Hybrid transformer core and method for manufacturing the transformer core

Abstract

The hybrid transformer core (10) includes grain-oriented steel columns (21-23) and yokes (11, 12). The yokes (11, 12) include a plurality of second layers including amorphous steel sheets bonded to one another by an adhesive coating on the peripheral regions of the major surfaces of the amorphous steel sheets.

Description

[Technical field]

[0001] FIELD OF THEINVENTION TRANSFORMER CORE AND METHOD OF MANUFACTURING A TRANSFORMER CORE FIELD OF THEINVENTION The present invention relates to transformer cores and in particular to transformer cores comprising both grain oriented and amorphous steels. [Background technology]

[0002] 2. Background of the Invention Power converters are used in the distribution and transmission of electricity. Shunt reactors and power transformers are significant sources of losses incurred during the transmission and distribution of electricity. It is desirable to provide a power transformer that reduces power losses.

[0003] No. 4,668,931 discloses a transformer core having one or more winding legs made from a plurality of silicon steel sheets and a pair of yokes made from a plurality of amorphous steel sheets. The yoke and legs are joined in series by joints between the silicon steel sheets and the amorphous steel sheets to form a magnetic loop circuit, thereby providing a transformer core having significantly improved core loss characteristics compared to power transformer cores formed solely from silicon steel sheets.

[0004] WO 2014 / 009054 A1 and EP 2 685 477 A1 disclose a hybrid transformer core including a first yoke of amorphous steel and a second yoke of amorphous steel, the hybrid transformer core further including at least two grain-oriented steel limbs extending between the first and second yokes, a first end of each of the at least two limbs being coupled to a first surface of the first yoke at a first connecting surface, and a second end of each of the at least two limbs being coupled to a second surface of the second yoke at a second connecting surface.

[0005] US Patent Application Publication No. 2004 / 0212269 A1 discloses a method for cutting shapes from an amorphous metal strip feedstock by a selective etching process. Multiple layers of these shapes are assembled by adhesive lamination to form bulk amorphous metal magnetic components of generally polyhedral shapes useful for highly efficient electric motors and induction devices.

[0006] Amorphous steel sheets can be formed by cutting ribbons of amorphous steel into sheets to form a stack of sheets that act as the amorphous steel layers. During assembly of the transformer core, the amorphous steel layers and the grain oriented steel layers can be stacked. When the amorphous steel ribbons are cut, undesirable corrugations may form in the sheets. This problem is exacerbated when the amorphous steel layers are formed by combining several amorphous steel sheets in a stack. To illustrate, large variations in thickness may occur between where the amorphous steel ribbon is cut and at a distance from where the amorphous steel ribbon is cut. This makes shape control more difficult, which is particularly critical in the joint area where the grain oriented steel layer and the amorphous steel layer are overlapped.

[0007] Another problem in controlling the shape during core assembly is that the low mechanical stiffness of the amorphous steel layers can lead to bending deformation (also called collapsing) of the yoke during core assembly. Additional insulating pads can be used to allow the core to be clamped, but it is desirable to reduce the mechanical collapse of the yoke during core assembly. Summary of the Invention [Problem to be solved by the invention]

[0008] overview There is a need to provide improved transformer cores and methods of manufacturing transformer cores. In particular, there is a need for transformer cores and methods of manufacturing transformer cores that provide improved control over shape during transformer core assembly while reducing losses during operation by employing a hybrid core structure. In particular, there is a need for such transformer cores and methods that provide improved rigidity and reduce the risk of yoke collapse during transformer core assembly. [Means for solving the problem]

[0009] According to embodiments of the invention there is provided a transformer core and a manufacturing method as set out in the independent claims. The dependent claims define embodiments.

[0010] The hybrid transformer core includes a column and a yoke. Each column includes a plurality of first layers of grain-oriented steel. One or more of the yokes include a plurality of second layers. Each second layer includes a pair of sheets of amorphous steel, the sheets of amorphous steel being bonded to one another by an adhesive coating on a peripheral region of a major surface of the sheets of amorphous steel, the major surface of the sheets of amorphous steel facing another sheet of amorphous steel in the second layer.

[0011] The major surface may include a central region surrounded by a peripheral region, the central region being free of the adhesive coating.

[0012] The peripheral region may extend around the entire central region so as to surround the central region. The entire outer perimeter area may be covered with an adhesive coating.

[0013] In the layers of the stack that form the yoke and column, each second layer may be bonded to a first layer.

[0014] The peripheral region may include four segments extending along four sides of the major surface, each segment having an average width measured perpendicular to a line along which the side extends and averaged along the extension of the side.

[0015] The average or maximum width (measured perpendicular to the line along which the edge extends) of the segment provided with the adhesive coating along said edge may be no more than 20 mm, no more than 15 mm, or no more than 10 mm.

[0016] A major surface of each sheet of amorphous steel may have a sheet length and a sheet width that is less than the length.

[0017] The major surface may be rectangular. The major faces may be mitered at their ends with a 45° cut.

[0018] The ratio of the maximum width of the longitudinally extending segment of the perimeter region carrying the adhesive coating to the sheet width may be less than 0.15, less than 0.1, or less than 0.07.

[0019] The ratio of the average or maximum width to the length of the sheet of the segment of the perimeter region carrying the adhesive coating extending along the cross-machine direction may be less than 0.15, less than 0.1, or less than 0.07.

[0020] The adhesive coating may be heat resistant to at least 300°C, at least 310°C, at least 320°C, at least 330°C, at least 340°C, at least 400°C or higher.

[0021] The adhesive coating may be heat resistant up to the annealing temperatures to which the first and second layers are exposed after being stacked.

[0022] The adhesive coating may be a silicone based coating or another type of heat resistant adhesive.

[0023] The adhesive coating may be an oven paint. The hybrid transformer core may further comprise an insulating material between adjacent second layers.

[0024] The insulating material may include an insulating adhesive. The insulating material may include an insulating powder.

[0025] The insulating material may be selectively disposed only where the second layer does not overlap the first layer, ie, only in portions of the yoke distinct from the bond areas.

[0026] The insulating material may be coated or sprayed onto the outer surface of the second layer.

[0027] The insulating material may be arranged such that within the second layer (ie, within the set of sheets adhesively bonded to form the second layer) there is no insulating material between adjacent sheets of amorphous steel.

