Functional Description
26
S811+ Soft Starter
MN03900001E—November 2012
Current Limit Start
This mode is typically used when it is necessary to limit the
maximum current during start-up due to line power
limitations or other considerations. During a Current Limit
Start the S811+ applies a constant voltage to the motor,
resulting in limited current flowing through the motor’s
windings. The level of current is set by the
Initial Torque
parameter. See below.
Note:
Current Limit Starts are not recommended on variable
torque load applications like fans and pumps.
Attempting starts with the Current Limit set to a value
of 20%
Initial Torque
or lower are not recommended
as the motor may not develop adequate torque to
accelerate properly.
Current Limit
Soft Stop/Pump Stop
The Soft Stop feature is used for applications that require a
controlled (ramp) extended stop. It is designed for high
frictional loads that tend to stop suddenly when voltage to
the motor is removed. During Soft Stop the voltage is
ramped to zero in the time set by the
Soft Stop Time
parameter. The Pump Stop feature (optional) is used for
pump applications that require special algorithms that bring
the application to a controlled stop to prevent water hammer
from occurring.
Note:
The Soft Stop mode is not an electronic brake function
and will not stop a motor any faster than it would
normally take to coast to a stop under load.
Soft Stop
Initial
Torque
Kick
Start
Torq
Kick Start Time
100%
Bypass
Bypass
Soft Start Time
Start
Run
Current
Time (Seconds)
Time (Seconds)
100%
Start
Run
Speed
Soft
Stop Time
100%
Run
Soft Stop
Speed
Time (Seconds)
Coast to Stop
(Speed)
Soft Stop Ramp
(Voltage)