Eaton ELC-PB, Руководство по программированию

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E L C P r o g r a m m i n g M a n u a l
F o r m o r e i nf o r m a t i o n v i sit :
w w w. e a t o n . c o m
MN05003003E
3-260
( )
S
t E
1
:
Integral value of E(t)
y
When
( )
t E
is smaller than 0 as the control mode is selected as forward or inverse,
( )
t E
will be regarded as “0"
Control mode PID equation
Forward, automatic E(t) = SV – PV
Inverse E(t) = PV – SV
y
Control diagram:
In diagram below, S is the derivative value, referenced to “(PV
﹣
previous PV)
÷
sampling
time”. 1 / S is integral value, referenced to “previous integral value + (error value × sampling
time)”. G(S) refers to the device being controlled.
G(s)
S
1/S K
I
K
P
K
D
+
+
+
PID
operation is within dotted area
+
y
The equation above illustrates that this operation is different from a general PID
operation in the way the derivative value is applied. To avoid the fault that the transient
derivative value could be too big when a general PID instruction is first executed, our PID
instruction monitors the derivative value of the PV. When the variation of PV is excessive, the
instruction will reduce the output MV
2. When control mode (
S
3
+4) is selected as K3 and K4:
y
The equation is exclusively for temperature control:
( ) ( ) ( )
⎥
⎦
⎤
⎢
⎣
⎡
+
⎟
⎠
⎞
⎜
⎝
⎛
+ =
S t E K
S
t E
K
t E
K
MV
D
I P
*
1 1 1
,
where
( ) ( ) ( )
t PV - t SV t E
=
y
Control diagram:
In diagram below, 1/KI and 1/KP refer to “divided by KI” and “divided by KP”. Because this
mode is exclusively for temperature control, users must use the PID instruction together with
the GPWM instruction. See Example 3 below for more details