A connecting terminal for copper-aluminum cable transition and a manufacturing method of a connecting module

Abstract

The application provides a preparation method of a connecting terminal for copper and aluminum cable switching, which comprises the following steps: preparing a copper-aluminum composite metal rod by using a continuous casting device; shearing and heat treating the copper-aluminum composite metal rod; machining the copper-aluminum composite metal rod; and reducing the pipe of one end of the rod. The application also provides a preparation method of a connecting module for copper and aluminum cable switching based on the connecting terminal. The preparation method of the application can be applied to most connecting terminals for copper and aluminum cable switching of photovoltaic systems according to application requirements. The copper-aluminum composite metal layer of the connecting terminal has sufficient thickness and excellent interface bonding strength through strict process control, can meet the requirement of thermal shock resistance in large current application, and has stronger environmental resistance and aging resistance. In addition, the composite rod can be produced according to standard parts, and only the machining parameters of the subsequent process need to be adjusted to be applicable to different specifications of cable application, thereby significantly reducing the production cost.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic system connection technology, and in particular to a copper-aluminum cable connection terminal and adapter module for connecting aluminum and copper cables in a photovoltaic system. Background Technology

[0002] To address climate change, green energy is being used more and more widely around the world. Among green energy sources, solar energy has received particular attention due to its cleanliness and ease of access, leading to the emergence of photovoltaic (PV) power plants. A PV power plant consists of PV modules connected in series and parallel to form a PV array, which is then connected by cables to create a PV power station.

[0003] Copper possesses excellent ductility, thermal conductivity, and electrical conductivity, making it the primary material for cables in current photovoltaic (PV) systems. However, as the main connecting cables in PV systems, copper cables are relatively expensive, resulting in higher operating costs. With the continuous expansion of PV power plant scale and the improvement of solar panel conversion efficiency, the amount and diameter of cables used are constantly increasing, leading to higher construction costs for PV systems and hindering their widespread adoption. Therefore, some industries have begun using aluminum cables to replace copper cables. While meeting the same current-carrying requirements, aluminum conductors cost only about one-third the price of copper cables. Consequently, in PV system connections, such as the busbar cables, which are used most extensively, aluminum core cables are now generally being used. However, aluminum core cables encounter a critical problem when used in photovoltaic systems. Currently, the cables used in the junction boxes of photovoltaic modules are copper core cables. When copper core cables are directly connected to aluminum core cables, electro-corrosion will occur at the copper-aluminum contact surface, affecting current conduction and thus electrical transmission performance. Therefore, when connecting photovoltaic systems, the aluminum core cables used for system connection cannot be directly riveted or welded to the connector cables of the module junction boxes. In addition, due to the safety requirements and efficiency of on-site operations, relatively dangerous or complex connection processes are not allowed.

[0004] See Figure 1The commonly used copper-aluminum connector shown is typically a copper-on-one and aluminum-on-one connection structure. The aluminum connector 110 and the copper connector 120 are joined together using a special welding process, such as friction welding. The aluminum connector 110 has a socket 111 for inserting the aluminum core of the aluminum cable, and the copper connector 120 has a socket 120 for inserting the copper core of the copper cable. While this type of copper-aluminum connector can form a composite metal layer of a certain thickness at the copper-aluminum interface through friction welding, significantly reducing interface corrosion, it still has significant drawbacks. First, this type of connector requires customized production for different product specifications, such as manufacturing connectors for cables of different diameters, resulting in very high processing costs. Second, even with friction welding, due to the different coefficients of thermal expansion of copper and aluminum, and the fact that the interface is not related to the riveting position of the cable and connector, the copper-aluminum interface is still relatively prone to breakage in the application environment due to aging, temperature shock, or tangential stress, leading to connection failure. Therefore, a more reliable connecting terminal for switching between aluminum and copper cables is needed. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for preparing a connecting terminal for copper-aluminum cable transitions.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a connecting terminal for copper-aluminum cable transition, the method comprising the following steps: Step 1: Prepare copper-aluminum composite metal rods using continuous casting equipment; the continuous casting equipment is a vertical continuous casting equipment, with copper melting crucible furnace and aluminum melting crucible furnace arranged side by side at the top. The outer mold of the cavity is set below the copper molten gate module, and the inner mold of the cavity is set inside the outer mold. A first cooling module is set around the upper part of the outer mold, and the outer copper metal layer of the copper-aluminum composite metal rod is formed under the action of the first cooling module. A second cooling module is set at a distance from the first cooling module at the lower part of the outer mold. During forming, the copper molten metal is first opened for melting. In the crucible furnace, the stopper rod allows molten copper to cool and crystallize in the annular copper metal crystallization zone between the inner and outer molds of the cavity, forming a copper tube. A traction machine continuously pulls out the cast copper tube, forming an aluminum metal crystallization zone inside the already cast copper tube in the lower half of the outer mold. Then, the stopper rod in the aluminum melting crucible furnace is opened, and molten aluminum is injected into the copper tube through the aluminum flow channel. Under the action of the second cooling module, an internal aluminum metal layer is formed on the copper-aluminum composite metal rod, creating a metallurgically bonded copper-aluminum composite layer of a certain thickness between the copper and aluminum metal interfaces. The temperature of the copper melt in the copper melting crucible furnace is maintained at 1250±10℃, and the temperature of the aluminum melt in the aluminum melting crucible furnace is maintained at 800±10℃. The temperature of the aluminum melt when it reaches the internal aluminum melt crystallization space formed by the copper tube that has completed crystallization first should not exceed 800℃. The traction speed of the traction machine continuously pulling out the copper tube is 67±1mm / min, and the flow rate of the cooling water in the second cooling module is controlled at 700±20L / hour. Step 2: Cut the copper-aluminum composite metal rod obtained in Step 1 into short rods according to the set length, and then heat treat the short rods by placing them in a heating furnace and holding them at 300℃ for 45-60 minutes, and then letting them cool naturally to obtain the copper-aluminum composite metal rod. Step 3: The copper-aluminum composite metal rod obtained in Step 2 is machined. A portion of the aluminum on the inner side of one end of the rod is cut away, leaving an aluminum layer of a certain thickness to form the first insertion hole for the core wire of the aluminum cable. The inner aluminum layer and the copper-aluminum composite metal layer at the other end are cut away to form a cavity, leaving only the outer copper layer. Step 4: The end of the copper-aluminum composite metal tube with the first socket and cavity processed in Step 3, which retains only the outer copper layer, is subjected to a tube shrinking process to form a second socket for the core wire of the copper cable to be inserted; in this way, a connection terminal for connecting copper and aluminum cables that can be used in photovoltaic systems is obtained.

