Rockwell Automation Publication 750-PM001N-EN-P - February 2017 337
Troubleshooting Chapter 6
N-1 and Re-Rate Functions
The N-1 feature is available on Frame 9 and larger drives. This feature allows the
drive to be run at reduced current limits if one of the paralleled inverter/
converter drive assemblies fails.
The letter N represents the number of drive assemblies in the drive. For example,
a frame 9 drive has two drive assemblies, therefore N=2. A Frame 9 drive running
the N-1 feature is running on one drive assembly, that is, N-1 =1.
The N-1 feature does not change the rating of the drive. It is a way to impose
temporary output restrictions on the drive until the damaged inverter/converter
drive assembly is repaired and reinstalled. Some customers can elect to oversize
their drives, to have redundant inverter/converter assemblies.
The Re-Rate function allows the rating of the drive to be changed. This
procedure is used when making long-term changes.
N-1 and Re-Rating with Integrated Motion on EtherNet/IP
These features cannot be used while the drive is in Integrated Motion on
EtherNet/IP mode. If these features are needed, disconnect the drive from the
EtherNet/IP network, perform the N-1 or Re-Rate procedure, then reconnect
the drive to the network.
Use the N-1 Feature
This procedure describes how to use the N-1 feature to run the drive at reduced
limits because an inverter/converter assembly has failed.
For information on assembly removal and general safety precautions that are
related to AC input and Common DC input PowerFlex 755 drives, refer to the
PowerFlex 750-Series AC Drives Installation Instructions, publication 750-
IN001.
1. Remove all incoming power to the drive.
2. Disconnect and remove the failed drive assembly from the cabinet.
The control pod can need to be moved from the disabled drive assembly to
one of the remaining drive assemblies. See the PowerFlex 750-Series AC
Drives Hardware Service Manual, publication 750-TG001
.
3. Energize the drive.
With the drive assembly removed, an F360 “N-1 See Manual” fault is
indicated.
You cannot flash update a drive that is using the N-1 feature.
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