Lecture Notes: Leading & Lagging Power Factor Differences

Introduction

• Power Factor: Ratio of watts (true power) to volt-amperes (VA, apparent power).
  • Unity (1) for resistive loads as voltage and current are in phase.
  • Reactive loads cause current and voltage waveforms to be out of phase.

Types of Reactive Loads

• Inductive Loads (e.g., electric motors)
  • Inductance opposes current flow.
  • Current waveform lags behind voltage waveform.
• Capacitive Loads
  • Current waveform leads voltage waveform.
• Non-Linear Loads
  • Do not shift waveform but distort it (e.g., rectifier power supplies).
  • Add harmonic distortion, mimicking capacitive behavior.

Lagging vs. Leading Power Factor

• Lagging Power Factor: Indicative of inductive reactance where current lags.
• Leading Power Factor: Indicative of capacitive reactance where current leads.
• Displacement Power Factor (DPF): Purely related to the phase difference between current and voltage.
• Total Power Factor: Includes both DPF and harmonic distortion.

Memory Aid

• ELI the ICE Man
  • ELI: Voltage (E) leads current (I) in an inductive (L) circuit.
  • ICE: Current (I) leads voltage (E) in a capacitive (C) circuit.

Practical Implications

• Reactive Load Impact
  • Predominantly inductive loads result in lagging power factor.
  • Capacitive reactance can cancel out inductive reactance.
  • Power Factor Correction: Capacitors are added to improve power factor towards unity.

Key Takeaways

• Understand the behavior of different types of loads on power factor.
• Recognize the importance of correcting power factor in electrical systems to improve efficiency.