CA2005429A1 - Transformers and cores for transformers - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method of making a transformer having a core composed of a web of magnetic amorphous metal of small thickness.
The laminations of the core of the transformer are the stacked turns formed by winding the web into a spiral having a window in the center. The coils are wound as integral structures having openings for telescoping the coils onto the core. for the telescoping, the core is cut and converted into a U-shaped structure on whose arms the coils are telescoped. The cut joint is a butt lap-step joint. To produce such a joint, the laminations are divi-ded into groups and each group is divided into steps which are spaced longitudinally of the web. After the coils are telescoped onto the core, the cut ends of the arms of the U are abutted to form a closed core. The cuts in the lam-inations that make up alternate groups in the stack are inclined to the longitudinal center line of the web at a first angle different from 90°. The cuts in the laminations that make up intervening groups in the stack are inclined oppositely to the cuts in the alternate groups at an angle which is also different from 90°. Because of the different inclination of successive cuts, the undesired abutting of laminations from different groups during the reclosing of the core is precluded. There is also disclosed a core and a transformer made by the method.

Description

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1 54,6l~8 TRA~SFORMERS A~D CORES FOR TRANSFORMERS
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BACKGROUND OF THE I~V~NTIO~ ~ -This lnvention relates to transformers, typically dis~ribution transformers, and lt has partlcular relation-ship to transformers whose cores are composed of lamlnatlons of amorphous metal of small thickness. Typically the thlck-ness of the lamlnations is of the order of O.OOl-inch.
'.~hlle this invention`is disclosed herein in detail as applied to a transformer having a core Or a wound amorphous metal web of small thickness, as to which this invention has unique advantages~ it ls understood that the adaptation of the prin-ciples of this invention to transformers of other types is within the scope of equivalents of this application and of any patent that may issue on or as a result thereof, typical-ly as the range Or equivalents is applled in Graver Tank &
~qfg. Co. v. Linde Air Products Co. 339 U.S. 605; 70 Supreme Court Reporter 854 (1950) and interpreted in Uniroyal v.
Rudkin-Wiley Corp. 5 USPQ 2d 1434 (CAFC 1988). -~
Patent 4,709,471 to Milan D. Valencic and Dennis A. Schaffer, assigned to Westlnghouse Electric Corporation 20 discloses a method for making the cores of these transfor- ~ ;
mers. Patent 4,761,630 to Frank H. Grimes and Eugenious Hammack, both also assigned to Westlnghouse Electric Corpor-ation, discloses structural features of these cores. Val-encic teaches that a web of the amorphous metal is wound into a closed spiral core loop or core structure with a window in the center. The turns of the sniral form the ', ' 20~5~
.

2 54,64 laminatlo~s of the core. These laminatlons ~orming the closed core structure are then cut in successive stepped groups and the closed structure is opened and converted into a U-shaped structure on whose arms the coils of the gransformers are telescoped. The arms of the U-shaped structure are then abutted to reconvert the U-shaped struc-ture into a closed structure. Grimes discloses a core as taught by Valencic with lapped steps.
To explain this inventlon so that those skilled in the art will understand it, it is desirable to discuss Grimes briefly. Figs. 3 and 4 of Grimes show highly en-larged a ~ragmentary part of the core as viewed in a direc-tion perpendicular to the edges Or the laminations. If Fig.

3 were extended to show the whole core, it would show the laminations in a race-track or circular annular shape. The structure shown is stepped with the steps lapped at their ad~oining laminations. For this application, each unit Or lamlnatlons A, B or C or D, E or F is defined as a step and the steps A, B and C together or D, E and F together are defined as a group. The lamlnations are typlcally only 0.001-inch ln thickness so that the step F has a thickness of 0.007. The thickness of group DEF is 0.021-inch. Grlmes says that there may be as many as thirty laminations in each step. In thls case, each group would have a thickness of 0.09-inch. There may also be less than seven lamenations in each step; in fact, there may be one lamination in each step.
While the teachings of Valencic and Crimes have made formidable contributions to the transformer art, a problem has been experienced in the construction of the core as taught by Valencic and Crimes. In the reconstitu- ~ -~
tlon of the core after the coils are telescoped in its arms, dlfficulty has been encountered in match~ng the separated ends of the lamlnations of the groups so that severed ends 35 of allminations on one slde of a group are ,joined during `~
reassembly to the ends o~ the same laminatlons on the oppo-site side o~ a group. The small thickness of the groups is a ma~or factor contributing to this problem. 'n pastpractice ''"' ~ '' `~

