The line currents of DC drives with a 6-pulse thyristor bridge will always contain, in addition to the fundamental wave, the 5th,
7th, 11th and 13th harmonics with empirical values of 22 %, 14 %, 9 %, 7.6 % , referenced to the fundamental wave. In the
case of several DC drives operating simultaneously on the mains, the different phase sequences of the harmonic currents will
produce a "statistical improvement" in the level of mains pollution.
Due to the dimensioning method adopted for the smoothing inductors, harmonic currents with contents of 40 %, 14 %, 9 %
and 7.6 % must be anticipated with AC drives featuring a 6-pulse diode bridge in 1-quadrant drives. Due to the identical phase
angle of the harmonic currents, several drives on the same mains can be regarded as one drive with the same total current.This
also applies for thyristor bridges in 4-quadrant operation.
Input bridges with IGBT switching elements enable the low-frequency harmonics to be substantially reduced, but conversely
create more high-frequency harmonics.
7th, 11th and 13th harmonics with empirical values of 22 %, 14 %, 9 %, 7.6 % , referenced to the fundamental wave. In the
case of several DC drives operating simultaneously on the mains, the different phase sequences of the harmonic currents will
produce a "statistical improvement" in the level of mains pollution.
Due to the dimensioning method adopted for the smoothing inductors, harmonic currents with contents of 40 %, 14 %, 9 %
and 7.6 % must be anticipated with AC drives featuring a 6-pulse diode bridge in 1-quadrant drives. Due to the identical phase
angle of the harmonic currents, several drives on the same mains can be regarded as one drive with the same total current.This
also applies for thyristor bridges in 4-quadrant operation.
Input bridges with IGBT switching elements enable the low-frequency harmonics to be substantially reduced, but conversely
create more high-frequency harmonics.
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