[0007] A method for preparing a connecting terminal for copper-aluminum cable transition, the method comprising the following steps: Step 1: Prepare copper-aluminum composite metal rods using continuous casting equipment; the continuous casting equipment is a vertical continuous casting equipment, with copper melting crucible furnace and aluminum melting crucible furnace arranged side by side at the top. The outer mold of the cavity is set below the copper molten gate module, and the inner mold of the cavity is set inside the outer mold. A first cooling module is set around the upper part of the outer mold, and the outer copper metal layer of the copper-aluminum composite metal rod is formed under the action of the first cooling module. A second cooling module is set at a distance from the first cooling module at the lower part of the outer mold. During forming, the copper molten metal is first opened for melting. In the crucible furnace, the stopper rod allows molten copper to cool and crystallize in the annular copper metal crystallization zone between the inner and outer molds of the cavity, forming a copper tube. A traction machine continuously pulls out the cast copper tube, forming an aluminum metal crystallization zone inside the already cast copper tube in the lower half of the outer mold. Then, the stopper rod in the aluminum melting crucible furnace is opened, and molten aluminum is injected into the copper tube through the aluminum flow channel. Under the action of the second cooling module, an internal aluminum metal layer is formed on the copper-aluminum composite metal rod, creating a metallurgically bonded copper-aluminum composite layer of a certain thickness between the copper and aluminum metal interfaces. The temperature of the copper melt in the copper melting crucible furnace is maintained at 1250±10℃, and the temperature of the aluminum melt in the aluminum melting crucible furnace is maintained at 800±10℃. The temperature of the aluminum melt when it reaches the internal aluminum melt crystallization space formed by the copper tube that has completed crystallization first should not exceed 800℃. The traction speed of the traction machine continuously pulling out the copper tube is 67±1mm / min, and the flow rate of the cooling water in the second cooling module is controlled at 700±20L / hour. Step 2: Cut the copper-aluminum composite metal rod obtained in Step 1 into short rods according to the set length, and then heat treat the short rods by placing them in a heating furnace and holding them at 300℃ for 45-60 minutes, and then letting them cool naturally to obtain the copper-aluminum composite metal rod. Step 3: The copper-aluminum composite metal rod obtained in Step 2 is machined. A portion of the aluminum on the inner side of one end of the rod is cut away, leaving an aluminum layer of a certain thickness to form the first insertion hole for the core wire of the aluminum cable. The inner aluminum layer and the copper-aluminum composite metal layer at the other end are cut away to form a cavity, leaving only the outer copper layer. Step 4: The copper-aluminum composite metal tube with the first socket and cavity processed in Step 3 is machined to form a U-shaped connection terminal with an open end. A first slot for the connection terminal is formed at one end of the first socket, and a second slot is formed at the cavity end.

[0008] Preferably, in step one, the flow rate of the cooling water in the first cooling module is controlled such that, while meeting the quality requirements for copper crystallization, the temperature of the copper tube formed after the copper liquid crystallizes in the first cooling module does not exceed 800°C.

[0009] Even more preferably, when the molten aluminum enters the internal molten aluminum crystallization space formed by the copper tube, the temperature of the copper tube and the molten aluminum is controlled at 750℃-800℃.

[0010] More preferably, the thickness of the outer copper layer of the copper-aluminum composite metal rod formed in step two is 2.0±0.2mm, the thickness of the copper-aluminum composite metal layer is 200±10μm, and the diameter of the inner aluminum layer is 17.2-18mm.

