Transformer Calculation Table
Free transformer calculation table: kVA to full-load amps for single-phase or three-phase (line-to-line), optional ideal turns ratio from Vp and Vs, +5% kVA and −5% voltage scenario rows, plus a plain-English guide to nameplates and code reality.
Summary: Build a quick transformer calculation table from a nameplate-style kVA rating, voltage, and whether the device is treated as single-phase or three-phase. The math returns full-load line current (amps) and optional ideal turns ratio from primary to secondary volts. It does not include impedance, temperature rise, harmonics, or inrush—engineering judgment still applies.
What this tool does — and does not (tap to expand)
- Does: computes I = kVA × 1000 ÷ V for single-phase, and I = kVA × 1000 ÷ (√3 × VL-L) for balanced three-phase using line-to-line voltage. Optional Vp : Vs ratio assumes an ideal transformer (no losses).
- Does not: replace short-circuit studies, NEC/NFPA tables as adopted locally, manufacturer test reports, or a licensed professional engineer’s stamp.
Educational use only. Always follow your jurisdiction’s electrical code, utility requirements, and equipment labeling.
Transformer calculation table (kVA → amps)
Enter the numbers you would normally read off a nameplate discussion or a one-line sketch note. After you calculate, you will see full-load current, an optional turns ratio, and a small scenario table—similar spirit to the mortgage calculator’s stress rows (here: a little extra kVA demand and a modest voltage sag).
Assumptions & methodology (short)
- Single-phase: IFL ≈ (kVA × 1000) ÷ V, with V the winding voltage you intend to pair with that kVA figure.
- Three-phase: IL ≈ (kVA × 1000) ÷ (√3 × VL-L) for a balanced load at unity power factor (same kVA convention as many pocket reference cards).
- Turns ratio (ideal): Np : Ns ≈ Vp : Vs for the voltages you enter (line values if that is what you typed).
- Power factor, efficiency, and harmonic K-factor are not applied here.