For copper busbars, IEC 61439-1 and common engineering practice recommend 1. To calculate Busbar Current, enter the width (mm), thickness (mm), and material carry capacity factor (amps/mm^2). The electrical power system consists of many incoming & outgoing feeder connections, for which busbars are necessary. A busbar is just a node (conductor or collection of conductors). In this new edition the calculation of current-carrying capacity has been greatly simplified by the provision of exact formulae for some common busbar configurations and graphical methods for others. Supports rectangular and round shapes.