2 Engineering
2.7 Brake resistors
DB1 variable frequency drive
11/20 MN040031EN
Eaton.com
43
2.7 Brake resistors
In certain operating conditions, the motor may run as a generator in certain
applications (regenerative braking operation).
Examples include:
•
Lowering in hoisting gear and conveyor applications
•
Controlled speed reduction in the case of large load inertias
(flywheels)
•
A fast speed reduction in dynamic travel drives
When the motor operates as a generator, its braking energy will be fed into
the variable frequency drive’s DC link via the inverter. The DC link voltage
U
DC
is increased as a result. If the voltage value is too high, the DB1 variable
frequency drive will disable its inverter, after which the motor will coast
uncontrolled.
If there is a brake chopper and a connected brake resistor R
B
, the braking
energy fed back into the variable frequency drive can be dissipated in order
to limit the DC link voltage.
DC1-S…B-A… variable frequency drives with a frame size of FS2 feature an
integrated brake chopper. The brake resistors are connected to the internal
braking transistor with terminals DC+ and BR so that they will be connected
in parallel to the DC link. In addition to this, the brake chopper must be enab-
led using parameter P-34 (= 1, 2, 3, 4).
The braking chopper will be switched on automatically if the braking energy
being fed back causes the DC link voltage to increase to the switch-on vol-
tage’s magnitude.
Device type
Mains connec-
tion
Voltage class
Brake chopper
on
Brake chopper
off
DB1-344D1FB-N2CC
DB1-34508FB-N2CC
DB1-349D5FB-N2CC
3-phase
400 V
780 V
756 V
