Cable cross-sectional area (mm²) = Current (A) ÷ Current density (A/mm²)
Cable cross-sectional area (mm²) = 2 × Length (m) × Current (A) × Resistivity (Ω·mm²/m) ÷ Voltage drop (V)
Single-phase cable size (mm²) = 2 × L × I × ρ ÷ Vd
Three-phase cable size (mm²) = 1.732 × L × I × ρ ÷ Vd
Current density method: S = I ÷ J
Voltage drop method: S = (2 × L × I × ρ) ÷ Vd
Three-phase voltage drop method: S = (1.732 × L × I × ρ) ÷ Vd
Copper resistivity (ρ) = 0.0175 Ω·mm²/m
Aluminum resistivity (ρ) = 0.0282 Ω·mm²/m
Cable size in mm² = Load current ÷ allowable current per mm²
Final cable size = Calculated size × safety factor
Safety factor commonly used = 1.25 to 1.5
Current formula: I = P ÷ V
Three-phase current formula: I = P ÷ (1.732 × V × PF)
Power formula: P = V × I
Three-phase power formula: P = 1.732 × V × I × PF
Cable size selection = higher of current-carrying capacity size or voltage-drop size