Transformers

A transformer having a transformer core that forms a magnetic flux path between and through a top yoke, leg, and bottom yoke of the transformer core. A winding can be disposed about the leg. Further, a flitch plate, which can have at least one slot that is configured to reduce eddy losses generated by the winding, can be disposed adjacent to the leg and extend between the top yoke and the bottom yoke. The flitch plate can be clamped to the top and bottom yokes by top and bottom clamps, respectively. The top and bottom clamps can each include at least one cutout that reduces an attraction of stray flux from the winding and into the corresponding top and bottom clamps. Additionally, at least one of the top clamp and the bottom clamp can include an internal lattice structure.

FIELD OF INVENTION

The present application relates generally to transformers, and more particularly, to core clamping structures for transformers.

BACKGROUND

Electrical systems and devices, such as transformers, remain an area of interest. Some existing systems have various shortcomings, drawbacks and disadvantages relative to certain applications. For example, transformer include clamping systems that can experience relatively high temperatures during operation that can damage the transformer and/or shorten the life span of the transformer. Additionally, at least certain types of transformers seek to prevent instances in which at least certain operating temperatures exceed temperature limits by increasing the size of at least certain transformer components, the size of the transformer tank, and the quantity of cooling medium, such as, for example, oil, in the transformer tank. Yet, such efforts can increase the size and weight, and thus the cost, of the transformer and associated system. Accordingly, there remains a need for further contributions in this area of technology.

BRIEF SUMMARY

Embodiments of the present invention includes a unique transformer. Other embodiments include core clamps, flitch plates, apparatuses, systems, devices, hardware, methods, and combinations for transformers. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith.

An aspect of an embodiment of the present application is a transformer having a transformer core that can include a top yoke, a bottom yoke, and a leg. The leg can extend between the top yoke and the bottom yoke. Further, the transformer core can be constructed to form a magnetic flux path between and through the top yoke, the leg, and the bottom yoke. The transformer can also include a winding that is disposed about the leg and a flitch plate that can be disposed adjacent to the leg, and which can extend between the top yoke and the bottom yoke. The transformer can further include a core clamp having a top clamp and a bottom clamp. The flitch plate can be clamped to the top yoke by the top clamp and clamped to the bottom yoke by the bottom clamp. Further, the top clamp and the bottom clamp can each include a cutout that is positioned and sized to reduce an attraction of stray flux from the winding into the corresponding top clamp and bottom clamp.

Another aspect of an embodiment of the present application is a transformer having a transformer core that can include a top yoke, a bottom yoke, and a leg. The leg can extend between the top yoke and the bottom yoke. Further, the transformer core can be constructed to form a magnetic flux path between and through the top yoke, the leg, and the bottom yoke. The transformer can also include a winding that is disposed about the leg, and a flitch plate that can be disposed adjacent to the leg, and which can extend between the top yoke and the bottom yoke. Additionally, the flitch plate can have at least one slot that extends through the flitch plate, and which is positioned along at least a portion of the flitch plate between the top yoke and the bottom yoke. The at least one slot can be configured to at least assist in reducing eddy losses generated by the winding. The transformer can further include a core clamp having a top clamp and a bottom clamp. The flitch plate can be clamped to the top yoke by the top clamp and clamped to the bottom yoke by the bottom clamp.

Additionally, an aspect of an embodiment of the present application is a transformer having a transformer core that can include a top yoke, a bottom yoke, and a leg. The leg can extend between the top yoke and the bottom yoke. Further, the transformer core can be constructed to form a magnetic flux path between and through the top yoke, the leg, and the bottom yoke. The transformer can also include a winding that is disposed about the leg, and a flitch plate that can be disposed adjacent to the leg, and which can extend between the top yoke and the bottom yoke. Additionally, the flitch plate can have at least one slot that extends through the flitch plate, and which is positioned along at least a portion of the flitch plate between the top yoke and the bottom yoke. The at least one slot can be configured to at least assist in reducing eddy losses generated by the winding. The transformer can further include a core clamp having a top clamp and a bottom clamp, the flitch plate can be clamped to the top yoke by the top clamp and clamped to the bottom yoke by the bottom clamp. Further, the top clamp and the bottom clamp can each include a cutout that is positioned and sized to reduce an attraction of stray flux from the winding into the corresponding top clamp and bottom clamp. Additionally, at least one of the top clamp and the bottom clamp can include an internal lattice structure.

