Rectangular shaped stranded wire

Abstract

A rectangular shaped stranded wire (10) according to the present invention has a plurality of strands (11) and is twisted in one direction. The plurality of strands (10) each include a conductor (12) and an insulating film (12) that covers the conductor (12). In any cross-section perpendicular to the longitudinal direction of the rectangular shaped stranded wire (10), a portion of the insulating film (13) of each of the plurality of strands (10) is positioned on the outer periphery of the rectangular shaped stranded wire (10).

Description

Flat shaped stranded wire

[0001] The present invention relates to a rectangular molded stranded wire.

[0002] Traditionally, enameled wire with a circular cross section has been used for windings in motors and coils. However, in recent years, enameled wire with a rectangular cross section has become increasingly popular in order to increase the space factor. When comparing enameled wires of the same thickness, enameled wire with a rectangular cross section has a larger cross-sectional area than enameled wire with a circular cross section. Therefore, a coil using enameled wire with a rectangular cross section also has a larger cross-sectional area than a coil using enameled wire with a circular cross section. It is thought that an increase in the cross-sectional area of ​​enameled wire increases eddy current loss due to magnetic flux linkage with the conductor. To address this issue, a conductor with a rectangular cross section is known that maintains a high space factor while suppressing eddy current loss by dividing the enameled wire (see, for example, Patent Document 1).

[0003] Patent Document 1 describes a stranded wire having multiple strands each coated with a first insulating layer, and a conductor having a second insulating layer coating the stranded wire. The conductor described in Patent Document 1 is made by twisting multiple strands together and then compressing and molding them so that the cross section has a predetermined shape. The compressed stranded wire is then coated with a second insulating layer to obtain the conductor. The multiple strands in the conductor described in Patent Document 1 include a first strand positioned on the inside and a second strand positioned on the outside. The cross-sectional shapes of the first strand and the second strand are polygonal, such as pentagonal or hexagonal.

[0004] JP 2009-199749 A

[0005] However, in the conductor described in Patent Document 1, the inner first wire is surrounded by the outer second wire in any cross section, which may reduce the heat dissipation of the first wire.

[0006] An object of the present invention is to provide a rectangular molded stranded wire having excellent heat dissipation properties.

[0007] In order to solve the above problems, according to one aspect of the present invention, a flat molded stranded wire can be provided, which has a plurality of strands twisted in one direction, wherein each of the plurality of strands includes a conductor and an insulating coating covering the conductor, and in any cross section perpendicular to the longitudinal direction of the flat molded stranded wire, a portion of the insulating coating is located on the outer periphery of the flat molded stranded wire for all of the plurality of strands.

[0008] According to the present invention, a rectangular molded stranded wire having excellent heat dissipation properties can be provided.

[0009] 1A to 1C are schematic cross-sectional views of a rectangular molded stranded wire. Fig. 2 is a flowchart showing a method for manufacturing a rectangular molded stranded wire. Fig. 3 is a schematic diagram showing the configuration of a manufacturing apparatus.

[0010] The following describes a rectangular molded stranded wire according to one embodiment of the present invention. The rectangular molded stranded wire is a winding wire that can be used for coils in electromagnetic circuits, various motors, reactors, etc. In this specification, when a numerical range is indicated by "to", the lower limit and upper limit are included in the numerical range.

[0011] (Structure of a rectangular molded stranded wire) Figure 1A is a schematic cross-sectional view of a rectangular molded stranded wire 10 according to the present embodiment, Figure 1B is a schematic cross-sectional view of another rectangular molded stranded wire 10 according to the present embodiment, and Figure 1C is a schematic cross-sectional view of a rectangular molded stranded wire according to a comparative example. In this specification, the "transverse cross-section of a rectangular molded stranded wire 10" refers to a cross-section perpendicular to the longitudinal direction of the rectangular molded stranded wire 10.

