The behavior of the technology controller corresponds to a PID controller with portions
Proportional component Amplification 444
Integral component Integral Time 445
Differential component Derivative Time 618
The sign of the amplification defines the control direction, i.e. if the actual value increases and the
sign of the amplification is positive, the output frequency is reduces (e.g. pressure control). With a
rising actual value and negative sign of the amplification, the output frequency is increased (e.g. in
temperature control systems, refrigerating machines, condensers).
The integral component can be used in order to reduce the stationary error (deviation between
actual value and setpoint) over time. If the integral component is too dynamic
1)
, the system may
become unstable and vibrate. If the integral component is too passive
2)
, the stationary error is not
compensated sufficiently.
For this reason, the integral portion must be adjusted plant-specifically.
1)
Dynamic behavior: Quick compensation of deviations.
2)
Passive behavior: Slow compensation of deviations.
By default, the differential component is set to Derivative Time 618 = 0 ms, i.e. it is deactivated.
If the compensation behavior of the PI controller (or P controller) is too slow, quicker compensation
can be reached by activating and adjusting the differential component (Derivative Time 618).
However, if the differential component is activated, the system has a higher tendency toward
vibration. For this reason, the differential component should be activated and changed carefully.
Bonfiglioli Vectron MDS GmbH recommends setting the times Integral Time 445 for the integral
component and Derivative Time 618 for the differential component to a value which exceeds the
sampling time which is 2 ms in the case of the ACU device.
Parameter Max. P-Component 442 limits the frequency change at the controller output. This
prevents vibrations of the system if steep acceleration ramps were selected.
Parameter Hysteresis 443 enables suppressing changes of the integral component outside of a
certain range (hysteresis range). This enables a more passive behavior of the technology controller.
This may be useful if the stator frequency cannot follow the reference frequency of the technology
controller. The Hysteresis 443 is referred, as a percentage, to the Rated Frequency 375, i.e.
typically 50 Hz.
The hysteresis is a limiting factor at the input of the integral component. High differences between
the current stator frequency and the technology controller output are limited in this way, excessive
integrating of the integral component is prevented.
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