MOTOR DESIGN

Motor FLC Calculator

Estimate motor full-load current from output power, system voltage, efficiency and power factor.

INPUTS

Calculation parameters

Enter project values below. The result updates when you calculate.

System

Line voltage

Motor output power

Efficiency η

Power factor cos φ

Design multiplier

Optional multiplier for your own design workflow; default 1.00.

Starting-current multiplier

× FLC

User-entered estimate only. Prefer manufacturer locked-rotor / starting-current data.

Use this as a preliminary current estimate. Nameplate, code-table and manufacturer starting data govern where required.

Result

READY

ESTIMATED FULL-LOAD CURRENT— A

Electrical input power—

Apparent power—

Design current—

Estimated starting current—

Input efficiency / PF—

Calculated FLC is an estimate from power, efficiency and power factor. Starting current is FLC multiplied by your screening factor, not a substitute for manufacturer locked-rotor or drive-start data.

Verification required: Results are calculation aids and are not guaranteed to be error-free or suitable for a specific project. Independently verify inputs, outputs, applicable standards, manufacturer data and project requirements before design release, procurement or installation.

Method

Mechanical output power is converted to electrical input power using efficiency, then current is obtained from real power and power factor.

1φ: I = Pout / (V · η · cosφ)
3φ: I = Pout / (√3 · V · η · cosφ)

01 · ESTIMATECalculate running current from output power, η and power factor.

02 · STARTINGUse manufacturer data where available; the multiplier is only an estimate.

03 · NEXT CHECKReview motor protection workflow →

Calculation method

I3φ = Pout / (√3 × U × η × cos φ)

Worked example

Load the worked example: 7.5 kW, 400 V three-phase, η = 0.90 and PF = 0.85. Estimated FLC is about 14.15 A; a 1.25 design multiplier gives 17.69 A and a 6× starting-current estimate gives about 84.9 A.

Frequently asked questions

Can I use this value as the breaker setting?

No. Check nameplate current, starting behaviour, the applicable code and manufacturer coordination data.

Which standards should I use?

Use the edition adopted for your project and jurisdiction. See the standards library for the scope of IEC, UL and NEC references.

Continue the design check

All calculators · Cable ampacity · Motor protection · Technical articles

Technical reference: manufacturer / certification body guidance.