[0028] The first and second layers may be stacked in a butt-lap configuration. The first and second layers may be stacked in a mixed step-lap / butt-lap configuration.

[0029] The first and second layers may be stacked in a single step wrap configuration, a multi-step wrap configuration, a miter wrap configuration, a mixed miter / butt wrap configuration, or another type of transformer core lamination technique.

[0030] In the bonded region, the first and second layers may be alternated. The second layer may extend continuously between the different bond regions.

[0031] Each two layers may have the same number of amorphous steel sheets. The thickness of each amorphous steel sheet may be less than the first thickness of each first layer.

[0032] The number of amorphous steel sheets in each second layer may be selected such that the second layer has a second thickness, the second thickness being the same as the first thickness to within 20%, to within 15%, or to within 10%.

[0033] Each yoke may include at least 1000, at least 2000, at least 3000, at least 4000, at least 5000, at least 6000, at least 7000 or more second layers.

[0034] Each column may include at least 1000, at least 2000, at least 3000, at least 4000, at least 5000, at least 6000, at least 7000 or more first layers.

[0035] According to another aspect of the present invention, a hybrid transformer core includes columns and a yoke. Each column includes a plurality of first layers of grain oriented steel. Each yoke includes a plurality of second layers. Each second layer includes a set of sheets of amorphous steel. The hybrid transformer core may further include an insulating material between adjacent second layers.

[0036] The insulating material may include an insulating adhesive. The insulating material may include an insulating powder.

[0037] The insulating material may be selectively disposed only where the second layer does not overlap the first layer, ie, only in portions of the yoke distinct from the bond areas.

[0038] The insulating material may be coated or sprayed onto the outer surface of the second layer.

[0039] The insulating material may be arranged such that within the second layer (ie, within the set of sheets adhesively bonded to form the second layer) there is no insulating material between adjacent sheets of amorphous steel.

[0040] A transformer according to the present invention may include a hybrid transformer core according to an embodiment and a number of windings.

[0041] The transformer may be a distribution transformer. The transformer may be a single phase distribution transformer.

[0042] The transformer may be rated up to 315kVA. The transformer may be rated at 315kVA or higher.

[0043] The transformer may be rated at least 315kVA and up to 2499kVA. The transformer may be rated at 2499kVA or greater.

[0044] The transformer may be a small power transformer. A method of manufacturing a transformer core may include providing a plurality of first layers of grain-oriented steel. The method may include forming a plurality of second layers. The forming of the second layers may include forming the second layers by placing several sheets of amorphous steel on top of each other and applying an adhesive coating, the adhesive coating being provided on a circumferential region of a major surface of the sheets of amorphous steel, the major surface of the sheets of amorphous steel facing another sheet of amorphous steel in the second layer. The method includes assembling the transformer core from the plurality of first layers and the plurality of second layers, the assembling including stacking the first and second layers to form columns and yokes of the transformer core.

[0045] Each second layer may be formed such that a major surface may include a central region surrounded by a peripheral region, and the central region may be left free of the adhesive coating.

[0046] Each second layer may be formed such that the peripheral region extends entirely around the central region so as to surround the central region.

[0047] Each second layer may be formed such that all of the peripheral area is covered with an adhesive coating.

[0048] Each second layer may be formed such that the peripheral region includes four segments extending along four sides of the major surface, each segment having an average width measured perpendicular to a line along which the side extends and averaged along the extension of the side.

[0049] The average or maximum width (measured perpendicular to the line along which the edge extends) of the segment provided with the adhesive coating along said edge may be no more than 20 mm, no more than 15 mm, or no more than 10 mm.

[0050] Each second layer may be formed such that a major surface of each sheet of amorphous steel has a sheet length and a sheet width that is less than the length.

[0051] Each second layer may be formed such that the ratio of the average or maximum width of a segment of the peripheral region extending along its length that is provided with an adhesive coating to the sheet width is less than 0.15, less than 0.1, or less than 0.07.

[0052] Each second layer may be formed such that the ratio of the average or maximum width of a segment of the outer periphery region carrying the adhesive coating along the width direction to the length of the sheet is less than 0.15, less than 0.1, or less than 0.07.

[0053] The method may further include an annealing step after stacking the first and second layers.

[0054] The method may further include cutting a sheet of amorphous steel from the ribbon.

[0055] The adhesive coating may be heat resistant to at least 300°C, at least 310°C, at least 320°C, at least 330°C, at least 340°C, at least 400°C or higher.

[0056] The adhesive coating may be heat resistant up to the annealing temperature used in the annealing step.

[0057] The adhesive coating may be a silicone based coating or other type of heat resistant adhesive.

[0058] The adhesive coating may be an oven paint. The method may further include disposing an insulating material between adjacent second layers in the stacking step.

[0059] The insulating material may include an insulating adhesive. The insulating material may include an insulating powder.

[0060] Disposing the insulating material between adjacent second layers in the stacking step may include coating, spraying, or spray coating the insulating material onto the second layers.

[0061] The insulating material may be disposed within the second layer (i.e., within the set of sheets adhesively bonded to form the second layer) such that the insulating material does not extend between adjacent sheets of amorphous steel.

[0062] Assembling the transformer core may include stacking the first layer and the second layer in a butt-wrap configuration.

[0063] Assembling the transformer core may include stacking the first and second layers in a mixed step-lap / butt-lap configuration.

[0064] Assembling the transformer core may include stacking the first and second layers in a single step wrap configuration, a multi-step wrap configuration, a miter wrap configuration, a mixed miter / butt wrap configuration, or another type of transformer core lamination technique.

[0065] In the bonded region, the first and second layers may be arranged alternately. The second layer may extend continuously between the different bond regions.

[0066] Each two layer may be formed having the same number of amorphous steel sheets. The thickness of each amorphous steel sheet may be less than the first thickness of each first layer.

[0067] The number of amorphous steel sheets in each second layer may be selected such that the second layer has a second thickness, the second thickness being the same as the first thickness to within 20%, to within 15%, or to within 10%.

[0068] Assembling the transformer core may include stacking at least 1000, at least 2000, at least 3000, at least 4000, at least 5000, at least 6000, at least 7000 or more second layers to form a yoke.

