Busbar ampacity calculator

Continuous current rating is computed from a steady-state heat balance: I²R losses against natural convection and radiation from the bar surface. Resistance is taken at operating temperature. The model assumes a single bar per position, edge mounted, freely ventilated in still air, at uniform temperature, carrying DC or low-frequency AC. It excludes skin and proximity effect, which become significant above roughly 10 mm thickness at 50 or 60 Hz, so thick-bar results run optimistic. Multi-bar factors follow the conventional grouping ratios: two bars are worth about 1.75 times one, not two, because the inner faces stop radiating usefully. DIN 43671 is the reference for design values.