Rockwell Automation 20D PowerFlex 700S with Phase I Control Reference Manual - Manual (Page 99)

Rockwell Automation Publication PFLEX-RM002D-EN-E - August 2013 99
Detail Drive Configuration and Operation Chapter 1
For the control to complete precharge and allow drive enable (See Parameter 156
[Run Inhibit Stat]), the following conditions must be met:
1. A user-controlled precharge enable must be present. The precharge enable
can be provided by hardware input or parameter configuration. This
selection is determined by the setting of parameter 838 [Digin1 Sel].
When parameter 838 is set to 14 “PreChrg/Disc” then the hardware
precharge control is selected and digital input 1 controls the user precharge
enable. If parameter 838 is set to any other value (i.e., not set to 14) then
the control uses parameter 411 [PreChrg Control], as the source for the
precharge enable. In this case, when [PreChrg Control] is set to zero, the
precharge control is disabled (held in precharge) and the drive is inhibited
from running (see parameter 156 [Run Inhibit Stat]). Otherwise when
[PreChrg Control] is set to one the user precharge is enabled. Using a
Digital Input for the precharge enable is recommended for common bus
systems where a drive may be disconnected and reconnected to the
common bus system. The Digital Input should be connected through an
auxiliary contact on the cabinet disconnect switch. Failure to provide a
hardware disconnect precharge control may lead to very large inrush
currents and associated drive damage if a reconnection is made before the
drive can sense the power loss. This precharge enable provides a user-
controlled permissive to the precharge function.
2. The drive must not be in an undervoltage condition. Parameter 409 [Line
Undervolts], sets the under voltage level as a percent of drive rated volts,
parameter 401 [Rated Volts]. An undervoltage is detected by comparing
the parameter 306 [DC Bus Voltage] to the percent of line voltage set in
parameter 409 [Line Undervolts] times parameter 401 [Rated Volts] times
the square root of 2. The undervoltage condition is displayed in parameter
555 [MC Status] bit 15 “DC Bus Low”.
3. The drive bus voltage must be stable (not rising). The bus voltage stable
condition is determined by comparing the bus voltage to a filtered value of
the bus voltage. Initially when power is applied to the drive the bus voltage
will rise as determined by the limited current controlled by the precharge
device. The filtered value of bus voltage will lag behind the actual bus
voltage until the bus capacitor charging is complete, then the values will
converge. A difference between the filtered and actual bus voltage
determines if the bus voltage is stable.
4. The drive must not be running (PWM active), except in coordination with
ride through. After the initial drive precharge has completed, a power loss
may present conditions for precharge to be restarted (ex. low bus voltage).
However, if the drive output is active (parameter 155 [Logic Status], bit 0
“Enabled”), the restart of precharge will be inhibited until the drive is
stopped (PWM not active). Also, see Power Loss/Ride Through on page
95 , for controller coordinated PWM disable and precharge operation. If
the drive is running and the user removes the precharge enable, this
condition will be ignored until the drive is disabled (PWM stops). Then
the precharge function will be started again.