Phase Shifting of Harmonics in AC Circuits of Rectifiers

The origin and transformation of harmonics in rectifier circuits is traced in order to remove the confusion and traps that develop. Phase shift between the primary supply and secondary voltages does not in itself change the harmonic content of the primary supply current. However, each harmonic current is shifted by a different angle, and every other one is shifted in the reverse direction. As a result, the waveshape of the composite current is altered, but the rms value is not changed. By proper choice of the phase-shift angle between two or more rectifiers, selected harmonics can be displaced and cancelled in the total supply current. The rms value will be altered, but the resulting reduction is generally small and unimportant.