West Control Solutions KS98-1 - Manual (Page 273)

Soft-Manual
Usual manual operation: with automatic r manual change-over, the last output value remains active and can be adjusted via
keys I / D. Transitions automatic r manual and vice versa are bumpless.
switch-over
In principle, the following s are possible: internal wi, second internal w2 and external we. With program control,
external we must be selected. The analog comes from APROG and is applied to input Wext.
y feedback control
Particularly suitable for processes in which load changes lead to process value drops. A load-dependent change to
(preferable) or process value is made. The evaluated and filtered output value is added to the in a separate function
block. Use the
Wext input and set the controller to we.
PI/P switch-over
When optimizing slow processes, e.g. big furnaces, the controller I action can cause problems: if starting up was opti -
mized, line-out can be slow; with optimization of the disturbance behaviour, there may be an important overshoot. This
effect is prevented by switching off the I action during start-up or with high control deviations (e.g. by applying a limit
contact to the control deviation) and switching it on again only when the process value approaches the . To prevent
permanent control deviations, the limit contact must be further away from the than the permanent control deviations.
Tracking
During switch-over from external or program setpoint to internal setpoint, setpoint or output value step changes may
occur. By means of the tracking function, the transition is bumpless. Process value tracking: During switch-over, the ef -
fective process value is used as internal setpoint. Setpoint-tracking: During switch-over, the external or program set -
point used so far is taken over as internal setpoint.
Behaviour with fail (configuration of the controller behaviour with sensor failure, xf)
Selected behaviour Effect with 3-point stepping
controllers Effect with other controllers
Neutral No output pulses No output pulses or 0%
Ymin Actuator is closed Ymin (= limiting)
Ymax Actuator is opened Ymax (= limiting)
Y2 Not selectable Y2 fixed, also with manual operation
Y2/Yman Not selectable Y2, adjustable in manual mode with ID
Ratio control
Particularly suitable for controlling mixtures, e.g. fuel-air mixture for ideal or stoichiometric
combustion. For taking e.g. the atomizer air into account, zero offset
N0 can be added.
x/xw differentiation
Dynamic changes of process value or setpoint affect control differently. x-differentiation: Process value changes (dis -
turbances) are used dynamically to permit better control results. xw-differentiation: Changes of process value (distur -
bances) and setpoint are used dynamically to permit a better control result. In this case, the improvement is dependent
of both disturbance and control behaviour.
Controller operating principle
The static operating principles for controllers with P or PD behaviour with adjustable working point Y0 are shown. On
controllers with I action, the working point is shifted automatically. The outputs (Â) are described with
h („hea-
ting“),
c („cooling“), („open“) and („close“).
9499-040-82711
Small controller ABC III-273