Three-phase / Single-phase Power (Supply Standards)
Calculate apparent, active and reactive power, line and phase current for single-phase or balanced three-phase loads using national/regional supply standards (China 220/380 V, Europe 230/400 V, US 120/277/480 V, Japan 100/200 V…) or a custom voltage — and work back from power to current.
Key points
The three-phase / single-phase power calculator uses the nominal voltage of the selected national supply standard (China 220/380 V, Europe 230/400 V, US 120/240/277/480 V, Japan 100/200 V, or a custom voltage). For balanced three-phase loads S = √3·U_L·I_L, for single-phase S = U·I; active power P = S·cosφ and reactive power Q = S·sinφ. Given active power it back-calculates current: three-phase I_L = P/(√3·U_L·cosφ), single-phase I = P/(U·cosφ). In a Y connection the phase current equals the line current, while in Δ the phase current is I_L/√3.
Inputs
Three-phase S = √3·U_L·I_L ｜ single-phase S = U·I ｜ P = S·cosφ ｜ Q = S·sinφCalculation model (updates with parameters)
| Supply standard / phase system | China 220 / 380 V · 50 Hz | Three-phase · 50 Hz |
| Line / phase voltage | 380 V / 220 V | U_L = √3·U_ph |
| Apparent power S | 6.582 kVA | S = √3·U_L·I_L |
| Active power P | 5.595 kW | This is what the energy meter bills |
| Reactive power Q | 3.467 kvar | Does no work but occupies transformer and line capacity |
| Power factor | 0.85 | below 0.9, power-factor penalty charges may apply |
| Line current I_L | 10 A | Three-phase line current (clamp meter on one phase conductor) |
| Phase current (Y / Δ) | 10 A / 5.774 A | Y: phase current = line current; Δ: phase current = I_L/√3 |
| Active power per phase | 1.865 kW | Shared equally by a balanced three-phase load |
Engineering notes
- For a balanced three-phase load, S = √3·U_L·I_L is independent of the Y / Δ connection, but the phase current is not: Y gives phase current = line current, Δ gives phase current = line current/√3.
- These are nominal voltages (China 220/380 V, Europe 230/400 V, …); real grids allow about ±10%. Choose “Custom voltage” to calculate with a measured value.
- For the same power the three-phase current is about 1/3 of the single-phase current; for single-phase loads above 32 A prefer a three-phase supply to save on conductors and breakers.
- A power factor below 0.9 may incur power-factor penalty charges; estimate the compensation with the “Power factor correction capacitor” tool.
FAQ
- What is Three-phase / Single-phase Power (Supply Standards) for?
- Calculate apparent, active and reactive power, line and phase current for single-phase or balanced three-phase loads using national/regional supply standards (China 220/380 V, Europe 230/400 V, US 120/277/480 V, Japan 100/200 V…) or a custom voltage — and work back from power to current.
- What is the formula for Three-phase / Single-phase Power (Supply Standards)?
- Core formula: Three-phase S = √3·U_L·I_L ｜ single-phase S = U·I ｜ P = S·cosφ ｜ Q = S·sinφ. The tool returns results instantly using this formula and the selected parameters.
- What engineering notes should I keep in mind when using Three-phase / Single-phase Power (Supply Standards)?
- For a balanced three-phase load, S = √3·U_L·I_L is independent of the Y / Δ connection, but the phase current is not: Y gives phase current = line current, Δ gives phase current = line current/√3. These are nominal voltages (China 220/380 V, Europe 230/400 V, …); real grids allow about ±10%. Choose “Custom voltage” to calculate with a measured value. For the same power the three-phase current is about 1/3 of the single-phase current; for single-phase loads above 32 A prefer…
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