A Comparison of Aluminum vs. Copper as Used in Electrical Equipment

The debate over the pros and cons of aluminum vs. copper conductors has been discussed for many years. Many of the concerns are based on old information and also misinformation. These concerns center on the very different properties of the two materials and their suitability for application within the Electrical Equipment Industry. Reliable performance from the conductors, the joints and terminations of the conductors is essential to the operation of the electrical system. With the recent increases in the cost of copper, customers are seeing these increases passed on to them by the equipment manufacturer. The variance in cost between equipment with copper versus aluminum conductors is now affecting the customer’s buying decision. This paper provides a comparison of the mechanical and electrical properties of copper (Cu) and aluminum (Al) and their relevance as applied to electrical distribution products. The offerings and impact of Cu and Al on various pieces of equipment is also discussed. The intended purpose is to provide the user with the information necessary to make an informed decision on the selection of copper or aluminum conductors within electrical equipment. INTRODUCTION Cu and Al are the two most commonly used materials for conductors and bus bars in electrical equipment. Each has positive and negative characteristics that affect their use in various applications. Both materials have been in continuous use in the electrical industry for many years. While aluminum is the most abundantly available of the two metals, the demand and scarcity of Cu have caused its cost to fluctuate widely. Silver is generally considered the best electrical conductor, however its high cost and low strength limits its use to special applications such as joint plating and sliding contact surfaces. For the purposes of this paper, the areas of discussion are: Current Carrying Capacity, Conductivity Physical Properties a. Expansion b. Weight c. Tensile Strength Connections and Terminations Plating and Environmental Concerns Product Offerings Cost Comparison Impact on Various Pieces of Equipment CURRENT CARRYING CAPACITY The electrical and mechanical properties of a material are dependent on its alloy. For the comparison between copper and aluminum in this paper, the copper is cold-worked electrolytic tough pitch copper similar to ASTM B187, alloy UNC C11000. The copper used in electrical equipment is nominally pure 98% conductivity commercially hard based on the International Annealed Copper Standard (IACS). Pure Aluminum is not used as an electrical conductor in equipment since it is too soft for mechanical assemblies and is thus alloyed with other materials. The Al alloy 1350 used prior to 1975 was designated as EC (Electrical Conductor) grade aluminum with a 99.50% aluminum content. Even though it has 61% the conductivity of Cu it lacked in mechanical properties making it less than ideal as a conductor in the equipment. Al alloy 6101 is the predominant aluminum bus bar material being utilized and is stronger than 1350 Al because it has been hardened by heat treatment, but it only has 56% the conductivity of copper. The reduced conductivity of AL 6101 does not mean that the Al conductor will run hotter than the Cu