These and other aspects of the present invention will be better understood in view of the drawings and following detailed description.

The foregoing summary, as well as the following detailed description of certain embodiments of the present application, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the application, there is shown in the drawings, certain embodiments. It should be understood, however, that the present application is not limited to the arrangements and instrumentalities shown in the attached drawings. Further, like numbers in the respective figures indicate like or comparable parts.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Certain terminology is used in the foregoing description for convenience and is not intended to be limiting. Words such as “upper,” “lower,” “top,” “bottom,” “first,” and “second” designate directions in the drawings to which reference is made. This terminology includes the words specifically noted above, derivatives thereof, and words of similar import. Additionally, the words “a” and “one” are defined as including one or more of the referenced item unless specifically noted. The phrase “at least one of” followed by a list of two or more items, such as “A, B or C,” means any individual one of A, B or C, as well as any combination thereof.

Referring now to the drawings, and in particularFIGS.1and2, some aspects of a non-limiting example of a transformer10are illustrated in accordance with an embodiment of the present invention. The embodiment of the transformer10depicted inFIGS.1and2is a three-phase “TY core” transformer. However, the transformer10can take other forms. Additionally, the transformer10can be any single-phase transformer or a multi-phase transformer, such as, for example, a three-phase transformer. Additionally, the transformer10can be a single or three-phase low voltage, medium voltage, or high voltage transformer, including transformers characterized as category I through category IV transformers under IEEE Standard C57.12.00-2015.

The transformer10can include a transformer core12, one or more windings14, and a core clamp16. The transformer core12can include, in various embodiments, a top yoke20and a bottom yoke22. Additionally, the transformer core12can include one or more main limbs or main legs24, e.g., main legs24A-C (collectively legs24), that can extend between the top yoke20and the bottom yoke22. Additionally, according to certain embodiments, the transformer core12can also include one or more side limbs or side legs26, e.g., side legs26A-B (collectively legs26), that can also extend between the top yoke20and the bottom yoke22. The number of main legs24and side legs26can vary with the needs of the application.

The transformer core12can be constructed to form a magnetic flux path, such as, for example, a low reluctance path, between, and through, its various components. For example, in the embodiment depicted inFIGS.1and2, the transformer core12is constructed to form a magnetic flux path between, and through, the top and bottom yokes20,22, main legs24, and, in at least some embodiments, the side legs26. However, the transformer core12can have a variety of other configurations and/or components that can thus result in the formation of different flux paths. Such variations can include, but is not limited to, the number of main and side legs24,26, and the material(s) used to construct the transformer core12. For example, whileFIG.1depicts a three phase transformer core12having three main legs24and two side legs26, and which can be made of electrical steel that can provide a relatively low reluctance magnetic flux path, a different number of main legs24, side legs26, and/or a different transformer core12material can, in at least certain situations, alter the flux path.

As shown in at leastFIG.1, according to the illustrated embodiment, windings14can be disposed about the main legs24A-C, while such windings14may, or may not, be disposed about the side legs26A-B. Further, according to certain embodiments, the windings14that are disposed about the main legs24A-C can include a plurality of windings, such as, for example, high, medium and/or low voltage windings that can be grouped together, and/or may include tap windings or other winding types disposed about each main leg24A-C. In other embodiments, the windings14disposed about any particular main leg24A-C can composed of different windings e.g., a high, medium and/or low voltage winding, or a tap winding, among other types of windings.

The core clamp16can include a top clamp30, a bottom clamp32, and a plurality of tie plates or flitch plates34,36, such as, for example, main leg flitch plates34A-C (collectively main flitch plates34) and side leg flitch plates36A-B (collectively side leg flitch plates36). The flitch plates34,36can be fixed or secured to each of the top clamp30and the bottom clamp32of the core clamp16in variety of manners, including, for example, via pins, fasteners, clips and/or other retaining and/or fastening features. Additionally, the flitch plates34,36can be constructed to transmit mechanical loads between at least the top yoke20and the bottom yoke22. Moreover, mechanical loads, e.g., tensile loads, can be transmitted between the top and bottom yokes20,22by the flitch plates34,36. The flitch plates34,36can also be configured to support the weight of the transformer10at least when the transformer10is introduced into a transformer tank, when the transformer10is moved, and against relatively high axial and radial forces that can be generated at least by high current that may be present in the windings14in connection with a short circuit in the power grid.

