Set your target power factor with confidence. See required capacitor kVAR for common site loads. Export results quickly for reports, tenders, approvals, and audits.
| Scenario | kW | Existing PF | Target PF | Voltage | Phase | Required kVAR |
|---|---|---|---|---|---|---|
| Concrete batch plant | 75 | 0.80 | 0.95 | 400 V | 3 | ~36.98 |
| Tower crane + hoist | 45 | 0.78 | 0.95 | 415 V | 3 | ~24.36 |
| Welding workshop | 20 | 0.72 | 0.90 | 230 V | 1 | ~13.24 |
Power factor correction is often treated as an electrical “nice to have”, but on construction sites it can directly affect generator loading, transformer utilization, feeder currents, and utility penalties. A low power factor forces higher kVA for the same useful kW, which increases current, heat, and voltage drop across temporary distribution. When you set a PF target (commonly 0.95 or above), you create a clear benchmark for design decisions and for acceptance testing during energization.
Begin with reliable measurements. Use a calibrated meter and record kW, kVA, PF, and current during normal production periods. Avoid motor starting peaks, welding bursts, and short idle windows. If you only have kVA from generator or transformer logs, estimate kW using the existing PF, then validate later with site readings. The calculator converts kW and PF into reactive power (kVAR) using the standard trigonometric relationship, then computes the kVAR of capacitance needed to shift from the existing PF to the target PF. Treat the output as the total corrective kVAR required at the measured operating point.
For variable sites, consider control strategy. A fixed capacitor bank can over-correct when load falls, especially at night shifts or during phased commissioning. Automatic stepped banks reduce this risk by switching stages to match demand. Where non-linear loads are present—VFD-driven pumps, site lifts, UPS units, or large rectifiers—check harmonics. Harmonics can overheat capacitors and create resonance with the network. Detuned reactors and correctly rated components are common mitigations, but selection should follow a power quality review.
Installation details matter in temporary power. Confirm capacitor voltage rating, frequency, ambient temperature limits, ventilation, enclosure ingress protection, and safe isolation for maintenance. Place the bank where it improves the upstream current, typically near the main distribution board or a large load group. After installation, re-measure PF under representative conditions and confirm that voltage remains within limits and protective devices operate normally.
Example data (illustrative): A concrete batch plant operates at 75 kW with PF 0.80 on a three-phase 400 V supply. If the target PF is 0.95, the required capacitor size is about 36.98 kVAR. Apparent power reduces from about 93.75 kVA to 78.95 kVA, lowering feeder current and improving capacity margin.
Always verify final sizing and switching with a qualified electrical engineer and follow local safety procedures.
It is the desired ratio of real power to apparent power. Raising PF reduces kVA and current for the same kW, improving utilization and helping avoid demand penalties.
Correction mainly changes reactive power. For a given operating condition, useful power stays roughly the same, while kVA and current fall as PF improves.
Yes for planning. Confirm the generator’s PF capability, voltage regulation, and any manufacturer limits. Re-check PF under typical load steps on site.
No correction is needed, so required kVAR is zero. Extra capacitance may cause over-correction, higher voltage, and nuisance tripping at light load.
Use fixed banks for steady loads. Use stepped banks where loads vary often, such as cranes, hoists, welding bays, and mixed site distribution.
Yes. Harmonics can overheat capacitors and create resonance. For VFDs or rectifiers, consider detuned reactors and verify harmonic levels with measurements or a study.
It is an estimate based on kVA and voltage. Cable impedance, unbalance, and harmonics can affect readings, so validate with meters after installation.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.