Flat conductor

Abstract

The present invention proposes a structural design for a flat conductor that enhances electrical stability, thereby reducing the risk of fire, and that is applicable to battery packs of electric vehicles (EVs) and energy storage systems (ESSs). The flat conductor design according to the present invention enables efficient arrangement of components even in confined spaces, and improves current efficiency when used in motor windings. In this case, in order to improve electrical characteristics, the flat conductor is designed to minimize voids within a cross section for a given width and thickness, thereby maximizing a space factor, which is defined as a ratio of the net cross-sectional area of the conductor to the gross cross-section area. Additionally, the radius of curvature of corners of the flat conductor is optimized to prevent damage to mica tape during an insulation process and to maintain a uniform insulation thickness during extrusion of an insulating coating.

Description

flat conductor

[0001] The present invention relates to a flat conductor, and more specifically, to a flat conductor that not only ensures electrical stability and prevents fire through structural design but also enables the efficient installation of components in confined spaces when applied to electric vehicles (EVs) and energy storage systems (ESS). Furthermore, the flat conductor of the present invention is expected to improve current efficiency when applied for motor windings.

[0002] Conventional flat conductor structures can be broadly classified into rectangular and round types. The rectangular type has a square shape with right-angled corners. However, one of the disadvantages of this shape is that when current is applied, a current bottleneck occurs at each corner, hindering the smooth flow of current. This leads to increased heat generation in the flat conductor, which becomes a factor that increases the risk of fire in the long term.

[0003] In addition, when using mica taping to prevent flame generation, there is a high risk that the tape will be easily damaged at right-angled corners. Furthermore, since the corners become distinctly visible during the process of extruding the insulation coating, the insulation layer becomes thin in these areas, increasing the likelihood of insulation breakdown, which can lead to electrical leakage and consequently increase the risk of fire.

[0004] On the other hand, while the round type, with its rounded corners, can resolve corner-related issues to some extent, it has other disadvantages. In the round type, empty spaces are created at the rounded corners, resulting in a reduction in the actual cross-sectional area compared to the rectangular type based on the same thickness and width. A decrease in cross-sectional area reduces the path for current to pass through, leading to increased electrical resistance. Higher electrical resistance lowers current transfer efficiency, and to compensate for this, the width and thickness of the flat conductor must be increased. However, this leads to a decrease in integration efficiency in situations where components must be placed in a compact space.

[0005] The present invention aims to improve electrical and space efficiency by designing each corner of a rigid flat conductor to be an optimal round type (edge ​​round type) to solve the problems mentioned in the prior art, thereby maximizing the actual cross-sectional area relative to the space (thickness × width) occupied by the flat conductor and minimizing empty space.

[0006] In addition, the purpose is to provide a flat conductor structure that ensures electrical stability by preventing heat generation at the corners when current is applied, and enables extrusion with a uniform thickness when insulating.

[0007] A flat conductor according to one embodiment of the present invention has a curved shape formed by giving curvature to four corners of a rectangular shape in a cross-sectional shape perpendicular to the longitudinal direction, where the width (W) is longer than the thickness (T), the width (W) is 2 to 10 times the thickness (T) (W = T × (2 to 10)), and the radius of curvature (R) is 0.125 to 0.25 of the thickness (T) (T × 0.125 < R < T × 0.25).

[0008] The radius of curvature (R) is 0.14 to 0.24 of the thickness (T) (T × 0.14 < R < T × 0.24).

[0009] The radius of curvature (R) is most preferably 0.19 of the thickness (T) (R = T × 0.19).

[0010] An insulating layer formed with a uniform thickness on the outside of the flat conductor may be additionally included.

[0011] A curved shape is formed by creating a sector arc of radius R from the center of a point located inside the rectangular shape at a constant distance from each corner of the rectangular shape; in this case, the center of the arc is a point inside the rectangle moved R in the width direction and R in the thickness direction from each corner.

[0012] The above flat conductor has a packing density of 90% or more.

[0013] The above flat conductor can be used in an electric vehicle battery pack or a power line of a vehicle, in which case the width (W) is 2 to 50 mm and the thickness (T) is 1 to 20 mm.

[0014] The above flat conductor can be used in a battery pack of an energy storage system, in which case the width (W) is 2 to 50 mm and the thickness (T) is 1 to 20 mm.

[0015] The above flat conductor can be used for winding electric vehicle motors, in which case the width (W) is 2 to 50 mm and the thickness (T) is 1 to 20 mm.

[0016] The material of the above flat conductor is preferably copper or aluminum.

[0017] The flat conductor structure according to the present invention has the characteristic of preventing heat generation at each corner when current is applied, thereby preventing the occurrence of fire.

