Molded case capacitor and method for manufacturing molded case capacitor

Abstract

A molded case capacitor (1) comprises a metal case (50), a resin case (10), a capacitor element (30), and an insulating resin (40). The resin case (10) is provided with a slit (13) that extends along the direction proceeding from a bottom surface (14) toward an opening (15).

Description

Case molded capacitor and method for manufacturing case molded capacitor

[0001] The present disclosure relates to a case molded capacitor and a method for manufacturing the same.

[0002] Patent Document 1 discloses a case-molded capacitor formed by housing a resin case in a metal case and providing a buffer layer between the resin case and the metal case. The resin case houses a capacitor element and a pair of bus bars, and is filled with liquid resin to cover the capacitor element, and the liquid resin is heated and hardened to form the case.

[0003] Japanese Patent Application Publication No. 2008-130640

[0004] In a molded-case capacitor in which the resin covering the capacitor element and the buffer layer are integrally formed, voids (air gaps, bubbles, etc.) may form between the metal case and the resin case. If a void is formed, a flashover may occur between the capacitor element and the metal case through the void when a voltage is applied to the molded-case capacitor.

[0005] One aspect of the present disclosure aims to realize a case-molded capacitor that reduces the possibility of void formation, thereby preventing flashover between the capacitor element and the metal case and maintaining good insulation between the capacitor element and the metal case for a long period of time.

[0006] In order to solve the above problems, a case-molded capacitor according to one embodiment of the present disclosure comprises a metal case, a resin case housed in the metal case and having a bottom surface and an opening facing the bottom surface, a capacitor element housed in the resin case, and insulating resin filled in the metal case and the resin case, wherein the resin case has a slit extending in a direction from the bottom surface toward the opening.

[0007] According to one aspect of the present disclosure, the possibility of void formation is reduced, thereby preventing flashover between the capacitor element and the metal case, thereby realizing a case-molded capacitor that can maintain good insulation between the capacitor element and the metal case for a long period of time.

[0008] It is a schematic diagram of a case molded capacitor according to the present disclosure. It is a perspective view showing the internal structure of the element body shown in Figure 1. It is a flowchart showing a method for manufacturing a case molded capacitor. It is a perspective view showing an overview of the element body shown in Figure 2. It is a diagram showing the flow of insulating resin when the insulating resin is filled into a resin case.

[0009] An embodiment of the present disclosure will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram of a case molded capacitor 1 according to the present disclosure. The case molded capacitor 1 is used, for example, as a power conversion device and a device for power factor correction. Specifically, the case molded capacitor 1 is installed in electric power equipment (not shown), such as a gas-insulated switchgear. The case molded capacitor 1 includes a metal case 50 and an element body 60.

[0010] The metal case 50 is a box-shaped container made of metal. The metal case 50 has a bottom surface 52 located at the bottom and an opening 51 provided at a position opposite the bottom surface. The metal case 50 accommodates an element body 60 through the opening 51. In the case-molded capacitor 1, multiple element bodies 60 may be accommodated in one metal case 50. In the example shown in FIG. 1 , two element bodies 60 are accommodated in one metal case 50. A partition plate 53 may also be provided in the metal case 50 to separate the two element bodies 60.

[0011] Fig. 2 is a perspective view showing the internal structure of element body 60 shown in Fig. 1. Fig. 3 is a perspective view showing an overview of element body 60 shown in Fig. 2. Element body 60 is a component including a capacitor. Element body 60 includes resin case 10, bus bars 20, capacitor element 30, and insulating resin 40.

[0012] The capacitor element 30 is housed in a resin case 10. The capacitor element 30 is, for example, a film capacitor wound into a cylindrical shape. A plurality of capacitor elements 30 are housed in the resin case 10. The plurality of capacitor elements 30 are connected to conductive lead wires 31. There are a plurality of lead wires 31, and the plurality of lead wires 31 are connected to a bus bar 20. The bus bar 20 is a relay part for distributing power to the plurality of lead wires 31, and is connected to the conductor wires 21. The conductor wires 21 are connected to the above-mentioned power equipment. As a result, the above-mentioned power equipment is electrically connected to the conductor wires 21, the bus bar 20, and the plurality of lead wires 31, and is further electrically connected to the plurality of capacitor elements 30.

[0013] The insulating resin 40 is filled into the metal case 50 so as to fill any voids inside the metal case 50. The insulating resin 40 is a resin that is liquid when filled and hardens when heated or over time. To simplify the explanation of the structure of the element body 60, only the insulating resin 40 filled inside the resin case 10 is shown in Figures 2 and 3, but in reality, the insulating resin 40 also fills the gap between the metal case 50 and the resin case 10 (outside the resin case 10).

[0014] Resin case 10, with capacitor element 30 and insulating resin 40 housed therein, is housed in metal case 50. Resin case 10 has slit 13, bottom surface 14, opening 15, long side surface 16, first short side surface 171, and second short side surface 172.

