Siemens SIRIUS 3RW50 Manual page 122

Functions
7.1 Soft starting
Parameter
Parameter
Starting voltage
Ramp up time
122
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. Set the starting voltage to a value that ensures that the motor
starts up immediately and smoothly once the start command reaches
the 3RW50 soft starter.
Factory setting: 30%
•
Setting range: 30 ... 100 %
•
The ramp up time determines the time taken to increase the motor
voltage from the parameterized starting voltage to the line voltage. This
has an influence on the motor's acceleration torque which drives the
load during the ramp-up operation. A longer ramp up time results in a
shorter acceleration torque across the motor ramp up time. The motor
therefore runs up more slowly and smoothly.
Set the length of the ramp up time so that the motor can reach its rated
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 3RW50 soft starter can switch itself off via the internal
overload protection function and signal a fault.
If parameter value "0" is set, the motor is switched on with a ramp up
time of approx. 100 ms.
Factory setting: 10 s
•
Setting range: 0 ... 20 s
•
SIRIUS 3RW50 soft starter
Manual, 09/2019, A5E35628455002A/RS-AA/001