1SFC132081M0201 | Installation and commissioning manual | Functions 79
7.3.1 Torque start ramp
When the Softstarter receives a start signal, the
Softstarter makes a quick ramp to set Start ramp initial
level. Then the Softstarter controls the output voltage so
that the output torque follows a specified optimal torque
curve during pre-set time to 100% nominal torque.
When the output voltage comes at 100% nominal voltage
(Top of ramp), the Softstarter closes the bypass.
To come at Top of ramp these conditions need to be met:
• The output voltage comes at 100% nominal voltage.
• The current is below 1.2 × nominal motor current.
The time between the start signal and when nominal
torque is reached is the start ramp time.
The start ramp time can be longer if the motor starts with
a very heavy load.
Example: If the Start ramp time is set to 2 seconds
and the motor starts with a heavy load. This can cause
that the output current does not go below set 120% of
nominal motor current when the pre-set start ramp time is
reached.
Configuration of the Torque start ramp with these
parameters:
Parameter Description Setting range Default
value
02.01 Start mode Set to Torque ramp. Voltage ramp,
Torque ramp,
Full voltage start
Voltage
ramp
02.03 Start ramp Initial level Sets the torque level from where the start ramp
initiates.
10 ... 99% 30%
02.04 Start ramp time Sets the time it takes for the voltage to come at 100%.
1 ... 120 s 10 s
03.05 Torque limit level Sets the limit for the torque during soft start with
torque control
20 ... 200% 150%
28.06 Torque profile start Sets the shape of the torque ramp during start.
• Constant setpoint is for centrifuge
• Linear is for compressor
• High inertia curve is for long conveyor belts
• Progressive curve is for centrifugal pump
Constant
setpoint,
Linear ramp,
Progressive
curve, High
inertia curve
Linear ramp
28.07 Torque finish Sets the operation torque for Torque start ramp setting
in percentage of base torque.
30 ... 500% 100%
28.08 Torque tune Sets the integration time of PI controller. 0 ... 1000% 100%
28.09 Torque ctrl gain Sets the speed of the voltage regulator during torque
start and stop. It seldom needs to be changed, but if
a dip occur in the torque curve during stop, increasing
this value might solve it.
0.01 ... 10 0.02
28.10 Torque PI integration time Sets the integration time of PI controller. 0.001 ... 10 s 0.004 s
28.11 Torque slip Sets the slip difference from nominal to pull-out torque
in percentage.
0.1 ... 100% 1.0%
28.12 Torque diff Sets the maximum desired difference between
reference and actual torque in percentage.
0.1 ... 100% 2.0%
28.13 Torque filter time Sets the Torque control filter time in seconds. 0.01 ... 10 s 0.02 s
7
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