What Is a Copper Buss Bar?
Copper buss bars are copper materials used in the current-carrying parts of electrical equipment, and are made of tough pitch copper or oxygen-free copper, which has excellent electrical and thermal conductivity.
Tough pitch copper (C1100) is a metal with a Cu purity of 99.9% or higher. It has excellent electrical and thermal conductivity as well as corrosion resistance and workability. Due to the presence of a trace amount of oxygen inside, it may react with hydrogen at high temperatures, resulting in hydrogen embrittlement.
Oxygen-free copper (C1020) contains less oxygen than tough pitch copper and has less resistance and distortion, so oxygen-free copper may be used in environments where hydrogen embrittlement is a concern. Oxygen-free copper is also widely used in vacuum equipment because of its low gas emission.
Applications of Copper Buss Bars
Copper buss bars are used as conductors for carrying large currents at high voltage in a variety of applications, including power distribution boards and circuits for controlling electric vehicles and trains.
Compared to round conductors, copper buss bars have the advantage of better conductivity and require less wiring space. In addition, there is no need to caulk the terminals; simply drill holes directly through copper buss bars and bolt them to the equipment. When conductors are thicker, it is necessary to consider the bending radius, but this is not necessary with copper buss bars.
Features of Copper Buss Bars
Copper buss bars require a minimum cross-sectional area based on the current value. The cross-sectional area is calculated by dividing the current value by the current density as follows:
- 125A or less: 3.0 or less
- 125 to 250 A or less: 2.5 or less
- 250 to 400 A or less: 2.0 or less
- 400 to 600A or less: 1.7 or less
In designing the actual cross-sectional area, the cross-sectional area is determined by taking into account the chamfering and forming of the material and the current density increase +5%.
Copper buss bars have screw holes to fix them to equipment. If the cross-sectional area of the screw holes exceeds 1/2 of the cross-sectional area without screw holes, it is not necessary to adjust the cross-sectional area of the screw holes to the cross-sectional area determined by the calculation.
In addition to copper, copper buss bars may also be made of aluminum. Although aluminum has lower tensile strength and conductivity than copper, it is less expensive and may be considered as a cost reduction plan. On the other hand, aluminum has lower conductivity, so the conductor volume must be larger than that of copper buss bars.