Industrial Electric Calculator

Using the electric calculators together, in design order

The tools follow the actual design workflow. If the load is given in kW, start with the power conversion calculator to get the load current in amps. A motor nameplate kW is shaft output, so enter the efficiency as well to get the supply-side current right. Next, enter that current, the one-way distance and the allowable voltage drop (%) — the voltage drop calculator shows the distance-based limits — in the wire size calculator; it picks the cross-section that meets both the ampacity and the voltage drop limit. Then use the breaker capacity calculator to choose the rating that protects the circuit. When the conductor size is already decided, or you are checking an installed run, use the voltage drop calculator to confirm that the receiving-end voltage stays within the distance-based limit.

The breaker capacity calculator picks a KS standard rating at or above the load current multiplied by the safety factor for the load type, searching the MCB ratings first up to 63 A and the MCCB ratings above that. It does not take the conductor ampacity as an input, so compare the chosen rating yourself against the effective ampacity (after derating) from the wire size calculator. On a general load, if the rating exceeds the ampacity, increase the conductor size until it no longer does. Motor and welder loads use larger safety factors for starting and intermittent duty, so their rating easily exceeds the ampacity; the designer should review separately how overload protection is provided. The cross-section the wire size calculator picks is the smallest standard size that meets both conditions, so anything smaller fails either the ampacity or the voltage drop limit. Wire sizing applies ambient-temperature and grouping correction factors to the ampacity tables of KS C IEC 60364 and the Korea Electro-technical Code (KEC). A frequently missed step is voltage drop when a conductor is picked from an ampacity table alone — never skip it for motor loads or long outdoor circuits.

The wire size and voltage drop calculators show their calculation steps and the standard or code they are based on, so you can cite the source in estimates and in documents submitted to the supervising engineer; check the cited provision against its current text before submitting. The breaker capacity calculator also shows its steps and the KS standard rating list, but its load-type safety factors are this calculator's defaults, not KEC values, so they cannot be cited as code requirements; what you can cite is what the code text itself says, such as the overload protection condition in KEC 212.4.1. The power conversion calculator uses the basic power equations (three-phase P = √3·V·I·cosφ), so there is no standard table to cite, and its power factor and efficiency are input assumptions — use nameplate values when you have them. Results are reference estimates; final design decisions should be reviewed by a licensed electrical engineer against site conditions and applicable regulations.