kVA Calculator

Multiply by the power factor: kW = kVA × cos φ. 100 kVA at a power factor of 0.8 is 80 kW. Going the other way, kVA = kW / cos φ.

For three-phase divide by √3 and the line-to-line voltage: I = kVA × 1000 / (√3 × V). For single-phase divide by the voltage: I = kVA × 1000 / V. 100 kVA at 400 V three-phase is 144 A per line.

About 1.44 A per kVA at 400 V three-phase and 4.35 A per kVA at 230 V single-phase. The power factor does not change this: amps follow the kVA, not the kW.

Their losses and heating depend on the current and the voltage, not on how much of the current does useful work. The manufacturer cannot know the load's power factor, so the rating is the apparent power the windings can carry.

Reactive power, the part of the apparent power that flows back and forth to build magnetic and electric fields without doing work. kVA² = kW² + kVAr². Capacitor banks supply kVAr locally to lift the power factor.

Convert the load's maximum demand to kVA, then pick the next standard size above it with allowance for growth. A generator also needs checking for motor starting, which the generator sizing calculator covers.