Siemens SIRIUS 3RW44 System Manual page 98

Device Functions
Typical applications for torque control
6-6
Note
The torque generated in the motor and controlled by the soft starter can at no
time be higher than the value of a similar direct start at the same speed.
Motor
torque (M)
Nm
M
Direct on-line starting
(maximum torque
that can be generated)
Parameterizable
limiting torque
N
Nom
Parameterizable
start voltage
M
1
Soft start
Torque-controlled and limited
M
2
Soft start
Torque-controlled
3 M
Load (e.g. Fan)
Figure 6-3:Function principle of torque control
Torque control is suitable for all applications, especially in cases where a
homogeneous and smooth run-up 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 6.2.3 "Breakaway Pulse in
Combination with the Voltage Ramp or Torque Control Starting Mode". The
"Torque control+current limiting (M+current limiting)" starting mode is
recommended for heavy starting (refer to Chapter 6.2.4 "Current Limiting in
Combination with the Voltage Ramp or Torque Control Starting Mode").
1
Acceleration
2
torque
3
Parameterizable
ramp time
Time (t)
s
Motor has run up and is
in nominal operation (n ).
Nom
The runup is detected and the
bypass contacts close.
SIRIUS 3RW44 System Manual
GWA 4NEB 535 2195-02 DS 04