How this calculation works
Hold real power constant while reducing the lagging reactive component to the entered target. Translate ideal total compensation into capacitance using the selected number of branches and branch voltage.
Required kvar = real kW × (tan(acos(initial PF)) − tan(acos(target PF))); branch C = total var / (branches × 2πf × branch voltage²)A worked example
At 10 kW, correcting an ideal lagging power factor from 0.8 to 0.95 requires about 4.213159 kvar. For the same line voltage, each star branch uses line voltage divided by square root three.
Good to know
Educational sinusoidal arithmetic, not capacitor-bank sizing approval or wiring guidance. No harmonics, resonance, detuning, switching, voltage-rating, discharge or protection design. Qualified review is required for actual equipment.
Reference: Schneider Electric: power factor correction principles (opens in a new tab) ↗
Real and apparent power are different quantities
The model holds real kW fixed. Apparent kVA is real power divided by power factor, while lagging reactive power follows the associated power-triangle angle.
The target must not be lower than the initial lagging power factor. This tool models ideal correction toward unity, not leading-load or harmonic power-factor behavior.
Connection changes the branch voltage
Single phase uses one branch across the entered voltage. Balanced three-phase delta uses three branches at line voltage, while star uses three branches at line voltage divided by square root three.
Capacitance is reported per branch, not automatically as a total sum of three physical capacitors. Mixing line and phase voltage would change the calculated branch capacitance by a factor of three.
An ideal kvar result is not a safe installation plan
Real equipment selection also depends on system harmonics, resonance, switching transients, protection and applicable component ratings. These are deliberately not inferred from a few steady-state numbers.
The page gives no wiring instructions or approved device choice. Use appropriate qualified electrical design review before treating a numerical scenario as an equipment specification.
Use the result with the next measurement
The VFD pump speed energy calculator considers a speed-dependent real-energy scenario. Reactive compensation and reducing real pump energy are different questions.
Educational sinusoidal arithmetic, not capacitor-bank sizing approval or wiring guidance. No harmonics, resonance, detuning, switching, voltage-rating, discharge or protection design. Qualified review is required for actual equipment.
A few questions, answered
Is capacitance per branch or total?
Per branch under the explicitly selected connection.
Does star use line voltage directly?
No, branch voltage is line voltage divided by √3.
Does this select safe equipment?
No, it is an ideal educational power-triangle model.