Harmonics are multiples of a fundamental frequency. In a 60Hz system, the 5th harmonic is 5 times that frequency, or 300Hz. The total amount of harmonics in a power system is sometimes referred to as Total Harmonic Distortion, or THD.

When harmonic currents are present in a power system they create poor power quality, also known as "dirty power". Harmonics are caused by devices that draw non-sinusoidal currents when a sinusoidal voltage is applied. Examples include Adjustable Speed Drives, 6-Pulse converters, and Uninterruptible Power Supplies.

The result of poor power quality is higher RMS voltages and currents in the system which could result in: Failed power factor correction capacitors, blown fuses, tripped circuit breakers, etc. Most damaging is the additional heat generated in transformers, where a 10°C rise in operating temperature can reduce the life of transformers, motors, or capacitors by as much as 50%.

For more detailed information on harmonics, view our Application Guide for Solving Harmonic Problems.

When power factor correction is needed in the presence of non-linear loads, or the amount of harmonic distortion must be mitigated to solve power quality issues or meet IEEE standards, the best solution is the application of harmonic filters. Filters must be carefully designed to avoid unexpected interactions within an electrical system.

Myron Zucker, Inc. offers both Passive (Fixed and Automatic) and Active Harmonic Filters designed to reduce the damaging levels of harmonics present in your system.