[0018] In addition, by designing the cross-sectional corners of the flat conductor into an edge-round type structure with an optimal radius of curvature (R) value, tape damage can be prevented during mica taping, and a uniform insulation thickness can be maintained even during insulation coating extrusion, thereby preventing fire caused by leakage current due to insulation breakdown.

[0019] In addition, the flat conductor structure according to the present invention minimizes space loss due to the corner R value relative to the space occupied by the product of the thickness and width of the flat conductor, thereby securing an actual conductor cross-sectional area occupancy ratio of 90% or more. This provides the advantage of increasing integration efficiency in a compact space when mounting automotive components. By designing the R value to be small, the cross-sectional area of ​​the flat conductor can be reduced compared to when the corner R value is large, while maintaining the same electrical characteristics, which is advantageous for securing extra space when installed in narrow spaces such as electric vehicle (EV) and energy storage system (ESS) battery packs.

[0020] In addition, when applied for motor winding, this structure can ensure quality by maintaining a uniform insulation thickness even during enamel coating or PEEK extrusion, and has the advantage of increasing integration efficiency by minimizing empty space during winding, thereby improving electrical efficiency.

[0021] FIG. 1 illustrates a cross-sectional view perpendicular to the longitudinal direction of a flat conductor according to one embodiment of the present invention.

[0022] FIG. 2 illustrates a comparison of the cross-sectional shape of a flat conductor according to the prior art and the cross-sectional shape of a flat conductor according to an embodiment of the present invention.

[0023] FIG. 3 illustrates a design drawing for explaining a flat conductor structure according to one embodiment of the present invention.

[0024] [Correction pursuant to Rule 91, September 30, 2025] Fig. 4 illustrates the results of the electrical characteristics of flat conductors according to their structure. Fig. 5 is a graph showing the change in packing density according to the radius of curvature (R) relative to the thickness (T) of the flat conductor. Fig. 6 is a diagram showing the change in insulation thickness uniformity and quality according to the radius of curvature (R) of the flat conductor. Fig. 7 is a table showing the results of withstand voltage evaluation and heat generation test after mica taping for each flat conductor structure. Fig. 8 is a data table showing the optimal radius of curvature (R) range that satisfies both packing density and insulation characteristics of the flat conductor.

[0025] Various embodiments are now described with reference to the drawings, and throughout the drawings, similar reference numerals are used to denote similar elements. For illustrative purposes, various descriptions are provided in this specification to facilitate an understanding of the invention. However, it is evident that these embodiments can be practiced without such specific descriptions. In other examples, known structures and devices are presented in the form of block diagrams to facilitate the description of the embodiments.

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. As the present invention is susceptible to various modifications and may take various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention. Similar reference numerals have been used for similar components in the description of each drawing.

[0027] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to indicate the presence of the features, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, steps, actions, components, parts, or combinations thereof.

[0028] In this specification, a bare bus bar refers to a bus bar in which the metal conductor is exposed without being coated with an insulating material.

[0029] In this specification, the Track Round Type refers to a shape in which curvature is applied to each of the four corners of a rectangular shape to form a rounded curve.

[0030] In this specification, flat conductors have a flat shape in the width direction and include both bus bars and flat wires. Flat conductors are classified based on their cross-sectional area, and may be classified as bus bars if the cross-sectional area is 10 sq (square millimeters) or more, and as flat wires if it is 10 sq or less.

[0031] The present invention relates to a flat conductor structure applicable to electric vehicle (EV) and energy storage system (ESS) battery packs and motor windings. More specifically, it relates to a structural design technology that secures electrical stability by making each corner of the flat conductor into an optimal rounded shape (giving curvature to each corner), unlike existing structures such as rectangular flat conductors that have no curvature at each corner.

[0032] Through this, the flat conductor design according to the present invention enables efficient placement of components even in confined spaces and has the advantage of improving current efficiency when used in motor windings.

[0033] In addition, in this case, to improve electrical characteristics, it was designed to minimize the void space within the cross-section of the flat conductor at the same width and thickness, and to maximize the fill factor, which is the ratio of the conductor's actual cross-sectional area.

[0034] In addition, the radius of curvature of the flat conductor edges was optimized to prevent damage to the mica tape during the insulation process and to maintain a uniform insulation thickness during insulation coating extrusion.

[0035] FIG. 1 illustrates a cross-sectional view perpendicular to the longitudinal direction of a flat conductor according to one embodiment of the present invention.

[0036] As illustrated in FIG. 1, a flat conductor according to one embodiment of the present invention forms a curved shape by giving curvature to four corners in a rectangular shape where the width (W) is longer than the thickness (T) in a cross-sectional shape perpendicular to the length direction. For convenience, this shape is defined as an edge-round type in the present invention.

