Composite capacitor core shaft and capacitor element

Abstract

The invention belongs to the technical field of power capacitor manufacturing, and particularly relates to a composite capacitor mandrel and a capacitor element. The composite capacitor core shaft comprises a core shaft body provided with a regular hexagon through hole, the core shaft body is composed of insulators, annular long holes are formed in the wall thickness of the two ends of the core shaft body in the length direction of the core shaft body, and an insulator interval is arranged between the two ends, close to each other, of the two annular long holes to form isolation. Heat conduction metal bodies are inserted into the two annular long holes respectively, the heat conduction metal bodies and the mandrel body are integrally formed, and the ends, away from each other, of the two heat conduction metal bodies make contact with metal spraying layers at the two ends of a metallized film on the capacitor element so that heat transfer of the capacitor element can be achieved. The internal hot spot temperature of the capacitor element is effectively reduced, the transverse heat conduction efficiency of the capacitor element is improved, the heat transfer effect is further improved, and the problem that heat dissipation and heat balance in the capacitor element with the enlarged geometric size become poor is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power capacitor manufacturing, and particularly relates to a composite capacitor core shaft and a capacitor element. Background Art

[0002] With the rapid development of domestic industry and agriculture and the increasing annual electricity consumption of enterprises, the demand for capacitors and the product quality have also increased rapidly. The self-healing capacitor is widely used in various occasions such as power, agriculture, and medical due to its self-healing characteristics, and is used to improve the power factor of the power grid and improve the power grid quality. The core shaft used for the self-healing capacitor is an important basic part of the power industry and the power electronics industry, and is widely used for winding various high-voltage capacitor elements, medium- and low-voltage capacitor elements, and DC capacitor elements.

[0003] At present, the internal heat of the self-healing capacitor element is mainly transferred to its surface through the polypropylene film. However, in actual operation, the self-healing capacitor element will be affected by its own heat generation and the thermal radiation of surrounding components. At this time, due to the slow heat conduction of the polypropylene film, the heat cannot be quickly transferred to the metallized layer, resulting in local overheating in the central position and surrounding areas of the self-healing capacitor element.

[0004] The core shaft used for the self-healing capacitor element is a cylindrical core shaft with a relatively high degree of standardization and mainly made of engineering plastics. Its internal is a regular hexagonal through hole. When in use, the regular hexagonal rod of the winding machine will penetrate into the regular hexagonal through hole of the core shaft and drive the core shaft to rotate for the winding processing of the self-healing capacitor element. In the prior art, the capacitor element is composed of a core shaft, a metallized film, and a metallized layer. As the geometric size of the capacitor element increases, the heat dissipation and internal thermal balance of the capacitor element become a bottleneck. Summary of the Invention

[0005] The purpose of the present invention is to provide a composite capacitor core shaft to solve the problem of poor heat dissipation and thermal balance inside the capacitor element with an increased geometric size in the prior art.

[0006] To solve the above problems, the present invention proposes a composite capacitor core shaft, and the technical solution adopted is: A composite capacitor mandrel includes a mandrel body provided with a regular hexagon through hole. The mandrel body is composed of an insulator. In the wall thickness at both ends of the mandrel body, annular long holes are opened along the length direction of the mandrel body. And an insulator spacing is formed between the two ends of the two annular long holes that are close to each other to form isolation. Heat-conducting metal bodies are respectively inserted into the two annular long holes, and the heat-conducting metal bodies are integrally formed with the mandrel body. The ends of the two heat-conducting metal bodies that are far away from each other are in contact with the sprayed metal layers at both ends of the metallized film on the capacitor element prepared by the composite capacitor mandrel to achieve heat transfer of the capacitor element. The insulator spacing is greater than the minimum creepage distance that can withstand the withstand voltage of the capacitor element, and the insulator spacing is adjustable according to the withstand voltage of the capacitor element. The temperature rise of the capacitor element prepared by the composite capacitor mandrel is reduced by 21.1% - 23.4%.

[0007] Further, the heat-conducting metal body is a cylindrical metal layer, and the cylindrical metal layer is inserted along the length direction of the annular long hole and is matched with the annular long hole.

