Rockwell Automation 20Y PowerFlex Active Front End User Manual
Page 155
Rockwell Automation Publication 20Y-UM001E-EN-P - July 2014
155
Application Notes
Appendix C
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An AFE can be connected while other parallel AFE units are running.
When connecting the AFE to the DC bus, follow these steps in the order
shown.
a. Precharged the isolated AFE.
When completed, the AFE control closes the contactor.
b. Close the DC disconnect to connect the AFE to the DC bus.
When disconnecting the AFE from the DC bus, follow these steps in the
order shown.
a. Stop the inverters and AFEs connected to the same DC bus from
modulating.
The AFE load must be zero before being disconnected to reduce the
load on the contactor.
b. Open the contactor of the AFE.
c. Open the DC disconnect switch.
d. Restart the other AFE units.
•
When AFEs are paralleled, the DC bus voltage at regeneration is 5%
higher than with a single AFE due to the 5% droop. See Drives in
Common Bus Configurations, publication DRIVES-AT002, for
supported drives that can be used in various AFE configurations.
•
Figure 52 on page 156
shows an example of paralleling two AFEs in their
IP20 2500 MCC Style enclosures, where each AFE has its own
precharging circuit, precharging control, and fusing on the DC bus output
and main contactor.
In this case, turn the disconnects (Q0) of all AFEs to ON, and set all of the
REM-AUTO-MAN selector switches on the door to AUTO to enable
automatic operation.
When turning on the main power, the two AFEs precharge automatically.
After charging, the contactors (K1) are closed and the AFEs start the
modulation. The control signal ‘Inverter Enable’ shown in
can be used to interlock the drives connected to the DC bus.