[0015] The resin case 10 is used to insulate the capacitor element 30 from the metal case 50. For example, if the element body 60 does not include the resin case 10, when the insulating resin 40 is filled into the metal case 50 housing the element body 60, the capacitor element 30 may come into contact with the metal case 50, and the insulating resin 40 may harden in that state. The resin case 10 can prevent contact and flashover between the capacitor element 30 and the metal case 50. The resin case 10 may be made of any resin that is insulating, strong, and elastic. The resin case 10 may be made of, for example, polypropylene, polyethylene terephthalate, nylon, or the like.

[0016] Bottom surface 14 is the surface at the bottom of resin case 10. Opening 15 is an opening provided at a position opposite bottom surface 14. Bottom surface 14 is rectangular and has one pair of long sides and one pair of short sides. The pair of short sides are referred to as first short sides 141 and second short sides 142, respectively.

[0017] The long-side side surfaces 16 are a pair of surfaces that contact the pair of long sides of the bottom surface 14. The first short-side side surfaces 171 are surfaces that contact the first short side 141, and the second short-side side surfaces 172 are surfaces that contact the second short side 142. The capacitor elements 30 are arranged side by side such that the cylindrical planar portions of the capacitor elements 30 face the long-side side surfaces 16.

[0018] The slits 13 are cuts provided to allow the insulating resin 40 to flow into the gap between the metal case 50 and the resin case 10. The slits 13 are provided to extend in a direction from the bottom surface 14 toward the opening 15. Specifically, the slits 13 are located on the bottom surface 14, the first short-side side surface 171, and the second short-side side surface 172. By providing the slits 13 on the bottom surface 14, the first short-side side surface 171, and the second short-side side surface 172, the insulating resin 40 can easily flow into the gap between the metal case 50 and the resin case 10, thereby reducing the occurrence of voids compared to when the slits 13 are provided only on the bottom surface 14. In particular, by providing the slits 13 on the first short-side side surface 171 and the second short-side side surface 172 rather than on the long-side side surface 16, the bending area of ​​the first resin member 11 and the second resin member 12 is reduced, making it easier to form the resin case 10.

[0019] The resin case 10 is composed of a first resin member 11 and a second resin member 12. The first resin member 11 and the second resin member 12 each have a long-side side surface 16 and a portion of the surface that constitutes the bottom surface 14, the first short-side side surface 171, and the second short-side side surface 172. As shown in FIGS. 2 and 3 , a slit 13 is formed between the first resin member 11 and the second resin member 12. In other words, the slit 13 is a gap that occurs between the first resin member 11 and the second resin member 12. The slit 13 is provided so as to run vertically in the long-side direction of the bottom surface 14, the first short-side side surface 171, and the second short-side side surface 172, which further facilitates the flow of the insulating resin 40 into the gap between the metal case 50 and the resin case 10.

[0020] Each of the first resin member 11 and the second resin member 12 is formed by bending a plate-shaped resin. Forming a conventional resin case 10 required multiple steps to form a sheet-shaped resin into a box shape, and also required a step to form slits. In contrast, the first resin member 11 and the second resin member 12 can be formed simply by bending a sheet-shaped resin to form a portion of the bottom surface 14, the first short-side side surface 171, and the second short-side side surface 172. This facilitates the formation of the resin case 10, reducing the manufacturing cost of the resin case 10.

[0021] [Method for Manufacturing Case-Molded Capacitor] A method for manufacturing the case-molded capacitor 1 according to the present disclosure will be described with reference to Figures 4 and 5. Figure 4 is a flowchart showing the method for manufacturing the case-molded capacitor 1. Figure 5 is a diagram showing the flow of insulating resin 40 when the insulating resin 40 is filled into the resin case 10. For ease of explanation, the description of components having the same functions as those described in the above embodiments will not be repeated.

[0022] First, a worker forms the resin case 10 by combining the first resin member 11 and the second resin member 12 so that a slit 13 is formed between them (S1, first step). For example, the worker forms the resin case 10 by combining the first resin member 11 and the second resin member 12 so that the bottom surface 14, the first short-side side surface 171, and the second short-side side surface 172 are positioned between the respective long-side side surfaces 16. At this time, for example, portions of the bottom surface 14, the first short-side side surface 171, and the second short-side side surface 172 may be connected to one another.

[0023] Next, the worker places the capacitor element 30 in the resin case 10 (S2, second step). At this time, the worker places the capacitor element 30 so that the flat surface of the capacitor element 30 faces the long side surface 16, for example.

[0024] The worker may perform the first and second steps simultaneously. For example, the worker arranges the long-side side surface 16 of the first resin member 11 as the bottom, arranges the flat surface of the capacitor element 30 facing the long-side side surface 16, and places the long-side side surface 16 of the second resin member 12 on top. At this time, while the capacitor element 30 is housed in the resin case 10, gaps that are slits 13 are formed between the bottom surface 14, first short-side side surface 171, and second short-side side surface 172 of the first resin member 11 and the bottom surface 14, first short-side side surface 171, and second short-side side surface 172 of the second resin member 12. In this manner, the worker may form the slits 13 in the resin case 10 and house the capacitor element 30 therein.

