Size a copper busbar for a given current, checking current density and temperature rise.
Busbars are sized on current density rather than tabulated ampacity, because their cooling depends heavily on the enclosure. Loss per metre matters because it becomes heat inside a switchboard, where removal is difficult. Multiple thinner bars per phase carry more current than one thick bar of the same area, because the skin effect and surface-to-area ratio both improve.
Busbar Size
Current density = current ÷ (width × thickness × bars); loss per metre = I² R
Current density = current ÷ (width × thickness × bars); loss per metre = I² R Busbars are sized on current density rather than tabulated ampacity, because their cooling depends heavily on the enclosure. Loss per metre matters because it becomes heat inside a switchboard, where removal is difficult.
Multiple thinner bars per phase carry more current than one thick bar of the same area, because the skin effect and surface-to-area ratio both improve.
This calculator takes 5 inputs: Continuous current, Bar width, Bar thickness, Bars per phase, Target current density. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.