Full-Load Current

Converting power to current, and why the result is not the motor table value.

1. What this check does

Converts a load given in kW, HP or kVA into line current for a single- or three-phase system.

Load value and unit, system voltage (line-to-line for three-phase), number of phases.
Power factor (kW, HP) and efficiency (optional for HP — see below).

Three-phase

I = \dfrac{S}{\sqrt{3}\,V} = \dfrac{P}{\sqrt{3}\,V\,\mathrm{PF}\,\eta}

S in VA, V line-to-line.

Single-phase

I = \dfrac{S}{V} = \dfrac{P}{V\,\mathrm{PF}\,\eta}

P = \mathrm{HP} \times 745.7\ \mathrm{W}

Shaft output. kW without η is treated as electrical input (η = 1).

Symbols

$S$	Apparent power	VA
$P$	Real power	W
$V$	Voltage, line-to-line for three-phase	V
$\mathrm{PF}$	Power factor
$\eta$	Efficiency (motor shaft output to electrical input)
$I$	Full-load current	A

Voltage is the nominal system voltage you enter. Operating at reduced voltage increases current for the same power.
Balanced three-phase load; no harmonic content.
HP with efficiency left blank uses the US federal minimum for a 4-pole enclosed motor of that rating (10 CFR 431.25, 2016 levels); the result says so.

This is not the NEC motor full-load current. Conductors and most protection for motors are sized from the NEC table values, not from nameplate or calculated current.
Motor service factor, starting current and unbalanced loads.

NEC 2023 430.6(A)(1), Tables 430.248 and 430.250 — motor full-load current for conductor sizing

Hand-calculated cases run on every change. See Validation.