Harmonic Filters

A harmonic filter is used to eliminate harmonic distortion caused by equipment in your facility. It can be wired either in front of the device to be protected or in front of the device causing the distortion.

Harmonic distortion usually presents itself as an overload in electrical equipment. Harmonics can also cause excessive current to flow on a building's neutral wiring, unexplained computer crashes, and overheated motors. Since a large piece of equipment, or too many devices can overload a circuit, it is important to have a qualified electrician measure the current on the circuit before assuming you have a harmonics problem. A harmonic filter trap can eliminate harmonic currents.

Harmonic currents appear in multiples of 60 Hz, the fundamental frequency (0 120 Hz, 180 Hz, 240 Hz, etc.) They are caused by equipment within your facility that uses current in a pulsing fashion and sometimes feeds harmonic currents back into your wiring. Loads which use current in this fashion are often called nonlinear loads. Some examples of these are:

  • Fluorescent lights,
  • Welders,
  • Battery chargers, and
  • Certain electronic equipment, such as computers.

A harmonics filter uses a series of capacitors, inductors, and resistors to shunt harmonic currents to ground. A filter unit may contain several of these elements, each designed to filter a particular frequency.