When the normal 50 Hz or 60 Hz sinusoidal wave that feeds ordinary electrical appliances and equipment becomes distorted, it not only contains the original waveform, the fundamental, but also a series of higher frequency sinusoidal waveforms that are multiples of the original waveform frequency. Harmonic distortion could be defined as the deviation of the voltage and/or current waveforms from the fundamental waveform. In his essay — What You Should Know About Harmonics — Inductotherm Corp.’s Michael Looby explained what induction melting foundries must understand about the distortion in the electric field that may affect productivity and performance.