Investigation of harmonics from variable speed drives with six pulse rectifiers under imperfect supply conditions

This paper presents an analysis on the variation of harmonic current components of variable speed drive from the idealised assumption under imperfect conditions. This variation includes the triplen harmonics with particular attention to the 3^rd harmonic current, under imperfect supply conditions. The relationship between the distortion of supply voltage and the production of the triplen harmonic currents is derived. The supply variations considered within this paper are 1-phase voltage reduction, and a voltage supply with harmonic distortion. The analysis presented in this paper shows the theoretical relationship between supply distortion and the production of 3^rd harmonic currents from the 6-pulse rectifier and is backed up by experimental results