West Control Solutions KS98-1 - Manual (Page 232)

Three-point controller
Switching controller with three switching statuses:
1. Heating switched on; r output Y1 = 1, Y2 = 0
2. Heating and cooling switched off; r outputs Y1 = 0, Y2 = 0
3. Cooling switched on; r outputs Y1 = 0, Y2 = 1
E.g. for temperature control with electrical heating (h) and cooling (c).
Adjust cycle time Tp1 and Tp2 as follows:
Tp Tu 1 0 25 <= · , (h) Tp Tu 2 0 25 <= · , (c).
With higher Tp1/Tp2, oscillations have to be expected. Cycle times Tp1 and Tp2 are the minimum cycle times
at 50% duty cycle.
PD/PD action
(
Tn = 0 = switched off Tn = Î)
The positioning range reaches from 100 % heating (Y1) to 100 % cooling (Y2). The proportional bands must be adapted to the
various heating and cooling power values. In order to keep the control variable constant, a defined amount of energy depen-
dent of is required. This causes a permanent control deviation, which increases with growing X
p(1,2).
DPID/DPID action
By means of the I action, line-out without permanent control deviation is possible. Transition from trigger point 1 (hea-
ting) to trigger point 2 (cooling) is without neutral zone. The proportional bands must be adapted to the various heating
and cooling power values.
Fig.: shows the static characteristic for inverse output action.
Direct/inverse switchover only causes exchanging of the outputs for “heating/cooling”.
Expressions “heating” and “cooling” may also mean similar processes (dosing acid/lye, ...).
The neutral zone is adjustable separately for the trigger points (X
sh1
, X
sh2
) i.e. it need not be symmetrical to the .
The type of positioning signals is selectable:
CFunc = 3-point heating switching, cooling switching
CFunc = cont/switch heating continuous, cooling switching
CFunc = switch/cont heating switching, cooling continuous
Combination “heating continuous” and “cooling continuous” is covered by “splitRange - continuous controller with
split-range behaviour”. r see also "continuous controller" page: 238.
Controller 9499-040-82711
III-232 Control behaviour
Output Y1 (heating)
Output Y2 (cooling)
Process value
Setpoint
Setpoint
100%
0%
100%
0%
Y1Â h Y2Â c
Xn100 Xn0 W0 Weff W100
Xeff
Xp2
Xp1=Xp'+Xp''
Xp' Xp''
Xsh1 Xsh2
actual
working point
Fig.: 56
Static operating principle
of a three-point controller