The number of main and side leg flitch plates34,36can vary with the needs of the application. Further, the flitch plates34,36can be disposed adjacent to one or more sides of a corresponding main and/or side leg24,26. For example, according to certain embodiments, the main and side leg flitch plates34,36can be positioned on opposing front and backsides of an associated main leg24or side leg26. Additionally, each flitch plate34,36can be oriented such that the flitch plate34,36is parallel to the corresponding main or side leg24,26to which the flitch plate34,36is disposed along. The flitch plates34,36can also be oriented such that opposing ends of the flitch plates34,36at least partially overlap an adjacent portion of the top yoke20and the bottom yoke22.

The core clamp16can be constructed to fix the transformer core12using the flitch plates34,36, such as, for example, to secure the transformer core12in a fixed arrangement using the flitch plates34,36. For example, the core clamp16can be constructed to secure the top yoke20, bottom yoke22, main leg(s)24, and side leg(s)26(if any), in engagement with each other, as well as in a fixed arrangement. Additionally, the core clamp16can be configured to bear any stresses tending to distort the transformer core12, or tending to displace some components (e.g., yokes20,22and/or legs24,26) of transformer core12from other components (e.g., other yokes20,22and/or legs24,26) of transformer core12. Thus, the core clamp16can be constructed to withstand a variety of loads, such as, for example, loads or forces stemming from the weight of the transformer10and/or loads or forces generated by short circuit conditions, among other forces, loads and stresses.

As shown in at leastFIG.2, according to certain embodiments, the top clamp30of the core clamp16can include a front top clamp member30A and a rear top clamp member30B, while the bottom clamp32of the core clamp16can include a front bottom clamp member32A and a rear bottom clamp member32B. The top clamp30and the bottom clamp32can also be constructed to clamp the adjacent top and bottom ends, respectively, of the flitch plates34,36to the adjacent portions of the transformer core30, such as, for example, to the top yoke20and the bottom yoke22. In this way, both ends of the main and side leg flitch plates34,36can be fixed to the transformer core12.

For example, the top ends of the main and side leg flitch plates34,36can be positioned on either side of the transformer core12, and can be clamped with other components of the transformer core12between at least the front top clamp member30A and the rear top clamp member30B of the top clamp30via use of clamp bolts or yoke bolts28, including, for example, tie bolts, among other fastener means. Similarly, the bottom clamp32can be constructed to clamp at least the bottom ends of the main and side leg flitch plates34,36between the front and rear bottom clamp members32A-B (seeFIG.2). According to certain embodiments, such clamping of the top and bottom portions of the main and side leg flitch plates34,36can include the main and side leg flitch plates34,36the top and bottom portions of the main and side leg flitch plates34,36being clamped against at least a portion of the adjacent top yoke20and bottom yoke22, respectively.

According to certain embodiments, the flitch plates34,36can have one or more slots in the flitch plates34,36. Such slots can provide areas within the flitch plates34,36are partially or completely devoid of material. Moreover, according to certain embodiments, such slots can provide openings or cut-outs that extend completely through opposing sides of the flitch plates34,36, as well as the area therebetween. The number and configuration of such slots can vary for different flitch plates34,36, as well as for different types and sized transformers. For example, according to certain embodiments, the number and/or configuration of slots for the main leg flitch plates34can be different than the number and/or configuration of the slots for the side leg flitch plates36. Additionally, according to certain embodiments, only some of the main leg flitch plates34and/or only some of the leg flitch plates36may include such slots. Additionally, according to certain embodiments, either the main leg flitch plates34or the side leg flitch plates36may contain slots.

For example,FIGS.3A-3Cillustrate non-limiting examples of flitch plates35,40,42that include one or more such slots38and which can be utilized for the previously discussed flitch plates34,36. More specifically,FIGS.3A and3Billustrate examples of flitch plates35,40that can include a plurality of slots38that extend lengthwise or vertically along the flitch plate35,40, whileFIG.3Cillustrates a flitch plate42having a single slot38. WhileFIGS.3A-3Cillustrate flitch plates35,40,42that include three slots38, two slots38, and one slot38, respectively, other embodiments38may include more slots38. Alternatively, as shown inFIG.3D, according to certain embodiments, the flitch plate44may not include any slot(s)38. Further, such slots38can be formed, or produced, in the flitch plates34,36in a variety of different manners, including, for example, via laser slotting and 3D printing, among other manners of forming or providing the slots38in the flitch plates34,36.

