Mechanical lugs are connectors that are used to connect power cables together, and they form an important part of a home electrical system. Mechanical lugs are available bolted with two screws or with four screws. They are typically ring shaped and are usually made of high-grade electrolyte copper or aluminum. They are suitable for big wires and electric cables and are available in three varieties: plain type, sight hole type (which is similar to the plain types, but with a bigger hole), and the connector type.
Mechanical lugs are suitable for brass lightning protection and where there may be plenty of vibration. These are also designed to be corrosion and abrasion resistant. The EX Burndy mechanical lugs act as conductors made with aluminum or copper. They can be single hole, double hole, or stacked with screws.
The history of aluminium lugs goes back to the early days of the 1960s. Back then, aluminum wires were being used generously in almost every home wiring system. Since the electrical wires were made of aluminum, it only became logical that the electricians would use aluminum lugs at the connection junctions.
Unfortunately for the electricians, they ran into a lot of problems about cable wire terminal. Connections were always broken at these junctions where aluminum lugs were being used, and as a result of this, electrical fires started occurring frequently. Electricians did not know why this was happening, because they thought aluminum is a very good conductor of electricity and they had been using it for a while.
When the fire happens frequently, a research finally revealed that aluminum lugs were the source of the problem. One of the problems was the formation of aluminum oxide which led to a large percentage of fires. The problem persisted even after trying a variety of combinations. Eventually, it was found that aluminum simply isn't the right metal for electrical wiring, and then copper used widely as a more effective replacement.
The great thing about using copper for lugs is that it overcomes all the problems that are found in aluminum lugs. The key to improved safety with copper lugs has something to do with the "co-efficient of thermal expansion". A higher co-efficient indicates greater risk of fire, and copper has an extremely low co-efficient of thermal expansion. Aluminum is a much cheaper metal than copper, so copper lugs and wiring can cost quite a bit more than aluminum ones. That is probably one of the main reasons why, back in the 1960s, manufacturers went with aluminum wiring before shifting to copper, and why aluminum lugs are sometimes used in wiring even today.
As far as functionality goes, they both serve similar purposes. The main difference between aluminum and copper is that aluminum is cheaper but causes problems, while copper is good but comparatively very expensive. The lure of the low cost of aluminum continues to drive electrical manufacturers to use aluminum wiring. However, accessories similar to aluminum have now been invented, and it is as safe as copper lugs. Bimetallic lugs are mostly useful where an aluminum cable has to be terminated by a copper bus bar or copper contact. If cable lugs of only copper or aluminum are used , a galvanic action occurs due to dissimilar contact. The use of bimetallic lugs thus ensures a technically sound and durable joint.
Different types of electric fittings offer different conductivities. Choosing the right cable accessories (such as switchgear, power lines, electrical insulator) can help prevent fire or electric shock accidents.