[0008] Further, the thickness of the cylindrical metal layer is 0.5 - 0.6 mm.

[0009] Further, the cylindrical metal layer is a cylindrical aluminum layer or a cylindrical copper layer.

[0010] Further, convex platforms are respectively arranged at the ends of the cylindrical metal layer that are far away from each other, and the two ends of the mandrel body are respectively cooperatively installed with the convex platforms on the cylindrical metal layer.

[0011] Further, the two annular long holes are symmetrically arranged at both ends of the mandrel body with respect to the central position of the mandrel body.

[0012] Further, the insulator is an engineering plastic.

[0013] Further, the melting point of the insulator is higher than the melting point of the metallized film on the capacitor element prepared by the composite capacitor mandrel.

[0014] Further, the internal hottest point temperature of the capacitor element prepared by the composite capacitor mandrel is reduced by 4.6 - 5.1 K.

[0015] This application also provides a capacitor element, including the above-mentioned composite capacitor mandrel.

[0016] Compared with the prior art, this application has the following beneficial effects: The present invention is an improved invention. In the present invention, heat-conducting metal bodies are respectively inserted into the annular long holes in the wall thicknesses at both ends of the mandrel body. At the same time, an insulator spacing is provided between the two ends of the two annular long holes that are close to each other to form isolation, ensuring the safety insulation of the heat-conducting metal bodies. The mandrel body of the present application is composed of a heat-conducting metal body and an insulator, changing the original insulator structure of the mandrel into a composite structure of an insulator and a heat-conducting metal body; and the ends of the two heat-conducting metal bodies that are far from each other are in contact with the sprayed gold layers at both ends of the metallized film on the capacitor element, so as to achieve heat transfer of the capacitor element, effectively improving the transverse heat conduction efficiency of the capacitor element, reducing the internal hot spot temperature of the capacitor element, and further improving the heat transfer effect, solving the problems of poor heat dissipation and thermal balance inside the capacitor element with a larger geometric size. At the same time, the setting of the insulator spacing ensures the safety insulation distance between the two heat-conducting metal bodies while ensuring a good enough heat transfer effect. The structure of the composite capacitor mandrel of the present application is simple and is particularly suitable for capacitor elements with a larger diameter.

[0017] The heat-conducting metal body is a cylindrical metal layer, and the cylindrical metal layer is inserted along the length direction of the annular long hole and is matched with the annular long hole. This structure further improves the heat transfer effect while improving the structural stability of the composite capacitor mandrel.

[0018] The thickness of the cylindrical metal layer is 0.5 - 0.6 mm. This structure can not only ensure its own heat-conducting area but also ensure the mechanical strength of the mandrel body, making the structure simple and the cost low on the basis of ensuring the heat transfer effect.

[0019] The cylindrical metal layer is a cylindrical aluminum layer or a cylindrical copper layer, which is convenient for applying different application scenarios according to different needs.

[0020] Bosses are provided at the ends of the cylindrical metal layer that are far from each other, and the two ends of the mandrel body are respectively fitted and installed with the bosses on the cylindrical metal layer, further improving the adaptability between the cylindrical metal layer and the mandrel body and the structural stability of the composite capacitor mandrel.

[0021] The two annular long holes are symmetrically arranged at both ends of the mandrel body with respect to the central position of the mandrel body, effectively preventing uneven heat transfer.

