Calculation worksheet
Transformer full-load current
Three-phase current chart at 208, 240, and 480 V, plus a custom single- or three-phase calculation.
Three-phase transformer full-load current
Amps = kVA × 1,000 ÷ (√3 × volts)
√3 ≈ 1.732 · Voltages are line-to-line · Current rounded to the nearest whole amp
| Transformer kVA | 208 V | 240 V | 480 V |
|---|---|---|---|
| 30 | 83 | 72 | 36 |
| 40 | 111 | 96 | 48 |
| 60 | 167 | 144 | 72 |
| 75 | 208 | 180 | 90 |
| 112.5 | 312 | 271 | 135 |
| 150 | 416 | 361 | 180 |
| 225 | 625 | 541 | 271 |
| 300 | 833 | 722 | 361 |
| 500 | 1,388 | 1,203 | 601 |
| 750 | 2,082 | 1,804 | 902 |
Uses √3 at full precision. These are calculated full-load currents, not breaker ratings or conductor sizes. Protection and conductor selection require separate review.
Enter your values and select Calculate to see a step-by-step result.
Reference2023 NEC Article 450; kVA current arithmetic
Full-load current only. Overcurrent protection and conductor selection have separate code requirements.