Rockwell Automation 20D PowerFlex 700S with Phase I Control Reference Manual - Manual (Page 96)

96 Rockwell Automation Publication PFLEX-RM002D-EN-E - August 2013
Chapter 1 Detail Drive Configuration and Operation
restored and the precharge has completed, ride through allows the drive to
continue normal operation, 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 allows 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 Higher AC Input “Stand Alone Drives”
For frames 5 and higher (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 under voltage level.
Precharge Frames 5 and Higher DC Input “Common Bus Drives”
There are two versions of these 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.