Patent Publication Number: US-10763030-B2

Title: Transformer and transformer core

Description:
FIELD OF THE INVENTION 
     The present application relates to transformers, and more particularly to transformer cores. 
     BACKGROUND 
     Transformers and transformer cores remain an area of interest. Some existing systems have various shortcomings, drawbacks and disadvantages relative to certain applications. For example, in some transformer cores, mitered joints between the yokes and the center leg may result in unnecessary scrap of the lamination material used to form the core, e.g., owing to notches being cut into the yoke to accommodate the center leg. Accordingly, there remains a need for further contributions in this area of technology. 
     SUMMARY 
     Embodiments of the present invention include a unique transformer. The transformer may include a first yoke formed of laminations oriented parallel to a first plane; a second yoke formed of laminations oriented parallel to the first plane; and a center leg formed of laminations oriented parallel to a second plane that is oriented at a non-zero angle relative to the first plane. The center leg includes a first end. The first yoke and the second yoke are in contact with the center leg at the first end. The transformer includes a coil disposed about the center leg, and a butt joint between the center leg and at least one of the first yoke and the second yoke. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
         FIG. 1  schematically depicts some aspects of an electrical power transformer in accordance with a non-limiting example of an embodiment of the present invention. 
         FIG. 2  schematically depicts some aspects of a core leg and a phase leg transformer in accordance with a non-limiting example of an embodiment of the present invention. 
         FIG. 3  schematically depicts some aspects of a transformer core in accordance with a non-limiting example of an embodiment of the present invention. 
         FIG. 4  schematically depicts some aspects of a transformer core in accordance with a non-limiting example of an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     For purposes of promoting an understanding of the principles of the Transformer, and Transformer Core, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nonetheless be understood that no limitation of the scope of the invention is intended by the illustration and description of certain embodiments of the invention. In addition, any alterations and/or modifications of the illustrated and/or described embodiment(s) are contemplated as being within the scope of the present invention. Further, any other applications of the principles of the invention, as illustrated and/or described herein, as would normally occur to one skilled in the art to which the invention pertains, are contemplated as being within the scope of the present invention. 
     Referring to the drawings, and in particular  FIGS. 1 and 2 , some aspects of a non-limiting example of an electrical power transformer  10  in accordance with an embodiment of the present invention are depicted. In one form, transformer  10  is a three-phase transformer system. In other embodiments, transformer  10  may be a single-phase transformer or any other type of electrical power transformer. Transformer  10  includes a transformer core  12 , and includes three phase leg transformers  14 ,  16  and  18 . Core  12  includes outer legs  20  and  22 , and a center leg  24 . 
     The assembled core  12  forms one or more flux paths through legs  20 ,  22  and  24  and yokes  26 ,  28 ,  30  and  32 . As set forth below, in some embodiments, a first flux path loop is formed between center leg  24 , yoke  26 , outer leg  20  and yoke  30 , and a second flux path loop is formed between center leg  24 , yoke  28 , outer leg  22  and yoke  32 . The flux path(s) formed in core  12  may vary with the needs of the application. 
     Legs  20 ,  22  and  24  are magnetically coupled via yoke pieces or yokes  26 ,  28 ,  30  and  32 , and together with yokes  26 ,  28 ,  30  and  32  form magnetic flux paths extending through core  12 . Center leg  24  forms a magnetic flux path with yokes  26 ,  28 ,  30  and  32 , to allow lines of magnetic flux to extend continuously through yoke  30 , center leg  24  and yoke  26 , and to allow lines of magnetic flux to extend continuously through yoke  32 , center leg  24  and yoke  28 . Outer leg  20  forms a magnetic flux path with yokes  26  and  30 , to allow lines of magnetic flux to extend continuously through yoke  26 , outer leg  20  and yoke  30 . Outer leg  22  forms a magnetic flux path with yokes  28  and  32 , to allow lines of magnetic flux to extend continuously through yoke  28 , outer leg  22  and yoke  32 . Thus, in some embodiments, a first flux path loop may be defined by center leg  24 , yoke  28 , outer leg  22  and yoke  32 , which may, for example, direct lines of magnetic flux in a clockwise or counterclockwise direction between mating legs and yokes. Similarly, in some embodiments, a second flux path loop may be defined by center leg  24 , yoke  26 , outer leg  20  and yoke  30 , which may, for example, direct lines of magnetic flux in a clockwise or counterclockwise direction between mating legs and yokes. 
