As a high-performance power transmission device, the composite shielded insulated tubular busbar body's bonding process between its composite layers directly determines the product's electrical performance, mechanical strength, and long-term operational reliability. Its core process revolves around the composite of the conductor, insulation layer, shielding layer, and outer sheath, achieving a tight bond between each layer through material selection, process control, and structural design.
The conductor, as the current carrier, is typically made of highly conductive copper or aluminum tubing. Before lamination, the conductor surface must be pre-treated. Mechanical grinding removes oxide layers, burrs, and pits, followed by cleaning the surface with anhydrous ethanol to ensure no dust, water stains, or oil residue remains. This step provides a clean and smooth substrate for subsequent interlayer bonding, preventing impurities from affecting the adhesion. For example, in one patented technology, the conductor surface roughness is significantly reduced after high-speed belt abrasion, creating ideal conditions for the encapsulation of rubber-based insulation layers.
The insulation layer of the composite shielded insulated tubular busbar body is a key functional layer of the composite structure, requiring high withstand voltage, low dielectric loss, and excellent aging performance. Common materials include polytetrafluoroethylene (PTFE), ethylene propylene diene monomer (EPDM) rubber, and silicone rubber. The bonding process between the insulation layer and the conductor primarily involves co-extrusion or wrapping. Co-extrusion involves multiple extruders operating simultaneously to sequentially wrap the conductor shielding layer, insulation layer, and insulation shielding layer onto the conductor surface. The layers bond at the molecular level through melt plasticization, eliminating gaps or air bubbles. For example, one patented invention uses a three-layer co-extrusion technology to sequentially form the conductor shielding layer, insulation layer, and insulation shielding layer on the conductor surface. The thickness of each layer is precisely controlled by the screw speed and traction speed to ensure bonding strength and insulation performance. The wrapping process involves semi-overlapping semiconductor paper or PTFE film around the conductor surface to form a uniform capacitance layer, followed by hot pressing or vacuum impregnation to ensure a tight bond between the wrapping layer and the conductor.
The shielding layer is divided into inner shielding and outer shielding. The former is used to equalize the electric field on the conductor surface, while the latter is used to suppress external electromagnetic interference. The inner shielding layer typically uses semiconductor materials, such as a mixture of EVA and EPDM rubber, which is directly wrapped onto the surface of the insulation layer through a co-extrusion process to form a smoothly transitioned electric field distribution. The outer shielding layer uses metal strips, such as copper or aluminum strips, which are wrapped around the insulation shielding layer through a coating process and then fixed by welding or crimping to ensure a reliable connection with the grounding system. For example, in a fully shielded composite insulated copper tube busbar, the outer shielding layer uses a composite structure of braided copper mesh and aluminum foil, which reduces the resistance value and improves anti-interference performance.
The outer sheath, as the outermost layer of the composite structure, needs to have weather resistance, flame retardancy, and mechanical protection functions. Common materials include polyolefins, heat-shrink tubing, and epoxy resin. The bonding process between the outer sheath and the shielding layer is mainly heat shrinking or injection molding. The heat shrinking process shrinks the heat-shrink tubing by heating, tightly wrapping it around the shielding layer to form a seamless protective layer; the injection molding process injects molten epoxy resin or polyolefin into a mold, integrally forming it with the shielding layer and improving overall mechanical strength. For example, a certain tubular busbar uses a polyolefin polymer insulation sheath, which is combined with a metal shielding layer through injection molding, achieving an IP54 protection rating and effectively preventing dust and moisture intrusion.
The quality control of interlayer bonding needs to be maintained throughout the entire production process. For example, in the co-extrusion process, the temperature, screw speed, and traction speed of each extruder layer must be precisely matched to avoid material decomposition due to excessive temperature or interlayer delamination due to speed differences. In the wrapping process, wrapping tension, overlap rate, and hot-pressing parameters must be strictly controlled to ensure a smooth and wrinkle-free wrapping layer. Furthermore, interlayer interface treatment is also crucial; for example, coating with coupling agents or performing plasma treatment can enhance the surface activity of the material and strengthen the interlayer bond strength.
The interlayer bonding process of a composite shielded insulated tubular busbar body is a complex process involving multiple stages and parameters requiring coordinated control. From conductor pretreatment to outer sheath molding, each process must take into account both material properties and process requirements. Through the combined application of technologies such as co-extrusion, wrapping, coating and heat shrinking, a tight bond and functional synergy between the layers are achieved, ultimately giving the product excellent electrical performance and mechanical reliability.
