kabelquerschnitt-berechnen.de

Three-Phase • Watts • Power

Calculate Power for Three-Phase

Calculate power from voltage, current and power factor cos φ.

Calculation Values

Note: This calculation is a technically sound simplification typical of online calculators. For practical sizing, standards, installation method, temperature, grouping, protective devices, cable type and manufacturer specifications must also be checked.

Formula Used

P = √3 × U × I × cos φ

P is the real power in watts, U the line-to-line voltage in volts, I the current in amps and cos φ the power factor.

FAQ

Frequently Asked Questions about Calculate Power for Three-Phase

Briefly explained: formula, use case and key limits of the calculation.

Which formula applies to three-phase power? +

For balanced three-phase systems, P = √3 × U × I × cos φ applies.

Which voltage is used in the formula? +

Usually the line-to-line voltage is used, for example 400 V.

Why is the power factor important? +

The power factor affects real power. With cos φ below 1, real power is lower than apparent power.

Which loads is the calculator suited for? +

The calculator is suited for rough calculations of balanced three-phase loads, for example motors or machinery.

Practical guidance

Understand three-phase power from current and voltage

This calculator finds the active power of a balanced three-phase load from line voltage, line current and power factor.

Input values explained

Current
Enter the expected operating current, not a fuse rating. Motors and electronic power supplies may draw much higher starting or peak currents.
Voltage
Enter the line-to-line voltage between two phases. This is commonly 400 V in low-voltage systems; 230 V is not the correct input here.
Power factor cos φ
cos φ is the ratio of active to apparent power. It is close to 1 for resistive heating loads; use the data-sheet value for motors and transformers.

Example: 16 A at 400 V

A three-phase motor draws 16 A per line at 400 V and has a power factor of 0.90.

P = √3 × 400 V × 16 A × 0.90 = 9,976 W

The active input power is about 9.98 kW. Without the power factor, the apparent power would be about 11.09 kVA.

Interpret active power correctly

The result is electrical active power for a balanced load. It does not give mechanical output, efficiency or starting current.

Calculation limits

  • Measure and assess each phase separately when the load is unbalanced.
  • Cable and protective-device design also requires starting behaviour and installation conditions.