Const_Ref Function Block; Softpot Function Block; Reference Increment And Decrement; Limitation - ABB DCS 500B Description

Functional Software description
CONST_REF func-
tion block
SOFTPOT function
block
Reference in-
crement and dec-
rement

Limitation

REF_SEL function
block
26
Only one of the five constant reference sources can be selected at
a time by means of inputs [ACT1] (1901), [ACT2] (1902), [ACT3]
(1903) or [ACT4] (1904). The Logic diagram is shown above. If
ACT1...ACT4 inputs are all in zero state, the reference value is set
to parameter DEF (1905). Otherwise the reference value is one of
REF1...REF4.
For example, if constant reference REF3 (1908) is used, input
[ACT3] (1903) has to be set to logical state 1 and inputs [ACT1]
and [ACT2] must be set to zero by the application. Normally, if in-
put pin is not connected at all, its state is zero. Block output OUT
(11901) value is set equal to parameter REF3 (1908).
The speed reference generated by the SOFTPOT (software po-
tentiometer) acts as an up/down counter. The function is shown in
the following figure.
Speed
reference
[INCR] = 1
Figure 13 SOFTPOT up/down function block
The input [INCR] (1918) activates incrementing of speed refer-
ence. The speed reference acceleration time is defined with pa-
rameter ACCEL 1 (1708) in RAMP GENERATOR function block.
The input [DECR] (1919) activates decrementing of speed refer-
ence. The speed reference deceleration time is defined with pa-
rameter DECEL 1 (1709) in RAMP GENERATOR function block.
The maximum and minimum limits for speed reference are set with
parameters OHL (1921) and OLL (1922).
If input [FOLLOW] (1920) is in logical state 1, the output of the
block OUT (11904) follows actual speed of motor (SPEED ACT)
signal.
The logical output ACT (11905) is in state 1 when either [INCR]
(1918) or [DECR] (1919) input is in state 1.
The speed references from different sources are collected to this
function block.
OHL = ouput high limit
t
[DECR] = 1
OLL = output low limit
DCS 500 Software Description