[0012] As shown in Figures 1A and 1B, the rectangular molded stranded wire 10 includes multiple strands 11, each of which is composed of a conductor 12 coated with an insulating layer 13 and a bonding layer 14. The multiple strands 11 are twisted in one direction. This allows the cross sections of the multiple strands 11 to be integrated and prevents the strands from becoming untwisted. The rectangular molded stranded wire 10 is also known as a rectangular litz wire, rectangular split winding wire, bunched strand, bunched conductor, or bunched conductor. The rectangular molded stranded wire 10 is defined as a stranded wire in which, when the periphery of a portion of any cross section is enclosed by multiple straight lines, the closed figure forms a rectangle. For example, the rectangular molded stranded wire 10 can be formed by compressing a strand of multiple conductors 12 in the vertical direction with a flat roller and then compressing it in the horizontal direction with a similar roller. Furthermore, considering the longitudinal position of the wire 11, for example, if the position of the cross section is shifted along the longitudinal direction of the rectangular molded stranded wire 10, the wire 11 located at the top left end in Fig. 1A will gradually shift to the right in the upper row and reach the top right end (see Fig. 1B). Next, this wire 11 will pass through the middle right end in Fig. 1B and reach the bottom right end in Fig. 1A. Next, this wire 11 will gradually shift to the left in the lower row and reach the bottom left end (see Fig. 1A). Next, this wire 11 will pass through the middle left end in Fig. 1B and reach the top left end in Fig. 1A.

[0013] Here, the number n of wires 11 is preferably within the range of 4 to 14. If the number of wires 11 is three or less, the cross-sectional area of ​​each wire 11 becomes large, which may increase eddy current loss in the conductor due to interlinkage magnetic flux. On the other hand, if the number of wires 11 is 15 or more, the inner and outer layers of the conductor may have different elongation rates during bending, which may reduce bending workability. Furthermore, the number n of wires 11 is preferably an even number. By using an even number of wires 11, the arrangement of the multiple wires 11 in the cross section of the rectangular molded stranded wire 10 can be approximately point-symmetric (symmetric in the width direction and the thickness direction). If the number n of wires 11 is odd, the wire arrangement may be disrupted (the wires are discontinuously rearranged when twisted), resulting in uneven deformation of each wire 11 and unstable structure and characteristics. In the example shown in FIGS. 1A and 1B, the number of wires 11 is 10, but in the examples described later, an example in which the number is 14 is mainly shown.

[0014] The twist pitch of the rectangular molded stranded wire 10 is preferably within a range of 16 to 35 times the outer diameter R (mm) of a circle equivalent to the cross-sectional area of ​​the thickness x width outer dimensions of a cross section (transverse cross section) perpendicular to the longitudinal direction of the rectangular molded stranded wire 10. If the twist pitch of the rectangular molded stranded wire 10 is less than 16 times the outer diameter R of the equivalent circle, the twist will be too tight, and there is a risk of wire breakage during production of the rectangular molded stranded wire 10. On the other hand, if the twist pitch of the rectangular molded stranded wire 10 is more than 35 times the outer diameter R of the equivalent circle, there is a risk of some of the wires 11 separating from the other wires 11, causing the shape of the rectangular molded stranded wire 10 to collapse.

[0015] In any cross-section of the rectangular molded stranded wire 10, a portion of the insulating layer 13 (strand 11) of each of the plurality of strands 11 is located on the outer periphery of the rectangular molded stranded wire 10. That is, all strands 11 are arranged so that a portion of each strand is exposed on the outer periphery of the rectangular molded stranded wire 10 in any cross-section. The arrangement of the plurality of strands 11 in the rectangular molded stranded wire 10 is not particularly limited as long as it satisfies the above requirements. The plurality of strands 11 have a single-layer structure consisting of only a first layer. Here, "layer" refers to a group of multiple strands within each concentric circle formed when the strands are arranged concentrically and twisted together in a stacked manner. Examples of single-layer structures of the plurality of strands 11 include the arrangements shown in Figures 1A and 1B. In any cross section of the rectangular molded stranded wire 10, the plurality of wires 11 are preferably arranged so that at least ((n-2) / 2) of the plurality of wires 11 are arranged in parallel in the width direction D perpendicular to the longitudinal direction to form a first row, and at least ((n-2) / 2) of the remaining plurality of wires 11 are arranged in parallel in the width direction D to form a second row adjacent to the first row. For example, in a cross section in a transition region where one wire 11 is transitioning from the first row to the second row and another wire 11 is transitioning from the second row to the first row, ((n-2) / 2) of the plurality of wires 11 are arranged in the first row, and the other ((n-2) / 2) of the plurality of wires 11 are arranged in the second row (see FIG. 1B). On the other hand, in the cross section of the region other than the transition region, (n / 2) of the multiple wires 11 constitute a first row, and the other (n / 2) wires 11 constitute a second row (see FIG. 1A ). In the transition region, only one wire 11 may transition from the first row to the second row, or from the second row to the first row. The number of wires 11 in the transition region may be multiple. The arrangement of the single-layered wires 11 is preferably a two-row arrangement in the cross section perpendicular to the longitudinal direction, from the viewpoint of excellent heat dissipation, since the high aspect ratio results in a large specific surface area.

