Power Factor Correction Guide for Industrial Plants
A practical guide to power factor correction for industrial plants. Covers capacitor banks, harmonics, detuned reactors, and energy savings calculation.
What is Power Factor
Power factor = Real Power (kW) / Apparent Power (kVA). Range: 0 to 1.
Low power factor (<0.9) causes: higher current, higher losses, voltage drop, utility penalties.
Goal: Improve power factor to >0.95 (utility requirement) or >0.98 (ideal).
Capacitor Bank Sizing
Formula: Qc = P × (tan φ1 - tan φ2), where P = active power (kW), φ1 = original angle, φ2 = target angle.
Example: 1000kW load, PF 0.8 → 0.98. Qc = 1000 × (0.75 - 0.20) = 550 kVAR.
Staging: Use multiple steps (e.g., 50 kVAR × 10 steps) for better compensation.
Harmonics and Detuned Reactors
Problem: Nonlinear loads (VFD, UPS, rectifiers) generate harmonics. Harmonics cause capacitor overheating and resonance.
Solution: Use detuned reactors (7% or 14% tuning) to avoid resonance.
Harmonic filter: Active or passive filters for severe harmonic distortion (THDi > 15%).
Installation Best Practices
Location: Install capacitor bank at load center (reduces cable losses).
Protection: Fuses or MCCB for each step. Discharge resistor for safety.
Ventilation: Capacitors generate heat. Provide adequate ventilation.
Maintenance: Check capacitor swelling, leakage, and contact overheating.
Energy Savings Calculation
Example: 1000kW load, PF 0.8 → 0.98.
Current reduction: I1/I2 = PF2/PF1 = 0.98/0.8 = 1.225. Current reduced by 18.4%.
Loss reduction: Ploss1/Ploss2 = (I1/I2)² = 1.225² = 1.50. Losses reduced by 33.3%.
Payback period: Usually 1-2 years (depending on electricity rates).