Busbar Current-Carrying Capacity Calculator

For busbar selection in panels and distribution systems, correct the DIN 43671 (copper) and DIN 43670 (aluminum) continuous current values for ambient and busbar temperature.

Formula used

Continuous current: I = I₀ × (Δθ / 30)^0.61 × √(R₆₅ / R)

Copper busbar current-carrying capacity table · bare (DIN 43671)

Indoors, free air, alternating current up to 60 Hz; wide face of the bar vertical, spacing between parallel bars equal to the bar thickness; continuous current (A) at 35 °C ambient and 65 °C busbar temperature. The value drops with the wide face horizontal. Columns are the number of parallel bars per phase; arrangements without a table value are shown as “–”.

Size (mm)1 bar2 bars3 bars4 bars
20×5274500690–
20×104278251180–
30×5379672896–
30×1057310601480–
40×54828361090–
40×10715129017702280
50×558399412401920
50×10852151020402600
60×5688115014402210
60×10985172023002900
80×5885145017502720
80×101240211027903450
100×51080173020503190
100×101490248032603980
120×101740286037404500
160×102220359046805530
200×102690431056106540

Copper busbar current-carrying capacity table · painted (DIN 43671)

Indoors, free air, alternating current up to 60 Hz; wide face of the bar vertical, spacing between parallel bars equal to the bar thickness; continuous current (A) at 35 °C ambient and 65 °C busbar temperature. The value drops with the wide face horizontal. Columns are the number of parallel bars per phase; arrangements without a table value are shown as “–”.

Size (mm)1 bar2 bars3 bars4 bars
20×5319560728–
20×104979241320–
30×5447760944–
30×1067612001670–
40×55739521140–
40×10850147020002580
50×5697114013302010
50×101020172023202950
60×5826133015102310
60×101180196026103290
80×51070168018302830
80×101500241031703930
100×51300201021503300
100×101810285037204530
120×102110328042705130
160×102700413053606320
200×103290497064307490

Aluminum busbar current-carrying capacity table · bare (DIN 43670)

Indoors, free air, alternating current up to 60 Hz; wide face of the bar vertical, spacing between parallel bars equal to the bar thickness; continuous current (A) at 35 °C ambient and 65 °C busbar temperature. The value drops with the wide face horizontal. Columns are the number of parallel bars per phase; arrangements without a table value are shown as “–”.

Size (mm)1 bar2 bars3 bars4 bars
20×5214392537–
20×10331643942–
30×5295526699–
30×104458321200–
40×5376658851–
40×10557103014601900
50×54557869951520
50×10667121017102210
60×553391011301750
60×10774139019402480
80×5688115014002180
80×10983172023802990
100×5846139016602580
100×101190205027903470
120×101390236032003930
160×101780296040004820
200×102160356047905710

Aluminum busbar current-carrying capacity table · painted (DIN 43670)

Indoors, free air, alternating current up to 60 Hz; wide face of the bar vertical, spacing between parallel bars equal to the bar thickness; continuous current (A) at 35 °C ambient and 65 °C busbar temperature. The value drops with the wide face horizontal. Columns are the number of parallel bars per phase; arrangements without a table value are shown as “–”.

Size (mm)1 bar2 bars3 bars4 bars
20×5254446570–
20×103937301060–
30×5356606739–
30×105369561340–
40×5456762898–
40×10677118016502190
50×555691610501580
50×10815140019402540
60×5655107011901820
60×10951161022002870
80×5851136014602250
80×101220200026603460
100×51050165017302660
100×101480239031104020
120×101730275035404560
160×102220347043905610
200×102710418052306660

Example: 50×10 mm bare copper busbar, 40 °C ambient

  1. Table value: for a single 50×10 mm bare copper bar per phase, I₀ = 852 A (35 °C ambient, 65 °C busbar).
  2. Correction: Δθ = 65 − 40 = 25 K (30 K under table conditions); with a busbar temperature of 65 °C the resistance correction stays 1, and the approximate relation gives the factor (25 / 30)^0.61 = 0.895.
  3. Result: I = 852 × 0.895 ≈ 762 A; cross-section 500 mm², current density 1.52 A/mm².

How many amps does a 30×10 copper busbar carry?

The DIN 43671 continuous current of a single 30×10 mm copper bar per phase is 573 A bare and 676 A painted (35 °C ambient, 65 °C busbar). An aluminum bar of the same size carries 445 A and 536 A respectively per DIN 43670. In an enclosed panel, the temperature rise is verified separately.

How many amps does a 40×10 copper busbar carry?

The DIN 43671 continuous current of a single 40×10 mm copper bar per phase is 715 A bare and 850 A painted (35 °C ambient, 65 °C busbar). An aluminum bar of the same size carries 557 A and 677 A respectively per DIN 43670. In an enclosed panel, the temperature rise is verified separately.

How many amps does a 60×10 copper busbar carry?

The DIN 43671 continuous current of a single 60×10 mm copper bar per phase is 985 A bare and 1,180 A painted (35 °C ambient, 65 °C busbar). An aluminum bar of the same size carries 774 A and 951 A respectively per DIN 43670. In an enclosed panel, the temperature rise is verified separately.

How many amps does a 80×10 copper busbar carry?

The DIN 43671 continuous current of a single 80×10 mm copper bar per phase is 1,240 A bare and 1,500 A painted (35 °C ambient, 65 °C busbar). An aluminum bar of the same size carries 983 A and 1,220 A respectively per DIN 43670. In an enclosed panel, the temperature rise is verified separately.

How is busbar capacity calculated?

The DIN table value is taken for the material, size, surface and number of parallel bars (35 °C ambient, 65 °C busbar) and corrected for the ambient and permitted busbar temperature.

What is checked in the final busbar selection?

Temperature rise in an enclosed panel must be verified according to IEC 61439. Busbar arrangement, spacing, connection points, short-circuit thermal withstand and electromechanical forces are checked separately.