[0011] More preferably, in step three, the first insertion hole formed by machining may or may not be connected to the cavity.

[0012] More preferably, in step one above, yttrium or lanthanum is added to the copper melt in the copper melting crucible furnace at a weight percentage not exceeding 0.02%; and lanthanum or cerium is added to the aluminum melting crucible furnace at a weight percentage not exceeding 0.02%.

[0013] According to another objective of the present invention, the present invention also provides a method for preparing a connecting module for copper-aluminum cable transition, wherein the method for preparing the connecting module for copper-aluminum cable transition, based on the above-described steps for preparing connecting terminals for copper-aluminum cable connection, further includes: Step 5: Connect and fix the copper cable and aluminum cable to one end of the prepared connector terminal, respectively. Insert the aluminum core of the aluminum cable into the first socket of the connector terminal, and insert the copper core of the copper cable into the second socket. Then, use a crimping method to fix the metal cores of the cables to the connector terminal; and... Step 6: Use injection molding to seal the connecting terminals and the ends of the copper and aluminum cables that are connected and fixed to the connecting terminals to form a connecting module for copper and aluminum cable conversion. The injection-molded insulating plastic block seals the connecting terminals and the ends of the copper and aluminum cables that are connected and fixed to the connecting terminals.

[0014] Preferably, in step five, the core wires of the copper and aluminum cables are connected to the sockets of the connecting terminals using a tight fit.

[0015] Preferably, the diameter of the connecting terminal is greater than or less than the outer diameter of the copper cable and the aluminum cable, so that a stepped structure is formed at the connection between the cable and the connecting terminal, which will form an axial obstruction at this point when the insulating encapsulation block is formed by injection molding.

[0016] The present invention discloses a method for manufacturing copper-aluminum cable adapter terminals for photovoltaic system connections. Designed according to application requirements, the method provides copper-aluminum cable adapter terminals applicable to most photovoltaic systems. Through strict process control, the copper-aluminum composite metal layer of the terminal has sufficient thickness and excellent interfacial bonding strength, meeting the thermal shock resistance requirements for high-current applications. The terminals also exhibit enhanced environmental resistance and aging resistance. Furthermore, the copper-aluminum composite metal rod of the terminal can be a standard component; only the machining dimensions need to be adjusted according to different cable specifications to accommodate various copper and aluminum cable applications. This simplifies component processing and significantly reduces production costs. The resulting copper-aluminum cable adapter module is structurally reliable, high-strength, and possesses excellent insulation and sealing properties, making it easily adaptable to photovoltaic system applications in various working environments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a connection terminal for converting aluminum cables to copper cables in the prior art. Figure 2 This is a schematic flowchart illustrating a method for preparing a connecting terminal for copper-aluminum cable switching according to an embodiment of the present invention. Figure 3 A schematic diagram of the continuous casting equipment structure of a copper-aluminum composite metal rod for preparing a copper-aluminum cable adapter connection terminal according to an embodiment of the present invention. Figure 4 For the reason Figure 3 A schematic diagram of the axial cross section of a copper-aluminum composite metal rod formed by shearing and heat treatment of a copper-aluminum composite metal rod prepared by a continuous casting equipment. Figure 5 To be Figure 4 A cross-sectional schematic diagram of an aluminum-copper composite metal tube formed by machining an aluminum-copper composite metal rod. Figure 6 To be Figure 5 A cross-sectional view of the connecting terminal for copper and aluminum cable conversion of the present invention, formed by shrinking one end of an aluminum-copper composite metal tube. Figure 7 This is a cross-sectional structural schematic diagram of a connecting terminal for copper and aluminum cable switching according to another embodiment of the present invention; Figure 8 for Figure 7 A schematic diagram of the left-hand structure of the connection terminals; Figure 9 This is a schematic flowchart illustrating a method for preparing a copper-aluminum cable adapter connection module according to an embodiment of the present invention. Figure 10 A schematic diagram showing the structure for connecting and fixing copper and aluminum cables to both ends of a copper-aluminum composite metal pipe; Figure 11 This is a schematic diagram of the structure of a connection module for copper and aluminum cable switching according to an embodiment of the present invention. Detailed Implementation

[0018] To provide a further understanding of the purpose, structure, features and functions of the present invention, detailed descriptions are provided below with reference to embodiments.

