High-Current Flexible Busbar

Each laminate is 1 mm thick; standard length is 3 m (9.84 ft). Ampacity depends on the permitted temperature rise above ambient: 30, 45 or 60 C. Pick the stack by your rated current and allowed rise.

A flexible busbar only earns its name if the stack can move. The PVC jacket is moulded so it touches under 20% of the copper surface - the rest stays free to slide between layers - which is also how the bar accepts tight site bends without fatigue. Because the ends are bare, drilled and bolted through the laminate stack, no cable lugs appear in the joint, cutting install time and removing the lug as a failure point. Every unit leaves the plant after a 100% hi-pot dielectric test and a UL 758 cold-bend check at -40 C, and the printed jacket code traces the lot. See also our flexible busbar design notes and the wider ampacity reference.

A solid copper bar costs less per amp but fights thermal expansion, vibration and mounting misalignment; a flexible laminated bar absorbs all three, which is why drives, transformer leads and rail equipment specify it. Where flexibility plus PVC insulation is the whole requirement, the adjacent flexible insulated busbar range shares the same laminate construction; where the bar must stay phase-isolated to ground, look at insulated copper busbars. Heat rejection across the thin sheets is covered in thermal management of busbars.

A high current flexible busbar is two material systems at once: the tinned laminate that conducts, and the PVC jacket that holds the stack together without locking it. The report below compiles the typical material figures both systems are quoted from.

Compliance wording here stays at the material level: the PVC jacket is self-extinguishing to UL 94 V-0 as a material, and RoHS is baseline on every lot. We do not list a named third-party certification number for the finished bar in this document; request the test and lot records when you need them. The tinned sheets themselves sit at electrolytic copper conductivity, and tinning protects the cut edges from oxide that would otherwise add joint resistance. The welded ends are bulk copper rather than folded sheet, so the bolted joint sees the same contact face it would see on a rigid bar - installers do not change their torque habits. Design context for the laminate build is in flexible busbar design notes.

Specifying the bar on the first pass takes three inputs: the current, the motion and the joint. The table turns each input into the drawing note we need to quote.

1. State the continuous load current and the short-time fault duty, then pick a rise band - 30, 45 or 60 K - from the flexible busbar ampacity chart.
2. Describe the bend envelope: fixed bend radius, number of bends, and whether the bar must twist during install.
3. Give the end hole pattern: stud size, hole spacing and the torque class of the equipment bolts.

The stack-and-width answer from step one is only the first pass: inside a tight cubicle the rise band tightens, and parallel runs share heat rather than fresh air. Transformer and switchgear leads usually land near the top of the range; consult the flexible busbar guide for the motion and jacket rules before freezing the drawing. Long runs bend on site only once: the factory pre-sets the main bend plane, and the install absorbs the last few millimetres of offset at the bolted ends. If the duty includes frequent short overloads, budget the layer count from the RMS current rather than the peak: the thin sheets shed heat fast, but the average loss still sets the steady rise.