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Power Factor Correction

Capacitor Bank Sizing · kVAR · Demand Charge Reduction

When to use: Use when a facility has a low power factor (typically caused by motors, transformers, and fluorescent lighting) and the utility is charging a power factor penalty or demand charges. Poor power factor increases apparent power (kVA), requiring larger conductors, transformers, and switchgear. A capacitor bank supplies reactive power locally, reducing the reactive current drawn from the utility. Most utilities target PF ≥ 0.95 to avoid penalties.

System Parameters
Real (measured) power
kW
Power Factor Settings
0.5 (Poor)0.95+ (Good)
0.801.00 (Unity)
Power Triangle
P (kW)
100
100
Q (kVAR)
88.2
32.9
S (kVA)
133.3
105.3
Required Capacitor Bank
55.3
kVAR (calculated)
Standard Size
60 kVAR
Benefits of Correction
kVA Reduction28.1 kVA
Current Reduction33.8 A
Current Before160.4 A
Current After126.6 A
Est. Annual Savings~$4042
Key Points
Q = P × (tan(θ₁) - tan(θ₂))
Install capacitors as close to load as possible
Fixed vs automatic (switched) banks — use auto for variable loads
Avoid over-correction — leading PF can cause ferroresonance
Check harmonics before installing — can amplify in resonant circuits