[0019] A schematic flowchart of a method for preparing a connecting terminal for copper-aluminum cable switching according to an embodiment of the present invention is shown. The method for preparing the connecting terminal includes the following steps: Step 1: Prepare copper-aluminum composite metal rods using continuous casting equipment. See details... Figure 3The continuous casting equipment includes a copper melting crucible furnace 1 and an aluminum melting crucible furnace 11 arranged side by side. Heating blocks 5 and 15 are respectively arranged around the two crucible furnaces. A copper molten gate module 2 is arranged below the copper melting crucible furnace 1, which has an annular copper molten flow channel. The outer mold 4 is arranged below the copper molten gate module 2, and the inner mold 3 is arranged inside the outer mold 4. Its top end abuts against the bottom of the copper melting crucible furnace 1, and its bottom end extends into the interior of the outer mold 4 by a certain distance. In this way, an annular copper molten flow channel is formed between the inner mold 3 and the outer mold 4, which communicates with the annular copper molten flow channel in the copper molten gate module 2, and together they form a copper molten flow channel 9. A first cooling module 6 is arranged around the outer mold 4, and a cooling block is arranged at intervals from the first cooling module 6. The second cooling module 7; an aluminum liquid gating module 12 is provided below the aluminum liquid melting crucible furnace 2, and a flow channel block 10 is provided between the copper liquid gating module 2 and the aluminum liquid gating module 12. A circulating aluminum liquid flow channel 19 is provided inside the aluminum liquid gating module 2, the flow channel block 10, and the inner mold 3; an annular copper metal crystallization zone is formed between the upper parts of the inner mold 3 and the outer mold 4, forming the outer copper metal layer of the copper-aluminum composite metal rod under the action of the first cooling module 6; during forming, the stopper 8 in the copper liquid melting crucible furnace 1 is first opened, and the copper liquid flows from the bottom of the copper liquid melting crucible furnace 1 into the annular copper liquid flow channel 9, cooling and crystallizing in the annular copper metal crystallization zone between the upper parts of the inner mold 3 and the outer mold 4 to form a copper tube, which is then continuously transported by a traction machine along... Figure 3 The arrow points outwards, forming an aluminum metal crystallization zone inside the copper tube, which has already been cast in the lower half of the outer mold 4. Then, the stopper 18 in the aluminum molten metal melting crucible 11 is opened, and the molten aluminum is injected into the copper tube through the aluminum molten metal flow channel 19. Under the action of the second cooling module 7, the internal aluminum metal layer of the copper-aluminum composite metal rod is formed, and a metallurgically bonded copper-aluminum composite layer of a certain thickness is formed between the copper and aluminum metal interfaces. In this application, standard cathode copper is used as the copper raw material; the aluminum content in the aluminum raw material is above 98.5%, including trace amounts of impurity elements such as Fe, Mg, and Zn.

[0020] In the continuous casting process of the copper-aluminum composite metal rods described above, the most critical aspect is to form an aluminum liquid crystallization space inside the copper tube mold after the copper tube mold is completed. That is, the aluminum liquid needs to enter the mold after the copper tube mold is completed to crystallize the inner aluminum metal and the copper-aluminum interface metallurgical composite layer. Therefore, the temperature of the copper liquid, the length of the copper crystallization zone (i.e., the length of the overlapping section of the inner mold 3 and the outer mold 4), the temperature and location of the first cooling module 6, the traction speed of the copper tube, the distance between the second cooling module 7 and the first cooling module 6, and the temperature of the aluminum liquid will all have a substantial impact on the quality of the final continuously cast composite metal rod.

[0021] In this invention, to reduce production costs and ensure that the prepared copper-aluminum cable adapter terminal can accommodate connections of copper and aluminum cables with different diameters, the copper-aluminum composite metal rod prepared in this invention has a diameter of 22mm, an outer copper metal layer thickness of approximately 2mm, and a metallurgically bonded copper-aluminum composite layer thickness of approximately 200μm. Therefore, the aluminum core diameter is approximately 18mm. Considering the need to leave a certain thickness of aluminum metal layer during aluminum core cutting, this copper-aluminum cable adapter terminal can accommodate aluminum busbars with a maximum aluminum core diameter of approximately 16mm and a cross-sectional area of ​​approximately 200 square millimeters. Its maximum current carrying capacity is suitable for distributed photovoltaic power stations of approximately 350KW, which basically meets the needs of most photovoltaic power stations. Thus, by simply adjusting the processing parameters (such as the aluminum core cutting amount and the copper tube shrinkage diameter) during subsequent machining and tube shrinking processes, cable connections suitable for different wire diameters in most photovoltaic power stations can be prepared.

[0022] Based on the above continuous casting product specifications, in step one, the temperature of the copper liquid in the copper melting crucible furnace 1 is maintained at 1250±10℃, and the temperature of the aluminum liquid in the aluminum melting crucible furnace 11 is maintained at 800±10℃. In particular, it is necessary to control the temperature of the aluminum liquid when it reaches the internal aluminum liquid crystallization space formed by the crystallized copper tube through the aluminum liquid flow channel 19, so as not to exceed 800℃. This is because although the copper tube has been crystallized and formed into a copper tube after being cooled by the first cooling module 6, it still has a relatively high temperature. If the temperature of the copper tube and the aluminum liquid is too high, it may cause the aluminum liquid to dope the outer copper tube too deeply or even penetrate the copper tube, making the wall thickness of the copper tube connected to the copper cable after subsequent machining too thin or even completely unusable. Moreover, if the contact temperature between copper and aluminum is too high, brittle compounds will form between copper and aluminum, which will easily lead to a significant reduction in the bonding strength of the interface. However, the temperature cannot be too low either, which will affect the mutual diffusion of copper and aluminum at the copper-aluminum interface.

