APFC panel — what it is, how it works, and how to size it
APFC = Automatic Power Factor Correction. It switches capacitor steps ON/OFF to keep PF near 0.95–0.99. In kVAh-based tariffs, it reduces billed units and demand by lowering kVA.
APFC panel basics
An APFC panel continuously measures PF and switches capacitor steps to compensate reactive power. This reduces current, transformer loading, and kVA-based charges.
What’s inside an APFC panel?
- —APFC controller (PF sensing + step logic)
- —Capacitor steps (kVAr)
- —Contactors/thyristor switching
- —Detuned reactors (recommended with harmonics/VFDs)
- —Protection: fuses, MCB/MCCB, temperature monitoring
Sizing rule of thumb
Sizing depends on your kW load and present PF vs target PF. An energy audit or incomer meter data makes the sizing accurate and avoids over-compensation.
Frequently asked questions
If poorly sized, it can cause leading PF or resonance with harmonics. Using detuned reactors and data-based sizing prevents this.
Solar doesn’t automatically fix PF. Many inverters operate near unity PF but your inductive loads still affect overall PF.
Track PF and kVAh/kWh gap before and after using a three-phase meter and your tariff’s penalty/rebate terms.
