Busbars are used for the distribution of power from a supply point to a variety of output circuits in electrical installations. They can be used in a range of applications ranging from vertical risers and carrying current to each floor of a multi-story building, to bars used entirely within a distribution panel or in an industrial process.
Temperature rise due to energy losses, energy efficiency, and lifetime cost, short-circuit current stresses and protection, joining methods and performance, and maintenance are the issues that need to be addressed in the design of busbar systems.
With regard to busbar materials, the properties of conductive material are necessary in order to achieve a long and stable service life at the minimum lifetime cost. These include low electrical and thermal tolerance; high mechanical resistance in stress, compression, and shear; high resistance to fatigue failure; low electrical resistance of surface films; ease of fabrication; high corrosion resistance; and reasonable first cost and high potential recovery value.
As a result, busbars are usually made of either aluminum or copper. Copper with high conductivity (HC) is far superior to aluminum for conductivity and strength. Higher density, which results in higher weight, is the only disadvantage of copper.
Compared to aluminum, the greater hardness of copper gives it better resistance to mechanical damage, both during erection and in service. Because of cold metal movement under the continuous application of high contact pressure, copper bus bars are also less likely to develop issues in clamped joints.
The higher copper elasticity module gives it higher beam stiffness compared to the same-dimensional aluminum conductor. The temperature variations in-service conditions require a certain amount of flexibility to be permitted in the design. The lower linear expansion coefficient of copper reduces the required degree of flexibility.
However, there are inherent joint and corrosion problems associated with contacts between dissimilar metals, such as between an aluminum busbar and terminals and switch contacts, which are usually always produced from copper or copper alloy. The root of the problem is that an exposed aluminum surface quickly forms an aluminum oxide hard-isolating film. On the other hand, the oxide film forming on the copper surface is conductive, which is another reason to use copper as a material for busbars rather than aluminum.
For control panels and switchboards, where the design requirements differ significantly from long vertical and horizontal busbars, the use of busbar profiles is growing. This is a growing market as busbar profiles offer distinct benefits such as material savings, lower assembly time, lower complexity and lower scrap.
Having said that, due to technical limitations, including more complex design, more intricate machine set-up, a more delicate production process, and more complicated packaging, profiles are more difficult and expensive to produce than flat bars. Such restrictions are now largely under control, however, and several manufacturers are currently producing hundreds or even thousands of different shapes for electrical applications. Many electrical parts, which are often cut from sheet metal, can be produced economically by cutting the profiled bar.
There are a number of benefits associated with the use of profiles, such as reduced skin impact, weight and cost savings, streamlined fixing and mounting, intellectual integrity preservation, and achievable economic benefits. In practice, certain key design concerns are to be avoided during the production process, such as sharp corners, deep narrow channels, and hollow chambers.
As far as ASTM B187 Copper Bus Bar joints are concerned, there are two types of joints: linear joints needed to assemble manageable lengths into the installation, and T-joints needed to make tap-off connections. Joints need to be mechanically solid, environmentally tolerant, and have low resistance that can be sustained throughout the load cycle and throughout the joint life.