Electrical Conductivity – The Electrical conductivity of aluminum is roughly 60% of copper. The resistivity of aluminum is 1.64 times that of copper. Comparing a copper bus bar carrying 1000 amps of current and having a cross sectional area of 1 square inch (4” x ¼”) to an aluminum bus bar needing to carry the same load current. The aluminum bus bar would need to have a cross sectional area of 1.64 square inches (5” x 3/8”). Considering that applications generally require both charge and return bus bars it is easy to see how space and airflow characteristics of the equipment may be influenced by the use of aluminum.
Thermal Conductivity – Aluminum has a thermal conductivity that varies from 62% for soft aluminum to 33% for hard (7075 T-6) of what copper is. Again this could influence the space and airflow characteristics of the equipment.
Creepage – Aluminum will creep approximately 25% to 33% more than copper during thermal cycling from changes in environment or load conditions. This causes aluminum connections to loosen over time creating resistance and therefore heat and eventual failure. Copper connections tend to stay tight.
Oxidizing – Aluminum readily oxidizes when exposed to air. A hard oxidation layer quickly forms an electrical insulating barrier on the surface. Copper also oxidizes in open air; however the oxidation is soft and conductive.
Copper Lugs - Copper lugs are the industry standard for connections. Copper lugs mated to an aluminum bus bar are susceptible to accelerated corrosion and an increase in resistivity. Even if the lugs have tin plating and oxide reducers are used at connection interfaces, increased resistivity is a byproduct of both corrosive environmental exposure and high current applications.
Cost – With copper being approximately 2 to 3 times the cost per pound of aluminum it is at first glance easy to see why it would make sense to use aluminum whenever possible as a substitute for copper. This is especially true for applications where space is available for the increased bus bar size. However there must be careful design considerations made when making this choice. Factors such as working environment, product reliability, service lifetime, and scheduled maintenance all are critical factors that must be looked at when considering using an aluminum bus bar.
For additional information regarding the price and operational factors involved with using Aluminum Bus bar, please contact us toll free at 800-394-4804.
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