[0069] Assembling the transformer core may include stacking at least 1000, at least 2000, at least 3000, at least 4000, at least 5000, at least 6000, at least 7000 or more first layers to form columns.

[0070] The method of manufacturing a transformer core may include providing a plurality of first layers of grain oriented steel. The method may include forming a plurality of second layers. The forming of the second layers may include disposing several sheets of amorphous steel on top of each other. The method may include assembling the transformer core from the plurality of first layers and the plurality of second layers, the assembling including stacking the first layers and the second layers to form columns and yokes of the transformer core. The method may further include disposing an insulating material between adjacent second layers in the stacking step.

[0071] The insulating material may include an insulating adhesive. The insulating material may include an insulating powder.

[0072] Disposing the insulating material between adjacent second layers in the stacking step may include coating, spraying, or spray coating the insulating material onto the second layers.

[0073] The insulating material may be disposed within the second layer (i.e., within the set of sheets adhesively bonded to form the second layer) such that the insulating material does not extend between adjacent sheets of amorphous steel.

[0074] A method of manufacturing a transformer according to the present invention may include forming a transformer core using a method according to an embodiment of the present invention and forming the transformer windings.

[0075] The method may further include disposing the transformer core and the transformer windings within a housing.

[0076] The transformer may be a distribution transformer. The transformer may be a single phase distribution transformer.

[0077] The transformer may be rated up to 315kVA. The transformer may be rated at 315kVA or higher.

[0078] The transformer may be rated at least 315kVA and up to 2499kVA. The transformer may be rated at 2499kVA or greater.

[0079] The transformer may be a small power transformer. According to another embodiment of the present invention there is provided a use of second layers to form a yoke of a hybrid transformer, each of the second layers comprising a pair of amorphous steel sheets adhered to one another by an adhesive coating on peripheral regions of major surfaces of the amorphous steel sheets, the major surfaces of the amorphous steel sheets facing another amorphous steel sheet in the second layer, the major surfaces including a central region surrounded by the peripheral regions, the central region being free of the adhesive coating.

[0080] The bond coating may be a heat resistant coating capable of withstanding the annealing temperatures to which the second layer will be exposed when assembled with the layer of grain oriented steel.

[0081] The adhesive coating may be a silicon-based adhesive coating or another type of heat resistant adhesive.

[0082] The use may include using an adhesive coating to enhance the mechanical stability of the second layer during the transformer core assembly step.

[0083] The use may include using the adhesive coating to control the shape of the second layer during the transformer core assembly step.

[0084] The following items are embodiments of the present invention. Item 1: A hybrid transformer core, comprising: columns, each of the columns including a plurality of first layers of grain oriented steel, the hybrid transformer core further comprising: The invention comprises one or more yokes, each of the yokes including a plurality of second layers, each of the second layers including a sheet of amorphous steel, the sheets of amorphous steel being adhered to one another by an adhesive coating on a peripheral region of a major surface of the sheet of amorphous steel, the major surface of the sheet of amorphous steel facing another sheet of amorphous steel in the second layer, the major surface including a central region surrounded by the peripheral region, the central region being free of the adhesive coating.

[0085] Item 2: The hybrid transformer core of item 1, wherein the peripheral region includes four segments, the four segments extending along four sides of the major surface, each of the four segments having an average or maximum width measured perpendicular to a line along which the side extends, and wherein the ratio of the average or maximum width of the adhesively coated segments of the peripheral region extending along the length direction to the width of the sheet is less than 0.15, less than 0.1, or less than 0.07, and / or the ratio of the average or maximum width of the adhesively coated segments of the peripheral region extending along the width direction to the length of the sheet is less than 0.15, less than 0.1, or less than 0.07.

[0086] Item 3: The hybrid transformer core of any one of the preceding items, wherein the bond coating is heat resistant to at least 300°C, at least 310°C, at least 320°C, at least 330°C, at least 340°C, or up to 400°C or higher.

[0087] Item 4: The hybrid transformer core of any one of the preceding items, wherein the adhesive coating is a silicone resin-based coating.

[0088] Item 5: The hybrid transformer core of any one of the preceding items, further comprising an insulating material between adjacent second layers.

[0089] Item 6: The hybrid transformer core of item 5, wherein the insulating material includes an insulating adhesive or an insulating powder.

[0090] Item 7: A hybrid transformer core of any one of the preceding items, wherein the first and second layers are stacked in a butt-lap configuration or a mixed step-lap / butt-lap configuration.

[0091] Item 8: A transformer comprising the hybrid transformer core of any one of the preceding items and a plurality of windings.

[0092] Item 9: The transformer is a distribution transformer, the transformer of item 8. Item 10: A method for manufacturing a transformer core, the method comprising: providing a first plurality of layers of grain oriented steel; forming a plurality of second layers, the forming of the second layers comprising forming the second layers by placing several sheets of amorphous steel on top of each other and providing an adhesive coating, the adhesive coating being provided on a periphery region of a main surface of the sheet of amorphous steel, the main surface of the sheet of amorphous steel facing another sheet of amorphous steel in the second layer, a central region of the main surface surrounded by the periphery region remaining free of the adhesive coating, the method further comprising: A method comprising assembling a transformer core from a plurality of first layers and a plurality of second layers, the assembling step including forming columns and one or more yokes of the transformer core by stacking the first layers and the second layers.

[0093] Item 11: The method of item 10, wherein the peripheral region includes four segments extending along four sides of the major surface, each of the four segments having an average or maximum width measured perpendicular to a line along which the side extends, and wherein the ratio of the average or maximum width of the adhesive coated segment of the peripheral region extending along the length direction to the width of the sheet is less than 0.15, less than 0.1, or less than 0.07, and / or the ratio of the average or maximum width of the adhesive coated segment of the peripheral region extending along the width direction to the length of the sheet is less than 0.15, less than 0.1, or less than 0.07.

[0094] Item 12: The method of items 10 or 11, further comprising an annealing step after stacking the first layer and the second layer.

[0095] Item 13: The method of any one of items 10 to 12, wherein the adhesive coating is heat resistant to at least 300°C, at least 310°C, at least 320°C, at least 330°C, at least 340°C, up to 400°C or higher, and / or the adhesive coating is a silicone-based coating or another type of heat resistant coating.

