TM_s-MEXT_ME28relC_00_12_19_EN
Technical manual
TRANSLATION OF THE ORIGINAL INSTRUCTIONS
123
21
ANNEXES
21.1
PID ADJUSTER CONTROL PARAMETERS
The EV software is equipped with some PID adjusters for controlling:
•
Cold request
•
Humidifier
The graph below shows the operating logic of a PID control:
∑
+
Setpoint
I
t
t
d
e
K
0
)
(
P
D
)
(
t
e
K
p
dt
t
de
K
d
)
(
∑
Process
Error
Output
-
Figure 21-1:
PID operating control logic
This type of control involves three types of action:
•
P
roportional action
•
I
ntegral action
•
D
erived action
The values of the three types of action can be modified to change the effects on the controlled output variable (inverter frequency, valve opening, steam production, fan
speed, etc.) and, therefore, the adjustment itself.
The default parameters of the controller allow sufficiently precise and rapid adjustment within the response times. However, in certain cases it may be necessary to make
certain changes depending on the required result of the adjustment.
The parameters can all be set under the
“Regulations” menu
, which can be accessed by entering the
“Service” password
.
For the default values, see the parameters table.
Below are a few guidelines concerning the effect of each action.
21.1.1
Proportional Action
The proportional action sets a basic control action for what is currently happening. The value of this action is proportional to the error, i.e. the deviation of the measured unit
in relation to the setpoint.
This action is defined using the proportional constant K
p
(also known as proportional gain) calculated with this formula:
𝐾
𝑝
=
100
𝐵
𝑝
Where B
p
is the value of the proportional band defined by one of the following parameters:
•
P20.18 (for temperature adjustment)
•
P20.21 (for humidity adjustment)
The proportional band B
p
defines the maximum error capable of bringing the proportional action to 100%.
A low B
p
value can therefore cause an extreme reaction even when there are slight variations in the error, while a high value ensures little variation of the control variable
even when there are serious errors.
The following table shows the reactions on the system caused by the
decrease
of the proportional band and resulting increase of the proportional constant.
Parameter
(Decreases)
Constant
(Increases)
Promptness of
response
Overshoot
Balancing time
Error at full power
Stability
B
p
K
p
Increases
Increases
Decreases (slightly)
Decreases
Worsens
21.1.2
Integral Action
The integral action is an action of control on the basis of what has happened in the past. The value of this action is proportional to the sum of the errors of the previous
moments.
This action is defined using the integral constant K
i
(also known as integral gain) calculated with this formula:
𝐾
𝑖
=
𝐾
𝑝
𝑇
𝑖
T
i
is the value of the integral time defined by one of the following parameters:
•
P20.05 (for the adjustment of direct expansion units with on/off compressor or chilled water units)
•
P20.06 (for the adjustment of direct expansion units with inverter compressor)
•
P20.22 (for humidifier adjustment)
•
P20.95 (for the adjustment of direct expansion units with compressors with delivery air adjustment active and Free Cooling).
The following table shows the reactions on the system caused by the
decrease
of the integral time and resulting increase of the integral constant.
