core

Abstract

A core for an electromagnetic device is discussed. In one example, the core comprises three arc-shaped rims. Each rim has a first end and a second end and is arranged around a central axis. The first end of the rim is interconnected at a first position along the central axis, and the second end of the rim is interconnected at a second position along the central axis. Each rim comprises a plurality of bent electrical steel strips. A method for manufacturing such a core is also discussed.

Description

Technology Field

[0001] The following describes a magnetic core for an electromagnetic device and a method for manufacturing a magnetic core. Background Technology

[0002] Magnetic cores are used in various electromagnetic devices such as transformers, electric motors, generators, and inductors. Transformers come in two structural forms: core-type and shell-type. The main difference between these forms lies in the arrangement of the core and windings. In core-type transformers, the windings surround the core, whereas in shell-type transformers, the core surrounds the windings.

[0003] In a core-type single-phase transformer, the magnetic core is typically in the form of a closed square or rectangular ring composed of an electric steel laminate, and the primary and secondary windings surround the core on opposing rims of the ring. However, in transformers equipped with primary and secondary coils on separate rims, large magnetic flux leakage generally occurs, resulting in poor voltage regulation and degraded overall performance.

[0004] A toroidal transformer is a core-type single-phase transformer composed of a toroidal core. The primary and secondary windings of a toroidal transformer are typically wound across the entire surface of the core and are separated by insulating material. Some of the advantages of toroidal transformers include higher efficiency, inherent shielding from electromagnetic interference, minimal signal distortion, a more compact structure, low mechanical humming, low heat generation, and small offload losses. The problem to be solved

[0005] Three-phase power is frequently used in power distribution systems. Three-phase power conversion requires three single-phase transformers within a three-phase bank or a three-phase transformer. An exemplary magnetic core (100) for a three-phase transformer is discussed with reference to FIG. 1. The core (100) comprises three substantially rectangular rings (102), each of which has a first rim (104) and a second rim (106). A primary winding and a secondary winding (not shown) are wound on each first rim (104). The three rectangular rings (102) are interconnected along the second rim (106) and spaced apart by 120 degrees. Each rectangular ring (102) includes an electric steel ring (108) that is laminated together. Typically, each electric steel ring (108) is cut from an electric steel sheet, and waste material—namely, the center of each electric steel ring (108)—is generated.

[0006] In addition, from a performance perspective, a transformer incorporating a core such as the core (100) suffers power loss due to harmonic distortion and noise in the power grid, particularly in low-voltage distribution networks, for example, due to the increased introduction of non-linear loads. means of solving the problem

[0007] A core suitable for an electromagnetic device is provided. This core may be suitable for electromagnetic devices such as transformers, electric motors, generators, and inductors. The core comprises three arc-shaped rims. Each rim has a first end and a second end and is arranged around a central axis. The first end of the rim is interconnected at a first position along the central axis, and the second end of the rim is interconnected at a second position along the central axis. Each rim comprises a plurality of bent electric steel strips.

[0008] The geometric structure of the core improves the material-radiation interaction of the magnetic circuit and physical form, thereby minimizing the distribution of magnetic flux density and thus minimizing both saturation spots and dead spots of low magnetic flux density compared to a core with a rectangular ring such as the core (100). This reduces core losses and requires less core mass.

[0009] The electric steel strips are not flat arc-shaped strips cut from electric steel sheets that are laminated together, for example, but are bent into arcs that are laminated together. This reduces the amount of waste material when forming the rim.

[0010] The arc-shaped rim can be semicircular, that is, have dimensions of 180 degrees. In another example, the arc-shaped rim can be a small arc, that is, have dimensions of less than 180 degrees. Alternatively, the arc-shaped rim can be a large arc, that is, have dimensions of more than 180 degrees.

[0011] The core may be suitable for a three-phase transformer. The core may also be equipped with more than three arc-shaped rims to accommodate additional phases.

