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Chapter 5
Function Modules
maximum = 7500 ---> (6 m3/h)
It is observed that in the VA case, even so the valve has capacity to inject 8 m3/h, is desired to limit
this outflow in 6 m3/h.
Parameters of the Process
Figure 43 shows the result of a test of an opened loop of the process. To execute this test, was
directly used the VA and VM variables, with its internal units.
VA
(4 m3/h)
5000
(2 m3/h)
2500
t
VM
(70 oC)
12000
979
(50 oC)
t
50 60
90
Figure 43: Open Loop Test
On this figure can be determined the 3 basic parameters, as explained previously.
Tm = 10 seconds (dead time, since the step was applied in t = 50 s and the reply initiated in t = 60 s).
T = 30 seconds (time constant, since the reply t initiated in = 60 s, and reached 63.21% of the
excursion in t = 90 s):
9792 = 6000 + (12000 – 6000) * 0,6321.
K = 2.4 (static gain of the process)
2.4 = 12000 – 6000
5000 - 2500
Tunning of the Controller
Since the test of opened loop was carried through, will be used the second tunning method previously
described on Notes of Application.
To use this method, beyond the determined parameters of the process in the previous section (Tm, T
and K), also it is necessary that the user informs others 2 parameters:
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