Power Factor Correction Calculator
Calculate optimal capacitor bank requirements with considerations for harmonics and VFDs in industrial applications
Power Factor Calculator
Power Factor Correction Guide
Power Factor (PF) is the ratio of real power (kW) to apparent power (kVA) in an electrical system. It measures how efficiently electrical power is being used. A high power factor indicates efficient utilization of electrical power, while a low power factor indicates poor efficiency and increased losses.
Power Factor = Real Power (kW) / Apparent Power (kVA)
In a completely resistive circuit, the power factor is 1.0 (or 100%). Most industrial loads are inductive and have power factors less than 1.0, typically ranging from 0.7 to 0.85 without correction.
Benefits of Power Factor Correction
- Reduced electricity bills by eliminating power factor penalties
- Increased system capacity and reduced voltage drop
- Lower distribution losses and improved voltage regulation
- Extended equipment life due to reduced system stress
- Improved electrical system efficiency
Correcting power factor in systems with Variable Frequency Drives (VFDs) and other non-linear loads requires special considerations:
- Harmonic Resonance Risk: Standard capacitors can create resonant circuits with system inductance, amplifying harmonics
- Detuned Reactors: Series reactors (typically 5-7%) shift resonant frequency below critical harmonic orders
- Tuned Harmonic Filters: Target specific harmonics (typically 5th) while providing power factor correction
- Modern VFDs: Often have near-unity input power factor but still generate harmonics
- Correction Location: Avoid individual correction at VFD loads; use central or group correction
Common Problems with PF Correction
- Capacitor failure due to harmonic overload
- System resonance causing voltage distortion
- Nuisance tripping of circuit breakers
- Overcorrection leading to voltage rise
- Reduced capacitor life in harmonic-rich environments
Fixed vs. Automatic Correction
- Fixed Capacitor Banks: Always connected, suitable for stable loads
- Automatic Capacitor Banks: Switched based on power factor needs, ideal for variable loads
- Hybrid Systems: Combination of fixed and switched stages for optimal correction
- Electronic Switching: Uses thyristors for transient-free switching, suitable for rapidly changing loads
Correction Location
- Individual Correction: Capacitors connected directly to large motor terminals
- Group Correction: Capacitors connected to distribution boards controlling several loads
- Centralized Correction: Capacitors connected at the main distribution board
- Combined Correction: A mixture of the above methods for optimal results
Special Filter Types
- Detuned Filters: Series reactor + capacitor, shifts resonance below harmonic frequencies
- Tuned Filters: Targets specific harmonic frequencies (typically 5th, 7th, 11th)
- Active Filters: Electronic devices that monitor and inject compensating currents
- Hybrid Solutions: Combination of passive and active technologies