Device functions
7.2 Startup modes
3RW44 soft starters
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Manual, 03/2017, NEB535219502000/RS-AB/008
Starting torque
The starting torque determines the switch-on torque of the motor. A lower starting torque
results in a lower locked-rotor torque and a lower starting current. The starting torque
selected must be sufficiently high to ensure that the motor starts straight away and smoothly
when the start command is issued to the soft starter.
Limiting torque
The limiting torque value specifies the maximum torque to be generated in the motor during
startup. This value also functions as an adjustable torque limit, for example.
The parameter value should be set to approx. 150 % to start the motor. It should be high
enough to ensure that the motor does not become stuck during run-up. This ensures that
enough acceleration torque is generated throughout the motor run-up phase.
Starting time
The length of the starting time determines the time in which the starting torque is increased
to the end torque.
A longer starting time results in a smaller acceleration torque over the motor run-up. This
results in a longer and smoother motor run-up. The length of the starting time should be
selected in such a way that the motor accelerates softly until it reaches its nominal speed.
If the starting time ends before the motor has completely run up, the torque is limited to the
set limiting torque until the soft starter recognizes the run-up process and closes the internal
bypass contacts.
Maximum starting time
The "Maximum starting time" parameter can be used to determine the time after which the
drive must have completed its run-up. If the drive is not operating under rated service
conditions after the specified interval has expired, the startup procedure is interrupted and a
fault message is generated.
