Free Engineering Tool
Power and motors
Power Factor Correction Calculator
Enter the load, your present power factor and the target. Get the capacitor kVAR to install and what it saves in kVA and current.
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- Your numbers never leave your device
Inputs
kW
V
Supply
Readout
ADD-kVAR
kVA before
-kVA
kVA after
-kVA
kVA released
-kVA
Current before
-A
Current after
-A
Current saved
-%
Formula
kVARcap = kW × (tan φ₁ − tan φ₂) · φ = arccos(PF)
Example: 100 kW at 0.75 needs about 55.3 kVAR to reach 0.95. Line current falls in proportion to the power factor ratio, here by about 21%.
Practical notes
- Pick the nearest standard bank size at or just above the result, usually built from steps of 5, 10, 25 or 50 kVAR.
- Do not aim for unity. Over-correction under light load pushes a leading power factor and can raise the voltage. 0.95 to 0.98 is a sensible target.
- Capacitor output scales with voltage squared, so a capacitor rated at 440 V gives about 89% of its kVAR on a 415 V supply.
- Where there are many variable drives or rectifiers, harmonics can overload plain capacitors. Use detuned (reactor-fitted) banks and measure first.
To measure the present power factor and load, a clamp meter with power functions is the simplest tool. The three-phase power calculator converts between kW, kVA and amps.
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