Harmonics

Harmonics are multiples of frequencies. To speak of a harmonic is to assume a basic, or fundamental frequency of which multiples can be discussed. Connecting a device to a power grid energizes the device with the frequency of the grid, say 50, 60 or 400 Hz. In discussions of power distribution, this frequency is called the fundamental frequency. Harmonic frequencies of 60 Hz are 120 Hz, 180 Hz 240 Hz, etc. A special number called the harmonic number delineates which multiple is referred to; the second harmonic is 120Hz, the third is 180Hz and so on.