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Transformer kVA sizing
Smallest standard transformer rating (kVA) that handles your connected load + headroom. Single-phase and three-phase, common dry-type sizes. Sanity-check; final design from the EOR.
Recommended transformer
500 kVA(3-φ)
Connected: 277.8 kVA; required after factors: 347.2 kVA.
kVA = kW ÷ PF. Multiply by load factor (1.25 for continuous loads ≥3 hours per NEC 215.2(A)(1)) and demand factor (per NEC 220). Phase changes the wiring but not the kVA sizing. Three-phase transformers are typically Y-Δ; phase-balancing is the engineer's call.
How it works
Total connected load is converted to kVA at the chosen voltage. We multiply by the load factor (default 1.25 for continuous loads per NEC) and the demand factor (default 1.0), then pick the smallest standard kVA size that covers it.
Standard sizes: 15, 30, 45, 75, 112.5, 150, 225, 300, 500, 750, 1000, 1500, 2000, 2500 kVA.
Built by Forward
Forward runs transformer kVA, wire-size, voltage-drop, panel demand load, generator sizing, plus the broader NEC/IBC/IMC calcs and Procore/Autodesk/OneDrive lookups over text.