ~: :
3~
SUPPLEMENTARY DISCLOSURE
The present supplementary disclosure is intended to better emphasize some advantageous and unique features of the core according to the invention and its method of manufac-ture~.
As indicated on page 8, last paragraph of the original disclosure; the laminations lengths A, B and C used for the ~ -manufacture o a transformer core according to the invention, are to be cut to selected lengt~ of square-ended s~rip 53.
The so-selected lengt~sare, in practice, easily determinable by one skilled in the art, simply by approximation.
However, a computerizable method for calculating the non-lineax increase in length of the lamination lengths, can be used if desired. Such a method is based on making an initial estimate of the required total length and then using the~appropriate taper for the estimated length to calculate the dimensions of each piece. The error in the initial estima-te~will then provide a correcting factor and the process can , ~
; ; be repeated until the exact degree of accuracy required is obtained. As aforesaid, this method can of course be ~ computerized.
For deslgn purposes;, a~method based on such an nitial estimate can be used~with~an accuracy of about 1%. ~ ;
The ~following equations usable for determining the length, volume~and ma~ss of a Star-shaped, tranaformer core with legs of~hexagonal form, are illustrative of such a method.
1) n =~ ~INTEGE~ ~
5 / : -- ( 1 ) 2 ~ * T~K
2~) ~ STR~ HT + 2 WID - ~ CLD ~ - (4 - ~f ) MBR
~ : 2 :` : ::
;~ 3~) Length =~ 3m STR + 3 ~ n2THX - 0.491 n CLD
~, ~
- - . .
, .
' - '. , . " ,, . ~
993~
4) Volume = 2 CLD * THK * Length 51 Mass = 0.97 * 7.65 x lO 6 * Volume = 7.42 * lO 6 * Volume wherein:
THK is the thickness of the electrical steel;
CLD is the core leg diameter (i.e.the maximum width of the core);
HT is the height of the winding window;
WID is leg centres (i.e. winding diameter);
STR is the centre line string length equivalent to first laminations;
MBR is the minimum bend radlus of core steel; and n 1s the number of layers of 1amlnations in the core.
As also indicated on page 9 at the end of the second Full paragraph o~ the origlnal disolosure, the portlorsE of . ~ .
the lamination layers which are cut at 90 protude;from the olnt~through the cores assembly.~ Thus, those portions form 20 ~ a wedge-llke~end portion on~each end of each core frame assembly. ~This~wedge-llke and portlon greatly assists in ;
reassembling~t~he core;after the frames have been annealed and/or wound~. Indeed, this~wedge joint helps in meshing es~s~entially one~layer at a time.~ ;
This~sdditional feature will become more apparent with reference to the accompan~ing, supplementary drawings whereiD; ~
Fig. 6;is a perspective view of the joint of a three-phase~star core; and~ ~ ~
3~0 ~ Flg. 6a is a partial view of one leg of the star core shown in Fig. 6, when separated from the other.
: .
, ~ ~: : v' ~:- ~ --; - . .
As c~ be seen, the profile of the wedge-shaped end portion E of the laminations of the core according to the inven-tion, which profile results from the shape of the lamination lengths and the way they are assembled, advantageously permits to achieve butt joining at either the top or bottom of the core structure. If the three C-shaped frame are separated, then the exposed end of each frame at the joint will have a wedge shaped profile as shown in fig. 6A. This particular feature makes it possible to separate the three legs of the core in order to fit the windings, and then to reassemble the core as a simple plug fitting assembly operation, because the profile at the ends of each frame allows progressive engagement.
EXAMPLE:
A model transformer core was manufactured in accordance with the present invention from 0.28 mm M4 grain oriented electrical steel.
This model core had the following details.
Widest lamination: 60 mm (corresponding to core leg diameter) Winding diameter: 130 mm (corresponding to the linear distance between a pair of leg centres) Winding height: 130 mm Lamination thickness: 0.28 mm Minimum bend radius: 3.0 mm This model core comprised 187 layers and 561 pieces for a total length of material of approximately 166 metres.
: .
:
3 ~
2~) ~ STR~ HT + 2 WID - ~ CLD ~ - (4 - ~f ) MBR
~ : 2 :` : ::
;~ 3~) Length =~ 3m STR + 3 ~ n2THX - 0.491 n CLD
~, ~
- - . .
, .
' - '. , . " ,, . ~
993~
4) Volume = 2 CLD * THK * Length 51 Mass = 0.97 * 7.65 x lO 6 * Volume = 7.42 * lO 6 * Volume wherein:
THK is the thickness of the electrical steel;
CLD is the core leg diameter (i.e.the maximum width of the core);
HT is the height of the winding window;
WID is leg centres (i.e. winding diameter);
STR is the centre line string length equivalent to first laminations;
MBR is the minimum bend radlus of core steel; and n 1s the number of layers of 1amlnations in the core.