[0012] The electric steel strip may be oriented electric steel. A bent arc-shaped oriented electric steel strip ensures that the grain orientation is maintained along the rim, for example, compared to a flat arc-shaped strip cut from a sheet of oriented electric steel. This maintains the symmetric behavior of the rim, as optimal magnetic properties are found in the grain direction.

[0013] Each rim can be spaced at equal intervals around the central axis. For example, in the case of a core consisting of three rims, the rims will be spaced at 120-degree intervals.

[0014] Each of the plurality of bent electric steel strips may include a first group of strips, a second group of strips, and a third group of strips, and the first group of strips is disposed between the second group of strips and the third group of strips. The first group of strips may have a first thickness, the second group of strips may have a second thickness, and the third group of strips may have a third thickness, and the first thickness may be greater than both the second thickness and the third thickness. The second thickness may be equal to the third thickness.

[0015] A first group of strips may consist of a first predetermined number of strips, a second group of strips may consist of a second predetermined number of strips, and a third group of strips may consist of a third predetermined number of strips, and the first predetermined number of strips may be greater than both the second predetermined number of strips and the third predetermined number of strips. The second predetermined number of strips may be the same as the third predetermined number of strips.

[0016] A strip of the first group may have a first width, a strip of the second group may have a second width, and a strip of the third group may have a third width, and the first width may be larger than both the second width and the third width. The second width may be the same as the third width.

[0017] Each rim can be configured to accommodate each primary winding and each secondary winding.

[0018] An electromagnetic device is provided comprising the aforementioned core, each primary winding disposed around each rim, and each secondary winding disposed around each rim. The electromagnetic device may be, for example, a transformer, an electric motor, a generator, or an inductor.

[0019] A method for manufacturing a core suitable for an electromagnetic device is provided. The core may be suitable for an electromagnetic device such as a transformer, electric motor, generator, and inductor. The method comprises the step of forming three sets of strips from one or more electric steel sheets by, for example, cutting, stamping, or punching. Each set of strips comprises a plurality of strips, and one or more electric steel sheets comprise an insulating surface layer. The method comprises the step of arranging each of the three sets of strips into a stack and bending each stack into an arc-shaped rim. Each rim has a first end and a second end. The method comprises the step of arranging each rim around a central axis, interconnecting the first end of the rim at a first position along the central axis, and interconnecting the second end of the rim at a second position along the central axis.

[0020] As discussed above, for example, if electric steel strips are bent rather than cut flat arc-shaped strips, the amount of waste material is reduced when forming rims.

[0021] This method may include, for each rim, between the step of bending each stack into an arc-shaped rim and the step of interconnecting the second ends of the rim at a second position along the central axis: the step of applying a primary winding around the rim, and the step of applying a secondary winding around the rim. The step of applying the winding around the rim may include winding a wire around the rim to form a winding. Alternatively, the step of applying the winding around the rim may include spinning the wire onto a bobbin and inserting the rim into the bobbin. By winding the rims before joining them together, the winding process is simplified because the rims have open ends.

[0022] Each rim may include a first group of strips, a second group of strips, and a third group of strips, wherein the first group of strips is positioned between the second group of strips and the third group of strips. The first group of strips may have a first thickness, the second group of strips may have a second thickness, and the third group of strips may have a third thickness, and the first thickness may be greater than both the second thickness and the third thickness. The second thickness may be equal to the third thickness.

[0023] A first group of strips may consist of a first predetermined number of strips, a second group of strips may consist of a second predetermined number of strips, and a third group of strips may consist of a third predetermined number of strips, and the first predetermined number of strips may be greater than both the second predetermined number of strips and the third predetermined number of strips. The second predetermined number of strips may be the same as the third predetermined number of strips.

[0024] A strip of the first group may have a first width, a strip of the second group may have a second width, and a strip of the third group may have a third width, and the first width may be larger than both the second width and the third width. The second width may be the same as the third width.

