Three Phase Power Calculator - Line Voltage & Current

Three-Phase Power Basics

Industrial motors, HVAC plants, and data-center feeds often run on three-phase AC because it delivers smooth rotating power with less copper than three separate single-phase lines. Balanced systems share one neutral in wye or circulate line currents in delta.

Power and Voltage Relations

$$P = \sqrt{3}\,V_{\text{line}}\,I_{\text{line}}\,\cos\varphi$$

For a balanced wye connection, phase voltage relates to line voltage by:

$$V_{\text{phase}} = \frac{V_{\text{line}}}{\sqrt{3}}$$

In delta, line voltage equals phase voltage. Apparent power is $S = \sqrt{3}\,V_{\text{line}}\,I_{\text{line}}$ and reactive power is $Q = S\sin\varphi$.

Example

A wye-fed load at 415 V line, 12 A line current, and 0.88 power factor draws about $P = \sqrt{3} \times 415 \times 12 \times 0.88 \approx 7.6\,\text{kW}$. Phase voltage is $415/\sqrt{3} \approx 240\,\text{V}$.

Frequently Asked Questions

What is line voltage?

Line voltage is measured between any two of the three phase conductors. It is what most nameplates list for three-phase equipment.

When do I use wye vs delta?

Wye gives lower phase voltage on each winding and often includes a neutral. Delta connects windings line-to-line with no neutral path.

Why is √3 in the formula?

Balanced three-phase voltages are 120° apart. The line-to-line magnitude is √3 times the phase magnitude in wye.

What if power factor is 1?

Real power equals apparent power. Reactive power is zero. Resistive loads like heaters often run near unity power factor.

Is line current the same as phase current?

In wye they are equal. In delta, line current is √3 times phase current. This calculator assumes balanced line current input.

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Three Phase Calculator

Three-Phase Power Basics

Power and Voltage Relations

Example

Frequently Asked Questions

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