     Phase leg transformers  14 ,  16  and  18  are disposed about respective legs  20 ,  22  and  24  of transformer core  12 . In one form, each phase leg transformer, e.g., an example of which is phase leg transformer  16  as illustrated in  FIG. 2 , includes a low voltage (LV) transformer coil assembly  34  and a high voltage (HV) transformer coil assembly  34  disposed about the respective transformer leg, e.g., a center leg  24 . In other embodiments, one or more additional coils may be included in one or more phase leg transformers, e.g., a medium voltage coil or a tap coil. In the embodiment of  FIG. 2 , center leg  24  is cruciform. In other embodiments, other leg geometries may be employed. 
     Referring to  FIG. 3 , some aspects of a non-limiting example of a transformer core  12  in accordance with an embodiment of the present invention are schematically depicted. In the embodiment of  FIG. 3 , center leg  24  is a rectangular leg. In other embodiments, center leg  24  may have a square, cruciform, round (or essentially round) cross section or any suitable cross section. Legs  20 ,  22  and  24 , and yokes  26 ,  28 ,  30  and  32  are each formed of a plurality of laminations, namely, plurality of laminations  38 , plurality of laminations  40 , plurality of laminations  42 , plurality of laminations  44 , plurality of laminations  46 , plurality of laminations  48  and plurality of laminations  50 , respectively. In one form, laminations  38 ,  40 ,  42 ,  44 ,  46 ,  48  and  50  are formed of electrical steel, such as low-loss high-permeability silicon steel. In other embodiments, other materials may be employed. 
     Plurality of laminations  38  are stacked in a direction  52  to form leg  20 . Similarly, plurality of laminations  40 ,  44 ,  46 ,  48  and  50  are stacked in direction  52  to form respective leg  22  and yokes  26 ,  28 ,  30  and  32 . Each lamination of plurality of laminations  38 ,  40 ,  44 ,  46 ,  48  and  50  for legs  20  and  22 , and for yokes  26 ,  28 ,  30  and  32  has major dimensions (i.e., exclusive of lamination sheet thickness) that extend in directions  54  and  56 , and is oriented parallel to a plane  58 . Each lamination  38 ,  40 ,  44 ,  46 ,  48  and  50  has a sheet thickness measured in direction  52 , which is perpendicular to plane  58 . In other embodiments, one or more of plurality of laminations  38 ,  40 ,  44 ,  46 ,  48  and  50  may be stacked in one or more other directions and/or may be three-dimensional laminations. 
     Yoke  26  and corresponding plurality of laminations  44  are coincident with respective yoke  28  and corresponding plurality of laminations  46 , i.e., disposed along the same line. Similarly, yoke  30  and corresponding plurality of laminations  48  are coincident with respective yoke  32  and corresponding plurality of laminations  50 . In one form, each of yokes  26 ,  28 ,  30  and  32  have the same length. In some embodiments, yokes  26 ,  28 ,  30  and  32  have the same average length, but the length of each lamination forming the yoke pieces may vary as needed to produce a desired step lap joint with an outer leg, e.g., a mitered step lap joint or a butt lap joint. In other embodiments, yokes  26 ,  28 ,  30  and  32  have the same average length, but the length of each lamination forming the yoke pieces may vary as needed to produce a desired step lap joint with an outer leg, e.g., a mitered step lap joint or a butt lap joint, and/or as needed to accommodate the steps of one or more cruciform legs. Leg  20  and corresponding plurality of laminations  38  are parallel to leg  22  and corresponding plurality of laminations  40 , which is parallel to plane  58 . Center leg  24  is parallel to outer legs  20  and  22 , except that the laminations of center leg  24  are stacked in a different direction than those of outer legs  20  and  22 , as set forth herein. 
