Motor Starting Current

Starting-current multiplier on full-load amps for DOL, star-delta, autotransformer, and soft-starter modes.

MotorsStarting

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This calculator requires JavaScript to compute its result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

I_\text{start} = I_\text{LRC} \cdot k_\text{method}, \quad k_\text{Y-Δ} = \tfrac{1}{3}, \; k_\text{auto} = a^2

Symbol	Meaning	Unit
$FLC$	Full-load current	A
$I_\text{LRC}$	Locked-rotor current = DOL × multiplier	A
$a$	Autotransformer tap ratio

Source: IEC 60947-4-1 - Contactors and motor starters

Starting-current multiplier on full-load amps for DOL, star-delta, autotransformer, and soft-starter modes.