As also indicated on page 9 at the end of the second Full paragraph o~ the origlnal disolosure, the portlorsE of . ~ .
the lamination layers which are cut at 90 protude;from the olnt~through the cores assembly.~ Thus, those portions form 20 ~ a wedge-llke~end portion on~each end of each core frame assembly. ~This~wedge-llke and portlon greatly assists in ;
reassembling~t~he core;after the frames have been annealed and/or wound~. Indeed, this~wedge joint helps in meshing es~s~entially one~layer at a time.~ ;
This~sdditional feature will become more apparent with reference to the accompan~ing, supplementary drawings whereiD; ~
Fig. 6;is a perspective view of the joint of a three-phase~star core; and~ ~ ~
3~0 ~ Flg. 6a is a partial view of one leg of the star core shown in Fig. 6, when separated from the other.
: .
, ~ ~: : v' ~:- ~ --; - . .
As c~ be seen, the profile of the wedge-shaped end portion E of the laminations of the core according to the inven-tion, which profile results from the shape of the lamination lengths and the way they are assembled, advantageously permits to achieve butt joining at either the top or bottom of the core structure. If the three C-shaped frame are separated, then the exposed end of each frame at the joint will have a wedge shaped profile as shown in fig. 6A. This particular feature makes it possible to separate the three legs of the core in order to fit the windings, and then to reassemble the core as a simple plug fitting assembly operation, because the profile at the ends of each frame allows progressive engagement.
EXAMPLE:
A model transformer core was manufactured in accordance with the present invention from 0.28 mm M4 grain oriented electrical steel.
This model core had the following details.
Widest lamination: 60 mm (corresponding to core leg diameter) Winding diameter: 130 mm (corresponding to the linear distance between a pair of leg centres) Winding height: 130 mm Lamination thickness: 0.28 mm Minimum bend radius: 3.0 mm This model core comprised 187 layers and 561 pieces for a total length of material of approximately 166 metres.
: .
:
3 ~
Claims (15)
1. A method of manufacturing a transformer core of star or Y configuration from an electrical steel strip wherein said core comprises three frames each of substantially C-shape in side view, the frames being arranted at substan-tially 120° apart, said method comprising the steps of:
cutting a length of strip into a plurality of lamination lengths, each group of three lamination lengths being separated from the adjacent group at each end by a cut at substantially 90° to its longitudinal axis, each said group forming a layer of the core, with the three lamination lengths in the group being separated from each other by cuts at substantially 60° to the longitudinal axis;
butt joining the ends of two of the lamination .
lengths cut at substantially 60° to the sides of a third lamination length adjacent an end of said third lamination length cut at substantially 90° to form a lamination layer;
and assembling the lamination layers to form the assembled core.
cutting a length of strip into a plurality of lamination lengths, each group of three lamination lengths being separated from the adjacent group at each end by a cut at substantially 90° to its longitudinal axis, each said group forming a layer of the core, with the three lamination lengths in the group being separated from each other by cuts at substantially 60° to the longitudinal axis;
butt joining the ends of two of the lamination .
lengths cut at substantially 60° to the sides of a third lamination length adjacent an end of said third lamination length cut at substantially 90° to form a lamination layer;
and assembling the lamination layers to form the assembled core.
2. A method as claimed in claim 1 wherein each C-shaped frame is substantially rectangular in cross-section.
3. A method of manufacturing a transformer core of star or Y configuration from an electrical steel strip wherein said core comprises three frames each of substantially C-shape in side view, the frames being arranged at substantially 120° apart, said method comprising the steps of:
cutting a first portion of said strip of increasing taper from a minimum width to a maximum width;
cutting a second portion of said strip of decreasing taper from a maximum width to a minimum width;
cutting each portion into a plurality of lamination lengths, each group of three lamination lengths being separated from the adjacent group at each end by a cut at substantially 90° to its longitudinal axis, each said group forming a layer of the core, with the three lamination lengths in the group being separated from each other by cuts at substantially 60° to the longitudinal axis;
butt joining the ends of two of the lamination lengths cut at substantially 60° to the sides of a third lamination length adjacent an end of said third lamination length cut at substantially 90° to form a lamination layer;
and assembling the lamination layers to form the assembled core.
cutting a first portion of said strip of increasing taper from a minimum width to a maximum width;
cutting a second portion of said strip of decreasing taper from a maximum width to a minimum width;
cutting each portion into a plurality of lamination lengths, each group of three lamination lengths being separated from the adjacent group at each end by a cut at substantially 90° to its longitudinal axis, each said group forming a layer of the core, with the three lamination lengths in the group being separated from each other by cuts at substantially 60° to the longitudinal axis;
butt joining the ends of two of the lamination lengths cut at substantially 60° to the sides of a third lamination length adjacent an end of said third lamination length cut at substantially 90° to form a lamination layer;
and assembling the lamination layers to form the assembled core.