[0016] The two-layer structure of multiple wires 11 includes the structure shown in Fig. 1C. The example shown in Fig. 1C includes wires 11 arranged in the central portion and wires 11 arranged so as to be located on the periphery. The wires 11 arranged in the central portion are not located on the periphery but are surrounded by wires 11 arranged so as to be located on the periphery. In this case, heat generated in the wires 11 in the central portion is difficult to dissipate, and the heat dissipation performance of the rectangular molded stranded wire 10 cannot be improved.

[0017] By arranging multiple wires 11 in a single layer, the wires 11 can be arranged at a high density. The space factor, defined by the following formula, is preferably 70% or more, more preferably 70% to 90%, and even more preferably 75% to 85%. A space factor of less than 70% may result in insufficient performance in coils and the like. On the other hand, a space factor of more than 85% may result in wire breakage. The rectangular molded stranded wire 10 of this embodiment can increase the amount of current flowing through the rectangular molded stranded wire 10 as the space factor increases, thereby contributing to the improvement of the efficiency and miniaturization of electromagnetic circuits, motors, and reactors. The space factor can be measured at any cross-section of the rectangular molded stranded wire 10. The cross-sectional area of ​​the rectangular molded stranded wire 10 is a polygon circumscribing the periphery of the cross-section. In other words, the cross-sectional area of ​​the rectangular molded stranded wire 10 refers to the area of ​​the wires 11 plus the gaps between the wires 11. Space factor (%) = (total cross-sectional area of ​​conductors 12) / (cross-sectional area of ​​rectangular molded stranded wire 10) × 100

[0018] As described above, each wire 11 is located on the outer periphery of the rectangular molded stranded wire 10. In other words, a portion of the wire 11 is in contact with the ambient atmosphere and is not covered with a coating such as resin. Therefore, when the rectangular molded stranded wire 10 is used in a motor or the like, the rectangular molded stranded wire 10 exhibits high heat dissipation properties. Furthermore, when the rectangular molded stranded wire 10 is bent, stress distribution in the bent portion can be made uniform.

[0019] In any cross-section of the rectangular molded stranded wire 10, the shape of each of the multiple strands 11 is preferably polygonal. Here, "polygonal" refers to a figure formed by connecting n points (corners) (n is an integer greater than or equal to 3) with n line segments. The line segments may be straight or curved. In this specification, "polygonal" also includes figures with rounded corners. The shape of the strands 11 in the cross-section may be triangular, rectangular, pentagonal, or any polygon with more than one side. In this embodiment, the shape of the strands 11 in the cross-section is rectangular or hexagonal. Furthermore, it is preferable that the longest side of the polygon of all the multiple strands 11 in the cross-section is located on the outer periphery of the rectangular molded stranded wire 10. In this way, by having the longest side of the polygon located on the outer periphery of the rectangular molded stranded wire 10, heat dissipation can be improved. In addition, when one polygon has two longest sides (when the two sides are the same length), it is sufficient that one of the two sides is located on the outer periphery of the rectangular molded stranded wire 10.

[0020] The wire 11 is a so-called enameled wire, and includes a conductor 12, an insulating layer 13 that covers the conductor 12, and a fusion layer 14 that covers the insulating layer 13. In this specification, the term "insulating coating" refers to both the insulating layer 13 and the fusion layer 14.

[0021] The conductor 12 is made of a metal with high electrical conductivity. Examples of the metal include copper, aluminum, copper alloys, and aluminum alloys. In this embodiment, the conductor 12 is a copper wire. The cross-sectional shape of the conductor 12 before twisting is not particularly limited. In this embodiment, the cross-sectional shape of the conductor 12 before twisting is circular. The outer diameter of the conductor 12 before twisting is preferably 0.1 mm or more, more preferably 0.2 mm or more, and particularly preferably 0.3 mm or more. Furthermore, the outer diameter of the conductor 12 before twisting is preferably 1.5 mm or less, more preferably 1.3 mm or less, and particularly preferably 1.1 mm or less.

