Three Phase Power Calculator — Free kW, Amps & Power Factor Tool | AllInOneTools
⚡ Electrical & Energy

Three Phase Power Calculator

Calculate kW, kVA, amps, power factor, and line/phase voltages for 3-phase electrical systems. Supports star (wye) and delta configurations with power triangle analysis.

3-Phase System
V
A
PF
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Power Triangle
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Voltage & Current

Three Phase Power Calculator: How to Calculate kW, kVA, Amps, and Power Factor

Three-phase power is the backbone of industrial and commercial electrical systems worldwide. It delivers power more efficiently than single-phase, uses less conductor material, and provides constant power delivery (unlike single-phase which pulsates). Understanding three-phase calculations is essential for electricians, engineers, and anyone working with industrial equipment, motors, or large electrical installations.

Core Three-Phase Formulas

Real Power: P(kW) = √3 × V_L × I_L × PF ÷ 1000
Apparent Power: S(kVA) = √3 × V_L × I_L ÷ 1000
Reactive Power: Q(kVAR) = √(S² − P²)
Current: I = P(W) ÷ (√3 × V × PF)
Power Factor: PF = kW ÷ kVA = cos(θ)

Star (Y): V_L = √3 × V_Ph, I_L = I_Ph
Delta (Δ): V_L = V_Ph, I_L = √3 × I_Ph
Worked Example — Industrial Motor
480V 3-phase, 50A line current, PF = 0.85
Apparent: S = √3 × 480 × 50 ÷ 1000 = 41.6 kVA
Real: P = 41.6 × 0.85 = 35.3 kW (47.4 HP)
Reactive: Q = √(41.6² − 35.3²) = 21.9 kVAR
Phase voltage (star): 480 ÷ √3 = 277V

Star (Wye) vs Delta Connections

PropertyStar (Y)Delta (Δ)
Line VoltageV_L = √3 × V_PhV_L = V_Ph
Line CurrentI_L = I_PhI_L = √3 × I_Ph
NeutralYes (4th wire)No
Best ForDistribution, unbalanced loadsMotors, balanced loads
Common Systems208/120V, 480/277V, 400/230V480V, 600V motors

Power Factor and the Power Triangle

Power factor measures how efficiently electrical power is being used. A PF of 1.0 means all power delivered is being used productively. Industrial motors typically have PF of 0.80–0.90, meaning 10–20% of the apparent power is reactive (wasted as magnetic fields). Low PF increases current draw, causing higher losses and utility penalties. Power factor correction using capacitor banks can raise PF to 0.95+, reducing current draw and utility costs by 10–20%.

Frequently Asked Questions

How do you calculate three phase power?
P(kW) = √3 × V_line × I_line × PF ÷ 1000. Example: 480V, 50A, PF 0.85 → P = 1.732 × 480 × 50 × 0.85 ÷ 1000 = 35.3 kW. For apparent power (kVA), remove the PF from the formula.
Star vs Delta — what's the difference?
Star (Y): V_line = √3 × V_phase, I_line = I_phase, has neutral wire. Delta (Δ): V_line = V_phase, I_line = √3 × I_phase, no neutral. Star for distribution/unbalanced loads; delta for motors/balanced loads.
How to convert line to phase voltage?
Star: V_phase = V_line ÷ √3. So 480V line = 277V phase, 400V = 230V, 208V = 120V. Delta: V_phase = V_line (same). Remember √3 ≈ 1.732.
How many amps for a 3-phase circuit?
I = P(W) ÷ (√3 × V × PF). Example: 10kW at 480V, PF 0.85 → I = 10,000 ÷ (1.732 × 480 × 0.85) = 14.2A. For kVA: I = kVA × 1000 ÷ (√3 × V).
What is power factor?
PF = kW ÷ kVA = cos(θ). Range 0-1. PF=1 = purely resistive (ideal). Motors: 0.8-0.9. Low PF means higher current for same real power. Corrected with capacitor banks to 0.95+, saving 10-20% on utility costs.
What is the power triangle?
P (kW, real) is the horizontal side, Q (kVAR, reactive) is vertical, S (kVA, apparent) is the hypotenuse. S² = P² + Q². PF = P/S. Inductive loads = lagging PF; capacitive = leading PF.
How to size a 3-phase generator?
Generator kVA = Total kW ÷ PF × 1.25 (safety margin). Example: 50kW at 0.85 PF = 58.8 × 1.25 = 73.5 → 75 kVA generator. Account for motor starting current (6-8× running).