US2829356A - Core structure - Google Patents

Description

April l, 1958 G. H. ALLEN 2,829,356

CORE STRUCTURE Filed April 24, v195e 4 JZ 23 28 3/ 4/ ,ff/ 9! 2 24 l i? INVENTOR.

. 45 I @ff/4L@ All/V @URE STRUCTURE Gerald H. Allen, Kalamazoo Township, Kalamazoo County, Mich., assigner to Allen Electric and Equipment Company, Kalamazoo, Mich., a corporation `of Michigan Application April 24, 1956, Serial No. 580,235

l Claim. (Cl. 336-212.)

This invention relates to transformerconstruction and relates particularly to a multi-leaved core construction having numerous structural assembly and operatingadvantages.

ln the manufacture of transformers having a laminated core, it has long been common to fabricate said cores vby punching the individual laminae from sheet material,

applying the transformer windings to a portion of the stacked laminae or core parts, and then to assemble the core in operating relationship within an enclircling frame member. For purposes of economy of both material and labor, there has long been developed several types of transformers, of which one is shown by U. S. Patent No. 1,297,161, wherein the core and frame members are stamped from a single sheet of metal and the core pieces are arranged in an H-shape so that the winding may be applied around the web of the H and beheld in place by the fianges thereof.

ln studing the design of this general `type of transformer, l have found that a number of important features have apparently been overlooked in previous designs of this character. These features, while not all unusual by themselves, when taken together in the overall pattern hereinafter discussed further, result in a transformer having unexpectedly desirable properties. Particularly, since these features often point in .conliicting directions, insofar as their functional results arecon cerned, l have discovered a point at which theycan -be balanced with excellent results.

Particularly, it is desirable to have the line of discontinuity between the core structure and the surrounding frame structure as long as possible in order to minimize the flux intensity at any point at which linx lines pass vfrom .one member across the line of discontinuity to the other member, whereby reluctance losses arerminimized.

Further, it is desired to have the anges on each side of the web or cross bar of the above mentioned core pieces long enough to receive the full amount of the winding and protect it to a maximum extent, yet without extending such flanges beyond the point at which they are functionally advantageous. On the other hand, too much extension of said iianges will result in unreasonable weakening of them and will present both stamping and assembly problems.

Accordingly, a principal object of the invention has been to provide a transformer construction of maximum magnetic eiciency with minimum of mechanical fabrication and assembly problems.

A further object of the invention has been to provide a transformer, as aforesaid, in which the flux density at all points where lines of linx pass a line of discontinuity between portions of metal carrying such flux is reduced to a minimum, but wherein said reduction remains consistent with easy mechanical fabrication and assembly.

A further object of the invention has been to provide a transformer, as aforesaid, whose general arrangement and construction is sufficiently like presently known trans- 2,829,356 AvE'attentati Apr. 1, i958 formers that it will be readily accepted by the market and Vwill be readily accepted and understood by manufactoring, utilizing and service personnel.

A further object of the invention has been to provide a transformer, as aforesaid, which can be manufactured at a very low cost.

A further obiect of the invention has been to provide .zi-transformer, as aforesaid, so designed that dimensional variations between the parts occurring during the fabrication thereof, such as variations occurring by the wearing of the punchingdies, will be either self-compensating orwill be self-absorbing and will therefore not interfere with the assembly and accurate inter-fitting of the parts.

A further object of the invention has been to provide a transformer, as aforesaid, wherein the winding can be rapidly applied thereto and will be adequately protected when in operating position.

A further object of the invention has been to provide a transformer, as aforesaid, which will be sturdy and capable of long and reliable use.

Other objects and purposes of the invention will be apparent to persons acquainted with devices of this general `type upon reading the following disclosure and `inspecting the accompanyingy drawings.

in the drawings:

Figure l is an oblique view of a transformer embodying the, invention.

Figure 2 is a sectional view taken along the linell-Il of Figure l.

Figure 3 is an enlarged lfragment of Figure 2.

Figure 4 is a fragment of FigureZ showing an alternate construction.

General description Theinvention provides a transformer itl (Figures l and 2) vhaving a core 9 comprised of an outer -frame portion irland a generally l-l-shaped inner portion l2.

