Full-load current for three-phase transformers, generators and switchboards, with the real power they deliver.
If you have the supply rating rather than the current, start with the kVA to kW calculator.
Every diagram and table on this page updates with the calculator above.
V is the line-to-line voltage. √3 ≈ 1.7320508.
About 722 A per phase on the low-voltage side.
Most three-phase errors come from mixing line and phase quantities. The relationship flips depending on whether the windings are connected in star or delta.
| Connection | Voltage | Current |
|---|---|---|
| Star (wye) | V_line = √3 × V_phase | I_line = I_phase |
| Delta | V_line = V_phase | I_line = √3 × I_phase |
The √3 appears exactly once in each configuration — on voltage for star, on current for delta.
The formula on this page always returns line current from line voltage, which is what you need for cables, breakers and switchboards. Phase current only matters inside the machine.
Common three-phase ratings at your selected voltage, with the kilowatts each supports at your power factor.
| kVA | Full-load current (A) | Real power (kW) |
|---|---|---|
| 25 kVA | 36.1 | 20 |
| 50 kVA | 72.2 | 40 |
| 75 kVA | 108.3 | 60 |
| 100 kVA | 144.3 | 80 |
| 150 kVA | 216.5 | 120 |
| 200 kVA | 288.7 | 160 |
| 250 kVA | 360.8 | 200 |
| 315 kVA | 454.7 | 252 |
| 400 kVA | 577.4 | 320 |
| 500 kVA | 721.7 | 400 |
| 630 kVA | 909.3 | 504 |
| 800 kVA | 1,154.7 | 640 |
| 1,000 kVA | 1,443.4 | 800 |
| 1,250 kVA | 1,804.2 | 1,000 |
| 1,600 kVA | 2,309.4 | 1,280 |
| 2,000 kVA | 2,886.8 | 1,600 |
Current is inversely proportional to voltage. That single fact drives the whole architecture of industrial distribution: move power at the highest practical voltage, step down close to the load.
Drag the voltage slider and watch the curve fall away. The kVA has not changed — only the current needed to move it.
Every standard rating against every common distribution voltage, recalculated live.
| kVA | 208 V | 400 V | 415 V | 480 V | 690 V |
|---|---|---|---|---|---|
| 100 kVA | 278 | 144 | 139 | 120 | 84 |
| 250 kVA | 694 | 361 | 348 | 301 | 209 |
| 500 kVA | 1,388 | 722 | 696 | 601 | 418 |
| 800 kVA | 2,221 | 1,155 | 1,113 | 962 | 669 |
| 1,000 kVA | 2,776 | 1,443 | 1,391 | 1,203 | 837 |
| 1,600 kVA | 4,441 | 2,309 | 2,226 | 1,925 | 1,339 |
| 2,000 kVA | 5,551 | 2,887 | 2,782 | 2,406 | 1,673 |
Full-load current sets the continuous rating, but protective devices also have to handle fault current, and that is set by the transformer impedance rather than its kVA.
Choose a device rated above the full-load current after any derating for enclosure temperature.
Approximate prospective fault current as full-load current ÷ per-unit impedance. A 500 kVA unit at 5% gives roughly 20 × FLC.
The device must interrupt that fault current safely — check the kA rating, not just the amp rating.
Confirm the upstream device does not trip before the downstream one on a downstream fault.
29 calculators built on the same maths as the tool above. Each one has its own inputs, interactive diagrams and worked examples.
Common questions about converting kva to amps (three phase).