Siemens SINAMICS S120 Function Manual page 127

If the inertia load has been specified, the speed controller (Kp, Tn) can be calcu-
lated by means of automatic parameterization (p0340 = 4). The controller para-
meters are defined in accordance with the symmetrical optimum as follows:
Tn = 4 * Ts
Kp = 0.5 * r0345 / Ts = 2 * r0345 / Tn
Ts = total of the short delay times (contains p1442 and p1452)
If vibrations occur with these settings, the speed controller gain Kp must be re-
duced manually. Actual speed value smoothing can also be increased (standard
procedure for gearless or high-frequency torsion vibrations) and the controller cal-
culation performed again because this value is also used to calculate Kp and Tn.
The following relationships apply for optimization:
S If Kp is increased, the controller becomes faster, although overshoot is reduced.
Signal ripples and vibrations in the speed control loop, however, increase.
S If Tn is decreased, the controller still becomes faster, although overshoot is
increased.
When speed control is set manually, it is easiest to define the possible dynamic
response via Kp (and actual speed value smoothing) first before reducing the inte-
gral time as much as possible. When doing so, closed-loop control must also re-
main stable in the field-weakening range.
To suppress any vibrations that occur in the speed controller, it is usually only nec-
essary to increase the smoothing time in p1452 for operation with an encoder or
p1442 for operation without an encoder or reduce the controller gain.
The integral output of the speed controller can be monitored via r1482 and the limi-
ted controller output via r1508 (torque setpoint).
Note
In comparison with speed control with an encoder, the dynamic response of drives
without an encoder is significantly reduced. The actual speed is derived by means
of a model calculation from the converter output variables for current and voltage
that have a corresponding interference level. To this end, the actual speed must be
adjusted by means of filter algorithms in the software.
© Siemens AG 2006 All Rights Reserved
SINAMICS S120 Function Manual, 03/2006 Edition
Operating Modes
Vector control
3-127