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40
Digistart IS User Guide
www.controltechniques.com
Issue: 4
7.3.1
Coast to stop
Coast to stop lets the motor slow at its natural rate, with no control from the soft starter. The time required to stop will depend on the
type of load.
7.3.2
TVR soft stop
Timed voltage ramp reduces the voltage to the motor gradually over a defined time. The load may continue to run after the stop
ramp is complete.
Timed voltage ramp stopping can be useful for applications where the stop time needs to be extended, or to avoid transients on
generator set supplies.
Figure 7-5 TVR soft stop
V
olt
ag
e
(%
fu
ll
vo
lta
ge
)
1
1: Stop time (Pr
2I
)
Time
7.3.3
Adaptive control for stopping
In an adaptive control soft stop, the Digistart IS controls the current in order to stop the motor within a specified time and using a
selected deceleration profile. Adaptive Control can be useful in extending the stopping time of low inertia loads.
NOTE
Adaptive control does not actively slow the motor down and will not stop the motor faster than a coast to stop. To
shorten the stopping time of high inertia loads, use brake.
Every application has a particular stopping profile, based on characteristics of the load and the motor. Adaptive Control offers three
different stopping profiles. Choose the adaptive control profile that best matches your application requirements.
Adaptive deceleration control
To use Adaptive Control to control stopping performance:
1. Select Adaptive Control from the Stop Mode menu (Pr
2H
)
2. Set the desired Stop Time (Pr
2I
)
3. Select the required Adaptive Stop Profile (Pr
2K
)
Figure 7-6 Adaptive control soft stop
S
pe
ed
4
2
3
1
Adaptive Control stop profile (Pr
2K
):
1. Early deceleration
2. Constant deceleration
3. Late deceleration
4. Stop time (Pr
2I
)
Time
Table 7-4 Adaptive deceleration control soft stop profiles
Adaptive Stop Profile
Application
Late Deceleration
High head systems where even a small decrease in motor/pump speed results in a rapid
transition between forward flow and reverse flow.
Constant Deceleration
Low to medium head, high flow applications where the fluid has high momentum.
Early Deceleration
Open pump systems where fluid must drain back through the pump without driving the pump
in reverse.