Rockwell Automation 7000 PowerFlex Medium Voltage AC Drive (B Frame) - Classic Control - Manual (Page 20)

Overview of Drive 1-3
7000 “B” Frame 7000-UM150I-EN-P – June 2013
The 6-pulse rectifier can be used in conjunction with a rectifier duty
isolation transformer as shown or with an AC line reactor. A rectifier
duty isolation transformer is required when the drive is being applied
to existing or retrofit motors or when the supply voltage is higher
than the drive rated voltage. (Refer to Specification 80001-005,
Rectifier Duty Transformers for more details on transformer
requirements and features.)
An AC line reactor can be used in front of the 6-pulse rectifier when
the drive is being applied to new motors. (Refer to Specification
80001-004, Requirements for Medium Voltage Motors Without
Common Mode Voltage Elimination). Elimination of the isolation
transformer reduces capital and installation costs, saves on valuable
floor space, and increases overall system efficiency.
Figure 1.2 – 6-pulse Rectifier with input waveforms
a) Line current without filter
b) Line current with filter
c) Line-to-line voltage at point of common coupling (PCC)
18-Pulse Rectifier
An 18-pulse phase controlled rectifier is shown in Figure 1.3. In an
18-pulse configuration, the IEEE 519-1992 requirements are met in
the majority of cases without the need for passive filters; however, a
multi-winding isolation transformer is required to mitigate the low
order harmonics by phase shifting principles. The 18-pulse solution is
superior to 6- or 12-pulse offerings in terms of lowering line side
harmonics.
Isolation transformers are available in both indoor dry type and
outdoor oil-filled designs for maximum flexibility in dealing with floor
space, installation costs, and control room air conditioner loading.
(Refer to Specification 80001-005, Rectifier Duty Transformers, for
more details on transformer requirements and features.)
a)
b)
c)