Three-Phase kVA to kW Calculator

How to Use This Calculator

This calculator converts three-phase apparent power (kVA) to real power (kW). Simply enter the kVA rating from your transformer, generator, or load, then enter the power factor (cos φ). The result shows the actual usable power in kilowatts. This is essential for sizing cables, circuit breakers, and understanding energy consumption.

Formula and Methodology

The conversion formula is straightforward: kW = kVA × cos φ. For three-phase systems, the apparent power S (kVA) is related to the line voltage V and line current I by S = √3 × V × I / 1000. The real power P (kW) is then P = √3 × V × I × cos φ / 1000 = S × cos φ. The power factor cos φ varies from 0 to 1; a value of 1 means all power is used for work, while lower values indicate reactive power from inductive or capacitive loads.

Practical Examples

Example 1: A three-phase motor has an apparent power of 50 kVA and a power factor of 0.85. Real power = 50 × 0.85 = 42.5 kW.

Example 2: A transformer rated at 100 kVA with a load power factor of 0.9 delivers 100 × 0.9 = 90 kW of real power.

Example 3: For a purely resistive load (cos φ = 1), 75 kVA equals 75 kW.

Tips and Best Practices

• Always verify the power factor from the equipment specification or measure it with a power analyzer.
• Use a power factor correction system if your cos φ is below 0.85 to reduce losses and utility penalties.
• Remember that this calculator assumes balanced three-phase loads. For unbalanced systems, consult an electrical engineer.