Electric Motors
Three-Phase Motor Current Calculator
The purpose of Three-Phase Motor Current is to turn real input power, line voltage, and power factor into line current. Keep the source condition with the saved result so later comparisons remain meaningful.
Enter values for Line current
Enter ratings or measurements that describe one scenario.
From inputs to result
This page evaluates I = Pinput ÷ (√3 × Vline × PF). The entered quantities are Real input power, Line voltage, and Power factor.
The defaults produce 24.60 A. Replace them with measurements from one operating state.
Calculate three-phase line current from real electrical input power. If you also need cable loss, continue with Motor Cable Power Loss Calculator.
Preparing the calculation
Use nameplate data and measurements from the same load and supply condition. Do not combine a worst-case value with unrelated nominal data.
Values used below a division bar must stay positive. Use the displayed unit for every field and document conversions separately.
- Real input power
- Default example: 15000 W. Enter real input power in W.
- Line voltage
- Default example: 400 V. Enter line voltage in V.
- Power factor
- Default example: 0.88. Enter power factor.
What the number means
Read Line current as the outcome of this equation, not as automatic equipment approval. Compare it with starting demand, running current, torque, efficiency, slip, and thermal loading.
Label alternate cases rather than overwriting the baseline.
Assumptions and limitations
If only shaft power is known, divide by motor efficiency before using this calculation.
Additional checks may be needed for load inertia, acceleration profile, harmonics, reduced-speed cooling, and mechanical loss. Document which effects were checked elsewhere in the analysis.
Use nameplate data and measurements from the same load and supply condition.
Sensitivity check
Change Real input power from 15000 W to 18000 W without altering the remaining fields. The calculated value shifts from 24.60 A to 29.52 A.
Keep both cases when the changed input represents genuine uncertainty.
Keep a reproducible record
Save real input power, line voltage, and power factor with line current. Add the date and any unit conversion.
Carry line current as the raw numerical value until the final step. Do not round between dependent calculations.
Common questions before using the result
What data should go into Three-Phase Motor Current?
Choose entries that describe the same case. Record supply arrangement, speed, duty cycle, enclosure, and winding temperature.
What assumptions affect Line current?
If only shaft power is known, divide by motor efficiency before using this calculation. Also consider load inertia, acceleration profile, harmonics, reduced-speed cooling, and mechanical loss.
Why might a second instrument give another answer?
Differences can come from starting method, service factor, enclosure, and thermal duty, measurement uncertainty, or values taken under different conditions.
Can I change several inputs at once?
Use separate labeled cases when more than one condition changes. Use nameplate data and measurements from the same load and supply condition.
Is the result a code-compliant design value?
No. Compare the value with starting demand, running current, torque, efficiency, slip, and thermal loading and apply relevant equipment and installation requirements.
When should I round line current?
Retain the raw result for comparison and create a separately rounded reporting value if needed.