[0025] The method comprises, between the step of bending each stack into an arc-shaped rim and the step of interconnecting the first ends of the rim at a first position along the central axis, for each rim: the step of machining the first end to form a first edge for aligning with the central axis at the first position, wherein the first edge has an inclusive angle of 120 degrees; and the step of machining the second end to form a second edge for aligning with the central axis at the second position, wherein the second edge has an inclusive angle of 120 degrees. Machining may include grinding, milling, sanding, and / or cutting. Cutting may be performed by a water jet or a laser. The inclusive angle is the angle between the outer sides of the ends. Machining of the rim ends enables a precise fit to the rim to minimize potential air gaps in the connection at the first and second positions.

[0026] The step of arranging each rim around the central axis may include arranging each rim at equal intervals around the central axis.

[0027] The insulating surface layer may include a curable varnish, and the method may include a step of curing the varnish within each rim before the step of arranging each rim around a central axis.

[0028] The step of interconnecting the first end of the rim and the step of interconnecting the second end of the rim may involve using an adhesive. The adhesive may be a metal-to-metal structural adhesive. Examples of suitable metal-to-metal adhesives include epoxy adhesives such as 3M EC-2216 B / A or Henkel MasterBond 11 HT; paste adhesives such as 3M EC-9323 B / A; or structural adhesive films such as 3M AF31 or LOCTITE EA 9673 AERO. The step of interconnecting the first end of the rim and the step of interconnecting the second end of the rim may involve clamping the rims together without an adhesive.

[0029] This method may include a step of annealing each rim, for example, to improve the magnetic properties of the rim and relieve internal mechanical stress of the rim, prior to the step of arranging each rim around a central axis. Brief explanation of the drawing

[0030] Further details, aspects, and embodiments of the present invention will be described merely by way of example with reference to the drawings. Elements in the drawings are illustrated for simplicity and are not necessarily drawn to scale. For ease of understanding, similar reference numbers are included in each drawing. Figure 1 is a schematic diagram of a conventional three-phase magnetic core. Figure 2a is a schematic diagram of a magnetic core. Figure 2b is a schematic exploded view of the magnetic core of Figure 2a. Figure 2c is a schematic plan view of the magnetic core of Figure 2a. Fig. 2d is a schematic front view of the magnetic core of Fig. 2a. Figure 2e is a table showing the number of stacked layers of the rim of the magnetic core of Figure 2a. Figure 3 is a schematic diagram of a magnetic core. Figure 4 is a flowchart of the core manufacturing process of a magnetic core. Figure 5 is a schematic plan view of a net for strips to be cut. Specific details for implementing the invention

[0031] Referring to FIGS. 2a through 2d, the magnetic core (200) comprises three arc-shaped rims (202) that are uniformly spaced around a central axis (204). Each rim (202) is substantially identical. The arc-shaped rim (202) is a 180-degree arc. Each rim has a first end (206) and a second end (208). Each first end (206) has a first edge (210) that lies along the central axis (204). Each second end (206) has a second edge (212) that lies along the central axis (204). The first ends (206) are joined together, and the second ends (208) are joined together. One or more of a primary winding, a secondary winding, and a modulation winding (not shown) may be wound on each rim (202).

[0032] Each rim (202) comprises a plurality of electric steel strips that are bent and laminated together. The use of thin steel laminates reduces power loss caused by eddy currents that occur when a sinusoidal voltage is applied to the winding. The cross-section of each rim is close to a circle by changing the strip width of the rim. The electric steel strips of each rim (202) are grouped into 15 strip sets, including a central strip set (220) and strip sets (222, 224, 226, 228, 230, 232, 234, 236, 238, 240, 242, 244).