4. A method as clalmed in claim 3 wherein each C-shaped frame is substantially hexagonal in cross-section.
5. A method as claimed in claim 3 wherein each C-shaped frame is substantially circular in cross-section.
6. A method as claimed in claim 1 or 3, further comprising rotating each lamination layer one third of a turn from the previous lamination layer prior to assembling it.
7. A transformer core of star or Y configuration comprising three frames each of substantially C-shape in side view, said frames being arranged at substantially 120°
apart and being made of a plurality of lamination n lengths cut off from an electrical steel strip and arranged in groups of three, each of said groups of three lamination lengths forming a layer of the core, wherein two of the three lamination lengths of a group have one end cut at substantially 90° and the other end cut at substantially 60° to its longitudinal axis whereas the third one has both of its ends cut at substantially 60° to its longitudinal axis, the ends cut at substantially 60°
of two of the three lamination lengths of a group being butt joined to the sides of a third lamination length having one of its end cut at substantially 90°, adjacent said end cut at substantially 90°, to form one of said layers of the core.
apart and being made of a plurality of lamination n lengths cut off from an electrical steel strip and arranged in groups of three, each of said groups of three lamination lengths forming a layer of the core, wherein two of the three lamination lengths of a group have one end cut at substantially 90° and the other end cut at substantially 60° to its longitudinal axis whereas the third one has both of its ends cut at substantially 60° to its longitudinal axis, the ends cut at substantially 60°
of two of the three lamination lengths of a group being butt joined to the sides of a third lamination length having one of its end cut at substantially 90°, adjacent said end cut at substantially 90°, to form one of said layers of the core.
8. The transformer core as claimed in claim 7, wherein each C-shaped frame is substantially rectangular in cross-section.
9. A transformer core as claimed in claim 7, wherein the lamination lengths are cut off from an electrical steel strip which has previously been cut into two portions of increasing and decreasing tapers,respectively.
10. .DELTA. transformer core as claimed in claim 9, wherein each C-shaped frame is substantially hexagonal in cross-section.
11. A transformer core as claimed in claim 9, wherein each C-shaped frame is substantially circular in cross-section.
12. A transformer core as claimed in claim 7 or 9, wherein each layer is rotated one third of a turn from the previous layer.
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
13. A method of manufacturing a transformer core of star or Y configuration from an electrical steel step wherein said core comprises three frames each of substan-tially C-shape in side view, the frames being arranged substantially 120° apart, comprising cutting a first portion of increasing taper from a minimum width to a maximum width;
cutting a second portion from a maximum width to a minimum width;
cutting each portion into a plurality of lamina-tion lengths, each group of three lamination lengths being separated from the adjacent group at each end by a cut at substantially 90° to its longitudinal axis, each said group forming a layer of the core, with the three lamination lengths in the group being separated from each other by cuts at substantially 60° to the longitudinal axis;
butt joining the ends of two of the lamination lengths cut at substantially 60° to the sides of a third lamination length adjacent an end of the third lamination length cut at substantially 90° to form a lamination layer such that the free ends can be similarly butt joined; and assembling the lamination layers to form the assem-bled core whereby the cross-section of each substantially C-shaped frame is an approximation to a substantially regular polyhedron of hexagonal or higher order, and the side C-shaped frame is substantially wedge shaped.
cutting a second portion from a maximum width to a minimum width;
cutting each portion into a plurality of lamina-tion lengths, each group of three lamination lengths being separated from the adjacent group at each end by a cut at substantially 90° to its longitudinal axis, each said group forming a layer of the core, with the three lamination lengths in the group being separated from each other by cuts at substantially 60° to the longitudinal axis;
butt joining the ends of two of the lamination lengths cut at substantially 60° to the sides of a third lamination length adjacent an end of the third lamination length cut at substantially 90° to form a lamination layer such that the free ends can be similarly butt joined; and assembling the lamination layers to form the assem-bled core whereby the cross-section of each substantially C-shaped frame is an approximation to a substantially regular polyhedron of hexagonal or higher order, and the side C-shaped frame is substantially wedge shaped.
14. A method of manufacturing a transformer core of star or Y configuration as claimed in claim 13 wherein each of the substantially C-shaped frames is replacably detachable from the assembled core for annealing and winding operations.
