Speed control
© KEB, 2012-10 COMBIVERT F5-A, -E, -H Page 7.7 - 3
7
7.7 Speed control
The speed controller is a PI controller.
A PT1 low pass lter is series-connected.
The integral factor Ki can be changed speed-dependent. The proportional factor Kp can be increased propor-
tionally to the control deviation.
In order to improve the control performance of the drive (low overshoot, higher dynamics), the speed controller
can be pre-controlled with known mass-moment of inertia.
7.7.1. Speed controller parameters
7.7.1.1 Initial setting
The speed controller is a PI controller.
The proportional factor "Kp speed" is adjusted in cS.06 and the integral factor "KI speed" in cS.09
7.7.1.2 Automatic adjustment of the speed controller (only at operating with motor model)
Kp (cS.06) and Ki (cS.09) of the speed controller can be preset by the inverter. For this the mass-moment of
inertia of the complete system (motor + rigidly coupled load) must be entered in cS.25 „inertia“.
After the input of the motor data once parameter Fr.10 "Reset eld-oriented control parameter" = 1 or 2 must
be written. Thus dependent on the adjusted rated power (dr.03) the mass-moment of inertia was pre-charged
for a standard asynchronous motor in cS.25. The value of cS.25 has the right dimension for 50Hz standard
motors, because at some applications the ratio of the load inertia is in a range of 0.5...2 x motor inertia.
Better results can be realized if the total moment of inertia is exactly preset. If the value is unknown it can be
determined.as described in chapter 7.7.2.
Parameter cS.26 „optimisation" determines the control characteristic which should be achieved by the calcu-
lated parameters.
Parameters for a dynamic, hard speed controller adjustment are calculated with cS.26 = 2. Interference fac-
tors, such as torsion or tolerance of the load coupling can intensify vibrations, so that a higher value must be
entered in cS.26.
Parameters for a very soft and slow speed controller adjustment are calculated with cS.26 = 15. Which value
between 2 and 15 is most suitable for the application is depending on the oscillation-grade of the total system.
An oscillation of the estimated speed is a possible disturbance at encoderless operation of asynchronous mo-
tors (ASCL). Extension of parameter "ASCL speed PT1 time" (ds.17) often enables a dynamic speed controller
adjustment, i.e. a smaller value for cS.26.
The precharging of the speed controller parameters can be deactivated with the adjustment of value "19 = off"
in cS.26.
The speed controller parameters are overwritten when the value for cS.26 is changed.
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