Rockwell Automation AK DBU - Dynamic Braking Unit 600/690 VAC - Manual (Page 17)

Installation/Wiring 1-5
Connection leads between Inverter and DBU
During switching of the braking unit’s IGBT the inductance of the leads
between the DC bus capacitors of the inverter and the DBU generates
short time (milliseconds) bus over voltage peaks.
These bus over voltages, which are dampened by the RC snubber circuits
in the DBU, must not exceed 200 volts.
Drives Connected to a Single Motor
For drives connected to a single motor this can be accomplished by the
following measures (see
Figure 1.2 ):
• The conductors must be bound together and run separatedly from
other conductors or multi-core cables (EMC shielded). This is to
reduce the cable inductance.
• Limiting the total cable length between the drive and the DBU to a
maximum of 3 m (120 in)
Connection example
Figure 1.2 Connection to single motor drive
Multiple Drives Coupled through a Common DC Bus
For a DBU that is connected to several drives which are coupled through
a common DC bus, the bus over voltages must also not exceed 200 V.
The inductance of the DC bus connection leads to the engaged DC bus
capacitors must be kept low by adhering to the following measures:
• Use short leads with low inductance.
• Locate the DBU as close as possible to the largest DC bus capacitors.
• Wires should be twisted
AC-Drive
10 11
DB-Resistor
Assembly
DBU
F2
R
DC- DC-
F1
Cable length
max.3m
DC+ DC+
Cable length
max.30m
BR1
BR2
Field
Installed
Fuses