As shown inFIGS.3A and3B, with respect to at least certain embodiments in which the flitch plates35,40have a plurality of slots38, the slots38may, or may not, generally be parallel to the other slots38in the flitch plate35,40. Further, whileFIGS.3A and3Billustrate each of the slots38as having generally uniform configurations and orientations, including vertical slots38having a length that terminates at locations that are approximately adjacent to each opposing end of the flitch plates35,40, according to certain embodiments, the shape, size, position, and/or orientation of at least one slot38can be different than that of at least one other slot38within the same flitch plate35,40, and/or with respect to one or more slots38in another flitch plate35,40.

The slots38can be configured in a manner that can at least assist in reducing eddy losses generated by windings14. Moreover, the slots38can be configured such that the generated eddy loses are reduced to a level that facilitates a reduction in the peak temperature of the flitch plates34,36, also referred to as flitch plate peak temperature, to an acceptable level, as compared to a flitch plate having no slots38, such as, for example the flitch plate44shown inFIG.3D. Such eddy losses and peak temperatures can be determined, for example, by measurement and/or by finite element modeling using a commercially available numerical software package, e.g., 3D magnetic and thermal analysis.

An increase in the number of slots38, such as, for example, to four or more slots38, in the flitch plate34,36, can, in at least certain embodiments, further lower eddy losses and flitch plate peak temperatures. Conversely, fewer slots38can, according to at least certain embodiments, be employed, but at the expense of having higher eddy losses and higher peak temperatures in the flitch plate. For example,FIG.3Billustrates a flitch plate40having two slots38, which may, in at least certain circumstances, be sufficient to reduce eddy losses and achieve acceptable flitch plate peak temperatures. Such a degree of reduction in eddy losses and flitch plate peak temperatures may be less than that attained with the three slot38flitch plate35shown inFIG.3A, such reductions in eddy losses and flitch plate peak temperatures still represent a substantial improvement over flitch plate configurations having a single slot38or no slots38. Flitch plate40may thus be used in some embodiments as a main leg flitch plate in the embodiment ofFIGS.1and2.

Similarly, as previously mentioned,FIG.3Cillustrates a flitch plate42having a single slot38, while the flitch plate44depicted inFIG.3Dhas no slots38. Although the single slot38flitch plate42shown inFIG.3Chas lower eddy losses and a corresponding lower peak flitch plate temperature than that of the flitch plate44having no slot38, the eddy losses and concomitant temperature are nonetheless higher than for the multi-slot38flitch plates35,40shown inFIGS.3A and3B. Accordingly, flitch plates35,40having a plurality of slots, e.g., 2, 3 or more slots38, may provide certain advantages with respect to at eddy losses and peak flitch plate temperatures. Further, with respect to at least certain embodiments, such benefits may result in use of flitch plates35,40having a plurality of slots38being preferable, compared at least to flitch plates42,44having one or no slots38, with at least some, if not all, of the main legs24and/or side legs26.

FIG.4illustrates a calculated flitch plate temperature rise versus the number of slots38in a flitch plate34for an exemplary three-phase, 432 MVA (mega volt-ampere) 230 kV (kilovolt) transformer. The depicted temperature rise inFIG.4is the increase in flitch plate maximum temperature resulting from eddy losses during operation of the transformer. As illustrated inFIG.4, the temperature rise associated with flitch plates having a plurality of slots38, e.g., two, three or four slots, is less than 20° C. (Celsius). Further, as shown, the maximum flitch plate temperature for flitch plates having a plurality of slots38is less than 105° C. during operation at 30° C. ambient temperature and 55° C. top oil temperature. However, for the flitch plate that has only a single slot38, the temperature rise increases substantially, e.g., by approximately 50% or more, relative to at least embodiments having a plurality of slots38, to approximately 30° C. Thus, the use of a plurality of slots38in a flitch plate provides a relatively substantial reduction in flitch plate temperature as compared to flitch plate having only a single slot38.

