Rockwell Automation Publication DRIVES-AT005D-EN-P - May 2022 117
Appendix D Mixed Architecture Resources
Logic Interlocking
In addition to normal DC bus voltage control, you also need to monitor DC bus overvoltage fault status of all frame 3…5 inverters and implement
fault detection logic and countermeasures to help prevent excessive DC bus voltage.
ATTENTION: A DC bus overvoltage fault on any 600V class PowerFlex 750-
Series frame 3…5 drives must initiate shutdown (prevent output IGBT
modulation) of all PowerFlex 750-Series frame 6…7 inverters and all
PowerFlex 755TM common bus inverters on the same common DC bus.
This will ensure there’s no regeneration from these inverters and
subsequent rise of the DC bus voltage. The logic to initiate shutdown of the
larger PowerFlex inverters can be accomplished with Logix application
code and EtherNet/IP communication or through hardwired digital I/O.
To mitigate damage to the frame 3…5 inverter units the shutdown
countermeasures should occur as quickly as possible and within 250
milliseconds of the first DC bus overvoltage trip event.
IMPORTANT Monitoring the health of the DC bus control equipment (chopper/DB
resistor, regen unit or regenerative bus supply) for fault conditions
that may prevent regeneration and DC bus voltage control is also
recommended. If the DC bus voltage control equipment faults you
should implement logic to shut down all inverters on the common
DC bus.
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