# Three-Phase Power Calculator

Calculate three-phase apparent, real, and reactive power for star (Y) and delta configurations. Enter voltage, current, and power factor for instant.

## What this calculates

Three-phase power systems are the backbone of industrial and commercial electrical distribution. This calculator computes apparent power (kVA), real power (kW), and reactive power (kVAR) using the formula P = sqrt(3) x V x I x pf, along with line and phase current relationships for star and delta configurations.

## Inputs

- **Line Voltage** (V) — min 0 — Line-to-line voltage (V_LL).
- **Line Current** (A) — min 0 — Line current in amperes.
- **Power Factor** — min 0, max 1 — Power factor (cos φ), typically 0.8-0.95 for industrial loads.
- **Configuration** — options: Star (Y / Wye), Delta (Δ) — Winding configuration of the load.

## Outputs

- **Apparent Power** (kVA) — Total apparent power (S = √3 × V × I).
- **Real Power** (kW) — Active power consumed (P = √3 × V × I × pf).
- **Reactive Power** (kVAR) — Reactive power (Q = √3 × V × I × sin φ).
- **Line Current** (A) — Current in the line conductors.
- **Phase Current** (A) — Current through each winding phase.

## Details

Three-phase power uses three alternating currents 120° apart, providing constant power delivery and more efficient use of conductors than single-phase. The total power is P = √3 × Vline × Iline × cos(φ), where cos(φ) is the power factor.

In a star (Y) configuration, each winding connects between a line and the neutral point. The phase voltage is Vline/√3, and the line current equals the phase current. In a delta (Δ) configuration, each winding connects between two lines. The phase voltage equals the line voltage, but the line current is √3 times the phase current.

The power factor represents the ratio of real power to apparent power. Inductive loads (motors, transformers) cause the current to lag the voltage, reducing the power factor below 1. Low power factor means more current is needed to deliver the same real power, increasing losses and requiring larger conductors. Power factor correction capacitors are commonly installed to improve the power factor toward unity.

## Frequently Asked Questions

**Q: What is the difference between star and delta configuration?**

A: In star (Y), each winding connects from a line to a common neutral. Phase voltage is V_line/sqrt(3), and line current equals phase current. In delta, each winding connects between two lines. Phase voltage equals line voltage, and line current is sqrt(3) times phase current.

**Q: What is power factor and why does it matter?**

A: Power factor is the ratio of real power (kW) to apparent power (kVA). A power factor of 0.85 means only 85% of the apparent power does useful work. Low power factor wastes energy, increases current, and may incur utility penalties.

**Q: Why is three-phase more efficient than single-phase?**

A: Three-phase delivers constant power (no pulsation), uses less conductor material for the same power capacity, and naturally produces rotating magnetic fields for motors. It is about 150% as efficient as single-phase per unit of conductor.

**Q: How do I convert between star and delta?**

A: For the same power and line voltage, a delta load draws sqrt(3) times more line current than the equivalent star load. Delta connections are often used for motors because they can be started in star (reduced voltage) and switched to delta (full voltage).

---

Source: https://vastcalc.com/calculators/technology/three-phase-power
Category: Technology
Last updated: 2026-04-21