[0023] During product trial production, it was found that the length of the aluminum crystallization zone, the casting speed of the copper tube, and the cooling water flow rate of the second cooling module 7 significantly affect the quality of the formed copper-aluminum composite metal rod during continuous casting. This includes the thickness, composition, and interfacial bonding strength of the formed copper-aluminum composite layer. Since the continuous casting mold is not easily modified after processing, the lengths of the copper and aluminum crystallization zones are essentially fixed. Therefore, in actual production, the main adjustments are made to the casting speed of the copper tube and the cooling water flow rate. In this embodiment, the length of the copper crystallization zone is designed to be approximately 40 mm, the length of the copper liquid annular channel in the copper liquid gating module 2 is approximately 15 mm, and the length of the aluminum crystallization zone is also designed to be approximately 40 mm. Trial production results show that, under the same cooling water flow rate, a faster casting speed results in a thinner interfacial copper-aluminum bonding layer and a lower interfacial bonding strength. This is because the contact time is short, preventing sufficient mutual diffusion between the copper and aluminum. However, if the casting speed is too slow, excessive copper-aluminum bonding can occur, affecting subsequent use. At the same drawing speed, a higher cooling water flow rate in the second cooling module results in faster cooling and crystallization, leading to a thinner copper-aluminum interface layer. This is because the copper-aluminum bonding time is shorter, resulting in insufficient diffusion. However, the bonding strength at the copper-aluminum interface is improved because the faster crystallization rate refines the grains, leading to better inter-diffusion bonding between copper and aluminum. However, the cooling water flow rate cannot be excessively increased; otherwise, not only will the copper-aluminum composite layer be too thin, but more importantly, casting defects will appear at the copper-aluminum interface. Therefore, ideally, a higher drawing speed should be used while appropriately controlling the cooling water flow rate.

[0024] Because the specific structure and size of the mold, as well as the specific construction, location, size, and flow control of the cooling module, will vary in actual production, the preparation method of this application is mainly based on the dimensions of the copper-aluminum alloy rod designed according to application requirements. The invention aims to achieve its objectives by controlling the crystallization temperature of the material and the copper tube drawing speed (i.e., the crystallization time of the molten metal in the crystallization zone), ensuring that the prepared copper-aluminum alloy rod meets the application requirements of subsequent copper-aluminum cable adapter terminals. For example, regarding the flow control of the cooling water in the first cooling module 6, while meeting the quality requirements of copper crystallization, the temperature of the copper tube formed after the copper liquid crystallizes in the first cooling module should not exceed 800℃. In a preferred embodiment, when the molten aluminum enters the internal aluminum liquid crystallization space formed by the copper tube, the temperature of the copper tube and the molten aluminum is controlled between 750℃ and 800℃. Regarding the flow control of the cooling water in the second cooling module 7, the flow rate of the cooling water should be appropriately controlled while maintaining a high drawing speed, so that the copper-aluminum composite layer of the prepared copper-aluminum composite metal rod has a certain thickness and that the interface bonding strength can withstand the thermal shock when a large current passes through. In a preferred embodiment, for the specifications of the copper-aluminum composite metal rod to be prepared in this application, in order to obtain copper tubes with excellent inner and outer surface quality, the crystallized copper tubes are continuously pulled out by a traction machine at a traction speed of 67±1mm / min, and the flow rate of cooling water in the second cooling module 7 is controlled at 700±20L / hour, so as to obtain copper-aluminum composite metal rods. After slicing the composite rods, the average thickness of the copper-aluminum composite layer is stable at about 200μm.

[0025] Step Two: Cut the copper-aluminum composite metal rod obtained in Step One into short rods according to the set length. Then, heat-treat the short rods by placing them in a heating furnace and holding them at 300℃ for 45-60 minutes, followed by natural cooling to obtain the desired result. Figure 4 The copper-aluminum composite metal rod shown has an outer copper layer 101, an inner aluminum layer 102, and a copper-aluminum composite metal layer 103 in between. The thickness of the outer copper layer 101 is 2.0±0.2 mm, the thickness of the copper-aluminum composite metal layer 103 is 200±10 μm, and the diameter of the aluminum layer 102 is 17.2-18 mm. Heat treatment of the short rod does not significantly change the thickness of the copper-aluminum composite layer, but it can significantly increase the interfacial bonding strength. The interfacial strength of the heat-treated copper-aluminum composite metal rod was tested on a material testing machine, and the average interfacial strength was approximately 45 MPa.

[0026] Step 3: Machining the copper-aluminum composite metal rod obtained in Step 2. See details below. Figure 5A portion of the aluminum on the inner side of one end of the rod is machined away, leaving an aluminum layer of a certain thickness to form a first insertion hole 104 for inserting the core wire of the aluminum cable. The diameter of the first insertion hole 104 can be machined according to the specifications of the aluminum cable used in the actual application. The inner aluminum layer 102 and the copper-aluminum composite metal layer 103 at the other end are machined away to form a cavity 105, leaving only a copper layer 101 of a certain thickness. In this embodiment, the first insertion hole 104 and the cavity 105 may or may not be connected.

