Overview
Bare stranded copper wire is an uninsulated conductor made by twisting multiple thin copper strands into a single flexible cable. It is a staple in electrical and industrial applications due to copper's exceptional electrical conductivity (second only to silver) and mechanical durability. The stranded design enhances flexibility compared to solid-core wires, making it ideal for installations requiring bending or vibration resistance. Common standards include ASTM B1 (hard-drawn) and B3 (soft-drawn), with variations in strand count (e.g., 7, 19, or 37 strands) to balance flexibility and strength.
Structure and Working Principle
The wire consists of multiple copper strands concentrically layered around a central core. Stranding reduces skin effect (uneven current distribution at high frequencies) and improves fatigue resistance. Copper's low resistivity (1.68×10⁻⁸ Ω·m at 20°C) ensures minimal energy loss during current flow. The absence of insulation allows direct contact with connectors or grounding rods, though it requires careful handling to prevent short circuits.
Key Features
High conductivity (≥100% IACS for pure copper) ensures efficient power transmission. The stranded structure provides 20-30% greater flexibility than solid wire of equivalent cross-section. Corrosion resistance is achieved through natural oxidation, forming a protective patina. Optional tinning (tin-coated copper) is available for harsh environments. Tensile strength ranges from 200-400 MPa, depending on temper (hard-drawn vs. annealed).
Application Areas
Primary uses include overhead power lines (as part of ACSR cables), grounding electrodes, and industrial busbars. It’s also used in transformer windings and lightning protection systems. In renewable energy projects, bare stranded copper connects solar panel arrays due to its UV resistance. Automotive applications include battery cables and chassis grounding, where flexibility is critical.
Maintenance and Precautions
Inspect regularly for corrosion, especially in saline or acidic environments. Clean oxidation with a wire brush or antioxidant paste if contact resistance increases. Avoid installation near alkaline materials (e.g., concrete without protective coatings) to prevent chemical degradation. Use proper tensioning tools to prevent strand breakage during installation.
B2B Procurement Guide
Specify strand count (e.g., 19-strand for moderate flexibility), copper grade (C11000 for 99.9% purity), and temper (annealed for easy bending). Confirm compliance with standards like ASTM B1 or IEC 60228. Bulk buyers should request mill test reports for conductivity verification. Consider tinned variants for marine applications. MOQs typically start at 100kg, with price breaks at tonnage quantities.