Siemens SIMOTRAS 6SG7050, Operating Instructions Manual

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01.04 Start-up
SIEMENS AG 6SG7000-0BA76
7-19
SIMOTRAS HD Operating Instructions
7.6.16 Counter-torque operation and premature switching over from counter-torque
stage to start-up stage
Counter-torque operation means that an electrical phase in opposition to the mechanical speed is
applied to the running motor in order to brake the drive.
The rotor resistance stage is connected to the greatest resistance during this process.
The counter-torque stage is left once the drive has been braked to zero speed
(switchover point S1a in Fig. 7.6.15.1).
If rotor stage S1 is connected before the speed reaches zero (switchover point S1b in
Fig. 7.6.15.1), the control range indicated by Mzus in Fig. 7.6.15.1 is gained.
The most common operating condition, where the response outlined above occurs, is the following:
Lifting gear with a large load:
The load is lowered at the maximum speed (power lowering).
The master switch is set to “zero position” or “Lift”.
A delay torque must now be applied in addition to the torque required to hold the load (e.g. 95% at
rated load). When the drive is in counter-torque mode (i.e. the load is still being lowered), the delay
torque becomes smaller as the speed reduces. If changeover takes place from the counter-torque
stage to the start-up stage at a specific negative speed, the torque range designated Mzus in the
diagram above is achieved.
•
The value at which the early switchover from the counter-torque stage to the start-up stage in
the “Delay lowering” operating condition occurs is set using parameter U630.
n
t
t
Actual speed
value
(K0167)
U630
t
S1
Lower
Lift
Premature switchover
to start-up stage S1
Master switch
setpoint
(K0198)
Control output S1
(B0526)
t
Counter-torque
stage
Y resistance
Fig. 7.6.16.1 Time characteristic for premature connection of start-up stage S1