Deviation 1: A deviation with a slope of 1
Deviation 2: A deviation with a slope of 2.5 (2.5 times bigger than deviation 1
D output 1, Td=0.5 s: Output from the D regulator when Td=0.5 s and the deviation is according to Devia-
tion 1.
D output 2, Td=0.5 s: Output from the D regulator when Td=0.5 s and the deviation is according to Devia-
tion 2.
D output 2, Td=1 s: Output from the D regulator when Td=1 s and the deviation is according to Devia-
tion 2.
The example shows that the bigger the deviation and the higher the Td setting is, the bigger is the output
from the D regulator. Since the D regulator is responding to the slope of the deviation, it also means that
when there is no change, the D output will be zero.
When commissioning, keep in mind that the Kp setting has influence on the D regulator output.
If the Td is adjusted to 0 s, the D regulator is switched OFF.
The differential action time Td must not be too high. This will make the regulation hunt similar
to a too high proportional action factor Kp
9.1.4 Relay control
When the relay outputs are used for control purposes, the regulation works like this:
55Hz45Hz 50Hz
Regulator
output
Fix up signal Up pulse
No reg. Fix down signalDown pulse
Hz
The regulation with relays can be split up into five steps.
AGC 100 Designer's Reference Handbook
4189340766 UK
PID controller (AGC 110 only)
DEIF A/S Page 145 of 152
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