Detailed construction VThe outer `portion il of the transformer core 9 is comprised of a plurality of preferably identical, laminated plates 16 which are generally rectangular in shape. The

4plates 16 are assembled or stacked to form a unitary structure and are held together'by Yelongated fasteners iigf adjacent y.to the four corners thereof. ,The fasteners in this particular embodiment are tubes of suitable length which extend through openings i5 in said plates and which are flared at their ends to prevent dislodgement of the plates. It is apparent that other types of fasteners suitable for this purpose may be used, if desired. rthe plates lo are each provided with a central opening i8 having iirst and second edges 2i) and 2i, respectively, which are substantially straight, equal in length and parallel with the end edges of the plate lo. The opening 18 has third and fourth edges 22 and 23, respectively. Each of the edges 22 and 23 has a concave, arcuate portion 24, which is preferably circular or elliptical in shape, comprising the major extent of the length thereof. The curvature of each portion 2li is such that, if extended, it would intersect the adjacent ends of the first and second edges 2li and 2li, respectively. However, at a point close to the respectively adjacent ends of the first and second edges, the radius of curvature of 0 portion 24 is progressively shortened in the region 26 until the curved edge intersects an imaginary line connecting corresponding ends of the first and second edges 20 and 21. The end portions Z7 of each of said edges 22 and 23 consist in this particular embodiment of straight segments lying along said imaginary line. Said end portions may, however, be provided with any desired shape.

The inner portion 12 of the transformer core consists of a plurality of laminated, generally H-shaped plates 36'. The plates 35B are identical and each have flanges 28 and 29 with convexly arcuate outer edges 31 and 32 which conform to the arcuate, concave shape of portion 24 and region 26 of the edges 22 and 23. In fact, the inner portion 12 may be stamped from the outer portion 11 to provide at least a part of the opening 13, thereby facilitating economical and speedy fabrication as well as to effect, and maintain even through various stages of die wear, a snug tit between said convex and concave edges. As a result of the H-shape of the plates 30, the edges 34 and 3S of the web 36 in each inner plate 3) are spaced from the corresponding, opposing edges 20 and 21, respectively, for receiving the winding 13 therebetween. Removal of the metal which produces this spacing is also accomplished during the stamping operation. The plates 30 are held in their laminated assembly by fasteners 33, which are of any convenient nature, such as bolts.

The plates 16 and 3@ are provided with mating recesses 37 which define a passageway, if desired, for a stacking key 3S, which key may be subsequently aixed permanently in place, or removed, as desired. Thus, the plates 16 and 30 must be oriented properly before they can be assembled on the stacking key.

The flanges 28 and 29 of plates 30 are of sufficient length that the entirety of the transformer winding 13 can be received therebetween to provide side support for the entire radial extent of that portion of said winding which lies between said flanges. The winding 13 may, if desired, be covered by any suitable protective cover 40, such as varnish. A pair of channel-shaped jackets 41, which are made of insulating material engage the said winding 13 on three sides and are provided with an open fourth side facing the edges 21 and 22 of frame portion 11. The outer edges 45 and 46 of each of the jackets converge toward each other to retain the winding 13 therewithin and engage the edges 20 and 21 of plates 16 to space the winding 13 from said edges and thereby maintain an air gap 47 therebetween., Said edges 45 and 46 are preferably slightly wider than the width of the air gap 47 and sufliciently resilient both to maintain the desired spacing and to absorb manufacturing varations between the parts. Alternatively, the edges 45 and 46 may be extended, if desired and as indicated at 45' and 46 in Figure 4, to overlap each other and thereby provide positive insulation of the winding from the face 20 instead of the air gap 47.

The engagement of the edges 31 and 32 of the inner plates 30 with the edges 22 and 23, respectively, of the outer plates 16 provides lines and areas of discontinuity between the inner portion 12 and the outer portion 11 of the core 9. Since these areas are curved away from the center of the transformer core 9, they provide the least possible llux intensity per unit of area while avoiding undesirable concentrations of flux in any given area. Also, the shape of the portions 11 and 12 provides the maximum permissible area of discontinuity available in this type of transformer which is commensurate with eicient manufacturing practices.

Although a particular, preferred embodiment of the invention has been disclosed above for illustrative purposes, it will be understood that variations thereof within the scope of such disclosure are fully contemplated unless specifically stated to the contrary in the appended claim.

I claim:

A transformer construction of the laminated core type, including in combination: a plurality of core elements arranged in superposed relationship, each of said elements including an external frame member having a central opening therewithin, said central opening having first and second parallel, substantially straight sides and third and fourth concavely curved sides facing each other; a generally H-shaped inner member with the remote edges of the legs thereof being curved to tit snugly against said third and fourth sides of said frame member, said legs extending to points spaced a slight distance from said first and second sides; a pair of channel-shaped insulating members, the webs of said channel-shaped members lying adjacent the respective edges of the web of said inner member, said channel-shaped members opening toward said first and second sides, respectively, with the outer ends of the legs thereof being curved toward each other and positioned against said first and second sides; transformer winding means wrapped around the webs of said inner member and said channel-shaped members, said winding means being of approximately the same depth as the depth of the legs of the inner member and lying within said channel-shaped members, said depth of said winding means being materially less than the depth of said legs of said channel-shaped members, whereby the outer ends of the legs of said channelshaped members maintain the outer edges of said winding means spaced from said first and second sides to provide an air gap therebetween.

References Cited in the iile of this patent UNITED STATES PATENTS 461,135 Stanley Oct. 13, 1891 1,260,743 Attila Mar. 26, 1918

Images