Accessories - Bosch Rexroth EFC 3600 Operating Instructions Manual

Bosch Rexroth AG

Accessories

12 Accessories
12.1 Brake Resistor
12.1.1 Brief Introduction
Energy regenerated when a 3-phase AC motor is decelerated (the frequency is re‐
duced) is recovered and fed into the frequency converter. To prevent over voltage of
the frequency converter, an external brake resistor may be used. A power transistor
discharges the DC bus voltage energy (braking voltage threshold at approx. 720 VDC
for 400 V model, and 380 VDC for 200 V model) to the brake resistor, and the energy is
lost as heat.
● If a resistance lower than the recommended value (and no less than the
minimum resistance) is used, contact the agent or manufacturer for cal‐
culation of resistance power.
● Safety and flammability of surrounding conditions shall be considered.
Keep all items 10 cm away from the brake resistor.
● A brake resistor can not work overload for a long time. 10 times of rated
load should not exceed 5 seconds.
● There could be smoking for the first use of the brake resistor as its sur‐
face uses organic silicon, which is normal and does not affect the per‐
formance of the brake resistor.
12.1.2 Brake Resistor Selection
Brake resistors with different power ratings are available to dissipate braking energy
when the frequency converter is in generator mode.
The adjacent tables list the optimal combination of frequency converter, brake unit and
brake resistor and the number of components required to operate one frequency con‐
verter with respect to a given moderating ratio OT.
OT Braking ratio
Tc Cycle time
Fig.12-1: Braking ratio
166/235
DOK-RCON03-EFC-3600***-IT01-EN-P
Rexroth Frequency Converter EFC 3600
Tb Braking time