Functional Software description
42
DCS 500 Software Description
•
Current Control
TORQ_REF_HANDLI
NG function block
The speed controller’s output is normally connected to input
[TREF
SPC] (2407)
and external torque reference to
[TREF EXT] (2408)
.
Torque Refer-
ence Selection
The TORQ REF HANDLING function block consists of the operat-
ing mode selector for the torque reference, and it is controlled by
parameter
TREF SEL (2406)
which has six different modes.
0
= no torque or speed control
1
= always selects the output of the speed controller
[TREF SPC] (2407)
as the torque reference. This is a
normal selection for speed control.
2
= always selects the external torque reference
[TREF EXT]
(2408)
as the torque reference. This is a normal selection
for torque control.
Note.
If the torque reference does not correspond to the
load, e.g. the drive load falls down suddenly, it is possible
to
prevent overspeed in the drive section by means of
parameter
OVERSPEEDLIMIT (2204)
.
3
= selects the minimum value from the external torque
reference or the speed controller output. A negative
speed difference (SPEED REF < SPEED ACT) causes
a change-over to speed control. A change-over from
speed control to torque reference takes place when the
torque reference is smaller than the speed controller
output and speed difference is positive
[TREF EXT] < [TREF SPC] and SPEED REF
≈
SPEED ACT)
4
= selects the maximum value based on the speed
difference. A positive speed difference (SPEED REF > -
SPEED ACT) causes a change-over to speed control. A
change-over from speed control to torque control takes
place when the torque reference is greater than the speed
controller output, ([TREF EXT] > [TREF SPC] and
SPEED REF
≈
SPEED ACT).
5
= Window control, external torque reference and speed
controller output are added. See more details in
paragraph
Window Control Principle
.
Summary of Contents for DCS 500B
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