2 ~ 9 3 54,648 a group of laminations is at ti~es erroneously matched with two opposing groups during reassembly. The error becomes ap~arent only on completion Or the ~oint reassem-bled when a spare ~roup of laminations with no matching companion groups remain. For example, with reference to `~ig. 3 Or ~rimes, the twenty-one laminations on the right of group ABC instead of being ~oined to the la~inations on the left of group ABC, are joined to the laminations on the left of group DEF. ~hen this happen~ the core as completed has unconnected laminations and must be repro-cessed. The deficiency is not dlscovered until after the core is co~pleted. In addition, after the above-described error occurs, an opposing error may occur during the con-tlnued reassembly, i.e., the laminations on the left of a group such DEF are ~olned to the lamlnations on the right of a group such as ABC. In thls case, the errors are com-pensatlng and are not discovered after the core is complèted and the core performance is deteriorated.
Another problem which arlses ln connectlon with cores in one Or whose yokes or legs severable Joint~ exist, has its roots in the principle that among the various fac-tors that govern the power to excite a transformer is the ~ ;
local net transverse cross-sectional area reduction which results from the gaps in the core that form the ~oint. ~;
The net cross-sectlonal area is reduced and the required exciting power is increased by the gaps in the laminations -~
at the ~oint. In cores formed of laminations of amorphous metal, this problem is particularly significant because, in use, such cores are operated at inductlons very near to -~
30! that which produces saturation. Appreciable reduction in ~;~
the nettransverse cross-sectional area of a core may result in saturation when the core is used. In a ~oint containing a large number of gaps, particularly if the gaps are stacked, there is a substantial reduction in net cross-sections area and a tendency for saturation to occur with corresponding adverse effect upon core losses.

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-' 4 54,648 '' Another problem which occurs when a butt-lap-step core ~oint as taught by Grimes is reasse~bled arises from the tendency of the laminatlons to adhere to each other such that more than one group o~ cut steps may be mismatched and mislocated against a single opposing group.
This error is also only discovered after the ~oint is com-pletely reassembled. The error occurs on the side of the joint where the longest lamiinations are on top viewing the ~oint being reassembled positioned horizontally. The short-er lamlnations Or ad~acent groups tend to adhere. Theopposite side'or the core where the longest laminations are at the bottom are "self separating" by groups.
It is'an ob~ect of this invention to overcome the above-described drawbacks and de~iciencies and to provide a method ~or accomplishing this purpose. Namely, it is an ob~ect Or the invention to provide a method o~ making a trans~ormer having a core Or amorphous metal, rormed by wlndln~ into a spiral a plurality of turns or laminations Or small thickness, whlch core has a severable ~oint that is opened to permit the telescoping o~ coils and thereafter reclosed by abutting the ends Or the severed laminations, in whose practlce, the mismatching Or abutted laminations during the reclosing shall be precluded.
It is also an ob~ect of this invention to provide a method of making a transformer in whose practice the trans-verse cross-sectional area at overlapping laminations at the gaps produced by severing the laminations shall be enhanced.
It is also an ob~ect Or this invention to provide a core and a transrormer made by the practice of the method.
SU~IMARY OF THE INVE~TION
In accordance with this invention, there is provi~ ~' ded a core whose ~oint is ~ormed by cutting the laminations, not at right angles to the longitudinal center line of the lamination~ or to any plane perpendicular to the laminations, but at an angle which differs appreciably from 90, thus enabling the cut ends of the same laminations to be readily identi~ied because they are at the same angle to the center .