FIG.4also illustrates values for a flitch plate having zero slots38, including a 59.3° C. temperature rise, resulting in a maximum flitch plate temperature of 144.3° C., which exceeds a maximum admissible temperature of 140° C. for normal life expectancy loading for at least certain flitch plates. Additionally, as the flitch plate having no slots38may not exhibit any reduction in eddy losses or peak temperature, such a flitch plate may be undesirable and not suitable for use as a main leg flitch plate24in at least some embodiments. However, such a flitch plate having no slots38, can according to certain embodiments, be suitable for use as a side leg flitch plate26that has no associated winding14, where eddy losses may thus be naturally lower because of an increased distance from a winding14, and thus may not generate undesirably high peak temperatures in the flitch plate.

As shown in at leastFIG.1, the top clamp30and/or bottom clamp32of the core clamp16can include one or more cutouts50. Moreover, one or both of the front and rear top clamp members30A-B, and/or one or both of the front and rear bottom clamp members32A-B, of the top and bottom clamps30,32, respectively, can include one or more cutouts50. According to certain embodiments, such cutouts50can represent features where a portion of clamp material having a predetermined shape is not present, as if that portion of material had been “cut out” from the top front and back clamp members30A-B and/or in bottom front and back clamp members32A-B. For example, the embodiment shown inFIG.1depicts exemplary cutouts50that are curved cutouts, e.g., curved arches, also referred to as scallops. Such cutouts50can, in various forms, be, or include, partial ellipses, such as, for example, a semi-ellipse or a quarter-ellipse, partial circles such as semi-circles or quarter circles, and/or other curved geometries. In the embodiment ofFIG.1, the cutouts50are, more particularly, semi-ellipses. Alternatively, or optionally, according to other embodiments, one or more of the cutouts50may include rectangular shaped cutouts and/or stepped arch (staircase) cutouts. However, according to certain embodiments, the clamps30,32can have cutouts50of different shapes and sizes.

Additionally, according to certain embodiments, the cutouts50can be sized and positioned in the top and bottom clamps30,32to expose a portion of the top yoke20and bottom yoke22, respectively. Further, the cutouts50can be alternatively formed in one or more locations in top and/or bottom clamps30,32having a cross-section in the form of an internal lattice structure, two examples of which are illustrated with top clamp members30A inFIGS.6B and6C. In still other embodiments, front and rear top clamp members30A-B, and/or the bottom front and rear clamp members32A-B, can have generally C-channel or box channel cross-sectional shapes, among other cross-sectional shapes. Compared to generally solid clamps, such as, for example, the clamp30depicted inFIG.6A, the inclusion of an internal lattice structure between opposing sides of the clamp30, as shown for example inFIGS.6B and6C, can provide extra cooling exchange surfaces that can enhance the cooling of the top and/or bottom clamps30,32, and thereby result in a decrease in the operating temperatures of at least the top and/or bottom clamps30,32during operation of the transformer10. Such decreases in operating temperature of top and/or bottom clamps30,32having an internal lattice structure can be further enhanced, and the operating temperature of generally solid clamps such as that depicted inFIG.6Acan also be reduced, by the inclusion of cutouts50that can be formed in the top and bottom clamps30,32, as is discussed below.

The cutouts50can be formed in the top and bottom clamps30,32in a variety of manners. For example, according to some embodiments, the cutouts50can be formed by cutting material off, or from, the front and rear top clamp members30A-B and the front and rear bottom clamp members32A-B. According to other embodiments, the front and rear top clamp members30A-B and/or the front and rear bottom clamp members32A-B can be formed with cutouts50formed therein, including, but not limited to, via a 3D printing process.

Additionally, the top and bottom clamps30,32can include one or more cutouts50, regardless of the type of cross sectional shape of the top and bottom clamps30,32. Moreover, the front and rear top clamp members30A-B and the front and rear bottom clamp members32A-B can have a variety of cross-sectional shapes, including, but not limited to, cross sectional shapes that are associated with flat plates. Further, the cutouts50can each have a height52and a width54, as shown for example byFIG.5. For at least certain types of shapes, including, for example, non-rectangular shapes, profiles, or perimeters, the height52of the cutout50may refer to the maximum or peak height of the cutout50. Additionally, the cutout50can be formed in one or more locations in front and rear top clamp members30A-B and/or front and rear bottom clamp members32A-B wherein front and rear top clamp members30A-B and/or front and rear bottom clamp members32A-B are in the form of flat plates with a solid cross-section (e.g., see front top clamp member30A ofFIG.6A).

