Device functions
7.2 Startup modes
3RW44 soft starters
Manual, 03/2017, NEB535219502000/RS-AB/008
123
Internal run-up recognition
The soft starter features internal run-up recognition. If it detects a motor run-up within the set
starting time, the ramp is canceled and the motor voltage is immediately increased to 100%
of the line voltage. The internal bypass contacts close and the thyristors are bridged.
NOTICE
The torque generated in the motor and controlled by the soft starter can never be higher
than the value of a similar direct on-line starting operation at the associated speed.
Figure 7-3
Function principle of torque control
Typical applications for torque control
Torque control is suitable for all applications, especially in cases where uniform and smooth
startup is required. For machines requiring a breakaway pulse (inverse load response, e.g. in
mills or crushers), the breakaway pulse must be set as described in chapter Breakaway
pulse in combination with the voltage ramp or torque control startup mode (Page 124). The
"Torque current limiting (M+current limiting)" startup mode is recommended for
heavy starting (refer to chapter Current limitation in combination with the voltage ramp or
torque control startup mode (Page 125)).