     In one form, plurality of laminations  42  are stacked in a direction  54  to form center leg  24 . In one form, each lamination of plurality of laminations  42  has primary dimensions (i.e., exclusive of lamination sheet thickness) that extend in directions  52  and  56 , and is oriented parallel to a plane  60 . Each lamination  42  of center leg  24  has a sheet thickness measured in direction  54 , which is perpendicular to plane  60 . Plane  60  forms an angle A with plane  58 . In one form, plane  60  is perpendicular to plane  58  or angle A is 90 degrees as illustrated in  FIG. 3 . In other embodiments, plane  60  may be disposed at other angles relative to plane  58 , e.g., other non-zero angles. In these other embodiments, angle A is greater than zero degrees and less than 90 degrees. In other embodiments, laminations  42  may be stacked in one or more other directions and/or may be three-dimensional laminations. 
     In one form, directions  52 ,  54  and  56  are mutually perpendicular. In other embodiments, directions  52 ,  54  and  56  may not be mutually perpendicular. In one form, the laminations of yokes  26 ,  28 ,  30  and  32  each have the same height, e.g., as measured in direction  56 . In other embodiments, the laminations that form each yoke may have two or more different heights, e.g., so as to maintain a desired cross sectional area for the flux paths, such as the cross sectional area of legs  20 ,  22  and  24  when viewed downward in direction  56  in  FIG. 3 . Similarly, the width of the laminations of legs  20  and  22  in direction  54 , and the depth of the laminations of leg  24  may be varied to achieve a desired cross sectional area for the flux paths therethrough, and may be the same or different throughout each leg. 
     Center leg  24  has a top end  62  and a bottom end  64 . Yokes  26  and  28  contact center leg  24  at top end  62  on opposing sides of center leg  24 . Center leg  24  and yokes  26  and  28  are constructed to form respective butt joints  66  and  68  between center leg  24  and yokes  26  and  28 . Yokes  30  and  32  contact center leg  24  at bottom end  64  on opposing sides of center leg  24 . Center leg  24  and yokes  30  and  32  are constructed to form respective butt joints  70  and  72  between center leg  24  and yokes  70  and  72 . Yokes  26  and  30  engage outer leg  20 . In one form, yokes  26  and  30 , and outer leg  20  are constructed to form respective mitered step lap joints  74  and  76 . In other embodiments, joints  74  and/or  76  may be another type of joint, e.g., butt or butt lap joints. Yokes  28  and  32  engage outer leg  22 . In one form, yokes  28  and  32 , and outer leg  22  are constructed to form respective mitered step lap joints  78  and  80 . In other embodiments, joints  78  and/or  80  may be another type of joint, e.g., butt or butt lap joints. In various embodiments, the joints between one or more of the legs and one or more of the yokes may take any suitable form. 
     Referring to  FIG. 4 , some aspects of a non-limiting example of a transformer core  12  in accordance with an embodiment of the present invention are schematically depicted. In the embodiment of  FIG. 4 , center leg  24  is cruciform, and includes a central portion  82 , first steps  84 ,  86  on each side of central portion  82 , and second steps  88 ,  90  adjacent to and outward of steps  84 ,  86 . Although only two steps per side of center leg  24  are illustrated in  FIG. 4 , it will be understood that the number of steps is illustrative only, and that the actual number of steps in any given embodiment may vary in accordance with the needs of the application. Steps  84  and  86  have the same length  92  in direction  54 , and steps  88  and  90  have the same length  94  in direction  54 . 
     Yokes  26  and  28  are subdivided into a plurality of subsets of laminations based on the number of steps on the corresponding sides of cruciform leg  24 , wherein the length of each subset varies based on the length of each step. Yoke  26  is subdivided into subsets  96 ,  98 ,  100 ,  102  and  104 , and yoke  28  is subdivided into subsets  106 ,  108 ,  110 ,  112  and  114 . Subsets  96 ,  104 ,  106  and  114  have the same length  116  in direction  54 . Subsets  98 ,  102 ,  108  and  112  have the same length  118 , which is shorter than length  116  by the lengths  92  of respective steps  84  and  86 . Subsets  100  and  110  have the same length  120 , which is shorter than length  118  by the lengths  94  of respective steps  88  and  90 . 
     As mentioned previously, embodiments of the present employ butt joints between the yokes and the center leg, which may, in some embodiments, reduce scrap, as compared to cores that use notched mitered joints between the yokes and the center leg. 