[0096] Item 14: The method of any one of items 10 to 13, further comprising, in the stacking step, disposing an insulating material between adjacent second layers, and optionally the insulating material comprises an insulating adhesive or an insulating powder.

[0097] Item 15: A method for manufacturing a transformer, in particular a distribution transformer, comprising the steps of: forming a transformer core using the method of any one of items 10 to 14; forming a transformer winding; and disposing the transformer core and the transformer windings within the housing.

[0098] Various effects and advantages are associated with the present invention: the hybrid core provides improved control over shape and / or mechanical properties during transformer core assembly while reducing losses during operation by employing a hybrid core structure; the bond coating provides improved mechanical stability to the layers assembled from amorphous steel sheets and the yokes formed from these layers while reducing problems associated with waviness of the individual sheets of amorphous steel; the effect of the bond coating on shape can be kept small by limiting the area of ​​the bond coating to the peripheral area of ​​the major surface of the amorphous steel sheet facing another amorphous steel sheet in a set of amorphous steel sheets forming a second layer.

[0099] The subject matter of the present invention will now be explained in more detail with reference to preferred exemplary embodiments thereof as illustrated in the accompanying drawings. [Brief description of the drawings]

[0100] [Figure 1] FIG. 1 is a schematic diagram of a hybrid transformer core according to an embodiment. [Diagram 2] FIG. 2 is a plan view of the hybrid transformer core of FIG. 1. [Diagram 3] FIG. 2 is a cross-sectional view of the joint area of ​​a hybrid transformer core. [Figure 4] FIG. 2 is a cross-sectional view of a yoke region of a hybrid transformer core. [Diagram 5] FIG. 1 is an exploded view of the second layer of amorphous steel sheet used in the hybrid transformer core. [Figure 6] FIG. 2 is a plan view of a bond-coated sheet of amorphous steel used in a hybrid transformer core. [Figure 7] 1A-1C are plan views illustrating examples of intermediate states during the assembly steps of a hybrid transformer core. [Figure 8] FIG. 2 is a cross-sectional view of a yoke region of a hybrid transformer core. [Figure 9] FIG. 2 is a flowchart of a method according to an embodiment. [Figure 10] 1A-1C are plan views of adhesively coated sheets of amorphous steel used in hybrid transformer cores with varying adhesive layer widths. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0101] Detailed Description of the Embodiments Examples of embodiments of the present invention will be described with reference to the drawings, in which like or similar reference numerals indicate like or similar elements. Some embodiments will be described in the context of a distribution transformer, but the embodiments are not limited thereto. Features of the embodiments may be combined with each other unless otherwise specified.

[0102] 1 is a perspective view of a hybrid transformer core 10 according to an embodiment. The hybrid transformer core 10 comprises a first yoke 11 and, optionally, a second yoke 12. The first and second yokes 11, 12 are formed using layers assembled from adjacent sheets of amorphous steel.

[0103] Although FIG. 1 shows two yokes 11, 12 made of amorphous steel, the hybrid transformer core may also have one yoke made of amorphous steel.

[0104] The hybrid transformer core 10 includes columns 21-23 (also referred to in the art as legs or limbs). Windings are wound around the columns 21-23 of the hybrid transformer core 10. The columns 21-23 may be formed by using layers of grain oriented steel.

[0105] Three columns may extend between the yokes 11, 12. In other variations, for example in a single-phase core-type transformer, only two columns may extend between the yokes 11, 12. Other configurations are possible.

[0106] Broadly speaking, transformers are commonly used to send electrical energy from one circuit to another through inductively coupled conductors. The inductively coupled conductors are defined by the windings of the transformer. The varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and therefore a varying magnetic field through the secondary winding. Some transformers, such as those used at power or audio frequencies, typically have cores made of high-permeability silicon steel. This steel has a magnetic permeability many times that of free space, so the core serves to confine the magnetic flux in a path that greatly reduces the magnetizing current and tightly couples the windings.

[0107] The disclosed embodiments relate to hybrid transformer cores, and in particular to a hybrid transformer core 10 that combines one or several yokes 11, 12 of amorphous steel (note the layers of amorphous steel overlapping layers of grain oriented steel at the joint areas) with columns 21-23 of grain oriented steel (note the layers of amorphous steel overlapping layers of grain oriented steel at the joint areas). Various lamination techniques can be used, such as butt lap, mixed step lap / butt lap, single step lap, multi-step lap, miter lap, mixed miter / butt lap, combinations thereof, or another type of transformer core lamination procedure.

[0108] The amorphous steel used in the first yoke 11 and the second yoke 12 may have the same isotropy in all directions, at least in the plane of the amorphous steel sheet.

[0109] The first yoke 11 may be considered a top yoke and the second yoke 12 may be considered a bottom yoke. The first yoke 11 and the second yoke 12 may be formed as beams. The beams may have one of several different shapes. The shape may be generally defined by the cross-section of the beams. For purposes of illustration, but not limited to, each of the first yoke 11 and the second yoke 12 may have a rectangular shaped cross-section. The columns 21-23 may have a rectangular cross-section, but are not limited to such.

[0110] The columns 21-23 are coupled to the first yoke 11 and the second yoke 12. As described in more detail below, each of the columns 21-23 may be formed by stacking first layers of grain-oriented steel. The first layers of grain-oriented steel may be stacked on top of each other along a lamination direction.

[0111] Each of the yokes 11, 12 may be formed by laminating second layers, generally made of amorphous steel. The second layers of amorphous steel may be stacked on top of each other along a lamination direction. Each second layer may consist of a set of amorphous steel sheets arranged on top of each other and adhesively bonded to each other using an adhesive coating. As will be explained in more detail below, the adhesive coating is provided in the peripheral region of a main surface of an amorphous steel sheet in the second layer, which main surface faces another amorphous steel sheet in the same second layer.

[0112] The stack of second layers formed during transformer core assembly should not be confused with a set of amorphous steel sheets used to form the second layers used later in the transformer core assembly. Each second layer may contain fewer than 25, fewer than 20, fewer than 15, or fewer than 10 amorphous steel sheets. At least 1000, at least 2000, at least 3000, at least 4000, at least 5000, or more second layers (each containing a much smaller number of adhesively bonded amorphous steel sheets) may be stacked during transformer core assembly.

