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Detuned Reactors

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Detuned reactors are series inductors installed with power-factor-correction (PFC) capacitor banks to deliberately shift the bank’s natural resonance below the 5th harmonic.

Specifications

Voltage Rating 400V to 690V
Power Rating 2.5KVAr to 100KVAr (Higher on request)
Insulation Class
F Class for dry type (H Class on request)
Cooling AN/AF
Applicable Standards IEC 60076-6, IS5553
Certifications CE ROHS

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  • Drive-heavy industries (steel, cement, paper, textiles, plastics): protect PFC capacitors under 5th/7th harmonics.
  • Data centers & telecom (UPS-rich feeders): keep kvar banks stable and cool.
  • Commercial campuses (malls, hospitals, airports, IT parks): avoid resonance and nuisance tripping.
  • Water & wastewater plants (pump VFD clusters): maintain PF without harmonic amplification.
  • Generator/weak grids (DG/CPP/microgrids): improve stability; prevent cap over-voltage.
  • Crane/hoist/elevator groups: handle rapid load swings with drives; reduce voltage flicker issues on PFC banks.
  • Retrofits of failing PFC panels: replace plain caps with detuned sets to stop frequent capacitor/breaker failures.

What they do?

  • Series reactors used with capacitor banks so the L–C branch resonates below the 5th harmonic, preventing harmonic overcurrent/overvoltage on capacitors and avoiding feeder resonance.

When to use

  • Plants with VFDs, welders, furnaces, drives-dominated HVAC, cranes/elevators.
  • Utilities/specs that mandate PF despite high background THD.
  • LV APFC panels and MV banks (11/22/33 kV) where resonance risk is non-negligible.

Sizing quick-guide

  • Choose a detuning percentage p% (reactor X at 50 Hz as % of capacitor |X|):
    • 5.67% → ~210 Hz (≈ 4.2nd)
    • 7% → ~189 Hz (≈ 3.78th) (most common)
    • 14% → ~134 Hz (≈ 2.68th) (very dirty systems / weak grids)
  • Tuning frequency:  f_t = f₁ √(1/p)  with  f₁ = 50 Hz  
  • Inductance per phase (given capacitor C):  L = p / ((2π f₁)² · C)  

Important effects (design around these)

• Capacitor terminal voltage rises:  Vcap ≈ Vbus / (1 − p)  → use higher-voltage caps (e.g., 440–480 V on 415 V at 7%).

• Net kvar delivered to bus drops:  Qbus ≈ Qcap (1 − p)  → a 100 kvar step gives ~93 kvar at 7%.

• Thermal current includes fundamental + residual harmonics → rate reactors and capacitors for RMS with THD.