Cable Lugs & Connectors
Aluminium cable onto a copper terminal — a CUPAL washer in the bolted joint, or a CUPAL plate between lug and bar.
The problem you need to solve
Wherever an aluminium cable meets a copper terminal — in a distribution board, an MCC, a substation — a bolted joint carries the current at the cable end. The IEC 61238 type tests (class 1-3: thermal cycling and short-circuit) expose the weakness: at an Al/Cu interface, the difference in thermal expansion (Al 23.1, Cu 16.5 µm/m·K) drives microslip inside the bolted joint, the oxide layer builds year after year, contact resistance rises. The classic workaround is manual antioxidant paste. But paste dries, gets skipped under time pressure, or goes on top of a degraded layer — the application is not consistent. And the crimp die on site is not always the same across an 8-die kit covering 16–300 mm²; picking the wrong one is a well-known source of failed terminations.
How CUPAL solves it
A CUPAL washer sits inside the bolted joint between the lug and the bar: the Al face meets the aluminium bar, the Cu face meets the copper lug. No paste, no dissimilar-metal contact inside a single bolted joint. In the IEC 61238-1-3 class 2b thermal cycling test (20 cycles from –10 to +90 °C) the bond-style interface drifts well inside the standard's 5 % tolerance on contact resistance. For cabinets with many cable ends and varied geometries, a custom CUPAL plate can replace a complex set of specialty lugs with a single plate matched to the panel's bolt pattern. EN 10204 2.2 with every shipment, 3.1 on request.
What it's designed for
Typical Al/Cu cable-lug joints
Four points where a CUPAL washer or transition plate saves daily time.
Al overhead service line → Cu service panel
The problem you need to solve. A LV aluminium service line lands on the copper busbar of a utility or commercial service panel. Outdoor, damp environment; without paste, visible corrosion appears within 2–3 years.
How CUPAL solves it. A CUPAL washer in the cable-lug-to-busbar bolted joint. Al face to the bar, Cu face to the lug. Standard tools, no paste.
MV Al cable → Cu switchgear bar
The problem you need to solve. A 6–30 kV aluminium cable, 95–300 mm², terminates onto the internal copper bar through a bolted lug. Multiple die sizes, variable paste application, inconsistent installation quality.
How CUPAL solves it. A CUPAL transition plate between lug and bar. The lug is crimped onto the Al cable in the usual way; the Cu face meets the bar through the plate — no direct Al/Cu contact.
PV / BESS DC disconnect: Al cable → Cu switch
The problem you need to solve. A 600–1500 VDC, 200–630 A DC system runs aluminium cable to the copper terminals of a DC disconnect switch. Tin-plated Cu versus bare Al surface finish friction differs; thermal cycling drives fretting corrosion, resistance creeps.
How CUPAL solves it. A CUPAL washer with a tin-plated Cu face to the switch terminal and Al face to the lug. Consistent surface behaviour; stable across the IEC 61238 class 2b cycle.
Distribution transformer Al auxiliary feeder → Cu bonding bar
The problem you need to solve. 0.4 kV, 50–120 mm² aluminium auxiliary cable terminates onto the transformer's copper bonding bar. Field crimping, variable tools, inconsistent paste — loose joints and hotspots in a few years.
How CUPAL solves it. A CUPAL washer in every Al/Cu bolted joint. The lug is crimped with the usual tool, the bimetal function lives in the washer — simple, inspectable, paste-free.
FAQs from contractors
Recommended CUPAL products
Applicable standards for this field
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