Harmonic Filters

The general definition describes an analog or digital device that measures the power quality on the grid side. The device injects current to compensate any unwanted deviations from the standard 50 or 60 Hz supply. Deviations can be mitigated partially or in full.

What Causes Harmonics?

The electrical power system in the United States is designed to operate at a frequency of 60 Hz. The harmonics generated by a typical “6-pulse” non-linear load will reflect the highest amount of energy between 300 and 780 Hz. Which is also known as the 5th and 7th order.

When electricity is generated, the current and voltage sine wave develop is rather close to perfect and has a very low harmonic distortion content. Non-linear loads such as Variable Frequency Drives (VFD), DC Drives, induction heating systems, UPS systems, battery chargers, arc furnaces, computer power supplies as well as LED and fluorescent lighting consume energy in such a way that the current consumption does not follow a sine wave. Since it is repeating, it is considered a harmonic rather than a transient which does not repeat. The current waveform reacts with the impedance of the power network and, using Ohm’s law, a distorted voltage waveform is developed.

The harmonics are an undesirable consequence of using such devices which lower power factors, reduces efficiency, develops circulating currents and causes electronic devices to operate incorrectly and fail prematurely.

Why Do You Need Them?

Typical applications for active filters are compensation of variable frequency drives and data-centers to reduce the load on UPS systems or compensating the effects of renewable energy sources on the grid. Voltage distortion harmonics can also cause operating problems such as nuisance tripping of breakers.

Since the consumers are generating the harmonics and making the electrical grid inefficient, the utility companies are starting to enforce maximum harmonic values of energy that can be reflected back onto the grid by the consumer. In the United States, this is often referred to as the IEEE-519 standard.

More than just harmonics

Besides providing correction for harmonics, our filters can correct for power factor (reactive power), Unbalance, Flicker and even resonance. Unbalance and flicker are often addressed on the medium or high Voltage grid.


The ADF family is suitable for most industrial filtering applications. The following are a few examples.

Problem Applications Benefits
Harmonics VFDs
UPS loads
Pump stations
Waste water treatment
Semiconductor manufacture
Meet industry regulation limits
Reduce impact on other equipment
Protect the investment by freeing up capacity
Save energy
Reduce neutral currents
Fast changing harmonics are easily dealt with
Communication notches are reduced
Flicker Welding lines
Weak networks
Generator applications
Electric Arc Furnaces
Reduce flicker levels to acceptable values
Improve welding efficiency and quality
Eliminate disturbance and voltage drops
Increase reliability due to reduced voltage drops
Resonances Smart grids
Wind power
Solar parks
Weak networks
Eliminate resonances allowing production to run undisturbed
Incompatible machinery will not work together
Eliminate component failure
Eliminate production interruptions
Unbalance IT applications
By balancing the load, the efficiency of the installation improves
Eliminate highly loaded single phases
Reactive IT loads
UPS loads
Dynamic loads
Capacitive loads
Solar parks
X-Ray, MRI
Restore power factor under dynamic loads
Restore capacitive power factors
ADFs are more cost-efficient that inductive compensation
Keep the voltage stable with very fast reactive compensation
Increase reliability due to reduced voltage drops

Product Solutions

ADF Tuning – Active Harmonic Filters

ADF Tuning (formally Comsys AB) provide customers with a full-range of active dynamic filters. Their solutions mitigate equipment malfunctions and allow companies to meet or exceeds the IEEE-519 standards.

APQ – Passive Harmonic Filters

Arteche Power Quality (APQ) develop a wide range of products to support the effective generation, generation, transmission, distribution & utilization of quality electrical power!