Cable Sizing Formula May 2026

[ V_d = \sqrt3 \times L \times I \times (R_ac \cos\phi + X \sin\phi) ]

[ I_rated \ge I_load \times k_1 \times k_2 \times \dots \times k_n ] cable sizing formula

[ I = \fracV_dR_cable ]

[ I_req = \fracI_loadk_t \times k_g \times k_s \times \dots ] Step 3: Select Cable from Tables Choose a cable where ( I_rated \ge I_req ). Step 4: Check Voltage Drop Voltage drop formula (single-phase): [ V_d = 2 \times L \times I \times (R_ac \cos\phi + X \sin\phi) ] [ V_d = \sqrt3 \times L \times I

Correction factors: ( k_t ) (40°C PVC) = 0.87 ( k_g ) (single circuit) = 1.0 ( k_s ) (air) = 1.0 cable sizing formula

Short-circuit thermal check (k for Cu/PVC = 115): [ A_min = \frac10,000 \times \sqrt0.1115 \approx 27.5 \text mm^2 ] 25 mm² is slightly below → upgrade to 35 mm² for fault withstand.

[ I_req = 84.9 / 0.87 \approx 97.6 \text A ]