Transformer sizing
Transformer Calculator for Project Load Sizing
Use the transformer calculator to turn a simultaneous load schedule into a planning kVA requirement. Enter each operating load, its power factor and the project's capacity allowance, then review the result against the required voltage and installation.
Transformer load calculator
Add each operating load. Only rows marked simultaneous are included in the planning total.
| Load name | Input type | Load | Power factor (kW) | Hours/day | Runs simultaneously | Remove row |
|---|---|---|---|---|---|---|
Planning estimate only. Confirm voltage, motor starting, nonlinear loads, ambient temperature, expansion requirements and applicable loading rules with the responsible electrical engineer.
Build a load schedule
List each load in kW or kVA with power factor, operating hours and whether it runs at the same time as other loads. Keep motor starting, nonlinear loads and expansion requirements visible as separate design inputs. Confirm primary and secondary voltages before calculating current.
Work through a selection example
An illustrative 240 kW simultaneous load at 0.8 power factor is 300 kVA. With a project-agreed 20 percent capacity allowance, the planning demand is 360 kVA. Review available ratings at or above that value, then check starting duty, ambient temperature and the applicable loading requirements.
| Item or condition | What to compare | Input or result |
|---|---|---|
| Load | 240 kW / 0.80 | 300 kVA |
| Example planning allowance | 300 × 1.20 | 360 kVA |
| Candidate review | Available rating ≥ 360 kVA | Starting, temperature, voltage |
Match a family to the site
For a ground-level cable network, review the three-phase pad-mounted family. For an indoor electrical room, review dry-type alternatives. Request the chosen configuration's outline drawing, losses, impedance, connection diagram and test-document scope before final selection.
Three-phase pad-mounted
Review outdoor, ground-level distribution options for cable networks.
View Three-Phase Pad-Mounted Models →Dry-type transformers
Compare indoor transformer alternatives for electrical rooms.
View Dry-Type Models →Transformer sizing questions
Is a fixed capacity allowance required for every project?
Set the allowance from the project's expansion plan and loading policy. The 20 percent figure in the worked example is illustrative, not a universal requirement.
How do I enter a load in kW or kVA?
Enter a positive kW value and its power factor, or enter a positive kVA value directly. The calculator converts kW to kVA by dividing by power factor.
Does the calculator select a final transformer model?
No. It estimates planning capacity from the simultaneous load schedule and allowance. Confirm voltage, starting duty, ambient temperature, harmonics, local standards and the applicable loading requirements with the project team.
Which transformer family should I review?
Review pad-mounted models for ground-level cable networks and dry-type models for indoor electrical rooms. Confirm the site layout and electrical specification before final selection.
Review your transformer duty
Share the calculated duty, voltage, site layout and destination specification with the relevant product team.