46 M301L
NOTE
The ability to accelerate a given load at a particular rate is limited
by the output power capability of the drive/motor combination. The
acceleration of high-inertia and high-friction loads may be affected by
the current limiting characteristics of the drive. Refer to Parameters: 16 -
CURRENT, 19 - FX BOOST, and 20 - AC BOOST for more information.
9 DECEL (DECELERATION TIME)
DECEL sets the deceleration rate for all speed reference sources. The DECEL setting is
the time to decelerate from BASE FREQUENCY to 0 Hz. As with Parameter 8 - ACCEL,
this is a linear function. If the drive is set to coast to a stop, DECEL will have no effect when
a STOP command is given. The range of adjustment for DECEL depends on horsepower,
voltage, and whether Dynamic Braking (DB) is being used. Refer to the table below:
DECELERATION LIMITS
HORSEPOWER / VOLTAGE RATING RANGE OF ADJUSTMENT
240/200 Vac 480/400 Vac 590/480 Vac WITHOUT DB WITH DB
(NOTE 1) (NOTE 2)
0.25 - 7.5 HP 1 - 7.5 HP ---- 0.3 - 3600 SEC 0.1 - 3600 SEC
10 - 15 HP 10 - 20 HP 1 - 7.5 HP 0.5 - 3600 SEC 0.1 - 3600 SEC
20 - 30 HP 25 - 60 HP 10 - 20 HP 1.0 - 3600 SEC 0.2 - 3600 SEC
---- ---- 25 - 60 HP 2.0 - 3600 SEC 0.2 - 3600 SEC
NOTE 1: 240/120 Vac units have the same limits as 240/200 Vac units.
NOTE 2: This parameter can be set as low as the value shown in the WITH DB column.
However, the value shown in the WITHOUT DB column is the operational limit
of a drive without dynamic braking. For example, DECEL can be set as low
as 0.1 seconds on a 10 HP, 480 Vac drive without dynamic braking, but the
actual minimum deceleration time would be 0.5 seconds.
If an attempt is made to decelerate a high-inertia load too quickly, the motor will regenerate
voltage back into the drive. This will cause the DC bus voltage to rise, which can result in
a HI VOLTS fault. In order to prevent faulting, the drive will enter DECEL FREEZE, which
halts the deceleration until the DC bus voltage returns to a normal level. The drive will
then begin to decelerate again, and if necessary, will enter DECEL FREEZE repeatedly
to avoid faulting. If a very short deceleration time is programmed, DECEL FREEZE may
not be able to compensate fast enough, resulting in a HI VOLTS fault.
In applications where very short deceleration times are required on high-inertia loads,
dynamic braking may be required. Consult the factory for more information on the Dynamic
Braking option.
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