[0113] 2 is a plan view of the hybrid transformer core 10 of FIG 1. The lamination direction is perpendicular to the plane of FIG 2.

[0114] The hybrid transformer core 10 includes a column region 31 in which first layers of grain oriented steel are stacked on top of each other along the lamination direction.

[0115] The hybrid transformer core 10 includes a yoke region 32 in which the second layers are stacked on top of each other along a lamination direction. Each second layer may include a pair of amorphous steel sheets adhesively bonded together, as described in more detail below.

[0116] The hybrid transformer core 10 includes a joint area 33 where a first layer of grain-oriented steel and a second layer of amorphous steel are overlapped. The first and second layers may alternate along the lamination direction in the joint area 33. It will be understood that it is possible to distinguish different second layers in the assembled transformer core. For the purposes of illustration, in each single layer of the lamination, the second layer is adjacent to the first layer. A joint area 33 is formed where the first and second layers overlap. As will be explained below, such a second layer includes multiple sheets of amorphous steel that can be adhesively bonded in a specific manner.

[0117] Other lamination techniques may be used. For purposes of illustration, butt lap, mixed step lap / butt lap, single step lap, multi-step lap, miter lap, miter / butt lap, combinations thereof, or another type of transformer core lamination procedure may be employed.

[0118] Figure 3 is a cross-sectional view of the hybrid transformer core 10 in the joint region 33. Figure 4 is a cross-sectional view of the hybrid transformer core 10 in the yoke region 32. The lamination direction extends in the plane of the drawing.

[0119] In the joint region 33 (shown in FIG. 3 ), first and second layers 40, 50 of grain-oriented steel alternate along the lamination direction. Each second layer 50 includes a plurality of sheets 51 of amorphous steel. The plurality of sheets 51 of amorphous steel are adhesively bonded to one another. The plurality of sheets 51 of amorphous steel may be adhesively bonded to one another using a heat-resistant adhesive coating that can withstand at least the annealing temperatures to which the second layers 50 will be exposed after the first and second layers are stacked in a transformer core assembly.

[0120] In the yoke region 32 (shown in FIG. 4), the second layers 50 are stacked together along the lamination direction. Each second layer 50 includes a plurality of sheets 51 of amorphous steel. As will be described in more detail with reference to FIGS. 5 and 6, the plurality of sheets 51 of amorphous steel are adhesively bonded together. The adhesive coating used to assemble the set of amorphous steel sheets 51 into the second layer 50 may be provided such that it does not extend between adjacent second layers 50. An insulating material may be disposed between adjacent second layers 50 within the yoke.

[0121] The number of amorphous steel sheets 51 in each second layer 50 may be selected depending on the thickness of the individual amorphous steel sheets 51 and the thickness of the first layer 40. Each first layer 40 may have a first thickness t1. The individual amorphous steel sheets 51 may have a sheet thickness t s The number n of the amorphous steel sheets 51 in each second layer 50 may be expressed as n×t s It may be selected so that t1.

[0122] The amorphous steel sheets 51 in each second layer 50 may be adhesively bonded to one another using an adhesive coating. In a transformer core, the adhesive coating may be provided in an area on a major surface of the amorphous steel sheet 51 that is limited to a peripheral region of the major surface that faces another one of the amorphous steel sheets 51 in the same stack. A central region of the major surface, surrounded by the adhesive covered peripheral region, may remain free of the adhesive coating.

[0123] The liquid adhesive may penetrate into the areas between the amorphous steel sheets 51 after it has been applied. This depends on the properties of the adhesive, such as viscosity. Thus, the adhesive coating may be formed by first stacking the amorphous steel sheets 51 together and then applying the adhesive to the outer edges of the stack, from where it penetrates between the amorphous steel sheets 51 in the stack.

[0124] 5 is an exploded view of a set of amorphous steel sheets 51a-51g adhesively bonded together to form a single second ply 50. A large number (e.g. at least 1000, at least 2000, at least 3000, at least 4000, at least 5000, at least 6000, at least 7000 or more) of second plies may be formed in this manner and stacked in a transformer core assembly step.

[0125] 5 shows seven amorphous steel sheets 51a-51g, the number of amorphous steel sheets may be different. For illustrative purposes, the number n of amorphous steel sheets 51 in each second layer 50 may be selected depending on the thickness of each amorphous steel sheet 51 and the thickness of the first layer 40.

[0126] A first sheet of amorphous steel 51a has a major surface facing another sheet of amorphous steel 51b in the same second layer. Only a peripheral region 52 of this major surface of the first sheet of amorphous steel 51a is covered with an adhesive coating used to adhesively bond the first sheet of amorphous steel 51a to the second sheet of amorphous steel 51b in the same second layer. A central region 53 of the major surface, surrounded by the peripheral region 52, may be free of an adhesive coating.

[0127] Similarly, the second sheet of amorphous steel 51b has a major surface facing another sheet of amorphous steel 51c in the same third layer. Only a peripheral region 52 of this major surface of the second sheet of amorphous steel 51b is covered with an adhesive coating that is used to adhesively bond the second sheet of amorphous steel 51b to the third sheet of amorphous steel 51c in the same second layer 50. A central region 53 of the major surface, surrounded by the peripheral region 52, may be free of an adhesive coating.

[0128] Similarly, the major surfaces of the amorphous steel sheets 51c-51f visible in Figure 5 that face the other amorphous steel sheets 51d-51g may have an adhesive coating extending over and limited to a peripheral region 52 of the major surface, leaving a central region 53 of the major surface free of adhesive coating.

[0129] The adhesive coating may be heat resistant to at least 300° C., at least 310° C., at least 320° C., at least 330° C., at least 340° C., at least 400° C. or higher. The adhesive coating may be a silicon-based paint capable of adhesively bonding adjacent ones of the amorphous steel sheets 51a-51g to one another while withstanding the annealing temperatures used in the manufacture of the transformer core. The adhesive coating may be another type of heat resistant adhesive.

[0130] 6 is a plan view of a major surface of amorphous steel sheet 51. The arrangement described with reference to FIG. 6 may be used for each of the major surfaces of amorphous steel sheets 51a-51f of FIG.

