A capacitor bank is an assembly of multiple capacitors electrically connected in parallel to provide reactive power compensation and improve power factor for electrical systems. Capacitor banks correct inductive loads including HVAC motors, transformers, and ballasts that consume reactive power.
Configuration and Sizing
Typical capacitor banks range from 5 kVAR to 600 kVAR in standard increments. Three-phase systems use three-phase capacitor units rated at 208V, 277V, 480V, or 600V. Sizing calculation: required kVAR equals load kW multiplied by (tangent of current power factor angle minus tangent of target power factor angle). A 100 kW motor at 0.85 power factor requires approximately 50 kVAR to reach 0.95 power factor.
Switched vs. Fixed Installation
Switched capacitor banks use automatic controllers to connect or disconnect capacitor steps based on reactive load measurement, maintaining target power factor within 0.95-0.98 range. Fixed banks provide constant compensation but cannot adapt to varying loads. Switched systems cost 30-50% more but reduce reactive power surcharges more effectively in variable-load facilities.
Installation and Maintenance
Capacitor banks require isolation switches, harmonic-filtering reactors, and protection fuses. Proper placement near load sources reduces feeder current. Maintenance includes annual thermography inspection and capacitor replacement at end-of-life (10-15 years). Costs range $50-150 per kVAR installed including labor and controls.