ABB DCS 500B, Description

Page: 41 / 228

Functional Software description
DCS 500 Software Description 33
Integral part Set-
ting during the
Control Mode
Changing Output from the integral part can be adjusted to a certain level by
setting the
[BAL] (2008) to logical state 1; then the value of [BAL
REF] (2009) is set to the output of the integral part. There is an-
other similar function controlled by [BAL2] (2010) and [BAL2 REF]
(2011) .
BAL REF and BAL inputs are used, for example, in the mechanical
brake control block of the standard program. BAL2 REF and BAL2
inputs are used in torque control. In torque control the integral part
of the speed controller follows the
OUT (12402) pin of the TORQ
REF HANDLING function block. This function provides an bum-
pless current reference during a change of control mode (for exam-
ple Torque --> Speed control).
Principle of
Drooping Drooping can be used if a certain amount of speed decrease is
needed when the load increases, for example, in the slave drive(s)
when they are speed controlled. Then the master and slave drives
do not conflict with each other before the slave(s) change to torque
control even if there is a slight speed difference between them. On
the other hand, drooping is used in drives where mechanical con-
nection is not strong enough to enable use of torque control.
Drooping Ad-
justment The amount of speed decrease caused by the load is defined by
the parameter
DROOPING (2013) . The scaling is 10=1%. With the
torque reference 4000 the speed will decrease 1% calculated from
the rated speed when DROOPING = 10.
SPEED
ACT
20000
OUT (12004)
SPC OUTPUT
4000 0
1% DROOPING
19000
18800
Figure 18 Drooping as a function of torque reference
SPEED_MONITOR
function block