If the drive trips on overvoltage, confirm that the green control power light is
on (5.3.1), the status contact is closed (5.3.6), and the amber DC bus light is
on (5.3.2). Watch the red “Active Braking” light on the front of the module
during a braking cycle. If it never illuminates, ensure that the module is either
configured as a master, or correctly wired to a properly configured master
(4.2.3). There must be exactly one master in the system. Check the DC bus
voltage and make sure the bus voltage at the braking module exceeds the
trip point of the module, i.e. 750VDC for a 460VAC nominal system. See
Table 2-3: DC Bus Voltage Rating.
If the red “Active Braking” light comes on, check the wiring to the load bank,
and check the current to the load bank with a clamp on current meter. If the
wiring to the load bank is good, make sure the DC bus fuse is good.
If the red “Active Braking” light comes on, and current is flowing to the load
bank, check to make sure that the module is sized properly for the system. If
the resistance of the load bank is too large, not enough current will flow to
allow for the braking energy to be dissipated. Check the system design to
make sure the braking requirements are matched with the braking module
capacity.
MASTER/SLAVE SYSTEMS
Master/Slave systems must be properly configured and operating to share
the load.
Check your system layout and make sure there is only one selected and
operating Master and that all the Slaves are properly wired to that Master.
Make sure that all the modules have the DC bus and control power lights on.
When the system is braking, watch the Active Braking lights on all modules.
They should all go on and off at the same time. If they do not, there may be
a wiring or module configuration issue.
If the lights all go on at the same time, check the current going to each load
bank as above and correct problems found with the wiring.
5.3.9. BRAKING LIGHT FLICKERS
During motor deceleration, the red braking LED may flicker if the braking
cycle energy is low. This is normal.
If the red braking light flickers when the inverter is idle, this may indicate high
voltage, excessive noise, or harmonics on the main system rectifier input AC
voltage. Check the incoming AC line for these problems. Consult the project
engineer for the appropriate corrective action.
In rare instances, the module is installed on a system that has very little
capacitance, or the inverters have been removed from the bus. This
configuration can cause damage to the braking module. See Section 7 in this
manual for more information.
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