ABB DCS 500B, Description

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Functional Software description
DCS 500 Software Description 31
Window Control
Principle
TIME
TORQ REF
+
SPC OUTPUT
SPEED ACT
SPC OUTPUT
WIN SIZE (2004)
SPEED ERROR > WIN SIZE / 2
SPEED ERROR < WIN SIZE / 2
SPEED ERROR = 0
Figure 16 Window control function
The idea of Window control is to deactivate the speed control as
long as the speed deviation remains within the set window. This
allows the external torque reference to affect the process directly.
Application ex-
ample for Win-
dow Control In master/follower drives, where the follower section is torque con-
trolled, the window control is used to keep the speed deviation of
the section under control. The speed error output to the speed
controller is zero when speed error is less than
WINSIZE/2 .
If the load of the follower disappears because of a disturbance in
the process, the speed error will be outside the window. The speed
controller works and its output
OUT (12004) is added to the torque
reference [TREF SPC] (2407) .
Speed control brings the speed difference back to the window. This
function could be called overspeed or underspeed protection in the
torque control mode.
Enabling the
Window Control The window control is activated by setting the input [WIN MODE]
(2003) to logical state 1.
The parameter TREF SEL (2406) in the TORQ REF HANDLING
function block must be set to value 5 when window control is used.
Determining the
Window Size The size of window determined by parameter WIN SIZE (2004) ,
scaling is the same as for the speed reference. See the previous
figure
"Window control function" .
Output connec-
tion points Output OUT(12001) is normally connected to [IN] (2006) input in
the SPEED CONTROL function block.