Power factor correction calculator
Calculate the capacitor bank to raise cos φ: load power, current and target cos φ — compensation power in kVAr and capacitance in µF.
Formulas
Required reactive power: Qc = P×(tan φ₁ − tan φ₂), where φ = arccos(cos φ). Capacitance: C = Qc/(2π·f·U²) — for 3-phase networks use line voltage U.
Why correct power factor
- Lower cable and transformer losses
- Free transformer capacity: 0.7 → 0.95 releases ~26%
- Avoid reactive energy penalties
- Lower line current
tan φ table
| cos φ | tan φ |
|---|---|
| 0.6 | 1.33 |
| 0.7 | 1.02 |
| 0.8 | 0.75 |
| 0.9 | 0.48 |
| 0.95 | 0.33 |
| 1.0 | 0 |
Related calculators
- kVA to kW — kva-kw
- Transformer sizing — transformer
- Cable size — cable-calculator
FAQ
What cos φ is considered good?
Industrial consumers are usually required to keep 0.92–0.95 or higher.
What capacitor for 50 kW at cos φ 0.8 → 0.95?
Qc = 50×(0.75−0.33) = 21 kVAr. At 400 V: C = 21000/(2π×50×400²) ≈ 418 µF.
Is overcompensation dangerous?
Yes — too much capacitance leads to leading power factor and voltage rise. Use stepped compensation.