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54,648 line. Speci~ically, the laminations for~ing the core may be subdivided into stacked groups. Alternate ~roups ~ay be cut biased, i.e., ~lith the cut inclined, not perpendicu-lar, to the cente~ line~ in one direction and the interven-ing groups ~ay be cut biased in the opposite direction, l.e., ~lith the cut inclined to the center llne oppositely ~ -to the cut through the alternate groups. The departure from perpendicularity may be the same in each direction. But cores whose ~olnts are ~ormed by cuts of the laminations of alternate groups inclined at dirferent angles to the center line are within the scope of equivalents of thls inv~ntion.
In i~act, the cuts through the laminations of either the alternate or the intervening ~roups may be at right angles to the center line and the cuts through the laminations of the other groups inclined. The cuts through the steps of each group are at the same inclination.
The laminations may be cut and the core processed to produce a transformer as disclosed in Valenaic. To pro-duce the based cuts, the cutter 66 shown in Fig. 6 o~ Val-encic may be set with the blades 77 and 78 at the appropri-ate angle to the longitudirlal center line Or the laminations.
For the purpose of this appllcation, the angle of inclination ~ `~
will be defined as the acute angle Or the cut to the longitu-dinal center line.
It is desirable that the departure of the angle o~ cut from the perpendicular to the center line be small, i.e., angle o~ inclination to the center line should desir-ably be large. In practlce, an angle o~ departure o~ about 3, i.e., an angle of inclination of about 87 has been ~`
30 round to be satisfactory. The adoption of a large angle ` :
of departure from the perpendicular complicates the settlng o~ the cutter and has a tendency to cause the brlttle lami~
nations to break. It has been found that with the cuts in- ~
clined at about 87 in opposite directions, the matching of ~ -the ends Or the lamination which are to be ~oined ls accom-plished successfully. Practice of the teachings o~ this application with the cuts inclined at angles substantially , ~ - ., ; :,, . . - .. . . ., , , , - , ZQC~

6 54,648 different ~rom 87 is understood to be wlthin the scope of equivalents of this application and of any patent which may issue on or as a result thereof.
In the practice oP this invention, the mismatch-ing of the ends of the several laminations of contiguousgroups is precluded by the opposlte biasing of these groups.
This invention also impro"ves the potential towards mechani-zation oP the ~oint reclosing by ePPectively separating se-quential groups in the ~oint. By cutting ~irst in one angled direction throughout a group, then reversing the angled directlon throughout the next group and by repeating this sequence through the whole core, the "herringbone"
geometry can be achieved on a wound core, i.e., an X-ray ~, through the severed ~oint taken perpendicular to the surPace of the web ~orming the laminations would have the appearance of a "herringbone" or "cross-stltched" ~oint.
When the core is opened to telescope the coils, the "opened" sheets are separated into oppositely cut groups and it becomes impossible to relocate odd and even groups together. Thus, the assembly problems which have occurred in the past are elimina~ed. I~ a double error occurs, the ~oint appears to be correctly closed, but the measured core losses increase enormously. This error also i9 eliminated.
BRIEF DESCRIPTION OF THE DRAl~INGS
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25, For a better understanding oP this invention, both as to its organization and as to its method oP operation, together with addltional ob~ects and advantages thereof, reference is made to the following description taken in con-nection with the accompanying drawings, in which: -30 , Figure 1 is a view ln isometric, generally, dia-grammatic, showing apparatus Por practicing this invention set to produce cuts in the laminations inclined in one dir-ection to the longitudinal center line oP the laminations;
Flg. 2 is a view slmilar to Fig. 1 with the appa-ratus set to ?roduce cuts in the laminations inclined in the opposite direction to the longitudinal center line;

