Skip to content
ENExplore Calculators

Motor Full Load Current Calculator

Work out motor full load current instantly with clear inputs, formula shown and shareable results.

About Motor Full Load Current Calculator

Motor nameplate power is mechanical output at the shaft, so the electrical input is that divided by efficiency. Full load current then follows from the three-phase relation. Direct-on-line starting draws roughly 6-8 times full load current, which is what sizes the protection and the supply.

Formula

Motor full load current

I = (kW / efficiency) x 1000 / (sqrt(3) x V x pf); DOL start current is about 6.5 x FLC

Worked example

With the default values below, Motor Full Load Current Calculator returns Full load current of 14.14. Change any input above and every figure here is recalculated in your browser.

Inputs used

Motor rating
7.5 kW
Supply voltage
400 V
Efficiency
89 %
Power factor
0.86

Results

Full load current
14.14 A
Electrical input power
8.43 kW
Direct-on-line starting current
91.93 A
Losses in the motor
0.93 kW

Step by step

  1. 1Values used
  2. 2Motor full load current
  3. 3Full load current= 14.14 A
  4. 4Electrical input power= 8.43 kW
  5. 5Direct-on-line starting current= 91.93 A
  6. 6Losses in the motor= 0.93 kW

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

Frequently Asked Questions

Should protection be set to full load current?

Overload protection is set on full load current, but short-circuit protection must let the starting surge through, so the two are sized differently.

Why does starting current matter for the supply?

The voltage dip during starting can trip other equipment. Star-delta, soft starters and VFDs all exist to limit that surge.

Related Calculators

Motor Full Load Current Calculator | Calcrivo