Harmonics are multiples (thirds, fifths, etc) or divisions of frequencies. In radio, harmonics can be used carry additional signals on a single base frequency. It is the harmonics of an audio...
A harmonic frequency is a multiple of the fundamental. If the frequency is 60Hz, then the 2nd harmonic is (2 * 60) 120 Hz, the third is (3 * 60) 180 Hz, etc.
in rotating machines the air gap permeance in front of the slots changes with rotating rotor that it change flux in air gap and affect the voltage and current in machine. baradaran from jondishapour...