Electrical input is not shaft output

Controlled Three-Phase Motor Power Calculator

Solve one balanced, sinusoidal three-phase operating point while keeping electrical input power, mechanical shaft output and motor loss explicitly separate.

Balanced sinusoidal scopeRMS line quantitiesNo IE-class lookupNo sizing decision

Controlled operating-point calculation

Do not use this arithmetic to size protection, conductors, contactors, a drive or a motor. It excludes starting and transient current, unbalance, harmonics, waveform distortion, converter losses, duty, service factor, thermal limits and code requirements. Live electrical measurements require qualified personnel, suitable instruments and the governing safe-work procedure.

Quantity to solveThe selected input becomes blank and read-only; all other quantities must describe the same operating point
RMS line-to-line voltage V_LL (V)Positive plain decimal; same operating point as every other input
RMS line current I_L (A)Positive plain decimal; balanced line-current basis
Displacement power factor cos φPositive decimal greater than 0 and not greater than 1
Efektiivsus ηP₂/P₁ at this operating point; positive decimal not greater than 1
Mechanical shaft output P₂Rated/nameplate output is not automatically the present operating output
Shaft-output unitMechanical horsepower uses the NIST 745.6999 W conversion factor
Operating-point and source recordRecord motor/nameplate ID, instrument or document, date/load state and where efficiency/PF came from
I confirm the inputs are RMS line quantities for one sufficiently balanced, sinusoidal three-phase operating point; they are not phase-to-neutral values or mixed operating states.
I understand that using rated/nameplate efficiency or power factor away from its rated test point makes shaft output an estimate, not a measurement or IEC efficiency determination.

Operating-point result

Solved quantity

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Mechanical shaft output P₂

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Electrical active input P₁

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Apparent input S

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Reactive-power magnitude |Q|

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Motor loss P₁ − P₂

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Line operating quantities

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Power factor and efficiency

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Model, formulas and units

P₁(kW) = √3 × V_LL,rms × I_L,rms × cos φ / 1000
P₂(kW) = η × P₁(kW)
S(kVA) = √3 × V_LL,rms × I_L,rms / 1000
|Q|(kvar) = S × √(1 − cos² φ)
P_loss(kW) = P₁ − P₂

The U.S. Department of Energy motor-load fact sheet gives the three-phase electrical input relation P₁ = √3·V·I·PF/1000 using RMS mean line-to-line voltage, RMS mean line current and power factor. Efficiency is η = P₂/P₁, so multiplying by η produces estimated mechanical shaft output P₂; it does not produce electrical active input.

The reactive result is an unsigned magnitude for the declared balanced sinusoidal displacement-power-factor model. It does not identify leading versus lagging operation and is not a valid harmonic/VFD reactive-power decomposition.

IEC and measurement boundary

IEC 60034-1:2026, Edition 15 is the current rating-and-performance standard and replaced IEC 60034-1:2022 in March 2026. The arithmetic above is not presented as an IEC 60034-1 formula.
IEC 60034-2-1:2024, Edition 3 specifies test methods for determining machine losses and efficiency. Entering a catalog or nameplate efficiency here does not reproduce those tests.
IEC 60034-30-1:2025, Edition 2 defines IE efficiency classes for a stated scope and test basis. This page does not infer IE1–IE5 from a calculated operating point or publish proprietary efficiency tables.
For unbalanced, distorted or converter-fed waveforms, use an appropriate three-phase power analyzer and governing method. Do not average unrelated voltage, current, PF and efficiency values.

Official evidence

U.S. DOE — Determining Electric Motor Load and Efficiency

Page 3, Equation 1 defines three-phase electrical input power from RMS mean line-to-line voltage, RMS mean line current and power factor; page 4 provides a worked measurement example.

IEC 60034-1:2026, Edition 15

Official current-edition, lifecycle and scope page for rotating-machine ratings and performance.

IEC 60034-2-1:2024, Edition 3

Official current-edition page for standardized loss and efficiency test methods.

IEC 60034-30-1:2025, Edition 2

Official current-edition page for line-operated AC motor IE efficiency classes and their scope.

NIST SP 811, Appendix B.9

Official conversion table: mechanical horsepower (550 ft·lbf/s) to watt, factor 7.456999 × 10².