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7 54,6~8 Fig. 3 is a view in side elevation generall~y dia- :
~rammatic o~ the apparatus shown in Fig. 1 for illustrating the manner in ,/hich a series of cuts of steps of the outer : :
groups Or laminations are produced in the ~ractlce of this invention;
~ig. 4 is a plan view taken in the direction IV-IV :
of Fig. 3;
Fi~. 5 is a view in side elevatlon similar to Fig.
3 illustratin~ the manner in which a series of cuts of steps ~f the inner group of laminations ~ust under the outer group are made in the practice of this inventlon;
Fig. 6 is a plan view taken in the direction VI-VI `:~
of Fig. 5;
Fig. 7 is a fragmental view in isometric, general-lyoiagrammatic, showing the manner in which the core struc-ture is reassembled at a group Or laminations cut at one inclination;
Fig. 8 is a fragmental view similar to Fig. 7 showing the manner in which the core structure is reassembled 20 at a group of laminatlons cut at the opposite inclination; : . .
Flg. 9 is a fragmentary view greatly enlarged taken in the direction towards the edges of the lamination :"
essentially in side elevation, showing a portion of a reas- ;~
sembled ~oint;
Fig. 10 is a view in side elevation of a core U-shaped structure formed in the practice of this invention rOr receiving the coils;
Fig. 11 is a view in side elevation of a transfor- :::~`~
mer in accordance with this invention; ~:
~ig. llA is a fragmentary diagrammatic view for aiding in the explanation as to how error from sticking :~
of laminations is precluded; : .
Fig. 12 is a fragmentary view in isometric, great- .
ly enlarged and generally diagrammatic, showlng the magnetic : .
flux path in a prior-art core through the turns at the ~unction between steps; and 2QOS~
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8 54,648 Fig. 13 is a greatly enlarged ~ragmentary view similar to Fig. 12 but showing the magnetic flux path in a core according to this invention.
DElAILED DESCRIPTIO'~ O~ PRACTICE Ai~D
5~MBO3IMENTS OF T~IS I`~E~JTION
The apparatus shown in Figs. 1 through 9 includes a support plate 21 on which a core structure 23 is disposed.
The core structure 23 is produced by windlng a web 25 of amorphous metal Or small thickness into a circularly annular spiral as taught by ~alencic. ~lhen thls spiral is dlsposed on plate 21 with its axis horizontal, it assumes the gener-ally Figure 8 conflguration shown in Figs. 1 through 6.
The turns of the spiral are the laminatlons 27 (Flg. 9) of the core structure 23.
In the practice of this invention, the laminations 27 of the core structure 23 are subdivlded as taught by Grimes into groups 29 and 29a (Fig. 9),each group being sub-divlded into steps 31. The steps of each group are spaced longitudinally along the core structure Z3 as shown in Fig.
9. Fig. 9 shows successlve groups 29 and 29a along the depth of the core structure. Group 29 may be taken as the topmost group and ~roup 2~a as the second group ~rom the top assumlng that the core structure 23 rests on plate 21 wlth the axis of the splral horizontal. In Fig. 9 the steps o~
the top ~roup 29 are labeled A, B, C, D and E and the steps of the group 29a are labeled ~, G, H, I and J. In actual practice Or the inventlon, there are a large number of groups 29 and 29a.
As shown in Figs. 1 and 2, the apparatus for prac-ticing the method of this invention includes a cutter 33havlng cutting blades 35 and 36. The cutter 33 is the same as is disclosed in Valencic. It is capable of ~roducing a s~uare cut through a predetermined number of laminations or stacks 37 and is positioned and is operable to cut the lami-natlons. '.owever, instead of being positioned to producea cut o~ lamlnatlons at right angle to the longitudinal cen-ter line 41 of the web, the blades 35 and 36 are posltioned 2 ll~S~29 9 54,648 inclined at an angle Y to the center line. The center line is re~erred to here as a convenient reference. The blades 35 and 36 are positioned lnclined at angle X to planes perpendicular to the surface of the web or to its edges where the edges are linear and narallel as shown.
Speciricall~, the number of laminations in a stack 37 are the number in a step 31 (Fig. 9)~ The lamlnatlons consti-tuting each step are raised for cutting by magnets (not shown) as disclosed in Valencic. This invention may be practlced with cutters other than that shown by Valencic.
In the practice of this lnvention, the cutter 33 is positioned with its blades inclined at angle X to the center line for cutting the steps A, B, C, D, ~ of the top group 29 (Figs. 3, 4). After each step is cut by the cut-ter, the severed lamination stacks on each side are removedby ma~netic or other means and ~olded over the ad~acent ends of the core structure 23. The cutter is then advanced to the right with reference to Figs. 1 and 3 with lts ~`-blades 35 and 36 inclined at angle X to the center line 20 41 or the support 21 is advanc~d to the left and the next -step is raised magnetically or by other means and cut and its severed parts removed and folded back. This operation continues u~til all steps A, B, C, D, E of the top group are cut. The severed ends 42 and 44 of the laminations of 25 each step are shown in Fig. 4. They are inclined at angle -X to the center line 41.
The core structure 23 is now in the state shown in Figs. 5 and 6 with the severed parts 43 and 45 of the top group 29 folded away from the ends of the structure. ; ~ -The cutter 33 is now positioned with its blades 35 and 36 inclined at an angle Y (Fig. 2) to the center line 41. The inclinaticn at angle Y may be equal and opposite to the in-cllnation at angle X. The steps F, G, ~, I, J are then cut and their severed parts folded back in succession. The 35 severed ends 47 and 49 of the steps F through J are shown -~
in Fig. 6. They are inclined at an an~le Y to the center line 41.

