Three-phase power delivers smooth, efficient power for motors and industry. In a star connection each phase sees the line voltage divided by √3; in a delta, each phase carries the line current divided by √3.
How to use the Three-Phase Power Calculator
- Connection
- Line voltage V_L
- Line current I_L
- Power factor
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose the connection, enter the line voltage, line current and power factor.
Inputs explained
| Field | What to enter |
|---|---|
| Connection | Choose one: Star (wye), Delta |
| Line voltage V_L | Units: V, kV, mV |
| Line current I_L | Units: A, mA, µA, kA |
| Power factor | A number |
What each result means
- Real power P = sqrt(3)×[Line voltage V_L]×[Line current I_L]×[Power factor]÷1000
- Apparent power S = sqrt(3)×[Line voltage V_L]×[Line current I_L]÷1000
- Reactive power Q = [Apparent power S]×sqrt(1 – [Power factor]^2)
- Phase angle = deg(acos([Power factor]))
Example values
How the main result changes when Line voltage V_L changes and everything else stays at the example values above:
| Line voltage V_L (V) | Real power P (kW) |
|---|---|
| 200 | 5.889 |
| 300 | 8.8335 |
| 400 | 11.7779 |
| 500 | 14.7224 |
| 600 | 17.6669 |
| 800 | 23.5559 |
Formula
P = √3·V_L·I_L·PF, S = √3·V_L·I_L, Q = √(S² − P²) · Star: V_ph = V_L/√3, I_ph = I_L · Delta: V_ph = V_L, I_ph = I_L/√3
Worked example
Inputs — Connection: Star (wye); Line voltage V_L: 400 V; Line current I_L: 20 A; Power factor: 0.85.
Results — Real power P = 11.77795 kW; Apparent power S = 13.85641 kVA; Reactive power Q = 7.29932 kVAR; Phase voltage = 230.94011 V; Phase current = 20 A; Phase angle = 31.7883 °.
Key terms
- Line voltage
- Voltage between two phase conductors.
Frequently asked questions
Why √3?
Line voltages are 120° apart, so V_L = √3·V_ph in star.
Is total power the same in star and delta?
Yes, for the same line voltage and current.
What is a balanced load?
Equal impedance on all three phases.
Why is three-phase used for motors?
It creates a rotating field and smooth torque.