Motor Starting Current Chart

Use this worksheet after the calculator result to keep running current, locked-rotor multiplier, starter method, estimated line starting current, starting kVA, and voltage-sag notes in one motor-start screen. A 50 HP, 460 V motor using 65 A FLA and a 6x direct-on-line start screens at 390 A inrush and about 311 kVA before soft-starter, VFD, transformer, and feeder checks.

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Quick reference table

A motor starting current chart is a calculator-led planning screen for inrush, not a generic motor table. For a 50 HP, 460 V motor with 65 A FLA and a 6x direct-on-line multiplier, the line starting current is 390 A and starting kVA is about 311 kVA before the electrician compares the result with the controller, transformer, feeder, and utility limit.

Motor starting result worksheet

Motor starting result worksheet
Result item	Record from calculator	Field use before the next decision
Running current basis	FLA, FLC, or nameplate current	Confirm which current value drove the inrush estimate
Locked-rotor multiple	Selected LRA multiple or code-letter estimate	Replace with manufacturer data when available
Starter method	DOL, soft starter, VFD, autotransformer, or tap setting	Keep method effects separate from motor current
Line starting current	Estimated amperes at the feeder	Compare with upstream device and transformer notes
Starting kVA	Apparent-power screen	Use for utility, transformer, and voltage-sag conversation

Starter method screening notes

Starter method screening notes
Starting method	What the chart should record	Common field check
Direct-on-line	Highest inrush screen from the selected multiplier	Check nuisance trip and voltage-sag exposure
Soft starter	Current-limit setting and ramp time	Check that reduced current still leaves enough acceleration torque
VFD start	Drive input current and bypass condition if present	Check drive manual, overload setup, and available fault current
Autotransformer or reduced-voltage tap	Tap percent and line-current factor	Check transition timing and controller ratings

Formula basis

Estimated line starting current = FLA x locked-rotor multiple x starting-method line-current factor.

FLA is the running-current basis used by the calculator, ideally tied to nameplate or documented table current.
Locked-rotor multiple is the selected inrush multiplier or manufacturer value.
Starting-method factor reflects DOL, soft starter, VFD, autotransformer, wye-delta, or other reduced-voltage behavior.
Starting kVA is the apparent-power screen calculated from voltage and estimated line starting current.

Worked examples

Pump started across the lineA service tech can record 65 A FLA, 6x DOL, 390 A line starting current, and about 311 kVA before checking transformer size and voltage sag at the pump controller.

Soft starter current-limit comparisonA controls electrician can keep the DOL estimate beside the soft-starter limit, ramp time, and percent reduction so the inrush result is not mistaken for a torque check.

Assumptions. Balanced load and line-to-line voltage assumptions behind this chart.

The worksheet uses calculator multipliers as planning inputs; manufacturer locked-rotor data, controller settings, and nameplate data should replace assumptions when available.
Voltage sag, acceleration time, nuisance tripping, transformer stiffness, and utility starting limits require separate project checks.
The result is a line-current estimate, so motor current, controller input current, and bypass current should be labeled separately when they differ.

Code and standard notes. Planning limits that should be checked before final equipment selection.

Use this chart as a calculator-led planning worksheet; verify nameplate data, manufacturer starting data, utility requirements, equipment ratings, and AHJ expectations before final use.

How to use this chart

1Start from the resultCopy the calculator current basis, locked-rotor multiple, starter method, line starting current, and starting kVA into the worksheet before adding field notes.

2Label the starter methodRecord whether the result is DOL, reduced-voltage, soft-starter, VFD, autotransformer, or tap based so line current is not confused with motor current.

3Prepare the next checksUse the worksheet to list manufacturer, utility, transformer, feeder, and upstream-device checks before treating the inrush value as usable.

Worksheet checklist. Record source basis, review gaps, and assumptions before using the chart result.

Record current basisWrite whether the current came from nameplate FLA, table FLC, measured current, or a formula estimate before interpreting inrush.
Record method settingsDocument the selected starting method and any current limit, tap, ramp time, bypass mode, or controller setting that changes line current.
Record source notesAdd transformer size, feeder length, available fault current, or utility-starting notes when those values affect the next field decision.

Common mistakes to avoid. Review these before turning chart current into an equipment decision.

Using a generic locked-rotor multiplier without recording whether actual motor or controller data is available for the installation.
Treating reduced line current as proof that acceleration torque, voltage sag, and upstream protection are acceptable.
Comparing two starter methods without labeling whether the value is motor current, line current, drive input current, or bypass current.

Frequently asked questions

These answers explain how to use the chart without turning a quick reference into a final design decision.

Is locked-rotor current the same as line starting current?

Not always. Reduced-voltage starters, soft starters, VFDs, and autotransformer taps can reduce line current compared with a direct-on-line locked-rotor estimate.

Can this chart select the starter?

No. It documents the calculator result so manufacturer data, utility limits, voltage-drop behavior, acceleration torque, and equipment ratings can be checked.