[0033] The strip sets on both sides of the central strip form a pair, and each strip set in the pair has substantially the same width and thickness. Strip set (222) forms a pair with strip set (224) and is placed on both sides of the central strip set (220). Strip set (226) forms a pair with strip set (228), strip set (226) is placed adjacent to strip set (222) and strip set (228) is placed adjacent to strip set (224). Strip set (230) forms a pair with strip set (232), strip set (230) is placed adjacent to strip set (226) and strip set (232) is placed adjacent to strip set (228). A strip set (234) is paired with a strip set (236), and the strip set (234) is positioned adjacent to a strip set (230), and the strip set (236) is positioned adjacent to a strip set (232). A strip set (238) is paired with a strip set (240), and the strip set (238) is positioned adjacent to a strip set (234), and the strip set (240) is positioned adjacent to a strip set (236). A strip set (242) is paired with a strip set (244), and the strip set (242) is positioned adjacent to a strip set (244), and the strip set (238) is positioned adjacent to a strip set (240).

[0034] The width of the strip set (222, 224) is smaller than the width of the central strip set (220). The width of the strip set (226, 228) is smaller than the width of the strip set (222, 224). The width of the strip set (230, 232) is smaller than the width of the strip set (226, 228). The width of the strip set (234, 236) is smaller than the width of the strip set (230, 232). The width of the strip set (238, 240) is smaller than the width of the strip set (234, 236). The width of the strip set (242, 244) is smaller than the width of the strip set (238, 240).

[0035] Referring to FIG. 2e, the thickness of each strip set is affected by the number of strips in each strip set, i.e., the number of laminates of electric steel. Each laminate may have a thickness of 0.2 mm to 0.5 mm. In the core (200), the number of strips in strip sets (222, 224) is less than the number of strips in the central strip set (220). The number of strips in strip sets (226, 228) is less than the number of strips in strip sets (222, 224). The number of strips in strip sets (230, 232) is less than the number of strips in strip sets (226, 228). The number of strips in strip sets (234, 236) is less than the number of strips in strip sets (230, 232). The number of strips in strip sets (238, 240) is less than the number of strips in strip sets (234, 236). The number of strips in strip set (242, 244) is the same as the number of strips in strip set (238, 240). In another example, the number of strips in strip set (242, 244) may be less than the number of strips in strip set (238, 240).

[0036] It should be understood that the grouping of strip sets used in the core (200) is an example of approximating a circular cross-section, and that many variations are possible. For example, each strip or laminate on both sides of the central strip may have a progressively smaller width relative to the central strip. Or there may be different numbers of strip sets. The number of strip sets may be odd to enable symmetry of the thickness and width of the strip sets around the central strip set.

[0037] FIG. 3 illustrates a core (250) that is substantially identical in composition to the core (200), having, for example, three arc-shaped rims (252) that are uniformly spaced around a central axis. The core (250) differs from the core (200) in that the width of all electric steel strips in the rims (252) is the same. Thus, the cross-section of each rim is not nearly circular but rectangular.

[0038] In an alternative configuration, the magnetic core has substantially the same overall geometry as the magnetic core (200), but the arc rim is formed from a plurality of flat arc strips rather than a bent strip that may be cut, for example, from an electric steel sheet. In other words, the orientation of the strips is perpendicular to the orientation of the strips of the magnetic core (200).

[0039] FIG. 4 illustrates a process (300) for manufacturing a core such as a core (200). In step 302, a set of electric steel strips is formed, and one set of strips is for the rim of the core. The strips may be formed, for example, by punching, stamping, or laser cutting the width and length of each strip from an electric steel sheet. The electric steel may be, for example, Thyseen-Krupp powercore® C or powercore® H.

[0040] FIG. 5 illustrates an exemplary set of templates (500) for cutting a plurality of strips (502) from electric steel sheets (504a, 504b, 504n).

[0041] Alternatively, the length of the strip may be cut from a roll of electric steel having the same width as the strip. As discussed in relation to the core (200), the strips in each set of electric steel strips may have the same width, or the width of the strip may be changed to approximate, for example, the circular cross-section of the rim.

[0042] In step 306, each set of strips is placed in a stack. In step 310, each stack is bent into an arc rim, for example, using a jig. The stack is bent by applying an external load in a direction perpendicular to the plane formed by the length and width of the strips.

