Low-voltage busbar connection bolts

Low-voltage busbar connections typically require high-strength steel bolts (class 8.8), proper washers, and specified torque values to ensure electrical and mechanical reliability.Bolt Material and TypeFor low-voltage busbar connections, class 8.8 steel bolts are commonly recommended, especially when connecting copper busbars (Cu ETP-NFA51-100) to devices like Masterpact NW circuit breakers, ensuring sufficient mechanical strength and electrical conductivity . Stainless steel bolts (A2 or A4) may be used in cases where corrosion resistance is critical, but they have higher resistivity and may carry less current, potentially affecting temperature rise and short-circuit test results . Mild steel bolts are acceptable in non-corrosive environments where eddy current heating is not a concern .Washers and TorqueBelleville washers or spring washers are recommended to maintain consistent clamping force and prevent loosening under thermal cycling or vibration . Correct torque values are essential to ensure proper electrical contact and mechanical stability. Torque specifications vary depending on bolt size and busbar material, but following manufacturer guidelines (e.g., Schneider Electric) ensures compliance with tested assemblies .Compliance with StandardsBusbar assemblies and their connections must comply with IEC 61439, which defines design verification, thermal performance, and mechanical integrity for low-voltage switchgear and control gear assemblies . Key considerations include:Thermal limits: Busbar connections must withstand maximum working load temperatures, typically up to 140°C for copper busbars .Mechanical integrity: Bolts and connections must maintain structural stability under short-circuit forces and vibration .Corrosion resistance: Materials should be selected based on environmental exposure to prevent degradation .Electrical performance: Connections must ensure low contact resistance to avoid excessive heating and energy loss .Practical RecommendationsUse high-strength steel bolts (class 8.8) for standard low-voltage busbar connections.Consider stainless steel bolts only if corrosion is a concern, but verify that the assembly has been tested with these bolts.Always use Belleville washers to maintain clamping force.Follow manufacturer-specified torque values to ensure proper electrical and mechanical performance.Ensure all materials and assembly practices comply with IEC 61439 for safety, thermal performance, and short-circuit withstand capability. By adhering to these requirements, low-voltage busbar connections will maintain reliable electrical contact, mechanical stability, and compliance with international standards.