An 18-pulse drive to typically will achieve about 4% to 6%
THD-i when operating at full load (assumes balanced and non distorted voltage
source). Distortion will increase as load is reduced and when voltages are not
balanced.
A 12-pulse drive typically achieves 12 – 15% THD-i when
operating at full load, (assuming balanced and non distorted voltage source).
Distortion will increase as load is reduced and when voltages are not balanced.
Filters are available for 12-pulse drives that will reduce current distortion
to 5% or less.
A 6-pulse drive without a DC or AC inductor may be as high
as 60-100% THD-i. However a 6-pulse
drive with 5% line reactor (or equivalent DC choke) achieves about 35% THD-i.
at full load (45% at 60% load) and with 3% line reactor (or equivalent dc
choke) achieves about 45% THD-i at full load (about 60% THDi at 60% load). Filters are available for 6-pulse drives that
will reduce current distortion to 5%, 8%, 10%, 12%.
