Harmonic Filtering Solutions

The increasing use of modern power electronic apparatus (drives, uninterruptible power supplies, etc.) produces nonlinear current and thus loads the network with harmonics. The capacitance of the power capacitor forms a resonant circuit in conjunction with the feeding transformer. Experience shows that the self-resonant frequency of this circuit is typically between 250 and 500 Hz, i.e. in the region of the 5th and 7th harmonics. Typical loads requiring harmonic filtering include 6 pulse drives (AC / DC), 3 phase UPS, frequency converters.

Active Harmonic Filters

With L&T Electrical & Automation active harmonic filters, reduce your THD levels to within IEEE/CEA limits. These filters are IGBT-based power converters. This filter injects negative of the harmonic current resulting in practically no harmonic distortion. Phase balancing and power factor correction is also achieved.


30-600 A Active filter in 3 phase 3 wire/4wire

Stand-alone & modular units

Response time less than 1 ms

Easy diagnosis of fault conditions with alarms

Easy configuration & parameter monitoring with LCD touch screen HMI

Reactors – Harmonic Filtering

Detuned harmonic filters are the series combination of a reactor and power capacitor. This filter offers higher impedance for high frequency harmonics. This prevents harmonic resonance and amplification.

7% reactor mitigates 5th harmonic & above

- For industries with drives, converters & other power electronic devices

14% reactor mitigates 3rd harmonic & above

- For IT industries

- For industries with high single-phase non-linear load


Available as 7% (189 Hz) & 14% (133 Hz) detuned filters

Copper & Aluminium wound reactors

Very low operating losses - 3 to 5 W / kVAr

High linearity - 1.8 times the rated current

Low noise

Auto-thermal cut-off