BusBar Rating Software

This Software package is designed to give indicative current ratings and power dissipated for Aluminium and Copper BusBars as used in switchboards and electrical distribution systems. The user is able to specify the thickness and the width of the BusBar for thicknesses above 1mm.

BusBar ratings are based on the expected surface temperature rise of the busbar. This is a function of the thermal resistance of the busbar and the power it dissipates. The thermal resistance of the busbar is a function of the surface area of the busbar, the orientation of the busbar, the material from which it is made, and the movement of air around it. The power dissipated by the bus bar is dependant on the square of the current passing through it, its length, and the material from which it is made.

Optimal ratings are achieved when the bar runs horizontally with the face of the bar in the vertical plane. i.e. the bar is on its edge. There must be free air circulation around all of the bar in order to afford the maximum cooling to its surface. Restricted airflow around the bar will increase the surface temperature of the bar. If the bar is installed on its side, (largest area to the top) it will run at an elevated temperature and may need considerable derating. The actual derating required depends on the shape of the bar. Busbars with a high ratio between the width and the thickness, are more sensitive to their orientation than busbars that have an almost square cross section.

Vertical busbars will run much hotter at the top of the bar than at the bottom, and should be derated in order to reduce the maximum temperature within allowable limits.

Maximum BusBar ratings are not the temperature at which the busbar is expected to fail, rather it is the maximum temperature at which it is considered safe to operate the busbar due to other factors such as the temperature rating of insulation materials which may be in contact with, or close to, the busbar. Busbars which are sleeved in an insulation material such as a heatshrink material, may need to be derated because of the potential ageing and premature failure of the insulation material.

The software provides calculation in both metric and imperial dimensions.

The power dissipation in busbars can be calculated for specific currents.

The Purchase Price for BusBar Calculations is $NZ35 or $US22.

Click here to download  Electrical Calculations (including busbar calculations)

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