West Control Solutions KS98-1 - Manual (Page 258)

Cascade operation is possible in the following operating statuses
(see also section operating pages on page 36 ):
w During automatic mode, the master variables ( and process value) are the relevant variables in the process. The
master controller is directly adjustable. The process value of the slave controller is only displayed. " Cascade" is
displayed.
w Like every slave controller, the slave can be switched over to its internalsetpoint or to W2 via control inputs. In this
case, display is "Casc-open" as when opening via the operating field. Now the slave controller becomes the pro-
cess-relevant variable and can be adjusted via the field (display "Slave” left in front of the setpoint). The master cir-
cuit process value is provided by the slave circuit rather than being controlled. Switching over between master or
slave setpoint operation is possible at any time.
w During manual mode, the process is influenced directly by the slave controller correcting variable. The slave cor -
recting variable is adjustable during manual mode. "Man" is displayed.
During manual mode, or when the slave works with the internal setpoint or W2, the cascade is opened.
The slave does not react on the master correcting variable any more. Suitable measures for master correcting
variable tracking by the slave process value should be provided in the engineering, in order to ensure bumpless
switchover to automatic mode (see example Fig.74 )
Cascade optimization
switchover disabling on the slave by means of parameter W Block prevents cascade opening via front panel operati -
on! This parameter can be used to influence the W/We/W
2
selection via the front panel.
+ Closing of the cascade will cause automatic slave switchover to the external We.
For identification of the data source, text “ Slave” is displayed right beside the unit field when the cascade is open.
A longer unit text can be overwritten partly.
+ Now only the first 4 characters of the unit are visible.
During cascade operation, the master information is displayed in the fields for , source, physical unit and X/XW bar -
graph. With open cascade (display “Slave”), the slave information is displayed instead.
Optimizing the cascade
In a cascade, the slave controller and, subsequently, the master controller must be optimized. Self-tuning entry
uu
on the cascade operating page always refers to the slave!
For master optimization, the master must be selected purposefully via the operating menu!
9499-040-82711
III-258 Controller applications:
AINP1
Inp1
fa
il
a/
m
in
c
dec
Y
lo
c k
hi
de
61
Temp. primary
OUT1
X 1
d1
81
CONTR
Weff
X
Y
XW
W
Yout1
Yout2
Bl-no
y1 y2 cf
a
il
of
f
a/
m
y/
y2
we
/w
i
pi
/p
or
u
n
os
ta
b
oe
rr
xw
su
p
X 1
X 2
X 3
Wext
OVC+
OVC-
Yp
Yhm
Yadd
Casc
hi
de lo
c k
in
c
dec
xf
yp
f
a/
m
w/
w2
we
/w
i
pi
/p
d
o
vc+
d
o
vc-
tr
a
c k
y/
y2 of
f
sm
/h
m
os
ta
rt
ws
to
p
gr
of
f
rs
ta
rt
o_hi
de
opl
oc
k
100 ts=11
Temp.Slave CONTR
Weff
X
Y
XW
W
Yout1
Yout2
Bl-no
y1 y2 cf
a il
of
f
a/
m
y/
y2
we
/w
i
pi
/p
or
u
n
os
ta
b
oe
rr
xw
su
p
X 1
X 2
X 3
Wext
OVC+
OVC-
Yp
Yhm
Yadd
Casc
hi
de
lo
c k
in
c
dec xf yp
f
a/
m
w/
w2
we
/w
i
pi
/p
d
o vc+
d
o
vc-
tr a
c k
y/
y2 of
f
sm
/h
m
os
ta
rt
ws
to
p
gr
of
f
rs
ta
rt
o_hi
de
opl
oc
k
101 ts=11
Temp. Master
AINP3
Inp3
fa
il
63
Temp.secundary
SCAL
Y 1 X 1
102 ts=11
100 >> 1000
OR
z1 not
z 1
d1 d2 d3 d4
104 ts=11
Man / Wint
SCAL
Y 1 X 1
105 ts=11
1000 >> 100
Tracking
Fig. 74 Engineering view of a cascade structure