Motor Inrush Current Calculator

Inputs

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Nameplate horsepower.
hp
Line-to-line voltage for three-phase; line voltage for single-phase.
V
Nameplate FLA, to express inrush as a multiple. 0 to skip.
A

Results

Default result
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Locked-rotor amps, min(LRA)
70.3A

Also computed

Locked-rotor amps, max78.9A

The band edge breakers, contactors and generators must ride through.

Locked-rotor kVA/hp, min5.6

Locked-rotor kVA/hp, max6.29

Multiple of FLA (max)5.64× FLA

Method notes 4 notes
  • Code-letter bands per NEC Table 430.7(B) (verified against two agreeing publications incl. the Article 430 text; same scale as NEMA MG-1). Letters I, O and Q are skipped by the standard.
  • This is across-the-line (full-voltage) starting. Soft starters, VFDs, wye-delta and autotransformer starting all draw less — by design.
  • The code letter gives a band, not a point: use the max edge for breaker instantaneous-trip and generator sizing, and the nameplate LRA when it is printed.
  • Inrush is kVA-driven, so LRA scales inversely with voltage: the same motor at 230 V draws twice the locked-rotor amps it would at 460 V.

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