[0022] The melting point of the insulator is higher than the melting point of the metallized film on the capacitor element prepared by the composite capacitor mandrel, effectively preventing the insulator from melting first under high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a structural sectional view of a conventional mandrel in the prior art; Figure 2 is a structural sectional view of the composite capacitor mandrel of the present invention; Figure 3 It is a schematic structural diagram of the composite capacitor mandrel of the present invention; Figure 4 It is a structural sectional view of the engineering plastic of the composite capacitor mandrel of the present invention; Figure 5 It is a structural sectional view of the aluminum part of the composite capacitor mandrel of the present invention; Figure 6 It is a schematic structural diagram of the capacitor element processed from the composite capacitor mandrel of the present invention; Figure 7 It is a schematic diagram of the internal hot spot temperature value of the capacitor element processed from the conventional mandrel in the prior art; Figure 8 It is a schematic diagram of the internal hot spot temperature value of the capacitor element processed from the cylindrical aluminum layer in the composite capacitor mandrel of the present invention; Figure 9 It is a schematic diagram of the internal hot spot temperature value of the capacitor element processed from the cylindrical copper layer in the composite capacitor mandrel of the present invention; In the figure, 1. Conventional mandrel, 2. Cylindrical aluminum layer, 3. Engineering plastic, 4. Mandrel body, 5. Metallized film, 6. Metallized layer. Specific embodiments

[0024] As cited in the background art, the heat dissipation and thermal balance inside a capacitor element with increasing geometric dimensions in the prior art deteriorate. Therefore, the present invention provides a composite capacitor mandrel, including a mandrel body 4 provided with a regular hexagon through-hole. The mandrel body 4 is composed of an insulator for insulation. Along the length direction of the mandrel body 4, annular long holes are opened in the wall thickness at both ends of the mandrel body 4, and an insulator spacing is provided between the two ends of the two annular long holes close to each other to form isolation. Heat-conducting metal bodies are respectively inserted into the two annular long holes to ensure the safe insulation distance between the two heat-conducting metal bodies on the basis of effective heat transfer. And the heat-conducting metal bodies are integrally formed with the mandrel body 4 to prevent the instability of the structure of the composite capacitor mandrel. One end of the two heat-conducting metal bodies away from each other contacts the spraying metal layers 6 at both ends of the metallized film 5 on the capacitor element prepared by the composite capacitor mandrel to achieve heat transfer of the capacitor element. The composite capacitor mandrel of the present application is composed of a heat-conducting metal body and an insulator, which changes the mandrel from the original insulator structure to a composite structure of an insulator and a heat-conducting metal body. And one end of the two heat-conducting metal bodies away from each other contacts the spraying metal layers 6 at both ends of the metallized film 5 on the capacitor element to achieve heat transfer of the capacitor element. The insulator spacing is greater than the minimum creepage distance that can withstand the withstand voltage of the capacitor element, and the insulator spacing is adjustable according to the withstand voltage of the capacitor element. While ensuring a sufficiently good heat transfer effect, the safe insulation distance between the two heat-conducting metal bodies is ensured, so that the temperature rise of the capacitor element prepared by the composite capacitor mandrel of the present application is reduced by 21.1% - 23.4%, effectively improving the transverse heat conduction efficiency of the capacitor element, reducing the internal hot spot temperature of the capacitor element, and further improving the heat transfer effect, solving the problem of deteriorated heat dissipation and thermal balance inside the capacitor element with increasing geometric dimensions. The structure of the composite capacitor mandrel of the present application is simple and is particularly suitable for capacitor elements with a larger diameter.

[0025] The embodiments of the present application are described in detail below. The examples of the embodiments are shown in the drawings, in which the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application and should not be construed as a limitation of the present application.

[0026] It should be noted that the terms "first", "second", etc. in the description, claims and above-mentioned drawings of the present invention are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0027] The structure of the conventional mandrel 1 in the prior art is as Figure 1 shown. Specifically, the conventional mandrel 1 is usually a hollow cylinder made of an insulating material (usually engineering plastic 3) with a high degree of standardization. Its outer surface is cylindrical, and inside is a regular hexagonal through-hole. When in use, the regular hexagonal rod of the winding machine will pass through the regular hexagonal through-hole and penetrate into the conventional mandrel 1, and drive the conventional mandrel 1 to rotate for the winding process of capacitor elements. Among them, the conventional mandrel 1 is usually composed of only one kind of insulating material. However, as the geometric size of capacitor elements increases, the heat dissipation and internal thermal balance of capacitor elements become bottlenecks.

[0028] In view of the problems existing in the above-mentioned prior art, the present application provides a composite capacitor mandrel.

