West Control Solutions KS98-1 - Manual (Page 272)


Hard manual ( sm/hm)
Safety output value Yhm. The controller output goes to the preset value immediately, when hard manual is active
(the controller is switched to manual mode directly). Keys I / D are without effect. Switch-over to automatic mode is
bumpless.

Cascade control
Particularly suitable for temperature control in e.g. steam boilers. A continuous master controller (load controller) provi -
des its output signal as an external to a slave controller, which varies the output value.

Override control (OVC)
r page 269
Limiting of the min. (OVC-) or max. (OVC+) output value to the value of an analog input. Limitation by override control
can be used e.g. with control continued by a different controller dependent of different conditions when reaching defi -
ned process statuses. The transitions from unlimited r limited output value and vice versa are bumpless.

Program control
The effective setpoint follows the profile of a programmer (APROG with APROGD) connected to input Wext; the con-
troller must be set to we (di9=0).

Process at rest
For a clear optimization attempt during self-tuning, the control variable must be in a stable position. Various rest condi-
tions can be selected:
Process behaviour with constant output
value Recommended
setting
Stability PIR_H is reached, if
A constant process value is reached in rel-
atively short time (standard process).
grad=0
the process value is constant during 1 minute.
After a relatively long time, a constant
process value is reached (slow process).
grad<0/>0
the process value decreases constantly during 1 minute (controller
inverse) or increases constantly during 1 minute (controller direct).
The process is affected from outside.
grad<>0
the process change is constant during 1 minute. The output action
is unimportant.

Ramp function
changes in ramps rather than in steps. See gradient control.

Control parameters
For controller optimization, the controller must be matched to the process characteristics
(r 5 Optimizing help, r 6 Self-tuning). The effective parameters are Xp1, Tn, Tv and Y0.
Dependent of controller operating principle, the following additional parameters are possible:
Tp1 (with 2-point/3-point controllers), Xp2 and Tp2 (with 3-point controllers),
Xsh and Tpuls and Tm (with 3-point stepping controllers).

Control behaviour
Generally, fast line-out to the without overshoot is required. Dependent of process, various control behaviours are de -
sirable for this process:
w easily controllable processes (k < 10%) can be controlled with PD controllers,
w processes with medium controllability (k 10...22%) using PID controllers and
w badly controllable processes (k > 22%) with PI controllers.

Controller OFF ( off)
With input off =1, there are no pulses at the switching output and the continuous outputs are 0%.

Self-tuning
For optimum process control, the controller must be matched to the process requirements. The time required for this purpose can
be reduced considerably by self-tuning (r 6 Self-tuning). During self-tuning, the controller makes one adaptation attempt during
which the control parameters are determined automatically from the process characteristics for fast line-out to the without over-
shoot.
9499-040-82711
III-272 Small controller ABC