Rockwell Automation GV3000/SE AC Gen. Purpose and Vector Drive Software Start-Up and Ref. Manual - Manual (Page 94)

4-8 GV3000/SE AC Drive Software Reference, Version 6.06
The time the motor takes to make any speed decrease (except a coast-to-rest stop) is
directly proportional to the value in this parameter. This parameter does not apply if
JOG is selected. See P.022 (Jog Ramp Decel Time).
Note that motor load inertia and input line conditions can extend the deceleration time
to a value greater than the preset time. With very fast deceleration times, regenerative
motor voltage may charge up the DC bus voltage, causing a high bus voltage (HU)
fault. To avoid a fault condition, extend the deceleration time for a longer period. If a
deceleration time faster than the acceptable range is required, installing an optional
Snubber Resistor Kit or Regenerative Braking Module Kit may prevent the fault.
For V/Hz regulation with dynamic braking (snubber resistor) disabled (H.017 = 0, 2, or
4), the deceleration time may be extended to prevent a high bus voltage (HU) fault
from occurring.
P.002 Decel Time 1 (RAMP 1)
For V/Hz regulation,
this parameter
specifies the amount
of time in which the
motor ramps from
Maximum Speed
(P.004) to zero
speed.
For vector regulation,
this parameter
specifies the amount
of time in which the
motor ramps from
Motor Top Speed
(U.017) to zero
speed.
Parameter Range: 1.0 to 999.9 seconds (V/Hz)
0.1 to 999.9 seconds (vector)
Default Setting: 20.0
Parameter Type: Tunable
Refer also to parameters: P.004 Maximum Speed
P.005 Current Limit
U.017 Motor Top Speed
U.024 High DC Bus Fault Avoidance Enable