15. A method of manufacturing a transformer core of star or Y configuration as claimed in claim 13 or 14 wherein the lamination lengths comprising each successive lami-nation layer are assembled on an adjacent core frame.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU6472 | 1978-10-19 | ||
| AUPD647278 | 1978-10-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1169932A true CA1169932A (en) | 1984-06-26 |
Family
ID=3767791
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000337928A Expired CA1169932A (en) | 1978-10-19 | 1979-10-18 | Transformer cores |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0010427B1 (en) |
| JP (1) | JPS5556615A (en) |
| CA (1) | CA1169932A (en) |
| DE (1) | DE2967567D1 (en) |
| IN (1) | IN152275B (en) |
| NZ (1) | NZ191840A (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2771109B2 (en) | 1994-03-16 | 1998-07-02 | 北村機電株式会社 | Wound iron core |
| DE19629930A1 (en) * | 1996-07-24 | 1998-02-05 | Siemens Ag | Core of a transformer with layered sheets, as well as a device and a method for producing the sheets |
| JP3794928B2 (en) | 2000-04-17 | 2006-07-12 | 東京精電株式会社 | Low noise and low loss reactor |
| TW527745B (en) | 2000-11-21 | 2003-04-11 | Dainichiseika Color Chem | Solidifying material for cell electrolyte solution, and cell comprising the solidifying material |
| CN102314997A (en) * | 2011-05-27 | 2012-01-11 | 广东海鸿变压器有限公司 | Amorphous alloy stereo roll iron core |
| IL217576A0 (en) * | 2012-01-17 | 2012-03-29 | Eliezer Adar | Three phase transformer and method for manufacturing same |
| FR3112648B1 (en) * | 2020-07-20 | 2023-04-14 | Safran Electrical & Power | Process for manufacturing loops for magnetic circuit |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE691531C (en) * | 1937-07-02 | 1940-05-29 | Aeg | Multiphase sheathed transformer |
| GB524285A (en) * | 1938-01-25 | 1940-08-02 | British Thomson Houston Co Ltd | Improvements in and relating to magnetic cores for transformers and like magnetic induction apparatus |
| US2366071A (en) * | 1939-05-25 | 1944-12-26 | Gen Electric | Stationary induction apparatus |
| US2458112A (en) * | 1947-01-20 | 1949-01-04 | Line Material Co | Three-phase transformer construction |
| GB662915A (en) * | 1948-11-26 | 1951-12-12 | Westinghouse Electric Int Co | Improvements in or relating to three-phase core structures for electrical induction apparatus |
| GB692845A (en) * | 1950-10-21 | 1953-06-17 | Asea Ab | Method for producing wound magnetic cores having approximately circular cross-section |
| GB708995A (en) * | 1951-05-08 | 1954-05-12 | British Thomson Houston Co Ltd | Improvements in and relating to magnetic cores |
| DE1011056B (en) * | 1953-07-08 | 1957-06-27 | Licentia Gmbh | Three-leg core of the temple type composed of three frame cores |
| FR1107583A (en) * | 1954-06-18 | 1956-01-03 | Cem Comp Electro Mec | Method of manufacturing magnetic circuits with wound sheets |
| GB830094A (en) * | 1956-12-18 | 1960-03-09 | Bbc Brown Boveri & Cie | Yoke for a magnetic circuit and method of producing same |
| FR1333285A (en) * | 1962-09-04 | 1963-07-26 | A R L Etablissements Augier So | New way of manufacturing magnetic cores and transformer windings |
| AR204449A1 (en) * | 1974-10-07 | 1976-02-06 | Ingenieria Electrica Ind Sa | MAGNETIC CIRCUIT FOR THREE PHASE ELECTRIC TRANSFORMERS |
| DE2702455A1 (en) * | 1977-01-21 | 1978-07-27 | Andreev | Three=phase transformer core - has three rectangular rings with parallel sides adjacent, to form triangular prism shape |
-
1979
- 1979-10-12 NZ NZ19184079A patent/NZ191840A/en unknown
- 1979-10-17 EP EP19790302237 patent/EP0010427B1/en not_active Expired
- 1979-10-17 DE DE7979302237T patent/DE2967567D1/en not_active Expired
- 1979-10-18 CA CA000337928A patent/CA1169932A/en not_active Expired
- 1979-10-18 IN IN1083/CAL/79A patent/IN152275B/en unknown
- 1979-10-19 JP JP13583679A patent/JPS5556615A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5556615A (en) | 1980-04-25 |
| NZ191840A (en) | 1983-06-14 |
| EP0010427B1 (en) | 1986-01-15 |
| JPS6227527B2 (en) | 1987-06-15 |
| IN152275B (en) | 1983-12-10 |
| EP0010427A1 (en) | 1980-04-30 |
| DE2967567D1 (en) | 1986-02-27 |
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