Busbar Design Basics

Busbar Design Basics High electrical conductivityonly silver is better than copper Good thermal conductorheat reaches surface quickly Strong (at working temperature)to withstand short circuit stresseslow creep Easy to jointresistant to corrosionMaterials for Busbar SystemsBusbar ratings are determined only by the maximum desired working temperature

At working temperature:heat generated = heat lostBusbar System Current RatingsBusbar System Current RatingsBusbar ratings depend on: Working and ambient temperatures Heat lost from the busbar by convection by radiation Heat generated in the busbarBusbar System Current RatingsBright copper has an emissivity of about 0.1

During use, the emissivity of the copper surface increases - and the current rating increases - as the copper darkens to reach an emissivity value of about 0.7

Tin plated copper has an emissivity of about 0.3 to 0.5

But painting bars reduces the current rating!

Minimum size calculationCalculation method:1Select working and ambient temperatures2Assume initial current density of 8 amps/mm23Find appropriate size in standard range4Calculate heat generated due to current5Calculate heat loss at working temperature6If 4>5, increase size and return to 4 When 4=