[0037] The flat conductor according to the present invention can be applied as a busbar for electric vehicle (EV) and energy storage system (ESS) battery packs, and can also be used as a flat wire for motor windings. Copper or aluminum is preferably used as the material for the flat conductor to secure electrical characteristics with a conductivity of 55% IACS or higher. Here, copper with a purity of 99.9% or higher is more preferable, and aluminum with a purity of 99.0% or higher is more suitable.

[0038] FIG. 2 illustrates a comparison of the cross-sectional shape of a flat conductor according to the prior art and the cross-sectional shape of a flat conductor according to an embodiment of the present invention.

[0039] The conventional Press Rigid Flat Conductor structure is of the rectangular type and is manufactured by processing sheet metal with a press. In addition to the press method, this rectangular structure can also be manufactured through billet extrusion, rolling, and drawing processes. Although rectangular flat conductors have the advantage of having the largest cross-sectional area and surface area based on the same width and thickness, quality defects may occur due to heat generation at the corners and uneven insulation thickness because each corner has a right-angled protruding edge.

[0040] To address this, these disadvantages can be compensated for by rounding the sharp corners. In this invention, a relationship between the optimal radius of curvature (R) according to the thickness (T) has been derived, which can maximize the cross-sectional area and surface area of ​​the flat conductor while simultaneously eliminating quality defects and reducing problems occurring at the corners, thereby improving electrical performance and insulation quality. I will now explain this part.

[0041] A flat conductor according to one embodiment of the present invention forms a curved shape by giving curvature to four corners in a rectangular shape where the width (W) is longer than the thickness (T) in a cross-sectional shape perpendicular to the longitudinal direction, and the width (W) is 2 to 10 times the thickness (T) (W = T × (2 to 10)), and the radius of curvature (R) is 0.125 to 0.25 of the thickness (T) (T × 0.125 < R < T × 0.25). Preferably, the radius of curvature (R) is 0.14 to 0.24 of the thickness (T) (T × 0.14 < R < T × 0.24). Most preferably, the radius of curvature (R) is 0.19 of the thickness (T) (R = T × 0.19).

[0042] For example, the optimal R of an edge-round type flat conductor according to one embodiment of the present invention, having a thickness of 4 mm, is 0.5 to 1.0 mm, preferably R is 0.56 to 0.96 mm, and the best mode R is 0.76 mm.

[0043] FIG. 3 illustrates a design drawing for explaining a flat conductor structure according to one embodiment of the present invention.

[0044] As illustrated in FIG. 3, when viewing a cross-section perpendicular to the longitudinal direction of a flat conductor, a curved shape is formed by creating a sector arc of radius R from the center of a point located inside the rectangular shape at a constant distance from each corner of the rectangular shape. In this case, the sector arc of radius R is formed to be in contact with the width and thickness of the rectangular shape, respectively. Therefore, the application location of the curvature, which is the center of the arc for applying the radius of curvature (R), is a point inside the rectangle that is moved R in the width direction and R in the thickness direction from each corner. At this time, the distance between the centers of the sector arc parallel to the long side of the rectangle in the width direction is the width opposite side (A), and the distance between the centers of the sector arc parallel to the short side of the rectangle in the thickness direction is the thickness opposite side (B).

[0045] Meanwhile, the flat conductor of the present invention may additionally include an insulating layer formed with a uniform thickness on the outside. The flat conductor of the present invention may be used in an electric vehicle (EV) battery pack or a power line of a vehicle, and may also be used in a battery pack of an energy storage system (ESS).

[0046] In addition, the flat conductors of the present invention include flat busbars or flat wires. Flat conductors are classified into busbars and flat wires. Busbars typically have a cross-sectional area of ​​10 mm² or more and are suitable for high-current and high-voltage applications. Designed as thick flat shapes, they can withstand high currents and have cross-sectional areas ranging from tens of mm² to hundreds of mm². They are primarily used for high-power distribution and connections between multiple circuits, enabling efficient power distribution. Additionally, they offer excellent heat dissipation and are easy to install, but they can occupy a large amount of space and be heavy, requiring caution during installation. Flat wires generally have a cross-sectional area between 1 mm² and 10 mm² and are used for small-power applications. They are designed in a thin and flexible form to save space and are suitable for transmitting low currents. They are primarily used for internal wiring of electronic devices or small-power applications, and their excellent flexibility makes them advantageous in complex wiring. However, due to their relatively low current capacity, they may not be suitable for high-power applications.

