Power Factor Correction Calculator
Size the capacitor bank in kVAr and see the current it saves
How It's Calculated
A capacitor bank supplies reactive power locally, so the supply only carries the load's active power and what reactive power remains. The reactive power to add is set by the change in the power factor angle:
where is the active power in kW, the angle of the existing power factor and the angle of the target. The bank is rounded up to whole capacitor steps, and the corrected power factor is worked back from what is installed. The current follows the apparent power:
The capacitance comes from : for a three-phase delta bank each of the three capacitors takes a third of the kVAr across the line voltage. The method is the one in the Schneider Electric Electrical Installation Guide, chapter L (“Power factor correction”); capacitor ratings themselves are covered by IEC 60831-1.
Worked Example
A 200 kW three-phase load on 400 V at a power factor of 0.75, corrected to 0.95 with 25 kVAr steps:
- , rounded up to 125 kVAr
- Corrected power factor = 0.969
- Current 384.9 A → 298.1 A, a 22.6% reduction
- Capacitance per phase (delta) = 829 µF
Frequently Asked Questions