High harmonic currents in fluorescent lamp circuits

Formulae associated with the percentage of high harmonics in the current in fluorescent lamp fixtures are derived for the cases of L and L-C ballasts. The third harmonic is analyzed carefully, and the theoretically predicted values are compared with those found experimentally. The agreement appears to be satisfactory. To meet the requirement of a standard, the power factor of the system is taken into account, which appears to be a nontrivial point. It appears, in particular, that the ballast which provides the lowest power sensitivity (w/sub 0/=2w) does not fit the requirement of the standard and the increase in the amplitude of the input voltage (by use of an input (auto) transformer) is not effective here. In contrast to this, for an L-C ballast with w/sub 0/=1.5w the standard requirement is met by a 220 V RMS line and the increase in V further reduces the role of the third harmonic current.<>