Rockwell Automation 20D PowerFlex 700S AC Drives with Phase II Control Reference Manual - Manual (Page 110)

110 Rockwell Automation Publication PFLEX-RM003E-EN-E - January 2011
Chapter 1 Detailed Drive Operation
restart allows the drive to continue normal operation by applying power to the
motor again. This operation is intended to protect the drive from excessive inrush
currents in the presence of input AC line disturbances and allow the drive to
continue normal operation without user intervention. However, there is also a
concern for safe auto-restart operation. By default the drive is configured to fault
and not auto-restart if the power line dropout lasts more than two seconds.
Precharge Frames 1…4
The precharge implementation and control varies with drive size and type. For
frames 1…4 the precharge hardware is located on the power circuit board. This is
basically a resistor and bypass relay in series with the positive DC bus between the
front-end rectifier and the bus capacitor. The bypass relay control is described
below. Also note that these drives can be wired for either AC line power or DC
common bus. The precharge function will work the same for either AC or DC
power input.
Precharge Frames 5 and Up - AC Input “Stand Alone Drives”
For frames 5 and up (AC input) the precharge function is implemented with an
SCR rectifier such that the SCRs are phase advanced to limit the inrush current
into the bus capacitor(s). This phase advanced precharge is not controlled by the
drive and should normally be completed by the minimum precharge time
required by the drive. The drive will not complete precharge until the bus voltage
is stable and above the undervoltage level.
Precharge Frames 5 and Up - DC Input “Common Bus Drives”
There are two versions of the DC input or common bus drives. The first has a
resistor with an SCR bypass in series with the positive DC bus in front of the bus
capacitor. The second does not have any precharge hardware and is intended for
user applications where the precharge hardware and control is provided by the
user. Drives with the resistor and SCR bypass (internal) have the same precharge
control as frame 1…4 above.
ATTENTION: The user must determine safe auto-restart and fault
configuration at the system and user level. Incorrect selection(s) may
result in personal injury due to machine motion.
ATTENTION: In cases where the user is providing the precharge
hardware and control, incorrect configuration and/or control may result in
drive damage.