Siemens SINAMICS S120 Function Manual page 119

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, there-
fore, performed more quickly.
The effect of the pre-control variable can be adapted according to the application
via the evaluation factor p1496. If p1496 = 100 %, pre-control is calculated in ac-
cordance 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 pre-control 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 % x p0310. Thus, the pre-control allows a new speed setpoint to be
approached without overshoot (prerequisite: the torque limiting does not act and
the moment of inertia remains constant).
If the speed controller is pre-controlled 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 pre-control is activated, the speed setpoint must be specified continu-
ously or without a higher interference level (avoids sudden torque changes). An
appropriate signal can be generated by smoothing the speed setpoint or activating
ramp-function generator rounding-off p1130 -- p1133.
The starting time r0345 (T
machine and describes the time during which the unloaded drive can be
accelerated with the rated motor torque r0333 (M
rated motor speed p0311 (n
r0345 = T
If these basic 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.
© Siemens AG, 2005. All rights reserved
SINAMICS S120 Function Manual, 06/05 Edition
) is a measure for the total moment of inertia J of the
start
Mot,rated

2π × n
Mot,rated
= J ×
Start 
60 × M
mot,rated
) from standstill to the
mot,rated
).

= p0341 × p0342 ×

Operating Modes
Vector control
(2π × p0311)
(60 × r0333)
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