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; ~ ~ 05 ~ 9 54,648 It is emphasized that where the angle of incli-nation to the center llne is large, typically 87, it is desirable that an~les X and Y be eaual and opposlte. The di~ference in inclinatlon of the cuts in successive groups is twice the lnclination for each ~roup. The capability of recognizing a mismatch is thus facilitated.
'~he cutter 33 is now repositioned with its blades 35 and 36 at an~le X to the center line 41 and the steps 31 of the third group from the top are cut. Then the cutter is again repositioned with its blade at angle Y to the center line and steps of the fourth group from the top are cut. The cuttin~ of odd-numbered ~roups from the top with cutter blade 35 set inclined at angle X to the center line and even-numbered ~roups with the cutter blade set inclined at angle Y to the center line is continued until the depth ` of the core structure is completely penetrated in the region of the cuts. The blades of the cutter are preferably so positioned that the cuts are spaced approximately symmetri-cally about the transverse center line 51 of the upper por-tion 53 of the core structure so that the length of the partsof the core structure 23 on each side of the cut region are approximately equal.
Once the width of the core structure 23 is pene-trated, the core structure is opened at the cut-through section and the core structure is processed typically as taught by Valencic, particularly with reference to Figs. 10 through 15 and 17 through 22 of this patent. It is under-stood that this invention is not confined to processing as taught by Valencic and that in the processing of core struc- -ture 23 departures from, or modifications of, Valencic's teaching as well as replacement o~ Valencic by entirely dif-ferent teachin~ may be adopted ~rithout affectlng the scope ~
Or this inventlon. ;
Durin~ the processing, the Joint where the core structure 23 is severed is opened and reclosed twice. Thefirst time the core is opened, mechanically manipulated and then reclosed to convert the structure into the desired ~ ,.

~05~29 11 54,648 shape for the stress-relief anneal. After the anneal, the structure is reopened a second tlme in the severed region forming ~he U-shaped structure 55, the coils 59 and 61 telescoped on its legs 57 and then reclosed. During the reclosln~, the cut ends 42 and 44 (~i~. 4) and 47 and 49 are abutted and lapped at the ~unctions between ad~acent steps startin~ rrom the lowermost group and continuing through the u~permost group assumlng the axis of the core is horizontal.
During the processing, the core structure is converted lnto the sel~-supporting structure 55 shown in Fig. 10 with arms 57. While the core structure 57 is sel~
supporting, the ends o~ the core structure which ~orm the ~oint in the cut region 63 can be manipulated ~rom the open position with reference to Fig. 10 to the closed posi-tion.
It is essential, partlcularly during the second reclosing a~ter the coils are telescoped on the legs thak mismatching between ad~acent groups be orecluded and this is accomplished in the practice o~ this invention as shown in Figs. 7 and ~. Fig. 7 shows the reclosing of the lamina~
tion Or a group 29 such as the group made up of the steps A, ~, C, D, E (Fig. 9). The inclined rull lines representing ends 42 and 44 are assumed to represent the ends of steps A, B, C, D, E and not the ends o~ individual laminations. The steps are folded over in sequence ~rom E to A. It is seen `
that the end 42 of each step is contiguous to and aligned -with end 44 Or the same step. Fig. 8 corresponds to the group 29 ad~acent to the group represented in Flg. 7 whose steps are F, G, ~, I, J. In this case, the cuts are inclined opposltely to the cut for the group of Fig. 7. In this case, the ends 47 of the steps J through F are contiguous to and aligned with the ends 49. If an attempt were made to abut the left-hand end of group 29 shown in Fig. 7 with the right-hand end of group 29a shown in Fig. 8, the ends 49 would be inclined as represented by the broken lines 71 in Fig. 7 and the misalignment would at once become obvious.