[0022] The insulating layer 13 covers the conductors 12 and insulates the conductors 12 from each other. Examples of materials for the insulating layer 13 include polymers such as polyurethane, polyesterimide, polyamide, polyamideimide, and polyimide. In this embodiment, the material for the insulating layer 13 is polyamideimide. The thickness of the insulating layer 13 before twisting and after rolling is not particularly limited as long as insulation properties can be ensured. From the viewpoints of heat dissipation and space factor, the thickness of the insulating layer 13 before twisting and after rolling is preferably thin. The insulating layer 13 is formed, for example, by baking onto the outer periphery of the conductor 12.

[0023] The fusion layer 14 covers the insulating layer 13. The fusion layer 14 contains a thermoplastic polymer having a melting point and glass transition point lower than those of the insulating layer 13. Examples of thermoplastic polymers contained in the fusion layer 14 include polyethersulfone, polyvinyl butyral, polyamide, and polyester. In this embodiment, the material of the fusion layer 14 is polyamide. The thickness of the fusion layer 14 before twisting and after rolling is not particularly limited as long as it can ensure insulation. A thin fusion layer 14 before twisting and after rolling is preferable. The fusion layer 14 melts during the annealing process described below and then solidifies again, thereby functioning as an adhesive to firmly secure the multiple strands 11 together. Therefore, in the rectangular molded stranded wire 10, adjacent strands 11 are secured by the fusion layer 14, which also functions as an adhesive.

[0024] The thickness of the insulating coating is preferably within the range of 0.005 to 0.025 mm. If the thickness of the insulating coating is less than 0.05 mm, the insulating performance will be reduced when the coil is formed. If the thickness of the insulating coating is more than 0.025 mm, the heat dissipation and space factor will be reduced. From the viewpoints of heat dissipation and space factor, the thinner the insulating coating, the better.

[0025] The outer periphery of the rectangular molded stranded wire 10 may be polygonal. Here, "polygonal" refers to a figure formed by connecting n points (corners) (n is an integer of 3 or greater) with n line segments. The line segments may be straight or curved. In this specification, "polygonal" also includes figures with rounded corners. The shape of the wire 11 in the cross section may be triangular, rectangular, pentagonal, or any polygon with more sides. In this embodiment, the outer periphery of the rectangular molded stranded wire 10 has an overall rectangular or rectangular-like cross section ( FIGS. 1A and 1B ) due to the manufacturing method described below, and its aspect ratio (the ratio of the widthwise length W to the thicknesswise length T) is, for example, 1.0 or greater and 5.0 or less. If the outer periphery of the cross section is rectangular, when the rectangular molded stranded wire 10 is used as a winding for a motor or coil, the wound state is stable and a packed structure is formed, resulting in superior conductor properties compared to polygonal shapes. The thickness length T and width length W are not particularly limited, but for example, the thickness length T is preferably within the range of 0.5 to 3.0 mm, and the width length W is preferably within the range of 1.0 to 6.0 mm. Similarly, each individual strand 11 in the rectangular molded stranded wire 10 also has a polygonal or polygon-like cross-sectional shape (Figures 1A and 1B). The aspect ratio (the ratio of the width length w to the thickness length t) is, for example, within the range of 1.0 to 5.0. However, the contours of the cross-sectional shapes of the entire rectangular molded stranded wire 10 and the individual strands 11 may include only curves or multiple curves and straight lines. Here, the length T in the thickness direction is the maximum length of the cross section in a direction perpendicular to the length W in the width direction D, and the length W in the width direction is the maximum length in the arrangement direction of the wires 11 in the cross section of the rectangular molded stranded wire 10. The width direction of the rectangular molded stranded wire 10 and the width direction of the wires 11 may be the same direction or different directions. Similarly, the thickness direction of the rectangular molded stranded wire 10 and the thickness direction of the wires 11 may be the same direction or different directions. In this embodiment, the width direction of the rectangular molded stranded wire 10 and the width direction of the wires 11 are the same direction, and the thickness direction of the rectangular molded stranded wire 10 and the thickness direction of the wires 11 are the same direction.