[0047] In addition, it is preferable that the flat conductor of the present invention has a packing density of 90% or more, which will be explained in more detail in the embodiments described later.

[0048] Below, the contents of the present invention will be further explained along with specific embodiments.

[0049] First, regarding the maximum R value in the structure of a flat conductor where W = T × (2 to 10), T = 4 mm, and W = 8 to 40 mm, it was confirmed that R < T × 0.25 through the results shown in Table 1 below.

[0050] [Correction pursuant to Rule 91 30.09.2025]

[0051] [Correction pursuant to Rule 91, Sept. 30, 2025] As shown in Fig. 5, in the design of flat conductors, the fill factor—which is the ratio of the actual conductor cross-sectional area to the thickness (T) within the optimal width (W) range—must be 90% or higher, and in particular, the condition R < T × 0.25 must be satisfied. For bare busbars for EV and ESS battery packs, the fill factor must exceed 90% to increase integration efficiency when installing components in the narrow space within the battery pack, which is crucial for space optimization. For flat wires used for EV motor windings, the fill factor must be 90% or higher to reduce winding resistance, thereby improving the efficiency of the electric motor. By reducing winding resistance, the motor's performance is improved. Therefore, maintaining a fill factor of 90% or higher is very important for the optimal flat conductor design that considers both electrical performance and space efficiency.

[0052] Next, regarding the minimum R value in the structure of the flat conductor, it was confirmed that T×0.125 < R through the results shown in Table 2 below.

[0053] [Correction pursuant to Rule 91 30.09.2025]

[0054] [Correction pursuant to Rule 91 30.09.2025] As shown in Fig. 6, when T×0.125 < R, the insulation thickness is uniform, so the quality of the product can be stably ensured.

[0055] Under the condition R < T × 0.125, the likelihood of uneven insulation thickness formation increases, thereby raising the risk of quality defects. In flat conductors, areas with thin and weak insulation may experience leakage current due to insulation breakdown when current is applied, potentially leading to a fire. Additionally, there is a possibility that the insulation layer may tear during bending. When T × 0.125 < R, the insulation thickness remains uniform, preventing fires caused by insulation breakdown.

[0056] When applied as flat wire for EV motor windings, excellent insulation characteristics are required in high-voltage EV systems. To this end, insulating materials such as enamel, PEEK, and polyimide may be used. In areas where the insulation or film thickness is thin, the adhesion between the conductor and the insulator weakens, potentially leading to separation and the formation of air gaps between them. These air gaps can induce partial discharge, which accelerates the degradation of the insulator; if the insulator fails, this can lead to motor damage. Therefore, uniform insulation thickness is critical.

[0057] Next, the electrical characteristics of flat conductors according to their structure were compared. An edge-round type flat conductor according to the present invention and a square type flat conductor were fabricated as comparative examples. Specimens with the same length of 100 cm (fabricated uniformly at both ends) were fabricated, and the cross-sectional area was 60 SQ. For the evaluation, an allowable current tester was used, with an applied current of 1000 A and an application time of 10 min.

[0058] Figure 4 illustrates the results of the electrical characteristics according to the structure of flat conductors. As shown in Figure 4, in the case of square-type flat conductors, the cross-sectional area of ​​the corners is small, so the current passes through a narrow space, making it highly likely that heat will be generated. This not only causes power loss but also increases the risk of fire in severe cases. Current bottlenecks at the corners cause these problems, and structural improvements to the corners are required to resolve them. In contrast, edge-round (R = T × 0.14) type flat conductors prevent current bottlenecks by smoothly mitigating the curvature of the corners. This allows current to flow more evenly and reduces heat generation. Since current is smoothly distributed at the corners, power loss is reduced and electrical stability is improved.

[0059] Next, the withstand voltage evaluation and electrical resistance measurements were performed after mica taping according to the structure of the flat conductor. The withstand voltage evaluation (2.6 kV x 1 min) was conducted after mica taping No. 1 on the flat conductor. A mica taping machine was used for the mica taping, and the mica tape consists of multiple layers, specifically resin / glass cloth / uncalcined phlogopite mica paper / glass cloth. Table 3 below summarizes the measurement results. As shown in Table 3, when mica taping was applied to a conventional square-type flat conductor, the tape tore due to high pressure on the sharp edges, resulting in a withstand voltage failure. Additionally, in the case of an edge-round type flat conductor, under the condition R < T × 0.125, the tape tore during bending due to high pressure on the sharp edges, resulting in a withstand voltage failure.

[0060] [Correction pursuant to Rule 91 30.09.2025]

[0061] Next, Table 4 below shows data on the optimal radius of curvature (R) values ​​for securing spatial and electrical characteristics.

