West Control Solutions N8800 - Manual (Page 49)

4.4 Switching behaviuor
With 8800 process controller, configuration parameter CYCL (ConF/ Cntr/
CYCL) can be used for matching the cycle time of 2-point and 3-point
controllers. This can be done using the following 4 methods.
4.4.1 Standard ( CyCl= 0 )
The adjusted cycle times t1 and t2 are valid for 50% or -50% correcting
variable. With very small or very high values, the effective cycle time is extended
to prevent unreasonably short on and off pulses. The shortest pulses result from
¼ x t1 or ¼ x t2. The characteristic curve is also called “bath tub curve”
Parameters to be adjusted: t1 : min. cycle time 1 (heating) [s]
( PArA/ Cntr) t2 : min. cycle time 2 (cooling) [s]
4.4.2 Switching attitude linear ( CyCl= 1 )
For heating (Y1), the standard method
(see chapter 4.4.1) is used. For
cooling (Y2), a special algorithm for
cooling with water is used. Generally,
cooling is enabled only at an
adjustable process temperature
(E.H2O), because low temperatures
prevent evaporation with related
cooling, whereby damage to the plant is avoided. The cooling pulse length is
adjustable using parameter t.on and is fixed for all output values.
The “off” time is varied dependent of output value. Parameter t.off is used for
determining the min “off” time. For output of a shorter off pulse, this pulse is
suppressed, i.e. the max. effective cooling output value is calculated according to
formula t.on / ( t.on + t.off) w 100%.
Configuration level
8800 process controller 49 Switching behaviuor
0,0
1,0
2,0
3,0
4,0
5,0
6,0
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95
Controller output [%]
relative
cycle
duration
T / T
1
t1
2 x t1
3 x t1
4 x t1
-50% -67% -80% -100% -30% -20% -10%
-6%
t.off t.on