Transformer core and lamination therefor

Aug. 17, 1965

R. C. BAENZIGER ETAL 3,201,731

TRANSFORMER CORE AND LAMINATION THEREFOR Filed Nov. 27, 1962

<img file="US3201731A_D0001.tif" />

INVENTORY. Irobert C.jBaen^i^e by Jztegej;

United States Patent Office

3,201,731

Patented Aug·. 17, 1965 .·?

3,201,731

TRANSFORMER CORE AND LAMINATION THEREFOR ’

SmFtte πΓ*^§δΓ’· and John _F. pj_egel.

Sei PaJk’in^SSIn^nOrS ‘° ®^lecir°-Netic Steel, iL. ^acniIIeiL^rk ΙΠ. _a corporation of Illinois ^MedSa£k¹⁹(S

-Si “ sxisr —tare »1 g™’, “X'»» erator Ld f ^{1Omagnetic induction device} * a flS ginamount of ^{iS a Ceriain} circuits fin Μ ° °^ne ,^parilcular example, in television beam deflection system. With the current trZi 5 SySi^^{011 d6Sign Using} -elE t, h!!^{ly p}°^sltloned components, shorter necked television

SO^are.,^several WS of controlling the leakage flux ‘ so as to avoid stray flux fields, one of which is to drorease ' £ “ ^a “rmer by increasiij SS ut, ox course, this is contrary to the trend town rd E* X · ^Ia7r a„d“ X

1VC iranstormei. Copper bands around the core tend tn contain the flux lines and reduce flux leakagl and oS '

A! hough effective, this manner of solution ΐ expensive' It has. now become a practice to make power trans' le™dU ancuT ^{teIevision circuits of} stacked inter- ₄₅n a can sth ρΓ? T’ “ ^transformer is enclosed ° · construction is expensive not only in that it includes .the extra element of a can but also in that in making the interleaved stacking it is necessary that the r«nif-^atl°^{nS be mdivlduaU}y handled. Thus, although the resulting core type transformer is effective for reducing component size, it is considerably more expensive in materia! cost and m labor expense than is preferred for television power transformer usage.

A general object of the present invention is to provide strachiml ¹?^proX^{ed siacked} lamination transformer core ⁵structure and lamination therefor permitting of relatively inexpensive construction, ease of assembly fnd mS lluA 1Cci£».cL^©, . ^A further object of the invention is to provide a lamination form adapted for use in a stacked lamination transformer core structure and which lamination is of a conguration so as to permit the stamping out of the metal strip with no substantial loss in material. * ^addi^ilOilal. ^obiect of the invention is to provide a wftif°the°· ^makm8 l^{he novel} Amination in accordance with the invention from a single strip of magnetically permeable metal and without the wasting of any significant amount of metal material.

fipd\T^Pt^CifiC i°i^{biect Of the invention is} to provide a modi- _7nfled U shaped lamination including two leg portions joined by a bight portion wherein the legs may be of any length within the limitation that one leg is shorter than the other leg by approximately the width of the bight portion. Ac^y;^{m Stamping out this} lamination from a rectangular portion, of a metallic strip it is possible to interdigitate the positions of the modified U blanks so that in the punching of one blank from the strip, that which is left *^S “ ^ldentical modified U blank. Laminations so formed are stacked into two complementary stacks, windings inserted over the legs of one stack and the two stacks butted whfeh a-rk ^bT^{ed U}~^{U core type} transformer for ^{the dls}.^tnbuted windings overlie the butted joints thereby reducing of flux leakage and substantially avoiding stiay flux lines. It is obvious that a shell type can be lormed from two core type structures with the same advantages m case,of assembly and reduction of flux leakage.

Further objects and features of the invention pertain to *^e Pa^'^ular arrangement and structure whereby the above identified and other objects of the invention are attained. The invention, its structure, its method of manutacture and its arrangement for use will be better understood by reierence to the following specification and drawings formmg a part thereof, wherein:

FIGURE 1 is a view in perspective of a modified U ητ^ίτ?,¹¹^ ?^{ccordance v/iih the} Present invention;

MG J RE 2 is a perspective view of two complementary stacks of laminations as shown in FIGURE 1 split and arranged for butting so as to form a core type transformer;

FIGURE 3A is an elevational view of a core type transformer made from the laminations of FIGURE 1;

FIGURE 3B is an elevational view of a shell type transformer made from the laminations of FIGURE 1· • ^F*GURES 4A and 4B illustrate two methods for stamping bxan^s in accordance with the invention from a strip of magnetically permeable material; and,

FIGURE 5 illustrates another method of stamping blanks m accordance with the invention from a strip of magnetically permeable material.

. Referring first, to FIGURE 1, there is shown therein m perspective view a lamination 10 made up of integrally formed leg portions 12 and 14 and a bight portion 16. The lamination 10 is a blank stamped from a thin sheet of magnetically permeable metallic material tor which the magnetic grain may or may not be oriented depending upon the cost requirements and the magnetic circuit standards to be met. The leg 12 is of a lenrth I and the bight portion 16 is of a width a. Preferentially then the leg portion 14 is of a length l-a, with the legs 14 and 12 each being of a width b. The bight portion 16 is of a length 3b, as shown. Where grain oriented material is employed it may be that it will be preferred to compensate for the difference between ingrain and cross-grain permeability by making the crossgrain dimension larger than the in-grain dimension. For example,, if the. lamination 10 were a blank of material gram oriented in the .direction indicated by the arrow 18 and if it were desired to compensate for the difference between, the magnetic permeability of the in-m-ain and cross-gram .areas, the dimension a would be greater than, the dimension b by an amount substantially in proportion to the difference between in-grain and cross_oram permeability of the magnetic material.

