Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - Classic Control - Manual (Page 19)

1-2 Overview of Drive
7000-UM150I-EN-P – June 2013 7000 “B” Frame
The PowerFlex 7000 has the additional benefit of inherent
regenerative braking for applications where the load is overhauling
the motor, or where high inertia loads need to be slowed down
quickly. Symmetrical Gate Commutated Thyristors (SGCTs) are
used for machine converter switches. Silicon-controlled rectifiers
(SCRs) (for 6/18 pulse) or SGCTs (for AFE rectifiers) are used for
the line converter switches.
Rectifier Designs
There are three offered designs for the rectifier of the PowerFlex
drive.
6-Pulse Rectifier
A 6-pulse thyristor phase controlled rectifier (with optional passive
tuned filters) is shown in Figure 1.2. The line current before and after
the filter is shown. It can be seen that the current before the filter
contains the 5
th , 7 th and 11 th harmonics, however, the current after the
filter is more sinusoidal since these harmonics are redirected through
the tuned filters. The tuned filters also serve to improve input power
factor to near unity. The total harmonic distortion (THD) of line
current with the 6-pulse rectifier and tuned filters is approximately
5.2%. The THD of line voltage (line-to-line) is approximately 2.6%.
(THD of line voltage is a function of system impedance.)
CONVERTER
LINE
DC LINK
MACHINE
CONVERTER
Figure 1.1 – PWM-CSI AC Drive