US1404826A - Core structure for transformers - Google Patents

Description

V. E. ALDEN.

CORE STRUCTURE FOR TRANSFORMERS.

, APPLICATION FILED JULYIO, 1918- mwsza Patented Jan. 31, 1922.

6 E W 0 T/ .m W ME I M WITNESSES: W3

UNITED STATES PATENT OFFICE.

VERN E. ALDEN, OF IB ALTIMORE, MARYLAND, ASSIGNOR TO WESTINGHOUSE EIIEC- TRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

CORE STRUCTURE FOR TRANSFORMERS.

To all whom it may concern:

Be it known that I, VERN E. ALDEN, a citizen of the United States, and a resident of Baltimore, '11 the State of Maryland, have invented a new and useful Improvement in Core Structures for Transformers, of which the following is a specification.

My invention relates to the construction of transformer core members and is particularly applicable to the construction of core members for large polyphase transformers which are built up of lamination layers.

In transformers of this type in which the core member is constructed of such laminated layers, the several layers are composed of punchings which are usually rectangular in shape and are built up around the transformer coils after the latter have been placed in position. It has been found that, when such transformers are designed for large-capacity service, the iron losses present therein are excessive. Moreover, when transformers attain the size necessary for large capacities, the punchings used become quitev large and unwieldy, especially those used to form the side portions of the transformer core member.

It is one ofthe objects of my improved form of construction to reduce the iron losses to a minimum by so constructing the lamination layers that the flux will be uniformly distributed among the different layers of the core member. To the end of attaining this object, I so proportion and arrange the air gaps between the various punchings forming a part of each layer, that the magnetic reluctance of all paths in parallel shall be substantially uniform, and also so arrange said punchings that there shall be no tendency for the magnetic flux to concentrate in any one layer of said transformer core member and thereby cause eX- cessive heating in said layer.

Another object of my invention is to construct a laminated-layer transformer core member which shall make use of smaller punchings than has heretofore been possible and thereby greatly reduce the cost of construction, since those punchings which are now discarded as too small for use in the larger transformers will then be used. Moreover, by the use of smaller punchings in the construction of laminated layers, the labor incident to the handling and placing coils.

1918. Serial No. 244,307.

in position of the large punchings will be greatly minimized.

The difliculties encountered in the present type of construction and the manner in which I propose to overcome said difliculties will be more readily understood by reference to the accompanying drawings in which Fig. 1 is a sectional view taken on the, line II of Fig. 2, both of said figures showing the manner in which the laminations are placed in a core-type transformer; Fig. 3 is a sectional view of a shell-type transformer, and Fig. 4.- is an elevational view of a portion of the transformer shown in Fig. 3.

Referring more particularly to Fig. 1, a transformer, comprising a core 1 and coil sections 2, 3 and 4, consisting of primary and secondary windings which embrace different leg portions of the core, are shown. It will be understood that the lamination layers are placed one on top of another to provide the built-up core member for such a transformer and it will be further observed that, in this figure, the type of transformer commonly known as the core type is shown.

Referring now more specifically to the exact form of construction of the individual lamination layers, it will be observed that the middle portionof the core is composed of long punchings 5 so alternated that the ends project first at one side of the coils and then at the other. In the layer shown, short punchings 6 and 7 are located at one side of the coils in end-to-end engagement with each other and with their outer ends in respective engagement with the side edges of the outer leg punchings 8 and 9. At the other end of the core, punchings 10 and 11 have side-edge engagement with ends of the punchings 8 and 9 and end engagement with the side edges of the projecting end of the punching 5., hen the next succeeding layer is placed on top of the one here shown, the manner of building the said layer is exactly-reversed, the punchings 10 and 11 and 6 and 7 of one layer being placed on top of the punchings 6 and 7 and 10 and 11 of the next adjacent layer, respectively, and the punchings 5,, -8 and 9 being reversed and so placed as to project oppositely from the The manner of building up the punchings in the waydescribed will be more clearly understood by reference to Fig. 2, in

sult in a layer having no air gaps being long member in which it will be observed that, at the point of abutment of the side portion of the core member and the interior or embraced portion of the said member, two air gaps are provided in alternate layers, while one gap is inserted in the layers which are sandwiched between said alternate layers.

