3 phase electrical power calculator - Aaron Graves, PhDude Replica

Interactive 3-Phase AC Power Calculator

Calculate real power (kW), current (A), or voltage (V) for a balanced three-phase system. You can also estimate apparent power (kVA), reactive power (kVAr), and output power based on efficiency.

What do you want to calculate?

Voltage type Balanced system assumption. Most industrial supplies use line-to-line input.

Line-to-Line Voltage (V)

Line Current (A)

Real Power (kW)

Power Factor (0 to 1)

Efficiency (%) Used only to estimate output power from calculated/entered real electrical power.

What this 3-phase calculator does

This tool helps you quickly solve common three-phase electrical calculations used in motor circuits, industrial panels, HVAC systems, and power distribution design. Instead of manually rearranging formulas each time, you can choose what you want to solve and get instant results.

It supports the most common scenarios in balanced AC systems:

Calculate real power (kW) from voltage, current, and power factor.
Calculate line current (A) when kW, voltage, and power factor are known.
Calculate required voltage (V) from kW, current, and power factor.
Show related values: apparent power (kVA), reactive power (kVAr), and phase angle.

Core formulas for 3-phase power

Using line-to-line voltage (VLL)

P(kW) = (√3 × VLL × I × PF) / 1000
S(kVA) = (√3 × VLL × I) / 1000
Q(kVAr) = √(S² − P²)

Using line-to-neutral voltage (VLN)

P(kW) = (3 × VLN × I × PF) / 1000
S(kVA) = (3 × VLN × I) / 1000
Q(kVAr) = √(S² − P²)

Both forms are equivalent in balanced systems because VLL = √3 × VLN.

How to use the calculator correctly

Select the quantity you want to solve: power, current, or voltage.
Choose your voltage type: line-to-line or line-to-neutral.
Enter known values and power factor.
Click Calculate.
Review the detailed output values and units.

Power factor tips

Resistive heaters are often near 1.0.
Motors commonly run around 0.75 to 0.95 depending on load.
A lower power factor increases current for the same kW load.

Example calculations

Example 1: Find real power

Given: VLL = 400 V, I = 25 A, PF = 0.90

Real power:

P = (√3 × 400 × 25 × 0.90) / 1000 = 15.59 kW

That means the system consumes about 15.6 kW of real electrical power.

Example 2: Find current for a motor load

Given: P = 30 kW, VLL = 415 V, PF = 0.86

I = (P × 1000) / (√3 × VLL × PF) ≈ 48.6 A

This value helps with cable sizing, breaker selection, and thermal checks.

Why efficiency is included

Electrical input power is not the same as mechanical output power in machines like motors and compressors. If efficiency is known, output estimate is:

Output kW = Input kW × (Efficiency / 100)

This is useful when converting between electrical demand and shaft output expectations.

Common mistakes to avoid

Mixing single-phase and three-phase formulas. The √3 factor is critical for line-to-line 3-phase calculations.
Using the wrong voltage type. Be clear whether your meter/spec gives VLL or VLN.
Ignoring power factor. Assuming PF = 1 for motor loads can understate current.
Applying to unbalanced loads. This calculator assumes balanced conditions.
Confusing kW and kVA. kW is real power; kVA is apparent power.

Practical applications

A 3-phase power calculator is useful for:

Motor feeder and branch circuit planning
Generator sizing checks
Energy audits and demand estimates
Power factor correction planning
Industrial maintenance troubleshooting

Important safety note

These calculations are for planning and estimation. Always verify against local electrical code, equipment nameplates, manufacturer data, and a qualified electrician or engineer before installation or modification.