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Technical data chapter "2.3 Braking resistor" 17
Commissioning chapter
"5.2 LXM32: Setting the braking resistor parameters"
54
See also chapter "3.1 Energy balance", page 22 for rating information.
Internal braking resistor A braking resistor to absorb braking energy is integrated in LXM32
drives. The device is shipped with the internal braking resistor active.
If the braking energy of all drives sharing a common DC bus is greater
than the energy the internal braking resistors can absorb, you must
use an external braking resistor. Consider the most extreme case of
your application in calculating the braking energy.
Example: In the case of an EMERGENCY STOP, all drives decelerate
simultaneously; the braking resistors must be able to absorb the entire
braking energy.
External braking resistor An external braking resistor is required in applications in which the
braking energy is greater than the energy that can be absorbed by the
drives sharing a common DC bus. Consider the most extreme case of
your application in calculating the braking energy.
Example: In the case of an EMERGENCY STOP, all drives decelerate
simultaneously; the braking resistors must be able to absorb the entire
braking energy.
LXM32: Monitoring LXM32 drives monitor the load on the connected braking resistor. The
load on the braking resistor can be read out.
The connection of the external braking resistor is short-circuit protec-
ted. A ground fault of the braking resistor is not detected.
Selection of the external braking
resistor
The rating of an external braking resistor depends on the required
peak power and continuous power with which the braking resistor can
be operated.
The resistance R is derived from the required peak power and the DC
bus voltage.
R =
P
max
U
2
R = Resistance value in Ω
U = Switch-on voltage braking resistor in V
P
max
= Required peak power in W
If 2 or more braking resistors are connected to one drive, note the fol-
lowing criteria:
• The braking resistors must be connected in parallel or in series so
the required resistance is reached. Only connect resistors with
identical resistance in parallel in order to evenly distribute the load
to all braking resistors.
• The total resistance of all external braking resistors connected to
one drive must not fall below a lower limit.
• The continuous power of the network of connected braking resis-
tors must be calculated. The result must be greater than or equal
to the actually required continuous power.
LXM32
3 Engineering
Common DC bus
33
MNA01M001EN, V1.01, 08.2014