Three-Phase Power Formulas
kVA = kW / PF. kVAR = sqrt(kVA^2 - kW^2). Line current = kVA x 1000 / (sqrt(3) x line voltage) = kVA x 1000 / (1.732 x V). Phase current (wye) = line current. Phase current (delta) = line current / 1.732. If you enter line current instead of kW, the calculator derives kVA = amps x V x 1.732 / 1000, then applies PF to get kW.
Frequently Asked Questions
Three-phase power is the standard form of AC power delivery for industrial and commercial applications. It uses three alternating currents offset by 120 degrees, providing smoother power delivery and more efficient motor operation than single-phase power. Most industrial equipment, large HVAC systems, and manufacturing machinery run on three-phase.
kW (kilowatts) is real power — the power actually doing useful work. kVA (kilovolt-amperes) is apparent power — the total power drawn from the supply. kVAR (kilovolt-amperes reactive) is reactive power, used by inductive and capacitive loads without doing useful work. Power factor = kW / kVA. kVA^2 = kW^2 + kVAR^2.
For a balanced three-phase system: Line current (A) = kW x 1000 / (1.732 x line voltage x power factor). For kVA: Line current = kVA x 1000 / (1.732 x line voltage). The factor 1.732 is the square root of 3, which appears in all three-phase power calculations.
Power factor (PF) is the ratio of real power (kW) to apparent power (kVA). A PF of 1.0 means all power is being used effectively. Inductive loads (motors, transformers) reduce PF below 1.0, causing the utility to supply more current than the load actually uses. Utilities may charge power factor penalties for PF below 0.90-0.95.
In a three-phase system, line voltage is the voltage between any two of the three conductors. Phase voltage is the voltage from any conductor to the neutral (in a wye system). Line voltage = phase voltage x 1.732 for wye configurations. Delta systems have no neutral, and line voltage equals phase voltage.
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