[0043] The electric steel strip may include a surface coating of an electrically insulating material. The surface coating may be cured, such as a varnish or paint. The curable surface coating within the strip stack may be cured in step 314. For example, the curable surface coating may be cured by heating the stack in an autoclave. The electrically insulating surface coating may be formed during the annealing of the electric steel strip. For example, the electric steel strip may undergo annealing in a roller furnace under an air atmosphere at a maximum temperature of 860°C for an immersion time of 1 to 2 minutes. Due to the air atmosphere, the cut edges of the electric steel strip are oxidized, creating an insulating coating. A coating thickness of 2 to 5 micrometers provides good electrical resistance and a high stacking factor.

[0044] Each rim has a first end and a second end. In step 318, the ends of the rims may be machined to create angled ends that allow the rims to mesh tightly with each other. For example, if there are three rims in the core being manufactured, the ends are machined at a 120-degree angle. The machining may include one or more of sanding, grinding, milling, and cutting such as waterjet cutting or laser cutting. Alternatively or additionally to step 318, a strip may be formed with an angled end in step 302. In some examples, the ends of the rims may be machined to create a lap joint that allows the rims to mesh tightly with each other.

[0045] In step 322, the rim may be annealed. If a curable surface coating is heat-cured in step 314, the annealing in step 322 may be included in step 314. In some examples, the core may be annealed after the rim is bonded in step 334. The annealing may be magnetic annealing to improve the magnetic properties of the rim. Additionally or alternatively, the annealing may be stress-relieving annealing to relieve internal mechanical stress of the rim caused by bending, for example, in step 310. For example, the annealing may include immersing in a box furnace with a protective atmosphere of preferably 100% nitrogen at 820°C to 850°C for 2 hours, and then cooling in the furnace to about 200°C to 300°C.

[0046] In step 326, one or more of the primary winding, secondary winding, and modulation winding may be applied to each rim. Applying the winding to the rim may be performed at any point before both ends of each rim are connected together in step 338, i.e., when there is at least one open end. Applying the winding around the rim may involve winding a wire around the rim to form the winding. Alternatively, applying the winding around the rim may involve spinning the wire onto a bobbin and inserting the rim into the bobbin. The winding process is simplified by winding the rim before joining the rims together. The winding may be distributed on the rim with or without spacers.

[0047] In step 330, the rim is positioned around a central axis. For example, the rim may be secured in place using clamps and / or jigs. In step 334, the first ends of the rim are joined together. In step 338, the second ends of the rim are joined together. Joining the ends of the rim together in steps 334 and 338 may involve using an adhesive, such as metal-to-metal structural adhesive. In addition to or alternative to joining using an adhesive, joining the ends of the rim together in steps 334 and 338 may involve clamping the rim together. Steps 334 and 338 may also be performed simultaneously.

[0048] Although the present invention has been described in relation to some embodiments, it is not intended to be limited to the specific forms described herein. Rather, the scope of the invention is limited only by the appended claims. Furthermore, while it may appear that features are described in relation to specific embodiments, a person skilled in the art will understand that various features of the described embodiments may be combined according to the present invention. In the claims, the terms “comprising” or “comprising” do not exclude the presence of other elements.

