How to use this tool
- Select the supply type and confirm whether voltage is line-to-line for three-phase.
- Enter voltage, current, power factor (AC), motor efficiency and shaft RPM.
- Compare electrical input, shaft output and estimated torque.
- Confirm the assumptions against the drive, motor nameplate and electrical installation requirements.
Calculation method and formula
Balanced three-phase input power P = √3 × Vline × Iline × power factor. Single-phase P = V × I × PF; DC P = V × I. Shaft torque = motor output power ÷ angular speed.
WORKED EXAMPLE
A balanced 400 V, 10 A three-phase load at PF 0.8 draws ≈5.543 kW of real input power. At 90% efficiency, shaft output is ≈4.988 kW.
What the calculation does not cover
- This is not a cable, circuit-breaker, contactor or motor-protection sizing tool.
- Variable-frequency drives, distorted waveforms, start-up current and unbalanced phases may require other models.
- Always follow electrical safety codes and qualified professional review.
Common questions
Why does three-phase use square root of three?
The √3 factor relates line voltage and line current to the total balanced three-phase apparent power.
Is calculated shaft torque the motor's maximum torque?
No. It is an estimated steady-state torque at the specified speed and output power.
Engineering use: This calculator is a transparent estimate for its defined model; confirm units, applicability, standards and engineering decisions independently.