Siemens SIPART DR21, Manual

Page: 95 / 242

3 Functional description of the structure switches
3.6 Controller output structures (S2, S49 to S55)
Manual
SIPART DR21
C73000-B7476-C143-08
95
D
S2 = 1: two-position controller, with 2 S-outputs heating/cooling;
optionally one K-output
This output structure is identical to the K-output structure in its switching options (see figure
3-22, page96 and figure 3-23, page97).
The controller can be operated exclusively as a two-position controller (both outputs as
switching outputs) or as a controller with one K-output and one switching output.
The output variable can only adopt two states for every switching
Δ
y, -
Δ
y. Switching
on or switching off. The relationship between switching on- and switching off is defined as
setting ratio =
switch-on duration
switch-on du switch-off duration
Switch on duration and switch off duration together give the period duration.
The setting range y from 0 to 100 % can be divided into two sub-ranges. The range Y1 with
a falling characteristic for cooling, the range 100% Y2 with rising characteristic for heating.
Two pulse stages are connected in series which transform the two sub manipulated vari-
ables into pulse-pause ratio. It is possible to use the manipulated variable limiting of y with
the parameters yA and yE, the setting ratio 1 is then not reached. Since the minimum pulse
duration or -pause can be set by tA or tE, further limiting is not normally necessary. A dead
zone can bset between these two sub manipulated variables. By changing Y1 or Y2 (oFPA)
the dead zone is preset and the slope adapted to the cooling- or heating aggregate.
Factory setting Y1 = Y2 = 50 % corresponds to dead zone = 0 %.
Every sub manipulated variable can be assigned a different period duration tP and tM
(onPA). In every chapter the setting ratio 0 to 1 is run through, whereby the shortest switch
on- or switch off duration is set with tE and tA (onPA). The period duration must be set so
that the respective best compromise between the minimum permissible switch on duration of
the actuator (e.g. contactor, solenoid valve, fan, cooling compressor), the switching fre-
quency and the resulting curve of the controller variable is found.
With structure switch S56 one of the outputs Y1 and Y2 can be switched to the analog
output (as of software version --B2).