[0026] (Method for manufacturing a rectangular molded stranded wire) Fig. 2 is a flowchart of a method for manufacturing a rectangular molded stranded wire 10. Fig. 3 is a schematic diagram showing the configuration of a manufacturing apparatus 100.

[0027] The rectangular molded stranded wire 10 can be manufactured, for example, by the following method. As shown in Figures 2 and 3, the manufacturing method of the rectangular molded stranded wire 10 includes a step of twisting the wires 11 (S110) and a step of rolling the twisted wires 11 (S120).

[0028] In the step (S110) of twisting the wires 11, a plurality of wires 11 (10 in this embodiment) are twisted. Specifically, as shown in FIG. 3 , a plurality of bobbins 110, each wound with a wire 11, are placed in the manufacturing apparatus 100. As described above, each wire 11 has a conductor 12, an insulating layer 13 covering the conductor 12, and a fusion layer 14 covering the insulating layer 13. The plurality of wires 11 drawn out from the bobbins 110 are joined together using a mandrel (not shown), and the plurality of bobbins 110 are rotated (see the dotted arrows in FIG. 3 ). This causes the plurality of wires 11 to be twisted in a fixed direction (clockwise or counterclockwise).

[0029] In the step (S120) of rolling the twisted wires 11, the twisted wires 11 are rolled in two mutually perpendicular directions to obtain the flat rectangular twisted wire 10. Specifically, as shown in FIG. 3 , tension is applied by a take-up machine 130, and the twisted wires are compressed by a rolling device 120. A known rolling device can be used as the rolling device 120. In this embodiment, the rolling device 120 has a pair of first rolling rolls 121 and a pair of second rolling rolls 122. The rotation axis of the first rolling roll 121 and the rotation axis of the second rolling roll 122 are perpendicular to each other. By passing between the pair of first rolling rolls 121 and the pair of second rolling rolls 122, the twisted wires 11 are formed into a flat rectangular shape whose cross section (transverse cross section) perpendicular to the longitudinal direction is rectangular or nearly rectangular. Although not specifically shown, the rolling device 120 may have a forming die including a die hole having a cross-sectional shape required for the rectangular formed stranded wire 10. In this case, the rolling step is performed by passing the stranded wire through the die hole. The rolling device 120 may also have a die hole and a rolling roll.

[0030] The rectangular molded stranded wire 10 is drawn out by a take-up machine 130 and wound around a take-up reel 140 .

[0031] (Effects) As described above, according to the present invention, a portion of the insulating coating is located on the outer periphery of the rectangular molded stranded wire 10 for all of the wires 11 in any cross section, so that the conductor 12 has excellent heat dissipation properties.

[0032] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited by these examples, and the embodiments can be modified without departing from the spirit of the present invention.

[0033] [Preparation of a Rectangular Molded Stranded Wire] (Example 1) The rectangular molded stranded wire of Example 1 was prepared as follows. First, a 0.3 mm diameter copper wire was coated with an insulating layer made of polyamideimide and a bonding layer made of polyethersulfone to obtain a wire. Ten of the resulting wires were placed on a bobbin in a manufacturing device. Next, the wires were twisted so that the pitch was 29 times the outer diameter (circle equivalent diameter) of the cross-sectional area of ​​the rectangular molded stranded wire, measured in a cross section perpendicular to the longitudinal direction, of the thickness x width of the outer dimensions. The wires were then rolled to obtain a rectangular molded stranded wire with seven wires arranged in the width direction and two wires arranged in the thickness direction. The space factor of the conductor in the rectangular molded stranded wire was 70% or more.

[0034] The space factor was determined by the following method. Calculation of Space Factor The thickness, width, and cross-sectional area of ​​the conductor in the cross section of the produced rectangular molded stranded wire were measured using a digital microscope (Keyence Corporation). The thickness, width, and cross-sectional area of ​​the conductor in the cross section of the rectangular molded stranded wire were averaged from three measurements. The space factor was calculated using the following formula: Space factor (%) = (total cross-sectional area of ​​conductor) / (thickness of rectangular molded stranded wire x width of rectangular molded stranded wire) x 100 The calculation results of the space factor were evaluated according to the following criteria: ◎: 75% or more ◯: 70% or more but less than 75% △: 65% or more but less than 70% ×: less than 65%

[0035] The thickness of the insulating coating was determined by the following method. Measurement of the thickness of the insulating coating: The thickness was measured on the cross section of the rectangular molded stranded wire using a digital microscope (Keyence Corporation). The thickness of the insulating coating was calculated as the average value of 20 measurements taken on one cross section.