[0029] Specific embodiment 1 of the composite capacitor mandrel of the present invention: In this embodiment, as Figure 2 , Figure 3 and Figure 4 shown, it includes a mandrel body 4 provided with a regular hexagonal through-hole. The mandrel body 4 is composed of an insulator. Annular long holes are provided along the length direction of the wall thickness at both ends of the mandrel body 4, and an insulator spacing is formed between the two ends of the two annular long holes close to each other to form an isolation. Heat-conducting metal bodies are respectively inserted into the two annular long holes, and the heat-conducting metal bodies are integrally formed with the mandrel body 4. The ends of the two heat-conducting metal bodies far away from each other are in contact with the sprayed gold layers 6 at both ends of the metallized film 5 on the capacitor element prepared by the composite capacitor mandrel to achieve heat transfer of the capacitor element. At the same time, the insulator spacing is greater than the minimum creepage distance that can withstand the withstand voltage of the capacitor element prepared by the composite capacitor mandrel, and the insulator spacing is adjustable according to the withstand voltage of the capacitor element. Among them, the insulator is engineering plastic 3. The temperature rise of the capacitor element prepared by the composite capacitor mandrel in the present application is reduced by 21.1% - 23.4%.

[0030] Specifically, in this embodiment, asFigure 5 As shown, the heat-conducting metal body is a cylindrical metal layer, which is inserted along the length direction of the annular long hole and is matched with the annular long hole. Convex platforms are provided at the ends of the cylindrical metal layer that are far from each other, and the two ends of the mandrel body 4 are respectively fitted and installed with the convex platforms on the cylindrical metal layer. During use, the two cylindrical metal layers are respectively inserted from the two ends of the mandrel body 4, and are fixedly matched with the two ends of the mandrel body 4 through the convex platforms on the cylindrical metal layer, ensuring the structural stability of the mandrel body 4, and ensuring that the ends of the two heat-conducting metal bodies that are far from each other are in contact with the sprayed gold layers 6 at the two ends of the metallized film 5 on the capacitor element. Among them, the cylindrical metal layer is a cylindrical aluminum layer 2. The thickness of the cylindrical metal layer is 0.5 - 0.6 mm. In other embodiments, the cylindrical metal layer can be a cylindrical copper layer.

[0031] Specific embodiment 2 of the composite capacitor mandrel of the present invention: Based on the above technical concept of the present invention, or on the basis of the specific embodiments of the present invention introduced above, another embodiment is provided below.

[0032] In this embodiment, as Figure 2 shown, the two annular long holes are symmetrically arranged at the two ends of the mandrel body 4 with respect to the central position of the mandrel body 4. At this time, the two annular long holes are symmetrically arranged at the two ends of the mandrel body 4 with respect to the insulator spacing. The melting point of the insulator is higher than the melting point of the metallized film 5 on the capacitor element prepared by the composite capacitor mandrel.

[0033] In other embodiments, the two annular long holes may be asymmetrically arranged at the two ends of the mandrel body 4 with respect to the central position of the mandrel body 4.

[0034] Specifically, the processing method of the composite capacitor mandrel of the present application is as follows: First, a cylindrical metal layer is prefabricated; second, the engineering plastic 3 is heated and melted; then, the cylindrical metal layer is placed in a mold, and the melted engineering plastic 3 is injected into the mold; finally, demolding is performed to obtain a complete composite capacitor mandrel. At this time, there is a cylindrical metal layer in the wall thickness outside the two ends of the composite capacitor mandrel, and the middle part is the engineering plastic 3.

[0035] The present invention also provides a capacitor element, including the composite capacitor mandrel described above.

[0036] The composite capacitor mandrel of the present application is used to process capacitor elements. The processing process of the capacitor elements is as follows: After winding the metallized film 5 around the composite capacitor mandrel of the present application and reaching a certain diameter, a gold spraying process is performed on the two cylindrical end faces at both ends of the composite capacitor mandrel of the present application, so that a cylindrical surface electrode with a thickness of about 1 mm is formed on each of the two end faces of the capacitor element, that is, the gold spraying layer 6, and then the capacitor element is processed, as Figure 6 shown. Among them, the distance between the two end faces of the capacitor element after gold spraying is the same as the length of the composite capacitor mandrel.

