The formulas are mathematically sound. The problem is not the math—it is the input assumptions .
Cable calculation is vital to ensure:
is a value provided by manufacturers or standard tables like IEC 60364 . 3. Short Circuit Capacity Formula Short Circuit Power Cable Sizing Explained - ELEK Software cable calculation formula
The cable calculation formula is an essential but incomplete tool. No single formula suffices. A competent engineer must apply four distinct checks (load heating, voltage drop, short-circuit withstand, harmonic neutral loading). Any guide that presents just "Iz = In × correction factors" without the other three is dangerously incomplete. The formulas are mathematically sound
Note: To express this as a percentage: $$% \textDrop = \left( \fracV_dV_\textsupply \right) \times 100$$ cable calculation formula