     Embodiments of the present invention include a transformer, comprising: a first yoke formed of a plurality of first yoke laminations oriented parallel to a first plane; a second yoke formed of a plurality of second yoke laminations oriented parallel to the first plane; a center leg formed of a plurality of leg laminations oriented parallel to a second plane that is oriented at a non-zero angle relative to the first plane, wherein the center leg includes a first end, and wherein the first yoke and the second yoke are in contact with the center leg at the first end; a coil disposed about the center leg; and a butt joint between the center leg and at least one of the first yoke and the second yoke. 
     In a refinement, the second plane is perpendicular to the first plane. 
     In another refinement, the center leg is a cruciform leg. 
     In yet another refinement, a first yoke lamination of the plurality of first yoke laminations is defined by a length dimension; and a second yoke lamination of the plurality of second yoke laminations is defined by the same length dimension. 
     In still another refinement, each first yoke lamination of the plurality of first yoke laminations and each second yoke lamination of the plurality of second yoke laminations have the same height. 
     In yet still another refinement, the transformer further comprises an outer leg, and a mitered joint between the first yoke and the outer leg. 
     In a further refinement, the plurality of first yoke laminations includes a first subset of laminations defined by a first length dimension, and a second subset of laminations defined by a second length dimension different than the first length dimension. 
     In a yet further refinement, the plurality of second yoke laminations includes a third subset of laminations defined by the first length dimension, and a fourth subset of laminations defined by the second length dimension. 
     In a still further refinement, the transformer is a 3-phase transformer. 
     Embodiments of the present invention include a transformer, comprising: a coil; a first plurality of laminations oriented parallel to a first plane; a second plurality of laminations oriented parallel to the first plane and coincident with the first plurality of laminations; and a third plurality of laminations oriented parallel to a second plane, wherein the second plane is disposed at a non-zero angle relative to the first plane; wherein the third plurality of laminations forms a magnetic flux path with both the first plurality of laminations and the second plurality of laminations; and wherein the coil is disposed about the third plurality of laminations. 
     In a refinement, the second plane is perpendicular to the first plane. 
     In another refinement, the first plurality of laminations forms a first yoke of a transformer core; the second plurality of laminations forms a second yoke of the transformer core; and the third plurality of laminations forms a center leg of the transformer core. 
     In yet another refinement, the transformer further comprises a butt joint between the center leg and at least one of the first yoke and the second yoke. 
     In still another refinement, a lamination of the first plurality of laminations is defined by a length dimension; and a lamination of the second plurality of laminations is defined by the same length dimension. 
     In yet still another refinement, each lamination of the first plurality of laminations and each lamination of the second plurality of laminations have the same height. 
     In a further refinement, the first plurality of laminations includes a first subset of laminations defined by a first length dimension, and a second subset of laminations defined by a second length dimension different than the first length dimension. 
     Embodiments of the present invention include a transformer core, comprising: a first plurality of laminations oriented parallel to a first plane; a second plurality of laminations oriented parallel to the first plane and coincident with the first plurality of laminations; and a third plurality of laminations oriented parallel to a second plane, wherein the second plane is disposed at a non-zero angle relative to the first plane, and wherein the third plurality of laminations forms a magnetic flux path with both the first plurality of laminations and the second plurality of laminations. 
     In a refinement, the second plane is perpendicular to the first plane; the first plurality of laminations form a first yoke of the transformer core; the second plurality of laminations form a second yoke of the transformer core; and the third plurality of laminations form a center leg of the transformer core. 
     In another refinement, the center leg is a cruciform leg. 
     In yet another refinement, the center leg is a rectangular leg. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment(s), but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as permitted under the law. Furthermore it should be understood that while the use of the word preferable, preferably, or preferred in the description above indicates that feature so described may be more desirable, it nonetheless may not be necessary and any embodiment lacking the same may be contemplated as within the scope of the invention, that scope being defined by the claims that follow. In reading the claims it is intended that when words such as “a,” “an,” “at least one” and “at least a portion” are used, there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language “at least a portion” and/or “a portion” is used the item may include a portion and/or the entire item unless specifically stated to the contrary.