FTCTTRp^ai?^{ner in},^w!]^{ich the} laminations 18 illustrated in FIGURE i are stacked in order to form a butted core 10 are ± “.^FIGF^RE 2- Therein the laminations 10 are arranged m a first stack 22 and in a second stack ciatedTith to® ^{22 provides a buttin}S 26 associated with the leg portions 12 and a butting face 28 associated with, the leg portions 14, and the stack 24 provides a butting face 36 associated with the le« nor tions 14 and a butting face 38 associated with the leg

3,201,731 «j&gt;

portions 12. In actual practice the laminations 10 may be arranged in the stacks 22 and 24 arid potted with any suitable resin, or clamped, or wired or pinned through mounting holes, not shown, so as to hold the laminations in stacks during assembly and mounting of the transformers.

'The manner in which the transformer of the type 'otherwise illustrated in FIGURE 2 is finally assembled is illustrated in FIGURES 3A and 3B. In FIGURE 3A there is shown a core type transformer assembled ; from stacks 22A and 24A of laminations as shown in FIGURE 2 and including transformer windings 40 and 42 overlying the abutting faces 26A-36A and 28A-38A, respectively. The exact nature of the windings 40 and 42 are not so important as the consideration that they do overlie the abutting faces thereby substantially reducing the leakage flux and confining the lines of stray flux to the transformer configuration. The stacks. 22 and 24 may be secured into place by any convenient bracket means which will bring the abutting faces into intimate association. Of course, the smoother and the more intimate the association between the abutting faces the less the air gap and the less the flux leakage.

In FIGURE 3B there is shown a shell type transformer assembled from stacks 22B and 24B and stacks 22C and 25 central window. 24C and arranged to provide a common center leg 46 and two outer legs 48 and 49. The center leg 46 has overlying it and the abutting faces thereof a transformer winding 52 and the legs 48 and 49 have overlying them and the abutting faces thereof transformer windings .54 and 56. The manner of mounting is optional, it being important only that the stacks be arranged to provide a substantially gapless and intimate mating between abutting faces.

FIGURE 4A illustrates the procedural steps that take place in stamping the laminations 10 from, a strip of magnetically permeable material 50. In this particular arrangement and in keeping with the definition set forth relative to FIGURE 1, the strip of material is selected to be of a width 4b. It is fed into a punch press provided with two simultaneous punching operations at consecutive punching stations. Thus, at the first stamping station, as illustrated in FIGURE 4A, the strip 50 is operated upon to punch out the blank 60 corresponding identically to the laminations 10 shown in FIGURE 1. Thereafter, the punch press operates so as to shift the punched strip to station 2 whereat the final punching operation takes place to sever the blank 62 from the strip 50 and complete the punching operation. At the same time that blank 62 is being punched at station 2 ₅₀another blank 6® is being punched at station 1. Thus, the punching operation is quick and efficient and produces blanks for laminations without waste of any strip material. FIGURE 4B illustrates another punching arrangement where a strip of material 5® of a width l+a 53 is subjected to a single punching operation whereby the blank 64 is stamped out leaving as a residual the blank 66, each of a configuration as shown in FIGURE 1.

A similar but more complicated punching operation is illustrated by the representation of FIGURE 5. There- 60 in the selected punch press is designed to have at least four active punching stations whereby punching operations can be carried out simultaneously. Specifically, again a strip 5® of a width 4b is fed into the punch press, not shown, and progresses therethrough in seven 65 stations. At station A, guide slots 70, 72, 74, 76, 78 and 80 are punched into the strip, which slots serve not only for alignment purposes during the subsequent stamping operations .but accurately position and identify the is stamped from the strip leaving in addition the blank 83. '

In the stamping operation of FIGURE 5 the punching of the guide slots does create some nominal waste but it does permit a better alignment and does provide for a greater exactitude in the punching of the surfaces that will form the abutting faces of the transformer core stacks. Other punching operations may be performed such, for example, as mounting holes in the laminations, if desired, and a shaving operation on the face of the guide slots that will form abutting faces of the transformer core. The first operation may be completed in either of the arrangements of FIGURES 4 and 5 by the inclusion of an extra preliminary punching station. Similarly, the shaving operation, may be added to the arrangement of FIGURE 5 by including between station A and station B a separate shaving station.

In practice, laminations suited for use in the construction of television power transformers have been stamped from strip steel of AISI grade M27 and of a 24 or 26 gauge. Core type transformers constructed in accordance with the scheme of the present invention are approximately three inches square with a one inch .square ' ' . This physical size may be varied according to the permeability of the selected material and the desired power capacity of the transformer to be constructed from the core.

From the foregoing it is clear that there has been provided herein a new and improved core construction and lamination therefor whereby a core type transformer can be constructed from laminations stamped from a strip of magnetic permeable material without waste of that material and wherein, specifically, the laminations are of 5 a modified U shape with one leg shorter than the other leg by a dimension corresponding to the width of the bight portion therein. Additionally, through use of such laminations it is possible to derive a transformer construction wherein windings carried on opposite legs of the transformer enclose and encompass the abutting faces of the lamination stacks in a manner so as to substantially reduce flux leakage and prevent the formation of stray flux lines. Thus, there is presented not only a simple and efficient lamination and method of making the same, but there is formed a transformer which can be made of relatively inexpensive permeable material. The principles described herein may also be employed in larger dimensions for the purpose of making laminations for high kva. power transformers.

Although the arrangement described herein is consid¹ ered at present to be preferred, it is understood that it merely exemplary of the principles of the invention and that variations and modifications may be made therein. It is intended to cover in the appended claims all such . variations and modifications as fall within the true spirit and scope of the invention.