What to check before ordering
A standard step down transformer can often be reverse fed, but not always. Taps sit on the high voltage winding, so reverse feeding puts them on the output where they behave differently, and inrush on a reverse fed unit is higher. Confirm with the manufacturer rather than assuming.
Current at each rating
Three phase full load current on both sides of a 240 V to 480 V transformer. The higher voltage side always carries less current for the same kVA.
| kVA | 240 V side | 480 V side |
|---|---|---|
| 15 | 36.1 A | 18.0 A |
| 30 | 72.2 A | 36.1 A |
| 45 | 108 A | 54.1 A |
| 75 | 180 A | 90.2 A |
| 112.5 | 271 A | 135 A |
| 150 | 361 A | 180 A |
| 225 | 541 A | 271 A |
| 300 | 722 A | 361 A |
| 500 | 1,203 A | 601 A |
Nameplate full load current, computed from the standard three phase formula. Free to cite with a link to this page. For any rating not listed, use the kVA to amps calculator.
Common questions
What transformer do I need to go from 240 V to 480 V
A step up transformer with a 1 to 2 ratio. Supplying 480 V machinery from a 240 V supply, and in some cases reversing a standard step down unit to run backwards. Most units for this conversion fall in the 15 to 150 kVA range.
How many amps does a 240 V to 480 V transformer draw
It depends on the kVA. At 100 kVA the 240 V side carries about 241 amps and the 480 V side about 120 amps. Current is kVA times 1000 divided by the voltage times the square root of three, so the higher voltage side always carries less current for the same kVA.
What should I check before ordering
A standard step down transformer can often be reverse fed, but not always. Taps sit on the high voltage winding, so reverse feeding puts them on the output where they behave differently, and inrush on a reverse fed unit is higher. Confirm with the manufacturer rather than assuming.