PMA KS 98, Руководство пользователя

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3
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.
3
Set-point switch-over
In principle, the following set-points are possible: internal set-point wi , second internal set-point w2 and external
set-point
we
. With program control, external set-point
we
must be selected. The analog set-point comes from APROG
and is applied to input
Wext
.
ü
y feedback control
Particularly suitable for processes in which load changes lead to process value drops. A load-dependent change to
set-point (preferable) or process value is made. The evaluated and filtered output value is added to the set-point in a
separate function block. Use the
Wext
input and set the controller to
we
.
ü
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 set-point. To
prevent permanent control deviations, the limit contact must be further away from the set-point than the permanent
control deviations.
3
Tracking
During switch-over from external or program set-point to internal set-point, set-point 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 set-point. Set-point tracking: During switch-over, the external or program
set-point used so far is taken over as internal set-point.
3
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
3
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.
3
x/xw differentiation
Dynamic changes of process value or set-point 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 set-point are used dynamically to permit a better control result. In this case, the improvement is dependent
of both disturbance and control behaviour.
3
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
(„heating“),
c
(„cooling“), („open“) and („close“).
Controller
Small controller ABC
Small controller ABC 166