Enter Values
Formula
Single-phase kVA = V × A ÷ 1000
Three-phase kVA = √3 × V × A ÷ 1000
For three-phase systems, use line-to-line voltage and line current.
Examples
Example 1
Three-phase, 480 V, 100 A
kVA = 1.732 × 480 × 100 ÷ 1000
kVA = 83.14 kVA
Example 2
Single-phase, 240 V, 50 A
kVA = 240 × 50 ÷ 1000
kVA = 12.00 kVA
Example 3
Three-phase, 4.16 kV, 25 A
kVA = 1.732 × 4160 × 25 ÷ 1000
kVA = 180.13 kVA
How to Apply the Result
Transformer ratings are normally expressed in kVA because heating depends largely on voltage and current rather than the load's power factor. Select the phase type, then enter the rated voltage and current for the same side of the transformer.
For a three-phase transformer, enter line-to-line voltage and line current. Do not mix primary voltage with secondary current.
Sizing Considerations
- Account for continuous-load requirements and expected future load growth.
- Check nonlinear load, harmonic, temperature, altitude, enclosure, and ventilation requirements.
- Verify primary and secondary protection, conductor sizing, grounding, and available fault current separately.
The calculated kVA is the load requirement at the entered operating point, not automatically the correct standard transformer size.