Rockwell Automation 20Y PowerFlex Active Front End User Manual
Page 159
Rockwell Automation Publication 20Y-UM001E-EN-P - July 2014
159
Application Notes
Appendix C
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 MCCB.
b. Open the MCCB 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 the various AFE configurations.
•
shows an example of paralleling two AFEs in their
IP21 Rittal enclosures, where each AFE has its own precharging circuit,
precharging control, and fusing on the DC bus output and input
contactor.
In this case, turn the disconnects (Q0) of all AFEs to ON, and set all of the
MCCB CONTROL 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 MCCB motor-controlled circuit breakers (Q1) 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.