REXROTH Fv Series, Instruction Manual

Page: 166 / 222

Definition for braking usage ED%
As the indication of above diagram, brake usage ED% is the ratio of the brak‐
ing time and the braking period, usually represented by percentage. When
ED% is selected, the resistance and the power of brake resistor must be tak‐
en into consideration so that enough time can be ensured for the brake unit
and the brake resistor to release the heat generated in the braking process.
Fig.10-2: Brake usage
10.3.2 Brake Resistor
Brief Introduction
Energy regenerated when a 3-phase AC motor is decelerated (the frequency
is reduced) 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 volt‐
age threshold at approx. 770 VDC) 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 calculation of resistance power.
● Safety and flammability of surrounding conditions shall be
considered. Keep all item 10 cm away from the brake resis‐
tor.
● 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 surface uses organic silicon, which is normal and does
not affect the performance of the brake resistor.
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 op‐
erate one frequency converter with respect to a given moderating ratio OT.
Bosch Rexroth AG DOK-RCON02-FV*********IB01-EN-P
Rexroth Frequency Converter Fv
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