[0131] The sheet of amorphous steel 51 has a sheet length and a sheet width, the sheet length being greater than the sheet width. The side of the sheet of amorphous steel 51 that extends along the sheet length is referred to as the "long side" and the side of the sheet of amorphous steel 51 that extends along the sheet width is referred to as the "short side."

[0132] The peripheral region 52 has a first segment 61 that extends continuously along a first long side of the sheet of amorphous steel 51. The peripheral region 52 has a second segment 62 that extends continuously along a first short side of the sheet of amorphous steel 51. The peripheral region 52 has a third segment 63 that extends continuously along a second long side opposite the first long side of the sheet of amorphous steel 51. The peripheral region 52 has a fourth segment 64 that extends continuously along a second short side opposite the first short side of the sheet of amorphous steel 51.

[0133] The adhesive covered peripheral region 52 has a first width w1 measured perpendicular to the extension of the first long side of the amorphous steel sheet 51. If this width varies along the extension of the first long side of the amorphous steel sheet 51, the maximum value is referred to as the first maximum width w1. If this width varies along the extension of the first long side of the amorphous steel sheet 51, the average of this width (average taken along the first long side) is referred to as the first average width w1.

[0134] The adhesive covered peripheral region 52 has a second width w2 measured perpendicular to the extension of the first short side of the amorphous steel sheet 51. If this width varies along the extension of the first short side of the amorphous steel sheet 51, the maximum value is referred to as the second maximum width w2. If this width varies along the extension of the first short side of the amorphous steel sheet 51, the average of the widths (average taken along the first short side) is referred to as the second average width w2.

[0135] The adhesive covered peripheral region 52 has a third width w3 measured perpendicular to the extension of the second long side of the amorphous steel sheet 51. If this width varies along the extension of the second long side of the amorphous steel sheet 51, the maximum value is referred to as the third maximum width w3. If this width varies along the extension of the second long side of the amorphous steel sheet 51, the average of this width (average taken along the second long side) is referred to as the third average width w3.

[0136] The adhesive covered peripheral region 52 has a fourth width w4 measured perpendicular to the extension of the second short side of the amorphous steel sheet 51. If this width varies along the extension of the second short side of the amorphous steel sheet 51, the maximum value is referred to as the fourth maximum width w4. If this width varies along the extension of the second short side of the amorphous steel sheet 51, the average of the widths (average taken along the second short side) is referred to as the fourth average width w4.

[0137] The ratio of the average or maximum width w1, w3 of the longitudinally extending segment of the outer periphery region 52 provided with the adhesive coating to the sheet width may be less than 0.15, less than 0.1, or less than 0.07.

[0138] The ratio of the average or maximum width w2, w4 of the segment of the perimeter region carrying the adhesive coating along the cross-machine direction to the length of the sheet may be less than 0.15, less than 0.1, or less than 0.07.

[0139] In the second layer 50, the amorphous steel sheets 51a-51g are adhesively bonded to one another, and an adhesive coating affecting the adhesive coating is applied to the adhesively coated peripheral area 52 of the main faces of the amorphous steel sheets 51a-51f, the main faces facing another sheet in the same second layer, which can be achieved by placing the amorphous steel sheets 51a-51f on top of one another (thereby forming a bundle of sheets 51a-51g) and then applying an adhesive coating along the outer edge. The sheets 51a-51g may be mechanically supported during the application of the adhesive coating, for example clamped from the top and bottom. The adhesive coating diffuses inwards so that the sheets 51a-51g are adhesively bonded by the adhesive coating extending over the peripheral area 52 of the main faces.

[0140] Although a substantially constant width of the area provided with the adhesive coating is shown diagrammatically in Figures 5 and 6, the width of the area provided with the adhesive coating may vary. For purposes of illustration, the adhesive distribution may depend on the consistency of the adhesive, the amount of adhesive used for bonding, the bonding procedure, and / or the pressing force applied to the amorphous laminate 50. However, the adhesive may be applied so as to be concentrated at or along a peripheral area on a major surface of the amorphous steel sheet 51.

[0141] Some of the adhesive may be unevenly distributed and may spread further towards the center of the amorphous steel sheet 51. If the adhesive is applied as a liquid, small traces of the liquid adhesive may reach the central region of the major surface of the amorphous steel sheet 51.

[0142] FIG. 10 is a diagram illustrating such an adhesive distribution. Although the adhesive may extend away from the edges, the average width (measured across each side of the rectangular major surface, but averaged along the sides) is still small compared to the width and / or length of the sheet.

[0143] 7 shows an example of an intermediate state of stacking the first and second layers 40, 50 in the transformer core assembly process. The second layer 50a in the first yoke 11 is adjacent to the first layer 40a in the first column 21 and the first layer 40c in the third column 23. In the joint area, the first layer 40a and the first layer 40c overlap the second layer of the underlying layer in the first yoke 11. In the joint area, the second layer 50a overlaps the first layer in the second column 22 of the underlying layer.

[0144] Another second layer 50b included in the second yoke 12 is adjacent to the first layer 40a included in the first column 21 and the first layer 40c included in the third column 23. In the joint region, the first layer 40b included in the second column 22 overlaps the second layer included in the second yoke 12 in the underlying layer.

[0145] At least in the yoke region 32 adjacent the bond region and where the first layer 40 is not present, an insulating material may optionally be disposed between adjacent second layers 50 to further reduce losses during operation of the transformer.

[0146] 8 is a cross-sectional view of the transformer core in the yoke region 32. An insulating material 71 is disposed between adjacent second layers 50. The insulating material 71 may be provided as a layer on an outer surface of the second layers 50. The insulating material 71 may include an insulating paint or an insulating powder. The insulating paint or powder may be provided by coating, spraying, or spray coating.

[0147] Although rectangular first and second plies are shown in Figures 2-8, the first and second plies may be mitered with 45 degree cuts at their ends.

[0148] FIG. 9 is a flow chart of a method 80 according to an embodiment. The method may optionally include cutting sheets of amorphous steel from the ribbon of amorphous steel. The sheets may be cut to have the same sheet length and sheet width.

