Transformer Full Load Currents
Quick Reference • Power Distribution
Transformer FLA Tables
Fast, contractor-friendly full load current (FLA) lookups for common single-phase and three-phase transformer sizes. Use this as a starting point for feeder sizing, OCPD selection, and coordination—then confirm with the nameplate.
Why FLA matters
FLA is the baseline for selecting conductors and protection. Higher voltage = lower current, which is why distribution at 480/600V helps reduce conductor size and heat.
Pro tip
If a primary current looks “too high,” check the voltage: low-voltage primaries (120/240V) can drive very large currents even at modest kVA.
Good to know
Three-phase spreads power across three conductors, so current per conductor is lower for the same kVA—often meaning smaller wire and less voltage drop.
1-Phase Transformer Full Load Amperage (FLA)
| kVA | 120V (1PH) FLA | 220V (1PH) FLA | 240V (1PH) FLA | 480V (1PH) FLA | 600V (1PH) FLA |
|---|---|---|---|---|---|
| 3 kVA | 25.0 A | 13.6 A | 12.5 A | 6.25 A | 5.0 A |
| 5 kVA | 41.7 A | 22.7 A | 20.8 A | 10.4 A | 8.3 A |
| 10 kVA | 83.3 A | 45.5 A | 41.7 A | 20.8 A | 16.7 A |
| 15 kVA | 125.0 A | 68.2 A | 62.5 A | 31.3 A | 25.0 A |
| 25 kVA | 208.3 A | 113.6 A | 104.2 A | 52.1 A | 41.7 A |
| 50 kVA | 416.7 A | 227.3 A | 208.3 A | 104.2 A | 83.3 A |
| 75 kVA | 625.0 A | 340.9 A | 312.5 A | 156.3 A | 125.0 A |
| 100 kVA | 833.3 A | 454.5 A | 416.7 A | 208.3 A | 166.7 A |
Quick check: For 1-phase, FLA scales roughly with kVA ÷ Volts. Doubling voltage cuts current about in half.
3-Phase Transformer Full Load Amperage (FLA)
| kVA | 220V (3PH) FLA | 240V (3PH) FLA | 380V (3PH) FLA | 460V (3PH) FLA | 480V (3PH) FLA | 600V (3PH) FLA |
|---|---|---|---|---|---|---|
| 3 kVA | 7.9 A | 7.2 A | 4.6 A | 3.7 A | 3.6 A | 2.9 A |
| 5 kVA | 13.2 A | 12.0 A | 7.7 A | 6.2 A | 6.0 A | 4.8 A |
| 10 kVA | 26.3 A | 24.0 A | 15.3 A | 12.4 A | 12.0 A | 9.6 A |
| 15 kVA | 39.5 A | 36.0 A | 22.9 A | 18.6 A | 18.0 A | 14.4 A |
| 25 kVA | 66.3 A | 60.0 A | 38.2 A | 30.9 A | 30.0 A | 24.0 A |
| 50 kVA | 132.5 A | 120.0 A | 76.4 A | 61.8 A | 60.0 A | 48.0 A |
| 75 kVA | 198.8 A | 180.0 A | 114.6 A | 92.7 A | 90.0 A | 72.0 A |
| 100 kVA | 265.0 A | 240.0 A | 153.0 A | 123.6 A | 120.0 A | 96.0 A |
| 250 kVA | 660.0 A | 600.0 A | 384.6 A | 305.1 A | 300.0 A | 240.0 A |
| 500 kVA | 1,320 A | 1,200 A | 769.7 A | 611.7 A | 600.0 A | 480.0 A |
| 750 kVA | 1,980 A | 1,800 A | 1,154.5 A | 917.5 A | 900.0 A | 720.0 A |
| 1000 kVA | 2,640 A | 2,400 A | 1,539.4 A | 1,223.3 A | 1,200 A | 960.0 A |
Quick check: For 3-phase, current is lower by a factor of ?3 compared to a comparable single-phase calculation at the same voltage.
Disclaimer: Values are typical calculated FLA and intended as a general guide. Actual FLA may vary with transformer design, impedance, efficiency, temperature rise, and manufacturer data. Always confirm using the transformer nameplate and applicable electrical codes.
