Transformer kVA Sizing and FLA

Total connected kVA + ANSI/IEEE step-series recommendation + primary / secondary FLA.

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Formula and source

Total connected kVA = Σ load_i; required kVA = connected × (1 + reserve%). Recommended size from the ANSI/IEEE C57 standard step series (15 / 30 / 45 / 75 / 112.5 / 150 / 225 / 300 / 500 / 750 / 1000). FLA = kVA × 1000 / (V × √phases).

ANSI/IEEE C57 standard kVA step series by name; NEC 2023 (NFPA 70). Article 450 (Transformers).

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