[0036] Examples 2 to 11, Comparative Examples 1 to 7 The rectangular molded stranded wires of Examples 2 to 11 and Comparative Examples 1 to 9 were produced in the same manner as the rectangular molded stranded wire of Example 1, except that the number of strands and the pitch ratio were as shown in Tables 1 and 2. When the number of strands was four, the wires were rolled so that two were arranged in the width direction and two in the thickness direction. When the number of strands was six, the wires were rolled so that three were arranged in the width direction and two in the thickness direction. When the number of strands was eight, the wires were rolled so that four were arranged in the width direction and two in the thickness direction. When the number of strands was ten, the wires were rolled so that five were arranged in the width direction and two in the thickness direction. When the number of strands was nine, the wires were rolled so that four were arranged in the width direction, two in the thickness direction, and one in a lateral direction. As with the rectangular molded stranded wire of Example 1, the space factor of each rectangular molded stranded wire was measured using the method described above.

[0037] [Evaluation of the molded rectangular stranded wires] Each of the molded rectangular stranded wires produced was evaluated for the following items.

[0038] Workability was evaluated in accordance with "5.1.2 Rectangular wire" of JIS C 3216-3:2011. Workability was evaluated according to the following criteria: ◯: No breakage or lifting of the wire occurred. ×: Breakage or lifting of the wire occurred.

[0039] - Formability Formability was evaluated by checking whether the rectangular molded stranded wire could be manufactured without breakage. Formability was evaluated according to the following criteria. "Breakage" refers to the breakage of the constituent wires during manufacturing, "twist collapse" refers to the stranded wire not maintaining its rectangular shape after molding, and "mountain jumping" refers to the local rearrangement of the wires, which has an adverse effect on moldability and external dimensions. ◯: The wire was manufactured properly without breakage, twist collapse, or mountain jumping. ×: The wire was manufactured improperly due to breakage, twist collapse, or mountain jumping.

[0040] Eddy current loss can be calculated using the following formula. Note that the external magnetic flux penetrates the conductor in a direction perpendicular to the width direction of the cross section. Eddy current loss: P = K x (1 / ρ) x f ２ ×B ２ ×a ３ ×b×c K: proportionality constant, ρ: volume resistivity (Ω m), f: frequency (Hz), B: magnetic flux density (T), a: length in the width direction of the cross section (mm), b: length in the thickness direction of the cross section (mm), c: length of the measurement section (mm). In the above formula, a corresponds to W or w in Figure 1A, and b corresponds to T or t in Figure 1A.

[0041] The eddy current loss was evaluated under the conditions that magnetic flux penetrated in a direction perpendicular to the longitudinal direction D perpendicular to the longitudinal direction of the rectangular molded stranded wire 10, the magnetic flux density was 0.03 T, and the frequency was up to 2 kHz. The value calculated using the formula for eddy current loss P shown above for a polygon tangent to the outer periphery of the cross section of the example or comparative example was divided by the value calculated using the formula for eddy current loss P shown above for the outer dimensions of the undivided wire, and the result was expressed as a percentage (%). The eddy current loss was evaluated according to the following criteria: ◎: Eddy current loss reduced to less than 20% ○: Eddy current loss reduced to 20-99% ×: No eddy current loss reduction effect was observed

[0042] Segmented conductor structure: The cross sections of the produced rectangular molded stranded wires were observed with a digital microscope (Keyence Corporation) to confirm whether or not they had a single-layer structure as shown in Figure 1 at any cross section. The segmented conductor structure was evaluated according to the following criteria: Good: A single-layer structure as shown in Figure 1A. Bad: Two-layer or more structure as shown in Figure 1C.

[0043] Heat dissipation evaluation Heat dissipation was evaluated based on a comprehensive assessment of the insulation coating thickness, eddy current loss, and segmented conductor structure, and was rated according to the following criteria: Good: The insulation coating thickness was 0.05 to 0.025 mm, and both the eddy current loss and segmented conductor structure were good or better. Bad: The insulation coating thickness was less than 0.05 mm or more than 0.025 mm, and either the eddy current loss or the segmented conductor structure was bad.

