What is Power factor and reactive power?
Power factor is the ratio of real power, measured in kW, to apparent power, measured in kVA. Reactive power, measured in kVAr, is drawn by motors, transformers and other inductive loads to sustain magnetic fields. A low power factor raises current and losses, and many utility tariffs penalize it or bill on kVA.
What it is
Real power does useful work, such as turning a motor or heating an element. Reactive power moves back and forth between the supply and inductive equipment without doing useful work, but it still flows through cables and transformers. Apparent power combines the two.
Power factor is real power divided by apparent power. A value close to one means most of the current is doing useful work. Plants with many motors, compressors and pumps often run at a lower power factor unless they install correction.
Correction is usually done with capacitor banks or active filters. Capacitors can fail or be switched wrongly, and harmonics from drives can complicate correction, so power factor needs ongoing measurement, not a one-time fix.
Who it applies to / where it is used
Power factor matters for industrial and commercial customers whose tariffs include kVA-based demand charges or power factor penalties and incentives. Tariff rules vary by utility and country, so check your own tariff schedule.
How it is measured / what evidence it needs
Power factor is measured by power quality meters at the incomer and on major feeders, alongside the bill.
- kW, kVA and kVAr at the main incomer
- Power factor by feeder and by time of day
- Capacitor bank stage status and health
- Harmonic distortion where variable speed drives are common
- Power factor charges or credits on the utility bill
How Aqueduct helps
Aqueduct reads power factor live on each feeder, so a failed capacitor stage is found before the bill arrives.
- aQ EnergySmart tracks power factor and kVA demand at the incomer and by feeder
- Alerts flag falling power factor and the feeders driving it
- Tariff configuration turns power factor changes into money
- Correction work routes through the customer's CMMS and is verified on the next readings