Designing Detuned PFI Capacitor Banks for Non-Linear Industrial Loads

Selecting proper reactor detuning ratios (7% vs 14%) to avoid LC resonance when upgrading Power Factor Improvement (PFI) plants.

1. Non-Linear Loads & Harmonic Resonance

Variable frequency drives, induction furnaces, and LED lighting draw non-sinusoidal currents. Standard capacitor banks create parallel resonance paths with distribution transformer inductance, multiplying harmonic voltages up to catastrophic levels.

2. Detuned Reactor Sizing

Series-connected iron-core reactors shift the natural resonant frequency of the PFI bank below the lowest dominant harmonic (typically the 5th harmonic at 250 Hz), safeguarding capacitors and achieving a steady 0.98 power factor.

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