Busbars
Short-circuit-rated Cu/Al transitions — cut precisely to your busbar geometry.
The problem you need to solve
One of the classic points in industrial power distribution where the aluminium riser busbar meets the copper collector busbar — in a transformer substation, a factory main distribution board, or a data centre PDU. Two loads act on this bolted transition simultaneously: stable contact behaviour expected over 10 years of operation per IEC 61439-6, and the short-circuit mechanical impulse per IEC 60865-1 which puts a force F ≈ 0.2 × Ip² / d on the busbar gaps. Because of the different thermal expansion coefficients of Al and Cu, the bolted joint enters micro-sliding, an oxide layer grows, and contact resistance creeps upward over many years. Under a fault, maximum mechanical stress appears precisely where corrosion has already added resistance.
How CUPAL solves it
A CUPAL transition segment (3–10 mm thick, cut to custom geometry) replaces the conventional compression bimetal lug or pasted bolted lug system. One piece of material, each side in contact with its own metal, the Al/Cu interface diffusion-bonded — no oxide enters the joint during operation. Mechanically, the bond is distributed over the full surface, not concentrated at the bolt hole; it does not loosen or develop micro-gaps under a short-circuit impulse. The copper busbar current density (per IEC 61439 / DIN 43671: 1.2 A/mm²) is maintained — the Al busbar does not need to be oversized by 33%, because the joint serves on the Cu side. Material certificate: EN 10204 2.2 standard, 3.1 on request.
Designed for
Where it's used
Four specific industrial points where the busbar transition is critical.
MV/LV transformer substation Al riser → Cu busbar
The problem you need to solve. On the LV side of an MV/LV transformer, the aluminium riser meets the copper busbar. Short-circuit current 25–50 kA, the impulse force between busbars concentrates on the bolted joint.
How CUPAL solves it. CUPAL busbar segment (e.g. 50×10 mm profile with M12 hole) between the riser and the busbar. The diffusion bond distributes the mechanical impulse across the full surface.
Data centre PDU branch: Cu trunk → Al branch
The problem you need to solve. Row-level power distribution: horizontal copper busbar (e.g. 60×10 mm) and vertical Al branch at the rack. 24/7 thermal cycling + 100+ A/ms dI/dt on UPS switchover; Al/Cu joint bolts lose preload within a few years.
How CUPAL solves it. CUPAL branch segment between the trunk and the vertical Al busbar. Contact resistance doesn't creep up, PDU load balancing stays stable.
Factory main distribution board Al parallel conductor → Cu main busbar
The problem you need to solve. Large facilities draw 1000–2000 A; three-phase Al cable(s) or Al busbar connects to the Cu main distribution board. The bolted joint loosens over 10+ years under thermal cycling + transient currents, contact resistance creeps.
How CUPAL solves it. Custom-size CUPAL transition block matching the cable entry and busbar hole pattern. Stainless bolt, no paste; Al oxide can no longer grow at the interface.
Old transformer substation retrofit without dismantling
The problem you need to solve. In a 1990s industrial distribution substation, the Al riser remains in place but the contact point has crept to 10+ mΩ. The joint must be brought back within IEC 61439 tolerance without full dismantling.
How CUPAL solves it. CUPAL sheet cut from DXF of on-site measured geometry — bolted replacement for the original pasted joint. No dismantling, no structural modification.
Compared to alternatives
Four common busbar transition solutions — on a multi-joint industrial distribution board.
| Solution | Long-term contact | Maintenance | Lead time | 10-year TCO / transition |
|---|---|---|---|---|
| Bolted Al/Cu + oxide-inhibiting paste | Deteriorates over time | Re-torque + paste every 2 years | From stock | High (labour hours) |
| Special bimetal busbar (imported) | Stable | None | 8–16 weeks, fixed geometry | High |
| Full copper busbar (Al-free) | Excellent | None | 4–6 weeks | High (weight + material price) |
| CUPAL custom cut | Stable | None | 2–4 weeks, any geometry | Low |
Common questions from industrial engineers
Recommended CUPAL products
Applicable standards for this field
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