[0027] Step 4: Tube Reduction. In a circuit system, under the same current carrying capacity, the diameter of the copper cable core is smaller than that of the aluminum cable core. Therefore, in order to meet the actual application requirements, the copper-aluminum composite metal tube with the first insertion hole 104 and cavity 105 processed in Step 3, which retains only the copper layer 101, needs to be reduced to form a second insertion hole 106 for the copper cable core to be inserted. The diameter of the second insertion hole 106 can be processed according to the specifications of the copper cable used in the actual application.

[0028] Thus, the connecting terminal 100 of this application, which can be used for connecting copper and aluminum cables in photovoltaic systems, is obtained.

[0029] In step one above, during the crystallization process of copper and aluminum metals, the finer the grains, the better the copper-aluminum diffusion effect, and the higher the quality of the formed copper-aluminum composite metal layer. Therefore, in addition to strictly controlling process parameters, rare earth elements that can refine grains can be added to the copper and aluminum liquids to improve the quality of the copper-aluminum composite metal layer. For copper, according to experimental results, adding no more than 0.02% (weight percentage) of yttrium (Y) or lanthanum (La) can not only refine the grains but also improve the conductivity of copper. For aluminum, adding no more than 0.02% (weight percentage) of lanthanum (La) or cerium (Ce) can significantly refine the grains and improve conductivity. The amount of rare earth added should not be too high, otherwise not only will grain growth occur, but some rare earths will also dissolve in the alloy crystals, thereby reducing conductivity.

[0030] In the above embodiments, the prepared connecting terminal is a cylindrical tubular structure. In another embodiment, the connecting terminal can also be prepared as a U-shaped slot-like structure, as shown in the figure. Figure 7 and Figure 8As shown, the processing procedure in step four above is as follows: the copper-aluminum composite metal tube with the first insertion hole 104 and cavity 105 processed in step three is machined to form a U-shaped connection terminal 100' with an open end. A first slot 104' of the connection terminal 100' is formed at one end of the first insertion hole 104, and a second slot 106' is formed at the end of the cavity 105. Specifically, a portion of the material in the copper-aluminum composite metal tube prepared in step three can be removed first, and then a U-shaped structure can be formed by stamping. Then, one end of the cavity 105 can be reduced in diameter to form a smaller-width second slot 106'. Compared with a circular insertion hole, the U-shaped slot makes the assembly of the cable core and the connection terminal easier, but the fixing strength of the core is slightly insufficient. More crimping points can be added during the subsequent crimping of the cable core and the connection terminal to reinforce the structure.

[0031] In the two embodiments of the present invention described above, the prepared connecting terminal is either a cylindrical tubular structure at both ends or a slot-like structure with a U-shaped cross-section at both ends. In another embodiment, it may also be a cylindrical tubular structure at one end and a slot-like structure with a U-shaped cross-section at the other end, which should be considered as an equivalent design to the above embodiments.

[0032] According to another objective of the present invention, the present invention also provides a method for preparing a connecting module for copper-aluminum cable switching, referring to... Figure 9 The method for preparing the connecting module for copper and aluminum cable switching, based on the above-mentioned steps for preparing connecting terminals for copper and aluminum cable connections, further includes: Step 5: Connect and secure the copper cable and aluminum cable to one end of the prepared connector terminal, respectively. (Refer to...) Figure 10 Insert the aluminum core wire 22 of the aluminum cable 20 into the first socket 104 of the connecting terminal, and insert the copper core wire 32 of the copper cable 30 into the second socket 106, then crimp them together, for example... Figure 10 As shown in the diagram, pressure is applied in the direction indicated by the arrow to further secure the metal core of the cable to the connecting terminal; in a preferred embodiment, the core of the copper and aluminum cables is tightly fitted into the socket of the connecting terminal during insertion.

[0033] Step Six: Using injection molding, the connecting terminals and the ends of the copper and aluminum cables connected and fixed to them are sealed to form a copper-aluminum cable adapter module. The injection-molded insulating encapsulation block 40 seals the connecting terminals and the ends of the copper and aluminum cables connected and fixed to them. The completed adapter module can be directly used in the cable connections of photovoltaic systems for connecting copper cables to aluminum cables, copper cables to copper cables, and aluminum cables to aluminum cables.

[0034] For the U-shaped connection terminal of another embodiment, the preparation method of the connection module for copper and aluminum cable conversion using it is the same as the above process, and will not be described in detail here.

[0035] In a preferred embodiment, see Figure 11 In this embodiment, the diameter (outer diameter) of the connecting terminal 100 can be greater than or less than the outer diameter of the copper cable and the aluminum cable. Thus, a stepped structure 41 is formed at the connection between the aluminum cable and the connecting terminal 100 and at the connection between the copper cable and the connecting terminal 100. When the insulating material is injection molded to form the insulating encapsulation block 40, an axial barrier will be formed at this point, which will improve the structural strength of the connecting module and prevent the insulating encapsulation block from loosening from the connecting terminal. The connecting module has a reliable structure, high strength, and excellent insulation and sealing effect, which can be easily adapted to photovoltaic system applications in various working environments, such as windy environments and corrosive environments.

