Siemens SINAMICS S120 Function Manual page 227

If the speed controller has been correctly adjusted, it only has to compensate for disturbance
variables in its own control loop, which can be achieved by means of a relatively small
change to the correcting variables. Speed setpoint changes, on the other hand, are carried
out without involving the speed controller and are, therefore, performed more quickly.
The effect of the precontrol variable can be adapted according to the application via the
evaluation factor p1496. If p1496 = 100%, precontrol is calculated in accordance with the
motor and load moment of inertia (p0341, p0342). A balancing filter is used automatically to
prevent the speed controller from acting against the injected torque setpoint. The time
constant of the balancing filter corresponds to the equivalent delay time of the speed control
loop. Speed controller precontrol is correctly set (p1496 = 100%, calibration via p0342) when
the I component of the speed controller (r1482) does not change during a ramp-up or ramp-
down in the range n > 20 % · p0310. Thus, precontrol allows a new speed setpoint to be
approached without overshoot. (Requirement: Torque limiting does not switch in and the
moment of inertia remains constant.)
If the speed controller is precontrolled through injection, the speed setpoint (r0062) is
delayed with the same smoothing time (p1442 or p1452) as the actual value (r1445). This
ensures that no target/actual difference (r0064) occurs at the controller input during
acceleration, which would be attributable solely to the signal propagation time.
When speed precontrol is activated, the speed setpoint must be specified continuously or
without a higher interference level (avoids sudden torque changes). An appropriate signal
can be generated by smoothing the speed setpoint or activating the ramp-function generator
rounding p1130 – p1131.
The starting time r0345 (T
and describes the time during which the unloaded drive can be accelerated with the rated
motor torque r0333 (M
If these supplementary conditions are in line with the application, the starting time can be
used as the lowest value for the ramp-up or ramp-down time.
Note
The ramp-up and ramp-down times (p1120; p1121) of the ramp-function generator in the
setpoint channel should be set accordingly so that the motor speed can track the setpoint
during acceleration and braking. This ensures that speed controller precontrol is functioning
optimally.
The acceleration precontrol using a connector input (p1495) is activated by the parameter
settings p1400.2 = 1 and p1400.3 = 0. p1428 (dead time) and p1429 (time constant) can be
set for balancing purposes.
Drive functions
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
) is a measure for the total moment of inertia J of the machine
start
) from standstill to the rated motor speed p0311 (n
mot,rated
Vector control
5.4 Speed controller
).
mot,rated
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