Power factor correction calculator — capacitor kVAR
Work out the capacitor bank needed to improve power factor from an existing value to a target: enter load kW, existing PF and target PF, and read kVAR, capacitance and capacitor current.
Capacitor bank sizing
Formula: kVAR = kW × (tan(acos(PF₁)) − tan(acos(PF₂))), capacitance C (µF) = kVAR × 10⁹ / (3 × 2πf × V²) and current Ic (A) = kVAR × 1000 / (√3 × V) per IEEE 18 / IEC 60831.
Worked example: 500 kW from 0.75 to 0.97 needs ≈315 kVAR.
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Frequently asked questions
How do I calculate the capacitor bank for power factor correction?
Required kVAR = kW × (tan(acos(PF₁)) − tan(acos(PF₂))), where PF₁ is the current power factor and PF₂ the target. A 500 kW load corrected from 0.75 to 0.97 needs about 315 kVAR (IEEE 18 / IEC 60831).
Why correct power factor?
A low power factor means the supply must deliver extra reactive current that does no work — larger cables, transformers and higher demand charges. Correcting a 0.75 load to 0.97 cuts the apparent current by about a quarter for the same real power.
How is the capacitor current calculated?
For a three-phase bank, capacitor current Ic = kVAR × 1000 / (√3 × V). In the example, 315 kVAR at 400 V draws about 455 A per phase — size the fusing/contactor for Ic × 1.3 to 1.43 to cover inrush.
AO Ctrl provides this tool for reference only.