ABB ACS850 - Multiple Braking Choppers; Braking Resistor Selection; Single Braking Resistor; Multiple Braking Resistors

31
Multiple braking choppers
In case two or more braking choppers of drive modules are active in the common DC
system, the same conditions as above must still be fulfilled.
•
cont, brave,gen
PP <
•
,max br,maxgen
PP <
Where P
br
ratings are now calculated from the individual ratings as follows:
• ...)PP(.PP
cont,brcont,brcont,brcont,br
+
+
×
+
=
321
80
• ...)PP(.PP
,maxbr,maxbr,maxbr,maxbr
+
+
×
+
=
321
70
P
br,cont1
and P
br,max1
are the values of the drive module with the highest braking power
ratings.
Braking resistor selection
The resistor(s) should be selected according to the regenerative power requirements.
The following conditions must be fulfilled.
Single braking resistor
• The resistance must be at least R
br,min
according to the braking chopper data of the
drive module.
• The selected resistance value R
br
should also fulfil the peak braking power
requirements. In the following calculations, the value of U
dc
is 840 V DC.
•
(
)
,maxgen
dc
brmin
P
U
RR
2
<<
• The selected braking resistor should be able to handle the braking energy
generated in fast dynamic situations (time is just a few seconds).
•
R gen
EdtP <
∫
Where E
R
is the energy pulse rating of the selected resistor.
• The nominal power rating of the resistor must be adequate for the average
regenerative power.
•
R, Nave,gen
PP <
Where P
N,R
is the nominal power rating of the resistor (steady state continuous load).
For a more detailed analysis and more optimal selection, the pulse load curves of the
selected resistor should be studied.
Multiple braking resistors
If two or more braking resistors are connected to the braking choppers of the drive
modules, the same conditions as above must still be fulfilled.
Common DC configurations