: Short-circuit withstand. ( k=115 ). ( S_min = \sqrt10000^2 \times 0.4/115 = \sqrt40\times 10^6/115 = 6324/115 = 55 mm^2 ). Required minimum 70 mm². Our 50 mm² fails. Therefore increase to 70 mm².
The current flowing through a conductor generates heat (Joule effect: ( P = I^2 R )). The cable dissipates heat to its surroundings. Ampacity is the maximum steady-state current a cable can carry without exceeding its maximum operating temperature (e.g., 70°C for PVC, 90°C for XLPE, 60°C for rubber). how to calculate cable size
For a three-phase circuit (line-to-line): [ V_d = \sqrt3 \times I_b \times (R \cos\phi + X \sin\phi) \times L ] : Short-circuit withstand
At thermal equilibrium: [ I^2 R(T) = \fracT_c - T_aR_th ] Where: 70°C for PVC