Rockwell Automation Publication 750-RM003A-EN-P - April 2018 25
Selection Considerations Chapter 1
Information about internal DC bus capacitance for most PowerFlex and
Kinetix DC input common bus inverters can be found in publication
DRIVES-AT005
, and publication DRIVES-AT002. Also consider additional
capacitor banks that can connect to the DC bus when calculating the external
DC bus capacitance.
See the applicable sections of the Drives in Common Bus Configurations with
PowerFlex 755TM Bus Supplies application technique, publication DRIVES-
AT005, to verify the PowerFlex 755TM bus supply and connected DC input
common bus inverter precharge and interlocking is properly configured for use
with the PowerFlex 755TM bus supply. The following items require attention
and are covered in the General Considerations section of publication
DRIVES-AT005
.
1. If drives without internal precharge are used and a disconnect switch is
installed between the DC input of the drive and the DC bus, you must
use an external precharge circuit between the disconnect switch and the
DC input of the drive.
2. If drives with internal precharge are used with a disconnect switch
installed between the DC input of the drive and the DC bus, you must
connect an auxiliary contact on the disconnect switch to a digital input
of the drive. The corresponding input must be set to the ‘Precharge
Enable’ option. This provides the proper precharge interlock, guarding
against possible damage to the drive when connected to a common DC
bus, especially for drives with auxiliary 24V DC control power.
3. The precharge status of the PowerFlex 755TM bus supply must be
interlocked with the connected drives, such that the drives are disabled
(not running) when the PowerFlex 755TM bus supply is in a precharge
state.
Table 4 - Maximum External DC Bus Capacitance
PowerFlex 700AFE, Maximum
External Capacitance
PowerFlex 755TM Bus Supply, Maximum External Capacitance
Frame 10 60,100 μF Frames 8…12 See Appendix A of publication
DRIVES-AT005.
Frame 13 98,300 μF
ATTENTION: Do not exceed the maximum DC bus capacitance as it can cause
damage to the bus supply precharge circuits.
ATTENTION: Kinetix servo drives and some PowerFlex drives do not
have built in precharging circuits. Exercise extreme care to confirm
proper precharging and interlocking is implemented for safe and
reliable operation of the DC bus system.
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