[0036] The present invention discloses a method for manufacturing copper-aluminum cable adapter terminals for photovoltaic system connections. Designed according to application requirements, the method provides copper-aluminum cable adapter terminals applicable to most photovoltaic systems. Through strict process control, the copper-aluminum composite metal layer of the adapter terminal achieves sufficient thickness and excellent interfacial bonding strength, meeting the thermal shock resistance requirements for high-current applications. During application, there is no shear force at the copper-aluminum interface, resulting in stronger environmental resistance and aging resistance, reducing the likelihood of interface failure and subsequent electrical transmission problems. Furthermore, the copper-aluminum composite metal rod of the adapter terminal can be a standard component; only the machining dimensions need to be adjusted according to different cable specifications to accommodate various copper and aluminum cable applications. This simplifies component processing and significantly reduces production costs. The resulting copper-aluminum cable adapter module exhibits reliable structure, high strength, and excellent insulation and sealing performance, making it readily adaptable to photovoltaic system applications in various working environments.

[0037] The present invention has been described in the above-described embodiments; however, these embodiments are merely examples for implementing the present invention. It must be noted that the disclosed embodiments do not limit the scope of the present invention. Conversely, any modifications and refinements made without departing from the spirit and scope of the present invention are within the scope of patent protection of the present invention.

Claims

1. A method for preparing a connecting terminal for copper-aluminum cable transition, characterized in that, The preparation method includes the following steps: Step 1: Prepare copper-aluminum composite metal rods using continuous casting equipment; the continuous casting equipment is a vertical continuous casting equipment, with copper melting crucible furnace and aluminum melting crucible furnace arranged side by side at the top. The outer mold of the cavity is set below the copper molten gate module, and the inner mold of the cavity is set inside the outer mold. A first cooling module is set around the upper part of the outer mold, and the outer copper metal layer of the copper-aluminum composite metal rod is formed under the action of the first cooling module. A second cooling module is set at a distance from the first cooling module at the lower part of the outer mold. During forming, the copper molten metal is first opened for melting. In the crucible furnace, the stopper rod allows molten copper to cool and crystallize in the annular copper metal crystallization zone between the inner and outer molds of the cavity, forming a copper tube. A traction machine continuously pulls out the cast copper tube, forming an aluminum metal crystallization zone inside the already cast copper tube in the lower half of the outer mold. Then, the stopper rod in the aluminum melting crucible furnace is opened, and molten aluminum is injected into the copper tube through the aluminum flow channel. Under the action of the second cooling module, an internal aluminum metal layer is formed on the copper-aluminum composite metal rod, creating a metallurgically bonded copper-aluminum composite layer of a certain thickness between the copper and aluminum metal interfaces. The temperature of the copper melt in the copper melting crucible furnace is maintained at 1250±10℃, and the temperature of the aluminum melt in the aluminum melting crucible furnace is maintained at 800±10℃. The temperature of the aluminum melt when it reaches the internal aluminum melt crystallization space formed by the copper tube that has completed crystallization first should not exceed 800℃. The traction speed of the traction machine continuously pulling out the copper tube is 67±1mm / min, and the flow rate of the cooling water in the second cooling module is controlled at 700±20L / hour. Step 2: Cut the copper-aluminum composite metal rod obtained in Step 1 into short rods according to the set length, and then heat treat the short rods by placing them in a heating furnace and holding them at 300℃ for 45-60 minutes, and then letting them cool naturally to obtain the copper-aluminum composite metal rod. Step 3: The copper-aluminum composite metal rod obtained in Step 2 is machined. A portion of the aluminum on the inner side of one end of the rod is cut away, leaving an aluminum layer of a certain thickness to form the first insertion hole for the core wire of the aluminum cable. The inner aluminum layer and the copper-aluminum composite metal layer at the other end are cut away to form a cavity, leaving only the outer copper layer. Step 4: The end of the copper-aluminum composite metal tube with the first socket and cavity processed in Step 3, which retains only the outer copper layer, is subjected to a tube shrinking process to form a second socket for the core wire of the copper cable to be inserted; in this way, a connection terminal for connecting copper and aluminum cables that can be used in photovoltaic systems is obtained.

