AC Cable Sizing

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• I = P / (V × pf) (1-φ)
• I = P / (√3 × V × pf) (3-φ)
• ρ_T = ρ₂₀ × [1 + α (T − 20)]
• A = (2 × ρ_T × L × I) / ΔV (1-φ)
• A = (√3 × ρ_T × L × I) / ΔV (3-φ)

AC current is derived from power, voltage and power factor, then the minimum conductor cross-section follows from the permitted voltage drop. Resistivity is corrected to the operating conductor temperature, and the result is rounded up to the next standard cross-section.

1. 1.Design currentP/(√3·V·pf)14.2 A
2. 2.Resistivity at Tρ₂₀[1+α(T−20)]0.02058 Ω·mm²/m
3. 3.Allowable dropV × vd%8.3 V
4. 4.Required area√3·ρ·L·I/ΔV1.83 mm²
5. 5.Rounded upnext standard size2.5 mm²

• • Balanced load, negligible reactance (short runs, ≤ 120 mm²).
• • Voltage drop is the governing criterion; ampacity is checked separately.
• • Standard PVC/XLPE insulated Cu/Al cable at the stated conductor temperature.