Harmonics are integer multiples of fundamental frequency. For example if the line frequency is 50 Hz, the 2nd harmonic is 100 Hz, the 3rd harmonic is 150 Hz, and so on. Two hundred years ago the mathematician Joseph Fourier showed that any shape of distorted wave could be disaggregated into the series of a fundamental sine wave plus various sinusoidal harmonics of that wave at various amplitudes. This has proven very important in electrical theory because electrical conductors and devices respond to the various harmonic components as if they were indeed distinct frequencies. Harmonic frequencies are added to power frequency at generation, transmission or load levels. For perfect functions of the power electronic components it is important to eliminate unwanted power frequency harmonics.