Claims

Claim 1 A magnetic core (200) suitable for an electromagnetic device, wherein the core comprises three arc-shaped rims (202), the rims are arranged around a central axis (204), each rim has a first end (206) and a second end (208), the first end of the rims are interconnected at a first position along the central axis, the second end of the rims are interconnected at a second position along the central axis, and each rim comprises a plurality of bent electric steel strips (222, 224, 226, 228, 230, 232, 234, 236, 238, 240, 242, 244) in the core: each of the plurality of bent electric steel strips is directional electric steel having a grain orientation maintained along the rim, and each of the plurality of bent electric steel strips comprises a first group of strips, a second group of strips, and a third group of strips, wherein the first group of strips is the second group of strips and A magnetic core disposed between a third group of strips; a first group of strips having a first thickness, a second group of strips having a second thickness, a third group of strips having a third thickness, the first thickness being greater than both the second thickness and the third thickness; a first group of strips having a first width, a second group of strips having a second width, a third group of strips having a third width, the first width being greater than both the second width and the third width. Claim 2 In paragraph 1, the rim is a magnetic core arranged at equal intervals around a central axis. Claim 3 A magnetic core, wherein, in paragraph 1 or 2, the second thickness is the same as the third thickness. Claim 4 In paragraph 1 or 2, the second width is the same as the third width, magnetic core. Claim 5 A magnetic core according to claim 1 or 2, wherein each rim is configured to accommodate each primary winding and each secondary winding. Claim 6 An electromagnetic device comprising: a magnetic core of claim 1 or 2; a primary winding disposed around each rim; and a secondary winding disposed around each rim. Claim 7 A method (300) for manufacturing a magnetic core suitable for an electromagnetic device, comprising the step (302) of forming three strip sets from one or more electric steel sheets, wherein each strip set comprises a plurality of strips and one or more electric steel sheets comprise an insulating surface layer; the step (306) of arranging each of the three strip sets into a stack; and the step (310) of bending each stack into an arc-shaped rim, wherein each rim has a first end and a second end; each of the plurality of bent electric steel strips is directional electric steel having a grain orientation maintained along the rim, and each rim comprises a first group of strips, a second group of strips, and a third group of strips, wherein the first group of strips is disposed between the second group of strips and the third group of strips; wherein the first group of strips has a first thickness, the second group of strips has a second thickness, and the third group of strips has a third thickness, and the first thickness is greater than both the second thickness and the third thickness; A method for manufacturing a magnetic core suitable for an electromagnetic device, comprising: a step in which a first group of strips has a first width, a second group of strips has a second width, a third group of strips has a third width, and the first width is greater than both the second width and the third width; a step of arranging each rim around a central axis (330); a step of interconnecting first ends of the rims at a first position along the central axis (334); and a step of interconnecting second ends of the rims at a second position along the central axis (338). Claim 8 A method for manufacturing a magnetic core suitable for an electromagnetic device, comprising, in the step of bending each stack into an arc-shaped rim and, between the step of interconnecting the second ends of the rim at a second position along a central axis, for each rim: the step of applying a primary winding around the rim; and the step of applying a secondary winding around the rim. Claim 9 A method for manufacturing a magnetic core suitable for an electromagnetic device, wherein, in claim 7 or 8, the second thickness is the same as the third thickness. Claim 10 A method for manufacturing a magnetic core suitable for an electromagnetic device, wherein, in claim 7 or 8, the second width is the same as the third width. Claim 11 A method for manufacturing a magnetic core suitable for an electromagnetic device, wherein, in accordance with claim 7 or 8, between the step of bending each stack into an arc-shaped rim and the step of interconnecting the first ends of the rim at a first position along a central axis, for each rim: the step of processing the first end to form a first edge for aligning with the central axis at the first position, wherein the first edge has an covering angle of 120 degrees; and the step of processing the second end to form a second edge for aligning with the central axis at the second position, wherein the second edge has an covering angle of 120 degrees. Claim 12 A method for manufacturing a magnetic core suitable for an electromagnetic device, wherein, in claim 7 or 8, the step of arranging each rim around a central axis comprises arranging the rims at equal intervals around a central axis. Claim 13 A method for manufacturing a magnetic core suitable for an electromagnetic device, wherein, in claim 7 or 8, the insulating surface layer comprises a curable varnish, and the method comprises the step of curing the varnish within each rim prior to the step of arranging each rim around a central axis. Claim 14 A method for manufacturing a magnetic core suitable for an electromagnetic device, wherein, in claim 7 or 8, the step of interconnecting the first end of the rim and the step of interconnecting the second end of the rim include using an adhesive. Claim 15 A method for manufacturing a magnetic core suitable for an electromagnetic device, comprising, in claim 7 or 8, a step of annealing each rim prior to the step of arranging each rim around a central axis. Claim 16 delete Claim 17 delete Claim 18 delete Claim 19 delete Claim 20 delete Claim 21 delete

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