Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

harmonic distortion
caused by the nonlinear transfer characteristics of a device or circuit. When a sinusoidal signal of a single frequency (the fundamental frequency) is applied at the input of a nonlinear circuit, the output contains frequency components that are integer multiples of the fundamental frequency (harmonics). The resulting distortion is called harmonic distortion.
total harmonic distortion
disturbance level an electromagnetic disturbance level due to all emissions from equipment in a system.

This is expressed as a ratio of the RMS value of the harmonic content to the RMS of the fundamental and is calculated as a percentage of the fundamental component.