Busbar current rating equation
This calculator estimates busbar current from cross-sectional area, current-density reference, material factor, and derating factor.
A = W × TI = A × J × Km × Kdwhere:
- A
- Busbar cross-sectional areamm2
- W
- Busbar widthmm
- T
- Busbar thicknessmm
- I
- Estimated current ratingA
- J
- Selected current density referenceA/mm2
- Km
- Material factor for copper or aluminum
- Kd
- Derating factor for enclosure and installation conditions
A real busbar rating depends on temperature rise, enclosure ventilation, spacing, plating, supports, and short-circuit withstand testing.
Assumptions
- Simple cross-section based estimate
- Copper reference unless aluminum is selected
- Temperature rise testing is not included
Important Warnings
- Final busbar rating depends on enclosure, spacing, ventilation, plating, temperature rise, and standard testing.
- Do not use this estimate as a certified rating.
FAQ
Why does enclosure design matter?
The same copper bar can run hotter in a sealed cabinet than in open air. Heat dissipation changes the practical current rating.
Can this size a busbar for short-circuit withstand?
No. Short-circuit thermal and mechanical withstand require separate calculations and tests.