Locked-rotor (inrush) current for a squirrel-cage induction motor - the basis for switchgear sizing and generator voltage-dip calculation.
Formula
$$ I_n = \frac{P}{\sqrt{3} \cdot U_L \cdot \cos\varphi \cdot \eta}, \quad I_s = k \cdot I_n $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $P$ | Motor rated power | kW | nameplate |
| $U_L$ | Line-to-line voltage | V | nameplate |
| $k$ | Locked-rotor multiplier | - | NEMA / IEC code |
Sources
- IEC 60034-12.