[0037] For different heat-conducting metal bodies, the performance of the composite capacitor mandrels composed of them is compared with that of the conventional mandrel 1, as follows: Using the cylindrical aluminum layer 2 as the heat-conducting metal body, the outer dimensions of the conventional mandrel 1 and the composite capacitor mandrel of the present invention are the same. Assuming that the geometric dimensions, materials, and structures of the capacitor elements processed by the two are the same except for the mandrels, and the heating power of the capacitor elements is set to 0.46 W, and the outer dimensions of the capacitor elements are both φ68 mm × 152 mm, a simulation software is used for calculation. Among them, the peripheral temperature of the capacitor elements is set to 55 °C, the circumferential surface of the capacitor elements is adiabatic, and only the gold spraying layers 6 on both sides dissipate heat through air convection, and the convection coefficient is taken as 5 W / m 2 .

[0038] At this time, the calculation result of the internal hot spot temperature diagram of the capacitor element using the conventional mandrel 1 is as Figure 7 shown. It can be obtained that the temperature of the internal hottest spot of the capacitor element using the conventional mandrel 1 is 76.8 °C, and the temperature rise relative to the peripheral environment is 21.8 K. The calculation result of the internal hot spot temperature value of the capacitor element using the composite capacitor mandrel of the present invention is as Figure 8 shown. It can be obtained that its internal hottest spot temperature is 72.2 °C, and the temperature rise relative to the peripheral environment is 17.2 K. Therefore, the temperature rise of the capacitor element using the composite capacitor mandrel of the present invention is reduced by 4.6 K compared with that of the capacitor element using the conventional mandrel 1, and the reduction ratio is 21.1%.

[0039] Using the cylindrical copper layer as the heat-conducting metal body, other parameter designs are the same as those when using the cylindrical aluminum layer 2 as the heat-conducting metal body. At this time, the calculation result of the internal hot spot temperature value of the capacitor element using the composite capacitor mandrel of the present invention is as Figure 9As shown, it can be obtained that the temperature of the hottest point inside is 71.7 °C, and the temperature rise relative to the peripheral environment is 16.7 K. Therefore, the temperature rise of the capacitor element with the composite capacitor core shaft of the present invention is reduced by 5.1 K compared with that of the capacitor element with the conventional core shaft 1, and the reduction ratio is 23.4%. This shows that using a cylindrical copper layer as the heat-conducting metal body has the same heat transfer effect as using a cylindrical aluminum layer 2 as the heat-conducting metal body, but aluminum has a smaller density, which can make the mass of the composite capacitor core shaft of the present invention smaller and the cost lower.

[0040] In summary, during use, the temperature of the hottest point inside the capacitor element during operation is directly related to the life of the capacitor element. For every 8 - 10 K increase in the temperature of the hottest point inside the capacitor element, the life will be reduced by half. For the capacitor element processed with the composite capacitor core shaft of the present invention, the temperature of the hottest point inside is reduced by 4.6 - 5.1 K, which is approximately half of 8 - 10 K. It is expected that the life of the capacitor element will be doubled.