[0149] The method includes a step 81 of forming a plurality of second layers 50 from sheets of amorphous steel. Each second layer 50 may be formed by placing several sheets of amorphous steel (e.g., six or more sheets 51) on top of each other and providing an adhesive coating to form the second layer 50, the adhesive coating being on a peripheral region 52 of a major surface of the amorphous steel sheet facing another amorphous steel sheet in the same second layer 50.

[0150] In step 81, the sheets of amorphous steel 51 within each second layer 50 may be adhesively bonded to one another using an adhesive coating.

[0151] For each second layer 50, forming the second layer 50 may include placing sheets of amorphous steel on top of one another (thereby forming a stack of sheets) and then applying an adhesive coating along the outer edge of the stack. The sheets may be mechanically supported, for example clamped from the top and bottom, while applying the adhesive coating to the edges. The adhesive coating diffuses inwardly so that the sheets are adhesively bonded with the adhesive coating extending over the perimeter regions of the major faces.

[0152] The step of forming the second layer may include curing the adhesive coating prior to stacking the first and second layers in a transformer core assembly step.

[0153] The adhesive coating applied may be heat resistant. The adhesive coating may be such that the pair of sheets in the second layer 50 remain adhesively bonded during the annealing step. The adhesive coating may be heat resistant in the sense that it does not liquefy, burn, and / or char when heated to a temperature that may be 300° C. or more, 310° C. or more, 320° C. or more, 330° C. or more, 340° C. or more, 400° C. or more. The adhesive coating may be heat resistant in the sense that it does not liquefy, burn, and / or char when heated in the annealing step 83.

[0154] The method includes a transformer core assembly step 82. The transformer core assembly step 82 may include stacking a first ply 40 of grain oriented steel and a second ply 50 formed from adhesively bonded sheets of amorphous steel to form the yoke and column of the transformer core. The first ply 40 and second ply 50 may be stacked in a butt lap configuration, a mixed step lap / butt lap configuration, single step lap, multi-step lap, miter lap, mixed miter / butt lap, combinations thereof, or other types of lamination procedures.

[0155] The method includes an annealing step 83. The annealing step 83 is performed after the first and second layers 40, 50 are stacked.

[0156] The method may include additional steps. By way of illustration, the method may include clamping the stacked arrangement of the first and second layers 40, 50.

[0157] The method may include winding a transformer winding around columns 21-23. The method may include attaching a connecting element to the winding.

[0158] The method may include placing the hybrid transformer core 10 together with the windings in a housing, such as a transformer tank. The yokes 11, 12 may be fastened to the housing by fastening means. The hybrid transformer core 10 may be fastened to the housing by fastening means on at least one of the yokes 11, 12. The fastening means may lock against vertical forces applied to the hybrid transformer core 10 during operation. The fastening means may isolate the hybrid transformer core 10 from the housing.

[0159] The method may include installing, testing, and / or operating the transformer.

[0160] The hybrid transformer core may be provided in a distribution transformer. The distribution transformer may be rated up to 315 kVA, 315 kVA or greater, 315 kVA or greater but not greater than 2499 kVA, or 2499 kVA or greater. The hybrid transformer core may be provided in a single phase distribution transformer. The hybrid transformer core may be provided in a small power transformer.

[0161] The use of adhesives to bond the amorphous steel sheets for hybrid core assembly provides a variety of benefits, such as mechanical stiffness, improved control over stack geometry, and potentially additional insulation between the amorphous sheets, as well as simplifying lamination. The adhesive coating is heat resistant to withstand annealing treatment of the hybrid core, which may be performed at temperatures in the range of about 340° C. The adhesive coating may be heat resistant to higher temperatures, such as temperatures of 400° C. or higher.

[0162] Adhesively bonding a sheet of amorphous metal 51 to form the second layer 50 in a dedicated step before the first and second layers 40, 50 are assembled facilitates handling and simplifies the assembly process of the transformer core.

[0163] By achieving the adhesive bond by providing an adhesive coating on the peripheral region of the adhesively bonded amorphous metal sheet 51, the amount of adhesive can be reduced compared to techniques in which the entire major surface of the amorphous metal sheet 51 is coated with adhesive. The reduced amount of adhesive coating allows for easier shape control.

[0164] Also, the adhesive bond along the perimeter region of the amorphous metal sheet 51 in the second layer 50 provides the second layer with power loss characteristics comparable to surface coated amorphous metal sheets. The loss test results are summarized in the table below as a function of magnetic flux density. Losses are averaged over multiple samples of several layers using a surface coating for the adhesive bond and multiple samples of several layers using an adhesive bond with a coating along the perimeter region.

[0165] [Table 1]

[0166] Thus, even if a sheet of amorphous metal is adhesively bonded only in the peripheral region, losses are still comparable to a sheet adhesively bonded with an adhesive coating on all of its major surfaces.

[0167] By using a heat resistant adhesive coating for the adhesive bond that can withstand the annealing temperatures, annealing or other heat treatments can be performed after the first and second layers are laminated in the transformer core assembly process. This is beneficial because amorphous steel sheets can be too brittle to be annealed prior to lamination in the transformer core assembly process.

[0168] Precise adhesive application techniques, and preparation of the amorphous layer 50 ready for lamination, are the solutions to control the shape of the second layer 50 of amorphous steel, thereby preventing large differences in core height, increasing yoke stiffness, and providing insulation between the core layers.

[0169] Adhesively bonded samples show lower specific losses compared to grain oriented steels over the nominal induction target range for the hybrid core yoke, ranging from 1.1 to 1.4 T. Providing an adhesive coating on the hybrid core amorphous metal sheets ensures adequate stiffness, controls the yoke geometry, provides insulation and speeds up the core assembly process.

[0170] Adhesive bonding of the amorphous metal sheets at the perimeter region results in layers 50 of amorphous metal ready for lamination with butt lap / mixed butt lap and step lap hybrid core assembly techniques. A variety of lamination techniques can be used, such as butt lap, mixed step lap / butt lap, single step lap, multi-step lap, miter lap, mixed miter / butt lap, combinations thereof, or another type of transformer core lamination procedure. Precise edge bonding controls the layer shape and provides adequate stiffness, which are key factors during proper hybrid core lamination process and clamping.

[0171] During hybrid core assembly, for each core layer, a thin adhesive or powder surface can be provided between the previously edge-bonded amorphous steel layers 50. This provides insulation between the layers to prevent further losses as a result of circulating currents.

