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

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.
<
P P
•
gen , ave br , cont
<
P P
•
gen ,max br ,max
Where P ratings are now calculated from the individual ratings as follows:
br
=
P P
•
br , cont br , cont
=
P P
•
br ,max br ,max
and P
P
br,cont1 br,max1
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
•
drive module.
The selected resistance value R
•
requirements. In the following calculations, the value of U
<
R R
•
min br
The selected braking resistor should be able to handle the braking energy
•
generated in fast dynamic situations (time is just a few seconds).
∫
<
P dt E
•
gen
Where E is the energy pulse rating of the selected resistor.
R
The nominal power rating of the resistor must be adequate for the average
•
regenerative power.
<
P P
•
gen , ave
Where P is the nominal power rating of the resistor (steady state continuous load).
N,R
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.
+ × +
0 8
. ( P P
1 2
br , cont
+ × +
0 7
. ( P P
1 2
br ,max
are the values of the drive module with the highest braking power
br,min
should also fulfil the peak braking power
br
( )
2
U
<
dc
P
gen ,max
R
N R ,
+
...)
3
br , cont
+
...)
3
br ,max
according to the braking chopper data of the
dc
is 840 V DC.
Common DC configurations
31