[0025] Next, the worker places the resin case 10 made in the second step into the metal case 50 and seals the metal case 50 (S3, third step). Specifically, the worker places the resin case 10 made in the second step into the metal case 50 through the opening 51. The metal case 50 is sealed by welding an iron plate 54 to the opening 51, for example, as shown in FIG. 5 .

[0026] Bolt holes 55 are formed in the steel plate 54. A thread groove is formed on the inner side of the bolt holes 55 so that a bolt can be screwed into them. Furthermore, a through hole is formed in the steel plate 54 for inserting the conductor wire 21, and the through hole in the steel plate 54 and the conductor wire 21 are connected via an insulator 56. The insulator 56 is made of, for example, ceramic, porcelain, or polymer. This electrically insulates the metal case 50 from the capacitor element 30, and the metal case 50 is hermetically sealed.

[0027] Next, the worker fills the metal case 50 created in the third step with insulating resin 40 (S4, step 4). Liquid insulating resin 40 is poured through the bolt holes 55. Arrows A to C in FIG. 5 indicate the flow of insulating resin 40. The insulating resin 40 first flows down toward the bottom surface 14 of the resin case 10, as indicated by arrow A. After flowing down to the bottom surface 14, the insulating resin 40 passes through the slits 13 in the bottom surface 14, as indicated by arrow B, into the gap between the metal case 50 and the resin case 10, and spreads across the bottom surface 52 of the metal case 50. As the insulating resin 40 is filled, it gradually flows into the gap between the metal case 50 and the resin case 10, starting from the bottom surface 14 of the resin case 10, as indicated by arrow C. By providing the slits 13 from the bottom surface 14 to the opening 15 in this way, the insulating resin 40 can be gradually filled from the bottom of the metal case 50, reducing the occurrence of voids.

[0028] Furthermore, the insulating resin 40 may be filled by vacuum filling, which can further reduce the occurrence of voids.

[0029] Furthermore, as described above, slits 13 are located on bottom surface 14, first short-side side surface 171, and second short-side side surface 172. Capacitor elements 30 are arranged side by side on long-side side surface 16. This allows insulating resin 40 to pass through capacitor elements 30 and flow to slits 13. This allows insulating resin 40 to be efficiently filled into metal case 50.

[0030] Insulating resin 40 may be a resin with low viscosity in a liquid state, such as urethane resin. In this case, insulating resin 40 can be easily filled into the gaps between capacitor elements 30 and the gaps between metal case 50 and resin case 10, reducing the occurrence of voids. Once filling is complete, bolt holes 55 are sealed with bolts.

[0031] Next, the worker hardens the insulating resin 40 filled in the metal case 50 created in the third step (S5). The hardening of the insulating resin 40 is carried out, for example, by heating the metal case 50 or by allowing time to pass, depending on the material of the insulating resin 40.

[0032] [Experiment] An earth insulation test was conducted using the case molded capacitor 1 according to the present disclosure and a conventional case molded capacitor. In the earth insulation test, the metal case 50 is grounded and a voltage is applied to the capacitor element 30 to test whether discharge occurs from the metal case 50. If discharge occurs from the metal case 50, it is determined that a void has occurred within the metal case 50 and that a flashover has occurred between the capacitor element 30 and the metal case 50 through this void.

[0033] Experimental results showed that discharge occurred in the conventional case molded capacitor, but no discharge occurred in the case molded capacitor 1 according to the present disclosure, even at the same voltage. Therefore, it can be said that the case molded capacitor 1 was able to reduce the occurrence of voids and also reduce the occurrence of discharge.

[0034] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure.

[0035] REFERENCE SIGNS LIST 1 case molded capacitor 50 metal case 60 element body 10 resin case 11 first resin member 12 second resin member 13 slit 14 bottom surface 15 opening 16 long side surface 171 first short side surface 172 second short side surface 20 bus bar 30 capacitor element 31 lead wire 40 insulating resin

Claims

1. A case-molded capacitor comprising: a metal case; a resin case housed in the metal case and having a bottom surface and an opening facing the bottom surface; a capacitor element housed in the resin case; and insulating resin filled in the metal case and the resin case, wherein the resin case has a slit extending in a direction from the bottom surface toward the opening.

2. A case-molded capacitor according to claim 1, wherein the resin case includes a first resin member and a second resin member, and the slit is a gap formed between the first resin member and the second resin member.

3. The case molded capacitor according to claim 2, wherein the first resin member and the second resin member are each formed by bending a plate-shaped resin.

4. A case-molded capacitor according to any one of claims 1 to 3, wherein the bottom surface is rectangular, and a pair of short sides forming the rectangle of the bottom surface are defined as a first short side and a second short side, the resin case has a first short side side surface that is in contact with the first short side and a second short side side surface that is in contact with the second short side, and the slits are located on each of the bottom surface, the first short side side surface and the second short side side surface.

5. A method for manufacturing a case-molded capacitor, comprising: a first step of combining a first resin member and a second resin member so that a slit is formed between them to form a resin case; a second step of accommodating a capacitor element in the resin case; a third step of accommodating the resin case in a metal case and sealing the metal case; and a fourth step of filling the metal case with insulating resin.

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