[0172] Various effects and advantages are associated with the present invention. The present invention provides a hybrid transformer core and a method for manufacturing the hybrid transformer core, which can keep losses low during operation by adopting a hybrid core structure, while providing improved control over the shape during transformer core assembly. For example, the stiffness of the yoke can be increased, reducing the risk of the yoke collapsing during transformer core assembly.

[0173] The methods and systems of the present invention may be used in conjunction with, but are not limited to, distribution or power transformers.

[0174] Although the present invention has been described in detail in the drawings and the above description, such description should be considered as serving as an explanation or illustration, not a limitation. Variations of the disclosed embodiments can be understood and realized by those skilled in the art and practicing the claimed invention by studying the drawings, the disclosure, and the appended claims. In the claims, the term "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that some elements or steps are recited in separate claims does not indicate that combinations of these elements or steps cannot be used effectively, specifically in addition to the actual claim dependency, and other meaningful claim combinations should be considered as disclosed.

Claims

1. A hybrid transformer core (10), comprising: columns (21-23), each of said columns including a plurality of first layers (40) of grain-oriented steel, said hybrid transformer core (10) further comprising: a hybrid transformer core (10) comprising one or more yokes (11, 12), each of said yokes comprising a plurality of second layers (50), each of said second layers comprising a plurality of amorphous steel sheets (51; 51a-51g) joined to one another by an adhesive coating on a peripheral region (52) of a main surface of said amorphous steel sheets (51; 51a-51g), said main surface of said amorphous steel sheets facing another amorphous steel sheet (51; 51a-51g) of the same second layer (50), said main surface comprising a central region (53) surrounded by said peripheral region (52), said central region (53) being free of said adhesive coating; said hybrid transformer core (10) further comprising: A hybrid transformer core (10) comprising a joining region (33), in which a plurality of first layers (40) of directional steel and a plurality of second layers (50) of amorphous steel are alternately superimposed only in each of the joining regions (33), and in regions other than the joining regions (33), only one of the first layers (40) or the second layers (50) is superimposed.

2. 2. The hybrid transformer core of claim 1, wherein the outer peripheral region (52) provided with the adhesive coating comprises four segments (61-64), the four segments of the outer peripheral region (52) provided with the adhesive coating extending along four sides of the main surface, each of the four segments having an average or maximum width (w1-w4) measured perpendicular to a line along which the side extends, the ratio determined as the average or maximum width of the four segments of the outer peripheral region provided with the adhesive coating extending along a length direction divided by the width of the sheet is less than 0.15 and / or the ratio determined as the average or maximum width of the four segments of the outer peripheral region provided with the adhesive coating extending along a width direction divided by the length of the sheet is less than 0.

15.

3. The hybrid transformer core (10) of claim 1 or 2, wherein the bond coating is heat resistant up to at least 300°C.

4. The hybrid transformer core (10) of any one of claims 1 to 3, wherein the adhesive coating is a silicone-based coating.

5. The hybrid transformer core (10) of any one of claims 1 to 4, further comprising an insulating material (71) between adjacent second layers (50).

6. The hybrid transformer core (10) of claim 5, wherein the insulating material (71) comprises an insulating adhesive or an insulating powder.

7. The hybrid transformer core (10) of any one of claims 1 to 6, wherein the first layer (40) and the second layer (50) are stacked in a butt-lap configuration or a mixed step-lap / butt-lap configuration.

8. A transformer comprising a hybrid transformer core (10) according to any one of claims 1 to 7 and a number of windings.

9. 9. The transformer of claim 8, wherein the transformer is a distribution transformer.

10. A method of manufacturing a transformer core (10), the method comprising the steps of: providing a first plurality of layers (40) of grain oriented steel; forming a plurality of second layers (50), the forming of the second layers (50) comprising forming a second layer by placing several amorphous steel sheets (51; 51a-51g) on ​​top of each other and providing an adhesive coating, said adhesive coating being provided on a circumferential region (52) of a main surface of said amorphous steel sheets (51; 51a-51g), said main surface of said amorphous steel sheets facing another amorphous steel sheet (51; 51a-51g) of the same second layer, a central region (53) of said main surface, surrounded by said circumferential region (52), remaining free of said adhesive coating, said method further comprising: the step of assembling the transformer core (10) from the plurality of first layers (40) and the plurality of second layers (50), the step of assembling including a step of stacking the first layers (40) and the second layers (50) to form columns (21-23) of the transformer core (10), one or more yokes (11, 12), and a joining region (33) in which the plurality of first layers (40) of grain-oriented steel and the plurality of second layers (50) of amorphous steel are alternately superimposed; The method according to claim 1, wherein only in each of the joining regions (33), a plurality of the first layers (40) of grain-oriented steel and a plurality of the second layers (50) of amorphous steel are alternately superimposed, and in regions other than the joining regions (33), only one of the first layers (40) or the second layers (50) is superimposed.

11. 11. The method of claim 10, wherein the adhesively coated peripheral region (52) comprises four segments (61-64), the four segments of the adhesively coated peripheral region (52) extending along four sides of the main surface, each of the four segments having an average or maximum width (w1-w4) measured perpendicular to a line along which the side extends, the ratio determined as the average or maximum width of the four adhesively coated segments of the peripheral region extending along a length direction divided by a width of the sheet is less than 0.15 and / or the ratio determined as the average or maximum width of the four adhesively coated segments of the peripheral region extending along a width direction divided by a length of the sheet is less than 0.

15.

12. The method of claim 10 or 11, further comprising an annealing step after stacking the first layer (40) and the second layer (50).

13. The method according to any one of claims 10 to 12, wherein the adhesive coating is heat resistant up to at least 300°C and / or the adhesive coating is a silicone based coating or another type of heat resistant coating.

14. The method of any one of claims 10 to 13, wherein the stacking step further comprises disposing an insulating material (71) between adjacent second layers (50), and optionally the insulating material (71) comprises an insulating adhesive or an insulating powder.

15. 1. A method of manufacturing a transformer, particularly a distribution transformer, the method comprising the steps of: forming a transformer core (10) using a method according to any one of claims 10 to 14; forming a transformer winding; and placing the transformer core (10) and transformer windings in a housing.

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