The cutouts50can be positioned and sized to reduce an attraction of stray flux from a winding14into the top clamp30and the bottom clamp32, and, more specifically, into the front and rear top clamp members30A-B and/or the front and rear bottom clamp members32A-B. Such reduction in attraction of stray flux can reduce the operating temperature of top clamp30and bottom clamp32. Additionally, in some embodiments, a reduction in the operating temperature of top clamp30and bottom clamp32can at least contribute to a reduction in the operating temperature of the flitch plates, and in particular, the main leg flitch plates24. More specifically, reducing the maximum temperature of top clamp30and bottom clamp32can reduce the conduction of heat from top clamp30and bottom clamp32to the flitch plates.

While the cutouts50can be situated at a variety of locations along the top and/or bottom clamps30,32, according to certain embodiments, the cutouts50are positioned at locations about the top and/or bottom clamps30,32that are most exposed to the leakage of flux coming out of the windings14. Thus, according to at least certain embodiments, the attraction of stray flux into top clamp30and bottom clamp32can be reduced by positioning the cutouts50at a location in the top clamp30and/or bottom clamp32that is relatively close to the main core legs24, and moreover, that is at or generally adjacent to the position of the active parts or windings14. Moreover, in order to reduce the attraction of stray flux from winding14into top clamp30and bottom clamp32, in some embodiments, the cutouts50are disposed at the locations where windings14are in relatively close proximity to top clamp30and bottom clamp32, such as, for example, at or in general proximity to the intersections between the main legs24and the top and bottom yokes20,22. Additionally, or alternatively, according to certain embodiments, the cutouts50can be positioned, and extend to, at least at the ends of the top clamp30and/or bottom clamp32, and moreover, at opposing ends of the top clamp30and/or bottom clamp32, as shown, for example, by at leastFIGS.8A-9B.

The attraction of stray flux can also decrease with increasing height52of the cutout50, as well as decrease with increasing a width54of cutout50. Accordingly, the maximum operating temperature of top clamp30and bottom clamp32can also be reduced with increasing height52of cutouts50, and with increasing width54of cutouts50.

The actual shape, size, and position of the cutouts50can be based on a variety of different considerations, including, for example, being configured and/or positioned at locations that prevent the cutouts50from interfering with the placement of support features of the transformer10. Thus, for example, referencingFIG.1, the largest size of the cutout50for a particular top and bottom clamp30,32, can be based on the location of one or more bottom supports58, top supports60, and/or by yoke bolt supports62, among other supports. According to certain embodiments, the bottom supports58and top supports60can, for example, be winding supports, including, but not limited to, foot supports or other supports constructed to provide support for windings14. Other supports can include, for example, yoke bolt supports62, which can, for example, support and accommodate yoke clamp bolts for clamping top and bottom yokes20,22between respective front and rear top clamp members30A-B and front and rear bottom clamp members32A-B. Thus, for example, at least a portion of an outer perimeter of the cutouts50can bounded by, or otherwise disposed immediately adjacent to, the respective top and bottom supports58,60, and/or yoke bolt supports62. Accordingly, with respect to the embodiment depicted inFIG.1, the height of one or more of the cutouts50can by limited by the location of the adjacent respective top and bottom supports58,60, while the width54of the cutout50can be limited by the spacing between the adjacent yoke bolt supports62. Further, as shown byFIG.1, according to certain embodiments, successive yoke supports62can be spaced apart from each other by a distance that can accommodate the cutout50that is positioned therebetween having a width that is greater than the width of the adjacent main leg24A,24B,24C. However, to the extent a support, including, for example, the above mentioned supports58,60,62, is to be positioned within a region that is defined by the cutout50, such supports can be constructed from a nonmagnetic material, including, for example, stainless steel.

While the above examples discuss the shape and size of the cutouts50being based, at least in part, on the location of various supports58,60,62, the shape and configuration of the cutouts50can also be based, at least in part, on other considerations. For example, according to certain embodiments, the height52of the cutout50, including, for example, the maximum height50for round or generally rounded cutouts50, can correspond to a vertical location at which a maximum temperature is anticipated to be present in a similar top and/or bottom clamp30,32that lacks any cutouts50, and/or the position along the cutout50at which a maximum temperature would be anticipated to be located if the cutout50were not present. Such a location of the anticipated maximum temperature can be attained in a variety of different manners, including, for example, by finite element modeling of a similar top and/or bottom clamp30,32having no cutouts50using a commercially available numerical software package, e.g., 3D magnetic and thermal analysis.