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12 54,648 Prior-art practice has been confronted b~ the ma~or problem that durln~ reassembly there is a tendenc~
~or the cut laminatlons on one side of two groups to adhere so that the ends o~ the outer of two adhering grou~s on one side may be ~oined to the ends o~ one group on the opposite side. In the practice Or this invention, the ~oining of two groups to one group is preclu~ed, Re~erence is made to Fig. llA for an understanding of this advantage. Fig. llA shows the ends 91 and 93 of three groups 95, 97, 99 which are to be ~oined during re-closing. There are five steps in each group, each step being represented by a single line. It is assumed that group 95 is on top and group 99 on the bottom. The cuts ln group 97 are inclined oppositely to the cuts in groups 95 and 99. It has been found that the adhering occurs when the longest sheets are on top, assumlng the core structure is positioned with its axis horizontal. It may be assumed that the la~inations of groups 95 and 97 at the end 91 have adhered but there has been no adhesion of the laminations o~ groups 95 and 9? at end 93. An attempt will then be made to Join ~roup 97 of 91 to group 95 o~ end 93. Since the cuts in group 97 are lnolined oppositely to the cuts in ~
group 95, the mismatch by the erroneous Joining of the ends ~ `
o~ groups 95 and 97 will be precluded.
The advantageous aspect of this invention with respect to the reduction of the crowdlng of the ~lux lines will now be explained with reference to Figs. 12 and 13.
Flg. 12 corresponds to a core structure ln which the cuts 42a-44a are at right angles to the longltudinal center llne 30 j as taught by prlor art and Fig. 13 corresponds toia core structure in which the cuts 42-44 are inclined to the center line 41 in accordance with this invention. In this discus-sion, it is assumed that the lamination or group of lamlna-tions Rl and R2 and Rl' and R2' are in a core of a trans-~ormer which is in operation.
In each view, the transition lamination ~1 and R2and Rl' and R2' at the ~unc~ion between ad~acent steps, for . :
13 54,648 example between step ~ and step D, of ~roup 29 are shown.
mhe flux lines ~1 and f2 are shown as flowing through Rl and R2 from Ll and L2 through the laminations R2 and Rl shown in ~ig. 12 and from Ll' and L2' through the lamlna-tions R2~ and Rl' shown in Fig. 13; in both cases from leftto right. The transition larlninations in Figs. 12 and 13 are reversed with re~erence t;o Fig. 9. To aid in the under-standing of the invention, dimensions are assumed; it is assumed that the width of the cut is 0.25-inch and the over-lap 0.375-inch. It is also assumed that the inclin~tion of the cut shown in Fig. 13 is at 60 to the center line.
With reference to Fig. 12, flux ~1 flows through Ll until it reaches gap Gl where it flows into and through R2. It then returns to Rl when it passes gap Gl. Flux f2 -15, flows through L2 until it reaches gap G2 where it flows into through Ll until it passes gap G2 when it rlows back through R2. Crowding of the flux ta}ces place in the regions in Ll at gap G2 and R2 at gap Gl where the rlux flows through com-mon channels.
One way to minimize this flux crowding and the `
resulting saturation and core loss lncrease is to spread the flux crowding over as large an area as practicable. In the prior art as shown ln Fig. 12, the crowdlng is spread over an area of 1.0 square inch 0.25 x 4. Once flux f2 pass-es gap G2, it reenters R2 before reaching the gap Gl. This reentry of flux f2 takes place over 0.375-lnch. The area is 0.375 x 4 - 1.50 square inches. The flux crowding can be reduced by lncreaslng the overlap. For example, for overlap "
of 0.5-lnch, the area ls 2 inches. But because of the limlted area over which the transltion is located, any in-crease in overlap would reduce the number of steps which may occur.
In the practice of this invention, the flux~ f2' flows from lamination L2' into laminatlon Ll' at gap G2' and reenters laminations R2' after it passes gap G2'. Flux fl' when reaching gap Gl' flows through R2'. It reenters Rl' after passin~ gap Gl'. In the practlce of this invention : ., : ~. . . : ,. ,,, .,: , , , "