In the transformer, as at present constructed, it has been usual to use a single place of the two punchings 6 and 7. I have found, however, that, by so employing two punchings instead of one, the iron losses are reduced to a minimum and the tendency for the magnetic. flux to concentrate in any one portion of the structure is eliminatedl Referring now toFig. 2, it is apparent that the method heretofore practised will replaced in parallel with a layer having two gaps and this will, in turn, cause a heavy concentration of the magnetic flux in the layer having no air gap. It is, therefore, the purpose of my invention to so divide the hitherto-used long member that the air gaps in adjacent layer's'will present substantially equal magnetic reluctance to the flux in said layers.

Moreover, I intend to so proportion the reluctance of the single gap that but one gap need be used in the portion of the lamination layer, as shown at the top of Fig. 1. This may readily be accomplished by making the gap between the punchings 6 and 7 slightly larger than usual, and the magnetic reluctance of said gap will then be equal to that presented by the sum of the reluctancesof the gaps between the long member. 5 and the two punchings 10 and 11.

In Fig. 3, I have shownthe construction I propose to use in a shell-type transformer. It will be observed that the coils in the shelltype transformer are embraced by the core member and it is, therefore, quite an advantage to be able to use the smaller punchings'in building up the interior portion of such a core member, especially in view of the fact that, for some of the large high voltage, three-phase, shell-type transformers, it

. is not possible to cut the long punchings from the ordinary sheets of commercial sheet steel.

Here again, it will be observed that, infi stead of a slngle long member bridging I across, and abutting against, the interior punching, I ha-veused two members and have'so placedthesingle air gap between these two members that amagn'etic reluctance equal to that interposed in the adjacent-"layer by the particular form thereof, is inserted in the lamination layer shown.

- Fig. 4 shows themanner in which the lamination layers are piled to form a core member for a transformer of the shell type in order to accomplish the purpose of my invention. x

lVhile I have shown the long member heretofore used as subdivided at'the middle of the zone of abutment to the interiorl-y extending member, it will be apparent that the air gap may be placed anywhere in this region so long as the reluctance of said gap is equal to the reluctance of two gaps of the layers immediately adjacent thereto and I, therefore, wish no further limitation to be placed on the structure shown herein than is imposed by the prior art or by the scope of the appended claims.

I claim as my invention:

1. In a transformer, the combination with a primary and a secondary coil, of a core structure comprising three legs and interconnecting side portions operatively associated with said coils, said core structure being built up of lamination layers, alternate layers of said side portions being provided with oneabutment joint and the remainder legs and the remainder of said layers being provided with one transverse air gap at the point of abutment with said core leg.

3. In a transformer, the combination with a primary and a secondary coil, of a core structure comprising three legs and interconnecting side portions operatively asso-' ciated with said coils, said core structure being built up of lamination layers, alternate layers of said side portions being provlded with two transverse air gaps at the point of abutment with one of said core legs and the remainder of said layers being provided with one transverse air gap at the point of abutment with said core leg, the reluctance of-the air gap of said last mentioned set of layers being substantially equal to that of the two air gaps in said rst mentioned set of layers.

4. In a transformer, the combination with a primary and a secondary coil, of a core structure comprising a centrally disposed core legand two side members operatively associated with said coils, said core structures'being built up of lamination layers,

certain ofsaid layers having the lamina- .tions of said centrally disposed core leg extending intermediate two spaced portions of side members and the remainder of said layers having an air gapprovided between two abutting portions of side members.

5. In a transformer, the combination with a primary and a secondary coil, of a core structure comprising a centrally disposed core leg and two side members operatively associated with said coils, said core structures being built up of lamination layers,

alternate of said layers of laminations having a portion of the centrally disposed core leg disposed intermediate two spaced portions of side members and forming two air gaps therein and the remainder of said layers of laminations being provided with an air gap of a magnetic reluctance equal 15 to that of the two air gaps of the next adjacent layers. a

In testimony whereof, I have hereunto subscribed my name this 25th day of June, 1918.

VERN E. ALDEN.

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