Siemens Sinamics S120 Function Manual page 153

Speed controller
The speed controller receives its setpoint (r0062) from the setpoint channel and its actual
value (r0063) either directly from the speed sensor (control with sensor (VC)) or indirectly via
the motor model (control without sensor (SLVC)). The system deviation is increased by the
PI controller and, in conjunction with the pre-control, results in the torque setpoint.
When the load torque increases, the speed setpoint is reduced proportionately when droop
is active, which means that the single drive within a group (two or more mechanically
connected motors) is relieved when the torque becomes too great.
Figure 4-6
The optimum speed controller setting can be determined via the automatic speed controller
optimization function (p1900 = 1, rotating measurement).
If the inertia load has been specified, the speed controller (Kp, Tn) can be calculated by
means of automatic parameterization (p0340 = 4). The controller parameters 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 reduced
manually. Actual-speed-value smoothing can also be increased (standard procedure for
gearless or high-frequency torsion vibrations) and the controller calculation performed again
because this value is also used to calculate Kp and Tn.
Drive functions
Function Manual, (FH1), 01/2012, 6SL3097-4AB00-0BP2
Speed controller
Vector control
4.3 Speed controller
151