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Motor Starting Voltage Dip Estimate

Estimate generator-bus voltage dip ratio, voltage change and remaining voltage from motor current and source short-circuit current using a simplified relation.

Inputs

Supply and motor currents

Range: 1–100,000 V

Use the voltage at the motor/source bus. Australian examples include 230/240 V single phase and 400/415 V three phase.

Range: 1–1,000,000 A

Use the source short-circuit current on the same basis required by the cited method and at the motor/source bus.

Range: 0–1,000,000 A

Enter motor rated full-load current from its nameplate or verified data.

Range: 0–1,000,000 A

Enter starting current for the selected motor and starter; do not substitute a generic multiple.

Result

Estimated incremental voltage dip
4.04
Estimated voltage-dip ratio
0.040404
Estimated incremental voltage change (V)
16.77
Estimated voltage during start (V)
398.23
Estimate calculated using the entered current values

Formula

Calculation logic

Formula definitions and substituted values.

Before relying on the result

  • Check a motor start against measured source strength
  • Compare a lower-current starter against direct starting
  • Estimate the additional voltage dip and compare it with equipment and supply requirements.

Related calculators

Estimate the additional voltage dip and compare it with equipment and supply requirements.