Busbar Power Dissipation

The total Power Dissipated in the busbar is dependent on the resistance of the bar, it's length and the square of the RMS current flowing through it.




The power dissipated in the busbar is proportional to the square of the current, so if the busbar has a cyclic load, the current should be the RMS current rather than the average. If the maximum current flows for a considerable period of time, this must be used as the current to determine the maximum busbar temperature, but the power dissipation is based on the square root of the maximum current squared times the period for which it flows plus the lower current squared times the period it flows all divided by the square root of the total time. For example, a busbar carries a current of 600 Amps for thirty seconds, then a current of 100 amps for 3000 seconds, then zero current for 3000 seconds. The power dissipation is based on an RMS current of sqrt(600x600x30 + 100x100x3000 + 0 x 3000)/sqrt(30 + 3000 + 3000) = 82.25 Amps.

To calculate the Power Dissipation of a busbar, enter in the width, length and thickness of the bar, and the RMS Current passing through it. Select the units as either metric or imperial. The program displays the Power Dissipated in both an aluminium bar of these dimensions and a copper bar of these dimensions. Enter the ambient temperature around the bar in either Celsius or Fahrenheit and the program will check the suitability of the bar for this application.