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Parameters
Parameters
Starting voltage
Ramp up time
Maximum starting time
Breakaway time
Breakaway voltage
8.1.4
Soft starting with torque control
Operating principle
Torque control means that the torque generated in the motor is linearly increased from a
parameterizable starting torque up to a parameterizable end torque within an adjustable
starting time.
The advantage over a voltage ramp is the improved mechanical run-up behavior of the machine.
The 3RW55 and 3RW55 Failsafe soft starters control the torque generated at the motor
SIRIUS 3RW55 and 3RW55 Failsafe Soft Starters
Equipment Manual, 02/2022, A5E35630887002A/RS-AF/006
Description
The starting voltage determines the starting torque of the motor. A lower starting voltage
results in a lower switch-on torque and a lower starting current. Select a starting voltage that
is high enough to ensure that the motor starts up immediately and smoothly when the start
command is issued to the 3RW55 or 3RW55 Failsafe soft starter.
•
Factory setting: 30%
•
Setting range: 20 ... 100%
•
In steps of: 5%
The ramp-up time determines the time taken to increase the motor voltage from the parame‐
terized starting voltage to the line voltage. This has an influence on the motor's acceleration
torque which drives the load during start-up. A longer ramp-up time results in a shorter ac‐
celeration torque across the motor ramp-up time. The motor runs up longer and more softly.
Set the ramp-up time so that the motor can reach its rated operating speed by the time the end
of the ramp-up reached. The actual motor starting time is load-dependent and can differ from
the parameterized ramp-up time.
If you choose a time that is too short, the ramp-up time ends before the motor has accelerated
to speed. A very high starting current that can reach the value of the direct starting current at
this speed then occurs. In this case, the 3RW55 and 3RW55 Failsafe soft starters can switch
themselves off via the internal overload protection function and signal a fault.
With the setting "0 s", the motor is switched on with a ramp-up time of approx. 100 ms.
•
Factory setting: 10 s
•
Setting range: 0 ... 360 s
•
In steps of: 0.1 s
This time determines the period after which the drive must have completed its start-up. If the
drive is not yet operating under rated conditions after the specified interval has expired, the
generalized phase control of the thyristors is interrupted and the line voltage is raised to 100%.
The setting "0 s" deactivates the maximum starting time.
Maximum starting time ≥ ramp-up time.
•
Factory setting: 0 s
•
Setting range: 0 ... 1 000 s
•
In steps of: 0.1 s
See Breakaway pulse for startup functions (Page 144)
Functions
8.1 Start-up
137
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