Siemens MICROMASTER 440 Operating Instructions Manual page 178

3 Functions
Freq. setpoint
Act. frequency
Fig. 3-81
When correctly adapted, then the speed controller only has to correct noise
quantities/disturbances in its control loop and this is achieved with a relatively low
manipulated quantity change. On the other hand, speed setpoint changes bypass
the speed controller and are therefore executed faster.
The effect of the pre-control quantity can be adapted, depending on the particular
application, using the pre-control factor P1496. Using P1496 = 100 %, the pre-
control is calculated according to the motor and load moment of inertia (P0341,
P0342). In order that the speed controller does not work against the torque setpoint
which is entered, a balancing filter is automatically used. The time constant of the
balancing filter corresponds to the equivalent delay time of the speed control loop.
The speed controller pre-control is correctly set (P1496 = 100 %, calibration via
P0342), if the I component of the speed controller (r1482) does not change during
a ramp-up or ramp-down in the range n > 20% * P0310. This means, using the pre-
control, it is possible to approach a new speed setpoint without overshoot
(prerequisite: The torque limiting does not intervene and the moment of inertia
remains constant).
If the speed controller is pre-controlled, then the speed setpoint (r0062) is delayed
with the same smoothing (P1442 or P1452) as the actual value (r1445). This
ensures that when accelerating, there is no setpoint – actual value difference
(r0064) at the controller input which would have been exclusively caused by the
signal propagation time.
When the speed pre-control is activated, it must be ensured that the speed setpoint
is continuously entered and without any significant noise level (avoid torque
surges). An appropriate signal can be generated by smoothing the analog signal
P0753 (refer to Section 3.6.3) or by activating the rounding-off function of the ramp-
function generator P1130 – P1133 (refer to Section 3.12.2).
178
Pre-control
P0341 P0342
P1496
r1084
=0
–
>0
T
i
Speed controller with pre-control
Droop
r1518
K
T
p
n
r1538
PI
Speed
controller
–
r1539
T
i
SLVC: P1452 P1470
VC: P1442 P1460
MICROMASTER 440 Operating Instructions
6SE6400-5AW00-0BP0
Issue 10/03
r1538
Torque
setpoint
r1539
K T
n
p
P1472
P1462