Alternatively, or additionally, the height52, and/or the width54, including maximum heights52and widths54, of the cutout50, can be based on anticipated or desired dielectric stress value, such as, for example, a predetermined value or limit for dielectric stress in the top clamp30and bottom clamp32, and moreover, dielectric stress in a solid or liquid insulation that is positioned around the top and/or bottom clamps30,32, including, for example, mineral oil and/or cellulose or ester and/or cellulose based insulators, such as, but not limited to, paper and pressboard. Such a predetermined dielectric stress value can vary with the needs of the particular application or by location within the transformer system10. For example, with respect to at least some embodiments or locations, the maximum allowable dielectric stress may be 11 kV/mm, whereas in others, the maximum allowable dielectric stress may be 6 kV/mm, or 2 kV/mm in other embodiments or locations. The predetermined dielectric stress value for various locations can be determined, for example, by measurement and/or by finite element modeling using an available numerical software package, e.g., 3D magnetic and thermal analysis, among other manners of determining the predetermined dielectric stress value.

As the dielectric stress can decrease with an increase in the height52, and also decrease with an increase in the width54, of the cutout50, the shape of cutout50, i.e., the profile, can be selected to achieve the predetermined dielectric stress value, and/or to reduce dielectric stress to or below a predetermined dielectric stress value. Accordingly, at least certain parameters relating to the shape or profile of the cutout50, such as, for example, height, radius, and/or width, among other parameters, can be selected to satisfy a predetermined dielectric stress value in the associated component(s), such as, for example, the top clamp30and/or bottom clamp32.

In view of the foregoing, according to certain embodiments, the location, size, and/or shape of the cutouts50can be based, at least in part, on at least one, if not all, of the following: thermal calculation, minimum dielectric distances, and mechanical constraints, including, but not limited to, the location of supports58,60,62and/or the mechanical limitations of the top and bottom clamps30,32. Moreover, according to certain embodiments, the configuration of the cutouts50, and thus associated form of the associated top and/or bottom clamps30,32, can be dictated by: thermal calculation, such as, for example, the maximum core clamp calculated temperature being less than the admissible limit); minimum dielectric distances, such as, for example, the distance from the core clamps16, which can be connected to ground, and windings14or cable with maximum voltage, which are to be higher than a predetermined dielectric value; and/or mechanical constraints, which can include the core clamps16being configured to support the transformer active part weigh and the short-circuit forces, axial forces, and/or radial forces, location of supports58,60,62, and/or the number of main and side legs24,26of the transformer core12, among other constraints.

FIGS.7A and7Billustrate some aspects of non-limiting examples of a single-phase “EY core” transformer10in accordance with embodiments of the present application. The transformer core12shown inFIGS.7A and7Bcan include a single main leg24, about which a winding14is disposed, and two side legs26A,26B. The core clamp16shown inFIG.7Aincludes a cutout50having a curved arch shape, e.g., a semi-ellipse, whereas the core clamp16shown inFIG.7Bincludes a cutout50having a stepped arch shape.

FIGS.8A-9Billustrate some aspects of non-limiting examples of a single-phase “D core” transformer in accordance with embodiments of the present application. As shown, the transformer core12includes two main legs24A,24B, with a winding14disposed about each main leg, but does not include any side legs, such as the side legs26shown inFIG.1. As shown, according to certain embodiments, the cutouts50can be positioned at, and extend to, opposing ends of the top and bottom clamps30,32. Further, according to certain embodiments, such cutouts50can have a generally rectangular configuration, such as, for example, a configuration in which the width54is larger than the height52of the cutout50. However, according to certain embodiments in which such a rectangular configuration of the cutouts50in the top and/or bottom clamps30,32is not mechanically feasible, then the cutout50can have a different configuration. For example, the cutouts50in the core clamp16of the embodiment shown inFIG.8Aeach include a one-half stepped arch shape, while the cutouts50in the embodiment depicted inFIG.8Beach have a half curved arch shape, e.g., a quarter-ellipse shape. With respect to the embodiment depicted inFIG.9Athe cutouts50each have a stepped arch shape, while the cutouts50shown inFIG.9Bincludes cutouts50each have a curved arch shape, e.g., a semi-ellipse shape.

