Understanding Power Factor

Power factor (PF) is defined as:

PF = cos(φ)

where φ is the phase angle between voltage and current. It ranges from 0 to 1, with 1 indicating maximum efficiency.

Key Concepts:

• Lagging Power Factor: Occurs in inductive loads where current lags voltage.
• Leading Power Factor: Occurs in capacitive loads where current leads voltage.
• Unity Power Factor: Ideal case where voltage and current are in phase (φ = 0).

Causes of Poor Power Factor

• Inductive Loads: Equipment like motors, transformers, and inductors cause current to lag voltage.
• Underloaded Motors: Running motors at less than their rated load reduces power factor.
• Harmonics: Nonlinear loads introduce harmonic distortions that affect power factor.

Effects of Poor Power Factor

• Increased losses in transmission lines due to higher current.
• Overloading of transformers and other equipment.
• Higher electricity costs for industrial users with penalties for low power factor.

Methods for Power Factor Improvement

• Capacitor Banks: Capacitors provide leading reactive power to balance lagging reactive power in inductive loads. Commonly used in industries to correct power factor.
• Synchronous Condensers: Synchronous motors operated at no load and overexcited act as leading power factor devices.
• Phase Advancers: Installed on the rotor of induction motors to improve power factor in large machines.
• Automatic Power Factor Correction (APFC) Panels: Systems that dynamically adjust power factor correction devices based on load changes.

Calculations for Power Factor Correction

Example Problem:

• System Load: 100 kW
• Existing Power Factor: 0.7
• Target Power Factor: 0.95

Solution:

1. Calculate reactive power:

   Q = P × (tan(cos-1(0.7)) - tan(cos-1(0.95)))

2. Determine the required capacitor size:

   Use the calculated Q to specify a capacitor bank.

Applications of Power Factor Correction

• Industries: Reduces energy bills and improves equipment life.
• Commercial Buildings: Enhances efficiency of HVAC and lighting systems.
• Power Grids: Minimizes transmission losses.

Conclusion

Poor power factor results from inductive loads and leads to inefficiencies. Correcting power factor with capacitors, synchronous condensers, and APFC panels improves system efficiency and reduces costs. Power factor correction is critical for industries, commercial buildings, and power grids.