Rockwell Automation 20D PowerFlex 700S AC Drives with Phase II Control Reference Manual - Manual (Page 111)

Rockwell Automation Publication PFLEX-RM003E-EN-E - January 2011 111
Detailed Drive Operation Chapter 1
Ride Through Operation
An incoming power loss to the drive is detected by a 22% drop in bus voltage or a
bus voltage that drops below the undervoltage level (as determined in parameter
408 [Power Loss Level] - see table below). The return of incoming power is
detected by an 11% rise in bus voltage and a bus voltage level greater than the
undervoltage level set in parameter 409 [Line Undervolts]. If the undervoltage
condition is selected as a fault (parameter 393 [BusUndervoltCnfg] = “2 -
FltCoastStop”), then the drive will not restart if the incoming power returns.
Upon sensing a power loss the drive can be configured to coast, continue
operation or change to flux only operation. (See
Ride Through Configuration
below).
In cases where the precharge control is independent or external to the drive,
(firmware) the ride through function can still be used to stop PWM operation,
saving controller power and restart operation until after the return of power is
sensed. In this case, the ride through sequence will not be directly coordinated
with the precharge operation. For external precharge hardware, functionality is
provided so that the user may provide coordinated operation.
Ride Through Configuration
The drive's response to a power disturbance can be selected in parameter 406
[Power Loss Mode].
Table 13 - Settings for Parameter 406 [Power Loss Mode]
Coast (default): The coast mode stops power to the motor (PWM disabled) and
the motor coasts until power returns or a fault occurs. At the time when the
motor PWM is disabled the precharge device bypass (where controlled by the
drive) is also opened. Then, the precharge logic is reset so that the drive starts
another precharge cycle. After the incoming power returns and the precharge
cycle has completed, the drive restarts normal operation.
Continue: This setting disables the ride through function. In this case the drive
will attempt to continue running the motor if the incoming power is disrupted. If
power returns before the drive has shut down, the precharge device is bypassed
and a large inrush current may occur. In this case drive damage is likely.
Flux Only: The drive's torque is set to zero when a power disturbance is detected.
The motor flux is continued until the disturbance goes away or until a power
408 Power Loss Level
Sets the percentage of the bus voltage at which ride-
through begins and modulation ends. Units:
Default:
Min/Max:
Scale: %
22.1
15/95
0 RW 16-bit
Integer
0 Coast
2 Continue
5 Flux Only
0.221 480Vac 2
Ч Ч
150Vdc =