Breakaway Pulse In Combination With The Voltage Ramp Or Torque Control Starting Mode - Siemens SIRIUS 3RW44 System Manual

6.2.3 Breakaway Pulse in Combination with the Voltage Ramp or Torque Control Starting Mode

Breakaway voltage
Breakaway time
SIRIUS 3RW44 System Manual
GWA 4NEB 535 2195-02 DS 04
This function is required for load machines with inverse torque behavior. Typical
applications are mills, crushers or drives with plain bearings. In such cases it
may be necessary to create a breakaway pulse at the beginning of the machine's
start process. The breakaway pulse is set via the breakaway voltage and the
breakaway time. Using the breakaway pulse, the high limiting friction of the load
can be overcome and the machine can be set into motion.
The breakaway pulse can be used in combination with the voltage ramp, torque
control or current limiting starting modes and is superimposed on these during
the whole breakaway time.
The breakaway voltage setting determines the breakaway torque to be
generated. Its maximum value can be 100 % of the start torque generated on
direct starting. The pulse should be high enough for the motor to start
immediately when the soft starter receives the start command.
The breakaway time specifies how long the breakaway voltage should be
applied. Upon completion of the breakaway time, the soft starter finishes its run-
up process with the selected starting mode, e.g. voltage ramp or torque control.
The selected breakaway time should be at least long enough so that, after the
configured time has elapsed, the motor does not remain stationary again but
rather accelerates further in the selected starting mode.
If 0 ms is set as the breakaway time (default), the breakaway pulse function is
deactivated.
Motor
torque (M)
Nm
Parameterizable
breakaway voltage
M
Nom
Parameterizable
start torque/
start voltage
Parameterizable
breakaway voltage
M
1
Direct on-line starting
(maximum torque that can be generated)
M
2
Soft start
Breakaway pulse combined with
torque regulation or voltage ramp
M
3
Load (e. g. Crusher)
Figure 6-4:Function principle of breakaway pulse/torque control
1
Acceleration
2
torque
3
Parameterizable
starting time
5_04_Funktionsprinzip Losbrechimpuls Drehmomentregelung .wmf
Device Functions
Time (t)
s
Motor has run up and is
in nominal operation (n ).
Nom
The runup is detected and the
bypass contacts close.
6-7