CHITEK conditions harmonic and reactive problems on industrial plant feeders using active harmonic filters (AHF) and static var generators (SVG). The usual triggers are VFD banks, welding equipment and induction furnaces. Sizing follows a measured harmonic spectrum at the point of common coupling, not the transformer rating alone.
Welding banks, induction furnaces, CNC servo drives and large VFD installations all inject harmonic current back into the plant feeder. The result is transformer overheating, recurring capacitor failures and unstable process equipment. CHITEK active harmonic filters (AHF) and static var generators (SVG) are installed at the transformer or at the feeder to bring distortion back inside the plant limits.
Reviewed by the CHITEK power quality engineering team · Last updated
Most industrial sites start by identifying which of the two problems is dominant. Distortion and reactive demand are measured separately in the survey, and either can be the binding constraint.
| Aspect | AHF (Active Harmonic Filter) | SVG (Static Var Generator) |
|---|---|---|
| What it does | Injects a compensating current that cancels the harmonic current drawn by non-linear loads. | Supplies or absorbs reactive power continuously to hold power factor and support voltage. |
| Primary target | Current distortion (THDi) and harmonic spectrum at the point of common coupling. | Power factor, voltage fluctuation and reactive demand across the load cycle. |
| Typical trigger | VFD banks, rectifiers, welding sets, induction furnaces, LED drivers, UPS rectifiers. | Low or swinging power factor, voltage sag and rise, weak or long feeders, EV load steps. |
| Behaviour at light load | Compensation scales with the measured harmonic current, so output falls as load falls. | Holds output as required to reach the target power factor even at near-zero active load. |
| Use in this sector | Feeder-level harmonic correction at the transformer or at the main incomer feeding VFD and furnace loads. | Reactive support where power factor penalties apply or where furnace switching causes voltage fluctuation. |
Ratings are set from the survey. Where a plant runs both VFD banks and furnaces, the two devices are normally combined rather than sized as alternatives.
Automotive / Shipbuilding / Steel Structure
Harmonic surge from batch arc welding
>25%
THD
Voltage flicker from induction furnace
Reactive
Fluctuation
Phase imbalance from servo drives
High
Zero-seq.
Refining / Fine Chemical / Oil & Gas
Harmonic stacking from multi-VFD installation
>18%
THD
Startup surge from large motors
6~10x
Inrush
Sag sensitive control infrastructure
>15%
Sag Depth
Wafer Fab / Packaging / PCB
Voltage sag at lithography scanners
< 5ms
Sag Tolerance
Harmonic pollution from FFU/VFD
>8%
THD
Phase imbalance at ATE/test floor
>5%
Unbalance
Each case below is written up the same way: what the site was, what the survey measured before anything was specified, what was installed, and what the acceptance test showed afterwards. Projects marked Typical Configuration are illustrative — sizing for those always starts from a site survey rather than from the table.
Electronics Manufacturing
Current distortion 20.06% → 2.58% on a VFD / compressor / pump feeder
Feeder TM8 at an electronics manufacturing plant, supplying variable-frequency drives, air compressors and cooling water pumps. The circuit already carried 390 kvar of capacitor compensation within a 780 kvar installed bank, and ran between 800 A and 1,000 A at a system power factor of 0.92.
Feeder TM8 supplies VFDs, air compressors and cooling water pumps, with 390 kvar of capacitor compensation on the circuit (780 kvar installed). Running current 800–1,000 A, system displacement power factor 0.92 before retrofit.
Distortion 20.06% → 2.58%
Results are reported for the TM8 feeder only. Other feeders at the same plant were not part of this contract and are not covered by the figures.
Non-linear loads: rectifiers in VFDs and servo drives, arc welders, induction melting furnaces and DC power supplies. They draw current in short pulses rather than as a sine wave, and those pulses appear as harmonic current on the feeder.
Yes, but where the filter CTs sample matters. If the CTs are on the grid side and the connection point sits downstream of a pure capacitor bank, the filter can excite LC resonance. Use selective filtering orders with anti-resonance control, or move CT sampling to the load side.
An AHF cancels harmonic current. An SVG supplies or absorbs reactive power and holds power factor. If the problem is distortion, start with AHF. If it is low power factor or voltage fluctuation, start with SVG. Plants running both VFD banks and furnaces often need both.
From a power quality survey at the point of common coupling: measure the harmonic spectrum, the reactive profile and the load cycle. Sizing from transformer kVA alone is the most common reason an installation ends up undersized.
Every project on this page started with a measured survey. Send us your single-line diagram and load list and we will tell you what we would measure first.
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