2Q~29 14 5~l,648 the incllnation is 60 and the cut is at 60 to the center llne 41. The area above gap G2' is 0.25 x 4.6 or 1.15 square inches. The area over which flux ~2' reenters R2' is .375 x 4.6 = 1.73 sauare inches. The increase in area in each case is produced without reducing the number of steps within the region. The smaller the inclination of the cut to the center line, the greater the area over which the crowding is spread.
'.'hile preferred embodiments and preferred practice of this invention have been disclosed herein, many modifica-tions thereof are feasible. This invention is not to be restricted except insofar as is necessitated by the spirit o~ the prior art.

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Claims (14)

1. An improved transformer core having a butt-lap-step transformer core joint, said transformer-core joint comprising a plurality of bias-cut laminations cut from a continuous web wound generally in a spiral, the said cut laminations being rejoined at their ends by butted joints after coil means are telescoped on said core, said plurality of laminations being divided into a plurality of groups of laminations, each group including a predetermined number of laminations, said bias cut precluding mismatching of butted lamination ends in the assembly of said core after said coil means has been telescoped thereon and lengthening the adjacent flux path at said butted joints.

2. The core of claim 1 wherein the core is formed by superimposing successive groups of the laminations in a generally spiral configuration, the bias cuts in lamina-tions of alternate groups being biased at a predetermined inclination to the longitudinal center line of said lamina-tions and the bias cuts on the intervening groups being biased at an opposite inclination to the center lines of said laminations.

3. The core of claim 1 wherein each group of laminations is subdivided into steps and the bias cut in the laminations of each group comprising a plurality of stepped cuts at the same bias.

4. The core of claim 2 wherein each group of laminations is subdivided into steps, the bias cuts in the laminations of each alternate groups comprising a plurality of stepped cuts at the predetermined inclination and the bias cuts in the laminations of each intervening group comprising a plurality of stepped cuts at the inclination opposite to said predetermined inclination.

5. A transformer including a core having coil means telescoped thereon, said core including a plurality of laminations of amorphous metal of small thickness wound generally in a spiral and defining a closed curve structure having a window within, the said coil means being wound as an integrated structure encircling the core, the said core having a butt-lap-step joint allowing the opening of said core to permit telescoping of said coil means and the re-closing of said core after said coil means are telescoped thereon, said butt-lap-step joint being formed by cutting in stepped relationship the laminations of groups in suc-cession, each group comprising a predetermined number of said laminations to open said core and abutting the ends of said cut laminations of each group to reclose said core after the coil means is telescoped thereon, the cuts in said lami-nations being biased inclined at a first predetermined angle appreciably different from 90° to the longitudinal center line of said laminations for laminations of alternate groups in said succession and inclined oppositely to said predeter-mined angle at a second predetermined angle appreciably different from 90° to said longitudinal center line of groups intervening between said alternate groups.

6. The transformer of claim 5 wherein each group of the alternate groups and the intervening groups is sub-divided into a plurality of steps and the cut in the lamina-tions of each group comprises stepped cuts in laminations of the steps of each group, the angle and inclination to the center line of the lamination of the stepped cut for each group being the same.

7. The method of making a transformer having a core and coil means whose turns are wound into an integrated coil structure having an opening therein for telescoping onto said core, said core being formed of a web of magnetic amorphous metal of small thickness, the said method including:

(a) winding said web into a generally spiral core structure having a plurality of superimposed lamina-tions about a window;
(b) subdividing said core structure into groups of laminations, said groups being stacked to form said core structure;
(c) producing first cuts through the laminations of each of alternate groups in said core structures, each said cut in the laminations of alternate groups along said core structure being inclined to the center line of said web in one direction at an angle appreciably different from 90°;
(d) producing second cuts through the laminations of each of the groups along said core structure intervening between alternate groups, each of said second cuts in the laminations of said intervening groups along said core structure being inclined to the center line of said web in a direction opposite to said one direction at an angle appreciably different from 90°;
(e) separating said laminations at said cuts and converting said core structure into a generally U-shaped structure whose arms terminate in said cuts;
(f) telescoping said coil structure in the arms of said U-shaped structure; and (g) guided by the difference between the inclina-tion of the severed ends of the laminations, rejoining the ends of the laminations of said groups, group by group, by abutting substantially only the ends of the lamination of each group only to the opposite ends of the lamination of the same group from which said first-named ends were severed, precluding the joining of the ends of the laminations of one group to the ends of the laminations of adjacent groups.

