The rated kVA of a transformer shall be the output that can be delivered for the time specified at rated secondary voltage and rated frequency without exceeding the specified temperature-rise limitations under prescribed conditions of test, and within the limits of established standards.
Preferred continuous kVA ratings of single-phase and three-phase distribution and power transformers are based on an average winding rise by resistance of 65oC, in accordance with winding temperature rise and are listed in Table 3.
| Single-phase transformers | Three-phase transformers |
|---|---|
| 5 | 15 |
| 10 | 30 |
| 15 | 45 |
| 25 75 | |
| 37.5 | 112.5 |
| 50 | 150 |
| 75 | 225 |
| 100 | 300 |
| 167 | 500 |
| 250 | 750 |
| 333 | 1000 |
| 500 | 1500 |
| — | 2000 |
| 833 | 2500 |
| 1250 | 3750 |
| 1667 | 5000 |
| 2500 | 7500 |
| 3333 | 10 000 |
| — | 12 000 |
| 5000 | 15 000 |
| 6667 | 20 000 |
| 8333 | 25 000 |
| 10 000 | 30 000 |
| 12 500 | 37 500 |
| 16 667 | 50 000 |
| 20 000 | 60 000 |
| 25 000 | 75 000 |
| 33 333 | 100 000 |