[0044] Table 1 shows the parameters and evaluation results of each rectangular molded stranded wire.

[0045]

[0046] As shown in Table 1, the rectangular molded stranded wires of Examples 1 to 16, in which a portion of all of the insulating coatings was located on the outer periphery of the rectangular molded stranded wire, had excellent heat dissipation properties. In particular, Examples 1 to 11, in which the twist pitch ratio of the rectangular molded stranded wire was 16 to 35 times and the number of strands was an even number within the range of 4 to 14, also had good space factor, moldability, and processability.

[0047] The rectangular molded stranded wire of Example 12, in which the twist pitch ratio of the rectangular molded stranded wire was less than 16 times, suffered from wire breakage during the step (S120) of rolling the twisted stranded wires 11, resulting in poor formability. The rectangular molded stranded wire of Example 13, in which the twist pitch ratio of the rectangular molded stranded wire was more than 35 times, suffered from poor formability because some of the strands 11 separated from the other strands 11, causing the shape of the rectangular molded stranded wire 10 to collapse. The rectangular molded stranded wire of Example 14, in which the number of strands was more than 14 and the twist pitch ratio of the rectangular molded stranded wire was more than 35 times, suffered from poor formability due to different elongation rates between the inner layer and the outer layer during bending of the conductor, and also suffered from poor formability because some of the strands 11 separated from the other strands 11, causing the shape of the rectangular molded stranded wire 10 to collapse. The rectangular molded stranded wire of Example 15, in which the number of strands was less than four, suffered from poor formability because the twisted wire was difficult to form into a rectangular shape during processing. The rectangular molded stranded wire of Example 16, which had more than 14 wires, had poor processability because the elongation rates of the inner layer and outer layer were different when the conductor was bent.

[0048] On the other hand, in Comparative Example 1, which had an odd number of strands and an insulating coating thickness of more than 0.025 mm, the divided conductor structure was two or more layers, some strands had insulating coatings that were not positioned on the outer periphery of the rectangular molded stranded wire, and the insulating coating was thick, so heat dissipation was poor and the space factor was low.In Comparative Example 2, which was a single wire, eddy current loss was large, which caused induced current to flow and Joule heat to be generated, so heat dissipation was poor.

[0049] The rectangular molded stranded wire according to the present invention is useful, for example, as a winding used in an electromagnetic circuit or a motor.

[0050] REFERENCE SIGNS LIST 10 Rectangular molded stranded wire 11 Wire 12 Conductor 13 Insulating layer 14 Fusion layer 100 Manufacturing device 120 Rolling device 121 First rolling roll 122 Second rolling roll 130 Take-up machine 140 Winding reel

Claims

1. A rectangular molded stranded wire having a plurality of strands twisted in one direction, wherein each of the plurality of strands includes a conductor and an insulating coating covering the conductor, and in any cross section perpendicular to the longitudinal direction of the rectangular molded stranded wire, a portion of the insulating coating is located on the outer periphery of the rectangular molded stranded wire for all of the plurality of strands.

2. The rectangular molded stranded wire according to claim 1, characterized in that the twist pitch of the rectangular molded stranded wire is within the range of 16 to 35 times the circular equivalent diameter of the outer shape of the cross section.

3. The rectangular molded stranded wire according to claim 1, characterized in that the number of said plurality of wires is an even number within the range of 4 to 14.

4. The rectangular molded stranded wire according to claim 1, characterized in that the outer periphery of the rectangular molded stranded wire has a rectangular shape.

5. The rectangular molded stranded wire according to claim 1, characterized in that the thickness of the insulating coating is within the range of 0.005 to 0.025 mm.

6. A rectangular molded stranded wire as claimed in claim 4, wherein the plurality of wires are arranged so that, in any of the cross sections, at least ((n-2) / 2) of the plurality of wires are arranged in parallel in the width direction to form a first row, and at least ((n-2) / 2) of the remaining plurality of wires are arranged in parallel in the width direction to form a second row adjacent to the first row.

7. A rectangular molded stranded wire as described in claim 1, wherein in any of the cross sections, the shape of each of the plurality of strands is polygonal, and the longest side of the polygon is located on the outer periphery of the rectangular molded stranded wire.

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