Guidelines for afes in ip21 rittal enclosure – Rockwell Automation 20Y PowerFlex Active Front End User Manual
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Rockwell Automation Publication 20Y-UM001E-EN-P - July 2014
Appendix C
Application Notes
Guidelines for AFEs in IP21 Rittal Enclosure
•
AFE units of different power sizes can be connected in parallel.
•
For AFEs in IP21 Rittal enclosures, a maximum of six AFEs can be
paralleled. However, this can be limited by the capacity of the DC bus bar.
•
Each AFE must have its own LCL filter.
•
Each AFE must have its own short-circuit protection on AC and DC
sides. See
for fusing information. When paralleling, you must
check the sufficient short-circuit capacity of the system.
•
The AFE units must be derated by 5% of their power rating.
•
Configure the following parameters for parallel operation:
–
Set Parameter 42 - [Modulation Type] to ‘3’.
–
Set Parameter 82 - [Ground I Lvl] to 100%.
–
Set Parameter 85 - [Droop] to 5% for current sharing of the AFEs.
–
Set Parameter 86 - [PWM Synch] to ‘1’ to reduce circulating currents
between AFEs connected to the same DC bus and fed from the same
power source.
•
If one of the paralleled AFEs is to be isolated from the AC and DC
voltages, you must isolate the AC input and DC output. The AC input
can be isolated with a circuit breaker or a disconnect switch. Contactors
are not suitable for isolating the AC input because they cannot be locked
in the safe position. The DC output can be isolated with a disconnect. A
load isolation switch or safety isolation switch can be used to isolate the
precharging circuit from the AC input.
•
Each AFE must use a separate precharging circuit, precharging control
switch, DC bus output fusing, and main contactor.
Each AFE controls its own precharging and main contactor. Therefore, it
is possible to disconnect the AFE when other parallel AFEs are powered
up but not modulating.
•
The fault relay of both AFEs must be interlocked with each other, such
that both AFEs are disabled (not running) when either AFE is faulted.
•
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 MCCB.
b. Close the DC disconnect to connect the AFE to the DC bus.