General Information About Busbar Systems
Friday, March 10, 2023
Today, one of the two metals is preferred as a conductor in busbar systems. These are copper or aluminum. All other properties other than weight are why copper is preferred as a better conductor. In addition, due to the higher current carrying capacity in lower sections than aluminum, the space needed for the distribution bus can be saved by using copper busbars, which is an important feature.
General Parameters to be Considered in the Design of the Busbar
When designing a busbar set, the designer must consider many parameters;
Electrically; A bar or set of busbars must be of the appropriate capacity for the desired current and must be taken into account that it will cause a voltage drop. For this, the "Continuous Loading Current in Copper Busbars" chart can be used.
Mechanically; The cross section and mechanical strength of the busbars depend on their mass and mode of use.
Skin Effect; It is an effect that causes the current to concentrate around the outer perimeter of the bar. This depends on the thickness of the busbar, the width/thickness ratio, the resistance and frequency of the busbar material. When looking at the skin effect coefficient of a rectangular bar, it is more advantageous to prefer busbars with a high width/thickness ratio. In busbars with the same cross-sectional area, preference for the one with a large surface is important in terms of cooling and a more uniform current density.
Considerations to Make a Good Busbar Connection
1) Contact Surfaces: Busbar surfaces should be thoroughly cleaned before contact, oxide-free and oil-free.
2) The surface height: (H) of the overlapping busbars should not be less than 5 times the thickness of the secondary busbar.
3) Clamping Force Required: (F) is directly proportional to the surface area (S) and the optimized constant k = 2.5 dN/mm2.
4) Calculation of Crimping Torque: Zinc-plated bichromatized 8.8 quality bolts should be used. A flat and serrated washer should be placed under the bolts. Tightening must be carried out with a torque wrench.
Zinc plating protects ferrous metals from the corrosive effect of oxygen and water vapor in the atmosphere. It prevents the iron in the galvanized part from coming into contact with air, when the coating cracks to reveal the ferrous metal, the zinc surrounding the fracture provides a kind of cathode protection for the iron. Corrosion from a chemical point of view is the formation of complex iron oxides on the surface of the metal. A zinc is more electropositive than iron. That is, by entering into a chemical reaction with another element, it can easily lose its valence electrons. If electrical contact is maintained with the metal containing iron, the zinc coating will be the first target of water and oxygen in the atmosphere. In addition, if the crack is small, the wear products of zinc will fill these slits.
Chromate plating is the process of chemically forming a film layer to increase the resistance to corrosion and to increase the adhesion of the paint to the surface in the materials to be painted. As the thickness of the film layer increases, corrosion resistance and electrical contact resistance increase.
5) When the hardness rating is 8.8: The integer part 8 describes the tensile strength of the material and is calculated as 8 x 100 = 800N/mm2.- If the decimal part is 0.8, it describes the tensile limit (called disproportionate elongation stress) and the tensile strength is calculated as x 0.8 = 800 x 0.8 = 640N/mm2.