2. A method for preparing a connecting terminal for copper-aluminum cable transition, the method comprising the following steps: Step 1: Prepare copper-aluminum composite metal rods using continuous casting equipment; the continuous casting equipment is a vertical continuous casting equipment, with copper melting crucible furnace and aluminum melting crucible furnace arranged side by side at the top. The outer mold of the cavity is set below the copper molten gate module, and the inner mold of the cavity is set inside the outer mold. A first cooling module is set around the upper part of the outer mold, and the outer copper metal layer of the copper-aluminum composite metal rod is formed under the action of the first cooling module. A second cooling module is set at a distance from the first cooling module at the lower part of the outer mold. During forming, the copper molten metal is first opened for melting. In the crucible furnace, the stopper rod allows molten copper to cool and crystallize in the annular copper metal crystallization zone between the inner and outer molds of the cavity, forming a copper tube. A traction machine continuously pulls out the cast copper tube, forming an aluminum metal crystallization zone inside the already cast copper tube in the lower half of the outer mold. Then, the stopper rod in the aluminum melting crucible furnace is opened, and molten aluminum is injected into the copper tube through the aluminum flow channel. Under the action of the second cooling module, an internal aluminum metal layer is formed on the copper-aluminum composite metal rod, creating a metallurgically bonded copper-aluminum composite layer of a certain thickness between the copper and aluminum metal interfaces. The temperature of the copper melt in the copper melting crucible furnace is maintained at 1250±10℃, and the temperature of the aluminum melt in the aluminum melting crucible furnace is maintained at 800±10℃. The temperature of the aluminum melt when it reaches the internal aluminum melt crystallization space formed by the copper tube that has completed crystallization first should not exceed 800℃. The traction speed of the traction machine continuously pulling out the copper tube is 67±1mm / min, and the flow rate of the cooling water in the second cooling module is controlled at 700±20L / hour. Step 2: Cut the copper-aluminum composite metal rod obtained in Step 1 into short rods according to the set length, and then heat treat the short rods by placing them in a heating furnace and holding them at 300℃ for 45-60 minutes, and then letting them cool naturally to obtain the copper-aluminum composite metal rod. Step 3: The copper-aluminum composite metal rod obtained in Step 2 is machined. A portion of the aluminum on the inner side of one end of the rod is cut away, leaving an aluminum layer of a certain thickness to form the first insertion hole for the core wire of the aluminum cable. The inner aluminum layer and the copper-aluminum composite metal layer at the other end are cut away to form a cavity, leaving only the outer copper layer. Step 4: The copper-aluminum composite metal tube with the first socket and cavity processed in Step 3 is machined to form a U-shaped connection terminal with an opening. A U-shaped first slot for the connection terminal is formed at one end of the first socket, and a U-shaped second slot is formed at the cavity end.

3. A method for preparing a connecting terminal for copper-aluminum cable transition as described in claim 1 or 2, characterized in that, In step one, the flow rate of the cooling water in the first cooling module is controlled to ensure that the temperature of the copper tube formed after the copper liquid crystallizes in the first cooling module does not exceed 800°C, while meeting the quality requirements of copper crystallization.

4. The method for preparing a connecting terminal for copper-aluminum cable transition as described in claim 3, characterized in that, When the molten aluminum enters the internal aluminum crystallization space formed by the copper tube, the temperature of the copper tube and the molten aluminum is controlled at 750℃-800℃.

5. The method for preparing a connecting terminal for copper-aluminum cable transition as described in claim 4, characterized in that, The outer copper layer of the copper-aluminum composite metal rod formed in step two has a thickness of 2.0±0.2mm, the copper-aluminum composite metal layer has a thickness of 200±10μm, and the inner aluminum layer has a diameter of 17.2-18mm.

6. The method for preparing a connecting terminal for copper-aluminum cable transition as described in claim 5, characterized in that, In step three, the first insertion hole formed by machining may or may not be connected to the cavity.

7. A method for preparing a connecting terminal for copper-aluminum cable transition as described in claim 1 or 2, characterized in that, In step one above, yttrium or lanthanum with a weight percentage not exceeding 0.02% is added to the copper melt in the copper melting crucible furnace; and lanthanum or cerium with a weight percentage not exceeding 0.02% is added to the aluminum melting crucible furnace.

8. A method for preparing a connecting module for copper-aluminum cable switching, characterized in that, The method for preparing the connecting module for copper and aluminum cable transition includes the method for preparing the connecting terminal for copper and aluminum cable transition as described in any one of claims 1-7, and the following steps: Step 5: Connect and fix the copper cable and aluminum cable to one end of the prepared connecting terminal respectively. That is, insert the aluminum core wire of the aluminum cable into the first socket of the connecting terminal, insert the copper core wire of the copper cable into the second socket, and then fix the metal core wire of the cable to the connecting terminal by crimping. as well as, Step 6: Use injection molding to seal the connecting terminals and the ends of the copper and aluminum cables that are connected and fixed to the connecting terminals to form a connecting module for copper and aluminum cable conversion. The injection-molded insulating plastic block seals the connecting terminals and the ends of the copper and aluminum cables that are connected and fixed to the connecting terminals.

9. The method for preparing a connecting module for copper-aluminum cable switching as described in claim 8, characterized in that, In step five, the core wires of the copper and aluminum cables are tightly fitted into the sockets of the connecting terminals.

10. The method for preparing a connecting module for copper-aluminum cable switching as described in claim 9, characterized in that, The diameter of the connecting terminal is greater than or less than the outer diameter of the copper cable and the aluminum cable. This creates a stepped structure at the connection between the cable and the connecting terminal, which will form an axial obstruction at this point when the insulating encapsulation block is formed by injection molding.

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