Fault analysis and countermeasures
When there is abnormality with the brake chopper, the thermal protection of
the brake chopper will be activated. A failure signal will be sent by the brake
chopper to the frequency converter. The abnormality of the brake chopper
may result in the failure and warning of the frequency. Make sure to find the
cause of failure and run it after the failure is removed.
Item Fault conditions Failure cause Countermeasures
1 The “POWER” light of brake chopper off Wrong connection
Check if “MASTER” is selected
and check wire connection
2 The “BRAKING” light of brake chopper off
Breakdown of brake chopper IGBT Replace brake chopper
Open circuit with brake resistor
Check brake resistor and its wir‐
ing
3
“Overvoltage” warning with the of fre‐
quency converter
Wrongly connected wires Check wires
Inadequate capacity of brake resis‐
tor and brake chopper
Check design and recalculate
Inappropriate brake chopper volt‐
age selection
Set again
4
Thermal protection device of brake chop‐
per acts caused by overheated radiator
High braking ratio Check design and recalculate
Environmental temperature > 40 ℃
Reduce environmental tempera‐
ture with cooling fans
Tab. 10-8: Fault analysis and countermeasures
10.2.2 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 items 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 electric performance of the brake resistor.
DOK-RCON02-FV*********-IB08-EN-P Bosch Rexroth AG 201/259
Rexroth Frequency Converter Fv
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