Harmonic filters - Filters mitigate distortion to protect equipment and improve power efficiency.

Harmonic filters are electrical devices used to mitigate the adverse effects of harmonics in a power system. Harmonics are voltage or current waveforms with frequencies that are integer multiples of the fundamental frequency of the power system (e.g., 60 Hz in the US). They are typically generated by "non-linear loads" such as power converters, variable frequency drives (VFDs), computers, and LED lighting.

How They Work
Harmonic filters function by providing a low-impedance path for these unwanted harmonic currents to flow, effectively diverting them away from sensitive equipment and back to the source or to the ground. This helps to restore the electrical waveform to its pure, sinusoidal shape, thereby improving power quality and protecting equipment.

There are two main types of harmonic filters, which operate on different principles:

1. Passive Harmonic Filters
Passive filters are constructed using combinations of capacitors, inductors, and resistors that are "tuned" to resonate at specific harmonic frequencies. When a harmonic current at that frequency enters the system, the filter provides a low-impedance path, allowing the harmonic to be shunted away from the main power line.

Advantages: They are simple, reliable, and cost-effective for mitigating a specific, known harmonic problem.

Disadvantages: They are not adaptable to changes in the load and can introduce resonance issues with the power system if not properly designed.

2. Active Harmonic Filters (AHFs)
Active filters are more advanced devices that use power electronics to dynamically cancel out harmonic currents. They work similarly to noise-canceling headphones.

How they work: The AHF continuously monitors the electrical system in real-time. When it detects an unwanted harmonic, it instantly injects a precisely opposite (180° phase-shifted) current into the system. This counteracting current cancels out the harmonic, eliminating the distortion.

Advantages: They are highly effective, adaptable to a wide range of harmonic frequencies and changing loads, and can also be used to improve power factor.

Disadvantages: They are more complex and have a higher initial cost than passive filters.

Applications and Benefits
Harmonic filters are essential in any environment with a high concentration of non-linear loads. Their use provides several key benefits:

Equipment Protection: Harmonics can cause electrical equipment to overheat, which reduces its lifespan and can lead to costly failures. Filters protect assets like motors, transformers, and power cables.

Energy Efficiency: By reducing harmonic currents, filters decrease power losses and improve the overall efficiency of the electrical system, which can lead to energy cost savings.

Improved Power Quality: They prevent voltage distortion and other power quality issues that can cause sensitive electronic equipment, such as computers and medical devices, to malfunction.

Compliance: Many countries and utilities have regulations (like IEEE 519) that limit the amount of harmonic distortion a facility can inject into the grid. Harmonic filters ensure compliance and prevent potential penalties.