In the case shown here, the preset I component is too large (parameter
Tn too small, Tn must be increased). The I-component integrates the
control deviation until it becomes 0. If integration proceeds too rapidly,
the actuating signal, i.e. the output signal of the controller, is too large.
As a result, the actual value fluctuates (fading) around the target value.
The hold-back time (parameter Tv) should be adapted using the formula:
Tv = Tn x 0.75 adapted.
The actual value increases relatively sharply towards the specified target
value. The proportional area settings seem to be correct. If the control devi-
ation becomes smaller, the actual value approaches the target value much
more slowly. The integration component (I-component) must compensate
for the drastic reduction of the proportional component (P-component). In
this case, the I component is integrated too slowly. The parameter Tn, which
specifies the integration interval, must therefore be reduced. The hold-back
time (parameter Tv) should be adapted using the formula: Tv = Tn x 0.75.
5.8.2 Overview of internal control parameters
The internal control compares the set temperature with the outflow tem-
perature and calculates the actuating signal, i.e. the measurement used for
heating or cooling.
Table 32: The following control parameters can be adapted for internal
control:
Characteristics
Designation
Unit
Xp
Proportional range
K
Tn
Adjustment time
s
Tv
Hold-back time
s
Td
Attenuation time
s
If Tv manual/auto is set to auto, Tv and Td cannot be modified. In
this case, they are derived with fixed factors of Tn.
The temperature limits Tih and Til also have an effect on the
control.
Fig. 42: Control parameters Tn and Tv too
small
Fig. 43: Control parameters Tn and Tv too
large
V6
Integral Process Thermostats and High-Temperature Thermostats
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