When two dissimilar metals come in contact with each other, it causes a ‘dissimilar metal corrosion or ‘galvanic action’. The aluminium cable and the copper lug barrel are two different metals when a copper lug is used for connecting the aluminium cable, hence the galvanic action occurs.
To prevent this dissimilar contact, Bi-Metallic lugs are used. The aluminum barrel will be in contact with the aluminium cable and the copper (forged flat palm with a hole) will be in contact with the copper busbar. Further, the aluminium barrel is friction-welded to the copper palm for a better transition between the barrel and palm. This way, galvanic corrosion is avoided and a technically sound and durable joint is achieved.
Manufacturing:
There are various ways to manufacture bimetallic lugs.
In one method, the electrolytic forged copper palm is friction-welded to the electrolytic aluminium barrel. In this method, copper and aluminium molecules are bonded together to create a strong and durable joint. Similarly, the aluminium and copper cables are joined using bi-metal in-line connectors ─ an aluminium barrel is provided for the aluminium cable, while a copper barrel is provided for the copper cable. Both parts (copper and aluminium) are friction-welded. The in-line connectors, pin-type connectors, etc. are manufactured based on the application of bi-metal terminals. Different combinations of bi-metallic compression joints are also available. These are designed and manufactured as per the distinct current carrying capacity of different types of cables.
For reducing contact resistance and corrosion the aluminium barrels are chemically treated; they are then filled with corrosion inhabitant to prevent oxidation of exposed surface (i.e., conductive type grease with a high dripping point) and then barrel ends are capped to avoid ingress of dust.
Application:
Bimetallic lugs are used most when aluminium cables need to be terminated to the copper bus bar or copper contact. It is safe and low cost. The single-hole Bimetallic Lug is used to terminate aluminium conductors onto copper bus bars in electrical applications, control panels, switchgear, combiner boxes in Solar Plants, etc.
Types of Bi-metallic Lugs & Connectors:
AXIS manufactures various types of Bi-metallic lugs and connectors and also offers customized products based on client specifications. For example, if the buyer needs additional combinations, the following can be manufactured-
1. Bi-metallic lugs – Aluminium barrel with copper palm (with single, double, or four holes)
2. Bi-metallic lugs with copper washer (Aluminium lug with copper washer)
3. Bi-metallic lugs reverse type (Copper barrel with aluminium palm)
4. Bi-metallic connectors – Straight type (for the same cross-section of Al & Cu cables)
5. Bi-metallic connectors – Reducing type (for different cross-sections of Al & Cu cables)
6. Bi-metallic connectors – Pin type (Aluminium barrel with solid copper pin)