Referring toFIGS.10A and10B, some aspects of non-limiting examples of a single-phase “DY core” transformer in accordance with embodiments of the present invention are illustrated. In the embodiments ofFIGS.10A and10B, the transformer core12includes two main legs24A,24B, with a winding14disposed about each main leg24A,24B, and two side legs26A,26B. The core clamp16of the embodiment ofFIG.10Aincludes cutouts50having a stepped arch shape, while the core clamp16of the embodiment ofFIG.10Bincludes cutouts50having a curved arch shape, e.g., a semi-ellipse shape.

FIGS.11A-12Billustrate some aspects of non-limiting examples of a three-phase “T core” transformer in accordance with embodiments of the present application. In the embodiments ofFIGS.11A-12B, the transformer core12includes three main legs24A,24B,24C with a winding14disposed about each main leg24A,24B,24C, and does not include any side legs. The core clamp16shown inFIG.11Aincludes cutouts50having a half-stepped arch shape, while the cutouts50depicted inFIG.11Bhave a half curved arch shape, e.g., a quarter-ellipse shape. Further, the core clamp16shown inFIG.12Aincludes cutouts50having a stepped arch shape, while the cutouts50shown inFIG.12Bhave a curved arch shape, e.g., a semi-ellipse shape.

FIG.13illustrates some aspects of a non-limiting example of a three-phase “TY core” transformer10. The embodiment ofFIG.13is the same as the embodiment ofFIG.1, with the exception that the cutouts50in the embodiment ofFIG.13are stepped arches, whereas the cutouts50of the embodiment ofFIG.1are curved arches in the form of semi-ellipses.

Similar to the transformer10shown inFIG.1, the transformers10shown inFIGS.7A-13can each include main leg flitch plates34having one or more slots38therein, and, with respect to the embodiments depicted inFIGS.7A,7B,10A,10B, and13, one or more side leg flitch plates36. Additionally, similar to the transformer10shown inFIG.1, the cutouts50shown inFIGS.7A-13can each be bounded by supports58,60(not shown), such as winding supports, and/or yoke bolt supports62(not shown). Additionally, or alternatively, the cutouts50in the top and bottom clamps30,32in the embodiments of7A-13can have a height52, including, for example, a maximum height, and width54, among other profile shapes, that is/are based on a maximum operating temperature in similar clamps that do not cutouts50. As previously discussed, such sizes for the cutouts50can, for example, be determined by analytical calculation. Further, according to certain embodiments, the size and/or shape of the cutouts50for the transformers10shown in7A-13can be based, at least in part, on a predetermined dielectric stress value, as also discussed above.

FIG.14is a table illustrating non-limiting examples of calculated core clamp temperature rise for some embodiments of the present invention vs. calculated core clamp temperature rise for some corresponding traditional core clamps. As seen with respect to the solid bottom clamps32, the inclusion of the cutouts50can for some transformer core types result in a maximum temperature rise over the oil being less than 60% of than the maximum temperature rise that is experienced with traditional bottom clamps32that do not have cutouts50. Similarly, the inclusion of the cutouts50in solid top clamp30can for some transformer core types result in a maximum temperature rise over the oil that is around 50%-75% lower than the maximum temperature rise that is experienced with traditional top clamps30that do not have cutouts50. WhileFIG.14provides exemplary data with respect to solid top and bottom clamps30,32that include cutouts50, the top and bottom clamps30,32having both cutouts50and an internal lattice structure, such as that depicted inFIG.6BorFIG.6C, can result in an approximately 30% further reduction in the maximum temperature rise.

Such reductions in the maximum temperature rise over the oil can provide a number of benefits for transformers10having top clamps30and/or bottom clamps32that have cutouts50. For example, with respect to at least transformers10in which the distance between the top yoke20and the bottom yoke22is dictated by heating, such as, for example stray flux in the core clamps that is exposed to magnetic fields (e.g. magnetic distance), such a reduction in temperature rise can result in a decrease in the distance between the top and bottom yokes20,22, and thereby reduce the core steel mass, transformer tank height drop, volume of oil in the transformer tank, and the distance from the winding14to the top and bottom yokes20,22. Further, with respect to at least transformers10in which the distance between the top yoke20and the bottom yoke22is dictated by dielectric stress (e.g. dielectric distances), such as dielectric constraints associated with assuring minimum dielectric distance between max potential (high voltage windings) and ground (which can be provided by a ground connection of the core12and/or core clamp16), such a reduction in temperature rise can result in a decrease in the temperature of the core clamp16.