8. The method of making a transformer having a core and coil means whose turns are wound into an integrated coil structure having an opening therein for telescoping onto said core, said core being formed of a web of magnetic amorphous metal of small thickness, the said method including:

(a) winding said web into a generally spiral core structure having a plurality of superimposed lamina-tions about a window;
(b) subdividing said core structure into groups of laminations. said groups being stacked to form said core structure;
(c) producing first cuts through the laminations of each of alternate groups in said core structure, each said cut in the laminations of alternate groups along said core structure being inclined to the center line of said web in one direction at an angle appreciably different from 90°;
(d) producing second cuts through the laminations of each of the groups along said core structure intervening between alternate groups, each of said second cuts being at a different angle to the longitudinal center line of said web through said first cuts;
(e) separating said laminations at said cuts and converting said core structure into a generally U-shaped structure whose arms terminate in said cuts;
(f) telescoping said coil structure in the arms of said U-shaped structure; and (g) guided by the difference in the angle of in-clination to the longitudinal center line of the web of the first cuts and the second cuts, rejoining the ends of the laminations of said groups, group by group, by abutting sub-stantially only the ends of the lamination of each group only to the opposite ends of the lamination of the same group from which said first-named ends were severed, precluding the Joining of the ends of the laminations of one group to the ends of the laminations of adjacent groups.

9. The method of claim 8 including subdividing each group into steps displaced longitudinally from each other along the web and producing first and second cuts each of which comprises cuts in the steps of each group dis-placed longitudinally along the web but at first angle to the longitudinal center line of the web for the alternate groups and at the second angle to the longitudinal center line of web for the intervening groups.

10. The method of making a transformer with reduced losses, the said method including:
(a) winding a web of magnetic amorphous metal into a spiral structure having a window in the center;
(b) subdividing the turns of said spiral into groups, each group being subdivided into steps;
(c) producing a series of cuts through the steps of each group in a region of said spiral, the cuts through the steps of each group being spaced longitudinally along said web in a predetermined direction; the cuts for each step of a group and the cut of the succeeding step termina-ting such that the last turn of a step of a group and the first turn of said succeeding step of said group overlap, whereby magnetic flux flowing through said last turn and through said first turn will be conducted together through one and the other of said last and first turns in the region of said cuts, producing crowding of the flux in said region, the said cuts being produced through all groups of said web;
(d) opening said spiral at said cuts;
(e) thereafter converting said spiral into a U-shaped structure;
(f) telescoping coils on the arms of said U-shaped structure; and (g) reclosing said groups in the region of said cuts, thus producing a transformer having the reclosed spiral structure as a core;
the said method being characterized by that the cuts through the steps are inclined to said longitudinal center line at an angle appreciably different from 90°, whereby the area of the core in the region of said crowding of said flux is increased.

11. The core of claim 2 wherein the angles of inclination of the bias cuts of the alternate groups and the intervening groups are substantially equal and opposite and depart from 90° to the center line by a small magnitude.

12. The core of claim 1 wherein the core is formed by superimposing successive groups of the lamina-tions in a generally spiral configuration, the bias cuts in at least alternate groups or the groups intervening between the alternate groups being inclined at an angle appreciably different from 90° to the center line web,

13. The transformer of claim 5 wherein the angles of inclination of the bias cuts of the alternate groups and the intervening groups are substantially equal and opposite and depart from 90° to the center line by a small magnitude.

14. The method of claim 7 wherein the angles of inclination of the first cuts and the second cuts are sub-stantially equal and opposite and depart from 90° to the center line of the web by a small magnitude.