[0041] Through the above description of the specific embodiments of the composite capacitor core shaft of the present invention, it can be seen that the composite capacitor core shaft of the present invention includes a core shaft body 4 provided with a regular hexagon through hole. The core shaft body 4 is composed of an insulator and is used for insulation. Annular long holes are opened along the length direction of the wall thickness at both ends of the core shaft body 4, and an insulator spacing is provided between the two ends of the two annular long holes close to each other to form isolation. Heat-conducting metal bodies are respectively inserted into the two annular long holes to ensure the safe insulation distance between the two heat-conducting metal bodies on the basis of effective heat transfer; and the heat-conducting metal bodies are integrally formed with the core shaft body 4 to prevent the instability of the composite capacitor core shaft structure; the ends of the two heat-conducting metal bodies far from each other are in contact with the sprayed metal layers 6 at both ends of the metallized film 5 on the capacitor element prepared by the composite capacitor core shaft to achieve heat transfer of the capacitor element. The composite capacitor core shaft of the present application is composed of a heat-conducting metal body and an insulator, which changes the core shaft from the original insulator structure to a composite structure of an insulator and a heat-conducting metal body; and the ends of the two heat-conducting metal bodies far from each other are in contact with the sprayed metal layers 6 at both ends of the metallized film 5 on the capacitor element to achieve heat transfer of the capacitor element; the insulator spacing is greater than the minimum creepage distance that can withstand the withstand voltage of the capacitor element, and the insulator spacing is adjustable according to the withstand voltage of the capacitor element. While ensuring a good enough heat transfer effect, the safe insulation distance between the two heat-conducting metal bodies is ensured, so that the temperature rise of the capacitor element prepared with the composite capacitor core shaft of the present application is reduced by 21.1% - 23.4%, effectively improving the transverse heat conduction efficiency of the capacitor element, reducing the internal hot spot temperature of the capacitor element, and further improving the heat transfer effect, and solving the problem of poor heat dissipation and thermal balance inside the capacitor element with a larger geometric size. The structure of the composite capacitor core shaft of the present application is simple and is particularly suitable for capacitor elements with a larger diameter.

[0042] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. The scope of patent protection of the present invention is subject to the claims. Any equivalent structural changes made by using the content of the specification and drawings of the present invention should, by the same token, be included in the protection scope of the present invention.

Claims

1. A composite capacitor core shaft, characterized in that: The invention comprises a mandrel body (4) provided with a regular hexagonal through hole, the mandrel body (4) being composed of an insulator, annular long holes being provided in the wall thickness at both ends of the mandrel body (4) along the length direction of the mandrel body (4), and an insulator spacing being provided between the two ends of the two annular long holes close to each other to form isolation, a heat-conducting metal body being respectively inserted into the two annular long holes, and the heat-conducting metal body being integrally formed with the mandrel body (4), and the ends of the two heat-conducting metal bodies away from each other being in contact with the gold-sprayed layers (6) at both ends of the metallized film (5) on the capacitor element prepared by the composite capacitor mandrel, so as to realize heat transfer of the capacitor element; the insulator spacing being greater than the minimum creepage distance capable of withstanding the withstand voltage of the capacitor element, and the insulator spacing being adjustable according to the withstand voltage of the capacitor element; and the temperature rise of the capacitor element prepared by the composite capacitor mandrel is reduced by 21.1%-23.4%.

2. The composite capacitor core shaft according to claim 1, characterized in that: The heat-conducting metal body is a cylindrical metal layer, which is inserted along the length direction of the annular long hole and matched with the annular long hole.

3. The composite capacitor core shaft according to claim 2, characterized in that: The thickness of the cylindrical metal layer is 0.5-0.6 mm.

4. The composite capacitor core shaft according to claim 2, characterized in that: The cylindrical metal layer is a cylindrical aluminum layer (2) or a cylindrical copper layer.

5. The composite capacitor core shaft according to claim 2, characterized in that: The cylindrical metal layers are each provided with a boss at one end away from each other, and the two ends of the core shaft body (4) are respectively mounted in cooperation with the bosses on the cylindrical metal layer.

6. The composite capacitor core shaft according to claim 1, characterized in that: The two annular long holes are symmetrically arranged at the two ends of the core shaft body (4) relative to the central position of the core shaft body (4).

7. The composite capacitor core shaft according to claim 1, characterized in that: The insulator is engineering plastic (3).

8. The composite capacitor core shaft according to claim 1, characterized in that: The melting point of the insulator is higher than the melting point of the metallized film (5) on the capacitor element prepared from the composite capacitor core shaft.

9. The composite capacitor core shaft according to claim 1, characterized in that: The internal hottest point temperature of the capacitor element prepared by the composite capacitor core shaft is reduced by 4.6-5.1K.

10. A capacitor element, characterized in that: A composite capacitor core shaft comprising any one of claims 1-9.

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