[0062] [Correction pursuant to Rule 91 30.09.2025]

[0063] [Correction pursuant to Rule 91 30.09.2025] Through Fig. 8, it was confirmed that the radius of curvature (R) is T×0.125 < R < T×0.25, preferably T×0.14 < R < T×0.24, and the best mode is R = T×0.19. In the range T×0.125 < R, a uniform insulation thickness can be secured and the desired electrical characteristics are satisfied. When R < T×0.25, the packing factor exceeds 90%, satisfying the requirements. When the packing factor is 90% or higher, the integration effect is excellent when installing components in narrow internal spaces when applied to a battery pack. In addition, when applied to an EV motor, the winding resistance is reduced, resulting in a superior improvement in electrical efficiency. Therefore, it was confirmed that the R value plays an important role not only in the uniformity of insulation thickness and electrical characteristics but also in the performance optimization of battery packs and EV motors.

[0064] Based on the above explanation, the numerical values ​​for the actual design of the flat conductor of the present invention are as follows.

[0065] First, regarding the thickness and width range, when using an edge-round type bare busbar for EV and ESS battery pack applications with flat conductors, a width (W) of 2mm to 50mm is suitable. If the width is less than 2mm, the heat dissipation effect in the EV's high-voltage system is insufficient, and when current is applied, the temperature rises, increasing electrical resistance and potentially leading to greater electrical losses. On the other hand, if the width exceeds 50mm, the space inside the battery pack becomes cramped, making it difficult to install the busbar.

[0066] Next, for flat conductors used in EV and ESS battery packs and motor windings using edge-round type flat wires, the thickness (T) is preferably 1 mm to 20 mm. If the thickness is less than 1 mm, the risk of damage increases when bolting to secure the busbar, and the fastening force weakens, which may cause the fixation to come loose. When used for motor windings, the number of windings increases, leading to reduced productivity. Additionally, if the thickness exceeds 20 mm, the heat dissipation effect is insufficient, and electrical resistance increases due to the temperature rise when current is applied, which may result in electrical loss.

[0067] Next, regarding the optimal ratio of width to thickness, the optimal ratio of width (W) to thickness (T) for improving the productivity and quality of edge-round type flat conductors is W = T x (2 to 10). If the width is less than twice the thickness, stability may be compromised during mounting, and if the width exceeds 10 times the thickness, the likelihood of warping and deformation occurring during the manufacturing process increases. This can reduce production speed and lead to quality defects. Therefore, optimal productivity and quality can be maintained when the width of the edge-round type flat conductor is between 2 and 10 times the thickness.

[0068] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as set forth in the following claims.

Claims

1. As a flat conductor, In a cross-sectional shape perpendicular to the length direction, a rectangular shape with a width (W) longer than the thickness (T) is formed into a curved shape by giving curvature to the four corners, and The width (W) is 2 to 10 times the thickness (T) (W = T × (2 ~ 10)), and The radius of curvature (R) is 0.125 to 0.25 of the thickness (T) (T × 0.125 < R < T × 0.25), Flat conductor.

2. In Paragraph 1, The radius of curvature (R) is 0.14 to 0.24 of the thickness (T) (T × 0.14 < R < T × 0.24), Flat conductor.

3. In Paragraph 1, The radius of curvature (R) is 0.19 of the thickness (T) (R = T × 0.19), Flat conductor.

4. In Paragraph 1, A further comprising an insulating layer formed with a uniform thickness on the outside of the flat conductor, Flat conductor.

5. In Paragraph 1, A curved shape is formed by creating an arc of a sector with radius R from the center of a point located inside the rectangular shape at a constant distance from each corner of the rectangular shape, and In this case, the center of the arc is a point inside the rectangle, which is moved R in the width direction and R in the thickness direction from each corner, Flat conductor.

6. In Paragraph 1, The above flat conductor has a fill factor of 90% or more, Flat conductor.

7. In Paragraph 1, The above flat conductor can be used in an electric vehicle battery pack or a vehicle's power line, and In this case, the width (W) is 2 to 50 mm and the thickness (T) is 1 to 20 mm, Flat conductor.

8. In Paragraph 1, The above flat conductor can be used in a battery pack of an energy storage system, and In this case, the width (W) is 2 to 50 mm and the thickness (T) is 1 to 20 mm, Flat conductor.

9. In Paragraph 1, The above flat conductor can be used for electric vehicle motor windings, and In this case, the width (W) is 2 to 50 mm and the thickness (T) is 1 to 20 mm, Flat conductor.

10. In Paragraph 1, The material of the above flat conductor is copper or aluminum, Flat conductor.

Images