Transformer Sizing
Required kVA from load and voltages.
Example
You enter
- Load (kW) 90
- Power factor 0.9
- Primary voltage (V) 480
- Secondary voltage (V) 208
- Phase three
You get
- Required kVA 100
- Next standard kVA 112.5
Details, formula, and sources
kVA = √3 × V_LL × I (three-phase) / V × I (single-phase); over-current protection per NEC 450.3.
NEC 2023 (NFPA 70). Section 450.3, Table 450.3(B).
Free read-only access at nfpa.org/freeaccess.
Estimate. AHJ and licensed electrician govern. Verify against the NEC edition adopted in your jurisdiction.
Field names used by the API: load_kW, power_factor, primary_V, secondary_V, phase, required_kVA, next_standard_kVA
- Voltage-tolerance band ANSI C84.1 ±5%ANSI C84.1 by name