Rockwell Automation 20B PowerFlex 70, PowerFlex 700 Reference Manual - Manual (Page 198)

Stop Modes
198 Rockwell Automation Publication PFLEX-RM001H-EN-P - June 2013
4. Ramp To Stop is selected by setting [Stop Mode x]. The drive will ramp the
frequency to zero based on the deceleration time programmed into [Decel
Time 1/2]. The “normal” mode of machine operation can utilize [Decel Time
1]. If the “Machine Stop” mode requires a faster deceleration than desired for
normal mode, the “Machine Stop” can activate [Decel Time 2] with a faster
rate selected. When in Ramp to Stop, the drive acknowledges the Stop
command by decreasing or “ramping” the output voltage and frequency to
zero in a programmed period (Decel Time), maintaining control of the motor
until the drive output reaches zero. The output transistors are then shut off.
The load/motor should follow the decel ramp. Other factors such as bus
regulation and current limit can alter the decel time and modify the ramp
function.
Ramp mode can also include a “timed” hold brake. Once the drive has reached
zero output hertz on a Ramp-to-Stop and both parameters [DC Hold Time]
and [DC Hold Level] are not zero, the drive applies DC to the motor
producing current at the DC Hold Level for the DC Hold Time.
Motor speed during and after the application of DC depends upon the
combination of the these two parameter settings, and the mechanical system.
The drive output voltage will be zero when the hold time is finished.
The level and uniformity of the DC braking offered at zero speed may not be
suitably smooth for many applications. If this is an application requirement, a
vector control drive, motion control drive or mechanical brake should be
used.
The drive output voltage will be zero when the hold time is finished
DC Hold Time
DC
Hold
Level
Stop
Command
Time
Output Voltage
Output Current
Motor Speed
Output Voltage
Output Current
Zero
Command
Speed