Three phase power calculator
In a star-connected system the line voltage is √3 times the phase voltage, because the two phase voltages you measure between are 120 degrees apart rather than opposite. That geometry is why 230 V phase-to-neutral gives 400 V phase-to-phase. 230 × 1.732 = 398. The same factor then appears in the power formula, and in the voltage-drop formula for the same reason.
Estimates for planning and study. Fixed wiring must be designed and installed to the wiring regulations that apply where you are, by someone competent to do it.
Three-phase real power is √3 × line voltage × line current × power factor. At 400 V, 32 A and 0.9 power factor that is 19.95 kW real from 22.17 kVA apparent. The √3 comes from the 120-degree phase relationship between lines.
How to calculate three-phase power
Three phase exists because it moves far more power down the same copper. The return currents in a balanced system cancel, so there is little or no neutral current and the conductors carry only what they need to. That is why industrial motors above a few kilowatts are almost always three phase, and why long-distance distribution is. The practical catch for anyone specifying equipment is balance: an unbalanced load puts current back in the neutral and the efficiency advantage starts to evaporate.
Questions
P = √3 × V(line) × I(line) × power factor for a balanced load. Apparent power drops the power factor term.
Phase to neutral is 230 V; phase to phase is 230 × √3 = 400 V. Both are available from the same four-wire supply.
In a star connection, yes. In a delta connection line current is √3 times the phase current, which trips people up when reading motor data.
I = P ÷ (√3 × V × pf). The current check row does exactly that as a cross-check on your inputs.
Yes. These formulas assume balance. For a badly unbalanced load, each phase has to be calculated separately and summed.